EÚ-odbor fluidního inženýrství Viktora Kaplana

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    Opportunities of hidden hydropower technologies towards the energy transition
    (Elsevier, 2024-11-23) Karapici, Valbona; Trojer, Alex; Lazarevikj, Marija; Pluskal, Tomáš; Chernobrova, Anna; Nezirić, Emir; Zuecco, Giulia; Alerci, Aldo Leonardo; Seydoux, Martin; Doujak, Eduard; Rudolf, Pavel
    Hydropower is the world's most exploited renewable energy source. It provides a substantial, flexible, and reliable source of renewable energy, complementing other renewables like solar and wind power. Besides conventional hydropower potentials and technologies, the development of technologies for the exploitation of hidden hydropower potentials is an ongoing process. This paper presents the current state of hidden hydropower technologies and links them with possible applications in different hydropower potentials. Technologies and potential applications are structured within three main groups (pressurized systems, hydro storage, unpressurized systems), with their mutual interconnections analysed and displayed throughout the paper. The opportunity for the application of hidden hydropower technologies in different roles within the energy system is recognized through the concepts of off- and on-grid roles, the prosumer concept, and on-site measurement powering. This paper shows that hidden hydropower technologies could emerge as significant contributors to a smoother energy transition, especially with the prosumer and off-grid concepts.
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    Effect of splitter blades on turbine mode of low specific speed pump
    (EDP Sciences, 2024-07-04) Bezdíček, Jiří; Chabannes, Lilian; Štefan, David
    The use of pump in turbine mode is an evolving research field. This article is mainly focused on the influence of splitter blades on the turbine mode of pump exclusively. CFD analysis on low specific speed pump geometry was performed. The geometry of sidewall gaps spaces between the rotor and stator system was also included in the computational model. Flow phenomena were compared with quantification of losses. In this case, entropy production theory was used for loss analysis. The effect of different computational meshes and turbulence models on the low-specific speed machine was also questioned. The numerical approach was used not only to obtain turbine characteristics and evaluate the effect of splitter-blades on the machine, which was main goal of this work but also to describe flow or carry out hydraulic loss analysis and visualise areas of most dominant losses. Volumetric efficiency, hydraulic forces, and influence of flow in sidewall gaps on torque generation were also investigated. The numerical model was validated using experimental data. Probable reasons for the difference between the experiment and simulation were estimated.
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    The new role of sustainable hydropower in flexible energy systems and its technical evolution through innovation and digitalization
    (Elsevier, 2024-09-01) Vagnoni, Elena; Gezer, Dogan; Anagnostopoulos, George; Cavazzini, Giovanna; Doujak, Eduard; Hočevar, Marko; Rudolf, Pavel
    Hydropower has played an important role in Europe in recent decades, offering a unique combination of safe, low-cost, and clean power generation. Today, it is still one of the largest renewable energy sources (RES), accounting for about 35 % of RES electricity generation. However, grid stability is threatened by the increasing amount of undispatchable RES. Flexibility and dynamics such as energy storage and rapid response are urgently needed to achieve EU policy goals. In such a context, hydropower can play a key role, not only as a provider of regulated renewable energy but also due to its ability to balance a renewable energy system in the short term and the medium/long term by pumped storage technology. All these aspects underline the new role of hydropower, which aims to strengthen grid stability and power supply resilience and to enable higher penetration of volatile RES. In this context, the aim of this paper is to demonstrate the role of hydropower at the European level as well as the needs and opportunities of modernization to fully exploit its potential. In particular, this study provides, the assessment of the today flexibility offered by hydropower to the power system at the European level by leveraging a database of information collected through the participants to the working groups of the COST Action Pen@Hydropower which includes stakeholders in the hydropower sector of 34 European countries. The study confirms the key role of hydropower in future energy scenarios with 30 % of the flexibility demand at all time scales met by hydropower. Furthermore, the paper presents a review of the digitalization solutions and innovative technologies that support the growth of a new generation of sustainable hydropower together with the modernization opportunities for existing hydropower plants. The results of this work have practical implications for stakeholders in the hydropower sector and policymakers as it provides evidence at the European scale of the role of hydropower technology in balancing the power system and the need to have supportive frameworks and adequate markets to fully exploit the European hydropower potential to achieve the energy transition goals.
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    Study of dynamic vortex structures of an incompressible liquid
    (EPJ Web of Conferences, 2024-07-04) Pochylý, František; Štefan, David; Fialová, Simona
    The study of non-stationary vortex structures arising at the inlet of centrifugal pumps and at the outlet of turbines of the Kaplan and Francis type is the subject of the presented paper. Specific attention will be paid to spatial vortices, characterized by curvature and twist. Spiral vortices will also be monitored as sources of spatial vortex motion. Their core will be expressed by a mathematical model in curvilinear coordinates. Helicity, which indicates the degree of vorticity, will also be determined by computational simulation of turbulent motion. The swirling motion will be induced by a specially designed diffuser-shaped vortex generator, simulating the inlet to the turbine draft tube. A significant result of the study of vortex structures will be the dependence of the twist of the streamline in relation to the Hessian matrix, expressed as a function of the pressure function. This dependence will be significant for the optimization of the hydraulic machines.
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    Hydrodynamic cavitation in minifluidic Venturi nozzle
    (EDP Sciences, 2024-07-04) Zeman, Radek; Rudolf, Pavel
    This article describes the design of a small Venturi nozzle for hydrodynamic cavitation wastewater treatment research. A water circuit powered by compressed air was set up for the experiment. The nozzle design allowed visualization of the cavitating flow directly in the nozzle using a high-speed camera. Experiments were carried out with the nozzle to obtain a visualization of the flow and the dependence of the loss coefficient on the cavitation number. Furthermore, computational modeling of the flow was performed based on the results obtained in the experiment. Cavitation could play an important role in removing pollutants from water that cannot be removed by conventional methods in water treatment plants. The ability to process large quantities of water is one of the great advantages of hydrodynamic cavitation, however, when testing the influence of cavitation on pollutants contained in water, the need for large quantities of tested water appears unnecessary, impractical, and expensive. Research is still needed to better understand the effects of cavitation on water purification, and small-scale experiments may be more suitable for this kind of task.