The nonlinear vibrations of a rotordynamic system that is subjected to nonsymmetric bearing clearance effects are considered. Particular attention is paid to the nonstationary response that occurs during passage through resonance. Based on an extended Jeffcott rotor model that includes the effects of nonsymmetric bearing clearances, the steady-state oscillations and their stability are also analyzed. The “normal-loose” rotor stiffness condition that occurs due to the bearing clearance effects is modeled through a discontinuous radial stiffness model. Expressions for the amplitude and phase-modulating functions are obtained. Frequency-amplitude relationships are derived. The effects of “normal-loose” rotor stiffness condition on the modulation of both the amplitude and phase of the near-resonance vibrations, as well as the stability of the rotor system, are systematically brought out. The effects of high-speed acceleration during run-up of the rotor are both qualified and quantified. Similarly, the case of run-down is analyzed.

Issue Section:
Gas Turbines: Structures and Dynamics
Topics:
Bearings, Rotors, Stability, Vibration, Stiffness, Clearances (Engineering), Resonance, Oscillations, Steady state
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