Influence of hypersonic thermo-chemical non-equilibrium on aerodynamic thermal environments

Severe aerodynamic heating phenomenon occurs in hypersonic flight. Thermal protection system design can be effectively guided by considering the influence of hypersonic thermo-chemical non-equilibrium on aerodynamic thermal environment. Park and Gupta's thermo-chemical non-equilibrium models were used to numerically calculate the 5 species (N₂, O₂, N, O, NO) and 17 groups of chemical reactions, and the influence of their thermo-chemical non-equilibrium on hypersonic vehicles' aerodynamic thermal environments was compared with that obtained from perfect gas and thermo-chemical equilibrium models. In the thermo-chemical non-equilibrium model, flow field temperatures are lower and shock standoff distances are smaller than those of the perfect gas model. The larger the gas density after shock wave is, the smaller the shock standoff distance is. Therefore, the shock standoff distance of thermo-chemical equilibrium model is the smallest due to the larger gas density caused by molecular dissociation and chemical reaction effects. The numerical heat flux loads of perfect gas and thermo-chemical equilibrium models are larger than the experimental data. There are small differences between Park's and Gupta's thermo-chemical non-equilibrium model when they are used to numerically calculate the shock standoff distance and aerodynamic load. The calculated values of heat flux load of Park's model are larger, while those of Gupta's model are in good agreement with the experiments. Therefore, Gupta's model is more reliable to predict hypersonic vehicles' aerodynamic thermal environments.