Comparative studies on double-layered protuberant foil bearing and Hydresil foil bearing

Abstract

In this paper, the hydrodynamic performance of a new double-layered protuberant gas foil journal bearing (DPGFB) was experimentally studied in a high-speed turbo-expander and compared with the conventional Hydresil foil journal bearing (HGFB). The material properties of supporting foils are important for the bearing performance such as load capacity and frictional damping. In both DPGFBs and HGFBs, two types of materials, stainless steel (0Cr18Ni9) and beryllium bronze (QBe1.7), have been used as supporting foil materials, and their effects on the bearing performance were discussed. A stable operation of turbo-expander with rotational speed up to 70,000 rpm was achieved in the tests of both of two types of bearings. Due to the larger stiffness of the foil layer, the DPGFBs had larger lift-off speed and larger gas film friction torque than HGFBs at high speed when the same foil material was used. The comparison showed that the bearings using 0Cr18Ni9 had a larger life-off friction torque. The synchronous vibration amplitudes of the rotors during the high speed operation and the shut-down process were smaller for DPGFBs than HGFBs, which indicated that the DPGFBs had a better damping performance than HGFBs.