The presentation will briefly cover 3 areas:

- Standard TGA testing of phenolic resin and the interpretation of the decomposition events as a function of heating rate. Current work including high rate tga (up to 500ºC/min) will be compared with previous high rate TGA in the literature.
- Results of preliminary analytical pyrolysis of phenolic resin to identify the condensable and gaseous, decomposition products.
- Preliminary molecular dynamics modeling of the thermal decomposition process of phenolic resin using ReaxFF.

It would be useful to discuss the current aspirations of the ablation community as well as the relevance of the approach outlined above.

]]>- Basic numerical method : STAB2 (1D implicit shrinking grid with multi-materials , contact resistances etc)
- Multiple Arrhenius decomposition from TGA, with arbitrary grouping (resin/fibres/contaminants)
- Equilibrium or non-equilibrium pyrolysis gas treatment
- Internal pressures from Darcy type law
- Iterative TPS sizing for input design rules.
- Adjoint scheme and simple optimiser for fitting of effective properties to arc heater or flight measurements (or sets of)
- Simple surface chemistry modules for surface energy balance:
- Carbon ablation (kinetic, diffusion limit, sublimation)
- Teflon model
- Melt failure (silica etc)
- Variable surface stoichiometry materials + failure
- Surface roughness evolution model based on differential ablation rates, shape factor and Dirling correlation. (used when coupling to flow codes)
- Flame front model with equilibrium/frozen burn treatment for pyrolysis gases for charring ablators. The burn efficiency is an empirical factor.

Boundary conditions can be defined in terms of temperature or heat flux.

]]>- Imponderable and Webex call-ins
- Overview of Results
- Discussion of Next Round of Intercalibration Test Conditions by Alexandre Martin
- Future Validation Experiments (round table discussion) by Jean-Marc Bouilly
- Outcome of the Workshop and Future Directions by Ioana Cozmuta

The current test case will be rebuilt using KCMA which has already been used for the similar efforts carried out in the frame of the European Ablation Working Group for the reconstruction of experimental measurements performed for graphite and carbon phenolic.

KCMA is based on a one dimensional approach and uses a surface energy balance at the material surface. It is based on a finite difference centred scheme accurate to the first order in time and the second order in space is used for solving the equations, and can compute TPS recession for stagnation point and cone configurations (for a dedicated point).

Several balance equations are solved for the gas and solid phases:

- The solid density accounting for pyrolysis;
- The gas density, taking into account pyrolysis, material porosity, changes of gas density under pressure effects, blockage;
- Gas momentum equation;
- Total energy conservation.

Porosity and gas friction within the material can be accounted for. The wall temperature and the mixture composition are calculated using the hypothesis of a wall at chemical equilibrium, and the surface temperature can be also imposed. Species mass fraction, temperature and density in the boundary layer are computed using the method of Gordon & Mc Bride and the data of JANNAF and/or Gurvich for computing the species specific heat, enthalpy and free entropy.

So far different materials can be handled by the tool. Carbonaceous materials, with and without pyrolysis, in this case carbon oxidation and sublimation are considered, while nitridation is not considered. The tool capabilities have been recently extended to silica based materials and melting of silica is taken into account for calculating the recession.

The results provided by the tool have been compared with the results obtained during the Pioneer-Venus mission, and the experimental data available for graphite and carbon phenolic. In the final contribution, numerical results on temperature distribution inside the material and char thickness for the defined test case will be predicted.

]]>Current material response models are inspired from the model of Kendall et al. published in 1968. This model has been able to reproduce within a reasonable accuracy, Arc Jet performance tests carried out on PICA in conditions relevant to NASA’s missions. Therefore, depending on the design layout and quantity of interest, current models are robust. In off design conditions, however, there is a strong need to improve current models. In the poster, a high-fidelity model, tailored for PICA family material architecture, is detailed and discussed. The model tracks the chemical composition of the gases produced during pyrolysis. As in the conventional model, it uses equilibrium chemistry to determine the recession rate. It also tracks the time evolution of the porosity of the material. Progress towards implementing this high-fidelity model in a code baptized, CAT, is outlined. Results for the workshop test case are presented as part of the verification process of the code development.

]]>- PAM_1, implementation of the state-of-the-art CMA model;
- PAM_2, 3D solver with a 3D treatment of the pyrolysis gas flow (averaged momentum equation);
- PAM_3, currently in development, will be a high-fidelity module including finite-rate chemistry, multicomponent diffusion, in-depth ablation, and coking.

PATO results for the 2011 ablation test case will be presented in the ablation test-case overview session [5 minutes, 2 slides]. A description of PATO will be detailed in the poster session with a summary of the test case results and an illustration of a 3D case with 3D pyrolysis gas.

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