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1
Hart, M. "Boundary layers on turbine blades." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305764.
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Ireland, Peter. "Internal cooling of turbine blades." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235870.
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Moore, Timothy David. "Automated inspection of turbine blades." Thesis, University of Manchester, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.762419.
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Höyland, Jörg. "Challenges for large wind turbine blades." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13545.
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With global climate problems receiving increasingly international political attention,most European nations are looking for sources of renewable energy. Wind turbines area promising source of renewable energy and their numbers have steadily increasedsince the introduction of the modern wind turbine in the 1970s. The largest units todayhave a rated power of 7 MW and blades ranging up to 62.5 m in length. Offshore windturbines have access to stronger winds with less turbulence, thereby increasing theenergy output of each unit. Offshore turbines will also have a lesser environmentalimpact than onshore turbines. It is believed that the development of offshore wind turbineswill encourage the development of even longer blades. The main spar geometry of a 100 m wind turbine blade was established in order to evaluatehow the use of carbon and glass fiber composites would affect the design. A hybridsolution using UD carbon fiber for global stiffness and ±45° glass fiber plies for bucklingresistance was also developed. The ultimate loads were calculated for blades with pitchcontrol and blades experiencing failure of pitch control during the 1-year and 50-yearextreme gust. The DNV-OS-J102 standard for wind turbines was used in the calculationof safety factors for both loads and material strength criteria. The distribution of ±45°anti-buckling plies by buckling analysis is extremely time consuming and therefore aprogram for automatic ply distribution was developed. The Matlab program interactedwith the FEM software Abaqus, defining input files and extracting results, and proved tobe highly efficient. The results from the FEM analyses were combined with a simple costmodel in order to evaluate both the weight and cost of the different spar solutions. Important weight reductions can be obtained by optimizing the performance of the composite laminate in the spar. Several sub-models of the 100 m spar were created withthe aim of optimizing the spar’s buckling performance. The angle and distribution ofboth the ±45° and UD plies were systematically altered in order to increase the bucklingload. The introduction of ply homogenization and core material in the flange was alsoevaluated and yielded the largest increases of buckling load. The results from the optimizedsub-models were implemented in a 100 m spar and found to decrease theamount of ±45° plies by 50 %. A 6 m scaled main spar of glass fiber composite was produced by resin infusion. Thespar was tested in a 4-point bending test and designed to fail by buckling of the topflange. In order to control the location of the buckling failure, an artificial imperfectionwas introduced in the middle of the top flange during manufacturing. The imperfectionis representative for imperfections found during manufacturing of wind turbine spars. Inaddition to measuring force and global deflection, 25 strain gages were installed tomonitor the spar. Finally, a FEM analysis of the 6 m spar was developed and correlated with the experimentalresults. By implementing the imperfection in the compression spar and the useof non-linear analysis, the strain patterns from the test results were successfully reproduced
5
Pearce, Robert. "Internal cooling for HP turbine blades." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:832038c9-e934-413d-bbb5-336ab4775055.
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Modern gas turbine engines run at extremely high temperatures which require the high pressure turbine blades to be extensively cooled in order to reach life requirements. This must be done using the minimum amount of coolant in order to reduce the negative impacts on the cycle efficiency. In the design process the cooling configuration and stress distribution must be carefully considered before verification of the design is conducted. Improvements to all three of these blade design areas are presented in this thesis which investigates internal cooling systems in the form of ribbed, radial passages and leading edge impingement systems. The effect of rotation on the heat transfer distribution in ribbed radial passages is investigated. An engine representative triple-pass serpentine passage, typical of a gas turbine mid-chord HP blade passage, is simulated using common industrial RANS CFD methodology with the results compared to those from the RHTR, a rotating experimental facility. The simulations are found to perform well under stationary conditions with the rotational cases proving more challenging. Further study and simulations of radial passages are undertaken in order to understand the salient flow and heat transfer features found, namely the inlet velocity profile and rib orientation relative to the mainstream flow. A consistent rib direction gives improved heat transfer characteristics whilst careful design of inlet conditions could give an optimised heat transfer distribution. The effect of rotation on the heat transfer distribution in leading edge impingement systems is investigated. As for the radial passages, RANS CFD simulations are compared and validated against experimental data from a rotating heat transfer rig. The simulations provide accurate average heat transfer levels under stationary and rotating conditions. The full target surface heat transfer in an engine realistic leading edge impingement system is investigated. Experimental data is compared to RANS CFD simulations. Experimental results are in line with previous studies and the simulations provide reasonable heat transfer predictions. A new method of combined thermal and mechanical analysis is presented and validated for a leading edge impingement system. Conjugate CFD simulations are used to provide a metal temperature distribution for a mechanical analysis. The effect of changes to the geometry and temperature profile on stress levels are studied and methods to improve blade stress levels are presented. The thermal FEA model is used to quantify the effect of HTC alterations on different surfaces within a leading edge impingement system, in terms of both temperature and stress distributions. These are then used to provide improved target HTC distributions in order to increase blade life. A new method using Gaussian process regression for thermal matching is presented and validated for a leading edge impingement case. A simplified model is matched to a full conjugate CFD solution to test the method's quality and reliability. It is then applied to two real engine blades and matched to data from thermal paint tests. The matches obtained are very close, well within experimental accuracy levels, and offer consistency and speed improvements over current methodologies.
6
Nowak, William J. "Fatigue stress analysis of turbine blades /." Online version of thesis, 2007. http://hdl.handle.net/1850/5467.
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Pitchford, Corey. "Impedance-Based Structural Health Monitoring of Wind Turbine Blades." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34946.
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Wind power is a fast-growing source of non-polluting, renewable energy with vast potential. However, current wind technology must be improved before the potential of wind power can be fully realized. One of the key components in improving wind turbines is their blades. Blade failure is very costly because blade failure can damage other blades, the wind turbine itself, and possibly other wind turbines. A successful structural health monitoring (SHM) system incorporated into wind turbines could extend blade life and allow for less conservative designs.
Impedance-based SHM is a method which has shown promise on a wide variety of structures. The technique utilizes small piezoceramic (PZT) patches attached to a structure as self-sensing actuators to both excite the structure with high-frequency excitations, and monitor any changes in structural mechanical impedance. By monitoring the electrical impedance of the PZT, assessments can be made about the integrity of the mechanical structure. Recent advances in hardware systems with onboard computing, including actuation and sensing, computational algorithms, and wireless telemetry, have improved the accessibility of the impedance method for in-field measurements.
The feasibility of implementing impedance-based SHM on wind turbine blades is investigated in this work. Experimentation was performed to determine the capability of the method to detect damage on blades. First, tests were run to detect both indirect and actual forms of damage on a section of an actual wind turbine blade provided by Sandia National Laboratories. Additional tests were run on the same blade section using a high-frequency response function method of SHM for comparison. Finally, based on the results of the initial testing, the impedance method was utilized in an attempt to detect damage during a fatigue test of an experimental wind turbine blade at the National Renewable Energy Laboratoryâ s National Wind Technology Center.Master of Science
8
Martinez-Tamayo, Federico. "The impact of evaporatively cooled turbine blades on gas turbine performance." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/47385.
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Valero, Ricart Omar Ruben. "Multidisciplinary concurrent optimization of gas turbine blades." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:b89d8f80-9134-4856-8223-5f55967c0bde.
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This thesis presents the study and development of optimization methods that can perform concurrent aerodynamic-aeroelastic blade optimization in a multi-bladerow environment, and for realistic turbomachinery blade geometries. The Nonlinear Harmonic Phase Solution Method has been chosen as the flow solution method of this work because of its capability to calculate the aeroelasticity features of interest (blade flutter) and the main flow aerodynamic performance in steady flow timescales. The first optimization method that is shown is a more generic non-gradient method with an improved version of a quadratic Response Surface Model. The new Re-Scaled Response Surface Model has shown marked convergence and performance improvements against traditional surrogate models. However, the computational cost of this method for cases with a large number of design variables limits its real applications. A gradient-based adjoint method is presented next as a cost-independent alternative that can accomplish efficient multi-bladerow optimization for a large number of variables within the current levels of computational power. The continuous adjoint system has been developed based on the same methodology as the flow solution method and it shows a more consistent relation between the flow field and its corresponding adjoint field, in agreement with the "anti-physics" information path. An adjoint interface treatment has been developed as an extension of the flow harmonic interface treatment. This unique treatment allows capture of the damping sensitivities of the vibrating blade to shape changes in adjacent rows. The application of this method to the design optimization of compressor and turbine stages has shown its capability to perform efficient multicomponent and multi-disciplinary design optimization of turbomachinery blades.
10
Dong, Yuan. "Boundary layers on compressor blades." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278266.
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Hettasch, Georg. "Optimization of fir-tree-type turbine blade roots using photoelasticity." Thesis, Stellenbosch : University of Stellenbosch, 1992. http://hdl.handle.net/10019.1/993.
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Thesis (MEng.)-- University of Stellenbosch, 1992.
140 leaves on single pages, preliminary pages i-xi and numbered pages 1-113. Includes bibliography. Digitized at 600 dpi grayscale to pdf format (OCR),using an Bizhub 250 Konica Minolta Scanner and at 300 dpi grayscale to pdf format (OCR), using a Hp Scanjet 8250 Scanner.Thesis (MEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 1992
ENGLISH ABSTRACT: The large variety of turbo-machinery blade root geometries in use in industry prompted the question if a optimum geometry could be found. An optimum blade root was defined as a root with a practical geometry which, when loaded, returns the minimum fillet stress concentration factor. A literature survey on the subject provided guidelines but very little real data to work from. An initial optimization was carried out using a formula developed by Heywood to determine loaded projection fillet stresses. The method was found to produce unsatisfactory results, prompting a photoelastic investigation. This experimental optimization was conducted in two stages. A single tang defined load stage and a single tang in-rotor stage which modeled the practical situation. The defined load stage was undertaken in three phases. The first phase was a preliminary investigation, the second phase was a parameter optimization and the third phase was a geometric optimization based on a material utilization optimization. This material optimization approach produced good results. From these experiments a practical optimum geometry was defined. A mathematical model which predicts the fillet stress concentration factor for a given root geometry is presented. The effect of expanding the single tang optimum to a three tang root was examined.
AFRIKAANSE OPSOMMING: Die groot verskeidenheid lemwortelgeometrieë wat in turbomasjiene gebruik word het die vraag na 'n optimum geometrie laat ontstaan. Vir hierdie ondersoek is 'n optimum geometrie gedefineer as 'n praktiese geometrie wat, as dit belas word, die mimimum vloeistukspanningskonsentrasiefaktor laat ontstaan. 'n Literatuur studie het riglyne aan die navorsing gegee maar het wynig spesifieke en bruikbare data opgelewer. Die eerste optimering is met die Heywood formule, wat vloeistukspannings in belaste projeksies bepaal, aangepak. Die metode het nie bevredigende resultate opgelewer nie. 'n Fotoelastiese ondersoek het die basis vir verdere optimeering gevorm. Hierdie eksperimentele optimering is in twee stappe onderneem. 'n Enkelhaak gedefineerde lasgedeelte en 'n enkelhaak in-rotor gedeelte het die praktiese situasie gemodeleer. Die gedefineerde lasgedeelte is in drie fases opgedeel. Die eerste fase was n voorlopige ondersoek. Die tweede fase was 'n parameter optimering. 'n Geometrie optimering gebasseer op 'n materiaal benuttings minimering het die derde fase uitgemaak. Die materiaal optimerings benadering het goeie resultate opgelewer. Vanuit hierdie eksperimente is 'n optimum praktiese geometrie bepaal. 'n Wiskundige model is ontwikkel, wat die vloeistukspanningskonsentrasiefaktor vir 'n gegewe wortelgeometrie voorspel. Die resultaat van 'n geometriese uitbreiding van die enkelhaaklemwortel na 'n driehaaklemwortel op die spanningsverdeling is ondersoek.
12
Esu, Ozak O. "Vibration-based condition monitoring of wind turbine blades." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21679.
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Significant advances in wind turbine technology have increased the need for maintenance through condition monitoring. Indeed condition monitoring techniques exist and are deployed on wind turbines across Europe and America but are limited in scope. The sensors and monitoring devices used can be very expensive to deploy, further increasing costs within the wind industry. The work outlined in this thesis primarily investigates potential low-cost alternatives in the laboratory environment using vibration-based and modal testing techniques that could be used to monitor the condition of wind turbine blades. The main contributions of this thesis are: (1) the review of vibration-based condition monitoring for changing natural frequency identification; (2) the application of low-cost piezoelectric sounders with proof mass for sensing and measuring vibrations which provide information on structural health; (3) the application of low-cost miniature Micro-Electro-Mechanical Systems (MEMS) accelerometers for detecting and measuring defects in micro wind turbine blades in laboratory experiments; (4) development of an in-service calibration technique for arbitrarily positioned MEMS accelerometers on a medium-sized wind turbine blade. This allowed for easier aligning of coordinate systems and setting the accelerometer calibration values using samples taken over a period of time; (5) laboratory validation of low-cost modal analysis techniques on a medium-sized wind turbine blade; (6) mimicked ice-loading and laboratory measurement of vibration characteristics using MEMS accelerometers on a real wind turbine blade and (7) conceptualisation and systems design of a novel embedded monitoring system that can be installed at manufacture, is self-powered, has signal processing capability and can operate remotely. By applying the conclusions of this work, which demonstrates that low-cost consumer electronics specifically MEMS accelerometers can measure the vibration characteristics of wind turbine blades, the implementation and deployment of these devices can contribute towards reducing the rising costs of condition monitoring within the wind industry.
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Husain, Al-taie Arkan Khilkhal. "Experimental Study of Radiation From Coated Turbine blades." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/4553.
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The specific power (or specific thrust) of modern gas
turbines is much influenced by the gas temperature at turbine
inlet. Even with the use of the best superalloy available and the
most advanced cooling configurations, there are competitive
pressures to operate engines at even higher gas temperatures.
Ceramic coatings operate as thermal barriers and can allow
the gas temperature to be increased by 50 to 220 K over the
operating gas temperature for an uncoated turbine .
It is important that the surface temperature of the blade
be determined as accurately as possible. Large uncertainties as
to the surface temperature require significant margins for safe
operation .
Blade surface temperatures can be determined with an
accuracy of 10 K using radiation pyrometry and about"30 to 40 K
by calculating the blade temperature based on---gas temperature
measurement of the exhaust gas plane. This'- makes pyrometry an
attractive option for advanced high temperature gas turbines .
However, there is little experience in measuring surface
temperatures of blades coated with ceramic coatings. There is
evidence that the. radiation signal picked up by the pyrometer
will not only depend on the surface temperature but also on a
number of optical properties of the coating. Important among
these are the emissivity of the coating and whether the coating
is translucent. Parameters affecting this are the coating
material, coating surface finish, coating thickness and whether
or not a bond coat is used .
This work explores these variables in a rig that simulates
the conditions within a turbine stage of a gas turbine engine. In
which six thermal barrier coating systems were tested. These
systems are of current interest to gas turbine manufacturers and
users. They include the latest advances in coating technology.
Four stabilized zirconia systems and two alumina based systems
were tested.
It was found experimentally that the surface emissivity of
these coating systems was invariant over the range 873 to 1023 K
surface temperature. It was found that the use of different
stabilizers did not affect the surface spectral emissivity.
In further experiments six turbine wheels were coated with
these systems and tested at turbine entry temperatures of 973,
1073, and 1173 K. It was found that the blade surface temperature
was function of the coating material, coating thickness and
turbine entry temperature. The blade surface temperature was also
function of the blade height being maximum at the blade tip and
minimum at the blade root .
It was found that the C-YPSZ was better insulator than the
rest of the systems. Whilst the blades coated with zirconia
based systems suffered minor loss near the edges, the two alumina
based systems were lost from more than a blade during the test.
This coating loss was picked up by. the pyrometer .
Analysis shows that the measured blade surface temperature
was within 10 K of that calculated. The use of 0.3 mm of C-YPSZ
on air cooled turbine blades caused 250 K surface temperature
increase and 270 K metal temperature decrease for turbine entry
temperature of 1673 K. The metal temperature reduction was as
high as 310 K for coating thickness of 0.5 mm.
14
Nichols, James Franklin. "Two-dimensional analysis of turbine blades and nozzles." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17673.
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Hultman, Hugo. "Validation of Forced Response Methods for Turbine Blades." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144.
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Khan, Sameer. "Probalistic Stress Rupture Life Analysis of Turbine Blades." Honors in the Major Thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/970.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Mechanical Engineering
17
Moffatt, Stuart. "Forced response prediction for industrial gas turbine blades." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2692/.
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A highly efficient aeromechanical forced response system is developed for predicting resonant forced vibration of turbomachinery blades with the capabilities of fully 3-D non-linear unsteady aerodynamics, 3-D finite element modal analysis and blade root friction modelling. The complete analysis is performed in the frequency domain using the non linear harmonic method, giving reliable predictions in a fast turnaround time. A robust CFD-FE mesh interface has been produced to cope with differences in mesh geometries, and high mode shape gradients. A new energy method is presented, offering an alternative to the modal equation, providing forced response solutions using arbitrary mode shape scales. The system is demonstrated with detailed a study of the NASA Rotor 67 aero engine fan rotor. Validation of the forced response system is carried out by comparing predicted resonant responses with test data for a 3-stage transonic Siemens industrial compressor. Two fully-coupled forced response methods were developed to simultaneously solve the flow and structural equations within the fluid solver. A novel closed-loop resonance tracking scheme was implemented to overcome the resonant frequency shift in the coupled solutions caused by an added mass effect. An investigation into flow-structure coupling effects shows that the decoupled method can accurately predict resonant vibration with a single solution at the blade natural frequency. Blade root-slot friction damping is predicted using a modal frequency-domain approach by applying linearised contact properties to a finite element model, deriving contact Droperties from an advanced semi-analytical microslip model. An assessment of Coulomb and microslip approaches shows that only the microslip model is suitable for predicting root friction damping.
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Al-Ajmi, Rashed. "Evaluation of vortex cooling systems for turbine blades." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364475.
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Cardew-Hall, Michael John. "Modelling and integrated inspection of cast turbine blades." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46985.
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Roberts, Quentin David Hurt. "The trailing edge loss of subsonic turbine blades." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624758.
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Greaves, Peter Robert. "Fatigue analysis and testing of wind turbine blades." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7303/.
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This thesis focuses on fatigue analysis and testing of large, multi MW wind turbine blades. The blades are one of the most expensive components of a wind turbine, and their mass has cost implications for the hub, nacelle, tower and foundations of the turbine so it is important that they are not unnecessarily strong. Fatigue is often an important design driver, but fatigue of composites is poorly understood and so large safety factors are often applied to the loads. This has implications for the weight of the blade. Full scale fatigue testing of blades is required by the design standards, and provides manufacturers with confidence that the blade will be able to survive its service life. This testing is usually performed by resonating the blade in the flapwise and edgewise directions separately, but in service these two loads occur at the same time. A fatigue testing method developed at Narec (the National Renewable Energy Centre) in the UK in which the flapwise and edgewise directions are excited simultaneously has been evaluated by comparing the Palmgren-Miner damage sum around the blade cross section after testing with the damage distribution caused by the service life. A method to obtain the resonant test configuration that will result in the optimum mode shapes for the flapwise and edgewise directions was then developed, and simulation software was designed to allow the blade test to be simulated so that realistic comparisons between the damage distributions after different test types could be obtained. During the course of this work the shortcomings with conventional fatigue analysis methods became apparent, and a novel method of fatigue analysis based on multi-continuum theory and the kinetic theory of fracture was developed. This method was benchmarked using physical test data from the OPTIDAT database and was applied to the analysis of a complete blade. A full scale fatigue test method based on this new analysis approach is also discussed.
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Yang, Jingting. "Carbon Nanotubes Reinforced Composites for Wind Turbine Blades." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1315410407.
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De, Cecco Stefano F. (Stefano Fabio) Carleton University Dissertation Engineering Mechanical and Aerospace. "The aerodynamics of turbine blades with tip damage." Ottawa, 1995.
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Liu, Pu. "Reducing the environmental impact of wind turbine blades." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270347.
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Wind energy, one of the most promising sources of clean energy, has developed rapidly over the last two decades. Wind turbines (WT) are arguably clean during operation, offering minimal pollution and zero CO2 emissions, but significant amounts of energy are used and CO2 emitted during their manufacture, and, furthermore, the turbines are environmentally problematic at end-of-life (EoL), especially the blades. WT blades are mainly made with composite materials comprising thermosetting resin and glass fibre. They are lightweight and strong but problematic to recycle. Large volumes of waste will be generated when these WT blades are decommissioned and environmental concerns have been raised. The main aim of this study is to understand the environmental impact of wind turbine blades and to find solutions to reduce it. A quantitative method is adopted, first evaluating the WT blade waste inventory then calculating its environmental impact, and finally analysing the differences between all possible EoL options in terms of environmental and financial performance. The results firstly identify the global wind turbine blade waste inventory with detailed generation time and location which could help policy makers to gain an understanding of the size and severity of this problem. Secondly, the outputs indicate where most impact is generated and identify what to prioritise to reduce waste and reduce environmental impact, which is of value to blade manufacturers and other stakeholders. Moreover, this work highlights previous incorrect assumptions and provides findings to build on for future work. Thirdly, ‘optimal’ EoL options for the WT blade waste have been characterized: the current ‘optimal’ EoL option is life extension; mechanical recycling is the current ‘optimal’ recycling option; chemical recycling will be the ‘optimal’ option for the future. Future research is suggested as aiming to improve the performance of recycled fibre or to reduce the energy consumption of recycling processes.
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Tapanlis, Orpheas. "Turbine casing impingement cooling systems." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711623.
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Duran, Serhat. "Computer-aided Design Of Horizontal-axis Wind Turbine Blades." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605790/index.pdf.
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Designing horizontal-axis wind turbine (HAWT) blades to achieve satisfactory
levels of performance starts with knowledge of the aerodynamic forces acting on
the blades. In this thesis, HAWT blade design is studied from the aspect of
aerodynamic view and the basic principles of the aerodynamic behaviors of
HAWTs are investigated.
Blade-element momentum theory (BEM) known as also strip theory, which is
the current mainstay of aerodynamic design and analysis of HAWT blades, is used
for HAWT blade design in this thesis.
Firstly, blade design procedure for an optimum rotor according to BEM theory
is performed. Then designed blade shape is modified such that modified blade will
be lightly loaded regarding the highly loaded of the designed blade and power
prediction of modified blade is analyzed. When the designed blade shape is
modified, it is seen that the power extracted from the wind is reduced about 10%
and the length of modified blade is increased about 5% for the same required
power.
BLADESIGN which is a user-interface computer program for HAWT blade
design is written. It gives blade geometry parameters (chord-length and twist
distributions) and design conditions (design tip-speed ratio, design power
coefficient and rotor diameter) for the following inputspower required from a turbine, number of blades, design wind velocity and blade profile type (airfoil type). The program can be used by anyone who may not be intimately concerned with the concepts of blade design procedure and the results taken from the program can be used for further studies.
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Fletcher, Daniel Alden. "Internal cooling of turbine blades : the matrix cooling method." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360259.
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Abdulqadir, Sherwan Ahmed. "Turbulence modelling for horizontal axis wind turbine rotor blades." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/turbulence-modeling-for-horizontal-axis-wind-turbine-rotor-blades(2536b213-3a0c-4977-ac39-916a9fce98d2).html.
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This Thesis aims to assess the reliability of turbulence models in predicting the flow fields around the horizontal axis wind turbine (HAWT) rotor blades and also to improve our understanding of the aerodynamics of the flow field around the blades. The simulations are validated against data from the NREL/NASA Phase VI wind turbine experiments. The simulations encompass the use of fourteen turbulence models including low-and high-Reynolds-number, linear and non-linear eddy-viscosity models and Reynolds stress models. The numerical procedure is based on the finite-volume discretization of the 3D unsteady Reynolds-Averaged Navier-Stokes equations in an inertial reference frame with the sliding mesh technique to follow the motion of the rotor blades. Comparisons of power coefficient, normalised thrust, local surface pressure coefficients (CP) and the radial variation of the section average of normal force coefficients with published experimental data over a range of tip-speed ratios, lead to the identification of the turbulence models that can reliably reproduce the values of the key performance indicators. The main contributions of this study are in establishing which RANS models can produce quantitatively reliable simulations of wind turbine flows and in presenting the flow evolution over a range of operating conditions. At low (relative to the blade tip speed) wind speeds the flow over the blade surfaces remains attached and all RANS models return the correct values of key performance coefficients. At higher wind speeds there is circumferential flow separation over the downwind surface of the blade, which eventually spreads over the entire surface, Moreover, within the separation bubble the centrifugal force pumps the flow outwards, which at the higher wind speeds suppresses the formation of the classical tip vortices. More refined RANS models which do not rely on the linear effective viscosity approximation generally lead to more reliable predictions over this range of higher wind speeds. In particular the Gibson-Launder version of the Reynolds stress transport model and the high-Re versions of the Lien et al non-linear k-ε produce consistently reliable simulations over the entire range of wind speeds. By contrast some popular linear effective viscosity models, like the SST (k-ω) and the v^2-f, perform the poorest over this complex flow range. Finally all RANS models are also able to predict the dominant (lowest) frequency of the pressure fluctuations and the non-linear effective viscosity models, the Launder and Shima version of RSM and the SST are also able to return some of the higher frequencies measured.
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Steptoe, William James. "Integral boundary layer heat transfer prediction on turbine blades." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/42188.
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Breslavsky, D. V., O. K. Morachkovsky, and N. V. Shyriaieva. "Nonlinear vibrations and long-term strength of turbine blades." Thesis, National Technical University "Kharkov Polytechnic Institute", 2010. http://repository.kpi.kharkov.ua/handle/KhPI-Press/41290.
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The method of a durability estimation of rotating turbomachinery blades at forced flexural-flexural-torsional vibrations is offered. The method is based on the methods of Continuous Damage Mechanics and the accurate strain analysis of the pre-twisted blades at the nonlinear vibrations with moderate displacements. The method to solve the strain analysis problem and turbomachinery blades high-cycle fatigue damage estimation as a result of nonlinear vibrations is presented.
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Wang, Lin. "Nonlinear aeroelastic modelling of large wind turbine composite blades." Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/12129/.
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The increasing size and flexibility of large wind turbine blades introduces significant aeroelastic effects, which are caused by fluid-structure interaction. These effects might result in aeroelastic instability problems, such as edgewise instability and flutter, which can be devastating to the blades and the wind turbine. Therefore, developing a reliable and efficient aeroelastic model to investigate the aeroelasticity characterisation of large wind turbine blades is crucial in the development of large wind turbines. There are several aeroelastic models available today for wind turbine blades. Almost all of them are linear models based on assumption of small blade deflections, and do not take account of large deflection effects on modelling responses and loads. However, with the increasing size and flexibility of large wind turbine blades, this assumption is not valid anymore because the blades often experience large deflections, which introduce significant geometric nonlinearities. Additionally, existing cross-sectional analysis models, which are used to extract cross-sectional properties of wind turbine composite blades for aeroelastic modelling, are either time-consuming or inaccurate. This thesis aims to provide a reliable and efficient aeroelastic modelling of large wind turbine blades through developing 1) a cross-sectional model, which can extract cross-sectional properties of wind turbine composite blades in a reliable and efficient way; and 2) a nonlinear aeroelastic model, which is capable of handling large blade deflections. In this thesis, a cross-sectional analysis model for calculating the cross-sectional properties of composite blades has been developed by incorporating classical lamination theory (CLT) with extended Bredt-Batho shear flow theory (EBSFT). The model considers the shear web effects and warping effects of composite blades and thus greatly improves the accuracy of torsional stiffness calculation. It also avoids complicated post-processing of force-displacement data from computationally expensive 3D finite-element analysis (FEA) and thus considerably improves the computational efficiency. A MATLAB program was developed to verify the accuracy and efficiency of the cross-sectional analysis model, and a series of benchmark calculation tests were undertaken. The results show that good agreement is achieved comparing with the data from experiment and FEA, and improved accuracy of torsional stiffness calculation due to consideration of the shear web effects is observed comparing with an existing cross-sectional analysis code PreComp. Additionally, a nonlinear aeroelastic model for large wind turbine blades has been developed by combining 1) a blade structural model, which is based on a mixed-form formulation of geometrically exact beam theory (GEBT), taking account of geometric nonlinearities; and 2) a blade load model, which takes account of gravity loads, centrifugal loads and aerodynamic loads. The aerodynamic loads are calculated based on combining the blade element momentum (BEM) model and the Beddoes-Leishman (BL) dynamic stall model. The nonlinear aeroelastic model takes account of large blade deflections and thus greatly improves the accuracy of aeroelastic analysis of wind turbine blades. The nonlinear aeroelastic model was implemented in COMSOL Multiphysics, and a series of benchmark calculation tests were undertaken. The results show that good agreement is achieved when compared with experimental data, and its capability of handling large deflections is demonstrated. After the validation, the nonlinear aeroelastic model was applied to the aeroelastic simulation of the parked WindPACT 1.5MW wind turbine blade and to the stability analysis of the blade. Reduced flapwise deflection from the nonlinear aeroelastic model is observed compared to the linear aeroelastic code FAST. The calculated damping ratio of the edgewise mode is much lower than the calculated damping ratio of the flapwise mode, indicating that edgewise instability is more likely to occur than flapwise instability. It is also demonstrated that improper rotor rotational speeds can result in edgewise instability.
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Amrud, Kim K. (Kim Khemraj) Carleton University Dissertation Engineering Mechanical. "Tip leakage in a planar cascade of turbine blades." Ottawa, 1985.
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Isaacs, David Paul Carleton University Dissertation Engineering Mechanical and Aerospace. "The aerodynamics of turbine blades with trailing edge damage." Ottawa, 1994.
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Schweitzer, Luiz Guilherme de Souza. "Laser cladding for epitaxial nickel base superalloys turbine blades." reponame:Repositório Institucional da UFSC, 2014. https://repositorio.ufsc.br/xmlui/handle/123456789/129625.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2014.Made available in DSpace on 2015-02-05T21:18:49Z (GMT). No. of bitstreams: 1 328410.pdf: 5168954 bytes, checksum: a55c798d806d29cc35e63be5e11587fe (MD5) Previous issue date: 2014
A prosperidade e larga utilização da aviação como meio de transporte civil, nacional e internacional, exige seriedade no condicionamento das aeronaves. A manutenção preventiva é um ponto fundamental para que sejam evitados desastres aéreos. A verificação dos motores é indispensável e, devido ao alto valor agregado, corresponde aos custos mais elevados de recondicionamento. As turbinas, por estarem sujeitas a elevada temperatura e pressão, geralmente apresentam o maior número de componentes danificados. Por esta razão há o interesse no desenvolvimento de técnicas para o reparo eficaz de pás de turbina. Erosão e formação de trincas são danos comuns que necessitam de recondicionamento. A recente aplicação de pás monocristalinas (SX), no lugar de policristalinas, apresenta vantagens por suportar melhor as elevadas temperaturas e com isto aumentar a eficiência dos motores [1, 2]. No entanto, não há um método reconhecido para o reparo das pás monocristalinas. A proposta deste trabalho consiste na aplicação de laser cladding com injeção de pó, devido a características como o tratamento localizado e controle de material fornecido. Este processo é apropriado devido principalmente à flexibilidade e baixo nível de diluição. Foram desenvolvidos dois métodos para promover o reparo de tais defeitos. Um método consiste na remoção completa de camadas de material onde estão situadas as trincas. O outro prevê a remoção de apenas um pequeno volume da estrutura afetada, através de um entalhe que retira o volume danificado. Com isto, a perda de material, o tempo de trabalho e os custos de manutenção podem ser drasticamente reduzidos. O entalhe tem de ser soldável e também permitir a solidificação de material no mesmo plano orientado como a microestrutura inicial. Para isto, um gradiente de temperatura deve ser introduzido a fim de orientar o crescimento de grão. No entanto, existem desafios para alcançar uma estrutura de cristal único sem rachaduras e poros, devido à distribuição de energia no interior do entalhe. Progressos atingidos e novos desafios são apresentados neste trabalho.
Abstract : The prosperity and widespread use of aviation as a civil national and international transport requires seriousness in the aircraft conditioning. Preventive maintenance is the key to avoid disasters. For that, is essential the check of engines, which corresponds to the higher reconditioning costs. The turbines, due to elevated temperature and pressure, usually have the highest number of damaged parts. For this reason, there is an interest in developing techniques for the efficient repair of turbine blades. Erosion and crack formation are common damages that require refurbishing. The recent application of single crystal (SX) turbine blades, instead of polycrystalline, present better withstands in high temperatures and thus increases the efficiency of the engines [1, 2]. However, a recognized method for the repair of SX turbine blades has to be developed. The proposal of this work involves the application of laser cladding with powder injection, due to characteristics such as localized treatment and control of the material injected. This process is particularly suitable due to flexibility and low dilution levels. There are two techniques developed to promote the repair of such defects. One way is by the removal of complete layers in which the cracks are located. Another possibility is to remove just a small volume of the affected microstructure. Therewith the loss of material and working time may be drastically reduced as well as the maintenance costs. The notch must be weldable and permit the material solidification in the same oriented plane as the original structure. For that, a temperature gradient has to be introduced in order to guide the grain growth. However, there are challenges to achieve a SX structure without cracks and pores due to energy distribution inside the notch. Current achievements and further challenges are presented in this work.
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Cardamone, Pasquale. "Aerodynamic optimisation of highly loaded turbine cascade blades for heavy duty gas turbine applications." Düsseldorf VDI-Verl, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:706-1493.
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Kuk, Victor H. M. "An investigation of particle trajectories and particle impact points in turbine film cooling hole system." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294380.
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Kilic, Muhsin. "Flow between contra-rotating discs." Thesis, University of Bath, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357401.
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Totemeier, Terry Craig. "Fatigue of an aluminium coated single crystal nickel-base Superalloy." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337308.
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Ali, Muhammad Anttho. "In-cloud ice accretion modeling on wind turbine blades using an extended Messinger model." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53870.
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Wind turbines often operate under cold weather conditions where icing may occur. Icing causes the blade sections to stall prematurely reducing the power production at a given wind speed. The unsteady aerodynamic loads associated with icing can accelerate blade structural fatigue and creates safety concerns.
In this work, the combined blade element-momentum theory is used to compute the air loads on the baseline rotor blades, prior to icing. At each blade section, a Lagrangian particle trajectory model is used to model the water droplet trajectories and their impact on the blade surface. An extended Messinger model is next used to solve the conservation of mass, momentum, and energy equations in the boundary layer over the surface, and to determine ice accretion rate. Finally, the aerodynamic characteristics of the iced blade sections are estimated using XFOIL, which initiate the next iteration step for the computation of air loads via combined blade element theory. The procedure repeats until a desired exposure time is achieved. The performance degradation is then predicted, based on the aerodynamic characteristics of the final iced blades.
The 2-D ice shapes obtained are compared against experimental data at several representative atmospheric conditions with acceptable agreement. The performance of a generic experimental wind turbine rotor exposed to icing climate is simulated to obtain the power loss and identify the critical locations on the blade. The results suggest the outboard of the blade is more prone to ice accumulation causing considerable loss of lift at these sections. Also, the blades operating at a higher pitch are expected to accumulate more ice. The loss in power ranges from 10% to 50% of the rated power for different pitch settings under the same operating conditions.
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Richards, Phillip W. "Design strategies for rotorcraft blades and HALE aircraft wings applied to damage tolerant wind turbine blade design." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53488.
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Offshore wind power production is an attractive clean energy option, but the difficulty of access can lead to expensive and rare opportunities for maintenance. Smart loads management (controls) are investigated for their potential to increase the fatigue life of damaged offshore wind turbine rotor blades. This study will consider two commonly encountered damage types for wind turbine blades, the trailing edge disbond (bond line failure) and shear web disbond, and show how 3D finite element modeling can be used to quantify the effect of operations and control strategies designed to extend the fatigue life of damaged blades.
Modern wind turbine blades are advanced composite structures, and blade optimization problems can be complex with many structural design variables and a wide variety of aeroelastic design requirements. The multi-level design method is an aeroelastic structural design technique for beam-like structures in which the general design problem is divided into a 1D beam optimization and a 2D section optimization. As a demonstration of aeroelastic design, the multi-level design method is demonstrated for the internal structural design of a modern composite rotor blade. Aeroelastic design involves optimization of system geometry features as well as internal features, and this is demonstrated in the design of a flying wing aircraft. Control methods such as feedback control also have the capability alleviate aeroelastic design requirements and this is also demonstrated in the flying wing aircraft example.
In the case of damaged wind turbine blades, load mitigation control strategies have the potential to mitigate the effects of damage, and allow partial operation to avoid shutdown. The load mitigation strategies will be demonstrated for a representative state-of-the-art wind turbine (126m rotor diameter). An economic incentive will be provided for the proposed operations strategies, in terms of weighing the cost and risk of implementation against the benefits of increased revenue due to operation of damaged turbines. The industry trend in wind turbine design is moving towards very large blades, causing the basic design criterion to change as aeroelastic effects become more important. An ongoing 100 m blade (205 m rotor diameter) design effort intends to investigate these design challenges. As a part of that effort, this thesis will investigate damage tolerant design strategies to ensure next-generation blades are more reliable.
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Gao, Zhihong. "Experimental investigation of film cooling effectiveness on gas turbine blades." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1557.
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Holst, Martin Aasved. "CFD Analysis of Wave Induced Loads on Tidal Turbine Blades." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18456.
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Abstract— The object of this paper is to investigate the influence of wave-current interaction on a tidal turbine. An experiment at Norwegian Marine Technology Research Institute (MARINTEK) has been carried out, and a CFD analysis has been performed in order to enhance the understanding of the wave induced loads on the tidal turbine. These loads are known to be the governing forces and it is therefore of great importance to predict them accurately. The CFD results are found to be trustworthy with calculated values close to experimental data. In addition to the wave-induced forces, the wake characteristics and wave influence on the wake are investigated. Results from Blade Element Moment Theory (BEM) are also compared to validate the accuracy of this method. CFD is a powerful tool if used properly, but it is computationally expensive, especially when dealing with complex geometry like a tidal turbine. A high performance computer (HPC) has been used to carry out the transient CFD wave-current simulations in order to obtain reliable results within reasonable time.
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Lewke, Bastian [Verfasser]. "Lightning Protection of Wind Turbine Blades and Hub / Bastian Lewke." Aachen : Shaker, 2010. http://d-nb.info/1122546319/34.
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Brooksbank, Edward J. "A numerical investigation of time resolved flows around turbine blades." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/4463.
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The complex nature of turbomachinery flows and the scale of associated flow phenomena such as shock waves and vortex shedding, apply constraints to the methods by which the flow can be analysed experimentally. Computational techniques have quite successfully been applied to the flow around turbine blades, but the transient and periodic phenomena observed in experimental studies have not been fully investigated. In this work an original working computational code is presented for time-resolved flows around turbine cascades. The code has been verified using test cases relevant to transonic flow. Some of the problems associated with computational techniques have been highlighted; these include the large number of schemes that are available, each with its own advantages and disadvantages. The code has been applied to a geometry representing highly loaded turbine blading currently under study at the National Research Council of Canada; this was also used extensively in previous computational and experimental investigations. The blading chosen has a relatively thick trailing edge, necessitated by cooling considerations. A distribution of the flow properties on the surface of the blade has been determined, from which an equivalent water table model has been designed based on the principle of the hydraulic analogy. The water table model thus generated represents a further method for experimentally investigating flow phenomena without the complexity of analysing very high frequency oscillations in situ. The timeresolved flow field has been computed showing unsteady phenomena. The unsteady phenomena have been shown to compare favourably with the unsteady features observed in preliminary experimental results. In the process, energy separation has been predicted to occur not only in the coupled wake region, but also for the first time within Kelvin-Helmholtz instabilities present in the trailing edge shear layers.
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Rahnama, Behzad. "Reduction of Environmental Impact Effect of Disposing Wind Turbine Blades." Thesis, Högskolan på Gotland, Institutionen för kultur, energi och miljö, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-217000.
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Wind power industry is expected to be one of the fastest growing renewable energy sources inthe world. The growth specially focuses on growing industries and markets, because ofeconomical condition for wind power development besides political decisions.According to growth of wind turbine industries, wind turbine blades are growing fast in both sizeand number. The problem that now arises is how to deal with the blades at the end of their lifecycle. This Master Thesis describes existing methods of disposing wind turbine blades.Moreover, the thesis considers alternative method of disposing blades, based on environmentaland safety consideration.
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Deilmann, Christian. "Passive aeroelastic tailoring of wind turbine blades : a numerical analysis." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55266.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 75-76).
This research aims to have an impact towards a sustainable energy supply. In wind power generation losses occur at tip speed ratios which the rotor was not designed for. Since the ideal blade shape changes nonlinearly with rising wind speeds currently used pitch control mechanisms can only approach the ideal blade deformation. However aeroelastic effects, which cause additional deformation, are almost unavoidable in flexible blade design and it is desirable to tailor these effects to our advantage by a controlled use of orthotropic material properties and a smart design of the blade structure. The idea of systematic aeroelastic tailoring is not new but research has not yet solved the design challenge partly due to the lack of accurate simulation tools. Passively adaptive rotor blades would enable systematic aeroelastic tailoring and have the potential to reduce the cost of energy by around 6% [1]. Within this thesis a design procedure for passively adaptive rotor blades has been developed. It consists of an aerodynamic simulation and optimization code (based on Blade Element Momentum Theory), a structural simulation (based on Finite Element Analysis) and a fluid structure interaction correction loop (based on CFD and FEM). Using the developed design code passively adaptive rotor blades have been designed for the NREL phase VI test turbine. The results show that an ideal passively adaptive blade could improve the efficiency of the test turbine by 3% to 6%.
(cont.) The proposed rotor designs can only approach these improvements. However they do improve the efficiency and since the design only requires a precisely calculated stacking of composite material layers, the cost for manufacturing will not increase significantly. This work is a contribution to solve the design challenge of passively adaptive rotor blades and further research may be based on it.
by Christian Deilmann.
S.M.
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Afzal, Mohammad. "Numerical modelling and analysis of friction contact for turbine blades." Licentiate thesis, KTH, MWL Strukturakustik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177920.
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High cycle fatigue failure of turbine and compressor blades due to resonance in the operating frequency range is one of the main problems in the design of gas turbine engines. To suppress excessive vibrations in the blades and prevent high cycle fatigue, dry friction dampers are used by the engine manufacturers. However, due to the nonlinear nature of friction contact, analysis of such systems becomes complicated. This work focuses on the numerical modelling of friction contact and a 3D friction contact model is developed. To reduce the computation time in the Newton-iteration steps, a method to compute the Jacobian matrix in parallel to the contact forces is proposed. The developed numerical scheme is successfully applied on turbine blades with shroud contact having an arbitrary 3D relative displacement. The equations of motion are formulated in the frequency domain using the multiharmonic balance method to accurately capture the nonlinear contact forces and displacements. Moreover, the equations of motion of the full turbine blade model are reduced to a single sector model by exploiting the concept of the cyclic symmetry boundary condition for a periodic structure. The developed 3D coupled numerical contact model is compared with a 3D contact model having uncoupled tangential motion and drawback of the uncoupled contact model is discussed. Furthermore, presence of higher harmonics in the nonlinear contact forces is analyzed and their effect on the excitation of the different harmonic indices (nodal diameters) of the bladed disk are systematically presented. Moreover, due to the quasi-analytical computation of the Jacobian matrix, the developed scheme is proved to be effective in solving the equations of motion and significant reduction in time is achieved without loss of accuracy.QC 20151130
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Bürkner, Falko [Verfasser]. "Biaxial Dynamic Fatigue Tests of Wind Turbine Blades / Falko Bürkner." Hannover : Gottfried Wilhelm Leibniz Universität, 2020. http://d-nb.info/1233426494/34.
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Zhang, Luying. "Rotating instability on steam turbine blades at part-load conditions." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:cf8ecad1-0fd2-49b7-8e28-6d00c62c173e.
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A computational study aimed at improving the understanding of rotating instability in the LP steam turbine last stage working under low flow rate conditions is described in this thesis. A numerical simulation framework has been developed to investigate into the instability flow field. Two LP model turbine stages are studied under various flow rate conditions. By using the 2D simulations as reference and comparing the results to those of the 3D simulations, the basic physical mechanism of rotating instability is analysed. The pressure ratio characteristics across the rotor row tip are found to be crucial to the inception of rotating instability. The captured instability demonstrates a 2D mechanism based on the circumferential variation of unsteady separation flow in the rotor row. The 3D tip clearance flow is found not a necessary cause of the instability onset. Several influential parameters on the instability flow are also investigated by a set of detailed studies on different turbine configurations. The results show that the instability flow pattern and characteristics can be altered by the gap distance between the stator and rotor row, the rotor blading and the stator row stagger angle. Some flow control approaches are proposed based on the observations, which may also serve as design reference. The tip region 3D vortex flow upstream to the rotor row is also captured by the simulations under low flow rate conditions. Its appearance is found to be able to suppress the inception of rotating instability by disrupting the interaction between the rotor separation flow and the incoming flow. Finally, some recommendations for further work are proposed.
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Wiratama, I. Kade. "Aerodynamic design of wind turbine blades utilising nonconventional control systems." Thesis, Northumbria University, 2012. http://nrl.northumbria.ac.uk/11375/.
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As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Individual pitch control system, adaptive blades, trailing edge microtabs, morphing aerofoils, ailerons, trailing edge flaps, and telescopic blades are among these techniques. Most of the above advanced technologies are currently implemented in, or are under investigation to be utilised, for blade load alleviation. The present study aims at investigating the potential benefits of these advanced techniques in enhancing the energy capture capabilities rather than blade load alleviation. To achieve this goal the research is carried out in three directions: (i) development of a simulation software tool suitable for wind turbines utilising nonconventional control systems, (ii) development of a blade design optimisation tool capable of optimising the topology of blades equipped with nonconventional control systems, and (iii) carrying out design optimisation case studies with the objective of power extraction enhancement towards investigating the feasibility of advanced technologies, initially developed for load alleviation of large blades, for power extraction enhancement. Three nonconventional control systems, namely, microtab, trailing edge flap and telescopic blades are investigated. A software tool, AWTSim, is especially developed for aerodynamic simulation of wind turbines utilising blades equipped with microtabs and trailing edge flap as well as telescopic blades. As part of the aerodynamic simulation of these wind turbines, the control system must be also simulated. The simulation of the control system is carried out via solving an optimisation problem which gives the best value for the controlling parameter at each wind turbine run condition. Developing a genetic algorithm optimisation tool which is especially designed for wind turbine blades and integrating it with AWTSim, a design optimisation tool for blades equipped with nonconventional control system is constructed. The design optimisation tool, AWTSimD, is employed to carry out design case studies. The results of design case studies reveal that for constant speed rotors, optimised telescopic blades are more effective than flaps and microtabs in power enhancement. However, in comparison with flap and microtabs, telescopic blades have two disadvantages: (i) complexity in telescopic mechanism and the added weight and (ii) increased blade loading. It is also shown that flaps are more efficient than microtabs, and that the location and the size of flaps are key parameters in design. It is also shown that optimisation of the blade pretwist has a significant influence on the energy extraction enhancement. That is, to gain the maximum benefit of installing flaps and microtabs on blades, the baseline blades must be redesigned.