Active Cooling Mechanism And Cooling Capacity Evaluation Of Thermal Protection Systems For Hypersonic Vehicle

Hypersonic vehicle is the developmental direction of modern vehicles. The extreme severe aerodynamic heating and special surrounding encountered by hypersonic vehicle due to the long time mission between and in aerosphere with high speed, which makes traditional thermal protection system exposed to more possible failure modes on dynamic and high temperature performance. The knowledge of active cooling thermal protection system with suitable active cooling capacity is crucial to solve the question for thermal protection of hypersonic vehicle. Active cooling thermal protection system with high cooling capacity, resistance of high heat flux in long time, realization the open loop or close loop control on temperature and heat flux, integration design of thermal protection-insulation and thermal management, which makes active cooling TPS to be a hot spot of research and key technology in research of hypersonic vehicle. In present paper, thermal protection of hypersonic vehicle subjected to severe aerodynamic heating in long time is investigated. The active cooling metallic thermal protection systems which have potential to apply to hypersonic vehicle is studied on. The main research contents of the papers are as follows:An integrated thermal protection-thermal insulation-thermal management design method and numerical model was developed base on the character and requirement of thermal protection system on hypersonic vehicle in order to quantitatively compare the cooling characteristic and cooling capacity of passive and active cooling thermal protection systems. The results indicate that the temperature of inner structure decreased when the insulation thickness increased, but the effect on the temperature decrease when the insulation thickness increased, meanwhile, this method is effective for thermal protection system which encountered short time heating load, not for long time heating load. The thickness of insulation would increase at least 2-3 double if the method of increasing the insulation thickness was employed. Active cooling has high cooling capacity and cooling efficiency for thermal protection system which encountered long time heating load and keep the temperature of inner structure within the operational temperature limit. The method and model are applied on the design and evaluation the cooling capacity of the transpiration thermal protection systems. The validity and engineering practice value are proofed.A theoretical model was developed to predict the effective thermal conductivities of the porous material base on the conduction and radiation as well as microstructure inside the porous material. The experiment on the effective thermal conductivities was conducted. The experimental results according to the predicted results indicate the model is availability and applicability, which is the basement for the design of active cooling thermal protection systems.Transpiration cooling thermal protection system was design and developed using the method of integrated thermal protection-thermal insulation-thermal management design method for area protection region under high heat flux of hypersonic vehicle. A high temperature experimental apparatus which was heating on the basement of the sample and with maximum temperature of 1500K(for 2 hour) was fabricated to test the active cooling capacity and efficiency. The cooling capacity of transpiration cooling thermal protection system was tested. The results indicate that the heat load eject capacity improved at last 70%, cooling capacity is 170-500kW/m2(for high temperature alloy) and the temperature of inner strucrure below boiling temperature of water(with traspiration cooling).A new method of appling spray cooling to metallic thermal protection was proposed for nose and leading edge of hypersonic vehicle. A novel spray cooling thermal protection system was design and fabricated using the method of integrated thermal protection-thermal insulation-thermal management design method. An oxyacetylene experiment platform was design and fabricated and the experiment of cooling capacity of spray cooling thermal protection system was conducted.