Nonlinear analysis of a geared rotor system supported by fluid film journal bearings

This paper presents a novel approach for modeling and analyzing a geared rotor-bearing system including nonlinear forces in the gear set and the supporting fluid film journal bearings. The rotordynamics system model has five degrees of freedom that define the transverse displacements of the shaft-gear centerlines and the relative displacement of the gear tooth contact point. The journal bearing nonlinear forces are obtained via a solution of Reynolds equation for lubricant film pressure utilizing the finite element method. Coexisting, steady-state, autonomous and non-autonomous responses are obtained in an accurate and computationally efficient manner utilizing the multiple shooting and continuation algorithms. This yields the full manifolds of the multiple bifurcation system. Chaos is identified with maximum Lyapunov exponents, frequency spectra, Poincare attractors, etc. The results reveal a dependence of the gear set contact conditions and system nonlinear response characteristics, i.e. jump, co-existing responses, subharmonic resonances and chaos on the choice of journal bearing parameters. The results also show that Hopf bifurcations, which occur along with oil whirl in a journal bearing system, can be attenuated by increasing the gear torque. (C) 2020 Elsevier Ltd. All rights reserved.