Intercalibration Results. Description and Results of a Predictive Model for Pyrolysis

We consider a model for in-depth pyrolysis using a continuum theory of mixtures. The material is assumed to be composed of a number of distinct solid and gas phases. The pyrolysis process is modeled as an inter-conversion of different constituent phases. The gas transport is assumed to be instantaneous and therefore gas momentum equation is not solved. We use data provided for Carbon Phenolic. Results show good (but not exact) agreement with FIAT results. Differences could be attributed to different treatment of the transport properties of the solid mixture and the integration of pyrolysis kinetics

Extension of the PECOS Quasi-steady Ablation Toolkit for Uncertainty Propagation

Low-order models are quite useful for sensitivity analysis and design. This work details work done on adding complementary pieces to the PECOS low-order, quasi-steady-state ablation model to facilitate uncertainty propagation. The PECOS quasi-steady state ablation model is a one-dimensional, quasi-steady-state, algebraic ablation model that uses finite-rate surface chemistry and equilibrium pyrolysis-gas-production submodels to predict surface recession rate. The material response model is coupled to a film-transfer boundary layer model to enable the computation of heat and mass transfer from an ablating surface. For comparison to arc jet data, a simple shock heated gas model is coupled. A coupled model consisting of submodels for the shock heated gases, film heat and mass transfer, and material response is exercised against recession rate data for surface and in-depth ablators. Comparisons are made between the quasi-state-state ablation model and the unsteady ablation code, Chaleur, as well as to other computations for a graphite ablator in arcjet facilities. The simple models are found to compare reasonably well to both the experimental results and the other calculations. Uncertainty propagation using a moment based methods is presented. The method is applied to a number of simplified sample problems, for both univariate and multivariate scenarios. The results of this study are discussed, and conclusions about the utility of the method as well as the properties of the ablation code are drawn