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

In this study, we report on reactive large-eddy simulations (LESs) of flow and combustion in the U.S. Air Force Research Laboratory Research Cell 19 cavity-based scramjet combustor. This case involves the combustion of ethylene that is injected into a cavity. It has previously been studied experimentally with multiple techniques, including particle image velocimetry, hyperspectral imagining, and laser-induced breakdown spectroscopy, as well as numerically using hybrid Reynolds-averaged Navier–Stokes/LES. Here, we build on the existing knowledge and provide an in-depth investigation of the flow and combustion using a pure LES approach. A range of fuel injection rates are studied, as well as the nonreacting case. This way we can disseminate how different amounts of combustion and the associated volumetric expansion affect 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 the LES and experiments. 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. This enables the use of the more complete LES results to further investigate the flow and combustion physics.