{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/90693"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/90693","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Computational analysis of thermo-acoustic instabilities in combustion chambers and afterburners","abstract":"A simplified model is introduced to study thermo-acoustic instabilities in asymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber’s geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. Furthermore, N−periodic geometries commonly prone to such instabilities include annular combustion chamber and afterburner configurations, hence, apart from the effect of model parameters the effect of geometry on the overall stability of the system is considered in this article. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al, 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.","abstract_html":"A simplified model is introduced to study thermo-acoustic instabilities in asymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber’s geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. Furthermore, N−periodic geometries commonly prone to such instabilities include annular combustion chamber and afterburner configurations, hence, apart from the effect of model parameters the effect of geometry on the overall stability of the system is considered in this article. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al, 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.","abstract_has_math":false,"creators":["Murthy, Sandeep Ravikumar"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["Sayadi, Taraneh"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-07-07T19:58:24Z","date_published":"2016-07-07T19:58:24Z","updated_at":"2026-07-22T22:26:34Z","subjects":["Thermo-acoustics","azimuthal instability","roots of unity formalism","modal analysis","non-modal analysis"],"languages":["en"],"rights":["Copyright 2016 Sandeep Ravikumar Murthy"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/90693","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Sayadi, Taraneh"]},{"key":"dc:creator","label":"Author","values":["Murthy, Sandeep Ravikumar"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2016-07-07T19:58:24Z","2016-04-29","2016-05"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Aerospace Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Thermo-acoustics","azimuthal instability","roots of unity formalism","modal analysis","non-modal analysis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2016 Sandeep Ravikumar Murthy"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/90693"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["A simplified model is introduced to study thermo-acoustic instabilities in asymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber’s geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. Furthermore, N−periodic geometries commonly prone to such instabilities include annular combustion chamber and afterburner configurations, hence, apart from the effect of model parameters the effect of geometry on the overall stability of the system is considered in this article. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al, 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-07-07 without embargo terms","The student, Sandeep Ravikumar Murthy, accepted the attached license on 2016-04-28 at 16:13.","The student, Sandeep Ravikumar Murthy, submitted this Thesis for approval on 2016-04-28 at 16:19.","This Thesis was approved for publication on 2016-04-29 at 09:13.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9581 on 2016-07-07 at 13:33:51","Made available in DSpace on 2016-07-07T19:58:24Z (GMT). No. of bitstreams: 2 MURTHY-THESIS-2016.pdf: 6623981 bytes, checksum: 7f96a58735a500d6e16c0402a2aa0e3c (MD5) LICENSE.txt: 4221 bytes, checksum: d224ccfa42086eeca843c9f5d6445ca2 (MD5) Previous issue date: 2016-04-29"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Computational analysis of thermo-acoustic instabilities in combustion chambers and afterburners"]}]}],"canonical_facts":{"dc:contributor":["Sayadi, Taraneh"],"dc:creator":["Murthy, Sandeep Ravikumar"],"dc:date":["2016-07-07T19:58:24Z","2016-04-29","2016-05"],"dc:description":["A simplified model is introduced to study thermo-acoustic instabilities in asymmetric combustion chambers. Such instabilities can be triggered when correlations between heat-release and pressure oscillations exist, leading to undesirable effects. Gas turbine designs typically consist of a periodic assembly of N identical units; as evidenced by documented studies, the coupling across sectors may give rise to unstable modes, which are the highlight of this study. In the proposed model, the governing equations are linearized in the acoustic limit, with each burner modeled as a one-dimensional system, featuring acoustic damping and a compact heat source. The coupling between the burners is accounted for by solving the two-dimensional wave equation over an annular region, perpendicular to the burners, representing the chamber’s geometry. The discretization of these equations results in a set of coupled delay-differential equations, that depends on a finite set of parameters. Furthermore, N−periodic geometries commonly prone to such instabilities include annular combustion chamber and afterburner configurations, hence, apart from the effect of model parameters the effect of geometry on the overall stability of the system is considered in this article. The system's periodicity is leveraged using a recently developed root-of-unity formalism (Schmid et al, 2015). This results in a linear system, which is then subjected to modal and non-modal analysis to explore the influence of the coupled behavior of the burners on the system's stability and receptivity.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2016-07-07 without embargo terms","The student, Sandeep Ravikumar Murthy, accepted the attached license on 2016-04-28 at 16:13.","The student, Sandeep Ravikumar Murthy, submitted this Thesis for approval on 2016-04-28 at 16:19.","This Thesis was approved for publication on 2016-04-29 at 09:13.","DSpace SAF Submission Ingestion Package generated from Vireo submission #9581 on 2016-07-07 at 13:33:51","Made available in DSpace on 2016-07-07T19:58:24Z (GMT). No. of bitstreams: 2 MURTHY-THESIS-2016.pdf: 6623981 bytes, checksum: 7f96a58735a500d6e16c0402a2aa0e3c (MD5) LICENSE.txt: 4221 bytes, checksum: d224ccfa42086eeca843c9f5d6445ca2 (MD5) Previous issue date: 2016-04-29"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/90693"],"dc:language":["en"],"dc:rights":["Copyright 2016 Sandeep Ravikumar Murthy"],"dc:subject":["Thermo-acoustics","azimuthal instability","roots of unity formalism","modal analysis","non-modal analysis"],"dc:title":["Computational analysis of thermo-acoustic instabilities in combustion chambers and afterburners"],"dc:type":["text"],"thesis:degree_discipline":["Aerospace Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:34Z"}