Pressure fluctuations during the pump power-trip of a low-head pump-turbine with the co-closing of guide vane and ball valve

Fu, Xiaolong; Li, Deyou; Song, Yechen; Wang, Hongjie; Yang, Jialiang; Wei, Xianzhu

doi:10.1016/j.est.2022.106470

Cited by 3 publications

(1 citation statement)

References 23 publications

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“…During the PTVC transients of a medium-head (H r = 439 m) pump-turbine, large-scale cavitation cavities are generated in the runner blade channels and draft-tube, and the cavity dynamic evolution induces transient velocity and pressure pulsations [9]. During a low-head (H r = 259 m) pump-turbine PTVC transients, two types of pressure pulsations with frequencies of 38-40 times of rotational frequency caused by Dean vortices in the spiral-case and local high pressure in the vane channels have been found, both of which mainly affect the axial hydraulic force on the runner [10]. During the transient process of power-trip with guide-vane rejection (PTVR), the transients can be more drastic because the guide-vanes are at a large opening and remain constant.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Runner Forces during Simultaneous Pump-Trip Transient Process of Two Pump-Turbines

Ke,

Yongguang,

Jinghuan

et al. 2024

J. Phys.: Conf. Ser.

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To ensure no cavitation and water column separation in pump-turbines, the suction heights of pump-turbines in high-head pumped-storage hydropower stations have to be decreased to about –100 m, which leads to high pressure in the draft-tube. During the pump-trip transient process of pump-turbines, the positive water hammer wave in draft-tube superposing the initial high pressure may cause an imbalance of rotating parts and even a lifting-up accident. To quantify the runner forces, two typical transient processes, with and without guide-vane closure after the simultaneous power-off of the two pump-turbines in one hydraulic system, were simulated by using the one-dimensional and three-dimensional coupled (1D-3D) computational fluid dynamics (CFD) method. The results show that the maximum upward axial force on the runner during the process without guide-vane closure (runaway) is significantly higher than that during the process with guide-vane closure. Two significant maximum upward axial forces were observed during the runaway process, and they were around the zero and the valley speed moments. The main causes are the pressure decrease in the runner’s high-pressure zone owing to high-speed bypass flows, and the spiral-case negative water-hammer wave and draft-tube positive water-hammer wave caused by discharge rise. However, the draft-tube positive water hammer wave superposing the high pressure did not cause the maximum axial force. The above two moments of highest axial forces during the runaway process and the proper guide-vane closure rule deserve special attention in the design and operation phases.

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Section: Introductionmentioning

confidence: 99%

Evolution of Runner Forces during Simultaneous Pump-Trip Transient Process of Two Pump-Turbines

Ke,

Yongguang,

Jinghuan

et al. 2024

J. Phys.: Conf. Ser.

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Numerical investigation on vortex characteristics in a low-head Francis turbine operating of adjustable-speed at part load conditions

Wang,

Yu,

Yan

et al. 2024

Energy

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Research on the Flow Characteristics in the Gap of a Variable-Speed Pump-Turbine in Pump Mode

Wang,

et al. 2024

Processes

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A variable-speed pump-turbine is the core component of a hydraulic storage and energy generation station. When the pump-turbine operates at a constant speed, its response to the power grid frequency is poor. In order to improve the hydraulic efficiency of the pumped storage unit, variable-speed units are used. However, there has been no numerical study on the effect of the rotational flow characteristics within the gap of a variable-speed pump-turbine. This paper calculates the flow characteristics within the gap of a variable-speed pump-turbine under three typical pump modes (maximum head minimum flow condition, minimum head maximum flow condition, and maximum speed condition). The research results indicate that the rotational speed significantly affects the pressure distribution, velocity distribution, and turbulent kinetic energy distribution within the crown and band gaps. The higher the speed, the larger the area of the high-pressure region before the runner inlet compared to other operating conditions, and similarly, the low-pressure area after the runner outlet is also larger than in other operating conditions. The change in speed mainly affects the internal flow field of the crown gap, with the most noticeable changes occurring in the pressure and flow velocity at the inlet and outlet of the crown gap. There is a clear trend of pressure drop and velocity increase within the gap as the speed increases. However, with the increase in speed, the pressure distribution and flow velocity within the band gap remain almost the same. In addition to speed changes, it is observed that the pressure within the gap and the flow velocity within the passages are also related to the head, especially in the condition of maximum head, where this relationship becomes more noticeable.

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Pressure fluctuations during the pump power-trip of a low-head pump-turbine with the co-closing of guide vane and ball valve

Cited by 3 publications

References 23 publications

Evolution of Runner Forces during Simultaneous Pump-Trip Transient Process of Two Pump-Turbines

Evolution of Runner Forces during Simultaneous Pump-Trip Transient Process of Two Pump-Turbines

Numerical investigation on vortex characteristics in a low-head Francis turbine operating of adjustable-speed at part load conditions

Research on the Flow Characteristics in the Gap of a Variable-Speed Pump-Turbine in Pump Mode

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