Modeling turbulent nonpremixed jet flames using fluent's PDF transport model: Effect of mixing model on flame extinction

Predictions of mean velocity, species, and temperature profile for Sandia piloted nonpremixed methane-air-turbulent jet flames D, E, and F, were compared to experimental data to assess the accuracy of FLUENT's joint composition probability density function transport equation model. A 9-species/5-step reaction computer assisted reduced mechanism was used together with the interaction by exchange with the mean mixing model. Results featured contour plots and profiles of mean and rms of key flow variables, and scatter plots to highlight local extinction. In general, the results of flame D showed good agreement with the experimental data. However, mass fractions of major species and temperature for flames E and F were highly overpredicted, indicating the need for a more detailed chemistry. The effect of mixing models on flame extinction was analyzed by applying the new Euclidean Minimum Spanning Tree mixing model, available in a beta version of FLUENT 6.2, to the higher Reynolds number flames. The mean species and temperature profiles obtained using EMST do not show a significant improvement over IEM, although scatter plots for the former seem to predict a greater amount of local extinction. Efforts towards using the partially premixed combustion model along with the LES solver in FLUENT were also discussed. This is an abstract of a paper presented at the 30th International Symposium on combustion (Chicago, IL 7/25-30/2004).