Abstract
During their operation, wind turbine blades are eroded due to rain and hail, or they are contaminated with insects. Since the relative inflow velocity is higher at the outer than at the inner part of the blades, erosion occurs mostly at the outer blade region. In order to prevent strong erosion, it is possible to install a leading edge protection, which can be applied to the blades after the initial installation, but changes the shape of the initial airfoil sections. It is unclear how this modification influences the aerodynamic performance of the turbine. Hence, it is investigated in this work. The NREL 5 MW turbine is simulated with clean and eroded blades, which are compared to coated blades equipped with leading edge protection. Aerodynamic polars are generated by means of Computational Fluid Dynamics, and load calculations are conducted using the blade element momentum theory. The analysis in this work shows that, compared to clean rotor blades, the worse aerodynamic behaviour of strongly eroded blades can lead to power losses of 9 % . In contrast, coated blades only have a small impact on the turbine power of less than 1 % .
Highlights
Since wind turbines operate in the lower atmosphere, they are exposed to the local weather.Rain, hail or even insects lead to the erosion of rotor blades
It can be expected that strong erosion and resulting delamination lead to even higher power losses
The aerodynamic coefficients computed by means of Computational Fluid Dynamics (CFD) were used in turbine load calculations, which were performed by the aeroelastic blade element momentum theory (BEM) code FAST v8 [24]
Summary
Since wind turbines operate in the lower atmosphere, they are exposed to the local weather. It is not known how much a leading edge protection changes the wind turbine performance for modern multi-MW turbines compared to eroded airfoil shapes This is the focus of this work, and in order to be able to reach the high Reynolds numbers of modern wind turbines, the investigation is done purely numerically. Corsini et al [8] report a numerical study of rain erosion on a 6 MW turbine and compared standard and aerodynamically optimized blades with each other They simulated erosion by a steady-state Euler-Lagrangian approach with droplet tracking using CFD, but they do not report any difference in total power or AEP between eroded and clean blades. The following work shall give a numerical estimation of the expectable losses due to erosion, and shall compare the wind turbine performance to coated blades equipped with leading edge protection. These polars were used in BEM calculations in order to estimate power and loads as well as the AEP for an exemplary site
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