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Research Papers: Fuel Combustion

Experimental Study of Methane Fuel Oxycombustion in a Spark-Ignited Engine

[+] Author and Article Information
Andrew Van Blarigan

Combustion Analysis Laboratory,
Department of Mechanical Engineering,
University of California at Berkeley,
Berkeley, CA 94720
e-mail: avanbla@berkeley.edu

Darko Kozarac

Faculty of Mechanical Engineering
and Naval Architecture,
University of Zagreb,
Zagreb 10000, Croatia
e-mail: darko.kozarac@fsb.hr

Reinhard Seiser

Department of Mechanical and
Aerospace Engineering,
University of California at San Diego,
La Jolla, CA 92093
e-mail: rseiser@ucsd.edu

Robert Cattolica

Department of Mechanical and
Aerospace Engineering,
University of California at San Diego,
La Jolla, CA 92093
e-mail: rcattolica@eng.ucsd.edu

Jyh-Yuan Chen

Combustion Analysis Laboratory,
Department of Mechanical Engineering,
University of California at Berkeley,
Berkeley, CA 94720
e-mail: jychen@me.berkeley.edu

Robert Dibble

Combustion Analysis Laboratory,
Department of Mechanical Engineering,
University of California at Berkeley,
Berkeley, CA 94720
e-mail: dibble@me.berkeley.edu

1Corresponding author.

Contributed by the Internal Combustion Engine Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received March 22, 2013; final manuscript received June 25, 2013; published online September 12, 2013. Assoc. Editor: Timothy J. Jacobs.

J. Energy Resour. Technol 136(1), 012203 (Sep 12, 2013) (9 pages) Paper No: JERT-13-1090; doi: 10.1115/1.4024974 History: Received March 22, 2013; Revised June 25, 2013

An experimental investigation of methane fuel oxycombustion in a variable compression ratio, spark-ignited piston engine has been carried out. Compression ratio, spark-timing, and oxygen concentration sweeps were performed to determine peak performance conditions for operation with both wet and dry exhaust gas recirculation (EGR). Results illustrate that when operating under oxycombustion conditions an optimum oxygen concentration exists at which fuel-conversion efficiency is maximized. Maximum conversion efficiency was achieved with approximately 29% oxygen by volume in the intake for wet EGR, and approximately 32.5% oxygen by volume in the intake for dry EGR. All test conditions, including air, were able to operate at the engine's maximum compression ratio of 17 to 1 without significant knock limitations. Peak fuel-conversion efficiency under oxycombustion conditions was significantly reduced relative to methane-in-air operation, with wet EGR achieving 23.6%, dry EGR achieving 24.2% and methane-in-air achieving 31.4%. The reduced fuel-conversion efficiency of oxycombustion conditions relative to air was primarily due to the reduced ratio of specific heats of the EGR working fluids relative to nitrogen (air) working fluid.

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References

Figures

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Fig. 1

Layout of experimental setup. the full loop was used when operating with wet EGR. The globe valve between plenums was closed when operating on dry EGR or air. PT = pressure transducer.

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Fig. 2

Measured fuel-conversion efficiency at each CR and spark-timing for case dry EGR 3

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Fig. 3

The combustion efficiency at each CR and spark-timing for case dry EGR 3

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Fig. 4

The CoV IMEP at each CR and spark-timing for case dry EGR 3

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Fig. 5

peak fuel-conversion efficiency versus O2 concentration for CR = 17 (CR = 17 produced the highest fuel-conversion efficiency for all cases). Error bars correspond to the calculated 95% confidence interval (see Appendix for a description of the uncertainty calculation).

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Fig. 6

Peak fuel-conversion efficiency of wet EGR for each CR tested

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Fig. 7

(a) Peak fuel-conversion efficiency of wet EGR, dry EGR, and air. Connected points are the peaks measured at different CRs for the same O2 concentration and (b) IMEP corresponding to the results shown in (a). Error bars correspond to the calculated 95% confidence interval (see Appendix for a description of the uncertainty calculation).

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Fig. 8

γ values versus CAD of the cylinder mixture for the peak fuel-conversion efficiency cases. The γ values reported are the average of these curves.

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Fig. 9

Fuel-conversion efficiency of the ideal OTTO cycle. Vertical lines are positioned at the average γ value of each case: Dry EGR = 1.21, wet EGR = 1.23, air = 1.30.

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Fig. 10

Normalized heat release curves of the three maximum fuel-conversion efficiency cases

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Fig. 11

Normalized heat release of wet EGR cases. Note that the 29.7% O2 case, which produced the highest overall fuel-conversion efficiency for wet EGR, is nearly identical to the air case.

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Fig. 12

Measured combustion efficiency of wet and dry EGR

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Fig. 13

Measured engine-out emissions of wet and dry EGR for CR = 17

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Fig. 14

CoV IMEP values for wet and dry EGR cases

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Fig. 15

Standard deviation of pressure transducer (95% confidence interval)—measured values were computed based on motoring data from 4 different test days

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