大型汽轮机组轴承座动力吸振现象分析

Analysis on the Dynamic Vibration Absorption of Bearings of the Large Turbo Unit

针对某大型汽轮机组轴承座异常振动现象,建立大型汽轮机组柔性支撑下转子-轴承-支撑系统动力学分析模型,从动力吸振新角度解释实际机组上发生的异常振动现象。研究结果表明,座缸式轴承支撑刚度较低,轴承座固有频率和转子系统固有频率有可能从设计时的大于50 Hz减小到50 Hz附近。一旦2个频率点重合,就容易发生动力吸振现象,转轴振动转移到轴承座振动上,导致轴振小而轴承座振动大。与此同时,系统固有频率点分解成2个频率点,分布在原固有频率两侧,出现双共振峰现象。

Aiming at the abnormal structural vibration occurred on the bearings of large turbo units, the dynamic model of the rotor-bearing-support system with flexible support is set up to analyze the abnormal structural vibration phenomenon using the dynamic vibration absorber theory. The result shows that the support stiffness of the bearings located on the exhaust cylinder is low. The natural frequencies of the bearings and the rotor system may be reduced from more than 50 Hz as being designed to less than 50 Hz. Once the natural frequencies of the beatings and the rotor system are superposed, the vibration absorbing phenomenon tends to occur. The shaft vibration transfers to the bearings, resulting in small shaft vibration and large beating vibration. At this time, the system natural frequency is decomposed into two, which are distributed on both sides of the natural frequency. Consequently, a double resonance peak appears.