Abstract: Proper understanding and evaluation of the aerothermal environment under mass injection conditions for high-speed aircraft are prerequisites to develop corresponding thermal protection technologies. To address the prediction of aerothermal environment in mass injection conditions, the numerical simulation method of mass injection was firstly established and verified in high-temperature nonequilibrium flow. Subsequently, a modified heat flux characterization formula were theoretically derived con-sidering comprehensive wall effects, including catalysis, ablation, pyrolysis and active injection. The new characterization method and heat reduction mechanisms were numerically investigated using a blunt wedge configuration in typical flight states. The results demonstrate the following: Using the heat flux ultimately experienced by the vehicle structure as the criterion for wall heat flux assessment aligns with traditional wall heat flux formula while also providing a reasonable evaluation of heat flux under complex wall effects. Conventional heat flux formula need to be corrected since it overestimates wall heat flux and under-estimates cooling efficiency when evaluating the thermal reduction effect of mass injection. The corrected heat flux expression under mass injection conditions includes heat conduction from flowfield, heat absorption/release from wall reactions, and for-mation enthalpy of injected media, degenerating into the traditional heat flux expression in non-ablative and non-injection con-ditions. For non-catalytic, non-ablative and active injection wall, heat flux consists solely of conductive heat flux; as a result, cooling effects of active injection is achieved by significantly reducing the normal temperature gradient at the wall. The cooling efficiency is further improved while incorporating the enthalpy of injected water vapor, but the dominant factor remains the reduction of conduction heat flux.

Key words: mass injection, aerodynamic heat flux, nonequilibrium, catalysis, ablation