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Self-excited circumferential instabilities in a model annular gas turbine combustor: Global flame dynamics

Worth, NA and Dawson, JR (2013) Self-excited circumferential instabilities in a model annular gas turbine combustor: Global flame dynamics. Proceedings of the Combustion Institute, 34. pp. 3127-3134. ISSN 1540-7489

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In this paper the global flame dynamics of a model annular gas turbine combustor undergoing strong self-excited circumferential instabilities is presented. The combustor consisted of either 12, 15 or 18 turbulent premixed bluff-body flames arranged around an annulus of fixed circumference so that the effect of flame separation distance, S, on the global heat release dynamics could be investigated. Reducing S was found to produce both an increase in the resonant frequency and the limit-cycle amplitudes of pressure and heat release for the same equivalence ratio. The phase-averaged global heat release, obtained from high-speed OH - chemiluminescence imaging from above, showed that these changes are caused by large-scale modifications to the flame structure around the annulus. For the largest S studied (12 flame configuration) the azimuthal instability produced a helical-like global heat release structure for each flame. When S was decreased, large-scale merging or linking between adjacent flames occurred spanning approximately half of the annulus with the peak heat release concentrated at the outer annular wall. The circumferential nature of the instability was evident from both the pressure measurements and the phase-averaged OH - chemiluminescence showing the phase of the heat release on either side of the annulus to be ≈180°apart and spinning in the counter clockwise direction. Both spinning and standing modes were found but only spinning modes are considered in this paper. To the best of the authors knowledge, these are the first experiments to provide a phase-averaged picture of self-excited azimuthal instabilities in a laboratory-scale annular combustor relevant to gas turbines. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Item Type: Article
Divisions: Div A > Fluid Mechanics
Div A > Energy
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:26
Last Modified: 17 Apr 2018 03:16