Numerical analysis of hydroinertia gas bearings with inclined supply holes for high-speed rotary machines

Hydroinertia gas journal bearings have been applied to solid-state nuclear magnetic resonance (NMR) as an example. This type of bearing can realize a stable operation for the ultra-high-speed rotation of an NMR sample tube as high as several million rpm, because these bearings utilize a large radial clearance compared with conventional externally pressurized bearings. To obtain even higher rotational speeds, inclined supply holes in the direction of shaft rotation have been proposed. The characteristics of these proposed bearings are examined in this study by numerical analysis because the actual NMR sample rotor is thin and long (with a diameter of 1 mm to 4 mm). The numerical analysis results of the hydroinertia journal bearings are reported in this study. Variation of the pressure distribution and the load capacity with respect to the effect of the radial clearance and the angle of the supply holes are described. The results show that a negative pressure is generated at large radial clearance, and the load capacity does not affect the angle. The pressure distribution was experimentally verified using a test rig, which has 10 mm diameter rotor.