0
Research Papers: Fundamental Issues and Canonical Flows

Stability Limits of Reversible-Pump Turbines in Turbine Mode of Operation and Measurements of Unstable Characteristics

[+] Author and Article Information
Grunde Olimstad

 Department of Energy and Process Engineering, NTNU University in Trondheim, Alfred Getz vei 4, Trondheim, 7491, Norwaygrunde.olimstad@ntnu.no

Torbjørn Nielsen

 Department of Energy and Process Engineering, NTNU University in Trondheim, Alfred Getz vei 4, Trondheim, 7491, Norwaytorbjorn.nielsen@ntnu.no

Bjarne Børresen

 Energi Norge, Næringslivets Hus, Middelthunsgate 27, Oslo, Norwaybbo@energinorge.no

J. Fluids Eng 134(11), 111202 (Oct 23, 2012) (8 pages) doi:10.1115/1.4007589 History: Received April 12, 2012; Revised September 01, 2012; Published October 23, 2012

Measurements have been performed on a reversible-pump turbine model installed in a closed loop conduit system. The characteristics of the unstable pump turbine in turbine mode show a hysteresis pattern. Hence the output of the system is dependent on the previous state of the flow and not only the input variables. The hysteresis pattern is a characteristic of the whole system, but is caused by the unstable pump turbine. The unstable part of the characteristics was measured by three different methods: 1) by transient sampling of data during the transition between operation modes, 2) by throttling valves that steepens the friction-loss curve, and 3) by switching the causality in the system such that the torque becomes an input parameter and the speed of rotation becomes an output parameter. In the valve throttling measurements a pressure dependency was seen for the characteristics at high nondimensional speeds. This was further investigated by additional measurements of the characteristics at three different pressure levels. A rigid-water-column stability analysis has been conducted. The classic H-Q criterion describes static stability for a pump turbine with constant speed of rotation. With the speed of rotation as a variable, there is a new static stability criterion in addition to the dynamic stability criterion.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Simple power plant system with indicated upper and lower reservoir, water conduits, and turbine

Grahic Jump Location
Figure 2

Limiting lines for the slope of the characteristics in turbine mode

Grahic Jump Location
Figure 4

Radial view of the runner blade surface

Grahic Jump Location
Figure 5

Meridional view of the runner blade surface

Grahic Jump Location
Figure 6

Performance diagram with labeled efficiency contours

Grahic Jump Location
Figure 7

Hysteresis flow-speed curves with 10 deg guide vane opening

Grahic Jump Location
Figure 8

Hysteresis Qed -Ned characteristics with 10 deg guide vane opening

Grahic Jump Location
Figure 9

Inputs to and outputs from the system

Grahic Jump Location
Figure 10

Transient measured characteristics for three different guide vane openings (α)

Grahic Jump Location
Figure 11

Stabilizing through valve throttling

Grahic Jump Location
Figure 12

Characteristic with torque as input

Grahic Jump Location
Figure 13

Standard deviations in the unstable zone

Grahic Jump Location
Figure 14

Comparison of the three measurement techniques

Grahic Jump Location
Figure 15

Final Qed -Ned characteristics

Grahic Jump Location
Figure 16

Final Ted -Ned characteristics

Grahic Jump Location
Figure 17

Pressure dependent characteristics

Grahic Jump Location
Figure 18

Marker sizes correspond to plus/minus three standard deviations

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In