Research On Key Technologies Of Partial Porous Externally Pressurized Gas Bearing

Externally pressurized gas bearing has been widely used in the field of aviation, semiconductor, weave, and measurement apparatus because of its advantage of high accuracy, little friction, low heat distortion, long life-span, and no pollution. In this thesis, based on the domestic and overseas researching development about externally pressurized gas bearing, the author investigated the partial porous externally pressurized gas thrust bearing by theoretical analysis, computer simulation, and experiments to improve its static charaterictics and stability. The effects of structure and operating parameters on partial porous externally pressurized gas bearing has been studied. Therefore, a theoretical foundation for the designing and application for the partial porous externally pressurized gas bearing has been presented.Based on the fractal theory, a model was established to demonstrate the relationship bewteen the porous graphite permeability and the fractal dimension. It can predict the permeability of porous graphite and show the effects of the pore size on the permeability.In this thesis, the author established a model about the static characteristics of partial porous externally pressurized gas thrust bearing, and it was analyzed by engineering solution and Finite Element Method (FEM). While using FEM, the second-order partial differential equation was reduced to one-order by adopting Galerkin weighted residual method, for decreasing the continuity degree requirement of the interpolation function and facilitating to the calculation.In order to simplify the calculation procedure, the Reynolds equation in the cylinder coordinates was transformed into the uniform Cartesian coordinates. It avoids an infinitesimal radius was introduced and gets rid of the bottleneck that the conformal transformation did not exist when radius was equal to zero. The FLUENT software used to compute the hydromechanics was utilized to simulate the partial porous externally pressurized gas bearing. The FLUENT software avoids programming for the solving Reynolds equation, which saves time largely. We can focus on studying the effects of the controlling parameters and initial conditions on the bearing characteristics. Meanwhile, it gives the pressure distribution and flow rate more straightly, and enhances the calculated accuracy.The stability of partial porous externally pressurized gas bearing was investigated by minor perturbation method and frequency region analytical solution. Pressure distribution function was divided into static and dynamic pressure distribution functions through minor perturbation method. Then, the static and dynamic pressure distribution functions were calculated by FEM. After the stiffness and the damping of externally pressurized gas bearing were obtained, the stability of the externally pressurized gas bearing was researched.By using the original laboratory rig, the experiments of static characteristics and the stability of partial porous externally pressurized gas bearing ware carried out. The results of experiments well agree with the FEM calculation and the FLUENT simulation, which proves the crediblity of the FEM calculation and the FLUENT simulation.