Fan structure

Abstract

A fan structure includes a hub and a plurality of blades extending from the periphery of the hub. The airflow generated by the fan forms a boundary layer on the surface of each blade. The present invention is characterized in that: each of the blades is provided with a plurality of polygonal dents, a turbulent flow is generated in each dent when the airflow passes through the dent, a plurality of the turbulent flows collect together to form an air film between the surface of blade and the boundary layer. By this structure, the distance of separating points from the boundary layer is extended, and the frictional force and noise caused by the rotation of the blades are reduced.

1 . A fan structure including a hub and a plurality of blades extending from the periphery of the hub, the airflow generated by the fan forming a boundary layer on the surface of each blade, characterized in that:
 each of the blades is provided with a plurality of polygonal dents, a turbulent flow is generated in each dent when the airflow passes through the dent, and a plurality of the turbulent flows collect together to form an air film between the surface of blade and the boundary layer.   
     
     
         2 . The fan structure according to  claim 1 , further including a casing, the casing being formed into a square frame and having an accommodating space, the hub and the blades being combined in the accommodating space. 
     
     
         3 . The fan structure according to  claim 2 , wherein the periphery of the casing is formed with at least one recessed portion recessed toward the accommodating space. 
     
     
         4 . The fan structure according to  claim 1 , wherein two adjacent sides of the polygonal dent form an angle. 
     
     
         5 . The fan structure according to  claim 1 , wherein each of the polygonal dents is formed into any one shape selected from the group constituting of triangle, quadrangle, pentagon, hexagon, heptagon and octagon. 
     
     
         6 . The fan structure according to  claim 1 , wherein each of the polygonal dents on the blades is formed into at least two shapes selected from the group constituting of triangle, quadrangle, pentagon, hexagon, heptagon and octagon. 
     
     
         7 . The fan structure according to  claim 1 , wherein the blade includes a first surface and a second surface opposite to the first surface, the polygonal dents are provided on the first surface and the second surface.