LES and RANS of Premixed Combustion in a Gas-Turbine Like Combustor Using the Flamelet Generated Manifold Approach

Dry-low NOx gas turbine technology relies on lean premixed combustion of fuel. Additionally the accurate prediction of turbulent premixed combustion is still very difficult. In the present paper the calculation of reduced chemistry is assessed efficiently through the use of the flamelet generated manifold (FGM), which is used in conjunction with a CFD code in a RANS as well as in an LES context. In order to predict the combustion phenomena in a high swirl and high Reynolds number flow (the SimVal setup, at atmospheric pressure with elevated temperature), the present model is used concomitantly with a pre-assumed PDF for which fluctuations are completely determined in terms of an algebraic model. The mixing model for the variance has an arbitrary model constant, and the results show that the flame stabilization is not very sensitive to the model parameter present in the model. Stabilization of the combustion occurs at a location comparable to that found in experiments. In order to investigate the effects of this parameter on the numerical solutions, first RANS simulations were addressed considering arbitrary values for this parameter, defined within a certain range, and in a next step the grid resolution was changed. LES calculations were also performed showing similar features predicted in RANS. It is found that with the use of FGM combustion features in gas turbine conditions can be reproduced in a robust way.