Seal performances in mechanical seals for an axial flow blood pump

A miniature intraventricular axial flow blood pump for left ventricular support are under development. One of the key technologies which requires for them is sealing of the motor shaft. In this study, to prevent the blood from back flowing into the motor side, mechanical seals were developed, and the tribological performance of them was investigated. In the experimental apparatus, the mechanical seal separates the bovine blood on the chamber side from the cooling water on the motor side. A leakage of the blood and a rate of hemolysis were measured. A torque of the shaft was measured by a torque transducer. A rotation speed of the shaft and a contact force of the seal faces were changed in the experiments. In order to estimate the lubrication regimes, the Stribeck Curve, which is a diagram of the coefficient of friction against the bearing characteristics number G, was drawn. As the results of experiments, both the leakage of the blood and the rate of hemolysis were very small. The friction loss was also very small. The condition of lubrication could be clarified by the Stribeck Curve.