| Effectively reducing the temperature rise of high-speed angular contact ball bearings has always been a hot research topic,and many research results are centered on how to effectively improve the lubrication efficiency of bearings.In order to ensure that the lubrication can effectively reduce the temperature rise in the bearing cavity,this paper proposes to add graphene to the oil-air lubrication of angular contact ball bearings for high-power high-speed electric spindles,and on the basis of the established mathematical model of thermal flow analysis of gas-liquid-solid threephase flow,the influence law of the gas-liquid-solid three-phase flow formed by compressed gas,lubricating oil and graphene particles in the bearing cavity on the thermal flow field of the bearing cavity is discussed.The results show that the cooling effect of oil-air lubricant with graphene particles is better than that of ordinary oil-air lubrication,and the best cooling effect is achieved when the concentration of graphene lubricant is 0.06%.The results of the study have some implications for the improvement of oil-air lubrication technology of angular contact ball bearings for high power high-speed electric spindles.The main research results are as follows:(1)Determination of the optimal conditions for the formation of graphene lubricant annular flow.Based on the hydrodynamic conservation equation,the thermal flow analysis mathematical model of the gas-liquid-solid three-phase flow formed by the compressed gas,lubricant and graphene particles in the high-speed angular contact ball bearing cavity is established to provide boundary conditions for the finite element analysis of graphene lubricant annular flow in the oil-gas channel,and the flow state of graphene lubricant in the oil-gas channel is analyzed at different compressed gas velocities,and it is determined that the compressed gas velocity of 30m/s and A stable graphene lubricant annular flow can be formed when the ratio of graphene lubricant velocity to compressed gas velocity is 1:10.(2)Determination of the thermal boundary conditions of the high speed angular contact ball bearing cavity.After analyzing the rotating characteristics of the ball,the heat generated by the bearing is derived,and then the heat flow density of the bearing under working conditions is obtained,and this is taken as the heat generation boundary condition of the bearing cavity;on this basis,the convective heat transfer between the compressed gas and graphene lubricant in the bearing cavity is analyzed,and the convective heat transfer coefficient of the bearing cavity is derived by using heat transfer theory,and this is taken as the heat transfer boundary condition of the bearing cavity.(3)Influence law of oil-air lubrication containing graphene on the temperature field of bearing cavity.The initial temperature field of the bearing cavity was obtained by using the above boundary conditions,and then the cooling simulation of the bearing cavity was carried out by using the oil-air lubrication containing graphene.The results show that the initial temperature field of the bearing cavity is significantly reduced under the condition of oil-air lubrication containing graphene,and the temperature of the bearing cavity tends to decrease first and then increase with the increase of graphene lubricant concentration,and the temperature of the bearing cavity is reduced to the lowest when the graphene lubricant concentration is 0.06%.(4)Influence law of graphene oil-air lubrication on the thermal flow field of bearing cavity.The graphene lubricant volume fraction,fluid velocity and graphene particle distribution in the bearing cavity were used as the influencing factors to analyze the influence law on the thermal flow field of the bearing cavity.The results show that: the larger the volume fraction of graphene lubricant in the bearing cavity,the lower the temperature in the region;the fluid velocity in the contact area between the inner ring and the ball of the bearing cavity is the largest,and the convective heat transfer coefficient on the surface of this region is the highest and the heat transfer capacity is the strongest;when the concentration of graphene lubricant is the same,the graphene particles spread more widely as the speed increases;when the concentration of graphene lubricant is larger,the graphene particles in the bearing cavity are more densely distributed,resulting in When the concentration of graphene lubricant increases,the distribution of graphene particles in the bearing cavity becomes more dense,resulting in the temperature field of the bearing cavity decreasing first and then increasing. |
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