具有初始弯曲的1000 MW 汽轮机低压转子的振动特征分析

摘要

Recently,steam turbines with large capacities are widely used.But,it's hard to maintain the concentricity of a rotor-bearing system during operating,especially,for one having multi-rotor within specified levels of vibration.Taking a LP B rotor of a 1000 MW USC steam turbine as an example,the lateral vibration of the LP B rotor based on finite element was studied.Responses due to mass unbalance and bent shaft were analyzed and compared. Calculation results showed that if the rotor is spinning at a constant speed,then it exhibits whirl;for the rotor supported by isotropic bearings,only forward whirl is excited;only backward whirl is excited when the rotor is supported by anisotropic bearings;when one cross-coupling stiffness is positive and the other is negative,the rotor may be unstable despite the presence of damping.%近年来，1000 MW 超超临界汽轮发电机组在中国得到快速发展。然而，运行经验显示，1000 MW 超超临界汽轮发电机组普遍存在振动偏大的现象，尤其低压转子两端的振动比较突出。转子振动的原因有很多，质量不平衡和轴系弯曲均会随着转子的每一次旋转周期性地给予转子一个固定的激振力。以某1000 MW 超超临界汽轮机的低压＃2转子为例，利用有限元的方法研究其弯曲振动特性，并对质量不平衡和弯轴故障引起的振动特征进行了对比分析。计算结果显示，转子在定速下旋转会出现因质量不平衡或弯曲而产生的涡动，当转子支撑在各向同性轴承上时，无论是激振力是正向或反向涡动，所引起的振动响应均为正进动；而当转子支撑在各向异性轴承上时，无论是激振力是正向或反向涡动，所引起的振动响应均将是为反进动。当交叉刚度呈异向（一个为正，一个为负）时，无论是否存在阻尼，转子将出现不稳定。