Dynamic analysis of a flexible rotor supported by hydrodynamic bearings with uncertain parameters

Abstract

This paper is dedicated to the analysis of uncertainties affecting the dynamic behavior of a flexible rotor containing three rigid discs and supported by two cylindrical fluid film bearings. A stochastic method has been extensively used to model uncertain parameters, the so-called Monte Carlo simulation. However, in the present contribution, the inherent uncertainties of the bearings’ parameters (i.e., the oil viscosity as a function of the oil temperature and the radial clearance) are modeled by using a fuzzy logic based analysis. This alternative methodology seems to be more appropriate when the stochastic process that characterizes the uncertainties is unknown. The analysis procedure is confined to the time domain, being characterized by the envelopes of the rotor vibration responses. The hydrodynamic supporting forces are determined by considering a nonlinear model, which is based on the solution of the dimensionless Reynolds’ equation for cylindrical and short journal bearings. Finally, an experimental analysis is performed for comparison purposes. The most significant results are associated with the changes in the dynamic behavior of the rotating machine as a result from the supporting forces that are modified according to the uncertainties introduced in the bearings.