| The journal bearing is the main supporting component the spool parts.The friction between the bearing bush and the journal is the main factor affecting the service life of the bearing.Surface texture is one if effective means to improve the lubrication effect of the journal bearing and reduce the friction.Therefore,it is of great significance to reveal the friction reduction mechanism and optimize the journal bearing texture parameters.This paper establishes a numerical calculation model of the two-phase flow of oil and air in a journal bearing cavity and performs a numerical solution based on the theory of gas-liquid two-phase flow.The influences of the position region of the surface texture,the axial and circumferential arrangement,the surface shape and the radial depth on the bearing capacity and friction coefficient are analyzed.The fluid flow characteristics of groove texture element in the fluid domain were investigated,and the mechanism of the effect of the asymmetry factor on the friction performance was analyzed.The main conclusions of this article are:(1)Analysis of the influence of eccentricity and deflection angle on the friction performance of journal bearings.The flow of lubricating oil in the journal bearing cavity is similar to the Couette Flow.The annular flow of lubricating oil in the bearing cavity can be simplified to a straight flow in a rectangular fluid domain.Oil is extruded by eccentric journal and the reaction force is the source of oil film bearing capacity.The eccentricity rate and deviation angle are the most important factors affecting the mechanical properties of j ournal bearings.The deflection angle changes linearly with the direction of the resultant force on the main shaft.In practical engineering applications,the magnitude and direction of the force on the main shaft can be judged based on this,judging and adjusting the working conditions;increasing the eccentricity can increase the load-bearing capacity of the main shaft,but too large eccentricity can easily destroy the elastohydrodynamic lubrication state.(2)Analysis of the influence of surface texture parameters on the friction performance of journal bearings.When the texture is arranged at the entrance and the middle of the convergent wedge,it can effectively improve the bearing capacity and reduce the friction factor;for the rectangular texture,the circumferential arrangement is better than the axial arrangement;the flow characteristics are mainly affected by the texture shape and the way the oil flows into the texture pit.The texture import and export method "from wide to narrow" is better than "from narrow to wide".The "cross" texture leads to the abrupt change of the flow direction of the lubricating oil due to its more edges and corners,and its dynamic pressure are larger,bearing capacity are better;the optimal radial depth is about 20μm for different surface textures;the composite texture is more conducive to improving the bearing’s load-carrying capacity and friction performance than a single type of texture.Therefore,a reasonable texture arrangement can effectively increase the bearing capacity and improve the operating conditions.(3)Analysis of the influence of surface texture asymmetry on the friction performance of journal bearings.The frictional performance of the groove texture with both ends connected to the air is better than that of the closed-end type and the one-end closed type connected to the air.The ratio of two wall surfaces of asymmetric texture is named as asymmetric factor H.The pressure on the upper wall of asymmetric texture with different asymmetric factor is greater than that of symmetric texture and non-textured conditions,when H<1,a single vortex is generated in the textured pit,and the dynamic pressure effect generated by the flow velocity of the lubricating oil at the outlet is excited,which increases the pressure on the upper wall surface;when H>1,the main reason for the pressure increase of the upper wall surface is the double vortices in the textural pits;With the increase of the rotating speed,the volume fraction of oil phase in the bearing cavity decreases.When H=0.25,the bearing capacity is the highest and the friction coefficient is the lowest. |
