Hydroinertia Gas Bearing System to Achieve 470m∕s Tip Speed of 10mm-Diameter Impellers

Abstract

A microbearing tester driven by an air turbine of 10mm diameter has been developed, and successfully used to test hydroinertia gas bearings with a shaft of 4mm diameter. The effects of bearing gas pressure conditions and bearing length to diameter ratio (L∕D) on the maximum achievable rotation speed were investigated. The maximum rotation speed of 890,000rpm, which corresponds to the DN number (the product of a shaft diameter in millimeter and a rotation speed in rpm) of 3,560,000, was achieved. At 890,000rpm, the tip speed of the turbine reaches approximately 470m∕s. Using the bearing system developed, the turbo components of a 100W class gas turbine and an air pump for 1kW class fuel cells can be tested.