Dynamic characteristics of a gliding arc plasma-assisted ignition in a cavity-based scramjet combustor

A gliding arc discharge with an averaged power of 630 W at atmospheric pressure was used to ignite an ethylene-fueled scramjet combustor with an inflow speed of Mach number 2.92. The instantaneous power of the plasma and the high-speed CH* chemiluminescence imaging of the ignition process was simultaneously measured to show dynamic characteristics of the gliding arc plasma-assisted ignition. The results show that the power spikes of the spark-type discharges are the key factor to generate the flame kernel in the scramjet combustor and the instantaneous power can reach 3168 W during the power spikes. The flame kernel ignited by the gliding arc discharge can be developed to form an initial flame, which can become larger with increasing contained discharge energy of the gliding arc. Moreover, a comparison between the successful initial flame and the failed initial flame is performed to demonstrate that the larger area of the successful initial flame can propagate for achieving the mainstream flame, whereas the failed initial flame generated multiple times until the successful initial flame was observed. It is concluded that the successful initial flame contains more discharge energy during the initial flame formation, leading to form the resident flame in the recirculation zone.