Research On High Oil Capture Efficiency Under-race Lubrication Technology Of High Speed Bearing For Aeroengine

Under-race lubrication is the key technology to lubricate and cool the aeroengine main bearing with high DN value.High efficiency axial and radial oil scoop is very important to realize under-race lubrication in compact structure.With the development of aeroengine to high speed and high power to weight ratio,the speed and load of the main bearing are increasing,which poses a new challenge to the oil capture efficiency of oil scoop.In view of the urgent need for high efficiency lubrication and cooling of main bearing with high DN value,and the actual situation of low oil capture efficiency of oil scoop with high speed and small size,this paper starts with the principle of under-race lubrication,establishes the physical model of oil collection process and oil-gas two-phase flow model,and studies the influence of speed,oil supply pressure and nozzle diameter on oil capture efficiency of lubrication structure with oil scoop.According to the assumption of maximum oil capture efficiency,a radial oil scoop structure based on new curved blade is proposed.The main research work and results are as follows:(1)Lubricating oil flow mechanism of under-race lubrication structure.Based on the principle of axial and radial oil scoop,the key factors affecting oil capture efficiency are identified.The physical model of the collision process between the oil jet and the blade is established,and the calculation method of the theoretical maximum oil capture efficiency of the radial oil scoop is obtained.The calculation formula of the maximum oil flow capacity of the radial oil thrower hole of the bearing inner ring is established,and the relationship curve between the centrifugal oil flow coefficient and the dimensionless number Re/(L/D)is obtained through tests.(2)Numerical simulation of oil-gas two-phase flow in oil capture process.Based on the VOF model,the flow models of axial and radial oil capture process are established,the numerical study of flow is carried out,and the physical mechanism of the formation and development of the internal flow field of the under-race lubrication structure is obtained.It is found that the deflection of the oil jet,the breakup and splash after the collision between the jet and the oil scoop blade are the key factors affecting the oil capture efficiency.The calculation method of oil capture efficiency in the numerical simulation is constructed.And the error between the simulation results of oil capture efficiency and the test results is about 5%.(3)Experimental study on oil collection structure under high speed and small size.An under-race lubrication test platform with a maximum rotation speed of 45000r/min was built.An automatic oil collection and measurement device with high precision(flow measurement accuracy ±0.2%)is developed,which realizes the oil automatic collection and high-precision measurement under the conditions of high oil temperature and high rotation speed.The oil capture efficiency of axial and radial oil scoop under different working conditions and structural parameters is experimentally studied.The oil capture efficiency of axial oil scoop is up to 99%,and that of traditional radial oil scoop is up to 60%.(4)Research on radial oil scoop based on a noval curved blades.Based on the assumption of maximum oil capture efficiency,the curve equations of the inner surface of the blade under different nozzle conditions are solved.It is found that the length of the truncated oil section on the inner surface of the blade is constant in the design state.A new type of oil scoop with proposed curve is designed.The simulation shows that under the condition of high speed(more than 35000r/min),the oil capture efficiency of the new curved blade scoop is 30% higher than that of the traditional blade scoop.The test results show that the maximum oil capture efficiency of the new curved blade scoop reaches 75%,and under the most unfavorable engine working conditions of high speed and low oil supply pressure,the oil capture efficiency is increased from 10% of the traditional blade scoop to more than70%,and the new curved blade scoop shows good robustness to working conditions parameters and nozzle structure.