Experimental Study On Friction And Wear Of Oil-air Lubrication Point Contact Sliding

Oil–air lubrication is an air–liquid,two-phase fluid lubrication technology,has many advantages,such as high lubrication efficiency,good sealing performance and clean and pollution-free.In the lubrication system of point contact friction pairs,such as roller bearings and high-speed motorized spindles,this high-efficiency and accurate lubrication method has been extensively used.Oil-air lubrication supply parameters have an important influence on the flow characteristics of lubricating oil at the friction interface and the heat dissipation behavior between the pairs,which is the key factor for determining the friction and wear properties of the matching pairs.If the parameter design is unreasonable,it will lead to the failure of lubrication conditions,which will lead to severe wear and even scrap of matching pairs.At present,the research on oil-air lubrication mainly focuses on the formation mechanism,application effect evaluation and analysis of air-liquid two-phase flow,while the friction and wear characteristics of point contact pairs under oil-air lubrication are less studied.In order to clarify the influence of oil-air lubrication on the tribological characteristics of pairs,this paper takes point contact sliding friction pairs as the research object,carries out oil-air lubrication point contact friction test,and combines convective heat transfer theory to analyze the heat dissipation,and investigates the influence of oil-air lubrication heat dissipation on the friction and wear characteristics.The main research work completed in this paper is as follows.(1)Design and verification of oil-air lubrication point contact test scheme.Firstly,the oil-air lubrication test scheme is designed,and the reasonable structure of the test system is carried out.Then,an oil-air lubrication point contact test system is built,and the related test analysis is introduced.Finally,dry friction,drip oil lubrication and oil-air lubrication friction tests were carried out on the oil-air lubrication point contact test bench.The rationality of the test scheme design and the reliability of the experimental equipment were verified by comparing with the existing research results.At the same time,the test results also show that the lubrication performance of oil-air lubrication is improved obviously with the increase of oil supply at a certain air supply speed.(2)The influence of oil-air lubrication position on point contact sliding wear characteristics was studied.Reasonable design of oil supply position,oil-air lubrication point contact sliding friction test,and combined with numerical simulation results to explore the influence of oil-air lubrication point contact sliding wear characteristics.Theresults show that,too large or too small injection distance and injection angle are not conducive to oil-air flow convergence at the contact point,resulting in the decrease of the oil-phase volume fraction between friction pairs and the increase of wear.When the injection point and the contact point are kept at a certain distance(Δx=2 mm,Δy=0 mm,θ=15°,30°),the lubricating oil is better to flow to the contact point,so that the oil phase volume fraction of the contact point is maximized and the wear is minimal.The wear mechanism of sliding friction is abrasive wear by changing injection distance and injection angle.(3)The influence of oil-air lubrication heat dissipation on the tribological characteristics of point contact pairs is studied.An ambient temperature heating device was designed to carry out oil-air lubrication tests at different air supply speeds and temperatures,and compared with drop oil lubrication tests to investigate the effect of oil-air lubrication heat dissipation on point contact tribological characteristics.The results show that the convective heat transfer capacity between pairs increases with the increase of air supply speed,and the friction coefficient and temperature rise decrease first and then increase.With the increase of ambient temperature,the convective heat transfer capacity between pairs is almost unchanged,the friction coefficient and wear mass decrease slightly,and the frictional flash temperature hardly changes,or the variation range is small.Increasing the air supply speed and the test environment temperature in the test results in varying degrees of wear on the surface of the specimen,but the wear mechanism is abrasive wear.In conclusion,reasonable design of system parameters can change the flow characteristics of lubricant at contact points,improve the heat dissipation performance between pairs,and reduce sliding friction and wear at point contact.The research work can provide reference for the performance development and design of oil-air lubrication system in engineering.