Experimental investigations and empirical relationship on the influence of innovative hub geometry in a centrifugal fan for performance augmentation

Abstract

Background: One of the problem areas of fluid flow in the turbomachine is its inlet region, manifested by flow distortions due to the induced fluid swirl accompanied by improper flow incidence onto the impeller. Further, the hub forms one of the main components of many of the turbomachines and it is found that there has not been significant study on geometrical modifications of the same in centrifugal fans for augmented performance. This is partially due to designers trying to reduce the cost of the overall machine. Objective: There is a scope for detailed parametric study and the present work involves an exploration of flow behavior by parametric variation of hub geometry in terms of both its shape and size. Methods: Experiments are carried out in order to determine the importance of hub with different size and shapes. The geometric models of hemi-spherical and ellipsoidal hubs are considered for the analyses in the present study. Results: An optimized ellipsoidal hub configuration is found to yield a relative improvement of about 7.5% for head coefficient and 7.7% increase in relative theoretical efficiency over the hub-less base configuration. Finally, correlations are developed for the optimized hub shape configurations. Conclusion: It is revealed from experimental analysis that hub plays a vital role in streamlining the flow at the inlet to the centrifugal fan and augments its performance.