IGNITION BY H_2/N_2 PLASMA TORCH IN SUPERSONIC AIR FLOW

摘要

Behaviors of ignition and flame holding of a fuel jet by H_2/N_2 plasma torches in a supersonic air flow were numerically investigated by solving the two-dimensional Navier-Stokes equations with full chemistry of the H_2/N_2/O_2 reaction system. Three volumetric fractions of H_2 (0, 5, 30%) in a mixed feedstock gas were compared to determine the effect of the addition of H_2 to the feedstock. The H_2 included in the mixed feedstock quickly reacted with the main air flow after injection and the combustion gas covered the plasma jet (PJ) downstream. The effects of the combustion of H_2 molecules included in the feedstock strongly appeared in only the H_2 30%/N_2 70% PJ. The high-temperature region around the H_2 30%/N_2 70% PJ was enlarged and maintained for a long distance by the combustion and many radicals were included as secondary products in the jet. Moreover, the flame region around the H_2 30%/N_2 70% PJ developed more quickly and more widely than that of the H_2 5%/N_2 95% PJ. These effects of the combustion of H_2 molecules included in the feedstock are thought to be reasons for the superiority of the H_2 30%/N_2 70% PJ to other PJs such as a N_2 PJ or an O_2 PJ examined in past experiments.