Performance Analysis On The Aerostatic Bearing Used In Vacuum Condition With COMSOL

With the development of electron beam exposure and three-coordinate measurement technology,the research of aerostatic gas bearings,the core support component of ultra-precision platforms,has played a decisive role.As the requirements of the ultra-precision machining environment change,the application environment of the aerostatic gas bearing is transformed into a vacuum environment.Compared with the atmospheric environment,the bearing's stiffness,bearing capacity and other performance changes significantly.At present,there are few theoretical analysis and numerical calculation methods for gas bearings in vacuum,and there are experiments that can verify theoretical analysis.In view of the above problems,this paper takes the single-orifice static thrust gas bearing that can be used in the vacuum environment as the research object,and calculates and theoretically analyzes the main performance of the conductance and the bearing in the bearing exhaust groove.According to the established vacuum experiment system,COMSOL software was used to model and simulate the air pressure distribution and the film in the vacuum chamber.Finally,a corresponding verification experiment was performed.Mainly completed the following four aspects of the work.(1)Calculate the leakage of the gas at the exhaust duct by calculating the equivalent duct conductance of the sealed area of the bearing.For the different conducting capacity of the straight pipe elbow to the gas in the vacuum system,the main researched gas flow range is determined.According to the molecular beam effect,the gas pressure distribution in the vacuum chamber was predicted.(2)the vacuum chamber was simulated by COMSOL software,and the pressure distribution inside vacuum chamber and pipe was obtained.In order to make the vacuum system get better pumping effect,the optimization and simulation are carried out from four aspects,including the shape,radius,distribution and vacuum pumping speed of the vacuum pipe.Compared with the original vacuum system,the pumping time is shortened,and the vacuum chamber pressure is reduced.(3)in order to achieve greater bearing capacity and reduce the leakage of bearings,the micro level gas film formed by gas bearings is modeled and simulated.Bearing external working environment: increasing air supply pressure and reducing external environmental pressure can achieve greater bearing capacity.Bearing geometric parameters: increasing the depth of the exhaust slot and increasing the number of exhaust slots can effectively reduce the leakage of bearings.(4)In view of the need for research on lubrication mechanism of static pressure gas bearing in vacuum environment,and the need for simulation verification,an experimental study was conducted in a designed vacuum chamber using a aerostatic gas bearing performance detection device,and theoretical calculations and simulation results were obtained.For comparison,the bearing performance,stiffness,and leakage of lubrication gas in the vacuum environment were obtained,providing reference for the structural design and performance optimization of the static pressure gas bearing and its sealing system.