Large-eddy Simulation of Flow and Combustion Dynamics in a Lean Partially-premixed Swirling Combustor

A lean partially premixed swirling combustor is studied by resolving the complete flow path from the swirl vanes to the chamber outlet with large-eddy simulation (LES). Flow and combustion dynamics for non-reacting and reacting situations are analysed. The influence of Reynolds number on the vorticity distribution and vortex rings formation for non-reacting cases is examined. A modified flame index is introduced to identify the flame regime during the partially premixed combustion. The combustion instability phenomenon is detected by applying Fourier spectra analysis. Several scalar variables are monitored to investigate the combustion dynamics at different operating conditions. The effects of swirl number, equivalence ratio and nitrogen dilution on combustion dynamics are studied in detail.