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Research of Systems for Providing the Quality of the Environment in the Car Cabin
Šíp, Jan ; Kavička, František (referee) ; Volavý, Jaroslav (referee) ; Lízal, František (advisor)
Optimal conditions of indoor environmental quality, especially thermal comfort and indoor air quality, are important because they lead to the active safety of passengers. Long-term exposure to inconvenient temperatures may cause thermal stress and negatively affects the driver’s cognitive functions. These include important abilities of drivers, such as concentration, vigilance, speed of decision-making and others. The inappropriate temperature in the cabin is one of the most dangerous factors causing car crashes. Air indoor quality is negatively affected by exhaust gases or particles from tire wear, which enter the car cabin during ventilation. This can be prevented by using an air recirculation system which does not supply outside air, but it is a closed circuit. This mode, however, causes high CO2 concentration in the cabin which can lead to excessive fatigue. This thesis deals with the influence of different ventilation systems on indoor environmental quality, i. e. thermal comfort and indoor air quality. A partial factor of thermal comfort is the flow field which was investigated downstream of a benchmark automotive vent. CFD was applied to determine the flow field downstream of a vent. The results were validated by experimental data acquired by Constant Temperature Anemometry. CFD has been also used for the evaluation of the thermal comfort of three novel ventilation systems (mixing, ceiling and floor ventilation). The results were validated by experimental data acquired by thermal manikin and climate chamber. Indoor air quality has been evaluated based on the Age of Air. The analytical empirical equation by Rajaratnam can be successfully used also to determine the throw of the jet, which is favorable, especially in light of the fact that both computational methods were not very accurate in velocity decay predictions. The Large Eddy Simulation and Reynolds-averaged Navier–Stokes method are suitable for evaluating the flow field downstream of the automotive vent. The diagrams of comfort zones were evaluated for all regimes based on equivalent temperatures. The best performance in terms of the highest level of human comfort was achieved by the ceiling ventilation in the summer conditions and by the floor ventilation in the winter conditions. From the point of view of the Age of Air, the ceiling air ventilation system is the most suitable for the winter conditions. In the summer conditions the Age of Air values for individual air ventilation concepts are very similar for both interior types.
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Analysis of the Effects of Internal Recirculation Channel of a Radial Compressor on Extending the Stable Working Area
Paulík, Lukáš ; Vacula, Jiří (referee) ; Novotný, Pavel (advisor)
The extension of the stable working area is very important especially for the radial compressors used in turbochargers. Compressors with high pressure ratio have a narrow stable operating region, which limits their practical use. One of the frequent modifications on radial compressor, concerning the extension of its range of stable work, is installation of an internal recirculation channel (IRC) in its inlet section. CFD programs are often used to simulate the flow through the turbomachines for optimizing the design of the IRC. Based on the extensive research, regarding the flow in the IRC and its location in the inlet of the compressor, suitable variants of its design were selected and applied to a radial compressor of the turbocharger. By simulating the flow in a radial compressor with the IRC, using Ansys CFX software, the compressor performance maps were determined. The best design of the IRC which meets the requirements for extending its stable working area was selected by evaluating the results of the simulations.
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CFD modelling of the initial phase of fouling inside convective section of a combustion facility
Zlámal, Filip ; Juřena, Tomáš (referee) ; Strouhal, Jiří (advisor)
The aim of this thesis was to create, based on the knowledge obtained from research, a CFD simulation of initial phase of fouling of solid particles during the combustion of solid fuels. The introduction of the work summarizes the mechanisms of fouling by solid particles. The introduction of the work summarizes the mechanisms of fouling by solid particles. Approaches to modelling the impact and deposition of particles are also described. A model is built, which is implemented in the ANSYS Fluent software with the addition of user-defined functions. The model is tested on a model of the convective part of an experimental device for burning solid fuels.
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CFD simulation of the hydrokinetic energy converter using flow-induced vibrations
Vaverka, Jakub ; Bezdíček, Jiří (referee) ; Klas, Roman (advisor)
Flow-induced vibrations on bodies of different shapes are investigated by CFD simulations. The influence of the mass of the body, the spring stiffness and the value of the added damping on the dynamic behaviour of the system is evaluated. A combination of the 6DOF function and a dynamic computational mesh is used to move the body around the y-axis solely by fluid flow. The output is an evaluation of the forces acting on the body, the trajectory of the body and the possible power that the body could generate by its motion.
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Modeling of process and power equipment fouling by solid pollutants
Strouhal, Jiří ; Turek, Vojtěch (referee) ; Hájek, Jiří (referee) ; Jegla, Zdeněk (advisor)
Modelling of particulate fouling based on Computational Fluid Dynamics enables to detect a risk of deposit development and to propose improvements in operating conditions and equipment design. The work focuses on the transport and sticking of solid particles. The size of the particles lies in the range from several up to dozens of m. The conditions correspond to the deposition of particles with a negligible liquid fraction and the deposition occurs due to particle deformation, gravity, adhesion, wall surface roughness, deposit deformation and dynamic friction. An emphasis is put on the selection of a suitable sticking model from the group of critical velocity models, which aside from the local conditions and the particle properties account for the impaction velocity. Sensitivity studies on the model settings were conducted to assess the significance of the model parameters and the included phenomena. The simulations were conducted on the case of an experimental facility for solid fuels combustion. Obtained results were compared to observed deposits.
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Numerical simulation of oil flow in bearing housing
Zogata, Filip ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis is concerned with the development of a computational model of the bearing node, since in the development of a synchronous generator, great emphasis is placed on the proper design of the bearing node, as this complex component has a direct effect on the overall efficiency of the generator. A large number of engineering experiments need to be used to test on the physical model, but it is also necessary to test using the numerical model, as the production of the prototype itself for testing is very costly, and therefore it is advisable to verify the prototype itself before production by a series of numerical simulations. Another important feature is the possibility to investigate even unfavourable or even extreme conditions, which are already very difficult, sometimes impossible, to test physically in the laboratory, and these numerical simulations can be divided according to several parameters, but in the field of bearing nodes we mainly encounter structural, dynamic, temperature or flow problems. This thesis in particular is focused on establishing a basic overview of computational fluid dynamics in the oil flow domain, while this knowledge is used in practice, as another objective is to develop a numerical model of lubrication of the aforementioned bearing node. However, this is a very complex problem, and therefore a study is first carried out to investigate the key components, and only by gradually adding different elements is the numerical model created in the Particleworks software environment, while a sensitivity study is carried out focusing on particle size. Subsequently, the individual partial results are summarized in the conclusion of this paper.
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Condensation heat transfer of water steam on cylindrical wall
Horká, Lucie ; Bašta,, Jiří (referee) ; Kabele,, Karel (referee) ; Hirš, Jiří (advisor)
The doctoral thesis is aimed at condensation heat transfer of water steam on a cylindric wall. This physical phenomenon of water steam condensation is examined and published in leading scientific journals for more than 100 years. The main aim of the doctoral thesis is study of the water steam condensation on a cylindrical wall. The result of the doctoral thesis is the theoretical and experimental determination of the heat transfer coefficient during the water steam condensation on the cylindrical wall. This coefficient is a basic parameter of design of all the thermal devices, which use the condensation heat of water steam in technical practice.
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The runner for the straight-flow turbine for small hydro power Sobotín
Žižka, Jakub ; Veselý, Jindřich (referee) ; Haluza, Miloslav (advisor)
The thesis deals with the problem of optimizing an existing unused turbine for use in a different location than the designed. The goal is to reduce the flow through the turbine by changing the runner geometry while increasing the head, with the least possible decrease in efficiency. The individual modifications of the hydraulic shape are based on the knowledge of the basic relations for the designing of hydrodynamic machines. Numerical fluid mechanics is a tool for validating the effect of individual adjustments. The hydraulic design of the new runner and draft tube of the axial propeller turbine with a fixed guide vanes is performed. Based on the CFD simulation, a universal turbine characteristic with a new hydraulic shape is compiled.
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Analysis of the turbine housing design in terms of heat leakage
Diakov, Jakub ; Lošák, Petr (referee) ; Vlach, Radek (advisor)
This diploma thesis deals with the judgment of usability of the topology optimisation of the Ansys Workbench program combined with thermo-mechanical fatigue and the non-linear material model of a turbine housing. The first part of the thesis includes research which serves for the purpose of understanding and for theoretical support of the practical part. The research part of the thesis at first gives reasons for the choice of the main aim of the thesis. The main aim of the thesis is the decrease of heat leak from the exhaust fumes due to the reason of the sooner combustion products processing and lower emissions production. The second chapter of the research analyses the construction and function of a turbocharger from the perspective of the geometry of the components and also from the perspective of the production and use of the components. The following chapter deals with the analysis of the energetic and thermal balance of the turbocharger. This chapter mentions the fundamental simplifications of the calculation problem and these simplifications are applied in the practical example. Next, the chapter analyses the thermo-mechanical fatigue, classification of the areas of fatigue and it also analyses the approaches used for the life expectancy predictions. The chapter of the research part deals with the selected areas of calculation and their theoretical basis. The last chapter analyses the fluid mechanics and the selected methods of the topology optimisation which are available in the selected calculation program. After the research part of the thesis, there follows the practical part which discusses a multiphysical example of the turbine housing optimisation from the perspective of heat leak and of the turbine housing being exposed to the thermo-mechanical fatigue. The practical part which is composed of several steps is based on the CFD analysis and this analysis is used for the purpose of gaining thermal conditions in order to calculate the transient thermal analysis. Out of the outcomes of the coupled transient thermal analysis, there is used the spatial temperature field which as a result of the expansivity of the material causes non-homogenous stress on the turbine housing. The practical part has an individual chapter dedicated to the usability of the topological optimisation in different types of tasks. One of the parts of this chapter includes is a suggestion of the methodology for determination of voltage limitation for the selected type of topological optimisation. The penultimate chapter in the practical part is dedicated to the topological optimisation of the turbine housing on the basis of the preceding voltage analysis and determined limitation. The last chapter includes performed validation of the optimised shape of the housing after the geometry is adjusted. The validation is performed from the perspective of steady state temperature of the output combustion products, of speed of heating of the optimised geometry and from the perspective of the comparison of the life expectancy determined in the thermo-mechanical fatigue. At the end of thesis, there are included conclusions discussed and suggested, scope for improvement and possibilities for continuation of further research.
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Stress-strength analysis of an impeller shaft using fluid-structure interaction modelling
Zifčáková, Barbora ; Vondál, Jiří (referee) ; Juřena, Tomáš (advisor)
This master’s thesis deals with numerical simulations of type FSI (Fluid Structure Interaction). Software used is ANSYS Fluent and ANSYS Mechanical. The aim of this thesis is to study the interaction between fluid flow in the mixing tank used in pharmaceutical industry to process eggshells and the agitator whose shaft has deformed during operation. CFD part consists of both one-phase and multi-phase transient simulations. The impact of solid body deformation on fluid flow is neglected hence only one-way Fluid Structure Interaction is considered for the simulations. Fluid flow in the tank and stress-strain behavior of the shaft is evaluated both in quasi-steady state and during start-up of the device. Computations showed that the impact of eggshells on agitator is negligible during operation (in quasi-steady state) unlike the behavior during start-up of the device when stresses and strains of the shaft are significantly higher. Possible reasons why the shaft deformed are presented and further numerical simulations are discussed and suggested.
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