BIFURCATION ANALYSIS OF HYDRODYNAMIC PLAIN JOURNAL BEARING LUBRICATED WITH COUPLE STRESS FLUID

Abstract

—The dynamic analysis of rotor bearing system supported by two couple stress fluid film journal bearings with
non-linear suspension is studied in this paper. The hydrodynamic pressure is generated entirely by the motion of the
journal and depends on the viscosity of the lubricated fluid. In this analysis the dynamic trajectory, the power spectra,
the Poincare maps, and the bifurcation diagrams are used to analyse the behaviour of the rotor centre and bearing
centre in horizontal and vertical directions under different operating conditions. The short journal bearing assumptions
are used for the analysis. The model consists of non-linear rotor equations of motion, which are system of nonlinear
differential equations. The generalized Reynold’s equation is derived for the selected system of rotor bearing. A non
dimensional parameter ‘l’ has been used for couple stress fluid. The method used to solve the dynamic equations is
Range Kutta by considering the effects of rotor speed and degree of rotor unbalance. The periodic, quasi-periodic, subharmonic and chaotic motion are demonstrated in this study. Results show that the dynamics of system depends on rotor
speed and degree of rotor unbalance. By using the couple stress fluid as lubricant dynamic stability of rotor bearing
system enhances considerably as compared to the system using Newtonian fluid as lubricant.