Large Eddy Simulations of the LAPCAT-II and the SSFE Combustor Configurations

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Abstract
In this study we demonstrate how combustion Large Eddy Simulation (LES) can be employed to investigate dual-mode ramjet flows in both a direct connect facility combustor experiment, enabling comparison with experimental data, and in the small-scale flight experiment combustor based on the LAPCAT-II Mach 8 MR 2 flight vehicle. The LES uses a recently proposed pathway-centric H2-air reaction mechanism capable of accurately representing the low-temperature chemistry together with state-of-the art subgrid flow and combustion models. For the direct-connect facility combustor results the comparison between experimental data and LES predictions shows strong sensitivity of the LES predictions to the surface roughness of the combustor walls, and when the surface roughness is taken into account, the LES results show good agreement with the experimental wall-pressure profiles and with the combustion luminosity images. For the full engine flow path of the LAPCAT-II small-scale flight experiment SSFE, the LES shows that the injected H2 rapidly self-ignites as a consequence of the efficient mixing pattern set up by the complex flow in the combustor. A vortex-pair develops along the intake, which together with the semi-struts close to the intake create a pair of longitudinal vortices that determine the flow in the isolator-combustor-nozzle.

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