Large-Eddy Simulation of Supersonic Combustion in a Mach 2 Cavity-Based Model Scramjet Combustor

In this study we report on reactive Large Eddy Simulations (LES) of flow and combustion in the US Air Force Research Laboratory Research Cell 19 cavity-based scramjet combustor. This case involves combustion of ethylene that is injected into a cavity. It has previously been studied experimentally with multiple techniques as well as numerically using hybrid RANS/LES. Here, we build on the existing knowledge and provide an in-depth investigation of the flow and combustion by use of a pure LES approach. A range of fuel injection rates are studied as well as the non-reacting case. This way we can disseminate how different amounts of combustion, and the associated volumetric expansion, in the cavity affects the shear-layer above the cavity, the recirculation zone, and the downstream shock-train. For example, an additional shock-train emerges from the start of the cavity when combustion is present, and it grows in intensity with increasing fueling rate from 50 to 110 slpm. For the cases studied, good agreement is found between simulations, LES, and experiments, Particle Image Velocimetry (PIV), Hyperspectral Imagining (HsI) and Laser Induced Breakdown Spectroscopy (LIBS). More specifically, the primary flow features, such as the shock train, primary and secondary cavity recirculation regions, and shear-layer lift due to exothermicity, are found to evolve similarly with increasing fueling rate in the experiments and the LES which enables using the more complete LES result to further investigate the flow and combustion physics.