IMPACT OF REACTION AND LOCATION OF A PILOT JET ON THE FLOW STRUCTURES IN A CO-ANNULAR SWIRL BURNER

The paper investigates the impact of heat release and pilot jet location on the swirling flow structures in a co-annular swirl burner without confinement. Two iso-thermal turbulent swirling flow cases and three turbulent premixed swirling flames are studied with the aid of large-eddy simulation. Two geometries are considered, one featuring a pilot lance flush with the outlet and one with retracted pilot lance. The Reynolds number is 35,000. Detailed comparisons with experimental data are performed for velocity statistics and generally good agreement is achieved. Furthermore, coherent structures are analyzed and local power spectra computed. In the non-reactive case with retracted pilot jet, a very strong precessing vortex core (PVC) is observed in both numerical results and the experiment. The PVC is weak in the non-retracted case. In the reactive cases where the whole central recirculation zone (CRZ) is enclosed in the high-temperature post-flame region, the PVC is almost completely suppressed