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Advances in Pumped Storage Hydraulic System

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A3: Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: closed (15 August 2022) | Viewed by 21810

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Special Issue Editors

Dr. Deyou Li

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Guest Editor

School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
Interests: hydraulic machinery; pump turbine; turbine; pump; turbopump; hydraulic instability; optimization strategy; transient process; flow control; cavitation flow; thermodynamic effects; stall control

Dr. Zhigang Zuo

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Guest Editor

State Key Laboratory of Hydro Science and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100085, China
Interests: hydro pump; fluid mechanics; fluid engineering; cavitation; bubble dynamics; hydraulic stability of hydraulic machinery

Prof. Dr. Pengcheng Guo

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Guest Editor

State Key Laboratory of Eco-hydraulics in Northwest Arid Region, School of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an 710048, China
Interests: hydraulic machineries; transient process; Vibrations and resonance; Energy storage and flexibility; computational fluid dynamics

Prof. Dr. Yongguang Cheng

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Guest Editor

State Key Laboratory of Water Resources and Hydropower Engineering Science, School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430072, China
Interests: transition process of hydraulic machinery and system; numerical simulation of complex flow field of hydropower engineering; pumped storage power generation technology; computational fluid dynamics
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Special Issue Information

Dear Colleagues,

In view of the threat of global warming due to excessive carbon emissions, new technologies for energy production and utilization have been proposed and applied around the world, which includes the rapid development of renewable energy sources such as solar energy, wind energy, hydropower, biogas, and biomass energy. The intermittent nature of most renewable energy sources, however, brings about new challenges related to the load balance and stability maintenance of the electrical grid. Energy storage units offer such solutions. At present, pumped storage remains the only grid-scale technology, characterized by its economics, technical maturity, and flexible start-up procedures. As a result, pumped storage hydropower stations have been widely used to perform peak, frequency, and phase regulations in electric grids.

This Special Issue contributes to recent achievements in the study of pumped storage hydraulic systems, including advances in analytical methods and numerical and experimental technologies. The main topics of interest include but are not limited to transient hydraulic instability of pumped storage hydraulic systems, intelligent optimization of hydraulic systems, hydraulic instability of pump turbines, hydraulic optimization of pump turbines, and the development of pumped storage hydraulic systems. In addition, submissions describing other types of hydropower technology, including Francis turbines, Pelton turbines, and bulb turbines, are also welcome in this Special Issue.

We look forward to considering your submissions.

Dr. Deyou Li
Dr. Zhigang Zuo
Prof. Dr. Pengcheng Guo
Prof. Dr. Yongguang Cheng
Guest Editors

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Keywords

pumped storage system
pump turbine
transient process
hydraulic instability
hydraulic optimization
one- and three- dimensional coupling method
fluid–structure interaction (FSI)
variable speed pumped storage unit
super high head pump turbine

Published Papers (14 papers)

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Research

18 pages, 6910 KiB

Open AccessArticle

Optimization of Setting Angle Distribution to Suppress Hump Characteristic in Pump Turbine

by Yonglin Qin, Deyou Li, Hongjie Wang and Xianzhu Wei

Energies 2023, 16(5), 2471; https://0-doi-org.brum.beds.ac.uk/10.3390/en16052471 - 05 Mar 2023

Cited by 3 | Viewed by 938

Abstract

Pump turbines play a quite important role of peak-valley shifting in the grid, and the hump margin is a critical criterion related to the safety and stability of operation in pump mode. Aiming at investigating the influence of runner outlet setting angle distribution on hump performance of a pump turbine, three runners with different linear distributions of setting angle at outlet were proposed, and the corresponding hump performance comparison was analyzed numerically through the SST k-ω turbulent model. The numerical result shows that, compared to the experiment, the relative errors of all simulated performances (energy characteristic, torque characteristic, and efficiency) were within 3%. Moreover, it was found that setting angle distribution modes could lead to a remarkably different performance in the hump region and, for the runner whose setting angle at shroud was 10° larger than that at hub, the hump safety margin could be increased from 4% to 4.5%. Thereafter, the corresponding mechanisms including energy input and hydraulic loss were investigated through the Euler head theory and the entropy method, respectively. It was found that hydraulic loss distribution played a more important role than the input energy on controlling hump performance. Moreover, for the runner with the largest hump margin, the hydraulic loss was distributed more evenly in the decreasing discharge direction, contributing to the elimination of hump performance. In addition, hydraulic loss distribution was calculated through local entropy production rate (LEPR) method. For all proposed runners, when the pump turbine entered the hump region from a normal operation point, the hydraulic loss was mainly concentrated in vaneless areas and guide/stay vane channels, while the runner with a large setting angle at shroud could better control the hydraulic loss distribution in both the spatial location and the discharge varying direction, increasing the hump margin. The design method presented in our paper is more likely to be applied in engineering applications. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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21 pages, 4870 KiB

Open AccessArticle

Numerical Investigation of Tip Leakage Vortex Cavitating Flow in a Waterjet Pump with Emphasis on Flow Characteristics and Energy Features

by Shujian Lv, Xincheng Wang, Huaiyu Cheng and Bin Ji

Energies 2022, 15(19), 6916; https://0-doi-org.brum.beds.ac.uk/10.3390/en15196916 - 21 Sep 2022

Cited by 3 | Viewed by 1335

Abstract

The Delayed Detached Eddy Simulation (DDES) turbulence model was coupled with a homogeneous cavitation model to analyze the tip-leakage vortex (TLV) cavitating-flow characteristics in a waterjet pump. The numerical results agree well with experimental data. The results show that the vortex evolution in the waterjet pump has three stages, which is similar to that around a hydrofoil, but the vorticity variations in the waterjet pump are more complicated. The relative-vorticity-transport equation was then applied to find the reason for the differences between the vorticity variation observed in the waterjet pump and that around a hydrofoil. The results indicate that the drastic fusion process of the TSV cavity and the TLV cavity in the waterjet pump resulted in the formation of triangular cavitation region near the blade tip that is difficult to reproduce by stationary hydrofoil simulation. This fusion process caused the local variation of fluid volume and further affected the vorticity transport. The entropy-production evaluation method considering the phase transition was then used to analyze the dissipation losses in the complex cavitation region. The results indicate that the drastic fusion process of the TSV cavity and the TLV cavity significantly influenced the entropy production rate distributions and enhanced the disturbance of the flow field. In addition, severe phase transition occurs in the drastic fusion region accompanied by huge phase-transition losses. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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18 pages, 2956 KiB

Open AccessArticle

Influence of the Gas Model on the Performance and Flow Field Prediction of a Gas–Liquid Two-Phase Hydraulic Turbine

by Shuaihui Sun, Pei Ren, Pengcheng Guo, Longgang Sun and Xiaobo Zheng

Energies 2022, 15(17), 6325; https://0-doi-org.brum.beds.ac.uk/10.3390/en15176325 - 30 Aug 2022

Viewed by 999

Abstract

A two-phase hydraulic turbine’s performance and flow field were predicted under different Inlet Gas Volume Fractions (IGVF) with incompressible and compressible models, respectively. The calculation equation of equivalent head, hydraulic efficiency, and flow loss considering the expanding work of compressible gas were deduced based on the energy conservation equations. Then, the incompressible and compressible results, including the output power and flow fields, are compared and analyzed. The compressible gas model’s equivalent head, output power, and flow loss are higher than the incompressible model, but the hydraulic efficiency is lower. As the IGVF increases, the gas gradually diffuses from the blade’s working surface to its suction surface. The gas–liquid separation happens at the runner outlet in the compressible results due to the gas expansion. The area of the low-pressure zone in the incompressible results increases with the IGVF. However, it decreases with the IGVF in the compressible results. As the gas expands in the blade passage, it takes up more flow area, causing the high liquid velocity in the same passage. The runner’s inlet gas distribution affects the liquid flow angle, causing the inlet shock and high TKE areas, especially in the blade passage near the volute tongue. The high TKE area in the compressible results is larger than the incompressible results because the inlet impact loss and the liquid velocity in the blade passage are higher. This paper provides a reference for selecting gas models in the numerical simulation of two-phase hydraulic turbines. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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20 pages, 47817 KiB

Open AccessArticle

Numerical Simulation Analysis on Hydraulic Optimization of the Integrated Pump Gate

by Songbai Li, Changrong Shen, Tao Sun, Li Cheng, Shuaihao Lei, Chenzhi Xia and Chenghua Zhang

Energies 2022, 15(13), 4664; https://0-doi-org.brum.beds.ac.uk/10.3390/en15134664 - 25 Jun 2022

Cited by 1 | Viewed by 1026

Abstract

Based on the Reynolds time mean N-S equation and standard k-ε turbulence model and using Computational Fluid Dynamics technology, this study aims to integrate the brake pump to carry out numerical simulation. Through the adoption of different arrangements of impending height and spacing, the hydraulic characteristics of the full tubular pump unit are analyzed. The two-dimensional streamline, velocity and pressure distribution, and three-dimensional streamline, axial velocity and vorticity distribution of the front pool of each scheme are displayed. The results show that the recommended pump installation height is 0.8 D_d, the maximum limit value of the pump station design specification; in the dual-pump mode, the recommended pump spacing is 2.00 D_s. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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19 pages, 7200 KiB

Open AccessArticle

Dynamic Response Analysis of Dual-Flow Channel Pump Station Structure under Water Pressure Pulsation

by Chengcheng Hou, Li Cheng, Weifeng Pan, Songbai Li and Weixuan Jiao

Energies 2022, 15(10), 3770; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103770 - 20 May 2022

Cited by 1 | Viewed by 1013

Abstract

The RNG k-ε model turbulence model is used to carry out a CFD numerical simulation of the dual-flow channel pumping station. Through the model test, the accuracy of the numerical simulation of the dual-flow channel pump device is verified. Using the harmonic response analysis method, the water pressure fluctuating load calculated under different startup conditions under the design water level is applied to the pumping station. In this way, the dynamic response law of the pump station structure under the action of water pressure pulsation is studied. The calculation results show that the values of pressure pulsation in the drainage condition and the water diversion condition are relatively close, and the main difference is the difference in the water levels of the inlet and outlet water. Under different working conditions, the amplitude of the pumping station building basically shows the characteristics that the vertical amplitude is greater than the horizontal amplitude. The maximum dynamic displacement under drainage condition is greater than that under the diversion condition, and the maximum dynamic displacement appears at the control gate. Under the three working conditions, the maximum dynamic stress of each characteristic part of the pumping station building is low. The maximum total dynamic stress under the drainage condition is greater than that under the diversion condition. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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18 pages, 5936 KiB

Open AccessArticle

Oscillation of Cavitating Vortices in Draft Tubes of a Simplified Model Turbine and a Model Pump–Turbine

by Sergey Skripkin, Zhigang Zuo, Mikhail Tsoy, Pavel Kuibin and Shuhong Liu

Energies 2022, 15(8), 2965; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082965 - 18 Apr 2022

Cited by 5 | Viewed by 1571

Abstract

The self-oscillation of the cavitating vortices is one of the dangerous phenomena of hydraulic turbine operation near full-load conditions. This work is an attempt to generalize data and expand insight on the phenomenon of self-excited oscillations by comparing the experimental results obtained on a simplified turbine and scaled-down pump–turbine models. In both cases, a series of high-speed imaging was carried out, which made it possible to study these phenomena with high temporal resolution. The high-speed imaging data was subjected to additional processing such as binarization, cropping, and scaling. For a simplified turbine model, the volume of the vapor cavity was calculated based on the assumption of the axial symmetry of the cavity, after which fast Fourier transform (FFT) analysis was carried out. A proper orthogonal decomposition (POD) analysis was also performed to examine individual modes in the original digital imaging data. For the pump–turbine, visualization data on the cavitation cavity oscillations were supplemented by pressure measurements in the draft tube cone to determine the frequency characteristics. Based on obtained experimental data, an improved one-dimensional model describing the oscillations of the cavitation cavity arising behind the hydraulic turbine runner is proposed. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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19 pages, 7965 KiB

Open AccessArticle

Study on Fiber Clogging Mechanism in Sewage Pump Based on CFD–DEM Simulation

by Shuihua Zheng, Chaojie Yang, Chaoshou Yan, Min Chai and Zenan Sun

Energies 2022, 15(5), 1598; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051598 - 22 Feb 2022

Cited by 2 | Viewed by 1821

Abstract

A large number of solid particles and fibrous impurities are always entrained in the fluid transported by a sewage pump, which can easily lead to the blockage of the sewage pump. In view of this, CFD–DEM simulations were conducted in this paper to reveal the fiber clogging mechanism in the sewage pump. A CFD–DEM coupling method with a fiber model was established and verified by an experimental benchmark, i.e., the rectangular flow channel. The method was then applied to a model sewage pump to, after mesh independence tests, analyze the effects of flow rate and fiber length on fiber motion and clogging. The results showed that the position of fiber retention coincides with the position of the vortex, mainly located at the inlet of the impeller, the head of the blade, the middle of the blade, and the tongue in the pump. In the case of a low flow rate, the fiber was more likely to cause blockage in the head of the blade, and in the case of a large flow rate, the fiber would wind around the tongue in the pump. At the same flow rate, long fiber was more likely to stay on the blade’s suction surface. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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19 pages, 8859 KiB

Open AccessArticle

Three-Dimensional CFD Simulations of Start-Up Processes of a Pump-Turbine Considering Governor Regulation

by Zhiyan Yang, Yongguang Cheng, Ke Liu, Xiaoxia Hou, Xiaoxi Zhang, Xi Wang and Jinghuan Ding

Energies 2021, 14(24), 8507; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248507 - 16 Dec 2021

Cited by 2 | Viewed by 1749

Abstract

The pumped-storage power station is an efficient stability regulator of the power grid. However, due to the instability of the pump-turbine in the S-shaped characteristic region, rotational speed fluctuation is easy to occur in the speed no-load condition, making synchronization with and connection to the grid difficult. To investigate the key factors of these difficult grid connections, the start-up processes of a practical pump-turbine under the lowest head condition were simulated by using the three-dimensional CFD method, in which the governor regulating equations with different regulating parameters were integrated successfully. The results show that the working points oscillate with the fluctuations of rotational speed, discharge, and torque, and different regulating parameters have a significant influence on the dynamic histories. In addition, the internal flow patterns, especially the backflows at the runner inlet, keep apparent values at the middle span (0.5 span) but have regular transitions near the shroud side (0.7–0.8 span). The faster the guide vanes adjust, the faster the backflows change, and the larger the macro parameters fluctuate. Overall, the instability of the start-up is the result of the periodical evolutions of backflows at the runner inlet, because the trend and period of the radial velocities at different inlet span locations are consistent with those of the discharge. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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18 pages, 5730 KiB

Open AccessArticle

Verification and Validation of Large Eddy Simulation for Tip Clearance Vortex Cavitating Flow in a Waterjet Pump

by Chengzao Han, Yun Long, Mohan Xu and Bin Ji

Energies 2021, 14(22), 7635; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227635 - 15 Nov 2021

Cited by 7 | Viewed by 1387

Abstract

In this paper, large eddy simulation (LES) was adopted to simulate the cavitating flow in a waterjet pump with emphasis on the tip clearance flow. The numerical results agree well with the experimental observations, which indicates that the LES method can make good predictions of the unsteady cavitating flows around a rotor blade. The LES verification and validation (LES V&V) analysis was used to reveal the influence of cavitation on the flow structures. It can be found that the LES errors in cavitating region are larger than those in the non-cavitating area, which is mainly caused by more complicated cavitating and tip clearance flow structures. Further analysis of the interaction between the cavitating and vortex flow by the relative vorticity transport equation shows that the stretching, dilatation and baroclinic torque terms have major effects on the generation and transport of vortex structure. Meanwhile the Coriolis force term and viscosity term also exacerbate the vorticity transport in the cavitating region. In addition, the flow loss characteristics of this pump are also revealed by the entropy production theory. It is indicated that the tip clearance flow and trailing edge wake flow cause the viscous dissipation and turbulent dissipation, and the cavitation can further enhance the instability of the flow field in the tip clearance. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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21 pages, 134469 KiB

Open AccessArticle

Influence of Upstream Disturbances on the Vortex Structure of Francis Turbine Based on the Criteria of Identification of Various Vortexes

by Tao Guo, Lihui Xu and Wenquan Wang

Energies 2021, 14(22), 7626; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227626 - 15 Nov 2021

Cited by 6 | Viewed by 1777

Abstract

The inter-blade passage vortex, the vortex rope of the draft tube, and the vortex in the guide apparatus are the characteristics of flow instability of the Francis turbine, which may lead to fatigue failure in serious cases. In the current study, in order to accurately capture the transient turbulent characteristics of flow under different conditions and fully understand the flow field and vortex structure, we conduct a simulation that adopts sliding grid technology and the large-eddy simulation (LES) method based on the wall-adapting local eddy viscosity (WALE) model. Using the pressure iso-surface method, the Q criterion, and the latest third-generation Liutex vortex identification method, this study analyzes and compares the inter-blade passage vortex, the vortex rope of the draft tube, and the outflow and vortex in the guide apparatus, focusing on the capture ability of flow field information by various vortex identification methods and the unique vortex structure under the condition of a small opening. The results indicate that the dependence of Liutex on the threshold is small, and the scale range of the flow direction vortex captured by Liutex is wider, but the ability of the spanwise vortex is relatively weak. The smaller the opening, the more disorderly the vortexes generated in each component and the more unstable the flow field. In the draft tube, the original shape of the vortex rope is destroyed due to the interaction between vortexes. Under the condition of a small opening, an inter-blade passage vortex is generated, affecting the efficient and stable operation of the turbine. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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14 pages, 5958 KiB

Open AccessArticle

3D CFD Simulation of Phase Resonance in a Pump Turbine with an Acoustic Model

by Yujian Fang, Ping Huang, Shibing Jin, Demin Liu, Jinfeng Zhang and Shouqi Yuan

Energies 2021, 14(22), 7539; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227539 - 11 Nov 2021

Cited by 1 | Viewed by 1377

Abstract

In order to understand the complex nature of the system dynamic phenomena, such as the strong vibration and noise caused by blade passage in the pump turbine, a state-of-the-art three-dimensional (3D) compressible transient simulation would be desirable to study the problem in depth. This study investigated the phase resonance (PR) that occurred during a full-load operation in the turbine mode of a pump turbine on a prototype scale. As a first step, the wave reflection at the boundaries, and the influence of the timestep and sound speeds on the behavior of traveling pressure waves inside a spiral casing, were studied. It was found that nonreflective boundary conditions and an appropriately small timestep are critical to capturing the wave reflection and superposition process inside a spiral casing; a certain kind of direct PR risk was detected in its system design. The detected direct PR differed from the well-known PR with two features: firstly, it was almost independent of the sound speeds, and secondly, the pressure distribution over the spiral circumference varied among the amplitudes. The latter feature was caused by pressure waves at every stator channel induced by a rotor stator interaction (RSI). The 3D flow simulation with an acoustic model, which couples the RSI and PR phenomena, would predict better results for understanding the problem than the simplified one-dimensional (1D) method. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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19 pages, 10628 KiB

Open AccessArticle

Investigations on Pressure Fluctuations in the S-Shaped Region of a Pump–Turbine

by Hongjie Wang, Jianpeng Wang, Ruzhi Gong, Chaoying Shang, Deyou Li and Xianzhu Wei

Energies 2021, 14(20), 6683; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206683 - 15 Oct 2021

Cited by 5 | Viewed by 1396

Abstract

Hydraulic pumped storage is a special power generation and electricity shortage technology, which is usually operated with thermal power and nuclear power units, and plays a key role in ultra-high voltage and smart grid. Pressure fluctuations are the main reasons for the instability of the S-shaped region of pump–turbines, which seriously affects their lifespan and operation stability. To reveal the mechanism and propagation law of pressure fluctuations in the S-shaped region as well as numerical simulations at the turbine, the braking and the reverse pump operating conditions of a pump–turbine were carried out. Numerical results were validated using the performance experiments, and the generation mechanism and propagation law of pressure fluctuation were analyzed in detail. The analyses show that high-amplitude pressure fluctuations mainly occur in the braking and reverse pump operating conditions. Under the braking condition, a 0.49-f_n low-frequency pressure fluctuation was captured, which is caused by the rotation of the backflow in the vanes. Under the reverse pump condition, a 0.19-f_n low-frequency pressure fluctuation was confirmed, which is caused by the periodic rotation of the vortex between the vaneless space. This study has important guiding significance for practical engineering application. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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18 pages, 14675 KiB

Open AccessArticle

Comparative Analysis of Strength and Modal Characteristics of a Full Tubular Pump and an Axial Flow Pump Impellers Based on Fluid-Structure Interaction

by Lijian Shi, Jun Zhu, Li Wang, Shiji Chu, Fangping Tang and Yan Jin

Energies 2021, 14(19), 6395; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196395 - 06 Oct 2021

Cited by 9 | Viewed by 1753

Abstract

Fluid-structure interaction (FSI) was used to determine the structural mechanical characteristics of full tubular and axial-flow pumps. The results showed that as the flow rate increases, the total deformation and equivalent stress are significantly reduced. The max total deformation (MTD) and the max equivalent stress (MES) of the full tubular pump impeller occur on the outer edge of the blade. There are two stress concentrations in the full tubular pump impeller, one of which is located in the outlet area of the rim, and the other is located in the outlet area of the hub. However, the MES of the axial-flow pump appears in the center of the blade hub. The performance difference between the full tubular pump and the axial-flow pump is mainly caused by the clearance backflow. The natural frequency of the full tubular pump is lower than that of the axial-flow pump on the basis of the modal results. The MES of the full tubular pump is mainly concentrated at the junction of the blade and the motor rotor, and the max thickness of the rim is 6mm, which can be more prone to cracks and seriously affect the safety and stability of the pump. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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21 pages, 24343 KiB

Open AccessArticle

Investigation of Water Injection Influence on Cloud Cavitating Vortical Flow for a NACA66 (MOD) Hydrofoil

by Zhijian Li, Wei Wang, Xiang Ji and Xiaofang Wang

Energies 2021, 14(18), 5973; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185973 - 20 Sep 2021

Cited by 4 | Viewed by 1688

Abstract

Re-entrant jet causes cloud cavitation shedding, and cavitating vortical flow results in flow field instability. In the present work, a method of water injection is proposed to hinder re-entrant jet and suppress vortex in cloud cavitating flow of a NACA66 (MOD) hydrofoil (Re = 5.1 × 10⁵, σ = 0.83). A combination of filter-based density corrected turbulence model (FBDCM) with the Zwart–Gerber–Belamri cavitation model (ZGB) is adopted to obtain the transient flow characteristics while vortex structures are identified by Q criterion & λ₂ criterion. Results demonstrate that the injected water flow reduces the range of the low-pressure zone below 1940 Pa on the suction surface by 54.76%. Vortex structures are observed both inside the attached and shedding cavitation, and the water injection shrinks the vortex region. The water injection successfully blocks the re-entrant jet by generating a favorable pressure gradient (FPG) and effectively weakens the re-entrant jet intensity by 46.98%. The water injection shrinks the vortex distribution area near the hydrofoil suction surface, which makes the flow in the boundary layer more stable. From an energy transfer perspective, the water injection supplies energy to the near-wall flow, and hence keeps the steadiness of the flow field. Full article

(This article belongs to the Special Issue Advances in Pumped Storage Hydraulic System)

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