Damping Characteristics of Rotor Vibration of Gas Bearing Generating Positive and Negative Pressure on The Bearing Surface

Abstract

The solid NMR (nuclear magnetic resonance) device can obtain high resolution as the hollow sample tube is rotated at ultra-high speed. The rotational speed exceeds over 4 million rpm. Hydro-inertia gas bearing is used in this device to support the rotor. The gas bearing can be operate high rotating speed although this type of bearing oprates by externally pressurized gas. In order to clarify the bearing characteristics,CFD (computation fluid dynamics) analysis has been conducted by authors. Negative pressure was generated localy in the bearing surface. It is thought that such pressure distribution contributes to realize of high speed rotation. This pressure distribution is expected to be affect the stability of vibration of the rotor. In this study,the vibration damping of the shaft supported by this bearing was measured and compared with the conventional type.