ABSTRAKT

This paper describes a Large Eddy Simulation of acoustic combustion instabilities in a dump combustor. It is shown that the main effect of acoustic waves entering the combustion chamber is to create large vortices and unsteady heat release when these vortices burn. The fact that the equivalence ratio of incoming gas is also modulated by acoustic waves was tested through a special simulation where the inlet equivalence ratio fluctuates but the total flow rate remains constant. This mechanism was shown to induce less destabilizing effects than the purely aerodynamical mechanism due to vortex formation and combustion.