Characteristics of Motion of an Impeller Supported by Dynamic Pressure Bearings in a Miniature Centrifugal Blood Pump

- Influence of Bearing Clearance -

Abstract

A left ventricular assist device (LVAD) is also used for right ventricular assist because a right ventricular assist device (RVAD) has not existed. LVADs should be driven at off-design point because the demanded head of a left heart is not different from that of a right heart. When blood pumps are driven at off-design point, the instability of impellers can occur and lead to damages of blood. In the present study, the instability of the impeller with two journal bearings in a RVAD under development was investigated. In experiments, performance tests of the RVAD were carried out and motions of the impeller were measured by two laser displacement sensors. As a result, it was confirmed that spectra of the frequency of vibrations of the rotor had two peaks which were the rotational component ω and the half of it, 0.5ω. Ratios of the amplitude of the vibration to the mean radial clearance c_d were about 0.25 at c_d=50 μm, 0.55 at c_d=100 μm. The vibrations could be associated with a whirling motion and the vibration at c_d=50 μm was stable.