Effects of cavity on solid fuel scramjet combustor characteristics under supersonic cross flow

The goal of this study is to investigate whether the cavity structure can enhance the mixing efficiency in solid fuel scramjet(SFSCRJ). A numerical simulation of a non-reactive supersonic flowfield in solid fuel scramjet combustor was presented. The turbulence model in the numerical simulations was the Stander k-ε model. A second-order-upwind difference scheme was used for simulating the dynamic flow associated with an axial symmetry. Compared with the combustor without cavity, the combustor with cavity was found to be able to enhance the mixing efficiency apparently. Compared with six combustors with different length-to-depth ratio(L/D) of the cavity, as the cavity L/D ratio decreased, the mixing efficiency firstly increased and then decreased. Results show that the mixing efficiency is not monotonically increasing or decreasing with the variation of the cavity L/D ratio. It reveals that there exists an appropriate cavity L/D ratio regarding the mixing or combustion efficiency and the total pressure loss. So there exists a best L/D ratio to get the best performance of the combustor. The investigation of the cavity L/D ratio would provide some insight into the design considerations of cavity for scramjet.