A magnetic fluid seal for rotary blood pumps: behaviors of magnetic fluids in a magnetic fluid seal with a shield

Y. Mitamura¹ - T. Yano² - W. Nakamura³ - E. Okamoto³

¹ Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
² Department of Machine Intelligence and Systems Engineering, Faculty of Systems Science and Technology, Akita Prefectural University, Yuri-Honjo, Japan
³ Department of Human Science and Informatics, School of Biological Science, and Engineering, Tokai University, Sapporo, Japan

Abstract
A magnetic fluid (MF) seal has excellent durability. The performance of an MF seal, however, has been reported to decrease in liquids (several days). We have developed an MF seal that has a shield mechanism. The seal was perfect for 275 days in water. To investigate the effect of a shield, behaviors of MFs in a seal in water were studied both experimentally and computationally. Two kinds of MF seals, one with a shield and one without a shield, were installed in a centrifugal pump. Behaviors of MFs in the seals in water were observed using a video camera. In the seal without a shield, the surface of the water in the seal waved and the turbulent flow affected behaviors of the MFs. In contrast, MFs rotated stably in the seal with a shield in water even at high rotational speeds. Computational fluid dynamics analysis has revealed a stationary secondary flow pattern in the seal and the small velocity difference between the magnetic fluid and the water at the interface. These MF behaviors prolonged the life of the MF seal in water. Figs 3, Refs 4.