1 ERC Symposium - Future Engines and Their Fuels

Transcription

1 Future Fuels and Reactivity Controlled Compression Ignition (RCCI) Rolf D. Reitz, Reed M. Hanson, Sage L. Kokjohn, Derek A. Splitter, Adam Dempsey, Bishwadipa Das Adhikary, Sandeep Viswanathan, ERC Students and Staff Engine Research Center, University of Wisconsin-Madison Acknowledgments DERC Member Companies DOE/Sandia National Labs Oak Ridge National Labs June 9, ERC Symposium - Future Engines and Their Fuels

2 Outline RCCI combustion background Experimental engines Modeling and experimental results Comparison of RCCI and conventional diesel Use of renewable fuels hydrated ethanol/diesel Conclusions 2 ERC Symposium - Future Engines and Their Fuels

3 IC engine combustion regimes Gasoline engine spark-ignition with flame propagation: High turbulence for high flame speed heat losses, NOx and UHC/CO knock (CR, fuels), throttling losses low thermal efficiency TE ~25% Diesel engine with spray (diffusion) combustion: Rich mixtures (soot), high temperatures (NOx) higher TE ~45% H/Premixed Charge Compression Ignition LTC, chemistry controlled: Sensitive to fuel, poor combustion/load control, low NOx-soot TE ~50% spark-ignition diesel H/PCCI 3 ERC Symposium - Future Engines and Their Fuels

4 Dual fuel Reactivity Controlled Compression Ignition Addition of second fuel allows significant control over autoignition characteristics Optimized stratification of fuel reactivity allows control of combustion duration 2 Single injection SOI = -55 o 12% direct injected n-heptane, PRF=0 88% premixed iso-octane, PRF=100 8 IMEP=5.5 bar, 2300 rev/min 4 ERC Symposium - Future Engines and Their Fuels

5 RCCI combustion Offers transient control Heat release occurs in 3 stages (SAE ) Cool flame reactions result from n-heptane (diesel) injection First energy release occurs where both fuels are mixed Final energy release occurs where lower reactivity fuel is located Changing fuel ratios changes relative magnitudes of stages Fueling ratio provides next cycle CA50 transient control AHRR [J/ o ] Cool Flame Primarly n-heptane PRF Burn n-heptane + entrained iso-octane Iso-octane Burn Crank [ o ATDC] Primarly iso-octane Delivery Ratio [% iso-octane] CA50=2 ATDC Intake Temperature [ o C] RCCI SOI = -50 ATDC 5 ERC Symposium - Future Engines and Their Fuels 5

6 Multiple injections for optimized RCCI Port injected gasoline Direct injected diesel Gasoline Injection Signal Squish Conditioning -80 to to -30 Crank Angle (deg. ATDC) KIVA plus Genetic Algorithms used to optimize multiple injection strategy Ignition Source Gasoline Diesel Diesel 6 ERC Symposium - Future Engines and Their Fuels

7 RCCI high speed combustion luminosity imaging Load: 4.2 bar IMEP Kokjohn, S. GDI SOI: -240 ATDC Musculus, M.P.B Speed: 1200 rpm CR SOI: -57 /-37 ATDC Reitz, R.D., Intake Temperature: 90 C ILASS-2011 Equivalence ratio: 0.42 Intake Pressure: 1.1 bar abs. Iso-octane mass %: 64 Bowl window Squish (upper) window 7 ERC Symposium - Future Engines and Their Fuels

8 Heavy- and light-duty ERC experimental engines Engine Heavy Duty Light Duty Engine CAT SCOTE GM 1.9 L Displ. (L/cyl) Bore (cm) Stroke (cm) Squish (cm) CR 16.1:1 15.2:1 Swirl ratio IVC ( ATDC) -85 and EVO( ATDC) Injector type Common rail Nozzle holes 6 8 Hole size (µm) Engine size scaling Staples et al. SAE HD LD 8 ERC Symposium - Future Engines and Their Fuels

9 RCCI experimental validation - HD Caterpillar SCOTE IMEP (bar) 9 Speed (rpm) 1300 EGR (%) 43 Equivalence ratio (-) 0.5 Intake Temp. ( C) 32 Intake pressure (bar) 1.74 Gasoline (% mass) Diesel inject press. (bar) 800 SOI1 ( ATDC) -58 SOI2 ( ATDC) -37 Fract. diesel in 1 st pulse 0.62 IVC (ºBTDC)/Comp ratio 143/16 Pressure [MPa] Effect of gasoline percentage 14 Experiment Simulation 12 Neat Diesel Fuel 76% 82% 89% 89% Gasoline Neat Gasoline Crank [ ATDC] * Hanson et al. SAE Apparent Heat Release Rate [J/ ] Computer modeling predictions confirmed Combustion timing and Pressure Rise Rate control with diesel/gasoline ratio Dual-fuel can be used to extend load limits of either pure diesel or gasoline 9 ERC Symposium - Future Engines and Their Fuels

10 RCCI high efficiency, low emissions, fuel flexibility Indicated efficiencies of 59% achieved with E85/diesel Emissions met in-cylinder, without need for after-treatment Considerable fuel flexibility, including single fuel operation Diesel can be replaced with <0.5% total cetane improver (2-EHN/DTBP) in gasoline - less additive than SCR DEF - LD vehicle: windshield bottle-size every oil-change interval NOx [g/kw-hr] So oot [g/kw W-hr] Gross Ind. Efficiency Heavy-duty RCCI (gas/gas+3.5% 2-EHN, 1300 RPM) Heavy-duty RCCI (E-85/Diesel, 1300 RPM) Heavy-duty RCCI (gas/diesel 1300 RPM) Splitter et al , Hanson et al HD Target (~2010 Levels) HD Target (~2010 Levels) Gross IMEP [bar] 10 ERC Symposium - Future Engines and Their Fuels

11 Comparison of conv. diesel and RCCI - KIVA CFD Pressure [bar] Average Temperature [K] RCCI Diesel TDC bar IMEP, 1300 rpm, 41% EGR Crank [ ATDC] Diesel SOI Retard Crank [ ATDC] TDC +4 RCCI Diesel Heat Release Rate [J/ ] Peak Temperature [K] Sharp end-of-combustion Peak temperatures reduced significantly compared to conventional diesel combustion Difference between peak and average temperatures very small for RCCI combustion Well mixed combustion event RCCI Diesel ERC Symposium - Future Engines and Their Fuels -8-4 TDC +4 Crank [ ATDC]

12 Comparison of conv. diesel and RCCI combustion High temperature in conventional diesel next to piston bowl surface Highest temperature for RCCI in center of chamber (adiabatic core) Region near liner has similar temperatures heat transfer differences are at piston bowl surface Temperature contours near CA50, Crank = 6.1 deg ATDC 12 ERC Symposium - Future Engines and Their Fuels

13 Comparison of conv. diesel and RCCI - KIVA CFD Gross Indicated Efficiency [%] SOI -20 ATDC RCCI SOI -12 o 7% of fuel energy High EGR Diesel Pinj 800 bar High EGR Diesel Pinj 1800 bar RCCI Combustion CA50 [ ATDC] RCCI: - Similar pressure rise rates - Significantly lower NOx and soot - 16% higher thermal efficiency - Reduced heat losses (~50%) - Improved end-of-combustion phasing Fuel Energy [%] RCCI (800 bar) High-EGR Diesel (1800 bar) Ringing (MW/m 2 ) Max PRR (bar/deg) Gross Indicate TE (%) Combustion Loss (%) ISNOx (g/kw-hr) ISsoot (g/kw-hr) Comb. Loss 48.5 Exhaust 20 Heat Loss 10 GIE 0 With HT Adiabatic With HT Adiabatic High-EGR Diesel RCCI 13 ERC Symposium - Future Engines and Their Fuels

14 Collaboration with Oak Ridge - Parks et al. DOE ACE ERC Symposium - Future Engines and Their Fuels

15 RCCI low emissions HC reduced with DOC 15 ERC Symposium - Future Engines and Their Fuels

16 Fuel flexibility and the future renewable fuels The fuel of the future is going to come from fruit like that sumac out by the road, or from apples, weeds, sawdust almost anything. There is fuel in every bit of vegetable matter that can be fermented. Henry Ford, % of fuel energy consumed in distillation-dehydration. Use of hydrated EtOH can give significant net energy gain 16 ERC Symposium - Future Engines and Their Fuels 16

17 Can Wet ethanol be used with RCCI? Cannot be used with SI engines due to lower flame speeds, misfire, condensation problems, phase separation of water with EtOH-gasoline Cannot be used with diesel engines due to high EtOH octane number Has been proposed for use in HCCI engines Berkeley, LLNL* High heat of vaporization: Gasoline = 308 kj/kg EtOH = 924 kj/kg H 2 O = 2400 kj/kg GT-Power predicted IVC temperature - port injected wet ethanol/gasoline 7 o 9 bar IMEP 52 o 20 o compressio on *Flowers et al. Improving Ethanol Life Cycle Energy Efficiency by Direct Utilization of Wet Ethanol in HCCI Engines, SAE ERC Symposium - Future Engines and Their Fuels

18 Can Wet ethanol be used with RCCI? CHEMKIN HCCI simulations - mixtures of hydrated ethanol and 20% diesel 5 bar 9 bar Use constant intake temperature Water mainly effects intake temperature 13.5 bar 16 bar Dempsey et al. ASME ERC Symposium - Future Engines and Their Fuels

19 Fuel reactivity stratification - EtOH/H 2 O & DI diesel KIVA CFD simulation 1300 rpm, 9 bar IMEP Fuel reactivity stratification with premixed Wet ethanol and DI diesel Wet ethanol gives large reactivity gradients reduces pressure rise rate 19 ERC Symposium - Future Engines and Their Fuels

20 Cylinder pressure and heat release with EtOH/H 2 O 5 bar IMEP 9 bar IMEP 13.5 bar 16 bar 20 ERC Symposium - Future Engines and Their Fuels

21 Thermal efficiency &emissions with 70% EtOH/H 2 O Diesel amount varied to control combustion phasing with 0% EGR 21 ERC Symposium - Future Engines and Their Fuels 21

22 Summary and conclusions RCCI offers practical low-cost pathway to >15% improved diesel engine fuel efficiency (lower CO 2 ) + meet emission mandates in-cylinder Inconvenience of two fuels already accepted by diesel industry (diesel/urea) RCCI is cost effective: - low cost port-injected less reactive fuel (e.g., gasoline, E85, wet EtOH, C/LNG) with optimized* low pressure DI of more-reactive fuel (e.g., diesel/additized gas) - Diesel or GDI (w/spark plug) operation can be retained (limp home). RCCI offers great fuel flexibility and transient response: - proportions of low and high reactivity fuels can be changed dynamically, based on fuels used with same/next-cycle combustion feedback control RCCI can be used with alternative fuels, including hydrated wet ethanol - significantly shifts net energy gain of bio-ethanol fuel production (75% of total distillation energy to remove last 20% of water in EtOH/H 2 O) - intake charge cooled significantly less charge air cooling with boosting - combustion is retarded due to water addition less EGR required - with a single grade of hydrated ethanol (70% ethanol-in-water) and 0% EGR, low NOx and soot predicted from 5 to 16 bar IMEP with peak GTE > 55% * WARF Patents pending 22 ERC Symposium - Future Engines and Their Fuels

23 Future Engines and their Fuels in Sweden today! 23 ERC Symposium - Future Engines and Their Fuels

24 Thank you for your attention! 24 ERC Symposium - Future Engines and Their Fuels

25 Thermal efficiency &emissions with 70% EtOH/H 2 O EGR varied to control combustion phasing with 20% diesel injection 25 ERC Symposium - Future Engines and Their Fuels 25

26 RCCI particulate matter reduced by DOC 26 ERC Symposium - Future Engines and Their Fuels

27 RCCI low particle number by 2 orders of magnitude 27 ERC Symposium - Future Engines and Their Fuels

28 RCCI provides high efficiency, low emissions HD engine gasoline/diesel RCCI gives near zero NOx and soot and peak gross thermal efficiency of 56% Pressure [bar] AHRR [J/deg] Experiment = Solid Simulation = Dash bar bar 9.3 bar 11.6 bar 14.6 bar Crank [ ATDC] Kokjohn et al. IJER 2011 Hanson et al. SAE Splitter et al. THIESEL 2010 NOx [g/kw-hr] Soot [g/kw-hr] Gross Ind. Efficiency [%] Ringing Int. [MW/m 2 ] 1300 rev/min EPA HD Limit 2010 EPA HD Limit Experiment Simulation IMEPg [bar] 28 ERC Symposium - Future Engines and Their Fuels