Duct mounted axial flow fan - has outside rotor driven impeller with blades rotating within duct contraction

摘要

An axial flow fan mounted on a duct, has its impeller (1) mounted on the drive shaft (3) of a motor (2) with an outside rotor carrying a set of blades (4). The motor/fan assembly is mounted within the dish-shaped casing (6) on struts. On the interior of the casing is a ring (7) with an inner diameter equivalent to the cylindrical envelope (20) of the impeller blade tips. The cross sectional shape of the ring is such that its radial thickness increases in air flow direction to a maximum and then decreases again over a total width of (a) of the ring. The casing has openings (15) in its base for the passage of air and the top of the casing has a socket-like extension to hold the brackets of the struts supporting the stator part of the motor. The struts and rings are extruded as one integral part.