Experimental study of microtabs in smart blades for wind turbines

Abstract

The goal of this thesis is to carry out an experimental study of the performance of smart blades reducing extreme and/or cyclic loads for their use in wind turbines. First of all, theoretical research about wind turbines and smart blades was done. Some of this information is explained in the thesis in order to set the background and make it more readable and understandable (Chapters 1 to 3). The next step was to choose a blade profile that would fit well the requirements of the experiments and the manufacture of the set up. Besides, one of the possible smart devices had to be chosen according to its expected performance and its feasibility. It had to be taken into account the technologies and tools that could be used for the construction of the set up, and the characteristics of the set up itself. Therefore, the main features of the set up had to be thought at this point, even though the final design was not decided. After all the preceding work, the setup was defined and built (Chapter 4). It consisted in a GU25 (5) 8-11, a profile designed by the University of Glasgow that is quite thick, and has a CL graph quite linear. It was made in balsa wood that would make it light and after sanding it the remaining surface would be reasonably smooth. Some holes next to the trailing edge were performed for the implementation of the microtabs. This blade was setup with a system for measuring the angle of attack in a test section, which included an aerodynamic balance for measuring the lift forces. The experiments (Chapter 5) consisted in measuring the lift forces in the blade with and without microtab for different angles of attack, with a solidity ratio of 100%. Also different speeds were tested, as the behaviour of the profile changes extremely depending on the Reynolds number. The used microtabs were made in balsa wood cutting sections and gluing them altogether with a solidity ratio of the 96%. It was tested at the 90% of the chord length due to space requirements in the blade. Finally, final conclusions (Chapter 6) and future research options (Chapter 7) are explained.