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Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing

Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing
Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing
Bluff-body stabilized flames are susceptible to combustion instabilities due to interactions between acoustics, vortical disturbances, and the flame. In order to elucidate these flow-flame interactions during an instability, an experimental and computational investigation of the flame-sheet dynamics of a harmonically excited flame was performed. It is shown that the flame dynamics are controlled by three key processes: excitation of shear layer instabilities by the axially oscillating flow, anchoring of the flame at the bluff body, and the kinematic response of the flame to this forcing. The near-field flame features are controlled by flame anchoring and the far-field by kinematic restoration. In the near-field, the flame response grows with downstream distance due to flame anchoring, which prevents significant flame movement near the attachment point. Theory predicts that this results in linear flame response characteristics as a function of perturbation amplitude, and a monotonic growth in magnitude of the flame-sheet fluctuations near the stabilization point, consistent with the experimental data. Farther downstream, the flame response reaches a maximum and then decays due to the dissipation of the vortical disturbances and action of flame propagation normal to itself, which acts to smooth out the wrinkles generated by the harmonic flow forcing. This behavior is strongly non-linear, resulting in significant variation in far-field flame-sheet response with perturbation amplitude.

1540-7489
1787-1794
Shanbhogue, Santosh
a200762c-6d82-4dd3-aa1d-d5cf6343a13f
Shin, Dong-Hyuk
aefc1292-87fd-48ab-94bc-a857692ccabe
Hemchandra, Santosh
8511fcc9-a6ad-4025-a7e1-d10e6de66877
Plaks, Dmitriy
1470dbbb-6105-4c53-9e48-45d533854555
Lieuwen, Tim
1c4f3e9b-2bfb-4618-8258-70f348f4b765
Shanbhogue, Santosh
a200762c-6d82-4dd3-aa1d-d5cf6343a13f
Shin, Dong-Hyuk
aefc1292-87fd-48ab-94bc-a857692ccabe
Hemchandra, Santosh
8511fcc9-a6ad-4025-a7e1-d10e6de66877
Plaks, Dmitriy
1470dbbb-6105-4c53-9e48-45d533854555
Lieuwen, Tim
1c4f3e9b-2bfb-4618-8258-70f348f4b765

Shanbhogue, Santosh, Shin, Dong-Hyuk, Hemchandra, Santosh, Plaks, Dmitriy and Lieuwen, Tim (2009) Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing Proceedings of the Combustion Institute, 32, (2), pp. 1787-1794. (doi:10.1016/j.proci.2008.06.034).

Record type: Article

Abstract

Bluff-body stabilized flames are susceptible to combustion instabilities due to interactions between acoustics, vortical disturbances, and the flame. In order to elucidate these flow-flame interactions during an instability, an experimental and computational investigation of the flame-sheet dynamics of a harmonically excited flame was performed. It is shown that the flame dynamics are controlled by three key processes: excitation of shear layer instabilities by the axially oscillating flow, anchoring of the flame at the bluff body, and the kinematic response of the flame to this forcing. The near-field flame features are controlled by flame anchoring and the far-field by kinematic restoration. In the near-field, the flame response grows with downstream distance due to flame anchoring, which prevents significant flame movement near the attachment point. Theory predicts that this results in linear flame response characteristics as a function of perturbation amplitude, and a monotonic growth in magnitude of the flame-sheet fluctuations near the stabilization point, consistent with the experimental data. Farther downstream, the flame response reaches a maximum and then decays due to the dissipation of the vortical disturbances and action of flame propagation normal to itself, which acts to smooth out the wrinkles generated by the harmonic flow forcing. This behavior is strongly non-linear, resulting in significant variation in far-field flame-sheet response with perturbation amplitude.

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More information

Published date: 2009
Organisations: Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 365274
URI: http://eprints.soton.ac.uk/id/eprint/365274
ISSN: 1540-7489
PURE UUID: 5e8d7a3c-6a84-4e5f-8ca3-b32a850ffd8d

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Date deposited: 29 May 2014 13:20
Last modified: 18 Jul 2017 02:23

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Contributors

Author: Santosh Shanbhogue
Author: Dong-Hyuk Shin
Author: Santosh Hemchandra
Author: Dmitriy Plaks
Author: Tim Lieuwen

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