Improvement of Stalling Characteristics of an Axial-Flow Fan by Radial-Vaned Air-Separators (1st Report, Effects of Radial-Vaned Air Separator)

Abstract

An improved construction of air separator was investigated with respect to stall prevention effect on a low-speed single-stage axial-flow fan. The fan is a rather lightly-loaded one. For directly scooping and rectifying the near-stalling flows, the device incorporates radial vanes embedded within its inlet circumferential cavity with their leading edges facing the moving tips of the fan rotor blades. Stall-prevention effects by the separator layout, relative location of the separator to the rotor-blades, and the effect of widths of the openings of the air separator inlet and exit were parametrically investigated. Those factors were observed to affect the fan performance characteristics, particularly the stalling points and curve configurations. As far as the particular fan is concerned, the device together with the best relative location has proved to be able to eliminate effectively the stall zone having existed in the original solid-wall characteristics, which has confirmed the promising potential of the device. This study has provided information for maximizing the stall prevention effect of the device and for minimizing the axial size of the device at least on lightly-loaded fans. With respect to simplifying the radial vanes and minimizing the radial extent of the device, the readers are asked to refer the second report of this investigation.