Numerical Calculation Research On Ablation Of Carbon Fiber Reinforced Silicon Carbide Matrix Composite

The aircraft will face serious aerodynamic heating problems during high-speed flight,and thermal protection of the aircraft is required to ensure the safety of the aircraft structure and the accuracy of the flight trajectory.As the most important thermal protection method,ablative thermal protection is the basis for the development of hypersonic aircraft.Ablation is a coupling interactive process of external flow field,surface ablation and internal heat transfer.The problem is complex,it requires the joint development of thermal protection materials,thermal protection system design,ground ablation test equipment and testing technology,and heat and mass transfer disciplines to solve.The ablation test provides basic data of material ablation,but it is often time-consuming and laborious.Numerical simulation calculation as a supplement to the test can not only help understand the ablation mechanism of materials,but also reduce the number of ablation tests to a certain extent.C/SiC composite material is gradually becoming the first choice for aircraft thermal protection due to its ablation resistance and high temperature resistance.COMSOL,as a multiphysics simulation software,has its advantages in solving the coupling problem of material ablation.This work mainly uses COMSOL to analyze the ablation problems of C/SiC composites,establish a material ablation model,and calculate the ablation temperature field distribution of the material and the ablation surface receding rate.Specifically,firstly,the thermochemical equations of material ablation are derived using the open system element conservation and surface thermochemical balance,and MATLAB programming is used to calculate,and the Newton-Raphson algorithm with parameters is used to solve the nonlinear equations.On this basis,the thermochemical ablation of C/SiC is analyzed and calculated,and the carbon-oxygen reaction,carbon-nitrogen reaction,and carbon sublimation,as well as the reaction of SiC to produce gaseous products and the oxidation of SiC to produce Si O₂ are considered.The dimensionless mass ablation rate of C/SiC and the equilibrium partial pressure of gaseous products at different temperatures and pressures are obtained and the calculation of thermochemical ablation of C/SiC-Zr B₂ has also been preliminarily explored.Then by analyzing the ablation process of C/SiC composites,a one-dimensional model of material ablation is established to obtain the one-dimensional non-steady heat transfer differential equation of the thermal response of material ablation.And the ramp function is used to add restricted heat flux to ensure the surface temperature of material will not significantly exceed the ablation stagnation temperature.By deriving the relationship between the dimensionless ablation rate and the ablated surface receding rate,the ablated surface receding of the material is realized by using the deformed geometry function of COMSOL.The dimensionless ablation rate,specific heat capacity,and thermal conductivity of the material are considered as a function of temperature,and the relationship between the material’s thermophysical parameters and temperature is obtained by fitting the Origin data.Finally,through COMSOL modeling and simulation,the ablation temperature field distribution and the ablation surface receding rate of the C/SiC material are obtained.The comparison between the calculation results of linear ablation rate and the test results of literature shows that the calculation results are in good agreement with the test results,and the errors are mainly the reason that the influence of liquid layer lose and the mechanical ablation during material ablation are not considered in the calculation process.