Ignition of hydrogen-air and methane-air mixtures at low temperatures by nanosecond high voltage discharge

The spatial uniformity of the gas-mixture combustion initiated by a high voltage nanosecond volume discharge is investigated at gas pressures of 0.3-2.4 atm and temperatures of 1000-2250 K. The experiments are carried out behind a reflected shock wave propagating in a methane-air mixture diluted with argon. The self-ignition time and the time of discharge-induced ignition are determined. It is found that, at relatively low pressures (≃0.5 atm), the discharge significantly (by 600 K) decreases the ignition temperature. At higher pressures (1.5-2 atm), the ignition temperature decreases by only 100 K. The discharge and the mixture combustion are monitored 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 as a means for igniting combustible mixtures. In addition we represent low-temperature experiments on different hydrocarbons oxidation in nanosecond discharge.