Influence mechanism of gas components on wall heat flux and skin friction

One way to address the thermal protection issue of hypersonic vehicles is through wall mass injection, which can successfully lower skin friction and wall heat flow. The effects of three distinct gases (pyrolysis gas, water vapor, and carbon dioxide) on aerodynamic force and thermal characteristics are compared and analyzed, and the numerical simulation of mass injection on the heat flux and skin friction of the wall is investigated using a two-dimensional blunt wedge as the calculation model. It is possible to determine that the pyrolysis gas injection lowers the convective and diffusion heat flux by splitting the heat flux into these two categories. Both carbon dioxide injection and water vapor enhance the diffusion heat flux while decreasing the convective heat flow. The effect of water vapor raising the diffusion heat flux is more noticeable, leading to an increase in the overall heat flux. Additionally, by lowering the velocity gradient close to the wall, all three gases can lessen the skin-friction of the wall, with pyrolysis gas injection having a greater impact.