Evaluation of radiation models for simulation of spherical diffusion flames in microgravity

In this study, the effects of various approximations used in modelling radiation for numerical simulation of transient spherical diffusion flames are investigated by comparison with the experiments. The experiments were performed in the drop tower at NASA-Glenn which provides a 2.2 seconds microgravity time during which the diffusion flame radius and the temperature field were measured as a function of time. Multiple tests were carried out for different fuel and oxidizer dilutions. Ethylene was used as the fuel. For simulation, a one-dimensional spherical diffusion flame model was developed that is capable of both steady and transient calculation. Through the comparison of experimental measurements and transient simulation results, the numerical model was validated. Different radiation models were applied and it was concluded that the statistical narrow band (SNB) combined with discrete ordinates method (DOM) reproduced the experimental results most closely. This study is helpful for better understanding of the interaction between gas radiation and flame extinction under microgravity conditions.