基于有限元法的水轮发电机转子偏心运行轴系模态分析

Shafting Modal Analysis for Rotor Off-centre Operation of Hydroelectric Generator Based on FEM

针对发电机质量偏心问题,分别探讨了偏心距离及导轴承刚度变化对机组振动特性的影响。首先对导轴承进行参数化处理,整机轴系建模后,通过FEM模态分析方法计算得到前10阶临界频率及振型的模态分析结果,进一步确定位移变形集中的危险点。然后对比不同约束条件下振型、临界频率、导轴承中心点振型轨迹,获得转子质量不对中造成的机组振动特性为因机组的转子偏心旋转造成轴瓦间隙逐步扩大,而机组振动信号中主频不变,计算结果与现场实际测量数据一致。

Aiming at the problem of mass eccentricity of generator,the influence of eccentric distance and bearing stiffness change on the vibration characteristics of the unit are discussed,respectively.Firstly,the guide bearing is parameterized.After modeling the whole shaft system,FEM modal analysis method is used to determine the first 10 order critical frequencies and mode of vibration.And then the dangerous points of displacement and deformation concentration is determined.By comparing the modes of vibration,critical frequency and the modes of vibration of the center point of the guide bearing under different constraints,it is concluded that the vibration characteristics of the unit caused by the incorrect rotor mass are as follows:the axis bush is gradually enlarged due to the eccentric rotation of the rotor of the unit,and the vibration characteristics that the main frequency is unchanged in the unit vibration signal.The calculated results are consistent with the field test data.