Steady wind performance of a 5 kW three bladed H rotor Darrieus Vertical Axis Wind Turbine (VAWT) with cambered tubercle leading edge (TLE) blades
Abstract The performance of a 5 kW three bladed H rotor Darrieus Vertical Axis Wind Turbine with cambered Tubercle Leading Edge NACA 0025 blades was established using computational fluid dynamics. 3D models and simulations of the VAWT were realized using CAD and CAE software, after which post processing analyses provided understanding of the VAWT and blade flow physics. Results showed the TLE to be detrimental to flow and performance of a cambered VAWT. Using torque, lift and drag data, the cambered TLE VAWT was shown to deviate significantly against the cambered VAWT over one complete converged rotation. Cambered TLE VAWT blades encounter reduced lift forces and increased drag forces leading to lowered and eventual reversal of torque values. The z vorticity and Q criterion visualizations further supported the numerical results with the post processed images showing vortices the size of the blade chord generated at blade wakes of the cambered TLE. The vortices emanate from the flow separation at the blade crests creeping in at the blade trailing edge at 75deg azimuth and reaching halfway through the blade chord length at 106deg azimuth. Spanwise separation was observed to be restricted at blade crests. The resulting flow degradation translated to the poor performance of the wind turbine.
Energy