| 摘要 |
<p>A centrifugal fan including a fan hub (15) lying generally in a plane normal to the axis of fan rotation (Ar) and having a central opening for receiving a motor housing, and a plurality of fan blades (13) of substantially identical construction spaced circumferentially evenly around the fan hub (15) and extending away from the fan hub (15) in a direction parallel to the axis (Ar) of fan rotation. Each fan blade (13) includes a leading edge at its innermost radial periphery, and the leading edge (13L), at least at the axially upper one-half section thereof, is convexly curved in the shape of a quarter ellipse having a major axis, Mg, substantially parallel to the axis (Ar) of fan rotation and a minor axis, mh, normal to the major axis Mg. The fan also includes a continuous shroud (14) joined to each fan blade (13) at an axially upper section of the radially outer portion thereof and the shroud (14) is concave in cross-section. The fan orifice (11) used in conjunction with the fan has an entry portion that is convex in cross-section and is in the form of a surface produced by rotating a planar line about a coplanar axis of generation that is coincident with the axis (Ar) of rotation of the fan, the planar line being a generally quarter segment of an ellipse having a major axis, Ma, substantially parallel to the axis of generation and a minor axis, mb, normal to the major axis Ma. <IMAGE></p> |
