Performance evaluation of wind turbine blades using blade element momentum theory and flow simulation techniques

Computational studies were performed to evaluate the performance of two wind turbine blades. The first study consisted of a computational flow simulation conducted to predict underperformance of a stall regulated wind turbine rotor. A hypothesis was proposed explaining the causes for the underperformance of an 8kW stall regulated wind turbine machine. The two main causes affecting the performance were due to poor manufacturing techniques as well as the aerodynamic design of the airfoil. 2-D Computational Fluid Dynamics (CFD) studies confirmed the causes of the underperformance for these blades and a good comparison with field data was obtained. The second study consisted of the performance prediction of a 56m wind turbine blade using CFD flow solving techniques and its comparison to that predicted by Blade Element Momentum theory. A full scale 3-D computational simulation based on Reynolds-Averaged Navier Stokes equations was carried out and the results for energy capture and other flow features obtained were compared to those predicted by BEM. The power estimation obtained from CFD was over predicted by 2.7% as compared to BEM. Spanwise vortex structures were observed which were deemed to be the primary cause for a shift in inflow angles along the span of the blade. Also, several 3-D flow field characteristics were identified and analysed which resulted from the 3-D simulation of the 56m wind turbine blade.