Abstract: The nonlinear dynamic stability of labyrinth seal-sliding bearing2unbalanced rotor systems is studied in thispaper. Under the periodic excitation of rotor unbalance, the whirling vibration of a rotor is synchronous if the rotation speed is below the stability threshold, whereas the vibration becomes severe and asynchronous which is calledunstable if the rotation speed exceeds the threshold. The Muszynska model of the seal force, short bearing andshooting method are used to investigate synchsonous solution of the dynamic equation of the rotor system, and thenbased on Floquet theory the stability of synchronous solution and unstable dynamic behaviors of the system are analyzed.

Key words: nonlinear vibration, stability, rotor, labyrinth seal, sliding bearing, shooting method