Sustained Cavity Combustion in a M = 3 Flow

Cavities provide a means for holding flames in high-speed combustion applications, such as scramjets. Detailed simulations of sustained combustion and a corresponding inert mixing cavity, based on recent experiments, are analyzed. Entrainment into the cavity is characterized by tracking of Lagrangian trajectories. These show the importance of large-scale unsteadiness and, particularly, how this is altered by combustion. Insufficient oxidizer within the cavity leads to a low-speed, fuel-rich region near the front wall. This region supplies fuel to the mixing shear layer above the cavity where most of the combustion occurs. This shear-layer combustion is self-sustaining, not reliant on the jet flame in the cavity. The deflection of the shear layer by the expansion associated with combustion in the cavity leads to a virtual throat and complex shock structure above the cavity, which couples with the mixing layer, altering its dynamics.