Flow and Combustion in a Supersonic Cavity Flameholder

Abstract

Simulations of both inert mixing and sustained combustion are analyzed for a cavity flameholder based on corresponding experiments. An round ethylene jet fuels a cavity with length-to-depth ratio and a 45° inclined downstream wall. Oxidizer mixes into the cavity from the core flow. The simulations reproduce shock angles and wall pressures of the corresponding experiment. The effects that cavity combustion has on the core-flow gas dynamics and cavity entrainment are analyzed in detail. Relative to the inert case, heat release leads to a complex core flow, with upstream boundary layers transiently separating and highly unsteady shocks over the cavity. Their collective effect is the formation of a virtual throat, which decreases the core flow to above the cavity. Lagrangian trajectories assess the roles that turbulence, combustion, and three-dimensional side-wall boundary layers have on oxidizer entrainment into the cavity. Overall, sustained cavity combustion suppresses entrainment by a factor of about 2.