Research On The Characteristics And Their Affecting Factors Of The Hydrostatic Thrust Bearing

Hydrostatic bearing could separate journal and bearing with the pressure fluid,make sure there is no direct contact between them.With the merits of high load capacity,low friction,low abrasion,high efficiency and low vibration,hydrostatic bearings are widely used in engineering domain,and meet the requirements of heavy and precision manufacturing equipment on bearing performance,becoming an important way for Highend equipment manufacturing to implement high precision and stability.This thesis study on hydrostatic thrust bearing which is an important part of hydrostatic bearings,conduct to investigate the influence mechanism of static and dynamic performances of lubricant film in bearing system.Firstly,the static and dynamic characteristics of thrust bearings with different recess lubricated by Newtonian lubricant are discussed,with the comparison on the results of different bearings,it is found that the performance of annular recess thrust bearing is the best.Then,the effect of lubricant on the bearing performance is studied,and propose that to improve the characteristic of the bearing,could instead of the traditional Newtonian lubricant with Non-Newtonian lubricant.After that,the effect of oil film structure on the bearing performance is analyzed considering bearing tilt,surface microstructure and thermal deformation of bearing surface.Finally,a testbed of annular thrust bearing is set up,and the theoretical results are demonstrated with experiment.The results of this study could be useful in the design and employ of thrust bearing.he main research contents of this thesis are as follow.(1)Based on thin film lubrication,generally governing equation of thin film has been derived from Navier-Stocks equation.Choosing thrust bearing as research object,the equation has been simplified,and the governing equation of thrust bearing has been obtained.With the studying on three recess(circular,annular and sector)of thrust bearing,it is found that the static performance of annular recess bearing is the best.During the discussion,considering the difference between theoretical results and experimental results when the small radius bearing is studied in the previous literature,a new method considering the inertia effect on the supply oil hole is proposed,which reduces the difference between the theoretical results and experimental results.Then,the dynamic performances of circular and annular recess bearings have been discussed,it is found that the dynamic performance of annular recess bearing is better.And on the same situation,the dynamic characteristic of thrust with orifice compensation is better than that of capillary compensation.Besides,the effects of recess pressure,recess area and recess location on the dynamic performance of annular recess thrust bearing are gave,and the empirical formula in the practical engineering could be revised.(2)The relationship between the shear stress and velocity gradient of traditional Newtonian lubricant is linear.As the requirements of bearing characteristics has been increasing during the actual working conditions,the traditional Newtonian lubricant has gradually been replaced by non-Newtonian lubricants.And the relationship between the shear stress and velocity gradient of non-Newtonian lubricant is nonlinear,which revises the difficulty in theoretical analysis of bearing characteristics.The effects of two kinds of non-Newtonian lubricants(couple stress lubricant and Rabinowitsch lubricant)on the static performances of bearing are discussed in this thesis.The static performances of annular recess thrust bearing lubricated with couple stress fluid are derived by conventional method,and the results show that the static performances of bearing could been improved by using couple stress lubricants.But as so far,there is no governing equation for thrust bearing lubricated with Rabinowitsch lubricant.Although the Indian researchers use energy integral method to study this problem,the process is tedious,the result of calculation is complex and the generalization is questionable.So this thesis proposes perturbation method and mean inertial method to improve the computational process.It is found that the results and computational process of mean inertial method are succinct,and the results agree well with the results of Indian researchers.Therefore,the average inertia method proposed in this paper has better generalization in the analysis on the static characteristics of the thrust bearing lubricated with Rabinowitsch fluid lubrication.(3)The change of oil film structure in three cases is introduced: the tilt between journal and bearing,surface micro-structure of the bearing and the temperature rise of the rotating bearing.Based on this,the effects of oil film structure on the performance of annular recess thrust bearings have been discussed.And during the discussion,the GaussLegendre formula is proposed to solve indefinite integral.It is found when the amplitude of the surface micro-structure is greater than the critical value ha0,the rotating of the bearing would enhance the load capacity of the bearing.At the same time,some criteria for the design of surface microstructures with the aim of optimizing the bearing capacity are given.It is also found that the flow rate and load capacity will oscillate with the change of the wavelength of the surface microstructures.In addition,the generally oil film temperature distribution equation is deduced,and the boundary conditions are given.When an annular recess hydrostatic thrust bearing is chosen as the concrete research object,a hypothesis about position independent of the oil film temperature is proposed.The hypothesis is tested experimentally,so during the discussion in the influence of temperature on bearing characteristics,the analysis process can be greatly simplified.(4)In order to verify the correctness of the preceding theoretical analysis,an annular recess hydrostatic thrust bearing test rig has been built,and the static characteristic and stiffness tests on the oil film have been designed.Kinds of sensors were used to collect the oil film pressure distribution,oil film temperature distribution,oil film thickness,flow rate and load capacity of worktable during the working process of the bearing,and the data acquisition instrument have been customized according to the number of sensors.From the analysis previous,the static bearing,it is found that the experimental results and the theoretical results are in good agreement for the static bearing,while in the situation of rotating bearing,there are differences between the theoretical calculations and experimental results,but the overall trend is consistent.And it can be illustrated that theoretical analysis is correct.