Straight-bladed Vertical-axis Turbine Research Articles

Study on Performance of a Straight-Bladed Vertical-Axis Turbine for Wave Energy Conversion by CFD

Study on Performance of a Straight-Bladed Vertical-Axis Turbine for Wave Energy Conversion by CFD

A straight-bladed vertical axis turbine for wave energy conversion: Effect of guide vane position on the performance

A straight-bladed vertical axis turbine for wave energy conversion has been proposed in order to develop a novel air turbine suitable for an oscillating water column based on a wave energy plant. This study aims at investigating the effect of guide vane position on the performance of a straight-bladed vertical axis turbine. The experimental study was performed using a wind tunnel. The rotor comprises four straight blades with a profile of NACA0018, chord length of 80.5 mm, pitch radius of R = 230 mm, and a blade width of 490 mm. The guide vane has a profile of a circular arc and a chord length of l = 87 mm. The distance between these two guide vanes w and the gap between the rotor blade and guide vane G were altered to investigate the effects of the guide vane solidity l/w and position G/R. In addition, we performed computational fluid dynamics (CFD) on exactly the same configuration as the experimental system to study the effect of the guide vane position. The experimental results indicated that the guide vane solidity l/w and position G/R suitable for the proposed turbine are obtained in the case of l/w = 1.09 and G/R = 0.11. The flow visualization was determined using CFD. Moreover, we confirmed the control of the flow separation by the setting of the guide vane.

Effects of the Reynolds number and the tip losses on the optimal aspect ratio of straight-bladed Vertical Axis Wind Turbines

Aspect Ratio (AR) is one of the main design parameters of straight-bladed vertical axis turbines. This paper will examine whether a high AR, with long blades and low tip losses, or a low AR, with a higher diameter and higher losses, is more suitable to achieve the maximum power output given a fixed cross-sectional area. Traditional Double-Multiple Stream-Tube (DMST) approaches are limited by a lack of tip loss formulations specifically conceived for vertical axis turbines. Therefore, a CFD-3D investigation covering a power range from micro-generation to MW has been done. Results show that both Reynolds number and tip losses strongly influence the aerodynamic performance of the rotor. More advantages seem to be achieved by limiting tip losses rather than increasing chord-based Reynolds number (Rec), addressing towards high AR at least for medium and large-size turbines. However, as turbine size and wind speed decrease, this difference narrows considerably. For micro turbines, tip losses are balanced by the effects of Rec, thus a variation of AR does not imply a variation of CP. For all the cases that have been analysed, turbine size and therefore Rec does not appreciably affect the normalized CP distribution along the blade, which only depends on AR.

Effect of Guide Vane on the Performance of a Straight-Bladed Vertical Axis Turbine for Wave Energy Conversion

Effect of Guide Vane on the Performance of a Straight-Bladed Vertical Axis Turbine for Wave Energy Conversion

Experimental Study on the Straight-bladed Vertical Axis Turbine for Wave Energy Conversion

Experimental Study on the Straight-bladed Vertical Axis Turbine for Wave Energy Conversion

波力発電用直線翼垂直軸タービン

波力発電用直線翼垂直軸タービン

波力発電用直線翼垂直軸タービン

波力発電用直線翼垂直軸タービン

Numerical Study on Self-Starting Performance of Darrieus Vertical Axis Turbine for Tidal Stream Energy Conversion

Self-starting performance is a key factor in the evaluation of a Darrieus straight-bladed vertical axis turbine. Most traditional studies have analyzed the turbine’s self-starting capability using the experimental and numerical data of the forced rotation. A 2D numerical model based on the computational fluid dynamics (CFD) software ANSYS-Fluent was developed to simulate the self-starting process of the rotor at constant incident water-flow velocities. The vertical-axis turbine (VAT) rotor is driven directly by the resultant torque generated by the water flow and system loads, including the friction and reverse loads of the generator. It is found that the incident flow velocity and the moment of inertia of the rotor have little effect on the averaged values of tip-speed ratios in the equilibrium stage under no-load conditions. In the system load calculations, four modes of the self-starting were found: stable equilibrium mode, unstable equilibrium mode, switch mode and halt mode. The dimensionless power coefficient in the simulations of passive rotation conditions is found to be, on average, 38% higher than those achieved in the simulations of forced rotation conditions.

Application of 2D numerical model to unsteady performance evaluation of vertical-axis tidal current turbine

Tidal current energy is renewable and sustainable, which is a promising alternative energy resource for the future electricity supply. The straight-bladed vertical-axis turbine is regarded as a useful tool to capture the tidal current energy especially under low-speed conditions. A 2D unsteady numerical model based on Ansys-Fluent 12.0 is established to conduct the numerical simulation, which is validated by the corresponding experimental data. For the unsteady calculations, the SST model, 2×105 and 0.01 s are selected as the proper turbulence model, mesh number, and time step, respectively. Detailed contours of the velocity distributions around the rotor blade foils have been provided for a flow field analysis. The tip speed ratio (TSR) determines the azimuth angle of the appearance of the torque peak, which occurs once for a blade in a single revolution. It is also found that simply increasing the incident flow velocity could not improve the turbine performance accordingly. The peaks of the averaged power and torque coefficients appear at TSRs of 2.1 and 1.8, respectively. Furthermore, several shapes of the duct augmentation are proposed to improve the turbine performance by contracting the flow path gradually from the open mouth of the duct to the rotor. The duct augmentation can significantly enhance the power and torque output. Furthermore, the elliptic shape enables the best performance of the turbine. The numerical results prove the capability of the present 2D model for the unsteady hydrodynamics and an operating performance analysis of the vertical tidal stream turbine.

波力発電用直線翼垂直軸タービン

波力発電用直線翼垂直軸タービン

Three-dimensional numerical simulations of straight-bladed vertical axis tidal turbines investigating power output, torque ripple and mounting forces

Three straight-bladed vertical axis turbine designs were simulated using Three-Dimensional (3D) transient Computational Fluid Dynamics (CFD) models, using a commercial Unsteady Reynolds Averaged Navier–Stokes (URANS) solver. The turbine designs differed in support strut section, blade-strut joint design and strut location to evaluate their effect on power output, torque fluctuation levels and mounting forces. Simulations of power output were performed and validated against Experimental Fluid Dynamics (EFD), with results capturing the impacts of geometrical changes on turbine power output. Strut section and blade-strut joint design were determined to significantly influence total power output between the three turbine designs, with strut location having a smaller but still significant effect. Maximum torque fluctuations were found to occur around the rotation speed corresponding to maximum power output and fluctuation levels increased with overall turbine efficiency. Turbine mounting forces were also simulated and successfully validated against EFD results. Mounting forces aligned with the inflow increased with rotational rates, but plateaued due to reductions in shaft drag caused by rotation and blockage effects. Mounting forces perpendicular to the inflow were found to be 75% less than forces aligned with the inflow. High loading force fluctuations were found, with maximum values 40% greater than average forces.

Simulating Pitching Blade With Free Vortex Model Coupled With Dynamic Stall Model for Conditions of Straight Bladed Vertical Axis Turbines

This study is on the straight bladed vertical axis turbines (VATs), which can be utilized for both wind and marine current energy. VATs have the potential of lower installation and maintenance cost. However, complex unsteady fluid mechanics of these turbines imposes significant challenges to the simulation tools. Dynamic stall is one of the phenomena associated with the unsteady conditions, and it is in the focus of the study. The dynamic stall effects are very important for VATs, since they are usually passively controlled through the dynamic stall. A free vortex model is used to calculated unsteady attached flow, while the separated flow is handled by the dynamic stall model. This is compared to the model based solely on the Leishman–Beddoes algorithm. The results are assessed against the measured data on pitching airfoils. A comparison of force coefficients between the simulations and experiments is done at the conditions similar to the conditions of H-rotor type VATs.

1313 波力発電用直線翼垂直軸タービンに関する実験的研究 : 案内羽根による性能改善(流体工学VII)

1313 波力発電用直線翼垂直軸タービンに関する実験的研究 : 案内羽根による性能改善(流体工学VII)

1208 波力発電用直線翼垂直軸タービンに関する研究

1208 波力発電用直線翼垂直軸タービンに関する研究

1009 波力発電用直線翼垂直軸タービンに関する実験的研究(タービン性能に及ぼすロータ翼型の影響)(OS10-2 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

1009 波力発電用直線翼垂直軸タービンに関する実験的研究(タービン性能に及ぼすロータ翼型の影響)(OS10-2 再生可能流体エネルギーの利用技術,OS10 再生可能流体エネルギーの利用技術)

0917 波力発電用直線翼垂直軸タービンに関する実験的研究(OS9 再生可能流体エネルギーの利用技術,オーガナイズドセッション)

In order to develop a novel air turbine suitable for OWC based plant,a straight-bladed vertical axis turbine for wave energy conversion has been proposed in this study.Performances of the proposed turbine under steady flow conditions have been investigated experimentally by using a wind tunnel in this study.The tested rotor has some straight blades with a profile of NACA0018,a pitch diameter of 472mm and a width of 0.490m.

1421 可動式案内羽根翼列を有する直線翼垂直軸風車の実証試験(OS14-4 再生可能流体エネルギー,オーガナイズドセッション)

1421 可動式案内羽根翼列を有する直線翼垂直軸風車の実証試験(OS14-4 再生可能流体エネルギー,オーガナイズドセッション)

510 可動式案内羽根を有する直線翼垂直軸風車のフィールド試験(流体工学V)

510 可動式案内羽根を有する直線翼垂直軸風車のフィールド試験(流体工学V)

A Straight-bladed Vertical Axis Wind Turbine with a Directed Guide Vane Row

A straight-bladed vertical axis wind turbine with a directed guide vane row has been proposed in order to enhance its torque. The experimental study of the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has some straight rotor blades with a profile of NACA0015, a diameter of 0.6 m and a height of 0.7 m. The guide vane row having 3 arc plates rotates around the rotor and is directed to the wind by aerodynamic force generated by tail vanes, so as to put the guide vane row in upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed guide vane row. Further, by the use of the guide vane row adopted in the study, the power coefficient of the proposed wind turbine was approximately 1.5 times higher than that of the original wind turbine which has no guide vane.

OS2-9 可動式案内羽根翼列を有する直線翼垂直軸風車(OS2 自然エネルギー,循環型社会における動力エネルギー技術)

A straight-bladed vertical axis wind turbine with a directed guide vane row has been proposed in order to enhance its torque. The experimental study on the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has 3 straight blades with a profile of NACA0015, a diameter of 0.6m and a blade height of 0.7m. The guide vane row having 3 arc plates rotates around the rotor and is directed to the wind by aerodynamic force generated by a tail vane, so as to put the guide vane row upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed guide vane row. Further, by the use of the guide vane row adopted in the study, the power coefficient of the proposed wind turbine was approximately 1.5 times higher than that of the original wind turbine which has no guide vane.