Multi-fault coupling study of a rotor system in experimental and numerical analyses

Abstract

Multi-fault rotor system is a hot spot in the study of rotor dynamics and fault diagnosis. The present study is aimed to deal with the vibration response and nonlinear behavior of a cracked rotor system with rub-impact supported by sliding bearings. A dedicated experiment is designed to verify the interaction between the several faults for a rotor system. These faults are crack, rub-impact and oil-film instability. The time domain plot, frequency spectrum and cascade spectra are employed to extract the response features of the rotor system. The numerical investigation is given to compare with the experiment results, which concentrates on the effect of crack depth and stator stiffness on the vibration response and system instability of the multi-fault rotor system. The bifurcation diagrams, frequency spectra, Poincare maps, and cascade spectra are used to analyze the nonlinear coupled behaviors of the multi-fault rotor system. The results from experiment and simulation indicate that the coupling effect exists in the faults of crack, rub-impact and oil-film instability. The crack interferes with the formation of oil whirl, that is, the oil whirl is delayed to appear. Moreover, enhancing the stator stiffness can restrain the appearance of the oil whirl and simplify the dynamic motion of the system. The study discloses the coupling phenomenon of multi-fault rotor system and presents the response characteristics and nonlinear dynamical behaviors of the interaction between multiple faults for such a rotor-bearing system.