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Special Issue "State-of the-Art, Challenges and Perspectives in Hydraulic Machines and Systems"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "K: State-of-the-Art Energy Related Technologies".

Deadline for manuscript submissions: closed (10 December 2021) | Viewed by 10544

Special Issue Editors

Dr. Sebastian Muntean
E-Mail Website
Guest Editor
Center for Fundamental and Advanced Technical Research, Romanian Academy - Timisoara Branch, Bv. Mihai Viteazul, no. 24, Ro-300223 Timisoara, Romania
Interests: computational fluid dynamics; experimental investigations; hydrodynamics and cavitation in hydraulic machinery; swirling flow control
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Pavel Rudolf
E-Mail Website
Guest Editor
Viktor Kaplan Department of Fluid Engineering, Faculty of Mechanical Engineering, Brno University of Technology, Technická 2896/2, 616 69 Brno, Czech Republic
Interests: hydraulic machines; cavitation; swirling flows; shape optimization; CFD; flow control; fluid–structure interaction
Prof. Dr. Giovanna Cavazzini
E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Padova, Padua, Italy
Interests: hydraulic machines; unstable behavior; CFD; design optimization; experimental investigation
Special Issues, Collections and Topics in MDPI journals
Dr. Eduard Doujak
E-Mail Website
Guest Editor
Fluid-Flow-Machinery Research Group, Institute for Energy Systems and Thermodynamics, TU Wien, Getreidemarkt 9/302, 1060 Vienna, Austria
Interests: design and optimization of components in hydraulic machinery; multistage pump-turbines for high head applications; lifetime assessment
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Pål-Tore Selbo Storli
E-Mail Website
Guest Editor
Waterpower Laboratory, Department of Energy and Process Engineering, Faculty of Engineering Sciences, Norwegian University of Science and Technology, Høgskoleringen 1, NO-7491 Trondheim, Norway
Interests: fluid–structure interactions in hydraulic turbines; system dynamics and generation flexibility

Special Issue Information

Dear Colleagues,

Modern hydraulic machines and systems are now facing new challenges associated with the variable demand on the energy market as well as limited energy storage capabilities. A great flexibility is required in operation over an extended range of regimes far from the best efficiency point. As a result, unsteady and transient phenomena occur in the operation of hydraulic machines and systems, diminishing their lifetime. The research topics in this Special Issue focus on: (i) the theoretical, numerical, and experimental investigations associated to the unsteady and transient phenomena developed in hydraulic machines, equipment, and systems, (ii) single-, two-, and multiphase phenomena in hydraulic machines and systems, (iii) innovative technologies and new concepts in hydraulic machines and systems to assess and to extend their lifetime, and (iv) passive, semiactive, and active control techniques applied to hydraulic machines to improve their performances.

Dr. Sebastian Muntean
Prof. Dr. Pavel Rudolf
Prof. Dr. Giovanna Cavazzini
Dr. Eduard Doujak
Prof. Dr. Pål-Tore Selbo Storli
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. Energies 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 2200 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

  • Theoretical, numerical and experimental investigations in hydraulic machines, equipment, and systems
  • Unsteady and transients phenomena in operation
  • Single-, two-, and multiphase phenomena in hydraulic machines and systems
  • Innovative technologies and new concepts in hydraulic machines and systems
  • Lifetime time assessment of the hydraulic machines and equipment
  • Innovative technologies and new concepts in hydraulic machines and systems
  • Passive, semiactive, and active control techniques in hydraulic machines

Published Papers (13 papers)

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Research

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Article
Fatigue Strength Analysis of a Prototype Francis Turbine in a Multilevel Lifetime Assessment Procedure Part II: Method Application and Numerical Investigation
Energies 2022, 15(3), 1165; https://doi.org/10.3390/en15031165 - 04 Feb 2022
Viewed by 463
Abstract
Part I of the publication series addressed the fundamentals of lifetime assessment of prototype Francis turbines. This paper (Part II) focuses on the numerical part of the procedure. The essential steps and requirements shall be presented (background). The starting points for the numerical [...] Read more.
Part I of the publication series addressed the fundamentals of lifetime assessment of prototype Francis turbines. This paper (Part II) focuses on the numerical part of the procedure. The essential steps and requirements shall be presented (background). The starting points for the numerical considerations are the pressure fields of the transient CFD simulations, which are exported per time step and applied to the existing structure via a fluid–structure interaction. That enables a transient mechanical stress calculation to be conducted, resulting in the fatigue analysis of the component to estimate the remaining lifetime. The individual model requirements should be represented accordingly and applied to the prototype facility (method). The results obtained from this application should be discussed and evaluated. It has to be mentioned that the validation of the numerical results will be performed at Part IV of this publication series (results). The present paper will end up discussing the results and conclusions about further data processing (Conclusion). Full article
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Article
Fatigue Strength Analysis of a Prototype Francis Turbine in a Multilevel Lifetime Assessment Procedure Part I: Background, Theory and Assessment Procedure Development
Energies 2022, 15(3), 1148; https://doi.org/10.3390/en15031148 - 04 Feb 2022
Viewed by 483
Abstract
Electricity generation is becoming increasingly flexible in Europe these days. Due to the integration of new renewable energy sources like wind and photovoltaic, other conventional resources, such as hydropower, operate within a brought range around their best efficiency point, thus leading to higher [...] Read more.
Electricity generation is becoming increasingly flexible in Europe these days. Due to the integration of new renewable energy sources like wind and photovoltaic, other conventional resources, such as hydropower, operate within a brought range around their best efficiency point, thus leading to higher dynamical loads at the water-bearing parts, especially at the runner and the guide vanes (background). By scrutinizing the literature of the past years, one could summarize the outcome in that way, that research projects focused either on model measurements with higher visual accessibility or, less often, on prototype measurements in existing power plants. Today prototype measurements are performed, if possible, to eliminate scaling effects. Moreover, increasing computing power allows prototype simulations to be carried out within a reasonable time. At the acknowledged research projects, prototype and model measurements and numerical simulations have been performed to identify the main gaps in Francis turbines’ lifetime assessment (methods). One special outcome of these investigations was the impracticality of numerical simulations and calculation time, respectively, of start and stop events. Therefore, a prototype measurement with focus at this operating point should be performed to provide more data and an insight into the unit’s behavior. The future goal is a comprehensive machine unit lifetime assessment of the water-bearing parts in a Francis turbine machine set (results). This complex task needs several steps, beginning from measurements through simulations towards data processing. A particular challenge is posed, when the assessment methods are applied to old machines. Full article
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Article
Water Hammer Control Using Additional Branched HDPE Pipe
Energies 2021, 14(23), 8008; https://doi.org/10.3390/en14238008 - 30 Nov 2021
Cited by 1 | Viewed by 545
Abstract
In pressurised pipeline systems, various water hammer events commonly occur. This phenomenon can cause extensive damage or even lead to a failure of the pumping system. The aim of this work is to experimentally re-examine the possibility of using an additional polymeric pipe, [...] Read more.
In pressurised pipeline systems, various water hammer events commonly occur. This phenomenon can cause extensive damage or even lead to a failure of the pumping system. The aim of this work is to experimentally re-examine the possibility of using an additional polymeric pipe, installed at the downstream end of the main pipeline, to control water hammer. A previous study on this topic investigated additional polymeric pipes connected to the hydraulic system with a short joint section of the same diameter as the main pipeline. In the current research, a different method of including an additional pipe was considered which involved connecting it with a pipe of a smaller diameter than the main pipeline. Three additional HDPE pipes, with different volumes, were investigated. The performance of the devices was studied for hydraulic transients induced by both rapid and slow, manual valve closures. Experimental results show that the additional polymeric pipe can provide significant pressure surge damping during rapid water hammer events. As the valve closing time lengthens, the influence of the additional pipe on the maximum pressure increase is reduced. The additional HDPE pipe does not provide notable protection against hydraulic transients induced by slow valve closure in terms of reducing the first pressure peak. No relationship between the volume of the additional pipe and the damping properties was noticed. The observed pressure oscillations were used to evaluate a one-dimensional numerical model, in which an additional pipe is described as a lumped parameter of the system. The viscoelastic properties of the device were included using the one element Kelvin–Voigt model. Transient flow equations were solved with the implicit method of characteristics. Calculation results demonstrate that this approach allows one to reasonably reproduce unsteady flow oscillations registered during experiments in terms of the maximum pressure increase and pressure wave oscillation period. Full article
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Article
Effect of Splitter Blades on Performances of a Very Low Specific Speed Pump
Energies 2021, 14(13), 3785; https://doi.org/10.3390/en14133785 - 24 Jun 2021
Cited by 1 | Viewed by 815
Abstract
The usage of splitter blades to enhance the performances of low specific speed pumps is common practice. Based on experimental and numerical studies, the influence of the addition of one and two splitter blades is investigated on a very low specific speed pump [...] Read more.
The usage of splitter blades to enhance the performances of low specific speed pumps is common practice. Based on experimental and numerical studies, the influence of the addition of one and two splitter blades is investigated on a very low specific speed pump to assess their impact not only on the performance characteristics but also on the losses in all pump domains. First, the main characteristic curves are discussed and it is shown that the usage of splitter blades enhances the head of the pump while not impairing its efficiency. Secondly, a detailed analysis of the losses in the pump reveals that splitter blades improve the flow in all parts of the pumps, but the volute. The flow at the impeller outlet shows that splitter blades largely benefit the slip factor and discharges a more blade-congruent flow in the volute. However, higher absolute velocity at the outlet of the impeller with splitter blades increases friction at the volute wall, as confirmed by the average wall shear stress in the different tested cases. Full article
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Article
Influence of Flow Divider on Overall Efficiency of a Hydrostatic Drivetrain of a Skid-Steer All-Wheel Drive Multiple-Axle Vehicle
Energies 2021, 14(12), 3560; https://doi.org/10.3390/en14123560 - 15 Jun 2021
Viewed by 692
Abstract
The efficiency of a skid-steer, all-wheel drive, multiple-axle vehicle with a hydrostatic drivetrain equipped with low-speed motors when it operates on soft terrain was studied. A flow divider enables a single pump to simultaneously power more than one motor circuit with different pressures [...] Read more.
The efficiency of a skid-steer, all-wheel drive, multiple-axle vehicle with a hydrostatic drivetrain equipped with low-speed motors when it operates on soft terrain was studied. A flow divider enables a single pump to simultaneously power more than one motor circuit with different pressures in each. It prevents kinematic discrepancy and improves vehicle mobility. There are two types of flow divider: spool type and gear type, where each type has its own set of performance characteristics, such as flow range, pressure drop, accuracy and application parameters. In the present work, the influence of the characteristics of both types of flow divider on overall vehicle driveline efficacy is described. Full article
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Article
Frequency Containment Control of Hydropower Plants Using Different Adaptive Methods
Energies 2021, 14(8), 2082; https://doi.org/10.3390/en14082082 - 08 Apr 2021
Cited by 2 | Viewed by 606
Abstract
With the growth in the share of variable renewable energy sources, fluctuations in the power generation caused by these types of power plants can diminish the stability and flexibility of the grid. These two can be enhanced by applying frequency containment using hydropower [...] Read more.
With the growth in the share of variable renewable energy sources, fluctuations in the power generation caused by these types of power plants can diminish the stability and flexibility of the grid. These two can be enhanced by applying frequency containment using hydropower plants as an operational reserve. The frequency containment in hydropower plants is automatically controlled by speed governors within seconds. Disturbances such as fluctuations in the net head and aging may diminish the performance of the controllers of the speed governors. In this study, model reference adaptive control approaches based on the Massachusetts Institute of Technology (MIT) rule and Lyapunov method were exploited in order to improve the performance of the speed governor for frequency containment control. The active power control with frequency control was enhanced by the aforementioned adaptive control methods. A mathematical model of a hydropower plant with a surge tank and medium penstock was constructed and validated through site measurements of a plant. It was shown that, as they are applicable in real life, both methods perform significantly better compared to conventional proportional-integrator control. Even in first five deviations, the performance of the conventional controller improved by 58.8% using the MIT rule and by 65.9% using the Lyapunov method. When the two adaptive control approaches were compared with each other, the MIT rule outputted better results than the Lyapunov method when the disturbance frequency was higher; however, the latter was more functional for rare disturbances. Full article
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Article
Influence of the Reshaped Elbow on the Unsteady Pressure Field in a Simplified Geometry of the Draft Tube
Energies 2021, 14(5), 1393; https://doi.org/10.3390/en14051393 - 03 Mar 2021
Cited by 1 | Viewed by 691
Abstract
The paper focuses on the influence of the reshaped elbow geometry of the draft tube on the unsteady pressure field under different operating conditions. The experimental investigations are conducted considering two simplified geometrical configurations of the draft tubes with sharp heel elbow and [...] Read more.
The paper focuses on the influence of the reshaped elbow geometry of the draft tube on the unsteady pressure field under different operating conditions. The experimental investigations are conducted considering two simplified geometrical configurations of the draft tubes with sharp heel elbow and modified/reshaped elbow, respectively. The discriminated power spectra (rotating and plunging components) of the acquired pressure signals on the wall are determined on five levels for seven operating conditions to quantify the influence of the reshaped elbow. The influence of the reshaped elbow on the fundamental frequencies of both rotating and plunging components and on the amplitude of the rotating component is negligible. In contrast, the equivalent amplitude associated with the root mean square of the plunging power spectrum that propagates along the hydraulic passage is mitigated up to 25% by the reshaped geometry of the elbow. The equivalent amplitude on the narrow band around the fundamental frequency of the plunging component is diminished with 40–50% by reshaping the elbow geometry of the simplified draft tube. Full article
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Article
Application of Computer Graphics Flow Visualization Methods in Vortex Rope Investigations
Energies 2021, 14(3), 623; https://doi.org/10.3390/en14030623 - 26 Jan 2021
Cited by 2 | Viewed by 1104
Abstract
Computer graphics visualization techniques for application on data from Computational Fluid Dynamics (CFD) simulations of the vortex rope, a phenomenon present in hydraulic turbines operating in off-design conditions, were devised. This included not only objects for visualization (what to visualize) but also methods [...] Read more.
Computer graphics visualization techniques for application on data from Computational Fluid Dynamics (CFD) simulations of the vortex rope, a phenomenon present in hydraulic turbines operating in off-design conditions, were devised. This included not only objects for visualization (what to visualize) but also methods of the visualization itself (how to do it). By means of advanced methods based particularly on volume rendering of Eulerian fields in combination with Lagrangian objects, various phenomena were captured, such as the motion of the vortex rope or the backflow zone. The data came from simulations using a scale-resolving hybrid turbulence model, the Stress-Blended Eddy Simulation. In such detailed simulations and other applications involving complex three-dimensional structures, proper visualization methods are needed to leverage the content captured in the resultant data. Full article
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Article
A Tandem Axial-Piston Unit Based Strategy for the Reduction of Noise Sources in Hydraulic Systems
Energies 2020, 13(20), 5377; https://doi.org/10.3390/en13205377 - 15 Oct 2020
Cited by 1 | Viewed by 724
Abstract
This article presents a novel passive fluid borne noise source reduction strategy, based on tandem axial-piston unit indexing with the usage of symmetric lines. The strategy consists of setting the phase between the two synchronous units to accomplish destructive interference in targeted unit [...] Read more.
This article presents a novel passive fluid borne noise source reduction strategy, based on tandem axial-piston unit indexing with the usage of symmetric lines. The strategy consists of setting the phase between the two synchronous units to accomplish destructive interference in targeted unit harmonics. A strategy capable of achieving destructive interference in all odd harmonics is investigated first analytically and then confirmed by a simulation study. Experiments on the proposed strategy confirmed its effectiveness at the first and third pump fundamental harmonics, and pressure ripple reduction was accomplished. The fluid borne noise source reduction in the first and third harmonic is verified to be propagated to pipe vibration and sound power. Regarding the first harmonic, pressure ripple was reduced by up to 18 dB; while for third harmonic, pressure ripple was reduced by up to 11 dB. In the experiment, however, noise cancellation is not achieved for the higher odd harmonics, as is instead found in the simulation. Conversely, transfer functions form pressure ripple to pipe wall acceleration are obtained experimentally, and a critical vibration band from 2000 Hz to 3000 Hz is identified as being crucial for effective overall sound power reduction. Full article
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Article
Numerical Simulation of the Flow in a Kaplan Turbine Model during Transient Operation from the Best Efficiency Point to Part Load
Energies 2020, 13(12), 3129; https://doi.org/10.3390/en13123129 - 16 Jun 2020
Cited by 4 | Viewed by 1075
Abstract
The aim of this study is to develop a reliable numerical model that provides additional information to experimental measurements and contributes to a better exploitation of hydraulic turbines during transient operation. The paper presents a numerical analysis of the flow inside a Kaplan [...] Read more.
The aim of this study is to develop a reliable numerical model that provides additional information to experimental measurements and contributes to a better exploitation of hydraulic turbines during transient operation. The paper presents a numerical analysis of the flow inside a Kaplan turbine model operated at a fixed runner blade angle during load variation from the best efficiency point (BEP) to part load (PL) operation. A mesh displacement is defined in order to model the closure of the guide vanes. Two different types of inlet boundary conditions are tested for the transient numerical simulations: linear flow rate variation (InletFlow) and constant total pressure (InletTotalPressure). A time step analysis is performed and the influence of the time discretization over the fluctuating quantities is discussed. Velocity measurements at the corresponding operating points are available to validate the simulation. Spectrogram plots of the pressure signals show the times of appearance of the plunging and rotating modes of the rotating vortex rope (RVR) and the stagnation region developed around the centerline of the draft tube is captured. Full article
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Review

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Review
The Impact of Water Hammer on Hydraulic Power Units
Energies 2022, 15(4), 1526; https://doi.org/10.3390/en15041526 - 18 Feb 2022
Viewed by 501
Abstract
Water hammer influences the life cycle of hydraulic passages and may even cause catastrophic structural failures. Several catastrophic failures of hydraulic power units have been reported in the literature due to the effects of transient regimes. The objective of the study is to [...] Read more.
Water hammer influences the life cycle of hydraulic passages and may even cause catastrophic structural failures. Several catastrophic failures of hydraulic power units have been reported in the literature due to the effects of transient regimes. The objective of the study is to highlight the global trend in water hammer assessment and to quantify the effect of factors influencing overpressure in hydraulic passages during load rejection in different hydropower plants. A brief and concise literature review is conducted to document the parameters associated with the water hammer phenomenon and to thereby identify the necessary prerequisites to validate theoretical and numerical results against experimental data. The purpose of the analysis is to identify extreme transient loads on hydraulic passages in order to properly adapt hydropower unit operation, to make recommendations for design and industry, and to guide the progress of adapted models and numerical simulations to capture complex phenomena. Empirical correlations are determined based on the experimental data that are transferable from one unit to another, even if a deep flow analysis is performed. The experimental results confirm that the rapid closure rate of the guide vanes has a significant impact on the phenomenon. A third order polynomial equation is applied to capture the general overpressure trends. Equation parameters change from case to case depending on the type of hydraulic power unit, closing rate and the type of hydraulic passage. The results confirm also that overpressure values depend significantly on other factors, some of which are not usually taken into account (e.g., runner speed). Experimental correlations make it possible to understand the water hammer phenomenon, which could help not just assessing and optimizing loads, but also verifying and validating more complex physical models, to ensure that hydraulic passages are reliable. A well-documented analysis also makes it possible to optimize equipment design, improve and adapt maintenance programs and to recommend appropriate operating parameters to increase equipment lifespan, while preventing incidents. Full article
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Review
A Review of Different Aspects of Off-Earth Drilling
Energies 2021, 14(21), 7351; https://doi.org/10.3390/en14217351 - 04 Nov 2021
Cited by 5 | Viewed by 665
Abstract
Off-Earth drilling may be assumed as the second phase of space exploration to discover the unrevealed subsurface on the planetary bodies. It accelerates future space objectives such as in-situ propellant production, mineral exploitation, and space tourism. Owing to the rampant progress in modern [...] Read more.
Off-Earth drilling may be assumed as the second phase of space exploration to discover the unrevealed subsurface on the planetary bodies. It accelerates future space objectives such as in-situ propellant production, mineral exploitation, and space tourism. Owing to the rampant progress in modern technology, the new drill tools mounted on the sophisticated robots are capable to drill the planetary regolith dispersed on the celestial objects; however, formidable obstacles such as microgravity, vacuum condition, and temperature fluctuation as well as the weight limitation, lack of real-time drilling analysis, and remote robot-operator communication impose pressing restrictions on the quick development of space drilling tools. In this study, research on the past and present aspects of off-Earth drilling has been implemented to illuminate the horizon of this technology in the near-term future. The context encompasses a detailed description of the limitations, applications and mechanisms of the different drilling techniques adopted for planetary bodies. A particular emphasis is put on the hydraulic power systems which have not been satisfactorily deployed in off-Earth drilling yet. The research strives to glance over the pivotal aspects of off-Earth drilling to contribute to the future drilling programs planned by the national and private space agencies. Full article
Review
Flow Inside the Sidewall Gaps of Hydraulic Machines: A Review
Energies 2020, 13(24), 6617; https://doi.org/10.3390/en13246617 - 15 Dec 2020
Cited by 4 | Viewed by 895
Abstract
The paper critically reviews the current state of the art in flow inside sidewall gaps of hydraulic pumps and turbines. It describes the consequences of the presence of this type of flow in turbomachinery and then relates it to other physical phenomena that [...] Read more.
The paper critically reviews the current state of the art in flow inside sidewall gaps of hydraulic pumps and turbines. It describes the consequences of the presence of this type of flow in turbomachinery and then relates it to other physical phenomena that determine the behavior, operating characteristics, and overall performance of the machine. Despite the small dimensions of the rotor-stator spaces, the flow in these regions can significantly affect the overall flow field and, consequently, efficiency. The circulation of the fluid inside the gaps and secondary flow that is caused by rotating elements influences the disk friction losses, which is of great importance, especially in the case of low specific speed pumps and turbines. The flow pattern affects the pressure distribution inside a machine and, thus, generates axial thrust. The presence of secondary flow also significantly changes the rotordynamics and can bring about undesirable vibrations and acoustics issues. This article aims to review and summarize the studies that were conducted on the mentioned phenomena. Experimental and numerical studies are both taken into consideration. It proposes some requirements for prospective research in order to fill current gaps in the literature and reveals the upcoming challenges in the design of hydraulic machines. Full article
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