Ignition and combustion enhancement in a cavity-based supersonic combustor by a multi-channel gliding arc plasma

A multi-channel gliding arc (MCGA) plasma was used to enhance ignition and combustion of ethylene fuel in a cavity-based scramjet combustor with an inflow speed of Ma = 2.92. Simultaneously electro-optical diagnostics were conducted to show characteristics of the MCGA-enhanced ignition and combustion, as well as simultaneous schlieren and CH* emission images. The voltage and current measurements demonstrate that the average power of the MCGA declines from 1824 W of an ignition state to 1196 W of a stable combustion state. Several flame kernels produced simultaneously by the power spikes of the MCGA can be merged to enhance the ignition, resulting in a faster speed of flame propagation (48% reduction in the flame propagation time) and a shorter ignition time (61% reduction in the ignition time) compared to the ignition by a single-channel gliding arc. The enhancement effect of the MCGA on combustion is more significant with an increasing global equivalence ratio. The wall pressure of the scramjet combustor in the presence of the MCGA at a global equivalence ratio of 0.22 is comparable to the pressure at a global equivalence ratio of 0.32 in the absence of the MCGA. The main reasons for the significant combustion enhancement may be the re-ignition of the cavity flame by the MCGA plasma, adding extra heat and reactive species to the flame in the shear layer.