Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Fatigue failure analysis of a wind turbine gearbox caused by torsional vibrations
Submission Author:
Alex De Pretto Mansano , SP
Co-Authors:
Alex De Pretto Mansano, Demetrio Cornilios Zachariadis
Presenter: Alex De Pretto Mansano
doi://10.26678/ABCM.COBEM2021.COB2021-2063
Abstract
In recent years, the demand for wind turbines for sustainable development has increased. Although wind turbines are able to convert wind energy into electrical energy, they are still an inefficient mechanism, since almost 60% of their failures occur in the mechanical transmission, known as gearbox, affecting structural integrity, and reducing efficiency and reliability. Based on this, the objective of this paper is to present the fatigue failure analysis of a wind turbine gearbox caused by the torsional vibrations, presenting methods, gear fatigue life prediction, the most common failures and how to mitigate them. Firstly, the 750 kW NREL wind turbine transmission will be shown in detail, which consists of a planetary gear system and two gear-pinion pairs. Secondly, the transmission will be modelled considering mesh stiffness, mesh damping and shaft stiffness, and the equations of motion will be derived using Lagrange mechanics. Finally, a PID control will be implemented to calculate bending and contact stresses and, consequently, determine the gears useful life. The simulation and the results were obtained using the numerical simulation software Matlab©, and the NREL 750 kW baseline turbine was modelled in Simulink / Simscape. The results showed that the transmission is able to operate within the required speed range out of the resonances. From a structural point of view, the contact stresses attained higher levels compared to the bending stresses, and as expected, some gears have stresses above 2048 MPa, making their useful lives drop dramatically and reducing gearbox life to less than 10 years, far below the 20 years life design requirements. The failures most likely to occur were tooth breakage in the planetary gear and pitting and scuffing on pinion-gear pairs.
Keywords
gearbox, Vibrations, fatigue, Failure analyis
