|
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.
Table of Contents:
|
|
Abstract |
I
|
|
Index |
II
|
|
List of Figures |
IV
|
|
List of Symbols |
VI
|
|
Introduction |
1
|
| 1. |
Theory of Wind Turbines |
5
|
| 1.1 |
Introduction |
5
|
| 1.2 |
The Betz Law |
6
|
| 1.3 |
Aerodynamics of the rotor |
13
|
| 1.4 |
Rotor Power Characteristics |
18
|
| 1.5 |
Number of Rotor Blades |
20
|
| 1.6 |
Horizontal Axis Wind Turbines (HAWT) |
22
|
| 1.7 |
Shrouded / Ducted Wind Turbines |
28
|
| 1.7.1 |
Ducted Rotor |
29
|
| 1.7.2 |
Turbine with a Diffuser Duct |
29
|
| 2. |
Methodology |
33
|
| 2.1 |
Introduction |
33
|
| 2.2 |
Computational Domain |
34
|
| 2.3 |
Computational Code |
41
|
| 2.3.1 |
Conservation Equations |
42
|
| 2.3.2 |
K-Epsilon Turbulence Model |
43
|
| 2.3.3 |
Discretization of the Conservation Equations |
45
|
| 2.4 |
MFR - Multiple Frame of Reference |
45
|
| 2.5 |
Parallel Processing |
46
|
| 2.6 |
Simulations |
47
|
| 3. |
Results |
48
|
| 3.1 |
Introduction |
48
|
| 3.2 |
Conventional Turbine |
49
|
| 3.2.1 |
Velocity Field |
49
|
| 3.2.2 |
Static Pressure Field |
52
|
| 3.2.3 |
Total Pressure Field |
53
|
| 3.2.4 |
Power of the Conventional Turbine |
55
|
| 3.2.5 |
Energy and Momentum Transfer |
57
|
| 3.3 |
Shrouded Turbine |
59
|
| 3.3.1 |
Velocity Field |
59
|
| 3.3.2 |
Static Pressure Field |
62
|
| 3.3.3 |
Total Pressure Field |
63
|
| 3.3.4 |
Power of the Shrouded Turbine |
65
|
| 3.3.5 |
Energy and Momentum Transfer |
66
|
| 3.3.6 |
The Betz Limit |
68
|
| 3.3.7 |
Cross Check Analysis with Traditional Shrouded Turbines |
69
|
|
Conclusions |
72
|
|
Bibliography |
73
|
|
Acknowledgments |
|
