Simulative Investigation of the Risk of Smearing Damage for a WT Gearbox Roller Bearing during Rotor-Induced Excitations

Wind turbine drivetrains can be subjected to highly dynamic loading conditions caused by grid faults, power converter faults and dynamic wind excitations. These loading conditions can cause additional wear and possibly damage their components. Some of the most critical components in the mechanical drivetrain are its bearings. High-speed shaft bearings are especially prone to failure. Smearing is one possible damage pattern for these bearings. Previous studies observed a highly increased smearing risk caused by generator-induced torque excitations. In contrast, this study focuses on rotor-induced torque excitations and investigates the resulting smearing risk. The goal is to ascertain the general damage potential stemming from rotor-induced excitations for high-speed shaft bearings regarding smearing. To this end, a detailed bearing model was integrated into a validated multibody simulation of a research nacelle which was operated on a test bench. A smearing criterion was used to evaluate the smearing risk. Multiple sinusoidal rotor-induced torque excitations were investigated. The resulting smearing risk is highly dependent on the excitation amplitude and frequency, with higher amplitudes resulting in a greater smearing risk. Regarding frequency, only excitations with frequencies close to the system’s first torsional eigenfrequency result in a significantly increased smearing risk. In general, the determined amplitudes and frequencies of rotor-induced torque excitations, necessary to cause a significant increase in smearing risk, are unlikely to occur in the field and therefore are of lesser importance to the high-speed shaft bearings than generator-induced torque excitations.