Numerical investigation on internal regressing shapes of solid-fuel scramjet combustor

The purpose of this paper is to investigate the combustion process and its change with time due to solid-fuel regression in a solid-fuel scramjet combustor. The combustion process is simplified in the sequence changing of three regression shapes. The solid fuel uses hydroxyl-terminated polybutadiene with a global one-step reaction mechanism. Numerical simulations based on the shear stress transport k-wω model are confirmed by experiments. The simulation data generally agree with the experimental data published in the literature. For simplification, three typical instants during the combustion process, implying three different internal shapes due to fuel regression, are considered. With the sequence of three regression shapes, the fuel diffusion from a solid-fuel surface becomes more extensive and, furthermore, enhances the global combustion efficiency, which is nearly up to 45%at the outlet of the combustor. The simulation results also reveal that the cavity in the combustor provides a fuel enrichment zone and a stable pool of hot reaction products.Athermal choke is caught in the flowfield for the initial geometry, whereas a shock train appears in the main flow and has a tendency to extend with the surface regression. The investigation of the combustion process in this work provides some insight into the design considerations for a combustor with a cavity for a solid-fuel scramjet.