Large eddy simulation of spray combustion in a model swirl burner using the two-phase spray flamelet model

Strong turbulence-chemistry interactions in turbulent spray combustion need to be closed by accurate combustion models in the framework of large eddy simulation (LES). The two-phase spray flamelet/ progress variable (TSFPV) model has exhibited good predictions in spray combustion simulation since it takes into account droplet evaporation effects during flamelet modelling. In our previous studies, the TSFPV model was validated on simple configurations of non-swirling jet spray flames. In this research, the model is further applied to the LES of the complicated configuration of the Cambridge model swirl burner. The M-shaped flame structure is well reproduced according to the comparisons of the simulation results with experimental images. The simulation results agree well with the experimental data in terms of quantitative statistics of droplet diameter and velocity. The complicated flame structures, especially for the inner flame brush in the two-phase spray combustion regime, are further analysed. Strong droplets/ flame interactions occur where some droplets penetrate the flame region, emphasising the influence of the evaporation source terms on the flame structure. The heat release rate in the inner flame region is greater than that in the outer flame region, which is consistent with the experiments. The droplet dynamics are analysed based on the scatter plots of droplet axial velocity and the results show that the behaviour of droplets of different sizes varies. The spray flame analyses promote the understanding of the complex spray flame structure in the complicated swirling flame configuration.