Phenomenon of labyrinth seal with low static pressure difference and large clearance

Abstract

This paper discusses the straight-through type labyrinth seal. This labyrinth seal is used for axial flow fans, which have an outer ring at the blade tip to seal the clearance between the ring tip and the fan shroud, in order to prevent the reverse flow or leakage. These fans are used for the cooling of automobile radiators. In these cases, the labyrinth seal is used in an extremely low static pressure difference and a large clearance. A significant decrease of the leakage rate was reported even when the labyrinth seal rotated in comparatively low speed in this unique condition according to the authors' former report. However, this phenomenon is different from past research. Furthermore the cause of this phenomenon has not been determined. Therefore, the internal flow was depicted with Computational Fluid Dynamics (CFD) in order to clarify the cause of this phenomenon. The results of CFD show that the leakage rate decreases significantly because the carry-over flow is intercepted in the expansion groove. This is the newly discovered phenomenon which occurs under the unique condition of an extremely low differential pressure. It has not been pointed out before as the reason why the rotation decreases the leakage rate.