Research On The Mechanism Of Dredging Thermal Protection System Of Hypersonic Vehicle Leading Edge

The dredging thermal protection structure (DTPS) is considered as thermalprotection system to prevent hypersonic vehicle whose leading edge should remainsharp outline at work from the serious aerodynamic heating. Dredging thermalprotection which is semi-passive thermal protection is different from the traditionalablation thermal protection system mechanism. Using heat transfer and heat convectionphysical properties of high thermal conductivity materials and high-performance heattransfer elements, it transfers heat power from high heat flux region to low one. Andthen the severe aerodynamic heating is released by radiating through a large number oflow heat flux area. It reduces local stagnation temperature sufficiently to allow the useof superalloy materials.The work in this thesis is about the mechanism of hypersonic vehicle’s DTPS. Thenumerical calculation model of hypersonic vehicle leading edge’s flow field isestablished. And the numerical calculation result is contrast with the wall heat flow ofopen experiment and the flow field distribution which is got by high-definition NPLSthat is observation techniques of hypersonic flow. The comparison results can approvethe numerical calculation model has good accuracy. The aerodynamic heating ofhypersonic vehicle’s leading edge can provide correct thermal environment conditionfor the research of mechanism of DTPS.According to the thermal elastic mechanics and classic heat transfer, thefundamental of hypersonic vehicle’s leading edge embedded high thermal conductivitymaterials is studied. Both nose cone and wing leading edge of hypersonic vehicle’sDTPS are researched under given condition. The distributions of thermal forceconditions which include temperature, temperature gradient and thermal stress arecontrasted when the leading edge structure has DTPS or not. Achieving the transfer ofheat from high temperature region to low one, the temperature of high heat flux area isreduced and the radiation cooling ability of integral DTPS is strengthened. The thermalprotection for the leading edge’s high temperature region is obtained. The influencingfactors which contain the thickness, length and thermal conductivity of highconductivity material layer, the black level of coating surface, the thermal load and thecontact thermal resistance of hypersonic vehicle leading edge’s DTPS to thermalprotection effect are discussed. These factors can provide a frame of reference for thedesign of structure and the selection of materials.For researching the mechanism of DTPS which has been embedded hightemperature heat pipe, the flow and heat transfer model of conventional liquid metalheat pipe has been built. Against the working principle and characteristics ofconventional liquid metal heat pipe, the wick and internal liquid metal are considered as a solid layer during the studying model. The complex flow and heat transfer processduring the heat pipe have been simplified. And its result is contrasted with experimentdata which can approve it has good accuracy when the working fluid is liquid metal.The heat transfer limits of conventional liquid metal heat pipe and their influencingfactors have been studied.Using the analytical methods of working temperature of heat pipe and consideringvapor chamber as high thermal conductivity virtual material, the best thermal protectioneffect of hypersonic vehicle leading edge’s DTPS which has been embedded hightemperature heat pipe has been researched. The two-dimension thermal protectionmechanics of curving leading edge’s DTPS is studied by using the analytical procedureof high temperature liquid metal heat pipe. The temperature distribution re contrastedwhen the leading edge structure has DTPS or not. Achieving the transfer of heat fromhead to after-body, the front head of the thermal load is weakened and the ability ofleading edge thermal protection is strengthened. The three-dimension integral model ofleading edge’s DTPS has been established when the cross section of heat pipe isconsidered as rectangle. Then the best thermal protection effect’s influencing factorswhich contain the width and length of heat pipe, the black level of coating surface andthe contact thermal resistance between heat pipe and coating are discussed.The integral heat-pipe-cooled leading edge structure (IHPCLE) is considered asthermal protection system to solve the questions which present leading edge’s DTPSalways have. The wick of IHPCLE composes by rectangle channel. The vapor chambercontains cylinder which is made up by capillary material to support structure and toprovide capillary force. As the complex flow and heat transfer process during theIHPCLE, the vapor chamber of IHPCLE is considered as a high thermal conductivitysolid layer and the wick and internal liquid metal is considered as compound body. Theheat transfer limits of IHPCLE are studied. When the working fluid is Na and Li, theapplicability of IHPCLE is researched under different working temperature.According to the DTPS of leading edge, both the structure of embedded coppersteel leading edge and IHPCLE system are designed. Using the xenon lamp as heatsource, the dredging thermal protection effect are proved though measuring thetemperature of leading edge which has DTPS or not.