This article reports the stability and dynamic characteristics of a passive gas foil bearing (MSGFB) in which multiple sliding beams provide the elastic support and Coulomb damping. The linear and nonlinear dynamic models of rotor-MSGFB system are established, both considering the complex contact constraints inside foil structures. The instability mechanism of rotor-foil bearing system is revealed from the equivalent dynamic stiffness and the critical whirl speed. The half speed whirl and the frequency locked vibrations are both observed in the simulations, indicating the nonlinearities of gas film and foil structure respectively. The results also show that larger rotor preload of MSGFB help suppress the half speed whirl vibrations and assist improving high speed rotor stability especially under the friction effect.
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