Event Title

Intercalibration Results. NIDA – A Non-Equilibrium based In-Depth Ablation Code

Start Date

3-3-2011 9:10 AM

Description

Charring ablative thermal protection system (TPS) has been commonly used to prevent the payload of a hypersonic or space exploration vehicle from exposure to high heat loads. The physical phenomena associated with the pyrolysis of the charring ablative material are very complex, that numerical simulations are needed to supplement the traditional TPS design methods for gaining a better understanding of the process. However, most of the existing state-of-the-art numerical models are built with the assumptions that (i) pyrolysis gases do not interact in-depth with the ablative material and (ii) pyrolysis gases released during the thermal decomposition of the resin phase are in chemical equilibrium. As a result, they fail to account for the heat absorption effect of the flowing pyrolysis gas and also predict the exit gas composition at the ablator surface incorrectly, thereby introducing significant uncertainties in the design process. In an attempt to overcome these drawbacks, a high-fidelity numerical model capable of accurately simulating the behavior of charring ablative TPS has been in development under NASA Constellation University Institutes Project. The NIDA (Non-equilibrium In-Depth Ablation) code is a quasi one-dimensional program that is designed to simulate decomposition of charring ablators and the transport as well as chemical reactions of the associated pyrolysis gas through the char layer as a continuum. Its unique aspect is that it models the transport and the chemical kinetics of pyrolysis gases through the ablator completely. Other features of NIDA include: (i) variable porosity of the char, (ii) temperature-dependent thermodynamic properties of char and pyrolysis gases, (iii) thermal non-equilibrium between the char and the pyrolysis gas mixture, (iv) surface recession, (v) Darcy's law to account for pressure variation, (vi) material decomposition, and (vii) in-depth pyrolysis. In this study we target the calibration of NIDA against existing codes, utilizing the theoretical ablator that has been

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Mar 3rd, 9:10 AM

Intercalibration Results. NIDA – A Non-Equilibrium based In-Depth Ablation Code

Charring ablative thermal protection system (TPS) has been commonly used to prevent the payload of a hypersonic or space exploration vehicle from exposure to high heat loads. The physical phenomena associated with the pyrolysis of the charring ablative material are very complex, that numerical simulations are needed to supplement the traditional TPS design methods for gaining a better understanding of the process. However, most of the existing state-of-the-art numerical models are built with the assumptions that (i) pyrolysis gases do not interact in-depth with the ablative material and (ii) pyrolysis gases released during the thermal decomposition of the resin phase are in chemical equilibrium. As a result, they fail to account for the heat absorption effect of the flowing pyrolysis gas and also predict the exit gas composition at the ablator surface incorrectly, thereby introducing significant uncertainties in the design process. In an attempt to overcome these drawbacks, a high-fidelity numerical model capable of accurately simulating the behavior of charring ablative TPS has been in development under NASA Constellation University Institutes Project. The NIDA (Non-equilibrium In-Depth Ablation) code is a quasi one-dimensional program that is designed to simulate decomposition of charring ablators and the transport as well as chemical reactions of the associated pyrolysis gas through the char layer as a continuum. Its unique aspect is that it models the transport and the chemical kinetics of pyrolysis gases through the ablator completely. Other features of NIDA include: (i) variable porosity of the char, (ii) temperature-dependent thermodynamic properties of char and pyrolysis gases, (iii) thermal non-equilibrium between the char and the pyrolysis gas mixture, (iv) surface recession, (v) Darcy's law to account for pressure variation, (vi) material decomposition, and (vii) in-depth pyrolysis. In this study we target the calibration of NIDA against existing codes, utilizing the theoretical ablator that has been