EP3692264A1

EP3692264A1 - An air silencer connectable to a compressor part of a turbocharger

Info

Publication number: EP3692264A1
Application number: EP17780713.8A
Authority: EP
Inventors: Aleksi KYTÖLÄ
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2017-10-04
Filing date: 2017-10-04
Publication date: 2020-08-12
Anticipated expiration: 2037-10-04
Also published as: EP3692264B1; WO2019068323A1

Abstract

L'invention concerne un atténuateur sonore (24) pouvant être relié à une partie de compresseur (12) d'un turbocompresseur (10), lequel atténuateur sonore comprend une partie de bride (26) comportant un passage d'air (54) configuré de façon à être relié à une ouverture d'admission d'air de la partie de compresseur d'une manière étanche vis-à-vis de l'air, un certain nombre de déflecteurs d'atténuation de bruit (50) étant séparés les uns des autres de façon à former un passage d'air (54) pour un air d'entrée à travers l'atténuateur sonore (24) vers le passage d'air (54), les déflecteurs (50) comprenant une plaque micro-perforée (56.1, 56.2) comportant une micro-perforation (53), et une plaque arrière (60), et un espace (57) disposé entre la plaque micro-perforée (56.1, 56.2) et la plaque arrière (60), l'espace (57) comprenant une matrice d'espacement (58.1, 58.2) réalisant un certain nombre de sous-cavités (64) dans l'espace (57) communiquant fluidiquement avec la micro-perforation (53).A sound attenuator (24) connectable to a compressor part (12) of a turbocharger (10), which sound attenuator comprises a flange portion (26) having a configured air passage (54) so as to be connected to an air inlet opening of the compressor part in airtight manner, a number of noise attenuation baffles (50) being separated therefrom. each other to form an air passage (54) for inlet air through the sound attenuator (24) to the air passage (54), the baffles (50) comprising a micro-wave plate perforation (56.1, 56.2) having a micro-perforation (53), and a backplate (60), and a gap (57) disposed between the micro-perforated plate (56.1, 56.2) and the backplate (60), space (57) comprising a spacer array (58.1, 58.2) providing a number of sub-cavities (64) in the space (57) fluidly communicating with the micro-perforation (53).

Description

An air silencer connectable to a compressor part of a turbocharger

Technical field

[001 ] The present invention relates to an air silencer connectable to a compres- sor part of a turbocharger according to the preamble of claim 1 .

Background art

[002] Internal combustion piston engines are considerable sources of noise to the surroundings. Such engine comprises several separate sources of noise. [003] A compressor wheel of a turbocharger is a significant source for high- frequency engine room noise which is commonly attenuated with an air filter silencer attached to the suction side of the turbocharger. Noise attenuating wool based silencers is commonly used for reducing the noise.

[004] For example US6736238B2 discloses an air intake silencer which com- prises a casing supporting an axially spaced array of three annular noise attenuating baffles each of which defines a central circular aperture centered on the axis of the casing. Each of the baffles are axially separated from each other and from an end cap and end flange, the baffles defining inlet flow passages. Each of the baffles, the end cap, and the end flange have the same general construc- tion comprising a layer of acoustic material sandwiched between a pair of perforated steel support flanges shaped appropriately.

[005] The manner of attaching the silencer to the turbocharger causes the turbocharger to bear all the weight from the silencer, which can cause problems if the whole package starts to vibrate due to engine vibrations and passing flow. A large and heavy silencer can increase the vibrations to the turbocharger which in turn might lead to damaging the turbine or compressor wheels that have a very small clearance to the casing. [006] An object of the invention is to provide smaller and more lightweight noise silencer which still accomplishes desired noise attenuation and pressure loss level.

Disclosure of the Invention

[007] Objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

[008] According to an embodiment of the invention an air silencer connectable to a compressor part of a turbocharger comprises a flange part provided with an air passage configured to be connectable with an air intake opening of the compressor part in an air tight manner, a number of noise attenuating baffles being separated from each other so as to form air passage for an inlet air through the air silencer to the air passage, and wherein the baffles comprise a micro-perfo- rated plate provided with a micro-perforation, and a back plate, and a space arranged between the micro-perforated plate and the back plate, and that the space comprises a spacer matrix providing a number of sub cavities in the space fluidly communicating with the micro-perforation.

[009] According to an embodiment of the invention the sub cavity has an effec- tive diameter De = (4 A)/P, in which A is the cross sectional area and P is the length of the perimeter of the sub cavity. The air silencer is configured to attenuate a selected frequency and the effective diameter is less than half of the wave length of the selected attenuation frequency.

[0010] According to an embodiment of the invention at least one of the baffles in the air silencer comprises a first micro-perforated plate and a second micro-perforated plate and between them a first space partially bordered by the first micro- perforated plate and a second space partially bordered by the second micro-perforated plate, in which the first and the second space are fluidly separated from each other. [001 1 ] According to an embodiment of the invention the first and the second spaces are separated from each other by a common back plate arranged between the first micro-perforated plate and the second micro-perforated plate.

[0012] According to an embodiment of the invention the spacer matrix extends evenly over the area between the back plate and the micro-perforated plate.

[0013] According to an embodiment of the invention the sub cavities of the spacer matrix are fluidly separated from each other.

[0014] According to an embodiment of the invention the spacer matrix comprises a honey-comb structure provided with wall extending perpendicular to the plane of the micro-perforated plate.

[0015] According to an embodiment of the invention the micro-perforated plate comprises circular openings having their diameter < 1 mm.

[0016] According to an embodiment of the invention the micro-perforated plate comprises circular openings having equal diameters, and that a distance be- tween centers of two adjacent openings to the diameter of the opening is less than 0,2.

[0017] According to an embodiment of the invention the micro-perforated plate corn-prises circular openings having equal diameters and equal distance between the openings, and that the ratio of a distance between centers of two ad- jacent openings to the diameter of the opening is less than 0,2.

[0018] According to an embodiment of the invention thickness of the micro-perforated plate is 0,5 - 2 times the diameter of the circular opening.

[0019] According to an embodiment of the invention the depth of the space is 2 - 25 times the diameter of the circular opening. [0020] According to an embodiment of the invention the micro-perforated plate comprises slit openings having their effective diameter < 1 mm [0021 ] According to an embodiment of the invention the flange part provided with central air passage and the noise attenuating baffles are of circular shape provided with central opening coaxial with the flange part, and that the silencer comprises an end cover arranged parallel with and at a distance from the flange part and that the noise attenuating baffles are stacked between the flange part and the end cover.

[0022] According to an embodiment of the invention the noise attenuating baffle is of circular shape provided with central opening coaxial with the flange part, and that radially inner and outer rims of the baffle are gas tightly sealed. [0023] According to an embodiment of the invention the first micro-perforated plate corn-prises openings having a first diameter and the second micro-perforated plate comprises openings having a second diameter, different from the first diameter.

[0024] This provides air silencer for a turbocharger the performance of which is considerably improved. The invention provides significantly wider attenuating bandwidth compared to traditional turbocharger silencers.

[0025] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0026] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates a turbocharger unit provided with an air silencer according to an embodiment of the invention, Figure 2 illustrates a baffle of an air silencer according to another embodiment of the invention, and

Figure 3 illustrates a cross sectional view of the baffle in the figure 2 according to an embodiment of the invention.

Detailed Description of Drawings

[0027] Figure 1 depicts schematically a turbocharger 10 which may be installed in an internal combustion piston engine. There is also shown an enlarged view W of a section relating to an air silencer 24. The turbocharger unit 10 comprises a compressor part 12 and a turbine part 18. The compressor part has an air inlet 14 and an air outlet 16, and the turbine part 18 has an exhaust gas inlet 20 and an exhaust gas outlet 22. The turbine part (turbine wheel, not shown) and the compressor part (compressor wheel, not shown) are mechanically connected by a shaft (not shown) so that the turbine wheel is arranged to rotate the compressor wheel. The turbocharger unit is provided with an inlet air silencer 24 through which the air to be compressed in the compressor part is arranged to flow as depicted by the arrows A. In this application the term silencer means a device which is to at least some extent capable of removing impurities from the gas and additionally or alternatively attenuate noise emitted from the compressor part.

[0028] In the embodiment of figure 1 the air silencer 24 comprises a flange part 26 at its one axial end and an end cover 28 at the opposite axial end, which are arranged parallel at a distance from each other. Between the flange part 26 and the end cover 28 there is arranged an air permeable filter element 30. The filter element 30 is of cylindrical shape and annularly arranged to circumscribe the rim area between the flange part and the end cover and having an axial length equals to the distance between the flange part 26 and the end cover 28. The flange part 26 comprises attaching means for attaching the air silencer 24 in connection with the air inlet of the compressor part 12. The flange part 26 is provided with a cen- tral air passage 32 so that the air, which has flown through the filter element 30 into the air silencer 24, may flow through the air passage 32 to the compressor part 12. [0029] Figure 1 depicts schematically a structure of an air silencer 24 according to an embodiment of the invention. The air silencer comprises a number of baffles 50 arranged one of the other in the axial direction D which correspond the direc- tion of the axis of the turbocharger. The baffles 50 are fixed to the air silencer by means of suitably threaded bars 52, such a stud bolts, which a fixed to the flange part 26. The baffles 50 are arranged such that there is an axial distance between the baffles 50 which form air passages 54 between the baffles 50. The baffles 50 are spaced so that there is a bushing 51 arranged to the bars 52 between each baffle 50, the axial length of which defines the width of the air passage 54. The package of the baffles and the bushings is tightened by the end cover 28 using the threaded bars 52.

[0030] Figure 2 depicts schematically a structure of a two-sided baffle 50 according to an embodiment of the invention showing the successive layers of the baffle 50 as cut-outs inside each other. The baffle 50 is advantageously made of metal. The baffle comprises a first micro-perforated plate 56.1 , provided with a micro- perforation 53, on a face of the baffle 50 along the surface of which the air is arranged to flow in the air silencer. According to an embodiment of the invention the micro-perforation advantageously consists of substantially circular openings. According to another embodiment of the invention the micro-perforation consists of substantially slit-like openings. In the figure 2 the micro-perforation is shown in exaggerated manner by small crosses for illustrative reasons. The next layer in the baffle 50 comprises a space 57 under the first micro-perforated plate 56.1 . Behind the space 57, opposite to the first micro-perforated plate 56.1 , there is a back plate 60 bordering the space 57. The space 57 is closed i.e. sealed in gas tight manner, at the radial edges 50.1 , 50.2 of the baffle 50. There is a first spacer matrix 58.1 arranged into the space 57. The spacer matrix 58 comprises multiple walls 62 extending between the micro-perforated plate 56.1 and back plate 60 so as to form a number of sub cavities 64 into the space 57. On the right side of the baffle 50 in the figure 2 the first spacer matrix 58.1 is presented visible below the first micro-perforated plate 56.1 . This demonstrates that the cross sectional area of each sub cavity 64 is such that more than one opening in the micro-perforation 64 opens into one sub cavity 64. The spacer matrix 58 extends over the area of the space. [0031 ] The next layer in the baffle, being behind the back plate in the figure 2, is the space 57 and after that a second micro-perforated plate 56.2, provided with a micro-perforation. Respectively there is a second spacer matrix 58.2 arranged into the space 57. Similarly to the first spacer matrix 58.1 , the second spacer matrix 58.2 comprises multiple walls 62 extending between the second micro- perforated plate 56.2 and the back plate 60 so as to form a number of sub cavities 64 into the space 57. Also the second spacer matrix 58.2 extends advantageously over the area of the space.

[0032] This way, the baffle 50 comprises the first micro-perforated plate 56.1 and the second micro-perforated plate 56.2 and between them the space 57 partially bordered by the first micro-perforated plate, as well as the second space partially bordered by the second micro-perforated plate 58.2, in which the spaces 57 are separated from each other by the common back plate 60. The space and the sub cavity are empty, i.e. filled only with the air. The sub cavities 64 are fluidly sepa- rated from each other. This way the adjacent sub cavities are not effected by each other and the air space in the sub cavity acts as locally reacting space, meaning that each one of the hole acts like an independent attenuator.

[0033] The first micro-perforated plate 56.1 , the first spacer matrix 58.1 and the back plate 60 form a first noise attenuator and the second micro-perforated plate 56.2, the second spacer matrix 58.2 and the back plate 60 form a second noise attenuator. According to an embodiment of the invention the first and the second attenuators are configured to attenuate noise at different frequency. In practise this means that the air silencer can be effective over wider frequency range.

[0034] As is disclosed in the embodiment of figure 2 the spacer matrix 58 in both of the noise attenuators comprises a honeycomb structure provided with wall extending perpendicular to the plane of the micro-perforated plate 56. Figure 3 shows a partial cross section view Ill-Ill of the figure 2 illustrating the structure of the baffle 50 shown in the figure 2.

[0035] The cross sectional area of the sub cavity defines an effective diameter, which can be defined to be De = (4 A)/P, in which A is the cross sectional area and P is the length of the perimeter of the sub cavity. According to an embodiment of the invention the effective diameter is less than half of the wave length of the selected attenuation frequency. In practical situation the air silencer is dimensioned to according to the selected attenuation frequency which usually is the dominant frequency of the noise. When a turbocharger is operating in normal conditions, the compressor and turbine blade tip rotating speeds are close to the speed of sound. In this case the biggest cause of the noise is at the blade passing frequency BPF originating from the compressor wheel, i.e. the dominant frequency. The blade passing frequency can be calculated by multiplying the number of compressor wheel blades C by the rotating frequency of the turbocharger shaft BPF = C ^■ f_Shan. The invention provides very effective silencer particularly for attenuating noise at the BPF.

[0036] The structure of the spacer matrix may be other than a honeycomb as long as the spacer matrix forms sub cavities which fulfils the condition set the effective diameter above.

[0037] Advantageously the micro-perforated plate comprises circular openings having their diameter < 1 mm.

[0038] At the ends, against the flange part and the end cover 28, the only one sided baffle, comprising only the first noise attenuator, may be used.

[0039] The baffle 50 is comprised of a plate with small holes with a diameter less than 1 mm. The hole operationally attached to a locally reacting sub cavity behind the holes. Attenuation is based on friction losses that occur when the air passes through the small holes and resonance that occurs caused by the sub cavity. The attenuated frequency range is significantly wider compared to a traditional resonator.

[0040] Attenuation bandwidth and intensity can be adjusted by changing diame- ter of the holes, depth of the sub cavity cooperating with the holes, thickness of the perforated plate, and perforation constant, i.e. area of the holes in respect to the area of the plate.

[0041 ] The friction losses occur as the sound waves move through the small holes. The amount of the losses depend on the parameters of the micro-perfo- rated plate and the properties of the fluid (air). The holes (and the perforation constant) need to be small enough so that they restrict the sound waves to propagate through them. Reactance causes the sound waves to resonate through the hole when the sound waves pass through the hole many times, the friction losses caused by the hole are also added many times. [0042] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the in- vention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Claims

1 . An air silencer (24) connectable to a compressor part (12) of a turbo- charger (10) comprising

a flange part (26) provided with an air passage (54) configured to be connectable with an air intake opening of the compressor part in an air tight manner, a number of noise attenuating baffles (50) being separated from each other so as to form air passage (54) for an inlet air through the air silencer (24) to the air passage (54),

characterized in that the baffles (50) comprise a micro-perforated plate (56.1 ,56.2) provided with a micro-perforation (53), and a back plate (60), and a space (57) arranged between the micro-perforated plate (56.1 ,56.2) and the back plate (60), and that the space (57) comprises a spacer matrix (58.1 , 58.2) provid- ing a number of sub cavities (64) in the space (57) fluidly communicating with the micro-perforation (53).

2. An air silencer (24) according to claim 1 , characterized in that the sub cavity (64) has an effective diameter De = (4 A)/P, in which A is the cross sectional area and P is the length of the perimeter of the sub cavity (64) and that the effective diameter is less than half of the wave length of the selected attenuation frequency.

3. An air silencer (24) according to claim 1 , characterized in that at least one of the baffles (50) in the air silencer (24) comprises a first micro-perforated plate (56.1 ,56.2) and a second micro-perforated plate (56.1 ,56.2) and between them a first space (57) partially bordered by the first micro-perforated plate (56.1 ,56.2) and a second space (57) partially bordered by the second micro-perforated plate (56.1 ,56.2), in which the first and the second space (57) are fluidly separated from each other.

4. An air silencer (24) according to claim 3, characterized in that the first and the second spaces are separated from each other by a common back plate (60) arranged between the first micro-perforated plate (56.1 ,56.2) and the second micro-perforated plate (56.1 ,56.2).

5. An air silencer (24) according to claim 1 , characterized in that the spacer matrix (58.1 , 58.2) extends evenly over the area between the back plate (60) and the micro-perforated plate (56.1 , 56.2).

6. An air silencer (24) according to claim 1 , characterized in the sub cavities (64) of the spacer matrix (58.1 , 58.2) are fluidly separated from each other.

7. An air silencer (24) according to claim 1 or 6, characterized in the spacer matrix (58.1 , 58.2) comprises a honeycomb structure provided with wall extend- ing perpendicular to the plane of the micro-perforated plate (56.1 ,56.2).

8. An air silencer (24) according to claim 1 , characterized in that the micro- perforated plate (56.1 , 56.2) comprises circular openings.

9. An air silencer (24) according to claim 8, characterized in that the diameter of the circular openings is < 1 mm.

10. An air silencer (24) according to claim 1 or 8, characterized in that the micro-perforated plate (56.1 , 56.2) comprises circular openings having equal diameters, and that a distance between centers of two adjacent openings to the diameter of the opening is less than 0,2.

1 1 . An air silencer (24) according to claim 1 or 8, characterized in that the micro-perforated plate (56.1 , 56.2) comprises circular openings having equal diameters and equal distance between the openings, and that the ratio of a distance between centers of two adjacent openings to the diameter of the opening is less than 0,2.

12. An air silencer (24) according to claim 10, characterized in that thickness of the micro-perforated plate (56.1 , 56.2) is 0,5 - 2 times the diameter of the circular opening.

13. An air silencer (24) according to claim 1 or 10, characterized in that the depth of the space (57) is 2 - 25 times the diameter of the circular opening.

14. An air silencer (24) according to claim 1 , characterized in that the micro- perforated plate (56.1 , 56.2) comprises slit openings.

15. An air silencer (24) according to claim 1 , characterized in that the flange part (26) provided with central air passage (54) and the noise attenuating baffles (50) are of circular shape provided with central opening coaxial with the flange part (26), and that the silencer (24) comprises an end cover arranged parallel with and at a distance from the flange part (26) and that the noise attenuating baffles (50)are stacked between the flange part (26) and the end cover.

16. An air silencer (24) according to claim 1 , characterized in that the noise attenuating baffle is of circular shape provided with central opening coaxial with the flange part (26), and that radially inner and outer rims of the baffle are gas tightly sealed.

17. An air silencer (24) according to claim 2, characterized in that the first micro-perforated plate (56.1 , 56.2) comprises openings having a first diameter and the second micro-perforated plate (56.1 , 56.2) comprises openings having a second diameter, different from the first diameter.