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Research Papers

Aerodynamic Design of High End Wall Angle Turbine Stages—Part I: Methodology Development

[+] Author and Article Information
G. Pullan

e-mail: gp10006@cam.ac.uk

E. M. Curtis

Department of Engineering,
Whittle Laboratory,
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), 021006 (Sep 26, 2013) (8 pages) Paper No: TURBO-12-1244; doi: 10.1115/1.4023905 History: Received December 17, 2012; Revised January 24, 2013

A design methodology is presented for turbines in an annulus with high end wall angles. Such stages occur where large radial offsets between the stage inlet and stage outlet are required, for example in the first stage of modern low pressure turbines, and are becoming more prevalent as bypass ratios increase. The turbine vanes operate within s-shaped ducts which result in meridional curvature being of a similar magnitude to the blade-to-blade curvature. Through a systematic series of idealized computational cases, the importance of two aspects of vane design are shown. First, the region of peak end wall meridional curvature is best located within the vane row. Second, the vane should be leant so as to minimize spanwise variations in surface pressure—this condition is termed “ideal lean.” This design philosophy is applied to the first stage of a low pressure turbine with high end wall angles.

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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

Detail of the blade section used in the cascade calculations: (a) section and (b) two-dimensional surface static pressure distribution

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Fig. 3

Static pressure contours on a quasi-orthogonal at mid axial chord for the low aspect ratio, unleant cascade geometry. The QO is shown on the left, with a meridional view and suction surface contours shown on the right. The dot-dash line indicates the location of the QO.

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Fig. 4

Static pressure contours on a quasi-orthogonal at mid axial chord for the high aspect ratio, leant cascade geometry

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Fig. 5

Static pressure contours on a quasi-orthogonal at mid axial chord for the low aspect ratio, leant cascade geometry

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Fig. 6

Schematic of the cascade with constant meridional radius of curvature

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Fig. 7

Static pressure contours on a quasi-orthogonal at mid axial chord for (a) rc,hub = 7.6h, (b) rc,hub = 5.0h, (c) rc,hub = 3.4h, and (d) ideal lean

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Fig. 8

Schematic of the cascade with nonuniform meridional turning

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Fig. 9

Average end wall static pressures with the blade downstream of the corner

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Fig. 10

The effect of nonuniform meridional turning on blade suction surface static pressure

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Fig. 11

Average end wall static pressure with the meridional turning at the blade trailing edge

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Fig. 12

Static pressure contours on a quasi-orthogonal through peak suction for the ideal lean case

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Fig. 13

Average end wall static pressures with the ideal lean blade

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Fig. 14

Static pressure contours on a quasi-orthogonal upstream of peak suction for the ideal lean case

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Fig. 15

Sketch illustrating the definition of the S1 and S2 streamsurfaces

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Fig. 16

Meridional view of the Build 8 and Build 9 turbine stages

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Fig. 17

Static pressure contours on a quasi-orthogonal at mid axial chord for the Build 9 NGV

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Fig. 18

Predicted surface static pressure distributions on the Build 8 and Build 9 NGVs: (a) root, (b) 25% span, (c) 50% span, (d) 75% span, and (e) tip

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