Wake effects of the aerodynamic performance of horizontal axis wind turbines
Success of vortex theories in the performance prediction of horizontal axis wind turbines largely depends upon accurate specification of the geometry of the vortex wake. In this study, two methods of vortex wake analysis are developed: a new simplified free wake method (SFW) and a prescribed wake method. In addition, an earlier wake model of helicopter rotors, referred to as the fast free wake method (FFW), is extended for wind turbine applications. In the FFW model, the flow field downstream of the rotor was partitioned into three regions: the near wake, modeled as a series of straight vortex lines; the intermediate wake, modeled as a number of vortex rings; and the far wake, taken to be a semi-infinite cylindrical wake. The methods of this work were compared with an existing unconstrained free wake analysis, with an existing rigid wake analysis, with a popular blade element momentum method and with existing experimental data. Airload parameters obtained by using the present methods were found to be in good agreement with those of a full free wake analysis. However, the computational times were greatly reduced. Furthermore, the predicted performance agrees well with the experimental data. Both the FFW and SFW methods out performed the rigid wake and the blade element momentum methods. A parametric study using the prescribed wake analysis indicated that at some expansion rates, corresponding to low wind conditions, the predicted power exceeded that of the rigid wake prediction and could in fact exceeds the Betz limit.
- Research Organization:
- Toledo Univ., OH (USA)
- OSTI ID:
- 5531885
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Lifting surface performance analysis for horizontal axis wind turbines
Wind energy conversion. Volume II. Aerodynamics of horizontal axis wind turbines