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Analysis of the Velocity and Pressure Fields of the Liquid Using Curvilinear Coordinates
Stejskal, Jiří ; Kozubková, Milada (referee) ; Kučera,, Radek (referee) ; Veselý, Jindřich (referee) ; Pochylý, František (advisor)
This work introduces a new method of hydraulic design of a centrifugal pump impeller. This method is based on a geometrical approach employing curvilinear coordinates that are used to formulate both the axisymmetrical flow model in a meridional shape and the final model of flow in a blade cascade taking into account the full 3D shape of the impeller blade. The solution to this model then directly provides the guidelines for shaping the impeller blade in order to suppress the secondary flows, thus increasing the impeller efficiency, which is demonstrated on a real impeller design case. The partial differential equations describing the flow in the blade cascade are numerically solved piecewise on each particular stream surface, which leads to a significant reduction of computational time.
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Computation of compression force on surface
Stejskal, Jiří ; Habán, Vladimír (referee) ; Čermák, Libor (advisor)
In technical computing we often need to find the resulting load on surface caused by the compression force. The aim of this thesis is to suggest one of the possible approaches to do so if the surface is given explicitly or by the coordinates of some of it's points. In the first section, the mathematical definition of the surface with some of it's important properties is mentioned. There is a basic theory of Bézier surfaces, which form the main part of this thesis in the second part. Further on, some results from the theory of surface integrals are mentioned. The last section describes the whole algorithm of computing the resulting load together with the MATLAB program which is added to this thesis. Three examples are given at the end.
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Design systems used in the field of electrical apparatuses
Stejskal, Jiří ; Krejčí, Jan (referee) ; Valenta, Jiří (advisor)
Bachelor´s thesis is engaged on the base of submitter´s requests company OEZ, s.r.o. and is divided into two parts. The first part of work deals with the most often used 2D CAD systems that are used by designers according to their answers in the area of suggestion of electric switchboards low voltage. In the work are described main possibilities of these systems, then what kinds of data format are supported by them. In the second part of the work are described programs established on calculation of warming switchboards. It goes about programs, which supply concrete producer of switchboard case, and further programs based on method of final elements and method of final volume, which enable graphic representation of results.
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Measuring of Velocity Profiles in Liquids by Using of UVP
Kárník, Jan ; Stejskal, Jiří (referee) ; Štigler, Jaroslav (advisor)
The following bachelor's thesis deals with one possible way of determination velocity profiles in liquids. Content of the thesis is focused mainly on the method of the UVP (Ultrasound Velocity Profile), on the ways and principles of measuring, on its pluses and cons and it´s comparison with the other conventional methods, like for the example the PIV (Particle Image Velocimetry) and LDA (Laser Doppler Anemometry). There is also the possible placement of the transducers to the measuring system discussed. Furthermore the thesis deals with trouble in the test measurement. At the beginning this work deals with familiarization with principle and function of the measuring device and with the device for the method UVP itself. Apart from the UVP measuring method the thesis also deals with short description of the competitive methods – PIV, LDA, which are used to measure the velocity profiles nowadays. Particular attention is given to the PIV method, which significance is currently growing. In conclusion, there is comparison of different methods with the UVP method made and there are the future steps to realize the successful measurement with UVP method also discussed.
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The nonstationary motion of solid body in a liquid
Stejskal, Jiří ; Hlavička, Rudolf (referee) ; Čermák, Libor (advisor)
Obsahem této práce je numerická simulace dvoudimenzionálního proudění nestlačitelné vazké kapaliny. Uvažujeme rotující elipsu soustředně umístěnou v kružnici. Prostor mezi elipsou a kružnicí je vyplněn kapalinou. Cílem je popsat proudění kapaliny vyvolané otáčející se elipsou, tzn. stanovit rychlostní pole a rozložení tlaku. Dále pak chceme stanovit přídavné silové účinky kapaliny působící na elipsu. Tyto výsledky získáme řešením Navierových-Stokesových rovnic metodou konečných prvků. Důraz je kladen na odvození numerického schématu v maticové formě vhodné pro numerickou implementaci. Časově závislá výpočetní síť je popsána pomocí Arbitrary Lagrangian-Eulerian (ALE) formulace. Pro obdržení relevantních výsledků je nutná stabilizace metody konečných prvků. Uvedené výsledky naznačují, že odvozená metoda je dostatečně přesná.
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Inverter 12V DC/230V AC
Stejskal, Jiří ; Huták, Petr (referee) ; Klíma, Bohumil (advisor)
This diploma thesis describes particular parts of power inverter such as gate driver, DSC, LC filter, low power supply, DC/DC converter and four-quadrant bridge and manner of its control by digital signal controller. Inverter is designated for generating of a mobile artificial electric grid (for example in a car).
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The design of an induser in front of the impeller
Klusák, Ondřej ; Stejskal, Jiří (referee) ; Haluza, Miloslav (advisor)
The main objective of the thesis is to verify the hydraulic inducer designs and to determine its effect on the cavitation characteristics of the pump. To increase the suction capability and cavitation resistance, the inducer is placed in front of the impeller centrifugal pump. Its role is to protect the impeller against the cavitation. The literary part of the thesis analyzes the issue of cavitation, its origin, development and termination of the cavitation bubble with so-called implosion. Special attention is devoted to describtion of cavitation effect occuring at the hydrodynamic pumps. In the theoretical part, the author is then dealing with the general principles and so far used approaches to the inducer design. The practical part of the thesis describes the process and the derivation of own designs of cylindrical inducer. The aim of the used, unconventional approaches to the inducer design is to achieve a constant pressure field and specific energy of the inducer design output. Partial variants of inducer blades design geometry are tested by the controlled calculation with CFD.
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Analysis of the Velocity and Pressure Fields of the Liquid Using Curvilinear Coordinates
Stejskal, Jiří ; Kozubková, Milada (referee) ; Kučera,, Radek (referee) ; Veselý, Jindřich (referee) ; Pochylý, František (advisor)
This work introduces a new method of hydraulic design of a centrifugal pump impeller. This method is based on a geometrical approach employing curvilinear coordinates that are used to formulate both the axisymmetrical flow model in a meridional shape and the final model of flow in a blade cascade taking into account the full 3D shape of the impeller blade. The solution to this model then directly provides the guidelines for shaping the impeller blade in order to suppress the secondary flows, thus increasing the impeller efficiency, which is demonstrated on a real impeller design case. The partial differential equations describing the flow in the blade cascade are numerically solved piecewise on each particular stream surface, which leads to a significant reduction of computational time.
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Noise emissions in farming chickens for fattening
STEJSKAL, Jiří
The thesis is focused on the sources of noise in agricultural operations in terms of noise emissions. Agricultural operation in this case was a hall for fattening chickens for meat. The main goal is practical to measure all sources of noise generated during the various operations fattening. The work was primarily necessary to choose suitable habitats for measuring noise sources and measurements of climatic conditions. Followed by calculation of equivalent noise levels and evaluation under applicable legislation. As part of the work was proposed noise protection measures, which would partly help reduce the impact of noise emissions.
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The design of an induser in front of the impeller
Klusák, Ondřej ; Stejskal, Jiří (referee) ; Haluza, Miloslav (advisor)
The main objective of the thesis is to verify the hydraulic inducer designs and to determine its effect on the cavitation characteristics of the pump. To increase the suction capability and cavitation resistance, the inducer is placed in front of the impeller centrifugal pump. Its role is to protect the impeller against the cavitation. The literary part of the thesis analyzes the issue of cavitation, its origin, development and termination of the cavitation bubble with so-called implosion. Special attention is devoted to describtion of cavitation effect occuring at the hydrodynamic pumps. In the theoretical part, the author is then dealing with the general principles and so far used approaches to the inducer design. The practical part of the thesis describes the process and the derivation of own designs of cylindrical inducer. The aim of the used, unconventional approaches to the inducer design is to achieve a constant pressure field and specific energy of the inducer design output. Partial variants of inducer blades design geometry are tested by the controlled calculation with CFD.
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