CN221220906U - Blade, impeller and air conditioner outdoor unit - Google Patents

Abstract

The application provides a blade, an impeller and an air conditioner external unit, wherein the blade comprises a blade root for being connected with a hub, a blade top opposite to the blade root, and a front edge and a tail edge which are positioned at two sides of the blade root and the blade top, wherein the front edge faces towards the windward side, the tail edge is opposite to the windward side, and smooth transition is realized between the front edge and the tail edge; the projection of the front edge is in a curve shape with two inflection points, the front edge forms a concave part from the inflection point close to the root of the blade, the front edge forms an upper convex part from the inflection point close to the top of the blade, and the upper convex part is connected with the concave part; the upper convex portion is convex compared with the trailing edge in the thickness direction of the blade, and the lower concave portion is concave compared with the trailing edge in the thickness direction of the blade. The blade structure can inhibit leakage vortex of the blade top clearance, and can increase the working flow of the impeller and reduce noise when being arranged on the impeller.

Description

Blade, impeller and air conditioner outdoor unit

Technical Field

The application relates to the field of impellers, in particular to a blade, an impeller and an air conditioner external unit.

Background

The blade is the most critical part of the fan impeller and is responsible for doing work on the gas, increasing the gas pressure and discharging the gas. The design of the shape, number, length and other parameters of the blades has an important influence on the performance of the fan. The existing blade mostly adopts a smooth blade design without inflection points. Because of the ubiquitous existence of the blade tip clearance, when fluid flows through the impeller designed by the inflection point-free smooth blade to do work, a part of fluid passes through the blade tip clearance under the action of pressure difference between a pressure surface and a suction surface, so that blade tip leakage vortex is generated, and the blade tip leakage vortex can reduce the mechanical performance of the impeller to cause loss and noise.

Disclosure of utility model

The application provides a blade, an impeller and an air conditioner external unit, which can inhibit leakage vortex of a blade top clearance, increase static pressure of a fan, increase working flow and reduce noise.

The application provides a blade, which comprises a blade root, a blade top and a leading edge and a trailing edge, wherein the blade root is used for being connected with a hub, the blade top is arranged opposite to the blade root, the leading edge and the trailing edge are positioned on two sides of the blade root and the blade top, the leading edge faces towards a windward side, the trailing edge faces away from the windward side, and smooth transition is realized between the leading edge and the trailing edge;

The projection of the front edge is in a curve shape with two inflection points, the front edge forms a concave part from the inflection point close to the root of the blade, the front edge forms an upper convex part from the inflection point close to the top of the blade, and the upper convex part is connected with the concave part; the upper convex portion is convex in the thickness direction of the blade compared with the trailing edge, and the lower concave portion is concave in the thickness direction of the blade compared with the trailing edge.

Optionally, the upper convex portion and the lower concave portion are both smooth curved surfaces, a curvature radius of the lower concave portion is larger than that of the upper convex portion, and a curvature of the lower concave portion is smaller than that of the upper convex portion.

Optionally, the inflection point near the root of the blade is a concave vertex with the greatest concave degree, and the concave distance of the concave vertex in the thickness direction of the blade is not more than 6% of the total length of the blade; the total length of the blade is the length between the blade root and the blade tip.

Optionally, the inflection point near the root of the blade is a concave vertex with the greatest degree of concave downward, and the length of the concave vertex from the plane where the root of the blade is located along the length direction of the blade is more than 10% of the total length of the blade and not more than 30% of the total length of the blade; the total length of the blade is the length between the blade root and the blade tip.

Optionally, the inflection point near the top of the blade is an upward convex point with the greatest upward convex degree, and the upward convex distance of the upward convex point in the thickness direction of the blade is more than 6% of the total length of the blade and is not more than 15% of the total length of the blade; the total length of the blade is the length between the blade root and the blade tip.

Optionally, the inflection point near the top of the blade is an upward convex point with the greatest upward convex degree, and the length of the upward convex point from the plane where the root of the blade is located along the length direction of the blade is more than 80% of the total length of the blade and is not more than 90% of the total length of the blade; the total blade length is the length between the blade root and the blade tip.

Optionally, the length of the connection part of the upper convex part and the lower concave part from the plane of the blade root is more than 20% of the total length of the blade and not more than 50% of the total length of the blade; the total blade length is the length between the blade root and the blade tip.

Optionally, the projection of the trailing edge is linear, and the blade tip, the blade root, the junction of the upper convex portion and the lower concave portion, and the trailing edge are in the same plane.

Optionally, the trailing edge has a thickness less than a thickness of the leading edge.

The application provides an impeller comprising a hub and blades according to any one of the above, wherein the blade roots of the blades are assembled around the circumference of the hub.

The application provides an air conditioner external unit which comprises an impeller.

In some embodiments, the blade comprises a blade root for connection with the hub, a blade tip disposed opposite the blade root, and a leading edge and a trailing edge on either side of the blade root and blade tip, the leading edge facing the windward side, the trailing edge facing away from the windward side, the transition between the leading edge and the trailing edge being smooth; the projection of the front edge is in a curve shape with two inflection points, the front edge forms a concave part from the inflection point close to the root of the blade, the front edge forms an upper convex part from the inflection point close to the top of the blade, and the upper convex part is connected with the concave part; the upper convex portion is convex compared with the trailing edge in the thickness direction of the blade, and the lower concave portion is concave compared with the trailing edge in the thickness direction of the blade. The blade structure can inhibit leakage vortex of the blade top clearance, and can increase the working flow of the impeller and reduce noise when being arranged on the impeller.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

Fig. 1 is a schematic view showing a three-dimensional structure of a blade according to an embodiment of the present application.

Fig. 2 is a schematic view showing a three-dimensional structure of a blade according to still another embodiment of the present application.

FIG. 3 is a schematic view of a blade leading edge curve according to one embodiment of the present application.

Fig. 4 is a schematic perspective view of an impeller according to an embodiment of the present application.

FIG. 5 is a graph showing the static pressure comparison of the test points of a leading edge non-inflection point design blower and a blower according to one embodiment of the application.

FIG. 6 is a graph showing the input current versus a leading edge non-inflection design blower and a blower according to one embodiment of the application.

FIG. 7 is a graph showing noise contrast for a leading edge non-inflection design blower and a blower according to one embodiment of the application.

Detailed Description

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the application. Rather, they are merely examples of apparatus and methods consistent with aspects of the application as detailed in the accompanying claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements. Likewise, the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. "plurality" or "plurality" means two or more. Unless otherwise indicated, the terms "front," "rear," "lower," and/or "upper" and the like are merely for convenience of description and are not limited to one location or one spatial orientation. The word "comprising" or "comprises", and the like, means that elements or items appearing before "comprising" or "comprising" are encompassed by the element or item recited after "comprising" or "comprising" and equivalents thereof, and that other elements or items are not excluded. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.

The blade comprises a blade root part, a blade top part, a front edge and a tail edge, wherein the blade root part is used for being connected with a hub, the blade top part is arranged opposite to the blade root part, the front edge and the tail edge are positioned at two sides of the blade root part and the blade top part, the front edge faces towards the windward side, the tail edge is opposite to the windward side, and the front edge and the tail edge are in smooth transition; the projection of the front edge is in a curve shape with two inflection points, the front edge forms a concave part from the inflection point close to the root of the blade, the front edge forms an upper convex part from the inflection point close to the top of the blade, and the upper convex part is connected with the concave part; the upper convex portion is convex compared with the trailing edge in the thickness direction of the blade, and the lower concave portion is concave compared with the trailing edge in the thickness direction of the blade. The blade structure can inhibit leakage vortex of the blade top clearance, and can increase the working flow of the impeller and reduce noise when being arranged on the impeller.

The application provides a blade, an impeller and an air conditioner external unit. The blade, the impeller and the air conditioner external unit according to the present application will be described in detail with reference to the accompanying drawings. The features of the examples and embodiments described below may be combined with each other without conflict.

The present application provides a blade 1, as shown in fig. 1-2, in some embodiments the blade 1 comprises a blade root 12 for connection with a hub, a blade tip 11 arranged opposite to the blade root 12, and a leading edge 13 and a trailing edge 14 on both sides of the blade root 12 and the blade tip 11, the leading edge 13 facing towards the windward side, the trailing edge 14 facing away from the windward side, the transition between the leading edge 13 and the trailing edge 14 being smooth. The blade 1 is typically mounted to a hub forming a rotating device, the blade leading edge 13 referring to the front edge of the blade or blade section, i.e. the side that is in direct contact with the air flow. The blade 1 is the key element in the device responsible for converting the gas flow or fluid into mechanical energy or generating pressure. In rotating machinery, the blade leading edge 13 is typically the first part to be impacted by a gas or fluid. The blade trailing edge 14 refers to the trailing edge of the blade or blade section, i.e. the side separated from the air flow or fluid. In rotating machinery such as wind turbines, aircraft engines, water pumps, fans, etc., the blade trailing edge 14 serves to determine the angle and manner in which the airflow or fluid exits the blade. The smooth transition of the leading edge 13 and the trailing edge 14 may reduce frictional resistance to surrounding fluid. Frictional resistance is the force of fluid through the blade that resists flow, and a smooth surface reduces this resistance, allowing fluid to flow more smoothly through the blade, reducing energy losses. Turbulence and drag can also be reduced, and a smooth curved surface can reduce the occurrence of turbulence. Turbulence is an irregular, chaotic swirling motion created during fluid flow that increases drag and energy loss. By maintaining a smooth surface of the blade, turbulence can be reduced, drag can be reduced, and efficiency of fluid flow over the blade can be improved. The smooth curved surface may reduce turbulence noise and vibration generation as the airflow or fluid flows over the blade. This is important for some applications sensitive to noise and vibrations (e.g. wind turbines, liquid pumps, etc.), which may improve the reliability of the device. In addition, the smooth curved surface is easier to clean. In some applications, the blade surface may accumulate dirt, sediment, or biological attachments, which may affect the performance and efficiency of the blade. The smooth surface reduces the adhesion of these contaminants and attachments, making the blade easier to clean and maintaining its good working condition.

The projection of the front edge 13 is in a curve shape with two inflection points, the front edge 13 forms a concave part 132 from the inflection point near the blade root 12, the front edge 13 forms an upper convex part 131 from the inflection point near the blade top 11, and the upper convex part 131 is connected with the concave part 132; the upper convex portion 131 is convex in the thickness direction of the blade compared to the trailing edge 14, and the lower concave portion 132 is concave in the thickness direction of the blade compared to the trailing edge 14. The provision of the upper protrusions 131 improves the stability, and the upper protruding blade leading edge 13 improves the flow direction and distribution of the air or fluid and improves the stability of the blade. This design may reduce the turbulence area, reduce the probability of flow separation and recombination, and thereby increase the stability of the blade. The provision of the upper lobe 131 may also reduce drag and in some cases the upper lobe leading edge 13 may reduce drag of the airflow or fluid. This is because the raised design can better control the flow of the air flow, reduce the separation and turbulence phenomena of the air flow, and further reduce the resistance. The design of the concave depression 132 also reduces drag, and the concave blade leading edge 13 improves airflow or fluid flow over the blade, reducing drag. By reducing the resistance to the airflow, the efficiency and performance of the blade may be improved. The concave depression 132 may also improve aerodynamic properties and the concave blade leading edge 13 may alter the flow direction and velocity profile of the airflow or fluid, thereby improving aerodynamic properties of the blade. This design reduces the turbulence area and improves the stability and control of the airflow.

As shown in fig. 1-2, in some embodiments, the trailing edge 14 has a thickness that is less than the thickness of the leading edge 13. Specifically, as wind or fluid passes over the leading edge 13 region of the blade, across the surface of the blade, and eventually reaches the trailing edge 14 region of the blade, a vortex, known as trailing edge vortex, is formed at the outlet of the blade due to the variation in the flow rate of the wind or fluid and the difference in the force conditions. The presence of trailing edge vortices reduces the lift and efficiency of the blade, while also increasing drag and energy consumption. To reduce the effect of trailing edge vortices, the trailing edge 14 of the blade is typically of a thin design, thereby reducing the formation of vortices. In contrast, the thick blade trailing edge 14 may cause more significant turbulence generation, thereby affecting the performance and efficiency of the fan or turbine.

In some embodiments, the upper protrusion 131 and the lower recess 132 are both smoothly curved, the radius of curvature r2 of the lower recess 132 is greater than the radius of curvature r1 of the upper protrusion 131, and the curvature of the lower recess 132 is less than the curvature of the upper protrusion 131. The design that the upward convex curvature is larger than the downward concave curvature can improve the structural strength and rigidity of the blade. The geometry of the upper lobe 131 is more tolerant of external loads and stresses, making the blade more stable and reliable during operation. Also as shown in connection with fig. 3, in some embodiments, the upper protrusion 131 has a large curvature and a small radius of curvature r1, and when wind or gas passes through the blade, a pressure difference is generated on the surface of the blade, thereby pushing the blade to rotate or generating power. The convex curvature of the blade can increase the contact area between the gas and the surface of the blade, and improve the gas grabbing and throwing capabilities of the blade, so that the flow speed and the pressure gain of the gas flow are increased. The curvature of the concave portion 132 is small, the curvature radius r2 is large, and if the concave curvature of the blade is larger than the convex curvature, the separation and turbulence of the air flow on the lower surface of the blade are increased, so that the resistance and energy loss are increased, and the working efficiency of the blade is reduced. Therefore, the convex curvature is larger than the concave curvature so as to realize better fluid dynamics performance and working efficiency.

The convexity and concavity of the blade may affect the distribution and flow characteristics of the airflow over the blade. The upward or downward convex distance with reasonable value can change the flow direction and speed distribution of the air flow, thereby producing the effect on the stability and the working effect of the blade. The convex and concave designs may also help to improve the flow transfer capability and pressure gain of the vane. An increase in vane length may require a corresponding adjustment in the extent and shape of the convexity and concavity to meet the desired flow and pressure requirements. As shown in fig. 3, a schematic view of a front edge 13 of a blade with two inflection points is shown, which is mounted on a hub 2, wherein a cylinder part is the hub 2, a solid curve connected to the hub 2 is a curve of the front edge 13 of the blade mounted on the hub 2, one end of the curve of the front edge 13 connected with the hub is a blade root 12, the other end is a blade top 11, a broken line connecting the blade top 11 and the blade root 12 is a straight line distance from the blade top 11 to the blade root 12, namely a total length 15 of the blade, and a direction perpendicular to the broken line is a thickness direction of the blade; the curved portion protruding in the thickness direction of the blade near the blade top 11 is an upper protruding portion 131, and the highest position of the upper protruding portion is an upper protruding apex 1311; the curved portion near the blade root 12 that is concave in the blade thickness direction is a concave portion 132, and the lowest portion of the concave portion is a concave apex 1321. The junction 16 is the boundary point between the upper convex portion 131 and the lower concave portion 132. After the blades are mounted on the hub 2, the blades rotate about the hub 2 as a rotation axis, R1 is a rotation locus of the joint 16, and R2 is a rotation locus of the convex apex 1311.

As shown in fig. 3, in some embodiments, near the inflection point of the blade root 12 is a concave apex 1321 where the concave portion 132 is most concave, and a concave distance h2 of the concave apex 1321 in the thickness direction of the blade is not more than 6% of the total length 15 of the blade; the total blade length 15 is the length between the blade root 12 and the blade tip 11. The concave distance h2 is controlled within a certain numerical range, so that the stability of the blade is facilitated, the too concave blade possibly generates flutter and resonance under the action of high-speed airflow, the stability and reliability of the blade are further reduced, noise can be generated, and the concave top point 1321 is in the concave distance of the thickness direction of the blade, which is not more than 6% of the total length 15 of the blade, so that the blade has the general stability and good silencing effect.

In some embodiments, the inflection point near the blade root 12 is a concave apex 1321 where the concave portion 132 is most concave, and the length of the concave apex 1321 along the length direction of the blade from the plane of the blade root 12 is more than 10% of the total length 15 of the blade and not more than 30% of the total length 15 of the blade; the total blade length is the length between the blade root 12 and the blade tip 11. If the position of the blade convex apex 1311 is not appropriate, this can cause the flow of the air stream to separate at the blade surface, creating turbulence and eddies. This will prevent the flow from passing smoothly over the vane, reducing the flow gain and pressure gain capabilities, resulting in reduced performance. The determination of the position of the convex apex 1311 of the blade can perform geometric modeling, flow field calculation and analysis on the blade, and the influence of a plurality of factors on the performance of the blade needs to be considered and experimental verification is performed.

In some embodiments, the inflection point near the blade top 11 is an upward convex vertex 1311 where the upward convex portion 131 protrudes to the greatest extent, and the upward convex distance h1 of the upward convex vertex 1311 in the thickness direction of the blade exceeds 6% of the total length 15 of the blade, and does not exceed 15% of the total length 15 of the blade; the total blade length 15 is the length between the blade root 12 and the blade tip 11. The upward protruding distance h1 is controlled within a certain numerical range, so that the stability of the blade is facilitated, the excessive upward protruding blade possibly generates flutter and resonance under the action of high-speed air flow, the stability and reliability of the blade are further reduced, noise can be generated, the upward protruding distance h1 of the upward protruding vertex 1311 in the thickness direction of the blade exceeds 6% of the total length 15 of the blade, and the blade which does not exceed 15% of the total length 15 of the blade generally has stability and good silencing effect.

In some embodiments, the inflection point near the blade top 11 is an upward convex vertex 1311 with the greatest upward convex degree of the upward convex part 131, and the length of the upward convex vertex 1311 along the length direction of the blade from the plane of the blade root 12 is more than 80% of the total length 15 of the blade, and is not more than 90% of the total length 15 of the blade; the total blade length 15 is the length between the blade root 12 and the blade tip 11. Poor positioning of the concave apex 1321 of the vane may increase the resistance to airflow through the vane. This will result in increased energy losses, reduced efficiency and possibly increased wind resistance or flow resistance. To determine the position of the concave apex 1321 of the blade, geometric modeling, flow field calculation, analysis and the like can be performed on the blade, and the influence of a plurality of factors on the performance of the blade needs to be considered and experimental verification is performed.

In some embodiments, the connection between the upper protrusion 131 and the lower recess 132 is greater than 20% of the total blade length 15, and not greater than 50% of the total blade length 15, the total blade length 15 being the length between the blade root 12 and the blade tip 11. So set up, the blade just can the atress even, can not receive the unusual extrusion and distortion that fluid passed through and lead to the blade fracture.

As shown in connection with fig. 2-3, in some embodiments, the projection of the trailing edge 14 is linear, and the blade tip 11, the blade root 12, the junction 16 of the upper protrusion 131 and the lower recess 132, and the trailing edge 14 are in the same plane. Blade tip 11 and blade root 12 are the areas of greatest force and torque application. The blade root 12 of the blade top 11 and the joint 16 are designed on the same straight line, so that higher structural strength and rigidity can be provided, and the design of the three parts and the tail edge on the same plane is beneficial to the stress stabilization of the whole blade, and the load generated during the working of the blade can be effectively borne. The straight line design helps to reduce hydrodynamic drag and turbulence generation. The blade tip 11 and blade root 12 and trailing edge 14, if having too complex a curvilinear shape, may cause separation and turbulence of the fluid in these areas, thereby increasing energy losses and drag.

The present application provides an impeller, as shown in fig. 4, comprising a hub 2 and blades 1 as described above, wherein the blade roots 12 of the plurality of blades 1 are circumferentially assembled on the circumferential side of the hub 2. The hub 2 is the supporting and connecting part of the blade 1, which is located at the blade root 12. The hub serves to secure and support the blades, enabling them to rotate and withstand the impact forces from the airflow or fluid. The hub 2 is typically made of a strong material (e.g. metal) and has sufficient strength and rigidity to maintain the stability of the blade. The connection between the blade 1 and the hub 2 is typically by bolts, welding or other means of connection. This connection must be strong and reliable enough to withstand the centrifugal forces, vibrations and impact forces to which the blades are subjected during rotation. In operation, the hub 2 is coupled by its hub to a main shaft or transmission of a rotating machine (e.g., a generator, a water pump drive system, etc.), thereby enabling the blades 1 to rotate with the hub 2. As the airflow or fluid passes over the blades 1, the blades convert their kinetic energy into mechanical energy, which is transferred through the hub 2 into the output system of the device.

By comparing the flow field with the inflection point impeller and the flow field without the inflection point impeller on the front edge 13 of the scheme, the swirl flow in the clearance of the blade top is obviously inhibited after the inflection point design on the front edge 13 is adopted, and the swirl influence area with the same strength is greatly reduced, so that the flow field is beneficial to the performance and noise performance of the fan provided with the impeller of the scheme.

The application provides an air conditioner external unit which comprises an impeller. In the experimental test of the air conditioner external fan, the existing mass production fan (the design of which the front edge has no inflection point) is compared with the fan with the inflection point at the front edge 13 designed according to the scheme, as shown in fig. 5, the air quantity (the positive correlation of static pressure of a measuring point and the air quantity) of the fan with the inflection point at the front edge 13 designed according to the scheme is not lower than that of the existing mass production fan, as shown in fig. 6, the fan power (the positive correlation of input current and power) designed according to the scheme is lower than that of the existing mass production fan, as shown in fig. 7, and the fan noise designed according to the scheme is lower than that of the existing mass production fan. Therefore, the air conditioner external unit with the impeller has the advantages of large air quantity, small power and good silencing effect.

Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It is to be understood that the application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims (11)

1. A blade, characterized in that the blade comprises a blade root for connection with a hub, a blade tip arranged opposite to the blade root, and a leading edge and a trailing edge on both sides of the blade root and the blade tip, the leading edge facing towards the windward side, the trailing edge facing away from the windward side, a smooth transition between the leading edge and the trailing edge;

The projection of the front edge is in a curve shape with two inflection points, the front edge forms a concave part from the inflection point close to the root of the blade, the front edge forms an upper convex part from the inflection point close to the top of the blade, and the upper convex part is connected with the concave part; the upper convex portion is convex in the thickness direction of the blade compared with the trailing edge, and the lower concave portion is concave in the thickness direction of the blade compared with the trailing edge.

2. The blade of claim 1, wherein the upper convex portion and the lower concave portion are each smoothly curved, a radius of curvature of the lower concave portion is greater than a radius of curvature of the upper convex portion, and a curvature of the lower concave portion is less than a curvature of the upper convex portion.

3. The blade according to claim 1, wherein the inflection point near the blade root is a concave apex at which the degree of concave depression is greatest, the concave apex being depressed by a distance of not more than 6% of the total length of the blade in the thickness direction of the blade; the total blade length is the length between the blade root and the blade tip.

4. The blade according to claim 1, wherein the inflection point near the blade root is a concave apex with the greatest degree of concave downward, and the length of the concave apex along the length direction of the blade from the plane of the blade root is more than 10% of the total length of the blade and not more than 30% of the total length of the blade; the total blade length is the length between the blade root and the blade tip.

5. The blade according to claim 1, wherein the inflection point near the top of the blade is an upward convex apex at which the upward convex degree is the greatest, and the upward convex apex has an upward convex distance in the thickness direction of the blade of more than 6% of the total length of the blade and no more than 15% of the total length of the blade; the total blade length is the length between the blade root and the blade tip.

6. The blade of claim 1, wherein the inflection point near the top of the blade is an upward convex apex with the greatest degree of upward convex, and the length of the upward convex apex along the length direction of the blade from the plane of the blade root is more than 80% of the total length of the blade and not more than 90% of the total length of the blade; the total blade length is the length between the blade root and the blade tip.

7. The blade of claim 1, wherein the junction of the upper protrusion and the lower recess is more than 20% of the total length of the blade and no more than 50% of the total length of the blade from the plane in which the blade root is located; the total blade length is the length between the blade root and the blade tip.

8. The blade of claim 1, wherein the projection of the trailing edge is linear, and the blade tip, the blade root, the junction of the upper protrusion and the lower recess, and the trailing edge are in the same plane.

9. The blade of claim 1 wherein the trailing edge has a thickness less than a thickness of the leading edge.

10. An impeller comprising a hub and a plurality of blades according to any one of claims 1 to 9, the blade roots of the plurality of blades being circumferentially assembled to the hub on the circumferential side thereof.

11. An air conditioner external unit comprising the impeller according to claim 10.