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THE RCCI ENGINEBreakthrough Fuel Efficiency, Low NOx & Soot Emissions



To CompeTe in the world’s fastest growing markets, engine manufac-turers and fleet operators need to meet increasingly stringent emissions require-ments while also improving fuel efficiency.

Fleet-wide efficiency goals and the need to reduce fuel consumption to meet current and future emission and efficiency mandates also reinforce the demand for a new generation of engine technologies.

A portfolio of recently patented engine technolo-gies developed by a team from the University of Wisconsin–Madison Engine Research Center led by Director Rolf Reitz solves a host of environmental and efficiency challenges by offering dramatic re-ductions in nitrogen oxide and soot emissions while boosting fuel economy. The technologies are now available for licensing through the Wisconsin Alum-ni Research Foundation, which patents and licenses discoveries arising from UW–Madison research.

Called reactivity controlled compression igni-tion, or RCCI, the base technology uses multiple injections of differing fuel types to optimize combustion phasing, duration and magnitude. Laboratory experiments performed at the Engine Research Center and at Oak Ridge National

1. Splitter, D.A., Wissink, M., DelVescovo, D., and Reitz, R.D., “RCCI Engine Operation Towards 60% Thermal Efficien-cy,” SAE Paper 2013-01-0279, 2013.

2. Kokjohn, S.L., Hanson, R.M., Splitter, D.A., and Reitz, R.D., “Fuel Reactivity Controlled Compression Ignition (RCCI): A Pathway to Controlled High-Efficiency Clean Combustion,” International Journal of Engine Research, Special Is-sue on Fuel Efficiency, Vol. 12, pp. 209-226, doi:10.1177/1468087411401548, 2011.

Laboratory demonstrate that engines utilizing these technologies attain exceptional fuel efficiency. The test engine has achieved an unprecedented 60 percent gross indicated efficiency1 in the laboratory (corresponding to a diesel fuel energy equivalent gross indicated specific fuel consumption of 141 g/kW-hr) with nitrogen oxide and soot emissions significantly below current limits in the U.S., EU and Japan. (Fig. 2)

Additional research published by the International Journal of Engine Research points to a 100-fold reduction in nitrogen oxide and a 10-fold reduction in soot when compared with a conventional diesel combustion engine.2 (Fig. 3)

Figure 1: Modified diesel intake manifold with port fuel injectors.

Figure 3: Comparison of heavy-duty RCCI and conventional combustion.

Figure 2: Comparison of light-duty RCCI and conventional combustion.


The RCCI technology portfolio (warf.org/RCCI) comprises nine related patents and patent pending technologies that enable the unique in-cylinder fuel blending, stratification and compression combustion process. WARF seeks partners to license and develop the RCCI technologies.

• P100054US01 – Reactivity Controlled Compression Ignition Engine; • P100054US02 – Fuel Reactivity Method Cuts Diesel Engine Emissions; • P110092US01 – Engine Combustion Control at Low Loads with

Reactivity Controlled Compression Ignition Combustion; • P110320US01 – Improved Compression Ignition Combustion in Rotary Engines for Higher Efficiency and Lower

Pollutant Emissions; • P07342US – Adaptive Fuel Injection Method Cuts Diesel Engine Emissions; • P06042US – Valve Method Cuts Engine Emissions, Boosts Combustion; • P03152US – Variable Valve Actuation Method to Enhance Combustion and Reduce Engine Emissions; • P01320US – Reducing Emissions and Controlling Combustion Phasing in HCCI Engines; and • P01108US – Use of Multiple Injections of Increasing Pressure to Reduce Diesel Engine Emissions.

“Reactivity Controlled Compression Ignition is a new and superior way to burn fuel in internal combustion engines. It improves fuel use efficiency and reduces carbon dioxide emission. Compared with a conven-tional diesel it reduces nitric oxides emission 100-fold and soot 10-fold.

Two fuels with differing reactivity are used. The lower reactivity fuel, e.g., gasoline, is injected early and is too dilute (lean) to self-ignite even at the high compression needed for high efficiency. The higher reactivity fuel, e.g., diesel, is injected later but early enough that mixing has time to prevent soot formation in locally rich cool regions and NOx formation in locally stoichiometric hot regions. The ratio of the two fuels provides an important control parameter to enable the engine to work optimally over ranges of speed, load and ambient temperature.

The level of understanding that made this RCCI discovery possible is the direct result of decades of thoughtful interaction between evolving theory and experiment by Professor Rolf Reitz, faculty and students at the Engine Research Center at the University of Wisconsin–Madison.

Future engines, especially those required for long haul of freight by road, river, rail or ocean, will compete to provide lowest cost of ownership while meeting minimum greenhouse gas and other emissions. RCCI provides an opportunity for a substantial advance in the way engines work their magic for the benefit of the world community.”

– John Clarke, B.Sc., CEng, MIMechE, Fellow SAE, Associate ASME Caterpillar Research (Retired)

Figure 4

http://www.warf.org/RCCI


With the ability to meet the world’s most restrictive regulatory standards while providing dramatic cost savings in fuel and after-treatment systems, the RCCI engine and its associated technologies promise a broad range of benefits for engine manufacturers; fleet owners; and producers of transportation, utility and auxiliary power equipment.

• Benefits for engine manufacturers: Implementation of the RCCI technology portfolio

enables compliance with U.S., EU and Japanese regulatory frameworks through 2016 while providing a basis for continued reductions. The technologies offer substantial savings in overall engine cost and weight due to significantly reduced requirements for injection pressure and engine heat rejection while lowering the reliance on NOx and soot after-treatment systems and maintaining standard frame and engine compartment metrics.

• Benefits for fleet owners: The RCCI engine technologies support increased

fleet efficiency through added fuel flexibility (e.g., RCCI allows the use of natural gas at high substitution rates), improved fuel economy and lowered reliance on costly after-treatment systems. The technologies also reduce operator input and fleet maintenance and lower the cost of ownership by reducing or eliminating the use of diesel exhaust fluid (DEF).

• Benefits across multiple engine markets: The technologies apply to automobiles; light-,

medium- and heavy-duty trucks and buses; off-road vehicles (agricultural, construction, industrial); locomotives; generator sets and marine vessels including large oceangoing ships (propulsion and auxiliary power).

Figure 5: Step load transient emissions of RCCI vs. conventional diesel combustion (CDC).

RCCI TeChnologIes offer end-to-end benefits for engine manufacturers, fleet owners and other engine applications

14

We found that RCCI operaHon is possible for a large fracHon of each drive cycle

RCCI-‐enabled engine increases fuel economy over city and highway drive cycles

RCCI results

Fuel economy benefit

(relative %)

Drive cycle by distance

(%)

Drive cycle by

time (%)

Total diesel fuel (%)

Diesel during RCCI (%)

UDDS +14 72 55 56 41

HWFET +15 88 86 44 37

US06 +8 66 56 66 31

NYCC +13 69 36 65 43 Figure 6: Estimated RCCI-enabled engine increases in fuel economy over city and highway drive cycles

(Curran et al. SAE 2014-01-1324).

14

We found that RCCI operaHon is possible for a large fracHon of each drive cycle

RCCI-‐enabled engine increases fuel economy over city and highway drive cycles

RCCI results

Fuel economy benefit

(relative %)

Drive cycle by distance

(%)

Drive cycle by

time (%)

Total diesel fuel (%)

Diesel during RCCI (%)

UDDS +14 72 55 56 41

HWFET +15 88 86 44 37

US06 +8 66 56 66 31

NYCC +13 69 36 65 43

City

Hwy < 60MPH

Aggressive

Low Speed Stop-and-Go

Drive Cycle


“Diesel engines have long been recognized for their fuel efficiency. However, while substantial progress has been made in reducing their emission of NOx and particulate matter, the remaining emissions of these criteria pollutants continue to be a source of environmental concern and are facing ever tighter emission regulations. The RCCI engine uses advanced, low temperature combustion techniques combined with multiple injections of a high and a low reactivity fuel at varying pressures to further reduce emissions and achieve even greater fuel efficiency. RCCI represents an important path forward in the effort to optimize the performance of diesel combustion systems.”

– Dennis Siebers, Engine Combustion Research Program Manager Sandia National Laboratories Combustion Research Facility

The RCCI engine and associated technologies over-come current diesel limitations by reducing both NOx and soot while also improving fuel economy. This is accomplished within the cylinder at lower injection pressure and temperature, thereby reducing the need for expensive NOx and soot exhaust after-treatment systems and high pressure injection systems.

The AdvAnTAges ARe dRAmATIC

• Fuel savings of up to 20 percent: The unique fuel injection system and highly effi-

cient combustion process improves performance for all engine uses, with fuel savings of up to 20 percent as compared to conventional diesel en-gines. The multifuel system uses a combination of two or more fuels with varying reactivities, e.g., diesel with gasoline, natural gas or ethanol.

• NOx reductions without after-treatment: The RCCI technologies reduce emissions of

nitrogen oxides through lower and more uniform combustion temperatures. The result is an overall reduction in NOx emissions with reduced need for expensive after-treatment systems that use nitrogen oxide catalysts

and diesel exhaust fluid. (Fig. 3)

• Soot reductions without after-treatment: Rather than injecting a single fuel charge late

in the cycle, the engine employs multiple charges injected very early in the cycle to generate low soot emissions during the combustion process. (Fig. 3)

• Reduced engine costs: The expensive high pressure diesel injector

can be replaced by a relatively inexpensive low pressure injector. Additionally, the RCCI engine technologies achieve soot and NOx control within the combustion chamber with the addition of an inexpensive port fuel injector for a diesel engine or by replacing the spark plug with an injector for a spark ignition engine.

• Reduced reliance on costly after-treat-ment systems and fluids:

Test results confirm that RCCI enables compliance with today’s most stringent EPA emissions regulations, in-cylinder, with reduced need for NOx or soot after-treatment systems and chemicals. In addition, the system is compatible with existing exhaust gas recirculation and after-treatment methods that would provide for further emission reductions.

• End-to-end benefits: From lower engine costs to reduced fuel

consumption to savings from fuel flexibility and reduced need for DEF and other operator inputs, the RCCI technologies offer dramatic, measurable advantages. At the same time, the documented emission reductions ensure regulatory compli-ance while signaling a commitment to superior environmental performance for manufacturers and fleet owners alike.

RCCI TeChnologIes advance state of the art in engine design


Figure 7


Figure 9: Fuel #1 is a lower reactivity fuel such as gasoline, natural gas or ethanol.

21

RCCI PM mass was highly reduced in the DOC)

Engine-out PCCI and RCCI mass were similar in magnitude but

The DOC reduced PM mass by 50% with RCCI vs. 30% with CDC and 10% with PCCI

DOC was effective for RCCI despite lower exhaust temperature

Cell 2, 6-7, 6-9, 6-10, GM engine

0 1 2 3 4 5 6 7

Par

ticle

Mas

s E

mis

sion

s (g

/hp-

hr)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Conventional Diesel

Post DOC

Engine Out

Diesel PCCI

Post DOC

Engine Out

Dual-Fuel RCCI

Post DOC

Engine Out

Reduction by DOC Conventional Diesel: 30 6% Diesel PCCI: 9 18% Dual-Fuel RCCI: 47 9%

±

± ±

RCCI post-DOC emissions 0.014 ± 0.001 g/hp-hr

Engine Condition: 2300 rpm, 4.2 bar BMEP*

iB4.4),8"C')0"/)R^;JcQgRI<B9),."=7)O&,."',)

RCCI post-DOC emissions 0.014 +- 0.001 g/hp-hr

Engine conditions: 2300 rpm, 4.2 bar BMEP (Prikhodko et al. SAE 2010-01-2266)

DieselOxidationCatalysts(DOC) further reduce particulates.

Engine-out PCCI andRCCI mass were similarin magnitude. However, the DOC further reduced PM mass by 47% with RCCI vs. only 30% with CDC and 9% with PCCI.

DOC was effective forRCCI despite lowerexhaust temperature • CDC: 411°C

• PCCI: 408°C

• RCCI: 247°C

*Samples shown for UTG-96/ULSD, stock pistons

RCCI shows near zero levels of soot in PM filter samplesFigure 8: Particle mass comparison (Daw 2013 ERC Symposium).


The RCCI engIne and associated technologies provide a broad range of engine power and torque char-acteristics suitable for automobiles; light-, medium- and heavy-duty trucks and buses; off-road vehicles (agricultural, construction, industrial); locomotives; generator sets and marine vessels including large oceangoing ships (propulsion and auxiliary power).

Engine-size scaling relationships are used to scale fuel injection parameters across engine platforms. Differences in compression ratio, engine speed and operating conditions are accommodated with adjustments to the fuel blend. The technologies also are applicable to rotary engines.

Control of fuel reactivity and stratification combine for a high-performance systemThe RCCI engine portfolio integrates important advances in combustion phasing and duration control to achieve its impressive performance profile. Key innovations include the use of fuels with differing reactivities delivered through multiple injections to achieve optimum fuel reactivity stratification. This enhanced combustion process improves performance, even at low loads or while idling.

• Multiple injections at varying pressures: The engine cycle starts with a pulse of lower

reactivity fuel (e.g., gasoline, natural gas or ethanol) during the early phase of the compression stroke. This fuel pulse is timed to mix with intake air so that it is too “lean” to produce appreciable soot or nitrogen oxides upon combustion, but not so lean that it creates significant amounts of unburned hydrocarbons and carbon monoxide. Smaller pulses of higher reactivity fuel (e.g., diesel, biodiesel or additive) then provide a locally richer fuel mixture for effective autoignition. The timing and volume of these pulses are optimized to control the combustion event to maximize efficiency. The use of varying injection pressures also aids ignition and cuts emissions by introducing further control over the combustion process. The first injection arrives at a lower pressure followed by subsequent injections at higher pressures.

• Variable valve actuation: In a traditional four-stroke engine, intake and ex-

haust valves open to allow air into the combustion chamber and again to release exhaust gases fol-lowing combustion. A fixed geometry and phasing mechanical camshaft opens and closes the valves. Newer technology called variable valve actuation (VVA) uses independently controlled camshaft profile and phasing to open and close valves at optimal times during the combustion cycle.

Port injection of low

reactivity fuel, i.e., gasoline/E85 (orange)

Direct injection of high reactivity fuel, i.e., diesel/B20

(blue)

Figure 10: Schematic of cylinder injection and fuel distribution (Curran et al. SAE 2014-01-1324).

IntakePFI DI

Exhaust

Figure 11: Schematic of engine injection and fuel distribution (Curran et al. SAE 2013-01-0289).

Port Fuel Injectors

Diesel Injectors

Exhaust

Intake Air

Turbo

CAC

Gasoline Fuel

System

Diesel Fuel

System DI Fuel Rail

PFI Fuel Rail

ER

G

Co

ole

r


sIngle Fuel opeRATIon wITh AddITIveRCCI can operate using a single fuel plus a small tank of cetane improving additive. As depicted in figure 13, RCCI is able to use port fuel injection of gasoline and direct injection of the same gasoline doped with a small quantity of additive, e.g., ethylhexyl nitrate (EHN). Results show that while there is a slight increase in NOx emissions using the additive, they are still lower than regulated levels. Additionally, soot emissions are lower and thermal efficiency is increased by using the additive as compared to operation with diesel fuel. (Fig. 14)

Such an operating strategy would only require refilling the additive at typical oil change intervals. Based on a 50 mpg estimate, a 3 gallon tank of additive would require refilling every 10,000 miles, which is less than DEF refilling intervals and amounts.

The RCCI engine can exploit VVA to introduce air into the combustion chamber at optimal times during the compression and power strokes to control the combustion process.

• Improved compression ignition: An initial injection of a lower reactivity fuel is fol-

lowed by injection of a higher reactivity fuel. This fuel reactivity stratification allows combustion in the chamber without use of a spark source.

Low = Prevents Autoignition Fuel Reactivity High = Promotes Autoignition

5.5 bar IMEP 9 bar IMEP5.5 bar IMEP 9 bar IMEP5.5 bar IMEP 9 bar IMEP40424446485052

GIE

(%)

0.000

0.002

0.004

0.006

Soot

(g/k

W-h

)

0.0

0.1

0.2

0.3

NO

x (g

/kW

-h)

E10 + E10/EHN E10 + Diesel Fuel

Figure 14: Emissions and performance comparison of single fuel plus additive RCCI (E10 + E10/EHN) and dual-fuel RCCI (E10 + Diesel Fuel) (Kaddatz et al. SAE 2012-01-1110).

Figure 12: Combustion mode spectrum (Curran 2013 U.S. DOE Annual Merit Review).

• Enhanced performance at low loads: Many advanced engines provide high output

and efficient fuel use, but performance declines markedly at low loads or while idling. The RCCI engine overcomes this obstacle through stratified fuel reactivity and a throttle upstream from the intake port to maintain the optimal fuel/air mixture.

The technology ensures low emissions and enhanced fuel economy across a wide range of engine loads. It can be combined with exhaust gas recirculation and exhaust after-treatment strategies.

Fuel TankAdditiveTank

Figure 13: Single fuel plus additive RCCI setup.


The Wisconsin Alumni Research Foundation is actively seeking industry partners to develop and incorporate the RCCI engine technologies into commercial products.

Please contact Chris Thomas (608.890.2524, [email protected]) to discuss licensing opportunities.To learn more about the RCCI engine technology portfolio, visit warf.org/RCCI.

Figure 6: Curran, S., Gao, Z., and Wagner, R. “Reactivity Controlled Compression Ignition Drive Cycle Emissions and Fuel Economy Estimations Using Vehicle Systems Simulations with E30 and ULSD,” SAE Technical Paper 2014-01-1324, 2014.

Figure 8: Daw, S., “Modeling Emissions Controls for RCCI Engines,” Presentation given at the University of Wisconsin–Madison Engine Research Center Symposium, “Engine Fuel Efficiency and Advanced Combustion,” 2013.

Figure 10: Curran et al. SAE 2014-01-1324. Figure 11: Curran, S., Hanson, R., Wagner, R., and Reitz, R., “Efficiency and Emissions Mapping of RCCI in a Light-Duty Diesel

Engine,” SAE Technical Paper 2013-01-0289, 2013.

Figure 12: Curran, S., “High Efficiency Clean Combustion in Multi-Cylinder Light-Duty Engines,” 2013 US DOE Annual Merit Review. www4.eere.energy.gov/vehiclesandfuels/resources/merit-review/sites/default/files/ace016_curran_2013_o.pdf

Figure 14: Kaddatz, J., Andrie, M.J., Reitz, R.D., and Kokjohn, S.L., “Light-duty Reactivity Controlled Compression Ignition Combustion using a Cetane Improver,” SAE Paper 2012-01-1110, 2012.



AbouT RolF ReITzRolf Reitz is a Wisconsin Distinguished Professor in UW–Madison’s College of Engineering where he serves as director of the Engine Research Center and director of the Direct-Injection Engine Research Consortium. The consortium currently counts 30 industrial members and three national laboratories among its participants.

His research interests include development of advanced computer models for predicting engine performance. With annual sponsored research funding totaling some $1 million per year, Reitz operates a heavy-duty diesel engine laboratory featuring a Caterpillar 3401E single-cylinder test engine equipped with prototype fuel injection systems. He was the first to demonstrate that use of multiple injections can produce signif icant emissions reductions in these engines.

Reitz also runs a high-speed engine laboratory featuring an automotive-size diesel engine with advanced electronically controlled fuel injection systems capable of multiple injections. His experi-mental spray research focuses on fuel drop breakup and atomization phenomena and his research has pioneered the use of computational fluid dynamics to understand the basic physical processes involved.

With major support from the U.S. Department of Energy’s Sandia laboratories, Caterpillar, GM and Ford, the Reitz research group currently includes two staff members, three postdoctoral students and about 17 students pursuing master’s and doctoral degrees. Reitz also supervises international visiting scientists.

Reitz and his group have won numerous industry and academic awards through the years includ-ing multiple presentations of the SAE International Harry L. Horning Memorial Award, the DOE Vehicle Technologies R&D Program Award in 2012 and the ASME Internal Combustion Engine Award in 2011. For more information, visit reitz.me.wisc.edu.

AbouT wARFWARF helps steward the cycle of research, discovery, commercialization and investment for the University of Wisconsin. Founded in 1925 as an independent, nonprofit foundation, WARF manages commercial opportunities on more than 1,500 technologies as it funds university research, obtains patents for discov-eries from campus labs and licenses the inventions to industry. For more information, visit www.warf.org.

Figure 15: UW–Madison Inventors Asst. Prof. Sage Kokjohn, Prof. Rolf Reitz, Reed Hanson, Ph.D. (not pictured: Derek Splitter, Ph.D.)

http://reitz.me.wisc.edu/site/index.php

Investing in research, making a difference.UW–Madison Campus | 614 Walnut Street, 13th floor | Madison, WI 53726 | 608.263.2500 | www.warf.org

03.14

To find out more about WARF’sReactivity Controlled Compression Ignition Technology Portfolio

visit warf.org/RCCI


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