Submitted by Amanda Freitas (amanda.freitas@ufpe.br) on 2015-04-17T13:47:41Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO João Marcus Pereira Lima e Silva.compressed.pdf: 3614233 bytes, checksum: 23563e62671e2a1ac7b7a0032bfaab6b (MD5) / Made available in DSpace on 2015-04-17T13:47:41Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO João Marcus Pereira Lima e Silva.compressed.pdf: 3614233 bytes, checksum: 23563e62671e2a1ac7b7a0032bfaab6b (MD5) Previous issue date: 2013-07-31 / O objetivo deste trabalho é apresentar uma proposta de modelagem abordando os circuitos internos de rotor destinada, à determinação das correntes presentes nestes. As simulações foram relizadas em MATLAB/SIMULINK® usando equações de fluxo. Também é mostrado o comportamento das correntes com a variação da velocidade da máquina a partir da resolução do sistema de equações resultante do modelo a parâmetros de circuito, parâmetros esses que são obtidos a partir dos dimensionais da máquina e dos materiais dos quais ela é constituída. Também são mostradas equações para obtenção das frequências de banda da fundamental, que são as indicadoras da existência de circuitos interrompidos. Estão inclusos também resultados da aplicação em um caso real para uma máquina de 150 MVA, contemplando variações de valores mecânicos da máquina, a exemplo da medida do encaixe entre a barra e o anel de curto-circuito (end ring) ou o valor da medida da parte inclinada das bobinas estatóricas e as distribuições de corrente nas barras por polo. Também são mostradas as formas de se calcular os parâmetros que alimentarão tanto as simulações, quanto o sistema de equações destinado à determinação das correntes, bem como o comportamento de cada corrente em cada barra com a variação do escorregamento. As dinâmicas de torque, ângulo de carga, correntes de armadura e velocidades do eixo da máquina são expostas para o caso de uma máquina sadia, ou seja isenta de defeitos, e de uma máquina defeituosa apresentando um circuito interrompido.

Orientador: Robson Pederiva / Dissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-07T00:56:52Z (GMT). No. of bitstreams: 1 Silva_GilbertoMachadoda_M.pdf: 1128289 bytes, checksum: e5a6e2d7aeb16be17a0a3d45dd834193 (MD5) Previous issue date: 2006 / Resumo: Aplica-se neste trabalho a metodologia de diagnóstico de falhas em sistemas mecânicos rotativos sustentados por mancais magnéticos ativos em conjunto com um sistema de controle ativo de vibração, excitados por forças de desbalanço e ruído branco. Este diagnóstico baseia-se no emprego das equações de correlações, através da formulação matricial de Ljapunov, para sistemas lineares estacionários juntamente com redes neurais artificiais. Este procedimento utiliza apenas as variáveis de estado medidas, através da correlação das variáveis de saída. É gerado um conjunto de relações envolvendo os parâmetros físicos do sistema juntamente com as matrizes de correlações das variáveis medidas. As falhas no sistema são detectadas através do monitoramento da variação dos parâmetros físicos e da comparação das funções de correlação teóricas e estimadas. As redes neurais artificiais são usadas para mapear as correlações que envolvem estados que não são medidos. Dado ao grande número de equações de compatibilidade resultantes, é proposta uma metodologia para selecionar as equações relacionadas com as falhas propostas. Com o método de diagnóstico de falhas proposto é possível detectar e discernir as falhas tanto mecânicas quanto elétricas, bem como sua localização no sistema / Abstract: This work applies the methodology of fault diagnosis in rotating machinery supported by active magnetic bearings and active con1rol systems, excited by unbalance and white noise. This diagnostic applies the correlation matrices based on the Ljapunov matrix formulation and artificial neural network for linear stationary systems. The procedure uses only measured state variables, computing the correlation between the output variables. It is possible to derive specific relations involving the physical parameter of the system and the correlation matrices of the measured variables. Faults in the system can be detected by monitoring the variation of the physical parameter through a comparison of theoretical and estimated correlation functions. Artificial neural networks are used to map the correlations involving the variables, which are difficult to be measured. There is a large number of resultant compatibility equations and it is proposed a methodology to select the equations that establish relationships with the faults. The proposed fault diagnosis method can detect the fault present in the system and it is also possible to distinguish between mechanical and electrical fault as well as their location in the system / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Orientador: Katia Lucchesi Cavalca Dedini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-22T17:27:08Z (GMT). No. of bitstreams: 1 Cavalcante_PaulaFrassinetti_M.pdf: 4909244 bytes, checksum: f9f88e5874d8b1727ede08f5831d24eb (MD5) Previous issue date: 1997 / Resumo: A análise do comportamento da fundação e sua influência na resposta do sistema completo rotor-suportes-fundação é fundamental para análise dinâmica deste sistema. Dessa forma, este trabalho apresenta uma metodologia para a análise do comportamento da fundação, usando técnicas de análise modal para determinar os parâmetros modais da fundação (massa, fator de amortecimento e freqüência natural). Para a identificação desses parâmetros, foi feita a análise das funções de transferências do modelo numérico da estrutura, onde a técnica utilizada foi a discretização da fundação pelo método dos elementos finitos. O cálculo das funções de transferência do modelo é feito para uma força de excitação harmônica unitária, atuando em um determinado nó do modelo discretizado. Em seguida, foram definidos alguns nós de interesse no modelo discretizado e aplicadas técnicas de análise modal para calcular as freqüências naturais da estrutura. A transformada de Fourier da resposta em freqüência do sistema é calculada e através do espectro de freqüências do sistema, é feita a escolha dos modos de vibrar mais significativos, associados às freqüências naturais que significantemente participam da resposta do sistema. Em seguida, é feito o cálculo dos parâmetros de massa, fator de amortecimento e rigidez dos modos considerados. A matriz de impedâncias mecânicas é obtida para estes modos. Os resultados obtidos foram plotados e analisados. Resultados adicionais mostrando todo comportamento da estrutura, cujos parâmetros foram identificados a partir de uma função de transferência analítica, são apresentados, cuja importância é relevante na implementação e comparação com o modelo físico / Abstract: The behavior analysis of foundation and its influence on the complete system response, rotor-bearings-foundation, is of great importance in its dynamic analysis. In this way, this work presents a methodology for behavior analysis of the foundation using modal analysis technique to determine the modal parameters of the foundation (damping factor, natural frequency and generalized mass). The analysis of the numeric modeI transfer functions of the structure was done in order to identify these parameters, where it was the discretization technique of the foundation using the finite element method. The functions of the model was obtained for a unit harmonic force exciting one node. Afterwards, some nodes of interest in the discretized modal was defined and modal analysis techniques used calculate the natural frequencies of the structural the Fourier Transform of the frequency response of the system is calculated. The shapes modes associated to the natural frequencies which participate of the system response significantly are chosen using the frequency spectrum. The mass, damping factor and stiffness of the considered modes are obtained afterwards. The mechanical impedance matrix is obtained for these modes. The results was plotted and analyzed. Further results showing the behaviour of the structure are presented whose parameter were identified by the analytical transfer functions its importance is relevant to implement and compare to the model physical / Mestrado / Projeto Mecanico / Mestre em Engenharia Mecânica

O presente trabalho consiste no projeto de um modelo em elementos finitos de um absorvedor dinâmico rotativo utilizando-se um material viscoelástico como componente dissipador do sistema. O absorvedor é composto por um anel de material viscoelástico interposto entre dois anéis de aço, o qual é fixado na extremidade livre de um sistema rotativo representado por um eixo flexível, suportado por dois rolamentos, no qual estão fixos dois discos igualmente espaçados do centro entre os dois mancais. O modelo em elementos finitos do sistema rotativo é validado com os dados experimentais do modelo real e suas velocidades críticas são determinadas baseadas no diagrama de Campbell e na resposta ao desbalanço em um dos discos. O modelo inicial do absorvedor dinâmico rotativo é replicado de um modelo da literatura e as respostas a uma excitação na forma de impulso são comparadas. O modelo desenvolvido equipara-se ao da literatura para frequências até 600 Hz, intervalo que compreende as velocidades críticas a serem amortecidas. A otimização do absorvedor é realizada através de variações da geometria do mesmo e são traçadas curvas de influência de cada parâmetro sobre suas frequências naturais. Com base nestas curvas são realizadas análises de influência conjunta dos parâmetros geométricos sobre tais frequências. Pelos resultados obtidos verifica-se a possibilidade da obtenção de um modelo que atue sobre modos de flexão específicos do sistema rotativo, atenuando as amplitudes de vibração das velocidades críticas correspondentes a cada modo. Uma vez obtidos os modelos de absorvedores dinâmicos correspondentes aos dois primeiros modos de flexão do sistema rotativo, ambos são acoplados ao sistema e se observa grande redução dos picos de amplitude do primeiro modo de flexão, enquanto os picos do segundo modo sofrem baixa alteração. / The present work concerns the development, optimization and validation of a finite element model of a dynamic vibration absorber using a viscoelastic material as the damping component. The dynamic absorber consists of a ring of viscoelastic material interposed between two rings of steel, which is fixed to the free end of a rotary system represented by a flexible shaft supported by two bearings, on which are fixed two discs equally spaced in the center of both bearings. The finite element model of the rotating system is validated with experimental data from the actual model and its critical speeds are determined based on the Campbell diagram and in its response to the imbalance. The initial model of the dynamic absorber is replicated from a model of the literature and the responses to an impulse excitation are compared. The developed model matches the literature one for frequencies up to 600 Hz, range comprising the critical speeds to be damped. The absorber\'s optimization is accomplished through variations of its geometry and influence curves of each parameter over its natural frequencies are drawn. Based on these curves, combined influence analyzes of the geometrical parameters over such frequencies are performed. From the results obtained, it can be seen the possibility of achieving a model that acts on specific bending modes of the rotation system, reducing the vibration amplitudes of the critical speeds corresponding to each mode. Once obtained the dynamic absorbers models corresponding to the first two modes of vibration of the rotatative system, both models are coupled to the system and it is observed great reduction of the amplitude of the first bending mode peaks, while the second mode suffer low peaks reduction.

Les problèmes vibratoires sont l'une des principales causes des maintenances effectuées sur les turbines de barrages hydroélectrique en France. Dans cette thèse CIFRE, subventionnée par la Division Technique Générale d’Électricité de France à Grenoble, nous voulons étudier numériquement les phénomènes physiques en jeu.Pour cela, chaque partie composant ce type de machine tournante est modélisée : la ligne d'arbre, les accouplements rigides, les paliers hydrodynamiques, la butée hydrodynamique à patins oscillants, les étanchéités et les efforts électromagnétiques. Celui du rotor est basé sur une approche classique 1D, prenant en compte des défauts d'accouplement rigide. Les paliers hydrodynamiques peuvent être alimentés par des rainures hélicoïdales : ceci est pris en compte dans la modélisation des paliers via un changement de variable dans l'équation de Reynolds. Concernant la butée hydrodynamique à patins oscillants, l'équation de Reynolds est explicitée en fonction des paramètres du système (rotor et patins). Un cas test est également présenté afin d'évaluer les différentes approches possibles pour l'intégration dans la modélisation du rotor et pour mieux appréhender la réponse dynamique d'une butée. Les joints d'étanchéités sont modélisés en linéarisant les efforts hydrauliques gouvernés par les équations du "bulk-flow" et sont donc représentés par des coefficients dynamiques de masse, d'amortissement et de raideur. Les efforts électromagnétiques au niveau de l'alternateur sont pris en compte via une formulation analytique des forces d'attraction sur chaque paire de pôles. Cela permet de gérer, par exemple, des défauts d'ovalisation ou de positionnement du stator.Une seconde partie est consacrée à l'étude d'une turbine complète. Y sont présentées différentes études de sensibilités des défauts les plus courants sur ce type de machine, le but étant d'en connaître l'influence sur le comportement dynamique de l'ensemble du rotor. / Vibration problems are one of the main causes leading to maintenances performed on the turbines of hydroelectric power generation systems in France. In this CIFRE dissertation, financed by Division Technique Générale d'Électricité de France in Grenoble, we shall numerically study the physical phenomena involved in turbine vibrations of this kind.Hence, each component of this type of rotating machinery is modeled: the rotor, the rigid coupling, the hydrodynamic bearings, the hydrodynamic tilting pad thrust bearing, the annular seals and the electromagnetic forces. The model of the rotor is based on classical 1D approach taking into account the defects of the rigid coupling. The hydrodynamic bearings can be fed by helicoidally grooves. This feature is taken into account in the numerical model of journal bearing by applying a variable transformation to the Reynolds equation. For the tilting pad thrust bearing, the Reynolds equation takes into account the displacements and the velocities of both the pads and the rotor. A test case is presented for evaluating the different numerical approaches of the tilting pad thrust bearing that can be integrated in a rotordynamic analysis. The annular seals are modeled by using linearized hydraulic efforts (i.e. stiffness, damping and added mass dynamic coefficients) modeled by the "bulk flow" system of equations. The electromagnetic efforts in the alternator are taken into account by using an analytic model of the forces of each pair of poles. This enables to tackle ovalisation or eccentricity defects of the stator.A second part is dedicated to the numerical study of a complete turbine. Different studies dealing with sensitivity analyses of most often-encountered defects of this type of rotating machinery are presented, the goal being to underline their influence on the dynamic behavior of the whole rotor.

Conventional rotating machine vibration monitoring techniques are based on the assumption that changes in the measured structural response are caused by deterioration in the condition of the rotating machine. However, due to changing rotational speed, the measured signal may be non-stationary and difficult to interpret. For this reason, the order tracking technique was introduced. One of main advantages of order tracking over traditional vibration monitoring techniques, lies in its ability to clearly identify non-stationary vibration data, and to a large extent exclude the influences from varying rotational speed. Several order tracking techniques have been developed and researched during the past 20 years. Among these techniques, Fourier Transform Based Order Tracking (FT-OT), Angle Domain Sampling Based Order Tracking (AD-OT) and Vold-Kalman Filter Order Tracking (VKF-OT) are the three most popular techniques and have been commercialised in software. While the VKF-OT is comparatively new, and both its theory and application are different from the other two techniques, the unique advantages of this technique has led to increased research attention in this field. This growing interest in research on the application of the VKF-OT technique on real machines, and its comparative advantages with respect to other order tracking techniques, inspired the present research. With this work, a comprehensive literature of electrical machine condition monitoring was surveyed, which gives a broad perspective of electrical machine monitoring methods ranging through electrical techniques, vibration techniques, temperature techniques and chemical techniques. To simply the process of applying VKF-OT in initial investigations, simulated single-degree-of freedom and two-degree-of freedom rotor models were established, and the application of the VKF-OT technique on these simulated models was explored. Because most of the current research draws significantly on an understanding of the VKF-OT theory, it was also necessary to review and summarize the current status of VKF-OT theory from previous work, as well as explore the procedures for selection of its filter bandwidth when dealing with real data. An experimental set-up for monitoring an electrical alternator was constructed. Real experimental data were subsequently used to compare the advantages and disadvantages of the three popular order tracking techniques. The unique time domain advantage of VKF-OT was implemented, using crest factor and kurtosis values as indictors of the fault condition of the machine. This gave encouraging results. / Dissertation (MSc)--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

The healthy condition of a rotating machine leads to safe and cheap operation of almost all industrial facilities and mechanical systems. To achieve such a goal, vibration-based condition monitoring has proved to be a well-accepted technique that detects incipient fault symptoms. The conventional way of On-Bearing Vibration Measurement (OBVM) captures symptoms of different faults, however, it requires a relatively expensive setup, an additional space for the auxiliary devices and cabling in addition to an experienced analyst. On-Shaft Vibration Measurement (OSVM) is an emerging method proposed to offer more reliable Faults Diagnosis (FD) tools with less number of sensors, minimal processing time and lower system and maintenance costs. The advancement in sensor and wireless communications technologies enables attaching a MEMS accelerometer with a miniaturised wireless data acquisition unit directly to the rotor without altering the machine dynamics. In this study, OSVM is analysed during constant speed and run-up operations of a test rig. The observations showed response modulation, hence, a Finite Element (FE) analysis has been carried out to help interpret the experimental observations. The FE analysis confirmed that the modulation is due to the rotary motion of the on-shaft sensor. A demodulation method has been developed to solve this problem. The FD capability of OSVM has been compared to that of OBVM using conventional analysis where the former provided more efficient diagnosis with less number of sensors. To incorporate more features, a method has been developed to diagnose faults based on Principal Component Analysis and Nearest Neighbour classifier. Furthermore, the method is enhanced using Linear Discriminant Analysis to do the diagnosis without the need for a classifier. Another faults diagnosis method has been developed that ensures the generalisation of extracted faults features from OSVM data of a specific machine to similar machines mounted on different foundations.

The de Broglie-Bohm (BB) approach to quantum mechanics gives trajectories similar to classical trajectories except that they are also determined by a quantum potential. The quantum potential is a "fictitious potential" in the sense that it is part of the quantum kinetic energy. We use quantum trajectories to treat quantum chaos in a manner similar to classical chaos. For the kicked rotor, which is a bounded system, we use the Benettin et al. method to calculate both classical and quantum Lyapunov exponents as a function of control parameter K and find chaos in both cases. Within the chaotic sea we find in both cases nonchaotic stability regions for K equal to multiples of π. For even multiples of π the stability regions are associated with classical accelerator mode islands and for odd multiples of π they are associated with new oscillator modes. We examine the structure of these regions. Momentum diffusion of the quantum kicked rotor is studied with both BB and standard quantum mechanics (SQM). A general analytical expression is given for the momentum diffusion at quantum resonance of both BB and SQM. We obtain agreement between the two approaches in numerical experiments. For the case of nonresonance the quantum potential is not zero and must be included as part of the quantum kinetic energy for agreement. The numerical data for momentum diffusion of classical kicked rotor is well fit by a power law DNβ in the number of kicks N. In the anomalous momentum diffusion regions due to accelerator modes the exponent β(K) is slightly less than quadratic, except for a slight dip, in agreement with an upper bound (K2/2)N2. The corresponding coefficient D(K) in these regions has three distinct sections, most likely due to accelerator modes with period greater than one. We also show that the local Lyapunov exponent of the classical kicked rotor has a plateau for a duration that depends on the initial separation and then decreases asymptotically as O(t-1lnt), where t is the time. This behavior is consistent with an upper bound that is determined analytically.

Neste trabalho, são inicialmente discutidas as dificuldades referentes à obtenção de resultados numéricos para a operação de uma turbina Savonius independentes do grau de discretização, tamanho de domínio de cálculo e de máximo tempo físico simulado. Também são relatadas as divergências entre as metodologias numéricas e experimentais adotadas por diversos autores, que dificultam análises e comparações dos resultados obtidos por meio dessas metodologias com os resultados próprios obtidos. Devido a esses fatos, no presente trabalho, uma série de procedimentos experimentais e numéricos são realizados para efetuar análises do escoamento sobre uma turbina eólica Savonius. Nos experimentos em canal aerodinâmico, perfis de velocidade e parâmetros da turbulência são obtidos pela técnica de anemometria de fio quente. Medições com o uso de tubos de Pitot e manômetros eletrônicos são efetuadas para avaliar a variação da pressão e os perfis de velocidade média em posições selecionadas. Além de dados para análise, informações úteis para uso como condições de contorno nas simulações numéricas também são obtidas. Os fenômenos são reproduzidos através de simulações numéricas pelo Método de Volumes Finitos, que solucionam as equações da continuidade, de Navier-Stokes com médias de Reynolds e do modelo de turbulência k-ω SST. Análises experimentais e numéricas considerando o escoamento sobre um cilindro, que mantém semelhanças com o escoamento sobre o rotor, também são realizadas. Simulações numéricas do escoamento sobre o cilindro são efetuadas, fornecendo resultados representativos do escoamento real, quando geometrias tridimensionais são aplicadas na modelagem numérica. Nas simulações do escoamento sobre o rotor Savonius em condição estática, resultados representativos do escoamento real são obtidos com o uso de uma modelagem que leva em consideração a rugosidade das pás do rotor, estacionado na posição angular de 90°. Para posições angulares menores, não se obteve uma boa concordância entre os resultados experimentais e numéricos. A realização deste trabalho fornece informações úteis para a análise do fenômeno e tem potencial para contribuir com futuros trabalhos desse tema. / This research work initially presents a discussion about the difficulties related to obtaining numerical results for the operation of a turbine Savonius independent of the degree of discretization, calculation domain size and maximum physical time of the simulation. The differences between the numerical and experimental methodologies adopted by various authors difficult the analysis and comparisons of the results obtained through these methods with the results obtained by the methodology. Due to these facts, in this research work, a series of experimental and numerical procedures are performed to conduct analyzes of flow over a Savonius wind turbine. In the experiments on aerodynamic channel, velocity and turbulence profiles parameters are obtained by the technique of hot wire anemometry. Measurements using Pitot tubes and electronic manometers are made to evaluate the variation of pressure and mean velocity profiles at selected positions. In addition to data analysis, useful information for use as boundary conditions in the numerical simulations are also obtained. The phenomena are reproduced through numerical simulations by Finite Volume Method, that solve the equations of continuity, Reynolds-averaged Navier–Stokes equations and the equation of the turbulence model k-ω SST. Experimental and numerical analyzes considering the flow over a cylinder, which holds similarities with the flow over the rotor, are also performed. Numerical simulations of the flow over the cylinder are made, providing results representative of the actual flow when three-dimensional geometries are applied in numerical modeling. In flow simulations over the Savonius rotor in static condition, at 90°, representative results of the actual flow are obtained using a model that takes into account the roughness of the rotor blades. For smaller angular positions a good agreement between experimental and numerical results was not obtained. This work provides useful information for the analysis of the phenomenon and has the potential to contribute to future work on this theme.

Diploma thesis is focused on conceptual design of Wankel rotary engine with performance between 30-60 kW. Performance of designed engine is determined to 35 kW and volume of one chamber amounts to 245,58 cm^3. In this thesis are step by step calculated geometrical properties of each design group which are afterwards put into 3D data. There is also solved cooling system of designed engine and design of geometrical and characteristic properties of parts of cooling system. Last but, not least there is solved placement of designed engine into frame of motorcycle. As suitable motorcycle has been chosen Honda CBR125R because it has very advantageous layout of frame.