Evaluation of combustion models for combustion-induced vortex breakdown

Abstract

Combustion induced vortex breakdown (CIVB) recently has been identified as a very complex cause for flame flashback in lean premixed swirl stabilised gas turbine burners. In the present study CIVB has been investigated computationally using Unsteady Reynolds-Averaged Navier–Stokes (URANS) and Large-Eddy Simulation (LES) methods of different complexity. URANS calculations of flashback at several operational conditions were performed on a simplified setup using the Schmid- and the Lindstedt–Vaos combustion models supplemented with flame quenching models to prevent the flame from propagating along the cold wall. The models have been validated and are evaluated with respect to pressure dependence using experimental data of a turbulent Bunsen flame showing that the Schmid-model is not capable of reproducing high pressure combustion. The calculated flashback limits are compared to experimental results. Good agreement between simulations and experiments for the whole operational range can be seen once the model setup is tuned to one single operating point. The LES of the flashback using artifical flame thickening offers a very detailed view to the flow phenomena around the flame tip which cannot be achieved in experimental investigations.

Keywords:

• reacting turbulent flow
• large eddy simulation
• reynolds averaged navier–Stokes
• vortex dynamics

Acknowledgement

The authors gratefully acknowledge the financial support by the DFG (German Research Council) and support from EKT Darmstadt providing the FLOWSI LES code.