EXPERIMENTAL INVESTIGATION OF DYNAMIC NONLINEARITIES IN ROTATING MACHINERY

摘要

This paper presents laboratory experimentsthat confirm and further explore earlier computer simulationsrelated to oil-whip and rub-impact. Both phenomena wereexplored using Spectrum Analysis, and Chaos trackingtechniques (e.g. Poincare' maps). The results show that oilwhipinduces quasi-periodic rotor vibrations, while rub-impactgenerates complex dynamical behavior, such as chaoticvibrational motion. The nonlinear oil-whip hysteresis loopresults presented confirm phenomena uncovered in previouscomputer simulations. A Sommerfeld number-consistent“instability threshold load” was experimentally observed, alongwith its corresponding hysteresis loop similar to the classicinstability speed hysteresis loop, but probably the mostimportant experimental discovery was a second Hopfbifurcation-Saddle node instability hysteresis loop (i.e., athigher speed than the classical hysteresis loop), separated by aregion of stable-in-the-small operation. Another result ofespecially high practical importance, was the discovery thatspectrum analysis of speed-up, or coast-down rotor-vibrationdata can be effectively used to locate the saddle node speed.