Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame

Benedetta Giulia Franzelli (1) , Eleonore Riber (1) , Laurent Y.M. Gicquel (1) , Thierry Poinsot (2)

1 CERFACS - Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique
2 IMFT - Institut de mécanique des fluides de Toulouse

This paper investigates one issue related to Large Eddy Simulations (LES) of self- excited combustion instabilities in gas-fueled swirled burners: the effects of incom- plete mixing between the gas injection and the combustion chamber. For simplicity reasons, many LES assume perfect premixing of the gases entering the combustion chamber. In practice this is rarely the case and this study addresses the question by comparing LES assuming perfect premixing and LES where the fuel jets are resolved and fuel/air mixing is explicitely computed. This is done for the Preccin- sta swirled burner which has been carefully studied experimentally at DLR. All previous LES studies of Preccinsta have assumed perfect premixing and this work demonstrates that this assumption is reasonable for stable flows but is not accept- able to predict self-excited unstable cases. This is shown by comparing LES and experimental fields in terms of mean and RMS fields of temperature, species and velocities as well as mixture fraction pdfs and unsteady activity for two regimes: a stable one at equivalence ratio 0.83 and an unstable one at 0.7.

Mots clés: Gas turbines; Turbulent non-perfectly premixed combustion; Large Eddy Simulation; Reduced chemistry; Thermo-acoustic instabilities

Domaines: Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Benedetta Giulia Franzelli, Eleonore Riber, Laurent Y.M. Gicquel, Thierry Poinsot. Large Eddy Simulation of combustion instabilities in a lean partially premixed swirled flame. Combustion and Flame, 2012, vol. 159, pp. 621-637. ⟨10.1016/j.combustflame.2011.08.004⟩. ⟨hal-00811961⟩