Test And Analysis On The Properties Of High Speed Rolling Bearing Lubricated With RP-3 Fuel And Air

The contest for air supremacy is a key factor affecting the outcome of modern warfare.With the development of war equipment,high performance UAV plays an increasingly important role in seizing air supremacy.Flexible maneuverability is an important aspect that determines UAVs’ performance.As the "heart" of UAV,turbojet must have excellent performance and high reliability.Rolling bearing is an important bearing lubrication part of turbojet.The bearing works in the environment of high temperature,high pressure and high speed.If the bearing is in a state of dry friction or boundary lubrication for a long time,it will cause spot welding or adhesion,and even cause the bearing shaft jammed.It seriously restricts the use of aircraft.Therefore,how to ensure good lubrication of bearings has important research significance.The turbojet engine studied in this paper uses RP-3 fuel self-lubrication,and the engine will produce a large amount of airflow in the process of running,the use of oil-air lubrication can optimize the structure of the lubrication system,to meet the lightweight requirements of aircraft.As a new lubrication technology,oil-air lubrication has the advantages of low fuel consumption and good heat dissipation.In the process of oil-air lubrication,the formation of annular flow in the oil-air pipeline is the key to the effective lubrication for the bearing.However,the viscosity,density,contact angle and other parameters of RP-3 are different from those of traditional lubricants.It is necessary to study the influence of RP-3 fuel on bearing lubrication under different working conditions.The paper carries out the numerical simulation to guide the experimental design according to the actual operation of the turbojet engine.The main study are as follows:(1)To study the influence of material properties of RP-3 fuel and various working conditions on annular flow in pipeline,establish a horizontal oil-air pipeline model and use Fluent to calculate the influence of different oil parameters on the formation of annular flow.The simulation results show that RP-3 has better film forming conditions than conventional lubricants,in which lower viscosity,contact angle and gas-liquid tension coefficient are more conducive to the formation of uniform annular flow.The annular flow of RP-3 in oil-air pipelines requires a lower air and oil supply than conventional lubricants,and the reduction of pipe diameter will not reduce the demand for oil supply.Therefore,compared with the standard of traditional lubricating oil,the length of oil-air pipeline can be reduced to optimize the engine construction.The pressure supply can be reduced to save air.The amount of oil pumped into the oil-air pipeline in a single time can be reduced.The higher frequency of oil supply can make the oil supply more stable.(2)According to the engine working conditions and design standards of rolling bearings,design the high speed bearing test bench under oil-air lubrication.Design the tolerance of key parts and the bearing arrangement.Check the 7002 series bearings,the results show that both7002 C and 7002A5 angular contact ball bearings can meet the requirements of working conditions.Make thermodynamic calculation The friction torque of oil-air lubrication is obviously smaller than that of grease lubrication.In the process of lubrication,forced convection is the main way of heat dissipation.However,when the air velocity reaches a certain level,the influence of continuously increasing the air velocity on bearing cooling decreases,and the formation of annular flow and the film covering of bearing rolling body are also affected.(3)Test the influence of different oil supply,air supply pressure,axial load,radial load and different speed on the temperature rise of 7002 C bearing.The results show that RP-3 fuel requires higher fuel supply than traditional lubricants on oil-air lubrication,and different rotating speeds have little effect on the range of fuel supply.The air supply pressure has a greater influence on bearing lubrication in a controllable range,and it is suggested to adopt lower air supply pressure under the condition of forming good lubrication.The influence of axial load on bearing temperature rise is greater than that of radial load for 7002 C bearings.