Physics-based flame dynamics modeling and thermoacoustic instability mitigation

The objectives of this work are (i) to investigate the coupled unsteady heat release mechanisms responsible for thermoacoustic instabilities under different flame anchoring configurations, (ii) to develop reduced-order models to predict the dynamic flame response, and (iii) to develop passive instability mitigation strategies by modifying the dynamics of the flame anchoring zone. The two different anchoring configurations investigated were the wake-stabilized flames and the perforated-plate stabilized flames. In order to investigate the wake-stabilized flames, experiments were performed in an atmospheric pressure, backward-facing step combustor. In this configuration, the dynamics are primarily governed by the flame-vortex interactions, whereas the equivalence ratio oscillations have minor impacts. Depending on the equivalence ratio, inlet temperature and the fuel composition, the combustor operates under different dynamic modes. The operating conditions at the transition between different modes were predicted by developing a model based on the acoustic and vortex time scales. A passive control strategy involving injection of steady air ow near the step in the cross-stream or streamwise directions were tested. Both injection configurations were able to suppress the instability under some operating conditions at which the unsteady interactions between the flame and the wake vortex were eliminated. The cross-stream air injection method eliminates these interactions by generating a new, steady recirculation zone upstream of the step. On the other hand, the streamwise air injection method eliminates these interactions by directly stabilizing the ow dynamics in the unsteady recirculation zone.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Altay, Hurrem Murat

Advisor dc:contributor.advisor

• Ahmed F. Ghoniem.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/49558

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/49558