Abstract
Aerodynamic journal microbearings with microtribological phenomena significantly influence the operating stability of microfluidic devices. The modified Reynolds equations including different rarefaction models are derived and are solved by the partial derivative method and relaxation iteration algorithm. The effects of Knudsen number and bearing parameters on the static and dynamic characteristics of microbearings are investigated in detail. The results show that the rarefaction effect plays a crucial role in the ultra-thin gas film lubrication. The maximum film pressure of Fukui–Kaneko (FK) model is lowest and the result in Boltzmann model is largest in small Knudsen number regions. As the Knudsen number increases further, the curve of FK model is coincident with that of the Boltzmann model in the transition regime. The direct stiffness coefficients of Boltzmann model increase with the increase of eccentricity ratio and aspect ratio, whereas the effect of Knudsen number on the damping coefficients yields a relatively complicated trend.
Highlights
Gas journal microbearing is of great importance in various microelectromechanical systems (MEMS)
The rarefied gas flow can be classified into three categories [10,11] on the basis of the Knudsen number Kn, which is defined as the ratio of the gas molecular mean free path λ0 to the characteristic length scale L, i.e., the slip region (0.001 < Kn < 0.1), the transition region (0.1 < Kn < 10), and the free molecular region (Kn > 10)
Hwang et al [20] proposed a new modified Reynolds equation which includes three adjustable coefficients in the velocity boundary conditions, and the results showed that the model produces good approximation to the Boltzmann model for a wide range of Knudsen numbers
Summary
Gas journal microbearing is of great importance in various microelectromechanical systems (MEMS). Zhang et al [30] numerically and experimentally studied the characteristics of hybrid bearings including friction between silicon nitride and bearing steel by molecular dynamics methods They showed that the effect of graphene on the lubrication of friction pair becomes greater when the pressure and shear velocity increases. The partial derivative method and iteration technique are applied to solve the modified Reynolds equations with different Poiseuille flow correctors, and the static and dynamic characteristics of micro gas journal bearings such as gas pressure distributions, dimensionless load capacity, friction coefficient and dynamic stiffness and damping coefficients are obtained for various. This work maybe provides new perspectives in understanding the dynamic properties of aerodynamic journal microbearings, which lays a foundation for the further stability of microbearing-rotor systems
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