Effect of preloaded gas foil conical bearing on the rotor dynamic performance of fuel cell air compressor

To investigate the effect of mechanical preload on the performance of gas foil conical bearing (GFCB), the Reynolds equation and elastic foil deformation were solved by the finite difference method (FDM). Three dimensional energy equation of the gas film is also derived and solved by FDM, and the influence of temperature rise on the static bearing performance is investigated. Moreover, the static and dynamic characteristics of GFCB were calculated and analyzed under different preload conditions. Based on the finite element method (FEM), a 5-DOF equation model considering radial and axial displacement was adopted for stability analysis of cone rotor system. In addition, the running test of an air compressor for Fuel cell vehicle supported by two shimmed GFCBs has been conducted to verify the actual effect of preload. The results show that the static load capacities, friction torque, and dynamic direct stiffness of GFCB are enhanced largely by the preload, especially under larger thickness. The consideration of gas film temperature can increase the bearing load capacities and friction torque, and will decrease the attitude angle. Both theory and experiment analysis show that the mechanical preload can improve the stability of high-speed cone rotor-bearing system, including the reduced axis trajectory and delayed occurrence of low-frequency vibration.