Influences of various orifice layouts on the properties of aerostatic journal bearings based on finite element method

Abstract

It is essential to thoroughly investigate influences of orifice layouts on properties of aerostatic journal bearings employed in ultra-high speed spindles. In this paper, four orifice layouts of aerostatic journal bearings which have a large length-diameter ratio are designed and investigated, particularly in light of the nonlinear compressible Reynolds equation and the associated computational analysis and algorithms using the FEM-based Galerkin weighted residual method. A series of pressure distributions as well as the load capacity, attitude angle, volume flow rate and air film stiffness of the aerostatic journal bearings for the cases of four orifice layouts are analysed with respect to different rotational speeds and eccentricity ratios. It can be concluded that increasing orifice sets is not beneficial to enhance the performance of the aerostatic journal bearing. The aerostatic journal bearing divided into two identical independent aerostatic journal bearings has relative optimal performance at rotational speeds from 0 r/min to 160,000 r/min, such as the highest load capacity, the lowest attitude angle and modest air film stiffness, however, with consumption of the largest quantities of pressurized gas. The designers can use the analysis results to optimize the orifice layout for improving the performance of the aerostatic journal bearing.