Experimental Study of Whirl Instability for Externally Pressurized Air Journal Bearings

Abstract

In this study the stability of externally pressurized air journal bearing which has a peripheral row of feed holes is experimentally investigated to make clear how the onset speed of selfexcited whirl is affected by the three factors of supply pressure, number of feed holes and bearing clearance. As the result, the following facts are revealed. (1) Under a certain supply pressure and number of feed holes exists an optimum clearance which gives a maximum whirl onset speed. (2) Under a certain supply pressure and number of feed holes exists a clearance which gives a maximum whirl frequency, and this clearance is slightly smaller than the optimum clearance. (3) The whirl onset speed is directly affected not by the supply pressure and the number of feed holes but by the whirl frequency and the bearing clearance. The item of (1) can be explained by those of (2) and (3).