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Numerical Modelling of Grate Combustion
Juřena, Tomáš ; Klemeš,, Jiří (referee) ; Žitný, Rudolf (referee) ; Hájek, Jiří (advisor)
Předkládaná práce je zaměřena na numerické modelování spalování tuhých paliv na roštu metodami výpočtové dynamiky tekutin (CFD). Jelikož výsledky CFD simulací roštového spalování závisí na kvalitě vstupních dat, která zahrnují i údaje o teplotě, hmotnostním toku a chemickém složení spalin vystupujících z lože, pozornost je věnována především procesům, probíhajícím v loži během spalování na roštu. Velká část práce je věnována vývoji spolehlivého modelu spalování v sypaných ložích, jelikož může napomoci zkvalitnit výsledky simulací i rozšířit znalosti principů spalování tuhých paliv v sypaných ložích. V rámci práce byl vyvinut jednorozměrný nestacionární model spalování v experimentálním reaktoru a implementován do počítačového programu GRATECAL 1.3 včetně grafického uživatelského rozhraní. Zvláštní důraz byl kladen na konzervativnost modelu. Proto byla vyvinuta metoda pro kontrolu hmotnostní a energetické bilance systému a následně aplikována v řadě studií, v rámci nichž byly odhaleny některé chyby týkající se definic zdrojových členů, které byly převzaty z literatury a opraveny. Pomocí modelu byla provedena analýza šíření čela sušení a reakce hoření koksu po výšce lože pšeničné slámy. Na základě výsledků těchto analýz bylo doporučeno zahrnout i modelování změny porozity částic paliva, aby šířka reakční zóny byla predikována korektně v případě, že je uvažována změna porozity celého lože. Rovněž vyvinutá bilanční metoda byla použita k analýze vlivu kritérií konvergence na hmotnostní a energetickou nerovnováhu simulovaného systému. Bylo zjištěno, že škálovaná rezidua rovnic všech veličin by měla poklesnout aspoň na hodnotu $10^{-6}$, aby bylo dosaženo nízké hmotnostní a energetické nerovnováhy a tudíž uspokojivě přesných výsledků ze simulací v loži. Druhá část práce je věnována vývoji a implementaci knihovny uživatelem definovaných funkcí pro komerční CFD nástroj ANSYS FLUENT, které slouží k propojení modelu lože s modelem komory reálné spalovací jednotky, aby byla umožněna dynamická změna okrajových podmínek na vstupu do komory v závislosti na výstupech ze simulací v loži. Vytvořené rozhraní pro propojení těchto dvou modelů je dostatečně obecné pro aplikaci na širokou škálu modelů roštových kotlů. Popsané výsledky přispívají k lepšímu porozumění numerickému modelování spalování na roštu, a to zejména ve fázi sestavování numerického modelu a nastavení parametrů řešiče pro kontrolu konvergence.
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Methods for Determination of Characteristic Parameters of Combustion Processes on the Basis of Experiments and Modeling
Bělohradský, Petr ; Klemeš,, Jiří (referee) ; Žitný, Rudolf (referee) ; Stehlík, Petr (advisor)
The present thesis is concerned with methods for determination and modeling of characteristic parameters of combustion of gaseous fuels. The focus is stressed on formation of nitrogen oxides and heat transfer from hot flue gases into combustion chamber’s walls. Experimental work, which is focused on testing of two burners with suppressed formation of nitrogen oxides, is an important part of the thesis. Its aim is to obtain data that is necessary for further processing and modeling. The work presents two methods that may be used in modeling of characteristic combustion parameters, namely the method based on statistical processing of data and the method based on computational fluid dynamics. The approaches are applied to two devices (burner with two-staged fuel supply, burner with two-staged air supply) with the objective to analyze their parameters. First approach covers detailed planning of burner test prior to its own carrying out (definition of the goal of experiment, choice of input factors and response, experimental plan) and subsequent statistical processing of experimental data. On the contrary, CFD approach offers simulations as an alternative option to traditional experimental methods. The simulation of combustion includes building of computational grid, setup of boundary conditions, turbulence model, heat transfer model and chemical kinetics. Results of simulations are compared with experimental measured data.
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Person Identification and Verification Using EEG
Žitný, Roland ; Orság, Filip (referee) ; Tinka, Jan (advisor)
The aim of this work was to create a brain-computer interface that reliably identifies and verifies a person using his electroencephalographic signals. Creating a user profile and verifying it is based on processing reactions to his own face, and the face of strangers or acquaintances. Algorithms such as bandpass and noise removal using wavelet transformation are user to filter signals. The classification of reactions is performed using a convolutional neural network or linear discriminant analysis. The average accuracy of the linear discriminant analysis is 66.2 % and of the convolutional neural network is 58.7 %. The maximum achieved accuracy was with linear discriminant analysis and at 93.7 %.
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Data Analysis for Predictive Maintenance of a Robotic Arm
Žitný, Roland ; Rozman, Jaroslav (referee) ; Janoušek, Vladimír (advisor)
The Mitsubishi MELFA robotic arms used in modern factories work almost without interruption and produce sensory data about their operation. Various analysis techniques can be applied to such data for predictive maintenance, which provide information on the condition and maintenance needs of such robotic arms. The proposed predictive maintenance process consists of a sensory data acquisition system using the slmpclient and mitsubishi-monitor libraries, an analysis method system with anomaly detection using a convolutional autoencoder, anomaly classification using convolutional neural networks, and data segmentation into segments of individual robot actions using hidden Markov models. Such analysis techniques provide information on the severity, type, and location of emerging faults and abnormalities in behavior, which then determine the time required to perform the required maintenance. This work presents a created chain of predictive maintenance processes, where the obtained findings provide valuable insights into the application of predictive maintenance of Mitsubishi MELFA robotic arms in an industrial environment.
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Self-excited oscillations of elastic tubes induced by fluid-structure interactin
Štembera, Vítězslav ; Maršík, František (advisor) ; Okrouhlík, Miloslav (referee) ; Žitný, Rudolf (referee)
1 Introduction The aim of this thesis was to develop a mathematical model that could describe the phe- nomenon of self-excited oscillations of flexible tubes induced by fluid-structure interaction between the tube wall and the inner fluid flow. The term self-excited means that the studied system has no oscillatory inner sources or bound- ary conditions, the harmonic motion originates in the system itself. Let us show some examples for the occurrence of this phenomenon in the human body: Pedley ([?]) mentions that vessel collapse is most readily seen in veins, such as in the veins of a hand raised above the level of the heart or in the jugular vein when a person is standing erect ([?]). In arteries1 , such a collapse can be observed only in some special cases, for example in the case when additional outer pressure is applied to the artery. One example is blood pressure measurement using a sphygmomanometer cuff. During this measurement, the so- called Korotkoff sounds, which are strongly believed to be connected to these self-excited oscillations of the brachial artery wall, appear. These Korotkoff sounds are used by medical doctors for pressure diagnostics and are known from the beginning of the 20th century2 . They disappear when the cuff is removed. Artery collapse is also probable if an artery is filled with...
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Person Identification and Verification Using EEG
Žitný, Roland ; Orság, Filip (referee) ; Tinka, Jan (advisor)
The aim of this work was to create a brain-computer interface that reliably identifies and verifies a person using his electroencephalographic signals. Creating a user profile and verifying it is based on processing reactions to his own face, and the face of strangers or acquaintances. Algorithms such as bandpass and noise removal using wavelet transformation are user to filter signals. The classification of reactions is performed using a convolutional neural network or linear discriminant analysis. The average accuracy of the linear discriminant analysis is 66.2 % and of the convolutional neural network is 58.7 %. The maximum achieved accuracy was with linear discriminant analysis and at 93.7 %.
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The phenomenon Milan Kostohryz.
Žitný, Radek ; HLAVÁČ, Jiří (advisor) ; MAREŠ, Vlastimil (referee)
This thesis presents research about the very successful career of the Czech musician and pedagogue Milan Kostohryz (1911-1998). He made a substantial contribution to composition of new pieces, re-building historical instruments, developing new instruments, revising many old compositions, and he gave instruction to a number of excellent players. His work made impact and gained recognition on an international level. The research in this thesis is based mainly on original written correspondence, and partially on personal memories of his contemporaries and family, as well as on a few public resources and preserved sound recordings.
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Simulation of collagen solution flow in rectangular capillary
Kysela, Bohuš ; Skočilas, J. ; Zitny, R. ; Stancl, J. ; Houska, M. ; Landfeld, A.
The viscoelastic properties of foods and polymers can be evaluated from flow of the material in capillary with specified dimension and shape. The extrusion rheometer equipped by capillary with rectangular cross-section was used for determination of the rheological behaviour of water collagen solution. The measurements of the axial profiles in longitudinal direction of the total stresses at capillary wall were performed for various shear rates. The linear viscoelastic model of Oldroyd B type: White-Metzner model was used for simulation of fluid flow in OpenFOAM software package. The simulations describe the effect of relaxation time on wall total stress in convergent-divergent capillary.
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Self-excited oscillations of elastic tubes induced by fluid-structure interactin
Štembera, Vítězslav ; Maršík, František (advisor) ; Okrouhlík, Miloslav (referee) ; Žitný, Rudolf (referee)
1 Introduction The aim of this thesis was to develop a mathematical model that could describe the phe- nomenon of self-excited oscillations of flexible tubes induced by fluid-structure interaction between the tube wall and the inner fluid flow. The term self-excited means that the studied system has no oscillatory inner sources or bound- ary conditions, the harmonic motion originates in the system itself. Let us show some examples for the occurrence of this phenomenon in the human body: Pedley ([?]) mentions that vessel collapse is most readily seen in veins, such as in the veins of a hand raised above the level of the heart or in the jugular vein when a person is standing erect ([?]). In arteries1 , such a collapse can be observed only in some special cases, for example in the case when additional outer pressure is applied to the artery. One example is blood pressure measurement using a sphygmomanometer cuff. During this measurement, the so- called Korotkoff sounds, which are strongly believed to be connected to these self-excited oscillations of the brachial artery wall, appear. These Korotkoff sounds are used by medical doctors for pressure diagnostics and are known from the beginning of the 20th century2 . They disappear when the cuff is removed. Artery collapse is also probable if an artery is filled with...
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The production technology of clarinet reeds and possible modifications
Žitný, Radek ; HLAVÁČ, Jiří (advisor) ; MAREŠ, Vlastimil (referee)
In my thesis I describe the known technologies of clarinet and saxophone reed making. These range from purely hand-made fabrication (as in the case of the production of oboe and bassoon reeds) to technologies with an extensive use of machine work, which allows for refined and accelerated production. I also describe what precedes the manufacturing of a reed itself, that is growing and harvesting of cane wood of which the reeds are made. Clarinet and saxophone reeds are the subject of much speculation in terms of durability, usage, warm-up, storage and especially their possible customization to the needs of each individual player. That is why in the second part of this thesis I focus on possible personilised modifications of reeds. To conclude I quote and comment on the most comprehensive records of reed adjustments available in the existing specialist literature. The aim of my research is to provide clarinetists and saxophonists with a manual where I present facts and methods of reed adjustment they may put in practice themselves, and therefore avoid having to rely on „selecting the best of the mediocre reeds available in the music shop". The thesis includes an illustrated appendix of sketches, adjustments, reeds and their packaging, cases and tools.
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