Research On Static And Dynamic Characteristics And Flow Field Supersonic Characteristic Of Micro-Groove-Orifice Aerostatic Journal Bearing Under High Gas Supply Pressure

As an important branch of gas bearing,aerostatic bearing has the outstanding advantages of small friction,high speed,low heating and high precision compared with the traditional lubrication technology,so it is widely used in the spindle system of ultra-precision machine tools.Aiming at the problem that the load capacity,stiffness and rotary accuracy of aerostatic journal bearing decreases under high gas supply pressure,this paper designs a new type of micro-groove-orifice aerostatic journal bearing(MGOAJB).By establishing a theoretical model of static and dynamic characteristics of bearings under high gas supply pressure,and using simulation software for calculation,the static and dynamic characteristics and supersonic characteristics of flow field of MGOAJB under high gas supply pressure are studied,and the accuracy of simulation calculation is verified through experiments.The theoretical basis and design method are provided for the study of static and dynamic characteristics and flow field supersonic characteristics of aerostatic journal bearings under high gas supply pressure.Due to the phenomenon of accelerated gas velocity,complex flow and drastic energy change in aerostatic bearing under high gas supply pressure,which is quite different from the traditional lubrication theory,Therefore,the governing equation of aerostatic journal bearing including inertia force and energy equation is established in this paper,and the SST k-ωturbulence model is introduced to obtain the theoretical model of the static characteristics of aerostatic journal bearings under high gas supply pressure.According to the calculation results of static characteristics,coupled with the dynamic model of spindle rotor,a theoretical model of dynamic characteristics of aerostatic journal bearings under high gas supply pressure is established.Based on the two-dimensional flow theory,a theoretical model of supersonic characteristics of MGOAJB under high gas supply pressure is established.A spindle system with MGOAJB is designed,and a three-dimensional model of the gas film flow field of MGOAJB is established.FLUENT software is used to develop a simulation analysis method for static characteristics of aerostatic journal bearing under high gas supply pressure.Taking traditional orifice-compensated aerostatic journal bearing(OCAJB)as comparison,and taking bearing capacity,stiffness and gas flow as indicators,the static characteristics of MGOAJB under high gas supply pressure are analyzed,and the effect of MGO structure on static characteristics of aerostatic journal bearing under high gas supply pressure is studied.Under high gas supply pressure,the influence of MGO structural parameters and spindle speed on static characteristics of MGOAJB is studied by taking the shape of groove section(rectangle,triangle,arc),groove depth,groove width,groove length and aperture as structural size parameters.By designing different number and position of MGO structure and four different layout modes: axial,through circumferential,sectional circumferential and oblique,the influence of the number and layout direction of MGO on the static characteristics of MGOAJB is studied.The static calculation results of aerostatic journal bearing under high gas supply pressure are coupled with the dynamic model of spindle rotor.Simulation software is used to analyze the dynamic characteristics of MGOAJB under high gas supply pressure,including each order mode,critical speed and rotary accuracy.Taking the traditional OCAJB as a comparison,the effect of MGOAJB on dynamic characteristics under high gas supply pressure is studied.By introducing SST k-ω turbulence model into the governing equation with simulation software,the supersonic characteristics of MGOAJB under high gas supply pressure are studied by taking the gas supply pressure,gas film thickness and orifice diameter as the influencing factors.By comparing with the OCAJB,the performance improvement of the MGO structure under high gas supply pressure under supersonic phenomenon is revealed.An aerostatic bearing spindle test bench is built to test the load capacity and spindle vibration response of MGOAJB under high gas supply pressure,and the correctness of simulation results is verified.It provides experimental basis for the availability of theoretical model and calculation method.