An experimental study on the combustion characteristics of an engine fuelled with coal-bed gas

By using natural gas blended with nitrogen to simulate coal-bed gas fuel, an experimental study is carried out on the combustion characteristics, including the duration of different combustion phases and the behavior of cycle variation of a single cylinder spark ignition engine, refitted from a diesel engine and fuelled with coal-bed gas. The results show that with the increase in nitrogen volume fraction, the moment corresponding to maximum cylinder pressure delays, pressure rising rate decreases and the duration of flame development phase increases markedly. When nitrogen volume fraction is 20%, combustion is stable. But with nitrogen volume fraction rising to 30%, the cycle to cycle variation increases obviously but the variation lowers in high load operations.