Numerical simulation of transient oscillations after abrupt multi-bearing rotor disbalance with the unbalanced rotor MOVING OVER the stator

A.G. Kostyuk, V.F. Shatokhin, S.D. Zimmerman

Given in the study are the algorithm and the results of the numerical simulation of the unbalanced rotor contact with the stator (brushing against the stator or movement over the latter) after the abrupt rotor disbalance. Rigidity and damping in bearings are expected to vary in horizontal and vertical directions of oscillations, and are frequency-dependent magnitudes (they depend on the rotor speed at the moment of its disbalance).  Besides, taken into consideration is damping in the rotor-stator contact place, related to the stator deformation (displacement), that can be ensured by means of special damping devices. It is shown that sufficient damping in the stator and rotor bearings results in the gradual abnormal movement damping and the rotor motion transition in the steady-state trajectory (the second depends on many factors, including the rotor disbalance rate). As it’s been found, development of asynchronous abnormal movement and significant radial forces in the contact place results from non-conservative forces originating during the contact process. These forces are identical in type to those in the sliding bearing oil film and to aerodynamic forces of operating flow in the turbine flow path and packings, which generate the rotor movement instability.

Key words: multi-bearing rotor, abnormal rotor movement over stator, asynchronous abnormal movement, abrupt rotor disbalance, rigidity and damping in bearings, in rotor-stator contact place.