Global ETD Search

1	Investigation Of Different Airfoils on Outer Sections of Large Rotor Blades Thuné, Sebastian, Soland, Torstein January 2012 (has links) Wind power counts for roughly 3 % of the global electricity production. In the chase to produce greener power, much attention lies on getting more electricity from the wind, extraction of kinetic energy, with help of wind turbines. Wind turbines have been used for electricity production since 1887 and have since then developed into more efficient designs and become significantly bigger and with a higher efficiency. The operational conditions change considerably over the rotor length. Inner sections are typically exposed to more complex operational conditions than the outer sections. However, the outer blade sections have a much larger impact on the power and load generation. Especially here the demand for good aerodynamic performance is large. Airfoils have to be identified and investigated on mid/outer sections of a 7.0 MW rotor with 165 m diameter. Blade performance criteria were determined and investigations like sensitivity analysis were made. With the use of XFLR5 (XFoil) and Qblade, the airfoils were made into a blade and tested with the blade element momentum theory. This simulation gave detailed information regarding performance and operational loads depending on the different airfoils used. These results were then validated in a professional aero-elastic code (Flex5), simulating steady state, turbulent and wind shear conditions. The best airfoils to use from this reports airfoil catalogue are the NACA 63-6XX and NACA 64-6XX. With the implementation of these airfoils, blade design 2 and 3 have a very high performance coefficient compared to large commercial HAWT rotors. wind turbine Rotor Blade HAWT
2	Feasibility Study of a 3D CFD Solution for FSI Investigations on NREL 5MW Wind Turbine Blade Bernardi, Giacomo January 2015 (has links) With the increase in length of wind turbine blades flutter is becoming a potential design constrain, hence the interest in computational tools for fluid-structure interaction studies. The general approach to this problem makes use of simplified aerodynamic computational tools. Scope of this work is to investigate the outcomes of a 3D CFD simulation of a complete wind turbine blade, both in terms of numerical results and computational cost. The model studied is a 5MW theoretical wind turbine from NREL. The simulation was performed with ANSYS-CFX, with different volume mesh and turbulence model, in steady-state and transient mode. The convergence history and computational time was analyzed, and the pressure distribution was compared to a high fidelity numerical result of the same blade. All the model studied were about two orders of magnitude lighter than the reference in computation time, while showing comparable results in most of the cases. The results were affected more by turbulence model than mesh density, and some turbulence models did not converge to a solution. In general seems possible to obtain good results from a complete 3D CFD simulation while keeping the computational cost reasonably low. Attention should be paid to mesh quality. HAWT CFD Aeroelasticity Energy Engineering Energiteknik
3	Modeling wind turbine blades by geometrically-exact beam and shell elements: a comparative approach. / Modelagem estrutural de pás de turbinas eólicas por meio de elementos de viga e casca: uma abordagem comparativa. Faccio Júnior, Celso Jaco 19 June 2017 (has links) The total wind power capacity installed in the world has substantially grown during the last few years, mainly due to the increasing number of horizontal axis wind turbines (HAWT). Consequently, a big effort was employed to increase HAWT\'s power capacity, which is directly associated to the size of blades. Then, novel designs of blades may lead to very fexible structures, susceptive to large deformation, not only during extreme events, but also for operational conditions. In this context, this thesis aims to compare two geometrically nonlinear structural modeling approaches that handle large deformation of blade structures: 3D geometrically-exact beam and shell finite element models. Regarding the beam model, due to geometric complexity of typical cross-sections of wind turbine blades it is adopted a theory that allows creation of arbitrary multicellular cross-sections. Two typical blade geometries are tested, and comparisons between the models are done in statics and dynamics, always inducing large deformation and exploring the accuracy limits of beam models, when compared to shells. Results showed that the beam and shell models present very similar behavior, except when violations occur on the beam formulation hypothesis, such as when shell local buckling phenomena takes place. / A capacidade total de energia eólica instalada no mundo cresceu substancialmente nos últimos anos, principalmente devido ao número crescente de turbinas eólicas de eixo horizontal. Consequentemente, um grande esforço foi empregado com o intuito de aumentar a capacidade de produção das turbinas eólicas, que está diretamente associada ao tamanho das pás. Assim, surgiram projetos inovadores quanto à concepção de pás de turbinas eólicas levando a estruturas bastante flexíveis, susceptíveis a grandes deslocamentos, não apenas em eventos extremos, mas também em condições normais de operação. Nesse contexto, a presente dissertação tem por objetivo comparar duas abordagens de modelos estruturais geometricamente não-lineares capazes de lidar com grandes deslocamentos de pás de turbinas eólicas: elementos finitos geometricamente exatos 3D de vigas e cascas. Em relação ao modelo de viga, devido à complexidade geométrica das seções transversais típicas de pás de turbinas eólicas, adota-se uma teoria que permite a criação de seções transversais arbitrárias multicelulares. Duas geometrias de pás s~ao testadas e comparações entre os modelos s~ao feitas em análises estáticas e dinâmicas, sempre induzindo grandes deslocamentos e explorando os limites de precisão do modelo de viga, quando comparado ao modelo de cascas. Os resultados indicam que os modelos de viga e casca apresentam comportamento muito similar, exceto quando ocorrem violações em hipóteses do modelo de viga, tal como quando ocorre flambagem local do modelo de casca. Beam Blades Cascas (Engenharia) Geometrically-exact HAWT Shell Turbinas Vigas
4	Modeling wind turbine blades by geometrically-exact beam and shell elements: a comparative approach. / Modelagem estrutural de pás de turbinas eólicas por meio de elementos de viga e casca: uma abordagem comparativa. Celso Jaco Faccio Júnior 19 June 2017 (has links) The total wind power capacity installed in the world has substantially grown during the last few years, mainly due to the increasing number of horizontal axis wind turbines (HAWT). Consequently, a big effort was employed to increase HAWT\'s power capacity, which is directly associated to the size of blades. Then, novel designs of blades may lead to very fexible structures, susceptive to large deformation, not only during extreme events, but also for operational conditions. In this context, this thesis aims to compare two geometrically nonlinear structural modeling approaches that handle large deformation of blade structures: 3D geometrically-exact beam and shell finite element models. Regarding the beam model, due to geometric complexity of typical cross-sections of wind turbine blades it is adopted a theory that allows creation of arbitrary multicellular cross-sections. Two typical blade geometries are tested, and comparisons between the models are done in statics and dynamics, always inducing large deformation and exploring the accuracy limits of beam models, when compared to shells. Results showed that the beam and shell models present very similar behavior, except when violations occur on the beam formulation hypothesis, such as when shell local buckling phenomena takes place. / A capacidade total de energia eólica instalada no mundo cresceu substancialmente nos últimos anos, principalmente devido ao número crescente de turbinas eólicas de eixo horizontal. Consequentemente, um grande esforço foi empregado com o intuito de aumentar a capacidade de produção das turbinas eólicas, que está diretamente associada ao tamanho das pás. Assim, surgiram projetos inovadores quanto à concepção de pás de turbinas eólicas levando a estruturas bastante flexíveis, susceptíveis a grandes deslocamentos, não apenas em eventos extremos, mas também em condições normais de operação. Nesse contexto, a presente dissertação tem por objetivo comparar duas abordagens de modelos estruturais geometricamente não-lineares capazes de lidar com grandes deslocamentos de pás de turbinas eólicas: elementos finitos geometricamente exatos 3D de vigas e cascas. Em relação ao modelo de viga, devido à complexidade geométrica das seções transversais típicas de pás de turbinas eólicas, adota-se uma teoria que permite a criação de seções transversais arbitrárias multicelulares. Duas geometrias de pás s~ao testadas e comparações entre os modelos s~ao feitas em análises estáticas e dinâmicas, sempre induzindo grandes deslocamentos e explorando os limites de precisão do modelo de viga, quando comparado ao modelo de cascas. Os resultados indicam que os modelos de viga e casca apresentam comportamento muito similar, exceto quando ocorrem violações em hipóteses do modelo de viga, tal como quando ocorre flambagem local do modelo de casca. Cascas (Engenharia) Turbinas Vigas Beam Blades Geometrically-exact HAWT Shell
5	Modélisation des systèmes éoliens verticaux intégrés aux bâtiments : modélisation du couple production / Bâtiment / Modeling of vertical axis wind systems integrated into buildings : modeling of coupling between Production / Buildings Jaohindy, Placide 20 August 2012 (has links) La technique d'intégration des systèmes éoliens verticaux (VAWT) au service des logements individuels, collectifs et tertiaires est une approche intéressante pour les acteurs de la maitrise d'énergie pour promouvoir une utilisation rationnelle de l'énergie. Le choix de l'implantation d'une éolienne en milieu urbain est déterminé par la hauteur des bâtiments, la vitesse du vent et l'intensité de turbulence du site. Les conditions de vents sévères à faible altitude sont favorables à une implantation de VAWT. Dans certaines villes, la hauteur moyenne des bâtiments est relativement faible et ceci fait qu'en ces lieux, les VAWTs sont appréciables par rapport aux HAWTs. La mécanique des fluides numériques (CFD) est mise en œuvre pour modéliser les écoulements d'air au travers d'éoliennes et des bâtiments. Un problème CFD modélisé avec un modèle de turbulence approprié donneront des résultats de simulations qui s'approcheront des réalités physiques et des résultats de l'expérimentation. Dans cette étude, les modèles standard k-" et SST k-! ont été utilisés. Après analyse des possibilités d'intégration d'une VAWT, la toiture reste la zone d'intégration la plus intéressante. En plus de l'étude aérodynamique, nous avons entamé une modélisation électrique de la chaîne de conversion de l'éolienne en utilisant le logiciel Matlab/Simulink. Le travail a été effectué dans le but de déterminer la puissance électrique susceptible d'être produite par l'éolienne. Pour finaliser cette étude, un modèle de couplage électrique de VAWTs avec un bâtiment considéré comme un modèle de charge est présenté. / The building integration of the vertical axis wind turbine (VAWT) to supply the individual, collective and tertiary residences consumption is an interesting approach that can help architects and the actors of the energy control to promote a rational use of renewable energy in the in homes. The choice of the location of the urban wind turbine type is determined by building height, wind speed and turbulence intensity of the site. The severe conditions of wind at low altitude are favorable for a VAWT installation. In some cities, the average buildings height is low, in these places, the VAWTs must be appreciable compared to the HAWTs. The modelling of the air flow through the wind turbine and the couple building-wind turbine involves the computation fluid dynamics (CFD). A problem modeled with a suitable turbulence model will give results that approach the physical reality and the experiment results. In this study, the standard k-" and SST k-! models were used. After analyzing the possibilities of VAWT integration, the roof is the most interesting integration area. In addition to CFD method, we have started to study the electrical model of the VAWT. The work was conducted to determine the electrical power generated by the wind turbine using Matlab/Simulink software. To complete the study, a VAWT model coupled with a building where the building is considered as a consumption model is presented. Éolienne à axe vertical (VAWT) Éolienne à axe horizontal (HAWT) Rotor Savonius Intégration architecturale Modélisation numérique CFD Modélisation éléctrique Vertical axis wind turbine (VAWT) Horizontal axis wind turbine (HAWT) Rotor Savonius Architecural integration of wind turbine Numerical modeling. CFD Electrical modeling.
6	Småskaliga vindkraftverk på byggnader i urban miljö : Möjligheter och hinder för ökad implementering / Small-scale wind turbines mounted on buildings in the urban environment : Possibilities and barriers for increased use Halvarsson, Patrik, Larsson, Emma January 2013 (has links) Intresset för småskaliga vindkraftverk på byggnader har ökat under de senaste åren. Allt fler människor blir mer energi- och miljömedvetna samt ser fördelarna med att elektriciteten produceras där den konsumeras; i den bebyggda miljön. Det är dock en större utmaning att installera ett vindkraftverk i urban miljö, jämfört med i öppet landskap, då det finns många faktorer som skall beaktas. Stadens komplexa uppbyggnad gör att vindens hastighet och riktning varierar och ger upphov till turbulenta strukturer i den omgivande luften. Många av dagens vindkraftverk kan ej operera effektivt vid turbulens, därför måste dessa vindkraftverken placeras på höga höjder för att nå den laminärt strömmande vinden över staden, vilket ger orealistiska längder på de master som krävs, även om vindkraftverket monteras på en byggnad. För att kunna utnyttja de vindar som uppkommer i urbana miljöer bör vertikalaxlade vindkraftverk med en helixformad geometri på rotorn användas. Dessa har visat sig vara både de effektivaste och de vindkraftverk som utsätter omgivningen för lägst nivå av störningar. Att placera ett vindkraftverk på en byggnad i urban miljö, där många människor vistas, kräver god kunskap om säkert montage samt vilka störningar som vindkraftverket kan generera. Ett vindkraftverk som monteras felaktigt kan bidra till hälso- och säkerhetsrisker, och om dessa risker blir för stora kan vindkraftverket tvingas att tas ur drift. För att vara säker på att vindkraftsanläggningen är tillförlitligt bör vindkraftverket och montaget vara stadardiserat och certifierat, något som i dagsläget saknas i Sverige. I dag finns inga direkta stöd för småskaliga vindkraftverk i Sverige, vilket är en bidragande faktor till att ekonomin kring dessa vindkraftverk är bristfällig. Elcertifikatsystemet som skall ge stöd åt förnyelsebar energi är inte utformat för småskalig elproduktion. Men i takt med att detta användningsområde för vindkraft utvecklas samt att priset för energi förväntas stiga kommer troligtvis byggnadsmonterade vindkraftverk bli en lönsam investering i framtiden. / The interest for small-scale wind turbines mounted on buildings has increased during the last couple of years. More and more people are giving more consideration to energy and environmental questions and are appreciative of the benefits of producing electricity where it is consumed; in the urban environment. However it is a greater challenge to install a wind turbine in the urban environment, compared to an open landscape, because of the many factors that needs to be taken in consideration. The complex structure of the city has an effect on the speed and direction of the wind and causes turbulent structures in the surrounding air. Many of today’s wind turbines cannot operate effectively in turbulence, this is why these turbines need to be placed on high heights to reach the laminar wind flow over the city, which gives unrealistic lengths of the towers that are required, even if the turbine is mounted on a building. To be able to utilize the existing wind in urban environments a vertical axis wind turbine with a helix shaped rotor should be used. These turbines have shown themselves to not only be the most effective but also the turbines that expose the surroundings to the lowest level of disturbances. To place a wind turbine on a building in an urban environment, where a lot of people reside, requires a good knowledge of how to securely mount the turbine but also what kind of disturbances that a turbine can emit. A turbine that is mounted incorrectly can contribute to health and safety hazards, and if these risks become to great the turbine may be forced to be taken out of operation. To be certain that the wind turbine and its components are trustworthy the turbine and mounting should be standardized and certified, a feature that don’t exist today in Sweden. Currently there is no direct support scheme for small-scale wind turbines in Sweden, which is a contributing factor to the inadequate economics surrounding these wind turbines. The Swedish system with certificates is meant to give support renewable energy but the system is not suited for small-scale production of electricity. But the more this field of application for wind turbines develops, together with the assumption of rising cost of energy will most likely make building mounted wind turbines a profitable investment in the future. wind power wind turbines small-scale HAWT VAWT certificates net-metering feed in tariffs attachment mounting building mounted vindkraft vindkraftverk småskaligt HAWT VAWT elcertifikat nettodebitering inmatningstariffer infästning montage byggnadsmonterad Civil Engineering Samhällsbyggnadsteknik
7	Prediction of Infrasound Emission from Horizontal Axis Wind Turbines Dazhuang He (11823935) 18 December 2021 (has links) Wind energy is one of the fastest-growing renewable energy technologies, and horizontal axis wind turbines (HAWT) have been the most common device to convert wind kinetic energy into electrical energy. As the capacities of wind turbines and scales of wind farm constructions are rapidly increasing over time, environmental impacts of wind energy are becoming more relevant and raising more attention than ever before. One of the major environmental concerns is noise emission from wind energy facilities, especially low-frequency noise and infrasound that allegedly cause so-called wind turbine syndrome. Therefore, a numerical simulation program capable to predict low-frequency noise and infrasound emission from wind turbines is a useful tool to aid future wind energy development. In this study of this thesis, a computer program named TDRIP (Time Domain Rotor Infrasound Prediction) is developed based on acoustic analogy theories. Farassat’s formulation 1A, a solution to Ffowcs Williams-Hawkings (FW-H) equation, is implemented in the TDRIP program to compute aerodynamically generated sound. The advantage of this program is its capability to simultaneously compute infrasound emission of multiple wind turbines in time domain, which is a challenging task for other aerodynamic noise prediction methods. The developed program is validated against results obtained from computational fluid dynamics (CFD) simulations. The program is then used to compute aerodynamic noise emitted from wind turbine rotors. The effects of wind direction, wind turbine siting, and phase of wind turbine rotation on consequent aerodynamic noise are investigated. Results of aerodynamic noise computation imply that wind turbine siting configuration or wind turbine phase adjustment can help reducing noise level at certain locations, which make the program ideal to be integrated into wind farm siting or control tools. Aerodynamic noise Horizontal Axis Wind Turbine (HAWT) Infrasound
8	Investigating the feasibility and soil-structure integrity of onshore wind turbine systems in Kuwait Almutairi, Badriya L. January 2017 (has links) Wind energy technologies are considered to be among the most promising types of renewable energy sources, which have since attracted broad considerations through recent years due to the soaring oil prices and the growing concerns over climate change and energy security. In Kuwait, rapid industrialisation, population growth and increasing water desalination are resulting in high energy demand growth, increasing the concern of oil diminishing as a main source of energy and the climate change caused by CO2 emissions from fossil fuel based energy. These demands and challenges compelled governments to embark on a diversification strategy to meet growing energy demand and support continued economic growth. Kuwait looked for alternative forms of energy by assessing potential renewable energy resources, including wind and sun. Kuwait is attempting to use and invest in renewable energy due to the fluctuating price of oil, diminishing reserves, the rapid increase in population, the high consumption of electricity and the environment protection. In this research, wind energy will be investigated as an attractive source of energy in Kuwait.
9	Dimensionering och konstruktion av passiv mekanisk pitch för småskaliga horisontalaxlade vindkraftverk / Design and construction of passive mechanical pitch for small-scale horizontal axis wind turbines Oljelund, David January 2020 (has links) För vindkraftverk i mindre skala används i huvudsak två sätt att avlasta vid höga vindhastigheter, stallreglering och girning ur vind. En tredje metod är att pitcha rotorbladet till en mindre attackvinkel. Då minskar belastningen på rotorbladet samtidigt som effektgenerering kan bibehållas. Arbetet redovisar en konstruktion för en fjädrande passiv mekanisk pitch som avgränsats till att enbart dimensionera en vridfjäder och tre lager. Konstruktionen riktas mot horisontalaxlade vindkraftverk med tre rotorblad med en rotordiameter upp till 20m. Ett idealt rotorblad modelleras matematiskt för att ta fram dimensionerande krafter och moment. Utifrån detta kan sedan vridfjäder och lager dimensioneras. Konstruktionen tillsammans med dimensioneringen visar att belastning av rotorbladet kan reduceras samt att krafter som är kopplad till effekten kan hållas mer eller mindre konstant för vindhastigheter 16 till 24 m/s. Resultat av dimensionering visar att både vridfjäder och lager kan relativt enkelt anpassas till olika axeldiametrar. Slutsatserna blir att om dimensionering görs enligt arbetet är det, åtminstone i teorin, möjligt att uppnå det önskade beteendet för pitchen. För vidare arbete och verifiering rekommenderas bland annat att göra reella tester för vridfjädern för att bestämma dess precision på grund av fjäderns små vinkelutslag. / For small-scale wind turbines, there are mainly two ways of reducing loads at high wind speeds, stall regulation and yaw the rotor out of wind. A third method is to pitch the rotor blade to a smaller angle of attack. This reduces the load on the rotor blade while maintaining power generation. The following work presents a design for a spring based passive mechanical pitch that is limited to only dimensioning a torsion spring and three bearings. The design is aimed at horizontal axis wind turbines with three rotor blades with a rotor diameter up to 20m. An ideal rotor blade is mathematically modeled to produce the forces and torques needed in order to properly dimension the torsion spring and bearings. The design shows that the load of the rotor blade can be reduced and that forces connected to the power can be kept more or less constant for wind speeds 16 to 24 m / s. The results of sizing show that both the torsion spring and bearings can be adapted to different shaft diameters relatively easy. The conclusions are that if dimensioning is done according to the presented results, it is possible, at least in theory, to achieve the desired behaviour. For further development and verification it is recommended to do real tests for the torsion spring to determine its precision due to small angle displacement in the spring. Wind turbine wind power pitch mechanical passive design dimension sizing HAWT axis horizontal axle small scale torsion spring spring loaded torsion BEM blade element mechanical engineering power production over rated wind tip speed ratio Vindkraft vind kraft pitch mekanisk passiv konstruktion dimensionering horisontalaxlad horisontal axlad horisontalaxlat småskala småskalig små skala vridfjäder torsionfjäder fjäderbelastad fjäder vrid torsion BEM Blad Element maskinteknik effektproduktion över märkvind löptal Mechanical Engineering Maskinteknik

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