Axial flow cooling fan

Abstract

The invention provides an axial flow cooling fan. The axial flow cooling fan comprises a frame body, a hub and a plurality of fan blades, the frame is provided with an air inlet and an air outlet. The hub is rotatably arranged in the frame body. The fan blades are annularly arranged on the hub so as to rotate along with the hub. Each fan blade is provided with a front side face and a rear side face opposite to each other, the front side faces face the air inlet, and the rear side faces face the air outlet. The surface roughness of the front side surface is different from the surface roughness of the rear side surface.

Description

Technical Field

[0001] The invention relates to a heat dissipation fan, in particular to an axial flow heat dissipation fan. Background Art

[0002] Axial flow fans have a simple structure and have air supply characteristics of large air volume and low static pressure, so they are widely used in cooling fans or ventilation fans for personal computers and servers. In order to improve the air supply characteristics of axial flow fans to reduce noise and other optimization purposes, the number and structure of fan blades are often adjusted, or various designs and tests are performed on the structure of the airflow passage.

[0003] For example, when an axial fan is used in a heat dissipation application, its obvious disadvantage is that the flow field pressure is relatively low. Therefore, how to improve this disadvantage is indeed a problem that relevant technical personnel need to solve. Summary of the invention

[0004] The present invention is directed to an axial flow heat dissipation fan, which adjusts the surface roughness of the front side and the rear side of each fan blade to adjust the pressure, direction and concentration of the airflow generated by the fan.

[0005] According to an embodiment of the present invention, an axial flow cooling fan comprises a frame, a hub and a plurality of blades. The frame has an air inlet and an air outlet. The hub is rotatably disposed in the frame. The blades are arranged around the hub to rotate with the hub. Each blade has a front side surface and a rear side surface opposite to each other, the front side surface faces the air inlet, and the rear side surface faces the air outlet. The surface roughness of the front side surface is different from the surface roughness of the rear side surface.

[0006] Based on the above, the axial cooling fan adjusts the surface roughness of the upper blade surface (front side) and the lower blade surface (rear side) of the fan blade to achieve the effect of adjusting the blade surface pressure. The pressure difference or flow rate difference between the front side and the rear side of the fan blade can be adjusted to meet the needs or according to the current flow field without changing the blade shape. Furthermore, the designer can also adjust the rough area of ​​the fan blade on the rear side according to the flow field distribution of the airflow on the fan blade surface and the required air outlet direction and concentration to meet the heat dissipation needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram of an axial flow cooling fan according to an embodiment of the present invention;

[0008] Figure 2 yes Figure 1 A simple side view of an axial cooling fan;

[0009] Figure 3 Show Figure 1 A partial bottom view of an axial flow cooling fan;

[0010] Figure 4 yes Figure 3 Schematic diagram of the structure of the rough area;

[0011] Figure 5 It is a simple schematic diagram of the fluid boundary layer;

[0012] Figure 6 is a partial bottom view of an axial flow cooling fan according to another embodiment of the present invention;

[0013] Figure 7 FIG. 4 is a schematic diagram of an axial flow cooling fan according to another embodiment of the present invention. DETAILED DESCRIPTION

[0014] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0015] Figure 1 FIG. 4 is a schematic diagram of an axial flow cooling fan according to an embodiment of the present invention. Figure 2 yes Figure 1 A simplified side view of an axial-flow cooling fan. Figure 3 Show Figure 1 Partial bottom view of the axial flow cooling fan. Please also refer to Figures 1 to 3 In this embodiment, the axial flow cooling fan 100 is suitable for electronic devices, such as a system fan or a CPU cooling fan set in a desktop computer, and includes a frame 110, a hub 120 and a plurality of blades 130. The frame 110 has an air inlet 111 and an air outlet 112. The plurality of blades 130 are arranged around the hub 120, and the hub 120 is rotatably arranged in the frame 110 and is located between the inlet 111 and the outlet 112. The hub 121 is connected and driven by a motor (not shown) to rotate along the direction RD with the axis AX as a reference, and at the same time, the blades 130 are driven to rotate along the direction RD with the hub 120 to generate airflow ( Figure 2 The light emitting diode (as shown by the arrow) enters the frame 112 from the inlet 111 and leaves the frame 110 from the outlet 112.

[0016] In detail, Figure 2 and Figure 3 As shown, each blade 130 has a front side surface S1 and a rear side surface S2 facing each other, the front side surface S1 faces the air inlet 111, and the rear side surface S2 faces the air outlet 112. Furthermore, each blade 130 also has a leading edge E1 and a trailing edge E2, which are the adjacent parts of the front side surface S1 and the rear side surface S2, respectively. When the blade 130 rotates with the hub 120, the leading edge E1 is located in the windward position, and the trailing edge E2 is located in the leeward position.

[0017] Figure 4 yes Figure 3Schematic diagram of the structure of the rough area, which is a gold image micrograph of the rough area 131. Please also refer to Figure 3 and Figure 4 More importantly, the blade 130 of this embodiment also has a rough area 131 located on the rear side surface S2 and occupying a part of the rear side surface S2, and the range of the rough area 131 extends radially along the blade 130, so as to extend from the hub 120 to the end edge ES of the blade 130. Here, the end edge ES can be regarded as the farthest side edge of the rear side surface S2 relative to the hub 120. In other words, Figure 3 As shown, for the fan blade 130, except for the hub 120, the leading edge E1, the trailing edge ES and the trailing edge E2 are adjacent in sequence. In this embodiment, the rough area 131 has an etched microstructure and has a plurality of etching particles 131a, and the roughness of the rough area 131 is defined by the etching depth of the etching microstructure of 10μm to 45μm and the number of etching particles 114a of 15 to 150 per centimeter. The above etching is for the mold for forming the fan blade 130. By forming an etching pattern on the mold, the corresponding pattern (rough area 131) can be smoothly formed on the fan blade 130.

[0018] Figure 5 is a simple diagram of a fluid boundary layer. Figure 5 , the following briefly describes the formation principle of vortex. Generally speaking, the boundary layer formed between the fluid and the surface of an object will be affected by the roughness of the surface of the object. Figure 5 As shown on the right, when the fluid pressure increases, the fluid at the inner edge of the boundary layer will gradually generate a reverse flow field E due to the viscous resistance of the object surface, causing the fluid to separate from the object surface. This fluid separation phenomenon is the main cause of the vortex.

[0019] Here, the boundary layer equations are:

[0020]

[0021] When the boundary condition y=0, u=v=0, and when y=∞, u=U(x), where u and v represent the velocity components of the fluid in the x and y directions, U(x) represents the flow velocity, μ represents the dynamic viscosity (dynamic viscosity coefficient), ρ represents the fluid density, the direction along the wall of the object is the x-axis, and the direction perpendicular to the wall is the y-axis.

[0022] based on Figure 5 The separation phenomenon of the boundary layer shown in this embodiment Figure 3 The rough area 131 can provide a basis for designers to adjust the airflow.

[0023] Please refer to Figure 2 and Figure 3In this embodiment, in order to increase the airflow pressure difference between the front side surface S1 and the rear side surface S2, the surface roughness of the front side surface S1 of this embodiment is different from that of the rear side surface S2, and in particular, the surface roughness of the rear side surface S2 is greater than that of the front side surface S1. Therefore, in this embodiment, a rough area 131 needs to be formed on the rear side surface S2, while the front side surface S1 remains a smooth surface, so as to achieve the effect of increasing the outlet air pressure of the axial flow cooling fan 100. Of course, in another embodiment not shown, the rough area 131 as described above can also be set on both the front side surface S1 and the rear side surface S2, but if the outlet air pressure is still to be increased, the surface roughness of the rear side surface S2 still needs to be greater than that of the front side surface S1.

[0024] Figure 6 This is a partial bottom view of an axial flow cooling fan according to another embodiment of the present invention. Figure 6 , different from the above, the axial cooling fan of this embodiment is intended to reduce noise, so a rough area 132 is formed on its rear side surface S2, and the rough area 132 extends from the hub 120 along the rear edge E2 to the end edge ES. Since for the fan blade 130, the airflow has been separated from the rear side surface S2 when it reaches the rear edge E2, but due to the difference in airflow pressure, turbulence will be generated on the rear side surface S2, thereby forming obvious aerodynamic noise. Therefore, this embodiment increases the degree of chaos of turbulence through the provision of the rough area 132, thereby making the turbulence offset each other, thereby achieving the effect of reducing noise.

[0025] Figure 7 is a schematic diagram of an axial flow cooling fan according to another embodiment of the present invention. Figure 7 The fan blade 130 of this embodiment combines the above Figure 3 and Figure 6 The embodiment feature is that the rough area 132 can effectively reduce the effect of turbulence, and the rough area 131 can increase the effect of the air outlet pressure, so that the rough areas 131 and 132 are adjacent to each other on the rear side surface S2 of the fan blade 130, wherein the roughness of the rough area 132 must be greater than or equal to the roughness of the rough area 131, so as to control the fluid separation point or provide a better control flow field.

[0026] Based on the above, the present invention also provides a design / manufacturing method for an axial flow cooling fan according to the above embodiment, that is, during the design phase, the blade shape of the initially designed fan blade is analyzed to check the separation state of the airflow and the fan blade, thereby adding a design rough area at a specific location of the fan blade, thereby controlling (adjusting) the direction and concentration of the outlet airflow. Figure 3 , Figure 6 or Figure 7 As shown in the embodiment, the position and range of the rough area on the surface of the fan blade 130 are adjusted according to the specific requirements of the axial flow cooling fan.

[0027] In summary, in the above-mentioned embodiment of the present invention, the axial cooling fan adjusts the surface roughness of the upper blade surface (front side) and the lower blade surface (rear side) of the fan blade to achieve the effect of adjusting the blade surface pressure, wherein the pressure difference or flow rate difference between the front side and the rear side of the fan blade can be adjusted to meet the needs or be adjusted according to the current flow field without changing the blade shape. Furthermore, the designer can also adjust the rough area of ​​the fan blade on the rear side according to the flow field distribution of the airflow on the fan blade surface and the required direction and concentration of the air flow to meet the heat dissipation needs.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An axial flow cooling fan, characterized in that: include: A frame having an air inlet and an air outlet; A wheel hub is rotatably disposed in the frame; as well as A plurality of fan blades are arranged around the hub to rotate with the hub, wherein each of the fan blades has a front side and a rear side opposite to each other, the front side faces the air inlet, the rear side faces the air outlet, and the surface roughness of the front side is different from the surface roughness of the rear side.

2. The axial flow cooling fan according to claim 1, characterized in that: The surface roughness of the rear side surface is greater than the surface roughness of the front side surface, so as to increase the air outlet pressure of the axial flow fan.

3. The axial flow cooling fan according to claim 1, characterized in that: The front side surface is a smooth surface, and a portion of the rear side surface has an etched microstructure.

4. The axial flow cooling fan according to claim 1, characterized in that: A portion of the front side surface or a portion of the rear side surface of each of the fan blades has an etched microstructure to improve surface roughness, the etched microstructure has an etching depth of 10 μm to 45 μm, and the number of etching particles of the etched microstructure is 15 to 150 per centimeter.

5. The axial flow cooling fan according to claim 1, characterized in that: A portion of the rear side surface of each of the fan blades has at least one rough area, and the rough area extends from the hub to the distal edge of the rear side surface, and the distal edge is the farthest point of the rear side surface relative to the hub.

6. The axial flow cooling fan according to claim 5, characterized in that: Each of the fan blades also has a leading edge and a trailing edge, which are respectively the adjoining parts of the front side surface and the rear side surface, and the rough area located on the rear side surface extends from the hub along the trailing edge to the distal edge.

7. The axial flow cooling fan according to claim 6, characterized in that: When the fan blade rotates with the hub, the leading edge is located at the windward side, and the trailing edge is located at the leeward side.

8. The axial flow cooling fan according to claim 6, characterized in that: The rear side surface of each blade has a plurality of rough areas in part, and the roughness of the rough area adjacent to the trailing edge is greater than or equal to the roughness of the rough area away from the trailing edge.

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