Numerical study of pyrolysis gas flow and heat transfer inside an ablator

A numerical simulation of a lightweight ablator in an arc-heated flow was carried out. Thermal response analysis of the ablator was coupled with thermochemical nonequilibrium analysis of an arc jet around the ablator. In the thermal response analysis, the pyrolysis gas flow inside the ablator was calculated in detail by solving the conservation equations. Phenomena such as heat conduction, pyrolysis of resin, surface reactions, and recession were also considered in the simulation. Furthermore, in order to evaluate the injection of the ablation gas (pyrolysis gas and carbonaceous gas generated by the surface reactions) from the ablator surface into the outer flow field, a computational fluid dynamics code was extended by including further chemical species besides those in the previous study. This also allowed the simulations for wider-range flow conditions such as a nitrogen flow and airflow. The simulation was conducted for flow conditions of a 20 kW arc-heated nitrogen flow and a 750 kW arc-heated airflow. The results from the former simulation were compared with the experimental data and the computational results using other models. This comparison showed that the effect of the pyrolysis gas flow on the thermal response was significant, and thus the detailed analysis considering the multidimensional pyrolysis gas flow led to a considerable improvement of the predictive performance.