Bearing Clearance in Design Calculation for Porous Aerostatic Thrust Bearings

Abstract

It has been reported that porous aerostatic bearings behave as if they were operating at a clearance larger than the measured bearing clearance, leading to pressure decrease within the gap and to flow rate increase. This implies that it is difficult to predict the bearing performance theoretically at a design stage, because bearing clearances effective for the design are not known. For one porous metal and three porous carbon bearings, theoretical air film pressures calculated by using the finite element method are compared to experimental ones and it is shown that applying an additional gap is a simple way to compensate the difference in the pressure between theory and practice. Taking into consideration the fact that the porous surface texture resembles Plateau texture, it is reasonable to apply the additional gap of the same magnitude to the parameters derived from the areal material ratio curve, in particular, for porous carbon bearings.