ABSTRACT
For lateral rotor vibration (LRV) analyses, those important “inputs” that present the biggest challenge are the dynamic properties (i.e., stiffness, damping, and inertia coefficients) for the components that dynamically connect the rotor to the stator (stator everything that does not rotate). These components include first and foremost the radial bearings. In many rotating machinery types (e.g., turbomachinery), other liquid-and gas-filled internal close-clearance annular gaps, such as in seals, are also of considerable LRV importance. Furthermore, the confined liquid or gas that surrounds a rotor component (e.g., centrifugal pump impeller and balancing drum) may also significantly contribute to the basic vibration characteristics of a rotating machine, in an interactive way much like bearings and
stability in centrifugal pumps, rotating stall in turbocompressors). Electromagnetic forces may also contribute. Most modern LRV research has been devoted to all these rotor-stator effects. One could justifiably devote an entire book just to this single aspect of LRV. This chapter focuses on bearing and seal LRV dynamic properties. Small clearances critical to these properties are of significant uncertainty because of manufacturing tolerances. Thus, LRV characteristics are really stochastic rather than deterministic. That is, if significant inputs are random-variable distributions, then so are the outputs.
