Aerodynamic Performance Improvement of Hybrid Darrieus-Savonius Vertical Axis Wind Turbine

Returning blades of Savonius vertical axis wind turbines make negative effects on total moment produced by the turbines especially at high TSRs. For hybrid Darrieus-Savonius VAWTs at dynamic mode, with TSR increment from self-starting to that of high values, returning blades of its Savonius part make the whole part to produce negative moment. In present work, in order to reduce negative effects of returning blades of Savonius VAWTs and consequently improve its aerodynamic performance, a wall is placed in front of them. Several configurations including two types of blade shapes with three types of wall placements are simulated three dimensionally and their output-moment and moment fluctuations are computed for one complete cycle. Desired Savonius VAWT with suitable wall which produces the most average-moment and the least moment fluctuations are mounted on a straight-blade Darrieus VAWT and they formed a hybrid VAWT. In comparison to straight-blade VAWT, at TSR of 0.9 proposed hybrid VAWT produces 2.3% more average-moment along with 40% less moment fluctuations. This means in term of TSR values, proposed hybrid VAWT has wider operating range in comparison to its general types.