Tesi sul tema "Rotors – Dynamics"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Rotors – Dynamics.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Rotors – Dynamics".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Jarroux, Clément. "Nonlinear transient dynamics of on-board rotors supported by Active Magnetic Bearings". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI069/document.
Testo completoAbstract (sommario):
De manière générale, les turbomachines sont des machines tournantes permettant la conversion des différents types d’énergie. Ces dernières sont composées d’une partie mécanique en rotation, appelée rotor, interagissant avec un fluide. La rotation a donc un rôle clé pour ces machines et la liaison entre les parties fixes et les parties tournantes, appelée palier, est primordiale pour un fonctionnement fiable et optimal. Les turbomachines supportées par des paliers magnétiques actifs (PMAs) sont de plus en plus utilisées par les industriels notamment grâce à l’absence de contact direct entre parties fixes et parties tournantes, permettant un gain d’énergie et une réduction des émissions de CO2. La plupart du temps, ces machines sont « embarquées » et reposent sur des supports mobiles. Les mouvements générés par ces supports doivent être considérés dans la prévision du comportement dynamique des turbomachines afin d’améliorer les designs en conséquence. Cette thèse est une contribution à l’étude des turbomachines supportées par des PMAs sujettes à de fortes sollicitations extérieures. L’approche est numérique et expérimentale. L’utilisation d’un banc d’essais académique composé d’un système rotor-PMA, aux propriétés d’une turbomachine industrielle, a permis de tester les modèles développés pour des cas de sollicitations extérieures de type séisme et choc, générées grâce à l'excitateur 6-axes de l'equipex PHARE. Il est montré que le modèle permet la bonne prévision du comportement réel de la machine. Cet outil pourra donc être utilisé pour des designs de type industrielTurbomachines are rotating machines enabling the conversion of the different types of energy. The latter are composed of a rotating mechanical part, called rotor, interacting with a fluid. Therefore, rotation play a key role in these machines and the mechanical link between the fixed and the rotating parts, called bearing, is essential for reliable and optimal operations. Turbomachines supported by active magnetic bearings (AMBs) are increasingly used by industrial companies, especially thanks to the absence of direct contact between fixed and rotating parts, enabling energy savings and reduction of CO2 emissions. Most of the time, these machines are "on-board" and are fixed on mobile supports. The motions generated by these supports must be considered in the prediction of the dynamic behaviour of turbomachinery in order to improve the designs accordingly. This PhD is a contribution to the study of turbomachines supported by AMBs subjected to strong external base motions. The approach is numerical and experimental. The use of an academic scale test rig comprising a rotor-AMB system, with the properties of an industrial turbomachine, allowed to test the developed models for cases of external solicitations such as earthquake and shock, thanks to the 6-axis shaker of the equipex PHARE. It is shown that the model provides good predictions of the behaviour of the machine for the tested cases. This tool can therefore be used for industrial designs
2
Matos, Catherine Anne Moseley. "Download reduction on a wing-rotor configuation". Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12058.
Testo completo
3
Rigsby, James Michael. "Stability and control issues associated with lightly loaded rotors autorotating in high advance ratio flight". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26536.
Testo completoAbstract (sommario):
Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: J.V.R. Prasad; Committee Member: Daniel P. Schrage; Committee Member: David A. Peters; Committee Member: Dewey H. Hodges; Committee Member: Lakshmi N Sankar. Part of the SMARTech Electronic Thesis and Dissertation Collection.
4
El-Shafei, Aly. "Dynamics of rotors incorporating squeeze film dampers". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/87804.
Testo completo
5
He, Chengjian. "Development and application of a generalized dynamic wake theory for lifting rotors". Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/12389.
Testo completo
6
Bitzer, Michael. "Identification of an improved body aerodynamics model for the BO 105". Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/13832.
Testo completo
7
Riley, Troy M. "Aeroacoustics and Fluid Dynamics Investigation of Open and Ducted Rotors". University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627667464605408.
Testo completo
8
Mendes, Ricardo Ugliara 1987. "Desenvolvimento de um sistema de atuação magnética para excitação de sistemas rotativos". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264158.
Testo completoAbstract (sommario):
Orientadores: Kátia Lucchesi Cavalca Dedini, Luiz Otávio Saraiva FerreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-17T15:03:09Z (GMT). No. of bitstreams: 1 Mendes_RicardoUgliara_M.pdf: 2835811 bytes, checksum: c8cae753b116c3893246e25fb64fdf4c (MD5) Previous issue date: 2011
Resumo: Máquinas rotativas apresentam um vasto campo de aplicação como aeronaves, fábricas, laboratórios e usinas de energia. Estas aplicações contêm eixos girando a altas velocidades que devem ter alto nível de confiabilidade. Assim, a análise do comportamento dinâmico destas bombas e turbinas é necessária para estabelecer padrões de funcionamento do equipamento. Ultimamente, com projetos feitos com auxílio de computador, modelos de elementos finitos de eixos incluindo mancais, discos, selos e acoplamentos têm sido desenvolvidos. Através destes modelos, o comportamento das máquinas pode ser previsto, permitindo projetos otimizados baseados nos cálculos de velocidades críticas e simulações de instabilidades do filme de óleo. Estas informações fornecem a base para o desenvolvimento de controladores para reduzir vibrações durante a partida de máquinas, assim como aceleração ou desaceleração através das velocidades críticas, ou ainda para controlar instabilidades do filme de óleo. Uma das técnicas aplicadas na identificação de parâmetros de máquinas e estruturas é a análise modal, a qual consiste em aplicar uma força de perturbação no sistema e, então, medir sua resposta. Entretanto, há uma dificuldade que traz limitações à excitação de sistemas com eixos rotativos, quando utilizando martelos de impacto ou shakers, uma vez que, devido ao atrito, forças tangenciais e ruídos indesejados podem ser aplicados ao sistema. Portanto, o estudo de uma técnica de excitação externa sem contato se torna de grande interesse. Neste sentido, o presente trabalho trata do estudo e desenvolvimento de um modelo em elementos finitos de máquinas rotativas integrado ao modelo de um atuador magnético como fonte de excitação externa, focando na resposta do modelo e sua interação com o atuador. Também é apresentada uma comparação entre simulações numéricas e testes práticos obtidos de uma bancada experimental
Abstract: Rotating machines have a wide range of application such as airplanes, factories, laboratories and power plants. These applications contain shafts rotating at high speeds that must have high trust levels. Thus, the dynamic behavior analysis of these pumps and turbines is required to establish operational patterns of the equipment. Lately, with computer aid design, shafts finite element models including bearings, discs, seals and couplings have been developed. Through these models the machines behavior can be predicted, allowing optimized design based on the critical speeds calculus and oil instabilities simulations. These informations provide the basis for controller development in order to reduce vibrations during the machines start-up and acceleration or deceleration through the critical speeds, or even to control oil instabilities. One of the technique es applied in parameters identification of machines and structures is the modalanalysis, which con sists of applying a perturbation force into the system and then to measure its response. However, there is a difficulty that brings limitations to the excitation of systems with rotating shafts when using impact hammers or shakers, due to friction, undesired tangential forces and noise that can be applied to the system. Therefore, the study of a non-contact technique of external excitation becomes of high interest. In this sense, the present work deals with the study and development of a finite element model for rotating machines using a magnetic actuator as source of external excitation, focusing on the model response and its interaction with the actuator. It is also presented a comparison between the numerical simulations and practical tests obtained from a rotor test rig
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
9
Medeiros, Everton Coelho de. "Projeto e avaliação do comportamento dinâmico de um conjunto de mancais hidrodinâmicos aplicados a um rotor Jeffcott /". Guaratinguetá, 2017. http://hdl.handle.net/11449/151475.
Testo completoAbstract (sommario):
Orientador: Mauro Hugo MathiasCoorientador: Willy Roger de Paula Mendonça
Banca: José Elias Toamzini
Banca: Everaldo de Barros
Resumo: Os estudos relacionados a máquinas rotativas são muito importantes no apoio e manutenção da operação de máquinas de grande porte, tais como turbo compressores ou turbinas. Modelos analíticos e numéricos têm sido aplicados por anos, entretanto, eles nem sempre apresentam as condições reais dessas máquinas. Por isso, o uso de procedimentos experimentais para a avaliação e validação de resultados de máquinas rotativas é importante para a etapa de projeto mecânico. O uso de modelos em escala, por exemplo, turbinas hidráulicas ou turbinas a vapor, tem sido comum nesta área. Um rotor é dividido em várias partes, sendo uma delas os elementos de suporte, mais especificamente os mancais. Os mancais podem ser divididos em vários tipos, os mais utilizados são os do tipo rolamento e tipo hidrodinâmico. Devido este último ser o mais encontrado em máquinas pesadas, seu estudo é muito importante. Este trabalho objetiva apresentar o projeto de um protótipo de um mancal hidrodinâmico e sua avaliação experimental. O mancal desenvolvido consiste de uma bucha de bronze montada sobre uma casa de mancal de alumínio e sistemas de vedação para o óleo lubrificante. As geometrias das buchas e as propriedades dos fluidos foram analisadas pela medição do comportamento dinâmico de um rotor apoiados por esses mancais. Esta avaliação foi baseada na medição de uma bancada do tipo Jeffcott apoiada em um par de mancais hidrodinâmicos em condições diversas, incluindo combinações entre mancais do tipo rolamento... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Studies related to rotary machines are very important to support and keep the operation of large machines such as turbochargers or turbines. Analytical and numerical models have been applied for years, however, they do not always present the real condition of these machines. Therefore, the use of experimental procedures for the evaluation and validation of rotating machine results is important for mechanical design step. The use of scale models, for example, hydraulic turbines or steam turbines, has been very common in this area. A rotor is divided into several parts, one of which is the support elements, more specifically the bearings. The bearings can be divided into several types, the most common are the ball/roller bearing and the hydrodynamic bearing. Due to the latter be the most applied in heavy machinery, his study is very important. This work aims to show the design of a prototype of a hydrodynamic bearing and its experimental evaluation. The developed bearing consists of a bronze bushing mounted on an aluminum bearing housing and sealing systems for lubricating oil. The bushing geometries and the properties of the fluids are analyzed by measuring the dynamic behavior of a rotor supported by these bearings. This evaluation was based on the measurement of a Jeffcott rotor test bench supported by hydrodynamic bearings under a variety of conditions, including combinations of rolling and hydrodynamic type bearings,variation of the internal geometry of the bronze bushing ... (Complete abstract click electronic access below)
Mestre
10
Jayasuriya, Arachige Tilak A. "Dynamics of unbalanced rotors on rigid and flexible bearings". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ48062.pdf.
Testo completo
11
Del-Mar, Jon. "Quantum molecular dynamics of methyl rotors in peptide links". Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272717.
Testo completo
12
Thiery, Florian. "Simplified models to evaluate nonlinear dynamics in hydropower rotors". Doctoral thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25641.
Testo completoAbstract (sommario):
In hydropower systems, it is essential to avoid catastrophic failures that lead to human and economic losses. Unfortunately, a hydropower rotor can behave abnormally since several nonlinear effects occur during start-up, shut-downs or when running at nominal speed. Weak nonlinear interaction in the bearings, electromagnetic interaction between the generator and rotor or fluid-structure interaction in turbines are typical nonlinear effects that may appear. Moreover, strong nonlinearities can also occur due to blade contacts and assembly errors. These types of nonlinearities can be dangerous in case of bad design of the rotor, and it could even lead to catastrophes in the worst case. In this thesis, simple models are used to describe the different types of nonlinearities, with focus on blade rubbing, bearings and electromagnetic interaction. These interactions are usually investigated on Jeffcott rotors or rigid rotors to reduce the dimension of the design space to a few important parameters only. The dynamics of the system are evaluated by using common tools such as Poincare sections, bifurcation diagrams, Maximum Lyapunov Exponent (MLE), Lyapunov spectrum and waterfall plots of the Fast Fourier Transform (FFT). The numerical results have been compared with experimental results to ensure that these models are satisfying in our range of study. Once these simple models have been verified, they can be used to simulate the full hydropower rotor by including all interaction types. A focus is made on the numerical methods to employ and reduction methods to gain computation time, as well as to know under which circumstances the nonlinear interactions have to be included in comparison with the linear analysis. As a result, this work intends to provide guidelines about the models to use to perform dynamic simulations on fullscale turbines and to know when a linear model can be sufficient to evaluate a machine at design stage or when changing any mechanical component in the hydropower rotor.
13
Leister, Tim. "Dynamics of rotors on refrigerant-lubricated gas foil bearings". Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI010.
Testo completoAbstract (sommario):
La technologie du palier à feuilles (GFB) est l’un des facteurs clés pour la transition envisagée vers des machines tournantes sans huile dans les futurs moyens de transport. Outre les nombreux avantages en termes de taille, de poids, d’efficacité et de propreté, les GFBs offrent la possibilité unique d’être lubrifiés par des fluides de travail tels que les réfrigérants. Cependant, l’analyse numérique des systèmes GFB–rotor lubrifiés par réfrigérant représente un problème interdisciplinaire d’une énorme complexité et d’intérêts contradictoires entre des approches de modélisation et de résolution exhaustives mais performantes. Dans ce mémoire de thèse, il est possible d’explorer et de surmonter les limites de faisabilité actuelles, ce qui permet d’établir une nouvelle stratégie permettant des analyses de stabilité et de bifurcationThe gas foil bearing (GFB) technology is considered one of the key factors for the intended transition to oil-free rotating machinery in future transportation systems. Besides numerous advantages in terms of size, weight, efficiency, and cleanliness, GFBs offer the unique ability to be lubricated with working fluids such as refrigerants. However, the computational analysis of refrigerant-lubricated GFB–rotor systems represents an interdisciplinary problem of enormous complexity and with conflicting interests between all-encompassing but efficient modeling and solution approaches. This thesis succeeds in exploring and pushing forward existing limits of feasibility and thereby establishes a new strategy that enables stability and bifurcation analyses
14
Velkova, Cvetelina Vladimirova. "Modélisation du comportement dynamique des rotors d’hélicoptères". Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0055/document.
Testo completoAbstract (sommario):
Modélisation du comportement dynamique des rotors d'hélicoptèresL'objectif de la thèse est l'étude et la modélisation du comportement dynamique et aérodynamique du rotor de l'hélicoptère en considérant à la fois les forces d'inertie et les forces aérodynamiques et en tenant compte des déformations élastiques des pales. L'algorithme de couplage proposé permet d'effectuer le calcul transitoire avec échange de données entre les solveurs fluide et structure à chaque pas de temps.La particularité de cette étude est l'utilisation du modèle aérodynamique de la ligne active, qui représente les forces de pale appliquées au fluide par des termes sources. Ces termes sources sont répartis dans les cellules de maillage à l'emplacement de la pale. Ainsi, la rotation, la torsion et le battement de la pale peuvent être représentés sans aucune déformation du maillage. Un avantage de la ligne active est que la simulation utilise un nombre réduit de nœuds, car des conditions aux limites «lois des parois» ne doivent pas être modélisées.Le cas d'un petit rotor expérimental d'hélicoptère est étudié en vol d'avancement. Les solveurs de fluide et de structure sont couplés pour calculer le comportement aérodynamique et dynamique du rotor. Pour ce faire, un algorithme de couplage faible en série décalé est appliqué. Les calculs itératifs sont contrôlés par un code spécialement conçu. Au début de chaque itération, le code calcule et répartit les termes sources dans le domaine fluide. A la fin du pas de temps, le code exécute le solveur de calcul de structure pour calculer un seul pas de temps. Ce solveur calcule le déplacement de la pale sous l'effet des forces aérodynamiques, élastiques et d'inertie et renvoi les résultats au solveur fluide. Les déplacements de la pale calculés servent de référence pour le solveur fluide au pas de temps suivant, pour distribuer les termes sources. Le calcul s'arrête lorsque le critère de convergence est vérifié.Afin de valider le cas simulé, des expérimentations sont réalisées en soufflerie. La puissance et la poussée aérodynamique du rotor sont mesurées. La Vélocimétrie par images de particules (PIV) est utilisée pour obtenir le champ de vitesse autour du rotor. Les mesures PIV à phase bloqué dans des plans azimutaux ont permis de reconstituer le champ d'écoulement 3D. La comparaison entre les résultats numériques et les expériences montre un bon accord et permet de valider la méthode de couplage proposéeMODELING THE DYNAMIC BEHAVIOR OF HELICOPTER ROTORThe aim of the thesis is the investigation and modeling of dynamic and aerodynamic behavior of helicopter rotor considering both inertial and aerodynamic forces and taking into account the elastic deformation of the blades. The proposed coupling algorithm allows the transient calculations with data exchange between the fluid and structure solvers at each time step.The particularity of this research is the use of an actuator line aerodynamic model, which represents the blade forces applied to the fluid as source terms. These source terms are distributed in the grid cells where the blade is located. Thus the rotation, flapping and torsion of the blade can be represented without any grid deformation. An advantage of the actuator line is that the simulation uses a reduced number of nodes, because the “wall” boundary conditions do not need to be modeled.The case of small experimental helicopter rotor is studied in forward flight. The fluid and structure solvers are coupled to calculate aerodynamic and dynamic behavior of the rotor. For this purpose, a loosely coupling serial staggered algorithm is applied. The iterative calculations are controlled by specially developed code. At the beginning of each iteration, this code calculates and distributes the source terms in the fluid domain. At the end of the time step, the code runs the structural solver to execute a single time step. This solver calculates the blade displacement under aerodynamic, elastic and inertial forces, and the results are returned to the fluid solver. The calculated blade displacements serve as reference in the next fluid step to distribute the source terms. The calculation stops when the convergence criteria are met.In order to validate the simulated case, measurements are carried on in the wind tunnel. The power and aerodynamic thrust of the rotor are measured. Particle Image Velocimetry (PIV) is used to obtain the velocity field around the rotor. Phase locked measurement in azimuth planes enabled to reconstruct 3D flow field. The comparison between numerical results and experiments shows good agreement and permits to validate the proposed coupling method
15
Robison, Rosalyn Aruna Venner. "Turbulence ingestion noise of open rotors". Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/243244.
Testo completoAbstract (sommario):
Renewed interest in open rotor aeroengines, due to their fuel efficiency, has driven renewed interest in all aspects of the noise they generate. Noise due to the ingestion of distorted atmospheric turbulence, known as Unsteady Distortion Noise (UDN), is likely to be higher for open rotors than for conventional turbofan engines since the rotors are fully exposed to oncoming turbulence and lack ducting to attenuate the radiated sound. However, UDN has received less attention to date, particularly in wind-tunnel and flight testing programmes. In this thesis a new prediction scheme for UDN is described, which allows inclusion of many key features of real open rotors which have not previously been investigated theoretically. Detailed features of the mean flow induced by the rotor, the form of atmospheric turbulence, asymmetries due to installation features, and the effect of rotor incidence are all considered. Parameter studies are conducted in each of these cases to investigate their effect upon UDN in typical static testing and flight conditions. A thorough review of the technological issues of most relevance and previous theoretical work on all types of turbulence-blade interaction noise is first undertaken. The prediction scheme is then developed for the case in which the mean flow into the rotor is axisymmetric. This shows excellent qualitative agreement with previous findings, with increased streamtube contraction resulting in a more tonal noise spectrum. The theoretical framework involves using Rapid Distortion Theory to calculate the distortion of an isotropic turbulence field (such as given by the von Karman spectrum) by the mean flow induced by the rotor (such as given by actuator disk theory), leading to an expression for the velocity incident upon the leading edge of the rotor blades. Strip theory is then used to calculate the pressure jumps across the blades, input as the forcing term in the far-field wave equation. Models are derived for open rotor-induced flow which account for the variation of blade circulation with radius, and the presence of the rotor hub and rear blade row. An investigation of appropriate turbulence models and realistic turbulence parameters is also undertaken. A key finding is that the heights of the tonal peaks are determined by the overall magnitude of the induced streamtube contraction (dependent on the total thrust generated) whereas the precise form of distortion (affected by the detailed components of the mean flow and the form of atmospheric turbulence present) alters the resulting broadband level. The prediction scheme is formulated in such a way as to facilitate extension to the asymmetric case, which is also fully derived. The model is applied in the first instance to the case of two adjacent rotors and then to the case of a single rotor at incidence. Under flight conditions, when distortion is reduced but UDN can still contribute a significant broadband component to overall noise levels, asymmetry is found to increase broadband levels around 1 Blade Passing Frequency but reduce levels elsewhere.
16
Ozbay, Serkan. "Extension-Twist Coupling Optimization in Composite Rotor Blades". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10422.
Testo completoAbstract (sommario):
For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different.
Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass.
A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept provides for tailoring of the structure without any additional weight penalty on the system.
17
Tian, Liang. "Investigation into nonlinear dynamics of rotor-floating ring bearing systems in automotive turbochargers". Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/43029/.
Testo completoAbstract (sommario):
As a high speed rotating device, a modern turbocharger rotor is commonly supported by floating ring bearings (FRBs), owing to their cost effectiveness for mass production and good damping performance. Thanks to the rapid growth of the power of the modern computer, rotordynamic analysis of turbocharger rotor-bearing systems becomes feasible, and it is closely related to the healthy operation and noise generation of turbochargers. The work in this thesis is concerned with the nonlinear rotordynamic modelling, simulation and analysis in the rotor-FRB system of turbochargers. The conventional linear eigenvalue analysis is shown first in a gradually deepening manner to provide a deeper insight into the results from nonlinear simulations and reported experimental results. It is subsequently found the onset of first two nonlinear jumps can be effectively predicted by the linearized FRB model, although the rotordynamic characteristics at higher rotor speeds can hardly be linearly predicted. The desired oil-film forces for nonlinear simulations are calculated from a newly proposed analytical method, which is extended from the Capone's journal bearing model. Stationary simulations under the perfectly balanced condition show two major subsynchronous components throughout the considered speed range, while the inclusion of in-phase unbalance places a considerable effect on the rotor response at relatively low speed and delays the occurrence of oil-film instability. However, at higher rotor speeds, the lower subsynchronous component can still establish the dominance. The engine induced vibrations are also considered, and it is seen the rotor response over the lower end of the speed range will be considerably affected, whereas, at higher rotor speeds, the engine induced vibrations can be suppressed by the dominant lower subsynchronous vibrations. Through carrying out many run-up and run-down simulations, the FRB outer clearance is found to be a critical parameter of the rotordynamic performance of the investigated TC rotor-FRB system, since distinct frequency maps are obtained with varying FRB outer clearances. The nonlinear effects of unbalance are also investigated, and it is observed the rotor response can be considerably affected by the amount and distribution of the imposed unbalance.
18
Liew, Andrew Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "A study of a rotor system with ball bearing induced non-linearities; and the development of transfer matrix techniques suitable for analysing such systems". Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2003. http://handle.unsw.edu.au/1959.4/19227.
Testo completoAbstract (sommario):
This thesis is concerned with enhancing analysis tools for evaluating the non-linear dynamics of rotor bearing systems and in particular those where non-linearity is likely to result in aperiodic or chaotic behaviour, such as rolling element bearing systems. The tool to be enhanced was the transfer matrix approach which has been extensively used in the past for analysing linear rotor bearing systems. However, its use for evaluating non-linear behaviour has been virtually non-existent. Hence, the major aim of the thesis is to extend transfer matrix capabilities to handle non-linear systems. To this end a harmonic balance transfer matrix technique capable of analysing non-linear systems with multiple pedestal supported bearings was first developed. However, this approach is restricted to periodic response. To enable the analysis of non-linear systems with non-periodic response and provide a stability check for the harmonic balance technique, a transient transfer matrix has also been developed. The softwares for both of these newly developed transfer matrix techniques have been successfully verified for various non-linear rotor bearing systems using an established system matrix based transient rotordynamics software as the yardstick. These developments have been published in refereed journals. To investigate systems with rolling element bearings, appropriate bearing modelling which incorporates angular contact and rolling element inertia needed to be developed and incorporated into transient analysis softwares. Theoretical results from this were compared to data obtained from an experimental test rig which was designed to represent the salient features of an F/A-18 aircraft mounted accessory drive. The rig allowed for variation of bearing preload, unbalance loading and bearing support stiffness and could be run up to 17,000rpm. Full details of the design and commissioning are presented. Results showed better agreement than linear analyses but significant differences were encountered. Errors were largely due to estimated bearing parameters, in particular bearing damping, which was found to be a sensitive variable, so that agreement between theory and experiment was mainly qualitative. Other sources of error were those associated with experimental measurement and limitations of the bearing modelling. Further improvement of the bearing model is needed if better quantitative agreement is to be obtained between the predictions and experiment.
19
Jonnalagadda, V. R. Prasad. "A derivation of rotor blade equations of motion in forward flight and their solution". Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/12963.
Testo completo
20
Lee, An Sung. "An experimental investigation of a noncontacting flexibly mounted rotor mechanical face seal". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16019.
Testo completo
21
Wileman, James Michael. "The rotordynamic coefficients of mechanical face seals having two flexibly-mounted rotors". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/17241.
Testo completo
22
Wileman, James Michael. "Dynamic analysis of eccentric mechanical face seals". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17343.
Testo completo
23
Zou, Min. "Real-time monitoring and control of a noncontacting mechanical face seal". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17650.
Testo completo
24
Reveles, Nicolas. "Advanced methods for dynamic aeroelastic analysis of rotors". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51904.
Testo completoAbstract (sommario):
Simulations play an integral role in the understanding and development of rotor- craft aeromechanics. Computational Fluid Dynamics coupled with Computational Structural Dynamics (CFD/CSD) offers an excellent approach to analyzing rotors. These methods have been traditionally “loosely-coupled” where data are exchanged periodically, motion is prescribed for CFD, and the updated loads have a static component for CSD. Loosely-coupled CFD/CSD assumes the solution to be periodic, which may not be true for some simulations. “Tightly-coupled” CFD/CSD, where loads and motion are exchanged at each time step, does not make this periodic assumption and opens up new avenues of simulation to research. A major drawback to tightly-coupled CFD/CSD is an increase in computational cost. Different approaches are explored to reduce this cost as well as examine numerical implications in solutions from tightly and loosely-coupled CFD/CSD. A trim methodology optimized for tightly-coupled simulations is developed and found to bring trim costs within parity of loosely-coupled CFD/CSD simulations. Aerodynamic loading is found to be nearly similar for fixed controls. However, the lead-lag blade motion is determined to contain a harmonic in the tightly-coupled analysis that is not an integer multiple of the rotor speed. A hybrid CFD/CSD methodology employing the use of a free-wake code to model the far-field effects of the rotor wake is developed to aid in computational cost reduction. Investigation of this approach reveals that computational costs may be reduced while preserving solution accuracy. This work’s contributions to the community include the development of a trim algorithm appropriate for use in tightly-coupled CFD/CSD simulations along with a detailed examination of the physics predicted by loose and tight coupling for quasi-steady level flight conditions. The influence of the wake in such cases is directly examined using a modular hybrid coupling to a free-wake code that is capable of reduced cost computations.
25
Mazer, Thiago Tazinazzo. "Cálculo em elementos finitos das frequências naturais dos modos de flexão de uma linha de eixo de unidade geradora hidráulica em escala /". Guaratinguetá, 2016. http://hdl.handle.net/11449/136448.
Testo completoAbstract (sommario):
Orientador: Mauro Hugo MathiasBanca: José Elias Tomazini
Banca: Carlos D'Andrade Souto
Resumo: A evolução das unidades geradoras hidráulicas é constante, sempre visando a redução de custos, mantendo ou melhorando os fatores de desempenho já alcançados. Em consequência disso têm-se em geral máquinas menores, com velocidade de rotação mais elevada e maiores solicitações mecânicas, além de estruturas com massa otimizada e consequentemente mais flexíveis. Nesse contexto, conhecer o comportamento dinâmico dos rotores das turbinas hidráulicas e ter a capacidade de simulá-los com precisão passa a ser fundamental. No presente estudo é desenvolvido um modelo em escala representativo de uma linha de eixo rotativo de turbina hidráulica de grande porte com o objetivo de avaliar o seu comportamento dinâmico, permitindo que os resultados teóricos possam ser comparados com resultados experimentais, este último não faz parte do escopo do presente trabalho. Em uma primeira etapa as dimensões do modelo em escala são determinadas por uma análise dimensional, que permite elaborar os desenhos tanto do rotor quanto de seus suportes. Os parâmetros de rigidez dos suportes são então determinados por meio de análise estrutural estática em elementos finitos (EF). Esses parâmetros são utilizados então na análise dinâmica do rotor, também em EF, permitindo obter o diagrama de Campbell (frequências naturais e seus respectivos modos em função da rotação do eixo) e a resposta harmônica ao desbalanceamento. Diferentes valores de amortecimento e desbalanceamento são assumidos nessa análise, e suas influências no comportamento dinâmico do rotor são avaliadas e discutidas. Também são avaliados os efeitos da estrutura base que suporta os mancais (fundação) na dinâmica da máquina rotativa como um todo. Por fim uma bancada experimental foi construída, sendo que a análise experimental fica como proposta para trabalhos futuros
Abstract: The evolution of hydro power units is constant, always aiming to reduce costs while maintaining or improving performance already achieved. Consequently the sizes of the components have being reduced, while rotational speed and mechanical stresses have being increased. Also, supporting structures have being optimized in weight, becoming more flexible. In this context, it is crucial to know the dynamic behavior of the rotors of hydro power units and to have the ability to simulate them accurately. In this study a representative model of a large hydro power rotor is developed in order to evaluate its dynamic behavior, allowing the comparison between theoretical results with experimental results, the latter is not part of scope of this work. In a first stage the scale model geometry is determined by a dimensional analysis, which allows elaborate the designs of the scaled rotor and its supports. The supports stiffness parameters are then determined by static structural finite element analysis (FEA). These parameters are used in rotor dynamic analysis, also in FEA, enabling the construction of Campbell diagram (natural frequencies and their respective modes shaft rotation function) and the harmonic response to unbalance. Different values of damping and unbalance are assumed in these analyses, and their influence on the rotor dynamic behavior are evaluated and discussed. The effects of the base structure supporting the bearings (also known as foundation) on the dynamics of the rotating machine as a whole are also evaluated. Finally an experimental bench was built, however the experimental analysis is proposed for future work
Mestre
26
Fulton, Mark V. "Stability of elastically tailored rotor blades". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12248.
Testo completo
27
Wang, Yi-Ren. "The effect of wake dynamics on rotor eigenvalues in forward flight". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13031.
Testo completo
28
Xie, Lihan. "Suivi numérique des bifurcations pour l'analyse paramétrique de la dynamique non-linéaire des rotors". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI018/document.
Testo completoAbstract (sommario):
Au cœur des moyens de transport, de transformation d'énergie, et de biens d'équipements, les machines tournantes peuvent avoir des comportements dynamiques complexes dus à de multiples sources de non linéarités liées aux paliers hydrodynamiques, à la présence de fissures, aux touches rotor-stator, ... Des phénomènes comme les décalages fréquentiels et donc de vitesses critiques, les cycles d'hystérésis avec sauts d'amplitudes, le changement brutal du contenu fréquentiel des réponses, sont des expressions de ces comportements. Résoudre les équations du mouvement induites par des modélisations avec des éléments finis de type poutre ou volumique, pour calculer les réponses à des sollicitations diverses (comme le balourd ou le poids propre), est réalisable avec des méthodes d'intégration pas à pas dans le temps mais au prix de temps de calcul prohibitifs. Cela devient particulièrement préjudiciable au stade du pré-dimensionnement où il est nécessaire de réaliser rapidement des études paramétriques. Aussi une alternative intéressante est de mettre en {\oe}uvre une méthode numérique, à la fois générale et efficace pour analyser la réponse non linéaire des rotors en régime stationnaire. La démarche proposée combine, dans un premier temps, la méthode de la balance harmonique (HBM) et la technique de bascule Temps-Fréquence (AFT) afin d'obtenir rapidement dans le domaine fréquentiel les réponses périodiques des rotors à grand nombre de degrés de liberté apportés par les éléments finis volumiques. Puis, l'association à la méthode de continuation par pseudo-longueur d'arc aboutit à établir continûment l'ensemble des solutions d'équilibre dynamique sur la plage de vitesse de rotation. Enfin la stabilité dynamique locale de la solution périodique est analysée grâce à des indicateurs de bifurcation basés sur l'évolution des exposants de Floquet. Ainsi sont détectées les bifurcations de branches de solutions périodiques de type point limite, point de branchement et notamment Neimark-Sacker. Leur localisation est déterminée précisément en résolvant un système augmenté constitué de l'équation du mouvement et d'une équation supplémentaire caractérisant le type de bifurcation considéré. En déclarant un paramètre du système (coefficient de frottement, jeu rotor/stator, amplitude de l'excitation,...) comme nouvelle variable, l'utilisation de la technique de continuation conjointement avec le système augmenté détermine directement le cheminement des bifurcations en fonction de ce paramètre sur la nappe des réponses non linéaires. Les suivis de bifurcations délimitent les zones de fonctionnement spécifiques, extraient efficacement l'essentiel du comportement dynamique et offrent ainsi une nouvelle approche pour dimensionner de façon efficace les systèmes notamment en rotation. Nombre des développements réalisés sont implantés dans le code de calcul Cast3MGenerally speaking, the rotating systems utilized in the energy production have a small rotor-stator gap, are able to run during long periods, and are mounted on hydrodynamic bearings. Rotor-stator interactions in case of blade loss, crack propagation due to fatigue, and a variable stiffness due to the nonlinear restoring forces of the bearings can make the rotordynamics nonlinear and the responses complicated: significant amplitude and frequency shifts are introduced, sub- and super-harmonics appear, and hysteresis occurs. It is of great importance to understand, predict and control this complicated dynamics. Due to the large number of DOFs and the broad range of study frequency, the computation time for solving the equations of motion by a temporal integration method can be quite prohibitive. It becomes particularly disadvantageous at the design stage where a parametrical study need to be quickly performed. An alternative numerical method, which is general and effective at the same time, is proposed in order to analyse the nonlinear response of the rotors at steady state. Firstly, the periodic responses of nonlinear rotors are calculated in the frequency domain by combining harmonic balance method (HBM) and alternating frequency-time (AFT). With the help of continuation method, all dynamic equilibrium solutions of nonlinear systems are determined for the range of study frequency. Then, Floquet exponents which are the eigenvalues of Jacobian are sought for stability analysis of periodic solutions. Then the local stability of the periodic solution is analysed through the bifurcation indicators which are based on the evolution of Floquet exponents. The bifurcations of periodic solution branch, such as limit point, branch point, and Neimark-Sacker bifurcation, are thus detected. By declaring a system parameter (friction coefficient, rotor / stator gap, excitation amplitude, ...) as a new variable, applying once again the continuation method to the augmented system determines directly the bifurcation's evolution as a function of this parameter. Thus, parametric analysis of the nonlinear dynamic behaviour is achieved, the stability boundary or the regime change boundary is directly determined. Numerous developments are implemented in the calculation code Cast3M
29
Reddy, Urmila Chennuru. "Whole field velocity measurements in three-dimensional periodic flows". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/12063.
Testo completo
30
Mittal, Manoj. "Modeling and control of a twin-lift helicopter system". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/12174.
Testo completo
31
Sareen, Ashish Kumar. "Rotorcraft airframe structural optimization for vibration and dynamic stress reduction including damping treatment". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12951.
Testo completo
32
Collins, Kyle Brian. "A multi-fidelity framework for physics based rotor blade simulation and optimization". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26481.
Testo completoAbstract (sommario):
Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Co-Chair: Dr. Dimitri Mavris; Committee Co-Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Daniel P. Schrage; Committee Member: Dr. Kenneth S. Brentner; Committee Member: Dr. Mark Costello. Part of the SMARTech Electronic Thesis and Dissertation Collection.
33
Cook, James Richard. "Development of an aeroelastic methodology for surface morphing rotors". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51807.
Testo completoAbstract (sommario):
A Computational Fluid Dynamics/Computational Fluid Dynamics (CFD/CSD) coupling interface was developed to obtain aeroelastic solutions of a morphing rotor. The methodology was implemented in Fully Unstructured Navier-Stokes (FUN3D) solver, which communicates aerodynamic forces on the blade surface to University of Michigan’s Nonlinear Active Beam Solver (UM/NLABS) and then imports structural deflections of the blade surface during each time step. Development of this methodology adds the capability to model elastic rotors with flexible airfoils. The method was validated through an aerodynamic work analysis, comparison of sectional blade loads and deflections with experimental data, and two-dimensional stability analyses for pitch/plunge flutter and camber flutter. Computational simulations were performed for a rotor in forward flight with the CFD/CSD solver and with a comprehensive CSD solver using finite-state (F-S) aerodynamics, and results were compared. Prescribed three-per-revolution camber deflections were then applied, and solutions of the CFD/CSD and comprehensive CSD computations indicated that three-per-revolution camber actuation has the potential to minimize hub forces and moments with deflections as small as 0.25%c. In anticipation of active rotor experiments inside enclosed facilities, the capability of CFD for accurately simulating flow inside enclosed volumes was examined. It was determined that URANS models are not suitable for rotor simulations in an enclosed facility, and components that are a distance of two to three rotor radii from the hub were also observed to have a large influence on recirculation and performance.
34
Sun, Cheng. "Quantum dynamics and tunnelling of methyl rotors studied by field-cycling NMR". Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10751/.
Testo completoAbstract (sommario):
Quantum dynamics and tunnelling of methyl rotors has been studied using field-cycling nuclear magnetic resonance (NMR) spectrometer, in a variety of samples. The characteristic frequency of the tunnelling motion of methyl groups has been investigated using both low-field dipole-dipole driven experiments and tunnel resonance level-crossing experiments. The classical hopping and quantum tunnelling of methyl groups have been studied by making temperature-dependent and field-dependent measurements of the spin-lattice relaxation time T1. The spectral density functions of the dipolar interaction, mediated by the rotation of methyl groups, have been directly plotted, and the correlation times characteristic of the rotational motion have been determined. Electron spin resonance (ESR) tunnel resonance spectra have been studied in samples with unpaired electrons by making resonant contact between the methyl tunnelling reservoir and the electron spins. The phenomenon of dynamic proton polarisation (DNP) has also been investigated in these samples. Experiments demonstrating the cooling of methyl tunnelling reservoir and the diffusion of energy amongst tunnelling reservoirs are presented. In low-field dipole-dipole driven experiments, in order to avoid the tunnelling transition saturation problem, the sideband stirring radiofrequency (rf) irradiation technique has been utilised and the low-field NMR spectra have been observed with enhanced sideband peaks. The rf irradiation time-dependence of the low-field spectra has been investigated. The experimental data is supported by numerical simulations, using appropriate theoretical models.
35
Camargo, Fabio Assis de [UNESP]. "Análise experimental e computacional de um ventilador centrífugo". Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151783.
Testo completoAbstract (sommario):
Submitted by FABIO ASSIS DE CAMARGO null (fabioacamargo@gmail.com) on 2017-10-01T17:50:03Z
No. of bitstreams: 1
Dissertação Fabio Assis de Camargo 2017.pdf: 2334192 bytes, checksum: 08f11624969ac9f08a9d018d78bea1f7 (MD5)Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-10-02T17:13:14Z (GMT) No. of bitstreams: 1 camargo_fa_me_guara.pdf: 2334192 bytes, checksum: 08f11624969ac9f08a9d018d78bea1f7 (MD5)
Made available in DSpace on 2017-10-02T17:13:14Z (GMT). No. of bitstreams: 1 camargo_fa_me_guara.pdf: 2334192 bytes, checksum: 08f11624969ac9f08a9d018d78bea1f7 (MD5) Previous issue date: 2017-08-18
Este trabalho objetivou um estudo do comportamento dinâmico de rotores em balanço, operando acima da primeira velocidade crítica, suportados em mancais de rolamento. Um caso particular de rotor em balanço, que consiste em um ventilador centrífugo de forno de reaquecimento de uma forjaria, foi selecionado para esse estudo. O rotor analisado encontra-se apoiado em mancais de rolamento, que estão montados em base metálica instalada em fundação de concreto. Alguns aspectos relevantes do comportamento dinâmico desse tipo de rotor foram estudados utilizando-se procedimentos experimentais e procedimentos computacionais. O estudo experimental foi desenvolvido sobre um rotor de ventilador centrífugo utilizado para alimentação de ar de combustão em forno industrial, que possui rotação nominal de 3550 rpm, vazão de 5,11 m3/s, pressão de operação de 1150 mm c.a. sendo acionado por motor de potência de 150 cv, de alto rendimento, com partida direta, montado sobre base rígida. Testes de batida (“ensaio estático de ressonância”) e medições de vibração em velocidade constante foram realizados sobre esse rotor em diferentes condições de operação, permitindo a obtenção dos espectros de frequência da resposta vibratória do sistema rotativo. Um procedimento computacional baseado no método de elementos finitos também foi desenvolvido para a determinação das frequências naturais do rotor suportado em mancais elásticos.
This work was focused on a study of the dynamic behavior of in-balance rotors operating above the first critical speed, supported on rolling bearings. A particular case of in-balance rotor, which consists of a centrifugal fan reheating forging furnace was selected for this study. The analyzed rotor is supported by ball bearings, which are mounted on metal base installed in concrete foundation. Some relevant aspects of the dynamic behavior of this rotor type were studied, using experimental procedures and computational procedures. The experimental study was carried on a rotor centrifugal fan used to supply combustion air in the kiln, which has a rated speed of 3550 rpm , flow 5.11 m3 / s operating pressure of 1150 mm WG being motor-driven power of 150 hp , high performance , direct starting , mounted on a rigid base. Hit Testing ("Bump Test") and constant speed vibration tests were performed on this rotor in different operating conditions, allowing to obtain the frequency spectra for the vibrational response of the rotating system. A computational procedure based on the finite element method was also developed to determine the natural frequencies of the rotor supported in elastic bearings.
36
Mendonça, Willy Roger de Paula [UNESP]. "Otimização dinâmica de rotores com eixos em compósito". Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/115839.
Testo completoAbstract (sommario):
Made available in DSpace on 2015-03-03T11:52:36Z (GMT). No. of bitstreams: 0
Previous issue date: 2014-09-02Bitstream added on 2015-03-03T12:06:23Z : No. of bitstreams: 1
000804878.pdf: 2650434 bytes, checksum: ef9e16c1a0c4300c6e8f770cf0a58ed0 (MD5)Esta tese apresenta o desenvolvimento de uma metodologia de otimização dinâmica e estrutural para rotores com eixos em material compósito. A dinâmica destes rotores difere das análises convencionais devido à existência de amortecimento interno no eixo. As equações de movimento destes rotores apresentam a influencia do amortecimento interno sobre o comportamento dinâmico dos rotores. Materiais compósitos podem ser manufaturados em diferentes sequências de laminação. Para obter as melhores propriedades mecânicas, que possibilitem aos rotores operarem, em condições de estabilidade dinâmica e de esforços estruturais, foi necessário o desenvolvimento de uma metodologia de otimização para obter o melhor projeto. Para a aplicação desta metodologia foi desenvolvido um algoritmo de otimização. Para fundamentar este desenvolvimento foram revisados conceitos da teoria clássica de laminação, dos modelos de amortecimento estrutural, da dinâmica de rotores com amortecimento interno, de elementos finitos e dos métodos de otimização. O método de otimização escolhido foi o genético. Dentro do algoritmo de otimização foram inseridos módulos de análise para calcular as propriedades equivalentes, de avaliação estrutural por critérios de falha e de análise dinâmica de rotores. Diferentes simulações demonstraram a importância da sequência de laminação sobre a dinâmica dos rotores. Dentre os resultados finais estão simulações de otimizações e uma análise dos principais parâmetros que influenciam a obtenção de soluções ótimas pela otimização
This thesis presents a development on dynamic and structural optimization method (multiobjective) for rotors mount on composite shafts. The dynamic analysis of these rotors differs from conventional analysis due to the existence of internal damping in the shaft. The equations of motion for these rotors represent the influence of internal damping on the dynamic behavior of the rotor system. Composite materials can be manufactured using different layups. To obtain the best mechanical properties, which allow rotors to operate in stability dynamic and allowable efforts structural conditions, it was necessary to develop a methodology for design optimizing. For the application of this methodology an optimization algorithm was developed. To support this development were reviewed: the classical lamination theory, models of structural damping, rotor dynamics with internal damping, finite elements and optimization methods. The optimization method chosen was algorithm genetic. Within the optimization algorithm were inserted analysis modules responsible for: calculate the equivalent properties, evaluate structurally by failure criteria and analyze the dynamics of the rotors. Several simulations have demonstrated the importance of the layup for rotor dynamics. Among the final results from optimization simulations, there are discussions about the influence of the each optimization parameters that influence the achievement of optimal solutions
37
Mendonça, Willy Roger de Paula. "Otimização dinâmica de rotores com eixos em compósito /". Guaratinguetá, 2014. http://hdl.handle.net/11449/115839.
Testo completoAbstract (sommario):
Orientador: Mauro Hugo MathiasBanca: José Elias Tomazini
Banca: Marcelo Sampaio Martins
Banca: José Rui Camargo
Banca: Everaldo de Barros
Resumo : Esta tese apresenta o desenvolvimento de uma metodologia de otimização dinâmica e estrutural para rotores com eixos em material compósito. A dinâmica destes rotores difere das análises convencionais devido à existência de amortecimento interno no eixo. As equações de movimento destes rotores apresentam a influencia do amortecimento interno sobre o comportamento dinâmico dos rotores. Materiais compósitos podem ser manufaturados em diferentes sequências de laminação. Para obter as melhores propriedades mecânicas, que possibilitem aos rotores operarem, em condições de estabilidade dinâmica e de esforços estruturais, foi necessário o desenvolvimento de uma metodologia de otimização para obter o melhor projeto. Para a aplicação desta metodologia foi desenvolvido um algoritmo de otimização. Para fundamentar este desenvolvimento foram revisados conceitos da teoria clássica de laminação, dos modelos de amortecimento estrutural, da dinâmica de rotores com amortecimento interno, de elementos finitos e dos métodos de otimização. O método de otimização escolhido foi o genético. Dentro do algoritmo de otimização foram inseridos módulos de análise para calcular as propriedades equivalentes, de avaliação estrutural por critérios de falha e de análise dinâmica de rotores. Diferentes simulações demonstraram a importância da sequência de laminação sobre a dinâmica dos rotores. Dentre os resultados finais estão simulações de otimizações e uma análise dos principais parâmetros que influenciam a obtenção de soluções ótimas pela otimização
Abstract: This thesis presents a development on dynamic and structural optimization method (multiobjective) for rotors mount on composite shafts. The dynamic analysis of these rotors differs from conventional analysis due to the existence of internal damping in the shaft. The equations of motion for these rotors represent the influence of internal damping on the dynamic behavior of the rotor system. Composite materials can be manufactured using different layups. To obtain the best mechanical properties, which allow rotors to operate in stability dynamic and allowable efforts structural conditions, it was necessary to develop a methodology for design optimizing. For the application of this methodology an optimization algorithm was developed. To support this development were reviewed: the classical lamination theory, models of structural damping, rotor dynamics with internal damping, finite elements and optimization methods. The optimization method chosen was algorithm genetic. Within the optimization algorithm were inserted analysis modules responsible for: calculate the equivalent properties, evaluate structurally by failure criteria and analyze the dynamics of the rotors. Several simulations have demonstrated the importance of the layup for rotor dynamics. Among the final results from optimization simulations, there are discussions about the influence of the each optimization parameters that influence the achievement of optimal solutions
Doutor
38
Tu, Chihyung. "Computer-aided design software for rotor dynamics analysis". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07102009-040616/.
Testo completo
39
Abras, Jennifer N. "Enhancement of aeroelastic rotor airload prediction methods". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28182.
Testo completoAbstract (sommario):
Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Smith, Marilyn; Committee Member: Bauchau, Olivier; Committee Member: Costello, Mark; Committee Member: Moulton, Marvin; Committee Member: Ruffin, Stephen.
40
Li, Yiguang. "Three-Dimensional Flow and Performance Simulation of Multistage Axial Flow Compressors". Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/4591.
Testo completoAbstract (sommario):
\Yith the current develop111ent in computer technology and Computational
Fluid D)"n<'tlllics techniques, t.he si11utlation within axial flow compressors becomes
1110re and 1110re pract.ical and beneficial to the compressor designs. Due to the
insufficient capabilit)" of today's COll1put.ers for three-dimensional unsteady flow
1110delling of 111Ult i~Llg(' axial flow compressors, sophisticated models of steady
state flow and perfor111ance 1110delling of the C0111prcssors deserve to be thoroughly
investigated.
In l1utltistage C0111pressor sinlulations with steady state methods, frame of reference
is fixed on blades and the c0111putational domains for rotors and stators
haye relati\"e rotation. One of the difficulties in such simulations is how to pass
information across the interfaces between blade rows without losing continuity.
Two 111ajor stead)" state modelling approaches, a mixing plane approach based
on Denton's circu111ferentially non-uniform mixing plane model and a deterministic
stress approach based on Adamczyk's average passage model, are investigated
and compared with each other through the flow predictions of the third stage of
Cranfield Low Speed Research Compressor at peak efficiency operating condition.
In the deterministic stress approach, overlapped solution domains are introduced
to calculate deterministic stresses in order to "close" the time-averaged
governing equation system and the influence of the downstream blade row of the
blade row under investigation has to be imposed through the simulation of bodyforce
and blade blockage effect of the downstream blade row. An effective method
of simulating bodyforce and blade blockage effect has been developed and proven
to be simple in programming.
ConYentionally, boundary conditions are specified in CFD calculations based
on experimental data or other empirical calculations. By taking advantage of the
special flow features in rear stages of multistage axial flow compressors where each
rear stage behaves like a repeating stage of its neighbouring stages in terms of
flow pattern at the inlet and the exit of these stages, a repeating stage model has
been developed aiming at significantly simplifying the boundary conditions when
simulating rear stages of a multistage axial flow compressor with only mass flow
rate and stage exit average static pressure required as global input.
A computer simulation system 1'/ STurbo3D has been developed to investigate
a11d assess different steady state simulation models within multistage compressor
environment. It has been proven that with the mixing plane model M STurbo3D is
able to predict flows in multistage low speed axial flow compressors with acceptable
accuracy. Application of the repeating stage model to the third stage of LS RC
shows that the prediction with this model has equivalent accuracy to the prediction
with the conventional boundary setting, and proves that the repeating stage
model is an effective alternative to the expensive complete compressor simulation.
The deterministic stress model provides more information of rotor-stator interaction
and slightly better performance prediction than the mixing plane model, but
the benefits of the model is not significant when applied to low speed axial flow
compressors.
41
Bangalore, Ashok K. "Computational fluid dynamic studies of high lift rotor systems using distributed computing". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12949.
Testo completo
42
Casey, Cody. "Crack detection in a rotor dynamic system by vibration monitoring". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17838.
Testo completo
43
Pinter-Krainer, Marc. "Molecular dynamics of methyl rotors and hydrogen bonds studied by high pressure NMR". Thesis, University of Surrey, 1996. http://epubs.surrey.ac.uk/959/.
Testo completo
44
Dakel, Zaki. "Stabilité et dynamique non linéaire de rotors embarqués". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0087/document.
Testo completoAbstract (sommario):
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 supportRotors 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
45
Galera, Larissa 1990. "Análise da influência das características geométricas de selos de fluxo aplicados a rotores". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263035.
Testo completoAbstract (sommario):
Orientador: Katia Lucchesi Cavalca DediniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-24T00:13:00Z (GMT). No. of bitstreams: 1 Galera_Larissa_M.pdf: 7841610 bytes, checksum: b4caff2b3c8de6cf54d4ef086fd47585 (MD5) Previous issue date: 2013
Resumo: A análise dinâmica de rotores visa prever o comportamento e identificar desvios caracterizados por meio das respostas dinâmicas do conjunto, fornecendo indicadores de mau funcionamento ou diagnóstico de falhas, e minimizando os riscos de paradas imprevistas no sistema. O estudo dinâmico de máquinas rotativas deve ser realizado considerando a interação entre os componentes envolvidos na sua construção, como por exemplo, rotores, eixos, mancais, selos de fluxo e estruturas de suporte. Os selos de fluxo causam forças de reação que podem ser representadas por coeficientes dinâmicos. Este componente é o principal responsável por diferenças entre um modelo usando apenas eixo-mancal e a vibração real do sistema, como por exemplo, em bombas centrífugas. Dentro deste contexto, este trabalho tem por objetivo a determinação dos coeficientes dinâmicos de três tipos de selos planos, sendo eles: cilíndrico, cônico e escalonado, os quais serão integrados ao modelo global de sistemas rotativos, de modo a tornar a análise do conjunto girante mais completa. A análise dos selos de fluxo será realizada utilizando o método de volumes finitos para determinar a distribuição de velocidade circunferencial e de pressão ao longo do selo, que caracterizam as forças de reação. Estas, por sua vez, podem ser representadas em coeficientes de rigidez, amortecimento e inércia. Além disso, será verificada a influência de diversos parâmetros geométricos e operacionais nestes coeficientes. A inserção dos coeficientes dinâmicos dos selos planos e a análise do conjunto girante, a partir do pacote computacional Rotortest®, permitirá verificar a influência desses tipos de selos no sistema rotativo, analisando como este elemento modifica as características do conjunto e como acopla o eixo à fundação
Abstract: The dynamic analysis of rotors aims to predict its behavior and identify deviations characterized by the dynamic response of the set, providing malfunction indications or failure diagnosis, and minimizing the risk of having unexpected halts on the system. The dynamic study of rotating machines must be conducted by taking in account the interactions between the components involved in its construction, such as rotors, shafts, bearings, fluid seals, and support structures. The fluid seals cause reaction-forces, which can be represented for dynamic coefficients. This component is mainly responsible for the differences between a model using only a rotor-bearing and the actual vibration of the set, for example in centrifugal pumps. In this context, this work aims the determination of the dynamic coefficients of three types of plain seals, namely: straight, tapered, and stepped seals, which will be integrated with the global model of rotating systems, in order to make the analysis of the rotating set more complete. The fluid seals analysis will be accomplished through the finite volume method in order to determine the circumferential velocity and pressure distribution along the seal, which characterizes the reaction forces. Those can be, in turn, represented by stiffness, damping, and inertia coefficients. Besides, it will be verified the influence of several geometric and operational parameters on these coefficients. The insertion of the dynamic coefficients of plain seals and the analysis of the rotating set in the computational package Rotortest®, will verify the influence of these seals on the rotating system, analyzing how this element modify the set's characteristics and the coupling of the shaft to the foundation
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestra em Engenharia Mecânica
46
Varney, Philip A. "Transverse fatigue crack diagnosis in a rotordynamic system using vibration monitoring". Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47655.
Testo completoAbstract (sommario):
To increase efficiency, shafts are made lighter and more flexible, and are designed to rotate faster to increase the system's power-to-weight ratio. The demand for higher efficiency in rotordynamic systems has led to increased susceptibility to transverse fatigue cracking of the shaft. Shaft cracks are often detected and repaired during scheduled periods of off-line maintenance. Off-line maintenance can be expensive and time consuming; on-line condition monitoring allows maintenance to be performed as-needed. However, inadequate (or a lack of) monitoring can allow rapidly propagating cracks to result in catastrophic shaft failure. It is therefore imperative to develop on-line condition monitoring techniques to detect a crack and diagnose its severity. A particularly useful method for transverse shaft crack detection/diagnosis is vibration monitoring.
Detection, and especially diagnosis, of transverse fatigue cracks in rotordynamic systems has proven difficult. Whereas detection assesses only the presence of a crack, diagnosis estimates important crack parameters, such as crack depth and location. Diagnosis can provide the operator with quantitative information to assess further machinery operation. Furthermore, diagnosis provides initial conditions and predictive parameters on which to base prognostic calculations.
There is a two-fold challenge for on-line diagnosis of transverse fatigue crack parameters. First, crack characterization involves specifying two important parameters: the crack's depth and location. Second, the nature of rotating machinery permits response measurement at only specific locations.
Cracks are typically categorized as breathing or gaping; breathing cracks open and close with shaft rotation, while gaping cracks remain open. This work concerns the diagnosis of gaping crack parameters; the goal is to provide metrics to diagnose a crack's depth and location. To this end, a comprehensive approach is presented for modeling an overhung cracked shaft. Two linear gaping crack models are developed: a notch and a gaping fatigue crack. The notch model best approximates experimentally manufactured cracks, whereas the gaping fatigue crack model is likely more suited for real fatigue cracks.
Crack diagnosis routines are established using free and forced response characteristics. Equations of motion are derived for both crack models, including excitation due to gravity and imbalance. Transfer matrix techniques are established to expediently obtain the steady-state system response. A novel transfer matrix technique, the Complex Transfer Matrix, is developed to distinguish forward and backward whirl components. The rotor's angular response is primarily employed in this work for crack detection and diagnosis. The overhung shaft induces an increased sensitivity to variations in crack depth and location. In addition, an available overhung rotordynamic experimental test rig allows for comparison of the current analytic results to previously obtained experimental results.
Under the influence of gravity, the steady-state response of the cracked system includes a prominent 2X harmonic component, appearing at a frequency equal to twice the shaft speed. The magnitude of the 2X harmonic is strongly influenced by the shaft speed. A resonant response occurs when the shaft speed reaches half of a system natural frequency. This work demonstrates that the profile of the 2X harmonic versus shaft speed is a capable diagnostic tool. Identification of the 2X resonance frequency restricts the crack parameters to certain pairs of location and depth. Following this limiting process, the magnitude of the 2X harmonic is used to identify the crack's depth and location. Orbital shapes at the rotor are discussed, as are orbital modes of the shaft deflection. Quantitative results and qualitative observations are provided concerning the difficulty of crack detection and diagnosis.
47
Camargo, Fabio Assis de. "Análise experimental e computacional de um ventilador centrífugo /". Guaratinguetá, 2017. http://hdl.handle.net/11449/151783.
Testo completoAbstract (sommario):
Orientador: Mauro Hugo MathiasCoorientador: Marcelo Sampaio Martins
Banca: José Elias Tomazini
Banca: Everaldo de Barros
Resumo: Este trabalho objetivou um estudo do comportamento dinâmico de rotores em balanço, operando acima da primeira velocidade crítica, suportados em mancais de rolamento. Um caso particular de rotor em balanço, que consiste em um ventilador centrífugo de forno de reaquecimento de uma forjaria, foi selecionado para esse estudo. O rotor analisado encontra-se apoiado em mancais de rolamento, que estão montados em base metálica instalada em fundação de concreto. Alguns aspectos relevantes do comportamento dinâmico desse tipo de rotor foram estudados utilizando-se procedimentos experimentais e procedimentos computacionais. O estudo experimental foi desenvolvido sobre um rotor de ventilador centrífugo utilizado para alimentação de ar de combustão em forno industrial, que possui rotação nominal de 3550 rpm, vazão de 5,11 m3/s, pressão de operação de 1150 mm c.a. sendo acionado por motor de potência de 150 cv, de alto rendimento, com partida direta, montado sobre base rígida. Testes de batida ("ensaio estático de ressonância") e medições de vibração em velocidade constante foram realizados sobre esse rotor em diferentes condições de operação, permitindo a obtenção dos espectros de frequência da resposta vibratória do sistema rotativo. Um procedimento computacional baseado no método de elementos finitos também foi desenvolvido para a determinação das frequências naturais do rotor suportado em mancais elásticos
Abstract: This work was focused on a study of the dynamic behavior of in-balance rotors operating above the first critical speed, supported on rolling bearings. A particular case of in-balance rotor, which consists of a centrifugal fan reheating forging furnace was selected for this study. The analyzed rotor is supported by ball bearings, which are mounted on metal base installed in concrete foundation. Some relevant aspects of the dynamic behavior of this rotor type were studied, using experimental procedures and computational procedures. The experimental study was carried on a rotor centrifugal fan used to supply combustion air in the kiln, which has a rated speed of 3550 rpm, flow 5.11 m3 / s operating pressure of 1150 mm WG being motor-driven power of 150 hp, high performance, direct starting, mounted on a rigid base. Hit Testing ("Bump Test") and constant speed vibration tests were performed on this rotor in different operating conditions, allowing to obtain the frequency spectra for the vibrational response of the rotating system. A computational procedure based on the finite element method was also developed to determine the natural frequencies of the rotor supported in elastic bearings
Mestre
48
Marpu, Ritu Priyanka. "Physics based prediction of aeromechanical loads for the UH-60A rotor". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47661.
Testo completoAbstract (sommario):
Helicopters in forward flight experience complex aerodynamic phenomena to various degrees. In low speed level flight, the vortex wake remains close to the rotor disk and interacts with the rotor blades to give rise to blade vortex interaction phenomena. In high speed flight, compressibility effects dominate leading to the formation of shocks. If the required thrust is high, the combination of high collective pitch and cyclic pitch variations give rise to three-dimensional dynamic stall phenomena.
Maneuvers further exacerbate the unsteady airloads and affect rotor and hub design. The strength and durability of the rotor blades and hub components is dependent on accurate estimates of peak-to-peak structural loads. Accurate knowledge of control loads is important for sizing the expensive swash-plate components and assuring long fatigue life.
Over the last two decades, computational tools have been developed for modeling rotorcraft aeromechanics. In spite of this progress, loads prediction in unsteady maneuvers which is critical for peak design loads continues to be a challenging task.
The primary goal of this research effort is to investigate important physical phenomena that cause severe loads on the rotor in steady flight and in extreme maneuvers. The present work utilizes a hybrid Navier-Stokes/free-wake CFD methodology coupled to a finite element based multi-body dynamics analysis to systematically study steady level and maneuvering flight conditions.
Computational results are presented for the UH-60A rotor for a parametric sweep of speed and thrust conditions and correlated with test data at the NFAC Wind Tunnel. Good agreement with test data has been achieved using the current methodology for trim settings and integrated hub loads, torque, and power.
Two severe diving turn maneuvers for the UH-60A recorded in the NASA/Army Airloads Flight Tests Database have also been investigated. These maneuvers are characterized by high load factors and high speed flight. The helicopter experiences significant vibration during these maneuvers. Mean and peak-to-peak structural loads and extensive stall phenomena including an advancing side stall phenomena have been captured by the present analyses.
49
Krothapalli, Krishnamohan Rao. "Helicopter rotor dynamic inflow modeling for maneuvering flight". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12066.
Testo completo
50
Berkman, Mert Enis. "An integrated Navier Stokes-full portential-free wake method for rotor flows". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12388.
Testo completo