An axial flow fan

Abstract

This invention relates to an axial flow fan, specifically within the field of air conditioning and refrigeration engineering technology, and solves the technical problem of high noise levels in existing axial flow fans. The axial flow fan of this invention includes a hub and blades. Continuously extending serrated teeth are provided at the trailing edge of the blades. These serrated teeth alter the pressure distribution in the trailing edge region of the blades, causing the high-pressure airflow portion of the blade's pressure surface to flow towards the negative pressure surface ahead of the blade, avoiding resonance with the airflow flowing near the blade tip. This prevents the amplification of T-S waves due to resonance, thus effectively reducing fan noise.

Description

Technical Field

[0001] The invention relates to the technical field of air conditioning and refrigeration engineering, and in particular to an axial flow fan. Background Art

[0002] With the continuous improvement of living standards, air conditioners have become more and more popular. Consumers have higher and higher requirements for the quality and performance of air conditioners. At present, the outdoor unit of the air conditioner generally has a large noise, which is mainly composed of motor noise and fan noise. Since the outdoor unit of the air conditioner generally uses an axial flow fan for forced convection heat exchange, the fan noise is generally generated by the axial flow fan. The fan noise is closely related to the vortex generated by the impeller in the air flow. When the sound wave generated by the tail vortex shedding at the trailing edge of the impeller satisfies a certain relationship with the frequency of the TS wave close to two dimensions on the blade surface, a feedback loop will be formed and the TS wave will be resonantly amplified, locking the tail vortex shedding frequency, forming a relatively sharp peak on the spectrum, and forming a larger fan blade surface vortex shedding noise. Therefore, in order to prevent the formation of a feedback loop to cause laminar boundary layer noise, some improvements need to be made to the axial flow fan structure. Summary of the invention

[0003] The present invention provides an axial flow fan, which is used to solve the technical problem of high noise of the axial flow fan in the prior art.

[0004] The present invention provides an axial flow fan, comprising a hub and a plurality of blades arranged on the outer circumferential surface of the hub, wherein the blades comprise a root portion connected to the hub, a tip portion opposite to the root portion, a trailing edge between the root portion and the tip portion, and a leading edge opposite to the trailing edge;

[0005] The radius of curvature where the tip portion is connected to the trailing edge is greater than the radius of curvature where the tip portion is connected to the leading edge;

[0006] The edge of the trailing edge is provided with continuous and uninterrupted saw-shaped teeth, and the saw-shaped teeth extend from the root to the tip.

[0007] In one embodiment, the projection curve of the sawtooth on the horizontal plane satisfies the following functional relationship:

[0008] f(x+7.5)=f(x)

[0009] Among them, the maximum and minimum values ​​of f(x) are 3.75 and -3.75 respectively.

[0010] In one embodiment, the thickness of the saw teeth is 0.9 mm.

[0011] In one embodiment, the middle of the blade is bent downward so that the intersection line of the root and the outer circumferential surface of the hub is configured as a curve with one end close to the upper end of the hub and the other end close to the lower end of the hub.

[0012] In one embodiment, the angle between the line connecting the two end points of the intersection line between the root and the hub and the axis of the hub is 60°.

[0013] In one embodiment, the ratio of the width of each blade to the outer diameter of the axial flow fan is 0.35-0.36; the ratio of the diameter of the hub to the outer diameter of the axial flow fan is 0.28-0.29.

[0014] In one embodiment, each of the blades is 56.9-57.8 mm above the upper end of the hub, and the distance between the top end of each blade and the feather base line is 81.4-82.6 mm.

[0015] In one embodiment, an axial hole for installing a rotating shaft is provided in the middle portion of the wheel hub, and radially distributed reinforcing ribs are provided between the inner circumferential surface of the wheel hub and the axial hole. The reinforcing ribs are arranged at equal intervals along the inner circumferential surface of the wheel hub, and the width of the reinforcing ribs is 4-4.3 mm.

[0016] In one embodiment, the axial hole is a stepped hole composed of a first inner hole and a second inner hole, the length of the first inner hole is 3-3.4 mm, and the length of the second inner hole is 81.6-82.8 mm.

[0017] In one embodiment, the inner wall of the second inner hole has a plane section extending along its axis, and the length of the plane section is 23-23.6 mm.

[0018] Compared with the prior art, the advantages of the present invention are: a continuously extending sawtooth is provided at the tail of the blade, and the sawtooth can change the pressure distribution state of the trailing edge area of ​​the blade, so that the high-pressure airflow part of the blade pressure surface flows to the negative pressure surface of the blade in advance, avoiding resonance with the airflow passing near the tip of the blade, that is, avoiding the generation of resonance amplified TS waves, and thus effectively reducing fan noise. Therefore, the present invention utilizes the edge of the trailing edge of the blade that is prone to generate vortices, and reduces the size of the vortex source area to reduce the noise source, thereby achieving the ultimate purpose of reducing noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Hereinafter, the present invention will be described in more detail based on embodiments and with reference to the accompanying drawings.

[0020] Figure 1 is a front view of an axial flow fan in an embodiment of the present invention;

[0021] Figure 2 is a rear view of an axial flow fan in an embodiment of the present invention;

[0022] Figure 3 is a top view of an axial flow fan in an embodiment of the present invention;

[0023] Figure 4 yes Figure 1 Sectional view at AA;

[0024] Figure 5 yes Figure 1 Sectional view at BB.

[0025] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale.

[0026] Reference numerals:

[0027] 1-hub; 2-blade; 11-shaft hole;

[0028] 12-strengthening rib; 21-trailing edge; 22-leading edge;

[0029] 23-saw teeth; 24-tip; 25-root;

[0030] 111 - first inner hole; 112 - second inner hole; 113 - plane segment. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] like Figure 1 As shown, the present invention provides an axial flow fan, including a hub 1 and a plurality of blades 2 arranged on the outer circumferential surface of the hub 1, the blades 2 including a root 25 connected to the hub 1, a tip 24 opposite to the root 25, a trailing edge 21 between the root 25 and the tip 24, and a leading edge 22 opposite to the trailing edge 21, that is, the trailing edge 21 and the leading edge 22 respectively connect the corresponding ends of the root 25 and the tip 24, and the connection between the tip 24 and the trailing edge 21 and the connection between the tip 24 and the leading edge 22 are both connected by arc transition.

[0033] Preferably, the number of blades 2 is 3-6, and the blades 2 are evenly distributed on the hub 1 .

[0034] The following description takes an axial flow fan having three blades 2 and whose rotation direction is counterclockwise as an example, that is, when the axial flow fan rotates, air flows in from the leading edge 22 area of ​​the blade 2, and is blown out from the trailing edge 21 area of ​​the blade 2 after the blade surface is pressurized. Figure 1As shown, the curvature radius R1 of the connection between the tip 24 and the trailing edge 21 is greater than the curvature radius R2 of the connection between the tip 24 and the leading edge 22; that is, the edge line of the leading edge 22 area is a curve that bends inward in the middle, and the edge line of the trailing edge 21 area is a curve that protrudes outward in the middle. That is, the windward edge of the blade 2 is concave inward, and the leeward edge is protruding outward, so as to increase the air supply volume and partially reduce the air supply noise.

[0035] Furthermore, continuous and uninterrupted saw teeth 23 are provided at the edge of the trailing edge 21, and the saw teeth 23 extend from the root 25 to the tip 24. The saw teeth 23 can change the pressure distribution state of the trailing edge 21 area of ​​the blade 2, so that the high-pressure airflow part of the pressure surface of the blade 2 flows to the negative pressure surface of the blade in advance, avoiding resonance with the airflow flowing near the tip 24, and thus avoiding the generation of resonance amplified TS waves, thereby effectively reducing fan noise.

[0036] In one embodiment of the present invention, the projection curve of the sawtooth 23 on the horizontal plane satisfies the following functional relationship:

[0037] f(x+7.5)=f(x)

[0038] Among them, the maximum and minimum values ​​of f(x) are 3.75 and -3.75 respectively.

[0039] That is, f(x) is a periodic function, and its minimum period is 7.5. Specifically, f(x) can be a sine function or a cosine function.

[0040] Furthermore, the thickness of the sawtooth 23 is 0.9 mm. The area where the sawtooth 23 is located on the blade 2 is the thinnest area, and the root 25 of the blade 2 is the thickest area. Figure 4 As can be seen in FIG. 2 , the thickness of the blade 2 decreases from the root 25 to the tip 24 .

[0041] like Figure 3 As shown, the middle of the blade 2 is bent downward (wherein downward refers to the leeward side of the blade 1), so that the intersection line of the root 25 and the outer circumferential surface of the hub 1 is constructed as a curve with one end close to the upper end of the hub 1 and the other end close to the lower end of the hub 1. That is, the blade 2 is connected to the hub 1 at an angle to increase the air supply.

[0042] Furthermore, the angle α between the line connecting the two end points of the intersection line S2 between the root portion 25 and the hub 1 and the axis of the hub 1 is 60°.

[0043] The ratio of the width b of each blade 2 to the outer diameter D of the axial flow fan is 0.35-0.36; the ratio of the diameter d of the hub 1 to the outer diameter D of the axial flow fan is 0.28-0.29. Specifically, the width b of the blade 2 is 202±0.95 mm, the outer diameter D of the axial flow fan is 570±1 mm, and the diameter d of the hub 1 is 164±0.75 mm.

[0044] like Figure 3 As shown, the distance H2 of each blade 2 above the upper end of the hub 1 is 56.9-57.8 mm, and the distance H1 between the top of each blade 2 and the feather base reference line S1 is 81.4-82.6 mm.

[0045] like Figure 2 As shown, an axial hole 11 for installing a rotating shaft is provided in the middle portion of the wheel hub 1, and radially distributed reinforcing ribs 12 are provided between the inner circumference of the wheel hub 1 and the axial hole 11. The reinforcing ribs 12 are arranged at equal intervals along the inner circumference of the wheel hub 1, and the width of the reinforcing ribs 12 is 4-4.3 mm.

[0046] Preferably, the number of the reinforcing ribs 12 is 6, the angle β1 between two adjacent reinforcing ribs 12 is 60°, and the minimum angle β2 between the reinforcing rib 12 and the plumb line is 10°.

[0047] like Figure 5 As shown, the front edge 22 has two identical rounded corners R3 on the left and right in the cross section, wherein R3 is 1-2 mm, and the thickness of the front edge 22 gradually decreases.

[0048] like Figure 4 As shown, the shaft hole 11 is a stepped hole composed of a first inner hole 111 and a second inner hole 112. The length L1 of the first inner hole 111 is 3-3.4 mm, and the length L2 of the second inner hole 112 is 81.6-82.8 mm.

[0049] Preferably, the inner wall of the second inner hole 112 has a plane section 113 extending along the axis thereof, and the length L3 of the plane section 113 is 23-23.6 mm. The plane section 113 can prevent the rotating shaft inserted into the shaft hole 11 from radial runout.

[0050] The technical effect of the present invention is described in detail by the following experimental data: As shown in Table 1, a parameter comparison between the axial flow fan of the present invention and the existing axial flow fan is listed.

[0051] Table 1 Comparison of test data between the axial flow fan in the embodiment of the present invention and the existing axial flow fan

[0052]

[0053] The axial flow fan of the present invention and the existing axial flow fan are both fans with three blades 2. According to the data comparison in Table 1, it can be seen that the air conditioner using the axial flow fan of the present invention has a large air volume and low noise.

[0054] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An axial flow fan, characterized in that: The invention comprises a hub (1) and a plurality of blades (2) arranged on the outer circumferential surface of the hub (1), wherein the blades (2) comprise a root portion (25) connected to the hub (1), a tip portion (24) opposite to the root portion (25), a trailing edge (21) located between the root portion (25) and the tip portion (24), and a leading edge (22) opposite to the trailing edge (21), wherein the leading edge (22) has two identical rounded corners R3 on the left and right in a cross section, wherein R3 is 1 mm to 2 mm, and the thickness of the leading edge (22) gradually decreases; The radius of curvature at the connection between the tip (24) and the trailing edge (21) is greater than the radius of curvature at the connection between the tip (24) and the leading edge (22); The trailing edge (21) is provided with continuous and uninterrupted saw-shaped teeth (23), and the saw-shaped teeth (23) extend from the root (25) to the tip (24); The projection curve of the sawtooth (23) on the horizontal plane satisfies the following functional relationship: f （ x +7.5）= f （ x ） in, f ( x ) has a maximum and minimum value of 3.75 and -3.75 respectively; The thickness of the sawtooth (23) is 0.9 mm; The area on the blade (2) where the saw-shaped teeth (23) are located is the thinnest area, the root (25) of the blade (2) is the thickest area, and the thickness of the blade (2) decreases from the root (25) to the tip (24); The middle of the blade (2) is bent downward, so that the intersection line of the root (25) and the outer circumferential surface of the hub (1) is constructed as a curve with one end close to the upper end of the hub (1) and the other end close to the lower end of the hub (1); The angle between the line connecting the two end points of the intersection line between the root (25) and the hub (1) and the axis of the hub (1) is 60°; The ratio of the width of each blade (2) to the outer diameter of the axial flow fan is 0.35-0.36; the ratio of the diameter of the hub (1) to the outer diameter of the axial flow fan is 0.28-0.29; The distance between each blade (2) and the upper end of the hub (1) is 56.9-57.8 mm, and the distance between the top of each blade (2) and the feather base line is 81.4-82.6 mm; A shaft hole (11) for mounting a rotating shaft is provided in the middle of the wheel hub (1), and radially distributed reinforcing ribs (12) are provided between the inner circumferential surface of the wheel hub (1) and the shaft hole (11), the reinforcing ribs (12) are arranged at equal intervals along the inner circumferential surface of the wheel hub (1), the width of the reinforcing ribs (12) is 4-4.3 mm, the number of the reinforcing ribs (12) is 6, the angle β1 between two adjacent reinforcing ribs (12) is 60°, and the minimum angle β2 between the reinforcing ribs (12) and the plumb line is 10°; The shaft hole (11) is a stepped hole formed by a first inner hole (111) and a second inner hole (112); the length of the first inner hole (111) is 3-3.4 mm, and the length of the second inner hole (112) is 81.6-82.8 mm; The inner wall of the second inner hole (112) has a plane section (113) extending along its axis, and the length of the plane section (113) is 23-23.6 mm.

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