Combustion Characteristics of the Solid-Fuel Ramjet with Star Solid Fuel

Flow field characteristics of and regression rate distribution for the solid-fuel ramjet (SFRJ) with star solid fuel were investigated by numerical and experimental methods. The experimental data were obtained by burning polyethylene using a connected-pipe facility. The three-dimensional code developed in the present study adopted third-order monotonic upwind scheme for conservation laws (MUSCL) and central difference schemes, advection upstream splitting method by pressure-based weight functions (AUSMPW+), flux vector splitting method, and second-order moment turbulence-chemistry model, together with the k-ω shear stress transport (SST) turbulence model. The solid-fuel surface temperature was calculated with the fluid-solid heat coupling method. The numerical results show that obvious circumferential flow exists in the SFRJ with star solid fuel. The regression rates are higher at the star tip and lower at the star bottom. The space-averaged regression rate of star solid fuel is slightly higher than that of the traditional single-port cylindrical solid fuel. Turbulent viscosity is a critical parameter affecting the regression rate distribution, and the circumferential flow in the SFRJ has an important influence on turbulent viscosity. Comparing the numerical and experimental regression rates, it is indicated that the developed code can generally predict the effect of fuel configuration on the regression rate, and further investigation is needed to improve the accuracy and reliability of the developed code. A sudden increase in pressure during the combustion of star solid fuel was observed experimentally, which requires further investigations.