A Straight-Bladed Vertical-Axis Turbine for Wave Energy Conversion

（Effect of Guide-Vane Geometry on Performance）

Abstract

This study proposes a straight-bladed vertical-axis turbine for ocean-wave energy conversion. The aim is to develop a novel air turbine suitable for an oscillating water column in a wave energy plant. For the purpose, the performances of straight-bladed vertical-axis turbines were investigated for different guide-vane geometries in a wind tunnel experiment. The rotor has four straight blades with an NACA0018 profile, a chord length of 80.5 mm, a pitch diameter of 460 mm, and a blade width of 490 mm. In this study, the guide-vane geometry was varied as arc, semi-arc, and semi-arc with two types of straight part. Under steady flow conditions, the turbine performance was evaluated by determining the input coefficient, the torque coefficient, the flow coefficient, and the turbine efficiency. The semi-arc blade geometry decreased the input coefficient and improved the starting characteristics of the turbine. Moreover, the semi-arc blade and the semiarc blade with a straight part improved the turbine efficiency over a wide range of flow coefficients.