Experimental Study on the Mechanism of Significant Stall Suppression Effects in an Axial Flow Fan Achieved by an Air Separator Device(Fluids Engineering)

Abstract

Radial-vaned air separators show a strong stall improvement effect in axial flow fans. Changes in the fan internal flow patterns achieved by the device have been made clear by Pitot-traversing mesurements. With a decrease in the fan flow rate the meridional streamline inclinations through the rotor blades have become more and more abrupt together with the circumferential velocities enlarged in the region, in contrast to relatively insensitive behavior tendency of the streamlines and flow patterns in the solid-wall condition. The stall suppression are suggested to have been achieved by the followings air separator effects; (1) suction of inflow casing boundary layers and elimination of embryos of stall, (2) separation of reversed flow from the main flow, (3) induction of the flow toward the casing wall and strengthening of stream-surface inclination, and (4) reinforcement of axi-symmetric flow structure. Combination of them appears to have caused the great stall suppression effect that would have been impossible by other types of stall prevention devices.