Abstract: This article investigates the nonlinear dynamic characteristics and stability of an axial flow compressor with tip clearance and ball bearings. The compressor rotor system is modeled with the aid of the finite element technique and a nonlinear ball bearing model. The aerodynamic destabilizing forces, i.e., the Alford forces, induced by the nonuniform tip clearance when the rotor is whirling, are acquired using known experimental data and a mathematic model. Simulation results show that the Alford forces and nonlinear bearing reactions provoke respectively the emergence of backward and forward resonance frequency components, and induce the system to lose stability. The experimental results are perfectly interpreted by the proposed analysis, which indicates that the combined effect of tip clearance and ball bearings is significant on the dynamic characteristics and stability of the rotor system.

Key words: compressors, rotors, Alford forces, ball bearings, stability, nonlinear vibration