Nonlinear analysis of herringbone gear rotor system based on the surface waviness excitation of journal bearing

Surface waviness generally exists in the bearing bushes of journal bearing due to manufacturing error and deformation wear, while most of the existing studies on journal bearing-rotor system idealizes the machined surface overlooking the waviness defects. The purpose of this study is to investigate the influence of surface waviness on the dynamic characteristics of the journal bearing- herringbone gear rotor system. A coupling dynamic model of the herringbone gear rotor system supported by journal bearings is proposed, which considers the bearing waviness, time-varying meshing stiffness, gear backlash, and flexible shaft. Based on the finite difference method, the nonlinear oil-film forces are obtained by solving the Reynolds equation with bearing waviness. The nonlinear behaviors of the herringbone gear rotor system are investigated from two aspects of waviness types (i.e., axial waviness, circumferential waviness, and axial-circumferential combined waviness) and waviness amplitude. The influence of bearing waviness on the system is analyzed by comparing the healthy system and the defective system. Results suggest that the appropriate bearing waviness contributes to the stability of the herringbone gear rotor system supported by journal bearings. The research may provide a reference value for the design of the journal bearing–herringbone gear rotor system.