| Air bearing has the advantages of high rotation accuracy,low friction,low temperature rise,long service life,etc.It has good applicability in high-speed precision machine tools,precision measuring instruments,high-speed rotors and other equipment.Due to low gas viscosity and strong compressibility,gas bearings are prone to instability.Therefore,it is necessary to accurately calculate the key parameters such as the bearing capacity,static stiffness,and the main bearing capacity,dynamic stiffness,dynamic damping and other parameters in the non-operating state of the bearing.The traditional research methods of hydrostatic bearing static and dynamic characteristics often require two-dimensional simplified solution to the Reynolds equation with many assumptions,and cannot accurately reflect the three-dimensional flow within the lubrication film and the static and dynamic characteristics of the bearing.In view of the limitations of the traditional methods,this article based on CFD,respectively,porous radial bearing and Thrust bearing as the research object,made the following work:Through 3D fluid flow control equations established finite element mathematical model of flow field in porous aerostatic bearing,combined with the actual situation,determine the internal flow field of the porous bearings fluid model and boundary condition,providing theoretical basis for the late CFD software analysis of dynamic characteristics;FLUENT computational fluid dynamics software was used to analyze the static behavior of the bearing under static loading.Systems of different air film clearances,different air supply pressures,different bearing areas,and different porous viscous drag coefficients were systematically investigated for bearing capacity,static stiffness,and volume.The influence of flow rate reveals the influence of working conditions,structure,and size difference on the static characteristics of porous bearings,and designs a more reasonable bearing structure.According to the data from the static analysis,choose the most optimized axial size and boundary conditions,by means of CFD dynamic grid and the dynamic bearing capacity under the dynamic load bearing,main stiffness,damping,cross the main stiffness,damping accurate calculation,cross bearing is studied under different working condition of gas film clearance and different speed of the dynamic characteristics.Using the bearing transient flow field calculation results combined with the FLUENT passive motion boundary calculation method 6DOF,the nonlinear curve of the axial trajectory under different working conditions of the upper rotor of the porous medium gas bearing is calculated and plotted.This method can effectively improve the complex motion of the traditional active motion boundary conditions by defining the tedious steps of the equation of motion,directly giving the rotor mass and motion state,and simulating the actual operation of the rotor-bearing system.The influence factors of the stability of the bearing film are analyzed by combining the rotor axis trace diagrams under different working conditions.The installation scheme of the porous shoe radial bearing is given,which improves the stability of the rotor-bearing system. |
