Numerical Investigation on the Mechanism of Transpiration Cooling for Porous Struts Based on Local Thermal Non-Equilibrium Model

Abstract

Struts as an important structure in the combustion chamber of hypersonic flight vehicles to inject fuel into main flow face a severe thermal environment. Transpiration cooling is considered as a potential method to provide a thermal protection for struts. This paper presents a numerical investigation on transpiration cooling for a strut based on Darcy–Forchheimer model and the local thermal non-equilibrium model and analyzes the mechanism of transpiration cooling. A coolant film and a velocity boundary layer are formed on the strut surface and the shock wave is pushed away from the strut, which can effectively reduce the heat load exerted on the strut. The temperature difference between coolant and solid matrix inside the porous strut is analyzed, a phenomenon is found that the fluid temperature is higher than solid temperature at the leading edge inside the porous strut. As flowing in the porous medium, the coolant absorbs heat from solid matrix, and the fluid temperature is higher than solid temperature at the stagnation point of the strut. The influence of coolant mass flow rate and various coolants on transpiration cooling is studied. As mass flow rate increases, the cooling efficiency becomes higher and the temperature difference between fluid and solid in the porous medium is smaller. The coolant with a lower density and a higher specific heat will form a thicker film on the strut surface and absorbs more heat from solid matrix, which brings a better cooling effect for strut.