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Thermoacoustic Modes of Quasi- One-Dimensional Combustors in the Region of Marginal Stability

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cam.issuedOnline2018-10-04
cam.orpheus.successThu Jan 30 10:53:41 GMT 2020 - Embargo updated
dc.contributor.authorSilva, CF
dc.contributor.authorYong, KJ
dc.contributor.authorMagri, L
dc.contributor.orcidMagri, Luca [0000-0002-0657-2611]
dc.date.accessioned2018-12-11T00:31:52Z
dc.date.available2018-12-11T00:31:52Z
dc.date.issued2019
dc.description.abstract<jats:p>It may be generally believed that the thermoacoustic eigenfrequencies of a combustor with fully acoustically reflecting boundary conditions depend on both flame dynamics and geometry of the system. In this work, we show that there are situations where this understanding does not strictly apply. The purpose of this study is twofold. In the first part, we show that the resonance frequencies of two premixed combustors with fully acoustically reflecting boundary conditions in the region of marginal stability depend only on the parameters of the flame dynamics but do not depend on the combustor's geometry. This is shown by means of a parametric study, where the time delay and the interaction index of the flame response are varied and the resulting complex eigenfrequency locus is shown. Assuming longitudinal acoustics and a low Mach number, a quasi-1D Helmholtz solver is utilized. The time delay and interaction index of the flame response are parametrically varied to calculate the complex eigenfrequency locus. It is found that all the eigenfrequency trajectories cross the real axis at a resonance frequency that depends only on the time delay. Such marginally stable frequencies are independent of the resonant cavity modes of the two combustors, i.e., the passive thermoacoustic modes. In the second part, we exploit the aforementioned observation to evaluate the critical flame gain required for the systems to become unstable at four eigenfrequencies located in the marginally stable region. A computationally efficient method is proposed. The key ingredient is to consider both direct and adjoint eigenvectors associated with the four eigenfrequencies. Hence, the sensitivity of the eigenfrequencies to changes in the gain at the region of marginal stability is evaluated with cheap and accurate calculations. This work contributes to the understanding of thermoacoustic stability of combustors. In the same manner, the understanding of the nature of distinct resonance frequencies in unstable combustors may be enhanced by employing the analysis of the eigenfrequency locus here reported.</jats:p>
dc.identifier.doi10.17863/CAM.33968
dc.identifier.eissn1528-8919
dc.identifier.issn0742-4795
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/286656
dc.language.isoeng
dc.publisherASME International
dc.publisher.urlhttp://dx.doi.org/10.1115/1.4041118
dc.subject40 Engineering
dc.subject4017 Mechanical Engineering
dc.subject4002 Automotive Engineering
dc.titleThermoacoustic Modes of Quasi- One-Dimensional Combustors in the Region of Marginal Stability
dc.typeArticle
dcterms.dateAccepted2018-07-17
prism.issueIdentifier2
prism.publicationDate2019
prism.publicationNameJournal of Engineering for Gas Turbines and Power
prism.volume141
pubs.funder-project-idRoyal Academy of Engineering (RAEng)
rioxxterms.licenseref.startdate2019-02-01
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserved
rioxxterms.typeJournal Article/Review
rioxxterms.versionAM
rioxxterms.versionofrecord10.1115/1.4041118

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