Nonlinear Vibration Damping Functions for Fluid Film Bearings

Curve-fitting functions are combined with transfer functions and special parameter groupings to demonstrate that amplitude-limiting effects of hydrodynamic bearings on vibrations associated with critical speeds of flexible rotors are due to nonlinear characteristics. It is shown that stable and/or critically-damped operation can be achieved by designing bearings within proper ranges of a “dynamic load number” and controlling unbalance expressed as principal axis deviation related to clearance. The form of the attitude angle function is shown to be particularly significant with respect to unbalance tolerance. Practical application techniques are illustrated.