Wind turbine blades with serrated teeth
Wind turbine blades with serrated teeth. Image: Bernd Zillich – Shutterstock.

Researcher Elena Llorente Trujillo, in her doctoral thesis, studied how the installation of serrated teeth on the trailing edge of blades influences the aerodynamic performance of wind turbines. Their results could increase the efficiency of wind turbines.

These devices and their effectiveness in reducing noise have been widely studied, but to date, no analysis has been carried out on the effect of these solutions on the operation of wind turbines.

Elena Llorente Trujillo.

The doctoral thesis obtained the qualification of exceptional and was supervised by the professor of the Department of Sciences of the Public University of Navarre, Miguel Arana Burgui and by the professor of the Department of Aerodynamics, Wind Energy and Propulsion from the Technical University of Delft, Daniele Ragni.

Según explica la autora de la tesis, se está produciendo un aumento continuo y estable de la potencia eólica en todo el mundo, lo que implica la instalación de parques eólicos en zonas más cercanas a núcleos urbanos y que el tamaño de los rotores también sea mucho bigger.

These two factors mean that the noise emitted by the wind turbine can become a reason for complaint if certain levels are exceeded.

Elena Llorente Trujillo.

To avoid this, the industry has proposed various solutions which reduce the level of acoustic power emitted; among them, the installation of serrated teeth on the trailing edge of the blades.

In his thesis “Effect of trailing edge serrations on the aerodynamic performance of wind turbines»Analyzed the impact of serrated teeth on the aerodynamic behavior of the wind turbine.

Initially, he carried out various theoretical analyzes of the problem and simulated 2D and 3D airflow geometries around a profile with serrated teeth, a profile with a flat plate and the profile without any device installed. This made it possible to compare and analyze aerodynamic coefficients, speed profiles, turbulence, wake modification, etc.

This theoretical study also studies the impact of the mounting angle of serrated teeth on the blade and the influence of the thickness of these devices on the aerodynamic behavior of the profile.

Elena Llorente Trujillo.

Satisfactory results

One of the most important results of the theoretical study was the derivation of an empirical law that predicts the lift coefficient of the jagged tooth profile from the data of the original profile. To validate this prediction law, an experimental campaign was carried out in the LTT wind tunnel at the Technical University of Delft (Netherlands).

In the experimental results, it was observed how the presence of serrated teeth in the profile leads to an increase in the lift and resistance coefficients and that these coefficients increase as a function of the mounting angle.

These data were compared to the data calculated from the proposed law and a good fit was found between the two results.

The next step was to use this law to extend the theoretical analysis to the complete wind turbine, with serrated teeth installed on its blades. “and an increase in production and expenses has been confirmed“.

Finally, to validate the theoretical production data, an experimental campaign was carried out in a real wind turbine on which serrated teeth were installed and “a significantly higher increase in production was observed in the real case, compared to“. Likewise, an experimental study of the acoustic impact of the aforementioned devices was carried out on the noise emitted by the wind turbine and a reduction in the acoustic power above 2dBA was verified.

Via www.unavarra.es

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