Thermal Protection And Infrared Radiation Characteristics For Hypersonic Aircraft

The hypersonic aircraft mainly refers to the new type of vehivle whose speed could be up to 5Ma or more. Many countries in the world are eager to develop this kind of technology, thanks to its nonconventional weapons performance, such as high mobility, rapid strike capability and long-range precise strike etc. With the birth of scramjet, the problem of power resource for hypersonic aircraft is settled, however, there is a new problem arising which is the aerodynamic heating phenomenon. This kind of problem would produce extremely high temperature on the local surface of aircraft, expecially on the position o f nose cone and flange. What’s more, high thermal radiation is generated due to the high surface temperature, which could make the aircraft easily found by the infrared detector. These factors are extremely serious thread for the aircraft survival ability. Therefore, it is quite important to improve the safety performance of aircraft by the designs of thermal protection and infaraed stealth.The photonic crystal could reflect all the radiation at some certain wavelength bands, because of its bandgap structu re. Meanwhile, this kind of material with low thermal conductivity shows great application value on the field of thermal protection and infaraed stealth.In this thesis, all the dicusses and analyses are based on the aircraft intermal and external temperature filed and the surface infaraed radiation characteristics. Firstly, the heat flux density of aircraft on the position of nose cone and the other surfaces is calculated by several engineering methods of aerodynamic heating, and the results calculated by difference methods are compared. The aircraft internal and external temperature field for one kind of hypersonic aircraft HIFRIE is simulated by using the calculated heat flux as the boundary condition, and the calculation results are compared with the res ults of using the method based on FLUENT fluid-thermal coupling simulation. The infaraed radiation for aircraft surface is calculated on account of the temperature field, fully considered the effects of atmosphere environment. Finally, the bandgap structur e for one dimensional photonic crystal is calculated by the method of Transfer Matrix Method(TMM), and six optimized designs are proposed. The thermal protection ability for a structure with photonic crystal is analyzed.The results indicated that the forbidden bandgap effects have extremely inbibitory effects on infrared radiation. By the method of “coupled optimized method” which is proposed in the thesis, the total infrared radiation intensity could be diminished by 96.94%. what’s more, the three-layer structure “C/Si C-PCSubstrate” propoed in the thesis, could effectly prevent the heat transferring into the substrate.The possibility for photonic crytal being the infrared stealth and thermal protection material is discussed and analyzed on the combinati on of photonic cryastal and thermal analysis. In the view of the above, six kinds of optimized methods and one kind of thermal protection material combination strategy are proposed. The works in the thesis provides a new thought for the design s of infaraed stealth and thermal protection, and have certain engineering application value.