Influences of inlet swirl distributions on an inter-turbine duct part I: Casing swirl variation

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Proceedings titleProceedings of the ASME Turbo Expo
ConferenceASME 2011 Turbo Expo: Turbine Technical Conference and Exposition, GT2011, 6 June 2011 through 10 June 2011, Vancouver, BC
Pages619630; # of pages: 12
SubjectAdverse pressure gradient; Aerodynamic performance; Blade tip vortex; Boundary-layer separation; Casing boundary layer; Counter-rotating vortices; Engine weight; Experimental data; Flow behaviors; Flow development; Flow physics; Inlet swirls; Swirl angles; Total pressure coefficients; Transition ducts; Turbine blade; Turbulence intensity; Wake flows; Boundary layers; Ducts; Exhibitions; Pressure gradient; Three dimensional; Turbomachine blades; Vortex flow; Wakes; Aerodynamics
AbstractThe inter-turbine transition duct (ITD) of a gas turbine engine has significant potential for engine weight reduction and/or aerodynamic performance improvement. This potential arises because very little is understood of the flow behavior in the duct in relation to the hub and casing shapes and the flow entering the duct (e.g., swirl angle, turbulence intensity, periodic unsteadiness and blade tip vortices from upstream HP turbine blade rows). In this study, the flow development in an ITD with different inlet swirl distributions was investigated experimentally and numerically. The current paper, which is the first part of a two-part paper, presents the investigations of the influences of the casing swirl variations on the flow physics in the ITD. The results show a fair agreement between the predicted and experimental data. The radial pressure gradient at the first bend of ITD drives the low momentum hub boundary layer and wake flow radially, which results in a pair of hub counter-rotating vortices. Furthermore, the radially moving low momentum wake flow feeds into the casing region and causes 3D casing boundary layer. At the second bend, the reversed radial pressure gradient together with the 3D casing boundary layer generates a pair of casing counterrotating vortices. Due to the local adverse pressure gradient, 3D boundary layer separation occurs on both the casing and hub at the second bend and the exit of the ITD, respectively. The casing 3D separation enhances the 3D features of the casing boundary layer as well as the existing casing counter-rotating vortices. With increasing casing swirl angle, the casing 3D boundary layer separation is delayed and the casing counter-rotating vortices are weakened. On the other hand, although the hub swirls are kept constant, the hub counter-rotating vortices get stronger with the increasing inlet swirl gradient. The total pressure coefficients within the ITD are significantly redistributed by the casing and hub counter-rotating vortices. Copyright © 2011 by ASME and The Crown in Right of Canada.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21271724
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Record identifier0f80b0c0-d500-4e0f-b01f-4350ef93c7b9
Record created2014-03-24
Record modified2016-05-09
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