大型船舶低速柴油机柔性曲轴三维振动

摘要

Engine block and crankshaft of a large low-speed marine diesel engine were lighted with CMS method and nonlinear condensed system dynamic equations where they are coupled each other with elasto-hydrodynamic lubrication mode.Contact forces between them are obtained by finite volume method according to Reynolds equation and Greenwood/Tripp asperity theory.A three-dimensional vibration model of the crankshaft was built up,and the modeling method and model are verified by comparison with the classic models.Results indicate that whole instantaneous characteristics of torsional vibration,lateral vibration and axial vibration of the crankshaft can be obtained simultaneously.The lateral and axial vibrations of crankshaft show typical nonlinear features.Horizontal lateral vibration of crankshaft is more harmful to the bearing shells than vertical lateral vibration in shock and vibration.The modeling method reveals the vibration mechanism and supports optimization design of the crankshaft.%运用模态综合法对大型船舶低速柴油机机体和曲轴有限元模型进行缩减,获得二者弹性流体动力润滑耦合下计入非线性缩减的系统动力方程,采用时域积分的Newmark方法进行数值求解.二者间接触力根据Reynolds方程和Greenwood/Tripp微凸峰接触理论,运用有限体积法获得.由此建立大型船舶低速柴油机柔性曲轴与柔性机体耦合下的三维振动计算模型,通过与经典模型计算结果对比,该建模方法和模型得到验证.结果表明:该计算模型能够同时获得曲轴瞬态整体扭振、横振和纵振三维振动形貌;曲轴的横振和纵振呈典型非线性分段特性;曲轴水平横振较垂直横振对轴瓦的振动冲击危害更大.该建模方法有益于进一步揭示曲轴的振动机理,为曲轴优化提供参考.