Ignition by H 2 /N 2 plasma torch in supersonic air flow

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.