Identification of Flame Transfer Functions Using LES of Turbulent Reacting Flows

Combustion systems can exhibit detrimental thermoacoustic instabilities, driven by unsteady heat release of the flame. For analysis and control of such instabilities, a characterization of the flame dynamics in terms of the so -called Flame Transfer Function (FTF), i.e. the normalized ratio of heat release to velocity fluctuations, is required. In the project reported here, LES simulations of a turbulent premixed swirl burner were carried out using the LES Solver AVBP developed at CERFACS. The system was excited using broadband perturbations at the inlet and then system identification methods were used to identify the FTF. Combustion was modeled using the Thickened Flame model with one-step kinetics. Results were compared to experiments and favorable agreement was obtained. Calculations required significant numerical resources and were carried out on the Linux Cluster and on the HRBLII Supercomputers of the Leibniz-Rechenzentrum in Garching using up to 256 cores.