Modeling of Flexible Rotor Structure-Lubrication Coupling and Analysis of Bearing Lubrication Characteristics Under Bidirectional Journal Misalignment

This study aims to investigate the influence of bidirectional journal misalignment—induced by external loads on a multi-support flexible rotor—on the lubrication characteristics of plain bearings. To this end, a structure-lubrication coupling model is established: First, the resultant force F = 30N is decomposed along circumferential directions, and the corresponding component forces in each direction are separately applied to the right journal end of the rotor. Subsequently, the finite element method is employed to solve for the rotor’s cross-sectional deflection and cross-sectional rotation angle field under various operating conditions; the equivalent journal tilt angle and projected phase angle (γ,α) are then extracted using the interval averaging method. These parameters are further incorporated into the modified oil film thickness expression, and combined with the numerical solution of the dimensionless Reynolds equation, the evolution laws and critical characteristics of the oil film thickness and oil film pressure field are obtained. The results demonstrate that the tilt angle (γ) exhibits a significant amplification effect; even a minor misalignment can lead to a rapid decline in the minimum oil film thickness (MOFT) and induce a nonlinear surge in the maximum oil film pressure (MOFP). The projection angle (α) governs the circumferential phase shift of the oil film. At α = 90°, the critical threshold for the attenuation of the MOFT is reduced by 70%, and the pressure peak shifts by over 30°, markedly altering the lubrication safety boundary. Under typical operating conditions, the critical tilt angle for α = 0° is 0.072°. The primary contribution of this paper lies in proposing and validating a coupled structural-lubrication model. This model integrates the bidirectionally misaligned journal parameters (γ,α)—derived from analyzing the structural deformation of the flexible rotor—with the computation of the oil film thickness and pressure fields. It establishes explicit lubrication safety criteria centered on the MOFT, MOFP, and critical tilt angle, thereby creating a quantitative link between journal bidirectional misalignment error and bearing lubrication failure.