Flame Response to a Pulsating Pilot Jet in an Unconfined Double-Concentric Swirl Burner

In lean premixed combustors, swirling flow is widely used to stabilize the flame via a swirl-generated central circulation zone (CRZ). However, the CRZ often exhibits a precessing vortex core (PVC) which may drive combustion instabilities. The paper investigates the occurrence of CRZ and PVC in an unconfined double-concentric swirl burner, and the flame response to a sinusoidal variation of the mass flow rate in the pilot jet, with the aid of large-eddy simulation (LES). The results are compared with a corresponding experiment and detailed analyses of the flow structures are performed. The isothermal flow is also simulated for comparison