Evaluation and performance prediction of a wind turbine blade

[摘要] The aerodynamic performance of an existing wind turbine blade optimised for low wind speedconditions is investigated. The aerodynamic characteristics of four span locations are determined fromsurface pressure measurements and wake surveys with a traversed five-hole probe performed in a lowspeed wind tunnel for chord Reynolds numbers ranging from 360,000 - 640,000.Two-dimensional modelling of the wind tunnel tests is performed with the commercial computationalfluid dynamics code FLUENT. The predictive accuracies of five eddy-viscosity turbulence models arecompared. The computational results are compared to each other and experimental data. It is foundthat agreement between computational and experimental results varies with turbulence model. Forlower Reynolds numbers, the Transitional-SST turbulence model accurately predicted the presence oflaminar separation bubbles and was found to be superior to the fully turbulent models considered. Thishighlighted the importance of transitional modelling at lower Reynolds numbers. With increasing anglesof attack the bubbles were found to move towards the leading edge and decrease in length. This wasvalidated with experimental data. For the tip blade section, computations implementing the k-εrealizable turbulence model best predicted experimental data. The two-dimensional panel methodcode, XFOIL, was found to be optimistic with significantly higher lift-to-drag ratios than measured.Three-dimensional modelling of the rotating wind turbine rotor is performed with the commercialcomputational fluid dynamics code NUMECA. The Coefficient of Power (Cp) predicted varies from 0.440to 0.565 depending on the turbulence model. Sectional airfoil characteristics are extracted from thesecomputations and compared to two-dimensional airfoil characteristics. Separation was found to besuppressed for the rotating case. A lower limit of 0.481 for Cp is proposed based on the experimentaldata.

[发布机构] Stellenbosch University