bluuebunny/crossref_metadata_2025 huggingface dataset:
Current-perpendicular-to-plane transport properties of 2D ferromagnetic material CrTe2
Authors: Wang 王 Jin 瑾 , Liu 刘 Yu 宇 , Wang 王 Taikun 太坤 , Xu 徐 Yongkang 永康 , Wang 王 Shuanghai 双海 , He 何 Kun 坤 , Deng 邓 Yafeng 亚峰 , Yan 闫 Pengfei 鹏飞 , He 何 Liang 亮
Published: June 2024

Heterostructures of van der Waals (vdW) ferromagnetic materials have become a focal point in research of low-dimensional spintronic devices. The current direction in spin valves is commonly perpendicular to the plane (CPP). However, the transport properties of the CPP mode remain largely unexplored. In this work, current-in-plane (CIP) mode and CPP mode for CrTe2 thin films are carefully studied. The temperature-dependent longitudinal resistance transitions from metallic (CIP) to semiconductor behavior (CPP), with the electrical resistivity of CPP increased by five orders of magnitude. More importantly, the transport properties of the CPP can be categorized into a single-gap tunneling-through model with the activation energy (E
a) of ∼ 1.34 meV/gap at 300–150 K, the variable range hopping model with a linear negative magnetoresistance at 150–20 K, and weak localization region with a nonlinear magnetic resistance below 20 K. This study explores the vertical transport in CrTe2 materials for the first time, contributing to understand its unique properties and to pave the way for its potential in spin valve devices.
Corrigendum: Corrections to a proposal for three categories of units within the SI (2024 Metrologia 61 033001)
Authors: Lehman John , Migdall Alan , Scherschligt Julia , Whitehead Lorne
Published: June 2024

In this corrigendum, we correct several typographical or typesetting errors and small but meaningful errors in tables 1, A.1 and A.3 found in the original manuscript. We emphasize as a correction that the Avogadro constant is not a dimensionless number. The corrections are placed according to the original organization: section 2, references, and appendix.
Stability analysis of a hydropower plant containing pipe and channel flows
Authors: Zheng Yang , Liu Wanying , Chen Jinbao , Chen Qijuan , Xiao Zhihuai
Published: June 2024

This work studies the operational stability of the tailrace network containing mixed types of flows in a hydropower station with the complex frequency-domain networked transfer matrix method. First, the networked transfer matrix of the system plant is built based on the dynamic equations of the pipes, channels and hydraulic boundaries in the system. Then, the model is applied to analyze the stable state of the water conveyance network of a hydropower plant located in southwest China. The values of hydraulic state variables at the critical stable point under the multi-machine operating condition are obtained via eigenvalue analysis. The proposed overall transfer matrix model is proved to achieve satisfactory performance by the comparison of the statistic indexes obtained from modeling computation and those from the measured data.
Research on incipient and critical cavitation of a Francis turbine
Authors: Yang Jing , Yao Liang , Liu Jie , Yue Bo , Ma Zhe , Sun Yong , Wang Zhengwei
Published: June 2024

Cavitation is an important performance index to evaluate the comprehensive performance of hydraulic turbine. Determination of the plant cavitation coefficient is one of the most important tasks in the design phase of a hydro-power station. In order to improve the design rationality of the cavitation coefficient, numerical simulations of a Francis turbine were carried out to study the cavitation evolution characteristics. A detailed comparative analysis were made to clarify the different cavitation coefficients and impacts on the Francis turbine. Discussions on plant cavitation coefficient selection of hydro-power plant were made form the perspective of cavitation influence on the unit. Based on these investigations, it can be concluded that a certain safety margin of incipient and critical cavitation coefficient were needed considering the rapid efficiency drop near the critical cavitation and serious pressure pulsation near the incipient cavitation condition. The ratio between the plant cavitation coefficient and critical cavitation of the studied Francis turbine were larger than the current standard in China, which means the good cavitation performance of the unit after it put into operation. This study can provide a reference for determining the cavitation coefficient more accurately and ensuring the operation safety of the unit.
Design of Pelton Turbine Test Stand in Plateau Environment
Authors: Cai Jinhan , Zhou Xuejun , Luo Hongying , Wang Zhengwei
Published: June 2024

In recent years, with the continuous development of China’s hydropower projects, Pelton turbines are gradually being valued, and the focus of development has shifted from plain areas to plateau areas. Environmental impacts such as high altitude, water temperature, and high sediment content in the plateau area have caused serious interference to equipment that originally worked in a stable environment, for example, the failure of the cooperation between the parts of the turbine and the mutual seizure, the increased wear of the nozzle needle, the decrease of the flow rate and the water outlet speed of the nozzle, and the decrease of the air pressure in the plateau environment lead to the change of the flow state of the nozzle. In view of the above problems, this paper puts forward the design scheme of impulse turbine test-bed, using the method of changing specific speed to determine the basic parameters of impulse turbine unit, so as to eliminate the influence of plateau environment on the normal operation of turbine, obtain the efficiency condition of model experiment under low ambient pressure, and improve the operation efficiency and reliability of turbine unit.
Investigation on large fluctuation transient process of high head Pelton turbine
Authors: Gao J , Han L , Wang H J , Liu Y X , Wei X Z , Qin D Q
Published: June 2024

With the development of hydropower in southern western China, the Pelton turbine is the only choice in this ultra-high head condition which is nearly 1000 m. However, the complex coupling structure of the internal and external flow of the Pelton turbine, the change of flow pattern during the transition process, and the fluid-solid interaction of the bucket greatly increases the difficulty of accurate numerical simulation. Therefore, there are relatively few studies and applications on the transition process of the Pelton turbine. In this paper, the theoretical analysis, numerical calculation on the internal complex flow and the external characteristics of the turbine during the large fluctuation transition process are carried out in three aspects. First, the internal flow mechanism under optimized conditions is investigated, such as Dean vortex pairs, secondary flow, etc. And then analyze the influence of the flow state distribution on the jet flow. Secondly, study the instability and flow characteristics in the large fluctuation transition process of the opening and closing process of the nozzle, and predict the mechanism of the jet flow and the impact on the bucket during the dynamic process. Finally, study change of the hydraulic characteristics under the dynamic process which provides a theoretical guarantee for the safe operation of the Pelton turbine.
Investigation on formation mechanism of cavitation channel vortex in the runner of Francis turbine
Authors: Wu Guangkuan , Xue Qiyao , Guan Ziwu , Guojun Zhu , Feng Jianjun
Published: June 2024

Cavitation channel vortices generally cause flow state more complex in the runner, leading to the work efficiency is reduced and the cavitation erosion on flow components is enhanced. In this paper, simulation of cavitation flow is carried out for a Francis turbine model, and the evolution of vortices in the runner during cavitation development is analyzed under partial load conditions. The results show that cavitation has a great influence on the morphology and distribution of attached vortices between blades, trailing vortices at the outlet edge of the blades, and vortex near the cone in the runner. With the gradual development of cavitation, the invasion effect of vortex rope in draft tube on the runner is enhanced, and the vortex near runner cone is gradually connected as a whole. Under the effect of the downstream reverse pressure gradient in local low-pressure area, the flow separation area gradually expands to the blade and upstream, and more singular points evolve on flow separation lines, which leads to more trailing vortices at the outlet of the blade and cavitation channel vortices are formed in serious cavitation stage.
The influence of guide vane opening on internal cavitation of Francis turbine
Authors: Chen Minjia , Luo Xingqi , Feng Jianjun , Lv Siqin
Published: June 2024

In response to the theme of national multi energy complementary power grid construction, hydropower stations need to frequently change the opening of active guide vanes. Operation deviates from the rated working condition. And output is adjusted to meet the flexible power demand of users. Cavitation phenomenon as the biggest problem restricting the eccentric operation of Francis turbine. Easily induce cavitation damage to the flow passage components of the unit and shorten the service life of the unit. Therefore, there is a good engineering research background for the cavitation characteristics inside Francis turbines in the process of exploring the variation of guide vane opening. This paper takes a high head Francis turbine as the research object, based on numerical simulation and model test. The results show that the maximum amplitude of the draft tube vortex gradually increases during the process of decreasing the opening. The degree of cavitation is gradually serious, and the streamline distribution of the flow field inside the impeller is uneven. As the opening of the guide vane gradually increases, the vortexof the draft tube gradually decreases. The cavitation degree is weakened, and the streamline distribution inside the impeller is significantly improved. With the increase of the guide vane opening, the low-speed area on the outlet surface of the impeller gradually decreases, resulting in a gradual reduction of the low-speed zone in the straight cone section of the draft tube, a smaller vortex, a weaker cavitation degree. The internal flow distribution of the impeller is significantly improved.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Numerical Investigation on internal flow characteristics of a mixed-flow pump with Tandem malposed blades
Authors: Chenhao Li , Xingqi Luo , Xitong Wu , Guojun Zhu , Like Wang , Xiaohang Wang
Published: June 2024

Mixed-flow pump plays an important role in national major projects and national economic construction. In this paper, a mixed-flow pump is taken as the research object, and the internal flow characteristics and the distribution of turbulent kinetic energy in the pump under different malposed angles of blade are studied by using numerical simulation and blade modification method. The results show that the pump efficiency and head are higher when the tandem blade angles (α) are 15° and 45°, and the pump head is the largest at the α =15°, increasing by 4.37%. Meanwhile, the high-pressure area inside the impeller was large, which had a higher pressurization performance. Under the rated flow condition, the velocity curve of α =15° changes most gently, which is close to the prototype velocity curve, and the single hump zone is not obvious. The tandem malposed blades can restrain the velocity fluctuation and improve the flow field in the impeller. At α =45°, the turbulent kinetic energy dissipation and the velocity fluctuation were the smallest; the flow field was the most stable. The research results have reference significance for the optimal design and selection of mixed flow pump.
Analysis of the Bubble Diameter Effect on the Gas-liquid Flow Characteristics of a Multiphase Rotodynamic Pump
Authors: Li Zhihao , Zhang Wenwu , Zhu Baoshan , Lu Jiaxing , Zhao Haoru
Published: June 2024

In order to study the effect of bubble diameter on the gas-liquid flow in the multiphase rotodynamic pump, steady simulations with different bubble diameters were conducted using ANSYS CFX17.0. When the inlet gas content IGVF is 10%, the pump head and efficiency decrease with the increased inlet bubble diameters, and there are different downward trends at different stages of bubble diameter increase. The pump head and efficiency with small bubble diameter (d≤0.3 mm) are much higher than those of large bubble diameter(d≥0.4 mm). A small amount of gas accumulates on both the blade suction and pressure surfaces near the hub under conditions of small bubble diameters. When the bubble diameter is large, A large amount of gas accumulates on the blade suction surface, and almost no gas accumulates on the blade pressure surface. Due to the density difference between gas and liquid phases, gas accumulates near the hub. The gas content rapidly decreases when away from the hub under small bubble diameter conditions, resulting in good gas-liquid fluidity and weak gas-liquid separation.
Erosion characteristics of a centrifugal pump based on rosin-rammler distribution of particles
Authors: Zhang Haili , Chen Mendi , Xia Guosheng , Tan Lei
Published: June 2024

Centrifugal pumps are widely used in water conservancy, agricultural irrigation and petrochemical fields, but the transferred fluid usually contains solid particles. With prolonged operation in a solid-liquid flow, the components of centrifugal pump are easily eroded, resulting in damaged components, shortened life and reduced efficiency. It is crucial to study the erosion characteristics on centrifugal pump in solid-liquid flow. In this work, based on the particles with Rosin-Rammler distribution in a pump station, the transient operation and erosion process of the centrifugal pump under sandy flow are simulated by using the Eulerian-Lagrangian method and Oka model. Results show that the erosion of R-R distribution is characterized by both large and small particle sizes, but it is closer to the latter condition due to the higher proportion of small particle sizes. The distribution ratio of average erosion rate on hub, blade and shroud is 1.18: 1.68: 1.00, and the most eroded areas are in the leading edge of blade and the trailing edge of the blade suction surface.
Research on the temperature field of a horizontal reactor coolant pump canned motor
Authors: Chen X H , Xu R , Lu J Q , Gong B , Wang D Z
Published: June 2024

The temperature of the flywheel and rolling bearing is a key factor in the stability and safety of the canned motor reactor coolant pump(RCP). The horizontal Canned motor reactor coolant pump (HRCP) is the guarantee of the small modular reactor (SMR) security. HRCP is smaller than traditional RCP, The design of heat shield and flywheel cooling channel reduce the temperature of the flywheel and rolling bearing. In order to calculate the cooling performance of the above two structures. Based on the model,a thermal-fluid-solid coupling method has been used to investigate the safety of the HRCP. Results show that the temperature of the water-lubricated rolling bearing is lower than the allowable temperature; but the temperature of the flywheel is too high. In order to reduce the flywheel temperature, the author proposes a new flywheel cooling channel.it is found that this structure has an obvious effect on reducing the flywheel temperature. This structural design provides a reference for the improvement of the canned motor RCP and the optimization of the flywheel design.
Numerical simulation of start-up and shutdown transient processes of super large flow and high-power centrifugal pump
Authors: Xia Guosheng , Ma Anting , Zhao Xuechu , Fan Honggang , Xu Yu
Published: June 2024

During start-up and shutdown processes, the transient flow of centrifugal pump is complex, which significantly affects the safe and stable operation of the entire pump station. In this paper, considering the effect of the transient process of the pump station, the start-up and shutdown transient processes of a large flow and high-power centrifugal pump was numerically simulated by use of STAR CCM+. The evolution of flow field in the volute and impeller was analyzed. The results show that the flow field of the impeller is filled with complex vortex structures of varying sizes at the beginning of the start-up process of a water pump. As the flow-rate increases, the fluid flow gradually tends to stabilize. During the shutdown process of the water pump, as the flow-rate decreases, the flow field vortices increase progressively, and the flow pattern is unstable. The research results provide a basis for the operation strategy of super large flow and high-power centrifugal pump.
Characteristic analysis of pressure fluctuation of the super large flow and high-power centrifugal pump during transient processes of the start-up and shutdown
Authors: Liu Shuai , Ma Anting , Zhao Xuechu , Fan Honggang , Xu Yu
Published: June 2024

The transient flow field of a super large flow and high-power centrifugal pump during start-up and shutdown is relatively complex and related to the safe and stable operation of the entire water conveyance system. In this study, we conducted a deep analysis of the start-up and shutdown transient processes of a large flow and high-power centrifugal pump. To realize the numerical simulation for the start-up and shutdown transient processes, we used the fluid dynamics calculation and analysis software STAR CCM+. The pressure at multiple monitoring points in the impeller, between stay vanes and impeller, volute, and suction pipe was monitored. In addition, FFT analysis method was used to conduct frequency domain analysis of the pressure at the monitoring points. The changing trend of pressure fluctuation mixing amplitude in the transient processes was discussed. This study provides scientific basis for the safe and stable operation of pump stations.
Experimental and numerical study on erosive wear in a dredge pump impeller
Authors: Guo T , Wang W , Cao L , Xing J
Published: June 2024

Experimental and numerical studies were carried out to study the serious erosive wear occurs in dredge pump impellers. The erosion rate model of medium coarse sand on high chromium cast iron was summarized from the test of gas driven sand impacting wet plate. During conveying tests in a pump-pipe model system, erosive wear in the impeller under the conditions of conveying dense flow of medium coarse sand was measured. A numerical method, in which multiple reference frames is used to treat the rotation of impeller domain and particle-wall reflection is implemented in relative reference frame, is applied to predict the particle trajectories in the model pump, and the erosion wear on the impeller is solved based on the erosion rate model. The wear predicted by numerical method is of the same order of magnitude as that predicted by experimental method, but is significantly lower than the latter. This may be due to the neglect of the wear in the disk clearance and the intensification of local wear caused by mold casting defects in the numerical prediction.
Analysis and application of suppression measures for protection misoperation caused by excitation inrush current of 15.75kV transformer
Authors: Dong J J , Yu T , Chen C J , Huang Y D , Zhong S H
Published: June 2024

This article briefly described the mechanism of transformer magnetizing inrush current, and introduced the principle of differential protection magnetizing inrush current suppression of Siemens 7UT682 protection device. Through the analysis and research of a differential protection malfunction trip event when a no-load closing power of a overhauled transformer, the method of optimizing the relevant parameter configuration of the protection device to avoid the excitation inrush current was proposed and achieved good application results.
A mechanism for efficiently controlling the safety risks of pumped storage power station construction
Authors: Wang H B , Zhang Z J
Published: June 2024

During the construction process of pumped storage power station, the management levels of the participating parties are uneven, and problems such as inaccurate risk identification and unreasonable control measures often occur, which affect the effective operation of the dual prevention mechanism. In order to improve the efficiency and effectiveness of risk management, the author has established a risk database covering the entire life cycle of engineering construction based on the recognition of dangerous and harmful factors in the construction process of pumped storage power station. This greatly enhances the comprehensiveness of risk identification and the effectiveness of measures. At the same time, based on the reasonable allocation of risk management resources according to the task level, information technology tools are used to approve and publish construction work plans, timely release, track and close-loop risk management tasks. Through online processes, the investigation and rectification of hidden dangers are automatically counted, analyzed and tracked, thereby reducing the risk level, eliminating accident hidden dangers, and improving work efficiency.
Mechanism study on the control of cloud cavitation by leading-edge tubercles on NACA0015
Authors: Zhao G S , Liang N , Cao L L , Wu D Z
Published: June 2024

In order to control cloud cavitation, the bio-inspired leading-edge tubercles are implemented on a NACA0015 hydrofoil. The cavitation experiments in a water tunnel are conducted to elaborate on the dynamic behaviors and control mechanisms. As observed, the cavitation with a mean length of 0.38 times chord length on baseline hydrofoil performs three-dimensional features and multiple shedding by the re-entrant jet impingements. Under the equivalent cavitation condition on LET hydrofoil, the cavities with a frothy appearance are produced and confined within the troughs, and the large-scale shedding and re-entrant jet are not identified. The proper orthogonal decomposition (POD) based on cavitation images is carried out to extract the dominant shedding structures. The leading modes of POD on baseline hydrofoil dictate the main shedding of cloud cavitation. The lateral cavities on the LET hydrofoil are well separated by the spanwise periodic tubercles and then the dominant POD modes appear as small-scale vortex pairs. The leading-edge tubercles could depress the three-dimensional cloud cavitation and the re-entrant jets, which is a promising method to control cavitation unsteadiness in hydraulic machinery.
Optimization of rotor blind hole parameters for inner-hole rotary cavitator
Authors: Li Dawei , Yang Yingjie , Ge Ning , Han Guihua , Zhu Yipeng , Jin Di
Published: June 2024

In order to study the cavitation characteristics of rotary cavitator and the optimization of blind hole parameters, this paper first deduces the blind hole geometric parameters (aperture, hole depth, and number of holes) that affect the cavitation effect, then uses a numerical simulation method to optimize the blind hole parameters that affect the cavitation effect based on the control variable method and gas phase contour. Using single factor analysis as the optimization criterion and gas phase volume as the optimization basis, the response surface method was applied to the multi-parameter optimization problem with interaction. The results indicate that the intensity of cavitation can be effectively increased by increasing the geometric dimensions of the blind holes’ diameter, depth, and number appropriately. On the other hand, the response surface method can be utilised to study the multi-parameter optimization problem in the multivariable system comprised of the geometric parameters of the blind hole of the cavitator rotor. This paper’s optimization research on the rotor parameters of inner-hole rotary cavitator provides a foundation and reference for future cavitator structure optimization research.