Characteristics analysis and dynamic responses of micro-gas-lubricated journal bearings with a new slip model

Abstract

In this paper, a new slip model based on kinetic theory of gases for gas-lubricated journal bearings in micro-electro-mechanical systems (MEMS) is applied using a physical approach. The corresponding modified governing equation and mathematic model are presented and the flow rate is plotted versus the inverse Knudsen number. Pressure distributions along the gas bearing at various Knudsen numbers and bearing numbers are plotted and the load carrying capacities are also obtained. A numerical analysis of a rigid rotor supported by gas-lubricated journal bearings is presented for dynamic behaviour. The slip flow effect on the properties, including pressure distribution, load carrying capacity and dynamic coefficients, of the micro-gas-lubricated journal bearings and dynamic responses of the micro rotor-bearing system are estimated and analysed in detail. It is shown that the dynamic coefficients increase with increasing bearing number except for two damping coefficients and the rotor-bearing system runs at a much higher rotating speed to keep stable when slip flow occurs. Moreover, the oscillation period of the rotor operating with the slip model is longer than that with the continuum flow. In addition, the whirl frequency is reduced from 0.422 to 0.079 under the slip effect. Therefore, the results of this study contribute to a further understanding of the characteristics and nonlinear dynamics of gas-film rotor-bearing systems in MEMS.

Dynamics of a small gap gas lubricated bearing with Navier slip boundary conditions

“…A decrease in the bearing stability is reported through a reduction in the dynamic (stiffness and damping) coefficients, leading to possible rotor contact with the housing in the case of a small axial disturbance. A corresponding study by Zhang et al (2008) reported similar outcomes when using modified slip coefficients in the second-order slip velocity boundary condition.…”

Thermohydrodynamic analysis of micro spherical spiral groove gas bearings under slip flow and surface roughness coupling effect

“…Figure 10 shows the three-direction bearing forces, F x , F y , and F z , which vary with eccentric ratios in different flow conditions as per isothermal hydrodynamic analysis. The bearing forces increase with an increase in eccentricity ratio under different flow conditions which has been described in reference (Zhang et al 2008). The action of gas film squeezing becomes significant with an increase in eccentricity ratio, thereby strengthening the bearing forces.…”

“…Moreover, the bearing forces under the slip flow region weaken significantly with a high eccentricity ratio. This decrease is because the minimum gas film thickness decreases at this high ratio to strengthen the slip flow (Zhang et al 2008). The bearing forces in the x-and y-direction, F x and F y , are almost similar, but these forces are considerably weaker than z-direction bearing force F z .…”

Experimental validation of impact energy model for the rub–impact assessment in a rotor system

“…But most of these researches are focused on the stability, bifurcation and chaos of the rotating machinery [8,9,11,[17][18][19][20][21][22]. Few discussions are presented for the severity of rub-impact.…”

“…Zhang et al [7] analyzed the rub-impact fault caused by geometric asymmetry between the rotor and stator, and discussed the grazing phenomenon of the single point rubbing in detail. Zhang and Meng [8][9][10][11][12][13][14][15][16] give a series of researches on the nonlinear Micro-Electro Mechanical Systems (MEMS), including stability, bifurcation and chaos. Also they do a number of detail researches on the influence of several nonlinear parameters to rotor systems.…”