Submitted by Maike Costa (maiksebas@gmail.com) on 2017-06-05T13:40:29Z No. of bitstreams: 1 arquivototal.pdf: 5062577 bytes, checksum: 50662b1886cf46d934e60415729f24cd (MD5) / Made available in DSpace on 2017-06-05T13:40:29Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5062577 bytes, checksum: 50662b1886cf46d934e60415729f24cd (MD5) Previous issue date: 2016-01-29 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Most rotating machines, especially those mounted on flexible shafts and bearings when it’s accelerating, tend to pass through critical speeds, which are speeds that can cause structural resonance in the system. Thus, there is a constant concern for seeking effective methods to reduce the effect of vibration when passing through such speeds. Currently there are many applications of "smart materials" as actuators in dynamical systems, in order to reduce vibrations in a frequency range next to the resonance zone. In this direction the use of actuators composed by shape memory alloys (SMA) assists in active control structures, due the capacity of stiffness variation with change of the temperature. This thesis presents a shaft-rotor system design with active bearing, using SMA springs and temperature control system based on fuzzy logic, to reduce the vibration amplitudes when passing through critical speeds. This reduction occurred from the system stiffness change (active support bearing), obtained by changing the temperature of the SMA springs. The theoretical and experimental results showed the system functionality, being achieved reductions of up to 61.5% in the peak amplitudes and 57.3% in terms of RMS signal during the passage through resonance zone. / A maioria das máquinas rotativas, sobretudo aquelas montadas sobre eixos e mancais flexíveis, quando de seu início de funcionamento, tendem a passar por velocidades ditas críticas, ou seja, velocidades que podem levar o sistema a entrar em ressonância estrutural. Assim, existe uma preocupação constante pela busca de métodos eficazes de atenuar o efeito da vibração quando da passagem por tais velocidades. Atualmente vêm-se estudando aplicações de “materiais inteligentes” como atuadores em sistemas dinâmicos, com o propósito de reduzir as vibrações numa faixa de frequência relacionada à região de ressonância. Nesta direção está o uso de atuadores compostos por ligas com memória de forma (LMF), que auxiliam no controle ativo de estruturas, devido à sua capacidade de variação de rigidez em função da mudança de temperatura. Apresenta-se, nesta tese, uma concepção de sistema eixo-rotor com mancal ativo, fazendo uso de molas LMF e sistema de controle de temperatura baseado na lógica fuzzy, visando reduzir as amplitudes de vibração quando da passagem por velocidades críticas. Tal redução ocorreu a partir da mudança de rigidez do sistema (mancal de suporte ativo), obtido pela mudança da temperatura das molas. Os resultados teóricos e experimentais do funcionamento do sistema mostraram a sua funcionalidade, sendo obtidas reduções de até 61,5% nas amplitudes de pico e de 57,3% em termos de RMS do sinal, durante a passagem pelas regiões de ressonância.

The possibility to save energy in synchronous machines operation by dismissing d-axis damping bars and surrogating them with active excitation current control in sectored field winding is proved. In particular a way to recover the energy of rotor oscillations during power regulation is shown by means of a studycase generator whereas a self-starting machine is analytically and numerically designed in view of its next construction and test. Principal design requirements and limits for both applications are presented and discussed.

Este trabalho apresenta a simulação numérica do escoamento turbulento em torno de uma turbina eólica de eixo vertical de pequeno porte, Savonius tipo helicoidal com torção de 180° nas pás. Com o intuito de avaliar a metodologia computacional empregada os resultados numéricos obtidos são comparados com os resultados experimental e numérico contidos no estado da arte. Também, compara-se o coeficiente de toque da turbina Savonius helicoidal com a turbina Savonius convencional. As simulações numéricas são baseadas no Método de Volumes Finitos, e para tal emprega-se o programa Fluent /Ansys versão 13.0 que resolve as equações da continuidade e as equações de Navier-Stokes com médias de Reynolds, juntamente com o modelo de turbulência . As simulações são desenvolvidas empregando diferentes malhas computacionais em estudos transientes, tridimensionais, com a turbina estacionária. A avaliação da qualidade da malha é realizada através do método de Índice de Convergência de Malha (GCI) o qual analisa o quão longe os resultados estão da solução assintótica para a malha utilizada. Após a análise da qualidade de malha, realizam-se simulações com a turbina em rotação as quais fazem uso da malha contendo uma região móvel possibilitando a imposição de uma velocidade angular ao rotor. O coeficiente de torque é obtido nas simulações e a partir dele calcula-se o coeficiente de potência. Além da análise do desempenho do rotor realiza-se uma análise qualitativa das características do escoamento sobre a turbina. A turbina Savonius helicoidal apresenta um valor de coeficiente de potência de 0,175 para a razão de velocidade de ponta de 0,58 considerando correção do efeito de bloqueio. Os resultados obtidos apresentam boa concordância com os resultados publicados por outros autores. / This dissertation presents the numerical simulation of the turbulent flow around of a small sized vertical axis wind turbine, consisting in a helical Savonius type with a 180° degree of blade twist. In order to evaluate the used methodology the obtained results are compared with the state of the art numerical and experimental data. It will be also presented the comparison between the torque coefficient of the conventional Savonius turbine and the helical Savonius turbine. The numerical simulations are based on the Finite Volume Method (FVM), using the commercial code Fluent/ANSYS version 13.0, which solves the continuity and Navier-Stokes through the Reynolds time-averaged methodology, including the turbulence model. The simulations are developed using different computational meshes for transient and three-dimensional studies with the stationary turbine. The evaluating the quality of the mesh is performed by of Grid Convergence Index (GCI) method which analyzes how far the results are the asymptotic solution to the mesh used. After the evaluation of the mesh quality, it was simulated a case considering the rotor motion using the moving mesh configuration, allowing the imposition of an angular velocity to the turbine. In the post-processing stage, it is possible to obtain the torque coefficient on the rotor shaft, allowing the calculation of the power coefficient for the turbine. In addition to the performance analysis, it is also made a qualitative analysis of the flow characteristics over the turbine rotor and in both cases presenting a good correspondence with the results in the literature. The helical Savonius turbine presents a value of power coefficient of 0.175 to a tip speed ratio of 0.58 whereas blocking effect correction.

Les rotors sont excités non seulement par le balourd tournant mais aussi par les différents mouvements de leur support : turbocompresseurs de véhicules, turbomoteurs aéronautiques, pompes à vide portées en sont des exemples industriels. Ainsi la conception de rotors robustes capables de bien fonctionner sous de telles conditions (excitations extrêmes) est nécessaire pour éviter des instabilités, source de défaillance catastrophique. Le présent travail a pour objectif de prévoir le comportement dynamique d’un rotor embarqué monté sur des paliers rigides ou élastiques hydrodynamiques et soumis à des excitations du support rigide. Les énergies cinétiques et de déformation ainsi que le travail virtuel des composants d’un rotor flexible tournant sont calculés. Le modèle proposé de rotor embarqué est basé sur les éléments finis de poutre de TIMOSHENKO. Il contient les effets relatifs à l’inertie de rotation des sections droites, à l’inertie gyroscopique, à la déformation de cisaillement d’arbre et à la dissymétrie géométrique de l’arbre et/ou du disque rigide et considère six types de mouvements déterministes (rotations et translations) du support. Suivant le type d’analyse utilisé pour le palier, les forces de rappel hydrodynamiques agissant sur l’arbre et calculées avec l’équation de REYNOLDS sont linéaires/non linéaires. L’utilisation des équations de LAGRANGE fournit les équations différentielles linéaires/non linéaires du mouvement du rotor embarqué en flexion par rapport au support mobile supposé rigide, qui représente un système de coordonnées non inertiel. Les équations du mouvement contiennent des termes paramétriques périodiques en raison de la dissymétrie géométrique du rotor et des termes paramétrique variables dans le temps en raison des rotations du support. Ces termes paramétriques sont considérés comme des sources d’excitation intérieure et conduisent à une instabilité dynamique latérale. Dans les applications numériques proposées, trois configurations de rotor embarqué sont analysées. Tout d’abord, un rotor symétrique monté sur des paliers rigides est soumis à un balourd combiné avec des mouvements de rotation constante et de translation sinusoïdale du support. Ensuite, un rotor avec une dissymétrie géométrique du disque monté sur des paliers rigides est excité par l’effet de balourd et par des mouvements combinés de rotation constante et de translation sinusoïdale du support. Enfin, un rotor symétrique monté sur des paliers hydrodynamiques est soumis au balourd et aux excitations sinusoïdales de rotation ou de translation du support. / Rotors are excited not only by the rotating mass unbalance but also by the different motions of their support: vehicle turbochargers, aircraft turbo-engines, carried vacuum pumps, are different industrial applications. Thus the design of robust rotors able to run well under such conditions (extreme excitations) and to avoid catastrophic failure is required. The present work aims to predict the dynamic behavior of an on-board rotor mounted on rigid or elastic hydrodynamic journal bearings and subjected to rigid support excitations. The kinetic and strain energies as well as the virtual work of the rotating flexible rotor components are computed. The proposed on-board rotor model is based on TIMOSHENKO beam finite elements. It includes the effects relative to the rotating inertia, the gyroscopic inertia, the shear deformation of shaft as well as the geometric asymmetry of shaft and/or rigid disk and considers six types of deterministic motions (rotations and translations) of the support. Depending on the type of analysis used for the bearing, the restoring fluid film forces acting on the shaft and computed with the REYNOLDS equation are linear/non-linear. The use of LAGRANGE’s equations yields the linear/non-linear differential equations of vibratory motion of the on-board rotor in bending with respect to the moving rigid support which represents a non-inertial reference frame. The equations of motion contain periodic parametric coefficients because of the geometric asymmetry of the rotor and time-varying parametric coefficients because of the support rotations. These parametric coefficients are considered as sources of internal excitation and can lead to lateral dynamic instability. In the proposed numerical application examples, three rotor configurations are studied. Firstly, a symmetric rotor mounted on rigid bearings is subjected to rotating mass unbalance combined with constant rotation and sinusoidal translation of the support. Secondly, a rotor with geometric asymmetry due to the disk mounted on rigid bearings is excited by the mass unbalance effect and by the combination of a constant rotation and a sinusoidal translation of the support. Thirdly, a symmetric rotor mounted on linearized/non-linear hydrodynamic bearings is subjected to the excitation due to the mass unbalance and to the sinusoidal rotational or translational excitations of the support.

Dans le contexte actuel, l'open-rotor contrarotatif connaît un regain d'intérêt. Cependant, en l'absence de carter extérieur, la prédiction des effets d'installation devient une problématique primordiale du cycle de conception. L'objectif de ces travaux de thèse est de construire une méthode de calcul qui permette à la fois de rendre compte de l'impact du bloc moteur sur la traînée de l'avion et de l'impact de l'installation sur les performances aérodynamiques des hélices. Suite à une étude bibliographique, nous nous sommes orientés vers le couplage des codes ligne portante LPC2 et RANS elsA, développés à l'Onera. La méthode de couplage se base sur la condition de disque d'action et est itérative afin de rendre compte de l'interaction.Dans un second temps, des résultats de calculs instationnaires et d'essais en soufflerie ont été comparés aux résultats fournis par le couplage afin de confirmer que ce dernier rendait bien compte des performances aérodynamiques du moteur en configuration installée. Afin de valider sur un large domaine de calcul, plusieurs configurations ont été utilisées, prenant en compte différentes installations, différentes hélices et plusieurs points de vol.Enfin, nous avons proposé une amélioration de la condition de disque d'action par une modélisation de la turbulence représentant l'impact du passage des hélices sur l'écoulement. En effet, en l'état actuel, cette condition n'est pas en mesure de retranscrire l'impact des hélices sur la turbulence, en particulier sur l'augmentation du taux de turbulence. C'est pourquoi une formulation originale d'un modèle de turbulence, basée sur les travaux de Mr Benay, a été proposée. / The counter rotating open rotor entered a period of renewed interest because of the current circumstances. However, due to the absence of outer casing, predicting the installation's effects became an essential issue of the design process. The objective of this thesis is to elaborate a calculation method able to give the impact of the engine on the aircraft drag as well as the installation impact on the propellers aerodynamic performances. As a result of a literature review, we headed for the coupling of the LPC2 lifting-line code and elsA RANS code, developed by the Onera. The coupling method is based on the actuator disc condition and was made iterative in order to take the interaction into account.In a second phase, results from unsteady simulations and wind tunnel experiments were compared to the coupling results so as to confirm that the later was able to produce the engine's aerodynamic performances under the influence of the installation. In order to validate the coupling on a wide computational domain, multiple configurations were used, taking different installations into account, with different propellers and multiple flight conditions.Finally, an improvement of the actuator disc condition was proposed through a turbulence modeling showing the impact of the blades passages on the flow. Indeed, the actuator disc condition is currently unable to faithfully transpose the propellers impact on the turbulence, especially on the turbulence rate increase. Therefore, an original formulation of a turbulence model was given, based on the works of Mr. Benay.

Dans le cadre du projet européen Clean Sky, Snecma construit un démonstrateur de Contra Rotating Open Rotor (CROR). La conception du système de régulation du moteur nécessite d'avoir connaissance du comportement aérodynamique de chacune des hélices du doublet. Les objectifs de cette thèse sont dans un premier temps de comprendre les interactions entre les différents éléments constitutifs d'un CROR ayant un effet sur les performances des hélices, d'isoler leurs contributions respectives et dans un deuxième temps de développer un modèle prédictif des performances individuelles des hélices d'un CROR intégrable dans un environnement de calcul de cycles thermodynamiques. Pour cela, le comportement des hélices en doublet est rapproché de celui d'hélices isolées dont les effets macroscopiques sont bien connus. Des calculs Euler et NS3D ont servi de base pour proposer un couplage entre les hélices isolées permettant de retrouver le champ de vitesses induits entre les hélices d'un calcul doublet. Pour respecter les exigences de rapidité d'exécution et de robustesse numérique imposées par l’environnement de calcul de cycles thermodynamiques, les performances individuelles des hélices du doublet sont calculées à partir de champs hélice isolée. Une approche monodimensionnelle permet de calculer les vitesses induites propres des hélices à partir de la traction et de la puissance absorbée et une méthode pour estimer les vitesses induites mutuelles à partir des vitesses induites propres est donnée. Le calcul des performances individuelles des hélices d'un doublet contrarotatif est itératif. Cette méthode estime les performances avec une erreur relative inférieure à 5%. Elle est utilisée dans le développement du système de régulation du démonstrateur CROR SAGE2. / Within the scope of the European research project Clean Sky, Snecma builds a ground demonstrator of the concept engine Contra Rotating Open Rotor (CROR). Engine control system design requires knowing how each propeller will behave aerodynamically under the interaction of each other. The aim of this work is to design a predictive model of contra rotating propeller individual performance fitting in a thermodynamic cycle calculation environment. A coupling is proposed in order to represent the dual propellers thanks to isolated propeller behavior. It has been shown that by matching the isolated propellers thrust and torque to the doublet values, the good values of mutual induced velocities can be found. Hence contra rotating propellers individual performance can be reached with a good variation in parameters. In addition to that, in order to meet withthermodynamic cycle calculation environment requirements of rapidity and numerical robustness, performance is calculated from pre-generated propeller maps. One-dimensional approach is used to calculate mutual induced velocities from propellers thrust and torque. Contra rotating propellers individual performance calculation is an iterative process. The method developed gives the performance within a 5% relative error margin and is currently used for the design of the ground demonstrator control system.

Ce travail de thèse porte sur les propriétés de stabilité des tourbillons hélicoïdaux, structures que l'on retrouve notamment dans le sillage des rotors d'hélicoptères et d'éoliennes.Dans une première partie, le développement spatio-temporel de l'instabilité d'appariement est caractérisé à l'aide d'un code numérique pseudo-spectral pour une allée infinie d'anneaux tourbillonnaires. On montre que ce modèle axisymétrique d'écoulement est en effet une bonne approximation du système hélicoïdal dans la limite des grands rayons et petits pas d’hélice. Dans ces conditions, et en utilisant un adimensionnement judicieux, on obtient également que le résultat théorique pour le taux de croissance spatio-temporel obtenu pour une double allée de tourbillons ponctuels s’avère être une bonne prédiction pour le cas hélicoïdal.Dans une seconde partie, on décrit comment un ou plusieurs tourbillons hélicoïdaux ont pu être générés de façon très peu perturbée à l’aide de modèles réduits de rotors dans le canal hydrodynamique du laboratoire. Grâce à l’introduction de perturbations d’amplitudes et de fréquences soigneusement contrôlées, le taux de croissance de l’instabilité d’appariement a pu être mesuré et comparé aux résultats théoriques. L’évolution non linéaire de ces perturbations ainsi que d’autres modes instables, à plus petites longueurs d’onde, ont également pu être observés expérimentalement pour la première fois.Enfin, ces résultats ont été appliqués au cas des rotors d’hélicoptères pour la prédiction du régime de Vortex Ring State (VRS) et à la transition vers la turbulence du sillage des éoliennes. / This thesis is devoted to the stability properties of helical vortices, which are of interest for applications such as helicopter and wind turbine wakes.In a first part, the spatio-temporal development of the pairing instability is characterised for an infinite array of vortex rings, using a pseudo-spectral numerical code. We show that this axisymmetric flow model is indeed a good approximation of the helical system in the limit of large helix radius and small pitch. Under these assumptions, and by using appropriate dimensionless variables, we also show that the theoretical result concerning the spatio-temporal growth rate for a double row of point vortices represents a good prediction for the helical case.In a second part, we describe how one or several helical vortices were generated in a carefully controlled way using small-scale rotor models in the water channel of the laboratory. Introducing perturbations with well-defined amplitudes and frequencies, the growth rate of the pairing instability could be measured experimentally and compared to theoretical predictions. The non-linear evolution of these perturbations, as well as other unstable modes of smaller wavelengths, were also observed experimentally for the first time.Finally, these results were applied to helicopter wakes for the prediction of the Vortex Ring State (VRS) regime and to the transition to turbulence in wind turbine wakes.

Cette thèse aborde la problématique de la conception optimale de structures composites stratifiées d’épaisseur variable. Les variables d’empilement définissent un problème d’optimisation combinatoire et des espaces de décisions de grande taille et potentiellement multimodaux. Les algorithmes d’optimisation stochastiques permettent de traiter ce type de problème et de tirer profit des performances et de l’anisotropie des plis composites pour l’allègement des structures composites stratifiées. Le but de cette étude est double : (i) développer un algorithme d’optimisation dédié aux composites stratifiés d’épaisseur variable et (ii) estimer le potentiel des composites stratifiés pour la maîtrise des performances aérodynamiques d’une pale de CROR composite.Dans la première partie de cette thèse, un algorithme évolutionnaire est spécialisé pour l’optimisation de tables de drapage et la gestion d’un ensemble de règles de conception représentatif des pratiques de l’industrie. Pour se faire, un encodage spécifique des solutions est proposé et des opérateurs de variations spécialisés sont développés.Dans la deuxième partie, l’algorithme est enrichi d’une technique de guidage basée sur l’exploitation d’un espace auxiliaire afin d'accroître son efficacité et d’intégrer davantage de connaissances des composites dans la résolution du problème.Finalement, la méthode est appliquée pour la conception d’une pale de CROR composite à l’échelle de la maquette de soufflerie. Au préalable, des processus itératifs de mise à froid et mise à chaud de la pale sont mis en place afin d’estimer la forme de la pale au repos et l’état de contraintes dans la pale en fonctionnement. / This thesis deals with the optimal design of variable-thickness laminated composite structures. The stacking variables define a combinatorial optimization problem and large decision spaces which are potentially multimodal. Stochastic optimization algorithms allow solving this type of problem and allow taking advantage from the performance and the anisotropic nature of unidirectional composite plies to lighten laminated composite structures.The purpose of this study is twofold: (i) developing an optimization algorithm dedicated to variable-thickness laminated composites and (ii) assessing the potential of laminated composites in influencing the aerodynamic performances of a composite CROR blade.Firstly, an evolutionary algorithm is specialized in order to optimize layup tables and handle a set of design guidelines which is representative of industrial practices. In this purpose, a specific encoding of the solutions is suggested and specialized variation operators are developed.Secondly, the algorithm is enriched with a guiding technique based on the exploitation of an auxiliary space in order to improve its efficiency and to include further composites-related knowledge for the resolution of the problem.Finally, the method is applied for the design of a reduced-scale composite CROR blade intended for wind-tunnel testing. Beforehand, iterative processes are implemented to estimate the shape of the non-operating blade and the stress state within the operating blade.

This term paper is focused on theory and calculation of an induction motor with solid rotor. It is divided into six chapters, the first one being an introduction and the last being a conclusion. Second chapter is dedicated to magnetism. There is briefly description of a skin depth of a conductor and calculation method for impedance of a conductive solid. Third chapter is focused on theory of an induction machines, their construction, equivalent circuit and some of their properties. Fourth chapter is dedicated to calculation of an induction motor with solid rotor and its parameters. Fifth chapter is comparing results of calculation done in fourth chapter for an already existing motor with measured values.

The master thesis deals with the construction and design of a high-speed synchronous machine with an outer rotor. The thesis is organised into three main chapters. The first chapter deals with machine design theory as well as mechanical limits, which are significant for high speed machines. This chapter also provides examples of applications of these electrical machines. In the second chapter, the initial design of the machine is calculated analytically. This machine design is optimised and the third chapter of this work shows the results of simulations using the finite elements method, including the evaluation of these results.