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Quality of fuel atomization from small pressure-swirl atomizers
Malý, Milan ; Broukal, Jakub (oponent) ; Jedelský, Jan (vedoucí práce)
The present thesis deals with measurement of spray characteristics of pressure-swirl atomizer by Phase Doppler Anemometry (PDA). The aim of these measurements is to investigate and compare spray characteristics using different liquids and different regimes of inlet pressure and determine if it is possible to replace kerosene with biofuels in terms of quality of atomization. The theoretical part deals with fundamental basics of the atomization of pressure-swirl atomizers and the principles of laser anemometry. The experimental part describes test bench, operating regiments and the setup of the experiment. Results contain visualization of spray, droplet size distribution inside spray, velocity and Sauter mean diameter (SMD) profile in various operation conditions as different downstream distance, various inlet pressure and different liquids.
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Measurement of spray characteristics using optical measurement methods
Ďurdina, Lukáš ; Otáhal, Jan (oponent) ; Jedelský, Jan (vedoucí práce)
The present thesis deals with measurement of spray characteristics of two pressure–swirl atomizers for a combustion chamber of a small–sized jet engine investigated on a cold test bench by means of Particle Image Velocimetry (PIV) and Phase-Doppler Anemometry (PDA). The aim of these measurements is to investigate and compare the spray characteristics of these nozzles in order to elucidate the possible impacts of the design change on the nozzle operation in the combustion chamber. The theoretical part deals with fundamental concepts of liquid atomization, design and performance of pressure–swirl atomizers and description of principles of the used laser diagnostic techniques. Next part describes design and operation of the test bench. The experimental part is devoted to experimental set-up and digital image processing and post–processing techniques of the gathered data. Results contain velocity vector fields, axial velocity profiles and droplet size distributions for various operating conditions of both nozzles.
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Vliv provozních parametrů na kvalitu rozprašování kapalin u dvou-médiových trysek
Zaremba, Matouš ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
Tato diplomová práce se zabývá měřením charakteristik sprejů šumivých trysek určené pro spalování odpadních a těžkých paliv. Trysky byly testovány za studena pomocí fázové Dopplerovského analyzátoru. Charakteristiky sprejů byly vyhodnoceny z vice různých provozních režimů tlaku, teploty a poměru plynu a kapaliny. Cílem těchto měření je porovnat provozní režimy a jejich vliv na kvalitu spreje. Teoretická část se zabývá základy rozpadu kapalin, rozpad v šumivých tryskách a principy laserových měřících metod. Praktická část se zabývá úpravou testovací tratě, nastavení a optimalizací měřícího laserového zařízení. Výsledky obsahují vizualizaci spreje, rychlostní profily a distribuci velikosti kapek při různých provozních režimech trysky.
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EFFECT OF FLOW PARAMETERS OF WATER AND AIR ATOMIZED SPRAYS ON COOLING INTENSITY OF HOT SURFACES
Boháček, Jan ; Střasák,, Pavel (oponent) ; Rudolf, Pavel (oponent) ; Horský, Jaroslav (vedoucí práce)
The present thesis is focused on an overall description of water jets and air atomized jets for cooling purposes using CFD methods namely ANSYS FLUENT. It comprises two main parts – the micro and the macro model. The micro model concerns with a numerical description of single droplet dynamics whereas the macro model deals with a numerical modeling of water jets as complicated droplet structures emanating from solid stream nozzle and flat fan nozzle. By and large, it is based on multiphase models and User Defined Functions (UDFs), which represents the background of the present thesis. In most of cases, the presented numerical models were compared either with experimental data or another numerical model. In the first part, the theory of each of three multiphase models is discussed. The first one, the Volume Of Fluid model (VOF), was used for simulation of single droplet dynamics designated as a micro model whilst last two multiphase models, the Euler-Euler model and the Euler-Lagrange model, were applied in the case of modeling of the entire water jet structure, which is contrarily designated as a macro model. The micro model concerns with a numerical study of free-falling water droplet. For small droplet diameters (~100µm) the standard surface tension model (Continuum Surface Force model, CSF) was proved to cause significant unphysical parasitic currents. Therefore, the thesis is also devoted to surface tension as a source term of body forces imposed in momentum equation, normal, curvature calculation and related issues. The macro model covers a numerical study of dynamics of the entire water jet structure i.e. the space between the nozzle exit and the wall where the jet impinges. It accounts for the complete geometry, for instance, support rolls, a slab and a mold bottom of a continuous caster. Firstly, the physics of a solid jet impact onto a hot plate was simulated using both, the VOF and the Euler-Lagrange model. As regards the case with the VOF model, a model for film boiling was designed and tested. Finally, both, the Euler-Euler model and the Euler-Lagrange model, were used for simulation of a flat jet horizontally spraying onto a hot slab inside a confined domain bounded by support rolls and a mold bottom. Concerning the simulation with the Euler-Euler model, a secondary breakup model was introduced based on the wave stability atomization theory. Concerning the Euler-Lagrange simulation, the dispersed phase (Lagrange particles) formed rather a continuous phase in some places, and therefore the coupling between Lagrange particles and the VOF model via UDFs was proposed.
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Experimental study of spray characteristics and functionality of small pressure-swirl atomizers
Malý, Milan ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present master thesis deals with an experimental study of spray characteristics from several small pressure-swirl atomizers used in a combustion chamber of turbojet aircraft engine. For decades, attention has been paid to improvement of their atomization characteristics but still there are possibilities which have not been examined yet. Investigations were carried out using various geometries of the individual elements of atomizer to find their effect on the spray. Measurements were made using a different number of entry ports (2, 3 and 4), various swirl chamber shapes (hemispheric; conical; curved convex and flat conical), and different spill-line orifice designs (axial and off-axis). Emphasis was placed on the assessment of spray stability wherein the fluctuating spray negatively affects the operating characteristics of the combustion chamber. Spray characteristics were probed using Phase Doppler analyser, spray circumferential homogeneity was rated by mechanical patternator and the liquid breakup was imaged by simple laser shadowgraph.
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Experimental study of spray characteristics and functionality of small pressure-swirl atomizers
Malý, Milan ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present master thesis deals with an experimental study of spray characteristics from several small pressure-swirl atomizers used in a combustion chamber of turbojet aircraft engine. For decades, attention has been paid to improvement of their atomization characteristics but still there are possibilities which have not been examined yet. Investigations were carried out using various geometries of the individual elements of atomizer to find their effect on the spray. Measurements were made using a different number of entry ports (2, 3 and 4), various swirl chamber shapes (hemispheric; conical; curved convex and flat conical), and different spill-line orifice designs (axial and off-axis). Emphasis was placed on the assessment of spray stability wherein the fluctuating spray negatively affects the operating characteristics of the combustion chamber. Spray characteristics were probed using Phase Doppler analyser, spray circumferential homogeneity was rated by mechanical patternator and the liquid breakup was imaged by simple laser shadowgraph.
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EFFECT OF FLOW PARAMETERS OF WATER AND AIR ATOMIZED SPRAYS ON COOLING INTENSITY OF HOT SURFACES
Boháček, Jan ; Střasák,, Pavel (oponent) ; Rudolf, Pavel (oponent) ; Horský, Jaroslav (vedoucí práce)
The present thesis is focused on an overall description of water jets and air atomized jets for cooling purposes using CFD methods namely ANSYS FLUENT. It comprises two main parts – the micro and the macro model. The micro model concerns with a numerical description of single droplet dynamics whereas the macro model deals with a numerical modeling of water jets as complicated droplet structures emanating from solid stream nozzle and flat fan nozzle. By and large, it is based on multiphase models and User Defined Functions (UDFs), which represents the background of the present thesis. In most of cases, the presented numerical models were compared either with experimental data or another numerical model. In the first part, the theory of each of three multiphase models is discussed. The first one, the Volume Of Fluid model (VOF), was used for simulation of single droplet dynamics designated as a micro model whilst last two multiphase models, the Euler-Euler model and the Euler-Lagrange model, were applied in the case of modeling of the entire water jet structure, which is contrarily designated as a macro model. The micro model concerns with a numerical study of free-falling water droplet. For small droplet diameters (~100µm) the standard surface tension model (Continuum Surface Force model, CSF) was proved to cause significant unphysical parasitic currents. Therefore, the thesis is also devoted to surface tension as a source term of body forces imposed in momentum equation, normal, curvature calculation and related issues. The macro model covers a numerical study of dynamics of the entire water jet structure i.e. the space between the nozzle exit and the wall where the jet impinges. It accounts for the complete geometry, for instance, support rolls, a slab and a mold bottom of a continuous caster. Firstly, the physics of a solid jet impact onto a hot plate was simulated using both, the VOF and the Euler-Lagrange model. As regards the case with the VOF model, a model for film boiling was designed and tested. Finally, both, the Euler-Euler model and the Euler-Lagrange model, were used for simulation of a flat jet horizontally spraying onto a hot slab inside a confined domain bounded by support rolls and a mold bottom. Concerning the simulation with the Euler-Euler model, a secondary breakup model was introduced based on the wave stability atomization theory. Concerning the Euler-Lagrange simulation, the dispersed phase (Lagrange particles) formed rather a continuous phase in some places, and therefore the coupling between Lagrange particles and the VOF model via UDFs was proposed.
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Vliv provozních parametrů na kvalitu rozprašování kapalin u dvou-médiových trysek
Zaremba, Matouš ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
Tato diplomová práce se zabývá měřením charakteristik sprejů šumivých trysek určené pro spalování odpadních a těžkých paliv. Trysky byly testovány za studena pomocí fázové Dopplerovského analyzátoru. Charakteristiky sprejů byly vyhodnoceny z vice různých provozních režimů tlaku, teploty a poměru plynu a kapaliny. Cílem těchto měření je porovnat provozní režimy a jejich vliv na kvalitu spreje. Teoretická část se zabývá základy rozpadu kapalin, rozpad v šumivých tryskách a principy laserových měřících metod. Praktická část se zabývá úpravou testovací tratě, nastavení a optimalizací měřícího laserového zařízení. Výsledky obsahují vizualizaci spreje, rychlostní profily a distribuci velikosti kapek při různých provozních režimech trysky.
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Measurement of spray characteristics using optical measurement methods
Ďurdina, Lukáš ; Otáhal, Jan (oponent) ; Jedelský, Jan (vedoucí práce)
The present thesis deals with measurement of spray characteristics of two pressure–swirl atomizers for a combustion chamber of a small–sized jet engine investigated on a cold test bench by means of Particle Image Velocimetry (PIV) and Phase-Doppler Anemometry (PDA). The aim of these measurements is to investigate and compare the spray characteristics of these nozzles in order to elucidate the possible impacts of the design change on the nozzle operation in the combustion chamber. The theoretical part deals with fundamental concepts of liquid atomization, design and performance of pressure–swirl atomizers and description of principles of the used laser diagnostic techniques. Next part describes design and operation of the test bench. The experimental part is devoted to experimental set-up and digital image processing and post–processing techniques of the gathered data. Results contain velocity vector fields, axial velocity profiles and droplet size distributions for various operating conditions of both nozzles.
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