Rotor Whirl in Compliant Auxiliary Bearings

Abstract

A general condition for steady circular whirl in auxiliary bearing clearances is developed for rotor/bearing systems, which are circularly isotropic. This condition is computed with a linear model and does not require transient simulation. It is established that such whirl, in the absence of other forcing mechanisms, is friction driven. As a result, the whirl must be backward and generally at a frequency that is very close to one of the resonances of the rotor/bearing system (neglecting the clearance). For lightly damped rotors, this frequency is most likely to be just below the lowest resonant frequency. Once the frequencies of interest are identified with the procedure, the bearing forces at these frequencies can readily be determined to allow computation of rotor forced response.