考虑瞬态冲击和弹性变形的滑动轴承特性与动力学响应
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摘要
同时考虑瞬态冲击载荷和轴瓦的弹性变形,模拟了舰船在风浪拍击时推进轴支承滑动轴承的润滑特性与动力学响应,研究了聚四氟乙烯(PTFE)弹性金属塑料瓦滑动轴承的最小油膜厚度、最大油膜压力和轴心轨迹随时间的变化情况。运用有限元法求解雷诺方程,将油膜力转化为轴瓦节点力计算了弹性变形;用欧拉法求解轴颈的动力学方程,计算了动态轴心轨迹。对比了刚性瓦与PTFE弹塑瓦滑动轴承的特性,结果表明,轴瓦弹性变形对油膜厚度和油膜压力分布的影响不可忽略,并且轴瓦弹性变形可以提高滑动轴承的承载能力。对比分析了4个不同方向瞬态冲击载荷作用下PTFE弹塑瓦滑动轴承的特性和轴颈的动态轴心轨迹,提出可通过改变轴承静载荷方向、减小瞬态冲击载荷方向与轴承偏心方向的夹角来增加最小油膜厚度,降低最大油膜压力,减小动态轴心轨迹的位移响应振幅,进而改善滑动轴承润滑状态,减小轴瓦的弹性变形量,提高轴承-转子系统的稳定性。
In consideration of transient impact load and elastic deformation of bearing pad,the lubrication properties and dynamic response of journal bearing supporting the propulsion shaft of ships under the action of wind and waves are simulated.The pad of journal bearing is elastic metal-plastic pad(EMP),made of polytetrafluoroethylene(PTFE).The variations of the minimum oil film thickness and maximum oil film pressure,as well as the journal orbits in time history are investigated.Solving the Reynolds equation with finite element method,the oil-film force is converted to nodal forces of pad to calculate the elastic deformation;solving the kinetic equation of journal with Euler method,the dynamic journal orbits are obtained.Comparison of the properties between rigid bearing and EMP bearing indicates that the elastic deformation of EMP bearing cannot be neglected,and the deformation could enhance the loading capacity.Through comparative analysis on the properties and dynamic journal orbits of EMP journal bearing under the transient impact loads from four directions,it is found that adjusting the direction of the bearing static load and decreasing the angle between the directions of transient impact load and the eccentric of journal can increase the minimum oil film thickness and reduce the maximum oil film pressure,hence the displacement response amplitudes of journal orbits are decreased.Consequently,the lubricating condition,the deformation of the journal pad and the operating stability are improved.
In consideration of transient impact load and elastic deformation of bearing pad,the lubrication properties and dynamic response of journal bearing supporting the propulsion shaft of ships under the action of wind and waves are simulated.The pad of journal bearing is elastic metal-plastic pad(EMP),made of polytetrafluoroethylene(PTFE).The variations of the minimum oil film thickness and maximum oil film pressure,as well as the journal orbits in time history are investigated.Solving the Reynolds equation with finite element method,the oil-film force is converted to nodal forces of pad to calculate the elastic deformation;solving the kinetic equation of journal with Euler method,the dynamic journal orbits are obtained.Comparison of the properties between rigid bearing and EMP bearing indicates that the elastic deformation of EMP bearing cannot be neglected,and the deformation could enhance the loading capacity.Through comparative analysis on the properties and dynamic journal orbits of EMP journal bearing under the transient impact loads from four directions,it is found that adjusting the direction of the bearing static load and decreasing the angle between the directions of transient impact load and the eccentric of journal can increase the minimum oil film thickness and reduce the maximum oil film pressure,hence the displacement response amplitudes of journal orbits are decreased.Consequently,the lubricating condition,the deformation of the journal pad and the operating stability are improved.
引文
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[2]RAO T,BISWAS S,HIRANI H,et al.An analytical approach to evaluate dynamic coefficients and nonlinear transient analysis of a hydrodynamic journal bearing[J].Tribology Transactions,2000,43(1):109-115.
[3]TICHY J,BOU-SAD B.Hydrodynamic lubrication and bearing behavior with impulsive loads[J].Tribology Transactions,1991,34(4):505-512.
[4]李震,桂长林,李志远,等.变载荷作用下轴-轴承系统动力学行为研究[J].机械设计与研究,2005,21(1):12-16.LI Zhen,GUI Changlin,LI Zhiyuan,et al.Study on dynamic behaviors of variably-loaded shaft-bearing system[J].Machine Design and Research,2005,21(1):12-16.
[5]GADANGI R K,PALAZZOLO A B,KIM J.Transient analysis of plain and tilt pad journal bearings including fluid film temperature effects[J].ASME Journal of Tribology,1996,118(2):423-440.
[6]CHA M,KUZNETSOV E,GLAVATSKIH S.A comparative linear and nonlinear dynamic analysis of compliant cylindrical journal bearings[J].Mechanism and Machine Theory,2013,64:80-92.
[7]GLAVATSKIH S,PARAMONOV A.PTFE-faced bearing technology:advantages and practical examples[C]∥Waterpower XVI Conference Proceedings.Tulsa,Oklahoma,USA:PennWell Corporation,2009.
[8]KUZNETSOV E,GLAVATSKIH S,FILLON M.THD analysis of compliant journal bearings considering liner deformation[J].Tribology International,2011,44(12):1629-1641.
[9]CHA M,ISAKSSON P,GLAVATSKIH S.Influence of pad compliance on nonlinear dynamic characteristics of tilting pad journal bearings[J].Tribology International,2013,57:46-53.
[10]张国贤,金楗,吴白羽.EMP径向滑动轴承弹性变形的有限元求解[J].润滑与密封,2000(6):2-4.ZHANG Guoxian,JIN Jian,WU Baiyu.A finite element analysis of EMP journal bearing[J].Lubrication Engineering,2000(6):2-4.
[11]张直明.滑动轴承的流体动力润滑理论[M].北京:高等教育出版社,1986:19-27.
[12]罗继伟,罗天宇.滚动轴承分析计算与应用[M].北京:机械工业出版社,2009:1-2.
[13]TAYLOR R I.The inclusion of lubricant shear thinning in journal bearing models[J].Tribology&Interface Engineering,1999,36:611-619.