UNIVERSITY OF WISCONSIN - ENGINE RESEARCH CENTER
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Improving Fuel Efficiency with Fuel-Reactivity-Controlled Combustion
Rolf D. Reitz,Reed Hanson, Derek Splitter,
Sage Kokjohn
Engine Research CenterUniversity of Wisconsin-Madison
http://reitz.me.wisc.edu
ERC Symposium 2009
Acknowledgements:Department of Energy/Sandia National Laboratory
• Contract DEFC26-06NT42628Caterpillar, Diesel Emission Reduction Consortium
UNIVERSITY OF WISCONSIN - ENGINE RESEARCH CENTER
2Outline
• Motivation
• Experimental Setup
• Experimental Results– Gasoline PPC– Dual-Fuel PCCI
• Conclusions
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3Motivation
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
Heightened concern for improved fuel efficiency – GHG, economy
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4MotivationPartially 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)
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Engine heavy-duty, flat cylinder head, shallow bowl
Bore x Stroke [mm] 127 x 154Connecting rod [mm] 255
Compression ratio 14.0Injector
Number of holes, diameter [μm] 8, 200
Operating conditionsEngine speed [rev/min] 1200
Swirl ratio 2.4Intake temperature [K],
Pressure [bar] 313, 2.0
Oxygen fraction @ IVC/EGR [%] 15.8/25
Pilot pulse split ratio [%] 30
Kalghatgi et al. SAE Paper 2007-01-0006
Fuel effects: diesel vs. gasoline
Injection profile
Ra, Yun, Reitz Int. J Vehicle Design 2009
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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
Gasoline Diesel
Diesel vs. gasoline - double injection
inj inj
7
CA= tdc
CA= +4
CA= +6
CA= +12
Diesel SOI = -2
CA= -8
CA= tdc
CA= +10
Gasoline SOI = -11
CA= +12
Diesel vs. gasoline - ignition delay
8
Diesel vs. gasoline - emissions
Use of gasoline fuel offers significant benefits for CIDI engines!
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9Outline
• Motivation
• Experimental Setup
• Experimental Results– Gasoline PPC– Dual-Fuel PCCI
• Conclusions
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10ERC Caterpillar Engine Lab
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
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11IVC-control camshaft and injectors• Use late IVC timing to lower effective CR and TDC temperatures.
• 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 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
Injection systems:
• Cat HEUI 315B
• Bosch Gen 2 Common Rail
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12Outline
• Motivation
• Experimental Setup
• Experimental Results– Gasoline PPC– Dual-Fuel PCCI
• Conclusions
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13Gasoline Experimental ConditionsDouble injections• A50
–EGR• Low Load (A25)
Single Injections• A50 with 40% EGR
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
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
Base Operating Conditions
Hanson et al. "Operating a Heavy Duty DICI Engine with Gasoline for Low Emissions," SAE 2009-01-1442, 2009
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14Effect of EGR - gasolineA50 double injection EGR sweep
• Simultaneous PM vs. NOx tradeoff can be achieved with sufficient EGR.
• Approach EPA H-D 2010 NOx and PM emissions levels at 45% EGR.
• Ignition Delay increases due to combination of EGR and low CN fuel.
2010
EID=SOI-CA50
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•Heat Release Rate increases as mixture becomes more homogeneous gasoline HCCI
•Combustion durations decrease with EGR.
Effect of EGR - gasoline
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• 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.
Effect of EGR - gasoline
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A50 Double Injection A50 Single Injection
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
Gasoline Single Injection - A50
• Equivalence ratiostratificationcontrols ignition
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18Outline
• Motivation
• Experimental Setup
• Experimental Results– Gasoline PPC– Dual-Fuel PCCI
• Conclusions
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19Fuel Reactivity Control: Dual-Fuel PCCI• 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)
Minimum ISFC PRF ~50
10 bar2000 rpm
Gasoline Diesel
- No DEF tank!
IVC = -132 deg. ATDC; Pivc = 2.32 bar)• Optimized dual-fuel operation requiresdifferent fuel reactivity for differentoperating conditions– Port fuel injection of gasoline– Direct injection of diesel fuel– Fuel blending in-cylinder
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• 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 minimum ISFC cannot be achieved with either neat diesel fuel or neat gasoline
6 bar IMEP
Modeling used for PRF & EGR Selection
9 bar IMEP11 bar IMEP
• KIVA GA optimization used to choose injection parameters
- SOI1 ~ -60°ATDC- SOI2 ~ -33°ATDC- 60% of fuel in first injection
(Kokjohn & Reitz – ICLASS-09)
gasoline
diesel
Experiments
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21Experiments: Dual-Fuel PCCI - 11 bar IMEP
-30 -20 -10 0 10 20 300
3
6
9
12
15
Crank [°ATDC]
Pres
sure
[MPa
]
0
600
1200
1800
2400
85%
78%
82%
Hea
t Rel
ease
Rat
e [J
/°]
SOI1 = -67°ATDCSOI2 = -33°ATDCInj. Pres. = 800 bar
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
0.0
0.1
0.2
0.3
78 79 80 81 82 83 84 850.000
0.005
0.010
0.015
NO
x[g
/kW
-hr] US 2010 HD Limit
Soot
[g/k
W-h
r]Gasoline [% of total fuel]
• Fuel reactivity controlled ignition
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22Effect of IVC: Dual-Fuel PCCI - 9 barNominal 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
•Stock cam (IVC 143) requires more gasoline to achieve similar combustion phasing/PRR
- PRR easily controlled with gasoline fraction
IVC 85 (73% Gas) IVC 143 (82% Gas) IVC 143 (89% Gas) IVC 115 (79% Gas)
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23Effect of IVC: Dual-Fuel PCCI - 9 bar
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!
158159160161162163
Net
ISFC
[g/k
W-h
r]
82 83 84 85 86 87 88 898
10
12
14
PRR
[bar
/deg
.]
Gasoline [% of total fuel]
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•0
•10
•20
•30
•40
•50
•60
•70
•80
•90
•100
D-FPCCI
Gas.PPCI
Conv.Diesel LTC
•Per
cent
of F
uel E
nerg
y [%
]
Dual-Fuel PCCI – Thermal Efficiency
Fuel-MEP
Q-MEPCL-MEP
HT-MEP
Ex-MEPI-MEPg
I-MEPn P-MEP
F-MEPBMEP
B F P Ex Ht C
I-MEPn
16% 14% 12% 11.7%
36% 37% 34% 31%
44% 45% 50% 53%
Conv. Diesel: Staples; LTC: Hardy; Gas PPCI: Hanson; D-F PCCI: Hanson
9–11 bar IMEP
25Wartsila-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
>50% Thermal Efficiency Engines
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26Conclusions• 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
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THANK YOU,
QUESTIONS?
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Dual fuel HCCI combustion
Minimum ISFC PRF ~50
3 bar – 2000 rpm
10 bar – 2000 rpm