A Comparative Study on Engine Performance of Modified Diesel Engine with Dual Biogas and Pure Biogas Fuel

Abstract

This paper presents a comparative study of engine performance on a modified engine to use Biogas dual fuel.  The engine used in this study was a small 353 cc, 7 HP Mitsubishi diesel, model DI-700.  This engine powered a 3KW generator which illuminated an electric light bulb.  Before adapting the engine to use Biogas Dual fuel, the compression ratio was 18:1.  The experiment indicated that the most efficient ratio of diesel fuel to Biogas is 30:70.  At this ratio there is no sign of engine failure at peak engine load.  The highest electrical load achieved was 3000 Watts.  The ratio of Biogas consumption was 24 liter/min and the ratio of diesel consumption was 10cc/min.  After modifying the Diesel engine to be a gasoline engine, the engine power was decreased to 9.88:1 while using only Biogas.  According to the results of using only Biogas, it appears the highest efficiency of the engine is 6.95% with the highest electrical load of 500 Watts, biogas consumption was 1.7 liter/min.  When the results are calculated the unit cost of using the diesel engine with Biogas is 4.02 baht per kilowatt-hour.  For the modified diesel engine using only Biogas the unit cost is 3.44 baht per kilowatt-hour.