汽轮发电机组轴系扭转振动对机械参数的敏感性分析

针对某300MW汽轮发电机组模型,分析了扭振固有频率和振型对汽轮发电机组轴系转动惯量和刚度的敏感性。计算结果表明:无论是轴系整体转动惯量或刚度、还是局部转动惯量或刚度的变化,都会对扭振特性产生明显的影响;局部转动惯量或刚度的改变对特定阶的扭振的影响虽然不及整体转动惯量和刚度变化的影响大,但也十分显著;对特定振型贡献较大的轴段对此阶轴系扭振影响较大,在振型图上表示为此阶振型在这一轴段处的斜率较大;在实际中可以通过改变轴系局部结构,使某阶扭振固有频率避开特定的值,从而达到调频的目的,而在对汽轮发电机组轴系扭振研究的建模过程中,要精确确定扭振特性敏感性较高的那些部位的机械参数。图4表2参8

Sensitivity Analysis of the Torsional Vibration Behavior of a Turboset's Rotor System to Changes of Its Mechanical Parameters

Aiming at a 300 MW turbo-generator model,the sensitivity of natural torsional frequencies and modes of vibration to the rotational inertia and stiffness of the turbo-generator rotor system are being analyzed.Calculation results show that the variation of the rotational inertia or stiffness either of the rotor system as a whole or only locational may both remarkably influence the rotor's torsional vibration characteristics.Although localized variation has an influence less than that of the rotor as a whole,but it's still notable.Rotor sections which contribute more to a certain mode of vibration have a larger influence on the pertaining order of torsional vibration.Looking at the modal shape,a larger slope can be observed at these sections of the rotor for the particular mode.Thus frequencies can be modulated by modifying the local construction of the rotor to make the natural torsional vibration frequency of a certain order avoid some specific value,herewith arriving at the objective of tuning.Therefore,it is very important,in the course of modeling for the purpose of studying the torsional vibration of a turboset's rotor system,to accurately determin the structural parameters of parts that have a relatively sensitive effect on the torsional vibration behavior.Figs 4,tables 2 and refs 8.