Application of circulation control aerofoils to wind turbines

Circulation control aerofoils potentially offer an additional means of load and power control for horizontal axis wind turbines by virtue of their rapid response time. Their suitability for these tasks has been assessed with respect to the power which they absorb, their interaction with aerofoils used on modern wind turbines, the infrastructure or hardware which they require and the degree to which they can affect the loads experienced by the turbine blades and other major components. It has been determined that the type of circulation control aerofoil most suited to use on wind turbine blades are those of the jet flap type and it has been realised that an ability to shed, as well as increase loads is advantageous in this application. To this end the behaviour of both negatively and positively deflected jets have been investigated with a two-dimensional computational fluid dynamics code, validated in the course of this work for such modelling. Particular emphasis has been placed on minimising the input power requirements of the circulation control aerofoils and in proposing an overall system that has the required level of robustness and reliability. A 2MW turbine has been modelled with a blade element momentum theory code in order to compare performance with and without circulation control aerofoils. These initial results show that there may be some positive benefits to be gained, but that the energy demands of the system place a hard limit on the degree to which circulation control aerofoils can determine the forces experienced by the turbine.