ABSTRACT
This chapter concentrates on rotor imbalance, the most prevalent single rotor problem, and bent rotors as the two are often confused since both give rise to a synchronous signal at shaft rotation speed. The discussion begins with a study of the distinction between rigid and flexible rotor, as an understanding of this is essential to progress. The formulation of the dynamics of rotor imbalance is set out, followed by a survey of balancing procedures using one and two-plane methods in both the influence coefficient and modal approaches.
The results of the two methods are compared and contrasted with examples. Possible problems, including nonlinearities, are discussed. One significant difficulty is the presence of a bend in the rotor and this scenario is analyzed. Balancing such a rotor involves some decisions depending on the machine operation requirements and the differing methods are discussed together with examples showing the effects.
