Research on the performance of active-passive combined thermal control for external thermal protection structure of hypersonic aircraft

High-speed aircraft encounter severe aerodynamic heating problems during flight, and their material and structural design are facing great challenges. Effective temperature control of load-bearing structures is crucial to their reliability. In this paper, a new combined thermal protection design scheme is proposed based on the characteristics of active and passive thermal protection. Its thermal control performance is analyzed, and the effects of structural geometric parameters (thickness, pipe shape and number) and the flow direction of the coolant on thermal protection performance are investigated through numerical simulations. The dimensions of the hybrid thermal protection structure are also optimized. The temperature dependence of the material properties are taken into consideration throughout these studies. The results show that when the inlet velocity of the coolant is 0.1 m/s, the structure can ensure that the temperatures of all material remain within the allowable range at steady state with a minimum thickness of 12 mm. With the combined effect of insulation material and convective cooling, the active–passive combined thermal protection structure achieves ideal effect with a relatively small coolant flow rate and thickness, effectively overcoming the limitations of single thermal protection.