الفهرس 
CHAPTER 1: INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 130 |  |  |
| | | from | 130 | | |
Abstract
The objective of the present investigation is set to develop and improve the performance of Savonius wind turbine in terms of power coefficient, torque coefficient and starting characteristics. This is to be achieved by both numerical and experimental investigations. The numerical results presented in this study are based on the three-dimensional incompressible unsteady Reynolds-Average Navier-Stokes (RANS) equations that are solved by employing ANSYS Fluent 15. Four turbulence models are tested using the standard k–ε model, the realizable k–ε model, the RNG k–ε model, and the SST k–ω model. Validation of the numerical methodology is performed using the available experimental data from the literature. The results indicated that the RNG k–ε turbulence model has more accurate results compared to the other studied models. Therefore, the simulation is extended using the RNG k–ε model as a suitable turbulence model for further predictions of different non-measured data.
A twisted modified Savonius rotor is proposed in the present work. The twist is performed on a modified profile of the rotor blade. The effect of twist angle on the performance of the proposed twisted modified rotor is numerically performed. The results show that, the twisted modified rotor with twist angle of 45o has the highest power coefficient ( ) and torque coefficient ( ) as compared with the other twist angles. The twisted modified rotor with optimum twist angle of 45o that obtained from the numerical computations is then fabricated and tested experimentally, to ensure its performance characteristics. The comparison between the performances of the twisted modified rotor and other three rotors is conducted. These three rotors are conventional rotor, twisted conventional rotor, and modified rotor without twisting. The experimental results successfully verify the numerical results at the used range of tip speed ratios. Furthermore, a parametric study is extended to improve the design and performance of the introduced twisted modified rotor with optimum twist angle of 45o. The parametric study includes the effect of overlap ratio, aspect ratio, and wind speed. It is concluded
ii
from the present study that, a performance gain in power coefficient of 75.3 % is achieved by using the introduced twisted modified rotor with optimum design, as compared with the conventional rotor which has =0.174. Moreover, the present twisted modified rotor with optimum design always has positive static torque coefficient values at all rotor angles.