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Advancements in the Complex Vortex Flow in Hydraulic Machinery

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 15440

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Special Issue Editors

Dr. Xijie Song

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Co-Guest Editor

Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
Interests: complex flow and vortex dynamics in pump turbine
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Dr. Ran Tao

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Guest Editor

College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China
Interests: energy loss mechanisms of pump–turbines; water jet propulsion; operation stability analysis of bulb turbines; tracking studies on spatial characteristics
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Dr. Yonggang Lu

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Co-Guest Editor

School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
Interests: hydroturbine; pump turbine; gas-liquid two-phase flow; solid-liquid two-phase flow; abrasion; CFD
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Dr. Can Luo

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Co-Guest Editor

College of Hydraulic Science and Engineering, Yangzhou University, Yangzhou, China
Interests: waterjet propulsion system; pump and pump station; hydroelectric power generation

Dr. Chuanliu Xie

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Co-Guest Editor

College of Engineering, Anhui Agricultural University, Hefei, China
Interests: waterjet propulsion system; pump and pump station; hydroelectric power generation

Dr. Haiyu Liu

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Co-Guest Editor

Yancheng Institute of Technology, Yancheng, China
Interests: cavitation; hydrofoil; axial flow pump

Special Issue Information

Dear Colleagues,

Water pumps and turbines are important hydraulic machinery in hydraulic engineering. In all kinds of hydraulic machinery, there are various forms of vortices, which lead to the complexity of the internal fluid dynamics of the runner and can put the safe and stable operation of the unit at risk. It is necessary to carry out relevant research to ensure thestability and safety of the operation of these pumps and turbines. We welcome scholars to contribute to this Special Issue to promote their research on internal vortices in hydraulic machinery. This Special Issue covers, but is not limited to, a wide range of topics, including:

Studies on the space-time evolution characteristics of vortices;
Cavitation vortex flow in hydraulic machinery;
High-efficiency design for vortex elimination under multiple working conditions;
Structural response of water pump turbines under hydraulic excitation;
Studies on the Karman vortex in water jet propulsion;
The vortex in the turbine startup process;

Dr. Xijie Song
Dr. Ran Tao
Dr. Yonggang Lu
Dr. Can Luo
Dr. Chuanliu Xie
Dr. Haiyu Liu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

pump and turbine
vortex
cavitation
water jet propulsion
hydraulic excitation
sediment erosion
operation stability
response

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Published Papers (7 papers)

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Research

19 pages, 8881 KiB

Open AccessArticle

Numerical Study on the Effect of Crown Clearance Thickness on High-Head Pump Turbines

by Lei Li, Dandan Yan, Xuyang Liu, Weiqiang Zhao, Yupeng Wang, Jiayang Pang and Zhengwei Wang

Water 2023, 15(19), 3397; https://doi.org/10.3390/w15193397 - 27 Sep 2023

Cited by 2 | Viewed by 1059

Abstract

In order to promote the development of new power systems and the consumption of clean energy, pumped storage hydropower stations tend to become increasingly larger in capacity and higher in head height. In this paper, a three-dimensional model of the full channel of a high-head pump turbine is established, and the influence of the gap thickness between the runner crown and the headcover on the internal flow field characteristics, pressure fluctuation characteristics and axial water thrust are studied by means of computational fluid dynamics (CFD). The results indicate that the area where the pressure and velocity vary greatly in the flow field of the crown clearance is at the seal of the labyrinth ring. In addition, the pressure balance pipe has a greater impact on the pressure and flow rate of the water passing through the clearance, and the crown clearance near the pressure balance pipe generates a vortex, resulting in energy loss. Decreasing the thickness of the clearance has no obvious effect on the pressure on the flow-passing components, and increasing the thickness of the clearance has a great change in the pressure values at the upper crown inlet, in front of the labyrinth ring of the crown and in front of the labyrinth ring of the band. The upper part of the vaneless area, the crown inlet and the lower ring inlet are close to the runner; hence, the interference from the rotating parts is the strongest. The effect of increasing the thickness of the crown clearance on the axial water thrust is greater than that of decreasing the thickness of the crown clearance. The pulsation frequency of the axial thrust on the crown, band and blade and the resultant force of the axial thrust increase with the increase in the crown clearance thickness. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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19 pages, 11015 KiB

Open AccessArticle

Internal Flow Phenomena of Two-Way Contra-Rotating Axial-Flow Pump-Turbine with Various Numbers of Blades in Pump Mode

by Ce An, Yiming Chen, Qiang Fu and Rongsheng Zhu

Water 2023, 15(18), 3236; https://doi.org/10.3390/w15183236 - 11 Sep 2023

Cited by 1 | Viewed by 1317

Abstract

The focus of this paper is to investigate how various numbers of blades impact the performance of a two-way contra-rotating axial-flow pump-turbine when operating in pump mode. In order to meet the two-way operation of the pump-turbine, the front and rear impellers are mirror-symmetric with the same hydraulic model, which ensures the consistent performance of the forward and reverse working conditions. However, when the two-stage impellers have the same number of blades, the dynamic–dynamic interference can be severe, which can threaten the stability of the unit. The present study explores the use of two-stage impellers with varying numbers of blades as a means of enhancing the performance of tidal energy units. By conducting numerical simulations on the front and rear impellers under different flow rates in pump mode, the impact of increasing the number of blades in each stage on the external characteristics of the pump-turbine is revealed. The internal flow characteristics of different models are analyzed, and the impact of the number of blades on the vortex is studied. Different blade numbers will have a certain impact on the internal flow of the two-way contra-rotating axial-flow pump–turbine. Increasing the number of blades will affect the development of tip-leakage vortices and promote their intersection with the wake. In addition, changes in the number of blades will have an impact on the location of the leading edge (LE) water impact on the rear impeller, which in turn affects the contours of vorticity of the rear impeller near the LE and the location of the suction surface (SS) flow separation. The findings of this study offer valuable insights for future research on the operation of contra-rotating axial-flow pump-turbines. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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15 pages, 5170 KiB

Open AccessArticle

The Transient Characteristics of the Cavitation Evolution of the Shroud of High-Speed Pump-Jet Propellers under Different Operating Conditions

by Gongchang Gan, Wenhao Shi, Jinbao Yi, Qiang Fu, Rongsheng Zhu and Yuchen Duan

Water 2023, 15(17), 3073; https://doi.org/10.3390/w15173073 - 28 Aug 2023

Cited by 3 | Viewed by 1287

Abstract

Pump-jet propellers are currently the mainstream propulsion method for underwater vehicles, and cavitation is an important factor limiting the high speed and miniaturization of pump-jet propellers. In order to explore the cavitation performance of high-speed pump-jet propellers, based on the modified SST turbulence model and the Zwart cavitation model, a three-dimensional numerical simulation of unsteady internal cavitation flow was carried out by comparing the impeller with specific speed n_s = 1920 using FLUENT 2020R2 software. At the same time, the occurrence and development process of cavitation under 0.95 Q, 1.0 Q, and 1.05 Q conditions were analyzed (Q is the mass flow), the changes in gas volume fraction in the impeller channel were captured, the distribution characteristics of cavitation under different NPSH values were explored, and the change law of cavitation with time was determined. The results show that, when NPSH dropped to 95 m, the impeller cavitation first occurred under the 1.05 Q operating condition, and the impeller cavitation volume fraction was 0.0379525. When NPSH dropped to 85 m, the impeller cavitation occurred under the 1.0 Q operating condition, and the impeller cavitation volume fraction was 0.0185164. When NPSH dropped to 80 m, the impeller cavitation occurred under the condition of 0.95 Q, and the volume fraction of the impeller cavitation was 0.013541. The high-speed pump-jet propeller had better anti-cavitation ability with a small flow rate. The cavitation distribution law under the three operating conditions was similar; cavitation was first generated on the impeller inlet edge and near the shroud, and the vacuoles with large volumes were mostly concentrated on the impeller inlet side. As the NPSH gradually decreased, the entire flow channel was gradually occupied by vacuoles. As the flow decreased, the corresponding NPSH also decreased. When NPSH dropped to 50 m, the volume fraction of the impeller under all three operating conditions reached around 0.4. As the cavitation only occurred on the suction surface, the volume fraction of the cavitation on the suction surface exceeded 0.8, at which time the impeller had already undergone severe cavitation. Within a complete cycle, bubbles first appeared at the inlet edge of the impeller (measured near the shroud) and gradually spread toward the middle and rear of the impeller, ultimately covering the suction surface of the impeller. Under the design condition, the experimental results of the model pump were consistent with the numerical simulation results, and the error was only 2.68%, thus verifying the reliability of the numerical simulation. The research results provide a reference for the in-depth study of the cavitation performance of high-speed pump-jet propellers and provide a good theoretical basis and practical significance in the engineering field for the high-speed and miniaturization process of high-speed pump-jet propellers. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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15 pages, 10164 KiB

Open AccessArticle

Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement

by Di Zhu, Zilong Hu, Yan Chen, Chao Wang, Youchao Yang, Jiahao Lu, Xijie Song, Ran Tao, Zhengwei Wang and Wensheng Ma

Water 2023, 15(9), 1785; https://doi.org/10.3390/w15091785 - 6 May 2023

Cited by 2 | Viewed by 2976

Abstract

Two-stage double-suction centrifugal pumps have both a large flow and high head. However, due to the complexity of their flow passage components, efficiency has always been a major problem, and the corresponding head is also prone to insufficiency. In this study, an improved design for a two-stage double-suction centrifugal pump unit with a specific speed of 25.9 was developed with the help of a computer. The computational fluid dynamics (CFD) method was used to evaluate the performance and loss of the unit in the process of improvement. The unit’s inlet division section, two semi-spiral suction chambers, two impellers for the first stage, two inter-stage channels, a double-suction impeller for the second stage, and the volute were able to be improved. Through a total of 39 improvements, the efficiency under multiple working conditions was comprehensively improved, and the head had a reasonable margin in meeting the requirements. After the improvements, the flow pattern in the inter-stage channel and volume were significantly improved through the check of the streamline. This research successfully improved the performance of a two-stage double-suction centrifugal pump unit, and it has significant engineering value. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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16 pages, 23742 KiB

Open AccessArticle

Influence of Installation Deviation of Thrust Bearing on Oil Film Flow of 1000 MW Hydraulic Turbine Unit

by Zhenwei Ji, Yishu Shi, Xinming Da, Jingwei Cao, Qijun Gong, Zhengwei Wang and Xingxing Huang

Water 2023, 15(9), 1649; https://doi.org/10.3390/w15091649 - 23 Apr 2023

Cited by 4 | Viewed by 2495

Abstract

The thrust bearing, as the only part bearing the axial load, is extremely important in vertical hydroelectric generating units. Its working condition directly affects the safe and reliable operation of the hydroelectric generating unit. However, during operation, the oil film is easily damaged under the influence of complex factors. Installation deviation is a key point that can cause temperature and pressure changes in the oil film, affecting the force on the bearing. This article takes the thrust bearing model of the 1000 MW Francis turbine unit of the Baihetan Power Station as the research object. Based on the fluid–solid coupling theory and CFD technology, the oil film characteristics of thrust bearings are analyzed, and the influence of inclination angles and installation deviation on the oil film flow performance of thrust bearings is discussed. The results show that as the inclination angle changes from 0.0030° to 0.0048°, the axial force changes from 856 t to 368 t, and there is an approximate linear correlation between them. The radial installation deviation has an effect on the axial force. Under the optimal working condition of an inclination angle of 0.0039°, when the radial deviation of the pad changes from 0 mm to 1 mm, the axial force changes from 1573 t to 1275 t. In the process of unit installation, it is necessary to pay attention to the installation deviation of the pad. The results provide guidance for the installation of the bearing, which helps to ensure the safe and stable operation of the station. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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12 pages, 10223 KiB

Open AccessArticle

Effect of Unbalanced Magnetic Pull of Generator Rotor on the Dynamic Characteristics of a Pump—Turbine Rotor System

by Weidong Wu, Jiayang Pang, Xuyang Liu, Weiqiang Zhao, Zhiwei Lu, Dandan Yan, Lingjiu Zhou and Zhengwei Wang

Water 2023, 15(6), 1120; https://doi.org/10.3390/w15061120 - 15 Mar 2023

Cited by 3 | Viewed by 2767

Abstract

In pumped storage units, the rotor-bearing electromagnetic system is under the joint influence of hydraulics, mechanics, and electromagnetics, and the mechanism of unit vibration problems is very complex to investigate. ANSYS software is used to establish a three-dimensional model of a pumped storage power plant’s rotor-bearing electromagnetic system, and the stiffness coefficient of the unbalanced magnetic traction forces is calculated using the Fourier series of the magnetic conductivity of the air gap. This shows that the nonequilibrium magnetic attraction increases non-linearly with increasing excitation current and eccentricity of the rotor. At each order, the critical velocity of the rotor system increases as the stiffness factor of the bearing increases, with the greatest increase in critical velocity at the third and fourth orders. In the first-order mode-oscillation pattern, the unbalanced magnetic attraction has an effect on the intrinsic frequency of the transverse oscillation, with a reduction in the amplitude of the intrinsic frequency by 34.65%. Axial and transverse modal vibrations manifest themselves as upward and downward motions and transverse oscillations in different portions of the rotor system, respectively, whereas torsional modal vibrations manifest as a radial broadening or reduction in the generator rotor, runner, and coupling portions of the rotor system. The results of the study provide a theoretical foundation and a computational method for the dynamic analysis and design of the rotor system of pumped storage power stations. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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13 pages, 5248 KiB

Open AccessArticle

Effect of Rotational Speed on Pressure Pulsation Characteristics of Variable-Speed Pump Turbine Unit in Turbine Mode

by Linmin Shang, Jingwei Cao, Xin Jia, Shengrui Yang, Sainan Li, Lei Wang, Zhengwei Wang and Xiaobing Liu

Water 2023, 15(3), 609; https://doi.org/10.3390/w15030609 - 3 Feb 2023

Cited by 11 | Viewed by 2815

Abstract

The pumped storage power station plays a vital role in modern power systems, where the key component is the pump turbine. Variable-speed operation can improve the operating efficiency of the pump turbine and increase the operating efficiency under turbine operating conditions and the automatic frequency regulation capability under pump operating conditions, thus obtaining higher efficiency and better stability. However, its operation characteristics are different from many conventional pumped storage units, which makes the study of variable-speed pump turbines more difficult. Therefore, in this paper, 10 representative pressure monitoring points are selected in the model to compare and study the flow characteristics and pressure pulsation characteristics of a variable-speed pump turbine at three speeds (N1-398.57 m/s, N2-412.16 m/s, and N3-428.6 m/s). According to our results, it is shown that the maximum pressure and pressure pulsation are small at low rotational speeds, which means that the unit will maintain better stability during the reduction in rotational speed and reducing the speed will not affect the safety and stability of the equipment. The purpose of this paper is to provide guidance for the safe operation of the unit and to improve the effect of speed in terms of dynamic behavior of variable-speed water pump turbine units. Meanwhile, this study will lay the groundwork for the optimal design of variable-speed pump turbines. Full article

(This article belongs to the Special Issue Advancements in the Complex Vortex Flow in Hydraulic Machinery)

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