CN112283154A

CN112283154A - Axial flow fan blade and air conditioner

Info

Publication number: CN112283154A
Application number: CN202011320997.0A
Authority: CN
Inventors: 黄伟青; 邱俊亮; 陈政; 孙鹏坤; 赖孝成; 葛小婷
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2021-01-29

Abstract

The application provides an axial flow fan blade and an air conditioner. This axial fan blade includes wheel hub (1) and blade (2), a plurality of blade (2) are arranged along the circumference of wheel hub (1), along the radial of wheel hub (1), pressure surface (25) of blade (2) include positive curvature surface section (251) and negative curvature surface section (252), smooth transition between positive curvature surface section (251) and the negative curvature surface section (252), positive curvature surface section (251) set up in one side that blade (2) are close to outer fringe (23), negative curvature surface section (252) set up in one side that blade (2) are close to inner edge (24). According to the axial flow fan blade, balance among air quantity, power and noise can be achieved, and the use performance of the axial flow fan blade is improved.

Description

Axial flow fan blade and air conditioner

Technical Field

The application relates to the technical field of air conditioning, in particular to an axial flow fan blade and an air conditioner.

Background

With the continuous upgrade of the national energy-saving and emission-reducing policy, the air conditioner is taken as the power consumption 'main force' in life, higher requirements are put forward on the energy efficiency ratio of products, the performance of the air conditioner is continuously improved, and meanwhile, the reduction of power consumption is imperative. The outdoor unit of the air conditioner has a plurality of power consumption modules: motors, controllers, compressors, etc. Besides the power consumption of the motor is related to the manufacturing process, the aerodynamic performance of the fan blade is also a large influence factor. A fan blade with excellent design can reduce the required power of a motor and the noise value and improve the integral energy efficiency ratio of an air conditioner under the condition that the air volume performance is unchanged.

At present, the axial flow fan blades which are mature in the market and applied to the outdoor unit of the air conditioner generally need to have the following characteristics:

1. the air outlet volume is large enough to meet the heat dissipation requirement of the system;

2. the running power is low, the electric energy loss is reduced, and the motor load is reduced;

3. the noise is low, and the relevant noise legal regulations are met.

The relationship of mutual influence and mutual constraint exists among the three indexes of air volume, power and noise, such as: if the air quantity is large enough, the axial flow fan blade is required to do more work to provide power, and the power of the fan blade during operation is larger; meanwhile, the large air volume also means that the air flow is quicker and stronger, so that the wind noise is more obvious, and the running noise of the axial flow fan blade is larger. The prior art lacks an axial flow fan blade which can balance the relationship among the three and realize the operation with large air quantity, low power and low noise.

Disclosure of Invention

Therefore, the technical problem that this application will be solved lies in providing an axial fan blade and air conditioner, can realize the balance between amount of wind, power and the noise, improves the performance of axial fan blade.

In order to solve the problem, the application provides an axial flow fan blade, including wheel hub and blade, a plurality of blades are arranged along wheel hub's circumference, and along wheel hub's radial, the pressure surface of blade includes positive curvature face section and negative curvature face section, and smooth transition between positive curvature face section and the negative curvature face section, positive curvature face section setting is close to one side of outer fringe at the blade, and negative curvature face section setting is close to one side of inner edge at the blade.

Preferably, the blade further comprises a front edge and a rear edge, the intersection point of the outer edge and the front edge is a blade tip, the intersection point of the outer edge and the rear edge is a blade tail, the blade is surrounded by the front edge, the inner edge, the rear edge and the outer edge, and the inner edge is located at the junction position of the blade and the hub; and/or the area of the negative curvature surface segment is greater than the area of the positive curvature surface segment.

Preferably, the maximum width of the positive curvature surface section in the radial direction on a plane perpendicular to the central axis of the hub is in the range of 10mm to 30 mm.

Preferably, on a cross section passing through the central axis of the hub and intersecting the outer edge and the inner edge of the blade, the length of a connecting line ab between the intersection point b of the inner edge and the cross section and the highest point a of the positive curvature surface section is L, the distance between the lowest point c of the negative curvature surface section on the cross section and the connecting line ab is H, K is H/L, and K is greater than or equal to 0.05 and less than or equal to 0.15.

Preferably, the value of K increases in a direction toward the trailing edge; and/or, the value of H increases in a direction toward the trailing edge.

Preferably, H.gtoreq.5 mm.

Preferably, a tangent to any point on the outer edge forms an angle α with a plane perpendicular to the central axis of the hub, α increasing in a direction from the tip to the tail of the blade.

Preferably, α is smallest at the tip and largest at the tail.

Preferably, the value of alpha at the leaf tip is alpha 1, and alpha 1 is more than 0 degrees and less than or equal to 10 degrees; and/or the value of alpha at the leaf tail is alpha 2, and alpha 2 is more than or equal to 60 degrees and less than or equal to 70 degrees.

Preferably, the root setting angle of the blade is 42 ± 5 °.

Preferably, the chord lines at the two ends of the outer edge of the blade are outer edge chord lines, the chord lines at the two ends of the inner edge of the blade are inner edge chord lines, and the chord length of the outer edge chord lines is more than 3 times of the chord length of the inner edge chord lines.

Preferably, the trailing edge is provided with a serrated section provided with a serrated notch.

Preferably, the saw-tooth gaps have the same depth, the number of the saw-tooth gaps is more than 5, the depth is more than 3mm, the tooth pitch is more than 5mm, and the ratio of the length of the saw-tooth section to the length of the rear edge is more than 1/2.

Preferably, the trailing edge of the blade is recessed to the side of the leading edge.

Preferably, a plurality of pits are distributed on the suction surface of each blade, and the number of the pits on a single blade is more than 30.

Preferably, the dimples are spherical, cylindrical, pyramidal or rectangular.

According to another aspect of the present application, an air conditioner is provided, which includes an axial flow fan blade, where the axial flow fan blade is the above axial flow fan blade.

The application provides an axial fan blade, including wheel hub and blade, a plurality of blades are arranged along wheel hub's circumference, and along wheel hub's radial, the pressure surface of blade includes positive curvature face section and negative curvature face section, and smooth transition between positive curvature face section and the negative curvature face section, positive curvature face section sets up the one side that is close to the outer fringe at the blade, and negative curvature face section sets up the one side that is close to the inner edge at the blade. This axial fan blade adopts the negative curvature face section at radial inboard, can produce and gather the wind effect, transport the low energy fluid of blade both sides to the blade middle part, increase and gather the wind effect, reduce the operating power, increase the amount of wind, adopt the positive curvature face section in radial outside, can reduce the vortex that blade outer fringe department produced, thereby reduce axial fan blade running noise, adopt the structure that positive curvature face section and negative curvature face section combine, can make the blade structure accord with fluid characteristic more, realize the amount of wind, the balance between power and the noise, when improving the amount of wind, effectively improve axial fan blade's work efficiency and performance.

Drawings

Fig. 1 is a perspective structural view of an axial-flow fan blade according to an embodiment of the present application;

fig. 2 is a schematic cross-sectional structure view of an axial-flow fan blade according to an embodiment of the present application;

FIG. 3 is a schematic view of an angular structure of an outer edge of an axial-flow fan blade at a blade tip according to an embodiment of the present application;

FIG. 4 is a schematic view of an angle structure of an outer edge of an axial-flow fan blade at a blade tail according to an embodiment of the present application;

fig. 5 is a schematic structural view of a mounting angle of an axial-flow fan blade according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of an axial-flow fan blade according to an embodiment of the present application;

fig. 7 is a surface static pressure distribution diagram obtained by performing fluid CFD simulation on a first fan blade in the prior art;

fig. 8 is a surface static pressure distribution diagram obtained by performing fluid CFD simulation on a second fan blade in the prior art;

fig. 9 is a surface static pressure distribution diagram obtained by fluid CFD simulation of a third fan blade in the prior art;

fig. 10 is a surface static pressure distribution diagram obtained by performing fluid CFD simulation on a first fan blade in the prior art;

fig. 11 is a comparison graph of actually measured air volume, power and efficiency of three axial flow fan blades of the prior art and the axial flow fan blade according to the embodiment of the present application;

FIG. 12 is a fluid line graph at the leading edge for two known blades and a blade of an embodiment of the present application;

fig. 13 is a graph of a stagger angle-air quantity curve and a stagger angle-power curve of a blade according to an embodiment of the present application.

The reference numerals are represented as:

1. a hub; 2. a blade; 21. a leading edge; 22. a trailing edge; 221. a saw-tooth notch; 23. an outer edge; 231. a blade tip; 232. the leaf tail; 24. an inner edge; 241. an inner chord line; 25. a pressure surface; 251. a positive curvature surface segment; 252. a negative curvature surface segment; 26. a suction surface; 261. and (4) pits.

Detailed Description

Referring to fig. 1 to 13 in combination, according to an embodiment of the present application, the axial flow fan blade includes a hub 1 and a plurality of blades 2, the plurality of blades 2 are installed on the periphery of the hub 1 and are arranged along the circumferential direction of the hub 1, along the radial direction of the hub 1, a pressure surface 25 of each blade 2 includes a positive curvature surface section 251 and a negative curvature surface section 252, the positive curvature surface section 251 and the negative curvature surface section 252 are in smooth transition, the positive curvature surface section 251 is disposed on one side of each blade 2 close to the outer edge 23, and the negative curvature surface section 252 is disposed on one side of each blade 2 close to the inner edge 24.

The blade 2 further comprises a front edge 21 and a rear edge 22, the intersection point of the outer edge 23 and the front edge 21 is a blade tip 231, the intersection point of the outer edge 23 and the rear edge 22 is a blade tail 232, the blade 2 is surrounded by the front edge 21, the inner edge 24, the rear edge 22 and the outer edge 23, and the inner edge 24 is located at the boundary position of the blade 2 and the hub 1.

This axial fan blade adopts negative curvature face section 252 at radial inboard, can produce and gather the wind effect, transport the low energy fluid of blade 2 both sides to the middle part of blade 2, increase and gather the wind effect, reduce the operating power, increase the amount of wind, adopt positive curvature face section 251 in radial outside, can reduce the vortex that blade 2 outer fringe department produced, thereby reduce axial fan blade running noise, adopt the structure that positive curvature face section 251 and negative curvature face section 252 combined together, can make the blade structure accord with the fluid characteristic more, realize the amount of wind, the balance between power and the noise, when improving the amount of wind, effectively improve axial fan blade's work efficiency and performance.

For a single blade, in each embodiment of the present application, the edge portion on the windward side is a leading edge 21, the edge portion on the leeward side is a trailing edge 22, an orthographic projection of the central axis of the hub 1 in a plane perpendicular to the central axis is a central point, the central point is a circle center, a circle is drawn through a certain point, and the circumferential direction is the circumferential direction; the direction of the line connecting the point and the central point is the radial direction.

The blade 2 comprises a pressure surface 25 and a suction surface 26 which are opposite, the pressure surface 25 faces the air outlet side of the axial flow fan blade, and the suction surface 26 faces the air inlet side of the axial flow fan blade. In the working process of the fan blade, the pressure surface 25 mainly bears positive pressure, and the suction surface 26 mainly bears negative pressure.

The positive curvature surface segment 251 has a positive radial curvature, i.e., is radially "convex", the negative curvature surface segment 252 has a negative radial curvature, i.e., is radially "concave", and the area of the negative curvature surface segment 252 is greater than the area of the positive curvature surface segment 251.

In one embodiment, the maximum width of the positive curvature surface segment 251 in the radial direction on a plane perpendicular to the central axis of the hub 1 is in a range of 10mm to 30mm, so that the width of the positive curvature surface segment 251 can be limited, and the occupied proportion of the positive curvature surface segment 251 on the pressure surface of the blade 2 can be further limited, so that the area of the positive curvature surface segment 251 is prevented from being too large to extrude the area of the negative curvature surface segment 252, and a large air volume can be provided for the axial flow fan blade.

On a cross section passing through the central axis of the hub 1 and intersecting the outer edge 23 and the inner edge 24 of the blade 2, the length of a connecting line ab between the intersection point b of the inner edge 24 and the cross section and the highest point a of the positive curvature surface section 251 is L, the distance between the lowest point c of the negative curvature surface section 252 on the cross section and the connecting line ab is H, K is H/L, and K is more than or equal to 0.05 and less than or equal to 0.15. When the K value is too small, the air flow is not concentrated, and the air outlet efficiency is reduced. And too big can lead to the air current angle to change, forms turbulent air current, is unfavorable for the promotion of the amount of wind, and under the same diameter, because the arc length increases, fan blade weight greatly increased has increased the consumption of motor moreover, consequently can lead to efficiency reduction. In a large number of CFD simulation and experiments, the optimal solution of air quantity, power and noise is sought, namely K is more than or equal to 0.05 and less than or equal to 0.15.

The value of K increases in a direction towards the trailing edge 22 of the blade 2.

The H value increases in a direction towards the trailing edge 22 of the blade 2.

In one embodiment H is 5mm or more, i.e. the depth of the depression of the pressure surface 25 of the blade 2 in the above-mentioned cross-section is 5mm or more.

The H value determines the depth of the depression of the pressure surface 25 of the blade 2 relative to the air outlet side, and the K value determines the radial leaf shape and the radial depression curvature of the blade 2. The L value of the same blade 2 is approximately unchanged, so the H value at different positions of the same fan blade is larger, and the K value is larger.

In the present application, the K value increases with the section closer to the trailing edge of the blade 2, which configuration facilitates a C-shaped pressure distribution at the pressure side 25 of the blade 2. When the blade 2 does work, the airflow enters from the front edge 21, the wind gathering effect is enhanced along with the increase of the radial sunken degree, the low-energy fluids on two sides of the blade 2 are transported to the middle part of the blade 2 and taken away by the main flow fluid, the radial flow of the airflow is reduced, the flow loss is reduced, the work efficiency is improved, and the air volume is effectively increased under the same power condition.

Referring to fig. 7 to 10, the surface static pressure distribution diagrams obtained by performing fluid CFD simulation on the blades with different K values in the prior art and the blades of the present application are shown.

According to the static pressure distribution on the surface of the blade, the pressure centers of the pressure surface and the suction surface of the blade 1 are concentrated, the peak values are both positioned at about 70% of the outer edge (from the blade tip to the trailing edge), and the positive pressure area of the pressure surface accounts for about 75% of the area of the whole pressure surface.

The peak values of the fan blades 2 are also positioned at about 70% of the outer edge (from the blade tip to the trailing edge), and the positive pressure area of the pressure surface accounts for about 75% of the whole area of the pressure surface.

The pressure center of the fan blade 3 is not obvious, and the positive pressure area of the pressure surface accounts for about 60 percent of the whole area of the pressure surface.

The pressure centers of the pressure surface and the suction surface of the axial flow fan blade are most concentrated, and the peak value is positioned at about 70% of the position from the blade tip to the rear edge; the positive pressure area of the pressure surface accounts for about 80% of the area of the whole pressure surface, which shows that the effective work done by the blades of the axial flow fan blade is more, and the area proportion occupied by the area in the same pressure range is higher, which shows that the working capacity of the axial flow fan blade is stronger. The CFD simulation results approximately match the actual measurement results.

As shown in fig. 11, it can be seen that the blade-shaped work-done efficiency of the axial-flow fan blade designed in the embodiment of the present application is the highest, that is, the air volume is higher under the same power, for the comparison graph of the measured values of the air volume, power and efficiency of the 4 axial-flow fan blades.

An included angle α is formed between a tangent line of any point on the outer edge 23 and a plane perpendicular to the central axis of the hub 1, and α increases in a direction from the blade tip 231 to the blade tail 232.

α is smallest at the tip 231 and largest at the tail 232.

The value of alpha at the blade tip 231 is alpha 1, and alpha 1 is more than 0 degrees and less than or equal to 10 degrees.

The value of alpha at the position of the leaf tail 232 is alpha 2, and the alpha 2 is more than or equal to 60 degrees and less than or equal to 70 degrees.

In the embodiment of the present application, the small inclination angle at the blade tip 231 is to make the airflow smoothly enter the blade working area according to a certain airflow angle, reduce the climbing effect of the airflow at the inlet, and reduce the inlet impact loss as much as possible; the alpha is gradually increased in order to gradually enhance the working effect of the blades 2 on the airflow, increase the working efficiency and improve the air volume.

As shown in fig. 12, it can be found that a fluid CFD simulation diagram of the blades of the two known axial-flow fan blades and the blades of the axial-flow fan blade according to the embodiment of the present disclosure shows that a fluid "climbing" phenomenon at the front edge of the blades of the known axial-flow fan blade is serious, and the "climbing" phenomenon will cause an increase in a negative pressure area in an area near the front edge air inlet of the pressure surface of the fan blade, and the negative pressure area will perform negative work on the overall performance of the fan blade, and thus, the consumption of the air volume is greater, and the power consumption is also higher. According to the axial-flow fan blade, the inclination angle and the concavity of the front edge of the blade 2 can effectively reduce the negative effect, and the inlet impact loss is reduced.

The line connecting the leading edge 21 and the trailing edge 22 is a chord line, the chord line forms a mounting angle beta with a plane perpendicular to the central axis of the hub, and the root mounting angle beta of the blade 2 is 42 +/-5 degrees.

When the installation angle is too small, the working capacity of the blades 2 on the airflow is greatly reduced, and the efficiency is low. When the setting angle is too large, the suction surface 26 of the blade 2 is often separated by the flow of air, thereby forming a separation zone. Because the gas energy in the separation area is lower, the airfoil resistance of the cross section of the axial flow fan blade is increased, the rotating torque of the blade 2 is increased, the input power is improved, and the air volume of the axial flow fan blade is reduced; and the fluid in the separation area forms a large amount of vortexes, so that high vortex noise is easily generated.

Referring to fig. 13, a graph of the relationship between the installation angle, the air volume and the power obtained by actual measurement after the installation angle of the blade is adjusted is shown. As can be seen from the figure, in a certain range, the air quantity and the power of the fan are increased along with the increase of the installation angle, and the power and the installation angle are in a linear relation. When the installation angle exceeds 50 degrees, the air quantity and the power drop suddenly because the fan enters a stall state. In the air quantity lifting stage, along with the increase of the installation angle, the air quantity increasing amplitude is gradually reduced.

Combining the whole blade-shaped depression degree and the outer edge inclination angle, and integrating the relation between the air volume and the power, in order to seek the maximum work efficiency, the blade root installation angle of the axial flow fan blade in the embodiment of the application is set to be beta 42 +/-5 degrees.

The chord lines at two ends of the outer edge 23 of the blade 2 are outer edge chord lines, the chord lines at two ends of the inner edge 24 of the blade 2 are inner edge chord lines 241, and the chord length of the outer edge chord lines is more than 3 times of the chord length of the inner edge chord lines 241, so that the characteristic of high air flow speed at the outer circumference is fully utilized, and the working capacity of the blade is improved.

In one embodiment, the trailing edge 22 is provided with a serrated section provided with a serrated notch 221.

The saw-tooth notches 221 have the same depth, the number of the saw-tooth notches 221 is more than 5, the depth is more than 3mm, the tooth pitch is more than 5mm, and the proportion of the length of the saw-tooth section in the length of the rear edge 22 is more than 1/2.

The shape of the indentations 221 may be V-shaped, U-shaped, semi-circular, square, or the like.

The trailing edge 22 of the blade 2 is recessed to the side of the leading edge 21.

The sawtooth-shaped notch 221 arranged on the rear edge can effectively reduce the noise value, according to CFD simulation analysis, the tail edge flowing area has rotating vortex, which is mainly caused by the fact that the speed and pressure difference between the pressure surface 25 and the suction surface 26 at the rear edge 22 is large to form pressure difference, and vortex noise is related to the vortex at the rear edge 22.

The maximum peak value of the vortex amount of the rear edge with the sawtooth-shaped notch 221 is arranged at the gathering position of the sawtooth tooth tips, so that the distribution area of the peak value of the vortex amount is effectively reduced, and the vortex noise is reduced. The noise value test performed under the same condition shows that, compared with the known axial flow fan blade, the noise of the fan blade with the sawtooth-shaped notch 221 on the rear edge of the embodiment is reduced by about 2 dB.

Meanwhile, the zigzag notch 221 can also reduce the overall weight of the fan blade, reduce the operating power and improve the acting efficiency of the fan blade under the condition of less influence on the air volume.

A plurality of pits 261 are distributed on the suction surface 26 of the blade 2, and the number of the pits 261 on a single blade 2 is more than 30. The depth of the concave pit is 0.5-2 mm, and the concave pit is adjusted correspondingly according to the size and the thickness of the blade 2.

The pit 261 has a spherical shape, a cylindrical shape, a pyramidal shape, or a rectangular parallelepiped shape. The columnar shape may be a cylindrical shape or a prismatic shape.

Because the during operation, the back (being the suction side) of axial fan blade can inevitably produce the vortex, and then produce the vortex noise, there is negative effects to operation noise value and tone quality, in this application, set up many sizes interval at the blade suction side of axial fan blade and be more even pit 261, the CFD simulation result shows, pit 261 can disperse and slow down suction side surface pressure differential, the vortex effect on suction side surface has been weakened, the vortex noise has been reduced, the unevenness on surface also has the effect of absorbed noise simultaneously. Noise value tests carried out under the same conditions show that compared with a blade with a smooth suction surface, the honeycomb-shaped pits arranged on the suction surface can effectively reduce the noise by about 1 dB.

Meanwhile, the honeycomb-shaped pits are similar to the sawtooth-shaped gaps, the overall weight of the fan blade can be reduced, the operating power is reduced, and the acting efficiency of the fan blade is improved under the condition of less influence on the air volume.

According to the embodiment of the application, the air conditioner comprises the axial flow fan blade.

It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. The foregoing is only a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present application, and these modifications and variations should also be considered as the protection scope of the present application.

Claims

1. The axial flow fan blade is characterized by comprising a hub (1) and a plurality of blades (2), wherein the plurality of blades (2) are arranged along the circumferential direction of the hub (1), the radial direction of the hub (1) is arranged, a pressure surface (25) of each blade (2) comprises a positive curvature surface section (251) and a negative curvature surface section (252), the positive curvature surface sections (251) and the negative curvature surface sections (252) are in smooth transition, the positive curvature surface sections (251) are arranged on one sides of the blades (2) close to outer edges (23), and the negative curvature surface sections (252) are arranged on one sides of the blades (2) close to inner edges (24).

2. The axial-flow fan blade according to claim 1, wherein the blade (2) further comprises a leading edge (21) and a trailing edge (22), the intersection point of the outer edge (23) and the leading edge (21) is a blade tip (231), the intersection point of the outer edge (23) and the trailing edge (22) is a blade tail (232), the blade (2) is enclosed by the leading edge (21), the inner edge (24), the trailing edge (22) and the outer edge (23), and the inner edge (24) is located at the intersection position of the blade (2) and the hub (1); and/or the area of the negative curvature surface segment (252) is larger than the area of the positive curvature surface segment (251).

3. The axial-flow fan blade according to claim 1, characterized in that the maximum width of the positive curvature surface section (251) in the radial direction on a plane perpendicular to the central axis of the hub (1) is in the range of 10mm to 30 mm.

4. The axial-flow fan blade according to claim 2, characterized in that on a cross section passing through the central axis of the hub (1) and intersecting the outer edge (23) and the inner edge (24) of the blade (2), a connecting line ab between an intersection point b of the inner edge (24) and the cross section and the highest point a of the positive curvature surface section (251) has a length L, and a distance H between the lowest point c of the negative curvature surface section (252) on the cross section and the connecting line ab is, wherein K is H/L, and K is 0.05 ≦ K ≦ 0.15.

5. The axial-flow blade according to claim 4, characterized in that along the direction close to said trailing edge (22), the value of K increases; and/or the value of H increases in a direction towards the trailing edge (22).

6. The axial-flow fan blade according to claim 5, wherein H is greater than or equal to 5 mm.

7. The axial-flow fan blade according to claim 2, wherein an included angle α is formed between a tangent of any point on the outer edge (23) and a plane perpendicular to the central axis of the hub (1), and the α increases progressively along a direction from the blade tip (231) to the blade tail (232).

8. The axial-flow fan blade according to claim 7, wherein the value of α at the blade tip (231) is α 1, 0 ° < α 1 ≦ 10 °; and/or the value of alpha at the position of the leaf tail (232) is alpha 2, and alpha 2 is more than or equal to 60 degrees and less than or equal to 70 degrees.

9. The axial-flow fan blade according to claim 1, characterized in that the root installation angle of the blade (2) is 42 ± 5 °.

10. The axial-flow fan blade according to claim 1, wherein chord lines at both ends of an outer edge (23) of the blade (2) are outer edge chord lines, chord lines at both ends of an inner edge (24) of the blade (2) are inner edge chord lines (241), and the chord length of the outer edge chord lines is more than 3 times of the chord length of the inner edge chord lines (241).

11. The axial fan blade according to claim 2, wherein the trailing edge (22) is provided with a serrated section provided with a serrated notch (221).

12. The axial-flow fan blade according to claim 11, wherein the saw-tooth notches (221) have the same depth, the number of the saw-tooth notches (221) is more than 5, the depth is more than 3mm, the pitch is more than 5mm, and the length of the saw-tooth segment accounts for more than 1/2 of the length of the trailing edge (22).

13. The axial-flow blade according to claim 2, characterized in that the trailing edge (22) of the blade (2) is recessed to the side of the leading edge (21).

14. The axial-flow fan blade according to claim 1, wherein a plurality of pits (261) are distributed on the suction surface (26) of the blade (2), and the number of the pits (261) on a single blade (2) is more than 30.

15. The axial-flow fan blade according to claim 14, wherein said dimples (261) are spherical, cylindrical, pyramidal or rectangular.

16. An air conditioner, comprising an axial flow fan blade, characterized in that the axial flow fan blade is the axial flow fan blade of any one of claims 1 to 15.