WO2020169498A1

WO2020169498A1 - Device for reducing fan-generated noise

Info

Publication number: WO2020169498A1
Application number: PCT/EP2020/054014
Authority: WO
Inventors: Luca D'ALESSANDRO; Stefano CAVERNI; Giovanni CAPELLARI; Sebastiano Conti; Francesco Mori; Simone MEDURI
Original assignee: Phononic Vibes S.R.L.; Politecnico Di Milano
Priority date: 2019-02-19
Filing date: 2020-02-17
Publication date: 2020-08-27
Also published as: IT201900002403A1; EP3927976A1; EP3927976B1

Abstract

The present invention relates to a device (10) for reducing fan-generated noise, comprising: a plurality of grid elements (201, 902) identifying a main development plane, and empty portions (202) delimited by the grid elements (201, 902) and configured for the passage of an air flow through the device (10), wherein each of the grid elements (201, 902) comprises a respective inner cavity (501, 903) delimited by side walls, the side walls defining at least one tube opening (401) facing a respective one of the empty portions (202) and substantially orthogonal to the main development plane, the inner cavity (501, 903) being acoustic resonant for reducing the fan-generated noise. The device (10) has a substantially circular overall shape (101, 102, 103, 104) having a substantially circular outer edge (203), first grid elements (201) of the grid elements (201, 902) having their main direction of development aligned to the outer edge (203), the first grid elements (201) being tangentially arranged and aligned with each other on concentric circumferences in the substantially circular overall shape (101, 102, 103, 104).

Description

Title: Device for reducing fan-generated noise

DESCRIPTION

Technical field

The present invention relates to a device for reducing fan-generated noise.

In general, the present invention finds application in the fields of ventilation, air conditioning, de-humidification, cooling or heating, and in any technical field where fans are present.

Prior art

Fans, namely axial pumps for air circulation, are noise sources when in operation. Indeed, a fan in rotation propagates an acoustic field, inter alia due to the interaction of the fan blades with the air and to engine noise, typically an electric motor, used to put the fan in rotation.

In several applications, it is desirable to acoustically attenuate or reduce a fan-generated noise.

Document n. US 10087954 (B2) relates to a fan equipped with a tube radially connected and external to the fan support, in communication at two different angular positions for noise reduction.

Document n. US7992674 (B2) relates to a fan system comprising a pair of resonators that form a dipole for reducing tonal frequencies, both downstream and upstream of the fan.

Document n. US9157362 (B2) relates to a covering for a fan in which a slot is obtained, said slot being configured to release exceeding air pressure, so as to reduce the radiated noise.

Document n. CA2555710 (Al) relates to a silencer for a passage, having soft acoustic sections and non-soft acoustic sections alternately arranged on the inner wall of the passage, in the length direction. The soft acoustic section is composed of an acoustic pipe array for duct walls, formed in a rectangular plate shape by arranging 1/4 wavelength acoustic pipes having a rectangular cross-sectional shape with one closed end and another opened end in parallel along the duct wall in a perpendicular direction. The openings of the acoustic pipe are alternately closed by rigid bodies such as aluminum plates.

However, the known solutions do not prove to be fully effective in limiting the propagation of an acoustic field generated by a fan.

Summary of the invention

An object of the present invention is to overcome drawbacks of the prior art.

A particular object of the present invention is to limit the propagation of an acoustic field generated by a fan more effectively.

A further particular object of the present invention is to provide a device that is effectively associated with a fan, for reducing the noise perceived by a receiver.

A further particular object of the present invention is to provide a device for reducing a fan-generated noise having a compact and robust construction.

These and other objects are achieved by a device for reducing fan generated noise according to the characteristics of the appended claims that form an integral part of the present disclosure.

An idea underlying the present invention is to provide a device for reducing fan-generated noise, comprising: a plurality of grid elements identifying a main development plane, and empty portions delimited by the grid elements and configured for the passage of an air flow through the device; each of the grid elements comprises a respective inner cavity delimited by side walls that define at least one tube opening facing a respective one of the empty portions and substantially orthogonal to the main development plane; the inner cavity is acoustic resonant, so as to reduce the noise generated by the fan. The device has a substantially circular overall shape having a substantially circular outer edge, wherein first grid elements of the grid elements have their main direction of development aligned to the outer edge and are tangentially arranged and aligned with each other on concentric circumferences in the substantially circular overall shape.

Advantageously, the inner cavity of the grid elements, being resonant, contributes limiting the propagation of the acoustic waves generated by the fan which the device is associated with. Advantageously, the noise- reduction effect is very high since all of the grid elements contribute to it synergistically.

Advantageously, the device has limited dimensions, meanwhile allowing the passage of an air flow passing through it, thus being effective when associated with a fan, in particular constituting a grid covering element thereof.

Advantageously, the device has a substantially circular overall shape which more effectively matches the shape of the fan having an impeller in (circular) rotation. As the grid elements and their inner cavities are aligned on concentric circumferences, it becomes possible to optimize the acoustic performance of the device, in terms of noise reduction, for a same occupied area of air flow.

In other words, advantageously, the device of the present invention is better suited to match and operate in connection with a fan, in order to effectively reduce fan-generated noise.

Advantageously, the grid device of the present invention allows reducing disturbances to passage of an air flow, meanwhile attenuating the passage of a sound field. In particular, the device of the present invention allows to minimize an obstructed area for the air flow.

Preferably, the grid elements delimit larger empty portions in a central zone of the substantially circular overall shape of the device, to leave as undisturbed as possible the air flow in the central zone. In particular, the air flow is notoriously defined by helicoidal trajectories; air streams include velocity vectors having a component perpendicular to the fan’s plane and a further circumferential component belonging to planes which are parallel to the fan’s plane. The device of the present invention allows to reduce disturbances by providing air passage according to a more aerodynamic characteristic, thus reducing turbulence downstream of the device and at the same time maintaining optimal characteristics for noise reduction.

Advantageously, the plurality of grid elements adjoined to each other contributes constituting a robust and practical device, particularly suitable for industrial or domestic uses.

Preferably, the grid elements have curved bodies shaped as circumference arcs which are tangentially arranged with a staggered configuration, to provide a radial contact interface between grid elements of difference circumferences. Therefore, advantageously, an improved bearing structure of the device is provided.

Preferably, the side walls define a tube opening while an end wall of the side walls, opposite the one tube opening, is closed. Advantageously, the device of the present invention achieves better compactness for a same number of tube openings involved.

Preferably, two grid elements adjacent to each other are adjoined at respective end walls, defining a closure between two respective inner cavities; more preferably the two inner cavities of two axially adjacent grid elements, are of equal length with each other.

In particular, the device according to the present invention is configured for being arranged with its main development plane, orthogonal to a una main propagation direction of the fan-generated noise.

Preferably, the inner cavity develops along the main development plane of the device; it is also possible that the inner cavity further develops outside the main development plane, with grid elements that are also curved in space.

Preferably, the first grid elements comprise at least a first group of inner first grid elements closer to a center of the substantially circular overall shape, and further comprise at least a second group of outer first grid elements closer to the substantially circular outer edge.

Advantageously, the first group and the second group of grid elements provide different acoustic resonant inner cavities, so as to reduce a wider frequency spectrum of fan-generated noise.

In particular, acoustic resonant inner cavities having different lengths are employed in the (inner) first group and in the (outer) second group, so as to provide acoustic resonators active on distributed frequencies, thus improving the noise-dampening capability of the device.

Preferably, second grid elements having their main development direction that is radially to the substantially circular outer edge may also be present, namely arranged radially in the substantially circular overall shape of the device. These second grid elements, advantageously, comprise a respective inner cavity for reducing the fan generated noise, and at the same time provide a radial frame for all the other first grid elements of the device, thus improving structural stability of its bearing structure.

Preferably, one or more of the side walls of the inner cavity may comprise one or more holes or slits, configured for increasing an acoustic field damping and for increasing the noise-reduction effectiveness.

Advantageously, the device according to the present invention makes a self-bearing structure that is associable with an opening of a fan casing or with a duct, in fluidic connection with one or more fans.

Advantageously, the grid elements are further configured for preventing the accidental access to the fan by a user’s hand, tools or anything else, thus increasing the safety of the overall apparatus.

Further features and advantages will become more apparent from the following detailed description of preferred, but not exclusive, embodiments of the present invention and from the dependent claims that outline preferred and particularly advantageous embodiments of the invention.

Brief description of the drawings

The invention is illustrated with reference to the following figures, provided by way of non-limiting example, in which:

Figure 1 illustrates a device according to the present invention, associated with a fan.

Figure 2 illustrates a first embodiment of a device for reducing fan generated noise according to the present invention.

Figure 3 illustrates the grid elements of the device of Figure 2.

Figure 4 illustrates a three-dimensional view of the grid elements of Figure 3.

Figure 5 illustrates a cut-through part of the grid elements of Figure 4.

Figure 6 illustrates the grid elements of a second embodiment of a device for reducing fan-generated noise according to the present invention.

Figure 7 illustrates a side view of the grid elements of Figure 6. Figure 8 illustrates a cut-through part of the grid elements of Figure 6, in a three-dimensional view.

Figure 9 illustrates a third embodiment of a device for reducing fan-generated noise according to the present invention.

Figure 10 illustrates the grid elements of the device of Figure 9.

Figure 1 1 illustrates a cut-through part of the grid elements of Figure 10, in a three-dimensional view.

Figure 12 illustrates the grid elements of a fourth embodiment of a device for reducing fan-generated noise according to the present invention.

Figure 13 illustrates a cut-through part of the grid elements of Figure 12, in a three-dimensional view.

In the different figures, analogous elements will be indicated with analogous reference numbers.

Detailed description

Figure 1 illustrates a device 10 for reducing fan-generated noise according to the present invention.

The device 10 is associated with a fan 1 1 that is a source of noise propagating as schematized. The device 10 may also be associated with more than one fan.

The device 10 is intended to limit the propagation of the acoustic field 12 generated by the fan 1 1 towards an outer receiver; therefore, the device 10 has remarkable validity in industrial and/or domestic applications.

In particular, the device 10 according to the present invention is configured for being arranged with its main development plane that is orthogonal to a main propagation direction of the noise generated by the fan 1 1.

Thus, the device 10 is configured for being associated with an opening of a fan casing or with a duct 13, in fluidic connection with the fan 1 1, being preferably transversally positioned in said opening or duct 13.

Figure 2 illustrates a first embodiment 101 of a device 10 for reducing fan-generated noise according to the present invention.

In the following figures, if a plurality of analogous elements is present (for instance, grid elements, empty portions, side walls, cavities, etc.), only one of them will be indicated by a reference number, for greater clarity; the other analogous elements, though not indicated by a specific reference number, will have to be intended as recomprised by analogy.

The device 101 comprises a plurality of grid elements 201 connected to each other, which will be further described. Said grid elements 201 are configured for constituting a bearing structure of the device 101.

The device 101 then comprises empty portions 202 delimited by the grid elements 201, which are configured for the passage of an air flow through the device 101.

The existence of a percentage “of voids” represented by the empty portions 202 ensures the passage and thus the air flow, through the device 101. This characteristic is particularly advantageous for applications in which the air flow is crucial, as most applications involving a fan, such as the fan 1 1 associated with the device 10.

Preferably, in the device 10 according to the present invention, the empty portions 202 have dimensions that are relatively greater towards the center of the device, for increasing said air flow, with respect to the dimensions towards the periphery of the device.

Furthermore, advantageously, the grid elements 201 are further configured as a safety for preventing accidental access to the fan 1 1 , by an operator’s hand, or tools or anything else.

The device 10 has an overall substantially circular shape 101, having a substantially circular outer edge 203.

In the present disclosure, the term“substantially circular” will refer to any shape associated to the device 10, which may be a circular shape or may also be a shape which closely resembles the circular one.

Examples of “substantially circular” shape include, for instance: circular, elliptical, or polygonal having a large number of sides (i.e. five or more sides), either regular or irregular based on size requirements or even on aesthetic considerations.

In other words, these “substantially circular” shapes represent continuous or discrete approximation of properly circular shapes.

Figure 3 illustrates the grid elements 201 of the device 101.

The grid elements 201 identify a main development plane of the device 101, namely the plane whereon the device 10 is placed predominantly, intuitively the transversal plane that is coincident with the view in Figure 3.

Each of the grid elements 201 comprises a respective inner cavity delimited by side walls, which will be further described. Indeed, in order to define the noise-reduction property and to trigger the sound- absorption mechanism, the grid elements 201 provide inner cavities each having at least one respective opening, in particular located in the division perimeter between the areas filled in by the grid elements 201 and the above-described empty portions 202.

In this way, the grid elements 201 essentially constitute tubes acting as acoustic resonant cavities and thus sound-absorbing. The delimitation of these tubes is represented not only by the two sets of inner and outer surfaces of the grid elements 201, but also by the division perimeter with the already described open portions 202.

Thus, the grid elements 201 may be tubes that are open on both ends, namely tubes comprising two respective openings that are opposite each other. The grid elements 201 may also be tubes open on one end, namely tubes comprising only one respective opening.

As it will be described, in any case the tubes represented by the grid elements 201 act as acoustic resonant cavities, having the one or more openings that are substantially orthogonal to the main development plane of the device 10, namely substantially aligned to the predominant direction of an air flow passing through the device 10.

First grid elements 201 of all the grid elements of the device 10 have their main direction of development which is aligned to the outer edge 203. In that, the first grid elements 201 are tangentially arranged and aligned with each other, on concentric circumferences, in the substantially circular overall shape 101.

In particular, the grid elements 201 have curved bodies shaped as circumference arcs, and are tangentially arranged with a staggered configuration, to provide a radial contact interface between radially adjacent grid elements 201 of different concentric circumferences.

Preferably, in the embodiment 101 and in further embodiments described hereinafter, the grid elements 201 delimit larger empty portions 202 in a central zone of the substantially circular overall shape 101. Figure 4 illustrates a three-dimensional view of the grid elements 201 of Figure 3.

In this view, it is possible to appreciate that the side walls of each of the grid elements 201 define a tube opening 401, facing one respective of the empty portions 202 and substantially orthogonal to the main development plane of the device 10.

When hit by a flow passing through the device 10, the tube opening 401 is substantially parallel to the flow direction and the cavity of each tube element is at least partially lying on a plane that is perpendicular to the flow direction. The inner cavity of the grid elements 201 is thus acoustic resonant, and adapted to reduce the fan-generated noise, by an acoustic damping effect.

In particular, the inner cavity of the grid elements 201 develops along the main development plane of the device 10.

In a variant (not represented) the grid elements 201 may comprise two respective tube openings 401, opposite each other, on ends of the grid element 201 which form an open-tube cavity.

The device of the present invention is particularly suitable for reducing particular frequencies of a sound field, based on the dimensional characteristics of the inner cavities, which may be defined in the design phase.

The device of the present invention is thus particularly effective in case of fan-generated noise, which has certain tonal characteristics given by the dimensional and operating parameters of the impeller.

Figure 5 illustrates a cut-through part of the grid elements 201 of Figure 4.

In this view it is possible to appreciate the inner cavity 501 of the grid elements 201. In particular, an end wall 502 between the side walls of the grid elements 201, which is opposite the tube opening 401, is closed in this preferred embodiment.

Preferably, in case of two grid elements 201 adjacent to each other, it is provided for them to be adjoined at the respective end walls 502, thus defining a closure between their two respective inner cavities 501. More preferably, the two inner cavities 501 of the grid elements 201 adjoined at the respective end walls 502 are of equal length with each other.

In other words, considering a tube equivalent to the combination of the two grid elements 201 adjoined at the respective end walls 502, said equivalent tube preferably has an intermediate closure, at its middle section.

In a variant (not represented) the inner cavity of the grid elements may further develop in space, namely outside the main development plane of the device 10; indeed, the determining characteristic for the resonant properties is essentially the length of the inner cavity, whereas its arrangement in space or trajectory may further be modified based on design criteria.

Figure 6 illustrates the grid elements of a second embodiment 102 of a device 10 for reducing fan-generated noise according to the present invention.

Preferably, the device 10 has an overall circular shape. For an overall substantially circular shape such as that of the embodiment 102, the first grid elements 201 are tangentially arranged and aligned with each other on concentric circumferences in the overall shape.

Again, first grid elements 201 of all the grid elements of the device 10 have their main direction of development which is aligned to the outer edge 203. In that, the first grid elements 201 are tangentially arranged and aligned with each other, on concentric circumferences, in the substantially circular overall shape 102. Figure 7 illustrates a side view of the grid elements 201 of Figure 6.

In this view it is possible to appreciate that said grid elements 201 are mechanically connected to each other, and thus configured for constituting a bearing structure of the device 101, in particular having a three-dimensional development in space of the‘pyramid’ type. In any case, even for embodiment 102 the main development plane of the device 10 is definable as a plane transversal to the view of Figure 7, namely parallel to the view of Figure 6.

Figure 8 illustrates a cut-through part of the grid elements of Figure 6, in a three-dimensional view.

Even in this view it is possible to appreciate the inner cavity 501 of the grid elements 201.

Figure 9 illustrates a third embodiment 103 of a device 10 for reducing fan-generated noise according to the present invention.

The device 10 comprises a plurality of grid elements 201 connected to each other and empty portions 202 delimited by the grid elements 201, which are configured for the passage of an air flow through the device 103.

The grid elements 201 delimit larger empty portions 202 in a central zone of the substantially circular overall shape 103, 104. In particular, in embodiment 103 the device 10 comprises a central empty portion 901, configured for maximizing the air flow.

Figure 10 illustrates the grid elements 201 of the device of Figure 9.

In addition to the already described grid elements 201, the device 103 comprises second grid elements 902 having their main development direction radially to an outer edge of the overall shape of the device 10, in particular being radially arranged in the circular overall shape 103.

Preferably, the second grid elements 902 further provide a radial frame within the substantially circular overall shape 103, so as to improve structural stability of a bearing structure of the device 10.

In the embodiment 103 of device, but also in the other described embodiments 101, 102 and 104 although not explicitly indicated in the figures, the grid elements 201 comprise at least a first group of inner first grid elements 91 1, which are closer to a center of the substantially circular overall shape 103.

Moreover, the grid elements 201 further comprise at least a second group of outer first grid elements 913, closer to the substantially circular outer edge 203.

More preferably, the first group of inner first grid elements 91 1 comprise inner cavities which are of shorter length 912 than a length 914 of inner cavities of the second group of outer first grid elements 913.

Thus, the first group 91 1 and the second group 913 of grid elements provide different acoustic resonant inner cavities, so as to reduce a wider frequency spectrum of fan-generated noise.

In general, a larger number of groups, i.e. three or more groups, of grid elements may be preferably provided, each having grid elements with cavities of different lengths so as to reduce a wider frequency spectrum of fan-generated noise.

In this view, it is possible to appreciate that the second grid elements 902 preferably comprise an inner cavity 903 having a tube opening 401 , facing one respective of the empty portions 202 and substantially orthogonal to the main development plane of the device 10, and further comprise an end wall 502 between the side walls of the grid elements 201, which is opposite the tube opening 401, and is closed. Preferably, the inner cavity 903 is acoustic resonant for further reducing the fan generated noise.

Figure 12 illustrates the grid elements of a fourth embodiment 104 of a device 10 for reducing fan-generated noise according to the present invention. In this embodiment 104, at least one of the side walls of the inner cavity, preferably one or both side walls parallel to the main development plane comprise one or more holes or slits 1201.

Said holes or slits 1201 are configured for increasing an acoustic field damping, thus increasing the reduction effectiveness of the fan generated noise.

Preferably, the distribution density of said holes or slits 1201 increases for grid elements that are closer to the center of said device, so as to have a greater number of holes or slits in areas where an air flow has locally higher speeds.

In other words, both the surface of the grid elements facing the fan and the opposite one, or any surface that may be inserted between these two surfaces without compromising the sound-absorption mechanism, may be equipped with holes or slits, so as to increase the acoustic filed damping and thus the sound-absorption property of the grid.

Even in this view it is possible to appreciate the inner cavity 501 of the grid elements 201, which constitutes a resonant configuration assisted by the holes or slits 1201.

Industrial applicability

Advantageously, the present invention allows performing an effect on the acoustic field radiated by a fan, though maintaining chances of air flow coming from the fan.

Among the applications of the present invention, there are ventilation, air conditioning, de-humidification, cooling or heating, and any technical field where fans are present and fan-generated noise shall be reduced. Considering the description herein reported, the skilled person will be in the position to conceive further changes and variants, in order to meet contingent and specific needs.

It is clear that, where there are no technical incompatibilities evident to the skilled person, the configurations of specific elements described with reference to some embodiments can be used in other embodiments herein described.

Therefore, the embodiments herein described are to be intended as non limiting examples of the invention.

Claims

1. Device ( 10) for reducing fan-generated noise, comprising: a plurality of grid elements (201, 902) identifying a main development plane, and empty portions (202) delimited by said grid elements (201, 902) and configured for the passage of an air flow through said device ( 10), wherein each of said grid elements (201, 902) comprises a respective inner cavity (501, 903) delimited by side walls, said side walls defining at least one tube opening (401) facing a respective one of said empty portions (202) and substantially orthogonal to said main development plane, said inner cavity (501, 903) being acoustic resonant for reducing said fan-generated noise, characterized in that: said device ( 10) has a substantially circular overall shape ( 101, 102, 103, 104) having a substantially circular outer edge (203), first grid elements (201) of said grid elements (201, 902) having their main direction of development aligned to said outer edge (203), said first grid elements (201) being tangentially arranged and aligned with each other on concentric circumferences in said substantially circular overall shape ( 101, 102, 103, 104).

2. Device according to claim 1, wherein said side walls define a tube opening (401) and wherein an end wall (502) of said side walls, opposite said tube opening (401), is closed.

3. Device according to claim 2, wherein two grid elements (201) adjacent to each other are adjoined at respective end walls (502), defining a closure between two respective inner cavities (501).

4. Device according to claim 3, wherein said two inner cavities (501) of said two grid elements (201) adjacent to each other are of equal length.

5. Device according to any one of claims 1 to 4, wherein said first grid elements (201) comprise at least a first group of inner first grid elements (91 1) closer to a center of said substantially circular overall shape ( 101, 102, 103, 104), and further comprise at least a second group of outer first grid elements (913) closer to said substantially circular outer edge (203), wherein said first group and said second group provide different acoustic resonant inner cavities, so as to reduce a wider frequency spectrum of said fan-generated noise.

6. Device according to claim 5, wherein said first group of inner first grid elements (91 1) comprise inner cavities which are of shorter length (912) than a length (914) of inner cavities of said second group of outer first grid elements (913).

7. Device according to any one of claims 1 to 6, wherein said inner cavity (501, 903) develops along said main development plane.

8. Device according to claim 7, wherein said inner cavity further develops in space, outside said main development plane.

9. Device according to any one of claims 1 to 8, wherein second grid elements (902) of said grid elements (201, 902) have their main development direction radially to said substantially circular outer edge (203), in particular being radially arranged in said substantially circular overall shape ( 103).

10. Device according to claim 9, wherein said second grid elements (902) comprise a respective inner cavity (903) being acoustic resonant for reducing said fan-generated noise, and further provide a radial frame within said substantially circular overall shape ( 103), so as to improve structural stability of a bearing structure of said device ( 10).

1 1. Device according to any one of claims 1 to 10, wherein at least one of said side walls of said inner cavity (501, 903), preferably at least one of said side walls that is parallel to said main development plane, comprises one or more holes or slits ( 1201) configured for increasing an acoustic field damping of said air flow passing through said device ( 10).

12. Device according to any one of claims 1 to 1 1, wherein said device ( 10) is adapted for being associated with an opening of a fan ( 1 1) casing or with a duct ( 13) in fluidic connection with said fan ( 1 1), and further adapted for being arranged with said main development plane being orthogonal to a main propagation direction of said fan-generated noise.

13. Device according to any one of claims 1 to 12, wherein said grid elements (201) are connected to each other, so as to constitute a bearing structure of said device ( 10).

14. Device according to claim 13, wherein said grid elements (201) have curved bodies shaped as circumference arcs and are tangentially arranged with a staggered configuration, to provide a radial contact interface between grid elements (201) of different concentric circumferences.

15. Device according to any one of claims 1 to 14, wherein said grid elements (201) delimit larger ones of said empty portions (202) in a central zone of said substantially circular overall shape ( 101, 102, 103, 104).