improving fuel efficiency with fuel-reactivity-controlled combustion

UNIVERSITY OF WISCONSIN - ENGINE RESEARCH CENTER

1

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


2Outline

• Motivation

• Experimental Setup

• Experimental Results– Gasoline PPC– Dual-Fuel PCCI

• Conclusions


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


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)

5

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

6

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!


9Outline

• Motivation



• Conclusions


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


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


12Outline

• Motivation



• Conclusions


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


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


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.

Effect of EGR - gasoline


17

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


18Outline

• Motivation



• Conclusions


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


20

• 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


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


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


22Effect of IVC: Dual-Fuel PCCI - 9 barNominal IMEP (bar) 9


EGR rate (%) 43



Intake pressure (bar) 2.0 1.74


Percent gasoline by mass 78% 82%





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)


23Effect of IVC: Dual-Fuel PCCI - 9 bar

Nominal IMEP (bar) 9


EGR rate (%) 43



Intake pressure (bar) 2.0 1.74


Percent gasoline by mass 78% 82%





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]


24

•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


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


27

THANK YOU,

QUESTIONS?

28

Dual fuel HCCI combustion

Minimum ISFC PRF ~50

3 bar – 2000 rpm

10 bar – 2000 rpm

improving fuel efficiency with fuel-reactivity-controlled combustion

Documents