Development And Research Of Oil-air Lubrication System Based On Two-phase Flow

In recent years,with the development of modern industry and the need for environmental protection,high-speed machining technology realized by high-speed electric spindles has been widely used in today’s manufacturing industry.In order to ensure the accuracy and stability of the high-speed electric spindle,the temperature rise of the bearing needs to be maintained within a small range.When the lubricant required for high-speed bearings is at the optimal value,an oil film is formed to separate the friction surface,and the temperature rise and wear are minimized.Therefore,high-speed electric spindles require continuous and trace amounts of lubricant.Traditional lubrication pumps can only achieve intermittent oil supply.The oil-air lubrication system uses airflow to deliver lubricant to the lubrication point,which solves this contradiction.Firstly,according to the characteristics of oil-air lubrication,the type of lubricating oil was selected,and the minimum oil supply was calculated using the Dowson minimum oil film thickness calculation formula.The design of the oil and gas transportation pipeline with spiral pipe is proposed,and the gas supply pressure is determined by combining the equivalent length method and the pressure drop formula of the spiral pipe.Combined with the flow pattern spectrum,it is preliminarily judged that the two-phase flow of oil and gas is annular flow.Combined with the Kelvin–Helmholtz theory,the instability of the oil and gas annular flow is analyzed.Secondly,an oil-air lubrication system for high-speed electric spindles is designed,which mainly includes a lubrication pump,an oil filter,an air filter and drying assembly,an oil-air mixer and an oil-air detector.The oil-air mixer,which is the core component of the oil-air lubrication system,has been redesigned to change the way of oil and gas mixing.In order to verify the superiority of the new oil-air mixer,simulations were carried out on each model,and a new theoretical model of oil and gas mixing was established.Thirdly,in order to verify the practicability and stability of the oil-air lubrication system,the technical indicators of the oil-air lubrication high-speed electric spindle test bench were determined according to the various parameters of the test bearing.The overall design scheme and selection of the test bench have been completed.Through preliminary debugging,the test bench can work normally within the speed of 0～50,000r/min,and the temperature and vibration are within the alarm limit,which meets the test requirements.At the same time,the measured speed will produce resonance between 34000 ～ 39000r/min and damage the equipment.It is necessary to avoid the electric spindle speed staying in the resonance range for a long time.Finally,in order to reduce the processing difficulty of the oil-air mixer and improve the accuracy of its lubricating oil quantification,the design of the oil-air mixer was optimized.By adding a sleeve at the dosing valve,the dosing valve is decoupled from the valve body.The spring was redesigned,and the life check and stability check of the spring were completed.The performance test of the optimized oil and gas mixer has been completed.Under sufficient oil pressure,the quantitative errors of the 0.03 ml and 0.01 ml oil-air mixers are in line with the industry standards,the new oil-air mixer has certain advantages and its quantitative is more accurate than other oil-air mixers of the same specification.