Dynamics response of an on-board rotor supported on modified oil-film force considering base motion

Abstract

In an on-board rotor journal bearing system, hydrodynamic bearing forces are affected by the coupling motion between rotor and base. To study the system dynamic response, a model of the on-board rotor supported on hydrodynamic bearing force is proposed in this paper. Motion equations of rigid disk and elastic shaft are derived by applying the Lagrange principle and finite element method. Based on the short bearing assumption and Hahn boundary condition, a modified oil-film force model of the hydrodynamic bearing is derived by introducing the base motion velocity. Under sinusoidal excitations of the base translational motion, dynamic responses of the on-board rotor bearing system are calculated by a Newmark time-step integration algorithm. Results are presented by time history, fast Fourier transforms, orbits and Poincare maps, and are compared with the response dominated by Capone's oil-film force model. The influences of amplitude and frequency of base motion on system dynamic behavior are investigated. Differences after introducing base motion velocity into the oil-film force model show that the convective velocity of the bearings should not be ignored in some extreme cases.