Experience with the Large Eddy Simulation (LES) Technique for the Modelling of Premixed and Non-premixed Combustion

Compared to RANS based combustion modelling, the Large Eddy Simulation (LES) technique has recently emerged as a more accurate and very adaptable technique in terms of handling complex turbulent interactions in combustion modelling problems. In this paper application of LES based combustion modelling technique and the validation of models in non-premixed and premixed situations are considered. Two well defined experimental configurations where high quality data are available for validation is considered as case studies to demonstrate the methods, accuracy and capability of the LES combustion modelling technique as a predictive tool. The large eddy simulation technique for the modelling flow and turbulence is based on the solution of governing equations for continuity and momentum in a structured Cartesian grid arrangement. Smagorinsky eddy viscosity model with a localised dynamic procedure is used as the sub-grid scale turbulence model. A swirl flame is considered as the nonpremixed combustion application. For non-premixed combustion modelling a conserved scalar mixture fraction based steady laminar flamelet model is used. A radiation model incorporating the discrete transfer method is also included in the non-premixed swirl flame calculations. For premixed combustion where the application considered here is flame propagation in a confined explosion chamber, a model based on dynamic flame surface density (DSFD) is used. It is shown that in both cases LES based combustion models perform remarkably well and results agree well with the experimental data.