Numerical investigation on the interaction mechanism between pyrolysis combustion reaction and shock wave in transpiration cooling

Transpiration cooling using fuel is vital for scramjet combustor thermal protection and payload enhancement. However, the interaction between fuel pyrolysis combustion and shock waves is a complex and important subject worthy of study. This paper establishes a transpiration cooling model integrated with pyrolysis combustion reaction under the action of shock waves, and the influence of different shock wave incident intensity on the thermal protection/drag reduction effect of transpiration cooling is explored. The results indicate that pyrolysis combustion reaction reduces the ability of transpiration coolant film to resist shock wave interference to boundary layer; when pyrolysis combustion is considered, both the width and thickness of the turbulent boundary layer increase during shock wave impingement. Additionally, pyrolysis combustion reaction can oppose the impact of shock wave-induced unstable distribution of shear stress, thus contributing to the reduction of thrust loss in combustion chamber. Given the growth of the shock wave intensity, the flow deflection of coolant becomes more pronounced, and both the width of the local high-temperature region and the temperature peak value increase. These findings provide insights for the structural optimization of engine transpiration cooling systems.