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Research Papers

PIV Maps of Tip Leakage and Secondary Flow Fields on a Low-Speed Turbine Blade Cascade With Moving End Wall

[+] Author and Article Information
P. Palafox

Department of Engineering Science, University of Oxford, Oxford, OX1 3PJ, United Kingdompepe.palafox@eng.ox.ac.uk

M. L. G. Oldfield

Department of Engineering Science, University of Oxford, Oxford, OX1 3PJ, United Kingdommartin.oldfield@eng.ox.ac.uk

J. E. LaGraff

Department of Mechanical, Aerospace Engineering, Syracuse University, Syracuse, NY 13244jlagraff@mame.syr.edu

T. V. Jones

Department of Engineering Science, University of Oxford, Oxford, OX1 3PJ, United Kingdomterry.jones@eng.ox.ac.uk

J. Turbomach 130(1), 011001 (Dec 14, 2007) (9 pages) doi:10.1115/1.2437218 History: Received March 30, 2006; Revised April 04, 2006; Published December 14, 2007

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110deg and blade chord of 1.0m. Data were obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0×105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle image velocimetry was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip end-wall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the undertip flow near the end wall due to the moving wall is observed and the effect on the tip leakage vortex examined.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Cascade Geometry. The cascade was mounted in an existing large wind tunnel.

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Figure 2

Cascade test section and moving belt

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Figure 3

Blade pressure profile

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Figure 4

Grid for mapping tip leakage and secondary flow; note the blade material is shaded in brown (gray)

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Figure 5

PIV instrumentation setup

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Figure 6

Smoke visualization of tip leakage vortex and passage vortex interaction for t∕h=0.58%, no moving belt

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Figure 7

Secondary flow at 63.5cm from TE for t∕h=0%

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Figure 8

Secondary flow at 63.5cm upstream from TE for t∕h=1.68%, moving belt off

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Figure 9

Secondary flow at 63.5cm upstream from TE for t∕h=1.68%, moving belt on

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Figure 10

Tip leakage flow at 63.5cm from TE for t∕h=1.68%

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Figure 11

Flow field in plane 15mm from the end wall for 30mm gap (t∕h=1.68%); note that the field of view does not extend to the outer blade surface (see Fig. 4)

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Figure 12

Plots of two-dimensional flow fields in three-dimensional graphs for t∕h=1.68%. At Fig. 1 you can see the planes that are 15mm from the end wall with magnitudes.

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Figure 13

Instantaneous vector maps at consecutive time intervals of lower part of secondary flow at 63.5cm from TE for t∕h=1.68%, moving belt on, averaged results over 10s shown

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