Analysis of the spatial uniformity of the combustion of a gaseous mixture initiated by a nanosecond discharge

The spatial uniformity of combustion in a gas mixture initiated by a high-voltage nanosecond volume discharge has been investigated at gas pressures of 0.3-2.4 atm and temperatures of 1100-2250 K. The experiments were carried out behind a reflected shock wave propagating in a mixture of methane and air diluted with argon. The autoignition time and the time of discharge-induced ignition were determined. It was found that, at relatively low pressures (∼0.5 atm), the discharge significantly decreased the ignition temperature (by 600 K). At higher pressures (1.5-2 atm), the ignition temperature fell by only 100 K. The emission from the discharge and combustion were registered with a nanosecond ICCD camera under various experimental conditions. Comprehensive measurements of the deposited energy and the waveforms of the discharge voltage and current with a nanosecond time resolution made it possible to determine the efficiency of this type of discharge for igniting combustible mixtures.