At the Division of Electricity at Uppsala university a project isconducted to develop a smaller wind turbine for conditions in theAntarctica. This is a part of a larger, international researchproject in the field of particle physics known as the Ariannaexperiment. The project consists of developing and installing avertical axle wind turbine of screwed Savonius type. A prototypeof this has been manufactured and installed 2016 in Antarctica forinitial testing and measurement.Wind turbines are subjected to complex and varied loads from windand rotation which gives rise to cyclical strain. The rotor bladesare particularly vulnerable, which imposes high material andconstruction requirements to avoid fatigue and failure, whichoften is caused by vibrations and oscillations. Vibrations can becharacterized in terms of the natural frequencies witch in shortmeans that the system, at specific frequencies, tend to oscillatewith increasing amplitude and at worst, resonate if these areexcited. How a complex design will behave by external periodicinterference is complicated to calculate analytically. Naturalfrequencies are therefore most often calculated using FEM-methodsand computer simulations.The aim of this thesis is to study how oscillating forces interactwith the natural frequencies and rotational loads for a specificSavonius wind turbine. How these are influenced by engineering,design and material selection. The goal is to draw conclusionsabout design and possible materials selection to avoid unnecessaryvibrations. Without this analysis, there is a risk of increasedwear and damage to the structure.The project includes such analysis of two different sizes of theSavonius turbine. A small 200x400 mm and a larger 1000x2000 mm.To understand the problem, a preliminary study of basic harmonicoscillation, strength of materials and of the existing prototypewas made. Following a requirement specification, somedelimitations were made so that the simulations would not be tooextensive. Subsequently, a minor design work was done to obtain 13different configurations of the turbine for simulation using FEM-methods.The result showed that none of the turbines rotational frequenciesis close to the turbine’s natural frequencies. However, accountmust be taken of cogging frequencies in the generator. These arewithin the range of the design's natural frequencies.All simulations of centrifugal force found that there isrelatively little tension at the selected maximum speed of 660 and132 revolutions per minute. However, as the results showed thatthe plates which are mounted between the rotor blades to providestability, creates greater stresses in the structure than thosewithout. Two proposals for the configuration of turbines have beenpresented in the report.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-326356 |
| Date | January 2017 |
| Creators | Zetterkvist, Victor |
| Publisher | Uppsala universitet, Industriell teknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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