particulate matter formation mechanisms in a direct
TRANSCRIPT
Particulate Matter Formation Mechanisms in a Direct-Injection Gasoline Engine
by
Jared Cromas
A thesis submitted in partial fulfillment of the requirements for the degree of
Master of Science
(Mechanical Engineering)
at the
University of Wisconsin – Madison
2003
i
Abstract
Experiments were conducted to determine the particulate formation mechanisms of a
single-cylinder direct-injection two-stroke gasoline engine. The engine was tested at four
operating points; an idle condition with a highly stratified mixture, a 2000 RPM low load
condition operated with an A/F of both 30:1 and 15:1, and a 2800 RPM moderate load 15:1
A/F condition. The engine utilized an air-assist injector that was also used as a N2-assist
injector to provide a slightly richer local mixture. Propane fuel was also used with the
injector to isolate the effects of spray impingement and fuel films. The oil-to-fuel ratio was
externally controlled to determine the lube oil effect on particulate matter (PM).
A venturi-type mini-dilution tunnel was designed and integrated to sample
particulates. It utilized a critical orifice supply that allowed the dilution ratio (DR) to be
changed and a case heater to maintain a sampling temperature at the instruments. A tapered
element oscillating microbalance (TEOM) was used to measure particulate mass and a
scanning mobility particle sizer (SMPS) was used to measure the number-based size
distribution. The total particulate mass measured from the TEOM was compared to
traditional gravimetric methods utilizing a Teflon filter and found to agree very well. NOx
and CO2 concentration measurements were made in the dilution tunnel to be used as a tracer
to determine DR.
Lubrication oil consumption (LOC) was found to have a large effect on the PM for
this two-stroke engine utilizing a lost oil system. Not only was the lube oil the dominant
effect on PM with the normal fuel-to-oil ratio, it was found to have a complex interaction that
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changed with engine parameters and not just increase the particulate mass by some
offset at all conditions. It was therefore determined that the engine would be operated at a
low oil-to-fuel ratio comparable to the LOC rates of four-stroke engines (oil sump systems).
An interesting trend in particulate mass with injection timing was observed at both
stoichiometric operating conditions. A local minimum in particulate mass was found for a
fairly retarded injection timing. The size distributions near this local minimum showed that
the particulates appeared to change mode.
Generally propane injection resulted in a significantly lower particle mass. It was
determined, however, that this is not entirely due to spray impingement. The fuel
composition was believed to be a significant effect when using propane and accounts for
some of the particulate mass difference.
Temperature was found to have a significant effect on particle mass. The observed
greater particulate mass for air-assist injection over N2-assist was likely due to higher in-
cylinder temperatures. Analysis of the size distribution curves suggests that temperature
strongly affects the small mode of particles. This corresponds with advanced timings, closer
to a homogeneous condition.
The local burning zone A/F had a large effect on particulate mass for very rich
mixtures (retarded timings). It also has a significant effect on the large particle mode seen in
the size distributions, believed to be elemental carbon particles.
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Acknowledgments
First, I�d like to thank my family. They always supported me and made sure that I
could have the things I need and do the things that I want. My dad helped with his
knowledge of engines and my mom made sure that I didn�t forget anything important.
I�d especially like to thank Amanda for all her support. Even though she was three
states away (MI) we never lost touch.
Thanks to my advisor, Dr. Jaal Ghandhi, for all his guidance throughout the project.
His wealth of engine and combustion knowledge was always useful and greatly appreciated.
Thanks also to Dr. David Foster, Dr. Rolf Reitz, Dr. James Schauer, and Dr. Tim Shedd for
their assistance in the completion of this project.
Some of the best discussions, as well the best distractions, were with my fellow grad
students. The grad students at the ERC are some of the greatest people to work with, not to
mention bar hop with. Special thanks to fellow grad students Brian Albert, Karen Bottom,
Andy Bright, Terry Dembroski, Nate Forster, Zach Foudray, Randy Herold, Ana Holguin,
Eric Hruby, Bob Iverson, Tongwoo Kim, Soochan Park, Dan Probst, Dave Rothamer, John
Stetter, Dennis Ward, and Matt Wiles. Special thanks also goes to Ralph Braun and Anton
Kozlovsky for their mechanical expertise and assistance.
I want to thank all my friends that I play hockey with, many of which are also at the
university. They gave me a good release so I didn�t go crazy working too much, not to
mention great people to go to the bar with. I also want to thank the guys from Madison
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Sports Car Club. There is nothing like talking shop with a bunch of fellow racers
and gearheads to come up with crazy ideas or radical solutions.
I want to thank all the members of the Wisconsin Small Engine Consortium (Mercury
Marine, Briggs and Stratton, Harley-Davidson, Kohler Company, Nelson Industries, and the
State of Wisconsin) for their financial assistance and all their technical guidance. Special
thanks to Brian McGuire and Mark Ruman for their technical assistance with the engine and
supplied parts, Eric Hudak for his technical assistance with emissions, and Blake Suhre for
his technical assistance with MotoTron.
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Table of Contents
Abstract ...................................................................................................................................... i Acknowledgments.................................................................................................................... iii List of Figures ........................................................................................................................ viii List of Tables ........................................................................................................................... xi Nomenclature.......................................................................................................................... xii 1.0 Introduction......................................................................................................................... 1
1.1 Motivation for Two-Stroke Direct Injection Research ................................................. 1 1.1.1 Emissions Regulation........................................................................................... 1 1.1.2 Environmental Impact of Particulate Matter........................................................ 2
1.2 Objectives ..................................................................................................................... 2 2.0 Background Discussion ...................................................................................................... 4
2.1 Traditional Two-Stroke Engines and Emissions........................................................... 4 2.2 Direct Injection Two-Stroke Engines ........................................................................... 6 2.3 Stratified Charge Combustion....................................................................................... 7 2.4 Emission Formation Mechanisms................................................................................. 8 2.5 Particulate Matter.......................................................................................................... 9
2.5.1 Particle Matter Formation .................................................................................. 11 2.5.1.1 Pool Fires .................................................................................................. 14 2.5.1.2 Lube Oil Consumption.............................................................................. 15
2.5.2 Particulate Kinetics ............................................................................................ 17 2.5.2.1 Inception ................................................................................................... 17 2.5.2.2 Surface Growth ......................................................................................... 18 2.5.2.3 Coagulation ............................................................................................... 19 2.5.2.4 Oxidation................................................................................................... 20
2.5.3 Particulate Dynamics ......................................................................................... 20 2.5.3.1 Adsorption/Desorption.............................................................................. 20 2.5.3.2 Condensation/Evaporation........................................................................ 21 2.5.3.3 Thermophoresis......................................................................................... 21 2.5.3.4 Diffusion ................................................................................................... 21 2.5.3.5 Inertial Impact........................................................................................... 22 2.5.3.6 Electrostatic Deposition ............................................................................ 22 2.5.3.7 Gravitational Deposition........................................................................... 22
2.6 Particulate Measurement............................................................................................. 22 2.6.1 Dilution Tunnel.................................................................................................. 23
2.6.1.1 Full-Flow Dilution Tunnel........................................................................ 24 2.6.1.2 Partial-Flow Dilution Tunnel.................................................................... 25
2.6.2 Gravimetric Methods ......................................................................................... 31 2.6.2.1 Particulate Filters ...................................................................................... 32 2.6.2.2 Tapered Element Oscillating Microbalance.............................................. 33
2.6.3 Optical Methods................................................................................................. 35
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2.6.3.1 Scanning Mobility Particle Sizer .............................................................. 36 3.0 Experimental Equipment .................................................................................................. 39
3.1 Engine ......................................................................................................................... 39 3.2 Dynamometer.............................................................................................................. 42 3.3 Engine Control ............................................................................................................ 43 3.4 Fuel Delivery System.................................................................................................. 43 3.5 Air Delivery System ................................................................................................... 44 3.6 Injection Systems ........................................................................................................ 45
3.6.1 Air-Assist Injection............................................................................................ 45 3.6.2 N2-Assist Injection ............................................................................................. 46 3.6.3 Propane Injection ............................................................................................... 46
3.7 Ignition System ........................................................................................................... 46 3.8 Cooling........................................................................................................................ 46 3.9 Exhaust........................................................................................................................ 47 3.10 Cylinder Pressure ...................................................................................................... 47 3.11 Emissions Measurement ........................................................................................... 48 3.12 Dilution Tunnel......................................................................................................... 50 3.13 Particulate Measurement........................................................................................... 52
3.13.1 Filter Sampling................................................................................................. 52 3.13.2 TEOM .............................................................................................................. 52 3.13.3 SMPS ............................................................................................................... 53
4.0 Results and Methodology ................................................................................................. 54 4.1 Engine Operating Conditions...................................................................................... 54 4.2 Data Reduction............................................................................................................ 56
4.2.1 Emissions Measurements................................................................................... 56 4.2.2 Particulate Measurements .................................................................................. 57
4.3 Mini-Dilution Tunnel Calibration............................................................................... 59 4.3.1 Dilution Tunnel Supply Test.............................................................................. 59 4.3.2 Dilution Ratio Test............................................................................................. 60 4.3.3 Performance Testing .......................................................................................... 62
4.4 Ambient sampling....................................................................................................... 64 4.5 Repeatability ............................................................................................................... 65 4.6 Particulate Mass Comparison ..................................................................................... 69 4.7 Filter Comparison Test ............................................................................................... 72 4.8 Lube Oil Test .............................................................................................................. 73
4.8.1 Stratified Condition Oil Test.............................................................................. 74 4.8.2 Homogeneous Condition Oil Test ..................................................................... 76
4.9 Oil Flow Equilibrium.................................................................................................. 78 5.0 Particulate Matter Results and Discussion........................................................................ 80
5.1 Idle .............................................................................................................................. 80 5.2 Stratified Combustion Test ......................................................................................... 84 5.3 Stoichiometric Combustion Test, Low Speed ............................................................ 91 5.4 Stoichiometric Combustion Test, Medium Speed ...................................................... 98 5.5 Particulate Matter Emissions Comparison................................................................ 103
5.5.1 Particulate Mass Rate....................................................................................... 103
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5.5.2 Literature Comparisons.................................................................................... 104 5.6 Formation Mechanisms............................................................................................. 108
5.6.1 Oil consumption............................................................................................... 108 5.6.2 Temperature ..................................................................................................... 110 5.6.3 Local Burning Zone A/F.................................................................................. 112 5.6.4 Spray Impingement.......................................................................................... 114 5.6.5 Fuel Short-Circuiting ....................................................................................... 116 5.6.6 Fuel Composition............................................................................................. 117
6.0 Summary......................................................................................................................... 119 6.1 Conclusions............................................................................................................... 120 6.2 Recommendations..................................................................................................... 122
Bibliography ......................................................................................................................... 123 Appendix A Dilution Ratio Calculations.............................................................................. 128 Appendix B Mass-Based Emissions Calculations ................................................................ 131 Appendix C Particulate Sampling Results............................................................................ 133
Appendix C.1 - Stratified Oil Test Condition................................................................. 134 Appendix C.2 - Stoichiometric Oil Test Condition ........................................................ 136 Appendix C.3 - Idle Test Condition................................................................................ 139 Appendix C.4 - Stratified Test Condition....................................................................... 143 Appendix C.5 � Low Speed Stoichiometric Test Condition........................................... 151 Appendix C.6 � Medium Speed Stoichiometric Test Condition .................................... 155
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List of Figures
Figure 2.1 � Source of HC Emissions for a Carbureted Two-Stroke [8]................................. 5 Figure 2.2 � Typical injection timing map for a DI engine. .................................................... 8 Figure 2.3 � Diagram Showing Composition of PM [15] ..................................................... 10 Figure 2.4 � Volume Weighted Particle Distribution Showing the Three Modes................. 11 Figure 2.5 � Dependence of PM on Injection Timing [19].................................................... 13 Figure 2.6 � Effect of Fuel Film Mass on Smoke Emissions [21]......................................... 14 Figure 2.7 � Relative Oil Consumption for a SI Engine [23] ................................................ 16 Figure 2.8 � Single Ring PAH (Benzene) and Multiple Ring PAH (Benzo[a]pyrene) with
Bonds [kinetics project] .................................................................................................. 18 Figure 2.9 � Multiple Ring Buildup By Hydrogen Abstraction Acetylene Addition Method
[27,28]............................................................................................................................. 19 Figure 2.10 � Correlation of Results for a Mini and Full Tunnel [35] .................................. 27 Figure 2.11 � Effect of DR (x-axis) on PM (y-axis) for a Venturi Type MDT [39] ............. 28 Figure 2.12 - Deviation of Exhaust Sample Flow From Controlled Value [32].................... 29 Figure 2.13 � NOx and Particulate Mixing in Mini Dilution Tunnel [35] ............................. 30 Figure 2.14 � Effect of Sampling Temperature on Particulate Mass [35] ............................. 31 Figure 2.15 - Effect of Sampling Temperature on SOF [38] ................................................ 31 Figure 2.16 � Schematic Showing the Operation of a TEOM Monitor................................. 34 Figure 2.17 - Schematic of DMA Operation [48].................................................................. 38 Figure 3.1 - Diagram Showing Spark Plug, Ports, Injector, & Transducer ........................... 41 Figure 3.2 � AVL Cylinder Pressure Transducer Calibration ............................................... 48 Figure 3.3 � Emission Sampling Flow Path........................................................................... 50 Figure 3.4 - Schematic of Mini-Dilution Tunnel ................................................................... 51 Figure 4.1 � Supply Air Mass Flow Rate as a Function of Supply Pressure ......................... 60 Figure 4.2 - DR as a Function of Supply Pressure for Both Flow Orifices ........................... 61 Figure 4.3 - Particulate Mass Measurements from TEOM for the DR Sweep ...................... 63 Figure 4.4 - Particle Size distribution Measurements from SMPS for the DR Sweep .......... 64 Figure 4.5 - Particle Distribution Effect of Compressor Oil in DT Supply Air..................... 65 Figure 4.6 � TEOM Repeatability for Three Engine Conditions........................................... 66 Figure 4.7 - SMPS Repeatability for Base Engine Condition................................................ 67 Figure 4.8 - SMPS Repeatability for Retarded Engine Condition......................................... 67 Figure 4.9 - SMPS Repeatability for Homogeneous Engine Condition ................................ 68 Figure 4.10 - PM Test Points Compilation Showing TEOM Repeatability .......................... 69 Figure 4.11 - Comparison of Mass Concentration from the TEOM and SMPS Measurements
......................................................................................................................................... 71 Figure 4.12 - Correlation Between Particulate Mass form the TEOM and SMPS ................ 72 Figure 4.13 - Comparison of Particulate Mass from Teflon Filter and TEOM ..................... 73 Figure 4.14 - Particulate Mass Results from Oil Test at 2000 RPM ..................................... 75 Figure 4.15 - Size distribution Curves for Oil Test at 2000 RPM ......................................... 76 Figure 4.16 - Particulate Mass Results from Oil Test at 2800 RPM ..................................... 77 Figure 4.17 - Size distribution Curves for Oil Test at 2800 RPM ......................................... 78
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Figure 4.18 - Size Distribution Measured as Oil Flow Rate Reaches Equilibrium ............... 79 Figure 5.1 - Particulate Mass Results for A/F Sweep at Idle Test Condition ........................ 81 Figure 5.2 - NOx Emissions for A/F Sweep at Idle Test Condition....................................... 82 Figure 5.3 - Particle Size Distribution for A/F Sweep at Idle Test Condition....................... 83 Figure 5.4 - Particle Size Distribution near Local Peak of 100 nm ....................................... 83 Figure 5.5 - Particulate Mass Results for Injection Sweep at Stratified Test Condition ....... 85 Figure 5.6 - CO Emissions for Injection Sweep at Stratified Test Condition........................ 86 Figure 5.7 - NOx Emissions for Injection Sweep at Stratified Test Condition ..................... 86 Figure 5.8 - Particulate Mass Results for Spark Sweep at Stratified Test Condition ............ 87 Figure 5.9 - Particle Size Distribution for Air and N2-Assist Injection Sweep at Stratified
Test Condition................................................................................................................. 88 Figure 5.10 - Mass Weighted Size Distribution for Air and N2-Assist Injection Sweep at
Stratified Test Condition................................................................................................. 89 Figure 5.11 - Particle Size Distribution for Propane Injection Sweep at Stratified Test
Condition......................................................................................................................... 89 Figure 5.12 - Mass Weighted Size Distribution for Propane Injection Sweep at Stratified
Test Condition................................................................................................................. 90 Figure 5.13 - Particle Size Distribution for Spark Sweep at Stratified Test Condition ......... 90 Figure 5.14 - Mass Weighted Size Distribution for Spark Sweep at Stratified Test Condition
......................................................................................................................................... 91 Figure 5.15 - Particulate Mass Results for Injection Sweep at 2000 RPM Stoichiometric Test
......................................................................................................................................... 93 Figure 5.17 - NOx Emissions for Injection Sweep at 2000 RPM Stoichiometric Test .......... 94 Figure 5.18 - HC Emissions for Injection Sweep at 2000 RPM Stoichiometric Test............ 94 Figure 5.19 - Particle Size Distribution for Air and N2-Assist Injection Sweep at 2000 RPM
Stoichiometric Test ......................................................................................................... 96 Figure 5.20 - Mass Weighted Size Distribution for Air and N2-Assist Injection Sweep at
2000 RPM Stoichiometric Test....................................................................................... 96 Figure 5.21 - Particle Size distribution for Propane Injection Sweep at 2000 RPM
Stoichiometric Test ......................................................................................................... 97 Figure 5.22 - Mass Weighted Size Distribution for Propane Injection Sweep at 2000 RPM
Stoichiometric Test ......................................................................................................... 97 Figure 5.23 - Particulate Mass Results for Injection Sweep at 2800 RPM Stoichiometric Test
......................................................................................................................................... 99 Figure 5.24 - HC Emissions for Injection Sweep at 2800 RPM Stoichiometric Test.......... 100 Figure 5.25 - Particle Size Distribution for Air and N2-Assist Injection at 2800 RPM
Stoichiometric Test ....................................................................................................... 101 Figure 5.26 - Mass Weighted Size Distribution for Air and N2-Assist Injection at 2800 RPM
Stoichiometric Test ....................................................................................................... 101 Figure 5.27 - Particle Size Distribution for Propane Injection at 2800 RPM Stoichiometric
Test................................................................................................................................ 102 Figure 5.28 - Mass Weighted Size Distribution for Propane Injection at 2800 RPM
Stoichiometric Test ....................................................................................................... 102 Figure 5.29 - Comparison of Particulate Mass Emission Rate for All Operating Conditions
....................................................................................................................................... 103
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Figure 5.30 - Comparison to Other Marine Outboard Engines (2-Stroke Carb, 4-Stroke Carb, and 2-Stroke DI reprinted from [54]) ...................................................... 104
Figure 5.31 - Comparison to Other Engines Including Diesel, DISI, and Port Fuel Injection (See Table 5.1, [14,17,18,55,56,57]) ............................................................................ 105
Figure 5.32 - Comparison Showing Particulate Mass Trend with Injection Timing (Ford data reprinted from [19]) ...................................................................................................... 107
Figure 5.33 - NOx Emissions for 2800 RPM Oil Test ......................................................... 110 Figure 5.34 - Comparison of PM for Air and N2-Assist Against CO .................................. 113 Figure 5.35 - Comparison of PM for Air-Assist and Propane Injections Against CO ........ 116
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List of Tables
Table 2.1 � Comparison of two- and four-stroke emissions [6]............................................... 4 Table 2.2 � Advantages and disadvantages of DI [10]. ........................................................... 6 Table 2.3 � Emission formation mechanisms for a DI two-stroke engine [11]. ...................... 9 Table 2.4 � Filter Types for Engine Testing [41]................................................................... 33 Table 2.5 � Filter Analysis Techniques [14,42,43] ................................................................ 33 Table 3.1 � Test Engine Specs ............................................................................................... 40 Table 3.2 � Amoco Indolene Fuel Properties......................................................................... 44 Table 3.3 � Haltermann EEE Fuel Properties ........................................................................ 44 Table 4.1 - Test Matrix........................................................................................................... 55 Table 5.1 - Reference Sources and Explanations for Engines Compared in Figure 5.31 .... 105
xii
Nomenclature
Φ Equivalence Ratio A/F Air-Fuel Ratio ATDC After Top Dead Center BDC Bottom Dead Center BSFC Brake Specific Fuel Consumption BTDC Before Top Dead Center CARB California Air Resources Board CO Carbon Monoxide CO2 Carbon Dioxide COV Coefficient Of Variation CPC Condensation Particle Counter dATDC Degrees After Top Dead Center dBTDC Degrees Before Top Dead Center DI Direct Injection DISI Direct Injection Spark Ignition DMA Differential Mobility Analyzer DR Dilution Ratio DT Dilution Tunnel EC Elemental Carbon ECU Engine Control Unit EGR Exhaust Gas Recirculation EOI End Of Injection EPA Environmental Protection Agency ERC Engine Research Center FID Flame Ionization Detector GDI Gasoline Direct Injection H/C Hydrogen to Carbon Ratio HC Hydrocarbon ICOMIA International Council of Marine Industry Applications ICPMS Inductively Coupled Plasma Mass Spectrometry IDI In-Direct Injection IMEPN Net Indicated Mean Effective Pressure JDM Japanese Domestic Market (Production in Japan) LOC Lube Oil Consumption MDT Mini Dilution Tunnel MFI/MPI Multiport Fuel Injection N2 Nitrogen NDIR Non-Dispersive Infrared NOx Nitrogen Oxides O Atomic Oxygen O2 Oxygen
xiii
OC Organic Carbon OH Hydroxyl Radical PAH Polyaromatic Hydrocarbon PFI Port Fuel Injected PM Particulate Matter PM10 Particulate Matter < 10 µm PM2.5 Particulate Matter < 2.5 µm PMP Polymethylpentane PTFE Polytetrafluoroethylene PUF Polyurethane Foam R & P Rupprecht & Patashnick RFG Reformulated Gasoline SCRE Single Cylinder Research Engine SI Spark Ignition SMPS Scanning Mobility Particle Sizer SO4 Sulfate SOA Start Of Air SOF Soluble Organic Fraction SOI Start Of Injection SOL Solid carbon particles SON Start Of Nitrogen SOP Start Of Propane SR Sample Ratio SWRI Southwest Research Institute TC Total Carbon TDC Top Dead Center TFE Tetrafluoroethylene TEOM Tapered Element Oscillating Microbalance TPM Total Particulate Matter VOC Volatile Organic Compound WSEC Wisconsin Small Engine Consortium
1
1.0 Introduction
1.1 Motivation for Two-Stroke Direct Injection Research
Two-stroke engines provide a number of advantages over other power sources. These
benefits include high power density, high specific power, low weight, simple mechanical
design, low friction, small size, and fewer moving parts. Due to these inherit traits the two-
stroke engine has found use in applications such as marine outboard engines, motorcycles,
dirt bikes, snowmobiles, recreational vehicles, and other on- and off-road applications. The
traditional two-stroke also has its drawbacks, including poor fuel economy and high exhaust
emissions.
Two-stroke manufacturers have developed direct injection (DI) technology to
overcome these problems. Using DI systems the two-stroke engine can now achieve lower
fuel consumption and exhaust emissions. This new design has drawbacks as well, including
complexity, cost, and weight. Also, a new exhaust emission resulting from DI operation is
particulate matter (PM). The formation of PM from gasoline engines needs to be studied to
understand the fundamental processes that cause it, such that improvements in engine out
emissions can be made.
1.1.1 Emissions Regulation
Federal regulations from the Environmental Protection Agency (EPA) and California
Air Resources Board (CARB) are in place that restrict the amount of exhaust emissions from
outboard marine engines [1,2]. This includes reduction in emission species through 2006 and
2
beyond. This regulation has severely limited the use of traditional two-strokes and has made
production DI engines available from most manufacturers, including Mercury Marine,
Bombardier, and Yamaha. Direct Injection technology has allowed industry to meet these
emissions regulations. However, CARB has recently petitioned Southwest Research Institute
(SWRI) to conduct a study of the PM emissions from marine two-stroke engines, which will
likely lead to future regulations [3]. Research in this area will allow for current design
considerations to reduce emission levels before a standard is set.
1.1.2 Environmental Impact of Particulate Matter
Particulate matter reacts in the atmosphere long after emission and has an impact on
environmental conditions and human health. Particulate emissions also contribute to
atmospheric pollution including smog and reduced visibility [4]. Health concerns including
respiratory conditions such as asthma and lung cancer, as well as heart conditions like
cardiovascular and cardiopulmonary disease, have shown to develop from PM emissions
[4,5]. Research leading to the reduction in PM emissions will reduce further environmental
conditions and health risks.
1.2 Objectives
The objective of this project is to investigate particulate formation in a direct injection
gasoline engine. This includes quantifying the amount of PM emission from a two-stroke
outboard engine, determining formation mechanisms that lead to particulates, and identifying
areas for PM reduction. These mechanisms will be determined from various tests by
3
changing operating conditions and input parameters. Combustion performance, standard
exhaust emission products, as well as PM mass and size measurements will be used to
analyze test results.
Engine tests were performed on a two-stroke direct-injection single-cylinder research
engine (SCRE). An air-assisted fuel injector was used for all fuel injection tests to provide a
finely atomized spray. The injection system was also modified to provide nitrogen (N2)
assisted fuel injection and propane fuel injection. A variety of injection and ignition timings
were used to isolate formation mechanisms.
This thesis will start by reviewing the background information relevant to the scope
of this project, including two-stroke emissions, stratified combustion, and particulate
emissions measurements. Next, the lab test cell and all experimental equipment will be
covered in detail. The results of engine testing will then be presented. Subsequently, a
discussion of the results and description of particulate formation mechanisms will follow.
Finally, conclusions and recommendations for future work will be suggested.
4
2.0 Background Discussion
2.1 Traditional Two-Stroke Engines and Emissions
Two-stroke engines have many advantages over competitive engines. High power
density and specific power come from a power stroke for every crankshaft revolution. Since
piston ports are used to intake fresh air and exhaust combustion gases instead of valves there
is no need for a complicated valvetrain system. This leads to simple design, small overall
size, light weight, low mechanical friction, and less moving components. Since the intake
and exhaust processes must take place at the same time some of the fresh charge that enters
the cylinder can exit out the exhaust before combustion. This leads to high hydrocarbon
(HC) emissions and fuel consumption in premixed charge engines.
Table 2.1 compares the measured exhaust emissions and fuel consumption of two-
stroke and four-stroke outboard marine engines [6].
HC [g/kW-hr]
CO [g/kW-hr]
NOx [g/kW-hr]
BSFC [kg/kW-hr]
Two-Stroke (216 cc, 7.4 kW) 275.7 589 0.76 0.970 Four-Stroke (280 cc, 7.4 kW) 25.4 334 4.76 0.542
Table 2.1 � Comparison of two- and four-stroke emissions [6].
It can be seen that the HC emissions and brake specific fuel consumption (BSFC) of two-
stroke engines are much higher, the carbon monoxide (CO) is slightly higher, and the
nitrogen oxides (NOx) are much lower. The higher CO is likely due to incomplete
combustion resulting from the scavenging process. The lower NOx is likely due to lower
5
combustion temperatures from a dilute mixture due to internal EGR from the scavenging
process.
The HC emissions primarily result from fuel short-circuiting and poor combustion.
Fuel short-circuiting results from the fresh charge exiting out the exhaust before combustion
takes place. Anywhere from 20-40% of the total air-fuel mixture can escape this way during
the scavenging process [7]. The amount of short-circuiting was found to be highly dependent
on load and independent of speed. Poor combustion results from insufficient mixing and
inconsistent gas exchange. Figure 2.1 shows the HC emissions at constant speed from a
carbureted two-stroke engine [8]. Notice the dependence of HC emissions and fuel short-
circuiting on load. At medium to high load the fuel short-circuiting is high because the
scavenging is less efficient and more fresh charge is lost to the exhaust, and this is the
dominant process affecting HC emissions. At low load poor combustion is the primary cause
of HC emissions. This is due to low scavenging efficiency and low volumetric efficiency,
resulting in inconsistent and dilute air-fuel mixtures.
Figure 2.1 � Source of HC Emissions for a Carbureted Two-Stroke [8]
6
2.2 Direct Injection Two-Stroke Engines
Direct Injection allows the fuel to be injected directly into the cylinder, eliminating
short-circuiting during the scavenging event. Direct injection spark ignition (DISI) engines
have been studied for more than 70 years [9], and are now being produced for outboard
engines. This is due to the potential to dramatically reduce HC emissions and fuel
consumption. The fuel can be injected after the ports are closed at low load, hence low HC
emissions. Also, the fuel consumption can be reduced from stratified combustion and lower
pumping losses. There are, however, challenges to implementing DI into production engines.
The system must be relatively low cost and lightweight so as not to negate some of the
inherent advantages of a two-stroke engine. Table 2.2 shows some of the advantages and
disadvantages of DI two-stroke engines [10].
Advantages Disadvantages Lower HC emissions due to little short-circuited fuel
Difficult to control air and fuel mixing
Lower fuel consumption Higher cost and more complex fuel More precise air-fuel control Higher NOx emissions at high load Potential for more stable combustion at low loads
Complex fuel calibration for smooth transition from low to high load
More robust starting Greater chance for spark plug fouling Reduced CO2 emissions Lower pumping work for intake process
Table 2.2 � Advantages and disadvantages of DI [10].
7
2.3 Stratified Charge Combustion
Direct Injection engines operate in two distinct combustion modes: stratified for low
speed, light load conditions and homogeneous for high speed, high load. Stratified
combustion utilizes an overall lean equivalence ratio (Φ) with an ignitable mixture at the
spark plug. This ignitable mixture usually has an air-fuel mixture near stoichiometric. The
burning zone can also contain fuel rich areas. Rich combustion leads to particulate and CO
emissions since there is not enough oxidizer for all the fuel. At high speed and/or high load
conditions, when more fuel needs to be injected, the use of stratified combustion is limited.
As load is increased the greater amount of fuel that is injected creates a locally richer
mixture. Combustion products from these richer mixtures cannot oxidize readily and create
particulates. Therefore the fuel needs to be injected early and a homogeneous mixture
formed for high speed, high load conditions. The transition between stratified and
homogeneous combustion presents problems for engine control strategies. The engine can
experience unstable combustion and a fluctuating torque output. Particulates, CO, and HC
emissions can result from improper mixture preparation. Figure 2.2 shows an example of an
injection control map for a DI engine.
8
LeanStratified
Late Injection
StoichiometricHomogeneousEarly Injection
Transitionregime
Loa
d
Speed
LeanStratified
Late Injection
StoichiometricHomogeneousEarly Injection
Transitionregime
Loa
d
Speed
Figure 2.2 � Typical injection timing map for a DI engine.
2.4 Emission Formation Mechanisms
To control and reduce engine emissions it is necessary to understand how they are
formed. A study was performed to determine the formation mechanisms for CO, NOx, and
HC emissions [11,12]. These mechanisms include overmixing of fuel spray, poor
combustion quality, burning zone air-fuel ratio (A/F), large spray droplets, wall wetting, fuel
short-circuiting, injector sac volume, cylinder deposits/oil film, burn phase/rate, and prior
cycle interactions. Table 2.3 lists these mechanisms and the associated emissions affected.
Some of these mechanisms will directly help to explain particulate emissions. Most of them
will affect particulates in some way because of the importance of HC emissions on PM.
9
Emission Formation Mechanism Major Emission Species Overmixing of fuel spray HC, COPoor combustion quality HC, COBurning zone air-fuel ratio HC, CO, NOx Large droplets from spray HC, CO, Soot Piston wall wetting HC, COShort-circuiting of unburned fuel HCCrevice/injector sac volume HCCylinder deposits/oil film HCBurn phasing/burn rate NOxPrior cycle interactions HC, CO, NOx
Table 2.3 � Emission formation mechanisms for a DI two-stroke engine [11].
2.5 Particulate Matter
PM can be defined as any species present in the exhaust gas that can be trapped on a
filter [13]. Sometimes total particulate matter (TPM) is referred to when specific studies are
being conducted on the chemical composition of particulates. In discussion TPM is the same
as PM. Soot is the term used to represent the solid carbon particles (SOL) that are black in
color. From these definitions it can be understood that soot and PM are not exactly the same
thing. PM includes many other species that can buildup on solid particles and be trapped on
filters. Figure 2.3 shows a diagram that illustrates the composition of PM and these species.
These include HC species, sulfates (SO4), soluble organic fraction (SOF), volatile organic
compounds (VOC), other condensed vapor phase compounds, and even trace metal
compounds from the fuel or lubricating oil. SOF comes from the organic compounds that
dissolve when the filter is placed in a solvent [14]. VOC include species that react in the
presence of an oxidizer and form gaseous products, thus coming off the filter [14].
Elemental carbon (EC) represents extended carbon ring particles that are opaque. Soot is EC.
10
Organic carbon (OC) represents most other carbon compounds that contain other elements.
TPM consists of various mixtures of EC, OC, SOF, SO4, and other condensed species.
Figure 2.3 � Diagram Showing Composition of PM [15]
PM is classified into three modes based on particle size: coarse, accumulation, and
nuclei modes. Figure 2.4 shows a typical particle size distribution indicating the different
modes [5]. The coarse mode consists of particles greater than about 2.5 µm in diameter
[5,16]. Coarse mode particles are usually mechanically generated or consist of coupled
smaller particles. PM10 refers to any particulate matter less than 10 µm and includes the
coarse mode. The accumulation mode, or sometimes referred to as fine mode, consists of
particles between 0.1 µm and 2.5 µm [5,16]. Accumulation mode particles are created from
the growth of nuclei mode particles. PM2.5 refers to any particulate matter less than 2.5 µm
and includes the accumulation mode. The nuclei mode, or sometimes referred to as ultrafine
mode, consists of particles smaller than 0.1 µm [5,16]. Nuclei mode particles result from
11
new particle formation. Ultrafine and nanoparticles usually refer to particles less than 100
nm and 50 nm, respectively.
1E-3 0.01 0.1 1 10 100
0
2
4
6
Volu
me
Wei
gted
Dis
tribu
tion
Particle Diameter [microns]
Nuclei Mode
Accumulation Mode
Coarse Mode
1E-3 0.01 0.1 1 10 100
0
2
4
6
Volu
me
Wei
gted
Dis
tribu
tion
Particle Diameter [microns]1E-3 0.01 0.1 1 10 100
0
2
4
6
Volu
me
Wei
gted
Dis
tribu
tion
Particle Diameter [microns]
Nuclei Mode
Accumulation Mode
Coarse Mode
Figure 2.4 � Volume Weighted Particle Distribution Showing the Three Modes
2.5.1 Particle Matter Formation
Particulates are formed in locally rich areas of combustion. In rich combustion zones
the ratio of carbon to oxygen atoms is high. The carbon atoms combine to form rings that
build up into particles. Particle oxidation is low since the local concentration of oxygen is
low. The engine out particulate mass is a balance between formation and oxidation. The
theoretical local Φ at which particle formation begins is near three [9]. The experimental
value at which formation begins is closer to 1.5 [9].
A study was done to measure the total carbon (TC) and total PM2.5 from a DISI four-
stroke engine [17]. Total carbon and PM2.5 were measured over a number of different
12
transient vehicle cycles. For all of the test cycles the PM2.5 mass was much larger than the
TC mass, indicating that the PM from the DISI engine includes other species like soluble
species, condensed species, sulfates, and trace metals.
In another study performed on transient vehicle cycles equipped with four-stroke
engines [18]. Indolene and reformulated gasoline (RFG) fuels with different compositions
were tested. The PM results were found to depend strongly on the fuel used. Indolene, with
much higher sulfur content than RFG, produced much higher particulate mass. This study
highlights the importance of composition and sulfates on DISI particulate mass. This study
also showed that condensed hydrocarbon species contribute to the particulate mass [18]. The
results illustrate the importance of hydrocarbon emissions on PM.
Maricq et al. investigated the PM from an air-assisted DISI four-stroke engine [19].
The injection timing and spark were varied under lean conditions on a DISI engine. Figure
2.5 shows the PM as a function of injection timing for the air-assisted injector and a fuel only
injector from an earlier study [19]. The injection timing represents start of air (SOA) for the
air-assisted case and end of injection (EOI) for the fuel only case. These plots show a unique
local minimum for PM at a retarded injection timing. Both injectors show this, however, the
minimum is more pronounced and lower for the air-assist injector. A similar result for the air
injector was seen for a higher speed and load case, with the minimum at a more advanced
injection [19]. The increase in PM for retarded injection timings is likely due to locally rich
burning zones from decreased mixing time. The increase for advanced conditions is more
unusual but may be due to incomplete combustion due to overmixing and may correlate with
coefficient of variation (COV) of net indicated mean effective pressure (IMEPN). Another
factor may be the dependence on oxygen in the formation of certain aromatic species [20].
13
Advanced injection timings allow for leaner mixtures which could promote the formation of
certain aromatic species that could lead to the formation of particulates. The HC emissions
show a similar trend as PM, exhibiting a minimum at a retarded injection timing close, but
not equal to, the timing for the PM minimum [20]. The increase in HC for advanced
conditions could also contribute to the increase in PM.
Figure 2.5 � Dependence of PM on Injection Timing [19]
14
2.5.1.1 Pool Fires
One possible source of PM from DISI engines are pool fires from fuel films on the
piston and other surfaces [21]. The liquid fuel films burn very rich and can create significant
particulate matter as witnessed by the luminous flame.. A study was done to examine the
relation of fuel films on PM for a wall-guided DISI four-stroke engine [21]. The film
thickness was measured in an optical engine using a refractive index matching technique.
Figure 2.6 shows the smoke emissions against fuel film mass from this study. The solid
circles were from a swirl injector and the open squares were from a multihole injector. The
graph shows a good correlation between smoke emissions and fuel film mass. Results from
this study also show that only thicker fuel films significantly affect PM. This can be seen in
the offset of the correlation in Figure 2.6.
Figure 2.6 � Effect of Fuel Film Mass on Smoke Emissions [21].
15
Kaiser et al. examined emissions from a DISI four-stroke engine, utilizing an air-
assisted injector and spray-guided combustion system [20]. One of the observations from
this study was that very little fuel impacts and remains on the piston or other surfaces. This
is contrary to the wall-guided system discussed above. In part, this is due to the spray-guided
system, which inherently has less fuel spray impingement, and may also be due to the fuel
only injectors used in the wall-guided system [20]. Fuel only injectors usually have a much
higher penetration and faster velocities [22]. The above conclusions suggest that engine and
injector design can play a major role on fuel films, pool fires, and subsequent PM emissions.
The study on fuel films by Drake et al. also suggest that their correlation between PM and
fuel film thickness may not be applicable to other engine and injector designs [21].
2.5.1.2 Lube Oil Consumption
The combustion of lubricating oils is a source of PM. The combustion of the
lubricating oil is directly related to the lube oil consumption (LOC). It is important to
understand LOC not only because it directly contributes to PM, but also to be able to separate
it from the combustion effects for analysis. Therefore the LOC consumption for spark
ignition (SI) engines is an important factor when studying particulates.
A good relative oil consumption benchmark of 0.20 % has been adopted by SWRI
[23]. Relative oil consumption represents the percentage of oil consumed to the total fuel
flow, thus 0.2 % is equivalent to one part oil for every 500 parts fuel (1:500). Figure 2.7
shows the results of the LOC for various speeds and loads of a broken in 3.8 L SI engine
[23]. The oil consumption is higher at light loads and high speeds, and also is below the 0.20
% benchmark for all conditions. Another study performed at SWRI on a 4-cylinder 2 L SI
16
engine showed the same trends with high LOC at light loads and high speeds [24]. However,
the relative LOC was as high as 0.40 %. This corresponds to one part oil for every 250 parts
fuel.
Figure 2.7 � Relative Oil Consumption for a SI Engine [23]
Umate et al. determined LOC for various piston ring designs [25]. No relative oil
consumption data was given, but the actual consumption data was given for all ring designs.
The LOC ranged from 4.6 to 15.8 gm/hr. If the lowest value corresponds to a low relative
consumption of 0.1 % then the highest value can reach near 0.3 % (1:333). This is a wide
range based on ring design for the same engine and running condition. Therefore, similar
engines can have very different LOC rates.
17
2.5.2 Particulate Kinetics
Chemical processes are important in the formation and growth of particulates. The
chemical processes of interest are particle inception, surface growth, coagulation, and
oxidation.
2.5.2.1 Inception
Inception refers to the intitial formation of solid particulate. This can occur from
nucleation or dehydrogenation of carbon compounds or soot precursers [26]. The precursors
to soot are polyaromatic hydrocarbons (PAHs) [26]. PAHs are carbon compounds that form
bonded carbon rings. Figure 2.8 shows a single ring PAH, Benzene (C6H6 or A1), and a
multiple ring PAH, Benzo[a]pyrene (C30H18 or A5) [27]. The formation of the first aromatic
ring is still not well understood. Many computational studies have been done to determine
the formation of the first ring [28,29,30]. These studies are determining the important
species and reactions that lead to the first ring and PAH formation. They show that a number
of different paths involving smaller HC species lead to ring formation and PAHs. Buildup
beyond the first carbon ring is better understood. It has been shown that acetylene (C2H2) is
the major species leading to multiple ring formations [26,28,29].
18
H
H
CC
C
C
C
C
H
H
H
H
=H
H
CC
C
C
C
C
H
H
H
H
H
H
CC
C
C
C
C
H
H
H
H
=
Figure 2.8 � Single Ring PAH (Benzene) and Multiple Ring PAH (Benzo[a]pyrene) with
Bonds [kinetics project]
2.5.2.2 Surface Growth
Surface growth is a chemical process and refers to the addition of species to already
formed soot particles. Surface growth is responsible for about 90% of the soot mass, while
inception accounts for the remaining 10% [26]. Acetylene is responsible for most of the
growth since it is present in larger quantities than PAH [26]. Carbon rings and soot particles
can grow by a process known as hydrogen abstraction acetylene addition [27,28]. First, a
hydrogen atom is abstracted from the carbon ring or particle. Subsequently, an acetylene
molecule takes the place of the hydrogen and bonds with the carbon. This process repeats,
forming more rings and larger particles. This process is illustrated in Figure 2.9. Growth in
this manner should be proportional to surface area. This is true at low temperatures. At high
temperatures it is proposed that growth is proportional to the surface area of active sites [31].
During buildup these active sites can be regenerated. This has been proposed to explain
observed experimental behavior.
19
Acetylene
addition
CC
H
CC
H
CC
H
C C H
C6H5, Phenyl, A1- A1C2H, Phenylacetylene A1C2H-
A1(C2H)2, 1,2 diethynylbenzene A2, Naphthelene
H-abstraction Acetylene
addition
H-abstraction
Ring formationAcetylene
addition
CC
H
CC
H
CC
H
CC
H
CC
H
CC
H
C C H
CC
H
C C H
C6H5, Phenyl, A1- A1C2H, Phenylacetylene A1C2H-
A1(C2H)2, 1,2 diethynylbenzene A2, Naphthelene
H-abstraction Acetylene
addition
H-abstraction
Ring formation
Figure 2.9 � Multiple Ring Buildup By Hydrogen Abstraction Acetylene Addition Method
[27,28]
2.5.2.3 Coagulation
Coagulation is the chemical or physical processes by which smaller particles interact
and form larger particles. Nuclei particles can coagulate to form accumulation mode
particles. This process occurs simultaneous to surface growth. Larger particles can also
coagulate to form coarse mode particles. The process of these larger particles physically
combining forms agglomerates. Agglomerates can be any shape and often do not form
spherical particles. The coagulation process results in a decrease in particle number while
the volume or mass remains constant.
20
2.5.2.4 Oxidation
Oxidation is a chemical process by which the particles react with an oxidizer to form
gaseous phase products. The main oxidizer for particulates is the hydroxyl (OH) radical.
Other species that play a role are atomic oxygen (O) and diatomic oxygen (O2), [28,29,30].
Oxidation is a very important process in the formation of engine out particulate emissions.
PM emissions result from the relative levels of formation, growth, and oxidation. Many
more particles are formed during combustion than are emitted out the exhaust. Most of the
particles are oxidized in the cylinder or exhaust pipe [26].
2.5.3 Particulate Dynamics
There are also a number of dynamical processes that affect particulates. Most of
these affect the measurement of PM, but some also affect the formation process. These
processes include adsorption/desorption, condensation/evaporation, agglomeration,
thermophoresis, diffusion, inertial impact, electrostatic and gravitational deposition. These
effects have been investigated in several studies [32,33].
2.5.3.1 Adsorption/Desorption
Adsorption is the adherence of species onto the particulates. Vapor-phase molecules
present in the exhaust can stick to the particles, thus contributing to the overall particle
formation and growth. The saturation ratio is the ratio of the partial pressure of the species to
the saturation pressure for the same species [14]. Adsorption takes place below the
saturation pressure [14]. Desorption is the opposite process of adsorption.
21
2.5.3.2 Condensation/Evaporation
Condensation is the transformation of gaseous species to liquid or solid form upon
interaction with condensation nuclei, i.e. particle. This takes place above the saturation
pressure for a species [14]. This process can continue until the saturation ratio drops below
saturation. At this point evaporation, the opposite of condensation, can take place.
2.5.3.3 Thermophoresis
Thermophoresis is a phenomenon where motion of species or particles occurs as a
result of a temperature gradient. It is important for particles because it results in motion
towards cool surfaces. The particles tend to see more collision from a higher temperature
zone thus experiencing a bulk motion towards a cooler region, i.e. walls. Once at cool walls
the particles tend to stick, thus affecting the amount of PM in the measurement stream. This
is a large effect in small tubes where the surface area is large relative to the flow area. To
keep thermophoretic deposition to a minimum the walls of all particulate sampling devices
should be heated and/or insulated.
2.5.3.4 Diffusion
Diffusion, or Brownian motion, is the random motion of particles due to a
concentration gradient. This random motion causes particle deposition along walls of tubes.
Smaller particles can diffuse quicker and therefore diffusional deposition is most important
for the very small particles. It is also more important for small diameter tubes as well. Since
it is difficult to control diffusional deposition, short sampling tubes are recommended.
22
2.5.3.5 Inertial Impact
Inertial impact can take place when particles cannot follow the bulk gas flow. When
the particles deviate from the bulk flow they can be deposited on sampling tube walls. Since
inertial deposition is also difficult to control, sampling lines should avoid sharp corners and
maintain isokinetic sampling.
2.5.3.6 Electrostatic Deposition
Electrostatic deposition takes place when charged particles are in a path with
electrically chargeable walls, like magnetic materials or plastics that can hold a static charge.
Particulates have a natural residual charge from the combustions process. To prevent
electrostatic deposition sampling lines should use electrostatically neutral materials.
2.5.3.7 Gravitational Deposition
Gravitational deposition occurs when particles drop out of the bulk flow since they
are heavier than the gas. It depends on the time the particles spend in any part of a sampling
system. This is a very small effect for particulates because of their very small size and mass.
2.6 Particulate Measurement
Currently there is no regulation or standard sampling procedure of PM for any
gasoline engine, marine application or otherwise. There are regulations and sampling
procedures for measuring diesel particulate emissions that involve the use of a dilution tunnel
(DT) and filter methods [34]. If future gasoline requirements involve PM sampling it is a
23
good assumption that some sort of dilution system and filter method will be adopted. The
dilution tunnel and filter methods for particulate sampling will be discussed, along with other
PM measurement methods.
2.6.1 Dilution Tunnel
A dilution tunnel is used in any system to measure particulate emissions. It dilutes
the engine exhaust with ambient air before instruments are used to sample PM. The purpose
of this is twofold; 1) to reduce the concentration of PM in the sample stream so as not to clog
or overwhelm the particulate analyzers and 2) to simulate the reactions the particulates
undergo after being emitted into the atmosphere. Most methods to sample PM would not
function at all or be very accurate at the concentration levels that are present in engine
exhaust. This is a bigger factor for diesel engines, but the level of PM in gasoline engines is
still too high. Since particulates react with species in the atmosphere it is necessary to take
this behavior into account when sampling. This is why ambient air is used in the dilution
process.
After the dilution process the particulate concentration is different than that which the
engine emitted. To determine the engine particulate level the amount of dilution must be
measured. This is accomplished by measuring the ratio of total flow through the DT to the
engine exhaust flow sampled. This ratio is defined as the dilution ratio (DR) and can be seen
in Equation 2.1. To measure the DR one of the exhaust emission species is used as a tracer,
usually carbon dioxide (CO2) or NOx. The mole percent of the exhaust species is measured
in the engine and after dilution, and then these are used to determine the DR. The detailed
calculation of the DR for the dilution tunnel used in this research can be seen in Appendix A.
24
sampledflowExhaust
DTtheinflowTotalDR ≡ (2.1)
The effect of the dilution tunnel on the particulate emissions is an important concern.
The DT as a measurement device should not affect the PM emissions from the engine in any
way beyond the simulated reaction with ambient air. Several things potentially affect the
amount of particulates, including DR, residence time, and temperature. DR affects the
relative level of species and particulates in the tunnel, which can change the particle
dynamics discussed previously. Residence time is the length of time the particulates spend
inside the tunnel before they are sampled. Temperature affects the level of condensation and
evaporation. These effects will be discussed in more detail with specific relation to the type
of tunnel used for this research.
Two types of dilution tunnels are normally used for particulate sampling, full-flow
and partial-flow. These two types will be discussed and their uses, similarities, and
differences analyzed.
2.6.1.1 Full-Flow Dilution Tunnel
A full-flow dilution tunnel uses fresh air to dilute all of the exhaust gas in a constant
volume sampling (CVS) method. In a full-flow tunnel the sample lines to the test
instruments sample a portion of the gas mixture in the dilution tunnel. Full-flow CVS
tunnels are the accepted method for sampling particulate emissions from diesel engines.
There is a standard testing set-up and procedure for full-flow CVS tunnels, so the results
from different systems should be very comparable [34]. Since they utilize all of the exhaust
25
gas the DR calculation and the final calculation to get engine out PM is relatively easy. CVS
tunnels are used for steady-state and transient testing.
Since the total exhaust flow must be diluted, this tunnel requires a very large source
of fresh air. The DR for a full-flow tunnel can be between 20 and 50 or even higher. This
means the source of fresh air needed is much more than the exhaust flow rate. Also, a full-
flow tunnel is very large and expensive to integrate into a lab.
2.6.1.2 Partial-Flow Dilution Tunnel
The major difference between a partial-flow and full-flow tunnel is that the partial
flow tunnel only samples a portion of the engine exhaust. Partial flow tunnels are also called
mini dilution tunnels (MDT). In a partial-flow tunnel the sample lines to the instruments
may sample all of the mixed gas in the tunnel or only a portion [32]. There are also a variety
of methods to sample the exhaust gas. A series of multiple tubes could be placed in the
exhaust where only one of these is used as the sample to the DT [35,36]. An ejector system
with pressurized driving air can be used to pull some of the exhaust through a tube into the
tunnel [37]. A venture nozzle can be used to create a pressure differential that allows exhaust
flow into the tunnel [38,39].
Partial-flow tunnels have some advantages over a full tunnel. Since not all of the
engines exhaust needs to be diluted the fresh air flow rate only has to be on the order of the
exhaust flow rate rather than many times more. This allows a MDT to be much smaller and
cheaper than a full tunnel. Mini tunnels usually use a lower DR than a full tunnel, which
further reduces the dilution air flow requirement. Mini tunnels are used for steady-state
testing and even have been used in transient sampling [32,35].
26
Mini tunnels also have some drawbacks. They are not an accepted method of testing
for certification or regulation. Since only a portion of the exhaust gas enters the tunnel, the
DR and final PM calculation are more difficult than for a full tunnel. The design of the
system to sample the engine exhaust is complex with many parameters that must be chosen.
Another potential drawback is the correlation of the results from a mini tunnel to
those of a full tunnel. To validate the use of a mini-tunnel the measurements should agree
with those from a full tunnel. Studies have been done to examine the particulate
measurements obtained from mini and full tunnels [35,40]. Results show that a very good
correlation can be achieved with mini tunnels [35,40]. Figure 2.10 shows the correlation of
various emission species sampled under steady-state testing with a mini and full tunnel from
one of these studies [35]. This study used a multi-tube-type mini tunnel over a wide range of
dilution conditions. The graphs show an excellent correlation between measured exhaust
emissions of CO, HC, Particulate, and NOx. The correlation is slightly worse, however still
very good, for species dependent on chemical composition, SOF and Sulfate. The correlation
for the gaseous emission of NOx is very important as well since it is used as the tracer to
determine DR. Similar correlation results were obtained in another study using a multi-tube
mini DT [40].
27
Figure 2.10 � Correlation of Results for a Mini and Full Tunnel [35]
Another concern with any DT is the effect that it has on the particulates. The
parameters of the DT that can affect the particulates include DR, residence time, and
temperature. The DR must be chosen so that consistent and accurate results are measured.
Figure 2.11 shows how DR affects particulate concentration for a venturi type mini tunnel
[39]. It can be seen that at dilution ratios less than around 10 the particulate measurement is
not very consistent. Above this level and the results are very consistent and independent of
the DR for a test. This is where tests need to be run in case the DR varies slightly over the
course of a test run. Another study using a mini tunnel shows similar results [38].
28
Figure 2.11 � Effect of DR (x-axis) on PM (y-axis) for a Venturi Type MDT [39]
Figure 2.12 shows the accuracy of the exhaust sample flow in a mini tunnel for
various dilution ratios [32]. The exhaust sample flow is very accurate for a DR of 30 or less.
Above this point the deviation of the actual exhaust sample flow to the controlled value starts
to increase. If the exhaust sample flow deviation is high then the control of the DR is less
accurate. Therefore, the tunnel should operate at a DR of 30 or less to maintain accurate
control of the DR.
29
Figure 2.12 - Deviation of Exhaust Sample Flow From Controlled Value [32]
The residence time is the amount of time the particulates have to react in the tunnel.
For a MDT this is just the travel time in the tunnel. This travel time is also the time for
mixing in the tunnel. It is critical to ensure complete mixing in the tunnel, especially when
only a portion of the diluted mixture is sampled. Figure 2.13 shows the DT mixing for a
multi-tube mini tunnel [35]. The deviation of particulate and NOx emissions inside the
tunnel are shown at different lengths, with and without an orifice. Without an orifice
complete mixing requires a tunnel length of 10 diameters. With an orifice to aid mixing,
only 5 diameters are required. A venture nozzle or other mixing aid can achieve similar
results as an orifice.
30
Figure 2.13 � NOx and Particulate Mixing in Mini Dilution Tunnel [35]
Temperature of the diluted mixture at the sampling point also affects the particulates.
The cooler the sample temperature the more vapor compounds that may be condensed onto
existing particulates or that may get trapped on a filter. Figure 2.14 shows the sample gas
temperature affect on particulates for a multi-tube-type mini tunnel [35]. The overall trend of
more particulates at cooler temperatures can be seen. Also, the effect of temperature is
greater (larger slope) for a light load (dotted line) diesel test point. This is due to the larger
percentage of SOF, VOC, and other organic compounds that are greatly affected by
condensation. Figure 2.15 shows the temperature effect for the soluble and insoluble portion
of PM emitted from a small diesel engine [38]. It can be seen that the temperature only
affects the soluble portion of PM. The temperature does not affect the insoluble portion
because it contains the solid phase particles that due not evaporate into the gas phase.
31
Figure 2.14 � Effect of Sampling Temperature on Particulate Mass [35]
Figure 2.15 - Effect of Sampling Temperature on SOF [38]
2.6.2 Gravimetric Methods
Gravimetric methods are those that measure the mass of PM to determine the
emission rate and total emission. This includes any method that uses filters to trap
particulates. Most of these test methods require particulates to be trapped on a filter for some
32
length of time and then later analyzed. There is at least one method that measures particulate
mass on the filter during a test.
The advantages of gravimetric methods are accuracy and versatility. Because filter
methods are directly measuring the particulate mass they are extremely accurate. Filter
methods are the only methods accepted for regulation and certification testing. The filters
can also be used for a very wide range of tests to determine other information beyond just
mass. The disadvantages are ease of use and test methodology. The filters usually require a
longer test period and the analysis is carried out after the mass is collected. Also, it is very
important to take filter samples and analyze them under controlled circumstances to ensure
accuracy and repeatability.
2.6.2.1 Particulate Filters
Particulate filters are any material placed in the sample stream for the purpose of
trapping PM. The types of filter used in engine testing include various forms of Teflon,
quartz, borosilicate glass, and polyurethane foam (PUF). Information on the filter types can
be seen in Table 2.4 as compiled from some reference sources [41]. These filters are placed
in the sample stream with a controlled flow rate. After the test is run the filters can be
analyzed and the mass emitted from the engine can be calculated.
33
Filter Teflo Fiberfilm Emfab TissuquartzMedia PTFE
with PMP Borosilicate glass fiber coated w/ TFE
Borosilicate microfibers w/ woven glass and bonded w/ PTFE
Pure quartz
Retention rate 99.99 % 96.4 % 99.99 % 99.99 % Max Temperature 200ºC 315.5ºC 260ºC 1093ºC
Table 2.4 � Filter Types for Engine Testing [41]
Analysis of filter samples includes a variety of tests to determine mass as well as
other physical and chemical information. Some of the results of analysis, test methods used,
and filter types used were compiled from some reference sources and shown in Table 2.5
[14,42,43].
Result Test Name Filter Type Mass Gravemetric analysis Teflon
EC/OC Thermal evolution and combustion analysis Quartz
SOF Soxhlet extraction Borosilicate glass microfiber
Trace metals ICPMS, X-ray fluorescence Teflon
Ionic species Ion chromatography, atomic absorption spectroscopy, colorimetry
Teflon
Organic compounds Gas chromatography/mass spectrometry Quartz, PUF
Table 2.5 � Filter Analysis Techniques [14,42,43]
2.6.2.2 Tapered Element Oscillating Microbalance
A tapered element oscillating microbalance (TEOM) is a real-time instrument that
measures particulate mass during a test while utilizing a filter. The TEOM uses a Pallflex®
Fiberfilm� (T60A20) or Emfab� (TX40) filter, the same types used for mass
34
measurements in EPA tests. This allows the TEOM to maintain the accuracy of a
gravimetric method while allowing the operator to monitor the mass in real-time. Figure
2.16 is a schematic representing the operation of a TEOM monitor. The filter is placed on
the end of a tapered element. The sample flow passes through the filter, then through the
element and out of the instrument. The element oscillates at its natural frequency, usually
between 180-320 Hz [44]. As mass is deposited onto the filter the natural frequency of
vibration decreases. The TEOM measures the oscillation frequency in real-time, as often as
0.21 seconds, and converts this to a mass according to a calibration constant [44]. The
calculation the TEOM software does is shown in Equation 2.2 [44].
Filter
Tapered Element
Exhaust gas inFlow exit
Filter
Tapered Element
Exhaust gas inFlow exit
Figure 2.16 � Schematic Showing the Operation of a TEOM Monitor
−= 2
02
10
11FF
KM (2.2)
where m is the mass, F1 is the current frequency, F0 is the initial frequency, and K0 is the
calibration constant.
One important test for a TEOM is the comparison of its results to filter sampling.
One study compared between a TEOM and filters at various flow velocities, temperatures,
35
and pressure drops across the filters [44]. This study showed a good and consistent
correlation between TEOM measurements and filter results for a number of sampling
conditions. Comparisons were also performed for transient conditions on a diesel engine
[45]. The results show that the TEOM gave a particulate mass that was about 10 percent
lower than filter weighing over all sample conditions. Since the TEOM results were
consistently lower they can still be used to analyze relative conditions.
2.6.3 Optical Methods
Optical methods are those that determine particulate mass or number distribution
through a correlation with an optical parameter. Some of these methods include a scanning
mobility particle sizer (SMPS), laser induced incandesance (LII), nepholemeter,
aethalometer, smoke meter, and photoacoustic instrument [17,46,47]. A nephelometer
measures the light scattered by the particulates. An aethalometer and smoke meter both
measure light extinction/absorption by PM. The photoacoustic instrument measures the
pressure wave given off by particles upon heating by a laser light source. Laser induced
incandesance measures the incandesance of soot particles when heated by a laser source.
The advantage of optical methods includes faster sampling times and quicker
response. The optical parameters can usually be measured in seconds, thus allowing the
instrument to give real-time particulate concentration. This eliminates the need to allow
particulate mass to deposit on a filter and the need for lengthy a posteriori analysis. The
response is also quicker due the speed with which the parameters can be measured.
The disadvantages of optical methods include expensive equipment and the
requirement for a correlation to get PM mass. The correlation to relate to PM mass may
36
depend on a lot of other variables in the system like the particulate concentration or other
species present in the sample [17,47]. The accuracy of any optical instrument is, therefore,
dependent on the accuracy of the correlation.
2.6.3.1 Scanning Mobility Particle Sizer
A SMPS is used to measure the particle number distribution over a specific particle
diameter range. It consists of a differential mobility analyzer (DMA) and a condensation
particle counter (CPC). The DMA separates the sample flow into single size particles so the
CPC can count them.
The DMA works on the principle of electrical mobility [46]. The schematic of its
operation is shown in Figure 2.17 [48]. The sample flow (polydisperse aerosol) first passes
through a neutralizer to bring the particles to an equilibrium charge distribution. The flow
then passes into a cylindrical section where it is joined with the sheath flow. The sheath flow
is generally much greater than the sample flow. This cylindrical section contains a high
voltage rod at its center. When the rod is given a voltage it tends to attract the charged
particles. The smaller a particle is for a given charge the faster it is attracted to the central
rod. The size that affects this is referred to as the mobility diameter. The mobility diameter
depends on the aerodynamic diameter and electrical charge [46]. For a given rod voltage
only one size, based on the mobility diameter, can enter the sample flow exit (monodisperse
aerosol) at the bottom center of the cylindrical section. The rest of the flow exits through the
bypass. The sample flow exit can now be supplied to a CPC for a particle count. By
changing the voltage applied to the central rod (scanning), different size particles can enter
the sample flow exit. The voltage range controls the size range of particles that can be
37
measured. The scan can be done fast, in as little as 30 seconds, but is usually done over 2
minutes to increase accuracy [16].
The CPC counts the number of particles by use of light scattering. The sample flow
exit from the DMA enters the CPC. The flow passes through a chamber with an alcohol
present. The alcohol condenses onto the particles causing them to grow in size. Most
particles normally grow to a uniform size, around 5-10 µm [16]. A light source is then
passed through the sample flow and measured with a photodetector. The CPC counts single
particles as they pass through the viewing area. The detection efficiency of the CPC is 50
percent for 10 nm particles [48]. To account for multiple particles in the view path the CPC
uses a correlation. This correlation is very accurate below concentrations of around 10,000
particles/cm3. Above this the correlation becomes worse and the accuracy decreases with
concentration. Software records the size of particle sampled and the number count to create
the particle number distribution.
38
Figure 2.17 - Schematic of DMA Operation [48]
39
3.0 Experimental Equipment
The Wisconsin Small Engine Consortium (WSEC) small engine test cell was used for
this project. The test cell has been used for a wide range of research projects and thus was
not designed to specialize in any particular area of engine testing.
The experimental equipment will be discussed according to the various purposes for
which they serve. The lab consists of the following components: engine, dynamometer,
engine control unit, fuel delivery system, air delivery system, injection systems, ignition
system, cooling, and exhaust. The data acquisition equipment consists of the following:
cylinder pressure, emissions measurement, dilution tunnel, and particulate measurement. A
diagram of the entire test cell can be found in prior publications [11].
3.1 Engine
The engine used for this project was a single-cylinder, loop-scavenged, direct-
injected, two-stroke engine from Mercury Marine Corporation. The geometry for this engine
was based on Mercury�s 2.4 liter V-6 Optimax outboard engine. The SCRE is one cylinder
of the Optimax with a displacement of 389 cm3. The engine is water-cooled. The rated
power is 20 kW at a rated speed of 5000 RPM. Table 3.1 lists the complete specifications for
the engine.
40
Bore 85.8 mm Stroke 67.3 mm
Displacement 389 cc Connecting rod length 139.7 mm
Combustion chamber volume 32.3 cc Geometric compressions ratio 11.2
Actual compression ratio 7.4 Exhaust port timing 95û ATDC
Intake transfer port timing 117û ATDC Intake boost port timing 117û ATDC
Crankcase volume 959 cc Swept volume from TDC to port opening 241 cc Geometric crankcase compressions ratio 1.4
Actual crankcase compression ratio 1.25 Table 3.1 � Test Engine Specs
The engine has a two-piece block; the lower part holds the main bearings and
crankshaft while the upper holds the cylinder liner and ports. The crankshaft main and rod
journals have needle roller bearings. The connecting rod also has roller bearings at the wrist
pin. The engine has two intake transfer ports, one intake boost port, and one exhaust port.
The boost port is located opposite the exhaust port. The two transfer ports are located 90
degrees from the boost port on either side. The upper block has removable pieces for the
transfer and boost ports. This allows changes to the intake port geometry. The layout of the
ports in the cylinder can be seen in Figure 3.1.
The cylinder head is custom made. It is aluminum with access provided for two spark
plugs, one injector (fuel or air), and one pressure transducer. The chamber was a bowl offset
towards the intake boost port side. The injector hole is mounted in the center of the bowl
pointed axially downward in the cylinder. The spark plug hole used during testing was at a
45º angle to the cylinder centerline on the exhaust port side of the injector. The other spark
plug hole, which was plugged for all tests, was at the same angle on the boost port side. The
41
pressure transducer was placed on the flat, squish portion of the chamber on the exhaust port
side. The layout of the cylinder head can be seen in Figure 3.1 also. The spark plug used for
testing was a Champion RC10ECC, which had an insulator projection of 7.2 mm, an
electrode projection of 12 mm, and a gap of 1.14 mm (.045�).
Figure 3.1 - Diagram Showing Spark Plug, Ports, Injector, & Transducer
42
Reed valves controlled airflow to the crankcase. The reed valves allow air to enter
the crankcase while the piston moves upward and prevent air from leaving while the piston
moves down. This allows the intake air in the crankcase to be compressed before being
transferred to the cylinder. The compressed intake air is then transferred to the cylinder by
the transfer and boost ports when they are open to the combustion chamber.
The engine is lubricating by a lost oil system. The oil enters the intake air stream just
downstream of the reed valves. The oil flow is controlled by an external pump, which
allowed independent control of oil flow and the oil-to-fuel ratio. The normal operation for
this engine was 1 part oil to 100 parts fuel (1:100). The oil used during all testing was
Mercury Premium Plus 2-cycle outboard oil. It meets or exceeds the TC-W3 2-cycle oil
standard.
3.2 Dynamometer
An eddy current dynamometer manufactured by Froude was used to absorb and
measure the load produced by the engine. The dynamometer is rated for 74.6 kW (100 hp) at
4700 RPM. The dynamometer could only be used to absorb the power of the engine, and not
to motor the engine. A Dialog dynamometer controller was used to control the operation of
the dynamometer to maintain the engine at a constant, set speed. The dyno was calibrated by
placing a known weight on a fixed torque-arm.
43
3.3 Engine Control
Engine events and parameters were controlled by a MotoTron control system. This
consisted of a Motorola MPC555 microcontroller engine control unit (ECU) and the
MotoTune software interface. The software allowed full control over fuel and air injection
timings, spark timings, amount of fuel delivered, throttle position, and more. The fuel
delivered and throttle position were normally controlled together. The throttle was an
electronic unit controlled by the ECU. A demand potentiometer was used as the input. The
higher the demand setting the more fuel the engine would receive. The ECU also controlled
the A/F; so along with the fuel delivered, the throttle position was controlled accordingly.
3.4 Fuel Delivery System
The fuel delivery system was designed to provide both high and low pressure fuel.
Only the low pressure system was needed for this project. The schematic of the complete
system can be found in prior publications [11]. For the low pressure system the fuel is pulled
from a tank using a lift pump. The fuel is then filtered and the flow was measured using a
Micro Motion D06 Coriolis mass flow meter. The mass flow meter was calibrated by
measuring the volume of fuel that passed through the meter in a set amount of time. After
this a second pump, capable of 790 kPa, supplied the fuel to the rail and injector. The excess
fuel from the rail passed through a fuel cooler before returning to the upstream side of the
second pump.
The fuels used in this project were Amoco Indolene and Haltermann EEE. Both of
these are standard composition gasoline test fuels. The properties of these two fuels can be
44
seen in Tables 3.2 and 3.3. The supply of Indolene was halted shortly after the start of
testing. All tests used EEE fuel unless otherwise mentioned.
Octane number (RON+MON)/2 92.4Octane sensitivity (RON-MON) 9.8H/C ratio 1.845Stoich A/F 14.5Specific Gravity .743Reid vapor pressure 62.7 kPaSulfur content <10 ppmNet heating value 42.97 MJ/kg
Table 3.2 � Amoco Indolene Fuel Properties
Octane number (RON+MON)/2 92.3Octane sensitivity (RON-MON) 8.6H/C ratio 1.84Stoich A/F 14.5Density .742 kg/lReid vapor pressure 63.43 kPaSulfur content .0028 wt %Net heating value 42.94 MJ/kg
Table 3.3 � Haltermann EEE Fuel Properties
3.5 Air Delivery System
The air delivery system consisted of intake air for the engine, pressurized air for the
air-assist injector, and supply air for the DT. The engine was normally operated with filtered
lab air. The filtered air first went into an inlet surge tank greater than 100 times the cylinder
volume to dampen pressure fluctuations. An electronic throttle unit was used to control how
much air entered the engine. The position of this throttle was controlled by the ECU.
45
The airflow to the engine could also be controlled and measured by means of a
critical flow orifice system. Compressed building air was supplied to a series of five
different size orifices by means of a high flow pressure regulator. The airflow could be
controlled and measured by selecting an orifice size and upstream pressure. The throttle was
then used to fix an inlet surge tank pressure based on the exhaust pressure.
The compressed building air was also used to supply the air injector. The air passed
through a toggle valve and a drier, before the rail at the engine.
The building air was also used to supply the DT. The DT supply air was turned on by
means of a one-inch ball valve. This supplied air to the DT system.
3.6 Injection Systems
Three different injection systems were used for this project: air-assist, N2-assist, and
propane. Each of these systems is described below.
3.6.1 Air-Assist Injection
The normal operation of this engine was via an Orbital air-assist injection system.
This is the system that Mercury uses on their Optimax two-stroke engines. The air pressure
is maintained at 650 kPa absolute by a regulator in the rail. The fuel in the rail is maintained
via a differential regulator at a pressure of 70 kPa above the air pressure (720 kPa). The fuel
from the rail is first injected into the chamber of the air injector. This injection event meters
the amount of fuel that will be injected into the engine. Next, the air injector delivers the
fuel-air mixture into the cylinder.
46
3.6.2 N2-Assist Injection
The N2 assist injection consists of the same components as the air-assist system,
except N2 was supplied to the rail instead of air. The regulator maintains the N2 pressure at
650 kPa absolute. A N2 and fuel mixture is then injected into the cylinder.
3.6.3 Propane Injection
The propane injection system consisted of the standard air injector and a different rail.
The air injector was used to inject the propane fuel and kept in its original location. An
aluminum rail was made to seal against the air injector. The rail had a fitting for a propane
supply line to be attached. Propane was supplied via a large cylinder with a regulator. The
propane pressure was maintained at 650 kPa absolute (80 psig) by the bottle regulator.
3.7 Ignition System
An inductive ignition system was used for all tests. The ignition system consists of
the spark plug, ignition coil, and control unit. The ECU controlled the timings for the
ignition events. The Mercury ignition coil provided the high voltage for the spark event.
3.8 Cooling
The engine cooling system used a 50/50 ethylene glycol and distilled water mixture
as coolant. The coolant was pumped from a storage tank into the cylinder head. The coolant
exited the engine via the block and then into a heat exchanger. The heat exchanger was used
47
to maintain the temperature of the coolant exiting the engine using cold building water, for
most test cases this was 50ûC. An emergency shutoff switch engages at 80ûC to prevent
overheating.
3.9 Exhaust
The exhaust of the engine passes through the exhaust pipe and into a surge tank 10
times the cylinder volume. The entrance to this surge tank contains a diffuser extending
halfway into the tank consisting of 50 radially drilled holes equaling twice the flow area of
the pipe. This was done to ensure thorough exhaust gas mixing. A butterfly valve was used
to control engine back pressure near atmospheric.
3.10 Cylinder Pressure
Cylinder pressure was measured using an AVL model QC42D-E C109 piezoelectric
pressure transducer. This model had two small water cooling passages. The transducer
coolant was maintained at 35ûC. The output from the transducer was sent to a Kistler model
5010 charge amplifier. This charge amp converted the transducers charge signal into a
voltage signal of appropriate range for recording. The output from the amplifier was sent to
a Hi-Techniques data acquisition computer. The transducer was calibrated using a dead
weight tester. The calibration of the transducer can be seen in Figure 3.2.
48
y = [536.19 kPa/V]x - 5.3091R2 = 1
0
1000
2000
3000
4000
5000
6000
0 2 4 6 8 10Voltage (Delta V)
Pres
sure
(KPa
)
Calibration dataLinear Curve Fit
Charge Amp.646 pC/kPa1000 kPa/mV
Hi-Tech536 kPa/V
AVL Piezoelectric pressure transducermodel # QC42D-E
Figure 3.2 � AVL Cylinder Pressure Transducer Calibration
3.11 Emissions Measurement
The emissions measurement system consisted of the analyzers and the sample lines.
The engine emissions were sampled after the exhaust surge tank using a sample probe and
sent to a three-way valve. The sampling probe consisted of 8 holes placed radially along the
tube in compliance with the ICOMIA test standards [49]. A sample from the DT was also
sent to the three-way valve. This valve was used to select between engine and tunnel
sampling. The heated filter and line were maintained at 190ºC. The rest of the emissions
flow path can be seen in Figure 3.3.
A Horiba five-gas analyzer emissions bench was used to measure exhaust species
concentration. The bench consisted of a cooling bath, filters, valves, analyzers, and
amplifiers. The cooling bath, controlled to 2ºC, consisted of water cooled by means of a
49
refrigerant system. The emissions sample passed through this bath to condense the water.
The sample then passed through a number of filters and solenoid valves inside the bench that
could be controlled from the front panel interface. This interface allowed the user to switch
between the various functions of the bench: idle, zero, span, sample, and calibration. While
in idle the bench sampled building air through all analyzers.
The Horiba bench contained the standard five-gas analyzers: CO, CO2, HC, NOx, and
O2. Each analyzer was paired with a matching amplifier. The CO and CO2 were both AIA-
23 non-dispersive infrared (NDIR) analyzers with OPE-115 and OPE-135 amplifiers,
respectively. The HC was a FIA-23A flame ionization detector (FID) with an OPE-435
amplifier. The NOx was a CLA-22A chemiluminescent analyzer with an OPE-235 amplifier.
The O2 was a MPA-21A paramagnetic analyzer with an OPE-335 amplifier.
The outputs from all the amplifiers were sent to a National Instruments 6024E data
acquisition card. LabView was used to collect and average the emissions data, along with
engine load and fuel flow.
50
Engine
Surg
e Ta
nkEx
haus
t
Dilution Tunnel
NOx
Horiba Bench
Heated Filter
Building Exhaust
On/OffOn/Off
3-way3-wayHC
O2
CO2
CO
F PP
F
F
F
F
FF
TT
P
F
F
T
= Heated line= Insulated line= Thermocouple
= Pump
= Filter
= Rotometer
PP
FF
F
TT
= Heated line= Insulated line= Thermocouple
= Pump
= Filter
= Rotometer
Coo
ling
Bat
h
TT
Figure 3.3 � Emission Sampling Flow Path
3.12 Dilution Tunnel
The DT was a pressure driven partial-flow mini-tunnel with a venturi nozzle for
exhaust sampling. A schematic of the entire tunnel can be seen in Figure 3.4.
51
Heater TEOM
SMPS
Filter
Engine
Supply Air650 kPa
Pressure Regulator
Flow OrificeVenturi Nozzle
Exhaust Sample Tube
Sample Ports
Butterfly Valve
BuildingExhaust
Heater TEOM
SMPS
Filter
Engine
Supply Air650 kPa
Pressure Regulator
Flow OrificeVenturi Nozzle
Exhaust Sample Tube
Sample Ports
Butterfly Valve
BuildingExhaust
Heater TEOM
SMPS
Filter
Engine
Supply Air650 kPa
Pressure Regulator
Flow OrificeVenturi Nozzle
Exhaust Sample Tube
Sample Ports
Butterfly Valve
BuildingExhaust
Figure 3.4 - Schematic of Mini-Dilution Tunnel
The dilution supply air was compressed building air at 650 kPa. This passed through
a Wilkerson model M30-06-S00 coalescing filter to remove any oil particles. A high flow
regulator was used to control the pressure upstream of the flow orifice. This was used to
control and measure the flow rate of dilution air supplied to the tunnel. A 2 kW, 10 W/in2
finned tubular heater was used to maintain the temperature at the sample ports to 50ºC.
A venturi nozzle was used to pull the exhaust gas into the tunnel and aid in mixing.
The flow through the nozzle created a dynamic vacuum at the throat. The end of the exhaust
sample tube was placed at the throat of the nozzle while the other end was placed facing into
the engine exhaust pipe after the surge tank. This sample tube was heated using a 250 W
heating rope. The exhaust gas exited the sample tube and mixed with the dilution air. The
long section of the tunnel acted as a mixing chamber. The transit time through the tunnel
(residence time) was about a second. The sample ports for the filter, TEOM, SMPS, and
52
emissions were facing into the dilution tunnel and were chosen to maintain isokinetic
sampling. The mixed dilution gas then passed by a butterfly valve that was used to control
the pressure in the tunnel.
The mini-DT and sample tubes were constructed out of stainless steel because it has
low conductivity and is electrostatically neutral.
Because the tunnel is partial flow the calculation of engine PM is relatively complex.
The DR as well as engine exhaust flow and sample flow must be known. The details of the
calculation can be seen in Appendix A.
3.13 Particulate Measurement
Particulate measurement was carried out using three different methods; Teflon filters,
a TEOM, and an SMPS. Each of these methods sampled from the end of the DT.
3.13.1 Filter Sampling
47 mm Gelman Teflo Teflon filters with a polymethylpentene (PMP) support ring
were used for gravimetric analysis of particulate mass. The filter was placed in a Gelman in-
line stainless steel filter holder with a metal support mesh. The flow rate through the filter
was controlled with a calibrated rotameter and needle valve.
3.13.2 TEOM
A Rupprecht & Patashnick (R&P) TEOM series 1105 diesel particulate monitor was
used to collect mass data. The TEOM used a 13 mm Emfab (TX40) filter attached to a
53
special plastic holder that was placed on the tapered element. The tapered element oscillated
around 246 Hz and data was recorded every 0.42 seconds. The flow rate through the TEOM
was controlled internally by a mass flow meter. The temperatures of the internal and external
sample lines, along with the TEOM head were maintained at 50ºC. The data were collected
using DOS based software provided with the TEOM.
3.13.3 SMPS
The SMPS consisted of a TSI model 3080 electrostatic classifier coupled to a TSI
model 3010 CPC. The electrostatic classifier was fitted with a long DMA used to sample
particle diameters between 7 and 300 nm. The sheath and sample flow were maintained at
10 and 1 liter per minute, respectively. The entrance to the classifier was fitted with a 0.71
mm impactor orifice to remove large particles from the flow.
The CPC used butanol as the working fluid that was changed weekly. The CPC
counted individual particles and was rated for concentrations less than 10,000 particles/cm3.
Above this concentration the correlation correcting for multiple particles in the sample path
was not as accurate. The output from the SMPS was connected to a desktop computer
running the TSI aerosol instrument manager software.
54
4.0 Results and Methodology
This chapter will present the engine operating conditions and testing methodology.
Next, some important points about data reduction will be shown. Finally, the preliminary
tests and results will be explained.
4.1 Engine Operating Conditions
All engine tests were conducted at or near modes on the International Council of
Marine Industry Applications (ICOMIA) marine outboard test cycle [49]. This test cycle was
adopted to represent the actual operating conditions of marine outboard engines. The load on
the engine is a function of the actual speed, rated speed (5000 RPM), and rated power (20
kW). This is shown in Equation 4.1.
5.1
=
SpeedRatedSpeedActualTorqueRatedLoadBoat (4.1)
A wide variety of engine operating conditions were chosen to isolate the mechanisms
affecting particulate emissions. The test matrix is shown in Table 4.1 that includes all of the
engine tests conducted.
55
Parameter Speed / Load
Air-Assist Injection Spark N2 Assist
InjectionPropane Injection Other
Idle, 800 A/F sweep A/F sweep A/F sweepSlight load 40:1,50:1,60:1 40:1,50:1,60:1 40:1,50:1,60:12000, 25% 81° - 67° BTDC 50° - 25° BTDC 81° - 69° BTDC 90° - 66° BTDC Filter Test30:1 A/F @ 40° Sp @ 72° Inj @ 40° Sp @ 46° Sp Oil Consumption
2000, 25% 224° - 74° BTDC 184° - 80° BTDC 203° - 73° BTDC15:1 A/F @ 38° Sp @ 38° Sp @ 36 - 46° Sp
2800, 45% 220° - 90° BTDC 180° - 90° BTDC 210° - 90° BTDC15:1 A/F @ 37° Sp @ 37° Sp @ 34° Sp
2800, 45%12:1 A/F
Oil Consumption
Engine Test Matrix for Particulate Studies
Table 4.1 - Test Matrix
N2-assist injection was used to create a slightly richer mixture in-cylinder by
eliminating the oxygen in the injected mixture. This allowed for a change in burning zone
A/F without a change in other parameters like time for mixing or spray penetration. Propane
injection was used to eliminate liquid fuel spray impingement, fuel films, and pool fires.
Since propane is a gaseous fuel, no fuel films would form on the piston, liner, or head
surfaces. However, using propane also changes mixing effects and fuel chemistry.
Therefore it is necessary to determine a method to compare propane injection conditions with
air- or N2-assist cases. One way to do this is to use CO emissions since they provide a good
indication of the local burning zone A/F. Test results can be compared between propane, air,
and N2 cases with equal levels of CO, ensuring to a first order that the local A/F would be
similar.
The A/F delivered to the engine is controlled by the airflow since the fuel is held
constant once the load is set. Some of the fresh air delivered exits directly into the exhaust
port due to the scavenging process. This results in a lower trapped A/F. To estimate the
trapped A/F the scavenging and trapping efficiencies were calculated using results from a
56
previous study performed on the same engine in which the scavenging and trapping
efficiencies were measured [50]. The scavenging and trapping efficiencies depend on the
delivery ratio, intake air density and exhaust gas density. The trapping efficiency is then
used to calculate the trapped A/F.
Due to the scavenging process in a two-stroke engine a significant amount of residual
gas is always present in the cylinder. The amount of exhaust gas recirculation (EGR) present
in the cylinder for all operating conditions was estimated using the scavenging efficiency
(ηS) calculated for the A/F estimate. The EGR based on total in-cylinder mass was
calculated from Equation 4.2, shown below.
Strapped
residual
total
EGR
mm
mmEGR η−=== 1 (4.2)
4.2 Data Reduction
Most of the measurements taken in the lab needed some method of post-processing.
Most of the data reduction was fairly simple and straightforward. Therefore, not all of the
data reduction techniques will be given. A couple very important data reduction procedures
do, however, warrant an explanation and methodology. These include emissions
measurements (and associated quantities) and the engine out particulate calculation.
4.2.1 Emissions Measurements
Emissions measurements include the standard 5-gas emissions as well as quantities
calculated from those measurements. These parameters include mass-based emissions and
57
exhaust A/F. Exhaust A/F ratio was calculated using a variety of methods. Both of the
widely accepted Spindt and Bartlesville methods were used [51,52]. The calculation of these
two methods can be found in the reference sources and will not be included here. A different
method developed at the University of Wisconsin was also used, which is included in
Appendix B. Two more methods involved the use of a carbon balance and an oxygen
balance [9]. These five methods were used to ensure consistency in the engine operating
condition and as a check on the emissions readings. The fuel flow for gaseous fuels was also
calculated from the exhaust A/F.
The emissions analyzers measured the mole fraction of species in the exhaust. Mass-
based emissions needed to be calculated from these mole fractions. The mass-based
emissions were calculated using the methods developed at the University of Wisconsin, all of
which can be seen in Appendix B. The detailed calculations for the emissions mass rate and
the A/F can be found in the reference source. The emissions mass rate is used to get the
brake specific emissions and emissions index. Brake specific emissions are normalized with
power output and the emissions index is normalized with fuel flow rate.
4.2.2 Particulate Measurements
The TEOM, SMPS, and Teflon filters all measure the diluted levels of particulates. It
is then necessary to correct these values to find the engine-out particulate rate based on the
engine operating condition and the dilution tunnel setting. The dilution ratio (DR) was
calculated by measuring the concentrations of a tracer species, NOx or CO2, in the engine
exhaust and the dilution tunnel. Another correction factor needs to be used since the mini-
dilution tunnel samples only a portion of the engine exhaust and the instruments only sample
58
a portion of the diluted mixture. This factor is referred to as the sample ratio (SR) and is only
necessary for partial flow dilution systems. The SR was calculated from knowledge of the
exhaust and sample flow rates. The detailed calculations for the DR and SR can be found in
Appendix A.
The largest source of uncertainty in calculating engine out particulate levels comes
from the calculation of DR. This is because the NOx or CO2 analyzers are not designed to
measure the low concentration levels that are present after dilution. The emission levels in
the tunnel are 20 times lower than in the engine but the lowest NOx or CO2 range was about
3 times lower. Based on this tradeoff the sample concentration was below 15 percent of the
analyzer range, and therefore not very accurate. To increase the measured accuracy the
analyzers were calibrated using a low concentration span gas before sampling from the DT.
The manufacturer�s stated accuracy was then applied to the low span gas level resulting in
lower uncertainties at low concentrations. The uncertainty in the emissions measurement
was found using the analyzer accuracy, from which the uncertainty in the DR measurement
was found. The reported uncertainty of all the particulate mass measurements corresponds to
the uncertainty in the DR measurement.
The uncertainty based on the square root of the number of particle counts (based on
Poisson arrival statistics) was calculated for a number of representative conditions; however,
the calculated error was below 5 %. Therefore, the largest source of uncertainty in the size
distributions was very qualitative. The SMPS used algorithms to correct the particles counts
based on number of large particles that may have multiple charges. The greater the number
of larger particles, the greater this correction, and the number of small particles become less
59
accurate. Therefore, if the size distribution for small particles is erratic, inconsistent, or
extremely high or low that portion of the distribution curve cannot be trusted as accurate.
4.3 Mini-Dilution Tunnel Calibration
Before particulate sampling, the MDT was calibrated. This included examining the
supply airflow, DR range, temperature, and sampling performance. These parameters were
investigated to determine if the DT was operating correctly within design specifications and
to ensure consistent particulate sampling.
4.3.1 Dilution Tunnel Supply Test
The critical flow orifice for the DT supply was calibrated to ensure accurate flow rate
measurements. Two different orifices were adopted for use with the DT. The large orifice
had a diameter of 0.1875 in. and the small orifice was 0.120 in. The pressure ratio across the
orifices was maintained above 1.893 to ensure choked flow. This made the control and
calculation of airflow easy and consistent. Figure 4.1 shows the results of the flow test of the
two orifices.
60
30
25
20
15
10
5
0
Mas
s Fl
ow R
ate
(g/s
)
800700600500400300200100Pressure (kPa)
.120" Orifice, Cd ~ 0.95 Calculated Measured w/ Filter
.1875" Orifice, Cd ~ 0.85 Calculated Measured w/ Filter
Figure 4.1 � Supply Air Mass Flow Rate as a Function of Supply Pressure
The test was conducted with the coalescing filter in use at all supply pressures. The
supply pressure is absolute so the flow is not choked until near 200 kPa. Also, the flow at
high pressures for the large orifice drops off. The capacity of the flow meter was most likely
exceeded. The deviation at those pressures is not important since the tunnel is not operated
in that range. The calculated flow under choked flow conditions agrees very well with the
measured flow over the entire range for both orifices. The deviation is also fairly consistent
over the entire range. This difference from the calculated curve was due to flow losses. The
flow coefficients were 0.85 and 0.95 for the large and small orifices, respectively.
4.3.2 Dilution Ratio Test
It was also useful to determine the range of dilution ratios that could be achieved in
the mini-tunnel. As the supply pressure is increased both the dilution airflow and exhaust
61
sample flow are increased. The tradeoff is such that the DR increases with supply pressure.
A further range of dilution ratios is achieved by changing the flow orifice. The small orifice
allowed less airflow to be supplied to the tunnel while also pulling less exhaust sample into
the venturi. The overall tradeoff was to decrease the dilution airflow faster than the exhaust
sample flow, therefore providing lower dilution ratios. The DR was measured using CO2 as
a tracer for various supply pressures as shown in Figure 4.2.
40
30
20
10
Dilu
tion
Rat
io (D
R)
8006004002000Supply Pressure (kPa)
Critical Flow
2/24 Large Orifice 2/26 Large Orifice Small Orifice
Figure 4.2 - DR as a Function of Supply Pressure for Both Flow Orifices
The DR follows a fairly linear increasing trend with supply pressure. A DR of 14 to
30 can be achieved with the small orifice and 27 to 37 with the large orifice. The two curves
for the large orifice were taken a couple days apart at the same engine operating condition to
determine repeatability. This shows the DR control is very repeatable for similar engine
conditions. The sampling tubes in the DT were sized to provide isokinetic sampling at a
62
dilution flow rate equivalent to a supply pressure of about 360 kPa. Therefore a good
operating point would be at a DR near 20 for the small orifice and near 30 for the large
orifice.
4.3.3 Performance Testing
To determine the performance of the DT a sweep of DR was conducted. This
determines the operating range for the MDT such that there are no inconsistencies or
inaccuracies at any particular point. The engine operating condition was held constant
throughout the DR sweep and Indolene fuel was used. The supply pressure was changed and
the DR was measured using NOx as the tracer. Figure 4.3 shows the engine out particulate
mass measured with the TEOM at each DR tested. The particulate mass is very consistent
over a wide range of dilution ratios. Only at the high end, DR near 30, does the value start to
deviate. This could be due to an inaccuracy of the exhaust sample flow at high dilution ratios
or to the large deviation from isokinetic sampling at the very high supply pressures. The
consistent result shows that the dilution process does not affect the particulate mass.
63
2.0
1.5
1.0
0.5
0.0
PM [g
/hr]
30252015DR
Figure 4.3 - Particulate Mass Measurements from TEOM for the DR Sweep
Figure 4.4 shows the particle size distribution for the DR sweep. It can be seen that
the DR does affect the size distribution significantly. There is a definite trend toward
nucleation (small particles) for high dilution ratios. Even though this trend is easily seen it
did not affect the total mass as seen in Figure 4.3. This is because for particles greater than
about 80 nm in diameter the difference is negligible, and most of the mass is contained in
these larger particles.
64
25x106
20
15
10
5
0Num
ber C
once
ntra
tion
[#/c
m3 ]
6 810
2 4 6 8100
2 4
Diameter [nm]
DR = 14.4 DR = 22.1 DR = 25 DR = 27.5 DR = 28 DR = 29.4 DR = 31 DR = 33
Figure 4.4 - Particle Size distribution Measurements from SMPS for the DR Sweep
4.4 Ambient sampling
The supply air should not affect the particulate mass in any significant way. Normal,
atmospheric air should be used to best simulate the effect on particulates after emission into
the ambient. The supply air used was compressed building air. This supply contains a small
amount of lubricating oil for the compressor. The amount of this oil and its contribution to
particulate mass needed to be considered. The mass of the dilution air measured with the
TEOM shows about a 0.02 mg effect over a half hour test. After installing the coalescing
filter the mass contribution was virtually zero. Figure 4.5 shows the particle distribution
during these tests. The compressor oil has a smooth shape and was significant compared to
the lab air. After filtration there are virtually no particles in the air stream.
65
0.0E+00
5.0E+04
1.0E+05
1.5E+05
2.0E+05
1 10 100 1000Diameter [nm]
dN/d
logD
p [#
/cm
3 ]
050100150200250300350400450500
dN/d
logD
p [#
/cm
3 ]
Building Air
Lab Air
Filtered Building Air
Oil Particle Size25 - 300 nm
(.025 - .3 µm)
Figure 4.5 - Particle Distribution Effect of Compressor Oil in DT Supply Air
4.5 Repeatability
The repeatability of the TEOM and SMPS measurements is of interest. To determine
this a number of separate tests were conducted. Figure 4.6 shows the particulate mass result
of one of these tests as measured with the TEOM for three repeated conditions taken about a
week apart. The engine was run at 2000 RPM, 10 N-m load with Indolene fuel at a flow rate
of 0.72 kg/hr and an oil ratio near 1:75. A base (good running) and retarded injection timing
condition were run with an A/F of 30 and a start of air (SOA) at 72 and 66 dBTDC,
respectively. A homogeneous mixture condition was run at an A/F of 15 with an early SOA
at 137 dBTDC. The figure shows the total accumulated engine particulate mass for each
case. The total masses with associated error bars are included at the end of each test. The
TEOM results agree very well for each of the three conditions. Figures 4.7, 4.8, and 4.9
66
show the SMPS data for the same test. The size distribution curves lie nearly on top of each
other with more of a difference for large particle numbers. This could be due to the accuracy
of the correlation used by the CPC since the maximum particle number is significantly higher
than 104 particles/cm3.
0.00.10.20.30.40.50.60.70.80.9
0 500 1000 1500 2000Time [s]
Tota
l Eng
ine
Mas
s [g
]
Base, SOA = 72Base repeatRetarded, SOA = 66Retarded repeatHomog, A/F=15Homog repeat
Figure 4.6 � TEOM Repeatability for Three Engine Conditions
67
0.0E+00
2.0E+08
4.0E+08
6.0E+08
8.0E+08
1.0E+09
1.2E+09
1.4E+09
1 10 100 1000Particle Diameter [nm]
dN/d
LogD
p [#
/cm
3 ]
Base
Figure 4.7 - SMPS Repeatability for Base Engine Condition
0.0E+002.0E+084.0E+086.0E+088.0E+081.0E+091.2E+091.4E+091.6E+09
1 10 100 1000Particle Diameter [nm]
dN/d
LogD
p [#
/cm
3 ]
Retarded
Figure 4.8 - SMPS Repeatability for Retarded Engine Condition
68
0.0E+00
2.0E+08
4.0E+08
6.0E+08
8.0E+08
1.0E+09
1.2E+09
1.4E+09
1 10 100 1000Particle Diameter [nm]
dN/d
LogD
p [#
/cm
3 ]
Homogeneous
Figure 4.9 - SMPS Repeatability for Homogeneous Engine Condition
To further judge the repeatability of the TEOM a number of identical or similar
engine operating conditions run throughout testing were compared. Figure 4.10 shows the
compilation or these data points. All of the points were taken at 2000 RPM, 10 N-m load,
and with a delivered A/F near 30. The data points enclosed in ovals have similar oil flow
rates; so therefore can be compared to judge repeatability. The data shows good consistency,
especially at the low oil flow case. The increased spread in points at high oil flow rates could
be in part a function of the accuracy of the controlled oil flow. Most of these points were
taken early, before the effect of oil on PM was fully examined, so that the oil flow was not
maintained as accurately as in the low oil tests.
69
0
0.5
1
1.5
2
2.5
66 67 68 69 70 71 72 73SOA [dBTDC]
PM [g
/kg-
fuel
]
Oil 1:400Oil 1:100Oil 1:75Oil 1:75
Figure 4.10 - PM Test Points Compilation Showing TEOM Repeatability
Two repeated injection sweeps were done at 2800 RPM, 16 N-m load, with a
delivered A/F near 15 and low oil flow. The mass results of these sweeps can be seen in
Figure 4.16 in the oil test section. The particulate mass is repeatable over the entire sweep.
The size distributions have a larger difference between the two test runs. The general shape
of the curves agrees well, with the largest spread seen at the low diameters. This is most
likely due to the low detection efficiency for these small particles.
4.6 Particulate Mass Comparison
The particulate mass as measured with the TEOM was compared to the mass
calculated from the size distribution measured with the SMPS. This provided a good cross-
70
check to ensure the accuracy of the measurements and also as an indication if either
instrument was not functioning properly. The mass concentration was calculated from the
mass measurements based on the sample flow rate and DR. The engine-out particle size
distribution was used to calculate a mass concentration (mg/m3) assuming a constant particle
density of 1.2 g/cm3.
The mass concentration calculated from the size distribution has some significant
inaccuracies associated with it. The first is the assumption of constant density. The density
is most likely different for different size particles and for different engine operating
conditions [53]. Therefore, the accuracy of the mass calculation is dependent on the
accuracy of the assumed density. The second is the presence of particles outside the size
range of the SMPS. If particles outside this range are present in the sample the SMPS will
not count them, and therefore, they will not be included in the size distribution.
The mass concentration comparison for the 2000 RPM stoichiometric test condition
can be seen in Figure 4.11. Details of the test condition will be given in the section
discussing PM results. The comparison for all of the tested conditions can be seen in Figure
4.12. The SMPS absolute results don�t compare that well with the TEOM measurements.
The SMPS is within about 30 percent for air and N2-assist and within 50 percent for propane,
likely due to the very low particulate mass. Other conditions show better accuracy, however,
there is never excellent quantitative agreement. More importantly, the shape of the SMPS
mass calculations match the trend of the TEOM very well. The trend is matched for air-
assist, N2-assist, and propane injections at all timings. This suggests that the size distribution
correlates well with the mass data, and even though it is not necessarily very accurate, it can
be used with confidence for observing qualitative trends in number and size.
71
0.05.0
10.015.020.025.030.035.040.0
50100150200250SOI [dBTDC]
Part
icul
ate
Mas
s C
once
ntra
tion
[mg/
m3 ] TEOM Air
SMPS AirTeom N2SMPS N2TEOM PropaneSMPS Propane
Figure 4.11 - Comparison of Mass Concentration from the TEOM and SMPS Measurements
72
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20 25 30 35 40 45TEOM [mg/m3]
SMPS
[mg/
m3 ]
Figure 4.12 - Correlation Between Particulate Mass form the TEOM and SMPS
4.7 Filter Comparison Test
The first test conducted was to compare the particulate mass obtained from the Teflon
filters to the end of test mass recorded from the TEOM. To do this an injection sweep was
performed while taking both TEOM and Teflon filter particulate samples. Two of the
injection timings were tested twice to gauge repeatability and accuracy. The engine was run
at a stratified condition at 2000 RPM, 9 N-m load, 0.72 kg/hr fuel flow rate of Indolene, and
with a delivered A/F of 30. The SOA injection timing was varied from 67 to 82 dBTDC with
a constant air pulse width and a spark timing of 40 dBTDC. Figure 4.13 shows the engine
out particulates as measured using the Teflon filter and TEOM. The TEOM data agrees well
with the Teflon filter masses and does not seem to under predict the particulate mass. This
73
could be due to the low mass loading that allows the TEOM to maintain high accuracy.
There are a couple points that seem to fall outside of the error bars but not by very much. A
couple of added sources of uncertainty from the Teflon filters are handling inaccuracies due
to operator and the level of loading is much lower than the filter�s capacity. The overall
accuracy of the TEOM is very good and can be used as a stand-alone particulate mass
measurement instrument.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
PM [g
/hr]
82 80 78 76 74 72 70 68SOA [dBTDC]
TEOM Teflon Filter
Figure 4.13 - Comparison of Particulate Mass from Teflon Filter and TEOM
4.8 Lube Oil Test
Since the two-stroke test engine utilizes a lost oil system the oil consumption is by
nature greater than four-stroke engines. Therefore, it was necessary to conduct a test to
determine whether the oil flow rate was affecting the measured particulate emissions. The
74
lube oil tests were run using a normal oil-to-fuel ratio of 1:100 and a high oil ratio of 1:50
(twice normal oil flow). For the low oil ratio an attempt was made to match the oil
consumption rate of an engine with a sump. The low oil ratio near, or lean of, 1:400 (one-
quarter normal oil flow) is believed to be close to, if not at, the LOC rate of four-stroke
engines [23,24]. The tests were conducted at two engine speeds, 2000 and 2800 RPM. The
2000 RPM case was stratified with a delivered A/F of 30 at 10 N-m load while the 2800 case
was more homogeneous with a delivered A/F of 15, corresponding to an overall rich
combustion due to scavenging, at 16 N-m.
4.8.1 Stratified Condition Oil Test
The particulate mass and size distribution results for the 2000 RPM case can be seen
in Figures 4.14 and 4.15. The particulate mass remains constant with injection timing but
changes very significantly as the oil ratio is increased. The PM increased more going from
normal to high oil than it did for the low to normal transition. This is interesting since the oil
flow is only doubled from normal to high and it is quadrupled from low to normal. This
illustrates two points. First, the effect of oil on particulate mass approaches a plateau near
the low oil ratio. Second, the more oil that is supplied to the engine the greater the effect on
particulate mass. The first point means that at the low oil ratio most of the PM should be
from the combustion process. The second point illustrates the strong dependence of PM on
oil consumption.
The size distribution changes noticeably as the oil flow is increased. As the oil
addition rate was increased the general trend is toward larger particles and a greater peak
number. Also, at the high oil flow the size distribution exhibits a dual mode shape. The peak
75
number density occurs near 30 nm for all conditions. The normal oil flow tests show an
increase in peak particle number and an increase of larger particles in the 30 to 80 nm range.
The high oil flow case has the same peak as the normal case but exhibits a second mode
around 70 nm. The higher particulate mass for the normal and high oil ratios is most likely
from the higher number density at larger particle diameters, since the larger particles carry
far more mass. It should be noted that the particle diameter is always plotted on a log scale
so that an equal change in particle diameter has smaller axis spacing at larger diameters. The
peak number density near 30 nm and the second mode near 70 nm come from the lube oil.
1.81.61.41.21.00.80.60.40.20.0
PM [g
/kg-
fuel
]
80 78 76 74 72 70 68SOA [dBTDC]
2000 RPM, 10 N-m, A/FDel=30 Low Oil (1:400) Normal Oil (1:100) High Oil (1:50)
Figure 4.14 - Particulate Mass Results from Oil Test at 2000 RPM
76
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 610
2 3 4 5 6100
2 3
Diameter [nm]
SOA = 72 Low Oil Normal Oil High Oil
Figure 4.15 - Size distribution Curves for Oil Test at 2000 RPM
4.8.2 Homogeneous Condition Oil Test
The particulate mass and size distribution results for the 2800 RPM case can be seen
in Figures 4.16 and 4.17. The particulate mass follows the same trends as those for the 2000
RPM case. That is, the higher the oil flow rate the greater effect on particulates and the low
oil ratio approaches a plateau. All the curves exhibit some dependence on injection timing.
The low oil case is thought to be dominated by the effects of combustion. The increases in
PM for the two most retarded timings at normal and high oil flow are also considered to be
combustion effects. The difference between the mass for the entire oil flow range at retarded
timings is due to the fact that the particle mass is substantial compared to the effect of oil.
The particulate mass for the normal and high oil flow cases increases as injection is
advanced, however, remains constant for the low oil ratio.
77
The size distribution also follows the same general trends as the 2000 RPM case. The
particle number and size increases with oil flow and the second size mode near 70 nm
appears for only the high oil ratio. The noticeable difference comes at the retarded injection
timings. The particle number is lower and the peak number happens at larger particles, even
for the low oil ratio curves. This occurs because the combustion effect is substantial
compared to the oil effect for the very late injections.
1.81.61.41.21.00.80.60.40.20.0
PM [g
/kg-
fuel
]
240 220 200 180 160 140 120 100SOA [dBTDC]
Low Oil, 1:400 Low Oil Repeat Normal Oil, 1:100 High Oil, 1:50
2000 RPM, 16 N-m, A/FDel=15
Figure 4.16 - Particulate Mass Results from Oil Test at 2800 RPM
78
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
Low oil, SOA=90 Low oil, SOA=240 Norm oil, SOA=90 Norm oil, SOA=240 High oil, SOA=90 High oil, SOA=240
Figure 4.17 - Size Distribution Curves for Oil Test at 2800 RPM
The main conclusion from these oil tests is that oil is a dominant source of PM in this
engine. This effect even overwhelms combustion under normal oil flow conditions used in a
production outboard engine. The amount of oil used by this engine is a major factor in the
formation of PM.
4.9 Oil Flow Equilibrium
It was necessary to reach steady-state operating conditions when using a low oil flow
rate. The engine was not operated on low oil flow at all times for durability reasons.
Therefore it was necessary to ensure that the oil flow rate and its contribution to PM reached
equilibrium. This was done by monitoring the size distribution, measured with the SMPS,
79
during the testing period. Figure 4.18 shows an example of the size distribution curves that
were seen during this period. The time associated with each curve represents the start of
sampling time after the oil ratio was set. The curves were measured every five minutes or so
until they reached steady-state. As the oil reaches low flow equilibrium the number of
particles and diameter both decrease. This series of curves were taken during the testing
period before each test. Once equilibrium was reached, particulate sampling could begin.
Initially the particulate mass was measured with the TEOM as well to ensure equilibrium was
reached, but it was determined that the SMPS provided reliable results.
35x106
30
25
20
15
10
5
0
dN/d
LogD
p [#
/cm
3 ]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
25 min 28 min 33 min 36 min 40 min 43 min 46 min
Increasing time afteroil flow rate was set
Figure 4.18 - Size Distribution Measured as Oil Flow Rate Reaches Equilibrium
80
5.0 Particulate Matter Results and Discussion
This chapter will present the PM testing results. It includes all the tests conducted to
isolate the mechanisms affecting PM and the discussion of these results. The oil test results
illustrate the need to run at low oil ratios to resolve combustion effects on PM; so all the
particulate tests presented in this chapter were run at low oil ratios (> 400:1 fuel-to-oil). To
minimize any variation in operating condition the N2-assist injection was run back-to-back
with the air-assist injection at each timing. The size distribution graphs can be hard to read,
so some data are omitted. The graphs will include the relevant points to illustrate the shape
of the distribution for different operating points as well as significant changes between them.
All inclusive size distribution graphs can be found in Appendix C. Mass weighted
concentrations are also shown for most conditions not as a mass comparison, but because it is
easier to spot the differences between particle numbers at large diameters. The distribution is
calculated from the particle size and number assuming a constant particle density of 1.2
g/cm3. First, the PM trends for each test condition will be explained in the appropriate
section. Then, mechanisms affecting all operating conditions and differences between air,
N2, and propane will be presented in the sections following the test results.
5.1 Idle
An idle test was performed at an 800 RPM, 5 N-m load operating condition that
provided a highly stratified mixture. The engine was run at slight load, versus ECU idle
speed control, to maintain engine speed with fixed injection and spark timings to ensure
81
consistent operation. Air-assist, N2-assist, and propane injections were run at 40:1, 50:1, and
60:1 delivered A/F. The estimate for EGR level was 30, 25, and 20 percent for the respective
A/F.
The particulate mass results are shown in Figure 5.1. The particulate mass for all
injections increased with A/F. The air-assist particulate mass is about 50 percent higher than
that for N2. Also, the air and N2 cases have a significantly higher particulate mass than the
propane case. The observed increase in PM with A/F is most likely due to a temperature
effect. The in-cylinder temperatures are believed to be higher since the NOx emissions
increase with A/F as shown in Figure 5.2. Also, the peak pressures increase with A/F, and
the combustion phasing advanced (location of peak pressure) with increases in A/F. The
higher temperatures thus promote particle formation. The exhaust temperatures also decrease
with A/F, which could decrease the amount of particle oxidation. Lower exhaust
temperatures may result from advanced combustion phasing.
2.0
1.5
1.0
0.5
0.0
PM [g
/kg-
fuel
]
65605550454035A/F
Air-Assist N2-Assist
Propane
~50%
Figure 5.1 - Particulate Mass Results for A/F Sweep at Idle Test Condition
82
050
100150200250300350400
35 40 45 50 55 60 65A/F
NO
x [p
pm]
Air-AssistN2-AssistPropane
Figure 5.2 - NOx Emissions for A/F Sweep at Idle Test Condition
The particle size distribution results are shown in Figure 5.3. Figure 5.4 centers on
the local peak for larger particles. The high numbers at particle diameters less than about 40
nm are very erratic and are most likely not an accurate representation. The distribution has a
peak near a particle diameter of 100 nm for the air and N2-assist cases. The shape of the
curves do not change very much over the range of A/F or between air and N2-assist. This
may show that the composition of the PM is similar for all of the test cases. The higher A/F
curves generally show a higher number of the particles near 100 nm diameters, which is a
good indication that they have a higher PM mass. The propane curves do not show a peak
but also do not drop off to zero near this diameter, however, they are significantly below the
air and N2 curves. The absence of the peak for propane might suggest that the particulate
composition is different than that for the EEE fuel.
83
4x106
3
2
1
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
A/F=40 Air A/F=50 Air A/F=60 Air A/F=40 N2 A/F=50 N2 A/F=60 N2 A/F=40 Propane A/F=50 Propane A/F=60 Propane
Figure 5.3 - Particle Size Distribution for A/F Sweep at Idle Test Condition
800x103
600
400
200
0
Num
ber C
once
ntra
tion
[#/c
m 3]
4 5 6 7 8 9100
2 3
Particle Diameter [nm]
A/F=40 Air A/F=50 Air A/F=60 Air
A/F=40 N2 A/F=50 N2 A/F=60 N2
A/F=40 Propane A/F=50 Propane A/F=60 Propane
Figure 5.4 - Particle Size Distribution near Local Peak of 100 nm
84
5.2 Stratified Combustion Test
A stratified operating condition was run at 2000 RPM, 10 N-m load with a delivered
A/F of 30 to provide a stratified mixture at light load. Injection and spark timing sweeps
were done within the range of stable engine operation. Air-assist, N2-assist, and propane
injections were all performed at this condition. The spark sweep was performed only for the
air-assist injection. The EGR level estimate for all cases was close to 32 percent.
The particulate mass results for the injection sweeps are shown in Figure 5.5. Three
data points have been omitted from this graph. Two retarded timings were run with propane
at a SOI of 66 and 72 dBTDC with a PM mass of 1.079 and 0.666 g/kg-fuel, respectively.
These points were omitted because they had extremely high COV of IMEP values, greater
than 40 percent. The air-assist SOI of 72 dBTDC with a PM mass of 0.355 g/kg-fuel was
also omitted because the data point was contaminated with lube oil based upon the similarity
of the size distribution curve with that of the oil test (See Figure 4.15).
The particulate mass for the air-assist case is fairly constant for advanced timings and
then increases as injection timings were retarded. This trend is seen for N2-assist injection,
however the magnitude is slightly lower than the air-assist case. The PM increase for
retarded injections is likely due to a rich burning zone A/F. As the SOI is advanced the
mixture becomes leaner resulting in lower particulate mass, as suggested by the decrease in
CO, shown in Figure 5.6. The burning zone A/F where the PM mass starts to level off (~77
dBTDC) is likely lean of stoichiometric judging from the constant CO for the advanced
timings. Therefore, the PM remains constant since the burning zone is no longer rich. The
NOx emissions, seen in Figure 5.7, start to level off for the advanced timings. Since the
85
burning zone A/F is near stoichiometric the in-cylinder temperatures should be near a peak.
Advancing the timing doesn�t increase the PM mass since the temperature does not change
much. The propane curve remains fairly flat over the entire stable operating range and the
particulate mass lies slightly greater than the flat portion of the air-assist curve.
The particulate mass results for the spark timing sweep are shown in Figure 5.8. The
particulate mass steadily increases as spark timing is advanced. Advancing the spark timing
gives less time for mixing so the mixture at the spark plug should be richer. The rich local
burning zone A/F gives rise to the increase in PM. Also, the combustion phasing is advanced
with spark advance, causing higher in-cylinder temperatures. This effect could also
contribute to the particulate mass.
0.5
0.4
0.3
0.2
0.1
0.0
PM [g
/kg-
fuel
]
100 95 90 85 80 75 70 65SOI [dBTDC]
2000 RPM, A/FT=23 Air-Assist N2-Assist Propane
Figure 5.5 - Particulate Mass Results for Injection Sweep at Stratified Test Condition
86
0.0
0.1
0.2
0.3
0.4
0.5
0.6
65707580859095100Injection Timing [dBTDC]
CO
[%]
SOASONSOP
Figure 5.6 - CO Emissions for Injection Sweep at Stratified Test Condition
0100200300400500600700800
65707580859095100Injection Timing [dBTDC]
NO
x [p
pm]
SOASONSOP
Figure 5.7 - NOx Emissions for Injection Sweep at Stratified Test Condition
87
0.4
0.3
0.2
0.1
0.0
PM [g
/kg-
fuel
]
50 45 40 35 30 25Spark [dBTDC]
2000 RPM, A/FT = 23
Figure 5.8 - Particulate Mass Results for Spark Sweep at Stratified Test Condition
The particle size distributions for air- and N2-assist injection timings are shown in
Figure 5.9 and for propane in Figure 5.11. The mass weighted size distributions for air- and
N2-assist injection timings are shown in Figure 5.10 and for propane in Figure 5.12. There is
a significant change in shape for retarded and advanced timings for all injections. For
retarded timings with air and N2 there is a significant number of particles above a diameter of
50 nm. This should be the dominant source of mass since each particle has much more mass
than the small ones. As injection is advanced the mode changes, that is the number of
particles near 50 nm drops to zero as the number of small particles increases. The mode
changes at the injection timing where the particulate mass, measured with the TEOM, stops
dropping and levels off. The mode change would suggest that the composition of the
particulates changes near this injection timing. This same trend is seen for propane injection;
however, the small particles start to increase at a diameter of 70 nm. Here the particulate
composition also undergoes a change.
88
The size distributions for the ignition timing sweep are shown in Figure 5.13 and the
mass weighted distribution is in Figure 5.14. The same trend seems to exist for advanced
ignition timing as that seen for retarded injection timing. Advanced spark timing results in a
richer burning zone A/F mixture, thus being somewhat equivalent to retarded injections in
that respect. As spark timing is retarded the mode changes and large numbers of small
particles are created.
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA=67 SOA=69 SOA=75 SOA=81 SON=69 SON=75 SON=81
Figure 5.9 - Particle Size Distribution for Air and N2-Assist Injection Sweep at Stratified
Test Condition
89
600
500
400
300
200
100
0
Mas
s W
eigh
ted
Con
cent
ratio
n [ µ
g/m
3 ]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA=67 SOA=69 SOA=75 SOA=81 SON=69 SON=75 SON=81
Figure 5.10 - Mass Weighted Size Distribution for Air and N2-Assist Injection Sweep at
Stratified Test Condition
16x106
1412
10
8
6
42
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOP=76 SOP=81 SOP=86 SOP=89
Figure 5.11 - Particle Size Distribution for Propane Injection Sweep at Stratified Test
Condition
90
400
300
200
100
0
Mas
s W
eigh
ted
Con
cent
ratio
n [ µ
g/m
3 ]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOP=76 SOP=81 SOP=86 SOP=89
Figure 5.12 - Mass Weighted Size Distribution for Propane Injection Sweep at Stratified
Test Condition
12x106
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
spark=30 spark=40 spark=50
Figure 5.13 - Particle Size Distribution for Spark Sweep at Stratified Test Condition
91
300
250
200
150
100
50
0
Mas
s W
eigh
ted
Con
cent
ratio
n [ µ
g/m
3 ]
5 6 7 8 910
2 3 4 5 6 7 8 9100
2 3
Particle Diameter [nm]
spark=30 spark=40 spark=50
Figure 5.14 - Mass Weighted Size Distribution for Spark Sweep at Stratified Test Condition
5.3 Stoichiometric Combustion Test, Low Speed
A stoichiometric operating condition was run at 2000 RPM, 11 N-m load
(approximately the same condition as the previous section) with a trapped A/F near 15 to
provide homogeneous and stratified mixtures at light load. A full injection sweep was done
with air-assist and propane injections. Nitrogen-assist was only done at 4 of the injection
timings to determine its effect relative to the air-assist sweep. The level of EGR for these
cases was near 40 percent.
The particulate mass results for the injection sweeps are shown in Figure 5.15. The
particulate mass for air-assist is highest at retarded injections and decreases as injection is
advanced until reaching a local minimum near 100 dBTDC before starting to increase again.
It then reaches a local maximum near 140 dBTDC before decreasing slightly for very
92
advanced timings. Since not all points were taken with N2-assist it cannot be stated with
certainty that it would follow the same shape as air-assist, however, there is no apparent
reason the trend should change. Propane injection appears to follow this shape, however, the
low PM levels prohibit this being a certain statement as well. The apparent difference arises
for advanced injections (greater than 130 dBTDC) where the propane particulate mass seems
to increase. This will be addressed in the propane discussion section even though it appears
to be an injection timing effect.
The rise in particulates from the local minimum for retarded injection timings is due
to a richer local burning zone A/F, which can be seen in Figure 5.16. The increase in PM
from the local minimum and subsequent local peak then decrease for advanced timings is
most likely an effect of temperature that is caused by a reduction in the overall rich burning
zone A/F. Since the mixture at the spark plug at the minimum PM is most likely rich, the
leaner A/F is closer to stoichiometric and results in higher in-cylinder temperatures. The
local PM peak at 140 dBTDC correlates with the peak NOx emissions, shown in Figure 5.17,
which supports the conclusion of higher temperatures. As the timing is advanced further, the
mixture becomes leaner and the temperature may start to drop off. Also, some of the fuel is
being short-circuited at advanced timings. This is supported from the sharp increase in HC
emissions, shown in Figure 5.18, and decrease in torque output. Now less fuel is available to
burn in-cylinder so lower temperatures and PM would be expected. There is another factor
that may be important at the local PM minimum; this was the worst operating point for the
engine. The torque and peak pressure were much lower than other timings and the COV was
higher. Much lower temperatures would be expected, as supported by a significant drop in
NOx emissions.
93
0.5
0.4
0.3
0.2
0.1
0.0
PM [g
/kg-
fuel
]
230 210 190 170 150 130 110 90 70SOI [dBTDC]
2000 RPM, A/FT = 15 Air-Assist N2-Assist Propane
Figure 5.15 - Particulate Mass Results for Injection Sweep at 2000 RPM Stoichiometric Test
0.0
0.5
1.0
1.5
2.0
2.5
7090110130150170190210230Injection Timing [dBTDC]
CO
[%]
SOA COSON COSOP CO
Figure 5.16 - CO Emissions for Injection Sweep at 2000 RPM Stoichiometric Test
94
050
100150200250300350400450
7090110130150170190210230Injection Timing [dBTDC]
NO
x [p
pm]
SOASONSOP
Figure 5.17 - NOx Emissions for Injection Sweep at 2000 RPM Stoichiometric Test
0
1000
2000
3000
4000
5000
6000
7000
7090110130150170190210230Injection Timing [dBTDC]
HC
[ppm
]
SOASONSOP
Figure 5.18 - HC Emissions for Injection Sweep at 2000 RPM Stoichiometric Test
The particle size distributions for air- and N2-assist injection timings are shown in
Figure 5.19 and for propane in Figure 5.21. The mass weighted size distributions for air- and
N2-assist injection timings are shown in Figure 5.20 and for propane in Figure 5.22. The
distributions show two distinct particle modes. For the most retarded timings with air-assist
a large particle mode is seen with a peak in the distribution near a particle diameter of 60 nm.
As the injection timing is advanced the peak decreases in both number and particle diameter.
95
Eventually the distribution changes to the small mode as the number of particles greater than
50 nm drops to zero and a large number of small particles arise. This change occurs near the
injection timing corresponding to the minimum PM mass in Figure 5.15. This same trend is
seen for N2 and propane as well. The retarded propane injections do not show a local peak
but maintain higher particle numbers above a diameter of 50 nm. The absence of a distinct
peak here is probably due to the much lower particulate mass for propane relative to the air
and N2 curves. The large mode exists for retarded timings where the burning zone A/F is
significantly rich. The large mode may be elemental carbon particles (soot) that form in rich
combustion zones where the carbon to oxygen ratio is high. The small mode exists for
homogeneous mixtures that have an overall A/F that is slightly lean. The small mode may be
organic carbon particles and other soluble and volatile compounds. These distributions and
trends suggest that locally rich stratified combustion produces a smaller number of large
particles leading to a high overall particulate mass. Homogeneous combustion produces a
large number of very small particles that contribute to a lower particulate mass than stratified
conditions.
96
14x106
12
10
8
6
4
2
0Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA=74 SOA=84 SOA=94 SOA=184 SON=79 SON=184
Figure 5.19 - Particle Size Distribution for Air and N2-Assist Injection Sweep at 2000 RPM
Stoichiometric Test
1200
1000
800
600
400
200
0
Mas
s W
eigh
ted
Con
cent
ratio
n [ µ
g/m
3 ]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA=74 SOA=84 SOA=94 SOA=184 SON=79 SON=184
Figure 5.20 - Mass Weighted Size Distribution for Air and N2-Assist Injection Sweep at
2000 RPM Stoichiometric Test
97
14x106
12
10
8
6
4
2
0Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOP=73 SOP=85 SOP=128 SOP=203
Figure 5.21 - Particle Size distribution for Propane Injection Sweep at 2000 RPM
Stoichiometric Test
140
120
100
80
60
40
20
0
Mas
s W
eigh
ted
Con
cent
ratio
n [ µ
g/m
3 ]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
SOP=73 SOP=85 SOP=128 SOP=203
Figure 5.22 - Mass Weighted Size Distribution for Propane Injection Sweep at 2000 RPM
Stoichiometric Test
98
5.4 Stoichiometric Combustion Test, Medium Speed
A stoichiometric operating condition was tested at 2800 RPM, 16 N-m load with a
trapped A/F near 15 to provide homogeneous and stratified mixtures at medium load. A full
injection sweep was performed with air-assist and propane injections. Nitrogen-assist was
again only tested at 4 of the injection timings. The EGR estimate for all cases was close to
30 percent.
The particulate mass results for the injection sweeps are shown in Figure 5.23 and
follow the same trends as the 2000 RPM stoichiometric test case. The overall shapes of the
curves are the same but with slightly advanced phasing and slightly higher magnitudes. The
air-assist has a local minimum near 100 dBTDC and a local maximum near 110 dBTDC. For
advanced timing the particulate mass seems to level off. The propane curve has a more
distinct shape, exhibiting a more significant local minimum and smoother increase in PM for
advanced timings.
The same reasoning from the 2000 RPM stoichiometric test applies to the trends
observed here as well. The increase in PM for retarded timings from the local minimum is a
local burning zone A/F effect and the trends for advanced timings are due to temperature.
One difference is the constant PM for very advanced injections. Less fuel may be short-
circuited at this engine speed since the ports are open for a shorter time. This is supported by
lower HC emissions, shown in Figure 5.24, compared to the 2000 RPM test. Since less fuel
is lost to the exhaust, the in-cylinder temperatures remain high, so the particulate mass
doesn�t drop. Another difference is seen at the local minimum. In this test the engine torque
remained high and the COV was low. Here the engine was running very well and the
99
particulate minimum is very apparent. This shows that combustion effects, not misfires and
running condition quality, dominate the effect on particulate mass. The local minimum for
the 2000 RPM test is therefore most likely due to combustion effects as well and not the poor
running condition.
0.70.60.50.40.30.20.10.0
PM [g
/kg-
fuel
]
240 220 200 180 160 140 120 100 80SOI [dBTDC]
2800 RPM, A/FT = 16 Air-Assist N2-Assist Propane
Figure 5.23 - Particulate Mass Results for Injection Sweep at 2800 RPM Stoichiometric Test
100
0500
10001500200025003000350040004500
80100120140160180200220240EOP [dBTDC]
HC
[ppm
]
SOASONSOP
Figure 5.24 - HC Emissions for Injection Sweep at 2800 RPM Stoichiometric Test
The particle size distributions for air- and N2-assist injection timings are shown in
Figure 5.25 and for propane in Figure 5.27. The mass weighted size distributions for air- and
N2-assist injection timings are shown in Figure 5.26 and for propane in Figure 5.28. The
same two distinct modes as in the 2000 RPM stoichiometric test are seen here for air, N2, and
propane injections. The large particle mode peaks near 60 nm for retarded timings. Propane
shows this similar mode but like the previous test there is no local peak, rather the rate of
decrease with respect to diameter decreases. The small particle mode starts to increase below
50 nm for advanced timings. The mode change also corresponds to the local PM minimum
from the mass results. The mode change suggests a difference in particulate composition
between the retarded and advanced timings. Like previously the large particles may be
elemental carbon produced from a locally rich burning zone A/F at retarded injections. The
small particles may be organics, volatiles, and/or solubles.
101
20x106
15
10
5
0
Num
ber C
once
ntra
tion
[#/c
m 3
]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA=90 SOA=100 SOA=180 SOA=220 SON=90 SON=100 SON=180
Figure 5.25 - Particle Size Distribution for Air and N2-Assist Injection at 2800 RPM
Stoichiometric Test
1200
1000
800
600
400
200
0
Mas
s W
eigh
ted
Con
cent
ratio
n [
µg/
m3 ]
5 610
2 3 4 5 6100
2 3
Particle Diameter [nm]
SOA=90 SOA=100 SOA=180 SOA=220 SON=90 SON=100 SON=180
Figure 5.26 - Mass Weighted Size Distribution for Air and N2-Assist Injection at 2800 RPM
Stoichiometric Test
102
20x106
15
10
5
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOP=90 SOP=110 SOP=150 SOP=210
Figure 5.27 - Particle Size Distribution for Propane Injection at 2800 RPM Stoichiometric
Test
180160140120100
80604020
0
Mas
s W
eigh
ted
Con
cent
ratio
n [
µg/
m3 ]
5 610
2 3 4 5 6100
2 3
Particle Diameter [nm]
SOP=90 SOP=110 SOP=150 SOP=210
Figure 5.28 - Mass Weighted Size Distribution for Propane Injection at 2800 RPM
Stoichiometric Test
103
5.5 Particulate Matter Emissions Comparison
Before discussing the results, the particulate mass results presented above should be
compared on an absolute level and with other relevant data.
5.5.1 Particulate Mass Rate
It is useful to compare the particulate mass emissions rate on an absolute scale.
Figure 5.29 shows this comparison for each test condition and injection type. The number
labels on the chart correspond to the operating conditions as follows; 1) Idle 2) Stratified 3)
2000 RPM stoichiometric 4) 2800 RPM stoichiometric. In general, as the engine load
increases the particulate mass emission rate increases as well. The idle condition tested with
EEE does not show this and has a higher emission rate than the low load cases.
00.10.20.30.40.50.60.70.80.9
1
PM [g
/hr]
MaxMin
Air Nitrogen Propane
12 3 1 1
2 24 334 4
Figure 5.29 - Comparison of Particulate Mass Emission Rate for All Operating Conditions
104
5.5.2 Literature Comparisons
Figure 5.30 shows the particulate mass rate compared to other outboard marine
engines, where the 2-Stroke Carbureted, 4-Stroke Carbureted, and 2-Stroke DI data was from
a study by Kado et al. [54]. Each of the engines tested by Kado et al. was run with
manufacturers recommended oil type and ratio [54]. The mass rate result of a normal oil-to-
fuel ratio test conducted shows good agreement with the other 2-Stroke DI. Also, the low oil
ratio result compares well with the four-stroke outboard engine.
0123456789
2-StrokeCarb
4-StrokeCarb
2-Stroke DI Mercury DIOil
Mercury DILow Oil
PM [g
/hr]
Figure 5.30 - Comparison to Other Marine Outboard Engines (2-Stroke Carb, 4-Stroke Carb,
and 2-Stroke DI reprinted from [54])
105
0.00
0.04
0.08
0.12
0.16
0.20
IDI D
iesel
Cummins
Dies
el
Euro D
iesel
Diesel
Mitsub
ishi G
DI
JDM D
IDISI
Mercury
W/ O
il
Mercury
Med
ium Lo
ad
Mercury
DI 2
-Stro
ke
Otto-D
I
2-Stro
ke M
oped
2-Stro
ke M
otorcy
cle
Toyota
MFI S
IMPI
PFI
PM [g
/km
]
Figure 5.31 - Comparison to Other Engines Including Diesel, DISI, and Port Fuel Injection
(See Table 5.1, [14,17,18,55,56,57])
Engine Primary Author Notes Reference IDI Diesel Maricq Reported as mg./mi, converted [55] Cummins Diesel Kweon Reported in g/kg-fuel, Converted to g/km by
assuming a fuel economy [14]
Euro Diesel Ntziachristos Reported in mg/km, converted [56] Diesel Eichlseder Reported as g/km [57] Mitsubishi GDI Cole Reported as mg./mi, converted [18] JDM DI Smallwood Reported as mg./mi, converted [17] DISI Maricq Reported as mg./mi, converted [55] Otto-DI Eichlseder Reported as g/km [57] 2-Stroke Moped Ntziachristos Reported in mg/km, converted [56] 2-Stroke Motorcycle Ntziachristos Reported in mg/km, converted [56] Toyota MFI SI Ntziachristos Reported in mg/km, converted [56] MPI Eichlseder Reported as g/km [57] PFI Maricq Reported as mg./mi, converted [55]
Table 5.1 - Reference Sources and Explanations for Engines Compared in Figure 5.31
106
Figure 5.31 shows the particulate mass rate in units of g/km (vehicle emission rates)
for a number of different engines including diesel, spark ignition, and DISI
[14,17,18,55,56,57]. The particulate data was reprinted from a number of sources that can be
seen in Table 5.1. Since all of the engines were tested under road loads, an estimate had to
be made of this to convert the particulate results from engine testing to g/km. This was done
by estimating the engine load necessary to maintain a vehicle speed similar to that reported in
the sources. Then the particulate mass and fuel flow were then used to calculate a g/km
emission rate. The road load used to generate the Mercury PM numbers in Figure 5.31 was
assumed to be about 7.5 kW (10 hp) at 100 km/hr(60 mph). Also, the fuel economy was
estimated for some of the vehicles that were tested in the reference sources, and along with
the particulate mass per unit fuel consumed was used to calculate an emission rate. These
two estimates were approximately equal so a comparison was deemed useful.
The particulate mass emission rate agrees pretty well with other DISI engines. In
general they are only a fraction of the levels emitted from diesel engine sources. Here, the
PM emission is significantly higher than automotive four-stroke engines utilizing port fuel
injection (PFI). The test case with a normal operating oil-to-fuel ratio of 1:100 was also
included. This case compares well with the moped and motorcycle two-stroke applications.
The mass rate is significantly higher with normal oil flow than other DI engines.
Figure 5.32 shows a comparison to an air-assist injection sweep performed on a DI
automotive engine by Maricq et al. [19]. The mass concentration is used for comparison,
which is calculated from mass emission rate and flow rate. The absolute mass concentrations
do not agree well, as the PM levels reported by Maricq et al. span almost two orders of
magnitude. Their mass concentration is reported from a calculation using the size
107
distribution, which may account for some of the difference. The PM emission trend is very
similar, as well as the phasing of the curves. This supports the PM emission trend containing
a local minimum seen for a wide range of injection timings.
0.1
1
10
100
4070100130160190220250SOA [dBTDC]
PM [m
g/m
3 ]
Ford - 1500 RPM, 3.2 bar IMEP, 20:1 A/F, 0% EGR
Merc - 2800 RPM, ~3 bar IMEP, 15:1 A/F, ~40 % EGR
Merc - 2000 RPM, ~2 bar IMEP, 15:1 A/F, ~40 % EGR
Figure 5.32 - Comparison Showing Particulate Mass Trend with Injection Timing (Ford data
reprinted from [19])
The size distribution measurements agree fairly well to other literature containing DI
engine applications [58,55]. The particle numbers agree fairly well with similar results taken
by Graskow et al.. The particle size corresponding to peak number and the particle number
for large diameter particles shows a good comparison [58]. Size distributions reported by
Maricq et al. also show a good agreement for large diameter particles near 100 nm [55]. A
good correlation at large particle diameters is important since that is where modt of the mass
108
is contained and the SMPS used during testing measures these larger particles more
accurately than the very small ones.
5.6 Formation Mechanisms
This section includes a discussion of the mechanisms that affect PM. Global effects
that are seen in all test conditions are discussed along with their relation to each other. The
observed differences in N2-assist injection and propane fuel are presented as well as their
relation to the global mechanisms.
5.6.1 Oil consumption
Oil is the dominant source of PM for this DISI two-stroke engine. The oil tests show
that the presence of oil is the major contribution to particulate mass. Lube oil may contain
heavy hydrocarbons and trace metals, each of which can contribute to the PM. Since oil has
a dominant effect on PM from two-stroke engines with a lost oil system the type and amount
of oil used may greatly affect the PM emissions. Both the combustion of the lube oil and the
short-circuited air containing oil contribute to PM. Oil short-circuited to the exhaust with the
fresh air can create active sites for other compounds to absorb/condense onto, or it may
absorb onto existing particles. Combustion of oil can create particles with the compounds
present in the oil that will not form gaseous phase emissions, e.g. ash.
Figure 4.15 shows that the peak number density near 30 nm and the second mode
near 70 nm come from the lube oil. It is unclear, however, if either of these size particles or
a combination of both come directly from the pyrolysis (combustion) of the oil or the
109
presence of unburnt oil that is short-circuited during the scavenging process. It is also
unclear which of these methods, if either, has a larger effect for higher oil flow rates. The
second mode may arise from one of these since it doesn�t appear until the fuel-to-oil ratio
exceeds a certain level.
Another interesting trend is the PM increase as injection is advanced for the normal
and high oil ratio cases, as seen in Figure 4.16. The combustion at a set injection timing was
unaffected by the oil flow rate, so the mass increase is entirely due to the effect of oil. This is
supported since the particulate mass at advanced timings for the low oil ratio remains
constant; indicating the only difference between each injection timing was the oil flow. The
cause for the PM increase for advanced timings is unclear but is possibly due to one of two
(maybe a combination of both) effects. First, more oil could pyrolize at the elevated
temperatures of the advanced timings. The in-cylinder temperatures are believed to be higher
because the combustion is moving towards a stoichiometric burning zone A/F. This is
supported since the NOx emissions increase with SOA, shown in Figure 5.33, and the peak
pressure is higher. Second, the oil present in the exhaust could act as nucleation sites for HC
(or vice versa) and form PM. As long as enough HC and oil are present this effect may play
a role. The oil is increased with oil flow rate and the HC emissions increase with advanced
injection timings due to short-circuiting.
110
0100
200300400
500600
700800
050100150200250300SOA
NO
x [p
pm]
Low OilNorm OilHigh Oil
Figure 5.33 - NOx Emissions for 2800 RPM Oil Test
5.6.2 Temperature
Temperature appears to have a significant effect on the PM emission from the engine.
All the operating conditions likely show some dependence on in-cylinder temperatures. The
idle A/F test seems to be controlled by temperature. The higher A/F might be expected to
show a decrease in particulate mass since the burning zone mixture should be leaner. In fact
the opposite is observed for both air- and N2-assist injections, PM increases with A/F.
Higher in-cylinder temperatures, suggested by the NOx emissions shown in Figure 5.2, could
cause this increase. Examining the PM trend with N2-assist injection also supports this
conclusion. The PM might be expected to increase with N2-assist injection over air since the
local burning zone A/F is richer. Again, the opposite trend is observed, PM decreases with
N2-assist. With N2-assist the local mixture is diluted and richer than for air-assist, resulting
in lower in-cylinder temperatures. This is supported by the significantly lower NOx
111
emissions seen in Figure 5.2 and slightly higher CO levels. Here again, the higher
temperatures with air-assist injection seem to cause an increase in particulate mass.
The same trend was also seen for the stratified test condition in Figure 5.5. The
particulate mass for N2-assist injection was lower than with air-assist. Here the in-cylinder
temperatures are again believed to be lower, supported by the observed lower NOx emissions
and higher CO as seen in Figures 5.7 and 5.6, which causes a decrease in PM.
The PM from both stoichiometric test conditions was also, in part, affected by
temperature for advanced injection timings from the local particulate minimum. The local
peak particulate mass corresponds to the peak NOx emissions, suggesting peak temperature,
for both test cases. The peak temperature occurs near a stoichiometric burning A/F, so that
advancing or retarding the injection from there should decrease in-cylinder temperatures.
This is shown by a drop in NOx emissions for both cases, which corresponds to an observed
decrease in particulate mass.
The temperature effect of increased particulates appears to only affect the small
particle diameter mode, less than about 50 nm. The large mode drops to zero for the
stoichiometric conditions before the temperature has an effect on the particulate mass. This
is also supported from examination of the stratified size distributions. For retarded injections
only the large particle mode exists for both air and N2-assist conditions. At these timings the
particulate mass for N2 is the same as the air-assist case, within the uncertainty. For
advanced timings the large mode falls to zero, the small mode increases, and the particulate
mass for N2-assist is noticeably lower than for air.
From these results the temperature seems to affect the small particles. The filters
corresponding to retarded injection timings where the large mode is seen in the size
112
distribution appear opaque and black in color. Therefore the large mode particles are
believed to be EC. This cannot be stated for certain without composition information,
however, is a logical conclusion. Advanced timings producing small mode particles are
believed to be more organic carbon compounds based on the more transparent appearance of
the filter. From this assumption the temperature appears to affect the organic portion of PM
much more than it does the EC. This seems likely that the volatiles and solubles would be
more sensitive to temperature.
5.6.3 Local Burning Zone A/F
PM is expected to form in locally rich combustion zones. Therefore, N2-assist
injection was used to provide a slightly richer mixture than air-assist. N2-assist should
provide a richer mixture without changing other parameters like spray penetration or
impingement. It does, however, affect the temperature based on the burning zone A/F, as
discussed previously. A correlation between PM and CO emissions would be expected to
show the effect of local A/F on particulates. Figure 5.34 shows this correlation for the air
and N2-assist injection timings taken for the stratified and stoichiometric cases. The N2-assist
points mostly lie below and to the right of those for air-assist. This means that for an equal
CO value the particulate mass for air is higher. This suggests that even though the burning
zone A/F is richer it is not the dominant source of PM.
113
0.6
0.5
0.4
0.3
0.2
0.1
PM [g
/kg-
fuel
]
2.52.01.51.00.50.0CO [%]
2000 Lean Air 2000 Lean N2 2000 Stoich Air 2000 Stoich N2 2800 Stoich Air 2800 Stoich N2
Figure 5.34 - Comparison of PM for Air and N2-Assist Against CO
The trend of increasing PM with CO is only seen for very retarded injections. The
local burning zone A/F only appears to have a strong affect on particulate mass for very rich
mixtures. This is seen at the idle and stratified test conditions. The late injection times and
high in-cylinder pressures create a very stratified and locally rich burning zone. The
particulate mass at idle was high relative to other conditions, despite the extremely lean
overall mixtures. This was also observed in the size distribution where a local peak in the
size distribution was seen for large mode particles at all A/F. It follows that a very rich
burning zone A/F would create these large mode particles since they are believed to be EC.
The same trends are seen at the stratified condition as the injection timing is retarded.
The effect of very rich mixtures is evident in both stoichiometric test conditions. The
local peak in the particulate mass for both cases is believed to have a burning zone A/F close
to stoichiometric. A leaner A/F from advanced injection would not be expected to directly
114
affect the PM. As the injection timing is retarded the burning zone mixture becomes rich.
This has the effect of indirectly lowering the particulate mass from lower combustion
temperatures. As the injection is retarded further the burning zone reaches the sooting limit
and PM starts to form. From here, retarding the injection creates a richer mixture and
increases particulate mass.
The local burning zone A/F appears to strongly affect the large mode particles,
therefore suggesting a strong correlation to the EC portion of the PM. The effect of local
burning zone A/F is dominant for very stratified mixtures at retarded injection times where
EC may be a substantial portion of the PM.
5.6.4 Spray Impingement
Propane was used in an attempt to isolate the fuel spray impingement (fuel films)
effect of the air-assist injection system. Since propane is a gaseous fuel no liquid fuel films
would be expected. The PM could then be compared between gasoline and propane by
matching CO emissions. This is shown in Figure 5.35 for propane and air-assist injection
cases. The result for propane injection at idle condition can be seen in Figure 5.1.
The particulate mass for propane injections is significantly lower than for the air-
assist cases for most test conditions. This suggests that spray impingement and fuel films
have a significant contribution to the particulate mass, however, this difference is not
believed to be entirely due to spray impingement. The spray impingement for air-assist cases
at very advanced timings, while the piston is moving away from the spray, should be
negligible. The particulate mass for propane then should be equal to that for the air-assist
injection. This is not seen, as there is always a significant difference between the particulate
115
mass for propane and air-assist. Therefore, this difference is also believed to be affected by
fuel composition (discussed in a later section).
Also, the exception to this is the stratified injection sweep seen in Figure 5.5, where
the PM mass for propane is slightly higher than for air-assist. There is no clear explanation
for this result. It may be due to the poor running condition of the engine on propane at this
speed and load based upon COV values. This is probably not likely. It could also be due to
the high CO emissions relative to the air-assist points at equal injection timings. This can be
seen in Figure 5.35 where the particulate mass for propane falls below that for air-assist for
equal CO emission (vertical comparison).
From these results the fuel composition may be affecting the particulate mass and it is
indistinguishable from the spray impingement effect. Since the effect of fuel films cannot be
confidently quantified, it is impossible to judge how much of an effect, if any in this engine,
spray impingement has on particulate mass.
116
0.5
0.4
0.3
0.2
0.1
0.0
PM [g
/kg-
fuel
]
2.01.81.61.41.21.00.80.60.40.20.0CO [%]
2000 Lean Air 2000 Stoich Air 2800 Stoich Air 2000 Lean Propane 2000 Stoich Propane 2800 Stoich Propane
Figure 5.35 - Comparison of PM for Air-Assist and Propane Injections Against CO
5.6.5 Fuel Short-Circuiting
Fuel short-circuited into the exhaust could possibly lead to PM emissions, especially
at very early injections where significant amounts of HC are present. However, short-
circuited fuel seems to be a small effect on particulate emissions in the present results. No
significant change in particulate mass for any tested conditions occurs for advanced timings
when short-circuited fuel could be a factor. This can be seen by comparing the PM at the
most advanced injection timings with the local minimum particulate mass for either
stoichiometric sweep. The particulate mass is about the same, however, the HC
concentration present in the exhaust for advanced timings is many times higher. If HC
emissions were leading to PM emissions there would be a significant difference expected
between these two points.
117
Short-circuited fuel only seems to contribute in a couple of conditions. First, it
contributes for advanced timings with significant oil flow present. The high concentration of
HC and the presence of oil in the exhaust may combine to form particles as described in the
oil consumption section. An increase in either HC emissions (advanced timings) or oil flow
increases the amount of particulate mass, observed in Figure 4.16. The second effect may be
for advanced propane injections. The particulate mass for propane appears to increase
slightly for advanced injections for the stoichiometric conditions. The short-circuited fuel
may be a cause for this increase and it becomes noticeable here because of the low levels of
existing particles from the propane cases.
5.6.6 Fuel Composition
Fuel composition may have a significant effect on particulate mass and composition
since formation is dependent on chemical kinetics. Propane is a gaseous fuel used to isolate
the effects of fuel films, however, the fuel composition is far different from gasoline and
similar liquid fuels. This creates a problem when trying to use some metric to compare these
dissimilar fuels. Visual examination of the TEOM filters, injectors, and spark plugs suggests
a vastly different particulate composition. The propane filter was opaque and light brown in
color. The injector and spark plug had the same color deposits in a thin coating that was
difficult to remove. The EEE test fuel filter was also opaque, but black in color. The injector
and spark plug had heavy black deposits. Most of the deposits were easily removed, leaving
a thin carbon coating.
Propane has a H/C of 2.66 while the EEE test fuel has a ratio of 1.86. Another factor
is the fact that propane has less carbon-carbon bonds than gasoline fuels. Both of these
118
suggest that propane has a lower tendency to soot [59]. It follows that the sooting limit for
propane is at a higher equivalence ratio.
119
6.0 Summary
A mini-dilution tunnel was designed and integrated to sample PM emissions from a
DISI two-stroke outboard engine. The tunnel is a venturi type that utilizes pressurized air as
a driver. The venturi creates a dynamic vacuum that pulls in exhaust gas and aids mixing in
the tunnel. The DT samples a portion of the exhaust gas and dilutes it with filtered fresh air.
The sampling instruments then sample a portion of the diluted mixture.
Teflon filters, a TEOM, and SMPS were used to sample particulates. The TEOM was
used to measure particulate mass. The Teflon filters were used to compare the TEOM mass
readings to a conventional method. After a good agreement was demonstrated between
TEOM and filter mass measurements, the filters were not utilized during particulate testing.
The SMPS measures the number-based size distribution.
Tests were conducted to verify DT operation, accuracy, and consistency. The tunnel
gave good flow results and DR stability. The range of DR that could be operated was tested
to determine the consistency of the tunnel and the best operating point for particulate
sampling. The particulate mass remained constant over the entire operational range of the
tunnel, signifying good repeatability and ensuring the sampling method was not affecting the
particulate mass.
The engine was run at stratified and homogeneous conditions. Air-assist and N2-
assist injections were used to examine the effect of A/F and temperature. Propane fuel was
used to examine the effect of spray impingement and fuel composition. Oil ratios were also
tested to determine the importance of lube oil consumption on PM.
120
The repeatability of the particulate sampling instruments was tested to confirm
accuracy and consistency. Conditions were repeated at stratified and homogeneous
conditions while measuring particulate mass and size distribution. Both the TEOM and
SMPS showed good repeatability.
6.1 Conclusions
The oil contribution to particulate mass was found to be a dominant factor for this
engine. The particulate mass decreased quickly when the oil-to-fuel ratio was changed from
1:50 to 1:100, and then more slowly when at an oiling rate of 1:400, comparable to the lube
oil consumption of a four-stroke engine. The large decrease in oil flow and subsequent
slower decreases in particle mass suggests that at 1:400 the engine is nearing a plateau and
the combustion effects should be significant. The shape of the size distribution for the
various oil ratios was determined. When the oil flow was increased to 1:100 the peak
number increased and larger particles were formed. When the oil was increased further to
1:50 the number peak remained similar and a second particle mode arose near 70 nm. It
should also be noted that the oil contribution is a compound effect, so that there is not just a
constant offset based on oil flow.
For injection timing sweeps at a trapped stoichiometric A/F an interesting PM trend
was observed. The particulate mass remained fairly constant for advanced timings. As the
injection was retarded the PM increased to a local peak, then decreased to a local minimum
as the timing was retarded more. The PM then increased sharply as the timing was retarded
further, where the maximum particulate was found. The particulates appeared to change
121
mode over the injection sweep. For retarded timings a large mode exists near 60 nm. As the
timing is advanced the large mode drops while the number of small particles increases
forming a small mode below 50 nm. The large particle mode may correspond to soot,
opaque elemental carbon particles. The small mode may contain organics, volatiles, and
solubles. The observed mode change corresponded to the local minimum particulate mass
for the stoichiometric test conditions, and where the PM mass levels off for the stratified
conditions.
Temperature was found to have a significant effect on particle mass. The particulate
mass for air-assist injection was greater than for N2-assist likely due to higher in-cylinder
temperatures. Also, the local peak particulate mass for the stoichiometric sweeps is most
likely an effect of temperature. Analysis of the size distribution curves suggests that
temperature strongly affects the small mode of particles. This corresponds with advanced
timings, more homogeneous conditions, and leaner A/F.
The local burning zone A/F had a large effect on particulate mass for very rich
mixtures (retarded timings). All injection sweeps at the most retarded timings have an
increase in particulate mass. This is also where the large particle mode is seen in the size
distributions. The burning zone A/F ratio likely has a strong effect on the large particle
mode.
Generally propane injection resulted in a significantly lower particle mass. However,
there may be a significant effect of the fuel composition, so the difference between the
propane and EEE test fuel cases is not entirely due to fuel films.
122
6.2 Recommendations
After analysis of particulate mass and size distributions for various operating
conditions, certain areas of future study may provide additional useful information. The
qualitative methods used to determine changes in the particulate composition are only so
useful and by no means quantitatively correct. Testing the chemical composition of the
particulates would be useful in trying to isolate certain formation mechanisms.
Experiments that may be able to isolate the effects of spray impingement and fuel
composition on PM would also prove useful. Trying to quantitatively measure the amount of
fuel films present in the engine could provide one method. More practical studies could be
done with various fuels. Using more volatile fuels, like isooctane, to decrease the amount of
fuel films present. Using fuels of different composition, like acetylene or aromatics, which
have different chemical structures and properties. Even using a different gas-assist to inject
the fuel. Argon, for example, has comparable density as N2 but with lower specific heat, so
the temperature change could be examined.
An oil tracing experiment may provide useful information. This study showed the
effects of oil consumption on particulate mass but made no effort to determine the
contribution at low oil ratios. Using a tracer technique, like SO2, or by testing for trace
metals or other compounds present in the PM and the oil, but not in the fuel, a quantitative
contribution could be estimated.
123
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128
Appendix A
Dilution Ratio Calculations
QE
QA
Qt
QDQS
ExhExhQE
QA
Qt
QDQS
ExhExh
Subscripts: t - Exhaust sample tube E - Engine exhaust A - Dilution supply air D - Dilution tunnel S - Dilution sample tube Measured quantities:
• Mass of particulates [g] • Concentration of particulates [g/m3] • Concentration of emission species Exhaust ([ ]E = [ ]t,) Dilution tunnel ([ ]D = [ ]S) Supply air ([ ]A) • Mass flow rate of air and fuel to the engine • Sample volumetric flow rate (QS) • Dilution airflow rate • Temperature and pressure in the dilution tunnel
Assumptions:
• The molecular weights of the engine exhaust, diluted exhaust, and dilution air are approximately equal (MWE ≈ MWD ≈ MWA)
• All species are completely mixed at the entrance to the exhaust sample tube and dilution sample tube
• The wet to dry conversion factor for ambient air and dilution air is assumed to be 1 (dry air)
Calculation:
129
Since the particulate mass is measured after the dilution process it is necessary to calculate the engine out mass. Equation A.1 shows how the sample particulate mass ([g]S) relates to the engine out mass ([g]E).
[ ] [ ] [ ] ( ) ( ) [ ]SSS
E
t
DS
S
D
t
EE gSRDRg
mm
mmg
mm
mmg ⋅⋅===
&
&
&
&
&
&
&
& (A.1)
where the dilution ratio (DR) and sample ratio (SR) are defined in Equations A.2 and A.3, respectively:
t
D
mmDR&
&≡ (A.2)
S
E
mmSR&
&≡ (A.3)
To calculate the DR NOx or CO2 is used as a tracer. Since these species are measured on a volumetric basis (mole fraction), it is necessary to convert them to a mass basis (mass fraction). The mole fraction and mass fraction are calculated from Equations A.4 and A.5 respectively. The mass flow rate of an individual species is calculated from Equation A.6. Since the exhaust concentrations are measured dry the wet to dry conversion factor (K) for the exhaust gas needs to be carried through.
100
][Ki =χ (A.4) EE
iiMW
MWK
MW
MWY ][][
100][== χ (A.5) Eii mYm && ⋅= (A.6)
The mass balance is taken at the venturi where the exhaust enters the dilution tunnel. The total balance is shown in Equation A.7. The mass balance for an individual species is shown in Equation A.8. tAD mmm &&& += (A.7) ttiAAiDDi mYmYmY &&& ⋅+⋅=⋅ ,,, (A.8) By combining Equations A.7 and A.8, then rearranging, Equation A.9 can be found.
AiDi
Aiti
t
D
YYYY
mm
,,
,,
−−
=&
& (A.9)
Substitution of Equation A.5 into Equation A.9, with the assumption about equal molecular weights, gives the DR shown in Equation A.10.
DRKmm
AD
At
t
D =−
−=][][][][
&
& (A.10)
To calculate the SR, information about the engine exhaust flow rate and sample flow rate is needed. The engine exhaust flow rate is calculated from the sum of airflow and fuel flow.
130
The sample volumetric flow rate must be converted to a mass flow rate by using the density of air at the conditions in the dilution tunnel. To calculate engine out particulate concentration ([g/m3]E) only the DR is needed. This is because the concentration of particulates (or emissions species) does not change entering the exhaust sample tube ([g/m3]E = [g/m3]t) or tunnel sample tube ([g/m3]S = [g/m3]D). This is shown in Equation A.11.
SSt
DD
t
DtE mgDRmg
mmmg
mmmgmg ]/[]/[]/[]/[]/[ 33333 ⋅====
&
&
&
& (A.11)
131
Appendix B Mass-Based Emissions Calculations
Measured quantities: • Concentration of emission species on a dry basis ([CO2]dry, [CO]dry, [HC]dry, [NOx]dry, [O2]dry) • Mass flow rate of fuel to the engine ( )fm& • Brake power (BHP) Assumptions: • MWA = 28.97 • MWNO2 = 46 Subscripts: f Fuel air Air exh Exhaust dry Dry basis Calculation: It is very useful to find the mass flow rate of the emission species. This can be calculated from the volumetric species concentration and knowledge of the fuel flow rate. Some necessary quantities that are not measured are shown in Equations B.1 �B.3. For all of the following calculations the HC emission needs to be on a C1 basis. The FID analyzer measures HC on a C3 basis so that all of these numbers are multiplied by 3 before being used in these equations. Equation B.1 calculates the total dry moles in the exhaust.
[ ] [ ] [ ] drydrydry
dryexhHCCOCO
n++
=2
,100 (B.1)
Equation B.2 estimates the H2 concentration in the exhaust from the CO concentration. Here N is the H/C ratio of the fuel. 2[ ] 0.25 [ ]dry dryH N CO= (B.2) Equation B.3 calculates the total number of moles of air.
[ ] [ ] [ ] [ ] [ ] [ ]{ } NNOOHCNHCOCOn
n drydrydrydrydrydrydryexh
air 25.05.025.05.05.0100
222, +++−−+=
(B.3)
132
These quantities are used to calculate the brake specific mass-based emissions of CO, HC, and NOx shown in Equations B.4, B.5, and B.6, respectively. The numerator in each of the equations is the mass flow rate of each emission species. The emissions index was calculated from the mass flow rate of emission species in g/hr divided by the mass flow rate of fuel in kg/hr. This results in a number normalized by fuel flow with units of g of emissions species per kg fuel.
,
[ ] 28.01100
dryexh dry f
f
COn m
MWBSCO
BHP
=
&
(B.4)
,
[ ]100
dryexh dry f
HCn m
BSHCBHP
=&
(B.5)
,
[ ]100
xNOX dryexh dry f
fX
MWNOn m
MWBSNO
BHP
=
&
(B.6)
The exhaust A/F, shown in Equation B.7, can also be calculated based on exhaust species concentration. This is on a dry basis because the humidity of the intake air was not measured.
( ) ,4.76/ air air dry
dryf
n MWA F
MW= (B.7)
133
Appendix C Particulate Sampling Results
Appendix C.1 Stratified Oil Test Condition 2000 RPM, 10 N-m, Delivered A/F = 30 Appendix C.2 Stoichiometric Oil Test Condition 2800 RPM, 16 N-m, Delivered A/F = 15 Appendix C.3 Idle Test Condition 800 RPM, 5 N-m Appendix C.4 Stratified Test Condition 2000 RPM, 10 N-m, Delivered A/F = 30 Appendix C.5 Low Speed Stoichiometric Oil Test Condition 2000 RPM, 10 N-m, Delivered A/F = 22 Appendix C.6 Medium Speed Stoichiometric Test Condition 2800 RPM, 16 N-m, Delivered A/F = 23
134
Appendix C.1 - Stratified Oil Test Condition
Description Oil test, 2000 RPM,~10 N-m, A/F=30, air injection, new TEOM filterof Test: Low oil, 1:400 Norm oil, 1:100 high Oil, 1:50
Date 07/24/03 Amb Temp 23.8 oC Am Press 99.8 kPa
Run Number 2 1 3 5 6 4 9 7 8
Hi-Techniques File La69 La72 La78 Na69 Na72 Na78 Ha69 Ha72 Ha78
TEOM File La69 La72A La78D Na69A Na72A Na78 Ha69 Ha72 Ha78
SMPS File,2000_oil_test 2 1 3 5 6 4 9 7 8
Spark Plug Type ChampionC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 264.9 265.0 264.9 265.0 265.0 265.0 265.0 265.0 265.0
Orifice Size # 4 4 4 4 4 4 4 4 4
Intake Air Flowrate kg/hr 21.59 21.59 21.59 21.59 21.59 21.59 21.59 21.59 21.59
Fuel Flowrate kg/hr 0.780 0.780 0.760 0.732 0.732 0.732 0.735 0.735 0.735
Measured A/F Ratio 27.7 27.7 28.4 29.5 29.5 29.5 29.4 29.4 29.4
Throttle Position % 24.9 24.9 24.8 24.9 24.9 24.9 25.1 25.1 25.1
Inlet Surge Tank Press kPa 100.0 100.1 100.1 99.9 100.0 100.1 100.0 99.9 100.0
Exh Surge Tank Press kPa 100.0 100.1 100.1 99.9 100.0 100.1 100.0 99.9 100.0
Oil Flowrate 0.182 0.180 0.182 0.758 0.758 0.758 1.517 1.518 1.518
SOA oBTDC 69 72 78 69 72 78 69 72 78
EOA oBTDC 31 34 40 31 34 40 31 34 40
Fuel Pressure psi 95 95 95 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00
Spark Timing oBTDC 40 40 40 40 40 40 40 40 40
Supply Pressure kPa 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2O gauge -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10 10 10 10
TEOM Pressure Drop inHg 3.0 3.0 3.5 4.0 4.0 4.0 6.0 5.0 5.0
Dilution Ratio 18.6 21.2 21.6 19.8 20.9 21.6 20.2 21.7 22.7
HC ppm 595.0 519.0 451.0 505.0 468.0 450.0 532.0 396.0 418.0
NOX (dry) ppm 301.0 464.0 756.0 363.0 515.0 799.0 400.0 582.0 857.0
CO (dry) % 0.250 0.189 0.149 0.200 0.156 0.132 0.221 0.170 0.138
CO2 (dry) % 7.365 7.514 7.551 7.412 7.491 7.541 7.497 7.582 7.619
O2 (dry) % 10.301 10.144 10.150 10.277 10.216 10.124 10.173 10.069 10.057
DT CO2 (dry) % .349 / .334 .363 / .340 .352 / .349 .337 / .333 .346 / .338 .358 / .349 .341 / .344 .348 / .336 .348 / .339
DT NOX (dry) ppm 14.5 / 15.7 19.9 / 21.0 32.1 / 33.2 16.9 / 17.3 22.1 / 24.0 33.6 / 35.5 17.2 / 19.8 25.1 / 25.1 35.6 / 35.0
PM g/hr 0.227 0.218 0.224 0.391 0.443 0.504 1.161 1.116 1.179
BSFC kg/kW-hr 0.367 0.398 0.392 0.368 0.368 0.377 0.359 0.360 0.369
BSCO g/kW-hr 23.8 19.3 15.1 19.1 14.9 12.9 20.3 15.7 13.1
BSNO g/kW-hr 4.7 7.8 12.5 5.7 8.1 12.8 6.0 8.8 13.3
BSHC g/kW-hr 8.4 7.9 6.8 7.2 6.6 6.5 7.3 5.4 5.9
BS(HC+NOx) g/kW-hr 13.1 15.7 19.3 12.9 14.7 19.3 13.3 14.3 19.2
EICO 64.8 48.6 38.4 52.0 40.5 34.2 56.7 43.6 35.4
EINOx 12.8 19.6 32.0 15.5 21.9 34.0 16.9 24.5 36.1
EIHC 22.9 19.8 17.3 19.5 18.0 17.3 20.3 15.1 15.9
AFR_dry 27.18 26.98 27.12 27.30 27.25 27.15 26.95 26.96 26.96
AFR_Carbon 27.69 27.49 27.58 27.82 27.75 27.68 27.42 27.46 27.43
AFR_Oxygen 27.29 27.09 27.22 27.41 27.35 27.25 27.06 27.07 27.06
AFR_Spindt 27.17 26.95 27.07 27.28 27.21 27.09 26.93 26.92 26.90
AFR_Bart 27.18 26.98 27.12 27.30 27.25 27.15 26.95 26.96 26.96
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 444 445 459 445 454 452 452 457 452
Exhaust Gas oC 299 288 304 306 306 307 307 308 308
Emissions Sample oC 109 98 104 111 113 111 109 103 111
Engine Load N-m 9.38 9.34 9.28 9.53 9.51 9.28 9.77 9.74 9.53
Engine Power kW 1.96 1.96 1.94 1.99 1.99 1.94 2.05 2.04 1.99
IMEP kPa 216 229 226 213 223 218 209 218 215
COV of IMEP % 4.60 4.00 2.70 5.10 4.00 3.50 4.00 4.80 3.40
Peak Cyl. Pres. (PCP) MPa 2.51 2.71 2.84 2.65 2.80 2.92 2.74 2.89 2.99
Location of PCP oATDC 7 6 4 7 5 3 7 4 3
135
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 710
2 3 4 5 6 7100
2 3
Diameter [nm]
Low SOA69 Low SOA72 Low SOA78 Norm SOA69 Norm SOA72 Norm SOA78 High SOA69 High SOA72 HighSOA78
136
Appendix C.2 - Stoichiometric Oil Test Condition
Description 2800 RPM, 50% load, ~15 N-m, oil contribution test, cleaned out crankcase and ports, new spark plug, A/F=15 (lean side)of Test: L=low oil flow (1:400), N=normal oil flow (1:100), H=high oil flow (1:50)
Date 06/18/03 Amb Temp 24.7 oC Amb Press 99.1 kPa
Run Number 3 1 2 4 5 9 10 7 8 6
Hi-Techniques File Loil90 Loil100 Loil120 Loil180 Loil240 Noil90 Noil100 Noil120 Noil180 Noil240
TEOM File Loil90 Loil100 Loil120 Loil180 Loil240 Noil90 Noil100 Noil120 Noil180 Noil240
SMPS File, 2800_oil 4 2* 3* 6 8 13 14 11 12 9
Spark Plug Type ChampionC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2800 2800 2800 2800 2800 2800 2800 2800 2800 2800
Orifice Upstream Press kPa 320.3 320.4 320.4 320.3 320.3 320.0 320.0 320.2 320.1 320.2
Orifice Size # 4 4 4 4 4 4 4 4 4 4
Intake Air Flowrate kg/hr 25.94 25.95 25.95 25.94 25.94 25.92 25.92 25.93 25.92 25.93
Fuel Flowrate kg/hr 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700
Measured A/F Ratio 15.3 15.3 15.3 15.3 15.3 15.2 15.2 15.3 15.2 15.3
Throttle Position % 27.0 27.0 27.0 27.0 27.0 27.0 27.0 27.0 27.0 27.0
Inlet Surge Tank Press kPa 99.4 99.5 99.4 99.4 99.3 99.2 99.1 99.3 99.3 99.3
Exh Surge Tank Press kPa 99.4 99.5 99.4 99.4 99.3 99.2 99.1 99.3 99.3 99.3
Oil Flowrate 0.391 0.392 0.394 0.391 0.390 1.702 1.702 1.703 1.703 1.703
SOA oBTDC 90 100 120 180 240 90 100 120 180 240
EOA oBTDC 29 34 54 114 174 29 34 54 114 174
Fuel Pressure psi 95 95 95 95 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30
Spark Timing oBTDC 37 37 37 37 37 37 37 37 37 37
Supply Pressure kPa 35 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2Og -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50 50
DT test time min 15 15 15 15 15 15 15 15 15 15
TEOM Pressure Drop inHg 6.5 4.0 6.0 8.0 8.5 7.0 9.0 3.0 5.0 3.0
Dilution Ratio 23.9 23.9 22.5 21.7 23.9 23.6 23.8 22.2 22.2 23.9
HC ppm 749.0 951.0 960.0 2515.0 6412.0 791.0 977.0 1015.0 2705.0 6315.0
NOX (dry) ppm 103.0 180.0 299.0 320.0 628.0 110.0 230.0 314.0 375.0 694.0
CO (dry) % 3.494 3.358 2.970 2.113 0.129 3.591 3.356 3.142 1.997 0.155
CO2 (dry) % 9.376 9.614 10.064 10.737 11.216 9.298 9.553 9.841 10.825 11.242
O2 (dry) % 4.392 4.362 4.138 4.129 5.028 4.317 4.284 4.178 4.094 4.958
DT CO2 (dry) % .385 / .385 0.393 .416 / .416 .437 / .441 .448 / .450 .386 / .385 .389 / .394 .401 / .406 .439 / .444 .452 / .452
DT NOX (dry) ppm 4.7 / 5.1 8.2 11.5 / 12.4 13.2 / 13.4 23.8 / 23.7 5.2 / 5.4 9.6 / 9.6 12.8 / 12.8 15.2 / 15.2 25.7 / 26.9
PM g/hr 0.80 0.62 0.41 0.43 0.36 1.05 0.73 0.58 0.91 1.16
BSFC kg/kW-hr 0.384 0.359 0.346 0.347 0.359 0.373 0.358 0.348 0.342 0.353
BSCO g/kW-hr 206.9 183.5 155.6 108.9 7.0 206.0 183.8 166.1 101.2 8.3
BSNO g/kW-hr 1.0 1.6 2.6 2.7 5.6 1.0 2.1 2.7 3.1 6.1
BSHC g/kW-hr 6.6 7.7 7.5 19.2 52.0 6.7 7.9 8.0 20.4 50.4
BS(HC+NOx) g/kW-hr 7.6 9.3 10.0 21.9 57.6 7.8 10.0 10.7 23.5 56.5
EICO 539.0 511.7 450.4 313.8 19.6 552.7 513.5 477.7 295.9 23.6
EINOx 2.6 4.5 7.4 7.8 15.7 2.8 5.8 7.8 9.1 17.3
EIHC 17.2 21.5 21.6 55.5 145.0 18.1 22.2 22.9 59.5 142.5
AFR_dry 15.72 15.70 15.74 15.67 16.19 15.59 15.64 15.66 15.64 16.15
AFR_Carbon 16.37 16.20 16.19 15.95 16.47 16.32 16.26 16.20 15.92 16.44
AFR_Oxygen 15.98 15.95 15.97 15.86 16.24 15.85 15.89 15.90 15.83 16.21
AFR_Spindt 15.88 15.84 15.87 15.76 16.15 15.75 15.78 15.79 15.73 16.11
AFR_Bart 15.72 15.70 15.74 15.67 16.19 15.59 15.64 15.66 15.64 16.15
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 601 580 592 606 597 609 593 591 611 597
Exhaust Gas oC 444 415 428 445 440 445 438 433 441 435
Emissions Sample oC 195 88 184 186 189 165 172 169 165 168
Engine Load N-m 15.12 16.18 16.78 16.71 16.16 15.56 16.22 16.69 16.97 16.42
Engine Power kW 4.43 4.74 4.92 4.90 4.74 4.56 4.75 4.89 4.97 4.81
IMEP kPa 284 312 312 318 311 296 309 313 322 317
COV of IMEP % 5.40 2.81 2.72 2.10 3.00 4.30 3.10 3.30 1.80 2.80
Peak Cyl. Pres. (PCP) MPa 2.39 2.88 2.95 3.04 2.84 2.45 2.91 2.97 3.07 2.93
Location of PCP oATDC 14 10 9 9 11 14 9 9 9 11
137
Description 2800 RPM, 50% load, ~15 N-m, oil contribution test, cleaned out crankcase and ports, new spark plug, A/F=15 (lean side)of Test: L=low oil flow (1:400), N=normal oil flow (1:100), H=high oil flow (1:50)
Date 06/18/03 6/28/03, T=24.6 deg C, P=99.2 kPa
Run Number 12 11 14 13 15
Hi-Techniques File Hoil90 Hoil100 Hoil120 Hoil180 Hoil240 loil90r Loil100r loil120r loil180r loil240r
TEOM File Hoil90 Hoil100 Hoil120 Hoil180 Hoil240 Loil90r2 Loil100r loil120r loil1802 loil2404
SMPS File, 2800_oil 16 15 18 17 19 23 20 22 21 24
Spark Plug Type ChampionC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2800 2800 2800 2800 2800 2800 2800 2800 2800 2800
Orifice Upstream Press kPa 320.4 320.4 320.4 320.4 320.4 320.5 320.6 320.5 320.5 320.5
Orifice Size # 4 4 4 4 4 4 4 4 4 4
Intake Air Flowrate kg/hr 25.95 25.95 25.95 25.95 25.95 25.96 25.96 25.96 25.96 25.96
Fuel Flowrate kg/hr 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700 1.700
Measured A/F Ratio 15.3 15.3 15.3 15.3 15.3 15.3 15.3 15.3 15.3 15.3
Throttle Position % 27.3 27.1 27.3 27.3 27.3 27.0 26.9 26.9 26.9 27.0
Inlet Surge Tank Press kPa 99.2 99.2 99.1 99.2 99.2 99.4 99.4 99.4 99.4 99.4
Exh Surge Tank Press kPa 99.2 99.2 99.1 99.2 99.2 99.4 99.4 99.4 99.4 99.4
Oil Flowrate 3.402 3.402 3.402 3.403 3.402 0.394 0.394 0.394 0.392 0.395
SOA oBTDC 90 100 120 180 240 90 100 120 180 240
EOA oBTDC 29 34 54 114 174 29 34 54 114 174
Fuel Pressure psi 95 95 95 95 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30
Spark Timing oBTDC 37 37 37 37 37 37 37 37 37 37
Supply Pressure kPa 35 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2Og -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50 50
DT test time min 15 15 15 15 15 15 15 15 15 15
TEOM Pressure Drop inHg 5.0 3.0 10.0 8.0 3.0 3.0 4.0 9.0 8.5 8.0
Dilution Ratio 23.2 23.4 22.5 22.1 23.2 24.1 22.4 22.5 20.8 23.8
HC ppm 1005.0 1051.0 1176.0 2665.0 6580.0 690.0 930.0 2850.0 6420.0
NOX (dry) ppm 109.0 228.0 319.0 326.0 685.0 109.0 205.0 306.0 323.0 648.0
CO (dry) % 3.714 3.399 3.170 2.375 0.146 3.586 3.402 3.072 2.042 0.140
CO2 (dry) % 9.122 9.563 9.869 10.558 11.290 9.482 9.645 10.114 10.899 11.349
O2 (dry) % 4.369 4.230 4.078 4.043 4.856 4.106 4.084 3.905 3.933 4.840
DT CO2 (dry) % .384 / .387 .401 / .397 .416 / .413 .427 / .442 .465 / .462 .386 / .385 .420 / .417 .417 / .418 .462 / .450 .460 / .463
DT NOX (dry) ppm 5.3 / 5.9 9.6 / 9.8 13.3 / 12.3 12.7 / 14.0 26.9 / 26.6 4.3 / 5.2 8.8 / 8.6 11.8 / 12.7 14.0 / 14.0 24.8 / 24.4
PM g/hr 1.34 1.11 1.52 2.04 2.26 1.17 0.55 0.47 0.44 0.49
BSFC kg/kW-hr 0.380 0.355 0.343 0.342 0.351 0.389 0.362 0.353 0.351 0.362
BSCO g/kW-hr 217.2 183.5 163.9 119.5 7.7 212.3 186.9 160.9 105.0 7.6
BSNO g/kW-hr 1.0 2.0 2.7 2.7 6.0 1.1 1.9 2.6 2.7 5.8
BSHC g/kW-hr 8.7 8.4 9.0 19.9 51.7 6.1 7.6 11.7 21.8 52.0
BS(HC+NOx) g/kW-hr 9.8 10.5 11.7 22.6 57.7 7.1 9.4 14.3 24.5 57.9
EICO 571.1 517.2 478.2 349.4 22.0 545.7 515.7 455.1 299.0 21.1
EINOx 2.8 5.7 7.9 7.9 17.0 2.7 5.1 7.4 7.8 16.0
EIHC 22.9 23.7 26.3 58.2 147.2 15.6 20.9 33.0 62.0 143.6
AFR_dry 15.49 15.54 15.51 15.41 15.98 15.46 15.47 15.31 15.44 16.02
AFR_Carbon 16.27 16.16 16.07 15.76 16.29 16.15 16.11 15.80 15.74 16.29
AFR_Oxygen 15.76 15.79 15.75 15.61 16.04 15.72 15.72 15.55 15.63 16.08
AFR_Spindt 15.65 15.69 15.64 15.51 15.94 15.62 15.61 15.44 15.53 15.99
AFR_Bart 15.49 15.54 15.51 15.41 15.98 15.46 15.47 15.31 15.44 16.02
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 600 590 588 604 596 604 582 588 612 602
Exhaust Gas oC 438 431 436 440 437 446 415 436 444 441
Emissions Sample oC 171 161 170 171 166 176 192 178 166 167
Engine Load N-m 15.26 16.34 16.92 16.97 16.51 14.90 16.00 16.42 16.53 16.01
Engine Power kW 4.47 4.79 4.96 4.97 4.84 4.37 4.69 4.81 4.84 4.69
IMEP kPa 290 307 322 325 316 293 317 319 329 321
COV of IMEP % 6.10 2.90 2.80 1.90 2.40 3.40 3.00 2.50 2.40 2.80
Peak Cyl. Pres. (PCP) MPa 2.43 2.90 3.02 3.12 2.93 2.48 2.94 2.98 3.02 2.84
Location of PCP oATDC 14 10 8 9 11 13 9 8 9 12
138
139
Appendix C.3 - Idle Test Condition
Description Idle test, 800 RPM, very light load, AFR sweep, fuel=EEEof Test:
Date 07/29/03 Ambient Temp 24.0 oC Ambient Press 99.6 kPa
Run Number 1 6 3 4 2 5
Hi-Techniques File I40a I40n I45a I45n I50a I50n
TEOM File I40a1 I40n2 I45a I45n I50a I50n
SMPS File, Idle 1 6 3 4 2 5
Spark Plug Type Champion RC10ECC, 12 mm RC10ECC, 12 mm RC10ECC, 12 mm RC10ECC, 12 mm RC10ECC, 12 mm RC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50 50
Engine Speed RPM 800 800 800 800 800 800
Orifice Upstream Press kPa 494.6 494.8 310.0 310.0 372.3 371.4
Orifice Size # 2 2 3 3 3 3
Intake Air Flowrate kg/hr 9.59 9.59 12.01 12.01 14.40 14.36
Fuel Flowrate kg/hr 0.250 0.250 0.250 0.250 0.250 0.250
Measured A/F Ratio 38.4 38.4 48.0 48.0 57.6 57.5
Throttle Position % 14.0 14.0 19.1 19.1 25.7 24.9
Inlet Surge Tank Press kPa 99.6 99.7 99.5 99.6 99.5 99.5
Exh Surge Tank Press kPa 99.6 99.7 99.5 99.6 99.5 99.5
Oil Flowrate 0.090 0.087 0.088 0.089 0.088 0.088
SOA oBTDC 46 46 46 46 46 46
EOA oBTDC 28 28 28 28 28 28
Fuel Pressure psi 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 5.00 5.00 5.00 5.00 5.00 5.00
Spark Timing oBTDC 33 33 33 33 33 33
Supply Pressure kPa 35 35 35 35 35 35
DT Back Pressure inH2O gauge -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10
TEOM Pressure Drop inHg 3.0 6.0 4.5 5.0 4.0 5.5
Dilution Ratio 23.6 23.0 20.9 19.4 20.8 21.0
HC ppm 1312.0 2177.0 1232.0 1560.0 1174.0 1431.0
NOX (dry) ppm 200.0 95.0 331.0 168.0 357.0 200.0
CO (dry) % 0.199 0.234 0.174 0.208 0.161 0.187
CO2 (dry) % 5.401 5.073 4.141 3.983 3.359 3.230
O2 (dry) % 13.028 13.158 14.793 14.751 15.870 15.901
DT CO2 (dry) % .250 / .241 .243 / .236 .208 / .211 .202 / .196 .183 / .180 .171 / .162
DT NOX (dry) ppm 8.2 / 7.9 4.9 / 5.7 15.0 / 15.4 8.2 / 8.5 16.4 / 16.8 9.3 / 9.2
PM g/hr 0.299 0.156 0.358 0.249 0.480 0.295
BSFC kg/kW-hr 0.510 0.581 0.595 0.556 0.641 0.641
BSCO g/kW-hr 34.2 46.1 44.7 50.1 53.8 63.0
BSNO g/kW-hr 5.7 3.1 14.0 6.6 19.6 11.1
BSHC g/kW-hr 33.5 63.7 47.0 55.8 58.3 71.5
BS(HC+NOx) g/kW-hr 39.2 66.8 60.9 62.5 77.9 82.6
EICO 67.1 79.3 75.0 90.2 84.0 98.2
EINOx 11.1 5.3 23.5 12.0 30.6 17.3
EIHC 65.7 109.6 78.9 100.5 91.0 111.6
AFR_dry 35.02 34.67 44.61 44.30 53.77 53.75
AFR_Carbon 35.68 35.79 45.39 45.59 54.72 55.04
AFR_Oxygen 35.16 34.81 44.78 44.48 53.97 53.96
AFR_Spindt 35.01 34.67 44.59 44.31 53.74 53.75
AFR_Bart 35.02 34.67 44.61 44.30 53.77 53.75
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 235 236 225 222 211 206
Exhaust Gas oC 148 141 145 145 146 144
Emissions Sample oC 71 67 66 65 66 64
Engine Load N-m 5.81 5.16 4.96 5.42 4.64 4.64
Engine Power kW 0.49 0.43 0.42 0.45 0.39 0.39
IMEP kPa 170 160 168 163 163 160
COV of IMEP % 8.60 23.50 12.50 10.30 11.50 12.50
Peak Cyl. Pres. (PCP) MPa 2.29 2.09 2.36 2.24 2.41 2.25
Location of PCP oATDC 6 7 5 6 4 5
140
Description Idle test, 800 RPM, very light loadof Test: AFR sweep, propane, new spark plug
Date 07/31/03 Ambient Temp 74.9 oC Ambient Press 98.6 kPa
Run Number 1 2 3
Hi-Techniques File pi40 pi50 pi60
TEOM File pi40 pi50A pi60A
SMPS File, 2000_propane_stoich 1 2 3
Spark Plug Type Champion RC10ECC, 12 mm RC10ECC, 12 mm RC10ECC, 12 mm
Coolant Temp oC 50 50 50
Engine Speed RPM 800 800 800
Orifice Upstream Press kPa 281.8 348.7 419.7
Orifice Size # 3 3 3
Intake Air Flowrate kg/hr 10.93 13.49 16.21
Fuel Flowrate kg/hr 0.270 0.262 0.256
Measured A/F Ratio 40.4 51.5 63.3
Throttle Position % 16.6 21.8 31.5
Inlet Surge Tank Press kPa 99.3 99.7 99.4
Exh Surge Tank Press kPa 99.3 99.7 99.4
Oil Flowrate 0.082 0.083 0.082
SOI oBTDC 47 47 47
EOI oBTDC 36 36 36
Fuel Pressure psi 80 80 80
Spark Timing oBTDC 28.00 28.00 28.00
Supply Pressure kPa 35 35 35
DT Back Pressure inH2O gauge -4 -4 -4
DT temperature oC 50.0 50.0 50.0
DT test time min 10 10 10
TEOM Pressure Drop inHg 6 6 6
Dilution Ratio 21.2 22.2 22.2
HC ppm 487.0 393.0 359.0
NOX (dry) ppm 168.0 259.0 291.0
CO (dry) % 0.2 0.1 0.1
CO2 (dry) % 4.608 3.608 2.909
O2 (dry) % 13.370 14.962 16.019
DT CO2 (dry) % .236 / .220 .198 / .181 .172 / .165
DT NOX (dry) ppm 9.0 / 7.6 11.4 / 11.2 12.9 / 12.6
PM g/hr 0.0 0.1 0.1
BSFC kg/kW-hr 0.529 0.535 0.557
BSCO g/kW-hr 36.690 32.893 34.104
BSNO g/kW-hr 5.7 11.3 16.3
BSHC g/kW-hr 15.7 16.4 19.2
BS(HC+NOx) g/kW-hr 21.3 27.7 35.5
EICO 69.3 61.5 61.3
EINOx 10.7 21.1 29.3
EIHC 29.6 30.6 34.6
AFR_dry 40.4 51.5 63.3
AFR_Carbon 41.24 52.52 64.58
AFR_Oxygen 40.59 51.72 63.49
AFR_Spindt 40.42 51.50 63.23
AFR_Bart 40.42 51.52 63.26
Exh. Manifold Vac. in H2O 0.00 0.00 0.00
Exhuast Manifold oC 247.0 227.0 206.0
Exhaust Gas oC 161 156 151
Emissions Sample oC 89 78 72
Engine Load N-m 6 6 6
Engine Power kW 0.51 0.49 0.46
IMEP kPa 187.00 184.00 181.00
COV of IMEP % 3 3 3
Peak Cyl. Pres. (PCP) MPa 2.38 2.44 2.46
Location of PCP oATDC 6.00 5.00 4.00
141
0
500
1000
1500
2000
2500
35 40 45 50 55 60 65A/F
HC
[ppm
]
AirN2Prop
050
100150200250300350400
35 40 45 50 55 60 65A/F
NO
x [p
pm]
Air-AssistN2-AssistPropane
0.00
0.05
0.10
0.15
0.20
0.25
35 40 45 50 55 60 65A/F
CO
[%]
AirN2Prop
2.02.53.03.54.04.55.05.56.0
35 40 45 50 55 60 65A/F
CO
2 [%
]
AirN2Prop
12.012.513.013.514.014.515.015.516.016.5
35 40 45 50 55 60 65A/F
O2
[%]
AirN2Prop
142
4x106
3
2
1
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 7 810
2 3 4 5 6 7 8100
2 3
Particle Diameter [nm]
A/F=40 Air A/F=50 Air A/F=60 Air A/F=40 N2 A/F=50 N2 A/F=60 N2 A/F=40 Propane A/F=50 Propane A/F=60 Propane
800x103
600
400
200
0
Num
ber C
once
ntra
tion
[#/c
m 3]
4 5 6 7 8 9100
2 3
Particle Diameter [nm]
A/F=40 Air A/F=50 Air A/F=60 Air
A/F=40 N2 A/F=50 N2 A/F=60 N2
A/F=40 Propane A/F=50 Propane A/F=60 Propane
143
Appendix C.4 - Stratified Test Condition
Description 2000 RPM, 10 N-m, air injection sweep, AFR=30, fuel=EEEof Test: taken at same time as N2, orbital injector, low oil flow (1:400)
Date 06/29/03 Ambient Temp 23.9 oC Ambient Press 99.8 kPa
Run Number 5 4 1 6 9 11
Hi-Techniques File Lair67 Lair69 Lair72 Lair75 Lair78 Lair81
TEOM File Lair67 Lair69 Lair72 Lair75 Lair78 Lair81
SMPS File, 2000_25_30lownew 5 4 1 6 9 11
Spark Plug Type ChampionRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 265.6 265.6 265.7 265.5 265.6 265.6
Orifice Size # 4 4 4 4 4 4
Intake Air Flowrate kg/hr 21.64 21.64 21.65 21.63 21.64 21.64
Fuel Flowrate kg/hr 0.800 0.800 0.800 0.800 0.800 0.800
Measured A/F Ratio 27.1 27.1 27.1 27.0 27.1 27.1
Throttle Position % 24.6 24.6 24.6 24.6 24.6 24.6
Inlet Surge Tank Press kPa 100.0 100.0 100.0 100.0 100.1 100.0
Exh Surge Tank Press kPa 100.0 100.0 100.0 100.0 100.1 100.0
Oil Flowrate 0.170 0.170 0.171 0.170 0.171 0.170
SOA oBTDC 67 69 72 75 78 81
EOA oBTDC 29 31 34 37 40 43
Fuel Pressure psi 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 6.00 6.00 6.00 6.00 6.00 6.00
Spark Timing oBTDC 40 40 40 40 40 40
Supply Pressure kPa 35 35 35 35 35 35
DT Back Pressure inH2O gauge -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50
DT test time min 10 12 12 10 10 12
TEOM Pressure Drop inHg 4.0 3.0 3.0 4.0 4.5 5.0
Dilution Ratio NOx 22.7 23.5 25.3 24.2 25.1 25.6
HC ppm 751 542 481 493 522 585
NOX (dry) ppm 297 372 486 617 710 715
CO (dry) % 0.240 0.191 0.145 0.139 0.124 0.122
CO2 (dry) % 7.312 9.235? 7.550 7.532 7.521 7.514
O2 (dry) % 10.431 10.307 10.183 10.225 10.259 10.272
DT CO2 (dry) % .318 / .308 .319 / .323 .321 / .324 .319 / .314 .330 / .315 .319 / .316
DT NOX (dry) ppm 12.5 / 12.0 14.4 / 15.2 17.6 / 18.3 24.0 / 23.6 26.3 / 26.6 26.1 / 26.0
PM g/hr 0.308 0.248 0.265 0.139 0.126 0.124
BSFC kg/kW-hr 0.402 0.388 0.394 0.402 0.400 0.386
BSCO g/kW-hr 25.1 19.6 14.7 14.4 12.8 12.2
BSNO g/kW-hr 5.1 6.3 8.1 10.5 12.1 11.7
BSHC g/kW-hr 11.6 8.3 7.3 7.6 8.0 8.7
BS(HC+NOx) g/kW-hr 16.7 14.5 15.4 18.1 20.1 20.4
BSPM g/kW-hr 0.154 0.120 0.131 0.070 0.063 0.060
EICO 62.3 50.4 37.4 35.9 32.1 31.6
EINOx 12.7 16.1 20.6 26.2 30.2 30.4
EIHC 29.0 21.2 18.4 18.9 20.1 22.5
AFR_dry 27.29 27.51 27.13 27.22 27.30 27.26
AFR_Carbon 27.74 28.20 27.57 27.64 27.70 27.66
AFR_Oxygen 27.40 27.61 27.23 27.32 27.39 27.36
AFR_Spindt 27.28 27.48 27.09 27.18 27.24 27.21
AFR_Bart 27.29 27.51 27.13 27.22 27.30 27.26
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 446 448 446 449 447 441
Exhaust Gas oC 306 307 307 308 307 305
Emissions Sample oC 122 118 116 121 114 115
Engine Load N-m 9.52 9.83 9.72 9.53 9.55 9.89
Engine Power kW 1.99 2.06 2.03 1.99 2.00 2.07
IMEP kPa 221 220 213 218 216 230
COV of IMEP % 5.60 4.10 4.50 5.00 2.50 2.70
Peak Cyl. Pres. (PCP) MPa 2.51 2.61 2.73 2.80 2.82 2.80
Location of PCP oATDC 7 7 6 4 4 5
144
Description 2000 RPM, 25% load, N2 injection sweep, AFR=30, fuel=EEEof Test: taken at same time as air, orbital injector, low oil flow (1:400)
Date 06/29/03 Ambient Temp 23.9 oC Ambient Press 99.8 kPa
Run Number 3 2 7 8 10
Hi-Techniques File LN69 LN72 LN75 LN78 LN81
TEOM File LN69 LN72 LN75 LN78 LN81
SMPS File, 2000_25_30lownew 3 2 7 8 10
Spark Plug Type ChampionRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 265.6 265.6 265.6 265.6 265.6
Orifice Size # 4 4 4 4 4
Intake Air Flowrate kg/hr 21.64 21.64 21.64 21.64 21.64
Fuel Flowrate kg/hr 0.800 0.800 0.800 0.800 0.800
Measured A/F Ratio 27.1 27.1 27.1 27.1 27.1
Throttle Position % 24.6 24.6 24.6 24.6 24.6
Inlet Surge Tank Press kPa 100.1 100.0 100.0 100.1 100.1
Exh Surge Tank Press kPa 100.1 100.0 100.0 100.1 100.1
Oil Flowrate 0.170 0.170 0.170 0.169 0.170
SON oBTDC 69 72 75 78 81
EON oBTDC 31 34 37 40 43
Fuel Pressure psi 95 95 95 95 95
Fuel per Cycle (FPC) mg 6.00 6.00 6.00 6.00 6.00
Spark Timing oBTDC 40 40 40 40 40
Supply Pressure kPa 35 35 35 35 35
DT Back Pressure inH2O gauge -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50
DT test time min 10 10 10 10 10
TEOM Pressure Drop inHg 3.0 3.0 4.0 4.5 5.0
Dilution Ratio CO2 24.0 24.3 24.3 24.4 23.8
HC ppm 1115 716 628 635 796
NOX (dry) ppm 140 157 187 199 207
CO (dry) % 0.246 0.197 0.161 0.135 0.138
CO2 (dry) % 7.197 7.385 7.419 7.441 7.385
O2 (dry) % 10.049 9.763 9.746 9.714 9.778
DT CO2 (dry) % .313 / .305 .317 / .309 .319 / .309 .319 / .309 .322 / .315
DT NOX (dry) ppm 5.9 / 6.2 6.8 / 6.7 8.5 / 7.2 9.5 / 8.2 9.4 / 8.9
PM g/hr 0.226 0.180 0.104 0.094 0.091
BSFC kg/kW-hr 0.406 0.386 0.376 0.370 0.369
BSCO g/kW-hr 25.9 19.7 15.7 13.0 13.2BSNO g/kW-hr 2.4 2.6 3.0 3.1 3.3
BSHC g/kW-hr 17.5 10.6 9.1 9.1 11.3
BS(HC+NOx) g/kW-hr 19.9 13.2 12.1 12.2 14.6
BSPM g/kW-hr 0.113 0.086 0.049 0.043 0.041
EICO 63.9 51.0 41.9 35.1 35.9
EINOx 6.0 6.7 8.0 8.5 8.9
EIHC 43.0 27.5 24.3 24.5 30.8
AFR_dry 26.58 26.46 26.57 26.55 26.54
AFR_Carbon 27.72 27.69 27.80 27.81 27.82
AFR_Oxygen 26.69 26.56 26.67 26.65 26.64
AFR_Spindt 26.58 26.45 26.55 26.53 26.53
AFR_Bart 26.58 26.46 26.57 26.55 26.54
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 446 446 448 444 440
Exhaust Gas oC 306 307 308 307 305
Emissions Sample oC 116 116 116 116 116
Engine Load N-m 9.42 9.91 10.17 10.33 10.38
Engine Power kW 1.97 2.07 2.13 2.16 2.17
IMEP kPa 217 224 221 231 223
COV of IMEP % 20.30 8.50 4.30 4.80 12.70
Peak Cyl. Pres. (PCP) MPa 2.24 2.34 2.42 2.48 2.48
Location of PCP oATDC 10 10 10 10 9
145
Description 2000 RPM, 25% load, propane injection sweep, AFR=30 Repeatof Test: fuel=propane, orbital injector, low oil flow (1:400)
Date 07/05/03 Amb Temp 24.0 oC Amb Press 99.2 kPa 07/18/03 24.2 °C 99.9 kPa
Run Number 6 3 4 1 5 2 7 5 6 4
Hi-Techniques File 2kpro66 2kpro72 2kpro76 2kpro81 2kpro81r 2kpro86 2kpro89 2krp86 2krp89 2krp97
TEOM File 2kpro66 2kpro72 2kpro76B 2kpro81A 2kpr81r 2kpro86 2kpro89A 2krp86x 2krp89z 2krp97
SMPS File, 2000_propane 6 3 4 1 5 2 7 16 17 15
Spark Plug Type ChampionC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 299.6 299.6 299.7 299.7 299.6 299.6 299.6 299.8 299.7 299.6
Orifice Size # 4 4 4 4 4 4 4 4 4 4
Intake Air Flowrate kg/hr 24.31 24.31 24.32 24.32 24.31 24.31 24.31 24.33 24.32 24.31
Fuel Flowrate kg/hr 0.771 0.837 0.810 0.818 0.800 0.825 0.793 0.830 0.817 0.846
Measured A/F Ratio 31.5 29.0 30.0 29.7 30.4 29.5 30.7 29.3 29.8 28.8
Throttle Position % 28.0 28.0 28.0 28.0 28.0 28.0 28.0 28.0 28.0 28.0
Inlet Surge Tank Press kPa 99.4 99.5 99.5 99.4 99.6 99.5 99.5 100.2 100.1 100.2
Exh Surge Tank Press kPa 99.4 99.5 99.5 99.4 99.6 99.5 99.5 100.2 100.1 100.2
Oil Flowrate 0.180 0.175 0.176 0.177 0.179 0.181 0.182 0.182 0.183 0.185
SOI oBTDC 66 72 76 81 81 86 89 86 89 97
EOI oBTDC 31 40 45 51 51 56 60 56 60 68
Fuel Pressure psi 80 80 80 80 80 80 80 80 80 80
Spark Timing oBTDC 46 46 46 46 46 46 46 46 46 46
Supply Pressure kPa 35 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2Og -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50 50
DT test time min 9 10 10 12 12 10 8 10 10 10
TEOM Pressure Drop inHg 6.5 6.0 6.0 5.0 6.5 5.5 7.0 3.0 3.0 3.0
Dilution Ratio 19.8 22.5 22.2 25.7 23.8 25.2 24.0 23.7 22.8 21.7
HC ppm 1380.0 945.0 378.0 237.0 300.0 413.0 530.0 414.0 573.0 1090.0
NOX (dry) ppm 273.0 372.0 520.0 711.0 729.0 741.0 629.0 756.0 687.0 518.0
CO (dry) % 0.365 0.512 0.291 0.241 0.255 0.289 0.183 0.228 0.165 0.171
CO2 (dry) % 5.569 6.127 6.313 6.484 6.301 6.436 6.223 6.542 6.438 6.519
O2 (dry) % 11.702 10.726 10.663 10.434 10.725 10.472 10.862 10.355 10.557 10.425
DT CO2 (dry) % .268 / .254 .261 / .256 .292 / .286 .279 / .273 .290 / .282 .277 / .267 .286 / .284 0.299 0.301 .303 / .298
DT NOX (dry) ppm 12.8 / 13.4 15.3 / 15.9 22.0 / 22.2 25.3 / 26.7 29.1 / 28.8 28.1 / 27.3 25.7 / 23.7 30.2 28.4 22.0 / 23.0
PM g/hr 0.789 0.527 0.191 0.176 0.145 0.280 0.109 0.186 0.126 0.203
BSFC kg/kW-hr 0.433 0.414 0.386 0.399 0.402 0.396 0.387 0.415 0.391 0.393
BSCO g/kW-hr 47.5 58.5 31.9 27.0 29.5 32.0 20.6 26.2 18.2 18.3
BSNO g/kW-hr 5.8 7.0 9.4 13.1 13.8 13.5 11.6 14.3 12.4 9.1
BSHC g/kW-hr 28.2 17.0 6.5 4.2 5.4 7.2 9.4 7.5 9.9 18.3
BS(HC+NOx) g/kW-hr 34.1 24.0 15.9 17.3 19.3 20.6 21.0 21.8 22.4 27.5
BSPM g/kW-hr 0.443 0.261 0.091 0.086 0.073 0.135 0.053 0.093 0.060 0.094
EICO 109.8 141.3 82.7 67.7 73.3 80.6 53.2 63.2 46.5 46.5
EINOx 13.5 16.9 24.3 32.8 34.4 33.9 30.1 34.4 31.8 23.2
EIHC 65.2 41.0 16.9 10.5 13.5 18.1 24.2 18.0 25.4 46.6
AFR_dry 31.55 29.04 30.03 29.71 30.38 29.48 30.67 29.30 29.78 28.75
AFR_Carbon 32.20 29.63 30.61 30.30 30.94 30.04 31.31 29.87 30.38 29.33
AFR_Oxygen 31.72 29.23 30.18 29.85 30.52 29.63 30.80 29.43 29.90 28.87
AFR_Spindt 31.57 29.08 30.01 29.68 30.35 29.45 30.63 29.26 29.73 28.72
AFR_Bart 31.55 29.04 30.03 29.71 30.38 29.48 30.67 29.30 29.78 28.75
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 444 472 470 465 471 477 461 478 461 467
Exhaust Gas oC 308 318 290 287 308 312 312 299 309 309
Emissions Sample oC 116 118 97 99 109 108 120 101 189 130
Engine Load N-m 8.51 9.66 10.01 9.77 9.53 9.96 9.81 9.55 9.98 10.29
Engine Power kW 1.78 2.02 2.10 2.05 1.99 2.08 2.05 2.00 2.09 2.15
IMEP kPa 213 239 236 247 230 229 230 240 237 240
COV of IMEP % 33.50 27.60 14.00 3.50 3.40 12.20 10.10 3.50 7.20 10.30
Peak Cyl. Pres. (PCP) MPa 2.41 2.62 2.77 2.88 2.88 2.88 2.79 2.93 2.86 2.73
Location of PCP oATDC 7 7 6 5 4 4 6 5 5 7
146
Description 2000 RPM, 25% load, spark sweep, AFR=30, fuel=EEE, orbital injectorof Test: low oil flow (1:400)
Date 06/30/03 Amb Temp 23.7 oC Amb Press 99.9 kPa
Run Number 3 2 4 1 5 6
Hi-Techniques File Lsp25 Lsp30 Lsp35 Lsp40 Lsp45 Lsp50
TEOM File Lsp25A Lsp30B Lsp35 Lsp40 Lsp45 Lsp50A
SMPS File, 2000_25_30spark 4 3 5 2 6 7
Spark Plug Type ChampionRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 265.7 265.7 265.7 265.7 265.6 265.7
Orifice Size # 4 4 4 4 4 4
Intake Air Flowrate kg/hr 21.65 21.65 21.65 21.65 21.64 21.65
Fuel Flowrate kg/hr 0.800 0.800 0.800 0.800 0.800 0.800
Measured A/F Ratio 27.1 27.1 27.1 27.1 27.1 27.1
Throttle Position % 24.5 24.5 24.5 24.5 24.5 24.5
Inlet Surge Tank Press kPa 100.1 100.1 100.1 100.0 100.1 100.1
Exh Surge Tank Press kPa 100.1 100.1 100.1 100.0 100.1 100.1
Oil Flowrate 0.175 0.176 0.176 0.175 0.176 0.176
SOA oBTDC 72 72 72 72 72 72
EOA oBTDC 34 34 34 34 34 34
Fuel Pressure psi 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 6.00 6.00 6.00 6.00 6.00 6.00
Spark Timing oBTDC 25 30 35 40 45 50
Supply Pressure kPa 35 35 35 35 35 35
DT Back Pressure inH2O gauge -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10
TEOM Pressure Drop inHg 5.0 5.0 5.0 5.0 5.5 5.5
Dilution Ratio NOx 22.3 24.7 25.3 26.2 25.5 25.7
HC ppm 772 593 509 487 536 546
NOX (dry) ppm 215 354 499 566 616 652
CO (dry) % 0.162 0.139 0.131 0.137 0.138 0.154
CO2 (dry) % 7.460 7.544 7.544 7.514 7.430 7.389
O2 (dry) % 10.267 10.166 10.187 10.199 10.346 10.383
DT CO2 (dry) % .311 / .301 .309 / .304 .312 / .302 .306 / .299 .305 / .300 .300 / .298
DT NOX (dry) ppm 9.3 / 8.7 13.4 / 13.4 18.8 / 18.1 20.0 / 20.4 23.0 / 22.2 23.5 / 24.0
PM g/hr 0.114 0.179 0.199 0.234 0.241 0.308
BSFC kg/kW-hr 0.377 0.367 0.379 0.396 0.412 0.421
BSCO g/kW-hr 15.7 13.1 12.8 14.1 14.9 17.0
BSNO g/kW-hr 3.4 5.5 8.0 9.5 10.9 11.8
BSHC g/kW-hr 11.1 8.3 7.4 7.4 8.6 8.9
BS(HC+NOx) g/kW-hr 14.6 13.8 15.4 17.0 19.5 20.8
BSPM g/kW-hr 0.054 0.082 0.094 0.116 0.124 0.162
EICO 41.7 35.7 33.8 35.5 36.1 40.4
EINOx 9.1 14.9 21.2 24.1 26.5 28.1
EIHC 29.5 22.6 19.5 18.7 20.8 21.3
AFR_dry 27.02 27.01 27.15 27.22 27.50 27.57
AFR_Carbon 27.50 27.49 27.61 27.72 27.95 28.02
AFR_Oxygen 27.12 27.10 27.25 27.32 27.60 27.67
AFR_Spindt 27.00 26.98 27.11 27.18 27.45 27.52
AFR_Bart 27.02 27.01 27.15 27.22 27.50 27.57
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 455 451 450 452 449 451
Exhaust Gas oC 313 310 312 310 311 311
Emissions Sample oC 123 123 121 113 121 120
Engine Load N-m 10.13 10.41 10.08 9.67 9.28 9.09
Engine Power kW 2.12 2.18 2.11 2.02 1.94 1.90
IMEP kPa 225 230 232 220 222 225
COV of IMEP % 5.20 4.10 3.40 4.30 4.20 3.20
Peak Cyl. Pres. (PCP) MPa 2.19 2.50 2.72 2.75 2.77 2.79
Location of PCP oATDC 13 9 6 6 4 4
147
0200400600800
1000120014001600
6065707580859095100Injection Timing [dBTDC]
HC
[ppm
]
SOASONSOP
0100200300400500600700800
60708090100Injection Timing [dBTDC]
NO
x [p
pm]
SOASONSOP
0.0
0.1
0.2
0.3
0.4
0.5
0.6
6065707580859095100Injection Timing [dBTDC]
CO
[%]
SOASONSOP
5.0
5.5
6.0
6.5
7.0
7.5
8.0
6065707580859095100Injection Timing [dBTDC]
CO
2 [%
]
SOASONSOP
9.0
9.5
10.0
10.5
11.0
11.5
12.0
6065707580859095100Injection Timing [dBTDC]
O2
[%]
SOASONSOP
148
0.000.020.040.060.080.100.120.140.160.18
2030405060Spark [dBTDC]
CO
[%]
0100200300400500600700800900
HC
, NO
x [p
pm]
COHCNOx
6
7
8
9
10
11
2030405060Spark [dBTDC]
CO
2, O
2 [%
]
CO2O2
149
14x106 1210
86420N
umbe
r Con
cent
ratio
n [#
/cm
3]
5 610
2 3 4 5 6100
2 3
Particle Diameter [nm]
SOA=67 SOA=69 SOA=72 SOA=75 SOA=78 SOA=81 SON=69 SON=72 SON=75 SON=78 SON=81
15x106
10
5
0Num
ber C
once
ntra
tion
[#/c
m 3
]
5 610
2 3 4 5 6100
2 3
Particle Diamter [nm]
SOP66 SOP72 SOP76 SOP81 SOP81 (r) SOP86 SOP86 (r) SOP89 SOP89 (r) SOP97
150
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3
]
5 610
2 3 4 5 6100
2 3
Particle Diameter [nm]
sp50 sp45 sp40 sp35 sp30 sp25
151
Appendix C.5 – Low Speed Stoichiometric Test Condition
Description 2000 RPM, 25% load, air injection sweep, AFR=15, fuel=EEE orbital injector N2 injectionof Test: New TEOM filter, SMPS #12 is SOA=224 w/ norm oil flow, low oil (1:400)
Date 07/24/03 Amb T 23.5 oC Amb P 100.0 kPa
Run Number 8 5 9 4 1 2 11 7 6 10 3
Hi-Techniques File 20a74 20a84 20a94 20a104 20a144 20a184 20a224 20n74 20n84 20n94 20n184
TEOM File 20a74 20a84 20a94 20a104 20a144A 20a184 20a224 20n74 20n84B 20n94A 20n184
SMPS File, 2000_gas_stoich 8 5 9 4 1 2 11 7 6 10 3
Spark Plug Type Champion 10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 450.4 450.4 450.3 450.5 450.4 450.4 450.4 450.4 450.4 450.4 450.4
Orifice Size # 3 3 3 3 3 3 3 3 3 3 3
Intake Air Flowrate kg/hr 17.39 17.39 17.38 17.39 17.39 17.39 17.39 17.39 17.39 17.39 17.39
Fuel Flowrate kg/hr 0.860 0.910 0.860 0.890 0.910 0.840 0.900 0.870 0.880 0.880 0.870
Measured A/F Ratio 20.2 19.1 20.2 19.5 19.1 20.7 19.3 20.0 19.8 19.8 20.0
Throttle Position % 19.4 19.4 19.4 19.4 19.5 19.9 19.6 19.5 19.4 19.4 19.9
Inlet Surge Tank Press kPa 99.9 100.1 99.9 100.0 100.0 100.0 100.1 100.0 100.0 99.9 100.0
Exh Surge Tank Press kPa 99.9 100.1 99.9 100.0 100.0 100.0 100.1 100.0 100.0 99.9 100.0
Oil Flowrate 0.177 0.179 0.178 0.182 0.180 0.180 0.177 0.179 0.177 0.177 0.180
SOA oBTDC 74 84 94 104 144 184 224 79 84 94 184
EOA oBTDC 34 44 54 64 104 144 184 39 44 54 144
Fuel Pressure psi 95 95 95 95 95 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 7.20 7.20 7.20 7.20 7.20 7.20 7.20 7.20 7.20 7.20 7.20
Spark Timing oBTDC 38 38 38 38 48 48 48 38 38 38 48
Supply Pressure kPa 35 35 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2Og -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10 10 10 10 10 10
TEOM Pressure Drop inHg 6.0 5.0 6.5 4.5 3.0 4.0 7.0 5.5 5.0 7.0 4.0
Dilution Ratio NOx 23.7 23.9 23.6 23.7 24.1 24.3 24.0 23.6 23.8 23.7 24.3
HC ppm 541 598 1007 1396 2956 5085 5989 877 872 1452 5039
NOX (dry) ppm 127 227 147 98 408 333 116 54 71 67 157
CO (dry) % 1.657 1.901 1.411 1.102 0.255 0.167 0.147 2.259 2.277 1.847 0.214
CO2 (dry) % 9.866 9.582 9.942 10.175 10.209 9.491 9.114 9.002 8.951 9.320 9.458
O2 (dry) % 5.733 5.930 5.827 5.768 6.312 7.351 7.894 5.559 5.570 5.469 6.452
DT CO2 (dry) % .410 / .405 .401 / .387 .416 / .407 .423 / .415 .424 / .407 .388 / .387 .386 / .371 .378 / .378 .378 / .366 .395 / .381 .393 / .379
DT NOX (dry) ppm 6.5 / 7.3 11.0 / 11.3 7.8 / 7.0 6.8 / 6.5 20.2 / 20.2 16.0 / 17.5 6.2 / 7.1 4.2 / 4.3 5.4 / 5.5 3.7 / 4.3 9.4 / 9.7
PM g/hr 0.375 0.234 0.127 0.107 0.184 0.147 0.128 0.216 0.238 0.14 0.17
BSFC kg/kW-hr 0.366 0.401 0.352 0.389 0.389 0.380 0.433 0.390 0.384 0.383 0.392
BSCO g/kW-hr 104.8 132.0 86.2 74.0 17.6 11.5 11.6 154.5 153.9 123.0 15.1
BSNO g/kW-hr 1.3 2.6 1.5 1.1 4.6 3.8 1.5 0.6 0.8 0.7 1.8
BSHC g/kW-hr 5.1 6.2 9.1 13.9 30.4 51.8 70.3 8.9 8.7 14.4 53.0
BS(HC+NOx) g/kW-hr 6.4 8.8 10.6 15.0 35.0 55.6 71.8 9.5 9.5 15.1 54.8
BSPM g/kW-hr 0.160 0.103 0.052 0.047 0.079 0.067 0.062 0.097 0.104 0.06 0.08
EICO 286.5 329.3 244.6 190.3 45.4 30.2 26.9 396.0 400.4 321.6 38.7
EINOx 3.6 6.5 4.2 2.8 11.9 9.9 3.5 1.6 2.1 1.9 4.7
EIHC 13.9 15.4 25.9 35.8 78.1 136.4 162.5 22.8 22.8 37.5 135.2
AFR_dry 18.23 18.23 18.30 18.28 18.82 19.03 19.22 17.62 17.63 17.56 18.21
AFR_Carbon 18.57 18.56 18.63 18.61 19.21 19.41 19.58 18.69 18.74 18.62 19.40
AFR_Oxygen 18.42 18.44 18.47 18.43 18.90 19.11 19.29 17.84 17.85 17.76 18.29
AFR_Spindt 18.32 18.33 18.37 18.33 18.81 19.01 19.21 17.74 17.75 17.67 18.20
AFR_Bart 18.23 18.23 18.30 18.28 18.82 19.03 19.22 17.62 17.63 17.56 18.21
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 546 519 547 570 511 482 491 519 498 531 486
Exhaust Gas oC 343 343 348 347 328 324 334 335 334 346 322
Emissions Sample oC 135 140 131 143 156 143 130 132 140 141 135
Engine Load N-m 11.21 10.83 11.67 10.95 11.18 10.56 9.92 10.66 10.92 10.97 10.60
Engine Power kW 2.35 2.27 2.44 2.29 2.34 2.21 2.08 2.23 2.29 2.30 2.22
IMEP kPa 238 225 225 221 237 232 217 222 239 237 227
COV of IMEP % 3.9 4.1 8.7 12.3 3.8 10.6 15.3 7.0 4.9 7.1 8.8
Peak Cyl. Pres. (PCP) MPa 2.45 2.76 2.19 1.80 2.61 2.40 1.99 2.18 2.41 2.04 2.32
Location of PCP oATDC 14 5 12 16 7 9 13 13 10 14 10
152
Description 2000 RPM, 25% load, propane injection sweep, AFR=15, fuel=propane, orbital injectorof Test: low oil flow (1:400)
Date 07/20/03 Ambient Temp 24.0 oC Ambient Press 99.8 kPa
Run Number 6 4 5 3 7 1 8 2
Hi-Techniques File 20pr73 20pr76 20pr85 20pr103 20pr128 20pr153 20pr178 20pr203
TEOM File 20pr73A 20pr76B 20pr85B 20pr103 20pr128A 20pr153 20pr178A 20pr203
SMPS File, 2000_propane_stoich 6 4 5 3 7 1 8 2
Spark Plug Type ChampionRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mmRC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50 50 50 50
Engine Speed RPM 2000 2000 2000 2000 2000 2000 2000 2000
Orifice Upstream Press kPa 500.2 500.4 500.3 500.4 500.2 500.5 500.2 500.5
Orifice Size # 3 3 3 3 3 3 3 3
Intake Air Flowrate kg/hr 19.30 19.30 19.30 19.30 19.30 19.31 19.30 19.31
Fuel Flowrate kg/hr 0.858 0.871 0.870 0.855 0.880 0.873 0.872 0.880
Measured A/F Ratio 22.5 22.2 22.2 22.6 21.9 22.1 22.1 21.9
Throttle Position % 22.0 21.9 22.0 22.0 22.0 22.0 22.0 22.0
Inlet Surge Tank Press kPa 99.5 99.5 99.5 99.4 99.5 99.7 99.6 99.6
Exh Surge Tank Press kPa 99.5 99.5 99.5 99.4 99.5 99.7 99.6 99.6
Oil Flowrate 0.180 0.177 0.177 0.176 0.176 0.175 0.177 0.177
SOI oBTDC 73 76 85 103 128 153 178 203
EOI oBTDC 42 45 55 75 100 125 150 175
Fuel Pressure psi 80 80 80 80 80 80 80 80
Spark Timing oBTDC 36 36 41 46 46 46 46 46
Supply Pressure kPa 35 35 35 35 35 35 35 35
DT Back Pressure inH2O g -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10 10 10
TEOM Pressure Drop inHg 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
Dilution Ratio 23.1 23.2 20.1 16.6 20.4 19.1 21.7 19.0
HC ppm 872.0 575.0 535.0 1373.0 989.0 2689.0 4028.0 4978.0
NOX (dry) ppm 106.0 119.0 231.0 170.0 260.0 382.0 351.0 250.0
CO (dry) % 1.006 1.001 0.921 0.425 0.492 0.179 0.144 0.137
CO2 (dry) % 7.809 8.058 8.149 8.228 8.571 8.264 7.826 7.640
O2 (dry) % 7.848 7.491 7.415 7.705 7.137 7.809 8.427 8.771
DT CO2 (dry) % .346 / .338 .355 / .347 .355 / .347 .361 / .345 .365 / .358 .363 / .343 .342 / .329 .337 / .325
DT NOX (dry) ppm 5.7 / 6.5 6.7 / 7.2 10.5 / 10.8 9.2 / 9.8 11.6 / 12.0 19.2 / 18.0 15.1 / 15.0 12.6 / 12.0
PM g/hr 0.075 0.060 0.024 0.041 0.026 0.080 0.054 0.081
BSFC kg/kW-hr 0.427 0.411 0.399 0.401 0.393 0.418 0.438 0.447
BSCO g/kW-hr 90.4 85.1 76.1 35.9 39.4 15.4 13.1 12.6
BSNO g/kW-hr 1.6 1.7 3.1 2.4 3.4 5.4 5.3 3.8
BSHC g/kW-hr 12.3 7.7 6.9 18.2 12.5 36.4 57.7 72.0
BS(HC+NOx) g/kW-hr 13.9 9.3 10.1 20.6 15.9 41.8 62.9 75.7
BSPM g/kW-hr 0.038 0.028 0.011 0.019 0.012 0.038 0.027 0.041
EICO 211.7 207.1 190.6 89.5 100.4 37.0 30.0 28.2
EINOx 3.7 4.0 7.9 5.9 8.7 13.0 12.0 8.5
EIHC 28.8 18.7 17.4 45.4 31.7 87.2 131.7 161.1
AFR_dry 22.48 22.16 22.18 22.59 21.94 22.10 22.13 21.94
AFR_Carbon 22.79 22.45 22.48 22.93 22.26 22.47 22.55 22.28
AFR_Oxygen 22.69 22.37 22.38 22.72 22.08 22.20 22.22 22.02
AFR_Spindt 22.58 22.25 22.25 22.61 21.96 22.08 22.10 21.91
AFR_Bart 22.48 22.16 22.18 22.59 21.94 22.10 22.13 21.94
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 511 508 497 504 521 480 475 452
Exhaust Gas oC 333 332 331 323 338 317 326 293
Emissions Sample oC 125 120 118 118 125 113 123 119
Engine Load N-m 9.58 10.11 10.42 10.18 10.71 9.98 9.52 9.42
Engine Power kW 2.01 2.12 2.18 2.13 2.24 2.09 1.99 1.97
IMEP kPa 211 221 221 223 227 228 220 221
COV of IMEP % 23.50 11.60 4.60 12.00 8.90 12.30 14.10 17.20
Peak Cyl. Pres. (PCP) MPa 2.08 2.22 2.53 2.17 2.29 2.49 2.37 2.24
Location of PCP oATDC 13 12 8 11 10 7 8 10
153
0
1000
2000
3000
4000
5000
6000
7000
050100150200250Injection Timing [dBTDC]
HC
[ppm
]
SOASONSOP
050
100150200250300350400450
050100150200250Injection Timing [dBTDC]
NO
x [p
pm]
SOASONSOP
0.0
0.5
1.0
1.5
2.0
2.5
50100150200250Injection Timing [dBTDC]
CO
[%]
SOA COSON COSOP CO
6
7
8
9
10
11
50100150200250Injection Timing [dBTDC]
CO
2 [%
]
SOASONSOP
5.05.56.06.57.07.58.08.59.0
50100150200250Injection Timing [dBTDC]
O2
[%]
SOASONSOP
154
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3
]
5 6 7 8 910
2 3 4 5 6 7 8 9100
2 3
Particle Diameter [nm]
SOA74 SOA84 SOA94 SOA104 SOA144 SOA184 SOA224 SON79 SON84 SON94 SON184
14x106
12
10
8
6
4
2
0
Num
ber C
once
ntra
tion
[#/c
m 3
]
5 6 7 8 910
2 3 4 5 6 7 8 9100
2 3
Particle Diameter [nm]
EOP42 EOP45 EOP55 EOP75 EOP100 EOP125 EOP150 EOP175
155
Appendix C.6 – Medium Speed Stoichiometric Test Condition
Description 2800 RPM, ~16 N-m, near stoich A/F, Air-assist N2-assistof Test:
Date 07/22/03 Amb T 23.5 oC Amb P 99.7 kPa
Run Number 6 1 5 4 10 9 11 7 2 3 8
Hi-Techniques File 28a90 28a100 28a110 28a120 28a140 28a180 28a220 28n90 28n100 28n120 28n180
TEOM File 28a90 28a100 28a110 28a120 28a140A 28a180 28a220B 28n90 28n100 28n120 28n180A
SMPS File, 2800_gas_stoich 6 1 5 4 10 9 11 7 2 3 8
Spark Plug Type Champion 10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m10ECC, 12 m
Coolant Temp oC 50 50 50 50 50 50 50 50 50 50 50
Engine Speed RPM 2800 2800 2800 2800 2800 2800 2800 2800 2800 2800 2800
Orifice Upstream Press kPa 458.3 458.4 458.1 458.3 458.4 458.2 458.4 458.2 458.2 458.6 458.2
Orifice Size # 4 4 4 4 4 4 4 4 4 4 4
Intake Air Flowrate kg/hr 36.79 36.79 36.77 36.79 36.79 36.78 36.79 36.78 36.78 36.81 36.78
Fuel Flowrate kg/hr 1.562 1.562 1.562 1.562 1.562 1.562 1.562 1.562 1.562 1.562 1.562
Measured A/F Ratio 23.6 23.6 23.5 23.6 23.6 23.6 23.6 23.6 23.6 23.6 23.6
Throttle Position % 36.6 36.2 36.6 36.6 36.8 36.4 36.0 36.6 36.2 36.2 36.4
Inlet Surge Tank Press kPa 99.8 99.8 99.7 99.7 99.8 99.7 99.8 99.8 99.7 99.8 99.6
Exh Surge Tank Press kPa 99.8 99.8 99.7 99.7 99.8 99.7 99.8 99.8 99.7 99.8 99.6
Oil Flowrate 0.391 0.390 0.390 0.391 0.392 0.392 0.392 0.390 0.390 0.390 0.392
SOA oBTDC 90 100 110 120 140 180 220 90 100 120 180
EOA oBTDC 24 34 44 54 74 114 154 24 34 54 114
Fuel Pressure psi 95 95 95 95 95 95 95 95 95 95 95
Fuel per Cycle (FPC) mg 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30 9.30
Spark Timing oBTDC 37 37 37 37 37 37 37 37 37 37 37
Supply Pressure kPa 35 35 35 35 35 35 35 35 35 35 35
DT Back Pressure inH2O g -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10 10 10 10 10 10
TEOM Pressure Drop inHg 5.0 3.0 5.0 5.0 7.0 6.5 7.0 5.0 4.0 4.0 6.0
Dilution Ratio NOx 20.6 22.3 22.0 22.6 20.9 21.9 22.2 19.8 20.1 22.1 23.5
HC ppm 265 529 601 663 872 3138 4078 347 530 661.0 2473.0
NOX (dry) ppm 873 1465 1718 1476 1238 938 867 508 781 893.0 954.0
CO (dry) % 0.948 0.578 0.362 0.242 0.136 0.130 0.122 1.113 0.743 0.361 0.142
CO2 (dry) % 8.821 8.993 9.141 9.241 9.157 8.398 7.954 8.623 8.883 9.154 8.558
O2 (dry) % 7.783 7.788 7.766 7.712 7.890 8.934 9.515 7.497 7.282 7.113 8.009
DT CO2 (dry) % .399 / .391 0.415 .410 / .395 .413 / .406 .415 / .410 .389 / .380 .365 / .361 .392 / .368 .400 / .386 .404 / .398 .389 / .379
DT NOX (dry) ppm 37.8 / 40.1 60.6 71.5 / 72.3 58.0 / 62.4 55.0 / 54.1 48.3 / 56.0 14.6 / 15.6 23.7 / 23.5 35.9 / 35.6 36.9 / 37.3 36.8 / 38.5
PM g/hr 0.628 0.381 0.524 0.471 0.315 0.407 0.339 0.912 0.392 0.384 0.453
BSFC kg/kW-hr 0.314 0.300 0.298 0.293 0.288 0.312 0.326 0.314 0.302 0.292 0.307
BSCO g/kW-hr 61.1 36.0 22.5 14.8 8.3 8.7 8.6 71.8 46.3 21.9 9.3
BSNO g/kW-hr 9.2 15.0 17.6 14.8 12.4 10.3 10.1 5.4 8.0 8.9 10.3
BSHC g/kW-hr 2.5 4.9 5.6 6.0 7.9 31.1 42.9 3.3 4.9 6.0 24.2
BS(HC+NOx) g/kW-hr 11.8 19.9 23.1 20.8 20.3 41.3 53.0 8.7 12.9 14.9 34.5
BSPM g/kW-hr 0.126 0.073 0.100 0.088 0.058 0.081 0.071 0.184 0.076 0.072 0.089
EICO 194.5 120.0 75.5 50.5 28.8 27.7 26.5 228.5 153.4 75.1 30.4
EINOx 29.4 50.0 58.9 50.6 43.0 32.9 30.9 17.1 26.5 30.5 33.5
EIHC 8.1 16.3 18.6 20.5 27.4 99.4 131.6 10.6 16.2 20.4 78.6
AFR_dry 21.66 21.94 22.10 22.09 22.35 22.46 22.79 21.20 21.23 21.34 21.81
AFR_Carbon 22.00 22.32 22.46 22.48 22.78 22.85 23.21 21.98 22.16 22.39 22.95
AFR_Oxygen 21.82 22.07 22.20 22.19 22.43 22.54 22.87 21.38 21.37 21.44 21.89
AFR_Spindt 21.68 21.90 22.02 22.02 22.28 22.40 22.73 21.25 21.24 21.30 21.75
AFR_Bart 21.66 21.94 22.10 22.09 22.35 22.46 22.79 21.20 21.23 21.34 21.81
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 606 590 590 590 595 553 538 603 585 588 559
Exhaust Gas oC 475 466 469 469 460 442 437 475 465 469 453
Emissions Sample oC 170 198 175 175 162 179 170 181 176 180 166
Engine Load N-m 16.97 17.78 17.89 18.18 18.50 17.07 16.33 16.95 17.69 18.24 17.34
Engine Power kW 4.97 5.21 5.24 5.33 5.42 5.00 4.79 4.97 5.18 5.35 5.08
IMEP kPa 335 341 354 361 359 344 329 327 346 355 344
COV of IMEP % 3.10 2.80 2.10 1.80 2.80 5.90 4.60 8.60 3.20 2.10 4.50
Peak Cyl. Pres. (PCP) MPa 3.19 3.41 3.40 3.21 3.09 3.09 2.65 2.92 3.15 3.07 3.19
Location of PCP oATDC 7 5 5 8 10 9 13 11 9 9 9
156
Description 2800 RPM, 50% load, propane injection sweep, AFR=17 (near stoich), orbital injectorof Test: ~15 N-m, new spark plug, low oil flow (1:400)
Date 07/21/03 Amb Temp 23.3 oC Amb Press 98.8 kPa
Run Number 8 6 3 2 4 1 5 7
Hi-Techniques File pr2890 pr2895 pr28100 pr28110 pr28130 pr28150 pr28190 pr28210
TEOM File pr2890 pr2895 pr28100 pr28110B pr28130A pr28150D pr28190 pr28210A
SMPS File, 2800_propane_stoich 8 6 3 2 4 1 5 7
Spark Plug Type Champion C10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mC10ECC, 12 mm
Coolant Temp oC 50 50 50 50 50 50 50 50
Engine Speed RPM 2800 2800 2800 2800 2800 2800 2800 2800
Orifice Upstream Press kPa 220.4 220.4 221.0 221.8 220.4 220.9 220.3 220.5
Orifice Size # 5 5 5 5 5 5 5 5
Intake Air Flowrate kg/hr 38.40 38.40 38.50 38.63 38.40 38.48 38.38 38.42
Fuel Flowrate kg/hr 1.389 1.417 1.456 1.494 1.517 1.530 1.542 1.539
Measured A/F Ratio 27.6 27.1 26.4 25.9 25.3 25.1 24.9 25.0
Throttle Position % 37.2 37.4 37.4 37.9 37.9 37.9 37.9 37.2
Inlet Surge Tank Press kPa 99.0 99.1 99.3 99.2 99.2 99.3 99.1 99.2
Exh Surge Tank Press kPa 99.0 99.1 99.3 99.2 99.2 99.3 99.1 99.2
Oil Flowrate 0.392 0.391 0.392 0.390 0.391 0.389 0.391 .391
SOA oBTDC 90 95 100 110 130 150 190 210
EOA oBTDC 40 45 50 60 80 100 140 160
Fuel Pressure psi 80 80 80 80 80 80 80 80
Spark Timing oBTDC 34 34 34 34 34 34 34 34
Supply Pressure kPa 35 35 35 35 35 35 35 35
DT Back Pressure inH2Og -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0 -4.0
DT temperature oC 50 50 50 50 50 50 50 50
DT test time min 10 10 10 10 10 10 10 10
TEOM Pressure Drop inHg 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
Dilution Ratio NOx 17.6 20.2 19.8 20.9 20.9 21.7 20.7 20.2
HC ppm 891 402 407 497 541 800 2096.0 3198.0
NOX (dry) ppm 399 571 756 972 1024 1168 1045.0 680.0
CO (dry) % 0.358 0.340 0.360 0.313 0.217 0.197 0.135 0.102
CO2 (dry) % 6.681 7.019 7.196 7.403 7.658 7.716 7.374 7.029
O2 (dry) % 10.027 9.555 9.271 8.989 8.645 8.728 9.090 9.649
DT CO2 (dry) % .316 / .314 .334 / .326 .341 / .335 .348 / .338 .362 / .349 .377 / .355 .343 / .339 .337 / .331
DT NOX (dry) ppm 21.1 / 21.4 29.9 / 27.3 34.8 / 36.7 42.4 / 44.6 44.0 / 47.6 49.2 / 51.4 47.8 / 46.5 30.6 / 32.7
PM g/hr 0.242 0.071 0.060 0.112 0.068 0.109 0.169 0.183
BSFC kg/kW-hr 0.331 0.316 0.314 0.315 0.305 0.308 0.317 0.328
BSCO g/kW-hr 31.0 27.4 28.1 23.9 15.7 14.2 10.0 7.9
BSNO g/kW-hr 5.7 7.6 9.7 12.2 12.2 13.8 12.8 8.7
BSHC g/kW-hr 12.1 5.1 5.0 6.0 6.2 9.1 24.5 38.9
BS(HC+NOx) g/kW-hr 17.8 12.6 14.7 18.2 18.3 22.9 37.2 47.6
BSPM g/kW-hr 0.057 0.016 0.013 0.023 0.014 0.022 0.035 0.039
EICO 93.6 86.8 89.6 76.0 51.6 46.2 31.7 24.1
EINOx 17.1 24.0 30.9 38.8 40.0 45.0 40.3 26.4
EIHC 36.6 16.1 15.9 19.0 20.2 29.4 77.3 118.6
AFR_dry 27.64 27.11 26.45 25.86 25.31 25.15 24.89 24.96
AFR_Carbon 28.19 27.61 26.92 26.32 25.81 25.44 25.41 25.48
AFR_Oxygen 27.79 27.25 26.59 25.99 25.43 25.26 24.99 25.06
AFR_Spindt 27.64 27.10 26.43 25.82 25.25 25.08 24.82 24.91
AFR_Bart 27.64 27.11 26.45 25.86 25.31 25.15 24.89 24.96
Exh. Manifold Vac. in H2O 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Exhuast Manifold oC 542 546 550 549 560 553 543 525
Exhaust Gas oC 424 432 438 442 447 435 439 424
Emissions Sample oC 157 160 156 149 162 121 154 148
Engine Load N-m 14.32 15.33 15.82 16.21 17.00 16.97 16.62 15.99
Engine Power kW 4.20 4.49 4.64 4.75 4.98 4.97 4.87 4.69
IMEP kPa 276 290 295 307 317 324 312 306
COV of IMEP % 16.10 3.90 4.70 7.10 6.30 2.50 4.40 8.20
Peak Cyl. Pres. (PCP) MPa 2.52 2.79 2.90 3.02 2.90 3.02 2.98 2.77
Location of PCP oATDC 12 11 9 8 10 9 9 11
157
0500
10001500200025003000350040004500
050100150200250EOP [dBTDC]
HC
[ppm
]
SOASONSOP
0
500
1000
1500
2000
50100150200250EOP [dBTDC]
NO
x [p
pm]
SOASONSOP
0.000
0.200
0.400
0.600
0.800
1.000
1.200
050100150200250EOP [dBTDC]
CO
[%]
SOASONSOP
566778899
10
050100150200250EOP [dBTDC]
CO
2 [%
]
SOASONSOP
6778899
101011
050100150200250EOP [dBTDC]
O2
[%]
SOASONSOP
158
20x106
15
10
5
0
Num
ber C
once
ntra
tion
[#/c
m 3
]
5 6 710
2 3 4 5 6 7100
2 3
Particle Diameter [nm]
SOA90 SOA100 SOA110 SOA120 SOA140 SOA180 SOA220 SON90 SON100 SON120 SON180
20x106
15
10
5
0
Num
ber C
once
ntra
tion
[#/c
m 3]
5 6 7 8 910
2 3 4 5 6 7 8 9100
2 3
Particle Diameter [nm]
EOP=40 EOP=45 EOP=50 EOP=60 EOP=80 EOP=100 EOP=140 EOP=160