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6 pages, 172 KiB

Open AccessEditorial

Advances in Hydrodynamics of Water Pump Station System

by Changliang Ye, Yuan Zheng, Kan Kan, Ran Tao and Huixiang Chen

Water 2024, 16(10), 1430; https://doi.org/10.3390/w16101430 - 17 May 2024

Viewed by 1234

Abstract

As an indispensable part of water conservancy engineering construction, the importance of pumping stations is reflected in several aspects [...] Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

Research

Jump to: Editorial

14 pages, 17576 KiB

Open AccessArticle

A Study on the Transient Characteristics of the Power-Off Transition Process of a Double-Volute Centrifugal Pump

by Lifeng Lu, Ziwei Ren, Zhongzan Wang, Wenjie Zhou, Siwei Li, Jin Dai, Chunxia Yang and Mengfan Dang

Water 2024, 16(12), 1707; https://doi.org/10.3390/w16121707 - 15 Jun 2024

Viewed by 686

Abstract

A double-volute centrifugal pump is a very important pump type; the internal flow field of a centrifugal pump will change drastically during the transition process of power failure, which will affect the safety and stability of the pump’s operation. In this paper, the [...] Read more.

A double-volute centrifugal pump is a very important pump type; the internal flow field of a centrifugal pump will change drastically during the transition process of power failure, which will affect the safety and stability of the pump’s operation. In this paper, the CFD numerical simulation method is used, and the UDF procedure is developed to realize the continuous update of the impeller speed at each time step. The working parameters, such as the torque and flow rate at the instantaneous moment, are obtained through the sequential iteration of each small step, and a numerical simulation of the power-off transient is carried out on a double-volute centrifugal pump; additionally, the changes in the external characteristic parameters and the internal flow field of the centrifugal pump are analyzed in detail. The results show that the double-volute centrifugal pump experienced four different modes after power failure, namely pump mode, braking mode, turbine mode, and runaway mode, and the absolute values of the runaway speed and runaway flow rate are 1.465 times and 1.21 times the initial values, respectively. Through the analysis of the flow field in different regions, the change processes of the generation, development, and disappearance of the vortex at each position of the centrifugal pump are obtained, and the change and development processes of the internal velocity gradient of the centrifugal pump are obtained. In addition, it is found that the high-speed area located in the second volute runner is larger than that of the first volute runner because the second volute runner is shorter and narrower than the first volute runner. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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19 pages, 19954 KiB

Open AccessArticle

Internal Flow Characteristics of Centrifugal Pumps under Different Startup Combination Schemes

by Xiaobo Zheng, Wei Wang, Pengli Zhang, Yongjian Pu and Yaping Zhao

Water 2024, 16(8), 1087; https://doi.org/10.3390/w16081087 - 10 Apr 2024

Cited by 2 | Viewed by 1469

Abstract

Pump station engineering is a water conservancy project used for long-distance water transfer, irrigation and drainage, and urban living and industrial water supply. Centrifugal pumps are one of the main pump types commonly used in pumping stations, and their operation is of considerable [...] Read more.

Pump station engineering is a water conservancy project used for long-distance water transfer, irrigation and drainage, and urban living and industrial water supply. Centrifugal pumps are one of the main pump types commonly used in pumping stations, and their operation is of considerable importance for the safety, stability, and efficient operation of pumping stations. This paper takes a large pumping station with seven centrifugal pump units as the research object and combines experimental research and numerical simulation. The axial flow velocity uniformity, average cross-sectional deviation angle, and hydraulic loss of the pump inlet section are evaluated, and the internal flow characteristics of the pump under different startup combination conditions are analyzed based on entropy generation and vorticity. This study also explores the operational performance of the pump station under different startup combination conditions, revealing the mutual influence mechanism between different startup combinations of pump stations and the internal and external characteristics of centrifugal pumps and introducing the optimal startup combination scheme for the pump station system. Research results indicate that the difference in energy loss of centrifugal pumps under different startup combinations is mainly manifested in the impeller and guide vane flow channels. For the two existing inlet flow channel structures in the pump station, the unit effectively operates when the inlet flow channel is tilted to the left. The optimal startup combination method of the pump station under different startup combinations is determined. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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20 pages, 27903 KiB

Open AccessArticle

Study on Impeller Optimization and Operation Method of Variable Speed Centrifugal Pump with Large Flow and Wide Head Variation

by Yang Zheng, Long Meng, Guang Zhang, Peng Xue, Xin Wang, Chiye Zhang and Yajuan Tian

Water 2024, 16(6), 812; https://doi.org/10.3390/w16060812 - 9 Mar 2024

Cited by 3 | Viewed by 1780

Abstract

The benefits of variable speed centrifugal pumps include high stability, a broad operating range, and adjustable input power. In water distribution systems, the pump units are increasingly using variable speed technology. The energy-saving features and operational stability of the pump station are directly [...] Read more.

The benefits of variable speed centrifugal pumps include high stability, a broad operating range, and adjustable input power. In water distribution systems, the pump units are increasingly using variable speed technology. The energy-saving features and operational stability of the pump station are directly impacted by the hydraulic performance and the operation strategy. In this study, CFD numerical analysis and model tests were adopted to design and evaluate the hydraulic performance of the variable speed centrifugal pump with large flow and wide head variation in Liyuzhou Pump Station. Under the premise of ensuring the wide head variation, the optimized centrifugal pump met the requirements of hump margin and efficiency in the high head zone and the cavitation margin in the low head zone. The test results demonstrated that the operational range of the variable speed centrifugal pump was successfully widened by reasonable hydraulic parameters selection and impeller optimization. The safe and efficient operational range of the variable speed unit was determined by means of taking the performance requirements of the pump’s maximum input shaft power, cavitation characteristics and pressure fluctuation into consideration. The scientific and reasonable operational path to meet the various operation needs was also investigated and determined for the pump station’s actual operation needs. A high efficiency, safe operation, and a simplified control logic were achieved by using the operational path, which makes it a reasonable potential guide for hydraulic design and operational optimization of variable speed centrifugal pumps with large flow and wide head range. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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19 pages, 11278 KiB

Open AccessArticle

Numerical Investigation of Inner Flow Characteristics of a Prototype Pump Turbine with a Single Pier in Draft Tube at Part Load Conditions

by Haiping Hu, Ming Xia, Xianghui Song, Zhengwei Wang and Mu Qiao

Water 2024, 16(1), 13; https://doi.org/10.3390/w16010013 - 20 Dec 2023

Viewed by 1222

Abstract

Pump turbines operate under various off-design conditions, resulting in complex internal flow patterns. This study employs Reynolds-averaged Navier–Stokes (RANS) numerical methods to investigate the flow characteristics of a prototype pump turbine with a single draft tube pier in turbine mode, and then, the [...] Read more.

Pump turbines operate under various off-design conditions, resulting in complex internal flow patterns. This study employs Reynolds-averaged Navier–Stokes (RANS) numerical methods to investigate the flow characteristics of a prototype pump turbine with a single draft tube pier in turbine mode, and then, the flow characteristics inside the draft tube are discussed with emphasis. Asymmetry between the pier-divided draft tube passage flows is inevitable due to the elbow section’s curvature. Most of the fluid flows out of one passage, while vortex motion dominates the interior of the other one, resulting in completely different pressure fluctuation characteristics for the two flow passages. The large-flow passage is mainly characterized by the wide band in the frequency domain, corresponding to the recirculation zone, while some of the measured points in the low-discharge passage exhibit frequency splitting under kinematic progression. Further analysis demonstrates a low-frequency peak corresponding to the complementary shape between the vortex rope and the recirculation zone. This work elucidates the effects of the pier on the flow behavior and pressure fluctuation characteristics inside the draft tube and fills the research gap on piers in the field of pump turbines. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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16 pages, 5510 KiB

Open AccessArticle

Analysis of Stress Characteristics of a Vertical Centrifugal Pump Based on Fluid-Structure Interaction

by Siwei Li, Yongsha Tu, Changliang Ye, Hongyeyu Yan, Jin Dai, Mengfan Dang, Chunxia Yang, Yuan Zheng and Yongbiao Li

Water 2023, 15(24), 4269; https://doi.org/10.3390/w15244269 - 13 Dec 2023

Cited by 1 | Viewed by 1596

Abstract

Vertical centrifugal pumps play a crucial role in numerous water conservancy projects. However, their continuous operation can lead to the development of cracks or even fractures in some centrifugal pump blades, resulting in a substantial adverse impact on the operation of the pumping [...] Read more.

Vertical centrifugal pumps play a crucial role in numerous water conservancy projects. However, their continuous operation can lead to the development of cracks or even fractures in some centrifugal pump blades, resulting in a substantial adverse impact on the operation of the pumping station unit and jeopardizing safe production. This study employs the fluid-structure interaction method to comprehensively investigate the modal characteristics of the impeller, both in an air environment and immersed in water. Furthermore, the analysis of static and dynamic stress attributes is conducted. The natural frequency of the impeller when submerged in water is significantly lower than its frequency in an air medium, typically accounting for approximately 0.35 to 0.46 of the air-based natural frequency. There are conspicuous stress concentrations at specific locations within the system, specifically at the rounded corners of the blade back exit edge, the impeller front cover, the middle of the blade inlet edge, and the junction where the blade interfaces with the front and back cover. It is crucial to underscore that when the system operates under high-flow or low-flow conditions, there is a pronounced stress concentration at the interface between the impeller and the rear cover plate. Any deviation from the intended design conditions results in an escalation of equivalent stress levels. Through dynamic stress calculations during a single rotational cycle of the impeller, it is discerned that the cyclic nature of stress at the point of maximum stress is primarily influenced by the number of blades and the rotational velocity of impeller. This research carries significant implications for effectively mitigating blade fractures and cyclic fatigue damage, thereby enhancing the operational reliability of vertical centrifugal pumps in water conservancy applications. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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18 pages, 6328 KiB

Open AccessArticle

Comparison of Pressure Pulsation Characteristics of Francis Turbine with Different Draft Tube Arrangement Direction

by Tao Zhang, Zilong Hu, Xinjun Liu, Jiahao Lu, Xijie Song, Di Zhu and Zhengwei Wang

Water 2023, 15(22), 4028; https://doi.org/10.3390/w15224028 - 20 Nov 2023

Viewed by 1465

Abstract

Hydroelectric power generation is an important clean energy source, and the stability of water turbine operation determines the quality of hydro energy utilization. For hydro turbines, the layout direction of the draft tube is often only considered from a structural perspective, ignoring the [...] Read more.

Hydroelectric power generation is an important clean energy source, and the stability of water turbine operation determines the quality of hydro energy utilization. For hydro turbines, the layout direction of the draft tube is often only considered from a structural perspective, ignoring the hydrodynamic characteristics. This study adopts the computational fluid dynamics method and verifies the effectiveness of numerical simulation with experimental results, analyzing the influence of asymmetric draft tube layout direction on pressure pulsation of mixed flow turbine. The results show that under different working conditions, there is basically no difference in efficiency corresponding to different inclined directions of the draft tube, and the relative difference in performance values is less than 1%. From the perspective of internal flow, the working condition has a greater impact on the flow, and the draft tube tilt has a smaller impact. Under strong swirling flow conditions in the draft tube, the variational mode decomposition of pressure fluctuation is carried out. Research has found 7 characteristic frequency bands including 140 Hz, 80–90 Hz, 40–46 Hz, 5.5–6.5 Hz, 2.5–3 Hz, 1.67 Hz, and <1 Hz. The frequency of the dominant mode corresponding to the left tilt is higher, while the amplitude of the runner frequency is slightly lower. In general, left tilt is not only more suitable for unit layout but also has a better effect on draft tube pressure fluctuation, which is worthy of application in engineering. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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16 pages, 4184 KiB

Open AccessArticle

Study on the Cavitation Characteristics of Shroud Clearance in Prototype and Model of a Kaplan Turbine

by Yali Zhang, Wendong Luo, Tao Chen, Lingjiu Zhou and Zhengwei Wang

Water 2023, 15(22), 3960; https://doi.org/10.3390/w15223960 - 14 Nov 2023

Cited by 2 | Viewed by 1356

Abstract

Model tests and model calculations are the most basic means currently available to study the characteristics of the axial-flow pumps and Kaplan turbines in a systematic manner. Large and medium-sized turbine units and axial-flow pumps must rely on model tests and model calculations [...] Read more.

Model tests and model calculations are the most basic means currently available to study the characteristics of the axial-flow pumps and Kaplan turbines in a systematic manner. Large and medium-sized turbine units and axial-flow pumps must rely on model tests and model calculations to ensure the performances of prototype units before designing. The conversions between models and prototypes are mainly carried out through similarity criteria. However, it is difficult to meet all the similarity criteria in the model tests and the similarity conversions, and the hydraulic and cavitation performances of the model and the prototype are often different. In this paper, numerical calculations of shroud clearance cavitation are performed on both the prototype and model using different cavitation coefficients. The results indicate that the prototype and model have a similar clearance cavitation flow regularity when the cavitation coefficient changes, but they have different energy characteristics and cavitation characteristics. In cavitation conditions, the prototype has higher energy characteristics than the model and the critical cavitation coefficient is similar to the model. When the cavitation coefficient is higher than the critical cavitation coefficient, compared to the model, the blade cavitation performance of the prototype is worse, and the clearance cavitation and runner chamber cavitation are more serious. If the cavitation coefficient decreases to the device cavitation coefficient, the runner chamber of the prototype will cavitate, even though the model has not cavitated yet. The comparison of shroud clearance cavitation between the prototype and the model can be used as a reference for the accuracy of similarity conversion results between the model and the prototype. It also has a positive impact on the design and operation of the prototype. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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23 pages, 3943 KiB

Open AccessArticle

Fractional-PID and Its Parameter Optimization for Pumped Storage Units Considering the Complicated Conduit System

by Xuan Zhou, Yang Zheng, Bo Xu, Wushuang Liu, Yidong Zou and Jinbao Chen

Water 2023, 15(21), 3851; https://doi.org/10.3390/w15213851 - 4 Nov 2023

Cited by 1 | Viewed by 1449

Abstract

Speed governing control is significant in ensuring the stable operation of pumped storage units. In this study, a state-space equation mathematical model of the pumped storage governing system considering the complex hydraulic pipeline structure of the pumped storage plant is proposed to describe [...] Read more.

Speed governing control is significant in ensuring the stable operation of pumped storage units. In this study, a state-space equation mathematical model of the pumped storage governing system considering the complex hydraulic pipeline structure of the pumped storage plant is proposed to describe the system’s dynamic behaviors under small disturbance conditions. Considering the frequent operating condition transitions and the complicated nonlinear dynamic characteristics of the pumped storage units, the fractional-order PID (FOPID) scheme that possesses a higher degree of control freedom than the traditional PID scheme is discussed in detail. To optimize the control parameters of the unit governor, an improved gravitational search algorithm (IGSA) that combines the basic searching mechanisms of the gravitational search algorithm and chaotic search, elastic sphere boundary treatment, and elite guidance strategy is developed. Comparative studies have been carried out under frequency and load disturbance conditions. Simulation results indicate that the control performance of FOPID is better than that of PID under diverse operating conditions and the proposed IGSA has satisfactory parameter optimization capability. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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13 pages, 9237 KiB

Open AccessArticle

Numerical Study on the Influence of Combined Rectification Facilities on the Flow in the Forebay of Pumping Station

by Xiaobo Zheng, Pengli Zhang, Wenjing Zhang, Yue Yu and Yaping Zhao

Water 2023, 15(21), 3847; https://doi.org/10.3390/w15213847 - 3 Nov 2023

Cited by 5 | Viewed by 1291

Abstract

The flow pattern of the forebay of the pumping station has a considerable effect on the operating efficiency and stability of the pump unit. A good forebay flow pattern can enable the pump unit to improve efficiency and operating conditions. This study takes [...] Read more.

The flow pattern of the forebay of the pumping station has a considerable effect on the operating efficiency and stability of the pump unit. A good forebay flow pattern can enable the pump unit to improve efficiency and operating conditions. This study takes a large pumping station as the research object and considers two rectification schemes, namely, a single bottom sill and a “bottom sill + diversion pier”. Without rectification facilities under different start-up schemes, the forebay flow pattern after the addition of rectification facilities is calculated, and the influence of single and combined rectification facilities is analyzed. Results show large-scale undesirable flow structures such as backflow and vortex in the forebay of the original design that without rectification facilities and uneven flow distribution occurs in the operating unit. The addition of a bottom sill in the forebay can control the central water beam from the water diversion pipe. The flow is divided to spread to both sides of the forebay and can be rectified twice after installing the diversion piers. The combined rectifier facility of “bottom sill + diversion pier” is beneficial to disperse incoming flow and make the flow distribution of each unit more uniform. The backflow and vortex inside the forepond are basically eliminated, and the flow state of the forepond is significantly improved. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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24 pages, 9871 KiB

Open AccessArticle

Study on the Transient Flow Characteristics of a Hump Water Pipeline Based on the Random Distribution of Bubbles

by Qingbo Wang, Jianyong Hu, Mingming Song, Hui Shen, Yu Zhou, Dongfeng Li and Feng Xie

Water 2023, 15(21), 3831; https://doi.org/10.3390/w15213831 - 2 Nov 2023

Viewed by 1729

Abstract

Aiming at establishing the transient flow characteristics of gas–liquid two-phase flow in high-undulation water pipelines, based on the bubble distribution law measured using physical tests, the bubble distribution law function was input into the hump-pipe fluid domain model, and CFD numerical simulation was [...] Read more.

Aiming at establishing the transient flow characteristics of gas–liquid two-phase flow in high-undulation water pipelines, based on the bubble distribution law measured using physical tests, the bubble distribution law function was input into the hump-pipe fluid domain model, and CFD numerical simulation was carried out for different flow rates and different air contents. The CLSVOF two-phase flow model and the RNG k-ε turbulence model were used to analyze the flow pattern evolution and pressure pulsation propagation in the process of gas–liquid two-phase flow through a hump pipe. The results show that the bubble size has a lognormal distribution, the equivalent diameter is between 3 mm and 10 mm, and the evolution of the flow pattern in the hump pipe is complex and violent. In the horizontal pipe section, there are three main flow patterns: bubble flow, wavy flow and segment plug flow. In the vertical pipe, there are two main flow patterns, slug flow and churning flow, and the flow pattern is affected by the flow rate and the air content rate. When air bubbles or air pockets in the pipeline flow through a certain area, this leads to a steep increase and decrease in the pressure pulsation amplitude in the region, and the pressure fluctuation is extremely frequent. Compared with the water flow rate, the air content is the main factor affecting the relative pressure pulsation amplitude under the condition of a 0.15-air content operating mode, which is generally approximately two to six times that of the 0-air content operating mode. The results of the research should facilitate the prediction of stagnant gas pipeline system bursts and water hammer protection, providing a theoretical basis and calculation parameters. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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14 pages, 4719 KiB

Open AccessArticle

Investigation of the Internal Flow in a Francis Turbine for Comparing the Flow Noise of Different Operation Conditions

by Tao Zhang, Gensheng He, Weilong Guang, Jiahao Lu, Xijie Song, Di Zhu and Zhengwei Wang

Water 2023, 15(19), 3461; https://doi.org/10.3390/w15193461 - 30 Sep 2023

Cited by 2 | Viewed by 1399

Abstract

Francis turbines are commonly used for water energy utilization in medium- to high-head sections. The high head may cause strong flow-induced noise problems and adverse effects during operation. In order to explore the causes and specific locations of flow-induced noise, this study evaluated [...] Read more.

Francis turbines are commonly used for water energy utilization in medium- to high-head sections. The high head may cause strong flow-induced noise problems and adverse effects during operation. In order to explore the causes and specific locations of flow-induced noise, this study evaluated the flow-induced noise of a Francis turbine under different loads. By using computational fluid dynamics simulation methods and sound power level evaluation methods, flow-induced noise analysis could be performed based on turbulent flow simulations. By comparing experimental and simulated values, three different load conditions were selected located in the allowed, restricted, and prohibited regions. The results indicated that the flow state of the operating points in the allowed region was good and the flow-induced noise was low, except near the guide vane. The swirling flow in restricted and prohibited regions was strong; in particular, the flow-induced noise in the draft tube was relatively high. Overall, the local flow-induced noise of the runner blade inlet edge was the strongest, and the relationship between the flow-induced noise of the draft tube and the rotating flow was the strongest. The flow-induced noise near the guide vane was the most related to the opening angle, and the larger the opening angle, the greater the noise was. This study can assist in the diagnosis of Francis turbine noise problems and related low-noise design in engineering. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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17 pages, 6130 KiB

Open AccessArticle

A Field Investigation of Stability Characteristics of Pressure Fluctuation and Vibration in Prototype Pump Turbine at Multiple Working Points

by Haiping Hu, Ming Xia, Xianghui Song, Weiqiang Zhao, Wei Wang and Zhengwei Wang

Water 2023, 15(19), 3378; https://doi.org/10.3390/w15193378 - 27 Sep 2023

Cited by 2 | Viewed by 1197

Abstract

In practical operation, pump turbines typically operate far from their designed working points, which has a significant impact on the stability of the unit’s operation. In this paper, we conducted a field test to investigate the stability characteristics of prototype pump turbines at [...] Read more.

In practical operation, pump turbines typically operate far from their designed working points, which has a significant impact on the stability of the unit’s operation. In this paper, we conducted a field test to investigate the stability characteristics of prototype pump turbines at different working points. By adjusting the given power of the generator in a stepwise manner to control its working point, we obtained the statistical and spectral characteristics of pressure signals and acceleration signals. In turbine mode, the result shows that, at low, medium, and high power, the variation in pressure fluctuation characteristics is influenced by three different factors, while vibration generally reaches its maximum value at approximately 50 MW. In pump mode, variations in pressure were observed among different measurement points in the low-frequency range, and the characteristics of vibration acceleration were influenced by both the rotor–stator interaction (RSI) and the structural modal frequencies. We emphasized that the high-frequency bands have influences on the unit comparable in magnitude to those of the rotor–stator interaction, which has rarely been mentioned in previous studies. Through detailed testing and analysis of the unit’s actual operation, we can gain a better understanding of its behavior and performance in the turbine and pump modes, and these results hold significant importance for ensuring the stability and reliability of the unit. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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18 pages, 5975 KiB

Open AccessArticle

Comparative Analysis of the Hydrodynamic Performance of Dual Flapping Foils with In-Phase and Out-of-Phase Oscillations

by Ertian Hua, Linfeng Qiu, Rongsheng Xie, Zhongxin Su and Wenchao Zhu

Water 2023, 15(18), 3275; https://doi.org/10.3390/w15183275 - 15 Sep 2023

Cited by 1 | Viewed by 1263

Abstract

In the context of the plain river network, conventional water pumps suffer several drawbacks, including inadequate efficiency, poor security, and costly installation costs. In order to improve the hydrodynamic insufficiency problem and enhance the hydrodynamic performance and applicability of flapping hydrofoils, this paper [...] Read more.

In the context of the plain river network, conventional water pumps suffer several drawbacks, including inadequate efficiency, poor security, and costly installation costs. In order to improve the hydrodynamic insufficiency problem and enhance the hydrodynamic performance and applicability of flapping hydrofoils, this paper proposes a bionic pumping device based on dual flapping foils. Based on the finite volume method and overlapping grid technology, the numerical simulation and experimental verification of the hydraulic performance of two typical motion modes of in-phase and out-of-phase oscillations are conducted, thereby providing a theoretical foundation for improving and optimizing the design of flapping hydrofoils. The results show that the out-of-phase oscillation has better hydraulic performance compared to the in-phase oscillation. The formation of the tail vortex structure plays a crucial role in determining the hydraulic efficiency of dual flapping foils, with in-phase oscillation forming a pair of vortex streets and out-of-phase oscillation forming two pairs of vortex streets. The pumping efficiency of the out-of-phase oscillation is significantly higher than that of the in-phase oscillation, reaching up to 38.4% at a fixed frequency of f = 1 Hz, which is an increase of 90.5% compared to the in-phase oscillation. The characteristic curve of the in-phase oscillation shows an “S” type unstable oscillation phenomenon, namely the hump phenomenon, while the out-of-phase oscillation does not show such a phenomenon, which can effectively expand its application range. In addition, the applicable head of the out-of-phase oscillation hydrofoil is lower, which can better meet the requirements of ultra-low head conditions. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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17 pages, 4558 KiB

Open AccessArticle

Investigation of Structural Strength and Fatigue Life of Rotor System of a Vertical Axial-Flow Pump under Full Operating Conditions

by Haoyu Li, Zhizhou Cai, Yuan Zheng, Jiangang Feng, Hui Xu, Huixiang Chen, Maxime Binama and Kan Kan

Water 2023, 15(17), 3041; https://doi.org/10.3390/w15173041 - 24 Aug 2023

Cited by 1 | Viewed by 1288

Abstract

Axial-flow pumps consider both the conventional pump mode and the pump as turbine (PAT) mode operation and put forward higher requirements for long-term operation stability and structural strength; therefore, it is of great engineering significance to evaluate the structural strength and fatigue life [...] Read more.

Axial-flow pumps consider both the conventional pump mode and the pump as turbine (PAT) mode operation and put forward higher requirements for long-term operation stability and structural strength; therefore, it is of great engineering significance to evaluate the structural strength and fatigue life of the rotor under full operating conditions. In this study, based on computational fluid dynamics and the one-way fluid-structure interaction algorithm, the structural strength and fatigue life of the rotor system of a large vertical axial-flow pump under full operating conditions were evaluated and studied. The results show that blade deformation and equivalent stress are generally higher in the PAT mode than in the pump mode. The maximum deformation in both modes occurs at the tip of the blade, while the area of stress concentration is at the root of the blade. Both the deformation and the equivalent stress increase with increasing flow rate. The minimum safety factor occurs at the blade root in both modes, and the safety factor in the PAT mode is relatively smaller than that in pump mode. Therefore, when designing and manufacturing axial flow pumps for turbine duties, priority should be given to material strength at the blade root during PAT mode operation to ensure safe and stable operation. The aim of this study is to provide technical references and theoretical foundations for evaluating the service cycle of axial-flow pumps and the influence on pump life under different operation modes. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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22 pages, 16393 KiB

Open AccessArticle

Analysis of the Energy Loss Mechanism of Pump-Turbines with Splitter Blades under Different Characteristic Heads

by Zhonghua Gui, Zhe Xu, Dongkuo Li, Fei Zhang, Yifeng Zhao, Lianchen Xu, Yuan Zheng and Kan Kan

Water 2023, 15(15), 2776; https://doi.org/10.3390/w15152776 - 31 Jul 2023

Cited by 3 | Viewed by 1420

Abstract

The operating efficiency of high-head pump turbines is closely related to the internal hydraulic losses within the system. Conventional methods for calculating hydraulic losses based on pressure differences often lack detailed information on their distribution and specific sources. Additionally, the presence of splitter [...] Read more.

The operating efficiency of high-head pump turbines is closely related to the internal hydraulic losses within the system. Conventional methods for calculating hydraulic losses based on pressure differences often lack detailed information on their distribution and specific sources. Additionally, the presence of splitter blades further complicates the hydraulic loss characteristics, necessitating further study. In this study, Reynolds-averaged Navier–Stokes (RANS) simulations were employed to analyze the performance of a pump turbine with splitter blades at three different head conditions and a guide vane opening (GVO) of 10°. The numerical simulations were validated by experimental tests using laser doppler velocimetry (LDV). Quantitative analysis of flow components and hydraulic losses was conducted using entropy production theory in combination with an examination of flow field distributions to identify the origins and features of hydraulic losses. The results indicate that higher heads are associated with lower growth rates of total hydraulic losses. In particular, the significant velocity gradients at the trailing edge of the splitter blades contribute to higher hydraulic losses. Furthermore, the hydraulic losses in the runner (RN) region are predominantly influenced by velocity gradients and not by vortices, with the flow conditions in the RN region impacting the hydraulic losses in the draft tube (DT). Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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14 pages, 5787 KiB

Open AccessArticle

Numerical and Experimental Study on the Process of Filling Water in Pressurized Water Pipeline

by Jianyong Hu, Qingbo Wang, Yuzhou Zhang, Zhenzhu Meng, Jinxin Zhang and Jiarui Fan

Water 2023, 15(14), 2508; https://doi.org/10.3390/w15142508 - 9 Jul 2023

Cited by 3 | Viewed by 2097

Abstract

As an important working condition in water conveyance projects, the water filling process of pipelines is a complex hydraulic transition process involving water–air two-phase flow with sharp pressure changes that can easily cause pipeline damage. In light of the complex water–air two-phase flow [...] Read more.

As an important working condition in water conveyance projects, the water filling process of pipelines is a complex hydraulic transition process involving water–air two-phase flow with sharp pressure changes that can easily cause pipeline damage. In light of the complex water–air two-phase flow during pipeline water filling, this study explores the water filling process of right-angle elbow pressure pipelines using CFD numerical simulations and physical model experiments, analyzing changes in water phase volume fraction, water-gas two-phase flow patterns, and hydraulic parameters in the pipeline under low flow rate conditions of 0.6 m/s and high flow rate conditions of 1.5 m/s. Results show that under low flow rate conditions, there is more local trapped gas at the top of the pipeline, causing negative pressure at local high points in the pipeline and forming a vacuum. Under high velocity conditions, water-gas two-phase flow changes more frequently in the pipeline, with a large number of bubbles collapsing at the top, resulting in large fluctuations in pipeline pressure. Finally, through physical experiments, the main flow patterns during water filling in right-angle elbows are verified and analyzed. These results have certain reference significance for formulating safe and efficient water filling velocity schemes for pressurized pipelines. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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18 pages, 4635 KiB

Open AccessArticle

Variable Speed Control in PATs: Theoretical, Experimental and Numerical Modelling

by Frank A. Plua, Francisco-Javier Sánchez-Romero, Victor Hidalgo, Petra Amparo López-Jiménez and Modesto Pérez-Sánchez

Water 2023, 15(10), 1928; https://doi.org/10.3390/w15101928 - 19 May 2023

Cited by 1 | Viewed by 1807

Abstract

The selection of pumps as turbines (PATs) for their respective use in energy optimisation systems is a complicated task, because manufacturers do not provide the characteristic curves. For this reason, some research has been carried out to predict them with computational fluid dynamics [...] Read more.

The selection of pumps as turbines (PATs) for their respective use in energy optimisation systems is a complicated task, because manufacturers do not provide the characteristic curves. For this reason, some research has been carried out to predict them with computational fluid dynamics (CFD) and mathematical models. The purpose of this study is to validate these two prediction methodologies of flow (Q) vs. head (H) curves through numerical modelling using the computational package OpenFOAM, together with a comparison with the experimental data obtained from a PAT for the case in which the nominal rotation speed of the machine varies. Depending on the configuration and working conditions of the PAT, the simulation performed with OpenFOAM was validated by calibrating it with the nominal curve of the pump and with another simulation performed with CFD workbench SOLIDWORKS FloEFD. Subsequently, the second methodology related to the analyses and mathematical models proposed to predict the Q vs. H curves were also validated with new models in OpenFOAM and the experimental data. The results show that these prediction methods are effective when a machine’s operating point is close to the BEP (best efficient point). The absolute error ranges obtained with these two prediction methodologies for rotation speeds of 880 rpm, 1020 rpm, 1200 rpm, and 1500 rpm are between 5 and 24%, 2 and 17%, 0 and 12%, and 1 and 24%, respectively. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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16 pages, 18258 KiB

Open AccessArticle

Investigation on Stall Characteristics of Centrifugal Pump with Guide Vanes

by Changliang Ye, Dongsen An, Wanru Huang, Yaguang Heng and Yuan Zheng

Water 2023, 15(1), 21; https://doi.org/10.3390/w15010021 - 21 Dec 2022

Cited by 8 | Viewed by 2409

Abstract

Stall usually occurs in the hump area of the head curve, which will block the channel and aggravate the pump vibration. For centrifugal pumps with guide vanes usually have a clocking effect, the stall characteristic at different clocking positions should be focused. In [...] Read more.

Stall usually occurs in the hump area of the head curve, which will block the channel and aggravate the pump vibration. For centrifugal pumps with guide vanes usually have a clocking effect, the stall characteristic at different clocking positions should be focused. In this paper, the flow field of the centrifugal pump under stall conditions is numerically simulated, and the rotor–stator interaction effects of the centrifugal pump under stall conditions are studied. The double-hump characteristic is found in the head curve by using SAS (Scale Adaptive Simulation) model. The hump area close to the optimal working condition is caused by hydraulic loss, while the hump area far away from the optimal working condition point is caused by the combined action of Euler’s head and hydraulic loss. The SAS model can accurately calculate the wall friction loss, thus predicting the double-hump phenomenon. The pressure fluctuation and head characteristics at different clocking positions under stall conditions are obtained. It is found that when the guide vanes outlet in line with the volute tongue, the corresponding head is the highest, and the pressure fluctuation is the lowest. The mechanism of the clocking effect in the centrifugal pump with guide vanes is obtained by simplifying the hydrofoil. It is found that when the downstream hydrofoil leading edge is always interfered with by the upstream hydrofoil wake, the wake with low energy mixes the boundary layer with low energy, which causes small-pressure pulsation. The results could be used for the operation of centrifugal pumps with guide vanes. Full article

(This article belongs to the Special Issue Advances in Hydrodynamics of Water Pump Station System)

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