The Vibration of a Rigid Shaft on Short Sleeve Bearings

Influence of Radial Clearance and Rotor Motion to Hemolysis in a Journal Bearing of a Centrifugal Blood Pump

Hemolysis due to narrow clearance of noncontact bearings is a critical problem for rotary blood pumps. We developed a centrifugal blood pump with a magnetic and hydrodynamic hybrid bearing, and found that the hemolysis in the narrow clearance depends not only on the clearance size, but also on the rotor stability. In this study, we quantified the relation between the hemolysis, radial clearance (c), and rotor stability through the measurement of the rotor motion and hemolysis. As a result, it was confirmed that the rotor of the current pump is stabilized within the oscillation of 20 microm in blood, and the hemolysis decreases with increase in the c, which is the opposite in the unstable rotor motion with the previous pump. In order to theoretically discuss this hemolysis tendency, we implemented hemolysis estimation in the c according to hydrodynamics and hemodynamics. This estimation can represent the measured hemolysis tendency, and revealed that the flow rate has large influence on the hemolysis in the c.

Lubrication and Wear Group: Oil-Whirl Characteristics of a Rigid Rotor in 360° Journal Bearings

An insight into the mechanism of oil whirl is obtained by investigating theoretically and experimentally its two main characteristics, frequency and amplitude. It is shown that the ratio of steady oil-whirl vibrational frequency to shaft speed may be predicted qualitatively by a linear treatment and some conclusions of a nonlinear treatment are also given. It is also concluded that oil-whirl amplitude can be restricted by the oil supply pressure.

Experiments involving the use of a rigid rotor supported on two fully lubricated 360° journal bearings are described and ratios of steady oil-whirl frequency to shaft speed as low as 0.37 reported.