Experimental study on aerodynamic heat and wall catalytic effects of hypervelocity flow

When aircraft enter/reenter the atmosphere at near and super-orbital speeds, such aircraft need to endure challenges posed by a hypervelocity flow environment. High enthalpy gas generated by strong shock wave compression causes violent aerodynamic heating to such aircraft. At this time, accurately predicting the aerodynamic thermal load becomes extremely difficult. Expansion tubes/tunnels are one of the few types of qualified ground facilities that can simulate hypervelocity flow. The JF-16 expansion tunnel at the Institute of Mechanics, Chinese Academy of Sciences, has successfully generated hypervelocity flows with speeds of more than 10 km/s. Accordingly, experiments have been conducted measuring the hypervelocity aerothermal and wall catalytic activity. The stagnation heat flux of a spherical model at high temperature and strong scour test flow with near and super-orbital velocities was successfully obtained at microsecond resolutions. It was found that the experimental stagnation heat flux is higher than the predicted levels according to the empirical formula and CFD simulations when the total enthalpy of the test gas is greater than 45 MJ/kg. In addition, the experimental stagnation heat flux based on a fully catalytic wall (with a Cu coating) is 53.93% higher than that based on a non-catalytic wall (with an Al2O3 coating). The numerical analysis indicated that 22.5% O and 37.3% N atoms remain at the stagnation point of the model under the non-catalytic condition. Meanwhile, under the fully catalytic condition, the atoms are all combined and cause a significant increase in the heat flux at the stagnation point. This analysis confirmed the experimental results.