Investigation of an unbalanced rotor system with bearing clearance and stabilising rods

Abstract

The nonlinear vibrations of a rotor system with bearing clearance and stabilising rods are considered. In this paper the main objective is to evaluate effects of applying stabilising rods and from a dynamical point of view find preferable parameter ranges. A piecewise linear two degrees-of-freedom model is proposed. The system is studied and evaluated by analysis of steady state, bifurcation diagrams, Lyapunov exponents and contact force. It is shown how transition lines (which separate different categories of motion), periodicity and sensitivity to small perturbation are affected by the parameters defining the stability rods. By applying specific stabilising rods the periodicity is changed for some parameter ranges, unstable areas are reduced, the total maximum normal contact force is increased while the dynamical part is mainly reduced. The analytical expressions for the transition limits can be used as a design tool to choose suitable parameters. It is concluded that the stability rods should be applied vertically and that high preloading and stiffness prevents the system from impact motion. The stabilising rods are effective tools to avoid nonlinear behaviors but it is necessary to carefully analyse the specific application.