Axial flow fan blade having a wavy wing and trailing edge serration

Abstract

The axial fan includes a hub rotatable about a fan axis and a plurality of fan blades mounted to the hub, one of which includes at least one wave extending spanwise on the fan blade and at least one serration extending along the trailing edge of the fan blade, the at least one wave and the at least one serration being positioned between 40% and 100% of the fan blade's span.

Description

Technical Field

[0001] The present invention generally relates to a fan adapted for use in an air conditioning system, and more particularly, for providing an acoustic benefit over conventional systems.

Background Art

[0002] In a fan or similar device, a flow of a gaseous medium, such as air, may be induced by one or more blades rotating in the medium, which may generate audible noise. The noise generated during the operation of the fan may be generated by mechanical components such as motors and bearings, or by aerodynamic acoustic mechanisms. Regarding the aerodynamic acoustic process, the unsteady flow along each blade element may cause pressure fluctuations that interact with the blade to generate noise. Some factors, including but not limited to the shape of the blade edge and the number of blades, affect the aerodynamic acoustic generation mechanism.

Summary of the Invention

Means for Solving the Problems

[0003] According to an embodiment, an axial flow fan includes a hub rotatable about a fan axis and a plurality of fan blades attached to the hub. One of the plurality of fan blades includes at least one wave extending in the spanwise direction on the fan blade and at least one serration extending along the trailing edge of the fan blade. The at least one wave and the at least one serration are disposed at a position between 40% and 100% of the span of the fan blade.

[0004] In addition to, or alternatively to, one or more of the above features, in a further embodiment, at least one wave is disposed adjacent to the trailing edge of the fan blade.

[0005] In addition to, or alternatively to, one or more of the above features, in a further embodiment, at least one wave is disposed between 30% and 100% of the chord of the blade when measured from the leading edge of the fan blade.

[0006] In addition to one or more of the above features, or alternatively, in a further embodiment, at least one serration is formed on the chord of the fan blade.

[0007] In addition to one or more of the above features, or alternatively, in a further embodiment, the height of at least one serration is equal to between 0% and 30% of the length of the chord of the fan blade.

[0008] In addition to one or more of the above features, or alternatively, in a further embodiment, the outer shape of at least one wave is generally smooth.

[0009] In addition to one or more of the above features, or alternatively, in a further embodiment, the outer shape of at least one wave is generally sharp.

[0010] In addition to one or more of the above features, or alternatively, in a further embodiment, at least one wave includes a plurality of waves.

[0011] In addition to one or more of the above features, or alternatively, in a further embodiment, the plurality of waves includes between two and six waves.

[0012] In addition to one or more of the above features, or alternatively, in a further embodiment, the outer shape of at least one serration is generally smooth.

[0013] In addition to one or more of the above features, or alternatively, in a further embodiment, the outer shape of at least one serration is generally sharp.

[0014] In addition to one or more of the above features, or alternatively, in a further embodiment, at least one serration includes a plurality of serrations.

[0015] In addition to one or more of the above features, or alternatively, in a further embodiment, a plurality of waves includes those between two serrations and six serrations.

[0016] In addition to one or more of the above features, or alternatively, in a further embodiment, at least one wave is equal in number to at least one serration.

[0017] In addition to one or more of the above features, or alternatively, in a further embodiment, the cross-section of the fan blade has a contoured airfoil shape.

[0018] In addition to one or more of the above features, or alternatively, in a further embodiment, the fan blade has sweep.

[0019] In addition to one or more of the above features, or alternatively, in a further embodiment, it includes a shroud connected to the tip of each of the plurality of fan blades, and this shroud is rotatable about the fan axis.

[0020] In addition to one or more of the above features, or alternatively, in a further embodiment, the axial flow fan is formed of a plastic material via an injection molding process.

[0021] In addition to one or more of the above features, or alternatively, in a further embodiment, when measured along the axial dimension, the amplitude of one or more waves is greater at the trailing edge than at the leading edge.

[0022] In addition to one or more of the above features, or alternatively, in a further embodiment, when measured along the axial dimension, the amplitude of one or more waves varies continuously from the trailing edge and is greater than at the leading edge.

[0023] According to another embodiment, the axial flow fan includes a hub rotatable about a fan axis, a plurality of fan blades attached to the hub, and a shroud attached to the tip of each of the plurality of fan blades. Each of the plurality of fan blades includes three waves extending in the blade width direction on the fan blade. The three waves are arranged between 40% and 100% of the blade width of the fan blade adjacent to the trailing edge of the fan blade. Each of the plurality of fan blades includes three serrations extending in the chord direction on the fan blade. The three serrations are arranged between 40% and 100% of the blade width of the fan blade adjacent to the trailing edge of the fan blade.

[0024] The subject matter regarded as the invention is particularly pointed out and distinctly claimed at the end of the specification. The above and other features, as well as the advantages of the present invention, will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0025]

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DETAILED DESCRIPTION OF THE INVENTION

[0026] A detailed description will be made of embodiments of the present invention with reference to the drawings as an example, together with advantages and features.

[0027] Referring now to FIG. 1, an example of a coil unit 20 of an HVAC system is shown. The coil unit 20 includes a heat exchanger 22 having a substantially square planar shape. However, embodiments in which the heat exchanger 22 has a rectangular, cylindrical, or other shape are also within the scope of the present invention. A compressor 24 fluidly connected to the heat exchanger 22 is disposed inside the heat exchanger 22 and is configured to compress refrigerant through a vapor compression cycle. A fan 26 configured to draw ambient air radially inward through the heat exchanger 22 is disposed in contact with the surface of the heat exchanger 22, and the heated air is then discharged upward through an opening 28.

[0028] A fan 26 with reduced noise characteristics is shown in more detail in FIGS. 2-4. Although the fan 26 is illustrated and described in connection with the coil unit 20, it should be understood that the fan 26 may be suitable for use in other air conditioning applications. The fan 26 is an axial flow fan and includes a hub 30 to which a plurality of fan blades 32 are attached. The plurality of fan blades 32 are generally equidistantly spaced around the outer periphery of the hub 30 and then extend radially outward. In an embodiment, as shown in FIG. 2, the distal ends of the fan blades 32 are connected to a shroud or casing 34, and the shroud 34 is rotatable with the fan blades 32. However, embodiments in which the fan 26 does not include a shroud, or embodiments in which the shroud is stationary relative to the fan blades 32, are also within the scope of the present invention. The hub 30, the fan blades 32, and the shroud 34, if included, may be separate components that are joined together, or alternatively, may be integrally formed, for example, by injection molded plastic or the like.

[0029] In the non-limiting embodiments shown, the fan 26 comprises an axial flow fan rotatable about the axis of rotation X. For example, a motor schematically shown at M may be operably connected to the fan 26 via a shaft or other connecting means such as a belt, rope or chain, and used to rotate the fan in the direction indicated by arrow R about the fan axis X. The motor M may be oriented generally vertically such that the axis of rotation of the motor M is disposed parallel or coaxial with the fan axis X. However, other types of configurations are also contemplated. During operation, the motor M drives the rotation of the fan 26 to move an air flow through the fan and along the flow path, for example from a heat exchanger or the like.

[0030] The fan 26 may include any number of fan blades 32. In the non-limiting embodiment shown, the fan includes nine fan blades. However, it should be understood that a fan 26 having any configuration including two or more blades is contemplated herein. The plurality of fan blades 32 may be substantially identical, but need not be.

[0031] Referring to FIG. 3, each fan blade 32 has a root 35 where the fan blade 32 contacts and attaches to the hub 30, and a tip 36 at the outer end of the blade 32 opposite the root 35. The "span" of the fan blade 32 as referred to herein is intended to describe the distance between the root 35 and the tip 36. Each blade 32 further has a leading edge 38 located upstream with respect to the direction of rotation and a trailing edge 40 located downstream with respect to the direction of rotation. The leading and trailing edges 38, 40 are joined to each other at the root 35 and the tip 36. In the non-limiting embodiment shown, the fan blade 32 is shown as having a sweep in a direction opposite to the direction of rotation R of the fan, referred to as reverse or backward sweep. However, fan blades 32 having a sweep in the direction of rotation of the fan, also referred to as forward sweep, and fan blades 32 having no sweep such that the tips 36 of the fan blades 32 are disposed generally in a plane are also contemplated herein.

[0032] FIG. 4 shows a cross-section of one of the plurality of fan blades 32, taken perpendicular to the radial axis of the fan blade 32. In the illustrated non-limiting embodiment, each fan blade 32 has a cross-section 42 in the form of an airfoil or profile that curves in the direction of rotation such that the leading edge 38 is convex and curves in a convex shape away from the leading edge in the direction of the trailing edge 40. The chord of the airfoil is a straight line extending between the leading edge and the trailing edge of the airfoil. Similarly, the mean camber line indicates the asymmetry of the airfoil. The mean camber line is located midway between the upper surface 44 and the lower surface 46 of the airfoil.

[0033] Referring now to FIGS. 5 - 8, in an embodiment, the airfoil 42 of the fan blade 32 is configured to vary over at least a portion of the blade width of the fan blade 32. As a result of this variation, the fan blade 32 can have a non-uniform structure, such as a "wavy" structure. As used herein, the terms "wavy" or "waves" can refer to undulations occurring in the blade width direction, such as radial undulations occurring in successive concentric regions of the blade from the hub, undulations extending directly linearly in a tangential direction from the leading edge to the trailing edge, or non-linear undulations of the hub perpendicular to the tip profile at any location on the blade from the leading edge to the trailing edge. In any of the embodiments disclosed herein, such undulations can vary in amplitude as a function of one or more parameters of the blade 32, such as the chord of the blade. For example, at corresponding radial positions, the blade can include waves with a lower amplitude near the leading edge compared to the waves at the trailing edge (when measured in the r-z plane of the accompanying drawings).

[0034] One or more parameters of the wavy fan blade 32 remain constant over the blade width of the blade 32. For example, the leading edge 38 of the fan blade 32 has a predetermined leading edge profile, and the position of the leading edge 38 at various locations over the blade width of the blade 32 is fixed relative to the required profile. Alternatively, or additionally, the camber or asymmetry of the fan blade 32 may be fixed overall over the blade width of the blade.

[0035] In an embodiment, the chord of the blade 42 varies over at least a portion of the fan blade 32, such as a portion of the fan blade 32 that is substantially adjacent to the tip 36. The chord varies over the entire or a part of the blade width of the fan blade 32. Since the camber remains constant, one or more undulations extending in the blade width direction, also referred to herein as "waves" 50, are naturally formed on the surface of the fan blade 32. As best shown in FIGS. 7, 7A, and 7B, the intersection angle between the camber and the chord adjacent to the leading edge 36 and the trailing edge 38 in each cross-section of the blade 32 is illustrated schematically as θ and is configured to vary with the variation of the chord. However, since the camber of the blade 32 is held constant, the intersection angle between the chord shown as θ1 and the camber adjacent to the leading edge 36 remains constant between the respective cross-sections. Similarly, the intersection angle between the chord shown as θ2 and the camber adjacent to the trailing edge 38 remains constant between the respective cross-sections.

[0036] In an embodiment, the total number of waves 50 formed on the fan blade 32 is, for example, 2 to 6 fan waves. For example, in the non-limiting embodiment shown in the figures, three waves are shown. However, it should be understood that fan blades 32 having any number of waves 50 formed thereon are considered to be within the scope of the present invention.

[0037] As previously suggested, the chord of the blade 42 may vary over only a part of the blade width of the fan blade 32. Since the wave 50 is generated by this variation of the chord, the wave 50 is similarly formed only over the portion of the fan blade 32 where the chord varies. In an embodiment, the wave 50 is located at a position between 40% and 100% of the blade width, or at the blade tip 36. Therefore, one or more waves 50 are offset from the root 35 of the blade. Further, the wave 50 is shown to be formed substantially adjacent to the trailing edge 40 of the fan blade 32. For example, the wave 50 may extend at a distance between 30% and 100% of the chord, with 100% of the chord located at the trailing edge 40. However, it should be understood that embodiments in which the wave 50 is located adjacent to the leading edge 38 are also within the scope of the present invention.

[0038] The change in the chord length may be configured such that the wave 50 has an overall smooth outer shape, i.e., there is no significant change that causes protrusions or irregularities. Alternatively, the change in the chord length may have a sharp and more angular outer shape, including the edges or tips. The amplitude of the wave measured parallel to the axis X of the fan may be substantially constant or, alternatively, may vary. In an embodiment, the portion of the wave closest to the trailing edge 38 may have a greater amplitude than the portion of the wave closest to the leading edge 36. In yet another embodiment, the amplitude of the wave 50 may vary continuously between the leading edge 36 and the trailing edge 38.

[0039] In another embodiment, best shown in FIG. 7, one or more serrations 52 are formed along an edge portion, such as the trailing edge, of the fan blade 32. In an embodiment, the serrations 52 are formed as a result of the wave 50. For example, even if the camber of the fan blade 32 is held constant, the serrations 52 may be generated when the camber varies across the blade width of the fan blade 32. Thus, the wave 50 and the serrations 52 may be connected such that each serration 52 corresponds to one or more waves 50.

[0040] One or more serrations 52 extend in the chord direction and are similarly disposed between 40% and 100% of the blade width. The serrations 52 of the blade may be "cut-outs" from the nominal trailing edge of the blade, and the chord at each serration is less than the chord of the nominal trailing edge. The nominal trailing edge is a virtual trailing edge that extends continuously from the non-wavy portion of the blade 32 to the tip 36 of the blade 32 when there are no waves or serrations on the blade 32. Alternatively, the serrations 52 may extend beyond the nominal trailing edge of the blade 32, and the chord at each serration 52 is generally greater than the nominal trailing edge. In the illustrated non-limiting embodiment, three serrations are shown. However, this specification contemplates fan blades 32 having any number of serrations 52, such as one serration, between two and six serrations, or more than six serrations.

[0041] The serrations 52 may have a smooth outer shape or, alternatively, a sharp and more angular outer shape. In an embodiment, the serrations 52 have a sawtooth shape with an amplitude between 0% and 30% of the chord. The serrations 52 may be positioned directly adjacent to each other such that there is no gap between adjacent serrations 52. Alternatively, a gap or space may be disposed between adjacent serrations 52.

[0042] By including undulations and / or serrations that are disposed generally adjacent to the trailing edge of the fan blade, a phase adjustment is created that provides an acoustic benefit over conventional fan blades. The undulations 50 and / or serrations 52 can reduce noise between 3 and 6 decibels.

[0043] Embodiment 1: An axial flow fan includes a hub rotatable about a fan axis and a plurality of fan blades attached to the hub, one of the fan blades including at least one undulation extending in a blade width direction on the fan blade and at least one serration extending along a trailing edge of the fan blade, the at least one undulation and the at least one serration being disposed at a position between 40% and 100% of the blade width of the fan blade.

[0044] Embodiment 2: The axial flow fan according to Embodiment 1, wherein the at least one undulation is positioned adjacent to a trailing edge of the fan blade.

[0045] Embodiment 3: The axial flow fan according to Embodiment 2, wherein the at least one undulation is disposed between 30% and 100% of the chord as measured from a leading edge of the fan blade.

[0046] Embodiment 4: The axial flow fan according to any of the preceding embodiments, wherein the at least one serration is formed in a chord of the fan blade.

[0047] Embodiment 5: The axial flow fan according to any one of the preceding embodiments, wherein the height of the at least one serration is equal to between 0% and 30% of the chord length of the fan blade.

[0048] Embodiment 6: The axial flow fan according to any one of the preceding embodiments, wherein the outer shape of the at least one wave is smooth as a whole.

[0049] Embodiment 7: The axial flow fan according to any one of the preceding embodiments, wherein the outer shape of the at least one wave is sharp as a whole.

[0050] Embodiment 8: The axial flow fan according to any one of the preceding embodiments, wherein the at least one wave includes a plurality of waves.

[0051] Embodiment 9: The axial flow fan according to Embodiment 8, wherein the plurality of waves includes between two waves and six waves.

[0052] Embodiment 10: The axial flow fan according to any one of the preceding embodiments, wherein the outer shape of the at least one serration is smooth as a whole.

[0053] Embodiment 11: The axial flow fan according to any one of the preceding embodiments, wherein the outer shape of the at least one serration is sharp as a whole.

[0054] Embodiment 12: The axial flow fan according to any one of the preceding embodiments, wherein the at least one serration includes a plurality of serrations.

[0055] Embodiment 13: The axial flow fan according to Embodiment 12, wherein the plurality of serrations includes between two serrations and six serrations.

[0056] Embodiment 14: The axial flow fan according to any one of the preceding embodiments, wherein the number of the at least one wave is equal to the number of the at least one serration.

[0057] Embodiment 15: The axial flow fan according to any one of the preceding embodiments, wherein the cross-section of the fan blade has an airfoil shape outlining a contour.

[0058] Embodiment 16: The axial flow fan according to any one of the preceding embodiments, wherein the fan blade has a sweep.

[0059] Embodiment 17: The axial flow fan according to any one of the preceding embodiments, further comprising a shroud connected to each tip of the plurality of fan blades, the shroud being rotatable about the fan axis.

[0060] Embodiment 18: The axial flow fan according to any one of the preceding embodiments, wherein the axial flow fan is formed of a plastic material through an injection molding process.

[0061] Embodiment 19: The axial flow fan according to any one of the preceding embodiments, wherein the amplitude of the one or more waves, when measured along the axial dimension, is greater at the trailing edge than at the leading edge.

[0062] Embodiment 20: The axial flow fan according to any one of the preceding embodiments, wherein the amplitude of the one or more waves, when measured along the axial dimension, continuously changes from the trailing edge to be greater than at the leading edge.

[0063] Embodiment 21: An axial flow fan comprising a hub rotatable about a fan axis, a plurality of fan blades attached to the hub, and a shroud attached to each tip of the plurality of fan blades, each of the plurality of fan blades including three waves extending in the blade width direction on the fan blade, the three waves being adjacent to the trailing edge of the fan blade and disposed between 40% and 100% of the blade width of the fan blade, each of the plurality of fan blades including three serrations extending in the chord direction on the fan blade, the three serrations being adjacent to the trailing edge of the fan blade and disposed between 40% and 100% of the blade width of the fan blade.

[0064] Although the present invention has been particularly shown and described with reference to exemplary embodiments shown in the drawings, those skilled in the art will recognize that various changes may be made without departing from the spirit and scope of the present invention. Accordingly, the present disclosure is not limited to the specific embodiments (s) disclosed, but is intended to cover all embodiments that fall within the scope of the appended claims.

Claims

1. A hub rotatable about a fan axis, and a plurality of fan blades attached to the hub, wherein one of the plurality of fan blades includes at least one wave having peaks and valleys arranged in the wing width direction from its tip on the fan blade, and at least one serration extending along the trailing edge of the fan blade, the at least one wave and the at least one serration are arranged over a range from 40% to 100% of the wing width in a state where 100% of the wing width is located at the tip of the fan blade, a front edge of the fan blade has a predetermined front edge profile, a camber angle at the front edge of the fan blade remains constant over the wing width of the fan blade, and a chord length varies over the wing width of the fan blade, an axial flow fan.

2. The axial flow fan according to claim 1, wherein the at least one wave is located adjacent to the trailing edge of the fan blade.

3. The axial flow fan according to claim 2, wherein the at least one wave is arranged such that the wave crest extends over a range from 30% to 100% of the chord length in a state where 100% of the chord length is located at the trailing edge of the fan blade.

4. The axial flow fan according to any one of claims 1 to 3, wherein an outer shape of the at least one wave is smooth as a whole.

5. The axial flow fan according to any one of claims 1 to 4, wherein an outer shape of the at least one wave is sharp as a whole.

6. The axial flow fan according to any one of claims 1 to 5, wherein the at least one wave includes a plurality of waves.

7. The axial flow fan according to claim 6, wherein the plurality of waves includes between two and six waves.

8. The axial flow fan according to any one of claims 1 to 7, wherein an outer shape of the at least one serration is smooth as a whole.

9. The axial flow fan according to any one of claims 1 to 8, wherein an outer shape of the at least one serration is sharp as a whole.

10. The axial flow fan according to any one of claims 1 to 9, wherein the at least one serration includes a plurality of serrations.

11. The axial flow fan according to claim 10, wherein the at least one serration includes between two and six serrations.

12. The axial flow fan according to any one of claims 1 to 11, wherein the at least one wave is equal in number to the at least one serration.

13. The axial flow fan according to any one of claims 1 to 12, wherein a cross section of the fan blade has a wing shape outlining a contour.

14. Further comprising a shroud connected to each tip of the plurality of fan blades, The axial flow fan according to any one of claims 1 to 13, wherein the shroud is rotatable about the fan axis.

15. The axial flow fan according to any one of claims 1 to 14, wherein the axial flow fan is formed of a plastic material via an injection molding process.

16. The axial flow fan according to any one of claims 1 to 15, wherein when measured along the axial direction of the fan axis, the amplitude of the one or more waves is greater on the trailing edge side than on the leading edge side.

17. The axial flow fan according to any one of claims 1 to 16, wherein when measured along the axial direction of the fan axis, the amplitude of the one or more waves changes continuously between the leading edge and the trailing edge.

18. A hub rotatable about a fan axis, A plurality of fan blades attached to the hub, A shroud attached to each tip of the plurality of fan blades, and comprising: Each of the plurality of fan blades includes three waves with crests and troughs arranged in the wing width direction from its tip on the fan blade. The three waves are adjacent to the trailing edge of the fan blade and are arranged over a range from a position between 40% and 100% of the wing width in a state where 100% of the wing width is located at the tip of the fan blade. Each of the plurality of fan blades includes three serrations extending in the chord direction on the fan blade. The three serrations are adjacent to the trailing edge of the fan blade and are arranged over a range from a position between 40% and 100% of the wing width in a state where 100% of the wing width is located at the tip of the fan blade. An axial flow fan, wherein the leading edge of the fan blade has a predetermined leading edge contour, the camber angle at the leading edge of the fan blade remains constant over the wing width of the fan blade, and the length of the chord changes over the wing width of the fan blade.

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