Numerical simulation of oxy-acetylene testing procedure of ablative materials for re-entry Space vehicles

A testing apparatus for flame exposure of ablative, high thermal flux-resistant materials has been designed and manufactured according to the ASTM E 285-80 standard. The test is useful for the selection of thermal protection systems (TPS) working as ablators and for the evaluation of their shielding performance. In order to support the material/component design and to offer new and differentiated tools for the screening phase of TPS materials, a CFD (computational fluid-dynamics) model of the burning test was developed. The model simulates the combustion of an oxygen-acetylene mixture occurring in a conventional welding torch, and calculates the heat flux incident on the sample and the related temperature fields. The validation of the model was obtained performing suitable instrumented tests enabling direct measurements of both incident heat flux and temperatures of the front and back surfaces of an ablative sample. Good agreement was found between numerical results and experimental measurements, encouraging the use of simulations for the design of the test environmental conditions.