Improved modeling method of inherently compensated aerostatic thrust bearings considering pressure depression

Abstract

For inherently compensated aerostatic bearings, the traditional modeling method of describing an air supply orifice with a nodal point results in computational errors when numerical discretization methods, such as the finite difference method, are used particularly for a small air-film thickness. To address this problem, this paper proposes an equivalent pressure-equalizing chamber model (EPECM) to consider the pressure depression around the orifice. First, numerical simulations of the circular centrally fed aerostatic thrust bearing (CCFATB) were conducted using computational fluid dynamics. The discharge coefficient and the radius of the pressure-depression region under various operation conditions were obtained. Subsequently, by combining these two key parameters, the EPECM was applied to analyze the static performances of the CCFATB and annular aerostatic thrust bearing (AATB). The air domain of the AATB was divided into non-uniform grids. The five-point difference scheme and nine-point difference scheme were adopted to solve the Reynolds equation respectively, and the computational results were compared. The proposed model and discretization method were verified by comparing the results with experimental and published data. It is found that the EPECM has a high computational accuracy and superior numerical iteration efficiency compared with the commonly used point-source assumption. The five-point difference scheme is able to deal with the non-uniform mesh model accurately. Moreover, the modified discharge coefficient and pressure-depression region radius calculated in this study provide useful data for performance analysis of inherently compensated air bearings.