Analysis Of Oil-air Lubrication Two-phase Heat Flow Coupling Characteristics Of High Speed Angular Contact Ball Bearing

High-speed angular contact ball bearings are the main supporting elements of high-speed electric spindles.Oil-air lubrication is the main lubrication method of high-speed electric spindle angular contact ball bearings.Convection heat transfer of oil-air lubrication two-phase is the main heat dissipation method of the bearings,which directly affects the temperature field of the bearings.The distribution of the two phases of oil and gas in the bearing cavity greatly affects the lubrication status of the bearing,and the temperature field and the flow field in the oil and gas lubrication of the bearing also interact and affect each other.Therefore,it is of great significance to study the heat flow characteristics of angular contact ball bearings.Based on the theories of elastohydrodynamic lubrication,rolling bearing dynamics,and computational fluid dynamics,a finite element analysis model of angular contact ball bearings is established.The coupling characteristics between temperature and flow fields in the process of bearing oil and gas lubrication are analyzed.The influence of compressible air model and viscosity-temperature effect on the distribution of lubricating oil and temperature field in bearing cavity is analyzed.The main conclusions are as follows:(1)After the compressed air enters the bearing cavity in oil and gas lubrication,the density of the air changes due to the changes in air pressure and bearing temperature,which in turn affects the distribution of the flow field and temperature field in the bearing cavity.As the bearing temperature rises,the viscosity of the lubricating oil will continue to decrease,which has a greater impact on the flow field and temperature field in the bearing cavity.(2)Considering the compressibility of air,the average oil phase volume fraction of the inner channel surface of the bearing fluid domain is increased by 28%,while the outer channel surface is increased by 10% compared with the constant air density.When the bearing temperature is higher,the air density is lower,and the average oil phase volume fraction of the channel of the bearing cavity is also increased.The oil and gas velocity value is larger under the condition that the compressibility of air.The value of oil and gas velocity in the inner channel is greater than that of the outer channel.Compared with the condition that the air density is constant,the average temperature value of the ball is 2.1? lower,the average temperature value of the inner ring of the bearing is lower by 2.2?,and the average temperature value of the outer ring of the bearing is 1.6? lower when the air density changes with temperature.(3)When the bearing temperature is low and the viscosity of the lubricating oil is large,the oil phase volume fraction of the bearing fluid domain is small.When the bearing temperature reaches 40? and the viscosity value of the lubricating oil is between 0.035-0.045Pa·s,the average oil phase volume fraction of the inner and outer channel surfaces of the bearing cavity and the ball surface is relatively high.When the bearing temperature increases and the viscosity of the lubricating oil decreases,the value of the oil and gas velocity gradually increases.Compared with the case where the viscosity of the lubricating oil is constant,considering the viscosity-temperature effect of the lubricating oil,the average temperature value of the ball is 2.625? higher,the average temperature value of the inner ring of the bearing is 4.54? higher,and the average temperature value of the bearing outer ring is 3.04? higher.The temperature of the ball is higher than the temperature of the bearing inner ring,and the temperature of the bearing outer ring is the lowest.