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Biogas Composition Effects




           This paper presents the experimental study on effects of compression ratio and biogas composition to performance of spark-ignition engines. Two biogas-fueled engines, which were converted from a ZH1115 diesel engine and a Toyota 3Y gasoline engine, feeded by biogas fuel with different CH4 concentrations were tested in this study. Engine load was produced by a FROUDE hydraulic dynamometer. In the research of biogas engine converted from a ZH1115 diesel engine, compression ratio of the original diesel engine was reduced to 14:1, 12:1 and 10:1.
           The simulation results fitted well with the experimental data. Optimal compression ratio for biogas-fueled spark-ignition engine was obtained at 12:1. At this optimal compression ratio, maximum engine power at 2,200 rpm can reach to the same that of the original diesel engine. Optimal ignition timing is varied from 34 CA degrees to 42 CAdegrees before TDC. Within nominal engine speed range, engine power was increased an average of 15% when CH4 concentration increases from 60% to 78%. In case of stationary biogas-fueled spark-ignition engine converted from a Toyota 3Y gasoline engine, the results showed that the maximum engine speed was decreased. This reduction was higher with respect to lower CH4 concentration. Engine power at nominal engine speed was reduced from 20% to 30% corresponding to varying from rich biogas to poor biogas.

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