ERC Symposium 2009 1 Improving Fuel Efficiency with Fuel-Reactivity-Controlled Combustion Rolf D. Reitz, Reed Hanson, Derek Splitter, Sage Kokjohn Engine Research Center University of Wisconsin-Madison http://reitz.me.wisc.edu Acknowledgements: Department of Energy/Sandia National Laboratory Contract DEFC26-06NT42628 Caterpillar, Diesel Emission Reduction Consortium
Outline 2 Motivation Experimental Setup Experimental Results Gasoline PPC Dual-Fuel PCCI Conclusions
Motivation 3 Heightened concern for improved fuel efficiency GHG, economy New diesel emissions regulations EPA 2010 on-highway H-D Euro 5,6 LTC (MK,PCCI,HCCI, etc.) Advantages Low NOx and PM emissions. High thermal efficiency. Disadvantages Load limits from high PRR and HRR. No direct control of combustion phasing. PPC hybrid combustion, between HCCI and diesel LTC. [1] [[1] N. Dronniou et.al, Volvo France, THIESEL 2008 Conference on Thermo- and Fluid Dynamic Processes in Diesel Engines
Motivation 4 Partially Premixed Combustion Increase ignition delay to add mixing time. 2 ways to achieve PPC High EGR rates Reduce PM formation with low combustion temperatures. (Akihama et al. SAE 2001-01-0655) Fuels Use low CN fuels and EGR to add ignition delay. (G. Kalghatgi et al. SAE 2007-01-0006) Optimize fuel reactivity. (Bessonette et al. SAE 2007-01-0191)
Fuel effects: diesel vs. gasoline Kalghatgi et al. SAE Paper 2007-01-0006 Engine heavy-duty, flat cylinder head, shallow bowl Bore x Stroke [mm] 127 x 154 Connecting rod [mm] 255 Compression ratio 14.0 Number of holes, diameter [μm] Injector Operating conditions 8, 200 Engine speed [rev/min] 1200 Swirl ratio 2.4 Intake temperature [K], Pressure [bar] Oxygen fraction @ IVC/EGR [%] 313, 2.0 15.8/25 Pilot pulse split ratio [%] 30 Injection profile Ra, Yun, Reitz Int. J Vehicle Design 2009 5
Diesel vs. gasoline - double injection Gasoline Diesel inj inj Start of injection: -137 and -9 (gasoline) -6 (diesel) deg atdc. Measured (Kalghatgi - 2007) ERC KIVA-CHEMKIN w/ PRF mechanism Ra, Reitz Comb&Flame 2008 6
Diesel vs. gasoline - ignition delay Diesel SOI = -2 Gasoline SOI = -11 CA= tdc CA= -8 CA= +4 CA= tdc CA= +6 CA= +10 CA= +12 CA= +12 7
Diesel vs. gasoline - emissions Use of gasoline fuel offers significant benefits for CIDI engines! 8
Outline 9 Motivation Experimental Setup Experimental Results Gasoline PPC Dual-Fuel PCCI Conclusions
ERC Caterpillar Engine Lab 10 3401E SCOTE Geometry Displacement (l) 2.44 Geometric Compression Ratio 16.1:1 Bore (mm) 137.20 Stroke (mm) 165.10 Connecting Rod Length (mm) 261.60 Squish Height (mm) 1.57 Number of Valves 4 IVC (deg BTDC) (modified cam) 85.00 IVO (deg ATDC) 335.00 Swirl Ratio (stock) 0.7 Piston Type Articulated Piston Bowl Geometry Stock Effective Compression Ratio ~10:1
IVC-control camshaft and injectors Use late IVC timing to lower effective CR and TDC temperatures. 11 Allow for later phasing of combustion. IVC timing of 85 BTDC lowered peak cylinder pressures 10 bar vs. IVC at 143 BTDC and lowered TDC temperatures by 100 K. Injection systems: Cat HEUI 315B Bosch Gen 2 Common Rail Injection System Bosch CR HEUI 315B Number of holes 6 8 Number of holes (stock) 6 Hole diameter (mm) 0.25 0.229 Hole diameter (mm) (stock) 0.169 Included spray angle (deg) 145 154 Included spray angle (deg) (stock) 126 Fuel pressure (bar) 1500 1500
Outline 12 Motivation Experimental Setup Experimental Results Gasoline PPC Dual-Fuel PCCI Conclusions
Gasoline Experimental Conditions 13 Double injections A50 EGR Low Load (A25) Single Injections A50 with 40% EGR Base Operating Conditions FTP Cycle Point A50 A25 Engine Speed [rpm] 1300 1300 IMEP net [bar] 11 6.5 Fuel Flow [mg/inj] 135 67.5 Pilot/Main % Split 30/70 30/70 Pilot SOI [ATDC] -137-137 Fuel Pressure [bar] 1500 1500 Hanson et al. "Operating a Heavy Duty DICI Engine with Gasoline for Low Emissions," SAE 2009-01-1442, 2009 Intake Temp [ C] 40 40 Exhaust Pressure [kpa] 207 159 Intake Pressure [kpa] 200 152 EGR [%] 0-45 0-30 Maximum PRR [bar/deg] 15 15
Effect of EGR - gasoline A50 double injection EGR sweep Simultaneous PM vs. NOx tradeoff can be achieved with sufficient EGR. 14 Approach EPA H-D 2010 NOx and PM emissions levels at 45% EGR. 2010 Ignition Delay increases due to combination of EGR and low CN fuel. EID=SOI-CA50
Effect of EGR - gasoline 15 Heat Release Rate increases as mixture becomes more homogeneous gasoline HCCI Combustion durations decrease with EGR.
Effect of EGR - gasoline 16 Pressure rise rates lower than typical HCCI engines, which can be between 10-30 bar/deg at a similar operating condition. Net ISFC decreases as combustion phasing is optimized and heat transfer is lowered.
Gasoline Single Injection - A50 A50 Double Injection A50 Single Injection 17 Equivalence ratio stratification controls ignition Injection Strategy Double Single EGR (%) 40.8 41 NOx (g/kwh) 0.41 0.37 HC (g/kwh) 2.68 1.39 PM (g/kwh) 0.021 0.026 CO (g/kwh) 6.76 5.53 ISFC net (g/kwh) 173.5 167.9 IMEP net (bar) 11.23 11.62 Maximum PRR (bar/deg) 12.4 9.0
Outline 18 Motivation Experimental Setup Experimental Results Gasoline PPC Dual-Fuel PCCI Conclusions
Fuel Reactivity Control: Dual-Fuel PCCI19 Bessonette et al. (SAE 2007-01-0191) extended HCCI load range by varying fuel composition 16 bar BMEP required 27 cetane fuel 3 bar BMEP required 45 cetane fuel HCCI modeling indicates minimum ISFC cannot be achieved with either neat gasoline or neat diesel fuel (Kokjohn & Reitz ICLASS-09) Optimized dual-fuel operation requires different fuel reactivity for different operating conditions Port fuel injection of gasoline Direct injection of diesel fuel Fuel blending in-cylinder IVC = -132 deg. ATDC; Pivc = 2.32 bar) 10 bar 2000 rpm - No DEF tank! Minimum ISFC PRF ~50 Gasoline Diesel
Modeling used for PRF & EGR Selection HCCI simulations were used to choose optimal EGR rate and fuel reactivity - 6, 9, and 11 bar IMEP - 1300 rev/min As load is increased the gasoline minimum ISFC cannot be achieved with either neat diesel fuel or neat gasoline 11 69 bar IMEP 20 Experiments KIVA GA optimization used to choose injection parameters -SOI1 ~ -60 ATDC -SOI2 ~ -33 ATDC - 60% of fuel in first injection (Kokjohn & Reitz ICLASS-09) diesel
21 Experiments: Dual-Fuel PCCI - 11 bar IMEP Nominal IMEP (bar) 11 Engine speed (rev/min) 1300 EGR rate (%) 45.5 Equivalence ratio (-) 0.77 Intake Temperature ( C) 32 Intake pressure (bar) 2.0 Total fuel (mg/cycle) 128 Percent gasoline by mass 78% 82% 85% Diesel injection pressure (bar) 800 Diesel SOI1 ( ATDC) -67.0 Diesel SOI2 ( ATDC) -33.0 Fract. of diesel fuel in pulse 1 (-) 0.65 IVC timing (ºATDC) -85 Fuel reactivity controlled ignition Pressure [MPa] NOx [g/kw-hr] Soot [g/kw-hr] 15 12 9 6 3 SOI1 = -67 ATDC SOI2 = -33 ATDC Inj. Pres. = 800 bar 78% 82% 0 0-30 -20-10 0 10 20 30 0.3 0.2 0.1 0.0 0.015 0.010 0.005 0.000 Crank [ ATDC] US 2010 HD Limit 85% 78 79 80 81 82 83 84 85 Gasoline [% of total fuel] 2400 1800 1200 600 Heat Release Rate [J/ ]
Effect of IVC: Dual-Fuel PCCI - 9 bar 22 Nominal IMEP (bar) 9 Engine speed (rev/min) 1300 EGR rate (%) 43 Equivalence ratio (-) 0.50 Intake Temperature ( C) 32 Intake pressure (bar) 2.0 1.74 Total fuel (mg/cycle) 96 Percent gasoline by mass 78% 82% Diesel injection pressure (bar) 800 Diesel SOI1 ( ATDC) -58.0 Diesel SOI2 ( ATDC) -37.0 Fract. of diesel fuel in pulse 1 (-) 0.62 IVC timing (ºATDC) -85-143 IVC 85 (73% Gas) IVC 143 (82% Gas) IVC 143 (89% Gas) IVC 115 (79% Gas) Stock cam (IVC 143) requires more gasoline to achieve similar combustion phasing/prr - PRR easily controlled with gasoline fraction
Effect of IVC: Dual-Fuel PCCI - 9 bar 23 Nominal IMEP (bar) 9 Engine speed (rev/min) 1300 EGR rate (%) 43 Equivalence ratio (-) 0.50 Intake Temperature ( C) 32 Intake pressure (bar) 2.0 1.74 Total fuel (mg/cycle) 96 Percent gasoline by mass 78% 82% Diesel injection pressure (bar) 800 Diesel SOI1 ( ATDC) -58.0 Diesel SOI2 ( ATDC) -37.0 Fract. of diesel fuel in pulse 1 (-) 0.62 IVC timing (ºATDC) -85-143 NOx and soot very similar for both cams well below US 2010 PRR < 10 bar/deg and net ISFC of 158 g/kw-hr! Net ISFC [g/kw-hr] PRR [bar/deg.] 163 162 161 160 159 158 14 12 10 8 82 83 84 85 86 87 88 89 Gasoline [% of total fuel]
Dual-Fuel PCCI Thermal Efficiency 24 9 11 bar IMEP I-MEPg I-MEPn BMEP Fuel-MEP Q-MEP B F P Ex Ht C CL-MEP HT-MEP Ex-MEP P-MEP I-MEPn F-MEP 16% 14% 12% 11.7% 36% 37% 34% 31% 44% 45% 50% 53% Conv. Diesel LTC Gas. PPCI D-F PCCI 100 90 80 70 60 50 40 30 20 10 0 Percent of Fuel Energy [%] Conv. Diesel: Staples; LTC: Hardy; Gas PPCI: Hanson; D-F PCCI: Hanson
>50% Thermal Efficiency Engines Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel is the most powerful and efficient prime-mover in the world. Bore 38, 1820 L, 7780 HP/Cyl at 102 RPM 25
Conclusions 26 PPC Gasoline - No traditional PM/NOx tradeoff - Approach 2010 EPA H-D on-highway truck emissions standards in-cylinder at 11 and 6 bar IMEP net - Low net ISFC and pressure rise rates A dual fuel HCCI/PCCI concept is proposed - Port fuel injection of gasoline (cost effective) - Direct injection of diesel fuel (moderate injection pressure) - Possibility of traditional diesel or SI (with spark plug) operation retained for full load operation PCCI operation at 6, 9, and 11 bar net IMEP was achieved with near zero NOx and soot and a reasonable PRR 53% indicated thermal efficiency was achieved while meeting US 2010 EPA standards in-cylinder
27 THANK YOU, QUESTIONS?
28 Dual fuel HCCI combustion 3 bar 2000 rpm 10 bar 2000 rpm Minimum ISFC PRF ~50