Research On High Confidence Of Numerical Simulation Method For Porous Aerostatic Bearings

Aerostatic bearing is an important core component in ultra-precision machine tools.They are widely used due to their advantages of high precision,minimal friction loss,and high speed.Aerostatic bearing made of porous materials have higher bearing capacity and stiffness than other types of aerostatic bearings,so porous aerostatic bearings are receiving more and more attention.The numerical simulation method is an important calculation tool for the research of porous aerostatic bearings.However,how to improve the confidence of numerical calculation and narrow the gap between the bearing simulation results and the actual operating performance is a problem to be solved in the development of new type of porous aerostatic bearings.To solve this problem,this paper analyzes the different internal flow field calculation models for porous aerostatic bearings firstly,and then discusses the influence of multi-source manufacturing error of the bearing restrictor on the static characteristics of bearings.and finally establishes the improved rotary error dynamically calculation model of aerostatic bearing.It provides a reliable simulation calculation model for the performance calculation of porous aerostatic bearing.The main research contents of this article are summarized as follows:(1)The calculation models for different internal flow fields of porous gas hydrostatic bearings were studied.Using the fluid computational fluid dynamics(CFD)software,a numerical solution model of porous aerostatic bearings was established.Based on the theory of internal flow field,the turbulent flow model and velocity slip model of porous bearings were proposed.Under the turbulence model and the slip model,the changes on the static performance of the bearing is analyzed.Finally,the superiority of the proposed internal flow field model is verified by the theoretical derivation results.(2)The influence of multi-source manufacturing error on the static characteristics of bearing was studied.Through the experimental measurement and mathematical fitting tools,established the manufacturing error model of the restrictor,and analyzed the influence of the manufacturing error of the restrictor on the static characteristics of the porous aerostatic bearing.Then the manufacturing error model of the combined spindle and restrictor was established and analyzed the influence laws of the static characteristics of the bearing.Finally,the accuracy of the multi-source manufacturing error model is verified by static experiment.(3)A improved dynamic calculation model of rotary error of porous aerostatic bearing was established.Based on the theory of fluid dynamics,the formula for calculating the dynamic bearing capacity of porous gas hydrostatic bearings was deduced.Based on the dynamic mesh technology,compared the advantages and disadvantages of different grid renewing methods.Then the motion algorithm of porous aerostatic bearing spindles was developed by using VS and analyzed the influence of the roundness of the main shaft on the bearing rotation error.Finally,the precision of the above-mentioned improved calculation model was verified by the rotation accuracy experiment.