Research on clearance flow characteristics of gas-lubricated journal bearings using the lattice Boltzmann method

Abstract

Gas-lubricated journal bearings (GLJBs) are widely utilized in rotating machines and the complex flow in ultra-thin clearances is a hot research topic. In this paper, the micro-clearance between the journal and housing of a GLJB was selected as the research object of a typically curved variable cross-section microchannel. In addition, the multiple-relaxation-time (MRT) model of the lattice Boltzmann method (LBM) was employed to analyze the shear flow characteristics. The generalized form of interpolation supplemented LBM (GILBM) based on the body-fitted grid was utilized due to complex geometry, and the Langmuir slip boundary model was introduced through the non-equilibrium extrapolation (NEE) method to simulate the rarefied airflow from the slip region to transition region. The velocity and pressure fields in the microchannel under different bearing parameters and operating conditions were described by the present model. What’s more, the gas backflow phenomenon was captured. Additionally, the effect of velocity slip on the performance characteristics of GLJBs was studied. It was found that with the increase of eccentricity ratio and rotor speed, or a decrease of clearance size, the load-carrying capacity and friction torque of GLJBs rise, and the occurrence of velocity slip weakens the static performances of GLJBs.

Keywords

• Gas-lubricated journal bearing
• lattice Boltzmann method
• Langmuir slip boundary
• Body-fitted grid