Experimental investigation on the flame stabilization modes of liquid kerosene in a cavity-based scramjet combustor

Abstract

The flame stabilization modes of liquid kerosene is investigated in a model scramjet combustor with flight condition of Ma 6. The effects of equivalence ratio and cavity configuration schemes on the flame stabilization modes are studied. Flame propagations and the evolution of the flow field from the ignition to the establishment of stable flame in the supersonic flow are acquired through high-speed photography and schlieren photography. Only cavity-recirculation-region stabilized combustion can be obtained in the single-cavity scramjet combustor. The intensity of combustion is weak and is termed as local ignition with low combustion efficiency. In the tandem-cavity scramjet combustor, the flame stabilization mode is largely determined by the total equivalence ratio. The flame could spread into the mainstream and even propagate against the supersonic flow as the equivalence ratio increases. The positive feedback mechanism between combustion and precombustion shock train is responsible for the evolutions of the flame stabilization modes, where the interactions between shock waves and turbulent boundary layer play a key role in the flame propagation process. The large-scale eddies in the shear layer of the upstream cavity shed at the cavity aft wall and could enhance the turbulent levels of the incoming flow of the downstream cavity. Consequently, an intense kerosene flame can be ignited in the tandem-cavity combustor. The flame could not spread to the mainstream in the single-cavity combustor due to the lower turbulence level weakening the interaction of combustion products in the recirculation zone with unburned reactants in the supersonic flow.