Lubrication analysis of low-speed and heavy-load journal bearing in wind turbine gearbox under different operating conditions

Abstract

Aiming at the working conditions of frequent starting, low speed and heavy load, and yaw tilting of radial sliding bearings in wind turbine gearboxes, a numerical analysis model of the lubrication performance coupled with instantaneous starting and operating conditions of radial sliding bearings was established based on the average Reynolds equation, and the start-up phase was analyzed. The motion trajectory of the shaft diameter and the axis center was used to obtain the change state of the bearing film thickness from the start-up to the stable stage; the influences of the comprehensive surface roughness, the journal inclination angle, and the journal rotation speed on the lubrication performance of the bearing during the whole stage of start-up and stable operation were studied respectively. The results show that the eccentricity has a maximum value in the starting stage, and the risk of film rupture caused by rough contact is the greatest. With the increase of the comprehensive surface roughness, the bearing capacity and friction coefficient both increase, and the maximum bearing capacity and friction coefficient in the starting stage are higher than those in the stable stage, which increase by about 13.62% and 131.58% respectively. With the increase of the inclination angle of the shaft diameter, the bearing capacity and friction coefficient both increase, and the maximum load capacity and friction coefficient in the starting stage are about 30% and 116% higher than those in the stable stage on average. With the increase of the speed, the bearing capacity of the bearing increases and the friction coefficient decreases, which is beneficial to improve the bearing performance. The calculation results provide an important basis for evaluating the wear risk of sliding bearings under frequent starting conditions, and provide a reference for the structural design and selection of sliding bearings, operating temperature, oil film pressure, etc.