Combustion Characteristics of a Single Cylinder Spark Ignition Engine Fueled with Coal Mine Methane

An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane (CMM). The CMM was simulated by the compressed nature gas (CNG)/nitrogen blend fuels. The cylinder pressure was measured. The maximum heat release ratio, the flame development duration and the main combustion duration were analyzed with the nitrogen volume fraction in the blends changing from 0% to 35%. The results indicate that the maximum cylinder pressure, the maximum rate of pressure, the flame development duration and the main combustion duration increase and the maximum rate of heat release decreases with increasing nitrogen fraction. When the level of nitrogen volume fraction in coal-mine methane is lower than 20%, the combustion process of engine is stable. But with the level of nitrogen volume fraction over 30%, the cycle to cycle combustion variation is large, especially under low load condition.