Ignition dynamics of a pulse detonation igniter in a supersonic cavity flameholder

The dynamics of using a pulse detonation wave to ignite a supersonic cavity flameholder was investigated. Fueling conditions ranging from lean to rich were investigated. Simultaneous 40-kHz schlieren imaging, OH planar laser-induced fluorescence, and chemiluminescence imaging were used to elucidate the fluid dynamics and combustion physics throughout the transient disruption of the ignition event. For moderate and rich fueling conditions, the ignition event stabilized combustion away from the detonation plume until the detonation products were fully exhausted. Ignition of leaner conditions required a low-level flame kernel to persist in the cavity step until the recirculating cavity flow field was re-established. The initial ignition mechanism was shown to be primarily driven by hot products from the detonation plume shedding into the low velocity region near the aft facing step in the cavity, followed by propagation and stabilization of a flame to a favorable region of the cavity. Quenching of cavity combustion at lean overall cavity mixtures was shown to be due to temporary backpressuring of cavity fuel injectors and cavity evacuation from the detonation pressure impulse.