基于有限元法的喷水推进轴系回旋振动分析

Analysis on whirling vibration of waterjet propulsion shafting based on finite element method

[目的]基于ANSYS仿真平台建立喷水推进轴系回旋振动的完整计算方法。[方法]首先,利用ANSYS命令流建立轴系参数化有限元模型,绘制轴系特征频率随转速的变化曲线,即坎贝尔图;然后,通过计算轴系的一次和叶片次回旋临界转速,绘制临界转速下轴系各节点绕转轴的轨迹,即涡动轨迹图;最后,对比分析推力轴承的布置方式和各轴承的支承刚度对临界转速的影响。[结果]结果表明:喷水推进轴系叶轮轴的回旋振动位移幅值最大;当推力轴承从艉密封前端移至推进泵内部时,轴系一阶一次正回旋临界转速下降了32.8%,一阶叶片次正回旋临界转速下降了31.3%,故推力轴承的布置方式对于喷水推进轴系回旋临界转速的影响较大;随着轴承支承刚度的增加,轴系一阶共振转速和叶片次正回旋临界转速的变化幅度均不超过8%,而一次正回旋临界转速的变化幅度不超过9%,故轴承支承刚度的变化对回旋临界转速的影响处于非敏感区,这将有利于轴系的稳定运转。[结论]研究成果可为喷水推进轴系回旋振动的安全性评估提供参考。

[Objectives]Based on the ANSYS simulation software platform,a complete calculation method for the whirling vibration of waterjet propulsion shafting is established.[Methods]First,a parameterized FE model of the shafting system is built using ANSYS command flow,then curves of the Eigen frequencies are drawn and a Campbell diagram is obtained.Next,the primary and blade whirling critical speeds are calculated,and the trajectory of each node of the shafting system around the axis at the critical speed is plotted.Finally,the influence of the arrangement of the thrust bearing and the stiffness of the bearing on critical speed are analyzed.[Results]The results show that the amplitude of the whirling vibration displacement of the impeller shaft is the largest.When the thrust bearing was moved from the front end of the tail seal to the inside of the propulsion pump,the critical speed of the first-order positive-whirling of the shafting decreased by 32.8%,and the critical speed of the first-order blades of positive-whirling decreased by 31.3%.Therefore,the arrangement of the thrust bearing has a greater impact on the critical speed of waterjet propulsion shafting.With the increase of bearing support stiffness,the change in the first-order resonance speed of the shafting and the critical speed of the first-order blades of positive-whirling are both less than 8%,and the change in the critical speed of the first order positive whirling is less than 9%.Therefore,whirling critical speed is not sensitive to bearing support stiffness,which is conducive to the stable operation of the shafting.[Conclusions]The results of this study can provide references for the safety evaluation of the whirling vibration of waterjet propulsion shafting.