TURBULENT FLAME MODELS FOR PREDICTION OF PRES- SURE OSCILLATIONS IN GAS TURBINE BURNERS

Humming is a dangerous, combustion-driven acoustic oscillation in gas-turbine burners, which may cause catastrophic damages, thus undermining manufacturers’ competitiveness. Therefore those systems require humming prevention, which, in turn, requires predictive tools which are both reliable and fast. As a matter of principle, both perturbations of stoichiometry and flame velocity affect heat release. Moreover, the mentioned perturbations also lead to fluctuations in flame surface area, which should be accounted for in the modeling stage. Therefore, the thermo-acoustic model described in this work considers a combustion model, which relies on the propagation of the regress variable. Simulations are carried out by means of OpenFOAM environment. Modeling of heat release includes nonlinearities. The model solves non-linearized averaged Navier-Stokes equations for compressible fluids. Thus, it includes both convection and sound propagation. The scope of the work is to verify the sensitivity of the heat release model to velocity fluctuations on the BRS (Beschaufelter RingSpalt) burner test-rig at the Technische Universitat Munchen. Two flame models are used: the Turbulent Flame Closure (TFC) model and the Flame Speed Closure (FSC) one. However, both of them predict the distribution of the heat release shifted closer to the exit of the burner. Thus, the phase of the flame heat response to acoustic perturbations is lower than the experimentally obtained values. Further evolution of humming amplitudes could be observed in the time domain.