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

16

Thank you for your attention !

Questions or Comments

DEER 2007 Conference August 16, 2007

17

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