Study On The Film Flow Field Of The Aerostatic Bearing Of The Annular Multi-hole Integrated Restrictor

Since aerostatic bearings had many advantages such as long life,good thermal stability,and high cleanliness,they were widely used in the fields of IT chip manufacturing,advanced optical manufacturing equipment,and medical equipment.However,aerostatic bearings still have problems such as low bearing capacity,low rigidity,and poor stability,which severely limit their development prospects.In response to the above-mentioned problems,the annular multi-hole integrated restrictor aerostatic bearing was adopted as the research object,and its influence law was studied by means of the process and structural parameters on its static and gas film flow field characteristics.The purpose is to improve the carrying capacity and working stability of aerostatic bearings,and to provide a theoretical basis for the further research on aerostatic bearings in the thesis.Firstly,the theoretical derivation of the governing equations applicable to aerostatic bearings was carried out.Based on the proposed physical model of the aerostatic bearing with an annular multi-hole integrated restrictor,the static characteristics of the aerostatic bearing were derived from simultaneous continuity equations,aerodynamic equations(NS equations)and gas state equations,etc.The mathematical model that can be used to solve the static characteristics of aerostatic bearing was deduced.The engineering calculation expressions were established for the bearing capacity and stiffness of the aerostatic bearing.Secondly,the finite difference method was used to carry out a numerical analysis of the static characteristics of aerostatic bearings.The gas lubrication control equation was discretized by the finite difference method,and the iterative expression of the numerical calculation was established by the over-relaxation iterative method.The research results show that the pressure value of the air film flow field gradually decreases to atmospheric pressure as it is far from the outlet position of the orifice.The annular multi-hole integrated throttling form can effectively improve the static characteristics of the aerostatic bearing.Thirdly,the complex gas film flow field near the orifice of the aerostatic bearing was studied by using the large eddy simulation method.According to the established physical model of the annular multi-hole integrated restrictor aerostatic bearing,the mesh was divided,and the large eddy simulation method was used to carry out the simulation calculation of the gas film flow field.The research results display that there is a sudden drop in pressure and in temperature near the outlet of the orifice,and separation phenomena in the gas film gap in the theme.The intensity of the cyclone in the gas film flow field of the aerostatic bearing increases with the gradual increase of the air supply pressure,but decreases with the increase of the number of orifices.The annular multi-hole integrated throttling form can significantly reduce the cyclonic strength of the outlet of the orifice.Finally,an experimental platform for the bearing capacity and micro-vibration of the aerostatic bearing of the annular multi-hole integrated restrictor was designed and built.The research results demonstrate that the experimental value of the bearing capacity of the aerostatic bearing are consistent with the change trend of the numerical solution using the finite difference method,and the micro-vibration experimental result are in good agreement with the influence law of the application of large eddy simulation.The theme was carried out through experiments on the physical model,working mechanism,load-bearing performance,gas film flow field and micro-vibration characteristics of the designed annular multi-hole integrated restrictor aerostatic bearing.The results of the study reveal that cyclone is one of the main causes of micro-vibration in aerostatic bearings,and the annular multi-hole integrated throttling form has a good suppression effect on the micro-vibration of the aerostatic bearing.The design idea of adopting annular multi-hole integrated restrictor not only helps to improve the load-carrying performance and working stability of aerostatic bearings,but also has positive guiding significance for the further research of aerostatic bearings.