Hydroinertia gas bearings for micro spinners

Abstract

Externally pressurized gas bearings with large bearing clearance are successfully used in ultra-high-speed micro spinners. For example, a micro spinner 4 mm in diameter is stably operated at more than 20 krps and its whirl ratio exceeds 20. In such bearings, the inertia effect of the gas flow in bearing clearance becomes predominant and its Mach number exceeds 1. As a result, gas pressure in the bearing clearance becomes negative. These bearings are called hydroinertia gas bearings, in contrast to the conventional hydrostatic gas bearings. Static characteristics of hydroinertia gas bearings are analyzed by considering the viscous effect of gas as wall friction, and the optimum design of hydroinertia gas bearings is shown. Experimental results on micro spinners and trial design of hydroinertia gas bearings for micro gas turbines are also discussed.