Establishment and Optimization of Ablation Surrogate Model for Thermal Protection Material

The temperature response calculation of thermal protection materials,especially ablative thermal protection materials,usually adopts the ablation model,which is complicated in process and requires a large amount of calculation.Especially in the process of optimization calculation and parameter identification,the ablation model needs to be called many times,so it is necessary to construct an ablation surrogate model to improve the computational efficiency under the premise of ensuring the accuracy.In this paper,the Gaussian process model method is used to construct a thermal protection material ablation surrogate model,and the prediction accuracy of the surrogate model is improved through optimization.

Editorial: Special subject on the mechanical behavior of thermal protection materials and structures

The thermal protection materials and structures are widely used in hypersonic vehicles for the purpose of thermal insulation, and their mechanical behavior is one of the key issues in design and manufacture of hypersonic vehicles. It is our great pleasure to present the seven papers in this special subject of Theoretical ＆ Applied Mechanics Letters （TAML） and introduce the recent progresses on the mechanical behavior of thermal protection materials and structures by the authors.

Multi-phase flow effect on SRM nozzle flow field and thermal protection materials

Multi-phase flow effect generated from the combustion of aluminum based composite propellant was performed on the thermal protection material of solid rocket motor(SRM) nozzle.Injection of alumina(Al2O3) particles from 5% to 10% was tried on SRM nozzle flow field to see the influence of multiphase flow on heat transfer computations.A coupled,time resolved CFD(computational fluid dynamics) approach was adopted to solve the conjugate problem of multi-phase fluid flow and heat transfer in the solid rocket motor nozzle.The governing equations are discretized by using the finite volume method.Spalart-Allmaras(S-A) turbulence model was employed.The computation was executed on the different models selected for the analysis to validate the temperature variation in the throat inserts and baking material of SRM nozzle.Comparison for temperatures variations were also carried out at different expansion ratios of nozzle.This paper also characterized the advanced SRM nozzle composites material for their high thermo stability and their high thermo mechanical capabilities to make it more reliable simpler and lighter.

Thermal Investigation for Solid Rocket Motor Nozzle Inserts Material

A time-resolved numerical computational approach, involving the combustion of double-base propellant is performed on thermal protection material for SRM nozzle. An implicit Navier-Stokes Solver is selected to simulate two-dimensional axial-symmetric unsteady turbulent flow of compressible fluid. The governing equations are discredited by using the finite Volume method. S-A turbulence model is employed. CFD scheme is implemented to investigate the temperature distribution causes at nozzle throat inserts composite material. Different parameters have been selected for the analysis to validate the temperature variation in the throat inserts and baking material of SRM nozzle. The advanced SRM nozzle composite material is also characterized for the high thermo stability and high thermo mechanical capabilities to make it more reliable, simpler and lighter.

Thermal response, oxidation and ablation of ultra–high temperature ceramics, C/SiC, C/C, graphite and graphite–ceramics

Various thermal protection materials exhibit obviously different and complicated thermal response,oxidation and ablation behavior,which are very important for the appropriate design and selection.However,the relative researches are very few currently.In this work,the thermal response,oxidation and ablation behavior of representative thermal protection materials including ultra-high temperature ceramics,C/SiC,C/C, graphite and graphite-ceramic were investigated systematically in strong heat flux,high enthalpy and low-pressure environments.Thermal response of these materials was analyzed based on experimental results and thermal energy balance that accounts for all of the heat transfer processes transporting energy into and out of the surface.Many factors were playing important roles in the thermal response including thermal conductivity,volumetric heat capacity,catalytic efficiency,emissivity and oxidation characteristics of the materials.The importance of each factor not only depends on the material characteristics such as material composition and phase content but also environment parameters including heat flux,enthalpy,pressure and testing time.The comparisons and relationships of oxidation and ablation behaviors for these materials under extreme environments were also illustrated in detail.Furthermore,thermal response and ablation behaviors of pre-oxidized material or repeated tests were also performed to evaluate the effect of pre-treatment on the performance and reusability of thermal protection materials.This work offers guiding significance for the appropriate design and selection of thermal protection materials.