Simulation studies on aerostatic thrust bearings with special reference to cryogenic turboexpanders

Abstract

The present paper details theoretical studies on aerostatic thrust bearings with special reference to cryogenic turboexpander rotors. A special case of 4.5K, 250W helium refrigerator has also been considered where both the turboexpanders are supported by aerostatic thrust bearings of similar dimensions. The bearings experience continuously changing ambient (discharge) pressure during the start-up and shut-down transients, thereby requiring a proper estimation of bearing characteristics for successful turboexpander operation at all times. Performance charts, in terms of load capacity, stiffness and bearing gas flow with respect to change in clearance have been presented for different bearing gas supply and discharge pressures.