Influence of Surface Microwave Discharge on Ignition of High-Speed Propane-Air Flows

Ignition of supersonic propane-air flow under conditions of low-temperature plasma of surface microwave discharge is experimentally studied. We show that both rich and poor mixtures ignite, and the combustion intensity is maximal for the stoichiometric mixture. The dependence of the supersonic propane-air flow ignition time on the reduced electric field, E/n, under conditions of nonequilibrium gas-discharge plasma is experimentally obtained. The induction period is shown to decrease from $1$ ms to $5$ $\mu$s with the increase in $E/n$ from $40$ to $200$ Td. The propagation velocity of the combustion front boundary (depending on the equivalent mixture ratio and the input microwave power) is maximal for the stoichiometric mixture and reaches $160$ m/s at $E/n=150$ Td. Under these conditions, the combustion temperature is about $3000$ K.