Rolling bearings are still widely used in aeroengines. Whenever rotors are modeled, rolling bearing components are typically modeled as linear/non-linear springs. In simpler models this spring is considered to have a constant mean value. However, the rolling bearing stiffness changes with time due to the positions of the balls with respect to the load on the bearing, thus giving rise to an internal excitation known as Parametric Excitation. Due to this parametric excitation the rotor – bearings system may contribute to rotor instability. Being able to identify these instability regions is an important tool for the designer, as it allows to prevent catastrophic failures since the early design stages.

In this paper, a Jeffcott rotor supported and excited by such rolling bearings is taken into account. In the first step, the expression for the time – varying stiffness of the bearings is analytically derived by applying the Hertzian Contact Theory. Then, the equations of motion of the complete system are provided. In this study, the Harmonic Balance Method (HBM) is used to as an approximate procedure for computing the responses of the structure in the steady state condition and more importantly to draw a stability map, thus dividing the input parameter space, i.e. rotational speed and rotor physical characteristics, into stable and unstable regions.


Rolling Bearing Parametric Excitation of a Jeffcott Rotor System

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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