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Air foil bearings are gradually applied in air compressors in fuel cell vehicles for the advantages of high speed, oil-free and non-contact. Advanced air foil bearings with different structures are used to improve the performance of air compressor. Accurate modeling of the complex structures in air foil bearings has become a research hotspot in recent years. This paper presents a theoretical model for a double-top-foil air foil journal bearing (DAFJB) for centrifugal air compressors used in fuel cell vehicles. The foil structure is modeled by finite element method (FEM) using shell elements. Coulomb law and penalty function method are applied to model the tangential and normal behavior of the contact areas. The local contact between the middle top foil and the bump foil, the bump foil and the bearing sleeve are modeled using node-to-segment contact method. The large-area contact behavior between two layers of top foils is modeled by simplified surface-to-surface contact scheme.

The performance of the air compressor influences that of the fuel cell system significantly. Therefore, it is urgent to develop a high-performance air compressor for fuel cell vehicles. In this paper, an analytical model of centrifugal compressor performance is established, which can predict the performance of centrifugal compressors under various speeds precisely. Then, the dynamic model of the electric-driven centrifugal compressor system is presented considering rotor dynamics and the dynamic characteristics of the motor. The torque ripple caused by the non-sinusoidal distribution of the permanent magnet field is considered. Based on experiment results, the output performance of the fuel cell stack is modeled. Finally, the influence of motor torque ripple on the performance of centrifugal compressor and fuel cell system is analyzed through simulations.