The presented diploma thesis deals with the design of an electrostatic precipitator for a domestic automatic wood fuel boiler. The individual chapters describe the products of the combustion process, the principles of charging dust particles, describe existing patents related to electrostatic precipitators, commercial electrostatic precipitators and the last part of the work calculates a mathematical model, according to which previously designed and evaluated separator variants were designed and evaluated. Based on the results, the optimal variant of the electrostatic precipitator designed for a domestic boiler is then selected.

This thesis will cover how two applications were developed using the commercial software COMSOL Multiphysics. The first application, the Joule heating application, simulates joule heating while taking the skin effect into consideration. The second application, the Corona Discharge application, is used to simulate corona discharges. It also estimates the initiation of charge propagation using the integration of the Townsend mechanism. The goal of this thesis is to verify that the COMSOL Application Builder can be used to create easy-to-use applications. With a high degree of accuracy and efficiency, it aims to aid Hitachi’s work with the design and effectiveness of bushings. These applications were developed to have similar graphical interfaces, making it easier for users to understand their functionality. Although a striking similarity in the graphical interfaces, the two applications have vastly different computational formulas, and physical properties, and are not based on the same COMSOL modules. The applications resulted in improving Hitachi’s workflow by significantly increasing efficiency and accuracy. The applications also contain a high degree of guidance to help the user optimize their results. However, as with all code-based projects, there is room for improvement. In the case of the Corona Discharge Application, one upgrade could be to allow the application to automatically find and calculate points with the highest potential. In conclusion, this thesis found that it is possible to create applications based onCOMSOL models, with a high degree of accuracy and efficiency, while still making them easy to use, interactive, and retaining all their physical properties.

An investigation of ion flow control was performed to determine the effect of a positive, DC corona discharge on the boundary layer profile along a flat plate and to examine its ability to prevent separated flow in a low-speed compressor cascade. Flat plate tests were performed for two electrode configurations at free-stream velocity magnitudes of 2.5, 5, 7.5, and 10 m/s. Boundary layer velocity profile data was taken to measure the performance of the electrode pairs. Ion flow control was also tested in the compressor cascade for a stagger angle of 25° at angles of attack equal to 6° and 12°. The cascade tests were performed at free-stream velocities of 5 and 10 m/s. Static tap data was used to characterize separated flow behavior and the effect of ion flow control on flow reattachment. A computational model was developed using the commercial CFD software Fluent. This model simulates ion flow control as a body force applied to the flow through user-defined functions. The study showed that the corona discharge has the ability to increase near-wall velocities and reduce the thickness of the boundary layer for flow over a flat plate. Ion flow control successfully prevented trailing edge separation in a compressor cascade for angles of attack of 6° and 12°; however, the flow control scheme was not able to prevent leading edge separation for angle of attack equal to 12°. The ion flow control CFD model accurately predicted flow behavior for both the flat plate and cascade experiments. The numerical model was able to simulate the boundary layer velocity profiles for flat plate tests with good accuracy, and was also able to predict the flow behavior over a compressor blade. The model was able to show the trends of separated and reattached flow over the blade surface. / Master of Science

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With increasing global population comes an increase in the need to safe and clean drinking water. Contaminants can arise in drinking water either naturally, or by the interaction of disinfection chemicals with naturally occurring materials, or simply due to by-products of the disinfection mechanism itself. Due to the oxidative nature of our disinfection treatments, these species are in highly oxidized states, and in some cases require chemical reduction to become less harmful. The present work demonstrates the capabilities of aqueous phase corona plasma in reductive treatment of oxidized contaminants found in drinking water. This study focuses on the treatment of the nitrate ion, bromate ion, chlorate ion and monobromoacetic acid, all of which can be found in typical drinking water systems. The second and third chapters within this thesis establish the optimal water matrix conditions for the treatment of bromate, chlorate and nitrate. These experiments investigate the influence of pH, temperature, presence and types of oxidative scavengers, dissolved gases and by-products that are made by this treatment process with these compounds. The main conclusion of these works is that aqueous phase corona discharge is capable of producing chemical compounds with sufficient energy to chemically reduce the nitrate, bromate and chlorate anions. Acidic conditions, under low dissolved oxygen scenarios facilitated the highest amount of reduction of the target contaminants, as well as having the presence of oxidative species scavengers. It was also observed that the anoxic environment could be obtained by introducing alcohols into the contaminated solution which generated sufficient cavitation and bubbling to strip the oxygen from solution. Through a comparison of various carbonaceous compounds as oxidative species scavengers, it was determined that the volatile alcohols provided a better performance than other soluble carbon sources, due to the decrease in dissolved oxygen. The fourth chapter considers different methods of introducing argon, oxygen and nitrogen into the test solution for the effect they would have on the treatment of solutions containing the bromate anion or monobromoacetic acid. The optimal pH for the treatment of monobromoacetic acid was also established, where again the acidic conditions prevailed. Tests were conducted to consider the effect of having the solution pre-saturated with the test gas, continually sparged, or with the gas passing through a hollow discharge electrode. The tests in which gas was blown through the discharge electrode greatly surpassed all other treatment regimes, where nitrogen provided the best removal for both contaminants under acidic conditions for bromate and under acidic and basic conditions for monobromoacetic acid. The fifth chapter provides conclusions for the overall thesis and recommendations for future work. / Thesis / Doctor of Philosophy (PhD)

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No description available.

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Les recherches actuelles dans le domaine des composites montrent l'utilisation croissante de matrices biodégradables et/ou de renforts fibreux naturels issus de ressources renouvelables. Néanmoins, une étape de compatibilisation fibres/matrice est très souvent nécessaire. Dans cette thèse, nous avons exploré une méthode physique : le traitement corona. Son impact sur les propriétés physicochimiques de différentes fibres a été étudié par XPS, mesure d'angle de contact et MEB. Il ressort qu'il entraîne principalement une oxydation de surface et une augmentation de sa rugosité. Nous avons évalué le comportement mécanique de composites, préparés par extrusion à partir de fibres de chanvre ou miscanthus et de matrices polypropylène (PP) ou acide polylactique (PLA). L'incorporation de renforts accroît la rigidité des matériaux et le transfert de contrainte et leur traitement permet d'obtenir des caractéristiques encore supérieures en raison d'un ancrage mécanique accru. Les valeurs optimales sont obtenues pour un taux massique de fibres de l'ordre de 20%. Les propriétés thermiques et thermomécaniques des composites ont été caractérisées par ATG, DMA et DSC. La stabilité thermique des matériaux est abaissée après incorporation de renforts bruts mais très largement améliorée (+ 15-20°C) après traitement des fibres. Dans certaines conditions, les fibres agissent comme des agents nucléants qui influent sur le processus de cristallisation et le taux de cristallinité. Le traitement des fibres par corona ne permet pas de retarder la dégradation des matériaux au cours d'un vieillissement accéléré en milieu humide et l'évolution des propriétés thermomécaniques est plus prononcée pour les matériaux à base de PLA plus hydrophile / The field of composites materials shows increasing use of biodegradable matrices and / or natural reinforcements from renewable resources. Nevertheless, a compatibilization step between fiber and matrix is necessary. In this PhD study, we have explored a physical method: corona treatment. Its impact on the physicochemical properties of different fibres has been studied by XPS, contact angle measurement and SEM. It appears that it mainly involves surface oxidation and roughness increase. We have also evaluated the mechanical behaviour of composites, prepared by extrusion from hemp or miscanthus fibres and polypropylene (PP) or polylactic acid (PLA) matrices. The incorporation of raw reinforcements increases the stiffness and the stress transfer. Composites based on treated fibres show better mechanical performances, resulting from an enhanced mechanical anchorage. The optimum values are obtained for 20% (wt) fibres content. The thermal and thermomechanical properties of composites have been characterized by TGA, DMA and DSC. The thermal stability of materials is reduced after incorporation of raw reinforcements but very much improved (+ 15 - 20 ° C) after treatment of fibres. Under certain conditions, the fibres act as nucleating agents that affect the crystallization process and crystallinity rate. The corona treatment of fibres does not delay the degradation of materials during an accelerated aging in humid environment and the evolution of the thermomechanical properties is more pronounced for PLA based materials because of its hydrophilic character.

Este trabalho traz como contribuição o início sistemático de estudos para o projeto e execução de ozonizadores dedicados a estações de tratamento de água e esgotos domésticos com tecnologia totalmente nacional. O objetivo é desenvolver um sistema que apresente custo reduzido de fabricação, implantação, manutenção e também boa eficiência na produção de ozônio. Equipamentos auxiliares para bombeamento e tratamento do ar não são necessários, além de ser possível a ampliação do sistema. Devido ao caráter multidisciplinar, este trabalho aborda a problemática da geração de subprodutos danosos ao homem e ao meio ambiente pelo uso de desinfetantes tradicionais, bem como um processo alternativo de tratamento pelo emprego do ozônio. Após descrever os fenômenos físicos envolvidos no método das descargas corona, um tratamento matemático apresenta elementos para o projeto ótimo deste sistema. Contudo, para viabilizar o uso de materiais disponíveis no mercado, os valores adotados nos arranjos iniciais seguiram aproximadamente estas indicações. Os ensaios foram realizados e a produção de ozônio foi obtida por titulação iodométrica. Os primeiros resultados foram tabulados e comparados com valores informados pelos equipamentos de mercado. Sugestões de implantação em campo para trabalhos futuros são apresentadas. / Studies for the project and execution of ozonizers dedicated to the wastewater and water treatment with total national technology were presented. The aim of this work consists of developing a system which minimize the manufacturing process, implementation and maintenance costs and also improves the ozone production efficiency. Accessory pumping equipments has been eliminated with the use of Venture\'s system to inject the ozone in liquid and air treatment has not been used to reduce costs. While this system loses efficiency with air no treatable, it allows a parallel and serial set-up to improve its performance. To support this work, an extended bibliographical analyzes has been carried out, which due to its multidiscipline characteristic was separated into studies of the traditional disinfectant procedures, alternative ozone treatment and, the physical corona discharges phenomena. The two prototypes were developed and, their obtained with the iodometric titration method, was also compared with those of market equipments. These preliminary comparisons have shown that these prototypes have a good performance inclusive with one of them having an ozone production superior than one of market equipments. Suggestions of implantation in field and other improvements for future work are also presented.