Evolutions of guide vane moment of a pump-turbine during runaway transient process after pump trip

Zheng, Yang; Cheng, Yongguang; Xia, Linsheng; Meng, Wanwan; Gao, Lili; Dai, Yongqian

doi:10.1088/1755-1315/240/7/072033

Cited by 5 publications

(3 citation statements)

References 3 publications

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“…From Figure 9a, it can be seen that the experiment head and shaft power were very close to the simulation head and shaft power, and the maximum error was less than 5%, indicating that the steady simulation of the LAPS based on the numerical model in this paper has high accuracy. From Figure 9b, it can be seen that the runaway speed of the pump after the power-off of the LAPS under the different heads was very close to that of the simulation, the variation law was highly consistent and the maximum error was less than 3%, indicating that the transient simulation of the LAPS based on the numerical model in this paper also has high accuracy [42,43]. Figure 9 shows the comparison between the experimental results and the simulation results [40,41].…”

Section: Model Validationsupporting

confidence: 52%

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

et al. 2023

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A large number of operation practices show that the reliability and stability of large axial flow pump systems will face significant challenges during the start-up process. If the start-up control mode or safety auxiliary facilities of large axial flow pump stations are unreasonable, start-up failure will easily follow. In order to find a scientific control strategy for the start-up of large axial flow pump stations, the start-up characteristics of large axial flow pump stations must be fully understood first. In this paper, based on the secondary development of Flowmaster software, a simulation study of the start-up process of a large axial flow pump system equipped with different safety aids is carried out. It is found that it is a very dangerous start-up control mode to delay the opening of the rapid-drop gate to reduce the maximum reflux value and reflux duration when the pump system is initially started. When the rapid-drop gate opens with a delay of 4 s, the power overload coefficient reaches 23.49, indicating that the possibility of start-up failure of the large axial flow pump system increases sharply the longer the gate delay is opened. The method of adding a flap valve to the rapid-drop gate can significantly weaken the instantaneous impact power of the unit and prevent the unit from overload. When safety auxiliary facilities with an additional disc valve on the fast descending gate are adopted, the backflow coefficient is within 0.2, the impact head coefficient is within 2, and the power overload coefficient is less than 0. The research results will provide an important reference value for comprehensively understanding the start-up characteristics of large axial flow pump stations and finding scientific and safe start-up control strategies.

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Section: Model Validationsupporting

confidence: 52%

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

et al. 2023

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“…In the transient process of power-trip with guide-vane closure (PTVC), after the generator is disconnected from the power grid, the pump-turbine rotational speed and discharge in pump direction decrease with the closure of guide-vanes, and the positive water hammer wave in the tailrace water conveyance system impacts on the low-pressure side of the runner, which will cause a significant increase in the axial force on the runner and may cause a lifting-up accident [7]. In addition, the rotational speed will gradually decrease from the pump direction to zero speed or even further develop to the turbine direction, and during this drastic speed change, the flow patterns in the pumpturbine are abnormally violent [8], accompanied by severe pressure pulsations, cavitation, vibrations and other problems threatening the safety of PSHSs. 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].…”

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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“…To undertake these important functions, the stability and safety of pumped-storage power systems are essential. However, some stability problems in operating pumped-storage power stations, such as violent vibration of pump-turbine units [6], grid connection failure [7,8], runner lifting-up [9], and rotor-stator crashing [10], were frequently reported. These problems were generally attributed to the frequent conversions of operating conditions, especially when the working points pass through the so-called S-and hump-shaped characteristics regions, in which intense flow and pressure fluctuations occur.…”

Section: Introductionmentioning

confidence: 99%

Differences of Flow Patterns and Pressure Pulsations in Four Prototype Pump-Turbines during Runaway Transient Processes

et al. 2020

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Frequent working condition conversions in pumped-storage power stations often induce stability problems, especially when the operating point enters the S-shaped region, during which flow transitions and pressure fluctuations are serious. The pump-turbines with different specific speed values show different characteristics, but their differences in stability features are still not clear. In this study, four different pump-turbines were selected to simulate the runaway processes from turbine modes. The similarities and differences of flow patterns and pressure fluctuations were analyzed. For the similarities, pressure pulsations increase gradually and fluctuate suddenly once the backflows occur at the runner inlets. For the differences, the evolutions of backflows and pressure pulsations are related to specific speeds and runner shapes. Firstly, it is easier for the lower specific speed turbines to enter the reverse pump mode. Secondly, the blade lean angle influences the position where backflows occur, because it determines the pressure gradient at the runner inlets. Thirdly, the runner inlet height influences pressure pulsations in the vaneless space, because the relative range of backflow transitions will be enlarged with the decrease of specific speed. Overall, investigating the mechanisms of flow pattern transitions and pressure variations is important for runner design and transient process control.

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Evolutions of guide vane moment of a pump-turbine during runaway transient process after pump trip

Cited by 5 publications

References 3 publications

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

Investigation on Start-Up Characteristics of Large Axial Flow Pump Systems Considering the Influence of Auxiliary Safety Facilities

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

Differences of Flow Patterns and Pressure Pulsations in Four Prototype Pump-Turbines during Runaway Transient Processes

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