William Cannella Chevron

Fuel Effects in Advanced Combustion -Partially Premixed Combustion (PPC) with Gasoline-Type Fuels

Vittorio Manente, Prof. Bengt Johansson, Prof. Per Tunestal

Lund Institute of Technology Department of Energy Sciences Division of Combustion Engines

Lund, Sweden

Work Done In Collaboration With:

Acknowledgement

SAE Publications: 2009-01-2668 2010-01-0871 2010-01-1471 2010-01-2198

Goals for Advanced Combustion Systems Improve engine efficiency/fuel economy and meet CO2 emissions regulations Lower engine-out NOx and PM/soot emissions to meet stricter regulations Reduce size, costs, and fuel consumption penalties of aftertreatment systems (especially NOx) Operate effectively over wide speed/load range In Europe: Options for mitigating diesel/gasoline supply/demand imbalance

-60 -50 -40 -30 -20 -10 0 100

0.2

0.4

0.6

0.8

1

CAD [TDC]

[a.u

.]

Load & CA50 Const.

Partially Premixed Combustion Characteristics:

Avoid conditions that cause NOx & soot formation in conventional diesel CI combustion -- form of PCCI

Fuel/air mixing intermediate between HCCI & conventional CI combustion (“partial premix”) Better performance than HCCI due to

some fuel/air stratification Approach:

One or two fuel injections

When used, first one placed @ -60 TDC to create homogeneous mixture (Similar to Toyota “Unibus” approach)

Last injection around TDC (to achieve CA50 @ MBT ~5-10˚ ATDC) - Stratification created by this injection triggers combustion.

Same energy content injected per fuel

EGR used to prevent early reaction during compression stroke

Pilot quantity function of:

-Fuel properties

-Operating conditions

Study Objectives

Test effects of properties of different gasoline range blends in HD CI engine operated under

Partially Premixed Combustion Mode

Different fuel properties/composition Different “reactivity”

Different ignition and combustion characteristics Different effective speed/load operating ranges

”Gasoline”Fuel RON MON C H/C LHV [MJ/kg] A/F stoich

FR47335CVX 99.00 96.90 7.04 2.28 44.30 15.10

FR47331CVX 92.90 84.70 6.90 1.99 41.60 14.02

FR47338CVX 88.60 79.50 7.21 1.88 43.50 14.53

FR47330CVX 87.10 80.50 7.20 1.92 43.50 14.60

FR47333CVX 80.00 75.00 7.16 1.97 43.70 14.65

FR47336CVX 70.30 65.90 7.10 2.08 43.80 14.83

FR47334CVX 69.40 66.10 7.11 1.98 43.80 14.68

Ethanol 107.00 89.00 2.00 3.00 26.90 9.00

Fuel Selection Gasoline-type fuels selected based on prior results which suggest gasoline may better achieve goals than diesel fuel in PPC due to higher volatility and longer ignition delay (SAE2006-04-3385, SAE2007-01-0006, SIAT 2009) Blends of refinery gasoline range components:

Studied fuel property effects by blending streams with different compositions and RON’s RON’s ranging from 69-99 Ethanol also tested

50 < ON < 75

90 < ON < 99

Typical Refinery Streams

Gasoline-range streams having octane numbers as low as ~50 exist in refineries and are used to make gasoline blends

Bosch Common Rail

Prail 1600 [bar]

Orifices 8 [-]

Orifice Diameter 0.18 [mm]

Umbrella Angle 120° [deg]

Engine / Dyno Spec

rcgeometric 14.3* [-]

BMEPmax 15 [bar]

Vd 1951 [cm3]

Swirl ratio 2.9 [-]

Issue: Old, first generation Bosch injector – impacts soot emissions

Scania D12 Heavy Duty Diesel Engine – Single Cylinder

* - Standard rcgeometric = 17.1

Engine Characteristics

Preferred PPC operating region:

If lambda is ~ 1.5 and EGR between 45 – 55 %, combustion should occur in the desired temperature range

Low NOx and low HC & CO!!!

In addition, should still be enough O2 to limit soot production.

30 35 40 45 50 55 60 65 701000

1200

1400

1600

1800

2000

2200

2400Adiabatic Flame Temperature

EGR Ratio [%]

Tem

pera

ture

[K]

λ=1λ=1.1λ=1.2λ=1.3λ=1.4λ=1.5λ=1.6λ=1.7λ=1.8λ=2λ=2.5λ=3λ=3.5λ=4

Achieving low CO, HC, NOx & soot: -Controlling T through EGR & λ

Base Test Conditions

Dyno LIMIT

11 2 4 6 8 10 12 14 16 18 20

300

320

340

360

380

400

420

440

Gross IMEP [bar]

Inle

t Tem

pera

ture

[K]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Injection Parameters

4 6 8 10 12 14 16 18 200

10

20

30

40

50

60

70

80

90

100

Gross IMEP [bar]

Pilo

t Rat

io [%

]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Higher ON gasolines & ethanol required significant amount fuel in pilot

Higher ON gasolines & ethanol required high Tin to run lower loads

Lower ON gasolines performed best with no pilot

Pilot Ratio vs. Load

T inlet vs. Load

2 4 6 8 10 12 14 16 18 200

0.5

1

1.5

2

2.5

Gross IMEP [bar]

Soot

[FSN

]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

2 4 6 8 10 12 14 16 18 200

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Gross IMEP [bar]

NOx [

g/kW

h]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX NOx below US10 limit for most fuels/conditions

(little to no aftertreatment needed!)

No correlation with RON/MON

Engine-Out NOx and Soot Emissions

0 5 10 15 20 25 300

0.5

1

1.5

2

2.5

3

Gross IMEP [bar]

Soot

[FSN

]

G. ON 99/97G. ON 98/88G. ON 97/86G. ON 93/85G. ON 89/80G. ON 87/81G. ON 80/75G. ON 70/66G. ON 69/66D. CN 52PRF20

Diesel Fuel (CN=52)

Significant improvement in soot when modern injection system used (but DPF still needed for gasolines)

Low RON

EtOH

NOx vs. Load

Soot vs. Load

4 6 8 10 12 14 16 18 20140

145

150

155

160

165

170

175

180

Gross IMEP [bar]

Gros

s Ind

icate

d Sp

ecific

Fue

l Con

sum

ptio

n [g

/kWh] Phase 4, 1300 [rpm]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

2 4 6 8 10 12 14 16 18 2095

95.5

96

96.5

97

97.5

98

98.5

99

99.5

100

Gross IMEP [bar]

Com

busti

on E

fficien

cy [%

]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Very high combustion and gross indicated efficiencies

over entire load range

2 4 6 8 10 12 14 16 18 2040

42

44

46

48

50

52

54

56

58

60

Gross IMEP [bar]

Gro

ss In

dica

ted

Effi

cien

cy [%

]EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Efficiencies Combustion Efficiency vs. Load

Gross Indicated Efficiency vs. Load

down to 150g/kwhr!

Gross Indicated Specific Fuel Consumption

Approaching 56%!

2 4 6 8 10 12 14 16 18 200

5

10

15

20

25

Gross IMEP [bar]

Max

Pre

ssur

e R

ise

Rat

e [b

ar/C

AD

]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Lower ON fuels had lower MPRR’s at high loads

Maximum Pressure Rise Rate (MPRR)

Load Operating Area If Tintake limited to ~330˚K:

o With no Tintake constraints, all fuels tested able to operate at all loads o With reasonable Tintake constraints:

• all fuels tested able to operate at the higher loads • only the lowest RON fuels able to operate at the lowest loads

2 4 6 8 10 12 14 16 18 20300

320

340

360

380

400

420

440

Gross IMEP [bar]

Inle

t Tem

pera

ture

[K]

EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX

Tintake vs. Load

-5 0 5 10 15 20 250

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Soot

[FSN

]

Combustion Phasing, CA50, [TDC]

FR47338CVXFR47335CVXFR47334CVX

-5 0 5 10 15 20 250

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Indi

cate

d NO

x [g/

kWh]

Combustion Phasing, CA50, [TDC]

FR47338CVXFR47335CVXFR47334CVX

Nissan MK type combustion, easier to achieve with fuels with high octane number.

CA50 Sweep: NOx – soot-efficiency

US 2010 Limits

For this engine system and mode of operation, optimal timing appears to be ~5-10˚ATDC

NOx vs. CA50 Soot vs. CA50

Gross Indicated Efficiency vs. CA50

17

Summary • Gasoline PPC enabled simultaneous achievement of high efficiency, low

emissions and acceptable MPRR’s at all loads tested (5-18 bar gross IMEP) in heavy duty CI engine with EGR~50%, λ =1.5, & CA50=5-10˚ATDC • Able to run all gasoline fuels and ethanol at all loads tested

Lower ON fuels could be run with reasonable intake T’s & 0% pilot Higher ON fuels (incl. ethanol) required high intake T’s & significant % fuel in

pilot to run @ lower loads

• Gross indicated efficiency between 52-56% attained for loads higher than 6 bar gross IMEP. (Gross ISFC’s down to 150 g/kwhr)

• Engine-out NOx below US2010 limits without aftertreatment • At highest load soot was between 0.2-2 FSN. (<0.5 FSN with modern

injection system). Acceptable level with DPF’s

• At high loads, Maximum Pressure Rise Rates (MPRR) were best for the lower ON fuels, with values of ~12 bar/CAD