The Effect of Manufacturing Variations on the Performance of Externally Pressurized Gas-Lubricated Journal Bearings

Abstract

This paper extends the previous work on the hybrid operation of externally pressurized gas bearings to include the effects of manufacturing variations on design performance of the slot entry configuration. Six aspects of manufacture are considered, and include the departure from the design conditions of (a) bearing clearance, (b) feed slot thickness, (c) bearing form, (d) bearing roundness, (e) bearing member alignment, (f) feed slot geometry. Computer predictions of the above effects have been made by introducing modifications to the programs developed to model gas bearing performance developed for solution using a finite difference technique. The results show how the load capacity of the bearings is affected by the departure of dimensions from their design conditions. The magnitude of the departure from the design performance is demonstrated in the figures presented. The performance predictions for the slot entry bearing are compared with results obtained from the orifice compensated journal bearing previously reported. Guidance is given on the limits of departure from initial design conditions which should be allowed for both types of bearing. Confirmation of the accuracy of design predictions has been achieved in this investigation by conducting experiments using test bearings which were very carefully measured to establish the real tolerance on manufacture. These bearings were tested on a specially designed experimental rig.