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Transition on the T106 LP Turbine Blade in the Presence of Moving Upstream Wakes and Downstream Potential Fields

[+] Author Affiliations
Maciej M. Opoka, Howard P. Hodson

University of Cambridge, Cambridge, UK

Paper No. GT2007-28077, pp. 1091-1104; 14 pages
doi:10.1115/GT2007-28077
From:
  • ASME Turbo Expo 2007: Power for Land, Sea, and Air
  • Volume 4: Turbo Expo 2007, Parts A and B
  • Montreal, Canada, May 14–17, 2007
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 0-7918-4793-4 | eISBN: 0-7918-3796-3
  • Copyright © 2007 by ASME

abstract

Boundary layer measurements were performed on a cascade of the T106 high lift low-pressure (LP) turbine blades that was subjected to upstream wakes and a moving downstream potential field. Tests were carried out at a low level of inlet freestream turbulence (0.5%) and at a higher (4.0%). It is found that perturbations in the freestream due to both disturbances are superposed on each other. This affects the magnitude of the velocity perturbations at the edge of the boundary layer under the wakes as well as the fluctuations in the edge velocity between the wakes. Furthermore, the fluctuations in the adverse pressure gradient on the suction surface depend on the relative phase of the upstream and downstream disturbances, providing an additional stimulus for clocking studies. Time-mean momentum thickness values calculated from LDA traverses performed near the suction surface trailing edge are used to identify the optimum relative phase angle of the combined interaction. Unsteady suction surface pressures, quasi wall shear stress and LDA data illustrate the resulting multimode process of transition, which is responsible for the observed clocking effects. The optimum relative phase angle of the upstream wake and the downstream potential field can produce 0.25% of efficiency improvement, through the reduction of the suction surface boundary layer loss. This reduction is mainly related to the calmed region and the laminar flow benefits that can be more effectively utilised than when only the upstream wakes are present. During the remaining parts of the cycle the features that are usually associated with the wake and the potential field effects are still present.

Copyright © 2007 by ASME
Topics: Turbine blades , Wakes

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