The aim of the current work was to analyze the effect of retrofitting vortex generators (VGs) on the blades of a constant RPM, pitch-regulated, megawatt-sized turbine suffering from surface roughness. Engineering modelling and experimental work were utilized, indicating that the degradation of energy production may be mitigated by the VGs. The modelling results indicated that the optimal configuration of VGs to maximize the annual energy production (AEP) depends on the degree of severity of surface roughness. Depending on blade surface condition and turbine characteristics, installation of VGs on an incorrect blade span or installation of too large VGs too far out on the blade may cause loss in the AEP. Therefore, engineering modelling is necessary before VGs may be retrofitted on a specific turbine. The modelling results indicated that the worse blade surface, the more gain may be obtained from the VGs.The work included a full-scale experimental validation of the present engineering model, lasting 27 months and comprising six turbines where VGs were mounted on three, each with a neighboring turbine as a reference. The turbines were analyzed in pairs, and the influence of the VGs was judged upon the relative difference in energy production before and after the installation. The reason was to limit measurement uncertainty. The results showed that all three turbines increased their energy production after the installation. Results from the three pairs showed an average increase in the energy production of 3.3%, being satisfactorily close to the average 2.8% predicted by the present engineering tool.
Abstract. Vortex generators have in recent years been used extensively on pitch regulated wind turbines. A new trend has been to use vortex generators on thinner airfoils on the outer part of the blades. However, not much data is available for thin airfoils with vortex generators. That is the reason to carry out wind tunnel tests on a NACA 633-418 airfoil with 18% relative thickness in the Stuttgart Laminar Wind Tunnel. The airfoil was tested in clean condition, but also with leading edge roughness and different heights and different positions of the vortex generators. Results of the airfoil performance in terms of polars, maximum lift and lift-drag ratio are shown with focus on how the vortex generators influence the performance of the airfoil.
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