The conventional journal bearing system is commonly used in the friction parts of mechanical devices,that is,journal bearing with smooth working surface.A very important factor of journal bearing is the formation of oil film by means of lubricant,and macro and micro geometric parameters of journal and bearing shells influence the formation of lubricating oil film.In the case of microscopic geometry,appropriate surface morphology may lead to increased bearing capacity and reduced friction torque in the journal bearing,and such surface morphology(texture)can directly affect the performance of journal bearing.In the dynamic research of the journal bearing-rotor system,the oil film not only plays the role of bearing load,reducing friction,eliminating wear,reducing vibration,inhibiting instability and cooling the bearing,but also affects the stability of the system as a link in the bearing-rotor-foundation system.In this paper,the surface texture technology is applied to the journal bearing,that is,the dimples texture is fabricated on the inner surface of the bearing by laser surface texture technology.Through numerical analysis,the influences of bearing structural parameters,dimple geometric parameters and distribution position on dynamic and static characteristics of journal bearings were studied,and the lubrication friction reduction mechanism,oil film bearing mechanism and influencing factors of oil film whirl were explored.Firstly,the numerical analysis model of the dimple-textured journal bearing was established,and the thickness equation of the dimple-textured film was characterized.The Reynolds boundary conditions of the corresponding nodes were given.After the dimensionless normalization,the dimensionless Reynolds equation was discretized and the relaxation iteration method was selected for numerical solution.The influence of bearing structure parameters,dimple geometry parameters and distribution position on lubricating performance parameters of journal bearing was discussed.The results show that the dimple texture can improve the bearing capacity of the divergent zone of the journal bearing,reduce the friction force and leakage volume,and play a positive role in lubrication,friction reduction and oil storage,and determine the optimal distribution location of the dimple texture.The structural parameters of journal bearing have great influence on the lubrication performance,so appropriate design parameters should be adopted according to actual working conditions.Then,the working state of the bearing is set,and the bearing structural parameters and dimple geometrical parameters are selected.Considering the temperature and viscosity of the lubricating oil,the film pressure field under the stable state of the system is determined according to the Reynolds equation of steady motion,and bearing capacity is obtained by integrating along the journal surface.The oil film force is simplified into linear spring and damping.The small parameter method is used to solve the Reynolds equation of unsteady motion,and four perturbation pressures are obtained.Then eight dynamic characteristic coefficients are obtained by corresponding integration.The results show that the eight dynamic characteristic coefficients of the dimple-textured journal bearing are all lower than those of the smooth surface bearing,and decrease with the increase of the dimple-textured journal bearing depth.The existence of dimple texture changes the influence of oil film force on journal,especially film whirl induced by cross stiffness and cross damping of oil film is reduced.Finally,the numerical analysis model of film bearing capacity was coupled with the rotor kinematics equation,and the four film stiffness coefficients and four damping coefficients obtained from the solution are substituted into the rotor kinematics equation matrix,and the eigenvalues of the rotor under various modes are solved,and modal analysis is carried out.The nonlinear characteristics of the bearing-rotor system under different working conditions are expressed according to Campbell diagram,rotor orbital diagram,modal vibration shape diagram and amplitude-frequency characteristic curve.Comparing the motion of the bearing-rotor system under different dimple texture depths,the research shows that the critical speed of the bearing-rotor system can be changed by the dimple texture bearing,and the whirl frequency of the system increases with the increase of the dimple texture depth,and the stability of the system increases. |