微小间隙内润滑油剪切流动引发的不稳定振动现象分析

Analysis of Unstable Vibration Caused by Shear Flow of Lube Oil in Micro-gap

针对微小间隙内润滑油剪切流动引发的不稳定振动现象,建立轴颈截面温差、转子热弯曲和转子振动求解模型。以2台发电机组的周期性振动波动为对象,分析润滑油温和不平衡力对汽轮发电机振动的影响。结果表明:轴承微小间隙内润滑油剪切流动带来的热弯曲效应在一定条件下有可能引发机组不稳定振动;适当增大进油温度、增加密封瓦间隙可以减小转子热弯曲变形,降低振动波动;不平衡力会激发起较大的涡动轨迹,通过动平衡方法可以减小轴承最大与最小油膜厚度差值,降低轴颈截面温差,稳定振动状态。

Aiming at the unstable vibration phenomenon caused by the shear flow of lube oil in micro-gap,solving models of journal section temperature difference,rotor thermal bending and rotor vibration were established.Taking the periodic vibration fluctuation of two generator units as research object,the influence of lube oil temperature and unbalanced force on the vibration of turbo-generator was analyzed.Results show that the thermal bending effect caused by the shear flow of lube oil in the bearing micro-gap may cause the unstable vibration of the unit under certain conditions.Properly increasing the oil inlet temperature and sealing pad clearance can reduce the thermal bending deformation of the rotor and reduce the vibration fluctuation.Unbalanced force will excite large whirl track.By using dynamic balancing methods,the difference between the maximum and minimum oil film thickness of the bearing can be reduced,the temperature difference in the journal section can be reduced,and the vibration state can be stabilized.