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Research Papers

Aerodynamic Design of High End Wall Angle Turbine Stages—Part II: Experimental Verification

[+] Author and Article Information
G. Pullan

e-mail: gp10006@cam.ac.uk

E. M. Curtis

Whittle Laboratory,
Department of Engineering,
University of Cambridge,
Cambridge, UK

S. Bather

Rolls-Royce plc.,
Derby, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received December 17, 2012; final manuscript received January 24, 2013; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(2), 021007 (Sep 26, 2013) (10 pages) Paper No: TURBO-12-1245; doi: 10.1115/1.4023906 History: Received December 17, 2012; Revised January 24, 2013

An experimental investigation of a turbine stage featuring very high end wall angles is presented. The initial turbine design did not achieve a satisfactory performance and the difference between the design predictions and the test results was traced to a large separated region on the rear suction-surface. To improve the agreement between computational fluid dynamics (CFD) and experiment, it was found necessary to modify the turbulence modeling employed. The modified CFD code was then used to redesign the vane, and the changes made are described. When tested, the performance of the redesigned vane was found to have much closer agreement with the predictions than the initial vane. Finally, the flowfield and performance of the redesigned stage are compared to a similar turbine, designed to perform the same duty, which lies in an annulus of moderate end wall angles. A reduction in stage efficiency of at least 2.4% was estimated for the very high end wall angle design.

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References

Figures

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Fig. 1

Schematic of a possible future IP and LP turbine

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Fig. 2

General arrangement of the IP turbine facility with the build 8 stage installed

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Fig. 3

Meridional view of the build 8 and build 9 turbines

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Fig. 4

Predicted surface static pressure distributions for the build 8 and build 9 NGVs. (a) Root, (b) 25% span, (c) 50% span, (d) 75% span, (e) tip.

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Fig. 5

Oil and dye surface flow visualization on the suction surface of the build 9 NGVs. Photo shows view looking upstream from the trailing edge.

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Fig. 6

Pitchwise mass averaged measured and predicted NGV exit axial yaw angle

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Fig. 7

Predicted suction surface streamlines from the design calculations for the build 9 vane (mixing length model). The geometry is shown in the top left of the figure. Note that the orientation of the vane is reversed compared to the flow visualization in Fig. 5.

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Fig. 8

Contours of various properties predicted on the build 9 vane suction surface using the 3% mixing length turbulence model. (a) Axial velocity, (b) radial velocity, (c) static pressure. Note that the orientation of the vane is reversed compared to the flow visualization in Fig. 5.

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Fig. 9

Predicted suction surface streamlines using the Spalart–Allmaras turbulence model. (a) Build 9, (b) build 8. Geometries are shown in the center left of the figure. Note that the orientation of the vane is reversed compared to the flow visualization in Fig. 5.

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Fig. 10

Suction surface static pressure distribution for a design with an extended chord

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Fig. 11

Effect of number off on the vane surface static pressure distribution

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Fig. 12

Effect of blade thickness on the blade surface static pressure distribution

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Fig. 13

Effect of NGV number off on stage efficiency

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Fig. 14

Midspan surface static pressure distributions for the chosen sectors

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Fig. 15

Oil and dye surface flow visualization. (a) Build 9A, (b) build 9B, (c) build 9C.

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Fig. 16

Measured loss coefficient Yp,U downstream of the build 9 sectors. (a) Build 9, (b) build 9A, (c) build 9B, (d) build 9C.

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