Flamelet Model of NOx in a Diffusion Flame Combustor

Abstract

This paper describes a model used for the prediction of the formation of nitrogen oxides in modifications of an industrial diffusion flame, natural gas fueled can combustor. The flowfield inside the modified combustors is calculated using a Navier-Stokes solver. A fast chemistry assumption is used for modeling the heat release. Calculated turbulence parameters are then used for the calculation of the NOx formation rate in the post-processing mode with the aid of a flamelet model. The flamelet model permits the use of detailed kinetics with only minimal computational expense. The dependence of the NOx formation rate on the mixture fraction and scalar dissipation is calculated separately for each given condition. The validation of the model predictions is based on field test data taken earlier on several low NOx modifications recently applied to an industrial, reverse flow can type combustor. The reduced level of NOx emissions was achieved in these modifications by changes in the air distribution within the combustor liner. A comparison of the predicted and measured NOx emission levels shows good potential of the flamelet model.