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Effect of Increasing Compression Ratio in a Light-Duty Natural Gas-Fueled Engine on Efficiency and Emissions
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Abstract
As a result of CAFE (corporate average fuel economy) requirements, the trend in passenger car engine design is to smaller displacement engines of higher specific output which provide reductions in vehicle driving cycle fuel consumption without an accompanying decrease in maximum power output. Design features such as four valves per cylinder and compact combustion chambers give these engines significantly different combustion characteristics than traditional pushrod OHV (overhead valve) engines. In general, their combustion chambers are fast burning, enabling the use of higher compression ratios without knock on unleaded gasoline. Since fuel consumption decreases with increasing compression ratio, and since natural gas has a substantially higher octane rating than the best unleaded gasoline, it would appear to be desirable to operate with even higher compression ratios in a dedicated natural gas engine.
Tests at different speeds and loads were carried out with a natural gas fueled, 16 valve DOHC (dual overhead cam) two-litre four-cylinder engine representative of current passenger car design. Compression ratios of 10.0 and 11.5 were evaluated. Results show that increasing the compression ratio has little effect on NOx but increases unburned hydrocarbons emissions. Modest part load fuel consumption improvements were observed. Torque output at WOT (wide open throttle) increased, but did not reach the value obtained with gasoline fueling at the lower compression ratio tested.
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Jääskeläinen, H. and Wallace, J., "Effect of Increasing Compression Ratio in a Light-Duty Natural Gas-Fueled Engine on Efficiency and Emissions," SAE Technical Paper 932746, 1993, https://doi.org/10.4271/932746.Also In
References
- Felt A. E. Krause S. R. “Effects of Compression Ratio Changes on Exhaust Emissions.” SAE Trans 80 710831 1971
- Benson J.D. Stebar R.F. “Effects of Charge Dilution on Nitric Oxide Emission from a Single-Cylinder Engine.” SAE 710008 1971
- Morgan C. R. Hetrick S. S. “Trade-offs Between Engine Emission Control Variables, Fuel Economy, and Octane.” SAE 750415 1975
- Fleming R. D. O'Neal G. B. “Potential for Improving the Efficiency of a Spark Ignition Engine for Ntaural Gas.” SAE 852073 1985
- Jääskeläinen H. E. Wallace J. S. “Performance and Emissions of a Natural Gas-Fueled 16 Valve DOHC Four-Cylinder Engine.” SAE 930380 1993
- Jääskeläinen H. E. Wallace J. S. “Effect of Closed Loop Fuel Control System Characteristics on Emissions from a Natural Gas Fueled Engine.” SAE 932747 1993
- Fox J. W. Cheng W. K. Heywood J. B. “A Model For Predicting Residual Gas Fraction in Spark-Ignition Engines.” SAE 931025 1993
- Lavoie G.A. Blumberg P.N. “A Fundamental Model for Predicting Fuel Consumption, NO x and HC Emission of the Conventional Spark-Ignited Engine.” Combustion Science and Technology 21 1980
- Novak J.M. Blumberg P.N. “Parametric Simulation of Significant Design and Operating Alternatives Affecting the Fuel Economy and Emissions of Spark-Ignited Engines.” SAE 780943 1978
- Thompson N. D. “Effect of Engine Operating Variables and Piston and Ring Parameters on Crevice Hydrocarbon Emissions.” MASc Thesis University of Toronto 1993
- Thompson N. D. Wallace J. S. “Effect of Engine Operating Variables and Piston and Ring Parameters on Crevice Hydrocarbon Emissions.”
- Caris D. F. Nelson E. E. “A New Look at High Compression Engines.” SAE Trans 67 1959
- Adams W.H. Hinichs H.G. Pischinger F.F. Adamis P. Schumacher V. Walzer P. “Analysis of the Combustion Process of a Spark Ignition Engine with a Variable Compression Ratio.” SAE 870610 1987
- Muranaka S. Takagi Y. Ishida T. “Factors Limiting the Improvement in Thermal Efficiency of S.I. Engine at Higher Compression Ratio.” SAE 870548 1987
- Sobue A. Kawamura T. Ninomiya T. “Development of a Four Cylinder SR Engine.” SAE 901714 1990