Effect of blade pitching on power coefficient of small-scale vertical axis wind turbine at different tip speed ratios

2019 ◽  
Vol 44 (3) ◽  
pp. 313-324 ◽  
Author(s):  
Ramesh K Kavade ◽  
Pravin M Ghanegaonkar
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Tube Model ◽  
Vertical Axis Wind Turbine ◽  
Stream Tube

This article analyses the effect of best blade pitching positions on the power coefficient of vertical axis wind turbine at different tip speed ratios. Analysis of the power coefficient of the vertical axis wind turbine is carried out for optimized six blade pitching curves. The first three pitching curves are designed for the tip speed ratios below 1.5 (0 <  λ < 1.5) and other three are for the tip speed ratios in the range of 0 <  λ < 3. The double multiple stream tube model is used for the present analysis. The results are compared between the optimized and sinusoidal pitching curves. It is concluded that the best optimized pitch position blade method improves the power coefficient than the typical sinusoidal blade pitching in the range of tip speed ratios 0 <  λ < 3.

scholarly journals Double multiple stream tube theory coupled with dynamic stall and wake correction for aerodynamic investigation of vertical axis wind turbine

2020 ◽  
Vol 23 (4) ◽  
pp. 771-780
Author(s):  
Anh Ngoc VU ◽  
Ngoc Son Pham
Keyword(s):  
Wind Turbine ◽  
Shape Function ◽  
Vertical Axis ◽  
Transformation Method ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Stream Tube ◽  
Aerodynamic Investigation

This study describes an effectively analytic methodology to investigate the aerodynamic performance of H vertical axis wind turbine (H-VAWT). An in-house code based on double multiple stream tube theory (DMST) coupled with dynamic stall and wake correction is implemented to estimate the power coefficient. Design optimization of airfoil shape is conducted to study the influences of the dynamic stall and turbulent wakes. Airfoil shape is universally investigated by using the Class/Shape function transformation method. The airfoil study shows that the upper curve tends to be less convex than the lower curve in order to extract more energy of the wind upstream and generate less drag of the blade downstream. The optimal results show that the power coefficient increases by 6.5% with the new airfoil shape.

Computational fluid dynamic analysis of roof-mounted vertical-axis wind turbine with diffuser shroud, flange, and vanes

2018 ◽  
Vol 42 (4) ◽  
pp. 404-415
Author(s):  
H. Abu-Thuraia ◽  
C. Aygun ◽  
M. Paraschivoiu ◽  
M.A. Allard
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes ◽  
Turbine Design

Advances in wind power and tidal power have matured considerably to offer clean and sustainable energy alternatives. Nevertheless, distributed small-scale energy production from wind in urban areas has been disappointing because of very low efficiencies of the turbines. A novel wind turbine design — a seven-bladed Savonius vertical-axis wind turbine (VAWT) that is horizontally oriented inside a diffuser shroud and mounted on top of a building — has been shown to overcome the drawback of low efficiency. The objective this study was to analyze the performance of this novel wind turbine design for different wind directions and for different guide vanes placed at the entrance of the diffuser shroud. The flow field over the turbine and guide vanes was analyzed using computational fluid dynamics (CFD) on a 3D grid for multiple tip-speed ratios (TSRs). Four wind directions and three guide-vane angles were analyzed. The wind-direction analysis indicates that the power coefficient decreases to about half when the wind is oriented at 45° to the main axis of the turbine. The analysis of the guide vanes indicates a maximum power coefficient of 0.33 at a vane angle of 55°.

Numerical Investigation of a Vertical Axis Wind Turbine Performance Characterization Using New Variable Pitch Control Scheme

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Amin A. Mohammed ◽  
Ahmet Z. Sahin ◽  
Hassen M. Ouakad
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Average Power ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Variable Pitch ◽  
De Algorithm

Abstract A double multiple streamtube model coupled with variable pitch methodology is used to analyze the performance characteristics of a small-scale straight-bladed Darrieus type vertical axis wind turbine (SB-VAWT). The numerical study revealed that a fixed pitch of −2.5 deg could greatly enhance the performance of the wind turbine. However, no improvement is observed in the starting torque capacity. Furthermore, the performance of upwind and downwind zones has been investigated, and it is found that the VAWT starting capacity is improved by increasing/decreasing the pitch angle upwind/downwind of the turbine. To optimize the performance, four cases of variable pitch angle schemes of sinusoidal nature were examined. The parameters of the sinusoidal functions were optimized using differential evolution (DE) algorithm with different cost functions. The results showed improvement in the power coefficient, yet with low starting capacity enhancement. Among the objective functions used in DE algorithm, the negative of the average power coefficient is found to lead to the best starting capacity with moderate peak power coefficient.

Reduction in the torque ripple of a vertical axis wind turbine through foil pitching optimization

2019 ◽  
Vol 44 (2) ◽  
pp. 115-124 ◽  
Author(s):  
Gareth Erfort ◽  
Theodor W. von Backström ◽  
Gerhard Venter
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Vertical Axis ◽  
Torque Ripple ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Similar Reduction ◽  
Vertical Axis Wind Turbines ◽  
Gradient Based

Vertical axis wind turbines have a place in the small scale renewable energy market. They are not currently implemented on a commercial scale but have found a niche space in urban areas. Here, the turbulent wind conditions and limited space are more easily tapped into with a vertical axis wind turbine. However, the challenges facing these types of turbines have hampered deployment. One of these issues is the fluctuating torque experienced during operation, which can lead to over-designed power trains. Genetic- and gradient-based optimization is applied to an analytical model of a vertical axis wind turbine, in order to reduce the torque fluctuation while attempting to maintain a high power coefficient. The reduction in torque ripple is achieved through a sinusoidal pitching motion of the blades. The torque ripple can be reduced by 10% with a similar reduction in power coefficient.

scholarly journals Numerical evaluation of aerodynamic performances of vertical-axis wind turbine rotor with flow concentrator

2020 ◽  
Author(s):  
Jelena Svorcan ◽  
◽  
Ognjen Peković ◽  
Toni Ivanov ◽  
Miloš Vorkapić ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Flow Simulations ◽  
Wind Speeds

With wind energy extraction constantly increasing, the interest in small-scale urban wind turbines is also expanding. Given that these machines often work in adverse operating conditions (Earth’s boundary layer, vortex trails of surrounding objects, small and changeable wind speeds), additional elements that locally augment wind velocity and facilitate turbine start may be installed. This paper investigates possible benefits of adding an optimized flow concentrator to a vertical-axis wind turbine (VAWT) rotor. Three-dimensional, unsteady, turbulent, incompressible flow simulations of both isolated rotor consisting of three straight blades and a rotor with flow concentrator have been performed in ANSYS FLUENT by finite volume method for several different operational regimes. This type of flow simulations is challenging since flow angles are high, numerous flow phenomena and instabilities are present and the interaction between the blades and detached vortices can be significant. The rotational motion of the blades is solved by the unsteady Sliding Mesh (SM) approach. Flow field is modeled by Unsteady Reynolds Averaged Navier-Stokes (URANS) equations with k-ω SST turbulence model used for closure. Both quantitative and qualitative examinations of the obtained numerical results are presented. In particular, the two computed power coefficient curves are compared and the advantages of installing a flow concentrator are accentuated.

Aerodynamic and aeroacoustic performance investigations on modified H-rotor Darrieus wind turbine

2021 ◽  
pp. 0309524X2110039
Author(s):  
Amgad Dessoky ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Wind Turbine ◽  
High Speed ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
3D Models ◽  
Power Coefficient ◽  
Design Parameters ◽  
Second Phase ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes

The present paper investigates the aerodynamic and aeroacoustic characteristics of the H-rotor Darrieus vertical axis wind turbine (VAWT) combined with very promising energy conversion and steering technology; a fixed guide-vanes. The main scope of the current work is to enhance the aerodynamic performance and assess the noise production accomplished with such enhancement. The studies are carried out in two phases; the first phase is a parametric 2D CFD simulation employing the unsteady Reynolds-averaged Navier-Stokes (URANS) approach to optimize the design parameters of the guide-vanes. The second phase is a 3D CFD simulation of the full turbine using a higher-order numerical scheme and a hybrid RANS/LES (DDES) method. The guide-vanes show a superior power augmentation, about 42% increase in the power coefficient at λ = 2.75, with a slightly noisy operation and completely change the signal directivity. A remarkable difference in power coefficient is observed between 2D and 3D models at the high-speed ratios stems from the 3D effect. As a result, a 3D simulation of the capped Darrieus turbine is carried out, and then a noise assessment of such configuration is assessed. The results show a 20% increase in power coefficient by using the cap, without significant change in the noise signal.

Numerical Study of Pitch Angle on H-Type Vertical Axis Wind Turbine

2012 ◽  
Vol 499 ◽  
pp. 259-264
Author(s):  
Qi Yao ◽  
Ying Xue Yao ◽  
Liang Zhou ◽  
S.Y. Zheng
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Vertical Axis ◽  
Azimuth Angle ◽  
Power Coefficient ◽  
Cfd Model ◽  
Vertical Axis Wind Turbine ◽  
Sliding Mesh ◽  
Mesh Technique

This paper presents a simulation study of an H-type vertical axis wind turbine. Two dimensional CFD model using sliding mesh technique was generated to help understand aerodynamics performance of this wind turbine. The effect of the pith angle on H-type vertical axis wind turbine was studied based on the computational model. As a result, this wind turbine could get the maximum power coefficient when pitch angle adjusted to a suited angle, furthermore, the effects of pitch angle and azimuth angle on single blade were investigated. The results will provide theoretical supports on study of variable pitch of wind turbine.

Numerical Research on the Characteristics of Lift-Drag Type Vertical Axis Wind Turbine

2012 ◽  
Vol 189 ◽  
pp. 448-452
Author(s):  
Yan Jun Chen ◽  
Guo Qing Wu ◽  
Yang Cao ◽  
Dian Gui Huang ◽  
Qin Wang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Chord Length ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Tip Speed Ratio ◽  
Middle Range ◽  
Parabolic Form ◽  
Cfd Method

Numerical studies are conducted to research the performance of a kind of lift-drag type vertical axis wind turbine (VAWT) affected by solidity with the CFD method. Moving mesh technique is used to construct the model. The Spalart-Allmaras one equation turbulent model and the implicit coupled algorithm based on pressure are selected to solve the transient equations. In this research, how the tip speed ratio and the solidity of blade affect the power coefficient (Cp) of the small H-VAWT is analyzed. The results indicate that Cp curves exhibit approximate parabolic form with its maximum in the middle range of tip speed ratio. The two-blade wind turbine has the lowest Cp while the three-blade one is more powerful and the four-blade one brings the highest power. With the certain number of blades, there is a best chord length, and too long or too short chord length may reduce the Cp.

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