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1
High-Efficiency, Ultra-Low Emission Combustion in a Heavy-Duty Engine via Fuel Reactivity Control
Rolf D. Reitz,Reed Hanson, Derek Splitter, Sage Kokjohn
Engine Research CenterUniversity of Wisconsin-Madison
http://reitz.me.wisc.edu
15th Diesel Engine-Efficiency and Emissions Research Conference August 3rd, 2009
Acknowledgements:Department of Energy/Sandia National Laboratory
• Contract DEFC26-06NT42628
Diesel Emission Reduction Consortium
UNIVERSITY OF WISCONSIN -
ENGINE RESEARCH CENTER
2
Outline
•
Motivation
•
Experimental Results–
Gasoline PPC
•
CFD Modeling –
Fuel reactivity
•
Experimental Results–
Dual-fuel PCCI
•
Conclusions
UNIVERSITY OF WISCONSIN -
ENGINE RESEARCH CENTER
3
Motivation
• Emissions regulationsEPA 2010 on-highway HDEuro 5,6
LTC (MK,PCCI,HCCI, etc.)Advantages
Low NOx and PM emissionsHigh thermal efficiency
DisadvantagesLoad limits from high PRR No direct control of combustion timing
PPC
–
“hybrid”
between HCCI and diesel LTCKalghatgi
“Mixed enough”
combustion
• Concern for improved fuel efficiency –
GHG, economy
Park & Reitz, CST, 2007Low emissions window
4
Motivation
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 SAE 2001-01-0655)•
Fuels–
Use low CN fuels and EGR to add ignition delay
(Kalghatgi
SAE 2007-01-0006)
–
Optimize fuel reactivity
(Bessonette SAE 2007-01-0191)
5
Engine heavy-duty, flat cylinder head, shallow bowl
Bore x Stroke [mm] 127 x 154Compression ratio 14.0
Diesel injector
Number of holes, diameter [m]
8, 200
Operating conditionsEngine speed [rpm] 1200
Swirl ratio 2.4
Intake temperature [C], Pressure [bar]
40, 2.0
Oxygen fraction @ IVC/EGR [%] 15.8/25
Pilot split ratio [%] 30
Kalghatgi: SAE Paper 2007-01-0006
Diesel vs. gasoline compression ignition
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120 140 160
crank angle [deg atdc]
mor
mal
ized
inje
ctio
n ve
loci
ty
Injection profile
30%70%
6
Numerical models
Single Zone SimulationsSENKIN engine codeERC reduced PRF mechanism
41 species, 130 reactions –
Ra & Reitz CNF, 2008
Multi-Dimensional ModelingKIVA-3V code coupled with CHEMKIN IIRNG k-ε
turbulence model
KH-RT drop break up model Grid-independent spray modelsDrop collision and coalescenceERC reduced PRF mechanism
KIVA Modeling -
Ra, Yun, Reitz Int. J. Vehicle Design 2009
7
Start of injection: -137 and -6 (diesel), -9 (gasoline) deg atdc. -
Measured (Kalghatgi et al. SAE 2007)Model: ERC KIVA-CHEMKIN w/ PRF mechanism
Diesel vs. gasoline -
double injection
0
2
4
6
8
10
12
-50 -40 -30 -20 -10 0 10 20 30 40 50
crank angle [deg atdc]
pres
sure
[MPa
]-100
100
300
500
700
900
1100
HR
R [J
/deg
]
P, ExpP, CalHRR, ExpHRR, Cal
inj
Gasoline
0
2
4
6
8
10
12
-50 -40 -30 -20 -10 0 10 20 30 40 50
crank angle [deg atdc]
pres
sure
[MP
a]
-50
50
150
250
350
450
550
HR
R [J
/deg
]
P, ExpP, CalHRR, ExpHRR, Cal
inj
Diesel
Pre
ssu
re (
MP
a)
8
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
9
Diesel vs. gasoline -
emissions
Additional time for mixing of gasoline offers benefits for CIDI engines!
0
0.05
0.1
0.15
0.2
0.25
0.3
-30 -20 -10 0 10 20start of main injection
calc
ulat
ed s
oot [
g/kg
-f]
0
2
4
6
8
10
12
14
16
18
AVL
sm
oke
opac
ity [%
]
Gasoline, calDiesel, calGasoline, expDiesel, exp
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
-30 -20 -10 0 10 20start of main injection [deg atdc]
NO
x [g
/kg-
f]
Gasoline, calGasoline, expDiesel, calDiesel, exp
diesel
gasoline
Soot
NOx
10
Outline
•
Motivation
•
Experimental Results–
Gasoline PPC
•
CFD Modeling –
Fuel reactivity
•
Experimental Results–
Dual-fuel PCCI
•
Conclusions
UNIVERSITY OF WISCONSIN -
ENGINE RESEARCH CENTER
11
ERC Caterpillar engine lab 3401E SCOTE
Displacement (l) 2.44
Geometric Comp. Ratio 16:1Bore (mm) 137Stroke (mm) 165
Number of Valves 4IVC (BTDC modified cam) 85/143Effective Comp. Ratio ~12-16
Swirl Ratio (stock) 0.7Piston Bowl Geometry Stock
Injection systems:Cat HEUI 315B, Bosch Gen 2 Common Rail1500 bar, 0.25 mm 6-hole
12
Gasoline experimental conditions
Double injection• A50
– EGR• Low Load (A25)
Single Injection
• A50 with 40% EGR
FTP Cycle Point A50 A25Speed [rpm] 1300 1300IMEP net [bar] 11 6.5
Pilot/Main % Split 30/70 30/70Pilot SOI [ATDC] -137 -137Injection Pressure [bar] 1500 1500
Intake Temp [°C] 40 40Intake Pressure [kPa] 200 152
EGR [%] 0-45 0-30
Baseline Operating Conditions
Hanson et al. "Operating a Heavy Duty DICI Engine with Gasoline for Low Emissions," SAE 2009-01-1442, 2009
13
Effect of EGR -
gasoline
A50 double injection EGR •
Simultaneous PM vs. NOx tradeoff can be achieved with sufficient EGR
EID=SOI-CA50
• Ignition Delay increases due to combination of EGR and low CN fuel
2010
• Approach EPA HD 2010 NOx
and PM emissions levels at 45% EGR
14
•
Combustion duration decreases with EGR
gasoline HCCI
(fixed CA50 requires earlier SOI)
•
Pressure rise rates increase (still lower than typical HCCI)
Effect of EGR -
gasoline
•
Net ISFC decreases: -
combustion phasing optimized
•
50% Indicated Thermal Efficiency approached
15
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
Max PRR (bar/deg) 12.4 9.0
Gasoline single injection -
A50
• Equivalence ratiostratificationcontrols ignitionand heat releaseprofile
50% indicated thermalEfficiency
16
Outline
•
Motivation
•
Experimental Results–
Gasoline PPC
•
CFD Modeling –
Fuel reactivity
•
Experimental Results–
Dual-fuel PCCI
•
Conclusions
UNIVERSITY OF WISCONSIN -
ENGINE RESEARCH CENTER
17
10 20 30 40 50 60 70 80 900.000
0.002
0.004
0.006
0.008
0.010
0.012 = 0.5 = 1.0 = 1.5 = 2.0
Igni
tion
dela
y (s
)
Pressure (atm)
0
20
40
60
80
100
120
140
Cra
nk a
ngle
at 2
000
rev/
min
10 20 30 40 50 60 70 80 900.0000
0.0002
0.0004
0.0006
0.0008
0.0010
0.0012
0.0014
0.0016
0.0018
0.0020
Cra
nk a
ngle
at 2
000
rev/
min
Igni
tion
dela
y (s
)
Pressure (atm)
= 0.5 = 1.0 = 1.5 = 2.0
024681012141618202224
-
Constant volume combustion with Tinit
=800-900 K
iso-octanen-heptane
• n-heptane
(diesel) delay ~6 x shorter than iso-octane (gasoline)• Diesel delay much less sensitive to pressure and equivalence ratio• Gasoline fuel requires boosted operation and/or high intake temperature
and locally rich but “mixed enough”
(low swirl, low injection pressure)
Comparison of diesel vs. gasoline ignition delay
• CHEMKIN –
ERC PRF Mechanism
2 deg 12 deg
18
• Optimized operation requires different fuel reactivity for differentoperating conditions: Dual-fuel– Port fuel injection of gasoline– Direct injection of diesel fuel
Fuel reactivity control: Dual-fuel PCCI
•
Bessonette
(SAE 2007-01-0191) extended HCCI load range by varying fuel composition
–16 bar BMEP
required 27 cetane fuel: gasoline-like–3 bar BMEP
required 45 cetane fuel: diesel-like
Gasoline Diesel
Fuel blending in-cylinder
-
No DEF tank!DieselExhaust“Fuel”
19
-
6, 9, and 11 bar IMEP- 1300 rev/min
iso-octane
gasolinen-heptane
diesel
6 bar IMEP
0 10 20 30 40 50 600
20
40
60
80
100
250
180 g/kW-hr
MISFIRE
190g/kW-hr
PR
F [-]
EGR Rate [%]
10 bar/deg.
5.6 bar/deg.
Modeling used for PRF & EGR selection
190 g/kW-hr
180 g/kW-hr
10 bar/deg.
170
190
210
230240
Net ISFC [g/kW-hr]
9 bar IMEP
16 bar/deg.
230
220
180
MISFIRE
210
190
200
11 bar IMEP
gasoline
diesel
Experiments• SENKIN ERC-PRF simulations
• As load is increased, minimum ISFC cannot
be achieved with either neat diesel or neat gasoline
EGR
PRF
Kokjohn
& Reitz –
ICLASS-09
20
* Kokjohn
et al. SAE 09FFL-0107
Charge preparationKIVA GA optimization used to choose injection parameters*-
Gasoline port injection
-
Diesel DI
- SOI1 ~ -60°ATDC- SOI2 ~ -33°ATDC-
60% of diesel fuel in first injection
21
Outline
•
Motivation
•
Experimental Results–
Gasoline PPC
•
CFD Modeling –
Fuel reactivity
•
Experimental Results–
Dual-fuel PCCI
•
Conclusions
UNIVERSITY OF WISCONSIN -
ENGINE RESEARCH CENTER
22
Experiments: Dual-fuel PCCI - 11 bar
-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 = -67ATDCSOI2 = -33ATDCInj. Pres. = 800 barIMEP (bar) 11
Speed (rpm) 1300
EGR (%) 45.5
Equivalence ratio (-) 0.77
Intake Temp. (°C) 32
Intake pressure (bar) 2.0
Gasoline (% mass) 78 82 85
Diesel inject pressure (bar) 800
SOI1 (°ATDC) -67
SOI2 (°ATDC) -33
Fract. of diesel in 1st
pulse 0.65
IVC (ºATDC) - 85
• Fuel reactivity controls ignition and heat release rate• Combustion phasing easily controlled with gasoline amount
161
168
175
78 79 80 81 82 83 84 850
7
14
Net
ISFC
[g/k
W-h
r]PR
R[b
ar/d
eg]
Gasoline [% of total fuel]
0.0
0.1
0.2
0.3
78 79 80 81 82 83 84 850.000
0.005
0.010
0.015N
Ox
[g/k
W-h
r] US 2010 HD Limit
Soot
[g/k
W-h
r]
Gasoline % of total fuel
23
-30 -20 -10 0 10 20 30 40 500
2
4
6
8
10
12
14
16
Crank [ATDC]
Pres
sure
[MPa
]
0
200
400
600
800
1000
1200
1400
1600
Hea
t Rel
ease
Rat
e [J
/]
SOI1 = -58ATDCSOI2 = -37ATDCInj. Pres. = 800 bar
Effect of Comp. Ratio: Dual-fuel PCCI
IMEP (bar) 9
Speed (rpm) 1300
EGR (%) 43
Equivalence ratio (-) 0.5
Intake Temp. (°C) 32
Intake pressure (bar) 2 1.74
Gasoline (% mass) 78 82
Diesel inject pressure (bar) 800
SOI1 (°ATDC) -58
SOI2 (°ATDC) -37
Fract. of diesel in 1st
pulse 0.62
IVC (ºATDC) -85 -143
•
Stock CR (IVC 143) requires more gasoline to achieve similar combustion -
PRR controlled with gasoline fraction
-30 -20 -10 0 10 20 30 40 500
2
4
6
8
10
12
14
16
IVC 11579% Gas
IVC 14382% Gas
Crank [ATDC]
Pres
sure
[MPa
] IVC 8573% Gas
0
200
400
600
800
1000
1200
1400
1600
Hea
t Rel
ease
Rat
e [J
/]
SOI1 = -58ATDCSOI2 = -37ATDCInj. Pres. = 800 bar
IVC 85 (73% Gas) IVC 143 (82% Gas) IVC 143 (89% Gas) IVC 115 (79% Gas)
24
Effect of Comp. Ratio: Dual-fuel PCCI
•
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]
IMEP (bar) 9
Speed (rpm) 1300
EGR (%) 43
Equivalence ratio (-) 0.5
Intake Temp. (°C) 32
Intake pressure (bar) 2 1.74
Gasoline (% mass) 78 82
Diesel inject pressure (bar) 800
SOI1 (°ATDC) -58
SOI2 (°ATDC) -37
Fract. of diesel in 1st
pulse 0.62
IVC (ºATDC) -85 -143
• NOx
and soot similar for both cams
well below US 2010
82 83 84 85 86 87 88 890.000
0.005
0.010
0.015
Soot
[g/k
W-h
r]
Gasoline [% of total fuel]
0.0
0.1
0.2
0.3US 2010 HD Limit
NO
x [g
/kW
-hr]
25
•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 SAE 2009-01-1124; LTC: Hardy 2006-01-0026, 2006; Gas PPCI: Hanson SAE 2009-01-1442, 2009; D-F PCCI: Kokjohn
SAE 09FFL-0107
9–11 bar IMEP
26
Simulation results
-20 -15 -10 -5 0 5 10 15 201E-5
1E-4
1E-3
0.01
Crank [ATDC]
Mas
s Fr
actio
n [-]
0
400
800
1200
1600
2000
oh
ch2oco
ic8h18nc7h16
HRR
Tem
pera
ture
[K] a
nd H
RR
[J/]
Temp
Temperature (K) n-heptane (-) iso-octane (-) Formaldehyde (-)
Extended combustion duration even as load is increasedUncharacteristic of PCI
combustionSmall diesel quantity provides
improved control compared to gasoline HCCI
27
Conclusions•
PPC “Mixed enough”
Gasoline
-
No traditional PM/NOx tradeoff
-
Approach 2010 EPA HD on-highway truck emission standards
in-cylinder at 11 and 6 bar net IMEP-
Low ISFC and pressure rise rate
•
Dual-fuel PCCI concept used to control fuel reactivity-
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
•
Dual-fuel operation at 6, 9, and 11 bar net IMEP achieved with near zero NOx and soot and reasonable Pressure Rise Rate
•
53% indicated thermal efficiency achieved
while
easily meeting US 2010 EPA standards in-cylinder
28
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
Dual-fuel surpasses 50% Thermal Efficiency engines
• If technology could be applied to all US Truck and Auto engines, oil consumption could be reduced by 1/3 = oil imports from Persian Gulf
29
30
US Petroleum consumption: 20.7 Million Barrels of Oil per Day*65% used in transportation = 13.5 MBOD
Truck and Automotive fuel usage reduction by Dual Fuel:4.2 MBOD Diesel: 45%
53%= improvement of 18% = 0.6 million barrels saved
9.3 MBOD
Gasoline SI: 30%
53%= improvement of 77% = 4.1 million barrels saved
Total saved = 4.7 MBOD = 34% of US transportation oil(23% of total US petroleum used ~ $1 Billion saved / 2 days)
• Could reduce transportation oil consumption by 1/3 = US imports from Persian Gulf
-
while surpassing 2010 emissions regulations
• US DOE/EERE FreedomCar
& 21st Century Truck fuel efficiency goals:50% increase in light-duty, 25% increase in heavy-duty
Fuel Efficiency and US Oil Consumption
http://www.eia.doe.gov/*
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