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.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a fan, in particular to a fan structure which is capable of reducing an aerodynamic drag.[0003]2. Description of Prior Art[0004]A conventional heat-dissipating system applied to a computer host or other electronic apparatus includes a heat-dissipating fan for generating compulsive airflow for dissipating the heat to the outside. Since the heat-dissipating fan operates for a long period of time, the heat-dissipating effect thereof is much relevant to its operating efficiency. On the other hand, if the noise generated by the heat-dissipating fan is too large, the user will feel very uncomfortable.[0005]In general, airflow is generated when a fan rotates. The airflow forms a thin layer, referred to as a boundary layer, when it passes through the surface of blades of the fan. The boundary layer of airflow may generate turbulent flows beyond separating points where the airflow separates from ...

AI Technical Summary

Benefits of technology

[0007]The present invention is to provide a fan structure, which is capable of reducing a frictional force and noise generated by the fan.

[0008]The present invention is to provide a fan structure, whereby the rotation of blades is smoother, labor-saving and power-saving, and the heat-dissipating efficiency of the fan is increased.

[0010]The present invention is to provide a fan structure, in which the periphery of a casing is formed with recessed portions recessed toward an accommodating space in the fan. With this arrangement, more external air can be introduced into an intake side and the exhaust resistance generated on an exhaust side can be lowered.

[0012]In comparison with prior art, the fan structure of the present invention is provided on the blade with a plurality of polygonal dents. When the airflow passes through the surface of each blade, the airflow is brought into contact with the periphery of each polygonal dent to generate a turbulent flow. The turbulent flow stays in the polygonal dent. A plurality of the turbulent flows collect together to form an air film for separating the surface of the blade from the boundary layer. Since the air film can extend the distance of the separating points from the boundary layer to thereby prevent the generation of the turbulent flows near the blades, the noise and the frictional force generated by the turbulent flows can be reduced. Therefore, the rotation of the blades is smoother, labor-saving and power-saving, and the heat-dissipating efficiency of the fan is increased.

Problems solved by technology

On the other hand, if the noise generated by the heat-dissipating fan is too large, the user will feel very uncomfortable.

The turbulent flows may cause the blades to vibrate and thus generate undesirable noise.

Further, due to the turbulent flows, a frictional force may generate between the surface of the blade and the airflow, which deteriorates the rotating efficiency of the fan.

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