Research On Lubrication Mechanism Of Multi-physics Coupling Of Piston Aero Engine Bearings

In piston-type aero engines,the main bearing and the connecting rod bearing are very important friction pairs,which can be abstracted as sliding bearings to study their lubrication state.The lubrication state of the sliding bearing directly affects the reliability,service life and economy of the engine friction pair.In this thesis,a series of theoretical basic researches are carried out based on the inclined journal-bearing system,including lubrication numerical model,control equation,lubrication solution method and boundary conditions.The research is divided into the following aspects:Consider elastic deformation of bearings and macroscopic cavitation effects.Based on the inclined journal lubrication model,the elastic deformation and macroscopic cavity model are coupled.Analyze the effects of elastic deformation and macroscopic cavitation on bearing lubrication performance.The research shows that different bearing restraints have a great influence on the radial deformation of the bearing.The bearing bushing and the bearing bush are half suspended,and the influence on the bearing performance is not obvious.The cavitation phenomenon increases the area of the low pressure region of the oil inlet end,reduces the bearing capacity of the oil film,and causes large voids.In the hole region,the density of the lubricating medium is low,and the density of the region near the hole boundary changes greatly.Consider the surface topography of the journal-bearing system.Gaussian random surface,non-Gaussian random surface and fractal surface model are established under the bearing lubrication deterministic model.Analyze the effect of surface roughness on the lubrication performance of misaligned bearings.The research shows that the oil film pressure distribution of the bearing's maximum oil film pressure position(?=3?/2)changes significantly,and the oil film pressure with non-Gaussian rough surface appears zigzag distribution.After the eccentricity and the rotational speed increase to a certain value(?=0.7,n=5000r/min),the end discharge flow Q does not change significantly,and the maximum oil film pressure,working torque and bearing capacity are significantly larger than the rough surface.Consider the surface morphology of the journal-bearing and the thermal effect of the lubricating oil.The surface profile of the bearing pad is coupled to the thermal effect model to analyze the effect on bearing lubrication performance.The research shows that with the increase of the inclination angle,the oil film pressure increases obviously,and the pressure of the oil film on the surface of the bearing pad increases greatly.The oil film pressure increases the viscosity of the lubricating oil.As the oil film pressure increases,the oil film temperature also increases significantly at the corresponding position.The end oil flow rate increases,the 0 m/s intermediate line is obviously biased towards the end,and the rough surface of the bearing bush has a great influence on the bearing capacity.