Research On Characteristics Of A Hydrodynamic Bearing With Gas-liquid Two-phase Flow And Surface Texturing

As an important supporting component,the performance of journal bearing directly affects the safe and stable operation of rotating machinery.As a functional surface which can improve the lubrication performance of friction pairs,surface texture has attracted extensive attention of researchers.Applying surface texture to journal bearings and analyzing the influence of texture parameters on the performance of journal bearings can provide new ideas for improving the performance of journal bearings.In addition,the phenomenon of oil film two-phase flow has always been the focus of bearing technology research,and the two-phase flow characteristics may play an important role in the surface texture characteristics.In this paper,a three-dimensional two-phase flow numerical analysis model of journal bearings is established to explore the effect of surface texture on the performance of journal bearings through numerical calculation.The main contents and conclusions of this paper are as follows:According to the hydrodynamic lubrication theory of journal bearings,a three-dimensional model of two-phase flow of CFD journal bearing with non-condensable gas was established,and the rationality of the model was verified.On this basis,groove and dimple surface textures are applied to journal bearings.The maximum oil film pressure,bearing capacity,friction coefficient and lubricant flow rate of journal bearings are taken as evaluation indexes,and the effects of surface texture distribution position and geometric parameters on the performance of journal bearings are analyzed.The results show that the proper location and geometric parameters of surface texture can improve the bearing performance to a certain extent;the lubrication performance of journal bearings can be improved when the surface texture is arranged in the convergent wedge in the loading zone,while the lubrication performance of journal bearings will be worse when the surface texture is arranged in the divergent wedge in the loading zone,and the local cavitation will be enhanced when the surface texture is arranged in the oil film cavitation zone.With the increase of area ratio(width),the lubrication performance of journal bearings becomes better;the existence of the optimum texture depth makes the lubrication performance of journal bearings the best,and the optimum texture depth is independent of area ratio(width);for groove texture,the lubrication performance of bearings becomes worse with the increase of texture length.According to the calculation method of dynamic characteristics and dynamic mesh technology,a three-dimensional CFD dynamic mesh model is established to solve the stiffness and damping coefficients of journal bearings.The validity and feasibility of the model are verified by comparison.The dynamic characteristics of textured journal bearings are solved by means of large disturbance.The effects of texture length,width and depth on the dynamic characteristics of journal bearings are further analyzed.The results show that with the increase of texture length,the stiffness coefficients decrease,the damping coefficient Cxy and Cyx remain unchanged,while the damping coefficient Cxx and Cyy decrease;with the increase of texture width,the stiffness coefficient Kxx and Kyx decrease,the stiffness coefficient Kxy and Kyy increase,the damping coefficient Cxy and Cyx remain unchanged,the damping coefficient Cyy decreases,and the damping coefficient Cxx increases;with the increase of texture depth,the stiffness coefficients decrease,the damping coefficient Cxy and Cyx remain unchanged,while the damping coefficients Cxx and Cyy decrease.According to the thermodynamic characteristics and gas-liquid two-phase flow characteristics of journal bearings,the relationship between oil film temperature rise and two-phase flow characteristics is analyzed,and a three-dimensional thermal coupling model of journal bearings is established.Comparing the results of flow field characteristics between thermal coupling model and adiabatic boundary model,the characteristics of journal bearings under different inlet oil temperature and speed are further analyzed,the effect of surface texture on the temperature field of journal bearings was studied.The results show that the temperature field calculation results of the thermal coupled model considering heat conduction are more in line with the actual situation than that of the adiabatic boundary model;with the increase of the imported oil temperature,the maximum pressure,bearing capacity,friction coefficient,temperature difference between inlet and outlet,and the ratio of cavitation volume decrease,and the flow rate of lubricating oil increases;with the increase of rotational speed,the friction coefficient,temperature difference between inlet and outlet,the ratio of cavitation volume and the flow rate of lubricating oil increase;surface texture has little effect on temperature parameters of Journal bearings.