effects of gasoline low-temperature heat release on engine ... presentations/session 3... ·...

SAE INTERNATIONALSAE INTERNATIONALDavid Vuilleumier, UC Berkeley 1

David VuilleumierFormerly: University of California, BerkeleyCurrently: Sandia National Laboratories

EFFECTS OF GASOLINE LOW-TEMPERATURE HEAT RELEASE ON ENGINE OPERATION AND PERFORMANCEWith a focus on gasoline compression ignition engines.

Coordinating Research Council 2nd Advanced Fuels and Engine Efficiency Workshop

November 1st – 3rd, 2016With contributions by:

Ben WolkFrithjof Schwerdt

Diego BestelMarco Mehl

Malte SchaferAlex Frank

Samveg SaxenaWilliam Pitz

Prof. Darko KozaracProf. Mani SarathyProf. Robert Dibble

And funding by:NSF/DOE

AEC MEETING AUG. 2014 BENJAMIN WOLK – UC BERKELEYCoordinating Research Council 2nd Advanced Fuels and Engine Efficiency Workshop, Nov. 2016

The US Relies on Liquid Fuels in the Transportation Sector

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Petroleum36%

Petroleum36%

Coal26%Coal26%

Natural Gas20%

Natural Gas20%

Renewables 9%Renewables 9%Nuclear 8%Nuclear 8%

Supply Source

Transportation28%

Transportation28%

Industrial21%

Industrial21%

Commercial & Residential 11%Commercial &

Residential 11%

Electric Power40 %

Electric Power40 %

Demand Sector

4%of transportation

3%of transportation

93%of transportation

3%of natural gas

13%of renewables

71%of petroleum

US Total in 2011 =28.5 trillion kW-hr2011 Primary Energy Consumption

US Department of Energy (2012)


• Kinetically controlled combustion engines often use fuels with moderate to long ignition delays, such as gasoline, ethanol, or methane

• Ignition delay times are sensitive to many factors, including temperature, pressure, and fuel and oxidizer concentrations

• Low and Intermediate Temperature chemistry can significantly shorten ignition delay times

• Well-defined in-cylinder conditions provide platform for studying fuel autoignition.

Kinetically Controlled Combustion and influences by Pre-Ignition Reactions

Credit: Saxena et. al. (2013)

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‐3.1

‐2.9

‐2.7

‐2.5

‐2.3

‐2.1

‐1.9

‐1.7

‐1.5

1 1.1 1.2 1.3 1.4

Log(

Igni

tion

dela

y tim

es)

1000/T [1/K]

Credit: Mehl et. al. (2015)Image: LLNL


Low-Temperature Heat Release Impacts Auto-Ignition

TDC = 360°CASjöberg and Dec (2007)

850 K 1000 K 1200 K

Hot ignitionH2O2 decompositionIntermediate temperature heat release (ITHR)

Low temperature heat release (LTHR)

550 K

PRF80 = 80% iso-octane + 20% n-heptane (liq. vol.)PRF80 = 80% iso-octane +

20% n-heptane (liq. vol.)

HCCI

Wolk (2014)

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Intermediate Temperatures


Gasoline-Ethanol Blends for studying Low-Temperature Heat Release in an HCCI engine

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FACE C Gasoline• 84 RON• 83 MON• 70% Iso-Paraffins• 24% N-Paraffins• 4% Aromatics

FACE A Gasoline• 84 RON• 83.5 MON• 86% Iso-Paraffins• 12% N-Paraffins• <1% Aromatics

Image: CRC

Fuels for Advanced Combustion (FACE) Gasolines

Engine Parameters

CR 17:1 Fuel Injection PFIDisp. .474 L Fuel Pressure 45 PSIBore 79.4 mm No. of Valves 2Stroke 95.5 mm IVO 2 °bTDCCon. Rod 144 mm IVC 47.5 °aBDCCoolant Temp. 95 °C EVO 47.5 °bBDC

Oil Temp. 100 °C EVC 8 °aTDC


HCCI Rate of Heat Release Profiles:φ=0.4, CA50 = 6 CAD aTDC

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Intake temp. limit

Intake Temperature Required for Constant Combustion Phasing (6°ATDC) as a function of intake pressure (φ=0.4)

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0% Ethanol

20% Ethanol

Pre-

igni

tion

heat

rele

ase

MO

RE

LESS

10% Ethanol


Seven Fuels Tested For Minimum GCI LoadThree AKI Levels

85 AKI: • 0% ethanol (FACE C Gasoline, Neat) • 23% ethanol (FACE J Gasoline, Blended)

88 AKI:• 7% ethanol (FACE C Gasoline, Blended)• 10% ethanol (Haltermann CARB LEV III Cert. Fuel)

91 AKI: • 0% ethanol (FACE G Gasoline, Neat)• 14% ethanol (FACE C Gasoline, Blended)• 36% ethanol (FACE J Gasoline, Blended, AKI 90,5)

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GCI Operating Conditions

HCCI Operating Conditions

Engine Speed (RPM) 850 1000 Intake Temperature (°C) 45 45 ‐ 130 Intake Pressure (bar) 1.05, 1.23, 1.4 1.0 ‐ 1.8

Injection Type DI PFI Injection Timing (dBTDC) 10 ‐ 40 Closed Valve Injection Pressure (bar) 400 4 External EGR Rate (%) 0 0

Coolant Temperature (°C) 105 Compression Ratio (‐) 16.5

IVO (°bTDC) 20 IVC (°bTDC) 140 EVO (°aTDC) 140 EVC (°aTDC) 8 No. of Valves 4 Bore (mm) 81 Stroke (mm) 95.5

Connecting Rod Length (mm) 144


Low-Load Sweep FACE J E23 – 1.05 Bar Intake Pressure

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• Lowest Stable Load – Lowest

injection duration at which the

standard deviation of IMEP does not

exceed 0.15 bar IMEP

• 1.05, 1.23, 1.4 bar intake pressures

• 15° - 40° bTDC Injection Timing

Sweep

• 850 RPM, 45° C intake

temperature


The Big Picture:Minimum Load for All Tested Fuels

91 AKI

85 AKI

88 AKI

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Research Octane Number (RON):• 600 RPM, 52°C Intake Temperature, 13° BTDC Spark• Comparison to Primary Reference Fuels

Motor Octane Number (MON):• 900 RPM, 149° C Intake Temperature, 19° – 26° BTDC Spark• Comparison to Primary Reference Fuels

Anti-Knock Index (AKI):• AKI = ( RON + MON ) / 2

Octane Index (OI):• OI = RON – K * S• S = RON – MON• Engine and Operating Point Specific

RON, MON, AKI, and OIWhat do they mean?

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The Octane Index shows good correlation to lowest-load performance -- R2 = 0.943

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K = -1.14


Octane Index Provides Best Correlation with Lowest-Load Performance

Correlation w/GCI Lowest-Load 1.4 Bar



RON R2 = 0.89 R2 = 0.93 R2 = 0.84

MON R2 = 0.09 R2 = 0.18 R2 = 0.53

AKI R2 = 0.63 R2 = 0.67 R2 = 0.56

OI R2 = 0.94 R2 = 0.98 R2 = 0.97

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LTHR Onset Intake Pressure was measured for all fuels tested in GCI operation.

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Low-Temperature Heat Release Behavior Correlates as well as Octane Index




OI R2 = 0.94 R2 = 0.98 R2 = 0.97

LTHR R2 = 0.95 R2 = 0.97 R2 = 0.98

Indicates LTHR may affect GCI Low-Load Performance

“Correlation does not imply causation”

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Low-Temperature Chemistry

Suppression

Increasing Sensitivity

Increasing LTHR

Ignition delays show same reactivity trend in Low-Temperature region

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25 bar, φ = 1.0


How does this relate back to ethanol?

Ethanol has modest AKI, but very high OI for low-load GCI conditions• Hence ethanol inhibits low-load GCI more than its AKI would suggest

Similar for Toluene

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Blending Components RON MON AKI OI

Ethanol 109 90 99 130

Toluene 121 107 114 137

Iso-Octane 100 100 100 100

N-Heptane 0 0 0 0


Summary and Conclusions

• Low-Temperature Heat Release is Pressure Sensitive• Increased boost pressures change fuel heat release behavior from

single-stage to dual-stage

• Ethanol Inhibits Low-Temperature Heat Release• Seen in both HCCI engine and ignition delay curves• Also well described by Octane Index

• LTHR Enables Low-Loads in GCI Engines• Fuels with lower LTHR tendency make low-load GCI operation

more difficult

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QUESTIONS?Thank You For Your Attention!

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Peak LT-HRR

Pin = 1.8 bar

P, T

P, TP, T

Cylinder Pressure and Average Cylinder Temperature at Peak LTHR

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700 750 800 850 900 950 10000

10

20

30

40

50

60

70

80

Temperature at Peak LT-HRR [K]

Pre

ssur

e at

Pea

k LT

-HR

R [b

ar]

1

2

3

4

5

6

7

8

9x 10

-3

Low-temperature heat primarily released at

T < 850 KP > 30 bar

Sca

led

HR

R a

t Pea

k LT

-HR

R

E20

E10

E0

↑ Pin & ↑ LTHR

Wolk

effects of gasoline low-temperature heat release on engine ... presentations/session 3... ·...

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