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Incorporating the velocity slip effect of the gas flow at the solid boundary, theperformance and dynamic response of a micro gas-bearing-rotor system are investigated inthis paper. For the characteristic length scale of the micro gas bearing, the gas flow in thebearing resides in the slip regime rather than in the continuum regime. The modifiedReynolds equations of different slip models are presented. Gas pressure distribution and loadcarrying capacity are obtained by solving the Reynolds equations with finite differentmethod (FDM). Comparing results from different models, it is found that the second orderslip model agrees reasonably well with the benchmarked solutions obtained from thelinearized Boltzmann equation. Therefore, dynamic coefficients derived from the secondorder slip model are employed to evaluate the linear dynamic stability and vibrationcharacteristics of the system. Compared with the continuum flow model, the slip effectreduces dynamic coefficients of the micro gas bearing, and the threshold speed for stableoperation is consequently raised. Also, dynamic analysis shows that the system responseschange with variation of the operating parameters including the eccentricity ratio, therotational speed, and the unbalance ratio.

Considering the velocity slip effect of the gas film at the solid boundary, the performance of a micro gas bearing is given. For the length scale of the micro gas bearing, the gas flow in the bearing is dominated by the slip regime instead of the continuum one. With different slip models, the modified Reynold's equations are obtained. Solving the Reynold's equation with finite difference method, the bearing forces are compared between the different models, and the second order slip model is found to fit the microelectromechanical systems (MEMS) case very well. Adopting the second order slip model, the dynamical coefficients and the stable threshold speed of the system are estimated based on the linear bearing force. And the dynamical response of the micro gas bearing is acquired with fourth-rank Runge-Kutta method. Compared with the results of the second order slip flow, the continuum flow overestimates the dynamical coefficients and underestimates the threshold speed. What is more, the period of the journal oscillation rose for the slip effect. [ABSTRACT FROM AUTHOR]

This paper employs a hybrid numerical method combining the differential transformation method (DTM) and the finite difference method (FDM) to analyze the nonlinear dynamic behavior of a rigid rotor supported by a micro gas bearing system (MGBS). It is shown that the results obtained for the orbits of the rotor center are in good agreement with those obtained using the traditional FDM approach. Moreover, the hybrid method avoids the divergence problem suffered by the FDM scheme at low values of the rotor mass and computational time step. The results presented in this study summarize the changes which take place in the dynamic behavior of the MGBS as the rotor mass and bearing number are increased over the ranges 0.01-0.16 and 1.0-5.0, respectively, and therefore provide a useful insight into the nonlinear dynamics of the bearing system. [ABSTRACT FROM AUTHOR]