Large-eddy simulation of combustion dynamics of lean-premixed swirl-stabilized combustor

A comprehensive numerical study of the combustion dynamics in a lean-premixed swirl-stabilized combustor is described. The analysis treats the conservation equations in three dimensions and takes into account finite-rate chemical reactions and variable thermophysical properties. Turbulence closure is achieved using a large-eddy-simulation technique. The compressible-flow version of the Smagorinsky model is employed to describe subgrid-scale turbulent motions and their effect on large-scale structures. A level-set flamelet library approach is used to simulate premixed turbulent combustion. The governing equations and the associated boundary conditions are solved by means of a four-step Runge-Kutta scheme along with implementation of the message passing interface parallel computing architecture. The analysis allows for a detailed investigation into the interaction between turbulent flow motions and oscillatory combustion of a swirl-stabilized combustor. Several physical processes responsible for driving combustion instabilities in the chamber have been identified and quantified, including the mutual coupling between acoustic wave motions, vortex shedding, and flame oscillations. In particular, the mechanisms of energy transfer from chemical reactions in the flame zone to acoustic motions in the bulk of chamber are carefully studied.