CUED Publications database

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

Kypraiou, AM and Dowling, AP and Mastorakos, E and Karimi, N (2015) Proper orthogonal decomposition analysis of a turbulent swirling self-excited premixed flame. In: UNSPECIFIED.

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Abstract

© 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. 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. 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. For the data post-processing, apart from a Fast Fourier Transform analysis, the Proper Orthogonal Decomposition technique was applied on the imaging data aiming at extracting information about the dynamics that are not captured through classical ensemble-averaging. 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 or Workshop Item (UNSPECIFIED)
Subjects: UNSPECIFIED
Divisions: Div A > Energy
Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:33
Last Modified: 03 Aug 2017 03:07
DOI: