+44 330 818 7254R. Gupta, K.K. Sharma
Vertical Axis Wind Turbine (VAWT) is self-starting, omni-directional, inexpensive, and especially viable in low wind speed regimes. Savonius, Darrieus, H-Darrieus, combined Savonius-Darrieus, and Darrieus-Savonius rotors are the types of VAWTs. The Darrieus rotor has low starting torque but provides high power coefficient for which it can be coupled to Savonius rotor that provides high starting torque. The combination of Darrieus and Savonius rotors thus exhibits high starting torque and high power coefficient. In this paper, an attempt was made to study the flow physics of a combined three-bladed, Darrieus-three-bucket-Savonius rotor using Fluent 6.0 CFD software. The height of the combined rotor was 20 cm. Four overlap conditions in the range of 10.87% to 25.87% were considered for the Savonius part of the combined rotor. Contours of relative speed magnitude and static pressure on various horizontal and vertical iso-planes were analysed as obtained from the CFD simulations. High performance of the combined rotor was attributed to the Darrieus rotor for the observed highest relative speed of the combined rotor near its top and also for the highest pressure and speed drop across the combined rotor at low overlap like 15.37%. Moreover, good aerodynamic performance of the combined rotor could be expected by the presence of the Darrieus rotor on top which having no wake been formed downstream of the combined rotor.
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