Low-noise axial flow fan blade and axial flow fan

Abstract

The utility model relates to the technical field of fan equipment, in particular to a low-noise axial flow fan blade and an axial flow fan. According to the technical scheme, the low-noise axial flow fan blade comprises a center hub support and a plurality of blade bodies. The center hub support comprises a shaft sleeve used for being connected with the rotating shaft, and the multiple blades are regularly connected to the center hub support in the circumferential direction. Blade tip sawteeth are arranged at the outer end part of the front edge of the blade; and the blade tip sawteeth account for 10-35% of the arc length of the front edge of the blade. The scheme has the advantages that the blade strength is improved, turbulent flow is reduced, and noise is lowered.

Description

Technical Field

[0001] This utility model relates to the field of fan equipment technology, and in particular to a low-noise axial flow fan blade and axial flow fan. Background Technology

[0002] Axial flow fans have a wide range of applications in daily life. Axial flow refers to airflow that moves in the same direction as the axis of the fan blades; examples include electric fans and air conditioner outdoor unit fans. Axial flow fans with axial flow blades are typically used in applications requiring high flow rates but low pressure, and are widely used in the air conditioning industry. Common axial flow fans mainly consist of a hub and multiple blades arranged around the hub. Although the structure is simple, the detailed structural parameters of each part of the axial flow fan require very high precision, significantly impacting its operation and noise control.

[0003] With technological advancements, the detailed design of axial flow fan blades has been continuously improved. However, some technical issues still need to be addressed. Most axial flow fan blades are manufactured using a single injection molding process with plastic, resulting in insufficient bending resistance. During high-intensity operation, the blades can collapse and deform under the influence of airflow resistance, leading to various adverse consequences: reduced airflow, poor impeller dynamic balance, and increased noise. The leading edge of the blades, in particular, is more prone to deformation because it is the first part to cut into the air during operation, generating friction and impact.

[0004] To address the issue of insufficient blade strength, some solutions involve integral ribs on the blades. While this method does improve the overall strength of the blades, it introduces new problems. Integral ribs not only fail to reduce noise but also disrupt the airflow direction, creating turbulence. This turbulence leads to reduced airflow and pressure, while increasing fan energy consumption. Furthermore, existing axial flow fan blades often generate significant noise during operation. This noise not only affects the user experience but can also cause interference in situations requiring a quiet environment. Therefore, effectively reducing noise while maintaining fan blade performance has become an important direction for current technological development.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] To address the aforementioned problems, the primary objective of this invention is to provide a low-noise axial flow fan blade that offers advantages such as increased blade strength, reduced turbulence, and lower noise.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A low-noise axial flow fan blade, the technical solution of which is as follows: includes a central hub support and multiple blades; the central hub support includes a bushing for connecting the rotating shaft, and multiple blades are regularly connected to the central hub support in a circumferential direction; the outer end of the leading edge of the blade is provided with a blade tip serration, and the blade tip serration occupies 10% to 35% of the arc length of the leading edge of the blade.

[0009] Furthermore, this application also proposes that the central hub bracket is constructed as a metal hub bracket, and the bushing is formed at the center of the central hub bracket; the central hub bracket also includes a plurality of connecting arms arranged circumferentially on the outer side of the central hub bracket, and the blade is connected to the outer end of the connecting arm.

[0010] Furthermore, this application also proposes that the outer end of the connecting arm is attached and fixed to the back pressure surface of the blade.

[0011] Furthermore, this application also proposes that through holes are provided on the outer end of the connecting arm and at the corresponding position of the blade, and the through holes on the connecting arm and the through holes on the blade are aligned and riveted together.

[0012] Furthermore, this application also proposes that the trailing edge of the blade is provided with serrations.

[0013] Furthermore, this application also proposes that the leading edge of the blade is constructed as an arc shape that gradually slopes backward from the front to the inner end, and the outer edge of the blade is constructed as an arc shape with the opening facing inward.

[0014] Furthermore, this application also proposes that a recessed area is formed on the pressure surface of the blade, which sinks towards the opposite pressure surface, and the recessed area extends to the trailing edge of the blade. A rib is formed on the edge of the recessed area on the blade. The rib includes only a first rib arranged along the leading edge of the blade and a second rib arranged along the outer edge of the blade. The first rib and the second rib intersect at the inner side of the outer end of the leading edge of the blade.

[0015] Furthermore, this application also proposes that the inner end of the first rib extends to the inner end of the leading edge of the blade or to the inner edge of the blade, and the rear end of the second rib extends to the middle rear side of the outer edge of the blade or to the trailing edge of the blade.

[0016] The primary objective of this invention is to provide an axial flow fan, comprising a motor and an axial flow fan blade connected to the output end of the motor; the axial flow fan blade is the aforementioned low-noise axial flow fan blade.

[0017] As described above, the low-noise axial flow fan blade and axial flow fan provided in this application include a central hub support and multiple blades. The central hub support includes a bushing for connecting the rotating shaft, and the multiple blades are regularly connected to the central hub support circumferentially. The outer end of the leading edge of each blade is provided with a serrated tip, the serration occupying 10% to 35% of the arc length of the leading edge. By providing serrated tips at the outer end of the leading edge of the blade, friction and impact between the blade and the air can be effectively reduced, thus lowering noise. Simultaneously, through a reasonable design of the blade structure and rib layout, the blade strength is improved, and turbulence is reduced, resulting in the advantages of increased blade strength, reduced turbulence, and lower noise. Attached Figure Description

[0018] Figure 1 This application provides a three-dimensional schematic diagram of the pressure surface of a low-noise axial flow fan blade.

[0019] Figure 2 A three-dimensional schematic diagram of the back pressure surface of a low-noise axial flow fan blade provided in this application.

[0020] Figure 3 The data graphs provided for this application are for experimental group 2.

[0021] Figure 4 The data provided for this application are from the control group. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0023] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more, unless otherwise expressly defined.

[0025] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0026] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] Example 1:

[0028] like Figures 1-2As shown, this embodiment relates to a low-noise axial flow fan blade, including a central hub support 1 and multiple blades 2. The central hub support 1 includes a bushing 11 for connecting the rotating shaft, and the multiple blades 2 are regularly connected to the central hub support 1 circumferentially. The outer end of the leading edge 21 of each blade 2 is provided with a blade tip serration 22, the serration 22 occupying 10% to 35% of the arc length of the leading edge 21. In this solution, the design of the blade tip serration 22 effectively reduces noise by reducing friction and impact between the leading edge 21 of the blade and the air. Specifically, the blade tip serration 22 can be implemented in various ways; for example, the shape of the serration can be triangular, trapezoidal, or other geometric shapes, and the depth and spacing of the serration can be adjusted according to specific applications. This technical solution, through the design of the blade tip serration 22, solves the technical problem of increased noise in axial flow fan blades during operation due to friction and impact between the leading edge 21 of the blade and the air. Compared with existing technologies, the technical solution of this application not only improves the noise reduction effect of the fan blades but also maintains their aerodynamic performance, avoiding the problems of turbulence and reduced airflow and pressure caused by the overall rib design. Therefore, the technical solution of this application has significant advantages in practical applications, effectively improving the performance and service life of axial fan blades.

[0029] Furthermore, the arc length ratio of the leaf tip serration 22 is within the range of 10% to 35%. After testing, while ensuring other structural features remained the same, the experimental group used three ratios for the arc length ratio of the leaf tip serration 22: 10%, 20%, and 35%. The control group used a design without the leaf tip serration 22. The relevant data are shown in the table below:

[0030]

[0031] Tests show that the blade tip serrations 22 within this range can significantly reduce noise, with a noise reduction of 3 decibels compared to the same fan blade without blade tip serrations 22.

[0032] Furthermore, in this design, the central hub bracket 1 is constructed as a metal hub bracket, with a bushing 11 formed at the center of the central hub bracket 1. The central hub bracket 1 also includes multiple connecting arms 12 arranged circumferentially on the outer side of the central hub bracket 1, with the blade 2 connected to the outer ends of the connecting arms 12. Specifically, the metal hub bracket can be made of aluminum alloy, stainless steel, or other high-strength metal materials to improve the overall structural strength and stability. The bushing 11, formed at the center of the central hub bracket 1, can be achieved through casting, forging, or machining to ensure the connection accuracy and reliability with the rotating shaft. The number of connecting arms 12 can be adjusted according to the specific requirements of the blade 2, typically from 3 to 6. The outer ends of the connecting arms 12 can be fixed to the blade 2 through welding, riveting, or bolting to ensure the connection's firmness. Thus, by using the combination of the metal hub bracket and the connecting arms 12, the technical problem of the connection structure between the blade 2 and the central hub bracket 1 is effectively solved. The high strength and stability of the metal hub bracket reduce the vibration and noise of the blade 2 during high-speed operation. The design of the connecting arm 12 makes the connection between the blade 2 and the central hub bracket 1 more secure, further improving the overall performance and noise reduction effect of the wind turbine. Compared with existing technologies, this technical solution has significant advantages in improving structural strength and reducing noise.

[0033] Furthermore, this application proposes that the outer end of the connecting arm 12 is fitted and fixed to the back pressure surface 23 of the blade 2. Specifically, by increasing the contact area and fit with the blade 2, the outer end of the connecting arm 12 enhances the connection strength between the connecting arm 12 and the blade 2. As a preferred embodiment, the outer end of the connecting arm 12 can be fixed to the back pressure surface 23 of the blade 2 by welding, bonding, or mechanical fixing. For example, the outer end of the connecting arm 12 can be designed as a curved surface that matches the shape of the back pressure surface 23 of the blade 2 to ensure a tight fit between the two. In addition, the outer end of the connecting arm 12 can also be provided with protrusions or grooves to further improve the fixing effect. Thus, this technical solution effectively solves the technical problem of insecure fixing between the connecting arm 12 and the blade 2 by increasing the contact area and fit between the connecting arm 12 and the blade 2. Specifically, the outer end of the connecting arm 12 is fitted and fixed to the back pressure surface 23 of the blade 2. This fixing method not only enhances the connection strength but also ensures that the blade 2 will not loosen or fall off due to airflow resistance when operating at high speed. Compared with existing technologies, this technical solution avoids the influence of the outer end of the connecting arm 12 on the air intake of the blade 2, thereby improving the stability and service life of the axial flow fan blade.

[0034] In a further preferred embodiment, through holes are provided on the outer end of the connecting arm 12 and at the corresponding location on the blade 2. The through holes on the connecting arm 12 are aligned with the through holes on the blade 2 and then riveted together. The through holes can be circular, elliptical, or other shapes suitable for riveting. The diameter and number of through holes can be adjusted according to actual needs to ensure the strength of the riveting. The riveting method can be traditional rivet riveting or other suitable riveting techniques, such as self-piercing riveting or hydraulic riveting. Specifically, during the riveting process, after the rivet passes through the through holes of the connecting arm 12 and the blade 2, the two ends of the rivet are pressed together using a riveting tool to form a strong connection. As a preferred embodiment, the rivet material can be the same metal material as the connecting arm 12 and the blade 2 to ensure the strength and durability of the connection.

[0035] Furthermore, the trailing edge 29 of the blade in this design is provided with serrations 24. The specific shape of the serrations 24 can be triangular, trapezoidal, or other irregular shapes, and the depth and spacing of the serrations 24 can be adjusted according to actual application requirements. For example, the depth of the serrations 24 can be between 1 mm and 5 mm, and the spacing can be between 2 mm and 10 mm. The arrangement of the serrations 24 can be uniform or non-uniform, depending on the distribution of airflow impact. In addition, the material of the serrations 24 can be the same as that of the blade 2, or a different material can be used to enhance the noise reduction effect. By providing serrations 24 on the trailing edge of the blade 2, the noise generated by the blade 2 due to airflow impact during operation can be effectively reduced. The serration structure 24 can disperse the airflow and reduce the direct impact of the airflow on the trailing edge 29 of the blade, thereby reducing noise generation. This design not only improves the operating efficiency of the axial flow fan blade, but also improves its noise control performance. Compared with the prior art, the technical solution of this application achieves a significant noise reduction effect through simple structural improvements, and does not adversely affect the airflow direction, thus maintaining the efficient operation of the fan blade.

[0036] Furthermore, the leading edge 21 of the blade is constructed as an arc shape that gradually slopes backward from the outer end to the inner end, while the outer edge 20 of the blade is constructed as an arc shape with its opening facing inward. The arc shape design of the leading edge 21, which gradually slopes backward from the outer end to the inner end, reduces direct friction and impact between the leading edge 21 and the air, thereby reducing the risk of blade deformation. Simultaneously, the inward-facing arc shape of the outer edge 20 helps optimize airflow and reduce noise generation. Through this structural design, the blade 2 can more effectively control airflow during operation, reducing noise and blade deformation caused by airflow impact. Specifically, the arc shape design of the leading edge 21 can be achieved in various ways. For example, the tilt angle of the leading edge 21 can be adjusted according to actual application requirements; a larger tilt angle results in a smaller contact area between the airflow and the leading edge 21, thus reducing friction and impact. Furthermore, the inward-facing arc-shaped design of the blade's outer edge 20 allows for optimized airflow by adjusting the radius of curvature of the arc. A smaller radius of curvature results in smoother airflow and less noise generation. As a preferred embodiment, the tilt angle of the blade's leading edge 21 can be set to 15° to 30°, and the radius of curvature of the arc of the blade's outer edge 20 can be set to 10% to 20% of the blade's length. Thus, the technical solution of this application effectively solves the technical problem of blade deformation and increased noise caused by friction and impact between the blade's leading edge 21 and the air. Compared with the prior art, the technical solution of this application not only improves the blade's resistance to deformation but also significantly reduces noise levels, thereby enhancing the overall performance and service life of the axial flow fan blade.

[0037] like Figure 1 and 2As shown, a recessed area 26 is formed on the pressure surface 25 of the blade 2, sinking towards the pressure surface 23. The recessed area 26 extends to the trailing edge 29 of the blade, and a rib is formed on the edge of the recessed area 26 on the blade 2. The rib includes only a first rib 271 arranged along the edge of the leading edge 21 of the blade and a second rib 272 arranged along the outer edge 20 of the blade. The first rib 271 and the second rib 272 intersect at the inner side of the outer end of the leading edge 21 of the blade. The recessed area 26 can be formed by a stamping process. Specifically, the recessed area 26 sinking towards the pressure surface 23 is formed on the pressure surface 25 of the blade 2 by a die. The depth and shape of the recessed area 26 can be optimized according to the size of the blade 2 and the airflow conditions. The ribs are formed by creating raised ribs at the edge of the recessed area 26 while pressing the recessed area 26. A first rib 271 is arranged along the edge of the blade leading edge 21, and a second rib 272 is arranged along the outer edge 20 of the blade, converging at the inner side of the outer end of the blade leading edge 21. Specifically, the inner end of the first rib 271 extends to the inner end of the blade leading edge 21 or the inner edge of the blade 2, and the rear end of the second rib 272 extends to the rear middle of the outer edge 20 of the blade or the trailing edge 29 of the blade.

[0038] In a preferred embodiment, the width and height of the first rib 271 and the second rib 272 can be adjusted according to the stress conditions of the blade 2 to enhance the overall structural strength of the blade 2. Specifically, this solution enhances the overall structural strength of the blade 2 and reduces deformation of the blade 2 during operation by forming a recessed area 26 and pressure ribs on the pressure surface 25 of the blade 2. The arrangement of the first rib 271 and the second rib 272 effectively disperses the impact force of the airflow on the blade 2, thereby reducing noise. This structural design not only improves the bending resistance of the blade 2 but also optimizes the airflow through the blade 2, reducing airflow disturbance and further reducing noise. The recessed area 26 extends to the trailing edge 29 of the blade. During the airflow from the leading edge 21 to the trailing edge 29 of the blade, the recessed area 26 will not disrupt the gas flow direction, avoiding turbulence, ensuring airflow and air pressure, and reducing energy consumption. Thus, this solution effectively reduces noise and energy consumption while improving the strength of the blade 2, solving the technical problems of deformation and increased noise caused by airflow resistance during the operation of the blade 2.

[0039] In a further embodiment, a bent portion 28 is constructed on the rear side of the middle of the outer edge of the blade outside the second rib 272, folding towards the back pressure surface 23; the rear end of the bent portion 28 extends to the trailing edge 29 of the blade; the width of the bent portion 28 gradually increases from front to back. Specifically, the bent portion 28 can be constructed by locally heating and applying pressure on the rear side of the middle of the outer edge of the blade, causing it to fold towards the back pressure surface 23. The rear end of the bent portion 28 extends to the trailing edge 29 of the blade, and its connection with the trailing edge 29 can be ensured by controlling the length and angle of the bent portion 28 during the folding process. The width of the bent portion 28 gradually increases from front to back, which can be achieved by gradually increasing the width of the bent portion 28 during the folding process, or by using mold design to achieve a gradual change in width. As a preferred embodiment, the width variation of the bent portion 28 can be precisely controlled by CNC machining technology to ensure a smooth transition with the outer edge of the blade. This application provides a brief and detailed overview. By constructing a bent portion 28 on the rear side of the outer edge of the blade, folding towards the back pressure surface 23, the structural strength of this area is enhanced, preventing blade deformation caused by airflow resistance during high-intensity operation. The rear end of the bent portion 28 extends to the trailing edge 29 of the blade, further improving the overall structural stability. Furthermore, the width of the bent portion 28 gradually increases from front to back, helping to optimize airflow and reduce airflow disturbance, thereby reducing noise and improving the operating efficiency of the fan. Compared with the prior art, this application not only improves the blade's bending resistance but also effectively reduces noise and improves the overall performance of the fan by optimizing airflow. Moreover, the bent portion 28 can be constructed by locally heating and applying external force on the rear side of the outer edge of the blade, causing it to fold towards the back pressure surface 23. The gradual increase in width of the bent portion 28 from front to back can be achieved by controlling the heating area and the applied external force during the folding process. In a preferred embodiment, the width variation of the bend 28 can be linear or non-linear to further optimize airflow. Thus, this technical solution, by providing a bend 28 folding back towards the pressure surface 23 on the rear side of the outer edge of the blade, can guide the airflow overflowing from the pressure surface, thereby reducing undercurrent, improving the efficiency of the impeller and fan, and eliminating noise caused by airflow turbulence. Furthermore, the bend 28 enhances the structural strength of the blade, effectively resisting airflow impact and reducing deformation. The width of the bend 28 gradually increases from front to back, further optimizing airflow and reducing noise. This design not only improves blade durability but also enhances the overall performance of the fan. Compared with existing technologies, this technical solution has significant advantages in improving blade strength and reducing noise.

[0040] Example 2:

[0041] This embodiment proposes an axial flow fan, including a motor and axial flow fan blades connected to the output end of the motor. The axial flow fan blades are the type described in Embodiment 1. This application solves the problem of excessive noise during the operation of axial flow fans by employing low-noise axial flow fan blades. The design of the low-noise axial flow fan blades effectively reduces friction and impact between the blades 2 and the air, thereby reducing noise. Compared with the prior art, the technical solution of this application significantly reduces the noise level while maintaining airflow and pressure, thus improving user comfort.

[0042] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A low-noise axial flow fan blade, comprising a central hub bracket (1) and a plurality of blades (2); the central hub bracket (1) includes a bushing (11) for connecting a rotating shaft, and the plurality of blades (2) are regularly connected to the central hub bracket (1) circumferentially; characterized in that: The blade (2) has a blade tip serration (22) on the outer end of the blade leading edge (21), and the blade tip serration (22) occupies 10% to 35% of the arc length of the blade leading edge (21).

2. The low-noise axial flow fan blade according to claim 1, characterized in that: The central hub bracket (1) is constructed as a metal hub bracket, and the bushing (11) is formed at the center of the central hub bracket (1); the central hub bracket (1) also includes a plurality of connecting arms (12) arranged circumferentially on the outside of the central hub bracket (1), and the blade (2) is connected to the outer end of the connecting arm (12).

3. A low-noise axial flow fan blade according to claim 2, characterized in that: The outer end of the connecting arm (12) is attached and fixed to the back pressure surface (23) of the blade (2).

4. A low-noise axial flow fan blade according to claim 2, characterized in that: Through holes are provided on the outer end of the connecting arm (12) and at the corresponding position on the blade (2). The through holes on the connecting arm (12) are aligned with the through holes on the blade (2) and then riveted together.

5. A low-noise axial flow fan blade according to claim 1, characterized in that: The trailing edge of the blade (2) is provided with serrations (24).

6. A low-noise axial flow fan blade according to claim 1, characterized in that: The leading edge (21) of the blade is constructed as an arc shape that gradually slopes backward from the front to the inner end, and the outer edge (20) of the blade is constructed as an arc shape with the opening facing inward.

7. A low-noise axial flow fan blade according to claim 1, characterized in that: The blade (2) has a recessed area (26) formed on the pressure surface (25) that sinks towards the opposite pressure surface (23). The recessed area (26) extends to the trailing edge (29) of the blade. The edge of the recessed area (26) forms a rib on the blade (2). The rib includes only a first rib (271) arranged along the edge of the leading edge (21) of the blade and a second rib (272) arranged along the outer edge (20) of the blade. The first rib (271) and the second rib (272) meet at the inner side of the outer end of the leading edge (21) of the blade.

8. A low-noise axial flow fan blade according to claim 7, characterized in that: The inner end of the first rib (271) extends to the inner end of the leading edge (21) of the blade or the inner edge of the blade (2), and the rear end of the second rib (272) extends to the middle rear side of the outer edge (20) of the blade or the rear edge (29) of the blade.

9. A low-noise axial flow fan blade according to claim 7, characterized in that: The second rib (272) has a bend (28) folded towards the back pressure surface (23) on the rear side of the middle of the outer edge of the blade. The rear end of the bend (28) extends to the rear edge (29) of the blade. The width of the bend (28) gradually increases from front to back.

10. An axial flow fan, comprising a motor and axial flow blades connected to the output end of the motor; characterized in that: The axial flow fan blade is a low-noise axial flow fan blade as described in any one of claims 1-8.

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