Numerical Analysis of a Rub-impact Rotor-bearing System with Mass Unbalance

In this article, vibration characteristics of a rub-impact rotor-bearing system excited by mass unbalance (including mass eccentricity and initial permanent deflection) are investigated. The nonlinear oil-film forces from the journal bearing are determined using the short bearing theory. The rubbing model used consists of the radial elastic impact and the tangential Coulomb friction. Through numerical calculation, the rotational speeds, mass eccentricities, initial permanent deflection lengths and angles between the mass eccentricity direction and the rotor initial permanent deflection direction are used as control parameters, investigating their effect on the rub-impact rotor-bearing system, with the help of bifurcation diagrams, Poincaré maps, spectrum plots and orbit maps. Complicated motions, including periodic, quasi-periodic, and even chaotic vibrations are observed. Results show that both of these kinds of mass unbalance [cj]including angles between them have great, but different, influence on the dynamic characteristics of the rub-impact rotor-bearing system. The results can be used to diagnose rub-impact faults and fluid-induced instability in this kind of rotor system, and this study may contribute to furthering understanding of the nonlinear dynamics of a rub-impact rotor-bearing system with mass unbalance.