Study On Mechanical Properties Of Yaw Bearings Used In Wind Turbines

Four point contact ball bearings are widely used in wind turbine yaw and pitch systems.It's one of the key transmission components of wind turbines,since its reliability directly affects the safe operation of the whole system.To study the yaw bearing system's mechanical properties,a finite element model was established based on the contact strength analysis theory and finite element method,and was verified using the theoretical mechanical model established in this thesis.Subsequently,the influence of the tower wind pressure acting on the contact load distribution of the bearing was studied,based on the theory of aerodynamics and the theory of fluid-solid coupling.Finally,the fatigue life of the bearing was calculated by using the contact load distribution obtained above.The research method of this thesis provides the basis for the calculation and verification of the wind turbine's yaw bearing,which has certain engineering practical value.The main research contents of this paper are as follows:(1)Established three – dimensional geometry model and finite element model of the yaw bearing,based on the finite element method and the Hertzian contact theory.And calculated the load distribution and angular distribution of the four-point contact ball bearing under extreme load working condition.(2)Carried out a theoretical mechanical model of the yaw bearing,using the Hertzian contact analysis theory,obtained the theoretical distribution of the contact load and the contact angle under the extreme load condition,and verified the accuracy of the finite element model established in 3rd chapter.(3)Analyzed the influence of the bearing's flexible supporting stiffness on the load distribution and the contact angle distribution,by using the ball-raceway contact finite element model established in Chapter 3.(4)Calculated the wind pressure acting on the tower by FLUENT,on the base of aerodynamic analysis theory,verified the accuracy of the results by national calculation standard,and simulated the effects of the wind pressure on the load distribution of the yaw bearing by using ANSYS Workbench.(5)Calculated fatigue life of the yaw bearing by ISO 281 standard and compared the influence between different models on the bearing life.Finally obtained the accurate and reliable fatigue life of the yaw bearing of the wind turbine.