Analysis of transient flow in a pump-turbine during the load rejection process

Fu, Xiaolong; Li, Deyou; Wang, Hongjie; Zhang, Guanghui; Li, Zhenggui; Wei, Xianzhu

doi:10.1007/s12206-018-0416-1

Cited by 29 publications

(12 citation statements)

References 27 publications

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“…The control equations are discrete with the finite volume method. The pressure staggering option (PRESTO) format was employed for the pressure item; a first-order upwind format was adopted for the velocity, the turbulent kinetic energy, and the turbulent viscosity coefficient item; and a pressure implicit with splitting of operators (PISO) method was applied for the coupling solution of the velocity and pressure equations [35].…”

Section: Equations Discretization and Boundary Conditionsmentioning

confidence: 99%

Research on Hydraulic Characteristics in Diversion Pipelines under a Load Rejection Process of a PSH Station

Zhou

Chen

2018

Water

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Transient analysis in diversion pipelines should be performed to ensure the safety of a hydropower system. After the establishment of a three-dimensional (3D) geometric model from the part upstream reservoir to the diversion pipeline end in a pumped storage hydropower (PSH) station, the hydraulic characteristics of the diversion system were solved by Reynold average Navier–Stokes (RANS) equations based on a volume of fluid (VOF) method under the condition of simultaneous load rejection of two units. The variations of the water level in the surge tank, the pressure at the pipeline end, and the velocity on the different pipeline sections with time were obtained through the calculation. The numerical results showed that the water level changing in the surge tank simulated by VOF was consistent with the field test data. These results also showed that a self-excited spiral flow occurs in the pipeline when the flow at the end of the pipeline was reduced to zero and its intensity decreased with the flow energy exhaustion. The discovery of the self-excited spiral flow in the study may provide a new explanation for the pressure wave attenuation mechanism.

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Section: Equations Discretization and Boundary Conditionsmentioning

confidence: 99%

Research on Hydraulic Characteristics in Diversion Pipelines under a Load Rejection Process of a PSH Station

Zhou

Chen

2018

Water

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“…[10], and flow analysis of pump turbine in load rejection was mentioned in Ref. [11]. However, these studies are only focused on the unit itself and do not take into account the requirements of the power system on the unit's operational performance.…”

Section: Introductionmentioning

confidence: 99%

Research on an Output Power Model of a Doubly-Fed Variable-Speed Pumped Storage Unit with Switching Process

Zhao

Ren

2019

Applied Sciences

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The doubly-fed variable-speed pumped storage (DFVSPS) is an effective method to balance the fluctuation of renewable energy generation and is an important means of frequency and voltage regulation of a power grid. Firstly, this paper introduces the structure and mathematical model of the DFVSPS unit. Secondly, the control methods of each switching stage in generating mode and pump mode are proposed, and the simulation study of each stage of DFVSPS switching process is carried out by MATLAB/Simulink. Thirdly, when studying the regulating effect of DFVSPS unit in the power system, due to the high switching frequency of converter in the electromagnetic transient model, the simulation speed is very slow and the data volume is large, so the model of DFVSPS unit needs to be simplified. By analyzing the dynamic behavior of the pumped storage power station, the mathematical model of output power of the DFVSPS unit is established, which includes start-up stage, load ramping stage, stable operation stage, load rejection stage and shutdown stage of generating mode and pump mode. Finally, the simplified model of DFVSPS unit is applied to a simple power system to verify its regulating effect on grid power.

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“…With the application of advanced design technology in the development of hydro turbines, the physical fluctuations in the labyrinth seals of Francis turbines have been the focus of a significant volume of research [6][7][8]. Meanwhile, transient processes, such as unit start-up and load rejection processes, are also important factors to be considered in the hydraulic design and optimization of the Francis turbines [9][10][11]. Here, hydropower accidents that are related to the occurrence of plant-vibration and turbine-lift during transient processes have often proved to be caused by a variety of hydraulic parameters in the labyrinth passages.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection

et al. 2019

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Labyrinth seals are not usually included in the numerical models of hydraulic machinery to simplify the geometric modeling, and thereby reduce the calculation burden. However, this simplification affects the numerical results, especially in the load rejection process, because disc friction losses, volume losses, and pressure fluctuations in the seal ring (SR) clearance passage are neglected. This paper addresses the issue by considering all of the geometrical details of labyrinth seals when conducting multiscale flow simulations of a high head Francis turbine under a transient load rejection condition using the commercial software code. A comparison of the numerical results that were obtained with the experimental testing data indicates that the calculated values of both torque and mass discharge rate are 8.65% and 5% slightly less than the corresponding values that were obtained from experimental model testing, respectively. The obtained pressure fluctuations of the Francis turbine in the vaneless zone and the draft tube appear to more closely match with the experimental test data when including SR clearance. Moreover, the flow rates through SR clearance passages were very small, but the pressure fluctuations among them were significantly enhanced under the minimal load condition. The numerical model with SR clearance can more accurately reflect the fact that the water thrust on the runner only fluctuates from 800 N to 575 N during the load rejection process, even though the water thrust on the blades varies from −220 N to 1200 N. Therefore, multiscale flow study is of great significance in understanding the effect of clearance flow on the load rejection process in the Francis turbine.

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Analysis of transient flow in a pump-turbine during the load rejection process

Cited by 29 publications

References 27 publications

Research on Hydraulic Characteristics in Diversion Pipelines under a Load Rejection Process of a PSH Station

Research on Hydraulic Characteristics in Diversion Pipelines under a Load Rejection Process of a PSH Station

Research on an Output Power Model of a Doubly-Fed Variable-Speed Pumped Storage Unit with Switching Process

Numerical Study on Flow Characteristics in a Francis Turbine during Load Rejection

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