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Hunter, William. "Actuator disk methods for tidal turbine arrays." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:bf8e95df-9e67-4c89-8d9d-1a608a8be0f4.
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Tidal stream energy presents challenges that will require the development of new engineering tools if designs are to harness this energy source effectively. At first glance one might imagine that tidal stream energy can be treated as wind with appropriate adjustment for fluid properties of water over air, and account taken of the harsher offshore environment; both waves and turbulence. However, it is now well accepted that the flow past turbines that are constrained by the local sea bed, sea surface, and possibly also neighbouring turbines and channel sides, will differ markedly from that of an ostensibly unblocked wind turbine. Garrett & Cummins (2007) were the first to demonstrate that operating a turbine in a non- negligibly blocked flow passage presents a different flow solution and importantly a significant opportunity to enhance the power that can be delivered by blocked turbines with the limit of power extraction exceeding the Lanchester-Betz limit for operation of unblocked wind turbines. Although it is impractical to array real turbines across the entire width of a channel it has been proposed to use short arrays of turbines making use of local constructive interference (blockage) effects; Nishino & Willden (2012) showed that although the phenomenal power limits of Garrett & Cummins are unobtainable in a real flow, a significant uplift in the limit of power extraction can be achieved for short fences of turbines arrayed normally to the flow in wide cross-section channels. However, it does not follow that rotors designed using unblocked wind turbine tools are capable of extracting any more power than they are designed for and hence the power uplift made available through blockage effects may be squandered. This thesis sets out to develop design tools to assist in the design of rotors in blocked environments that are designed to make use of the flow confinement effects and yield rotors capable of extracting some of the additional power on offer in blocked flow conditions. It is the pressure recovery condition used in wind turbine design that requires relaxation in blocked flow conditions and hence it is necessary to resort to a computational framework in which the free stream pressure drop can be properly accounted for. The tool of choice is a computational fluid dynamics embedded blade element method. As with all models with semi-empirical content it is necessary to select and test correction models that account for various simplifications inherent to the use of the blade element method over a fully blade resolved simulation. The thesis presents a rigorous comparison of the computational model with experimental data with the various correction methods employed. The tool is then used to design rotors, first for unblocked operation, with favourable comparison drawn to lifting line derived optimal Betz rotor solutions. The final objective of the study is to design rotors for operation in short fence configurations of four turbines arrayed normally to the flow. This is accomplished and it is shown that by using bespoke in situ rotor design it is possible to extract more power than possible with non-blockage designs. For the defined array layout and operating conditions, the bespoke rotor array design yields a power coefficient 26% greater than the implied Betz limit for an unblocked rotor and 4% greater than operating a rotor designed in isolation in the same array.
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Maidana, Cristiano Frandalozo. "Desenvolvimento de turbinas de múltiplos discos : estudo de modelos analíticos e análise experimental." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/127907.
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Neste trabalho é realizada a concepção, projeto, construção e ensaio de turbinas de múltiplos discos para a verificação dos principais parâmetros e metodologias utilizadas para o projeto e análise do equipamento, além de estudar formas de otimização do equipamento. Assim, uma turbina de múltiplos discos é construída e testada com diferentes configurações de rotores, em uma bancada experimental construída e dimensionada especialmente para esse fim, além da implementação dos métodos analíticos pesquisados no software Engineering Equation Solver (EES). Assim, uma comparação entre os resultados experimentais obtidos por Rice e os modelos de analíticos disponíveis, mostra que o modelo do fator de atrito (FA) é o que melhor representa a operação do equipamento, além de ser o mais versátil dos métodos testados, permitindo que a turbina seja dimensionada e otimizada para várias configurações de construção. Já os resultados experimentais obtidos com um dos protótipos de turbina construído e operado com ar comprimido, mostram que, com modificações simples da geometria, configuração e acabamento superficial dos discos que compõem o rotor, é possível aumentar a eficiência isentrópica em até 35% em relação a turbina padrão montada com a configuração padrão de rotor (discos lisos), sem acarretar prejuízo em alguns dos principais benefícios da utilização deste tipo de equipamento. Os resultados experimentais obtidos mostram também que a eficiência diminui significativamente com o aumento da folga entre o raio externo do rotor e a parte interna da carcaça.This work is performed conception, design, construction and testing of multiple-disks turbines (MDTs) for the verification of key parameters and methodologies used for the design and analysis of machine as well as consider ways to equipment optimization. Thus, a multiple-disk turbine is constructed and tested with different impeller configurations, in a test rig especially constructed and dimensioned for this purpose, besides the implementation of the analytical methods in software Engineering Equation Solver (ESS). Thus, a comparison between the experimental results obtained by Rice and analytical models available, shows that the friction factor model (FF) is what best represents the operation of the equipment, and is the most versatile of the tested methods, allowing the turbine is sized and optimized for various building configurations. Since the experimental results obtained with one of the turbine prototypes built and operated with compressed air, show that with simple modifications of geometry, configuration and surface finish of the disks that make up the rotor, it is possible to increase the isentropic efficiency by up to 35% compared the standard turbine rotor mounted with the default configuration (flat disks), without causing damage in some of the major benefits of using this type of equipment. The experimental results also show that efficiency decreases significantly with increasing clearance between the outer radius of the rotor and the internal part of the housing.
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Romanoski, Glenn Roy. "The fatigue behavior of small cracks in aircraft turbine disk alloys." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/32577.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.Includes bibliographical references (leaves 245-258).
by Glenn R. Romanoski, Jr.
Ph.D.
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Khoramzad, Elham. "Fretting fatigue life analysis for a gas turbine compressor blade-disk material combination." Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284357.
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In order to analyse fretting fatigue life of dove-tail joints used in the compressor stage of a gas turbine, experimental study of different material combinations was conducted using rectangular fatigue specimen and bridge type pads. Specimen and pad interaction was simulated numerically and obtained results was used as input for 2 different crack propagation life prediction methods. The combined effect of stress and fretting damage which was characterised by means of Ruiz parameter was used in order to estimate the crack initiation and finally numerical results were compared to experimental fretting fatigue life. The aim of this thesis was to study the contact fatigue behaviour of titanium alloy (Ti-6Al-4V) in combination with steel alloy (22NiCrMoV12-7).
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Oo, Htet Htet Nwe. "Actuator Disk Theory for Compressible Flow." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1727.
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Because compressibility effects arise in real applications of propellers and turbines, the Actuator Disk Theory or Froude’s Momentum Theory was established for compressible, subsonic flow using the three laws of conservation and isentropic thermodynamics. The compressible Actuator Disk Theory was established for the unducted (bare) and ducted cases in which the disk was treated as the only assembly within the flow stream in the bare case and enclosed by a duct having a constant cross-sectional area equal to the disk area in the ducted case. The primary motivation of the current thesis was to predict the ideal performance of a small ram-air turbine (microRAT), operating at high subsonic Mach numbers, that would power an autonomous Boundary Layer Data System during test flights. The compressible-flow governing equations were applied to a propeller and a turbine for both the bare and ducted cases. The solutions to the resulting system of coupled, non-linear, algebraic equations were obtained using an iterative approach. The results showed that the power extraction efficiency and the total drag coefficient of the bare turbine are slightly higher for compressible flow than for incompressible flow. As the free-stream Mach increases, the Betz limit of the compressible bare turbine slightly increases from the incompressible value of 0.593 and occurs at a velocity ratio between the far downstream and the free-stream that is lower than the incompressible value of 0.333. From incompressible to a free-stream Mach number of 0.8, the Betz limit increases by 0.021 while its corresponding velocity ratio decreases by 0.036. The Betz limit and its corresponding velocity ratio for the ducted turbine are not affected by the free-stream Mach and are the same for both incompressible and compressible flow. The total drag coefficient of the ducted turbine is also the same regardless of the free-stream Mach number and the compressibility of the flow; but, the individual contributions of the turbine drag and the lip thrust to the total drag differs between compressible and incompressible flow and between varying free-stream Mach numbers. It was concluded that overall compressibility has little influence on the ideal performance of an actuator disk.
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Cigeroglu, Ender. "Development of microslip friction models and forced response prediction methods for frictionally constrained turbine blades." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1181856489.
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Akagi, Raymond. "Ram Air-Turbine of Minimum Drag." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2261.
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The primary motivation for this work was to predict the conditions that would yield minimum drag for a small Ram-Air Turbine used to provide a specified power requirement for a small flight test instrument called the Boundary Layer Data System. Actuator Disk Theory was used to provide an analytical model for this work.
Classic Actuator Disk Theory (CADT) or Froude’s Momentum Theory was initially established for quasi-one-dimensional flows and inviscid fluids to predict the power output, drag, and efficiency of energy-extracting devices as a function of wake and freestream velocities using the laws of Conservations of Mass, Momentum, and Energy. Because swirl and losses due to the effects of viscosity have real and significant impacts on existing turbines, there is a strong motivation to develop models which can provide generalized results about the performance of an energy-extractor, such as a turbine, with the inclusion of these effects. A model with swirl and a model with losses due to the effects of viscosity were incorporated into CADT which yielded equations that predicted the performance of an energy-extractor for both un-ducted and ducted cases. In both of these models, for this application, additional performance parameters were analyzed including the drag, drag coefficient, power output, power coefficient, force coefficient, and relative efficiency.
For the un-ducted CADT, it is well known that the wake-to-freestream velocity ratio of 1/3 will give the maximum power extraction efficiency of 59.3%; this result is called the Betz limit. However, the present analysis shows that reduced drag for a desired power extraction will occur for wake-to-freestream velocity ratios higher than the value of 1/3 which results in maximum power extraction efficiency. This in turn means that a turbine with a larger area than the smallest possible turbine for a specified power extraction will actually experience a lower drag.
The model with the inclusion of swirl made use of the Moment of Momentum Theorem applied to a single-rotor actuator disk with no stators, in addition to the laws of Conservation of Mass, Momentum, and Energy from the CADT. The results from the model w/swirl showed that drag remains unchanged while power extracted decreases with the addition of swirl, with swirl effects becoming more severe for tip speed ratios below about 5. As for CADT, reduced drag for a specified power extraction can be achieved when the wake-to-freestream velocity ratio is higher that than which provides maximum power extraction efficiency. The model w/losses due to viscosity incorporated the losses into the Conservation of Energy relationship. The results from the model w/losses showed that there is a distinct wake-to-freestream velocity ratio at which minimum drag for a specified power output is achieved, and that this velocity ratio is usually—but not always—higher than that for which the power extraction efficiency is a maximum.
It was concluded that a lower drag for a specified power output of an energy-extractor can usually be achieved at a wake-to-freestream velocity ratio higher than that which produces the v maximum power extraction efficiency. The latter condition, known as the Betz limit for CADT, and which defines the minimum size for a turbine to provide a specified power extraction, is therefore not the correct target design condition to achieve lowest drag for a small Ram-Air Turbine to power BLDS.
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Foran, Derek. "Experimental and Numerical Modeling of a Tidal Energy Channeling Structure." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32387.
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Tidal power, or the use of tides for electricity production, exists in many forms including tidal barrages, which exploit tidal head differentials, and turbines placed directly in regions with large tidal current velocities. The latter is actively being investigated in many countries around the world as a means of providing renewable and wholly predictable electricity (cf. wind, solar and wave power). The expansion of the in-stream tidal industry is hindered however by several factors including: turbine durability, deployment and maintenance costs, and the lack of abundant locations which meet the necessary current velocities for turbine start-up and economic power production. A new novel type of augmentation device, entitled the ‘Tidal Acceleration Structure’ or TAS (Canadian patent pending 2644792), has been proposed as a solution to the limited number of coastal regions which exhibit fast tidal currents. In preliminary investigations, the TAS, a simple Venturi section consisting of walls extending from the seafloor to above the high water mark in an hourglass shape, was found as able to more than double current velocities entering the device. The results indicated a significant advantage over other current channeling technologies and thus the need for more in-depth investigations.
The main objective of the present study was to optimise the design of the TAS and to predict the power that a turbine placed within it could extract from flow. To do this, two principal methods were employed. Firstly, a 1:50 scale model of the TAS was tested and its shape optimised in a 1.5 m wide flume. Secondly, a 3D numerical model (ANSYS Fluent) was used for comparison with the experimental results. During the tests, a TAS configuration was found that could accelerate upstream velocities by a factor of 2.12. In separate tests, turbines were simulated using Actuator Disc Theory and porous plates. The TAS-plate combination was found to be able to extract up to 4.2 times more power from flow than the stand-alone plate, demonstrating that the TAS could provide turbines with a significant advantage in slower currents.
Though further research is needed, including the testing of a larger TAS model in conjunction with a small in-stream turbine, the results of this thesis clearly demonstrate the potential of the TAS concept to unlock vast new areas for tidal energy development.
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Lošák, Petr. "Optimalizace modálního tlumení lopatek vysokotlakých stupňů parních turbín." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233951.
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Steam turbine rotor is a very complicated assembly, typically consists of several rotor rows. Due to design limitations and increasing demands on the efficiency of the steam turbines, it is practically impossible to avoid all of the resonant states. The significant vibrations can occur, for example, due to passing resonance state during turbine start up or run out. In the worst case the turbine operates state is close to the resonance state of the rotor row. This leads to the significant oscillation of the bladed disk, and may results in the blade (or blade to disk joints) high cycle fatigue. These parts are highly loaded components and any cracks are unacceptable. Therefore it is absolutely necessary to damp vibration by using, for example, passive damping elements. The damping element analyzed in this thesis is a strap with an isosceles trapezoidal cross section, which is placed in the circumferential dovetail groove in the blade segmental shrouding. The sliding between the contact surfaces leads to the dissipation of energy which causes decreasing of undesirable vibrations. The main aim is to design the optimal dimensions of the strap cross-section with a view to the most effective damping of vibration for a particular turbine operating state. Considered bladed disk has 54 blades which are coupled in 18 packets by segmental shrouding. The damping element is paced in circumferential dovetail groove created in the shrouding. This type of damping element is suitable especially for damping vibrations in the axial direction and only with the mode shape with the nodal diameters. The modal properties of the bladed disk are influenced by the sliding distance. Since the friction force depends on centrifugal force acting on the damping element and on the angle of the side walls of the strap and groove, the sliding distance can be influenced by the damping element dimensions. During the optimization process the best possible size of middle width, height and angle of damping element cross-section is searched. The strap weight, contact area size and flexural stiffness of damping element can be influenced by these parameters. Their change has also impact on the size of the contact pressure and thus on the size of relative motion as well. As stated previously, the damping efficiency is influenced by the relative motion between the damping element and shrouding. Numerical simulation in time domain is very time-consuming, especially for systems containing nonlinearities. In order to verify dynamic behavior of the computational model with the passive friction element in numerical simulations, the simplified model is created. The model is created in the ANSYS environment. The main requirement imposed on this model is to have as small number of degrees of freedom as possible, so the time needed to perform the simulation is reduced to a minimum. To satisfy this requirement the simplified model is a cantilever beam with rectangular cross section. The dovetail groove is created in this model in longitudinal direction. In this groove is damping element. In addition to damping element dimensions optimization, the influence of each design variable on model dynamic behavior is studied. The results are verified experimentally. Experiment also shows other interesting results that confirm the damping element influence on the modal characteristics. The gained knowledge is used to optimize the dimensions of the damping element in the model of the bladed disk.
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Pishva, S. M. R. (S Mohammed Reza) Carleton University Dissertation Engineering Mechanical. "Rejuvenation of gas turbine discs." Ottawa, 1988.
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Філімоніхін, Г. Б., А. Ю. Невдаха, G. Filimonikhin, and A. Nevdakha. "Технологія складання роторів барабанно-дискової конструкції методом двох пробних складань із заміром биттів на призмах." Thesis, Львівська політехніка, 2011. http://dspace.kntu.kr.ua/jspui/handle/123456789/6158.
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Розроблена технологія складання міжопорних роторів барабанно-дискової конструкції газотурбінних двигунів методом двох пробних складань із заміром биттів на призмах. Розроблені відповідні типові техпроцеси, математична модель ротора, алгоритми розрахунків, що забезпечують техпроцеси. Ефективність розроблених техпроцесів перевірена комп’ютерним моделюванням та натурними випробуваннями на спеціально створеному стенді. The technology of gas turbine motors inbearing drum-disk construction by two test assembly method with test of the prism pulsation was created. Corresponding typical processes, mathematic model of the rotor, added algorithms, which ensure technical processes, were created. The efficiency of created technical processes was checked by computer modulation and natural testing on the special provided stand.
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Невдаха, А. Ю., Г. Б. Філімоніхін, A. Nevdakha, and G. Filimonikhin. "Використання 3D моделі ротора барабанно-дискового типа для апробації технології складання роторів ГТД методом двох пробних складань." Thesis, ЧДТУ, 2012. http://dspace.kntu.kr.ua/jspui/handle/123456789/6159.
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Описуються 3D модель ротора барабанно-дискового типу, яка створена для апробації типових процесів складання роторів та комп’ютерної програми для числових розрахунків, що забезпечують процес складання роторів ГТД БДТ методом двох пробних складань, написаної в середовищі швидкої розробки прикладних програм Borland Delphi. Describe Rotor 3D model of drum-disk type that is created to test the typical process of assembling rotors and computer programs for numerical calculations that ensure the process of folding rotors by two assemblages test written in an environment of rapid application development Borland Delphi.
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Невдаха, А. Ю., and A. Nevdakha. "Вплив на похибку визначення оптимальних кутів повороту деталей ротора ГТД неточностей заміру биття його контрольних поверхонь." Thesis, КІНПАТРІ ЛТД, 2012. http://dspace.kntu.kr.ua/jspui/handle/123456789/6161.
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Описується дослідження впливу на похибку визначення оптимальних кутів повороту деталей ротора ГТД неточностей заміру биття його контрольних поверхонь, з використанням комп’ютерної програми та 3D моделі ротора. Impact on the accuracy of determining the optimal angles of rotation of the rotor's parts, metering the inaccuracies beating of its control surfaces investigated by using a multifactor experiment with a 3D model of the rotor GTE. According to the research develops recommendations to reduce the specified error.
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Невдаха, А. Ю., and A. Nevdakha. "Технологічне забезпечення якості складання між опорних роторів барабанно-дискового типу методом двох пробних складань." Thesis, ПП ""Екслюзив-Систем", 2013. http://dspace.kntu.kr.ua/jspui/handle/123456789/6160.
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Наводяться кінцеві результати апробації технологічного забезпечення якості складання між опорних роторів барабанно-дискового типу методом двох пробних складань. We present the final results of quality assurance testing process assembly between the supporting rotor drum-disk type test by two assemblages.
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Carvalho, José Filipe Trilha de. "Predição numérica do torque em uma turbina tesla com rotor estacionário." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/174394.
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O presente estudo apresenta a análise numérica do escoamento do fluido de trabalho em uma turbina Tesla com rotor estacionário. O estudo de independência de malha prevê o uso de aproximadamente 2 milhões de volumes, com desempenho semelhante ao das malhas mais refinadas, apresentando uma economia significativa de esforço computacional. Três modelos de turbulência da abordagem RANS são aplicados com o objetivo de estabelecer uma metodologia para estudos futuros com dados experimentais. Os diferentes modelos de turbulência fornecem resultados para a predição do torque na turbina, com uma variação abaixo de 1 % entre si. Ar é usado como fluido de trabalho a pressão manométrica de 2,5 bar, alcançando velocidades no entorno de 310 m.s-1 na região da garganta do bocal e na região de jato livre, logo após a descarga do bocal. Essa condição permite afirmar que a turbina funciona na sua condição de máxima vazão, com o número de Mach próximo ao valor unitário, com escoamento compressível A velocidade na região interna entre discos chega a um valor máximo de 100 m.s-1. Na ausência de dados experimentais e de literatura, um estudo paramétrico com diferentes condições de operação da turbina é realizado a fim de verificar a qualidade dos resultados simulados. A vazão mássica é estimada com base na temperatura e pressão do fluido de trabalho, modelado como gás ideal. Os resultados preditos pelo modelo numérico para o torque no rotor é de 2,09 N.m com pressão manométrica de 1,5 bar e vazão mássica de 33,58 g/s, 2,22 N.m com pressão manométrica de 2,0 bar e vazão mássica de 40,29 g/s, e 2,38 N.m com pressão manométrica de 2,5 bar e vazão mássica de 53,73 g/s. A temperatura foi de 300 K mantida constante para as três análises. Para os casos analisados, o número de Mach na garganta do bocal convergente apresentou uma tendência ao valor unitário, variando entre 0,7 a 1, o que sugere que o bocal está trabalhando na sua condição máxima de vazão do fluido de trabalho.The present study presents the numerical analysis of the working fluid flow in a Tesla turbine with stationary rotor. The mesh independence study predicts the use of approximately 2 million volumes, with similar performance to those most refined meshes, presenting a significant saving of computational effort. Several turbulence models of the RANS approach are applied with the aim of establishing a methodology for future studies with experimental data. The different turbulence models provide very close results for turbine torque prediction, with a variation below 1% between them. Air is used as working fluid at a pressure of 2.5 bar gauge, reaching velocities around 310 m.s-1 in the throat region of the nozzle and in the free jet region, just after the discharge of the nozzle. This condition allows to state that the turbine works in its maximum flow condition, with the Mach number close to unitary value, with a compressible flow The velocity in the inner region between disks reaches 100 m.s-1. In the absence of experimental data and literature, a parametric study with different operating conditions of the turbine is performed in order to verify the quality of the simulated results. The mass flow rate is estimated based on the temperature and pressure of the working fluid, modeled as the ideal gas. The results predicted by the numerical model for the torque in the rotor is 2.09 N.m with gauge pressure of 1.5 bar and a mass flow rate of 33.58 g/s, 2.22 N.m with gauge pressure of 2.0 bar and a mass flow rate of 40.29 g/s, and 2.38 N.m with gauge pressure of 2.5 bar and flow mass of 53.73 g/s. The temperature was 300 K kept constant for all three cases. For the analyzed cases, the Mach number in the throat of the convergent nozzle showed a tendency to the unit value, ranging from 0,7 to 1,0 which suggests that the nozzle is working in its maximum flow condition of the working fluid.
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Michelet, Nicolas. "Modélisation numérique de l'impact d'une ferme hydroliennes sur les conditions hydrodynamiques et sédimentaires du Passage du Fromveur en Mer d'Iroise." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC237/document.
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En dépit d’un développement opérationnel actuel seulement émergeant le long des côtes françaises, l’extraction de l’énergie cinétique des courants de marée par les hydroliennes apparaît, dès à présent, comme une solution prometteuse pour contribuer, localement, à la transition énergétique de territoires insulaires déconnectés du réseau électrique continental, ayant des besoins électriques limités, et situés dans des espaces naturels sensibles et/ou touristiques intégrant un patrimoine visuel à préserver. Ce travail de thèse se consacre à la modélisation numérique tridimensionnelle des impacts hydrodynamiques et sédimentaires d’hydroliennes d’axe horizontal déployées dans le site pilote d’implantation de fermes hydroliennes du Passage du Fromveur, au cœur du parc naturel marin d’Iroise, à la pointe Bretagne. Les simulations numériques se basent sur le modèle océanographique ROMS (« Regional Ocean Modelling System ») modifié pour intégrer un sous-modèle théorique de disque actuateur assimilant l’hydrolienne à un disque poreux opposant à l’écoulement une force équivalente à la poussée de la turbine. La méthode est validée avec des mesures effectuées en laboratoire dans le sillage d’un disque poreux de 10 cm de diamètre (D) immergé dans un courant permanent. Une résolution spatiale minimale égale à D/10 est nécessaire pour reproduire les observations. Après une étude de convergence numérique à échelle réelle, le modèle ROMS est appliqué, selon une approche gigogne de maillages imbriqués focalisée sur le Passage du Fromveur, pour examiner les interactions des sillages et les effets cumulés au sein d’un parc de huit turbines de 10 m de diamètre susceptible de satisfaire au besoin énergétique de l’île d’Ouessant. L’agencement des turbines suit les recommandations communément adoptées avec une disposition en quinconce et des espacements longitudinaux de 10D et latéraux de 5D. En condition de vive-eau moyenne, le désalignement du courant au pic de flot exacerbe les interactions entre sillages, réduisant la production énergétique du parc de près de 15 % par rapport à celle du pic de jusant. Ce déficit de production énergétique est limité à 2 % en ramenant l’espacement latéral des turbines à 3D. Les prédictions de ROMS sont enfin exploitées pour appréhender l’influence de cette dernière configuration de parc sur la dynamique sédimentaire locale. Les principaux effets attendus concernent (i) le dépôt de sédiments de plus de 2 mm de diamètre dans le sillage des dispositifs et (ii) la mise en mouvement de cailloutis de 5 cm de diamètre entre les sillagesIn spite of a present only emerging operational development along the coast of France, the extraction of the kinetic energy of tidal currents by turbines appears as a promising solution to contribute locally to the energetic transition of insulary territories that are not connected to the continental electricity grid, with limited power needs, and are located in protected and touristic natural areas with a visual heritage to preserve. This doctoral thesis was devoted to the three-dimensional numerical modelling of the hydrodynamic and sedimentary impacts induced by horizontal-axis turbines deployed within the pilot site of the Fromveur Strait, in the natural marine Iroise park, off western Brittany. Numerical simulations are performed with the oceanographic model ROMS (Regional Ocean Modelling System) modified to integrate a theoretical actuator-disk sub-model that assimilates the device to a porous disc opposing the flow with a force equal to the turbine’s thrust. This method was assessed against laboratory measurements within the wake of a porous disc with a diameter (D) of 0.1 m immersed in a permanent flow. A spatial resolution as small as D/10 was required to reproduce observations. After a numerical convergence study at full scale, ROMS was applied, using a nested grid approach targetted towards the Fromveur Strait, to examine wake interactions and cumulative effects within an array of height turbines of 10-m-diameter expected to fulfill the energy need of the island of Ushant. The array layout followed the commonly recommended staggered configuration with respective longitudinal and lateral spacings of 10D and 5D. During spring tidal conditions, the misalignment of the peak flood flow enhanced the wake interactions, reducing by about 15% the array power production in comparison with the peak ebb flow. This lack of power production capacity was lowered to 2% by reducing the lateral spacing to 3D. ROMS predictions were finally exploited to address the influence of this last array of turbines on the local sediment dynamics. Main effects were expected on (i) the deposition of sediments with diameter over 2 mm within the turbine wakes and (ii) the setting in motion of gravels with a diameter of 5 cm between the wakes
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Chen, J. H. "Oxidation of nickel-base superalloys for turbine disc and advanced turbine blade applications." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597544.
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Isothermal and cyclic oxidation tests were carried on three "chromia" forming superalloys, Astroloy, Udimet 720 and Waspaloy used as turbine disc materials, and two advanced single crystal superalloys, CMSX4 and RR3000, developed as turbine blade materials, with and without Pt-aluminide coatings. For the turbine disc materials, external chromia scales were formed to protect the alloy substrate and also some internal oxidation developed. The oxidation behaviour was mainly related to the contents of aluminium, chromium and titanium and also the microstructure. For "alumina" forming superalloys without coatings, both CMSX4 and RR3000 formed a continuous alumina subscale after a period of transition oxidation at temperatures above 1000oC in isothermal tests. However the two alloys cannot form an alumina scale at 900oC and thus the growth rate of scale at 900oC was higher than at higher temperatures. The reduction of sulphur content to less than 1 ppm in CMSX4 was shown to improve the scale adhesion in the cyclic tests. For the Pt-aluminide coated CMSX4 and RR3000 excellent oxidation resistance was revealed in both isothermal and cyclic tests at 1100oC due to the formation of adherent alumina scale on the surface. As a result, the oxidation behaviour was very similar between the isothermal and cyclic tests. A deleterious effect was found in the interdiffusion zone of the Pt-aluminide coated alloys due to void and microcrack formation. This was attributed to the inward diffusion of platinum which caused the formation of needle-like TCP phases due to the high contents of rhenium in the two alloys.
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Chang, Min Carleton University Dissertation Engineering Mechanical. "Damage tolerance of Inconel 718 turbine disc material." Ottawa, 1991.
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Mohamad, Abdulwahed Amin. "Dynamic characteristics of rotating shrouded-bladed-disc." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/847813/.
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This investigation deals with the vibration problem of a rotating shrouded bladed disc and with the dynamic stresses of blades and packets of turbine blades. The wave propagation technique in periodic structures is introduced into the finite element method to reduce the overall number of degrees of freedom. The application of wave propagation technique to discs, disc-blades and shrouded bladed disc results in a small size eigenvalue problem which is easily solved to obtain the frequencies and mode shapes of these assemblies under the effects of rotation, disc thickness variations, disc flexibility and other design parameters. The numerical integration is used to evaluate the integrals of the stiffness and mass matrices of the variable thickness discs. The influence of rotational speeds and other design parameters such as; pretwist angles and stagger angles on the free vibration characteristics of blades, curved beams and packets of blades is studied using finite element method. The results of the natural frequencies are compared with the experimental results and with the results of other investigators. The dynamic stresses of blades and packets of blades are derived from the eigenvectors obtained in the vibration study of these components. The effects of rotational speeds, pretwist angles, stagger angles and shrouding on the dynamic stresses are studied.
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Pang, Hon Tong. "Effect of microstructure variation on turbine disc fatigue lives." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274024.
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Wilson, Alison Sarah. "Stability of nickel-base superalloys for turbine disc applications." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/279061.
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Requirements for increased operating efficiencies mean that future generations of aero-engines will need to operate at temperatures beyond the capabilities of current nickel-base superalloys. As a result, new alloy compositions for turbine disc applications are being developed. Optimising these alloy compositions requires balancing directly competing requirements. Increased Cr contents are needed to provide environmental resistance and increased concentrations of other refractory metals to improve solid solution strengthening. However, these elements compromise the alloyâs long-term microstructural stability by promoting the formation of topologically close-packed (TCP) phases, which are deleterious to alloy performance. High $\gamma^\prime$ volume fractions, which are needed to provide high-temperature strength, exacerbate the problem by increasing the concentration of these elements in the $\gamma$ phase. Therefore, an understanding of TCP formation and the compositional limits of stability is vital in the design of new alloys. This thesis presents a combination of fundamental studies of TCP phase formation in model alloys and microstructural assessment of the thermal stability of developmental alloy compositions. Knowledge of the effect of individual elements on thermal stability is important to enable the development of optimised alloy compositions. As a result, the first fundamental study investigated the effect of Co content on thermal stability. An unexpected transition in $\sigma$ precipitation behaviour after 500 hours at 800°C was observed between 12 and 16 at.\% Co. It is proposed that this behaviour may be due to the effect of Co on the $\gamma$/$\gamma^\prime$ partitioning behaviour of other elements. Preliminary results from further fundamental studies investigating the effect of the Mo/W ratio and B content on thermal stability are also presented. Decreasing the Mo/W ratio was found to reduce the quantity of $\sigma$ precipitation and promote the precipitation of a W-rich phase. B additions were found to promote the precipitation of the M$_3$B$_2$ phase. Thermodynamic predictions are frequently used to inform alloy design as an alternative to time-consuming and costly experiments. However, the accuracy of solvus temperature predictions for TCP phases has not been thoroughly considered. In this work, it was found that differential scanning calorimetry could be used as a means of measuring $\sigma$ solvus temperature in a series of alloys designed to be sufficiently unstable with respect to $\sigma$ precipitation. Comparison of experimental results with thermodynamic solvus temperature predictions revealed a significant underprediction of the $\sigma$ solvus temperatures for all of the studied alloys. This can inform our use of such predictions during alloy design. The ability to quantify the amount of TCP precipitation that occurs is extremely important when assessing the thermal stability of alloys. A new method was applied to the problem of TCP quantification, involving synchrotron X-ray diffraction of solid aged samples. This was an attempt to avoid some of the problems identified with the commonly used quantification method, which involves electrolytic extraction of minor phases, and assess the accuracy of the results produced by this method. Samples of a currently used commercial alloy, RR1000, were investigated following ageing for up to 5000 hours at 800°C, revealing the evolution of phases at this temperature. The presence of extremely low quantities of minor phases was successfully detected in the solid samples using this method. However, these quantities were too low for this to be a reliable method of quantification for commercial alloys. In parallel with these fundamental and technique-based studies, the thermal stability of a number of candidate alloys, which were developed during the design of a next-generation disc alloy by Rolls-Royce, was assessed. The alloys were characterised following a variety of thermal exposure temperatures and durations, which were determined by industrial needs at the time. Various minor phases were identified depending on the alloy compositions, including the TCP phases, $\sigma$ and $\mu$, as well as MC and M$_{23}$C$_6$ carbides and M$_3$B$_2$ borides.
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Yan, Huiyu. "Co-Al-W based alloys for turbine disc applications." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/30710.
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In 2006, a new A1-L12 Co-Al-W ternary system, where the L12 - γ' phase Co3(Al,W) coexists with the FCC Co matrix, was discovered. This new L12 phase has been found to exhibit the flow stress anomaly and is coherent with the matrix. It has been proposed that it can form the basis of a new generation of high temperature alloys superior to nickel base superalloys, the performance of which are reaching a plateau. The operating efficiency of jet engines ultimately depends on the temperature capability of the materials used in the turbine. Therefore, this possibility is of great interest to the gas turbine industry. In this project, the influence of different alloying additions to Co-Al-W base alloys on the phase metallurgy has been investigated. Alloys were fabricated by vacuum arc melting and hot rolling. Mo, V and Fe lower the γ' solvus temperature, whereas Ti and Ta are beneficial. Addition of Cr improves the oxidation behaviour. However, too much Cr destabilises the γ/γ' microstructure. When a continuous phase field was established between Ni3Al and Co3(Al,W), it was found that increasing the Ni content in the Co-Al-W-Cr base alloy increases the γ' solvus temperature and stabilises the γ/γ' microstructure. Alloying effects on oxidation behaviour were also studied. The oxide scale in the non-Cr containing alloys was not found to be protective and the thickness was in most cases greater than 100μm after 196 hours at 800°C. It was found that a 10 at.% Cr addition is sufficient to modify the oxidation behaviour such that a three-layer oxide scale is formed. The outer layer is an Al2CoO4, spinel, the middle layer contains both CrO2 and Cr2O3, and the inner layer is Al2O3. These three layers with low oxygen diffusivity adhere well to both the substrate and each other and protect the alloy against high temperature oxidation. Synchrotron and neutron diffraction experiments were performed on Co-7Al-5W-2Ta and Co- 6Al-6W-2Ti (at. %) alloys. The HRPD instrument at the ISIS time of flight neutron source was found to produce the most satisfactory results, with the fundamental and superlattice peaks being easily separable. The new I12 diffractometer at the Diamond synchrotron X-ray source had poorer resolution. Thus, whilst more data was obtained, the results were less reliable. The new Vulcan diffractometer at the Spallation Neutron Source at the Oak Ridge National Laboratory also suffered from poor resolution, despite the high neutron flux that was available. The latter two instruments, however, had the benefit of being able to perform in-situ loading experiments. Hence, it was possible to assess the elastic behaviour of the two phases at temperature. It was found that the -Ti containing alloy has a lower lattice misfit than the -Ta alloy, and that the misfit values increase with temperature. The room temperature misfit is large and positive (~ 0.5 %), in contrast to the small negative misfit observed in nickel superalloys. It was found that the Co3(Al,W) phase is less stiff than the Co matrix in all orientations, this is an undesired feature which means that load shedding will occur to the γ phase.
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Ghaem, Sigarchian Sara. "Modeling and Analysis of a Hybrid Solar-Dish Brayton Engine." Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104425.
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Büche, Dirk [Verfasser]. "Multi-Objective Evolutionary Optimization of Gas Turbine Components / Dirk Büche." Aachen : Shaker, 2004. http://d-nb.info/117053208X/34.
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Skelton, Daniel Kenneth. "High temperature fatigue crack propagation of a turbine disc alloy." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621066.
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Carter, Jace A. "EFFECT OF MATERIAL ANOMALIES ON FATIGUE LIFE OF TURBINE DISKS." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1316211638.
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Olafsson, Sveinn V. "Random vibrations of bladed-disk assembly under cyclostationary excitation." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43261.
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Random vibration of a bladed-disk assembly is studied. A stochastic model for the excitation is developed. A unique feature of this model is the statistical periodicity of the blade forces called cyclostationary. A random process is called wide sense eyeclostationary and its statistics are periodic in time. Factors like the turbulent nature of the flow around the blades, the variability in their geometry, and their nonuniform deterioration contribute to the uncertainty in the excitation. In periodic structures, like the bladed-disk assembly, small variation in the blade excitation may lead to high variability in the response.
The model developed includes both random and deterministic excitation. A comparison of the responses due to the random and the deterministic part shows the significance of taking into account the variability in the blade forces.
Therefore the assumption that the blade forces are all equal, used by all methods for vibration analysis of bladed disk assemblies, may lead to erroneous estimates of their response, reliability and expected life.
It is shown that the response is a cyclostationary process. Therefore the cyclostationary property is preserved from the input to the output. Furthermore the frequency of the second moment of the response is equal to two times the frequency of the excitation.Master of Science
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Ivanell, Stefan S. A. "Numerical computations of wind turbine wakes." Doctoral thesis, Stockholm : Royal Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9916.
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Patounas, Dimitrios S. "Disc heat transfer in gas turbine H.P. compressor internal air systems." Thesis, University of Sussex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444011.
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Shen, Gangshu. "Modeling microstructural development in the forging of Waspaloy turbine engine disks /." Connect to resource, 1994. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1193083993.
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Bradley, Christopher Michael. "Microstructural characterization and heat treatment of A-286 turbine buckets." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Manning, Elizabeth Phillips Hughes. "Development of a polycrystalline Ni base superalloy for gas turbine disc application." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246610.
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Hunt, David W. "The stability & mechanical properties of a nickel-base turbine disc alloy." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404302.
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Crudden, D. J. "Alloys-by-design : applications to polycrystalline nickel superalloys for turbine disc applications." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b60e1854-cae4-4dd3-8d6f-cec1351e4c17.
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The nickel-based superalloys have been a key enabler to the development of modern gas turbine engines. Since their introduction the chemical complexity of these alloys has increased significantly, with current generation nickel-based superalloys usually containing over 10 different elements. It is this combination of alloying additions that is responsible for the superior high temperature properties these alloys exhibit. Traditionally, alloy design has invoked considerable use of trial-and-error based approaches involving costly and exhaustive processing backed up by empirical property testing. In this work a computational materials design approach is developed. This method links physically-faithful composition-dependent models with thermodynamic calculations to understand material behaviour. By doing this it is possible to consider large compositional design spaces and isolate alloys expected to have optimal performance for specific applications. The scope of this research has been to apply the computational model to the design of a polycrystalline nickel-based superalloy for turbine disc applications in next generation jet engines. The design trade-offs encountered when developing the new alloy are highlighted. Alloy compositions which are predicted to be optimal for turbine disc applications are isolated. These alloys have been manufactured using a scaled down version of the commercial production method. The newly manufactured alloys have been characterised using microstructural evaluation, mechanical testing and corrosion testing. The experimental results have been compared with modelling predictions in order to determine the capability of the computational approach.
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Odemark, Ylva. "Wind-turbine wake flows - Effects of boundary layers and periodic disturbances." Doctoral thesis, KTH, Strömningsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144475.
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The increased fatigue loads and decreased power output of a wind turbine placed in the wake of another turbine is a well-known problem when building new wind-power farms and a subject of intensive research. These problems are caused by the velocity gradients and high turbulence levels present in the wake of a turbine. In order to better estimate the total power output and life time of a wind-power farm, knowledge about the development and stability of wind-turbine wakes is crucial. In the present thesis, the flow field around small-scale model wind turbines has been investigated experimentally in two wind tunnels. The flow velocity was measured with both hot-wire anemometry and particle image velocimetry. To monitor the turbine performance, the rotational frequency, the power output and the total drag force on the turbine were also measured. The power and thrust coefficients for different tip-speed ratios were calculated and compared to the blade element momentum method, with a reasonable agreement. The same method was also used to design and manufacture new turbine blades, which gave an estimate of the distribution of the lift and drag forces along the blades. The influence of the inlet conditions on the turbine and the wake properties was studied by subjecting the turbine to both uniform in flow and different types of boundary layer in flows. In order to study the stability and development of the tip vortices shed from the turbine blades, a new experimental setup for phase-locked measurements was constructed. The setup made it possible to introduce perturbations of different frequencies and amplitudes, located in the rear part of the nacelle. With a newly developed method, it was possible to characterize the vortices and follow their development downstream, using only the streamwise velocity component. Measurements were also performed on porous discs placed in different configurations. The results highlighted the importance of turbine spacings. Both the measurements on the turbine and the discs were also used to compare with large eddy simulations using the actuator disc method. The simulations managed to predict the mean velocity fairly well in both cases, while larger discrepancies were seen in the turbulence intensity.QC 20140424
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Eskner, Mats. "Mechanical Behaviour of Gas Turbine Coatings." Doctoral thesis, KTH, Materials Science and Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3776.
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Coatings are frequently applied on gas turbine components inorder to restrict surface degradation such as corrosion andoxidation of the structural material or to thermally insulatethe structural material against the hot environment, therebyincreasing the efficiency of the turbine. However, in order toobtain accurate lifetime expectancies and performance of thecoatings system it is necessary to have a reliableunderstanding of the mechanical properties and failuremechanisms of the coatings.
In this thesis, mechanical and fracture behaviour have beenstudied for a NiAl coating applied by a pack cementationprocess, an air-plasma sprayed NiCoCrAlY bondcoat, a vacuumplasma-sprayed NiCrAlY bondcoat and an air plasma-sprayed ZrO2+ 6-8 % Y2O3topcoat. The mechanical tests were carried out ata temperature interval between room temperature and 860oC.Small punch tests and spherical indentation were the testmethods applied for this purpose, in which existing bending andindentation theory were adopted for interpretation of the testresults. Efforts were made to validate the test methods toensure their relevance for coating property measurements. Itwas found that the combination of these two methods givescapability to predict the temperature dependence of severalrelevant mechanical properties of gas turbine coatings, forexample the hardness, elastic modulus, yield strength, fracturestrength, flow stress-strain behaviour and ductility.Furthermore, the plasma-sprayed coatings were tested in bothas-coated and heat-treated condition, which revealedsignificant difference in properties. Microstructuralexamination of the bondcoats showed that oxidation with loss ofaluminium plays an important role in the coating degradationand for the property changes in the coatings.
Keywords:small punch test, miniaturised disc bendingtests, spherical indentation, coatings, NiAl, APS-NiCoCrAlY,VPS-NiCrAlY, mechanical properties
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Li, Zhisong. "Advanced Computational Modeling for Marine Tidal Turbine Farm." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337889611.
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Blackmore, Tom. "Grid generated turbulence and actuator disc representations of tidal turbines." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/361942/.
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Delhelay, Davinder Singh. "Nonlinear finite element analysis of the coupled thermomechanical behaviour of turbine disc assemblies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ46072.pdf.
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Ong, C.-L. "Computation of fluid flow and heat transfer in rotating disc-systems." Thesis, University of Sussex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233697.
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Raub, Corey Bevan. "Geometric analysis of axisymmetric disk forging." Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1172778393.
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Muller, Yann-Aël. "Etude du méandrement du sillage éolien lointain dans différentes conditions de rugosité." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2040/document.
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Le phénomène connu sous l'appellation "méandrement" (ou meandering) désigne les variations aléatoires de la trajectoire du sillage aérodynamique d'une éolienne. Ce phénomène est responsable de contraintes mécaniques particulières sur les éoliennes positionnées dans le sillage d'autres éoliennes et joue donc rôle dans la conception et dans la prévision de production des parcs éoliens.Ce travail propose d'étudier le méandrement par des moyens expérimentaux et numériques. La problématique est traitée en deux parties, la première portant sur la modélisation de l'écoulement de couche limite atmosphérique, avec une attention particulière portée à la modélisation des grandes échelles de la turbulence atmosphérique. La seconde partie porte sur l'étude du sillage d'un disque actuateur soumis à un écoulement atmosphérique. Chacune de ces parties comporte un volet expérimental et un volet numérique. La modélisation numérique instationnaire de l'écoulement atmosphérique fait intervenir une technique de génération stochastique de champs de vitesse turbulente avec évolution temporelle, spécialement développée au cours de la présente thèse et à laquelle un chapitre spécifique est dédié.L'un des principaux résultats est que le méandrement du sillage est fortement corrélé avec les grandes échelles de la turbulence atmosphériqueThe phenomenon known as meandering describes the unsteady trajectory variations of the wake of a wind turbine. This phenomenon is responsible for specific mechanical stresses on turbines positioned in the wake of other turbines. As such, this phenomenon must be accounted for in the design and operation of wind turbine plants.This work uses numerical fluid simulation and wind tunnel testing in order to study the meandering of the wake of a wind turbine. The subject is discussed in two parts. The first part discusses the modeling of the atmospheric boundary layer, with a focus on the large scales of the atmospheric turbulence. The second part is a study of the behavior of the wake of an actuator disc model in atmospheric wind conditions.Both parts include experimental and numerical work. The numerical simulation of the atmospheric boundary layer involves the generation of synthetic turbulent velocity time series by mean of a stochastic technique developed during this thesis, to which a chapter is dedicated.One of the main results of this work is that the meandering is highly correlated with the large scales of the atmospheric turbulence
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Hasselqvist, Magnus. "Aspects of creep-fatigue in gas turbine hot parts /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/tek678s.pdf.
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Abdul, Rahman Anas. "Numerical modelling of full scale tidal turbines using the actuator disc approach." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31246.
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In recent years, the actuator disc approach which employs the Reynolds-Averaged Navier-Stokes (RANS) solvers has been extensively applied in wind and tidal energy field to estimate the wake of a horizontal axis turbine. This method is simpler to administer and requires moderate computational resources in modelling a tidal turbines rotor. Nonetheless, the use of actuator disc approximation in predicting the performance of tidal devices has been limited to studies involving an extremely small disc (e.g. rotor diameter of 0.1 meter). The drawback of a small scale actuator disc model is the overestimation of essential parameters such as the mesh density and the resolution of the vertical layers, making them impractical to be replicated in a regional scale model. Hence, this study aims to explore the methodology on implementation of the Three- Dimensional (3D) actuator disc-RANS model in an ocean scale simulation. Additionally, this study also aspires to examine the sensitivity of the applied momentum source term and its validity in representing full-size tidal devices. Nonetheless, before the effectiveness of an actuator disc in a regional model can be tested, tidal flow models for the area of interest needed to be set up first. This was essential for two reasons: (a) to ensure accurate hydrodynamic flow conditions at the deployment site were replicated, (b) to give confidence in the outputs produced by the regional scale actuator disc simulations, since in-situ turbine measurement data from a real deployment site were difficult to source. This research was undertaken in two stages; in the first stage, a numerical model which can simulate the tidal flow conditions of the deployment sites was constructed, and, in the second stage, the actuator disc method which is capable of modelling an array of real scale-sized tidal turbines rotors has been implemented. In the first stage, tidal flow simulations of the Pentland Firth and Orkney Waters (PFOW) were conducted using two distinct open-source software - Telemac3D, which is a finite element based numerical model, and Delft3D, which is a finite difference based model. Detailed methodologies in developing a 3D tidal flow model for the PFOW using both numerical models were presented, where their functionality, as well as limitations were explored. In the calibration and validation processes, both models demonstrated excellent comparison against the measured data. However, Telemac3D was selected for further modelling of the actuator disc considering the model's capability to perform parallel computing, together with its flexibility to combine both structured and unstructured mesh. In the second stage, to examine the actuator disc's accuracy in modelling a full size tidal device, the momentum source term was initially applied in an idealised channel study, where the presence of a 20-meter diameter turbine was simulated for both single and array configurations. The following parameters were investigated: (i) size of the unstructured mesh utilised in the computational domain, (ii) variation in disc's thickness, (iii) resolution of the imposed structured grid to represent turbine's enclosure, (iv) variation in the vertical layers, and (v) influence of hydrostatic and non-hydrostatic formulations on the models' outputs. It is to be noted that the turbine's support structures have not been included in the modelling. The predicted velocities and computed turbulence intensities from the models were compared against laboratory measurement data sourced from literature, where excellent agreement between the model outputs and the data from literature was observed. In essence, these studies highlighted the efficiency and robustness of the applied momentum source term in replicating the wake profiles and turbulence characteristics downstream of the disc, hence providing credence in implementing the actuator disc method for a regional scale application. Subsequently, the validated actuator disc method was applied to the Inner Sound region of the Pentland Firth to simulate arrays of up to 32 tidal turbine rotors. The wake development, flow interactions with the rotor arrays, and flow recovery at the Inner Sound region have been successfully mapped. Also, this study highlighted the importance of employing optimal numerical margins, specifically for the structured grid and horizontal planes, as both parameters were relevant in defining the disc's swept area. As published materials on the implementation of actuator disc approach within a regional scale model is still scarce, it was aspired that this work could provide some evidence, guidance and examples of suggested best practice in effort to fill the research gap in modelling tidal turbine arrays using the actuator disc approach.
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Connor, Leigh. "The development of a dual microstructure heat treated Ni-base superalloy for turbine disc applications." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/252160.
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This thesis considers the effect of applying a dual microstructure heat treatment (DMHT) process to two turbine disc forgings. Each for the forgings has been manufactured from a different polycrystalline Ni-base superalloy. Particular emphasis is placed on fully characterising the microstructure of each forging. The subsequent evaluation of mechanical properties can then by compared to the microstructure of that region. In chapters 3 and 4, the microstructural response of both forgings to the DMHT process is established. Chapter 3 looks at the effect of the heating rate and maximum temperature achieved during the DMHT process and compares it to a detailed characterisation of the primary γ’ precipitate population and the γ grains. Chapter 4 evaluates the effect of the cooling cycle from the DMHT process and compares it to the development of intra-granular secondary and tertiary γ’ populations. The work contained in chapter 5 examines the tensile performance throughout both of the forgings, and remarks on whether any negative effect on mechanical properties has developed due to the DMHT process. Comparisons are made between measured tensile properties and microstructure, a post mortem review of the failed fracture surfaces and TEM analysis of the failed tensile specimens are also undertaken. Any change in deformation behaviour between a fine γ grain microstructure in the bore and a coarse γ grain microstructure in the rim can then be observed. In chapter 6 the effect of creep deformation on the RR1000 DMHT forging is determined. The microstructural variations that occurred as a result of the DMHT process are compared to the measured creep properties to determine the advantages and disadvantages of the DMHT process. This will ensure not only it is not detrimental to the creep properties, but the process also provides a foundation for improved temperature capabilities at the rim of the disc. A post mortem TEM analysis of the failed tensile specimens is also undertaken to discover if a change in the creep behaviour occurs between the microstructures observed in the bore and rim of the forging.
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Kearsey, Richard M. "Development and characterization of a damage-tolerant microstructure for a Ni-base turbine disc alloy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0022/MQ52391.pdf.
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Fleury, Rodolfo Miguel Nogueira. "Investigation of fretting fatigue in turbine fir tree blade to disc joints at high temperature." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:9c030512-cc59-46f0-bd88-e81d85dedd4b.
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Fretting fatigue is the phenomenon of combined contact and fatigue loads which may accelerate crack initiation and reduce the operational life of components. One of the most relevant problems of fretting fatigue occurs in the blade to disc assemblies, particularly those in the hot stages of gas turbines. The 'fir-tree' blade to disc assemblies in gas turbines operate at extreme conditions of loading and temperature, and the presence of multiple frictional contact points, often interacting with other stress concentrators, makes it an extremely challenging problems in solid mechanics. This thesis focus on two aspects of the problem found in 'fir-tree' assemblies: i) what is the impact of using single-crystal blades on the contact tractions and fretting fatigue behaviour; and ii) what is the effect of edge rounding on the contact tractions between the blade and disc?
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Everitt, Stewart. "Developments in advanced high temperature disc and blade materials for aero-engine gas turbine applications." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348897/.
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The research carried out as part of this EngD is aimed at understanding the high temperature materials used in modern gas turbine applications and providing QinetiQ with the information required to assess component performance in new propulsion systems. Performance gains are achieved through increased turbine gas temperatures which lead to hotter turbine disc rims and blades. The work has focussed on two key areas: (1) Disc Alloy Assessment of High Temperature Properties; and (2) Thermal Barrier Coating Life Assessment; which are drawn together by the overarching theme of the EngD: Lifing of Critical Components in Gas Turbine Engines. Performance of sub-solvus heat treated N18 alloy in the temperature range of 650°C to 725°C has been examined via monotonic and cyclically stabilised tensile, creep and strain controlled low cycle fatigue (LCF) tests including LCF behaviour in the presence of a stress concentration under load-control. Crack propagation studies have been undertaken on N18 and a particular super-solvus heat treatment variant of the alloy LSHR at the same temperatures, in air and vacuum with 1s and 20s dwell times. Comparisons between the results of this testing and microstructural characterisation with RR1000, UDIMET® 720 Low Interstitial (U720Li) and a large grain variant of U720Li have been carried out. In all alloys, strength is linked to a combination of γ' content and grain size as well as slow diffusing atoms in solid solution. High temperature strength improves creep performance which is also dependent on grain size and grain boundary character. Fatigue testing revealed that N18 had the most transgranular crack propagation with a good resistance to intergranular failure modes, with U720Li the most intergranular. Under vacuum conditions transgranular failure modes are evident to higher temperature and ΔK, with LSHR failing almost completely by intergranular crack propagation in air. For N18 significant cyclic softening occurs at 725°C with LCF initiation occurring at pores and oxidised particles. An apparent activation energy technique was used to provide further insights into the failure modes of these alloys, this indicating that, for N18 with 1s dwell, changes in fatigue crack growth rates were attributed to static properties and for LSHR, with 20s dwell in air, that changes were attributed to the detrimental synergistic combination of creep and oxidation at 725°C. Microchemistry at grain boundaries, especially M23C6 carbides, plays an important role in these alloys. Failure mechanisms within a thermal barrier coating (TBC) system consisting of a CMSX4 substrate, PtAl bond coat, thermally grown oxide (TGO) layer and a top coat applied using electron beam physical vapour deposition have been considered. TGO growth has been quantified under isothermal, two stage temperature and thermal cyclic exposures. An Arrhenius relation was used to describe the TGO growth and produce an isothermal TGO growth model. The output from this was used in the QinetiQ TBC Lifing Model. Thermo-mechanical fatigue test methods were also developed including a novel thermocouple placement permitting substrate temperature to be monitored without disturbing the top coat such that the QinetiQ TBC Lifing Model could be validated. The importance of material, system specific knowledge and performance data with respect to a particular design space for critical components in gas turbine engines has been highlighted. Data and knowledge regarding N18, LSHR and TBC systems has been added to the QinetiQ’s databank enhancing their capability for providing independent advice regarding high temperature materials particularly in new gas turbine engines.
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Kearsey, Richard M. (Richard Michael) Carleton University Dissertation Engineering Mechanical and Aerospace. "Development and characterization of a damage tolerant microstructure for a Ni-base turbine disc alloy." Ottawa, 2000.
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Büche, Dirk. "Multi-objective evolutionary optimization of gas turbine components /." [S.l.] : [s.n.], 2003. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15240.
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