Thermal Analysis Of Double Row Tapered Roller Main Bearing Of Large Wind Turbine

Rolling bearings are one of the most widely used mechanical parts,as well as in wind power equipment.As the main load-bearing part of wind turbine,the main bearing is required to have high reliability and excellent performance.The working environment of the main bearing is harsh,and the external load is complex and changeable,which often leads to the increase of friction and wear on the contact surface of each part in the bearing,the increase of friction heat generation,and the abnormal phenomenon of temperature rise.The abnormal working temperature of the main bearing has become one of the main faults of the wind turbine,which brings great safety hazards to the wind turbine and also loses the benefits of the wind field.By studying the relevant research results,it is found that most of the research focuses on the main bearing fault diagnosis and temperature prediction,and there is less analysis of the main bearing heat generation mechanism and the overall temperature field of large wind turbines.Therefore,this paper takes the double row tapered roller main bearing of FL3506-2000 wind turbine as the research object.Based on Hertz contact theory,elastohydrodynamic lubrication theory and rheological characteristics of grease,the force,lubrication and friction characteristics of the main bearing are studied.Then,the thermal analysis of the main bearing is carried out by local method,and the three-dimensional temperature field distribution of the main bearing is obtained by steady-state thermal simulation.The main contents of this paper are as follows :Firstly,the structural characteristics and size parameters of the main bearing of FL3506-2000 wind turbine are briefly summarized.The force analysis is carried out,and the overall mechanical model of the main bearing is established.The distribution of the contact load inside the main bearing is obtained by solving the mechanical equilibrium equation by programming.The mechanical analysis of the main bearing when the external load changes shows that the overturning moment has the greatest influence on the contact load.Secondly,based on Hertz contact theory,the contact analysis of tapered roller with inner and outer raceways and inner ring rib is carried out,and the parameters and stress distribution in the contact area are obtained.Based on the elastohydrodynamic lubrication theory,the oil film thickness of the contact area between the tapered roller and the inner and outer rings under the condition of grease lubrication is calculated,and the lubrication state is judged according to the film thickness ratio.At the same time,combined with the rheological properties of the grease,the friction force on each contact area is obtained.Then,on the basis of the above research,the local method is used to establish the overall heat generation calculation model of the main bearing.The steady-state thermal simulation of the main bearing is carried out by Ansys,and the three-dimensional temperature field distribution is obtained.The highest and lowest temperature areas of the main bearing are located on the surface of the maximum loaded roller and the outer surface of the outer ring respectively.Based on the thermal analysis finite element method,the influencing factors of the temperature rise of the main bearing are analyzed.The results show that the speed is the main index affecting the temperature rise of the bearing.Finally,by comparing the calculation results of contact stress and heat generation between roller and raceway of different convex rollers,the convex type suitable for tapered roller of main bearing is selected,and the optimal roller modification curve is calculated.The heat generation analysis of the main bearing after roller modification shows that the lubrication and friction characteristics in the contact area between the roller and the raceway are improved,and the overall temperature of the main bearing is decreased.