| Tapered roller bearing is a key component in the gearbox of high-power wind turbine,whose life has a significant influence on the normal operation of wind turbine.According to IEC61400-4 standard,the wind turbine should meet the requirement of not less than 20 years of service life,namely,the life of bearings in the wind turbine gearbox should not be less than 20 years.However,the fatigue life test of bearings in wind turbine gearbox has long cycle,high cost,complex working conditions,and there is no mature and effective test bench for the life and reliability test of bearings in the wind turbine gearbox above 4.5MW,which has seriously restricted the rapid development of taper roller bearings of high-power wind turbine gearbox.Therefore,it is of great significance to improve the fatigue life of the wind turbine and promote the research and development of bearings in wind turbine gearbox,which is realized by accurately calculating and predicting the fatigue life of bearings of wind turbine gearbox,and evaluating the reliability of fatigue life.In this paper,the structure and transmission route of a 4.5MW wind turbine gearbox are analyzed,and the mechanical balance equation of the planetary frame shaft of the gearbox is established.Taking tapered roller bearing 3171（b3）as the research object,the equivalent load and equivalent speed of tapered roller bearing are calculated by weighted average method based on Load Duration Distribution（LDD）load spectrum of input shaft,and the fatigue life of tapered roller bearing is calculated according to Hertz contact theory.The results show that the calculated fatigue life of the bearing is1.77×106h,and the bearing life exceeds 20 years,which meets the service requirements.The Romax simulation model is established to simulate and analyze the fatigue life,maximum contact load and maximum contact stress of tapered roller bearing 3171,the influence of torque,rotational speed,temperature and preload on the fatigue life of the bearing.As the results indicated,the influence law of torque on fatigue life of bearing show a trend of S type curve,the influence law of rotational speed on fatigue life of bearing show a trend of inverse ratio curve,the influence law of temperature on fatigue life of bearing show a trend of normally distributed.With the increment of preloaded,the fatigue life of bearing first increases and then decreases,when the preloaded quantity amounts to about 20 microns,the bearing 3171 has reached the maximum life.Taking the tapered roller bearing 3177（b4）as the research object,the equivalent fatigue life of tapered roller bearing is simulated by Romax software.A GM model is established to predict the fatigue life of tapered roller bearing by using grey system theory,and the prediction accuracy reaches 97.12%.The relationship between fatigue life and reliability of bearing is established by using Weibull distribution theory,and the shape parameter and scale parameter of Weibull distribution are estimated by the least square method.The results show that the relative errors of the estimated and assumed values of shape parameter and scale parameter are 0.07%and 0.1%,respectively.Under90%reliability,the relative error between the estimated life and the simulated life of the bearing is 0.24%.The reliability of bearing b4 for 20 years is 94.2%. |
