Threshold stability curves for a nonlinear rotor-bearing system

Abstract Design parameters of fluid film bearings affect the stability of rotor-bearing systems, which can be characterized using so called threshold speed and a threshold curve (depending on a shaft speed and a chosen design parameter). The paper brings a detailed study of the shape of the threshold curve for a rigid rotor supported on a plain bearing. A novel comparison of stability threshold curves obtained employing various approaches to the hydrodynamic force modelling for all relevant bearing parameters is presented. Hydrodynamics forces are solved using four approaches: the infinitely short (IS) approximation, the infinitely short approximation extended by multiplicative correction polynomials for finite-length journal bearings (IScor), the finite differences method and the finite elements method. The influence of run-up time and acceleration is also investigated. All obtained threshold curves are compared to the analytical expressions for the threshold curves calculated for the IS approximation.