An Experimental Study on the Performances of Drum Type Centrifugal Ventilators of Varying Axial Lengths

Abstract

The forms of the runner of the multiblade drum type centrifugal ventilators, of which the “Sirocco” is the best known, and most popularly adopted in our collieries seem somewhat disadvantageous for a uniform flow of air. The air axially sucked in must suddenly change its direction radially in order uniformly to go out from the periphery, but this is impossible unless the air has no moving inertia. Thus more or less eddy formations due to this cause are inevitable with the runner, and the writer observed that the eddy phenomena decreased by shortening the axial length of the runner. But, then, the ratio, between the amount of frictional surfaces for the air, to the cross rectional area in the casing, would increase, thus causing more frictional loss of energy, if assumed that the quantity of air treated is proportional to the axial length of the fan. The purpose of this experiment is to investigate how the fan performrnces change with fans of varying axial lengths, owing to these l wo opposite influences, keeping other conditions as unchanged as possible.