Numerical investigation on cavity length for solid fuel scramjet

The goal of this study is to investigate into the influence of the cavity for solid fuel scramjet (SFSCRJ) combustion performance, mainly on the length-to-depth ratio(L/D) of cavity. Scientific visualization of the numerical simulations by the Shear Stress Transport (SST) k-ω model allows a detailed analysis of shocks and waves. A second-order-upwind computational fluid dynamics is used for simulating the dynamic flow associated with an axisymmetric, cavity installed combustor under reacting conditions. The combustor inlet condition airflow is set as Mach number of 1.6, total temperature of 1156 K and average air mass flow rate of 0.184kg/s. The solid fuel uses the hydroxyl-terminated-polybutadiene (HTPB) with a global one step reaction mechanism. Numerical simulations are confirmed by the experiments. The study concerns the combustion enhancement when a cavity is installed in the solid fuel supersonic combustor. The primary emphasis is to examine the sensitivity of the primary properties due to variations on the cavity L/ D ratio ranging from 3-5. The cavity effect is discussed from a viewpoint of total pressure loss, combustion efficiency, thrust, specific thrust and specific impulse. The combustor with cavity is found to enhance combustion efficiency while decreasing the pressure loss, compared with the case without cavity. It is noted that there exists an appropriate length of cavity regarding the combustion efficiency and total pressure loss. The investigation of the cavity L/D ratio would provide some insight into the design considerations of cavity for solid fuel scramjet.