Heat Transfer and Flow Characteristics on the Rotor Tip and Endwall Platform Regions in a Transonic Turbine Cascade

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dc.contributor.authorArisi, Allan Nyairoen
dc.contributor.committeechairNg, Wing Faien
dc.contributor.committeememberDiller, Thomas E.en
dc.contributor.committeememberO'Brien, Walter F. Jr.en
dc.contributor.committeememberLowe, K. Todden
dc.contributor.committeememberEkkad, Srinathen
dc.contributor.departmentMechanical Engineeringen
dc.date.accessioned2016-01-27T09:00:11Zen
dc.date.available2016-01-27T09:00:11Zen
dc.date.issued2016-01-26en
dc.description.abstractThis dissertation presents a detailed experimental and numerical analysis of the aerothermal characteristics of the turbine extremity regions i.e. the blade tip and endwall regions. The heat transfer and secondary flow characteristics were analyzed for different engine relevant configurations and exit Mach/Reynolds number conditions. The experiments were conducted in a linear blowdown cascade at transonic high turbulence conditions of Mexit ~ 0.85, 0.60 and 1.0, with an inlet turbulence intensity of 16% and 12% for the vane and blade cascade respectively. Transient infrared (IR) thermography technique and surface pressure measurement were used to map out the surface heat transfer coefficient and aerodynamic characteristics. The experiments were complemented with computational modeling using the commercial RANS equation solver ANSYS Fluent. The CFD results provided further insight into the local flow characteristics in order to elucidate the flow physics which govern the measured heat transfer characteristics. The results reveal that the highest heat transfer exists in regions with local flow reattachment and new-boundary layer formation. Conversely, the lowest heat transfer occurs in regions with boundary layer thickening and separation/lift-off flow. However, boundary layer separation results in additional secondary flow vortices, such as the squealer cavity vortices and endwall auxiliary vortex system, which significantly increase the stage aerodynamic losses. Furthermore, these vortices result in a low film-cooling effectiveness as was observed on a squealer tip cavity with purge flow. Finally, the importance of transonic experiments in analyzing the turbine section heat transfer and flow characteristics was underlined by the significant shock-boundary layer interactions that occur at high exit Mach number conditions.en
dc.description.degreePh. D.en
dc.format.mediumETDen
dc.identifier.othervt_gsexam:7089en
dc.identifier.urihttp://hdl.handle.net/10919/64501en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectGas Turbinesen
dc.subjectHeat--Transmissionen
dc.subjectTransonicen
dc.subjectSquealeren
dc.subjectSecondary Flowsen
dc.subjectFilm Coolingen
dc.subjectEndwallen
dc.subjectRotor Tipen
dc.subjectExperimentalen
dc.subjectComputational fluid dynamicsen
dc.titleHeat Transfer and Flow Characteristics on the Rotor Tip and Endwall Platform Regions in a Transonic Turbine Cascadeen
dc.typeDissertationen
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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