| As a new type of sliding lubrication bearing, gas bearing is gradually taken seriously by people. It runs noiseless, low friction, no heat, small vibration and long service life, which is not restricted by the wear. Spherical spiral groove aerodynamic bearing is a new type of structure of the journal bearing, it can not only bear radial and axial load, but also has compact structure and high gyration precision, which is widely used in the gyroscope, attitude control device, rotating machinery and other equipment. Either the performance or structure is superior to other types of aerodynamic bearing. Based on the computational fluid dynamics, gas lubrication theory and dynamic theory, the steady-state characteristic, dynamic characteristic and stability are analyzed, the main work is as follows:In order to research the steady-state flow field characteristics of spherical spiral groove aerodynamic bearings, the bearing’s lubrication analysis mathematical model is established. Based on CFD technology, and using the FLUENT software of fluid dynamics to analyze the 3D gas film pressure field of the spherical spiral groove aerodynamic bearings. It reveals the laws that effect of the rotation speed, eccentricity, groove width ratio, groove depth ratio, helix angle, groove number, and gas film clearance under different rotation speed on the steady-state bearing gas film pressure and the bearing capacity, and on this basis the structure of bearing parameters are optimized. The results show that the FLUENT can easily and accurately simulate the complex flow field in the gas film area, and the higher rotation speed, the more obvious gas bearing internal hydrodynamic effect. Therefore, choosing reasonable bearing structural and operating parameters contributes to improve the lubrication performance and bearing capacity.The model of rotor-bearing system is built, and using the FLUENT software of fluid dynamics to simulate unsteady flow by boundary moving based on dynamic mesh finite volume method. Through the custom UDF program to calculate the rotor rotating speed and displacement perturbation, and rotation speed and velocity perturbation, and analysis the change of the nonlinear gas film force. The moving boundary of the journal caused by rotational movement is changed into static boundary for avoiding the grid distortion, and the dynamic development process of gas thickness and three-dimensional nonlinear pressure distribution are achieved. Though calculating the difference of stiffness and damping coefficient, the influence law of speed and eccentricity ratio on the dynamic characteristic coefficients has been gained, and exploring the gas bearing’s transient nonlinear dynamic behavior. On the basis of solving the dynamic characteristic coefficients, the axes orbits of rotor with the different rotation speed are acquired. The results show that the influence of the bearing’s speed and eccentricity on the dynamic characteristics is significant, and a reasonable choice of the bearing’s speed and eccentricity contributes to improve the dynamic characteristics. The results of the study for aerodynamic bearing in the operation of the complex environment improve stability provides theoretical predictions. |
