The dynamics of multiple interacting swirl-stabilized flames in a lean-premixed gas turbine combustor

The presence of strong interactions between adjacent flames is inevitable in most practical gas turbine combustion systems. Despite the fundamental and practical importance of this configuration, an accurate description of the dynamics of multiple interacting swirl-stabilized flames is still lacking. To better understand the key processes, we have examined flame transfer/describing functions (FTF/FDF) of two interacting lean-premixed flames in a model gas turbine combustor equipped with two identical fuel nozzles. Unlike non-swirling flames, two adjacent swirl-stabilized flames are defined as having either co-rotating or counter-rotating interaction, depending on the relative direction of azimuthal velocity components. The FTF/FDF of interacting swirl flames for these two impingement conditions are analyzed in reference to the corresponding single nozzle (SN) data to provide physically important insight into the nature of flame-flame interactions in a multi-nozzle (MN) environment. It is first shown that both FTF and FDF are heavily influenced by the combination of swirl rotational directions, since the local flame/flow properties in the interacting region are mainly controlled by the jet impingement patterns. Our results suggest that there is considerable discrepancy between the SN and MN data, implying that the use of SN FTF data for the prediction of the MN flame dynamics can lead to erroneous results. Quantitative analyses of extensive self-excited instability data reveal that the degree of temporal synchronization between adjacent flames is a necessary condition for the onset of the instabilities. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.