A blade, an axial-flow fan blade and a fan

Abstract

The present invention relates to the technical field of fans, and particularly relates to a blade, an axial-flow fan blade and a fan. The blade includes a pressure surface, a suction surface, a blade root, a blade tip, a leading edge portion and a trailing edge portion. The cylindrical surface where the blade root is located is defined as the blade root reference surface, the cylindrical surface where the blade tip is located is defined as the blade tip reference surface, the cylindrical surface located between the blade root reference surface and the blade tip reference surface is the 1 / 2 reference surface, and the cylindrical surface located between the blade tip reference surface and the 1 / 2 reference surface is the 3 / 4 reference surface; the maximum distance between the leading edge portion and the trailing edge portion at the blade root reference surface is l1, the maximum distance between the leading edge portion and the trailing edge portion at the 1 / 2 reference surface is l2, the maximum distance between the leading edge portion and the trailing edge portion at the 3 / 4 reference surface is l3, and the maximum distance between the leading edge portion and the trailing edge portion at the blade tip reference surface is l4, and l1 < l2 < l3 < l4. It can effectively increase the outlet wind speed, make the aerodynamic performance of the blade match the motor, and ensure the air volume of the fan made of the blade.

Description

Technical Field

[0001] The present invention relates to the technical field of fans, and particularly relates to a blade, an axial-flow fan blade and a fan. Background Art

[0002] As the core component of an electric fan, the axial-flow fan blade plays a decisive role in the air volume and noise of the whole machine. When designing the blade profile of a common axial-flow fan blade, a continuous smooth surface shape is mostly adopted. As shown in Figures 1 to 3 , the section lines of each section are smoothly transitioned and have a small camber. This kind of blade profile design is fast, the airflow directionality is forward, and the air outlet is divergent.

[0003] During operation, the motor drives the fan blade to rotate at a high speed to drive the airflow to flow forward. In order to make the fan have high energy efficiency, that is, the ratio of the work done by the fan to the power consumed by the motor is the largest, it is very crucial to reasonably match the fan blade and the motor load. If the aerodynamic performance of the fan blade does not match the motor, the actual working point of the motor will be in an overload operation state, the main-phase current of the motor will increase, and the secondary-phase current of the motor will increase during light-load operation. When the main and secondary-phase currents of the motor increase, the copper loss increases and the temperature rise increases. In order to reduce the temperature rise of the motor, the motor cost will increase accordingly. Therefore, reasonably designing the fan blade to make the aerodynamic performance of the fan blade match the motor will enable the motor to operate efficiently and reduce the motor cost.

[0004] The applicant found in the research that the installation angle and bending degree of the section lines of each section of the fan blade are the key to determining the aerodynamic performance of the fan blade. Reasonably adjusting the section line of the fan blade can effectively increase the outlet air speed and ensure the air volume of the electric fan. Summary of the Invention

[0005] Therefore, the purpose of the present invention is to provide a blade, an axial-flow fan blade and a fan whose aerodynamic performance can match the motor.

[0006] A blade provided by the present invention includes a pressure surface, a suction surface, a blade root, a blade tip, a leading edge and a trailing edge. Define the cylindrical surface where the blade root is located as the blade root primitive surface, the cylindrical surface where the blade tip is located as the blade tip primitive surface, the cylindrical surface located between the blade root primitive surface and the blade tip primitive surface as the 1 / 2 primitive surface, and the cylindrical surface located between the blade tip primitive surface and the 1 / 2 primitive surface as the 3 / 4 primitive surface;

[0007] The maximum distance between the leading edge and the trailing edge at the blade root primitive surface is l1, the maximum distance between the leading edge and the trailing edge at the 1 / 2 primitive surface is l2, the maximum distance between the leading edge and the trailing edge at the 3 / 4 primitive surface is l3, and the maximum distance between the leading edge and the trailing edge at the blade tip primitive surface is l4, where l1 < l2 < l3 < l4.

[0008] 35mm ≤ l1 ≤ 45mm, 85mm ≤ l4 ≤ 95mm.

[0009] Above the 1 / 2 elementary plane, a concave portion is provided on the pressure surface so that the suction surface includes a convex surface.

[0010] In the region between the center line of the blade and the trailing edge portion, the degree of depression of the concave portion is the largest.

[0011] At the blade root elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the blade root elementary plane is α1; at the 1 / 2 elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the 1 / 2 elementary plane is α2; at the 3 / 4 elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the 3 / 4 elementary plane is α3; at the blade tip elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the blade tip elementary plane is α4; α1 > α2 > α3 > α4.

[0012] 35° ≤ α1 ≤ 45°, 5° ≤ α4 ≤ 15°.

[0013] At the blade root elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f1; at the 1 / 2 elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f2; at the 3 / 4 elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f3; at the blade tip elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f4, f3 > f1, f3 > f2, f3 > f4.

[0014] f1 = f4, f2 = 1.5f1, f3 = 2f1.

[0015] The blade is swept back.

[0016] The swept-back angle of the blade is θ, 8° ≤ θ ≤ 15°.

[0017] Above the 3 / 4 elementary plane, the suction surface has a concave portion so that the pressure surface has a convex surface.

[0018] At the top end of the leading edge portion of the blade, there is a blade tip angle, and the radius of the blade tip angle is R, 3 mm ≤ R ≤ 6 mm.

[0019] The present invention also provides an axial flow fan blade, including a hub and a plurality of the above-mentioned blades uniformly distributed along the circumferential direction of the hub.

[0020] The diameter of the hub is d, and the outer diameter of the axial flow fan blade is D, 0.25 ≤ d / D ≤ 0.3.

[0021] There are 7 blades.

[0022] The present invention also provides a fan, including the axial-flow fan blade described above.

[0023] The technical solution of the present invention has the following advantages:

[0024] 1. For the blade provided by the present invention, by making l1 < l2 < l3 < l4, the outlet wind speed can be effectively increased, the aerodynamic performance of the blade can be matched with the motor, and the air volume of the fan made of the blade can be guaranteed.

[0025] 2. For the blade provided by the present invention, above the 1 / 2 elementary plane, a concave portion is provided on the pressure surface so that the suction surface includes a convex surface, which can effectively increase the static pressure of the pressure surface of the blade, improve the work capacity of the blade, and further increase the outlet wind speed and the efficiency of the fan blade.

[0026] 3. For the blade provided by the present invention, in the region between the center line of the blade and the trailing edge portion, the depression degree of the concave portion is the largest, which can increase the work capacity of the middle and rear parts of the blade and further improve the aerodynamic performance.

[0027] 4. For the blade provided by the present invention, at the root elementary plane of the blade, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the root elementary plane of the blade is α1; at the 1 / 2 elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the 1 / 2 elementary plane of the blade is α2; at the 3 / 4 elementary plane, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the 3 / 4 elementary plane of the blade is α3; at the tip elementary plane of the blade, the included angle between the connecting line of the leading edge portion and the trailing edge portion and the tangent line of the leading edge portion at the tip elementary plane of the blade is α4; α1 > α2 > α3 > α4. The installation angle at the blade root is large, which can effectively ensure the strength of the blade without a large increase in load.

[0028] 5. For the blade provided by the present invention, at the root elementary plane of the blade, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f1; at the 1 / 2 elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f2; at the 3 / 4 elementary plane, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f3; at the tip elementary plane of the blade, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion and the trailing edge portion is f4, f3 > f1, f3 > f2, f3 > f4, which can effectively increase the static pressure of the pressure surface of the blade, improve the work capacity of the blade, and further increase the outlet wind speed and the efficiency of the fan blade.

[0029] 6. The blade provided by the present invention is swept-back, that is, the blade is inclined and bent along the oncoming flow direction. This can not only make the wind blade generate circumferential and axial forces, but also generate a radial force. The radial force can effectively change the thickness of the airflow boundary layer, improve the airflow efficiency, and reduce power and noise.

[0030] 7. For the blade provided by the present invention, above the 3 / 4 elementary plane, the suction surface has a concave portion, so that the pressure surface has a convex surface. Such a setting can delay the separation of the airflow when the airflow is about to flow out of the wind blade, effectively reduce the separation of the tail airflow, improve the flow efficiency, and improve the noise.

[0031] 8. For the blade provided by the present invention, the tip of the leading edge of the blade has a leaf tip angle, and the radius of the leaf tip angle is R, where 3 mm ≤ R ≤ 6 mm. The design of the leaf tip angle can reduce the generation of eddy currents and separated vortices at the leading edge, and reduce the aerodynamic noise.

[0032] 9. The axial flow wind blade provided by the present invention includes a hub and a plurality of the above-mentioned blades evenly distributed circumferentially along the hub. This axial flow wind blade can effectively increase the outlet wind speed, make the aerodynamic performance of the wind blade match the motor, and ensure the air volume of the fan.

[0033] 10. For the axial flow wind blade provided by the present invention, the diameter of the hub is d, and the outer diameter of the axial flow wind blade is D, where 0.25 ≤ d / D ≤ 0.3, which can reasonably control the airflow separation and airflow pressure. Description of the Drawings

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0035] Figure 1 is a schematic diagram of an axial flow wind blade in the prior art;

[0036] Figure 2 is Figure 1 a cross-sectional view at the root of the axial flow wind blade shown;

[0037] Figure 3 is Figure 1 a cross-sectional view at the tip of the axial flow wind blade shown;

[0038] Figure 4 is a front view of the axial flow wind blade provided in the embodiment of the present invention;

[0039] Figure 5 is Figure 4Partial structural schematic diagram of the axial flow fan blade;

[0040] Figure 6 Structural schematic diagram of the axial flow fan blade provided in the embodiment of the present invention;

[0041] Figure 7 is Figure 6 Cross-sectional view of the blade of the axial flow fan blade at the blade root elementary plane;

[0042] Figure 8 is Figure 6 Cross-sectional view of the blade of the axial flow fan blade at the 1 / 2 elementary plane;

[0043] Figure 9 is Figure 6 Cross-sectional view of the blade of the axial flow fan blade at the 3 / 4 elementary plane;

[0044] Figure 10 is Figure 6 Cross-sectional view of the blade of the axial flow fan blade at the blade tip elementary plane;

[0045] Figure 11 is Figure 6 Side view of the axial flow fan blade.

[0046] Explanation of reference numerals:

[0047] 1 - Hub; 2 - Blade; 21 - Leading edge part; 22 - Trailing edge part; 23 - Blade root part; 24 - Blade tip part; 25 - Pressure surface; 26 - Suction surface; 31 - Blade root elementary plane; 32 - 1 / 2 elementary plane; 33 - 3 / 4 elementary plane; 34 - Blade tip elementary plane. Detailed implementation manners

[0048] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0050] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] Embodiment 1

[0053] This embodiment provides a blade, which can be applied to an axial-flow fan blade. In one embodiment, as Figures 4 to 11 shown, the blade 2 includes a pressure surface, a suction surface 26, a blade root 23, a blade tip 24, a leading edge 21, and a trailing edge 22. Define the cylindrical surface where the blade root 23 is located as the blade root elementary surface 31, the cylindrical surface where the blade tip 24 is located as the blade tip elementary surface 34, the cylindrical surface located between the blade root elementary surface 31 and the blade tip elementary surface 34 as the 1 / 2 elementary surface 32, and the cylindrical surface located between the blade tip elementary surface 34 and the 1 / 2 elementary surface 32 as the 3 / 4 elementary surface 33.

[0054] The maximum distance between the leading edge 21 and the trailing edge 22 at the blade root elementary surface 31 is l1, the maximum distance between the leading edge 21 and the trailing edge 22 at the 1 / 2 elementary surface 32 is l2, the maximum distance between the leading edge 21 and the trailing edge 22 at the 3 / 4 elementary surface 33 is l3, and the maximum distance between the leading edge 21 and the trailing edge 22 at the blade tip elementary surface 34 is l4, where l1 < l2 < l3 < l4.

[0055] For the blade provided in this embodiment, by making l1 < l2 < l3 < l4, the outlet wind speed can be effectively increased, so that the aerodynamic performance of the blade 2 matches the motor, and the air volume of the fan made of the blade 2 is ensured.

[0056] In one embodiment, 35 mm ≤ l1 ≤ 45 mm and 85 mm ≤ l4 ≤ 95 mm.

[0057] Based on the above embodiment, in one embodiment, as Figure 6 shown, above the 1 / 2 elementary surface 32, a concave portion is provided on the pressure surface, so that the suction surface 26 includes a convex surface. It can effectively increase the static pressure of the pressure surface of the blade 2, improve the work capacity of the blade 2, and further increase the outlet wind speed and the efficiency of the fan blade.

[0058] On the basis of the above-described embodiments, in one embodiment, in the region between the center line of the blade 2 and the trailing edge portion 22, the degree of depression of the concave portion is the largest. Such a setting can increase the work capacity of the middle and rear portions of the blade 2 and further improve the aerodynamic performance.

[0059] On the basis of the above-described embodiments, in one embodiment, at the blade root elementary plane 31, the included angle between the connecting line of the leading edge portion 21 and the trailing edge portion 22 and the tangent line of the leading edge portion 21 at the blade root elementary plane 31 is α1; at the 1 / 2 elementary plane 32, the included angle between the connecting line of the leading edge portion 21 and the trailing edge portion 22 and the tangent line of the leading edge portion 21 at the 1 / 2 elementary plane 32 is α2; at the 3 / 4 elementary plane 33, the included angle between the connecting line of the leading edge portion 21 and the trailing edge portion 22 and the tangent line of the leading edge portion 21 at the 3 / 4 elementary plane 33 is α3; at the blade tip elementary plane 34, the included angle between the connecting line of the leading edge portion 21 and the trailing edge portion 22 and the tangent line of the leading edge portion 21 at the blade tip elementary plane 34 is α4; α1 > α2 > α3 > α4. The large installation angle of the blade root 23 can effectively ensure the strength of the blade 2 without a large increase in load.

[0060] In one embodiment, 35° ≤ α1 ≤ 45° and 5° ≤ α4 ≤ 15°.

[0061] As Figures 7 to 10 shown, at the blade root elementary plane 31, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion 21 and the trailing edge portion 22 is f1; at the 1 / 2 elementary plane 32, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion 21 and the trailing edge portion 22 is f2; at the 3 / 4 elementary plane 33, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion 21 and the trailing edge portion 22 is f3; at the blade tip elementary plane 34, the maximum distance between the inner side surface of the cross-section of the blade and the connecting line of the leading edge portion 21 and the trailing edge portion 22 is f4, and f3 > f1, f3 > f2, f3 > f4. Specifically, the inner side surface of the cross-section of the blade refers to the concave surface. At the blade root elementary plane 31 and the 1 / 2 elementary plane 32, the inner side surface of the cross-section of the blade refers to the pressure surface. At the 3 / 4 elementary plane 33 and the blade tip elementary plane 34, when the suction surface has a concave portion, the inner side surface of the cross-section of the blade refers to the suction surface. Such a design can effectively increase the static pressure of the pressure surface of the blade 2, improve the work capacity of the blade 2, and further increase the outlet wind speed and the efficiency of the wind blade.

[0062] In one embodiment, f1 = f4, f2 = 1.5f1, and f3 = 2f1.

[0063] On the basis of the above-described embodiments, in one embodiment, asFigure 11 As shown Figure 11 Figure 11 The direction of the arrow in Figure 11 is the oncoming flow direction. The blade 2 is swept back, that is, the blade 2 is inclined and bent along the oncoming flow direction. This can not only make the wind blade generate circumferential and axial forces, but also generate a radial force. The radial force can effectively change the thickness of the air flow boundary layer, improve the air flow efficiency, and reduce power and noise.

[0064] In one embodiment, the sweep angle of the blade 2 is θ, and 8° ≤ θ ≤ 15°.

[0065] On the basis of the above embodiment, in one embodiment, above the 3 / 4 elementary plane 33, the suction surface 26 has a concave portion so that the pressure surface has a convex surface.

[0066] As Figure 5 Figure 5 As shown, at the top of the leading edge portion 21 of the blade 2, there is a leaf tip angle. The radius of the leaf tip angle is R, and 3 mm ≤ R ≤ 6 mm. The design of the leaf tip angle can reduce the generation of eddy currents and separation vortices at the leading edge portion 21, and reduce aerodynamic noise.

[0067] Example 2

[0068] This example provides an axial flow wind blade, which includes a hub 1 and a plurality of blades provided in Example 1 uniformly distributed along the circumference of the hub 1.

[0069] It has been proven through tests that for the axial flow wind blade provided in this example, compared with the ordinary wind blade in the prior art, the wind speed at the center of the wind blade is significantly increased by 1 m / s, and the air volume is increased by 2 m 3 / min. At 1100 rpm, the motor power is reduced by 2 W, and the motor temperature rise is reduced, which is beneficial to cost control. This axial flow wind blade can match with the motor, improve energy efficiency, reduce the motor cost, and at the same time can effectively reduce the buzzing sound during high-speed rotation and improve the sound quality.

[0070] In one embodiment, the diameter of the hub 1 is d, and the outer diameter of the axial flow wind blade is D, and 0.25 ≤ d / D ≤ 0.3. This can reasonably control the air flow separation and air flow pressure.

[0071] In one embodiment, the number of the blades 2 is 7. In other alternative embodiments, the number of the blades 2 can be an odd number such as 3, 5, 9, etc.

[0072] Example 3

[0073] This example provides a fan, which includes the axial flow wind blade provided in the above example.

[0074] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A blade, characterized in that, It includes a pressure surface (25), a suction surface (26), a blade root (23), a blade tip (24), a leading edge part (21), and a trailing edge part (22). The cylindrical surface where the blade root (23) is located is defined as the blade root elementary surface (31), the cylindrical surface where the blade tip (24) is located is defined as the blade tip elementary surface (34), the cylindrical surface located between the blade root elementary surface (31) and the blade tip elementary surface (34) is the 1 / 2 elementary surface (32), and the cylindrical surface located between the blade tip elementary surface (34) and the 1 / 2 elementary surface (32) is the 3 / 4 elementary surface (33). At the blade root elementary surface (31), the maximum distance between the leading edge part (21) and the trailing edge part (22) is l1. At the 1 / 2 elementary surface (32), the maximum distance between the leading edge part (21) and the trailing edge part (22) is l2. At the 3 / 4 elementary surface (33), the maximum distance between the leading edge part (21) and the trailing edge part (22) is l3. At the blade tip elementary surface (34), the maximum distance between the leading edge part (21) and the trailing edge part (22) is l4, and l1 < l2 < l3 < l4. Above the 1 / 2 elementary surface (32), there is a concave part on the pressure surface (25) so that the suction surface (26) includes a convex surface. In the area between the center line of the blade and the trailing edge part (22), the degree of depression of the concave part is the largest. Above the 3 / 4 elementary surface (33), the suction surface (26) has a concave part so that the pressure surface (25) has a convex surface.

2. The vane according to claim 1, characterized in that, 35mm ≤ l1 ≤ 45mm, 85mm ≤ l4 ≤ 95mm.

3. The blade according to claim 1, characterized in that, At the blade root elementary surface (31), the included angle between the connection line of the leading edge part (21) and the trailing edge part (22) and the tangent line of the leading edge part (21) at the blade root elementary surface (31) is α1. At the 1 / 2 elementary surface (32), the included angle between the connection line of the leading edge part (21) and the trailing edge part (22) and the tangent line of the leading edge part (21) at the 1 / 2 elementary surface (32) is α2. At the 3 / 4 elementary surface (33), the included angle between the connection line of the leading edge part (21) and the trailing edge part (22) and the tangent line of the leading edge part (21) at the 3 / 4 elementary surface (33) is α3. At the blade tip elementary surface (34), the included angle between the connection line of the leading edge part (21) and the trailing edge part (22) and the tangent line of the leading edge part (21) at the blade tip elementary surface (34) is α4, and α1 > α2 > α3 > α4.

4. The blade according to claim 3, characterized in that, 35°≤α1≤45°，5°≤α4≤15°。 5. The blade according to claim 1, characterized in that, At the elemental plane of the blade root (31), the maximum distance between the inner side surface of the cross-section of the blade and the line connecting the leading edge portion (21) and the trailing edge portion (22) is f1; at the 1 / 2 elemental plane (32), the maximum distance between the inner side surface of the cross-section of the blade and the line connecting the leading edge portion (21) and the trailing edge portion (22) is f2; at the 3 / 4 elemental plane (33), the maximum distance between the inner side surface of the cross-section of the blade and the line connecting the leading edge portion (21) and the trailing edge portion (22) is f3; at the elemental plane of the blade tip (34), the maximum distance between the inner side surface of the cross-section of the blade and the line connecting the leading edge portion (21) and the trailing edge portion (22) is f4, and f3 > f1, f3 > f2, f3 > f4.

6. The blade according to claim 5, characterized in that, f1 = f4, f2 = 1.5f1, f3 = 2f1.

7. The blade according to claim 1, characterized in that, The blade is swept back.

8. The blade according to claim 7, wherein, The sweep angle of the blade is θ, where 8° ≤ θ ≤ 15°.

9. The blade according to claim 1, characterized in that, At the tip of the leading edge portion (21) of the blade, there is a blade tip angle, and the radius of the blade tip angle is R, where 3 mm ≤ R ≤ 6 mm.

10. An axial flow fan blade, characterized in that, It includes a hub (1) and a plurality of blades as described in any one of claims 1 - 9 evenly distributed circumferentially along the hub (1).

11. The axial flow fan blade according to claim 10, wherein, The diameter of the hub (1) is d, and the outer diameter of the axial flow fan blade is D, where 0.25 ≤ d / D ≤ 0.

3.

12. The axial flow fan blade according to claim 10, wherein, The number of the blades is 7.

13. A fan, characterized in that, It includes the axial flow fan blade as described in any one of claims 10 - 12.

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