Fan assembly and airflow passage structure thereof

1. An airflow passage structure for use with a fan, wherein said fan has a blade and a frame having an airflow inlet, said airflow passage structure comprising:

a sidewall having an uneven thickness; and

an airflow channel defined by an inner surface of said sidewall, and comprising a channel entrance and a channel exit, wherein said sidewall is in connection with said frame of said fan, a continuous and integrated passage is formed by said inner surface of said sidewall and an inner surface of said frame of said fan, said blade is disposed in said continuous and integrated passage, said channel exit is in communication with said airflow inlet of said fan, and the diameter of said airflow channel is non-uniformly distributed, wherein the thickness of each portion of said inner surface of said sidewall is greater than the thickness of said inner surface of said frame, the thickness of said inner surface of said frame is a constant, said airflow channel has a narrowest portion located at a thickest portion of said sidewall, said channel entrance is closer to said narrowest portion of said airflow channel than said channel exit, each of the diameter of said channel entrance and the diameter of said channel exit is greater than the diameter of said narrowest portion of said airflow channel, and a radius of said airflow channel at said narrowest portion is less than a radius defined from a center of said fan to an edge of said blade along a radial direction.

2. The airflow passage structure according to claim 1 , wherein from said channel entrance to said channel exit, the diameter of said airflow channel gradually decreases and then gradually increases.

3. The airflow passage structure according to claim 1 , wherein said airflow passage structure is a hollow structure.

4. The airflow passage structure according to claim 1 , wherein said inner surface of said sidewall is arc-shaped.

5. The airflow passage structure according to claim 1 , wherein said sidewall comprises a first segment, a second segment and a third segment, wherein said first segment and said third segment have the shapes of hollow cones, wherein said second segment is arranged between said first segment and said third segment and has a shape of a hollow cylinder.

6. The airflow passage structure according to claim 1 , wherein a ratio of the diameter of said narrowest portion to the diameter of said channel entrance is ranged from 0.6 to 0.95.

7. The airflow passage structure according to claim 1 , wherein a ratio of the diameter of said narrowest portion to the diameter of said channel exit is ranged from 0.6 to 0.95.

8. The airflow passage structure according to claim 1 , wherein a ratio of the distance between said narrowest portion and said channel exit to the distance between said channel entrance and said channel exit is ranged from 0.35 to 0.80.

9. The airflow passage structure according to claim 1 , wherein said airflow passage structure further comprises plural fixing parts, which are disposed on said sidewall, wherein said airflow passage structure is installed on said fan through said fixing parts.

10. The airflow passage structure according to claim 9 , wherein said airflow passage structure is installed on said fan by screwing, adhering or fastening means.

11. A fan assembly, comprising:

a fan having a blade and a frame, wherein said frame has an airflow inlet; and

an airflow passage structure comprising a sidewall for defining an airflow channel, wherein said airflow channel comprises a channel entrance and a channel exit, said sidewall is in connection with said frame of said fan, a continuous and integrated passage is formed by said inner surface of said sidewall and an inner surface of said frame of said fan, said blade is disposed in said continuous and integrated passage, and said channel exit is in communication with said airflow inlet of said fan, wherein said sidewall has an uneven thickness so that the diameter of said airflow channel is non-uniformly distributed, the thickness of each portion of said inner surface of said sidewall is greater than the thickness of said inner surface of said frame, and the thickness of said inner surface of said frame is a constant, wherein said airflow channel has a narrowest portion located at a thickest portion of said sidewall, said channel entrance is closer to said narrowest portion of said airflow channel than said channel exit, each of the diameter of said channel entrance and the diameter of said channel exit is greater than the diameter of said narrowest portion of said airflow channel, and a radius of said airflow channel at said narrowest portion is less than a radius defined from a center of said fan to an edge of said blade along a radial direction.

12. The fan assembly according to claim 11 , wherein said airflow passage structure further comprises a covering member, which is arranged at said channel entrance.

13. The fan assembly according to claim 12 , wherein said covering member is a grating structure with plural concentric slices, wherein said slices has rectangular, streamline-shaped, curvy shape or stationary blade shape cross sections.

14. The fan assembly according to claim 12 , wherein said covering member is integrally formed, and made of plastic or metallic material.

15. The fan assembly according to claim 11 , wherein from said channel entrance to said channel exit, the diameter of said airflow channel gradually decreases and then gradually increases.

16. The fan assembly according to claim 11 , wherein said sidewall has an arc-shaped inner surface.

17. The fan assembly according to claim 11 , wherein said sidewall comprises a first segment, a second segment and a third segment, wherein said first segment and said third segment have the shapes of hollow cones, wherein said second segment is arranged between said first segment and said third segment and has a shape of a hollow cylinder.