An experimental study of combustion and emissions in a spark-ignition engine fueled with coal-bed gas

Coal-bed gas has been considered an attractive alternative fuel for internal combustion engines due to its abundant source and low emissions. In the present study, a combustion system with a swirl chamber has been developed for a spark-ignition engine using coal-bed gas. Detailed experiments have been carried out to investigate the combustion and emission characteristics of the engine operating with three different grades of coal-bed gas. The results have shown that this combustion system allows satisfactory operation of the engine with a wide range of methane content in the supplied coal-bed gas. For all tested conditions, the CO emission has a maximum value of 0.062%, and the HC emission is less than 380 ppm. The NO emission increases with the engine load but is less than 1800 ppm, demonstrating a great advantage of coal-bed gas as a relatively clean engine fuel.