Design and experimental verification of the vehicle compressor rotor system with inhomogeneous foil bearings

In this paper, the design and experimental verification of the rotor system with gas foil bearings are carried out with a vehicle compressor developed in our laboratory. The designed rotating speed 100,000 rpm with 50 g/s mass flow and 1.8 pressure ratio. The journal foil bearing with inhomogeneous bump foil is designed and tested by a push-pull device to evaluate the structure stiffness of bump foil. The result shows that the stiffness curves of two bearings with the same manufacturing process are not consistent, which indicates the uncertainly in the manufacture of foil bearings and it is necessary to obtain the foil stiffness data by experiment. A multi-disc model is established to simulate the impeller in the finite element model (FEM) for the vehicle compressor is too short to ignore the impeller width. The stiffness and damping coefficients of foil bearings are used to proceed rotordynamic analysis. The vibration experiments indicate that with the operating speed enhancement, the center orbit falls smaller. When the rotating speed increases to about 60,000 rpm, two sub-synchronous frequency occur and remain at 150 and 307 Hz finally. Two radial acceleration peaks appear at 9736 and 25,828 rpm respectively, which are close to the critical speed of damped Campbell diagram. The compressor performance map shows that the pressure ratio of the compressor is slightly lower than the design value due to the eccentricity of the foil bearing, which can be solved by increasing the operating speed. This paper provides some reference value for the design and experiment of vehicle compressor supported by the foil bearings.