超燃冲压发动机热管理系统不同工质冷却性能对比研究

The thermal management system of scramjet based on closed Brayton cycle can achieve thermal protection of the engine and generate electric energy simultaneously.Regarding the selection of working fluids for the thermal management system of scramjet engines,a quasi-one-dimensional model of cooling channels was adopted to compare the cooling performance of closed Brayton cycle working fluids.The wall temperature of the cooling channel in the literature was used to validate the model,and the heat transfer effects of n-decane,supercritical carbon dioxide(S-CO₂),and helium(He)were studied under different heat flux and mass flow rates.The results show that with the increase of heat flux,the outlet temperature,the maximum value of wall temperature and the heat transfer coefficient of n-decane increase.The wall temperature of the S-CO₂ cooling channel show a trend of first decreasing to 400 K and then increasing to over 800 K,indicating local heat transfer enhancement at a distance of approximately 0.08 m from the inlet to the downstream.However,as the mainstream temperature gradually move away from the pseudo-critical region,the heat transfer coefficient of S-CO₂ first decrease and then stabilize at 0.5×10⁴ W/ (m²·K).After moving away from the pseudo-critical temperature region,the wall temperature is very high.Due to the large heat transfer coefficient of helium,the maximum wall temperature is only about 550 K under the condition of 4 g / s,and the cooling ability is the best among the three working fluids.