| Temperature rise and anisotropic character are two main resistances for journal bearing in its application at high rotating speed conditions.The object of this study--spiral oil wedge journal bearing shows distinctive characteristics just in this two aspect,which makes it suitable for high speed precise system.In this paper,the lubrication mechanism and the unique characteristics of the bearing have been investigated theoretically and experimentally with a view to optimizing design and its application.Firstly,in the aspect of the internal mechanism,the pressure distribution, fluid flow separation character and the oil film rupture have been studied theoretically.The mathematical models for hydrodynamic lubrication of the spiral oil wedge journal bearing are established based on the analysis of configuration of the bearing.In order to deal with the difficulty resulted from the uncertain shape of oil film;a performance calculation method and the relevant software are developed for journal bearing with arbitrarily cavities.The validity of several assumptions for Reynolds equation is studied involving oil film rupture pressure, pressure boundary condition,and the influence of turbulence flow.The results show that the Reynolds number is smaller than that of turbulence flow in the studied extent,and the performance of the bearing considering the turbulence has a little difference from that of laminar flow.Fluid flow separation character and the oil film rupture status are investigated on spiral oil wedge journal bearing.The results reveal that the spiral oil cavities of the bearing enhanced the axial flow velocity of the lubricant;oil cavity with suitable spiral angle can separate the cold oil and heated oil efficiently.Spiral cavity and higher oil supply pressure can speed up the lubricant for spreading out in the clearance of the bearing,which can decrease the oil film rupture. Secondly,the directional performances of the spiral oil wedge bearing are studied comparing with axial straight cavity bearing.Since the normal configuration bearing shows different performances at different directional loads because of its axial straight oil cavities,the spiral oil cavities make the pressure distribution in different section move along with circumferential direction,which make the static and dynamic performances of the bearing show little difference in different circumferential direction,the characteristic of the bearing is suitable for the condition with loads rotating with in circumferential direction,such as boring machine.Compared with straight oil cavity bearing,the influence of asymmetrical pressure distribution caused by spiral oil cavities on deflection torque and the influences of the misalignment caused by shaft deformation or assembly error on bearing performance are studied theoretically.The results show that with the same shaft misalignment,the minimum of oil film thickness of the spiral oil wedge bearing is great than that of normal bearing,and the deflection torqueof the bearing is far smaller than that of normal bearing,that is to say,the spiral oil wedge bearing has less sensitivity to misalignment than normal bearing.The influences of the oil cavity structure on the static and dynamic performance has been studied on spiral oil wedge journal bearing.The results show that,the spiral cavity decreases the load capacity to some extent,however the oil outflow quantity from the bearing significantly increased,which is useful for slowing down the temperature rise.Outlet holes have little influence on pressure distribution,load capacity and dynamic performance,but it can increase the oil outflow quantity greatly,which can decrease the temperature rise greatly. The oil supply pressure has little effect on load capacity of the bearing,but higher oil supply pressure makes the lubricant flowed into the bearing spread out quickly,which is useful for formation of the oil film and avoidance of the oil film rupture.A thermohydrodynamic lubrication model of the spiral oil wedge journal bearing is established and solved using streamline upward finite differential method.The results show that the temperature distribution varies greatly not only with circumference direction,but also with axial direction,which is great different from that of normal straight oil cavity bearing.The regions of higher temperature are decentralized from the normal bearing,and the maximum temperature rise is lower than that of straight oil cavity bearing.The results also indicated that the spiral angle has great influence on the temperature distribution, and the optimized temperature rise appears with the spiral angle of 0.3 to 0.5.Finally,a test rig for spiral oil wedge journal bearing is designed and manufactured for further research.In order to facilitate the acquisition of the pressure,an infrared wireless slip ring is developed,and the pressure sensor calibration methods are analyzed.The fluid flow separation character,the oil film rupture status,the pressure distribution of the oil film and the effects of the outlet holes and the oil supply pressure on the bearing performance are investigated.The experimental results have demonstrated the correctness of the theoretical results,and found a number of new features in oil film rupture,the fluid flow status of lubricant,pressure distribution and the effect of outlet holes on temperature rise.These results have great value for further research and the application of the bearing.This project is supported by National Natural Science Foundation of China (No.50275089)...
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