CFD Analysis of the Characteristics of a Shrouded Turbine

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Inhaltsangabe:Abstract: Wind energy is an increasingly import source of renewable, clean energy. In spite of this, only the methods and the materials of construction have improved over time, while the basic working principle of the wind turbine is still the same as it was centuries ago. In this thesis we have increased the power of a wind turbine by a factor of 4 in a fluid dynamic simulation, using a very simple external shroud system. We have also extended the theory of wind turbines (limit of Betz), to include this new kind of device and show why past attempts to augment the power of a wind turbine by means of shroud systems have failed. A detailed analysis of the device and its functioning principle is presented in this thesis - optimization studies need to be done in the future. Inhaltsverzeichnis:Table of Contents: AbstractI IndexII List of FiguresIV List of SymbolsVI Introduction1 1.Theory of Wind Turbines5 1.1Introduction5 1.2The Betz Law6 1.3Aerodynamics of the rotor13 1.4Rotor Power Characteristics18 1.5Number of Rotor Blades20 1.6Horizontal Axis Wind Turbines (HAWT)22 1.7Shrouded / Ducted Wind Turbines28 1.7.1Ducted Rotor29 1.7.2Turbine with a Diffuser Duct29 2.Methodology33 2.1Introduction33 2.2Computational Domain34 2.3Computational Code41 2.3.1Conservation Equations42 2.3.2K-Epsilon Turbulence Model43 2.3.3Discretization of the Conservation Equations45 2.4MFR - Multiple Frame of Reference45 2.5Parallel Processing46 2.6Simulations47 3.Results48 3.1Introduction48 3.2Conventional Turbine49 3.2.1Velocity Field49 3.2.2Static Pressure Field52 3.2.3Total Pressure Field53 3.2.4Power of the Conventional Turbine55 3.2.5Energy and Momentum Transfer57 3.3Shrouded Turbine59 3.3.1Velocity Field59 3.3.2Static Pressure Field62 3.3.3Total Pressure Field63 3.3.4Power of the Shrouded Turbine65 3.3.5Energy and Momentum Transfer66 3.3.6The Betz Limit68 3.3.7Cross Check Analysis with Traditional Shrouded Turbines69 Conclusions72 Bibliography73 Acknowledgments