NO prediction in turbulent flames using LES/FGM with additional transport equations

The prediction of combustion processes using Large Eddy Simulation (LES) combined with tabulated chemistry and presumed probability density modeling has proven to be very successful and become very popular, especially in academia, during the last years. A variety of time and length scales occur within combustion systems which need to be resolved. The comparably slow unsteady flow is well described by the LES, whereas Flamelet Generated Manifolds (FGM) provide a good means to represent the fast chemical reactions. However, the slow production of minor species such as nitrogen oxide is not well captured by the manifold defined by fast evolving major species. To overcome this deficiency, an additional transport equation for nitrogen oxide (NO) is solved here. The source term of NO is taken from the chemistry database depending on mixture fraction and progress variable. Two different modeling assumptions for this source term are presented in this paper. The models are applied to a standard test case from the Sydney bluff body flame series and compared to experimental data and the classic FGM approach. Both models show a large improvement over the results obtained by the standard FGM model.