Dynamic Characteristic Analysis And On-line Monitoring Research Of Wind Turbine Pitch Bearing

Wind energy is a kind of renewable energy which contains huge wealth.Today,it is strongly advocated to use clean energy.Wind power generation technology obviously meets the future development trend.With the construction of a large number of wind farms,wind power technology has developed rapidly all over the world.At the same time,higher requirements are put forward for the structural strength of wind turbines and the maintenance work in the operation process.The wind turbine is mainly composed of tower,frame,generator,gearbox,main shaft,hub,blade and other mechanical parts.As the connection between blade and hub,pitch bearing bolt is one of the important fastening parts of the wind turbine,which plays an important role in the operation of the wind turbine.In this paper,through the mechanical analysis of the wind turbine blade root load,the failure mechanism of the pitch bearing bolt is studied,and a design scheme of the on-line monitoring device for the pitch bearing bolt of the wind turbine is proposed according to the failure type of the bolt.The real-time monitoring of the pitch bearing bolt and the elimination of the hidden trouble are of certain engineering practical significance.This paper takes the pitch bearing bolt of 2MW wind turbine as the research object,and studies from the following aspects.Based on the basic theory of aerodynamics and the turbulence wind speed model,according to the load situation of the wind turbine blade and the connection structure with the pitch bearing,through the analysis of the load distribution of the pitch bearing bolt,the calculation method of the load strength of the pitch bearing bolt is obtained,which provides a theoretical basis for the strength analysis and failure mechanism research of the bolt.The first six natural frequencies of each model are obtained by modal analysis of three-dimensional model of blade and pitch bearing.Through the comparison of the natural frequencies before and after the model,the change rule of the stiffness is obtained,and then the influence of resonance on the pitch bearing bolt is studied,which provides the theoretical basis for the bolt failure mechanism.According to the analysis of the actual working condition of the wind turbine,the dynamic strength analysis model of the pitch bearing bolt under the three-dimensional turbulent aerodynamic load,gravity load and centrifugal force load is established.The stress distribution of the pitch bearing bolt is obtained by finite element analysis under the condition of normal operation and partial bolt fracture failure.Compared with the traditional bolt strength analysis,this paper can get more real bolt stress trend,maximum stress value and its location.It provides a theoretical basis for more accurate monitoring of key bolts of pitch bearing.According to the working principle of wind turbine and the failure type of pitch bearing bolt,a design scheme of on-line monitoring device for pitch bearing bolt is proposed.The reliability of the device is ensured by a large number of experiments on the monitoring principle and monitoring equipment,which is of great significance for the normal operation of the wind turbine.