Ignition in a supersonic flow by a plasma jet of mixed feedstock including CH 4

Abstract

Ignition tests of hydrocarbon fuels in a supersonic airflow by plasma jet (PJ) torches of mixed feedstock, including methane (CH 4), such as N 2/CH 4 and N 2/CH 4/O 2 mixtures, were conducted. The Mach number of the airflow was 2.0, and the total temperature and total pressure of the main flow were those of room conditions. The wall pressure increase due to combustion of hydrocarbon fuels for the N 2/CH 4 PJ exceeded those of pure O 2 and N 2 PJs at high electric power input. Equilibrium calculations showed that the main species in high-temperature PJ, aside from N 2, were H 2, H, and HCN. Considering the slight impact of the HCN species on ignition delay time, the combustion enhancement by the N 2/CH 4 PJ was caused primarily by the existence of a large amount of H and H 2 dissociated from CH 4 molecules in the PJ. Moreover, the addition of O 2 to the N 2/CH 4 feedstock further enhanced the combustion and stability of the N 2/CH 4 PJ. The existence of O 2 increased the temperature and the number of H radicals in the PJ exhaust.