流体机械转子系统非线性振动机理研究

Study on nonlinear vibration mechanism of fluid machinery rotor system

为解决现有转子的线性振动模型难以精确描述转子非线性振动的问题,建立了基于Muszynska非线性密封力模型的转子-密封-轴承系统的非线性运动模型。运用四阶龙格-库塔法求解了转子系统的非线性运动方程,分别分析了在3000,8500,12000,15000 r/min转速下转子的轴心轨迹图;还求解了转速、转子结构和轴承尺寸等参数下的振动分岔图。基于建立的非线性振动模型,搭建了转子-密封-轴承系统试验台,探究了压强对转子轴心轨迹振动的影响,最终从模拟和试验2个方面探究了转子的振动规律,为进一步的优化提供基础。结果表明,在转子转速由3000 r/min增大到12000 r/min的过程中,轴心轨迹图由无量纲半径为0.4的圆形逐渐变为成倍周期图型;当转速超过15000 r/min时,转子的振动变得没有规律,变成混沌图;从转子不同影响参数下的分岔图发现,转子系统的振幅与转速和密封长度成正比,与密封间隙和轴承润滑长度成反比;在设计转子结构时可以通过增加密封间隙或延长轴承润滑长度的方式降低振幅。在转子系统中,影响最大的因素是转子转速,其次是转子结构。

In order to solve the problem that it is difficult for the linear vibration model of the existing rotor to precisely describe nonlinear vibration of rotor,a nonlinear motion model for rotor-seal-bearing system based on the Muszynska nonlinear seal fluid force model was established.The nonlinear motion equations were solved by the fourth-order Runge-Kutta partial differential solution method.The axis orbit diagram at 3000,8500,12000 and 15000 r/min were analyzed to solve the vibration bifurcation diagrams under such parameters as rotating speed,rotor structure and bearing size.Based on the established nonlinear vibration model,a rotor-seal-bearing system test bench was built to explore the influence of pressure on the vibration of the rotor axis trajectory,and finally the vibration law of the rotor was explored from two aspects:simulation and experiment,which provides a basis for the next optimization.The results show that with the increase of the rotational speed from 3000 r/min to 12000 r/min,the axis orbit diagram of the rotor is gradually changed from a dimensionless radius of 0.4 circle to a double-period circle.When the speed exceeds 15000 r/min,the rotor vibration becomes lawless,and turns to the chaos graph.From the bifurcation diagrams under difference influence parameters of the rotor,it can be found that the amplitude of the rotor system is proportional to the rotational speed and seal length,and is inversely proportional to seal clearance and bearing lubrication length.When designing the rotor structure,the amplitude can be reduced by increasing the seal clearance or extending the lubrication length of the bearing.In the rotor system,the biggest influence factor is rotor speed,followed by the rotor structure.