The dynamics of a parallel-misaligned and unbalanced rotor system under the action of non-linear oil film forces

A mathematical model of a parallel-misaligned rotor system with mass eccentricity that is supported on journal bearings is discussed and its dynamic behaviours are analysed under the action of non-linear oil forces in the present work. First, some assumptions are introduced, such as the long bearing model, small parallel misalignment between rotors and tiny eccentricity of discs, the misaligned displacement constraint between two rotors is taken into account, and the motion equations are deduced by the Lagrange method of undetermined multiplier. Then, the rotor orbits, Poincare maps, and bifurcation diagrams of the system are studied by a numerical method; the results show that there exists some unrevealed motions and phenomena in the parallel-misaligned and unbalanced rotor system such as period 2, 3, 6, and 7 motions besides chaotic oscillations and so on.