By using a plasma jet (PJ) torch with 1.5 kW input power as an igniter, successful ignition for liquidkerosene fueled combustion experiment was conducted in a direct-connected supersonic test facility. The incoming flow has total temperature of 950 K and local Mach number of 1.8, corresponding to Mach 4 flight condition. In this study, several optical techniques, including high speed photography, high speed schlieren photography, and planar laser scattering (PLS) technique, were combined to study the ignition process, flame propagation, and mixing features of liquid kerosene fuel with air around the cavity. The effect of fuel injection position, injection pressure, and feedstock gas on ignition performance has been analyzed. The results indicate that local mixing is a critical factor for ignition. It is also shown that the PJ torch with N 2 + H 2 feedstock is superior to the PJ torch with N 2 feedstock for the ignition of liquidkerosene fuel. These results are valuable for the future optimization of kerosene-fueled scramjet engine when using a PJ torch as an igniter.

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