measurement of real-world emissions from heavy … of real-world emissions from heavy-duty diesel...
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Measurement of Real-World Emissions from Heavy-Duty Diesel Vehicles:
The State-of-the-Art
Mridul Gautam, Greg Thompson, Nigel Clark, Dan Carder, Wes Riddle, Don Lyons
Department of Mechanical and Aerospace EngineeringWest Virginia University
NATIONAL RESEARCH CENTER FOR ALTERNATIVE TRANSPORTATION FUELS, ENGINES AND EMISSIONS
West Virginia UniversityFuels, Engines, and Emissions Research
Purpose of In-use Emissions Measurements
• Technology Development and/or Assessment
• Enforcement
• Compliance
• I/M
• Screening
• Inventory
Available Tools• Engine Test Cells
– Simulated Routes– FTP
• Chassis Dynamometers
• On-road, On-board Emissions Measurement Systems– AEI, Columbus, IN– Horiba, Ann Arbor, MI– Sensors, Saline, MI
Challenges to Measurement of On-board, On-road Diesel Emissions
• False positives ; Error minimization• Torque (or percent load) broadcast• Exhaust flowrate measurement• Fuel quality variability• Emissions characteristics from current and future engines/exhaust
aftertreatment systems (NO, NO2, OC dominated PM emissions)• Current definition of particulate matter.
• Obsession with brake-specific emissions– It is recognized that the FTP (brake-specific emissions) is essential – However, in-use fuel-specific emissions would eliminate majority of
challenges associated with collecting brake-specific emissions in the field (application dependent)
• Instrumentation– Advances in systems development have not been fast enough– Portability; Bulk
West Virginia University, Morgantown,WV 26506
In-Use Emissions Work at WVURelated to Consent Decrees
• PHASE I: DEVELOPED MOBILE EMISSIONS MEASUREMENT SYSTEM FOR ON-BOARD, IN-USE HEAVY-DUTY VEHICLE APPLICATIONS
• PHASE II: DEVELOPED IN-USE EMISSIONS TESTING PROCEDURES, AND TEST ROUTES
• PHASE III: CONDUCTED EMISSIONS TESTING ON A VARIETY OF IN-SERVICE DIESEL ENGINES (≤MY1998)USING THE WVU MOBILE EMISSIONS MEASUREMENT SYSTEM (MEMS) TO CHARACTERIZE REAL-WORLD EMISSIONS FROM SUCH ENGINES
West Virginia University, Morgantown,WV 26506
In-Use Emissions Work at WVURelated to Consent Decrees (…Cont’d)
• PHASE IV: CONDUCTING ON-ROAD COMPLIANCE MONITORING OF HEAVY-DUTY DIESEL VEHICLES (≥MY2002) USING THE MONITORING TECHNOLOGY, AND PREVIOUSLY DEFINED TESTING PROCEDURES (AND DRIVING ROUTES) DEVELOPED BY WVU, AND APPROVED BY THE US EPA.
Mobile Emissions Measurement System
(MEMS)
Exhaust Samplingand Conditioning
FlowMeter
EngineInterface
AmbientSensors
ExhaustConstituentsNOx & CO2
Differential Pressure,Absolute Pressure,and Temperature
Engine Speed,Vehicle Speed,
& Torque
Ambient Temperature,
Pressure,& Humidity
GPS
Vehicle Speed & Location
Mobile Emissions Measurement System
West Virginia University,Morgantown, WV 26506
NOX MASS EMISSION RATES ON SAB2SW ROUTE – MEMS AND
LABORATORY: CUMMINS ISM 370
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Time (s)
NO
x (g
/s)
Dilute LaboratoryRaw MEMS
Comparison of Brake Specific Emissions Results
from the FTP Test Cell and MEMS
-4.39%
524.0
548.0
CO2(g/bhp-hr)
-0.18%Percent Difference
4.389MEMS
4.397Laboratory
NOx(g/bhp-hr)FTP Cycle
Exhaust Stack Measurements
Current Status and Future Direction
• CO2– Solid State NDIR
• Current “garage-grade” NDIR microbenches have served the purpose
– New Direction – “Sensor-on-a-chip” (a hot-bolometer). Silicon microbridge elements with photonic bandgap modified surfaces.
• CO– Improvements are needed to current solid-state “garage-grade”
NDIR’s ability to measure low levels of CO from diesel engines
t (m sec)
I (m
A)
t (m sec)
T (K
)
λ (µm )
Flux
(a.u
.)
λ (µm )
Flux
(a.u
.)
λ (µm )
Flux
(a.u
.)
t (m sec)
T (K
)
Source driver
Source temperature
Source emission
Optical efficiency
Gas attenuation
Dual wavelength source/detector
Detector response
Sensor-on-a-Chip (NDIR)
Current Status and Future Direction
• NOx
– Zirconium oxide sensors• Results are better with a NOx converter. • Avoid using the sensor in the raw exhaust stream
– Current “garage-grade” NDUV may not fully account for noise attenuation, interferences, lamp decay
– New Direction – UV Resonance Absorption Spectroscopy
UV-Resonance Absorption Spectroscopy• Simple photometer technology• Excellent agreement with other
standard methods• No critical components:
– Hot measurement, no chiller– Direct measurement of NO2 ,
no converter– No ozone generator, no
vacuum pumps etc.• Calibration with long-term stable,
gas-filled calibration cells• Simultaneous measurement of
up to 3 gas components NO, NO2, NH3 0.0
0.1
0.1
0.2
0.2
0.3
0.3
0.4
200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580
WL in nm
Abs
orpt
ion
0
10
20
30
40
50
60
70
80
90
100
Lam
p In
tens
ity
NO NO2 EDL
NO
NO2
Current Status and Future Direction• Total Hydrocarbons
– NDIR detectors are not recommended for diesel exhaust– Heated Flame Ionization Detectors serve well– New Direction – Reduce the size and complexity of the FIDs.
Systems are available, but prone to breakdowns• Exhaust Flowrate
– Considering the system accuracy, turn-down ratio, meter drift, measurement frequency, response time, size and weight, robustness (including operation in harsh environments), low backpressure on the engine, etc.
• Averaging pitot tubes (e.g. Annubar), the AEI system• Others:
– Ultrasonic flowmeters (size/temperature limitations), – Hot-wires (response time limitations), – ECU based value (calculated value), – Intake measurements (system leaks, time delays, secondary air
pump during cold start, positioning in the intake system)
Current Status and Future Direction
• Torque and Engine Speed
– Engine Speed is an Accurate Measurement– Inference of Engine Power is Possible via Publicly
Broadcast ECU Information– Engine Torque/Power Can Be Inferred to Within ±10% of
Laboratory Measurements• Engine Maintenance History• Lug Curve• Accessory Loading• Ambient Conditions Limitation• Operate Within the NTE Zone• Use Good Engineering Judgment
Current Status and Future Direction
• Uncertainties associated with Exhaust Flowrateand Torque measurements can be avoided by Fuel Specific Measurements
• Only concentration measurements will be required
Brake Specific Emissions
NOx
CO2
=(g/bhp-hr) NOx
(g/bhp-hr) CO2
=
(Density)*(Exhaust Mass Flow Rate)*(Concentration)NOx
bhp-hr
(Density)*(Exhaust Mass Flow Rate)*(Concentration)CO2
bhp-hr
NOX Index(Fuel Specific Emissions)
(Concentration of NOx) x (Exhaust flow rate) x MWNOx
(Concentration of CO2) x (Exhaust flow rate) x (12.011+1.008*(H:C))
grams of NOx / kg of Fuel
•NOx concentration•CO2 concentration•Fuel H:C ratio
Engine Operation Over an On-road Route
0
200
400
600
800
1000
1200
1400
1600
1800
500 1000 1500 2000
Engine Speed(RPM)
Engi
ne T
orqu
e(ft-
lb)
lug curveTorqueN loN hi15% ESC Speed30% Torque30% Power Torque
NTE Zone: Engine Operation and Brake Specific NOxas a function of Engine Speed and Engine Load
0
200
400
600
800
1000
1200
1400
1600
1800
500 1000 1500 2000
Engine Speed(RPM)
Engi
ne T
orqu
e(ft-
lb)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
NTE
bsN
Ox
(g/b
hp-h
r)
lug curveNTE TorqueN loN hi15% ESC Speed30% Torque30% Power TorqueNTE bsNOx
3-D plot of Brake Specific NOx as a function of Engine Speed and Engine Load
1 2 0 01 4 0 0
1 6 0 01 8 0 0
2 0 0 0
2
3
4
5
8 0 01 0 0 0
1 2 0 01 4 0 0
1 6 0 01 8 0 0
NTE
bsN
Ox
(g/b
hp-h
r)
Engine Load (ft-lb
)E ng ine S peed (R P M )
Errors in Torque Broadcast(Simulated SAB-to-BM Route)
-500
0
500
1000
1500
2000
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Time (s)
Engi
ne L
oad
(ft-lb
)
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00Inferred Torque from Lab Gen. Lug Curve (ft-lb)Lab Torque (ft-lb)Inferred Torque from Manf. Lug Curve (ft-lb)% Difference
Simulated SAB-to-BM Route – NTE Zone
0
200
400
600
800
1000
1200
1400
1600
1800
500 1000 1500 2000
Engine Speed(RPM)
Engi
ne T
orqu
e(ft-
lb)
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
lug curveTorqueN loN hi15% ESC Speed30% Power Torque%Difference
Ratio of bsNOx/bsCO2 vs. Time
0.0000
0.0020
0.0040
0.0060
0.0080
0.0100
0.0120
0.0140
0 500 1000 1500 2000 2500 3000
Time (s)
ratio
of b
sNO
x/bs
CO
2
ratio from on-road data
ratio from ftp cycle
Ratio of bsNOx/bsCO2 vs. Power
0.000
0.005
0.010
0.015
0.020
0.025
0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00
Power(hp)
Rat
io(N
Ox/
CO
2 )
0.000
2.000
4.000
6.000
8.000
10.000
12.000
bsN
Ox
(g/b
hp-h
r)
Ratio on road
Ratio from FTP cycle
bsNOxStandard bsNOx
.00928
5.0g/bhp-hr
In-use Particulate Matter EmissionsMajor Challenge:
• Definition of particulate matter• Current definition of particulate matter emissions is
valid in a multi-million dollar brick-and-mortar engine/chassis dynamometer test cell
• EPA is hoping to demonstrate “equivalency” between portable PM instruments and test cell methods.– On integrated PM measurements
• Several years down the road unless definition of PM is modified.
Real-Time Particulate Mass Monitor (Quartz Crystal Microbalance)
• In-use, On-board applications (capable of handling severe vibrations)
• Test cell applications• Ultra-clean (US EPA 2007
Standards) engines• Older “dirty” engines• Sample Conditioning
System provides accurate dilution up to 1:2000
• NOx, CO2, CO, HC• CAN network
communication & RS232, GPS
Continuous TPM Measured withTPM Trace vs. Power: FTP Cycle
-1000
-500
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 200 400 600 800 1000 1200 1400
Time(s)
Con
cent
ratio
n (u
g/m
3)
-100
-50
0
50
100
150
200
Pow
er(h
p)
The RPM-100 (QCM) in a Backpack and on a Caterpillar D11 Dozer with a 3508 V-8
MEMS & RPM 100
Gravimetric PM Comparisons Between the RPM-100 and
the Full-flow Dilution Tunnel
Test 01 Test 02 Test 03 MARI RPM 100 Integrated PM Mass 0.74 1.97 1.73
Full-Flow Dilution Tunnel Gravimetric Integrated PM Mass 0.71 1.75 1.79
Percent Difference 4.2% 12.6% -3.4%
Note: The RPM-100 sampled from the raw exhaust stream. The resultant error includes all sources of errors in the emissions measurement systems (exhaust flow rate; concentration; data acquisition; etc.)
Conclusions
• Re-visit the definition of particulate matter• Give serious consideration to fuel-specific
emissions measurements• Move all on-board emissions measurement
systems out of the truck cab and onto the exhaust stack – make accurate and precise measurements more vehicle driver/owner friendly.
• New, accurate sensors are available• Need to focus on measurement of emissions
(species and concentrations), which will be encountered in 2007.
West Virginia University,Morgantown,WV 26506
West Virginia University,Morgantown,WV 26506
The End
Engine Speed Histogram for the Candidate Routes Mack CH Tractor and Trailer
With a Nominal 60,000 lbs GVW
0
10
20
30
40
50
Eng. Spd. (rpm)
Per
cent
age
of T
ime
(%)
SAB2SAB 16.22 1.69 1.49 3.42 12.86 24.30 31.43 8.59
SAB2SW 9.99 1.23 1.80 1.14 5.81 21.95 43.17 14.90
SW2SAB 10.50 1.97 3.34 2.20 7.19 14.42 45.40 14.98
SAB2BM 9.81 0.53 1.96 1.69 8.68 16.77 45.31 15.27
BM2SAB 10.86 1.83 1.51 2.20 10.31 18.48 32.86 21.93
WAHSPA1 17.04 1.87 2.12 3.79 12.35 28.13 25.14 9.57
WASHPA2 20.46 2.87 3.40 4.14 10.79 30.78 19.10 8.45
WASHPA3 4.36 0.56 0.89 0.87 7.84 35.04 45.44 4.99
0 - 700 700 - 900 900 - 1100 1100 - 1300 1300 - 1500 1500 - 1700 1700 - 1900 1900 - 3000
ECU-Derived Engine Power Histogram for the Candidate Routes Mack CH Tractor and Trailer With a Nominal
60,000 lbs GVW
0
10
20
30
40
50
ECU Power (hp)
Per
cent
age
of T
ime
(%)
SAB2SAB 21.95 24.97 6.62 4.81 4.78 4.97 5.38 4.69 4.53 17.01 0.28
SAB2SW 19.56 15.18 3.62 2.40 2.14 2.48 3.16 3.34 5.26 42.29 0.56
SW2SAB 25.75 17.65 2.96 2.05 1.46 2.24 2.91 4.35 5.13 34.89 0.62
SAB2BM 21.96 14.13 2.40 2.69 2.61 2.60 2.59 2.89 2.86 44.36 0.90
BM2SAB 31.52 18.16 2.91 2.01 1.47 1.80 2.23 2.58 2.62 34.13 0.58
WAHSPA1 27.31 27.88 3.27 3.26 2.82 4.42 4.58 5.01 4.91 16.19 0.35
WASHPA2 23.72 29.83 4.55 4.08 3.47 4.88 5.43 5.47 5.08 13.18 0.32
WASHPA3 21.01 9.85 5.71 4.92 5.13 4.92 4.89 5.70 4.55 32.96 0.36
-200 - -25 -25 - 25 25 - 75 75 - 125 125 - 175 175 - 225 225 - 275 275 - 325 325 - 375 375 - 425 425 - 475
Inference of Engine Power
0
100
200
300
400
500
600
500 1000 1500 2000 2500 3000Engine Speed (rpm)
Shaft
Tor
que (
ft-lb)
0
20
40
60
80
100
120
ECU
Perce
nt Lo
ad (%
)
LugCurve
Lug Curve Percent Load
Curb Idle Load
Curb Idle Percent Load
Ratio of bsNOx/bsCO2 vs. Power
0.000
0.005
0.010
0.015
0.020
0.025
0.00 100.00 200.00 300.00 400.00 500.00
Power(hp)
Rat
io (N
ox/C
O2 )
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4.500
bsN
Ox
(g/b
hp-h
r)
Ratio on road
Ratio from FTP cycle
bsNOxStandard bsNOx
0.00628
0.00864
4.0 g/bhp-hr
0
400
800
1200
1600
30 60 90 120 150 180Time (s)
Shaft
Tor
que (
ft-lb)
LaboratoryMeasured
ECU Inferred,LaboratorySupplied
Engine Torque
0
500
1000
1500
2000
0 100 200 300 400Time (s)
Engin
e Spe
ed (r
pm)
LaboratoryECU
Engine Speed
Results – Steady State Instantaneous Engine Speed and Torque
• Constant 1500 rpm• 10 Second Period • Torque Varied From 325 ft-lb to Maximum•
0%
0%0.1%
0.1%
0.2% 9.7% 13.1%
4.7%
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