A Phase-Plane Simulation for Investigating the Effect of Unbalance Magnitude on the Whirl of Rotors Supported on Hydrodynamic Bearings

Abstract

This paper describes a digital simulation of the dynamics of an unbalanced rigid rotor supported on hydrodynamic bearings. Whirl orbits can be developed from the start of rotation until the operating constant speed is attained. Response spectra are obtained to illustrate the trend of the influence of the magnitude of unbalance speed, average film viscosity, load, clearance and rotor start-up acceleration on the whirl amplitudes. The simulation procedure which is based on the phase-plane-δ method provides a general and effective tool of analysis for this class of problems. Although a rigid rotor on a simplified isoviscous film is considered for illustration, the procedure can be readily extended for the simulation of multirotor flexible shafts with more accurate film characteristics without making simplifying assumptions regarding the shape of the orbit or the film behavior.