Rotational Ratio Response Analysis of Flexible Rotor Vibrating System

Abstract

In this study, a new method is developed for analysing rotor vibration due to harmonic excitation, in particular, to excitation with frequency multiple of rotational speed, with aim at a computer aided designing for unbalance vibration. vibration due to balls or blades passing. and so on. This new technique, developed by expaning the concept of quasi-modal transformation. is more applicable than the usual modal one. The quasi-modal transformation is characterized by mode synthesis of the following two mode shapes. One is a mode shape obtained by undamped critical speed analysis of rotor shafting restricted at its bearing points. The other is a deflection mode shape caused by forced displacement on the bearing points. Only this new method is effective especially to the analysis of harmonic vibration response of rotor with multi-level shafting. The effectiveness is demonstrated by a 3-disc rotor, and an X-ray tube unitincluding a casing.