TURBULENT PREMIXED LES COMBUSTION MODELS BASED ON FRACTAL FLAME SURFACE DENSITY CONCEPTS

With increasing computational power, Large Eddy Simulation (LES) is being widely used to study and develop a better understanding of turbulent combustion. A variety of subgrid combustion models have been proposed to investigate premixed combustion in LES. One of the physical aspects that can be exploited, are the fractal characteristics of premixed flames which have been confirmed in several experimental works. In this work the performance of a simplified version of an already established sub-grid flame surface density combustion model, which is based on the fractal characteristics of the flame surface is investigated. The original model was derived on the basis of theoretical models, experimental and direct numerical simulations databases and its performance was validated with data from the available literature. The simplifications to the established flame surface density model are discussed, and its performance is validated in comparison to the original model. Secondly numerical simulations with both models at conditions typical for spark-ignition engines and industrial gas turbines are validated against experimental data. It is found that both original and simplified models are suitable for LES of low to high turbulent premixed combustion in ambient and elevated pressure conditions.