Basic Research On The Application Of Oil-air Lubrication In Cylindrical Roller Bearings

Cylindrical roller bearing is a key component of large rotary machinery bearing,with the increasingly bad working conditions,the lubrication requirements of cylindrical roller bearings are increasing day by day.The application of oil-air lubrication in cylindrical roller bearings has a good prospect.Therefore,it is of great academic value and practical significance to carry out the basic research on cylindrical roller bearings under the condition of oil-air lubrication.In this paper,the experimental equipment of oil-air lubrication was developed according to the test demand.The spatial flow field model of oil-air lubrication in contact with raceway/roller line was established.The movement of oil and air in the pipeline and the distribution of oil phase in the flow field were observed.The gas-liquid two-phase flow characteristics and oil-phase distribution characteristics of oil-air lubricating device were analyzed.Then the contact lubrication parameters of raceway/roller line were conducted on a machine of friction and wear testing,and analyzed the dynamic behavior of friction of the contact pair of raceway/roller line under the condition of oil-air lubrication.Then the microscopic analysis of the spot after test was carried out.Furthermore,the lubrication characteristics of the contact pair of raceway/roller line were studied.The main research conclusions were as follows:（1）Study on numerical simulation of oil-air lubrication flow field in contact with raceway/roller lineBy observing the two-phase flow in the pipeline,it was found that the air phase drived the oil phase along the pipe wall in a"wavy"manner within the pipe and formed tiny droplets of oil at the outlet of the pipe.It conformed to the characteristics of stable and safe circulation pattern.The oil phase distribution at different time was analyzed.It was found that the oil phase had a collision with the roller when entering the contact pair.Under the action of pressure,the oil phase along the roller had shifted at both ends.And the oil phase at the contact side was covered in a gradual process.Oil phase distribution shape was"wing".And gradually completed the evolution until fully spread out.The oil film thickness also increased.（2）Study on dynamic behavior of raceway/roller line contact frictionUnder the condition of oil and air lubrication,the friction coefficient curves of different oil and air parameters all contained four stages,namely running-in,fall,climb and stability.For oil supply,the stable friction coefficient gradually reduced with the increased of oil supply,and the number of cycles needed to enter the stable stage also decreased gradually.When the oil supply was 0.1ml/min,the friction coefficient fluctuated when it entered the stabilization stage,and the friction coefficient after stabilization was high.This is due to the oil supply time interval was large,the formation of lubricating oil film continuity was poor.For the oil pressure,the friction coefficient after the stability as the oil pressure increased,it obvious showed a trend of decreasing first and then increasing.Among them,when the oil pressure was about 1.5Mpa,the friction coefficient entering the stable stage was the smallest.For the air supply velocity,the friction coefficient decreased gradually with the increased of the air supply velocity.For air supply pressure,the friction coefficient decreased gradually with the increased of air supply pressure.For the oil temperature,as the oil temperature increased,the friction coefficient of change trends was inapparent and around 35℃of friction coefficient was minimized after stabilization.This might be the viscosity value of the lubricating oil at about 35℃most in line with the conditions for oil film formation.（3）Study on contact lubrication characteristics of raceway/roller lineCombined with microscopic analysis found that the wear mechanism under the condition of oil-air lubrication was peeling,abrasive wear and oxidation wear.The products of oxidation wear mainly included Fe O,Fe₂O₃and Fe₃O₄.As for oil supply,with the increased of oil supply,the furrows and peeling effect on the surface of the abrasive spot all slowed down and the lubrication effect was getting better gradually.On the whole,the influence on oil-air lubrication performance was obvious.For oil pressure,the surface of the speck was mainly abrasive wear and oxidation wear.The surface peeling and furrow effect were more obvious when the oil pressure was larger or smaller.For the air supply speed,with the increased of the air supply speed,the phenomenon of speckle peeling was slowed down,and the lubrication effect was better.For the air supply pressure,with the air supply pressure increased,the peeling and furrow effect on the surface of the spot were reduced and the lubrication effect became poor.This might be related to the rate at which the oil droplets entered the contact pair.For oil temperature,with the increased of oil temperature,when the oil temperature was too high,the abrasive wear on the speckle surface was more serious and the lubrication effect was worse,the lubrication effect was poor.The lubrication effect was relatively best when the oil temperature was about35℃.This might be because when the oil temperature was too high,the viscosity of the lubricating oil was too low to form a stable lubricating oil film and the time of direct contact between friction pairs was longer.