Colloquia

Summary

As global priorities shift towards sustainable energy, the importance of wind energy increases. In recent decades, the size of wind turbines has increased to capture more energy per turbine. This increase in size poses challenging conditions for the wind turbine blades, in addition to facing harsh environmental conditions, can reach tip speeds of over 300 km/h. As a result, surface degradation in the form of leading edge erosion (LEE) of turbine blades becomes more prevalent. LEE is caused by the impacts of rain and hail that can have negative consequences on the aerodynamic performance of the wind turbine, reducing the lift and increasing the drag by up to 53% and 314%, respectively. This can lead to a drop in annual energy production (AEP) of up to 3.7%. In addition to the negative aerodynamic effects of LEE, it can also affect the aeroacoustic signature of the wind turbine, as the surface roughness can distort the boundary layer into becoming turbulent, thereby amplifying the self noise of the airfoil. A common complaint during the approval of a wind farm is the noise pollution experienced by surrounding communities. Because a goal is to increase the lifespan of a wind turbine blade, quantifying the aeroacoustic effect of the wind turbine blade that has undergone erosion is of importance, as at the beginning of the life cycle of the noise generated by the blade can be deemed acceptable but the sound characteristics over time may change.

Therefore, this research investigated the following question: Can leading edge erosion on wind turbine blades be detected through its influence on aeroacoustic noise signatures?

This study investigates the impact of leading edge erosion (LEE) using the aeroacoustic wind tunnel facility at the University of Twente. Seven erosion models were placed on the DU97-W-300 airfoil to simulate the conditions of leading edge erosion without damaging the airfoil surface. The experiments were carried out at Reynolds numbers of 800.000,700.000 and 600.000 at the maximum lift-to-drag ratio. Using a microphone array and beamforming techniques, the effect of leading edge erosion was measured. The goal was to determine if the LEE could be detected by comparing it to the undamaged condition. The research provides insights into the modeling of roughness under non-ideal scaling conditions and offers insight into the relation between the roughness-induced turbulent boundary layer and the aeroacoustic effects.