Adaptive Injection Strategies (AIS) for Ultra-Low
Emissions Diesel Engines
Yong Sun*, Eric D. Weninger, Rolf D. Reitz
Engine Research Center, University of Wisconsin-Madison
Acknowledgments:
Caterpillar, Inc.
DOE/Sandia National Labs
Diesel Emissions Reduction Consortium (DERC)
DEER 2007 Conference
Detroit, MI
08/16/2007
2 OUTLINE
• Motivation and background • Adaptive Injection Strategy (AIS) • Simulation and optimization
– Two-Stage Combustion (TSC -- HCCI + Diffusion combustion) optimization using AIS
– Late injection event optimization – Early injection event optimization
• Engine experiments – Preliminary experimental results of TSC using AIS
• Conclusions
DEER 2007 Conference August 16, 2007
0 2 4 6 8 100.0
0.1
0.2
0.3
0.4
0.5
0.6
PM [g
/bhp
-hr]
NOx [g/bhp-hr]
1988
1991
200420072010
3 MOTIVATION AND BACKGROUND • More and more stringent emission standards • Low Temperature Combustion (LTC) – low NOx & PM
• Problems in diesel Homogeneous Charge Compression Ignition (HCCI) Combustion
HCCI
Conventional
DieselPCCI
(Kamimoto, Akihama, Pickett)
• Early ignition: ÆEGR ÆVVA ÆVCR
• Evaporation: Æintake air preheating ÆSMD
• HC & CO • Spray-wall impingement: ÆAdaptive Injection Strategy (AIS)
Variable Injection Pressure (VIP) Variable Geometry Spray (VGS)
• Extension to higher loads: ÆTwo-Stage Combustion (TSC)
DEER 2007 Conference August 16, 2007
4 ADAPTIVE INJECTION STRATEGY (AIS)
Hollow-cone &
Multi-hole
• Variable Geometry Spray (VGS)
Variable Spray Angle Variable Spray Pattern
• Variable Injection Pressure (VIP) Liquid penetration of non-evaporating sprays vapor penetration of evaporating sprays:
1/4⎛ ΔP ⎞ s = 2.95 d t (Hiroyasu, H.)⎜ ⎟ 0ρ⎝ a ⎠
Maximum liquid penetration of evaporating sprays:
b ρ f Ca ⋅ d ⎛ 2 ⎞2
(Siebers, D.)s = ⎜ +1⎟ −1 a ρa tan( /2) ⎜
⎝ B T ( a , a , f ⎟⎠θ P T )
DEER 2007 Conference August 16, 2007
5 AIS APPLICATION
• Low-pressure (<50MPa, 5~25MPa) narrow-angle injection -- Early injection: intake or early compression stroke ÆHCCI, PCCI combustion
-- Post injection: late expansion or exhaust stroke Æ DPF, LNT regeneration
• High-pressure (>50MPa, above 100MPa) wide-angle injection -- Late injection: late compression or early expansion stroke Æ conventional diesel, PCCI combustion
TDC BDC
TDC
BDC TDC
• Low load: HCCI combustion Æ early injection
• Medium load: Two-Stage Combustion (TSC) Æ early + late injections -- Sun, Y., SAE 2006-01-0027
• High load: conventional diesel combustion Æ late injection
(US Patent filed)
DEER 2007 Conference August 16, 2007
6 ENGINE SPECIFICATIONS
1.0Swirl Ratio
137.2 × 165.1Bore× Stroke [mm]
16.1:1Compression Ratio
IVC=-143, EVO=130 EVC=-355, IVO=335
Engine valve timing (°CA ATDC)
2.44Displacement [L]
Caterpillar 3401 SCOTE Engine Type
-85IVC (°CA ATDC) 57Load (%)
1737Speed [RPM] 5Mode
DEER 2007 Conference August 16, 2007
DEER 2007 Conference August 16, 2007
7
60 ° btdc
90 ° btdc
bdc
20 ° btdc
140 °
120 °
110 °
90 °
70 °
52 °
Nominal Spray Angle
AIS SIMULATION USING TWO INJECTORS
Bosch 150MPa
127°
8-hole 127um
Bosch 10MPa
90°
6-hole 170um
Intake stroke early compression
stroke
late compression stroke
around TDC
8 NUMERICAL ANALYSIS
• KIVA3V R2 (ERC sub-models) -CHEMKIN-GA code • RNG k-ε turbulence model •KH-RT break up model -- high-pressure MHN spray • Recalibrated KH model -- low-pressure MHN spray • Droplet vaporization, collision and wall-film models • ERC’s reduced n-heptane mechanism (30 species and 65 reactions) • Reduced NO mechanism, two-step phenomenological soot model • Genetic Algorithms (GA) -- merit function
Bf = a b c d⎛ NOx ⎞ ⎛ HC ⎞ ⎛ PM ⎞ ⎛ BSFC ⎞+ + +⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ NOx * ⎠ ⎝ HC * ⎠ ⎝ PM * ⎠ ⎝ BSFC * ⎠
-- Emission targets are 2010 EPA heavy-duty highway diesel engine emission standards.
PM: 0.0134 g/kW-hr NOx: 0.2681 g/kW-hr
HC: 0.1876 g/kW-hr BSFC: 200 g/kW-hr
-- Penalty functions based on the physical constraints of the engine DEER 2007 Conference August 16, 2007
9 LATE INJECTION EVENT OPTIMIZATION
• Genetic Algorithm (GA) was used to optimize four engine operating parameters at mode 5 (homogeneous assumption for the early injection) • Range of parameters explored
Parameter Lower Limit Upper Limit
IVC (°CA) -143 -83 SOLI (°CA) -10 21
Premixed fraction (-) 0.2 0.9 EGR ratio (%) 0 60
• Merit function 100f = 2 10 ⎛ NOx ⎞ ⎛ HC ⎞ ⎛ PM ⎞ ⎛ BSFC ⎞+ + +⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ NOx * ⎠ ⎝ HC * ⎠ ⎝ PM * ⎠ ⎝ BSFC * ⎠
DEER 2007 Conference August 16, 2007
10 HCCI + LATE INJECTION OPTIMUM
Best case after 100 generations IVC (°CA) SOLI (°CA) EGR (%) Premixed fraction
-95 17 28 0.7 Results of the best case so far
(g/kW-hr) BSFC Soot NOx HC CO Optimum 211.4 0.017 0.174 0.014 0.123
Target 200 0.0134 0.2681 0.1876 16
Max
. in-
cylin
der t
empe
ratu
re (K
) 2500
2000
1500
1000
12
8
4Pres
sure
(MPa
)
0-50 -25 0 25 50
500-40 -20 0 20 40 60 80
CA (Deg. ATDC) CA (Deg. ATDC) DEER 2007 Conference August 16, 2007
11
SOI: -270°CA
SOI: -180°CA
SOI: -120°CA
0
5
10
15
20
25
30
0.00
0.15
0.30
0.45
0.60
0.75
0.90 W
all-f
ilm fu
el fr
actio
n [%
]
Inho
mog
enei
ty (N
SD
)
EARLY INJECTION OPTIMIZATION #
2
#
( ) cells
i i i
cells
i i
m
m
δ
δ
Φ − Φ
Φ
∑
∑
-360 -310 -260 -210 -160 -110 -60 SOI [Deg. ATDC]
DEER 2007 Conference August 16, 2007
10.0
0.5
0.5
Peak cylinder temperature (K)
Equ
ival
ence
ratio
1400 1600 1800 2000 2200 24000.0
0.5
1.0
1.5
2.0
CO(g/kg f)1900.01630.01360.01090.0
820.0550.0280.0
10.0
NO(g/kg f)170.0145.8121.6
97.473.148.924.7
0.5
Soot(g/kg f)5.54.84.13.42.61.91.20.5
NO
SootCO
10.0
145.0
280.0
1090.0
1630.0
0.5
12.6
24.7 97
.4
Peak cylinder temperature (K)
Equ
ival
ence
ratio
1400 1600 1800 2000 2200 24000.0
0.5
1.0
1.5
2.0
CO(g/kg f)1900.01630.01360.01090.0
820.0550.0280.0
10.0
NO(g/kg f)170.0145.8121.6
97.473.148.924.7
0.5NO
CO
10.0
12 TSC USING AIS
0.1876 0.014 2.040 HC
0.123 12.889
CO 0.1810.033Injection
0.26810.0134Target 0.1740.017Homogeneous
NOxSoot(g/kW-hr)
(iso-surface: phi=0.2)
(homogeneous assumption) • IVC: -95°CA • EGR: 28% • HCCI: 70% • Diffusion: 30% • SOLI: 17°CA • SOEL: -120°CA
-50 -40 -30 -20 -10 0 10 20 30 40 50 0
2
4
6
8
10
12
14
16
Pre
ssur
e [M
Pa]
CA [Deg. ATDC]
homogeneous injection
-
-
-
-
-
145.0
280.0
1090.0
1630.0
Peak cylinder temperature (K)
Equ
ival
ence
ratio
1400 1600 1800 2000 2200 2400 0.0
0.5
1.0
1.5
2.0
CO(g/kg-f) 1900.0 1630.0 1360.0 1090.0 820.0 550.0 280.0
10.0
CO
Clean Combustion
Regime
(Sung Wook Park, ERC, UW-Madison)
DEER 2007 Conference August 16, 2007
13 TSC & AIS USING ONE INJECTOR
• Wide angle (130°) w/ VIP — Incompatibility w/ HCCI operation — Later SOI, larger fueling rate
Included angle: 90° Æ 130°
SOEL: -120°CA Æ -100°CA
Injector: 6-hole Æ 8-hole (Tanabe, K., SAE 2005-01-007)
(g/kW-hr) Soot NOx HC CO two injectors 0.033 0.181 2.040 12.889 one injector 0.030 0.229 3.376 9.895
Target 0.0134 0.2681 0.1876 Pre
ssur
e [M
Pa]
16
14
12
10
8
6
4
2
0
two injectors one injector
-50 -40 -30 -20 -10 0 10 20 30 40 50 CA [Deg. ATDC]
DEER 2007 Conference August 16, 2007
14 Preliminary TSC Experimental Results
VGS LTC Dual Mode Combustion Experimental Conditions First injection: 100 deg. BTDC
160 0.1 70% of fuel Injection pressure 10MPa.
0.075 Second injection:120
-60 -40 -20 0 20 40 60 C A [ A TD C ]
Pres
sure
[bar
]
17 deg. ATDC
30% of fuel,
Injection pressure 130MPaNA
HR
R
0.05
80
0.025
40 0
0 -0.025
Smooth_Pressure(BAR) NAHRR
EGR (%) 21.83 BSFC (g/kW-hr) 245.2833 NOx (g/kW-hr) 0.5667 HC (g/kW-hr) 6.1953 NOx + HC (g/kWhr) 6.7621 PM (g/kW-hr) 0.1426 CO (g/kw-hr) 13.899
DEER 2007 Conference August 16, 2007
15 CONCLUSIONS
• Use of Adaptive Injection Strategies (AIS) is an effective way to minimize diesel spay-wall wetting and to enable advanced combustion strategies.
• Low-pressure injection is superior to conventional high-pressure injection for HCCI charge preparation.
• A low-pressure early injection, followed by a high-pressure late injection provides Two-Stage Combustion (TSC) that shows great potential to achieve low engine-out emissions (2010 levels) and fuel consumption at medium engine load when engine operating parameters are optimized.
• One injector with VIP and a fixed spray included angle can be used for practical implementation of the TSC concept - (patent applied for).
Further work is in progress to explore AIS/TSC concepts at other speed/load conditions, and for different engine displacements.
•
DEER 2007 Conference August 16, 2007
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Thank you for your attention !
Questions or Comments
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Backup Slides
DEER 2007 Conference August 16, 2007
Tanabe, K., SAE 2005-01-007
18 AIS IMPLEMENTATION
• Variable Spray Angle • Variable Geometry Spray (VGS)
Hollow-cone spray (Kawaguchi, A.) Multi-hole Nozzle (MHN) spray • Variable Spray Pattern
– Caterpillar Inc., mixed mode injector (DEER 2004)
-- Hou et al., SAE 2007-01-0249, Micro-Variable Circular Orifice (MVCO) injector
• Variable Injection Pressure (VIP) • Reitz et al., US Patent: 6,526,939 B2 •
dual rail type CRS pressure intensifier type CRS
DEER 2007 Conference August 16, 2007