Dynamic analysis of a high-speed micro compressor supported by spiral-grooved hydrodynamic air bearing

Spiral-grooved hydrodynamic air bearings are used in high-speed machines due to their advantages of oil-free, low friction, and compact structure. This paper aims to investigate the dynamic characteristics of a high-speed rotor supported by spiral-grooved hydrodynamic air bearings and the effects of spiral groove parameters. A mathematical model of the rotor-bearing system is developed by coupling the rotor nonlinear motion equations and the bearing dynamic Reynolds equation. The finite element method combined with the Runge-Kutta method is employed simultaneously to obtain the nonlinear trajectory of the rotor-bearing system. The theoretical model is verified by experiments on the built micro compressor prototype. The numerical predicted onset speed of the sub-synchronous motion of the rotor-bearing system agrees well with the experimental observations. Furthermore, the effects of radius clearance, groove depth, groove angle, groove axial and circumferential width on the dynamic performance of the rotor-bearing system are analyzed. The results show that radius clearance has the most significant influence, followed by groove depth, groove axial, and then circumferential width. The groove angle has the least impact.