Design and Evaluation of Wind Turbine Models
Islam Mohammed Mahmoud Mohammed;
Abstract
Vertical Axis wind turbines (VAWT) are of many different types. The Darrieus version is chosen for its many merits over other types; such as ease in manufacturing, small weight to volume ratio and high tip speed ratio. Therefore, investigation and optimization of the parameters that affect the performance of Darrieus wind turbine was performed in the present work. The implemented methodology can be further applied to other wind turbine types. The proposed development incorporates the following sequences:
1- Numerically estimation of the performance of wind turbine models using software Fluent 14.5.
2- Design and implementation of a shape optimization system using Genetic algorithm, Fluent 14.5 and Gambit.
3- Using finite element method to calculate and obtain natural frequencies of mechanical structure using software Ansys 14.5.
The following lines summarize each of these development activities and demonstrate the benefits gained from each.
1. A mathematical model was established and its behaviour was verified usinga published experimental results, for a three-straight blades Darrieus wind turbine. Realizable K- turbulence model with standard wall function is used in the present work.After establishing domain and mesh independent tests, the boundary conditions for domain and mesh size were estimated. It was found that the y+ values resulted near all blade walls are around 40, which fall within the recommended range [best-practice CFD (30 < y+ < 300)]. The result produced by the developed mathematical model was more accurate than that developed by other researchers.
2. Twelve models created with different number of blades and blade chord lengths to study there effect on the performance of Darrieus wind turbine. It was found that, max power coefficient and its corresponding tip speed ratio were obtained at number of blades equal two and increase in power coefficient related to castelli wind turbine by 3.35%. Increasing in blade chord length increase the power coefficient till a certain limit after which power coefficient was dramatically decreased due to increase in solidity and decreasing corresponding tip speed ratio. Both torque ripple factor and normal force on turbine blade were decreased with increasing of the number of blades and decreasing the blade chord length.
3. The location of Air flow Barrier was investigated for three straight blades Darrieus wind turbine. It was observed that, power coefficient was increased with increasing barrier length.And the Barrier angle at which max power coefficient was obtained was found to be 80˚. The highest power coefficient and lowest torque ripple factor obtained when Barrier location was just before wind turbine.
4. Shape optimization system established to optimize duct shape for three straight blades Darrieus wind turbine. From this optimization; it found that, wind turbine at duct throat was the best location at which the power coefficient was increased by 120% and the torque ripple factor was decreased by 84%.
After investigating the mechanical model it was found that,the number of turbine supports was to be increased To overcome the dynamic behaviour of the turbine,. And to decrease blade’s static stress, due to normal and centrifugal forces, both of the number of suspension arms and turbine supports were to be increased.
1- Numerically estimation of the performance of wind turbine models using software Fluent 14.5.
2- Design and implementation of a shape optimization system using Genetic algorithm, Fluent 14.5 and Gambit.
3- Using finite element method to calculate and obtain natural frequencies of mechanical structure using software Ansys 14.5.
The following lines summarize each of these development activities and demonstrate the benefits gained from each.
1. A mathematical model was established and its behaviour was verified usinga published experimental results, for a three-straight blades Darrieus wind turbine. Realizable K- turbulence model with standard wall function is used in the present work.After establishing domain and mesh independent tests, the boundary conditions for domain and mesh size were estimated. It was found that the y+ values resulted near all blade walls are around 40, which fall within the recommended range [best-practice CFD (30 < y+ < 300)]. The result produced by the developed mathematical model was more accurate than that developed by other researchers.
2. Twelve models created with different number of blades and blade chord lengths to study there effect on the performance of Darrieus wind turbine. It was found that, max power coefficient and its corresponding tip speed ratio were obtained at number of blades equal two and increase in power coefficient related to castelli wind turbine by 3.35%. Increasing in blade chord length increase the power coefficient till a certain limit after which power coefficient was dramatically decreased due to increase in solidity and decreasing corresponding tip speed ratio. Both torque ripple factor and normal force on turbine blade were decreased with increasing of the number of blades and decreasing the blade chord length.
3. The location of Air flow Barrier was investigated for three straight blades Darrieus wind turbine. It was observed that, power coefficient was increased with increasing barrier length.And the Barrier angle at which max power coefficient was obtained was found to be 80˚. The highest power coefficient and lowest torque ripple factor obtained when Barrier location was just before wind turbine.
4. Shape optimization system established to optimize duct shape for three straight blades Darrieus wind turbine. From this optimization; it found that, wind turbine at duct throat was the best location at which the power coefficient was increased by 120% and the torque ripple factor was decreased by 84%.
After investigating the mechanical model it was found that,the number of turbine supports was to be increased To overcome the dynamic behaviour of the turbine,. And to decrease blade’s static stress, due to normal and centrifugal forces, both of the number of suspension arms and turbine supports were to be increased.
Other data
| Title | Design and Evaluation of Wind Turbine Models | Other Titles | تصميم و تقييم نماذج من توربينات الرياح | Authors | Islam Mohammed Mahmoud Mohammed | Issue Date | 2014 |
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