Heat reduction mechanism and aerodynamic optimization of combined non-ablative thermal protection system concept

摘要

The heat reduction mechanism of the combined non-ablative thermal protection system (CNA-TPS) is studied by numerical method. The CNA-TPS consists of blunt body, spike and opposing jet. The results show that the spike pushes the original bow shock wave away from the blunt body and converts it into the oblique shock wave, thus reducing the intensity of shock wave. In addition to reducing the intensity of reattachment shock wave, the low-temperature jet gas can directly cool the spike. The CNA-TPS has obviously weaker reattachment shock wave than single spike and single opposing jet. Therefore, the CNA-TPS has the higher heat reduction efficiency than the other two configurations, and the non-ablative property of the CNA-TPS is guaranteed by the low-temperature jet gas. On this basis, the single-objective and multi-objective aerodynamic optimizations of the CNA-TPS are carried out. The design variables are the diameter of nozzle and total pressure ratio of opposing jet. The objective function and constraint of the single-objective optimization are total heat flux of blunt body and mass flow rate of opposing jet respectively, while the above two parameters are considered as the objective functions in the multi-objective optimization. The Multi-Island Genetic Algorithm is adopted for the single-objective optimization, and the heat reduction efficiencies of CNA-TPS before and after optimizations are compared. Finally, the weighting method and the NSGA-II method are adopted for the multi-objective optimization, and the Pareto frontiers obtained by the two methods are compared.