Investigation on the fluctuation of hydraulic exciting force on a pump-turbine runner during the load rejection process

Fu, Xiaolong; Li, Deyou; Wang, H. J.; Zhang, G. H.; Wei, Xianzhu; Qin, D. Q.

doi:10.1088/1755-1315/163/1/012101

Cited by 7 publications

(5 citation statements)

References 16 publications

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“…Up to now, there are a few studies about the hydraulic forces of the pump-turbine runner during transient scenarios. Fu et al [19,20] investigated the runner forces of a model pump-turbine during load rejection with guide-vanes closing, and the results indicate severe fluctuations when the pump-turbine runs in low-discharge conditions. Xia et al [21] pointed out that these fluctuations are influenced by the guide-vane closing rules, and the 'first fast then slow' closing rule can suppress the high-amplitude runner forces effectively.…”

Section: Introductionmentioning

confidence: 99%

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Zhang

Cheng

Zheng

et al. 2020

IET Renewable Power Generation

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To enhance the power grid's stability and safety, pumped-storage power stations (PSPSs) have to keep themselves stable and safe strictly. However, instabilities happen frequently in some PSPSs due to the S-shaped characteristics of pumpturbines. When the operating point goes through the S-shaped region, intensive radial forces on the runner could cause shaft swing of the turbine-generator unit. In this study, the runaway transient scenarios of a pump-turbine in a model PSPS were simulated by using a one-dimensional and three-dimensional coupled computational fluid dynamics model, and the influence of the unit rotational inertia on the runner radial forces was investigated. The results show that when the pump-turbine runs in the S-shaped region, large rotational inertia is easier than a small one to induce abrupt increases in runner radial forces. The reason is that large rotational inertia gives slower changes in rotational speed and discharge, providing enough time to generate unstable and uneven flow patterns in the pump-turbine. This indicates that apart from the running away region in the characteristics plane, the running away duration is also essential for the transient instability of a pump-turbine. The finding is different from the traditional understandings and should be considered when selects the rotational inertia of a pump-turbine unit. ρ 0 initial density ρ density σ standard deviation of the relative discharges ω angular velocity at the current time-step ω p angular velocity at the previous time-step

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Section: Introductionmentioning

confidence: 99%

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Zhang

Cheng

Zheng

et al. 2020

IET Renewable Power Generation

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“…This is because the pump turbine can operate flexibly to adjust the grid load, which means the pump turbine needs to work at the lower operating point and undergo frequent transition processes. A large number of experiments and simulation studies have been carried out to study the flow field and structural field characteristics of the pump turbine [1][2][3][4][5]. Some studies have included a wearing ring, because the clearance flow on the crown and near the band has been shown to have a significant effect on hydraulic excitation.…”

Section: Introductionmentioning

confidence: 99%

A Simulation Study of Hydraulic Vibration caused by Clearance Flow in a Pump Turbine

Hu¹,

Mao

Qiao³

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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The pumped-storage power station needs to adjust the load to meet the needs of the power grid at any time and cannot always operate under the best working conditions. In practical operation, vibration phenomenon with complex inducements occasionally occurs. In the stable operation of the Baishan energy storage power station, the headcover vibrates obviously. To find the cause of vibration, this paper modeled the unit flow area, used the numerical simulation method for steady and unsteady calculation, extracted the pressure fluctuation information in the flow field, and then analyzed the possibility of strong vibration caused by the instability of the flow field. The results show that there is a low frequency component of pressure fluctuation caused by the spiral motion of the fluid in the sealing groove in the upper canopy clearance flow, which may be the inducer of the vibration of the headcover.

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“…Yang [5] pointed out that the unstable vortex structure in MFC of pump-turbine is another reason for the force fluctuations during the runaway transient process after pump-trip. Fu [6] concluded that the fluctuation frequency of axial force was caused by the reverse flow and helical vortex flow in the draft tube during the load rejection transient process. However, research for the axial force in CFC is very limited.…”

Section: Introductionmentioning

confidence: 99%

Influence factors of clearance leakage flowrate and clearance hydraulic axial force of pump-turbine

Hou

Cheng

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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The clearance flow of pump-turbine has significant influence on hydraulic forces of the runner, which is related to safety of the unit. To clarify the influence factors, clearance flowrate and clearance hydraulic axial force of a prototype pump-turbine were analyzed by 3D CFD simulations. The results show that the rotational speed, and the smallest radial sizes of clearance inlet, outlet, and the seal ring sizes are the determinant factors for clearance leakage flowrate, while the rotational speed and the radial size at clearance inlet are the major factors for clearance axial force. The rotational speed of rotating surfaces mainly affects the strength of rotating shear flow, while geometric sizes mainly affect the hydraulic loss of leakage flow. By assuming that the clearance region as several ring pipes, we obtained the simplified calculation formulas for estimating clearance leakage flowrate and clearance axial force. The flowrate can be expressed as a function of the water head difference across the clearance region, the rotational speed, and the sizes of clearance inlet, outlet and sealing ring, while the clearance axial force is a function of the inlet pressure and the square of both radius and rotational speed. The formula calculations agree with the numerical simulations well. This paper can provide a reference for runner clearance size design.

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Investigation on the fluctuation of hydraulic exciting force on a pump-turbine runner during the load rejection process

Cited by 7 publications

References 16 publications

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

A Simulation Study of Hydraulic Vibration caused by Clearance Flow in a Pump Turbine

Influence factors of clearance leakage flowrate and clearance hydraulic axial force of pump-turbine

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