Research On Radiation-conduction-permeation Heat Transfer Characteristics Of Multilayer Microwave Transparent Structures

Microwave transparent antenna window is a key component of radar detection system of hypersonic vehicle.In long-time hypersonic flight,the microwave transperant antenna window will bear severe aerodynamic heating,so reliable thermal protection design must be carried out.The microwave transperant antenna window with heat insulation function usually consists of a composite multilayer structure composed of various materials,such as the microwave transperant heat protection layer,the microwave transperant heat insulation layer,air layer and the microwave opaque layer.The high temperature heat transfer of the microwave transperant insulation layer is related to heat conduction,radiation and permeation in porous media under pressure difference.The heat and mass transfer mechanism is complex.At present,there is a lack of research on the mechanism of high temperature heat transfer of hypersonic vehicle microwave transperant antenna window under intense aerodynamic heating,and insufficient understanding of its characteristics.Therefore,it is not only an urgent need for the development of hypersonic technology,but also an important theoretical significance to study the heat transfer mechanism of the microwave transperant structures in hypersonic vehicle at high temperature.In this paper,aming at the multilayer microwave transperant stuctures in hypersonic vehicle,the mechanism and characteristics of transient coupled radiationconduction-permeation heat transfer are studied by physical modeling and numerical simulation.The main contents include the following aspects.In order to meet the thermal insulation design requirements of the multilayer microwave transperant structure,the arbitrary multilayer structures composed of absorping,isotropically scattering layer,air layers and the microwave opaque layer,and the temperature dependence and spectral selectivity of thermophysical and radiative properties of materials are considered.A one-dimensional transient coupled heat transfer model and the numerical solution method of high temperature radiationconduction are established using Finite Volume method and Monte Carlo Ray-tracing method,and the corresponding calculation codes are programmed.After a validation of program,the influences of material properties on the transient temperature field of multilayer structures are fully analyzed.Considering the high porous characteristics of light thermal insulation materials and the differential pressure effects during flight,a one-dimensional transient coupled heat transfer model of gas permeation and heat conduction-radiation for multilayer micro-nano porous insulation structures under differential pressure is established based on Darcy's law.Through the Finite Volume method and Monte Carlo Raytracing method,a numerical solution method for one-dimensional transient coupled radiation-conduction-permeation heat transfer of multilayer structures at high temperatures is proposed and the corresponding calculation codes are programmed.It can be applied to the coupled heat transfer analysis of multilayer structures with temperature-dependent properties and time-varying pressure on both sides of the structure.Using this method,the effects of permeability and radiation on coupled heat transfer of multilayer insulation structures under inconsistent pressure differences are simulated and analyzed.Required by the engineering demand,based on OpenFOAM open source platform,a three-dimensional permeation heat transfer calculation module is developed,and combined with the radiation-heat conduction equivalent calculation module in the platform,a three-dimensional radiation-conduction-permeation coupled heat transfer simulation is carried out.The transient temperature distribution characteristics of three-dimensional thermal insulation structures under inconsistent pressure difference,heat flux and pressure in different regions are analyzed.The influence of permeability and radiation heat transfer on the temperature field of three-dimensional thermal insulation structure is investigated.Through the research,the calculation program for analyzing the transient coupled heat transfer process of the multilayer microwave transperant structure at high temperature is programed.A depper understanding of the mechanism and characteristics of the transient coupled heat transfer at high temperature of the multilayer microwave transperant structures is formed,and the effects of thermal conduction,radiation and permeation parameters of structure and material on the coupled heat transfer process are discovered,which provides the basic knowledge and technical foundation for the thermal insulation design of the hypersonic vehicle's microwave transperant structures.