Numerical Study Of Active Film Cooling Of Hypersonic Vehicle

When the aircraft is flying at hypersonic speed,it will face extremely serious problems of aerodynamic heating and aerodynamic drag,the former affects the structural safety of the aircraft,and the latter affects the flight speed of the aircraft,so it is necessary to take measures to prevent heat and reduce drag for high-speed aircraft.In view of the most serious aerodynamic heating of the hypersonic vehicle head,this thesis studies the thermal protection system of the blunt head body of the hypersonic vehicle with active film cooling,and uses the commercial software FLUENT to simulate the flow field of the blunt body with the thermal protection system,and analyzes the cooling mechanism and cooling effect factors of the thermal protection system,in order to obtain a reasonable design scheme of the thermal protection system.In this thesis,based on the existing experimental model,the corresponding flow field is numerically simulated,and the distribution results of flow field performance parameters are obtained,and the numerical simulation results are compared with the experimental results to verify the applicability and accuracy of the numerical simulation model.A numerical study is carried out on the thermal protection system using reverse jet to realize film cooling,the influence of total pressure ratio of reverse jet on thermal protection performance and drag reduction performance is analyzed and discussed,and the applicable range of attack angle of reverse jet thermal protection system is discussed.because the heat flow on the windward side increases with the increase of the angle of attack,when the angle of attack reaches 10°,the maximum heat flow on the windward side is very close to that of the blunt body without cooling.The cooling method produced by reverse jet is no longer applicable.The numerical simulation of the flow field of the blunt body with forward-facing cavity thermal protection is carried out,and the effects of different upwind cavity diameter-depth ratio on the external flow field,wall heat flux distribution and aerodynamic resistance of the blunt body are analyzed.The study shows that the upwind cavity structure can effectively reduce the aerodynamic heating problem of the bluff body standing point area,and the windward cavity structure can achieve a better thermal protection effect through simple shape design;the deeper the cavity is,the more obvious the thermal protection effect on the blunt head external wall is.The larger the diameter of the cavity is,the lower the heat flux density at the lip of the leading edge cavity of the aircraft is.With the combination of upwind cavity and reverse jet cooling,the flow field of blunt body with combined thermal protection system in flight environment is numerically simulated,and the thermal protection efficiency and its influencing factors are analyzed.The results show that the thermal protection performance of the combined thermal protection system is much better than that of a single reverse jet or upwind cavity,and a small reverse jet total pressure ratio can achieve good thermal protection performance when the cavity size and jet Mach number are fixed.When only changing the jet Mach number,the greater the jet velocity is,the better the thermal protection effect of the combined thermal protection system is.In the scope of this study,the smaller concave cavity is more conducive to jet gas expansion to form a stable flow,and the heat protection effect is better than that of coarse diameter concave cavity;when the size of the fixed concave cavity changes the depth of the concave cavity,the deeper the concave cavity is in the scope of this study,the more complex the shock wave structure inside the concave cavity is,the better the heat protection performance is;the passivated lip is not conducive to reducing the heat flux of the wall.