Abstract
In order to further explore and study the influencing factors and regulars of the gas film flow field at the outlet of the orifice of the aerostatic bearing, the large eddy simulation method was used to calculate the N-S equation in the calculation area of the gas film flow field at the outlet of the orifice of the aerostatic bearing, and the overrelaxation iteration method was used to solve the Reynolds equation in the other calculation areas, which was proposed in this paper. Based on the physical model of the outlet of the orifice of the aerostatic bearing, the solution area of the gas film flow field of the aerostatic bearing was solved, and the calculation results were analyzed and discussed. The results showed that there was a sharp drop of the gas film pressure at the outlet of the orifice of the aerostatic bearing and the separation of the gas film pressure p became inconsistent in the thickness direction of gas film clearance h. It was assumed that there was a critical ratio θ between the gas film clearance h and the orifice diameter d of the aerostatic bearing, and when the ratio of gas film clearance h to the orifice diameter d was greater than the critical ratio θ, various fluctuations of the gas film flow field began to appear, which may be the initial signal state of the gas film flow field of the aerostatic bearing starting to transition to turbulence. It provided a theoretical basis and guidance for further study of the transition lubrication mechanism between the laminar and the turbulent flow at the outlet of the orifice of the aerostatic bearing in this paper.
Highlights
Aerostatic bearings, with clean and dry air as the lubricating medium, have the advantages of high precision, low friction, no pollution, long service life, good thermal stability, and flexible structure design, which have been widely used in IC manufacturing equipment, precision manufacturing equipment, precision measuring instruments, and other equipment [1,2,3]
With the requirements of high precision development of submicron and even nanometers in precision and ultraprecision manufacturing and measurement, various factors that have been neglected to affect the performance of aerostatic bearings in the past are gradually being considered and concerned [4,5,6]. e microvibration of the aerostatic bearing is different from the self-excited vibration of the air hammer during the motion support process. e microvibration is mainly produced by the flow of the internal gas in the aerostatic bearing, whose amplitude is only nanometers to submicrons and frequency is from tens of hertz to thousands of hertz [7]
Mori [12] researched the pressure distribution in the gas film of the parallel disk thrust aerostatic bearing and proposed that there was a sharp pressure drop at the outlet of the orifice of the disk thrust bearing. He found that the pressure distribution in the gas film of the aerostatic bearing did not steadily decrease from the outlet of the orifice to the
Summary
Aerostatic bearings, with clean and dry air as the lubricating medium, have the advantages of high precision, low friction, no pollution, long service life, good thermal stability, and flexible structure design, which have been widely used in IC manufacturing equipment, precision manufacturing equipment, precision measuring instruments, and other equipment [1,2,3]. Miyatake and Yoshimoto [15] obtained the flow coefficient by comparing the results of CFD simulation and the results of solving the Reynolds equation by FDM, obtained the gas film pressure distribution of the thrust aerostatic bearing by solving the Reynolds equation, and found that the thrust aerostatic bearing with small orifice had a large damping and stiffness coefficient Chen and He [16] found cyclones in the flow field near the orifice outlet through CFD simulation of ring throttle and orifice throttle of aerostatic bearings and put forward the view that the cyclones cause the microvibration of aerostatic bearings earlier in the world. In order to further explore and study the influencing factors and regulars of the film flow field at the outlet of the orifice of aerostatic bearings, the large eddy simulation method was used to calculate the N–S equation in the calculation area of the gas film flow field at the outlet of the orifice of aerostatic bearings, and the overrelaxation iteration method was used to solve the Reynolds equation in the other calculation areas, which was proposed in this paper. e factors that affected the stability of the gas film flow field were discussed, and the bearing capacity of the aerostatic bearing was tested. e research and analysis of the gas film flow field at the outlet of the orifice of aerostatic bearings had an important research and guiding significance for further improving the application and promotion of the gas lubrication support technology in precision and ultraprecision motion mechanisms and instruments in this paper
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