Experimental shock tube study of ignition promotion for methane under engine relevant conditions

The ignition delay time of methane and various methane-additives mixed homogeneously with air has been measured experimentally using a reflected shock technique for pressures from 16 to 40 atm and temperatures from 950 to HOOK. A non-constant-specific-heat model has been developed for calculating initial experimental conditions. A good agreement has been found between the model and the experimental results. The ignition delay time measured in the current study has been found to depend strongly on temperature and moderately on pressure, and is significantly different from that reported by previous workers whose experiments have been conducted at lower pressures. Empirical equations correlating the ignition delay time with the initial temperature, pressure and fuel concentration have been obtained based on the experimental results. Hydrogen and DME (dimethyl ether) have been investigated for their efficiencies as ignition promoters for methane under engine relevant conditions. A prominent reduction of the ignition delay has been found for methane with 35% hydrogen added. With 15% hydrogen addition, the promotion effect is mainly evident at low pressures. DME has been found to cause moderate reduction on the ignition delay of methane. Computational results using detailed reaction mechanisms have shown disagreements with the current experimental measurements. Further tuning of the mechanisms has been suggested for high-pressure methane ignitions.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat