Research on the cooling performance of the discontinuous transpiration surface structure for the leading edge of a hypersonic vehicle

Transpiration cooling is an efficient thermal protection technology that can be applied to hypersonic aircraft. This paper takes the leading edge transpiration cooling system of aircraft as the research object, the full-field coupling numerical method is mainly used to study the cooling performance of the transpiration cooling system of the aircraft leading edge with a flight altitude of 20 km and a flight Mach number of 6. The correctness and accuracy of the numerical method and results are validated by comparison with experimental data in reference. The effects of 5 different types of coolant gases and injection rates on the cooling effectiveness of a transpiration cooling system with a single transpiration surface arrangement are first studied. The results show that helium gas with a larger specific heat capacity has better cooling performance. As the coolant injection rate increases, the average temperature of the solid wall decreases, but the coolant will be wasted. In order to improve the utilization rate of coolant and achieve system weight reduction and large area thermal protection, solve the problem of uneven surface temperature and high stagnation point temperature of the porous media, a discontinuous transpiration surface structure is designed, and the effectiveness of varying distances between the two transpiration surfaces and the combination of varying porosity on the cooling performance of the discontinuous transpiration surface structure are studied. The results show that an increase in the distance between transpiration surfaces can reduce the coolant flow rate at the stagnation point, leading to a slight increase in the temperature at the stagnation point and a decrease in cooling efficiency of about 10 %. At the same time, the temperature at the rear wall of the second transpiration surface decreases and the average efficiency is improved. When the variable porosity of the discontinuous transpiration surface is applied, the stagnation point temperature is reduced from 1218.17 K to 486.72 K, the cooling efficiency at the stagnation point is greatly improved, and the maximum reaches 0.874.