Développement d’un modèle structural simplifié d’analyse en fatigue d’une pale d’éolienne de 2.05 MW en conditions nordiques basée sur des données partielles

Abstract

The energy transition is a multi-pronged issue on a global scale. In Canada, a better integration of renewable energies, and particularly of wind energy in northern conditions, is necessary to decrease the carbon footprint. This research project proposes a simplified structural analysis approach, based on partial data, to evaluate the loading and fatigue life of wind turbine blades used in northern conditions, for a desired period of operation. The structural analysis methods of a blade, at the design stage, require a multitude of data, which are generally not accessible to wind farm operators. Therefore, this work aims to develop a simplified and accessible approach that will allow to obtain the loading perceived by the blades as well as the cumulative damage on the entire blade for a period of operation. To do so, the generalities of the wind energy sector as well as the characterization of the reference wind turbine (2.05 MW) used in this work are first detailed. The loading study is done according to the simplified approach (using SCADA data), according to the blade element momentum theory and according the bending beam theory. In order to characterize the bending stiffness distribution in the main strain axis, the estimation of the elastic properties by optimization method and by the classical laminate theory (with samples gathered from a blade) is then considered. The research concludes with the study of fatigue life, according to the Germanischer Lloyd standard. The objective is to study the difference in cumulative damage between two time periods with a minimum of data. The loading analysis is conclusive with an average deviation of 15 % for the bending moments evaluated by the simplified approach compared to the data obtained on sensors. The difficulty in characterizing the thrust coefficient explains the discrepancy between the simplified method, the blade element theory and experimental data. Second, for the evaluation of the bending stiffness distribution, the numerical optimization method, based on modal properties, converges to a multitude of solutions that satisfy the targeted natural frequencies. This array of solutions is problematic and could be avoided by adding more constraints to the model, such as more natural frequencies or local values of bending stiffness. The evaluation of the bending stiffness obtained with the collected samples results in a respective deviation for the first three natural frequencies of 19.9 %, 19.5 % and 6.0 %. The structural reconstruction of the blade leads to an error of about 23 % for the total mass of the blade. The assumptions made about the dimensions of the spar cap and shear webs are considered to be the greatest sources of error in this structural reconstruction. Finally, the study results over a three-hour period tend to indicate that the validity of the bending stiffness greatly influences the fatigue life, and that the critical area is localized at the trailing edge.

Date	17 Jun 2022
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Simon Joncas (Supervisor), André Bégin-Drolet (Co-supervisor) & Charles Godreau (Co-supervisor)