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Large Eddy Simulation of Flame Flashback by Combustion Induced Vortex Breakdown

Eike Tangermann
Institut für Mathematik und Rechneranwendung, Universitat der Bundeswehr Munchen Werner-Heisenberg-Weg 39, 85577 Neubiberg, Germany

Markus Klein
Institut fur Mathematik und Rechneranwendung Universität der Bundeswehr München W.-Heisenberg-Weg 39, Neubiberg, Germany

Michael Pfitzner
Department of Aerospace Engineering, Institute for Thermodynamics, University of the Federal Armed Forces Munich, 85577 Neubiberg, Germany

Sinopsis

Flame flashback is a major concern during the design of lean premixed gas turbine combustors. One particular mechanism of flame flashback in swirl stabilized combustors is the combustion induced vortex breakdown (CIVB), where the flame can propagate upstream against flow velocities far higher than the local turbulent flame speed. In the present work flame flashback by CIVB has been investigated for two combustors of different scale using large eddy simulation. The LES offers full access to a well resolved flow field and allows a detailed analysis of the fluid mechanical processes happening around the flame tip. The method is shown being able to reproduce the operating points limiting stable operation. The analysis of each flashback process then reveals, that the driving mechanism is different for both combustors depending on their size and the swirl velocity field. Either a baroclinic push or a flame propagation by stretching of the flow can be observed.