A component mode method for modelling the dynamics of turbo-generator sets

Abstract

The paper gives details of a procedure for forming a complete model for the dynamics of a turbo-generator set on a desk-top computer. A reduction procedure is used on each of the principal rotating components in turn, extracting the important information and eliminating unwanted degrees of freedom before assembling into the global system. Finite element models of the high pressure and intermediate turbine rotors, the low pressure rotor and the generator are presented. The degrees of freedom retained are such that they can be measured at the on-site situation and this is an important feature of the method. Because the sub-components are related to real physical entities, the predicted characteristics of these can be checked against some simple test data, which can be used to enhance the model if necessary. There are three important uses for the model: performing a stability analysis, aiding in the balancing process, and in-health monitoring of the rotating parts. While the stability evaluation demands a good model for bearing and foundations, the balancing process can be carried out without knowing these properties. It is to providing a reliable rotor model to aid in the balancing process that is the principal thrust of this paper. The method is illustrated by applications to 350 and 500 MW sets.