Centrifugal fan

摘要

The centrifugal fan with single or double intake is provided with a fan impeller of the closed type which is formed of a rotating bladed wheel (10) having at least a covering element (13). The blades (11) of the fan impeller (16) are flat and are backwardly inclined with respect to the direction of rotation of the fan impeller and the covering element (13) comprises along the direction of flow a frustoconical surface portion (13A), a first curved surface portion (13B) and a second curved surface portion (13C), wherein the radius of curvature of the first curved surface portion is smaller than the radius of curvature of the second curved surface portion.