Thermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructures

Handle URI:
http://hdl.handle.net/10754/599999
Title:
Thermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructures
Authors:
Taamallah, Soufien; LaBry, Zachary A.; Shanbhogue, Santosh J.; Ghoniem, Ahmed F.
Abstract:
© 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. We investigate the onset of thermo-acoustic instabilities and their link to the mean flame configurations - or macrostructures - under acoustically coupled and decoupled conditions. Methane-hydrogen mixtures are used to explore the role of the fuel in changing the flame macrostructure, as determined by chemilumi-nescence, as the equivalence ratio (φ) varies. We observe four different configurations: a columnar flame (I); a bubble-columnar flame (II); a single conical flame (III); and a double conical flame (IV). We also observe different thermo-acoustic modes in the lean regime investigated, φ ∈ [0.5-0.75], that correspond to different flame configurations. By changing the combustor length without affecting the underlying flow, the resonant modes of the combustor are shifted to higher frequencies allowing for the decoupling of heat release fluctuations and the acoustic field over a range of equivalence ratio. We find that the same flame macrostructures observed in the long, acoustically coupled combustor arise in the short, acoustically decoupled combustor and transition at similar equivalence ratios in both combustors. The onset of the first fully unstable mode in the long combustor occurs at similar equivalence ratio as the flame transition from configuration III to IV. In the acoustically decoupled case, this transition occurs gradually starting with the intermittent appearance of a flame in the outer recirculation zone (ORZ). Spectral analysis of this phenomenon, referred to as "ORZ flame flickering" shows the existence of an unsteady event occurring over a narrow frequency band centered around 28 Hz along with a weaker broadband region at lower frequency in the range [1-10] Hz. The tone at 28 Hz is shown to be associated with the azimuthal advection of the flame by the outer recirculation zone flow. Changes in the fuel composition, by adding hydrogen (up to 20%), do not affect the correspondence between the thermo-acoustic modes and the flame macrostructures, but shift the transition points to lower equivalence ratio.
Citation:
Taamallah S, LaBry ZA, Shanbhogue SJ, Ghoniem AF (2015) Thermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructures. Proceedings of the Combustion Institute 35: 3273–3282. Available: http://dx.doi.org/10.1016/j.proci.2014.07.002.
Publisher:
Elsevier BV
Journal:
Proceedings of the Combustion Institute
KAUST Grant Number:
R12-CE-10; KUS-110-010-01
Issue Date:
2015
DOI:
10.1016/j.proci.2014.07.002
Type:
Article
ISSN:
1540-7489
Sponsors:
This work was supported by the Center of Clean Water and Clean Energy at MIT and KFUPM, and KAUST, under the Grant Nos. R12-CE-10 and KUS-110-010-01, respectively.
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorTaamallah, Soufienen
dc.contributor.authorLaBry, Zachary A.en
dc.contributor.authorShanbhogue, Santosh J.en
dc.contributor.authorGhoniem, Ahmed F.en
dc.date.accessioned2016-02-28T06:34:05Zen
dc.date.available2016-02-28T06:34:05Zen
dc.date.issued2015en
dc.identifier.citationTaamallah S, LaBry ZA, Shanbhogue SJ, Ghoniem AF (2015) Thermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructures. Proceedings of the Combustion Institute 35: 3273–3282. Available: http://dx.doi.org/10.1016/j.proci.2014.07.002.en
dc.identifier.issn1540-7489en
dc.identifier.doi10.1016/j.proci.2014.07.002en
dc.identifier.urihttp://hdl.handle.net/10754/599999en
dc.description.abstract© 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. We investigate the onset of thermo-acoustic instabilities and their link to the mean flame configurations - or macrostructures - under acoustically coupled and decoupled conditions. Methane-hydrogen mixtures are used to explore the role of the fuel in changing the flame macrostructure, as determined by chemilumi-nescence, as the equivalence ratio (φ) varies. We observe four different configurations: a columnar flame (I); a bubble-columnar flame (II); a single conical flame (III); and a double conical flame (IV). We also observe different thermo-acoustic modes in the lean regime investigated, φ ∈ [0.5-0.75], that correspond to different flame configurations. By changing the combustor length without affecting the underlying flow, the resonant modes of the combustor are shifted to higher frequencies allowing for the decoupling of heat release fluctuations and the acoustic field over a range of equivalence ratio. We find that the same flame macrostructures observed in the long, acoustically coupled combustor arise in the short, acoustically decoupled combustor and transition at similar equivalence ratios in both combustors. The onset of the first fully unstable mode in the long combustor occurs at similar equivalence ratio as the flame transition from configuration III to IV. In the acoustically decoupled case, this transition occurs gradually starting with the intermittent appearance of a flame in the outer recirculation zone (ORZ). Spectral analysis of this phenomenon, referred to as "ORZ flame flickering" shows the existence of an unsteady event occurring over a narrow frequency band centered around 28 Hz along with a weaker broadband region at lower frequency in the range [1-10] Hz. The tone at 28 Hz is shown to be associated with the azimuthal advection of the flame by the outer recirculation zone flow. Changes in the fuel composition, by adding hydrogen (up to 20%), do not affect the correspondence between the thermo-acoustic modes and the flame macrostructures, but shift the transition points to lower equivalence ratio.en
dc.description.sponsorshipThis work was supported by the Center of Clean Water and Clean Energy at MIT and KFUPM, and KAUST, under the Grant Nos. R12-CE-10 and KUS-110-010-01, respectively.en
dc.publisherElsevier BVen
dc.subjectFlame configurationsen
dc.subjectMethane-hydrogenen
dc.subjectPremixed turbulent combustionen
dc.subjectSwirling flowen
dc.subjectThermo-acoustic instabilitiesen
dc.titleThermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructuresen
dc.typeArticleen
dc.identifier.journalProceedings of the Combustion Instituteen
dc.contributor.institutionMassachusetts Institute of Technology, Cambridge, United Statesen
kaust.grant.numberR12-CE-10en
kaust.grant.numberKUS-110-010-01en
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