Nonlinear dynamic analysis of a vertical rotor-bearing system

摘要

Nonlinear dynamic model of a vertical rotor-bearing system is developed based on nonlinear bearing forces. Nonlinear dynamic behaviors are studied comprehensively through numerical analyses, such as bifurcation diagrams, waterfall diagrams, rotor center orbits, Poincare maps, and frequency spectrums. Factors which affect those behaviors, including structural arrangement, rotor mass unbalance, clearance and length of bearing, are investigated as well. Analytical results show that, in vertical arrangement, period doubling bifurcation occurs in advance and the system stability decreases dramatically. When the rotor motion becomes unstable, vertical rotor-bearing system generates sub-synchronous vibrations that are much lower than half-frequency component (0.5x). The stability of vertical rotor-bearing system increases with the increases in rotor mass unbalance and bearing length, but it decreases with the increase in bearing clearance.