Optimum structural design of thermal protection for supersonic aircraft by using photonic crystal material

With the rapid development of the supersonic aircraft technology, the aircraft Mach number continues increasing, but on the other hand, the working condition becomes progressively poor. The photonic crystals (PCs) material could reflect the energy of the thermal radiation effectively and prevent heat transferring into the substrate due to its low thermal conductivity. Consequently, the PCs material could be applied to thermal protection for the supersonic aircraft. In this paper, the aircraft state of Mach 5 is set as the target operating condition, and the PC thermal protection ability is simulated by the method of computational fluid dynamics. Based on the theory of the electromagnetics, the characteristics of the photonic band gaps for three-dimensional PCs are calculated and the effects of PCs' medium radius, refractive index, and lattice constant are fully taken into account. For the three-dimensional diamond PCs' structure, two major categories and totally five optimized design schemes are proposed, through combining the condition of supersonic aircraft aerodynamic heating. Results show that the temperature is reduced by 948.4 K when the heat passes through thermal protection layer and reduced by 930.4 K when the heat passes through PC layer. By the method of "coupled optimization strategy (COS)," the energy density which enters into substrate material would decrease by 7.99%. In conclusion, the thermal protection capacity for supersonic aircraft could be effectively improved by using the PCs.