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dc.contributor.authorWang, Guoqing
dc.contributor.authorGuiberti, Thibault
dc.contributor.authorXia, Xi
dc.contributor.authorLi, Lei
dc.contributor.authorLiu, Xunchen
dc.contributor.authorRoberts, William L.
dc.contributor.authorQi, Fei
dc.date.accessioned2021-02-15T06:31:29Z
dc.date.available2021-02-15T06:31:29Z
dc.date.issued2021-02-02
dc.identifier.citationWang, G., Guiberti, T. F., Xia, X., Li, L., Liu, X., Roberts, W. L., & Qi, F. (2021). Decomposition of swirling flame transfer function in the complex space. Combustion and Flame, 228, 29–41. doi:10.1016/j.combustflame.2021.01.032
dc.identifier.issn0010-2180
dc.identifier.doi10.1016/j.combustflame.2021.01.032
dc.identifier.urihttp://hdl.handle.net/10754/667418
dc.description.abstractIn this work, we propose an analytical decomposition of the flame transfer function (FTF) in the complex space. The decomposition provides new insight into the relationship between the local heat release oscillator and the global flame response of a periodically oscillating system in the linear regime. The FTF of a premixed methane-air swirling flame is decomposed using two-region and pixel-by-pixel division of the chemiluminescence images. The two-region decomposition uses horizontal or vertical dividing lines to examine the effects of dividing positions and orientations. The complex curves of the two-region division are more sensitive to the dividing line's position than its orientation. The pixel-by-pixel decomposition provides detailed distributions of the weighting factor, weighted gain, and phase of all local oscillators. The weighted gain distribution highlights the inner fluctuating region (IFR) and outer fluctuating region (OFR), as well as the node region. These regions are mainly controlled by the radial velocity and its fluctuations induced by the vortices in the inner and outer shear layers. The unwrapped phase, which gradually increases as the downstream distance from the injector increases, highlights the convective characteristics of the oscillating heat release rate. Angular wavenumbers and phase velocities are deduced from the phase distribution. The phase velocities agree well with the mean velocities measured with particle image velocimetry. Sorting all the local oscillators in the ascending phase allows constructing complex curves that favorably represent the FTF. The algebraic sum of weighted gain and the efficiency of phase interference are calculated to examine the phase interference. Phase interference plays a large role in suppressing the global fluctuating amplitude of the heat release rate. The local extrema at low and intermediate frequencies are attributed to in- or out-of-phase interference, while the reduced local response also explains why small FTF gains are observed at high frequencies.
dc.description.sponsorshipThis research is supported by National Natural Science Foundation of China (91941301) and King Abdullah University of Science and Technology (KAUST) (BAS/1/1370–01–01).
dc.publisherElsevier BV
dc.relation.urlhttps://linkinghub.elsevier.com/retrieve/pii/S0010218021000468
dc.rightsNOTICE: this is the author’s version of a work that was accepted for publication in Combustion and Flame. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Combustion and Flame, [228, , (2021-02-02)] DOI: 10.1016/j.combustflame.2021.01.032 . © 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subjectGlobal flame response
dc.subjectLocal heat release rate
dc.subjectPixel-by-pixel division
dc.subjectComplex vector composition
dc.subjectPhase velocity
dc.titleDecomposition of swirling flame transfer function in the complex space
dc.typeArticle
dc.contributor.departmentClean Combustion Research Center
dc.contributor.departmentMechanical Engineering Program
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.identifier.journalCombustion and Flame
dc.rights.embargodate2023-02-02
dc.eprint.versionPost-print
dc.contributor.institutionKey Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
dc.identifier.volume228
dc.identifier.pages29-41
kaust.personWang, Guoqing
kaust.personGuiberti, Thibault
kaust.personRoberts, William L.
kaust.grant.numberBAS/1/1370–01–01
dc.identifier.eid2-s2.0-85100096486


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