Abstract: The foil gas bearings are widely used in fuel cell air compressors and aircraft ventilation systems due to their advantages of oil-free lubrication, high speed, low friction power consumption, and good vibration reduction performance. In the actual operation of fuel cell air compressors, the rotor is not only subjected to the aerodynamic load of the compressor, but also needs to match the corresponding load at different operating speeds. The rotor system exhibits complex transient response under accelerated variable load conditions. Mismatched acceleration may lead to an increase in amplitude during the acceleration process, thereby affecting the dynamic stability of the rotor system. In response to the above issues, a theoretical model of accelerated rotor dynamics of the foil gas dynamic pressure bearing rotor system is established. Corresponding numerical algorithms are proposed and developed. The model and algorithm are used to provide a reasonable quantitative explanation for the dynamic performance of the rotor system during the transition process of accelerating variable load, such as the axis trajectory. The results of research find that as the rotational speed increases, the phenomenon of rotor vortex becomes more pronounced, and the dynamic equilibrium stable region gradually approaches the center of the bearing; During the acceleration transition process, the vortex center of the rotor moves towards a stable position at a constant speed. The longer the acceleration time, the smoother the vortex climb process. In the first half of the acceleration process, the distance of the rotor moves is greater than in the second half; The aerodynamic load of the fuel cell air compressor causes an uneven acceleration and climb process of the rotor, and the axial displacement is consistent with the changes in aerodynamic load, while the gas film component is opposite to the changes in aerodynamic load.

Key words: fuel cell air compressors, foil gas bearings, rotor system dynamics, accelerated conditions, aerodynamic load