碳化材料三维烧蚀热响应有限元计算研究

Numerical Simulation Research on Three-Dimensional Ablative Thermal Response of Charring Ablators

针对碳化烧蚀热防护材料三维温度场计算问题进行了研究。采用弹簧松弛法模拟防热层表面后退运动,应用化学反应动力学模型描述材料内部热解过程,内部温度场计算模型考虑了防热材料的热传导、热解吸热、热解气体在碳化层内的流动以及热解气体与碳化层之间的热交换。对控制方程采用有限元方法进行离散,时间方向采用Newton-GMRES隐式迭代推进求解。将计算结果与经典程序的计算结果及实验数据进行了比对,初步验证了计算方法的可靠性,并通过球头算例展示了程序对三维问题的良好处理能力。

The computational method of the three-dimensional thermal response of the charring ablators is researched. The internal pyrolysis kinetics of the ablating materials obey the Arrhenius law. Effects of thermal decomposition, pyrolysis gas flow and surface recession on in-depth temperature distribution are all considered. The governing differential equations are discretized according to the Galerkin finite element method, and the semi-diseretized equations are solved with the Newton-GMRES method with second order implicit time integrators. Verification results from the exact solutions are presented to show the spatial and temporal orders of the accuracy. As part of a code validation study, the computational results are compared to the thermal response data. Capability of the code to deal with the three-dimensional problem is evaluated by a bulb-shape model ease.