Flame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustion

Handle URI:
http://hdl.handle.net/10754/598338
Title:
Flame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustion
Authors:
Shanbhogue, S.J. ( 0000-0002-0481-7945 ) ; Sanusi, Y.S.; Taamallah, S.; Habib, M.A.; Mokheimer, E.M.A. ( 0000-0002-5774-8517 ) ; Ghoniem, A.F.
Abstract:
© 2015 The Combustion Institute. In this paper, we report results from an experimental investigation on transitions in the average flame shape (or microstructure) under acoustically coupled and uncoupled conditions in a 50 kW swirl stabilized combustor. The combustor burns CH4/H2 mixtures at atmospheric pressure and temperature for a fixed Reynolds number of 20,000 and fixed swirl angle. For both cases, essentially four different flame shapes are observed, with the transition between flame shapes occurring at the same equivalence ratio (for the same fuel mixture) irrespective of whether the combustor is acoustically coupled or uncoupled. The transition equivalence ratio depends on the fuel mixture. For the baseline case of pure methane, the combustor is stable close to the blowoff limit and the average flame in this case is stabilized inside the inner recirculation zone. As the equivalence ratio is raised, the combustor transitions to periodic oscillations at a critical equivalence ratio of φ=0.65. If hydrogen is added to the mixture, the same transition occurs at lower equivalence ratios. For all cases that we investigated, flame shapes captured using chemiluminescence imaging show that the transition to harmonic oscillations in the acoustically coupled cases is preceded by the appearance of the flame in the outer recirculation zone. We examine the mechanism associated with the transition of the flame between different shapes and, ultimately, the propagation of the flame into the outer recirculation zone as the equivalence ratio is raised. Using the extinction strain rates for each mixture at different equivalence ratios, we show that these transitions in the flame shape and in the instability (in the coupled case) for different fuel mixtures collapse as a function of a normalized strain rate : κextDU∞. We show that the results as consistent with a mechanism in which the flame must overcome higher strains prevailing in the outer recirculation zone, in order to stabilize there.
Citation:
Shanbhogue SJ, Sanusi YS, Taamallah S, Habib MA, Mokheimer EMA, et al. (2016) Flame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustion. Combustion and Flame 163: 494–507. Available: http://dx.doi.org/10.1016/j.combustflame.2015.10.026.
Publisher:
Elsevier BV
Journal:
Combustion and Flame
KAUST Grant Number:
KUS-110-010-01
Issue Date:
Jan-2016
DOI:
10.1016/j.combustflame.2015.10.026
Type:
Article
ISSN:
0010-2180
Sponsors:
This research was funded by KAUST, grant number KUS-110-010-01 and KFUPM, grant number R12-CE-10.
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorShanbhogue, S.J.en
dc.contributor.authorSanusi, Y.S.en
dc.contributor.authorTaamallah, S.en
dc.contributor.authorHabib, M.A.en
dc.contributor.authorMokheimer, E.M.A.en
dc.contributor.authorGhoniem, A.F.en
dc.date.accessioned2016-02-25T13:18:58Zen
dc.date.available2016-02-25T13:18:58Zen
dc.date.issued2016-01en
dc.identifier.citationShanbhogue SJ, Sanusi YS, Taamallah S, Habib MA, Mokheimer EMA, et al. (2016) Flame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustion. Combustion and Flame 163: 494–507. Available: http://dx.doi.org/10.1016/j.combustflame.2015.10.026.en
dc.identifier.issn0010-2180en
dc.identifier.doi10.1016/j.combustflame.2015.10.026en
dc.identifier.urihttp://hdl.handle.net/10754/598338en
dc.description.abstract© 2015 The Combustion Institute. In this paper, we report results from an experimental investigation on transitions in the average flame shape (or microstructure) under acoustically coupled and uncoupled conditions in a 50 kW swirl stabilized combustor. The combustor burns CH4/H2 mixtures at atmospheric pressure and temperature for a fixed Reynolds number of 20,000 and fixed swirl angle. For both cases, essentially four different flame shapes are observed, with the transition between flame shapes occurring at the same equivalence ratio (for the same fuel mixture) irrespective of whether the combustor is acoustically coupled or uncoupled. The transition equivalence ratio depends on the fuel mixture. For the baseline case of pure methane, the combustor is stable close to the blowoff limit and the average flame in this case is stabilized inside the inner recirculation zone. As the equivalence ratio is raised, the combustor transitions to periodic oscillations at a critical equivalence ratio of φ=0.65. If hydrogen is added to the mixture, the same transition occurs at lower equivalence ratios. For all cases that we investigated, flame shapes captured using chemiluminescence imaging show that the transition to harmonic oscillations in the acoustically coupled cases is preceded by the appearance of the flame in the outer recirculation zone. We examine the mechanism associated with the transition of the flame between different shapes and, ultimately, the propagation of the flame into the outer recirculation zone as the equivalence ratio is raised. Using the extinction strain rates for each mixture at different equivalence ratios, we show that these transitions in the flame shape and in the instability (in the coupled case) for different fuel mixtures collapse as a function of a normalized strain rate : κextDU∞. We show that the results as consistent with a mechanism in which the flame must overcome higher strains prevailing in the outer recirculation zone, in order to stabilize there.en
dc.description.sponsorshipThis research was funded by KAUST, grant number KUS-110-010-01 and KFUPM, grant number R12-CE-10.en
dc.publisherElsevier BVen
dc.subjectCombustion instabilityen
dc.subjectExtinction strain rateen
dc.subjectFuel compositionen
dc.subjectScalingen
dc.subjectSwirling flowsen
dc.titleFlame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustionen
dc.typeArticleen
dc.identifier.journalCombustion and Flameen
dc.contributor.institutionMassachusetts Institute of Technology, Cambridge, United Statesen
dc.contributor.institutionKing Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabiaen
kaust.grant.numberKUS-110-010-01en
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