Effects of Gear Box Vibration and Mass Imbalance on the Dynamics of Multistage Gear Transmission

Abstract

The objective of this paper is to present a comprehensive approach to analyze the dynamic behavior of multi-stage gear transmission systems with the effects of gear box induced vibrations and rotor mass-imbalances. The modal method, using undamped frequencies and planar mode shapes, is used to reduce the degree of freedom of the system. The various rotor-bearing stages as well as the lateral and torsional vibrations of each individual stage are coupled through localized gear mesh tooth interactions. Gear box vibrations are coupled to the gear stage dynamics through bearing support forces. Transient and steady state dynamics of lateral an torsional vibrations of the geared system are examined in both time and frequency domains. Vibration signature analysis techniques will be developed to interpret the overall system dynamics and individual modal excitations under various operating conditions. A typical 3- staged geared system is used as an example. Effects of mass imbalance and gear box vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.