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Research Papers

Tip Clearance Effect on the Flow Pattern of a Radial Impulse Turbine for Wave Energy Conversion

[+] Author and Article Information
Bruno Pereiras

Department of Energy and Fluid Mechanics Engineering, University of Valladolid, Paseo del Cauce 59, 47011 Valladolid, Spainbrunopereiras@eis.uva.es

Francisco Castro

Department of Energy and Fluid Mechanics Engineering, University of Valladolid, Paseo del Cauce 59, 47011 Valladolid, Spaincastro@eis.uva.es

Abdelatif el Marjani

Turbomachinery Laboratory, Ecole Mohammadia d’Ingénieurs (EMI), University of Mohammed V Agdal, Avenue Ibn Sina, B.P. 765, Agdal Rabat, Moroccomarjani@emi.ac.ma

Miguel A. Rodríguez

Department of Energy and Fluid Mechanics Engineering, University of Valladolid, Paseo del Cauce 59, 47011 Valladolid, Spain

J. Turbomach 133(4), 041019 (Apr 25, 2011) (10 pages) doi:10.1115/1.4002409 History: Received August 10, 2009; Revised March 04, 2010; Published April 25, 2011; Online April 25, 2011

Turbines for wave energy conversion have a special feature to be taken into account in the study of the tip leakage flow: These turbines are self-rectifying, which work inside a cyclically bidirectional flow alternatively as an inflow/outflow turbine. The phenomena at the blade tip will be different in these two situations. Moreover, it is necessary to take into account the tip clearance of the guide vanes because it has a significant influence on the rotor performance. A previously developed numerical model has been used for this study. The geometry proposed by Setoguchi (2002, “A Performance Study of a Radial Impulse Turbine for Wave Energy Conversion  ,” Journal of Power and Energy, 216, pp. 15–22) is used in the model. Three different tip clearance sizes have been simulated to compare the influence of the tip clearance size on the performance. Results show that changing the size of the tip clearance from 0% to 4% of the blade span reduces the turbine maximum efficiency by up to 8%. However, the efficiency reduction is more pronounced when the turbine works as an inflow turbine because the tip clearance effect is more important in the inner part of the rotor, since flow velocities are higher and the relative casing motion is lower. This study achieves its main aim, which is to improve knowledge about the phenomena related to the tip clearance and its influence on the performance of radial impulse turbines.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 4

Turbine sketch with circumferential reference surfaces (2)

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Figure 5

Velocity triangles

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Figure 6

Reference sections

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Figure 7

Planes perpendicular to the rotation axis

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Figure 8

Reference cross-surfaces inside the rotor

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Figure 9

Turbine performance in function of tc: (a) CA and (b) CT

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Figure 10

Stationary efficiency, η

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Figure 11

Flow angles in surface C

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Figure 16

Total pressure contours in XY planes for inflow: φ≈−2.1, range≅−1480/20 Pa, and scale=75 Pa/isoline

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Figure 17

Total pressure contours in radial cross-surfaces inside the rotor for inflow: φ≈−2.1, range=−1480/20 Pa, and scale=75 Pa/isoline

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Figure 18

Total pressure contours in XY planes for outflow: φ≈2.6, range=−900/1500 Pa, and scale=120 Pa/isoline

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Figure 19

Total pressure contours in radial cross-surfaces inside the rotor for outflow: φ≈2.6, scale=−900/1500 Pa, and 120 Pa/isoline

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Figure 1

Geometries of impulse turbines

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Figure 2

Blades and vanes profiles of the M8 geometry (9)

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Figure 3

Case t/b=4.4%. Mesh resolution in the tip clearance:10 cell/mm in Z-axis direction (16)

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Figure 12

Flow angles in surface D

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Figure 13

Sketch of the tip leakage flow in radial turbines (14)

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Figure 14

Influence of the tip clearance size in surface C: (a) inflow and (b) outflow

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Figure 15

Influence of the tip clearance size in surface D

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