Investigation On The Two-phase Flow And Heat Transfer Inside High-speed Ball Bearings For In Vehicular Transmission

With the vehicle transmission having higher power density, the rotating speed of bearings increases, and large amounts of heat is induced, which thereby influence the performance and service life of bearing. Therefore, in order to control the temperature rise,the deep understanding for the characteristics of non-isothermal two-phase flow in bearings is required. Focusing on the problem of non-isothermal two-phase flow in high speed ball bearings lubricated by injection, this paper study on the characteristics of non-isothermal two-phase flow, the effect of parameters and the experiment on non-isothermal two-phase flow in ball bearings.Firstly, this paper establishes the coupled model of two-phase flow field in bearing cavity, and the solid area including shaft, bearing seat, inner and outer rings of bearing,cage and rolling element. MRF is applied to solve the numerical transfer of relative motion,VOF model is used for two-phase flow, and then the non-isothermal flow characteristics when lubricated by injection is obtained by numerical calculation. Simultaneously, a new simplified method to calculate the average temperature in bearing is proposed. The temperature of inner ring is higher than that of outer ring, and it is more uniform along axial direction. The inner flow field of ball bearing and the temperature distribution of outer ring are negatively correlated: the temperature decreases when lubricating oil is abundant,therefore the inner flow field and the axial distribution of temperature in outer ring is not uniform, with lower temperature near the nozzle, and temperature increasing along the rotating direction, while then declining when approaching the nozzle on the other side.Based on the numerical model of coupled heat transfer on ball bearing, the effect of parameters is studied through establishing and analysis on different models with various parameters, such as operating speed, injection flow rate, number of nozzles and injection speed. The temperature will increase when operating speed rises, as well as the average speed of flow field and the churning torque. The highest oil content appears near the nozzle,however, when rotating speed changes, the position of highest oil content moves along the rotating direction. When rotating speed increases, the ununiformity of oil and air becomes weak in bearing, and the temperature of outer ring becomes more uniform; the temperature of bearing declines with the increase of amount of lubricating oil. Compared with that in inner ring, the temperature change in outer ring is insignificant; the temperature of bearingdeclines with the increase of the number of nozzles, and oil and air distribution in inner flow field in ball bearings with multi-nozzles presents a periodical variation with the number of nozzles. In each period, the oil and air distribution is similar with that only one nozzle is used. Therefore, the temperature of outer ring and flow field present a similar pattern, and churning torque also increases when the number of nozzles increases. With higher injection speed, the temperature of bearing increases. It is not effective to improve the oil content near the position with lowest oil content rate by altering the injection speed. The study on the characteristics of non-isothermal two-phase flow provides a reference for the accurate lubrication method.Finally, the experiment system for injection lubrication in bearing is improved with the use of UMT. Various flow field pattern are obtained by SLR camera, verifying the result from numerical calculation. Meanwhile, the frictional torque is measured by torque sensor,and the regulation of that is also obtained when the injection parameters and rotating speed change.