A nonlinear pyrolysis layer model for analyzing thermal behavior of charring ablator

• We develop a new pyrolysis layer model for solving problems on thermal behavior of charring ablator.
• We analyze the nonlinear influence caused by moving interfaces and temperature dependent thermal properties.
• This study will be helpful for the design of the thermal protection system in reentry vehicles.

Understanding the pyrolysis phenomena experienced by charring ablators used in thermal protection systems for manned reentry vehicles is crucial for their design. A one-dimension nonlinear pyrolysis layer model without surface recession has been developed to explore the thermal behavior of charring ablator when subjected to an aerodynamic hyper-thermal environment. The charring ablator in this model consists of three distinct zones: char, pyrolysis and virgin material. The heat and mass transfer, the two moving interfaces and the temperature-dependent thermal properties in charring materials undergoing pyrolysis are considered in the formulation of the model. The governing differential equations are derived, and its implicit finite difference formulations are programmed in MATLAB. Examples are given to demonstrate the effectiveness and accuracy of this model. The thermal response of charring material with antioxidants is also predicted under actual service conditions.