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Research Papers

The Effect of Land Taper Angle on Trailing Edge Slot Film Cooling

[+] Author and Article Information
Julia Ling

Mechanical Engineering Department,
Stanford University,
Stanford, CA 94305
e-mail: jling@sandia.gov

Christopher J. Elkins, John K. Eaton

Mechanical Engineering Department,
Stanford University,
Stanford, CA 94305

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 9, 2014; final manuscript received July 14, 2014; published online December 23, 2014. Editor: Ronald S. Bunker.

J. Turbomach 137(7), 071003 (Jul 01, 2015) (8 pages) Paper No: TURBO-14-1128; doi: 10.1115/1.4029174 History: Received July 09, 2014; Revised July 14, 2014; Online December 23, 2014

Trailing edge slot film cooling is a widely used method of protecting the thin trailing edge of turbine blades from hot gas impingement. The structures that separate the slots, known as “lands,” come in a variety of configurations which can be broadly classified as either “tapered” or “straight.” This paper examines the effect of the land taper angle on the mixing of the coolant flow with the main flow by comparing three configurations: a case with straight lands, a previously reported case with slightly tapered lands, and a case with strongly tapered lands. In each case, the slot width and the land width at the plane of the slot exit are kept constant. For each configuration, the mean volumetric coolant concentration distribution and three-component velocity field were measured using magnetic resonance imaging (MRI) techniques. It is shown that the land taper angle has a strong effect on the mean flow features and coolant surface effectiveness. Furthermore, the impact of the lands configuration on the flow field and concentration distribution is seen not just in the cutback region, but also in the wake of the blade.

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References

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Figures

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Fig. 1

Schematic of the channel

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Fig. 2

Schematic of the straight lands airfoil

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Fig. 3

Top views of the three trailing edge configurations. Side view of strongly tapered trailing edge configuration also shown: (a) straight lands, (b) slight taper, and (c) strong taper.

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Fig. 4

Contours of u in streamwise slices spaced 2.7h apart. (a) Straight lands, (b) slight taper, and (c) strong taper.

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Fig. 5

Regions of flow separation. (a) Straight lands, (b) slight taper, and (c) strong taper.

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Fig. 6

Contours of wx in streamwise slices spaced 2.7h apart. Streamlines seeded in center slot, 0.8 h from the bottom surface. (a) Straight lands, (b) slight taper, and (c) strong taper.

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Fig. 7

Contours of c. Axial slices spaced 2.5h apart. (a) Straight lands, (b) slight taper, and (c) strong taper.

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Fig. 8

Contours of film effectiveness η (%). (a) Straight lands, (b) slight taper, and (c) strong taper.

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Fig. 9

Film effectiveness η (%) averaged over: the entire airfoil span (solid –), the breakout surface only (dashed - -), and the lands only (dotted...)

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Fig. 10

Average film effectiveness η (%) averaged over: the entire breakout surface (filled symbols) and the entire land surface (open symbols). Data also shown from Benson et al. [12] and Murata et al. [14].

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