Impellers, mixed flow fans and air conditioners

Abstract

The present invention discloses an impeller, a mixed flow fan and an air conditioner. The impeller includes a wheel cover, a wheel hub and a plurality of blades. The wheel cover includes an inner cavity extending along an axis, and the inner cavity has an air inlet end and an air outlet end arranged oppositely; the wheel hub is arranged in the wheel cover; the plurality of blades are connected between the inner surface of the wheel cover and the outer surface of the wheel hub, and the blades are twisted blades, and the surface of the twisted blades includes a first surface segment, a second surface segment and a third surface segment, and the second surface segment is located between the first surface segment and the third surface segment and is concave toward one side of the rotation direction of the impeller relative to the first surface segment and the third surface segment. The twisted blade of the present invention is a double twisted structure, so that the surface of the blade extends in multiple directions, thereby effectively adapting to the changes in the speed of the airflow in multiple directions and thereby reducing the separation of the airflow flow in the internal flow channel, avoiding the generation of a large number of vortices and thereby optimizing the airflow flow condition of the entire fan.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical appliances, and in particular to an impeller, a mixed flow fan and an air conditioner. Background Art

[0002] The air duct system is one of the components of the air conditioner that is used to accelerate the heat exchange of the air in the air conditioner's working area. In the air duct system of the air conditioner, the designer selects and matches the appropriate fan according to the actual needs corresponding to the different models and specifications of the air conditioner to meet the working quality and comfort of the air conditioner.

[0003] In order to meet the air volume and pressure head indicators of the air conditioner, the air duct system of the air conditioner in the related art adopts a mixed flow fan. Since the air inlet direction of the mixed flow fan is generally along the axis of the hub, and the air outlet direction is generally inclined at a certain angle relative to the axis, the air flow in the flow channel of the mixed flow fan includes component velocities along different directions. The blades of the mixed flow fan in the related art are smooth surfaces, so that the airflow with component velocities in different directions will have a more serious boundary separation phenomenon when passing through the blade surface, thereby causing the generation of vortices. Summary of the invention

[0004] The invention provides an impeller, a mixed flow fan and an air conditioner to avoid air flow separation.

[0005] A first aspect of the present invention provides an impeller, comprising:

[0006] The wheel cover comprises an inner cavity which penetrates along the axis, and the inner cavity has an air inlet end and an air outlet end which are arranged oppositely;

[0007] a wheel hub disposed in the wheel cover; and

[0008] A plurality of blades are connected between the inner surface of the wheel cover and the outer surface of the wheel hub, and the blades are twisted blades, the surface of the twisted blades includes a first surface segment, a second surface segment and a third surface segment, the second surface segment is located between the first surface segment and the third surface segment and is recessed toward one side of the rotation direction of the impeller relative to the first surface segment and the third surface segment.

[0009] In some embodiments, the first surface segment, the second surface segment and the third surface segment are transitioned by arc surfaces.

[0010] In some embodiments, the surface of the twisted blade is a curved surface and includes a first curved surface segment, a second curved surface segment, and a third curved surface segment.

[0011] In some embodiments, the blade further includes a trailing edge located on one side of the wind outlet end, and a projection of a contour line of the trailing edge on the longitudinal projection plane is a concave arc line, and the concave arc line is concave toward the outer side of the blade.

[0012] In some embodiments, the concave arc has a first endpoint and a second endpoint, and a length of a chord between the first endpoint and the second endpoint ranges from [10 mm, 30 mm].

[0013] In some embodiments, the length of the chord between the first endpoint and the second endpoint is 19 mm.

[0014] In some embodiments, the concave arc has a first endpoint and a second endpoint, wherein the angle between the tangent of the concave arc at the first endpoint and the chord is in the range of [10°, 50°]; and / or the angle between the tangent of the concave arc at the second endpoint and the chord is [10°, 50°].

[0015] In some embodiments, the concave arc has a first endpoint and a second endpoint, wherein the angle between the tangent of the concave arc at the first endpoint and the chord is 31°; and / or the angle between the tangent of the concave arc at the second endpoint and the chord is 31.5°.

[0016] In some embodiments, the blade includes a blade root connected to the outer surface of the hub and extending along the outer surface of the hub, and a blade outer edge opposite to the blade root, and the projection of the contour line of the blade outer edge on the longitudinal projection plane passing through the axis is a variable inclination curve, and the angle between the tangent of the variable inclination curve and the longitudinal reference line gradually increases from the air inlet end to the air outlet end.

[0017] In some embodiments, the variable inclination curve is a first S-shaped curve.

[0018] In some embodiments, a projection of the blade root on the longitudinal projection plane is a second S-shaped curve.

[0019] In some embodiments, the blade further includes a leading edge located on the wind inlet end side, and a projection of a contour line of the leading edge on a transverse projection plane perpendicular to the axis is a concave curve.

[0020] In some embodiments, the number of blades is between 6 and 20.

[0021] A second aspect of the present invention provides a mixed flow fan, comprising an impeller as described in any one of the first aspect of the present invention.

[0022] A third aspect of the present invention provides an air conditioner, comprising the mixed flow fan according to the second aspect of the present invention.

[0023] Based on the technical solution provided by the present invention, the impeller includes a wheel cover, a wheel hub and a plurality of blades, the wheel cover includes an inner cavity extending along the axis, and the inner cavity has an air inlet end and an air outlet end arranged oppositely; the wheel hub is arranged in the wheel cover; the plurality of blades are connected between the inner surface of the wheel cover and the outer surface of the wheel hub, and the blades are twisted blades, the surface of the twisted blades includes a first surface segment, a second surface segment and a third surface segment, the second surface segment is located between the first surface segment and the third surface segment and is concave toward the rotation direction of the impeller relative to the first surface segment and the third surface segment. The twisted blade of the present invention is a double twisted structure, so that the surface of the blade extends in multiple directions, thereby effectively adapting to the changes in the speed of the airflow in multiple directions and reducing the separation of the airflow flow in the internal flow channel, avoiding the generation of a large number of vortices and optimizing the airflow flow condition of the entire fan.

[0024] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a schematic diagram of the three-dimensional structure of an impeller according to an embodiment of the present invention;

[0027] Figure 2 for Figure 1 The schematic diagram of the cross-sectional structure of the impeller shown;

[0028] Figure 3 for Figure 2 A partial enlarged structural schematic diagram of an impeller shown;

[0029] Figure 4 for Figure 1 The structure diagram of the impeller shown is after the wheel cover is removed;

[0030] Figure 5 for Figure 4 A schematic diagram of the three-dimensional structure of one of the leaves;

[0031] Figure 6 for Figure 1 The schematic diagram of the top view of the impeller shown;

[0032] Figure 7 for Figure 6 A partial enlarged structural schematic diagram of the impeller in FIG.

[0033] Figure 8 for Figure 1 The schematic diagram of the structure of the impeller as seen from above is shown;

[0034] Figures 9 to 11 for Figure 4 A schematic diagram of the projection structure of another blade on the longitudinal projection plane;

[0035] Fig.12 A velocity vector diagram in the inlet flow passage of a mixed flow fan in the related art;

[0036] Fig.13 FIG. 1 is a velocity vector diagram in the inlet flow passage of a mixed flow fan according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0039] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0040] According to the following Figures 1 to 13 The specific structure of the impeller in the embodiment of the present invention is described in detail.

[0041] like Figure 1 , Figure 2 , Figure 4 as well as Figure 5 As shown, the impeller of the embodiment of the present invention includes a hub 1, a wheel cover 3 and a plurality of blades 2, wherein the wheel cover 3 includes an inner cavity penetrating along the axis, and the inner cavity has an air inlet end and an air outlet end arranged oppositely; the hub 1 is arranged in the wheel cover 3; and the plurality of blades 2 are connected between the inner surface of the wheel cover 3 and the outer surface of the hub 1. The blade 2 is a twisted blade. The twisted blade includes three surface segments from the air inlet end to the air outlet end, and the three curved surface segments are the first surface segment, the second surface segment and the third surface segment, wherein the second surface segment is located between the first surface segment and the third surface segment and is concave toward the rotation direction of the impeller relative to the first surface segment and the third surface segment. That is to say, the twisted blade of the present embodiment is a double twisted structure, so that the surface of the blade extends in multiple directions, thereby effectively adapting to the changes in the speed of the airflow in multiple directions and reducing the separation of the airflow flow in the internal flow channel, avoiding the generation of a large number of vortices and optimizing the airflow flow condition of the entire fan.

[0042] The first surface segment, the second surface segment and the third surface segment of this embodiment are transitioned by arc surfaces, so that the velocity direction of the airflow of this embodiment will not change suddenly when flowing along the wall surface, thereby further reducing the generation of vortices.

[0043] Specifically, Figure 5 As shown, each surface segment of the twisted blade of this embodiment is a curved surface segment, namely a first curved surface segment 2A, a second curved surface segment 2B and a third curved surface segment 2C. Setting each surface segment as a curved surface segment enables the surface of the twisted blade of this embodiment to better adapt to airflows with multiple speed directions.

[0044] Furthermore, the blade 2 of this embodiment further includes a trailing edge 23 located at one side of the wind outlet end. Fig. 9 As shown, the projection of the trailing edge 23 on the longitudinal projection plane is a concave arc line. And the concave arc line is concave toward the outer side of the blade. The outer side of the blade mentioned here refers to the side away from the blade body. Figure 6 As shown, when looking up at the impeller from below, the trailing edge 23 of the blade 2 is roughly concave in shape to adapt to airflows of different speeds and directions and thus avoid the formation of vortices when the airflow is discharged.

[0045] In practical application, the two endpoints of the concave arc are respectively the first endpoint C and the second endpoint D, the length of the chord CD is in the range of [10 mm, 30 mm], the angle e between the tangent of the concave arc at the first endpoint C and the chord is in the range of [10°, 50°], and the angle f between the tangent of the concave arc at the second endpoint D and the chord is [10°, 50°]. Preferably, in this embodiment, the length of the chord CD is 19 mm, the angle e between the tangent of the concave arc at the first endpoint C and the chord is 31°, and the angle f between the tangent of the concave arc at the second endpoint D and the chord is 31.5°.

[0046] like Figure 5 As shown, the blade 2 includes a blade root 24 connected to the outer surface of the hub 1 and extending along the outer surface of the hub 1, and a blade outer edge 22 opposite to the blade root 24. The projection of the contour line of the blade outer edge 22 on the longitudinal projection plane passing through the axis L is a variable inclination curve, and the angle between the tangent line of the variable inclination curve and the longitudinal reference line gradually increases in the direction from the air inlet end to the air outlet end.

[0047] The projection of the blade outer edge 22 on the longitudinal projection plane of the embodiment of the present invention is a variable inclination curve, and the angle between the tangent of the variable inclination curve and the longitudinal reference line gradually increases, so that the blade of this embodiment gradually guides the airflow in the flow channel, thereby avoiding a large pressure gradient and reducing flow losses.

[0048] It should be noted that the transverse projection surface of the embodiment of the present invention is perpendicular to the axis L of the impeller. The longitudinal projection surface of the embodiment of the present invention needs to pass through the axis L of the impeller. And for any blade, the longitudinal projection surface refers to the longitudinal projection surface of the blade facing the direction of the axis L. For example, Figure 4 The longitudinal projection plane corresponding to the blade located in the front side of the hub 1 and in the middle of each blade 2 is the longitudinal projection plane parallel to the paper surface. In other words, the position of the longitudinal projection plane is different for different blades. The longitudinal reference line of the embodiment of the present invention is located in the longitudinal projection plane and is parallel to the axis L, and the transverse reference line is perpendicular to the axis L.

[0049] In some embodiments, Fig.10 As shown, the variable inclination curve includes a third endpoint B located at the air inlet side and a first endpoint C located at the air outlet side, wherein the inlet angle d between the tangent line of the variable inclination curve at the third endpoint B and the longitudinal reference line is in the range of [20°, 85°]. The outlet angle g between the tangent line of the variable inclination curve at the first endpoint C and the longitudinal reference line is in the range of [10°, 70°].

[0050] Optionally, through experiments, when the inlet angle d is set to 50° and the outlet angle g is set to 57.7°, the flow loss of the airflow is minimal.

[0051] In this embodiment, if Fig.10 As shown, the variable inclination curve is a first S-shaped curve. Specifically, the first S-shaped curve of this embodiment has an inflection point and includes a first curve segment and a second curve segment respectively located on both sides of the inflection point, and the ratio between the curvature radius R1 of the first curve segment and the curvature radius R2 of the second curve segment is in the range of [0.2, 5].

[0052] Optionally, experiments have shown that when the curvature radius R1 of the first curve segment is set to 125 mm and the curvature radius R2 of the second curve segment is set to 38 mm, the flow loss of the airflow is minimal.

[0053] like Fig.11 As shown, in this embodiment, the projection of the blade root 24 on the longitudinal projection plane is a second S-shaped curve.

[0054] Specifically, the second S-shaped curve includes a fourth endpoint A located at the air inlet side and a second endpoint D located at the air outlet side, wherein the inlet angle m between the tangent line of the second S-shaped curve at the fourth endpoint A and the transverse reference line is in the range of [65°, 120°]; the outlet angle n between the tangent line of the second S-shaped curve at the fourth endpoint D and the transverse reference line is in the range of [10°, 65°]. The transverse reference line here is also not an absolute transverse reference line, but is located in the longitudinal projection plane passing through the axis L and is perpendicular to the axis L.

[0055] Optionally, an entrance angle m between a tangent line of the second S-shaped curve at the fourth endpoint A and the transverse reference line is 91°, and an entrance angle n between a tangent line of the second S-shaped curve at the second endpoint D and the transverse reference line is 24°.

[0056] like Figure 5 As shown, the blade 2 also includes a leading edge 21 located on the side of the wind inlet end. Figure 6 and Figure 7As shown, the projection of the contour line of the leading edge 21 on the transverse projection plane perpendicular to the axis L is a concave curve. That is to say, looking down at the impeller from above, the shape of the leading edge 21 of its blade 2 is generally a concave surface, which reduces the intake resistance and the direct impact on the blade, thereby improving the intake smoothness and making the fan run efficiently and with low noise.

[0057] It should be noted that the transverse projection plane of the embodiment of the present invention is not an absolute transverse projection plane, but a relative transverse projection plane. No matter how the impeller is placed, the transverse projection plane is perpendicular to the axis L of the impeller.

[0058] When the impeller of this embodiment is applied to a mixed flow fan and the mixed flow fan is applied to an air conditioner, the number of blades is set to 6 to 20.

[0059] According to the following Figures 1 to 11 The structure of the impeller in a specific embodiment of the present invention is described in detail.

[0060] like Figure 1 As shown, the impeller of this embodiment includes a hub 1, a wheel cover 3 and a plurality of blades 2; wherein the wheel cover 3 has an inner cavity extending along the axis, and the inner cavity has an air inlet end and an air outlet end respectively located at two ends. The air inlet end is located at the upper side, and the air outlet end is located at the lower side. Figure 2 As shown, the outer surface of the hub 1 is roughly conical. The wheel cover 3 is coaxially sleeved on the outer side of the hub 1. A plurality of blades 2 are connected between the outer surface of the hub 1 and the inner surface of the wheel cover 3. Figure 5 As shown, each blade 2 includes a leading edge 21 located on the wind inlet side, a trailing edge 23 located on the wind outlet side, a blade root 23 connected to the outer surface of the hub 1 and extending along the outer surface of the hub 1, and an outer edge 22 opposite to the blade root 23.

[0061] like Figure 6 and Figure 7 As shown, in the top view of the impeller, the leading edge 21 of this embodiment has a first intersection point E intersecting with the hub 1 and a second intersection point F intersecting with the wheel cover 3. At this time, the leading edge 21 is a concave curve connecting the first intersection point E and the second intersection point F. In other words, the projection of the contour line of the leading edge 21 in the transverse projection plane perpendicular to the axis L is a concave curve. The projection of the blade 21 of the impeller of this embodiment in the transverse projection plane is a concave curve to reduce the intake resistance and the direct impact of the airflow on the blade, thereby optimizing the intake conditions and facilitating the efficient and low-noise operation of the fan.

[0062] In this embodiment, the direction of the concave curve is consistent with the rotation direction of the impeller. Figure 7 As shown, the impeller of this embodiment rotates counterclockwise. Such an arrangement can further improve the air intake smoothness.

[0063] Specifically, the concave curve of this embodiment includes a lobe line. For example, the lobe line trajectory can be obtained by using the following equation.

[0064] x=p*m1*k*t / n1+t 3 ;

[0065] y=m1*k*t 2 / n2+t 3 ;

[0066] Among them, k is a parameter used to adjust the chord length of the concave curve; p=±1 is used to adjust the direction of the concave curve; the value range of t is; m1, n1, and n2 are used to adjust the curvature of the concave curve.

[0067] In this embodiment, if Figure 6 and Figure 7 As shown, the angle a between the tangent of the concave curve at the first intersection E and the tangent of the contour line of the wheel hub 1 at the first intersection E is in the range of [20°, 150°], preferably, the angle a is 70°. And the angle b between the tangent of the concave curve at the second intersection F and the tangent of the wheel cover 3 at the second intersection F is in the range of [20°, 150°], preferably, the angle b is 78.5°.

[0068] In this embodiment, the distance between the projection of the maximum bending point O of the concave curve on the chord connecting the first intersection point E and the second intersection point F and the first intersection point A is 20%-85% of the chord length. The maximum bending point O here refers to the point on the concave curve with the largest distance from the chord.

[0069] In this embodiment, the distance c between the maximum bending line O and the chord line ranges from [2 mm to 12 mm]. Preferably, the distance c between the maximum bending line O and the chord line is 2.4 mm.

[0070] like Figure 3 As shown, the projection of the leading edge 21 on the longitudinal projection plane is an inclined line, and the vertical distance between the inclined line and the transverse reference line gradually increases in the extension direction from the radial inner side to the radial outer side. The transverse reference line here refers to a transverse reference line passing through the radial inner end point of the inclined line and perpendicular to the axis. Preferably, the maximum vertical distance h between the inclined line and the transverse reference line is in the range of [0, 15 mm]. More preferably, h is 6.7 mm.

[0071] In some embodiments, the number of blades is between 6 and 20.

[0072] Figures 9 to 11 It is the projection of a single blade on the longitudinal projection plane.

[0073] like Fig.10As shown, the projection of the outer edge 22 of the blade 2 of this embodiment on the longitudinal projection plane is a variable inclination arc, and the inclination angle between the tangent of the variable inclination arc and the longitudinal reference line gradually increases from the air inlet end to the air outlet end.

[0074] Specifically, Fig.10 As shown, the outer edge 22 of this embodiment is an S-shaped curve.

[0075] In some embodiments, Fig.10 As shown, the variable inclination curve includes a third endpoint B located at the air inlet side and a first endpoint C located at the air outlet side, wherein the inlet angle d between the tangent line of the variable inclination curve at the third endpoint B and the longitudinal reference line is in the range of [20°, 85°]. The outlet angle g between the tangent line of the variable inclination curve at the first endpoint C and the longitudinal reference line is in the range of [10°, 70°].

[0076] Optionally, through experiments, when the inlet angle d is set to 50° and the outlet angle g is set to 57.7°, the flow loss of the airflow is minimal.

[0077] Through the above optimization design, such as Figure 2 As shown, the internal flow channel of the mixed flow fan of this embodiment is special in form, so that the airflow flows in along the impeller axis L and then flows out obliquely. Specifically, in the longitudinal projection plane, the impeller flow channel of this embodiment is roughly a flow channel curve M1M2, and the angle α between the tangent of the flow channel curve M1M2 at the air inlet end and the longitudinal reference line is in the range of [0, 30°], and the angle β between the tangent at the air outlet end and the transverse reference line is in the range of [0, 80°]. Optionally, the angle α between the tangent of the flow channel curve M1M2 at the air inlet end and the longitudinal reference line is 10 degrees, and the angle β between the tangent at the air outlet end and the transverse reference line is 40 degrees.

[0078] A simulation experiment was conducted on the mixed flow fan of this embodiment, and compared with the simulation of the mixed flow fan before optimization. The experimental data are shown in the following table. During the simulation experiment, the noise measurement point was 0.5m from the fan outlet.

[0079]

[0080] From the simulation data, we can see that when the air volume is similar, the fan speed is significantly reduced after optimization, the noise value is reduced under the same air volume, the operating efficiency and pressure head are improved, and the fan aerodynamic performance and wind noise level are significantly improved. Fig.12 and Fig.13 It can also be found from the comparison of the velocity vector diagram that after optimization, the direction of the airflow entering along the guide ring has changed significantly, the airflow has shifted to the middle of the flow channel, and through the intake rectification, the flow velocity distribution has become more uniform and the velocity gradient has been significantly reduced.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. An impeller, characterized in that: include: The wheel cover (3) comprises an inner cavity extending through the axis, and the inner cavity has an air inlet end and an air outlet end which are arranged opposite to each other; A wheel hub (1) is arranged inside the wheel cover (3); as well as A plurality of blades (2) are connected between the inner surface of the wheel cover (3) and the outer surface of the wheel hub (1); the blades (2) are twisted blades, the twisted blades are double twisted structures, and the surface of the twisted blades comprises a first surface segment, a second surface segment and a third surface segment from the air inlet end to the air outlet end; the second surface segment is located between the first surface segment and the third surface segment and is concave toward one side of the rotation direction of the impeller relative to the first surface segment and the third surface segment.

2. The impeller according to claim 1, characterized in that: The first surface segment, the second surface segment and the third surface segment are transitioned by arc surfaces.

3. The impeller according to claim 1, characterized in that: The surface of the twisted blade is a curved surface and includes a first curved surface segment, a second curved surface segment and a third curved surface segment.

4. The impeller according to claim 1, characterized in that: The blade (2) further comprises a trailing edge (23) located at one side of the air outlet end, wherein the projection of the contour line of the trailing edge (23) on a longitudinal projection plane passing through the axis is an inwardly concave arc line, and the inwardly concave arc line is concave toward the outer side of the blade.

5. The impeller according to claim 4, characterized in that: The concave arc has a first endpoint (C) and a second endpoint (D), and the length of the chord between the first endpoint (C) and the second endpoint (D) is in the range of [10 mm, 30 mm].

6. The impeller according to claim 5, characterized in that The length of the chord between the first end point (C) and the second end point (D) is 19 mm.

7. The impeller according to claim 4, characterized in that: The concave arc has a first endpoint (C) and a second endpoint (D), wherein the angle (e) between the tangent and the chord of the concave arc at the first endpoint (C) is in the range of [10°, 50°]; and / or the angle (f) between the tangent and the chord of the concave arc at the second endpoint (D) is [10°, 50°].

8. The impeller according to claim 4, characterized in that The concave arc has a first endpoint (C) and a second endpoint (D), wherein the angle (e) between the tangent and the chord of the concave arc at the first endpoint (C) is in the range of 31°; and / or the angle (f) between the tangent and the chord of the concave arc at the second endpoint (D) is 31.5°.

9. The impeller according to any one of claims 1 to 8, characterized in that The blade comprises a blade root (24) connected to the outer surface of the hub (1) and extending along the outer surface of the hub (1), and a blade outer edge (22) opposite to the blade root (24); a projection of a contour line of the blade outer edge (22) on a longitudinal projection plane passing through the axis is a variable inclination curve; and in a direction from the air inlet end to the air outlet end, an angle between a tangent line of the variable inclination curve and a longitudinal reference line gradually increases.

10. The impeller according to claim 9, characterized in that The variable inclination angle curve is a first S-shaped curve.

11. The impeller according to claim 9, characterized in that The projection of the blade root (24) on the longitudinal projection plane is a second S-shaped curve.

12. The impeller according to any one of claims 1 to 8, characterized in that The blade (2) further comprises a leading edge (21) located on the side of the air inlet end, and the projection of the contour line of the leading edge (21) on a transverse projection plane perpendicular to the axis is a concave curve.

13. The impeller according to claim 1, characterized in that The number of the blades (2) is 6 to 20.

14. A mixed flow fan, characterized in that: Comprising an impeller as claimed in any one of claims 1 to 13.

15. An air conditioner, characterized in that: Comprising the mixed flow fan as claimed in claim 14.

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