Based on the nonlinear dynamics theory

the stability and bifurcation of a symmetrical rotor supported in self-acting gas bearings were studied.A dynamic model of self-acting gas journal bearings and Jeffcott rotor system was established

meanwhile the finite element method was used to approach the time-dependent Reynolds equation

thus obtaining the gas film force.Furthermore

the longterm nonlinear dynamic behaviors of the system were simulated numerically

so the system state trajectory of journal center was acquired.Moreover

the system state trajectory

phase diagram

bifurcation diagram and power spectrum were adopted to analyze the nonlinear behaviors of system and the stability of unbalanced response.The results show that this method could give a deep understanding of whirling instability of the gas film bearings-rotor system.