Experimental and Analytical Studies of the Lean Operational Limits in Methane Fuelled Spark Ignition and Compression Ignition Engines

The observed lean and rich operational limits in a spark ignition engine of the variable compression ratio type fuelled with either methane or propane are shown to be amenable to correlation in terms of a calculated mean mixture temperature at the time of passing the spark. Moreover, using a detailed chemical kinetics model for the oxidation of lean methane-air mixtures in a compression ignition engine, the autoignition of methane-air mixtures is examined. It is shown that these autoignition limits are also influenced by the mean charge temperature and the kinetic and thermal sensitizing of the charge through mixing with residual gases.