Hysteresis Characteristic in the Hump Region of a Pump-Turbine Model

Deyou Li, Hongjie Wang, Jinxia Chen, Torbjørn K. Nielsen, Daqing Qin and Xianzhu Wei
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Deyou Li: School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Hongjie Wang: School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Jinxia Chen: School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Torbjørn K. Nielsen: Waterpower Laboratory, Norwegian University of Science and Technology, Trondheim 7491, Norway
Daqing Qin: School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Xianzhu Wei: School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China

Energies, 2016, vol. 9, issue 8, 1-18

Abstract: The hump feature is one of the major instabilities in pump-turbines. When pump-turbines operate in the hump region, strong noise and serious fluctuations can be observed, which are harmful to their safe and stable operation and can even destroy the whole unit as well as water conveyance system. In this paper, a low specific speed ( n q = 36.1 min ?1 ) pump-turbine model was experimentally investigated. Firstly, the hump characteristic was obtained under 19 mm guide vane opening conditions. More interestingly, when the hump characteristic was measured in two directions (increasing and decreasing the discharge), characteristic hysteresis was found in the hump region. The analysis of performance characteristics reveals that the hump instability is the result of Euler momentum and hydraulic losses, and different Euler momentum and hydraulic losses in the two development processes lead to the hysteresis phenomenon. Then, 12 pressure sensors were mounted in the different parts of the pump-turbine model to obtain the time and frequency characteristics. The analysis of the corresponding fast Fourier transform confirms that the hump characteristic is related to low-frequency (0.04–0.15 times rotational frequency) vortices. The occurrence and cessation of vortices depend on the operating condition and measurement direction, which contribute to the hysteresis feature. Finally, the type of the low-frequency vortices was analyzed through the cross power spectrum.

Keywords: pump turbine; hump characteristic; hysteresis characteristic; experimental investigation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2016
References: View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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