Intercalibration Results. Nonequilibrium Ablation and Pyrolysis: A Fundamental Approach

The Nonequilibrium Ablation and Pyrolysis (NEQAP) code implements a one-dimensional ablation and pyrolysis model derived from first principles for Carbon-Phenolic Thermal Protection Systems. Traditionally, ablation models assume in-depth pyrolysis gases to be in chemical equilibrium as well as in thermal equilibrium with surrounding char material. The goal of NEQAP is to remove these assumptions in order to study the effects they have on current material response predictions including pyrolysis gas composition in-depth and their flux into the boundary layer. The pyrolysis gas densities in-depth are computed by solving species mass conservation equations for a homogeneously reacting ow through a porous medium with the velocities approximated by Darcy\u27s Law. In addition to the mass conservation equations, the char and gas temperatures are treated separately via two energy conservation equations. The temperature inside the virgin layer is computed through a separate energy equation. Due to a lack of heterogeneous kinetic data, the porosity is computed through a temperature curve derived from Thermogravimetric Analysis data for PICA. Surface recession is governed by a detailed energy balance along with the carbon deposition model of Park. The model predicts temperature distribution and pyrolysis gas composition inside the char layer and the composition of their flux into the boundary layer over time. In addition, both m_c and m_g which are the mass removal rates of the surface and phenolic resin respectively, are predicted as part of the solution