DYNAMIC STALL REDUCTION IN A 1KW VERTICAL AXIS WIND TURBINE ROTOR BY A PASSIVE FLOW CONTROL METHOD

Abstract

Wind power is a commercially-proven, fast growing form of electricity generation that provides a significant amount of clean, renewable, and cost-effective energy in many countries around the world. Wind power generation has so far favored the multi-megawatt horizontal axis wind turbine (HAWT) over the vertical axis wind turbine (VAWT) technology. Principal advantages of the VAWT technology are: (a) omni-directional operation independent of the directional changes in the wind, (b) heavy components such as the electric generator installed close to the ground, (c) simple design, less manufacturing and maintenance costs, (d) small operating space requirement (high farm power density), and (e) low environmental impact and noise signature [1, 2]. These properties support the application of VAWT in urban environments. However, the VAWT characterizes lower power coefficient Cp compared to the HAWT due to the presence of dynamic stall and associated blade-wake interaction induced vibrations. Dynamic stall occurs because of a large and periodic variation in the angle of attack (angle formed between the blade chord and relative wind speed) during rotation. Research has shown that an optimized/modified aerodynamic shape of the VAWT rotor can improve the flow characteristics and thus improve the power coefficient Cp [3]. This study is focused on applying a leading edge (LE) slat as a passive flow control device in order to reduce the dynamic stall over the rotor blades. The complex aerodynamics of the VAWT is analyzed using computational fluid dynamics (CFD) models and compared with the available test data. ANSYS Fluent and associated tools have been used as the CFD pre-processing and solver packages for the present study. A 1kW VAWT has been used as the test case. Two-dimensional (2D) unsteady simulations are performed for the baseline rotor design and the advance rotor design with the LE slats. Potential improvements in the rotor performance are observed