EP2884115A1

EP2884115A1 - Axial fan with blade leading edge that protrudes axially upstream of the hub and that includes a bent (kink) as seen in a radial direction perpendicular to the radial extension of the blade

Info

Publication number: EP2884115A1
Application number: EP14197397.4A
Authority: EP
Inventors: Jaehyuk Jung
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2013-12-12
Filing date: 2014-12-11
Publication date: 2015-06-17
Anticipated expiration: 2034-12-11
Also published as: KR20150068665A; ES2731810T3; US20150167677A1; KR102200395B1; EP2884115B1

Abstract

Provided is an axial fan. The axial fan includes a hub to which a central shaft is coupled and a plurality of blades coupled to the outside of the hub to rotate. The blade includes a hub connection part defining an end of the blade, the hub connection part being coupled to an outer circumferential surface portion of the hub, a tip defining the other end of the blade, a first wing part extending at a first preset gradient from the tip, and a second wing part extending from the first wing part towards the hub, the second wing part having a second preset gradient.

Description

BACKGROUND

The present disclosure relates to an axial fan.
In general, air conditioners are apparatuses for cooling or heating an indoor space. Such an air conditioner includes a compressor for compressing a refrigerant, a condenser in which the refrigerant discharged from the compressor is condensed, an expander in which the refrigerant passing through the condenser is expanded, and an evaporator in which the refrigerant expanded in the expander is evaporated.
The condenser and the evaporator of the air conditioner function as heat-exchangers which perform heat-exchange between the refrigerant and external air. The condenser and the evaporator are disposed in an indoor unit or an outdoor unit. The heat-exchanger disposed in the indoor unit is called an indoor heat-exchanger, and the heat-exchanger disposed in the outdoor unit is called an outdoor heat-exchanger.
Here, an axial fan for blowing air toward the outdoor heat-exchanger may be disposed in one side of the outdoor heat-exchanger that is disposed in the outdoor unit.
The axial fan includes a hub connected to a rotating shaft of a motor and a plurality of blades coupled to the outside of the hub. When the axial fan is rotated by driving a motor, a pressure difference is generated between front and rear surfaces of the blades. A suction force which allows air to flow is generated due to the pressure difference.
Thus, external air is suctioned into the outdoor unit by the suction force of the axial fan. Here, the external air passes through the heat-exchanger disposed at a side of an air suction hole of the outdoor unit. Also, the external air is heat-exchanged with the refrigerant flowing into the heat-exchanger to allow the refrigerant to be condensed or evaporated, and then the external air is discharged out of the outdoor unit by the blowing operation of the axial fan.
The axial fans according to the related art include a hub coupled to a central shaft thereof and a plurality of blades coupled to an outer surface of the hub. The central shaft is coupled to a motor to rotate.
The hub has an approximately cylindrical shape. Also, the hub has a front surface portion defining a front surface, a rear surface portion defining a rear surface, and an outer circumferential surface portion to which the plurality of blades are coupled. Also, each of the blades includes a hub connection part is coupled to the outer circumferential surface portion of the hub and a tip defining an end of the blade.
In the axial fans according to the related art, the hub may have a relatively large diameter in comparison to the total diameter of the axial fan. For example, the hub may have a diameter of about 30% to about 35% of the total diameter of the axial fan. In this case, the axial fan may be deteriorated in efficiency due to a flow separation phenomenon, and noises may be generated.
That is, since the outer circumferential surface portion of the hub is disposed in a direction parallel to a flow direction of air, friction with air may be generated. Thus, the flow separation phenomenon occurs on the outer circumferential surface portion of the hub due to the friction. In addition, a strong vortex is generated by the flow separation phenomenon, and flow losses of the fan and strong noises occur by the vortex.

SUMMARY

Embodiments provide an axial fan that has improved fan efficiency and is reduced in flow noise.
In one embodiment, an axial fan includes: a hub to which a central shaft is coupled; and a plurality of blades coupled to the outside of the hub to rotate, wherein the blade includes: a hub connection part defining an end of the blade, the hub connection part being coupled to an outer circumferential surface portion of the hub; a tip defining the other end of the blade; a first wing part extending at a first preset gradient from the tip ; and a second wing part extending from the first wing part towards the hub, the second wing part having a second preset gradient.
The hub may have a cylindrical shape, and the hub may include: a front surface portion facing an air blow direction; a rear surface portion facing an air discharge direction; and an outer circumferential surface portion defining an outer circumference of the cylindrical shape.
The blade may include a boundary portion that divides the first wing part from the second wing part, and the second wing part may be bent from the boundary portion towards the front surface portion of the hub.
The blade may include: a leading edge defining an front end in a rotation direction; and a trailing edge defining a rear end in the rotation direction, wherein the boundary portion may include: a first end contacting the trailing edge; and a second end contacting the leading edge.
An angle at which the second wing part is bent from the second end portion may be greater than that at which the second wing part is bent from the first end.
The second wing part may extend from the first end to the hub in a direction corresponding to the extension direction of the first wing part and be bent at a preset angle to extend from the second end in the extension direction of the first wing part.
The angle bent from the first wing part toward the second wing part may be about 0° at the first end and may range from about 50° to about 70° at the second end.
An area of a portion at which the hub connection part and the outer circumferential surface portion of the hub are coupled may be variable in a clockwise or counterclockwise direction.
The hub connection part may include: a front end extending along the front surface portion of the hub; and a rear end extending inclined with respect to the rear surface portion of the hub.
A distance between the front end and the rear end may gradually increase in the counterclockwise direction of the outer circumferential surface portion of the hug and gradually decrease in the clockwise direction of the outer circumferential surface portion of the hub.
A virtual circle (C) connecting the tips of the plurality of blades to each other may be defined, and a ratio of a radius (R2) of the virtual circle to a radius (R2) of the outer circumferential surface portion from a center of the hub may range from about 10% to about 25%.
The first and second wing parts may be integrated with each other.
In another embodiment, an axial fan includes: a hub having a front surface portion, a rear surface portion, and an outer circumferential surface portion; and a plurality of blades coupled to the outer circumferential surface portion of the hub to rotate; wherein the blade may include: a tip defining an outer end of the blade; an outer wing part extending at a first preset gradient from the tip; an inner wing part extending from the outer wing part towards the hub, the inner wing part having a second preset gradient; and a boundary portion defined between the outer wing part and the inner wing part, the boundary portion is bent from the outer wing part toward the inner wing part.
The first preset gradient and the second preset gradient may be different from each other.
The axial fan may further include a central shaft, wherein an angle between the outer wing part and the central shaft may be greater than that between the inner wing part and the central shaft.
The blade may include a leading edge defining a front end in a rotation direction and a trailing edge defining a rear end in the rotation direction, the boundary portion may include a first end contacting the trailing edge and a second end contacting the leading edge, and an angle at which the inner wing part is bent from the second end may be greater than that at which the inner wing part is bent from the first end.
A pitch angle of the blade may gradually increase toward the hub.
In one embodiment, the details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a view of an outdoor unit according to an embodiment.
Figs. 2 to 4 are views of an axial fan according to an embodiment.
Fig. 5 is a cross-sectional view taken along line I-I' of Fig. 2.
Fig. 6 is a view of a hub connection part of a blade according to an embodiment.
Fig. 7 is a view of first and second wing parts of the blade according to an embodiment.
Figs. 8A to 8C are views illustrating a shape of a pitch angle of the blade when the second wing part is not adopted in the blade.
Figs. 9A to 9C are views illustrating a shape of a pitch angle of the blade when the second wing part is adopted in the blade.
Fig. 10 is a graph of results obtained by comparing changes in power consumption of the axial fan according to the related art and the axial fan according to an embodiment.
Fig. 11 is a graph of results obtained by comparing changes in noise of the axial fan according to the related art and the axial fan according to an embodiment.
Fig. 12 is a graphic view illustrating vorticity occurring around the fan when the axial fan according to the related art operates.
Fig. 13 is a graphic view illustrating vorticity occurring around the fan when the axial fan according to an embodiment operates.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, that alternate embodiments included in other retrogressive inventions or falling within the spirit and scope of the present disclosure will fully convey the concept of the invention to those skilled in the art.
Fig. 1 is a view of an outdoor unit according to an embodiment.
Referring to Fig. 1, an outdoor unit 10 of an air conditioner according to an embodiment includes a case 11, a heat-exchanger 20, an axial fan 100, a motor, a compressor 40, and a blocking plate 50. The blocking plate 50 may be disposed to partition the inside of the air conditioner into an electric component room in which the compressor 40 is disposed and a heat-exchange room in which the axial fan 100 is disposed.
An air suction part 15 into which external air is suctioned and an air discharge part 16 through which the air heat-exchanged in the heat-exchanger 20 is discharged are disposed in the case 11. For example, the air suction part 15 may be disposed in a rear surface portion and a side surface portion of the case 11, and the air discharge part 16 may be disposed in a front surface portion of the case 11.
The heat-exchanger 20 is disposed inside the case 11 allowing external air to be heat-exchanged with a refrigerant. The heat-exchanger 20 may be bent from one side of the axial fan 100.
Figs. 2 to 4 are views of the axial fan according to an embodiment.
Referring to Figs. 2 to 4, the axial fan 100 according to an embodiment includes a hub 110 disposed to be rotatable by a central shaft 110a and a plurality of blades 120 coupled to the outside of the hub 110. The central shaft 110a is coupled to the motor to rotate.
The hub 110 may have a cylindrical shape or a circular pillar shape. In detail, the hub 110 includes a front surface portion 112 defining a front surface of the hub 110, a rear surface portion 114 defining a rear surface of the hub 110, and an outer circumferential surface portion 113 defining a circumferential surface of the cylinder.
Here, the front surface or a front side of the hub 110 represents a direction in which air is blown, that is, a direction in which air is suctioned, and the rear surface or a rear side of the hub 110 represents a direction in which air is discharged. Hereinafter, description about the directions of the axial fan will be equally applied.
The blade 120 includes a first wing part 130 that extends with a first preset curvature (gradient) from the tip 123 toward the hub 110 and a second wing part 140 that extends with a second preset curvature (gradient) from the first wing part 130 toward the hub 110.
The first and second preset curvatures are different from each other. In detail, an angle defined by the first wing part 130 and a central axis of the hub 110 may be greater than that defined by the second wing part 140 and the central axis of the hub 110.
A boundary portion 135 is defined between the first wing part 130 and the second wing part 140. That is, the boundary portion 135 may be a line for distinguishing the first wing part 130 from the second wing part 140. The second wing part 140 may have a shape that is rather sharply bent from the boundary portion 135 towards the hub 110, that is, towards the front surface portion 112 of the hub 110. Thus, the boundary portion 135 may be called a "bent portion".
The first wing part 130 may be called an "outer wing part", and the second wing part 140 may be called an "inner wing part". For example, the first and second wing parts 130 and 140 may be integrated with each other.
The blade 120 includes a hub connection part 121 coupled to the outer circumferential surface portion 113 of the hub 110 and a tip 123 defining an end of the blade 120. The hub connection part 121 defines an inner end of the blade 120, and the tip 123 defines an outer end of the blade 120.
The tip 123 is disposed on an outer end of the first wing part 130, and the hub connection part 121 is disposed on an inner end of the second wing part 140.
The blade 120 includes a leading edge 125 defining a front end in a rotation direction thereof and a trailing edge 126 defining a rear end in the rotation direction. In Fig. 3, the axial fan 100 may rotate in a counterclockwise direction.
The blade 120 includes a pressure surface 127 facing an air blowing direction and a negative pressure surface 128 facing an air discharge direction. The pressure surface 127 may be understood as a surface that faces the front side to receive a pressure of air, and the negative pressure surface 128 may be understood as a surface that faces the rear side as a surface opposite to the pressure surface 127.
When the tip 123 of each of the plurality of blades 120 extends in a clockwise or counterclockwise direction, a virtual circle C may be defined. A distance from the center of the hub 110 or the central shaft 110a to an outer circumference of the virtual circle C, that is, a radius of the axial fan 100 is referred to as R1. Also, a distance from the center of the hub 110 or the center axis 110a to the outer circumference of the hub 110, that is, a radius of the hub 110 is referred to as R2.
The hub 110 may have a relatively small size in comparison to the total size of the axial fan 100.
In detail, the outer circumferential surface portion 113 of the hub 110 defines one sidewall of a passage through which air passes when the axial fan 100 rotates. The outer circumferential surface portion 113 of the hub 110 is parallel to an air flow direction to cause friction with air. Thus, a flow separation phenomenon may occur due to the friction to deteriorate fan efficiency.
Thus, when the hub 110 has a relatively large size in comparison to the total size of the axial fan 100, a friction area may increase. As a result, the air passage may have a narrow width to deteriorate performance of the axial fan 100.
Therefore, in the present embodiment, a relative size of the hub 110 may be determined so that a ratio of R2 to R1 is in the range of about 10% to about 25%. That is, in comparison to the axial fans according to the related art, the hub may have a relatively small size.
As described above, since the hub 110 has the relatively small size, the friction force occurring between the air flow and the hub 110 may be reduced. Thus, generation of vortex may be prevented to improve the fan efficiency.
Fig. 5 is a cross-sectional view taken along line I-I' of Fig. 2, and Fig. 6 is a view of a hub connection part of a blade according to an embodiment.
Referring to Figs. 5 to 6, the outer circumferential surface portion 113 of the hub 110 to which the central shaft 110a is coupled and the plurality of blades 120 coupled to the outer circumferential surface portion 113 are coupled to the axial fan 100 according to an embodiment.
Each of the blades 120 includes a hub connection part 121 coupled to the outer circumferential surface portion 113 of the hub 110. The hub connection part 121 defines the inner end of the blade 120.
A portion at which the hub connection part 121 and the outer circumferential surface portion 113 of the hub 110 are coupled has an area that is variable along the outer circumferential surface portion 113. That is, in FIG. 6, the portion at which a hub connection part 121 and the outer circumferential surface portion 113 of the hub 110 are coupled has an area that gradually increases in a counterclockwise direction and gradually decreases in a clockwise direction.
In detail, the hub connection part 121 includes a front end 121a disposed on a side of the front surface portion 112 of the hub 110 and a rear end 121b disposed on a side of the rear surface portion 114 of the hub 110. In detail, the front end 121a may extend adjacent to the front surface portion 112 of the hub 110, and a rear end 121b may extend adjacent to the rear surface portion 114 of the hub 110. The front end 121a may be understood as a portion facing a front side of the hub connection part 121, and the rear end 121b may be understood as a portion facing a rear side of the hub connection part 121.
The front end 121a may extend in approximately parallel along the outer circumferential surface of the front surface portion 112, and the rear end 121b may extend inclinedly with respect to the rear surface portion 114. Thus, a distance between the front and rear ends 121a and 121b may gradually increase in a counterclockwise direction and gradually decrease in a clockwise direction on the outer circumferential surface portion 113 of the hub 110.
As described above, the hub connection part 121 may have a variable coupling area coupled to the outer circumferential surface portion 113 of the hub 110 in a clockwise or counterclockwise direction. Thus, the blade 120 may be stably coupled to the outer circumferential surface portion 113 of the hub 110.
Fig. 7 is a view of the first wing part and the second wing part of a blade according to an embodiment.
Referring to Fig. 7, the second wing part 140 according to an embodiment extends from the first wing part 130 towards the outer circumferential surface portion 113 of the hub 110. Also, the second wing part 140 is bent in one direction with respect to a center at the boundary portion 135.
Thus, with respect to a direction perpendicular to the center shaft 110a of the hub 110, the extending direction of the first wing part 130, i.e." a curvature or gradient of the first wing part 130 may be formed different from that of the second wing part 140, i.e., a curvature or gradient of the second wing part 140.
In detail, the blade 120 includes a leading edge 125 defining a front end in the rotation direction and a trailing edge 126 defining a rear end in the rotation direction.
The leading edge 125 includes a first leading edge 125a disposed on the first wing part 130 and a second leading edge 125b disposed on the second wing part 140. Also, the trailing edge 126 includes a first trailing edge 126a indisposed on the first wing part 130, and a second trailing edge 126b indisposed on the second wing part 140.
The first and second leading edges 125a and 125b and the first and second trailing edges 126a and 126b may be distinguished from each other with respect to the boundary portion 135.
The second trailing edge 126b extends in a direction corresponding to an extension direction of the first trailing edge 126a. That is, the second trailing edge 126b extends from the first trailing edge 126a to the hub 110 in a state where the second trailing edge 126b is not bent.
In summary, it is understood that an angle at which the second wing part 140 is bent from the first wing part 130, i.e., a bent angle at a position at which the boundary portion 135 contacts the rear trailing edge 126 is about 0°. Here, the position at which the boundary portion 135 contacts the rear trailing edge 126 may be defined as a first end 135a.
On the other hand, the second leading edge 125b is bent in a predetermined direction with respect to the extension device of the first leading edge 125a to extend to the hub 110. In FIG. 7, the extension direction of the first leading edge 125a is denoted by a virtual line la, and the extension direction of the second leading edge 125b has a set angle θ1 with respect to the line la.
That is, it is understood that , an angle at which the first wing part 130 is bent from the second wing part 140, i.e., a bent angle at a position at which the boundary portion 135 contacts the leading edge 125 is about 01. For example, the bent angle θ1 may range from about 50° to about 70°. Here, the position at which the boundary portion 135 contacts the front leading edge 125 may be defined as a second end 135b.
In summary, although the blade 120 is not bent at the first end 135a of the boundary portion 135, the blade 120 may be bent somewhat at the second end 135b of the boundary portion 135. In other words, an angle at which the second wing part 140 is bent from the second end 135b may be greater than that at which the second wing part 140 is bent from the first end 135a.
As a result, the second wing part 140 extends in a direction corresponding to the extension direction of the first wing part 130 from the trailing edge 126. On the other hand, the bent angle in the extension direction of the first wing part 130 may gradually increase towards the leading edge 125.
According to the above-described constitutions, the blade 120 according to the present embodiment may have a large pitch angle. Thus, an amount of air achieved by the rotation of the wings may be sufficiently secured. This will be described later with reference to the accompanying drawings.
Figs. 8A to 8C are views illustrating a shape of the pitch angle of the blade when the second wing part is not adopted in the blade, and Figs. 9A to 9C are views illustrating a shape of the pitch angle of the blade when the second wing part is adopted in the blade.
Figs. 8A to 8C illustrate a state in which a pitch angle gradually decreases toward the inside of the blade, i.e., the hub when the blade shape according to the related art is adopted (α1 > α2 > α3). Here, the pitch angle may be understood as an angle of a part of the blade with respect to a horizontal surface or horizontal line 11. Also, the horizontal surface or horizontal line may be understood as a surface or line that is perpendicular to the central axis of the hub.
In detail, Fig. 8A illustrates a state in which the pitch angle of a tip of the blade is α1, and Fig. 8B illustrates a state in which the pitch angle defined at a radius position that corresponds to about 70% of the blade from the center of the hub is α2. Here, the radius position of about 70% may be understood as a position corresponding to about 70% of a distance from the hub to the tip of the blade.
Also, Fig. 8C illustrates a state in which the pitch angle defined at a radius position that corresponds to about 40% of the blade 120 from the center of the hub is α2.
The pitch angles α1, α2, and α3 may be expressed by the following relational equation. $α 1 < α 2 < α 3$
That is, in the case of the blade shape according to the related art, the pitch angle gradually decreases toward the inside of the blade. In this case, since the rotation force of the blade acting on the air is less, the fan performance may be deteriorated, and noises may increase.
Figs. 9A to 9C illustrate a state in which the pitch angle gradually toward the inside of the blade 120, i.e., the hub when the blade shape according to the present embodiment is adopted.
Fig. 9A illustrates a state in which a pitch angle of the tip 123 of the blade 120 is β1, and Fig. 9B illustrates a state in which the pitch angle defined at a radius position that corresponds to about 70% of the blade 120 from the center of the hub 110 is β2. Also, FIG. 9C illustrates a state in which the pitch angle defined at a radius position that corresponds to about 40% of the blade 120 from the center of the hub 110 is β3.
The pitch angles β1, β2, and β3 may be expressed by the following relational equation. $β 1 > β 2 > β 3$
That is, in the case of the blade shape according to the present embodiment, the pitch angle gradually increases toward the inside of the blade. In this case, since the rotation force of the blade acting on the air is great, the fan performance may be improved, and noises may be reduced.
Fig. 10 is a graph of results obtained by comparing changes in power consumption of the axial fan according to the related art and the axial fan according to an embodiment, and Fig. 11 is a graph of results obtained by comparing changes in noise of the axial fan according to the related art and the axial fan according to an embodiment.
Referring to Fig. 10, an amount of air is defined as an X-axis, and power consumption due to an operation of the axial fan is defined as a Y-axis.
As the air amount increases, the power consumption tends to increase. Also, it is seen that an increasing degree in the power consumption is smaller in the case of adopting the axial fan according to an embodiment of when compared to the case of adopting the axial fan according to the related art. Therefore, when the axial fan according to an embodiment operates, the power consumption may be reduced in comparison to the axial fan according to the related art.
Referring to Fig. 11, an amount of air is defined as an X-axis, and noise values caused by the operation of the axial fan are defined as a Y-axis.
As the air amount increases, the noise values tend to increase. Also, it is seen that an increasing degree in noise is smaller in the case of adopting the axial fan according to an embodiment when compared to the case of adopting the axial fan according to the related art.
Therefore, when the axial fan according to the present embodiment operates, the noises may be reduced in comparison to the axial fan according to the related art.
Fig. 12 is a graphic view illustrating vorticity occurring around the fan when the axial fan according to the related art operates, and Fig. 13 is a graphic view illustrating vorticity occurring around the fan when the axial fan according to an embodiment operates.
Referring to Fig.12, when the axial fan according to the related art operates, an unsteady flow as shown by reference symbol S1, that is, strong vortex is generated by a flow separation phenomenon due to an air friction around the hub 110.
In addition, it is seen that the unsteady flow is generated at a side of the tip of the blade due to the influence by the strong vortex as shown by reference symbol S1.
On the other hand, referring to Fig. 13, when the axial fan according to the present embodiment operates, it is seen that the vorticity generated around the axial fan, i.e., the hub 110 and the tip 123 of the blade 120 is smaller in comparison to the case of Fig. 12.
As described above, the axial fan according to the embodiments may have a relatively small hub height or diameter and include the first and second wing parts of which the blades have curvatures or gradients different from each other. Thus, the vortex that may occur around the fan may be prevented.
According to the embodiments, since the hub has a relatively small height and diameter, and the first and second wing parts of the blade is improved in structure, the operation efficiency of the axial fan may be improved, and the flow noises may be reduced.
Particularly, the second wing part having the curvature different from that of the first wing part including the tip of the blade may be disposed inside the first wing part with respect to the boundary portion as a center, and the second wing part may be coupled to the hub. Therefore, the axial fan may be compact to increase the flow area of the air passing through the outside of the hub.
Also, the front end of the hub connection part disposed on the second wing part may be disposed adjacent to the front surface portion of the hub, and the rear end of the hub connection part may be inclinedly disposed so that the rear end is closer to the rear surface portion of the hub. Therefore, even though the hub decreases in height, the large pitch angle of the blade may be maintained.
Also, since the hub has a small size, costs required for manufacturing the hub may be reduced.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

An axial fan comprising:
a hub (110) to which a central shaft (110a) is coupled; and

a plurality of blades (120) coupled to the hub (110) to rotate,
wherein each one of the blades comprises:

a hub connection part (121) defining an end of the blade (120), the hub connection part (121) being coupled to an outer circumferential surface portion of the hub (110);

a tip (123) defining the other end of the blade (120);

a first wing part (130) extending at a first predetermined gradient from the tip (123); and

a second wing part (140) extending from the first wing part (130) towards the hub (110), the second wing part (140) having a second predetermined gradient.
The axial fan according to claim 1, wherein the hub (110) has a cylindrical shape, and
the hub (110) comprises:
a front surface portion (112) facing an air blow direction;

a rear surface portion (114) facing an air discharge direction; and

an outer circumferential surface portion (113) defining an outer circumference of the cylindrical shape.
The axial fan according to claim 2, wherein each blade comprises a boundary portion (135) that divides the first wing part (130) from the second wing part (140), and
the second wing part (140) is bent from the boundary portion (135) towards the front surface portion (112) of the hub (110).
The axial fan according to claim 3, wherein each blade comprises:
a leading edge (125) defining an front end in a rotation direction; and

a trailing edge (126) defining a rear end in the rotation direction,

wherein the boundary portion (135) comprises:
a first end (135a) formed at the trailing edge (126); and

a second end (135b) formed at the leading edge (125).
The axial fan according to claim 4, wherein an angle at which the second wing part (140) is bent from the second end (135b) is greater than that at which the second wing part (140) is bent from the first end (135a).
The axial fan according to claim 5, wherein the second wing part (140) extends from the first end (135a) to the hub (110) in a direction corresponding to the extension direction of the first wing part (130) and is bent at a preset angle to extend from the second end (135b) in the extension direction of the first wing part (130).
The axial fan according to claim 6, wherein the angle bent from the first wing part (130) toward the second wing part (140) is about 0° at the first end (135a) and substantially ranges from 50° to 70° at the second end (135b).
The axial fan according to any one of claims 2 to 7, wherein an area of a portion at which the hub connection part (121) and the outer circumferential surface portion (113) of the hub (110) are coupled is variable in a clockwise or counterclockwise direction.
The axial fan according to claim 8, wherein the hub connection part (121) comprises:
a front end (121a) extending along the front surface portion of the hub (110); and

a rear end (121b) extending inclined with respect to the rear surface portion of the hub (110).
The axial fan according to claim 9, wherein a distance between the front end (121a) and the rear end (121b) gradually increases in the counterclockwise direction of the outer circumferential surface portion (113) of the hub (110) and gradually decreases in the clockwise direction of the outer circumferential surface portion (113) of the hub (110).
The axial fan according to any one of claims 2 to 10, wherein a virtual circle (C) connecting the tips (123) of the plurality of blades (120) to each other is defined, and
a ratio of a radius (R1) of the virtual circle to a radius (R2) of the outer circumferential surface portion (113) from a center of the hub (110) ranges from about 10% to about 25%.
The axial fan according to any one of claims 1 to 11, wherein the first and second wing parts (130, 140) are integrated with each other.
The axial fan according to any one of claims 1 to 12, wherein the first preset gradient and the second preset gradient are different from each other.
The axial fan according to claim 13, wherein an angle between the first wing part (130) and the central shaft (110a) is greater than that between the second wing part (140) and the central shaft (110a).
The axial fan according to any one of claims 1 to 14, wherein a pitch angle of the blade gradually increases toward the hub (110).