Experimental study of a self-rectifying biradial air turbine with fixed guide-vanes arranged into two concentric annular rows

Abstract The self-rectifying biradial air turbine was proposed to equip wave energy converters of the oscillating-water-column type. There are two configurations: with fixed guide vanes and a radially more compact one with axially-sliding guide vanes. The added complexity of the movable guide-vane mechanism represents a drawback in offshore environments. The configuration with fixed guide vanes is the object of the present investigation using a novel stator design. The guide-vanes were radially shifted from the rotor and the single row of guide-vanes, located on each side of the rotor, was replaced by two concentric rows of guide-vanes, with wider circumferential spacing for the exit-flow. The work comprised the design, construction and experimental study of a 0.5 m rotor diameter turbine model tested under steady flow. Experimental results show that the new stator design provides significant reduction in the flow stagnation pressure losses at the exit guide vanes, while appropriately turning the flow admitted into the rotor. The measured efficiency reaches a peak of 0.728 and is above 0.6 over a wide range of flow coefficients.