Wind Turbine Performance Improvements using Active Flow Control Techniques

Abstract

Abstract The ability of a wind turbine to react to rapid fluctuations in wind velocity is blunted by the massive rotational inertia of the rotor assembly as a whole, as well as the mass of individual blades bearing upon pitch change mechanisms. Thus, wind turbines often operate with a less than optimal relationship to the instantaneous wind conditions. A wind turbine interacting with slow fluctuations in wind velocity may suffer a loss in potential energy extraction due to stalling of the blades. Interaction with rapid fluctuations in wind velocity can subject a wind turbine to the phenomenon of dynamic stall, which produces severe variations in the aerodynamic loads upon the blades resulting in major structural issues. Flow separation is a major contributing factor to the aerodynamic challenges associated with wind turbine operation. The ability to control or reduce the magnitude of regions of separated flow over an airfoil can play a significant role in reducing the negative effects associated with turbine operations in fluctuating wind conditions. The use of Air Jet Vortex Generators (AJVG) has been shown to provide net increases in power output on full scale turbines. In addition, AJVG's have been shown experimentally to reduce the fluctuating aerodynamic loads associated with dynamic stall. Such devices are ideal for use in rapidly fluctuating conditions, as there is potential for an active flow control technique with a rapid response time which would be more difficult to achieve with fixed Vane Vortex Generators (VVG). The current work details experiments carried out with a new type of AJVG that has proven to consume less energy compared with traditional devices. The use of such a device on full scale wind turbines may lead to greater net gains in power output, as well as reducing the magnitude of aerodynamic loads associated with dynamic stall.