Estimation Of Surface Heat Flux And Shape Reconstruction Of 2-D Ablation Using The Model Predictive Inverse Method

Ablative thermal protection system is the main thermal protection technology for re-entry vehicles.It is an important basis for designing re-entry vehicle ablative thermal protection systems by effectively predicting the changes in the internal temperature field and ablation boundary of ablation materials.Because of the serious difficulty in directly measuring the heat flux distribution on the surface of the ablation process,the Inverse Heat Transfer Problem(IHTP)method is used to indirectly estimate the heat flux distribution on the ablation surface by using the temperature measurement information from the temperature sensors arranged inside the ablation material which provides a feasible solution for predictive the ablation material internal temperature field and ablation boundary variation.Based on the idea of model predictive control,this paper studies the estimation of two-dimensional ablation surface heat flux and boundary shape reconstruction.The paper focuses on the inversion of the thermal boundary conditions for the ablation heat transfer process.The main work of the dissertation includes:(1)Combining Finite Element Method(FEM)and Moving Mesh Technology(MMT),a numerical method(FEM-MMT)for solving two-dimensional ablation heat transfer problems is established.In the numerical calculation process,it is not necessary to re-divide the grid each time,only the coordinate position of the grid node is adjusted,the grid note number do not change.What's more,this method overcome the difficulty to re-align the grid due to the change of the geometry domain of the ablation process.The FEM-MMT calculation method was used to numerically simulate the two-dimensional ablation heat transfer problem.Under the given ablation surface heat flux distribution conditions,the prediction results of the variation of the internal temperature field and ablation boundary shape of the ablation material is obtained.(2)According to the established two-dimensional ablation heat transfer process mechanism model,the corresponding equations of the step response function of the heat transfer process are constructed.The influence matrix of the system is obtained by solving this control equation.Basing on this influence matrix,the internal temperature response prediction model of the two-dimensional ablation heat transfer is established.What's more,it lays a necessary foundation for the further realization of surface heat flux distribution inversion and ablation boundary shape reconstruction in the ablation heat transfer process.(3)Based on the system model predictive control theory,a Model Predictive Inverse Method(MPIM)for two-dimensional ablation inverse heat transfer problem is established.The temperature prediction information and measurement information at the internal temperature measurement point of the ablation material are used.Through the online rolling optimization,the optimal time series of the heat flux distribution to be inverted is obtained.(4)Using the aforementioned MPIM inversion method,the estimation of surface heat flux and ablation boundary shape reconstruction of two-dimentional ablation heat transfer process are studied.Through numerical experiments,the effects of temperature measurement error at the measurement point,future time steps,and other factors on the inversion results are analyzed,and the above-mentioned MPIM inversion method is preliminarily confirmed to solve the problem of transient surface heat flux estimaton and ablation boundary shape reconstruction of ablation heat transfer process...