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Potential of Mini Gurney Flaps as a Retrofit to Mitigate the Performance Degradation of Wind Turbine Blades Induced by Erosion

Papi, Francesco; Melani, Pier Francesco; Alber, Jörg; Balduzzi, Francesco; Ferrara, Giovanni; Nayeri, Christian Navid; Bianchini, Alessandro

FG Experimentelle Strömungsmechanik

Leading edge erosion of wind turbine blades is still an important challenge for wind energy professionals, both at research and industrial level. While the efficiency and durability of materials and coatings are improving rapidly, it is important to explore innovative solutions at the aerodynamic design level to mitigate the adverse effects of surface erosion. For that, a preliminary analysis on the use of Mini Gurney Flaps (MGFs) is presented in the study. High-fidelity Computational Fluid Dynamic (CFD) simulations are used to evaluate the impact of severe leading edge (LE) erosion on the performance of the FFAW3-241 airfoil on the rotor blade of the DTU 10-MW Reference Wind Turbine, which is used as test case. CFD lift and drag polars of the eroded airfoil show that MGFs are able to partially recover aerodynamic efficiency caused by erosion; this suggested evaluating their use as a retrofit solution for blades that already experienced leading edge erosion damage. When tested on the DTU 10MW RWT blade, results show how, if sized correctly, MGFs perform as predicted: the lift curve is shifted back to its design value and performance is improved with respect to the eroded blade. Moreover, as one would expect, higher than optimal MGFs resulted in excessive lift increases and thus decreased performance, even in the case of LE-erosion. Although these devices behave as intended however, based on the results of this paper, performance decreases are noted at high tip-speed-ratios (TSR), due to the blade operating in off-design conditions.