Numerical investigation on the dual influence mechanism of combustion cracking reaction on thermal protection/resistance in transpiration cooling

Transpiration cooling is an effective method in solving the complex and variable thermal environment. Employing fuel as a coolant has proven to be an efficacious approach for enhancing the aircraft payload, but the combustion-cooling coupling effect of fuel as coolant is a worthy study subject. The present study utilizes n-decane as coolant to conduct a numerical simulation of the transpiration cooling involving combustion reaction under supersonic conditions, based on thermal equilibrium model. Combustion liberates heat in outer zone of boundary layer, it also strengthens turbulent heat transport capacity of the fluid, consequently enhancing heat transfer of high-enthalpy mainstream to porous wall. Simultaneously, combustion reaction enlarges low momentum region within the boundary layer. This reduction in the influence of the aerodynamic thermal load is beneficial for thermal protection. Boosting the coolant injection rate can effectively diminish wall temperature, but it also induces an increase in wall friction coefficient. Furthermore, enhancing coolant injection rate causes a growth in comprehensive heat transfer coefficient and subsequently weakens whole thermal protection effect. Research conducted in this paper furnishes a valuable reference for the thermal protection where hydrocarbon fuel serves as a coolant.