Proceedings of ASME Turbo Expo 2017,June 26-30, 2017, Charlotte, NC USA
Authors: Joerg Alber, Georgios Pechlivanoglou, Christian Oliver Paschereit, Jochen Twele, Guido Weinzierl

This paper presents a modeling strategy of the aerodynamic Gurney flap effect on two-dimensional airfoils and, subsequently, on the rotor blade performance of horizontal axis wind turbines. The first part consists of the parametric investigation of 23 airfoil polar data-sets, derived from different, but comparable, wind tunnel experiments. They are evaluated and processed in terms of the lift and drag increase caused by Gurney flaps in comparison to each Baseline configuration. Consequently, a modeling strategy is developed, transforming Baseline- into Gurney flap polar data for varying flap-heights. The results of the emerging Gurney Flap Polar Calculator are successfully validated against the experimental lift and drag curves. In the second part, polar data-sets are generated for a wide range of Gurney flap-heights based on the blade design of the NREL 5 MW Reference Turbine, which are imported into the rotor simulation software Qblade. Thereupon, blade optimization strategies are examined regarding the two main Gurney flap applications on rotor blades: the retrofit and the design solution. The optimized retrofit solution on existing blades indicates power performance improvements, albeit at the expense of increasing structural loads. The optimized design solution on to-be-constructed blades, on the other hand, suggests chord-length reductions, while keeping the performance characteristics on a similar or even enhanced level. It is concluded that, in general, aerodynamic improvements are achieved by relatively small Gurney flap-heights, which are applied at specific blade positions. Guido Weinzierl SMART BLADE ® GmbH Berlin, Germany g.weinzierl@smart-blade.com