Research On Heat Transfer Inverse Problem Based On Thermal Protection Structure And Its Application

With the rapid development of hypersonic vehicles,thermal protection structures have become a hot topic at home and abroad.In this paper,the theoretical research and experimental verification for a typical thermal protection structure were carried out to solve the inverse heat transfer problem.Firstly,Kirchhoff transform was introduced into the nonlinear heat conduction control equation,and an implicit finite difference method was used to solve the forward heat transfer problem.Compared to the results of ABAQUS,the numerical method of heat conduction was verified to be effective under various boundary conditions.Secondly,based on the Levenberg-Marquardt(L-M)algorithm,a multistage methodology consisting of two successive steps was proposed: In the first period,the initial values of unknown parameters were supposed to linearly change with temperature.Then the linearly changed values of thermal parameters obtained by LMA in the first period were taken as the new initial values to identify the temperature-dependent thermal parameters in the second period.The advantages and disadvantages of this method were compared with the initial value set to a fixed value in four aspects: calculation accuracy,calculation time,influence of initial values and temperature measurement errors.Thereafter,a high-temperature-heating experiment was conducted to verify the feasibility of the method.The temperature-dependent thermal conductivity and heat capacity of the thermal insulating tile were identified by using the measured temperature history,and compared with the reference values measured by the instrument.It can be observed that the error of the inversion results is within a reasonable range and the algorithm is effective.Then,the inversion of material parameters in three-dimensional models with anisotropic material parameters was investigated via combining Isight and ABAQUS.ABAQUS was used to solve the forward heat transfer problem,and the L-M algorithm was used to identify the parameters.An example was also made to verify the effectiveness of the method.Finally,the inverse heat transfer problem method was applied to the identification of the bonding state of the thermal insulating tile.The temperature history of the lower surface of the skin was measured and the heat flux density of the bonding layer with time can be obtained by L-M inversion algorithm.The bonding state of the thermal insulating tile was effectively identified by numerical calculation under three conditions of bonding layer: perfect bonding layer,1/3 bonding defect on corner and 1/3 bonding defect in middle.