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Research Papers

Numerical Study of the Flow Past a Turbine Blade Tip: Effect of Relative Motion Between Blade and Shroud

[+] Author and Article Information
Sumanta Acharya

Professor
e-mail: acharya@tigers.LSU.edu

Louis Moreaux

Turbine Innovation and Energy Research Center,
Louisiana State University,
Baton Rouge, LA 70803

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received December 22, 2012; final manuscript received May 28, 2013; published online October 23, 2013. Editor: David Wisler.

J. Turbomach 136(3), 031015 (Oct 23, 2013) (9 pages) Paper No: TURBO-12-1251; doi: 10.1115/1.4024842 History: Received December 22, 2012; Revised May 28, 2013

Turbine blade tips are often the most susceptible to material failure due to the high-speed leakage flow and associated large thermal loadings. In this paper, the effect of the blade rotation and relative motion between the blade tip and shroud is studied numerically. Three different simulations have been undertaken: (1) a static case where the blade and the shroud are stationary (used as the reference case) (2) a linearly moving blade (or shroud) and (3) a rotating blade. Comparisons between cases 1 and 2 identify the effects of relative motion, while comparison between cases 2 and 3 delineate the effects of rotational Coriolis and centrifugal forces. Geometric effects were also studied through different combinations of tip gaps and squealer depths with the relative motion and rotational effects included. The calculations were done using a commercial flow solver, Fluent, using a block body-fitted mesh, Reynolds-averaged transport equations and a turbulence model. Results confirm the significant effects of the relative motion between the blade tip and shroud, and indicate that the assumption of pressure-driven leakage flows for blade tips is inappropriate. While rotational forces also play a role, the magnitude of their effects are relatively small compared to the relative motion effects. Geometric effects are also important with the lower tip clearance reducing leakage flow and allowing the tip coolant to migrate towards the SS with relative motion.

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References

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Yang, H., Acharya, S., Ekkad, S., Prakash, C., and Bunker, R., 2002(a), “Flow and Heat Transfer Predictions Past a Flat-Tip Blade,” ASME Paper No. GT2002-30190. [CrossRef]
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Acharya, S., Yang, H., Prakash, C., and Bunker, R., 2002(c), “Numerical Simulation of Film Cooling Past a Turbine Blade Tip,” ASME Paper No. GT2002-30553. [CrossRef]
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Figures

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Fig. 1

Schematic of the blade geometry and computational domain. Inlet is on the left, outlet is on the right, and periodic conditions are imposed on the front and back surfaces.

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Fig. 2

Different blade tip configurations considered

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Fig. 3

Configurations for the different simulations

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Fig. 4

Cp versus X/Cx. Experimental data from Kramer et al. [10].

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Fig. 5

Film cooling effectiveness, BR = 2.0, top-computational, bottom-experimental [10]

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Fig. 6

Film cooling effectiveness contour (a) 3 × 106 cells (b) 4 × 106 cells and (c) 5 × 106 cells

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Fig. 7

Film cooling effectiveness value at three different points on the blade tip

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Fig. 8

Blade tip heat transfer coefficient contour (units of h are W/m2 K)

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Fig. 9

Blade tip film cooling effectiveness contour

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Fig. 10

3D path lines for stationary, linearly moving, and rotating cases

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Fig. 11

Streamline and velocity magnitude for stationary, linearly moving, and rotating cases

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Fig. 12

Suction side heat transfer coefficient (h) contour (see Fig. 8 for h scale) for stationary, linearly moving, and rotating cases

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Fig. 13

Suction side film cooling effectiveness contour for stationary, linearly moving, and rotating cases

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Fig. 14

Blade tip heat transfer coefficient (h) contour (see Fig. 8 for h legend)

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Fig. 15

Blade tip film cooling effectiveness (η) contour (see Fig. 9 for η legend)

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Fig. 16

Suction side heat transfer coefficient (h) contour (see Fig. 8 for h legend)

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Fig. 17

Suction side film cooling effectiveness (η) contour (see Fig. 13 for η legend)

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Fig. 18

3D path lines for the three geometrical cases

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