非同期并列时机组轴系扭振的时频分析

Time-Frequency Analysis of Shafting Torsional Vibration Caused by Asynchronous Juxtaposition

三维有限元模型能较好地描述轴系的复杂结构,精确地反映倒角、凹槽等应力集中截面的扭应力情况。以某660 MW汽轮发电机组轴系为研究对象,介绍了应用ANSYS软件求解轴系扭振响应的过程,分析了机组非同期并列时的轴系扭振特性。分析表明:非同期并列时,各截面扭应力幅值迅速达到最大值,之后逐渐振荡衰减,故障对低发间转子危害较大;扭应力主要包括前两阶扭振固有频率和少量的工频成分,不同截面处各模态分量所占比例不同;120°和180°2种非同期并列情况时的扭振响应特性基本相似,前者的扭应力响应大于后者。研究结果有助于提高机组安全管理水平。

The three-dimensional finite element model can not only well describe the complex structure of the shafting system,but also accurately reflect the torsional stresses of the stress-concentrated cross sections such as the chamfer and the groove.In this paper,the shafting system of one 660-MW turbo-generator is studied,and the process of solving the torsional vibration response with ANSYS software is presented.The analysis on the response properties of the torsional vibration caused by asynchronous juxtaposition indicates that the torsional stress amplitude of each section reaches the maximum value rapidly,and then oscillates and weakens gradually.Faults are harmful to the rotor between the low-pressure cylinder and the generator.The torsional stress consists of the first two orders of natural frequencies of the torsional vibration and a small amount of power frequency components,and the proportion of the model component of different cross-sections differs from each other.Additionally,the responding characteristics of the torsional vibration are roughly similar both in 120° and 180° asynchronous juxtaposition,with the former one outweighing the latter one.The research results are helpful to improve the safety management of the unit.