Load case selection for finite element simulations of wind turbine pitch bearings and hubs
Abstract. Finite element simulations of large rolling bearings and structural parts are an indispensable tool in the design of wind turbines. Unlike simpler structures or smaller bearings in rigid environments where analytical formulas suffice, wind turbine components require a more comprehensive approach. This is because analytical formulas often fall short in predicting load distributions and stresses, leading to inadequate designs. However, due to the size of the finite element models and operational loads involved, it’s necessary to strike a balance between achieving realistic results and keeping computational times manageable. This study focuses on the selection of load cases for simulations of pitch bearings and hubs of wind turbines. The models for these contain the hub, the pitch bearings, the inner parts of three blades, and any necessary interfaces parts. The simulation results allow the calculation of static and fatigue strength. Given the complexity of the problem, with each rotor blade having six degrees of freedom, five types of loads, and the pitch angle, the potential combinations of loads would result in an unmanageably high number of required simulations. The present work exploits relationships between load components and the rotor position to reduce the number of load cases needed for fatigue calculations. The IWT 7.5-164 reference turbine and three commercial turbines serve as the basis for case studies which include bin counts and exemplary finite element simulations. The blade’s azimuth angle and bending moments of one blade allow determining the loads at all three blade roots with a reasonable degree of confidence.
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