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.