Proper orthogonal decomposition analysis of a turbulent swirling self-excited premixed flame

Kypraiou, A.-M., Dowling, A., Mastorakos, E. and Karimi, N. (2015) Proper orthogonal decomposition analysis of a turbulent swirling self-excited premixed flame. In: 53rd AIAA Aerospace Sciences Meeting, Kissimmee, FL, USA, 5-9 Jan 2015, (doi: 10.2514/6.2015-0425)

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Thermoacoustic oscillations constitute a serious threat to the integrity of combustion systems. The goal of the present work is to determine the effect of the equivalence ratio (φ), inlet flow velocity (U), and burner geometry on the characteristics of the self-excited oscillations and to reveal the dominant mechanisms. It also focuses on the data post-processing aiming at extracting information about the dynamics that are not captured through classical ensemble-averaging, and hence the Proper Orthogonal Decomposition technique is used. Experiments were conducted with a fully-premixed air/methane flame stabilized on a conical bluff body. Self-excited acoustic instabilities were induced by extending the length of the combustion chamber downstream of the bluff body. The flame was visualised using OH* chemiluminescence and OH PLIF at 5 kHz. Proper Orthogonal Decomposition (POD) and Fast Fourier Transform analysis were conducted on the imaging data. A strong effect of the chamber length was found, which primarily drove the generation of acoustic oscillation and flame-vortex interaction. Significant differences in the flame roll-up were found when either the burner geometry or the equivalence ratio was altered. Changes were detected in the frequency of oscillations, which showed a general trend to increase with φ and U and decrease with the length of the duct. Analysis of the POD modes allowed an estimate of the convection speed of the flame structures associated with the dominant frequency and it was found that this convection speed was about 1.5 U for most conditions studied.

Item Type:Conference Proceedings
Glasgow Author(s) Enlighten ID:Karimi, Dr Nader
Authors: Kypraiou, A.-M., Dowling, A., Mastorakos, E., and Karimi, N.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Copyright Holders:Copyright © 2015 American Institute of Aeronautics and Astronautics
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.
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