Flow Theory and Performance of Tangential Fans

Abstract

The investigation reported here deals with the conditions of flow through a tangential fan. In order to gain a better understanding of the flow an experimental apparatus for testing the fan was designed. Detailed measurements of velocity and pressure through the impeller interior were carried out. The results indicate that a combined vortex is the main component of the flow, namely, a forced vortex, surrounded by a potential vortex (free vortex). The centre of the combined vortex lies inside the impeller and its location does not change with impeller speed. A suitable theoretical model of the flow was developed and acceptable correlation was found between it and the measured flow field. It was found that the flow regime through the impeller interior could be controlled and that the location of the combined vortex centre and its strength would be regulated by the shape and location of a diffuser baffle. A secondary flow perpendicular to the main flow, hitherto not mentioned, was found and an explanation of this phenomenon is offered. Test results show that the fan efficiency increases with increasing impeller speed in the test range. Previous available works on the subject are reviewed.