Structural Optimization And Mixed Lubrication Analysis Of The Coupled Journal-Thrust Water Lubricated Bearings

Research subject derives from national defense basic scientific research project “Innovative design theories and methods of XXX based on multi-field couplings model”,project from Naval University of Engineering “Design and prototype development of water lubricated bearing”.Compared with the traditional diesel propulsion system,the shaftless rim drive propulsion system has many advantages in terms of ship propulsion efficiency,space utilization,ship concealment,etc.,and thus the medium-diameter integrated bearing for the ship shaftless rim propulsion system.The special structural form and its application environment and lubrication performance put forward more demanding requirements.This paper comprehensively applies the coupled analysis methods of fluid mechanics,tribology,elastic mechanics,etc,to analyze the mixed lubrication characteristics of radial thrust bearing under the conditions of multi-media coupling including interface roughness,elastic deformation,journal deflection and complex working conditions.The lubrication structure of the coupled journal-thrust bearing is optimized and the lubrication mechanism is revealed,which lays a foundation for improving the tribological performance of the coupled journal-thrust bearing,which lays a foundation for improving the tribological performance of the integrated bearing.The specific research contents are as follows:(1)Based on the average Reynolds equation of Patir-Cheng,this chapter derived the Reynold equation of radial bearing and thrust bearing under multi-parameters such as coupling surface roughness and flow factor,which solved the problem of coupling solution such as hydrodynamic lubrication,rough interface contact,elastic deformation and misalignment.Finally,a mixed elastohydrodynamic lubrication numerical model was established.(2)According to the working condition requirements of the integrated bearing of the diameter,the polymer plastic material was selected as the bearing material,and the structural form of the radial bearing and the thrust bearing in the coupled journal-thrust bearing system was preliminarily designed.In addition,the boundary conditions of the integrated bearing were set to ensure the continuity of pressure and flow at the common boundary.The multi-factor coupling lubrication calculation program for the integrated bearing was developed,and the mathematical model and the numerical method were verified by comparison simulation.Sexuality,finally,the optimal number of grids was determined by considering the convergence speed and calculation accuracy.(3)Using Fortran software to solve the hybrid lubrication numerical solution of the integrated bearing.The load capacity and lubrication performance of the radial bearing under different microgroove bottom shapes such as semi-elliptical,rectangular,left triangle,right triangle and isosceles triangle,and the mixed lubrication behavior of the thrust bearing under different tilt angles was studied,so as to optimize the structure of the coupled journal-thrust bearing.(4)Based on the optimized numerical calculation model of the coupled journal-thrust bearing,the fluid dynamic pressure distribution,contact pressure distribution and elastic deformation distribution of the integrated thrust bearing in the coupled and uncoupled state were analyzed.The effects of coupling effect on the bearing performance and lubrication performance of radial bearing and thrust bearing under different working conditions such as load,rotation speed and journal deflection were studied,which reveals the hybrid lubrication mechanism of the integrated bearing.The research shows that the coupling effect simultaneously increases the bearing capacity of the radial bearing and the thrust bearing,and reduces the friction coefficient of the radial bearing.However,the friction coefficient of the thrust bearing affects the bearing capacity,water film shear force and micro-convex contact force.The distribution law is not obvious.And the coupling effect of the coupled journal-thrust bearing is more obvious in the elastic flow stage,but weak in the mixed lubrication stage.