Large eddy simulation and a model-based analysis of the acoustic response of a premixed flame in a swirl combustor

Lean premixed combustion reduces NOx emissions but increases the risk of thermoacoustic instabilities. This study investigates the acoustic response of a turbulent premixed swirling flame using large eddy simulation (LES) in OpenFOAM, incorporating a modified reactingFoam solver and the partially stirred reactor model for C 2 H 4 /air combustion. The simulated flame transfer function (FTF) shows good agreement with experimental data. To further study the FTF shape, we employed the swirl flame transfer function framework, estimating directly five of the six independent parameters from the LES data and determining the tangential fluctuation coefficient by fitting the FTF dip from the LES. Key modulation factors—including fluctuations in the tangential velocity, spatial decay rates of perturbations, and the phase difference between axial and tangential perturbations—were systematically examined. The results demonstrate that the FTF characteristics can be effectively modulated through rational design of swirler geometry and flow parameters. This work provides valuable insights into the physical mechanisms governing flame dynamics, contributing to a better understanding of thermoacoustic instabilities.