Denna rapport ger förslag på olika metoder att automatiskt justera flytläget på en statiskt förankrad boj, en överblick över de processer som styr ändringen av vattennivån och en statisktisk analys på vattennivåförändringarna vid Stockholm, Kungsholmsfort och Kungsvik. Beroende på vattenivåns variation finns olika metoder för justering. Områden med små variationer av vattennivå lämpar det sig bäst utan någon som helst justering av flytläget. Områden med inte för stora tidvattensförändringar bör justeras med ett system bestående av vinsch, växellåda med en utväxling på 10 000:1, en 12 V DC motor, ett skötselfritt 12 V batteri, en luftlindad linjärgenerator och en trådtöjningsgivare. Områden med stora variationer i tidvatten behöver en avlastning för motorn i form av en fjäder och dämpare. De monteras horizontellt inuti bojen för att skyddas från den yttre miljön. Den statistiska analysen påvisade de största vattennivåändringarna vid både Kungsviks och Kungsholmsforts mätstationer, båda uppvisade ett intervall på 1,6 m mellan minimum och maximum. Kungsvik var den station med de största dagliga variationerna, detta på grund av tidvattnets påverkan i området. / This thesis gives examples of different methods of automated adjustment of floatation level for a static moored buoy, an overview of the theories behind water level change and a statistical analysis of the water level changes for Stockholm, Kungsholmsfort and Kungsvik. Depending on the range and frequency of the water level change different methods of adjustment are recommended. For areas with small changes in sea level the best choice would be no adjustment of the floatation level. Areas that are influenced by moderate tidal ranges should incorporate a system of regulation consisting of a winch, gearbox with a gear ratio of around 10,000:1, 12 V DC motor, 12 V maintenance free battery, air coiled linear generator and a strain gauge. For areas with large tidal ranges the previous system should be complimented with a horizontally mounted spring, inside the buoy, to lessen the loads on the motor. The statistical analysis found the largest extremes in water level of the three sites to be at Kungsvik and Kungsholmsfort, both exhibiting a range of almost 1.6 m. Kungsvik was the station with the largest daily variations, this is because this is the only station influenced by tidal variations.

In this study, the efficiency of linear and rotational tuned mass dampers (TMD) and lever type vibration isolators (LVI) in improving ride comfort is investigated based on a vehicle quarter-car model. TMDs reduce vibration levels by absorbing the energy of the system, especially at their natural frequencies. Both types of TMDs are investigated in the first part of this study. Although linear TMDs can be implemented more easily on suspension systems, rotational TMDs show better performance in reducing vibration levels / since, the inertia effect of rotational TMDs is higher than the linear TMDs. In order to obtain better results with TMDs, configurations with chain of linear TMDs are obtained in the second part of the study without changing the original suspension stiffness and damping coefficient. In addition to these, the effect of increasing the number of TMDs used in the chain configuration is investigated. Results show that performance deterioration at lower frequencies than wheel hop is reduced by using chain of TMDs. In the third part of this study, various configurations of LVIs with different masses are considered and significant attenuation of vibration amplitudes at both body bounce and wheel hop frequencies is achieved. Results show that TMDs improve ride comfort around wheel hop frequency while LVIs are quite efficient around body bounce frequency. Finally, parameter uncertainty due to aging of components and manufacturing defects are investigated.

Tolerances play an important role in product fabrication. Tolerances impact the needs of the designer and the manufacturer. Engineering designers are concerned with the impact of tolerances on the variation of the output, while manufacturers are more concerned with the cost of fitting the parts. Traditional tolerance control methods do not take into account both these needs. In this thesis, the author proposes a framework that overcomes the drawbacks of the traditional tolerance control methods, and reduces subjectivity via fuzzy set theory and decision support systems (DSS). Those factors that affect the manufacturing cost (geometry, material etc) of a part are fuzzy (i.e. subjective) in nature with no numerical measure. Fuzzy comprehensive evaluation (FCE) is utilized in this thesis as a method of quantifying the fuzzy (i.e. subjective) factors. In the FCE process, the weighted importance of each factor affects the manufacturing cost of the part. There is no systematic method of calculating the importance weights. This brings about a need for decision support in the evaluation of the weighted importance of each factor. The combination of FCE and DSS, in the form of Conjoint Analysis (CA), is used to reduce subjectivity in calculation of machining cost. Taguchi's quality loss function is considered in this framework to reduce the variation in the output. The application of the framework is demonstrated with three practical engineering applications. Tolerances are allocated for three assemblies; a friction clutch, an accumulator O-ring seal and a Power Generating Shock Absorber (PGSA) using the proposed framework. The output performances of the PGSA and the clutch are affected by the allocated tolerances. On using the proposed framework, there is seen to be a reduction in variation of output performance for the clutch and the PGSA. The use of CA is also validated by checking efficiency of final tolerance calculation with and without use of CA.

Magistro darbe analizuotos vakuuminių saulės kolektorių, skirtų vandeniui šildyti sistemos energetiniai parametrai, rodikliai ir konstrukcijos. Taip pat šiame darbe nagrinėjama vakuuminio saulės kolektoriaus energetinės charakteristikos. Darbą sudaro dvi dedamosios dalys: analitinė ir praktinė darbo dalys. Analitinėje dalyje apžvelgtos skirtingų tipų saulės kolektorių charakteristikos, saulės kolektorinių vandens šildymo sistemų veikimo principas ir panaudojimo galimybės. Trumpai apžvelgta perteklinės energijos panaudojimo galimybės ir saulės kolektorių sistemos projektavimo principas. Praktinėje darbo dalyje tirta saulės kolektorinė vandens šildymo sistema gamybinėmis sąlygomis. Atskleistas sistemos veikimo mechanizmas, ištirtas kolektorių našumas skirtingomis darbinėmis sąlygomis. Darbo pabaigoje suformuluotos atlikto tyrimo išvados. Pateiktos rekomendacijos tirtos saulės kolektorinės vandens šildymo sistemos administraciniam personalui. / Master's thesis analyses vacuum solar collectors for water heating system energy parameters, indicators and construction. Also vacuum solar collector system energy characteristics. The work consists of two component parts: the analytical and practical parts of the research. In the analytical part is an overview of the different types of solar collector performance, solar water heating systems operation and utilization. Short overview of surplus energy utilization possibilities and solar system design principle. In the practical part of the thesis is investigated solar collector water heating system under production conditions. Revealed mechanism of the system, investigated thermal performance under different operating conditions. In the end of research thesis conclusions are formulated. Recommendations were given for tested solar collector water heating system administrative personnel.

Orientador: Gustavo Luiz Chagas Manhães de Abreu / Resumo: Diversos estudos relacionados à atenuação de vibrações utilizando materiais inteligentes vem sendo amplamente explorados no meio acadêmico. Neste âmbito, as Ligas de Memória de Forma (LMF) se destacam por apresentarem dissipação de energia vibratória devido ao seu comportamento histerético promovido pelo efeito pseudoelástico. No presente trabalho, dois sistemas com um e dois graus de liberdade, contendo mola helicoidal de LMF como elemento resiliente, são implementados numericamente para demonstrar a atenuação de vibrações ocasionada pelas transformações de fase presentes no material. Para cada um dos sistemas mecânicos investigados, dois modelos termomecânicos são confrontados numericamente visando a obtenção das características de cada modelo em representar a atenuação de vibrações dos sistemas submetidos à carregamentos termo-mecânicos. O trabalho termina comentando as potencialidades da proposta apresentada, discutindo as facilidades e dificuldades encontradas na sua implementação e apontando para o desenvolvimento de futuros estudos. / Mestre

Les machines frigorifiques à absorption ammoniac-eau sont prometteuses dans les domaines de la climatisation solaire et de la valorisation des rejets thermiques pour l’industrie. Pour permettre à ces machines de devenir compétitives par rapport aux systèmes à compression mécanique de vapeur, l’amélioration de leur efficacité et la baisse de leur coût sont nécessaires. C’est dans ce contexte que s’inscrit ce travail de thèse.L’étude se concentre sur l’absorbeur qui est un des composants les plus critiques de la machine à absorption en matière de taille, de coût et d’efficacité. L’objectif est d’étudier numériquement et expérimentalement les transferts couplés de masse et de chaleur dans l’absorbeur dans le but de prédire et d’améliorer ses performances.Deux absorbeurs à film tombant sont étudiés, dans lesquels la solution pauvre et la vapeur entrent en haut et le fluide caloporteur entre en bas. Le premier est un échangeur à plaques soudées et le deuxième est un échangeur à plaques et joints avec des dimensions et des profils de plaques différents.L’analyse expérimentale de ces deux absorbeurs est réalisée dans des conditions réelles de fonctionnement sur un prototype instrumenté de machine à absorption ammoniac-eau de 5 kW. Ce dispositif permet une analyse globale des débits de vapeur absorbés, des flux thermiques évacués et des efficacités d’absorption. Une analyse plus locale est aussi réalisée à l’aide de mesures de températures à l’intérieur des canaux de refroidissement dans l’absorbeur plaques et joints. Les résultats montrent une importante corrélation entre la puissance frigorifique produite par la machine à absorption et les performances de l’absorbeur. Mais ce prototype étant une machine réelle, les variables d’entrée de l’absorbeur ne peuvent pas être contrôlées. Un modèle numérique est donc nécessaire pour dissocier l’impact des différentes variables sur les performances de l’absorbeur.Un modèle 1D d’un absorbeur à film tombant est donc développé. Il est basé sur des bilans de masses, d’espèces et d’énergies, des équations de transferts de masse et de chaleur et des conditions d’équilibre à l’interface liquide-vapeur. Les résistances aux transferts de masse sont considérées dans les phases liquide et vapeur et des corrélations empiriques sont utilisées pour calculer les coefficients de transfert de masse et de chaleur.Ce modèle est validé expérimentalement avec les données globales aux bornes des deux absorbeurs et avec les mesures de températures le long des canaux du fluide de refroidissement puisqu’une différence maximale de 15% est observée. Il permet donc l’analyse détaillée des phénomènes de transferts de masse et de chaleur le long de l’absorbeur et facilite l’étude du procédé d’absorption.Enfin, une étude de sensibilité paramétrique est réalisée avec ce modèle pour discuter des résultats expérimentaux et pour identifier les pistes d’amélioration des performances de l’absorbeur et donc de la machine à absorption. / Ammonia-water absorption chillers are promising both for solar air conditioning and for industry processes. To become competitive compared to electric compression chillers, their efficiency needs to be improved and their cost has to be decreased. This thesis study takes place in this context.The focus is put on the absorber, which is one of the most critical component of absorption chillers in terms of compactness, cost and efficiency. The purpose is to study numerically and experimentally coupled heat and mass transfers which occur in the absorber in order to predict and improve its overall performances.Two falling film absorbers are analysed. In both of them, the poor solution and the vapour enter at the top and the coolant fluid enters at the bottom of the absorber. The first absorber is a brazed plate heat exchanger and the second is a gasketed plate-and-frame heat exchanger with different geometric dimensions and plates corrugations.The experimental study of these two absorbers is performed in real working conditions on an instrumented ammonia-water absorption chiller prototype of 5 KW. Thanks to this device, a global analysis of vapour absorbed mass flow rates, absorbed heat fluxes and mass effectiveness is achieved. A local analysis is also performed thanks to temperature measures inside channels of coolant fluid in the gasketed plate-and-frame heat exchanger. Results show a strong correlation between the absorption chiller cooling capacity and the absorber performances. However, since this prototype is a real chiller, absorber inlet variables cannot be controlled. Thus, a numerical model is necessary to dissociate the impact of these variables on the absorber performances.A 1D numerical model of the absorber is developed. It is based on mass, species and enthalpy balances, mass and heat transfer equations and equilibrium conditions at the vapour/solution interface. Mass transfer resistances in both liquid and vapour phases are considered while heat and mass transfer coefficients are calculated using empirical correlations.This model is validated experimentally with global data at the inlet and the outlet of the absorber and temperature measures along the absorber coolant fluid channels. A maximal relative error of 15 % is observed. Therefore, a detailed analysis of combined heat and mass transfers along the absorber and the absorption process study is performed thanks to this model.A parametric study is also performed with this model to discuss experimental results and find ways to improve the absorber performances and thus the absorption chiller performances.

Submitted by GILBERTO BUENO DE OLIVEIRA JUNIOR null (gilberto.bueno@yahoo.com.br) on 2016-02-03T13:55:05Z No. of bitstreams: 1 Dissertação - Concentrador Solar - VERSÃO FINAL - V0017.pdf: 5444637 bytes, checksum: 24e8c86834b9e8a8354dc9e314104039 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-02-05T11:29:33Z (GMT) No. of bitstreams: 1 oliveirajunior_gb_me_bauru.pdf: 5444637 bytes, checksum: 24e8c86834b9e8a8354dc9e314104039 (MD5) / Made available in DSpace on 2016-02-05T11:29:33Z (GMT). No. of bitstreams: 1 oliveirajunior_gb_me_bauru.pdf: 5444637 bytes, checksum: 24e8c86834b9e8a8354dc9e314104039 (MD5) Previous issue date: 2015-12-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The searching for renewable energy sources has mobilized much of the scientific community, which work is tireless in pointing out feasible solutions to use clean energy. Solar energy is natural choice among others, because its availability and amount. A known way to use this energy is by focusing solar rays through parabolics, which allow rays concentration to a small area. The advantage of this type of project is to produce thermal energy at high temperatures. This energy has a wide application on producing other forms of energy such as electric power in turbines since solar concentrators provide steam at high pressure and temperature. The goal of this study is to build a solar concentration device and measure the energy produced, as well its efficiency in transformation. Thus, was built up a parabolic concentrator and a solar tracker to motion in three dimension, which allows device alignment towards incidence of solar rays. Was utilized a pumping system to flowing thermal fluid at high temperatures through the absorber. The energy balance of this thermal fluid, led to obtain behavior curves of net power and system efficiency. The experimental was divided in two parts. On the first one, was obtained the stagnation temperature and the other one, was measured the eficiency over a circulating thermal fluid. The stagnation temperature measured in december was 476,5°C, at 4:25PM. The second part of tests has shown an efficiency of 33% on first one assay. However when was utilizing another form to measure the solar irradiation (theoretic approach), the efficiency rises between 45% to 55%, regarding steady state conditions. Furthermore, this work allowed discussions to discover ways to increase the energy efficiency. / A busca por formas alternativas de energia tem mobilizado grande parte da comunidade científica, cujos trabalhos são incansáveis em apontar soluções viáveis para o aproveitamento das energias renováveis e limpas. A energia solar se destaca dentre todas pela sua disposição e quantidade. Uma forma já conhecida de sua utilização é através da concentração em sistemas parabólicos, que permitem o direcionamento dos raios do Sol para uma pequena área. A vantagem deste tipo de projeto é a produção de energia térmica a altas temperaturas e pressões. Essa energia concentrada possui grande aplicação, pois permite a conversão eficiente em energia elétrica, produzidas em turbinas a vapor. O objetivo deste trabalho foi construir um dispositivo termo-eletrônico para concentração solar e, com isso, quantificar a energia produzida, bem como sua eficiência. Assim sendo, foi construído um concentrador parabólico e um rastreador solar com movimento tridimensional, que permite o alinhamento do equipamento com a incidência dos raios do Sol. Foi utilizado ainda, para circulação no interior do absorvedor, um sistema de bombeamento de fluido térmico de alto ponto de ebulição e que não sofria deformação a altas temperaturas. O balanço energético no dispositivo permitiu obter as curvas de potência útil e da eficiência do sistema. O experimento foi dividido em duas partes. Na primeira parte, foi obtida a temperatura de estagnação e na outra parte, foi medida a eficiência energética sobre o fluido térmico em circulação. A temperatura de estagnação medida em dezembro foi de 476,5 °C, às 4:25 PM. A segunda parte dos testes mostrou uma eficiência de 33% no primeiro ensaio. No entanto, quando se utilizou uma outra forma de medir a irradiação solar (abordagem teórica), a eficiência aumentou, permanecendo entre 45% a 55%, considerando regime permanente. Além disso, possibilitou a discussão de formas de incrementar a sua eficiência. / Capes: 2012/2014

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-29Bitstream added on 2014-06-13T19:35:06Z : No. of bitstreams: 1 mesquitaneto_c_me_ilha.pdf: 1673109 bytes, checksum: 0f8131abf5fc45715c92abece81e6a7a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho é apresentado uma proposta de absorvedor de vibrações ajustável tipo viga sanduíche utilizando fluido Magnetoreológico no centro. Para o desenvolvimento deste projeto foi realizada uma revisão sobre os vários tipos de absorvedores e algumas aplicações. Em seguida foi realizado um estudo sobre o comportamento do fluido magnetoreológico, mostrando como este material inteligente varia suas propriedades quando submetido a um campo magnético. O objetivo do estudo foi verificar as propriedades do sistema para realização de um futuro controle, que é realizado através da variação do campo magnético. Avaliou-se, também, a relação com a corrente elétrica, quais os parâmetros que o influenciam e como podemos produzir um campo magnético com a intensidade desejada. Para avaliar as características do sistema foi utilizado o modelo no programa Ansys, com o objetivo de se verificar o comportamento do sistema. Para encontrar as características reais do sistema foi utilizado o modelo na forma de espaço de estados modais, identificado através do método PEM, Método de Predição de Erros (do inglês Prediction Error Methods PEM). Os testes experimentais foram realizados para se adquirir conhecimento do comportamento dinâmico deste tipo de fluido e, verificar se há repetibilidade nas medidas / This work presents a proposal of a tunable vibrations absorber type sandwich beam, using the Magnetorheologic fluid in the intermediate layer. For the development of this study a revision of some types of absorber with some applications was carried out. After that, a study of the behavior of the magnetorheologic fluid was carried through, showing as this intelligent material tunable its properties when submitted to a magnetic field. The objective of this analysis was to verify the properties of the system for implementation of a future control, which is based on the variation of the magnetic field. It was realized an analysis of the relation of the electric current and the parameters that influence it, in order to produce a magnetic field with the desired intensity. The characteristics of the system were verified through a mathematical model obtained with the software Ansys. The real characteristics of the system were found through the identification method PEM, Prediction Error Methods, using modal space states formulation. Experimental tests were carried out in order to obtain know how of the dynamic behavior of this type of material

Submitted by RAFAEL DE OLIVEIRA SILVA null (rafa_engemec@hotmail.com) on 2017-04-24T14:27:25Z No. of bitstreams: 1 dissertacao_final.pdf: 3521819 bytes, checksum: b08a60dcaa91691a2bf36a0cc59992e6 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-26T13:27:52Z (GMT) No. of bitstreams: 1 silva_ro_me_ilha.pdf: 3521819 bytes, checksum: b08a60dcaa91691a2bf36a0cc59992e6 (MD5) / Made available in DSpace on 2017-04-26T13:27:52Z (GMT). No. of bitstreams: 1 silva_ro_me_ilha.pdf: 3521819 bytes, checksum: b08a60dcaa91691a2bf36a0cc59992e6 (MD5) Previous issue date: 2017-03-31 / Diversos estudos relacionados à atenuação de vibrações utilizando materiais inteligentes vem sendo amplamente explorados no meio acadêmico. Neste âmbito, as Ligas de Memória de Forma (LMF) se destacam por apresentarem dissipação de energia vibratória devido ao seu comportamento histerético promovido pelo efeito pseudoelástico. No presente trabalho, dois sistemas com um e dois graus de liberdade, contendo mola helicoidal de LMF como elemento resiliente, são implementados numericamente para demonstrar a atenuação de vibrações ocasionada pelas transformações de fase presentes no material. Para cada um dos sistemas mecânicos investigados, dois modelos termomecânicos são confrontados numericamente visando a obtenção das características de cada modelo em representar a atenuação de vibrações dos sistemas submetidos à carregamentos termo-mecânicos. O trabalho termina comentando as potencialidades da proposta apresentada, discutindo as facilidades e dificuldades encontradas na sua implementação e apontando para o desenvolvimento de futuros estudos. / Several studies regarding the vibration attenuation using intelligent materials have been widely explored in the academic world in engineering. In this context, the shape memory alloys (SMAs) exhibit vibratory energy dissipation due to their hysteretic behavior caused by the pseudoelastic effect. In the present work, two systems with one and two degrees of freedom, containing a SMA helical spring as a resilient element, are numerically implemented to demonstrate the vibration attenuation of the system caused by the phase transformations present in the SMA spring. For each considered mechanical systems, two thermomechanical models are numerically confronted in order to obtain the characteristics of each model in representing the vibration attenuation of the systems submitted to thermo-mechanical loads. This work is concluded presenting the potentialities of the design methodology proposed and future developments to be implemented.

A otimização de combustíveis nucleares para uso em reatores a água pressurizada pode ser obtida pelo aumento da taxa de queima do combustível. Para isso, no entanto, é necessário levar em conta o aumento na reatividade inicial no reator, causada pelo maior enriquecimento do combustível. Esse problema, por sua vez, pode ser contornado por meio da introdução dos chamados venenos queimáveis diretamente nas pastilhas combustível de UO2. Alguns elementos do grupo das terras-raras possuem propriedades físicas e químicas que os tornam apropriados para esse uso dentro de reatores. Para caracterizar a microestrutura do combustível UO2 utilizado em reatores a água pressurizada dopado de érbio, pastilhas de UO2-Er2O3 foram preparadas, com teor de Er2O3 variando de 1,0 a 9,8 wt%, e analisadas por difração de raios X (DRX) para determinar se houve a formação de solução sólida pelo composto e determinar a variação do parâmetro de rede da solução em função da concentração de érbia. Apesar da análise por DRX ter mostrado que todo o érbio se incorporou à rede de UO2, ela também evidenciou a emergência de uma segunda fase, de estrutura do tipo fluorita, e cuja fração mássica aumenta em função do teor de érbia, enquanto seu parâmetro de rede diminui. Esses resultados são compatíveis com o fenômeno de segregação de defeitos, que consiste na formação de microdomínios segregados da rede principal nos quais há uma concentração maior dos defeitos i.e. são regiões mais ricas em érbio. Assim, a análise por DRX mostrou que houve formação de solução sólida de (U,Er)O2, mas que são necessários ajustes nos parâmetros de sinterização para que seja obtida uma solução monofásica. / Optimization of nuclear fuel for use in pressurized water reactors can be achieved by obtaining higher burnups. This, however, requires the excess reactivity caused by increasing the fuels enrichment to be taken into account, which can be done by introducing burnable absorbers into the UO2 fuel pellets themselves. Some of the rare earth elements have thermal and mechanical properties that make them appropriate for use inside the reactor. In order to characterize the microstructure of erbium-doped UO2 fuel, sintered UO2-Er2O3 pellets were prepared, with Er2O3 content ranging from 1.0 to 9.8wt%, and analyzed by X-ray diffraction to determine whether the composite formed solid solutions and, if so, evaluate the lattice parameter as a function of erbia concentration. While XRD analysis showed the Er2O3 completely dissolved in the UO2 powder, it also evidenced the emergence of a second fluorite-type phase, whose phase fraction increases and lattice parameter decreases with increasing erbia concentration. Analysis of the diffraction patterns showed this emerging phase has the same crystalline structure as the host lattice, but with a smaller lattice parameter. These results are compatible with the phenomenon of defect segregation, which consists in the formation of microdomains with a higher concentration of defects i.e. rare-earth richer regions. Thus, XRD analysis showed the formation of (U,Er)O2 solid solution, but such that there are still adjustments in the sintering parameters that need to be made in order to achieve a single-phase solid solution.