Dynamic friction and microturbine performance using a planar-contact encapsulated microball bearing

Abstract

Successful demonstration and characterization of a radial inflow microturbine supported on a planar-contact encapsulated microball bearing is presented. Reliable operation of the air-driven silicon microturbine is shown for nearly 1,000,000 revolutions at speeds, pressure drops, and flow rates of up to 10,000rpm, 0.45psi, and 3.5slm, respectively. Incorporation of a gas thrust plenum enables comprehensive spin-down friction characterization of the encapsulated microball bearing. An empirical power-law model for dynamic friction has been developed for speeds and loads of 250-5,000rpm and 10-50mN, respectively, corresponding to torques of 0.0625-2.5µNm and friction coefficients of 0.0005-0.025.