ACOUSTIC DYNAMICS OF A SWIRL PREMIXED COMBUSTOR WITH DIFFERENT OPERATING CONDITIONS

The effects of inlet swirl and external excitation on the flow field and combustion acoustic modes in a low NOx premixed combustor are experimentally investigated using a 100kW laboratory rig. It combines different operating conditions with variations in swirl number and varying levels of external excitation which are critical factors influencing the flow- flame interaction within the combustor. Results show the formation of a vortex induced central recirculation zone (CRZ) for the two swirl conditions which increase in length and width with changes in the swirl strength and forcing. The flow structure eventually merges with the high momentum flow region, a feature common to many swirl combustors. The acoustic oscillations were observed to be affected by the variations in the swirl strength with further dynamics at different levels of excitation. Accurate combination of these conditions (swirl, and excitation) could be advantageous in suppressing the intensity of the destructive acoustic instabilities in the burner. Results of this nature provide information for the design of an active control system for the combustor. (C) 2017 The Authors. Published by Elsevier Ltd.