Dynamic stall controlling of the Darrieus wind turbine using turbo-sail airfoils

Abstract

Darrieus wind turbine is categorized to vertical axis wind turbine driven by lift force. This study aims to improve performance of the wind turbine by preventing dynamic stall at low tip speed ratios. Turbo-sail airfoils, so-called, is one of the devices which can reduce stall state by blowing thin tangential jet on concave surface of wings. A small model of Darrieus wind turbine which has turbo-sail airfoils as its blade was built and tested in a wind tunnel. Stall controlling performance of turbo-sail airfoils applied for Darrieus wind turbine was investigated by visualizing flow field around the blade. From phase- averaged PIV data, it revealed that dynamic stall vortex was suppressed and attached flow state was achieved by the stall controlling. Pressure field was obtained from phase-averaged PIV by solving Poisson’s equation. It revealed that strong negative pressure area beside suction surface of blade was greatly reduced by the stall controlling. Also, local power coefficient at each visualized phase angle were evaluated and improvement of local power coefficient by the stall controlling was confirmed.