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Flows in Complex Systems

Dependency on Runner Geometry for Reversible-Pump Turbine Characteristics in Turbine Mode of Operation

[+] Author and Article Information
Grunde Olimstad

e-mail: grunde.olimstad@ntnu.no

Torbjørn Nielsen

e-mail: torbjorn.nielsen@ntnu.no
Department of Energy and Process Engineering,
Norwegian University of Science and Technology,
Alfred Getz Vei 4,
Trondheim 7491, Norway

Bjarne Børresen

Energi Norge,
Næringslivets Hus,
Middelthunsgate 27,
Oslo 0307, Norway
e-mail: bbo@energinorge.no

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF Fluids ENGINEERING. Manuscript received February 13, 2012; final manuscript received October 7, 2012; published online November 20, 2012. Assoc. Editor: Bart van Esch.

J. Fluids Eng 134(12), 121102 (Nov 20, 2012) (9 pages) doi:10.1115/1.4007897 History: Received February 13, 2012; Revised October 07, 2012

Characteristics of a reversible-pump turbine have been measured with five different leading edge profiles in turbine mode. These profiles varied the inlet blade angle and the radius of curvature. Further geometry parameters have been investigated through numerical simulations. The pump turbine tested has much steeper flow-speed characteristics than a comparable Francis turbine. The most obvious geometry difference is the inlet part of the runner blades, where the blade angle for the pump turbine is much smaller than for the Francis turbine. Two different blade angles have been tested on a physical model and computational fluid dynamics (CFD) simulations have been performed on four different angles. Both methods show that a smaller blade angle gives less steep characteristics in turbine mode, whereas the measured s-shape in turbine brake- and turbine pumping mode gets more exaggerated. Long-radius leading edges result in less steep characteristics. The unstable pump turbine characteristics are in the literature shown to be a result of vortex formation in the runner and guide vane channels. A leading edge with longer curvature radius moves the formation of vortices towards higher speed of rotation.

Copyright © 2012 by ASME
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References

Pejovic, S., Krsmanovic, L., Jemcov, R., and Crnkovic, P., 1976, “Unstable Operation of High-Head Reversible Pump-Turbines,” 8th IAHR Symposium on Hydraulic Machinery and Cavitation, Leningrad, USSR, pp. 283–295.
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Apfelbacher, R., and Etzold, F., 1988, “Energy-Saving, Shock-Free Throttling With the Aid of a Reverse Running Centrifugal Pump,” KSB Technische Berichte, Frankenthal, 24e(68), pp. 33–41.
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Nielsen, T. K., and Olimstad, G., 2010, “Dynamic Behaviour of Reversible Pump-Turbines in Turbine Mode of Operation,” 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machine, Honolulu, HI.
Widmer, C., Staubli, T., and Ledergerber, N., 2011, “Unstable Characteristics and Rotating Stall in Turbine Brake Operation of Pump-Turbines,” ASME J. Fluids Eng., 133(4), p. 041101. [CrossRef]
Hasmatuchi, V., Farhat, M., Roth, S., Botero, F., and Avellan, F., 2011, “Experimental Evidence of Rotating Stall in a Pump-Turbine at Off-Design Conditions in Generating Mode,” ASME J. Fluids Eng., 133(5), p. 051104 [CrossRef].
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Yamabe, M., 1972, “Improvement of Hysteresis Characteristics of Francis Pump-Turbines When Operated as Turbine,” ASME J. Basic Eng., 94(3), pp. 581–585. [CrossRef]
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Figures

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Fig. 1

RPT versus Francis characteristics

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Fig. 2

Pump turbine runner geometry

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Fig. 8

Flow-speed characteristics of profile A

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Fig. 10

Turbine efficiency for profile A

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Fig. 11

Head-flow characteristics in pump mode

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Fig. 9

Torque-speed characteristics of profile A

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Fig. 12

Flow-speed characteristics of profile B

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Fig. 13

Torque-speed characteristics of profile B

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Fig. 14

Head flow curve for profile B in pump mode

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Fig. 15

Efficiency for profile B in pump mode

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Fig. 16

Flow-speed characteristics of profile A and B

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Fig. 17

Comparison of original and profile C in turbine mode

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Fig. 18

Comparison of profiles C and D in turbine mode

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Fig. 19

Efficiency in turbine mode

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Fig. 20

Comparison of original blade versus profile D in pump mode

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Fig. 21

Comparison of profiles C and D in pump mode

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Fig. 22

Efficiency in pump mode

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Fig. 23

Measured versus simulated characteristics

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Fig. 24

Internal blade angle distribution from inlet [0] to outlet [1]

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Fig. 25

Inlet blade angles

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Fig. 27

Different internal blade angles

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Fig. 28

Characteristics for different internal blade angle

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Fig. 29

Characteristics for different inlet blade angles

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Fig. 30

Characteristics for different radii

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Fig. 31

Different number of blades

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