A Numerical Study On The Performance Of Aerostatic Bearing Using Slip Models

For the problem of slip flow effect inside the aerostatic bearing in condition of small gas film clearance, the 1st order slip model (Maxwell slip model), Wu (2008) new slip model and 2nd order slip model are incorporated. In addition, continuum model Reynolds equation and each slip model Reynolds equation are obtained by using the hybrid scheme of the Finite Volume Method (FVM). Then, using the 1st order slip, Wu (2008) new slip, and 2nd order slip velocity to correct mass flow of orifices. Based on the principle of flow equilibrium, the correction flow equilibrium equations for orifices are established. When aerostatic bearings work under small gas film clearance (less than 4.0?m) and high rotational speed (greater than 1.0×104r/min), the numerical study on the performance of aerostatic bearing using variable step size and SOR iterative algorithm.Pressure distribution in the aerostatic bearing under continuum model,1st order slip, Wu(2008) new slip, and 2nd order slip models are analyzed by the software MATLAB. Finally,the performance of continuum model compares with 1st order slip, Wu (2008) new slip, and 2nd order slip models under different gas film clearance, rotational speed, eccentricity. It will indicate the following conclusions:(1) When the gas film clearance becomes less than 1.0?m, continuum model is far overestimates gas pressure around the minimum gas film clearance. Furthermore, the gas pressure of 1st order slip model is higher than Wu (2008) new slip model. Then, the gas pressure of 2nd order slip model is lower than Wu (2008) new slip model;(2) Furthermore, the smaller gas film clearance, the higher deviation between continuum model and each slip model. Continuum model is no longer valid under micro gas film clearance;(3) In order to accurately estimate the gas pressure, capacity and stiffness of aerostatic bearings. This requires slip boundary conditions to correct continuum Reynolds equation and the flow equilibrium equations for orifices under small gas film clearance;(4) It is shows that the Reynolds equation, airflow velocity, and the out mass flow rate are employing a new slip flow model developed by Wu (2008). It will require better performance of aerostatic bearings. Those will provide a theoretical basis to the research of the performance of bearings in micro-scale.