ABSTRACT:

The purpose of this paper is to investigate the hydrodynamics of a straight-bladed vertical-axis water turbine (VAWT). In addition, the effect of turbine radius and different cross-sectional shapes of the blade is studied. Based on Computational Fluid Dynamics method, the numerical method is performed by virtue of a commercial package code to obtain the torque and the power of the turbine. It is shown from the result that among all tested blade cross-sectional shapes, NACA0012 outperforms all simulated hydrofoil cases. The rotor radius affects the turbine performance. Doubling the rotor radius may approximately bring about the increase of the turbine outputs to the power of two. The result also elucidates that the output torque subject to certain angles may be negative due to the wake effect which causes the drag force's augmentation applied onto the turbine blade. For the smaller output torque or negative output torque in some cases, it is recommended that the pitch angle of the turbine blade be adjusted for a certain degree so as to divert the lower torques to higher ones.

INTRODUCTION

The continual consumption of fossil fuel has pushed the oil prices to a record-breaking high point, which adds burden to the world growing economy these years, not to speak of the environmental concern that is contributed by its burning. Hence the world community has nowadays laid more and more stress on the development of renewable energies, one of which is ocean current power. EPRI estimates that in the US alone, the total energy in all regions with the average wave power density can be more than 10kW/m to 2100 TWh/yr and Canada tidal resource is much higher than the US (Roger, 2006). The conversion from the ocean current energy into mechanical and electrical energy also gives rise to the water turbine development.

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