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Study of the Dissipation in Spiraling Vortical Structures
Štefan, David ; Drábková, Sylva (referee) ; Koutník,, Jiří (referee) ; Skoták, Aleš (referee) ; Rudolf, Pavel (advisor)
This work deals with study of swirling flows where the spiral vortical structure appears. The main relation is to flow seen in the draft tube cone of hydraulic turbines operated out of the design point (i.e. best efficiency point). In this cases large coherent vortex structure (vortex rope) appears and consequently high pressure pulsations are propagated to the whole machine system leading to possible restriction of turbine operation. This flow features are consequence of flow instability called vortex breakdown in case of Francis turbine operated at part load (flow rate lower than optimal one). The present study is carried out using simplified device of swirl generator in order to access similar flow conditions as can be found in real hydraulic turbines. Both the dynamic and dissipation effect of spiral vortex breakdown are investigated. The first part of thesis deals with spiral form of vortex breakdown. The experimentally measured velocity profiles (LDA) and wall static pressures are correlated with numerical simulations carried out using open-source CFD package OpenFOAM 2.2.2. The high speed camera recording of cavitating vortex core is used to obtain image ensemble for further post-processing. The dissipation effect of spiral vortex structure is in detail discussed based on computed flow fields. The second part of thesis is dedicated to the application of POD decomposition to the study of spatio-temporal features of spiral vortex dynamics. Firstly the POD is applied to the both the experimentally obtained image ensemble of cavitating vortex and numerically computed static pressure fields. Secondly the comprehensive analysis of spiral vortex mitigation effect by the axial water jet is analyzed. The collaborative study employing the swirl generator apparatus designed by the researchers from Politehnica University of Timisoara in Romania is performed and changes in spatio-temporal vortex dynamic are studied. In this study the numerical data (in a form of three-dimensional pressure and velocity fields) are obtained using commercial CFD software ANSYS Fluent R14.
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Optimization of the siphon swirl turbine draft tube
Mach, Jiří ; Haluza, Miloslav (referee) ; Rudolf, Pavel (advisor)
The goal of this diploma thesis is to design a new shape of the draft tube, which will be easier to manufacture while maintaining good strength and hydraulic properties. First part of this thesis is devoted to the formulation of the problem, description of the swirl turbine, principle of operation, the basic variants of arrangement, also the function of the draft tube, its efficiency and other formulas. In the second part of this thesis is a CFD and strength analysis of the original design, also a new design is proposed and the possibility of optimization using ANSYS Fluent Adjoint solver.
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Study of hydroenergy potential exploitation of given location
Kollár, Martin ; Hudec, Martin (referee) ; Rudolf, Pavel (advisor)
For the objective of my Bachelor`s thesis I chose an assessment of hydropower potential and a design of machinery in the small hydropower plant construction on the river Váh in Trenčianske Biskupice site. I divided hydropower potential into three parts. First part is the past then present and last is future status. I have subsequently used these information in the design of machinery, including turbine and its associated penstock and draft tube. Part of my thesis also contains appropriate design solution for control gate of intake and outflow, trash rack and trash rack machine. I prepared and presented two possible alternatives together with the drawing documentation which are at the end of my paper compared and evaluated.
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Feasibility study of the pumped storage power station
Kratina, Jakub ; Duchan, David (referee) ; Dráb, Aleš (advisor)
Pumped storage power stations are an integral part of all power systems. At pre-sent, they represent perhaps the only option to accumulate more surplus electricity. It is also built as a proven regulatory element of the power system. The content of this bachelor thesis is a study of feasibility of the pumped storage power stationt (PVE Podlešín) in the Vaňov area. The introduction deals with the issue of pumped srorage power station. Then the design of a technical solution for the power plant construction follows. The main part of the study is the elaboration of drawing documentation and technical reports.
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The computation of draft tobe of the turbine for giving parameters
Žák, František ; Veselý, Jindřich (referee) ; Haluza, Miloslav (advisor)
This diploma thesis describes design of a new shape of the draft tube for small hydro Katovice with maintaining built dimension. First part of this thesis is devoted to the formulation of the problem, description of basic function of the draft tube, its efficiency and other formulas. In the second part of this thesis the analysis is made for original design supported by CFD calculation. Furthermore a new design of the draft tube is made with comparison of original draft tube.
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Flow control in a hydraulic turbine draft tube
Litera, Jiří ; Štefan, David (referee) ; Rudolf, Pavel (advisor)
Hydraulic energy is one of the most important sources in the world for electricity production. Nowadays the trend is to limit the production of the electricity from fossil fuels and to protect the environment. The main idea is to use more renewable energy sources such as wind and solar energy. Unfortunately, these alternative sources are strongly dependent on current weather conditions, which causes the instability of the electrical grid. Luckily pumped storage and hydraulic power plants provide the solution. However, it requires an extension of the operating range of the hydraulic machines. For that reason, the water turbines now operate over and extended range of regimes, that can be quite far from the best efficiency point. Hence two types of unstable two-phase flows in the Francis turbine draft tube occur: part load overload. This diploma’s thesis is focused on the Francis turbine operating at the part load. During part load conditions the helical vortex rope is being developed in the draft tube, it causes pressure pulsation and it can lead to the hydro-acoustic resonance, which damages the elements of the power plant. The aim is to eliminate the pulsation by jet control of the swirling flow in the draft tube. In the diploma’s thesis, various approaches to jet control of the flow in conical diffuser are tested using the computational fluid dynamics.
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Contradictions analysis of small water power Ostravice.
Kupčík, Roman ; Skoták, Aleš (referee) ; Haluza, Miloslav (advisor)
The main subject of the diploma thesis „Contradiction analysis of small water power Ostravice“ is solution of reduced output of small water power plant on the river Ostravice near the town Vratimov. Power plant equippment is axial flow Kaplans turbine RA – 3,5 – 0 1000 with runner diametr 1000 mm. Low output is caused by draft tube. New draft tube is designed in this masters thesis. For hydraulic layout was used CFD software Fluent. The aim of this work is finding of optimal shape which leads to increasing of power from current 30 kW to projected 55 kW.
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