Effect of Axial Gap between Diffuser Inlet and Impeller on Efficiency and Flow Pattern of Centrifugal Fans

Abstract

Inlet is one of the basic elements of squirrel cage fan that can have great effect on performance and losses, especially between inlet exit and first section of impeller width. In this paper the effect of axial gap between inlet diffuser and impeller on performance and flow pattern is considered. Three diffuser inlet sizes with respect to impeller size (smaller, nearly same and bigger than inner impeller diameter) and three axial gaps within the available dimensions of the casing and impeller were chosen. Numerical simulations were performed to find the effect of this axial gap on flow pattern, performance and efficiency. From the simulation of each case study, flow pattern and its mechanism and the causes that affecting the efficiency and performance due to axial gap are analyzed and presented.