Numerical Investigations on the Influence of Innovative Hub Geometry Design for Augmented Performance in a Low Speed Centrifugal Fan

Abstract

Inlet region of a centrifugal fan is considered as one of the important flow domains which provides air into the impeller with adequate flow incidence. There is a dire need for flow guidance for incoming air in order to minimize induced swirl losses in the vicinity of eye of the impeller. An extrusion type of structure, commonly termed hub, is attached to the impeller of turbo machineswhich is used to reduce inlet turning losses and thereby enhancing the performance of the machine in terms of overall static pressure rise. It is seen from a careful literature survey that there has not been significant research on the effect of hub of various shapes and sizeson performance improvement. Analytical tool like computational fluid dynamics (CFD) capture the physics of flow losses encountered especially at the inlet region. This research work attempts to explore numerically the contributions of hub of hemi-spherical and ellipsoidal shapes and parametrically varied sizes on overall performance of the fan. The analysis shows that amongst hemi-spherical and ellipsoidal hub configurations considered in this work, an optimized ellipsoidal hub configuration is found to yield a significant contribution of about 8.4 % for head coefficient and 8.6 % in relative theoretical efficiency over the hub-less base configuration. Finally correlations are developed for the optimized hub shape configurations.