Study On The Dynamic And Static Characteristics Of Micro-orifice Throttling Aerostatic Thrust Bearings

Aerostatic bearings are widely used in various high-speed and high-precision equipment because of their characteristics of high speed,high precision,no pollution and basically not affected by temperature rise.Micro-orifice throttling as a new gas throttling method has been gradually accepted in the field of gas lubrication.However,there are still many deficiencies in the structural design and dynamic and static performance of micro-orifice throttling aerostatic Bearings.In this paper,microporous throttling aerostatic thrust bearing is taken as the research object,the static and dynamic performance of the bearing is simulated and solved,and explore the influence of bearing parameters on its performance.By analyzing the simulation results,some guidance and suggestions are given to the optimal design of bearing structure.The main research contents of this paper are as follows:(1)Gambit software is used to complete the establishment of gas bearing flow field model,mesh division and boundary condition definition.Fluent software is used to simulate and solve the fluid model of the bearing.The effects of working parameters and structural parameters on static bearing capacity,static stiffness and mass flow rate of bearings are studied.The results show that the static bearing capacity can be increased by increasing gas supply pressure,increasing the diameter and number of micro-orifice restrictor,and decreasing the depth of micro-orifice restrictor,but the effects on stiffness and mass flow rate are different.It is found that when the ratio N between the diameter of the distribution circle D and the bearing outer diameter D1 of the micro-orifice restrictor is between 0.5-0.75,the bearing has better comprehensive performance.In addition,by comparing the static characteristics of three different types of bearing with micro-orifice restrictor,small-orifice restrictor and slit restrictor,the influence of different parameters on the static characteristics of the three bearings is studied.The results show that under the same total throttle area,the bearing capacity and stiffness of the small-orifice throttle bearing with pressure sharing cavity are greater than those of the micro-orifice throttle bearing,but the gas mass consumed by the small-orifice bearing is also greater than that of the micro-orifice bearing.When the total throttling area of micro-orifice bearings and slit bearings is not equal,the bearing capacity,stiffness and mass flow rate curves of micro-orifice bearings and slit bearings are highly consistent.Therefore,it can be considered that under certain circumstances,the two types of bearings have a certain degree of interchangeability.(2)The influence of gas supply pressure,initial gas film thickness and step load on dynamic characteristics of bearings is studied by using the Fluent module and Transient Structural module integrated on ANSYS Workbench platform with the method of tow-way fluid-structure interaction simulation.The response curves of gas film thickness and bearing capacity with time were obtained under different conditions under step load.The results show that when the bearing is affected by step load,the gas film will produce damping vibration,and the vibration law of the gas film thickness and bearing capacity curve is opposite,and the adjustment time of the bearing to reach the stable state is generally not more than 8ms.At the same time,the study shows that increasing the gas supply pressure and decreasing the gas film thickness are beneficial to reduce the vibration amplitude and improve the vibration frequency of the gas film.The increase of step load only increases the vibration amplitude of atmospheric membrane and bearing capacity,but has no effect on vibration frequency.Reducing the initial gas film thickness and the step load is beneficial to reducing the adjustment time,but the gas supply pressure has little influence on the adjustment time.By comparing the dynamic characteristics of micro-orifice bearings and slit bearings,the results show that under the same conditions,when the gas film thickness of the bearing is between12μm-18μm,the gas film change after the stabilization of the micro-orifice bearings is smaller than that of the slit bearings,when the gas film thickness is between 18μm-24μm,the gas film change after the stabilization of the micro-orifice is larger than that of the slit throttling.By comparing the maximum amplitude of gas film and bearing capacity,it can be found that the maximum vibration amplitude of micro-orifice throttling is larger than that of slit throttling under the same condition.The analysis of vibration frequency shows that the vibration frequency of micro-orifice throttling is less than that of slit throttling under the same condition.(3)The bearing entity is designed,and the experimental platform system for testing the static and dynamic characteristics of micro-orifice bearing is built,and the experimental platform system and testing equipment are described in detail.The comparison between the experimental data and the simulation results shows that the errors of static bearing capacity is less than 10% under different gas supply pressures,and the experimental and simulation results have a high consistency.However,for different gas supply pressure,bearing dynamic characteristic experiment and the simulation results and comparison: after exposure to the step load and the simulation results measured adjustment time is greater than the adjustment time,compared the changes of the gas film of the stable quantity condition can be found that the experimental measured variation than the results of simulation,error range within 40%.