HARMONIC-BALANCE ANALYSIS OF GENERAL SQUEEZE FILM DAMPED MULTIDEGREE-OF-FREEDOM ROTOR-BEARING SYSTEMS

Squeeze film dampers introduce nonlinear motion dependent damper force s into otherwise linear rotor bearing systems, thereby considerably co mplicating their analysis. Noncircular orbit type dampers, such as uns upported or uncentralized dampers, have generally necessitated transie nt solutions, which are computationally prohibitive for design studies of large order systems, particularly for systems with low damping. By utilizing harmonic balance with appropriate condensation, it is possi ble to considerably reduce the number of simultaneous nonlinear equati ons inherent to this approach. The stability (linear) of the equilibri um solutions may be conveniently evaluated using Floquet theory, parti cularly if the damper force components are evaluated in fixed, rather than rotating, reference frames. The versatility of this technique is illustrated on systems of increasing complexity with and without dampe r centralizing springs. Of particular interest, is its applicability t o unsupported systems illustrating how such systems can lift off and, with further increase in speed, the damper forces can be linearized ab out the orbit center.