Effect of number of blades on aerodynamic forces on a straight-bladed Vertical Axis Wind Turbine

Li, Qingan; Maeda, Takao; Kamada, Y.; Murata, Junsuke; Furukawa, Kazuma; Yamamoto, Masayuki

doi:10.1016/j.energy.2015.07.115

Cited by 175 publications

(48 citation statements)

References 22 publications

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“…The principle of tip vortex is the airflow on the positive pressure surface of blade around the tip of blade to the negative pressure surface of blade. Similar conclusion of generation mechanism of vorticities including tip vortex can be found in the studies of Ferreira et al [19] in 2009 with PIV experiments and Li et al [41] in 2016 with pressure measurements. Moreover, from Figures 6c, 7c and 8c which include local enlarged views, it is clearly observed that vortex B around the rotor shaft can affect the vortex C around the blade.…”

Section: Resultssupporting

confidence: 74%

Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

et al. 2017

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Abstract:Wind velocity distribution and the vortex around the wind turbine present a significant challenge in the development of straight-bladed vertical axis wind turbines (VAWTs). This paper is intended to investigate influence of tip vortex on wind turbine wake by Computational Fluid Dynamics (CFD) simulations. In this study, the number of blades is two and the airfoil is a NACA0021 with chord length of c = 0.265 m. To capture the tip vortex characteristics, the velocity fields are investigated by the Q-criterion iso-surface (Q = 100) with shear-stress transport (SST) k-ω turbulence model at different tip speed ratios (TSRs). Then, mean velocity, velocity deficit and torque coefficient acting on the blade in the different spanwise positions are compared. The wind velocities obtained by CFD simulations are also compared with the experimental data from wind tunnel experiments. As a result, we can state that the wind velocity curves calculated by CFD simulations are consistent with Laser Doppler Velocity (LDV) measurements. The distribution of the vortex structure along the spanwise direction is more complex at a lower TSR and the tip vortex has a longer dissipation distance at a high TSR. In addition, the mean wind velocity shows a large value near the blade tip and a small value near the blade due to the vortex effect.

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Section: Resultssupporting

confidence: 74%

Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

et al. 2017

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“…This experiment revealed that the tip speed ratio increased with the increase of the pressure difference on the blade surface. Based on this experiment, Li et al [19] in 2015 further investigated the influence of the number of blades on the aerodynamic characteristics of the Sb-VAWT via a torque meter. The results of this experiment showed that the peak value of the power coefficient of the Sb-VAWT decreased with the increase of the number of blades.…”

Section: Introductionmentioning

confidence: 99%

Effect of Blade Pitch Angle on the Aerodynamic Characteristics of a Straight-bladed Vertical Axis Wind Turbine Based on Experiments and Simulations

et al. 2018

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Abstract:The blade pitch angle has a significant influence on the aerodynamic characteristics of horizontal axis wind turbines. However, few research results have revealed its impact on the straight-bladed vertical axis wind turbine (Sb-VAWT). In this paper, wind tunnel experiments and CFD simulations were performed at the Sb-VAWT to investigate the effect of different blade pitch angles on the pressure distribution on the blade surface, the torque coefficient, and the power coefficient. In this study, the airfoil type was NACA0021 with two blades. The Sb-VAWT had a rotor radius of 1.0 m with a spanwise length of 1.2 m. The simulations were based on the k-ω Shear Stress Transport (SST) turbulence model and the wind tunnel experiments were carried out using a high-speed multiport pressure device. As a result, it was found that the maximum pressure difference on the blade surface was obtained at the blade pitch angle of β = 6 • in the upstream region. However, the maximum pressure coefficient was shown at the blade pitch angle of β = 8 • in the downstream region. The torque coefficient acting on a single blade reached its maximum value at the blade pitch angle of β = 6 • . As the tip speed ratio increased, the power coefficient became higher and reached the optimum level. Subsequently, further increase of the tip speed ratio only led to a quick reversion of the power coefficient. In addition, the results from CFD simulations had also a good agreement with the results from the wind tunnel experiments. As a result, the blade pitch angle did not have a significant influence on the aerodynamic characteristics of the Sb-VAWT.

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“…Further, the lift coefficient CL and the drag coefficient CD are obtained by the non-dimensional lift force FL and drag force FD per unit blade as determined by equations (1) and (2) from the dynamic pressure and chord length c. They are given by the following equations: Maeda et al, 2012) and Li (Li et al, 2015(Li et al, , 2016b(Li et al, , 2016c(Li et al, , 2016d.…”

Section: Non-dimensional Lift and Dragmentioning

confidence: 99%

Experimental investigation of load fluctuation on horizontal axis wind turbine for extreme wind direction change

Sang

Murata

Morimoto

et al. 2017

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The operating conditions of Horizontal Axis Wind Turbine (HAWT) are extremely complex in natural surroundings. One of the wind conditions is called extreme wind direction change which has been specified in the International Electrotechnical Commission (IEC) 61400-1 standard. External conditions can generate extreme loads which may affect the power coefficient and the lifetime of HAWTs. This paper attempted to compile the evaluation of the aerodynamic forces acting on a small HAWT under extreme wind direction change condition in the wind tunnel experiments. An Avistar airfoil is used for the two-bladed and three-bladed wind turbines. This study is intended to clarify the load fluctuation when sudden wind direction change reacts to two-bladed and three-bladed wind turbines. A vane system is used to generate the wind direction change. A 6-component balance is used to measure the forces and the moments acting on the entire wind turbine in the three directions of x, y and z-axes. The results show that when the extreme wind direction change is generated, the yaw moment fluctuation amplitude of two-bladed wind turbine is about 39% larger than that of the three-bladed one. The strong dependence of the inflow timing of the wind direction change on the fluctuation amplitude can be seen only for the two-bladed wind turbine.

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Effect of number of blades on aerodynamic forces on a straight-bladed Vertical Axis Wind Turbine

Cited by 175 publications

References 22 publications

Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

Numerical Investigation of the Tip Vortex of a Straight-Bladed Vertical Axis Wind Turbine with Double-Blades

Effect of Blade Pitch Angle on the Aerodynamic Characteristics of a Straight-bladed Vertical Axis Wind Turbine Based on Experiments and Simulations

Experimental investigation of load fluctuation on horizontal axis wind turbine for extreme wind direction change

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