bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strength Evaluation of the Flow Passage Stationary Structures of a Large Francis Turbine Unit
Authors: Jiang L , Xiao J , Zhao W , Huang X 
Published: June 2024

Abstract
The multifield design and multifield coupling performance of the Francis turbine unit is a topic that needs to be studied deeply. In this paper, the strength evaluation of the stationary structures of the flow passage of a large Francis turbine unit under extreme conditions has been performed based on the fluid-structure coupling theory. The calculated stationary structures include the spiral casing, bottom ring, and head cover. The pressure load applied on the structures is 1.5 times the maximum head of the unit. The results show that there is stress concentration in the spiral casing, and the weld length with equivalent stress greater than 345 MPa reaches 800 mm; the maximum stress at the rib plate of the head cover reaches 357 MPa, which is greater than the yield limit 345MPa. Based on the evaluation results, the local and overall defects of the unit design can be found. The suggested strength evaluation methodology can provide references for the optimization of the unit and a theoretical basis for the operation of the unit.
Dynamic stress analysis of a large capacity Pelton turbine runner
Authors: Zishi Liu , Yexiang Xiao , Hongping Min , Quanwei Liang , Jie Liu , Xiaodong Wang , Qiyuan He , Haijun Li 
Published: June 2024

Abstract
The dynamic stress characteristics of a Pelton turbine runner is an important index to evaluate the stability of unit. Aiming to analyse the dynamic stress of a large capacity prototype Pelton turbine runner influenced by the unsteady impact load of a high-speed jet, the unsteady flow simulation was firstly taken for the Pelton turbine runner to conclude the hydraulic model of internal flow and the performance parameters. Then, the dynamic stress of the Pelton runner was solved by fluid-structure coupling numerical method. The dynamic stress variation trend of several monitor points distributed on the splitter, brim, bucket root was analysed. It is concluded that the impact load of the jet could lead to the significant change in the dynamic stress on specific location of the bucket surface, and the stress concentration was found at the bucket root.
Analysis of oil film flow characteristics and lubrication performance of thrust bearing of 1000MW Hydraulic Turbine Unit
Authors: Shi Yishu , Wu Siyuan , Huang Xingxing , Liu Xingmin 
Published: June 2024

Abstract
Hydro-generator unit is the core component of the hydropower station, and the stability of the shaft system directly determines the safety of the hydropower station. Thrust bearing is the only component to bear axial load, and working performance directly affects the stable operation and efficiency of the unit. In this study, a full 3D model of the shaft system of a 1000 MW hydro-generator unit is established, and the oil flow of thrust bearing oil film and oil in the oil tank considering the spray system and the overall model is analysed by means of the thermo-hydrodynamic method. The results show that the load increases with increasing inclination angle. Within certain limits, the pressure and temperature of the oil film increase with increasing inclination. And there are many vortices in the tank. Although the spray system reduces the oil churn, the lubricating oil flow between pads is chaotic. The loss is mainly caused by the chaotic flow between pads. Analyzing the effects of oil film thermal effects on bearing loads, lubricant flow, and bearing surface temperatures of tilting pads provides valuable insights for bearing design and maintenance guidance.
State of the art of technical background and practicality of pressure balance pipes for pumped storage turbine
Authors: Wang Haoyang , Zhao Yifeng , Wei Huan , Qin Jun , Zhang Fei 
Published: June 2024

Abstract
Pressure balance pipe is an important technical solution for the internal pressure balance of pump turbine and is widely used in pumped storage power units. This article systematically explains the application of pressure balance pipes in pump turbines, and sorts out three typical pressure balance application methods: the external pressure balance pipe structure balances the external side of the upper wearing ring and the lower wearing ring, the internal pressure balance pipe structure balances the internal side of the upper wearing ring and the draft tube, which improves the axial water thrust distribution of the unit and avoid uneven distribution of the axial water thrust on the runner. The spiral case pressure balance pipe realizes the control of water ring flow in the vaneless area under the synchronous condenser mode and pressure water by balancing the pressure of the spiral case and draft tube. For the above three structures, the current research progress, main problems and future development directions are elaborated.
Pressure Fluctuation analysis of pump-turbine in turbine mode under the same head condition
Authors: Zhang Fangfang , Li Na , Xiao Ruofu , Tao Ran 
Published: June 2024

Abstract
As the key technical part of pumped-storage power station, the efficient and stable development of pump-turbine units is of great significance for renewable energy power generation. However, pump-turbine units have the characteristics of complex and variable operation conditions. In addition, under different guide vane openings, operation conditions of pump-turbine units also show different flow patterns and pressure fluctuation characteristics. For the sack of studying the pressure fluctuation characteristics of pump-turbine units in turbine mode, a dynamic model of a pump-turbine unit is established in this research. Based on SST k-ω turbulence model, combined numerical simulation and experimental test, pressure fluctuation laws in vaneless region and draft tube under three typical guide vane openings are carried out. The results indicate that, by increasing the guide vane opening, the pressure fluctuation intensity of each monitor point is decreased. Furthermore, the pressure fluctuation at the monitor points in vaneless region between guide vane and the runner presents a periodic change rule, which is mainly due to the two-stage rotor and stator interference between guide vane and runner, and between runner and draft tube. The research further clarifies the pressure fluctuation law in turbine mode, and provides theoretical reference for long-term sustainable development of pump-turbine units.
Suppression mechanism of transient pressure during the turbine runaway of an ultra-high head pump-turbine
Authors: Fu Xiaolong , Lv Jingwei , Li Deyou , Wang Hongjie , Qin Daqing , Wei Xianzhu 
Published: June 2024

Abstract
Pressure fluctuation (PF) is a serious issue in transitions of the ultra-high head (UHH) pump-turbines (PTs). To explore the mechanism and control method of PF, the turbine runaway process (TRP) of an UHH PT was simulated using the one- and three-dimensional coupled method. The study suggested that the local backflow (BF) near the high-pressure (HP) inlet of the impeller blocked the impeller channel and induced water hammer. The local BF near the HP inlet of the impeller were closely related to the ratio of rotational speed to PT head. To suppress the BF this study proposed an improved impeller channel with 5 degree spread angle in meridian plane. The study found that the increase of rotational speed and transient pressure variations induced by water hammer could be suppressed successfully by using the improved impeller. The study provided important reference for the design and optimization of the UHH PTs.
Numerical Investigation on the Spatiotemporal Correlation between Hydraulic Loss and Vortex at Turbine Mode of a Pump-turbine
Authors: Qin Y L , Li D Y , Wang H J , Liu Z S , Wei X Z , Wang X H , Song Y J 
Published: June 2024

Abstract
Hydraulic loss and vortex analysis are two most widely-used methods investigating flow characteristics from macroscopic view and microscopic view respectively although the correlation between these two methods are still not fully clarified. Based on kinetic energy equation and Boussinesq hypothesis, hydraulic loss is resulted from the joint work of the dissipation loss and the transportation loss in flow domain while vorticity can be further divided into local rigid rotational part and deformational part with the help of the newly proposed concept Liutex. Thereafter, enstrophy as well as vorticity transport intensity is selected as the count part of hydraulic loss through dimensional analysis. Finally, the spatial correlation between hydraulic loss and vortex evolution in small guide vane opening at turbine mode is analyzed with the help of SST k–ω model and the temporal correlation at runaway point is analyzed through DES model. For spatial correlation, the dissipation loss and transportation loss are mainly caused by the deformational enstrophy Ω
S
and the rigid vorticity transport intensity T
R
, respectively. For temporal correlation, the correlation order nearly remains unchanged while the degree of correlation decreases to some extent. Based on our work, the hydraulic loss caused by different structure of vortex can be quantified and compared.
Three-Dimensional Numerical Simulation of Pumped Storage Unit No-Load operation with PID control before Grid-Connected
Authors: Guo Junxun , Zhou Daqing 
Published: June 2024

Abstract
The “S” characteristic curve has been a persistent challenge for low-head grid connection of pump-turbine units. The stability of the no-load operation before grid connection directly determines the success of grid connection. In order to accurately simulate the characteristics of the no-load operation before grid connection, this paper applies a PID speed controller model to the full flow system 3D simulation of the pumped storage unit, using user-defined functions and dynamic grid technology. The calculation results were compared with the conventional transient calculation method and field test data, which verified the reliability of the calculation method and solved the shortcomings of the conventional transient calculation method, especially in terms of pressure pulsation. The application of this speed controller model provides a new method for studying the instability of the “S” characteristic curve in pump-turbine units.
Analysis of the cause of the 40Hz frequency component in spiral casing of a high-head pump turbine
Authors: Jia W B , Guan Z W , Liang Q W , Liu Y , Wang Z N , Cheng H , He Q Y 
Published: June 2024

Abstract
Vibration and noise problems affect the safe and stable operation of pump turbines. For the design of pump turbines, it is crucial to accurately identify the excitation sources and their evolution laws that cause vibration and noise. Based on numerical calculation methods, this paper studies the 40Hz frequency component that occurs in the spiral case of a prototype pump turbine during operation in a power plant. Upon analysis of the internal flow characteristics of the spiral case, the study examines the causes for the formation of pressure pulsations at this frequency component and their transmission laws.
Three-dimensional simulations of load rejection processes of a variable-speed pump-turbine under different initial rotational speeds
Authors: Yang Z Y , Gong L J , Fang H , Deng X F , Li Y H , Liao T T 
Published: June 2024

Abstract
The load rejection transient process is one of the most dangerous operating conditions in pumped storage power stations. When the operating point slides through the S-shaped region quickly, the pressure fluctuations increase sharply and the unit vibrates obviously. In variable-speed units, the different initial rotational speeds have significant effects on the operating point trajectories during load rejection processes. In this paper, under the same head and guide vane opening, the load rejection processes with different initial rotational speeds were simulated by using three-dimensional methods, and the variations of rotational speed, discharge and torque were obtained and analyzed. The results show that the changes of initial rotational speeds affect the shapes of velocity triangle at the runner inlet and outlet, and causes the flow separations and vortices in the runner and draft tube, which leads to different efficiency and torque of the pump-turbine under initial steady conditions. In addition, during load rejection processes, the maximum values of macro parameters and pressure fluctuations, and the transitions of flow patterns have obvious differences because of these different initial rotational speeds.
Analysis of stability characteristics of pump-turbine in a pumped-storage power station with large head variation
Authors: Chengjun Li , Delou Wang , Zhiwen Zhao , Liangyu Xiao , Shunyi Chen , Wenbin Gu , Ran Dai , Yanhong Liu 
Published: June 2024

Abstract
The head variation is a key index of pumped storage power station, which is related to the operation stability of pump-turbine. The greater the head variation, the more difficult it is to ensure the operation stability of the unit. In this paper, the pressure pulsation of the pump-turbine with a large head variation is measured, and its amplitude and frequency characteristics are analysed. The prototype results are compared with the model test results. Similarities and differences of the pressure pulsation characteristics between the prototype and model are obtained. At the same time, the vibration characteristics of the prototype unit is measured, and the correlation analysis of the pressure fluctuation characteristics and the head variation is made. Then, the stability characteristics of pump turbines in the pumped storage power station are obtained. It guides the operation of the power station.
Study on phase resonance risk coefficient of pumped-storage units
Authors: Zhang Tao , Li Jinwei , Yang Weibin , Liu Yanyan 
Published: June 2024

Abstract
In this paper, 48 pumped-storage units (rated output of a single unit is not less than 100MW) put into operation or under construction in China were taken as the research object, and the risk of phase resonance caused by pressure wave propagation in the spiral casing of the unit was studied. The risk coefficient of phase resonance under the matching relationship between different rotational speeds and the number of guide vanes and blades was analyzed, and the advantages and disadvantages of the matching relationship between different rotational speeds and the number of guide vanes and blades were compared. The fitting formulas of the circumferential Mach number with rated head due to the pressure wave propagating along the spiral casing under two equivalent diameters were proposed, which provided references for the optimal hydraulic design of pumped-storage units.
Preliminary study on power regulation rapidity in pump mode of variable-speed pumped storage unit with DFIM
Authors: Liu Yuanhong , Yang Weijia , Yang Jin , Huang Yifan , Shao Zixuan 
Published: June 2024

Abstract
Variable-speed pumped storage unit (VSPSU) has a wider power regulation range than fixed-speed pumped storage unit (FSPSU) in pump mode. When conducting large-amplitude power regulation, the operating point changes greatly, and the influence of various parameters on the power response in this transient process is not yet clear. In order to study the power regulation rapidity of VSPSU in pump mode, the factors affecting the response rapidity and overshoot of power under fast speed control strategy are explored through numerical simulation of a variable-speed pumped storage plant (VSPSP) model, in which doubly fed induction machine (DFIM) is adopted. The factors include power command, controller parameters of governor (Kp-g
, Ki-g
), and controller parameters of converter (Kp-c
, Ki-c
, Kp-c2
, Ki-c2
). Accordingly, preliminary study is conducted on the parameter matching law for obtaining the fastest power response, and suggestions on the settings of the parameters are provided. The results show that the fastest power response can be obtained when adopting a step power command and the VSPSU has the fastest response rate of 12.5%/s when adjusting 30% power using the parameters recommended in this paper. This study could provide technical support to the practical operation of VSPSU.
Study on dynamic stress variation of head cover bolt during transient operation of pump turbine
Authors: Chen Liu , Li Hailing , Huang Mei , Liu Yang , Ren Shaocheng , Li Jinwei , Jiang Mingli , Sun Mingjun , Cao Weihua 
Published: June 2024

Abstract
The head cover bolt is an important connecting part of pump turbine, if it is damaged, it will affect the operation safety of the unit and the power station. During the transient process, such as start-up and load rejection in extreme case, the head cover bolt is subjected to complex load action, and its stress also changes, and extreme cases may occur. The dynamic stress level of the bolt will have a certain influence on its fatigue life, therefore, in order to further study the dynamic stress level and variation law of the bolt, this paper relies on a pumped-storage station, the dynamic stress of the head cover bolt during the start-up and load rejection is measured, and the pressure pulsation between the head cover and the runner and the bladeless zone are collected synchronously. Through the data analysis, the bolt dynamic stress level and variation law and the correlation between stress and pressure fluctuation under the power generation and pumping conditions are summarized.
Effect of crown gap thickness on axial force of high-head pump turbine
Authors: Li Lei , Yan Dandan , Liu Xuyang , Zhao Weiqiang , Wang Yupeng , Wang Zhengwei 
Published: June 2024

Abstract
The size of the runner crown gap is one of the factors affecting the volume loss of the pump turbine, and the unreasonable gap thickness is unfavourable to the unit operation. By establishing a three-dimensional full-channel fluid domain model of a high-head pump turbine, and using the computational fluid dynamics (CFD) method to perform numerical calculations on models with different crown gap thicknesses, the effects of axial water thrust on runners with different upper crown gap thicknesses are clarified. The results of simulation indicates that the resultant force of axial water thrust on the runner is vertically upward under different gap thicknesses, which is far less than the weight of the whole rotating part. The axial water thrust is very sensitive to the change of the seal gap value, the greater the seal gap value, the greater the axial water thrust on the unit, and the axial water thrust begins to decrease after increasing to a certain value. The research results are referable for the study of the gap flow characteristics and the crown gap design.
Study on the flow characteristic of pump turbine at partial load
Authors: Wang Wei , Guo Miao , Zhao Weiqiang , Xu Chao 
Published: June 2024

Abstract
Pump turbine adopts the same runner to realize forward pumping for pumping condition and reverse power generation for turbine condition, which is a widely used power equipment in pumped storage power station. Compared with conventional pump units or turbine units, the pump turbine has a complex internal flow, especially under part load conditions, and the vibration and noise problems of the structure are prominent. In this paper, the internal flow characteristics of the pump turbine at 60% load are studied by numerical simulation. The low-frequency pressure pulsation 3.5fn
and 5.5fn
that occur under this operating condition are analyzed. The results show that under partial load conditions, the opening of the guide vane decreases, the angle of attack of the water entering the runner increases, and the rotating stall phenomenon occurs in the pump turbine. The stall vortices show periodic variations on the blade inlet pressure surface and undergo the processes of vortex reduction, fusion, splitting and increase, respectively. The frequency of change is 0.5 times the runner rotation frequency (0.5fn
). The frequency of the corresponding monitoring points in the 7 blade rotor is 7 times (1fn
-0.5fn
), which is 3.5fn
.
Vibration Characteristic Analysis of Pump-turbine head cover based on Fluid-Solid Coupling
Authors: Zhou J P , Fan Y M , He Q Y , Wang S J , Zhao H L , Sun F , Tang Q 
Published: June 2024

Abstract
For the high-head pump-turbines, the runner is installed in a chamber with narrow spaces to the head cover in real work condition. The presence of rigid walls alters the added mass of the surrounding fluid, which in turn affects the natural frequencies and mode shapes of the head cover for the narrow space fluid. In this paper, the influence of the narrow space on the vibration characteristics and frequency reduction ratio of pump-turbine head cover was investigated based on fluid-solid coupling technique. The mode shapes of the head cover were checked and compared to the experimental data. The comparison demonstrates a high level of agreement between the numerical simulation and experimental findings. This study presents a systematic and dependable approach for analyzing vibration characteristics, which has a great significance for the safe and stable operation of the pump-turbine.
Numerical simulation on the flow characteristics of a pump-turbine in load rejection process
Authors: Cao Jingwei , Liu Xin , Zeng Chongji 
Published: June 2024

Abstract
Pumped storage plays a crucial role in maintaining the stability of the power grid, with the pump-turbine being the key component. The flow characteristics of the pump-turbine during transient processes have a significant impact on the unit’s safety, particularly in load rejection scenarios. In this study, a 1D transient simulation is conducted to analyze the flow characteristics of a pump-turbine during load rejection using the Quasi-static method. The study focuses on the flow patterns and axial hydraulic thrust. The results indicate that the unit operates in turbine, braking, and pumping modes during load rejection, with the streamline becoming chaotic. This complex flow pattern also leads to notable variations in the axial hydraulic thrust, ranging from -92t to 405t. The findings presented in this paper are valuable for ensuring the safety of pump-turbines and can serve as a reference for their optimization and operation.
Research on Radial Force of the Volute Pump with Stay Vanes at Medium-high Specific Speed
Authors: Zhang G , Feng J H , Su Y Y , Wu X D , Zeng G Y , Zhang T 
Published: June 2024

Abstract
In this paper, to study unsteady hydraulic excitation characteristics of the impeller in stay vane volute pump, the radial force of that is investigated by vector analysis, time-frequency analysis and unsteady flow field analysis etc. Results show that the radial force distribution on the impeller has a linear relationship with the number of the blade under high flow conditions. Furthermore, the radial force has obvious directivity under low flow conditions. The radial force of the impeller is mainly distributed on the blade and the shroud. Interestingly, it is found that the radial force on the impeller is smaller than the radial force on the blade and shroud respectively, when there are cross peaks between the blade and the shroud. In addition, the results of the unsteady flow field analysis reveal that the radial force distribution of the impeller is unbalanced under low flow conditions. This result is due to the fact that jet wake forms at the impeller outlet and radial vortex leads to rotating stall in the flow channel. This work may provide some theoretical references for the optimal design and stable operation of the stay vane volute pump.