Air movement fan with protrusions on the leading and trailing edges of the blades

摘要

An air movement fan has a plurality of elongate fan blades 1, each blade having a leading edge 7 and a trailing edge 8, both of which have a plurality of protrusions 3, 9 spaced along their length. The protrusions 3, 9 on the leading edge and trailing edge merge into elongate bumps 19 projecting from a surface of the blade and extending towards the other edge, the bumps merging smoothly with said surface of the blade to form valleys between adjacent protrusions. Preferably the protrusions on the leading edge are offset from those on the trailing edge by half the distance between protrusions which may be sinusoidal, arcuate, rectangular or hyperbolically tangent in profile.