L'objectif de ce travail de thèse est d'étudier analytiquement et numériquement le comportementdynamique non-linéaire des rotors, en prenant en compte des effets significatifs comme les grandesdéformations en flexion, les non-linéarités géométriques et le cisaillement. Le manuscrit est diviséen trois parties principales. Dans la première partie, le principe de Hamilton est utilisé pour formulerles équations du mouvement qui prennent en compte un ensemble d’effets non-linéaires comme desdéformations d'ordre supérieur en flexion et le cisaillement. De plus, si les supports du rotor nepermettent pas à l'arbre de se déplacer dans la direction axiale, il y a alors une force dynamiqueharmonique agissant axialement sur le rotor en fonctionnement. Ces modèles se composentd’équations différentielles non-linéaires du deuxième et du quatrième ordre.Les deux parties suivantes sont consacrées à la résolution des différents modèles non-linéairesdéveloppés dans la première partie. Des méthodes analytiques et numériques sont appliquées afin detraiter les équations non-linéaires du mouvement. Une méthode basée sur des développementsasymptotiques, la méthode des échelles multiples (MEM) est utilisée. Les courbes de réponse sonttracées pour différentes résonances possibles et l'effet de la non-linéarité est discuté par rapport àl'analyse linéaire. La réponse forcée du système provoquée par un balourd est également présentéepour plusieurs configurations du rotor. Lorsque les déformations de cisaillement sont prises encompte, l'analyse est effectuée pour différents élancements afin de mettre en évidence cet effet sur ladynamique d’un système arbre-disque / The objective of the present work is to investigate the nonlinear dynamic behavior of the rotorsystems analytically and numerically, taking into account the significant effects, for example, higherorder large deformations in bending, geometric nonlinearity and shear effects.This thesis is dividedinto two major parts. In the first part, Hamilton’s principle is used to derive the equations of motionwhich take into account various effects, for example, nonlinearity due to higher order largedeformations in bending and shear effects. In addition, if the supports of the rotor do not allow theshaft to move in the axial direction, then there will be a dynamical force acting axially on the rotoras it operates. The mathematical models are composed of coupled nonlinear differential equations ofthe 2nd and the 4th order.In the second part, the resolution of various nonlinear models developed in the first part isaddressed. Analytical and numerical methods are applied for treating the nonlinear equations ofmotion. A method based on asymptotic developments, the method of multiple scales (MMS) is used.The response curves are plotted for different possible resonance conditions and the effect ofnonlinearity is discussed with respect to the linear analysis. The forced response of the system due toa mass unbalance is also presented for various configurations of the rotor. When shear deformationsare taken into account, the analysis is performed for various slenderness ratios to highlight sheareffects on the dynamics of the shaft-disk rotor systems

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.

This thesis is intended to provide fundamental information for the construction and analysis of rotordynamic theoretical models, and their comparison the experimental systems. Finite Element Method (FEM) is used to construct models using Timoshenko beam elements with viscous and hysteretic internal damping. Eigenvalues and eigenvectors of state space equations are used to perform stability analysis, produce critical speed maps, and visualize mode shapes. Frequency domain analysis of theoretical models is used to provide Bode diagrams and in experimental data full spectrum cascade plots. Experimental and theoretical model analyses are used to optimize the control algorithm for an Active Magnetic Bearing on an overhung rotor.

This paper deals with an implementation trigonometric collocation method for ANSYS program system and its application with databases additional stiffness, mass and damping effects of journals or hydrodynamic dampers.

This Master’s thesis deals with rotordynamics analysis of asynchronous generator rigid coupling with water turbine shaft. The purpose of this thesis was to determine influence of connection of generator with water turbine by rigid coupling to reactions in bearings. This problem was solved in two ways. The first option focused on model without influence of inaccuracies whereas there were inaccuracies included in the second option. The problem was solved by computational modeling by software Ansys.

No description available.

<p dir="ltr">Current industrial processes are energy and carbon emission intensive. Amidst the growing demand for decarbonization, it is critical to utilize alternate sources of energy and innovative technologies that could improve efficiency and reduce power consumption. In this context, twin-screw compressors are used extensively in commercial and industrial applications. Profile optimization and capacity modulation solutions (e.g., slide valves, variable-speed, etc.) are continuously investigated to improve the performance and operation of the compressors. This study focuses on an exploratory investigation of an additively manufactured twin-screw compressor with internal cooling channels to achieve a near isothermal compression process by evaluating both the potential compressor performance improvement and the structural integrity by means of rotordynamics and fatigue analyses.</p><p dir="ltr">To predict the compressor performance, complex coupling between compression process and heat transfer during the operation of the compressor must be investigated. The interactions between solid (i.e., rotors) and fluid phases (i.e., air and coolant) were modeled using a transient 3D CFD model with conjugated heat transfer (CHT). The CFD model predicted compressor performance parameters such as isentropic efficiency, heat transfer rate, work input and compression forces on the rotors. The performance of the twin-screw compressor with internal cooling channels has been compared with a conventional twin-screw compressor for which experimental data was available. Further investigations have been conducted at different operating conditions, including various pressure ratios, rotational speeds, and mass flow rates to improve the compressor efficiency. The results of the CFD model were used to quantify compression loads, assess the characteristics of the heat transfer processes, and optimize the internal flow through the cooling channels. As the rotors can be affected by stress accumulation and deformations due to their hollowness and reduced wall thickness over time, this study also established a detailed rotordynamic simulation model and a fatigue model using the actual compression forces obtained from previous CFD studies. Both hollow and solid rotors have been analyzed and compared. The bearing loads have been verified against Campbell diagrams whereas the fatigue results have been compared with experimental testing. With the validated model, the hollow rotor compressor durability was analyzed and compared with the conventional rotors. Lastly, a general mechanistic model to better understand bearing loads and frictional losses in a twin-screw compressor is also established and studied.</p><p dir="ltr">The CHT study concluded that the hollow rotor with single-phase internal cooling yielded to an increase in isentropic efficiency of 1% for the higher pressure ratio and 2% for lower pressure ratio at 19,000 RPM. More importantly, the hollow rotors also showed a decrease of 40 K and 20 K in discharge temperatures for the two operating conditions respectively, thereby arriving closer to isothermal conditions and reducing the thermal stresses on the rotors. The rotordynamic study revealed that the male rotor would endure highest amount of von Misses stress reaching up to 338 MPa for the pressure ratio of 3.29 bar and 19,000 RPM. Because of this, a maximum fatigue factor of safety of 5 occurs on the male rotor. From the analyses, the rotors were deemed to be safe and optimized for the designed operating conditions and proof of concept rotors were additively manufacturers with an Inconel alloy through Direct Metal Laser Sintering.</p>

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais / INCT-EIE - Instituto Nacional de Ciência e Tecnologia De Estruturas Inteligentes em Engenharia / UFU - Universidade Federal de Uberlândia / Este trabalho apresenta uma investigação numérica e experimental sobre o comportamento dinâmico de um sistema rotativo submetido a uma excitação pela base. Na área de aplicações aeronáuticas, o motor de uma aeronave é considerado um típico rotor embarcado, no qual seu comportamento dinâmico é afetado pela excitação da base. O modelo matemático do rotor é obtido a partir das equações de Lagrange e do método de elementos finitos, considerando as energias de deformação e cinética do eixo e as energias cinéticas do disco e da massa desbalanceada. A base do sistema rotativo é considerada rígida. As equações de movimento do sistema são utilizadas para determinar as respostas de vibração do rotor a partir das excitações devido ao desbalanceamento e ao movimento da base. Na análise numérica foi investigada uma máquina rotativa composta por um eixo horizontal flexível contendo dois discos e apoiada em suas extremidades. As diferenças entre o comportamento de rotores de base fixa e em movimento foram exploradas. Uma máquina rotativa composta por um eixo horizontal flexível apoiada em suas extremidades e um disco rígido foi utilizada na validação experimental do modelo adotado. As respostas de vibração do modelo matemático construído e medidas experimentalmente foram comparadas. Diferentes análises foram realizadas nos domínios de tempo e da frequência, onde foram obtidos funções de resposta em frequência, órbitas, respostas ao desbalanceamento e o diagrama de Campbell. Os resultados obtidos representam adequadamente o comportamento do sistema. / In the present work, a numerical and experimental investigation regarding the dynamic behavior of a rotating machine subjected to a base excitation is presented. Regarding the aeronautical applications, the aircraft engine is considered a typical onboard rotor which has its dynamic behavior influenced by base excitations. The mathematical model of the rotor is derived from the Lagrange’s equation and the finite element method, which is obtained by considering the strain and kinetic energies of the shaft, and the kinetic energy of the discs and mass unbalance. In this case, the base of the rotor system is considered as being rigid. The resulting differential equations are used to provide information about the vibration responses of the rotor under base and unbalance excitations simultaneously. In the numerical analysis a rotating machine composed by a horizontal flexible shaft containing two rigid discs and supported by two ball bearings was investigated. The differences between the dynamic behavior of a fixed base and onboard rotors were explored. A rotating machine is composed by a horizontal flexible shaft, one rigid disc, and two self-aligning ball bearings was used in the experimental validation of the adopted model. The vibration responses of the mathematical model and the experimental results were compared. Different analyses were performed both in the time and frequency domains, as generated by the orbits, unbalance response, and Campbell diagram. The obtained results adequately represent the behavior of the system. / Dissertação (Mestrado)

This dissertation thesis consists rotordynamics of modern turbocharger. First part begins with prediction of critical speed, prediction of onset instability of oil whirl and oil whip by XLTRC2 and comparison with measured data (Cascade diagram, shaft motion, FFT analysis). List of measurement method for the detection of the natural frequency of turbocharger (EMA). Create software for long term monitoring and recording and output data size reduction. Detection of critical speed by defined measurement methodology without using software simulation with measured data from the Cascade diagram, move the rotor shaft motion in the bearing, FFT analysis and results from measurements of natural frequencies. Comparison of predicted data (critical speed, prediction of onset instability) program XLTRC2 with the values measured by this approach measurement (waterfall diagram, shaft motion, FFT analysis)

No description available.