Large eddy simulation of a hydrogen-fueled scramjet combustor with dual cavity

Large eddy simulation (LES) has been carried out to investigate a hydrogen-fueled scramjet combustor with dual cavity, where a Reynolds-Averaged Navier–Stokes (RANS) model is used for near-wall treatment. The recycling/rescaling method is adopted to generate unsteady turbulent inflow conditions for the LES. Experimentally-observed flow and combustion structures are reasonably well captured and explained by the simulation. The results show that the intersection of the bow shock waves and the concentrated heat release generate a high-pressure region between the cavities, which induces great pressure gradients as well as evident flows in the transverse direction, pushing the fuel jets towards the combustor walls. Consequently, strong interactions occur between the fuel jets and the cavity aft walls, promoting the fuel transport into the cavity. Meanwhile, the cavity recirculation regions are considerably extended and distorted, and the mass exchange between the fluids in and out of the cavities may be greatly enhanced. In contrary, these flow structures support the concentrated heat release around the cavity by enhancing the fuel–air mixing and increasing the residence time of the combustible. Then, a positive feedback loop is formed by this close coupling of flow and heat release. It is also observed that the combustion downstream of the cavity is confined within narrow regions near the combustor walls due to the decreased fuel jet penetration in the farfield.