Effect of surface ablation on aerodynamic heating over a blunt cone in hypersonic airflow

Abstract

The hypersonic airflow around a blunt cone coupled with carbonaceous surface ablation is numerically simulated to analyze the impacts of ablation on aerodynamic heating. Ablative reactions, including oxidation, nitridation, and sublimation, are found to affect aerodynamic heating mainly through the surface thermal effect (STE) and the gas-phase chemistry thermal effect (GCTE). Specifically, the sublimation reactions produce significant STE and GCTE. The STE of the sublimation reactions is not always endothermic. Downstream along the cone surface, the condensation of gas-phase C atoms on the wall leads to heat release. The GCTE is exothermic and increases the boundary layer temperature. The oxidation reaction generates weak GCTE but powerful STE, which is exothermic overall. On the contrary, nitridation reaction only leads to appreciable GCTE, characterized by releasing heat. The STE of nitridation is quite small and can be neglected. Oxidation and nitridation reactions often dominate the downstream region of the cone. In addition, in the head region where the ablation reactions are intense, ablation processes could generate considerable diffusive heat flux, increasing the total incident heat flux. Simultaneously, mass ejection can carry away much heat from the surface.