An active noise reduction intake muffler and a noise reduction method

Abstract

The present invention discloses an active noise reduction intake silencer and a noise reduction method, comprising a silencer shell and a silencer assembly, wherein the silencer shell is provided with a receiving chamber, the silencer assembly is arranged in the receiving chamber, the silencer shell is further provided with an air inlet and an air outlet, the cross section of the receiving chamber gradually increases from the air inlet to the air outlet; the silencer assembly comprises a silencer plate; the silencer plate comprises a plate-shaped vertical strip porous portion, the ends of the vertical strip porous portion are fixedly connected to the silencer shell, and the receiving chamber is divided into a plurality of silencer chambers, the vertical strip porous portion is provided with a filling chamber, the filling chamber is provided with a loudspeaker assembly and a vertical strip sound-absorbing cotton sheet; the vertical strip sound-absorbing cotton sheet is provided with a through hole, the loudspeaker assembly is arranged in the through hole. The silencer can achieve noise reduction of the fan by eliminating the main frequency noise and sound waves in other bands, and reduces the resistance of the silencer so that it can be used in EMUs.

Description

Technical Field

[0001] The present invention relates to the technical field of fan noise reduction, and in particular to an active noise reduction intake muffler and a noise reduction method. Background Art

[0002] Cooling fans are a common component in rail transit vehicles. Existing locomotives and EMUs all use cooling fans as an external air source for forced cooling of traction motors. As rotating impellers, cooling fans generate aerodynamic noise caused by steady and unsteady forces acting on the blades and casing. This is the fan's primary noise source and a significant noise source in rail transit vehicles, considered source noise. The high noise levels of cooling fans have been criticized by users at all levels, including drivers and passengers.

[0003] The cooling fan outlet is connected to the vehicle's cooling duct via a flexible air duct, and the inlet is open. Due to sound propagation, the noise source of an open fan is located at the inlet. Therefore, installing a muffler at the inlet of an open fan effectively reduces noise. Existing imported mufflers used in civilian fans have excessive resistance, increasing the static pressure requirement of the fan. Due to power, size, and weight limitations within the vehicle, they cannot be used directly. Summary of the Invention

[0004] The present invention provides an active noise reduction intake muffler and a noise reduction method, so as to overcome the problem that the resistance of a traditional muffler is too large and it cannot be directly applied to the cooling fan in rail transit vehicles for noise reduction.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] An active noise reduction intake muffler includes a muffler housing and a muffler assembly, wherein the muffler housing is provided with a receiving cavity, the muffler assembly is disposed in the receiving cavity, the muffler housing is further provided with an air inlet and an air outlet, and the cross-section of the receiving cavity gradually increases from the air inlet to the air outlet;

[0007] The muffler assembly includes a muffler plate;

[0008] The silencer plate includes a plate-shaped vertical porous portion, the ends of which are fixedly connected to the silencer shell and divide the accommodating cavity into several silencer cavities. The vertical porous portion is provided with a filling cavity, in which a loudspeaker component and a vertical sound-absorbing cotton sheet are provided; the vertical sound-absorbing cotton sheet is provided with a through hole, and the loudspeaker component is provided in the through hole.

[0009] Furthermore, the muffler shell is composed of four isosceles trapezoidal plates whose oblique sides are connected in pairs.

[0010] Furthermore, one end of the muffler housing close to the air outlet is externally connected with a square flange corresponding to the flange structure of the inlet filter, and the muffler housing and the inlet filter are fixedly connected by bolts;

[0011] One end of the muffler housing close to the air inlet is externally connected with a circular flange corresponding to the threaded hole of the fan volute, and the muffler housing is fixedly connected to the fan volute by bolts.

[0012] Furthermore, the vertical porous portion is perpendicular to the plane where the square flange is located and the plane where the circular flange is located.

[0013] Furthermore, a plurality of groups of the speaker components are evenly spaced apart in the vertical porous portion, each group of the speaker components includes two speakers facing in opposite directions, and each speaker can eliminate noise for the adjacent muffler cavity.

[0014] Furthermore, the vertical porous portion includes two identical trapezoidal porous plates and two rectangular connecting plates with the same width and different lengths. The parallel and opposite sides of the two trapezoidal porous plates are equal in length, and the parallel ends of one trapezoidal porous plate are fixedly connected to the parallel ends of the other trapezoidal porous plate through the connecting plates of corresponding lengths.

[0015] Furthermore, the noise reduction assembly further includes an inner cavity porous portion and an inner cavity sound-absorbing cotton sheet;

[0016] The inner cavity porous part is composed of four isosceles trapezoidal porous plates whose oblique sides are connected in pairs, and a corresponding flange is provided at the end close to the square flange. The muffler shell and the inner cavity porous part are fixedly connected by bolts, and the inner cavity sound-absorbing cotton sheet is arranged between the outer wall of the inner cavity porous part and the inner wall of the muffler shell.

[0017] Furthermore, the vertical porous portion also includes a mounting portion, and the two oblique ends of the trapezoidal porous plate are provided with the mounting portion, and the mounting portion is provided with a mounting hole, and the inner cavity porous portion is provided with a threaded hole corresponding to the mounting hole, and the mounting hole and the threaded hole of the inner cavity porous portion are fixedly connected by bolts to thereby fix the vertical porous portion and the inner cavity porous portion.

[0018] Furthermore, the trapezoidal porous plate is provided with a plurality of circular holes arranged in a ring shape and a plurality of rectangular holes arranged at even intervals.

[0019] A noise reduction method for an active noise reduction intake muffler comprises the following steps:

[0020] S1: Extract two groups of fan signals and obtain corresponding noise signals. One group is the signal at high speed of the fan, and the other group is the signal at low speed of the fan. The high speed is 2840r / min-2970r / min, and the low speed is 1420r / min-1485r / min. The sound frequency of the noise signal is k times the product of the number of fan blades and the speed, f=kzn / 60, where z is the number of blades, n is the operating speed in r / min, and k=1, 2;

[0021] S2: Generate reverse noise signals of corresponding frequencies according to the extracted noise signals, and pre-store the reverse noise signals in the speakers 231 as the frequencies of the reverse sound sources.

[0022] Beneficial effects: The present invention arranges a speaker assembly in the muffler shell to provide a reverse sound source to eliminate the main frequency noise, and arranges vertical sound-absorbing cotton to absorb sound waves in other bands, thereby achieving noise reduction for the fan in a wider frequency band; the muffler shell is arranged to have a structure with a gradually increasing opening from the air inlet to the air outlet, which reduces the resistance of the muffler while improving the noise reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 This is an exploded view of an active noise reduction intake muffler of the present invention;

[0025] Figure 2 This is a schematic structural diagram of an active noise reduction intake muffler according to the present invention;

[0026] Figure 3 Schematic diagram of the structure of the muffler housing in the present invention;

[0027] Figure 4 Schematic diagram of the structure of the porous part of the inner cavity in the present invention;

[0028] Figure 5 Schematic diagram of the structure of the speaker assembly in the present invention;

[0029] Figure 6 Schematic diagram of the structure of the muffler plate in the present invention;

[0030] Figure 7 This is an application diagram of an active noise reduction intake muffler in the present invention.

[0031] In the figure: 1. Muffler shell; 11. Air inlet; 12. Air outlet; 13. Square flange; 14. Round flange; 2. Muffler assembly; 21. Muffler plate; 22. Vertical porous portion; 221. Trapezoidal porous plate; 222. Connecting plate; 223. Mounting portion; 23. Speaker assembly; 231. Speaker; 24. Vertical sound-absorbing cotton sheet; 25. Inner cavity porous portion; 26. Inner cavity sound-absorbing cotton sheet; 3. Inlet filter; 4. Fan volute. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Fan noise is primarily aerodynamic, primarily rotational. Rotational noise is discrete, with its primary acoustic frequency being a multiple of the rotational speed multiplied by the number of blades, with 1st and 2nd frequencies being the primary frequencies. Since the cooling fans used on EMUs utilize motors with fixed frequencies, the speeds of the cooling fans used on EMUs and locomotives are deterministic. That is, for the same fan, the primary frequency corresponding to each fixed speed is fixed. Therefore, the primary frequency noise signal at the operating speed can be pre-tested, and an inverse noise signal of the corresponding frequency can be generated and pre-stored in the speakers for noise reduction.

[0034] This embodiment provides an active noise reduction intake muffler, such as Figures 1 to 6 As shown, it includes a muffler housing 1 and a muffler assembly 2, the muffler housing 1 is provided with a receiving cavity, the muffler assembly 2 is arranged in the receiving cavity, the muffler housing 1 is further provided with an air inlet 11 and an air outlet 12, and the cross-section of the receiving cavity gradually increases from the air inlet 11 to the air outlet 12;

[0035] The end of the muffler housing 1 close to the air outlet 12 is connected to a square flange 13 corresponding to the flange structure of the inlet filter 3, and the muffler housing 1 is fixedly connected to the inlet filter 3 by bolts; the end of the muffler housing 1 close to the air inlet 11 is connected to a circular flange 14 corresponding to the threaded hole of the fan volute 4, and the muffler housing 1 is fixedly connected to the fan volute 4 by bolts.

[0036] Specifically, if Figure 2 As shown, the muffler housing 1 in this embodiment is composed of four isosceles trapezoidal plates with their oblique sides connected in pairs. Figure 7As shown, the cross section of the accommodating cavity, that is, the surface of the muffler housing 1 facing the fan volute 4 is square, and the side length of the square gradually increases in the direction away from the fan volute 4. This structure can gather airflow and thus better reduce noise.

[0037] Specifically, if Figure 6 As shown, the silencer assembly 2 includes a silencer plate 21; the silencer plate 21 includes a plate-shaped vertical porous portion 22, the ends of the vertical porous portion 22 are fixedly connected to the silencer housing 1, and the accommodating cavity is divided into a plurality of silencer cavities, the vertical porous portion 22 is provided with a filling cavity, and a sound-speaking assembly 23 and a vertical sound-absorbing cotton sheet 24 are provided in the filling cavity; the vertical sound-absorbing cotton sheet 24 is provided with a through hole, and the sound-speaking assembly 23 is arranged in the through hole.

[0038] Specifically, if Figure 2 As shown, the silencer plate 21 divides the airflow channel into several independent chambers. The more silencer plates 21 there are, the better the noise reduction effect is, but the resistance to the airflow will increase. Therefore, in this embodiment, in order to reduce the air duct resistance while ensuring the noise reduction effect, preferably, the number of silencer plates 21 is 3, and the accommodating cavity of the muffler housing 1 is divided into 4 silencer cavities.

[0039] Specifically, vertical sound-absorbing cotton sheets 24 are provided to absorb sound waves in other bands, thereby achieving noise reduction of a wider frequency band of the fan and achieving a better noise reduction effect.

[0040] Specifically, if Figure 3 As shown, flanges are provided at both ends of the muffler housing 1. The square flanges 13 facilitate the connection of the muffler to the Figure 7 The inlet filter 3 shown in the figure can evenly introduce the air flow and significantly reduce the air flow noise; the circular flange 14 is convenient for connecting the muffler. Figure 7 The fan volute 4 shown in the figure has a structure that facilitates quick connection and installation, and is also convenient for cleaning and replacement of the inner cavity sound-absorbing cotton sheet 26.

[0041] The vertical porous portion 22 is perpendicular to the plane where the square flange 13 is located and the plane where the circular flange 14 is located.

[0042] Specifically, in this embodiment, the position of the vertical bar muffler portion 22 is set to be parallel to the inflow direction of the cooling air, that is, the contact area between the vertical bar muffler portion 22 and the cooling air is reduced, thereby further reducing the air duct resistance.

[0043] Several groups of the speaker components 23 are evenly spaced in the vertical porous portion 22 . Each group of the speaker components 23 includes two speakers 231 facing in opposite directions. Each speaker 231 can eliminate noise for the adjacent muffler cavity.

[0044] Specifically, if Figure 1 As shown, since the air flow channel is divided into four silencer cavities by three silencer plates 21, in order to achieve the purpose of effective noise reduction, three groups of speaker components 23 are evenly arranged in each vertical porous portion 22, and the ends of the speakers 231 pass through the through holes of the vertical sound-absorbing cotton sheets 24 and are fixed in the vertical porous portion 22. Figure 5 As shown, each group of speaker assemblies 23 includes two independent speakers 231 placed in opposite directions, so that each muffler cavity has at least three speakers 231 for providing reverse sound sources for eliminating the main frequency noise; since the two outermost muffler plates 21 are placed with three groups of speaker assemblies 23 in opposite directions, in order to ensure that the muffler frequency characteristics of each muffler cavity are the same, each muffler cavity has three speakers 231 for providing reverse sound sources. Therefore, in this embodiment, the middle muffler plate 21 is not provided with a speaker assembly 23.

[0045] Specifically, the speaker 231 is provided with a signal receiver, which can receive the fan power supply frequency from the locomotive or the fan high-speed or low-speed signal from the motor car, and play the corresponding reverse audio according to the signal.

[0046] The vertical porous portion 22 includes two identical trapezoidal porous plates 221 and two rectangular connecting plates 222 with the same width and different lengths. The parallel and opposite sides of the two trapezoidal porous plates 221 are equal in length. The parallel ends of one trapezoidal porous plate 221 are fixedly connected to the parallel ends of the other trapezoidal porous plate 221 by the connecting plates 222 of corresponding lengths.

[0047] Specifically, if Figure 6 As shown, two parallel sides of a trapezoidal porous plate 221 and two parallel sides of another trapezoidal porous plate 221 are welded and fixed through two rectangular connecting plates of the same width and different lengths to form a vertical porous portion 22. The porosity of the connecting plate 222 is 0. Since the connecting plate 222 is directly opposite to the airflow, this arrangement can ensure that when air is taken in, the vertical sound-absorbing cotton piece 24 arranged inside the vertical porous portion 22 will not be directly impacted by the airflow, thereby affecting the sound elimination effect.

[0048] The silencer assembly 2 also includes an inner cavity porous portion 25 and an inner cavity sound-absorbing cotton sheet 26; the inner cavity porous portion 25 is composed of four isosceles trapezoidal porous plates with the oblique sides connected in pairs, and a corresponding flange is provided at the end close to the square flange 13. The silencer shell 1 is fixedly connected to the inner cavity porous portion 25 by bolts, and the inner cavity sound-absorbing cotton sheet 26 is arranged between the outer wall of the inner cavity porous portion 25 and the inner wall of the silencer shell 1.

[0049] Specifically, if Figure 1 and Figure 4As shown, the inner wall of the muffler shell 1 is provided with four inner cavity sound-absorbing cotton sheets 26, which absorb sound waves in other bands to achieve better noise reduction effects. The inner cavity sound-absorbing cotton sheets 26 are arranged between the inner cavity porous portion 25 and the inner wall of the muffler shell 1. The inner cavity porous portion 25 matches the structure of the muffler shell 1. The inner cavity porous plate 25 can be installed into the interior of the muffler shell 1. At the same time, the inner cavity porous portion 25 is provided with a flange corresponding to the square flange 13. The two flanges are docked and fixed by bolts to fix the muffler shell 1 to the inner cavity porous plate 25.

[0050] The vertical porous portion 22 also includes a mounting portion 223. The two oblique ends of the trapezoidal porous plate 221 are provided with the mounting portion 223. The mounting portion 223 is provided with a mounting hole. The inner cavity porous portion 25 is provided with a threaded hole corresponding to the mounting hole. The mounting hole and the threaded hole of the inner cavity porous portion 25 are fixedly connected by bolts to fix the vertical porous portion 22 to the inner cavity porous portion 25.

[0051] Specifically, if Figure 6 As shown, a total of four mounting portions 223 are provided at the four oblique ends of the two trapezoidal porous plates 221, two mounting holes are provided on each mounting portion 223, and the inner cavity porous portion 25 is provided with a number of threaded holes corresponding to the mounting holes. Through this arrangement, the vertical strip porous portion 22 is fixedly installed in the inner cavity porous portion 25 to ensure the noise reduction effect.

[0052] The trapezoidal porous plate 221 is provided with a plurality of circular holes arranged in a ring shape and a plurality of rectangular holes arranged at even intervals.

[0053] Specifically, if Figure 6 As shown, a circular hole is provided on the trapezoidal porous plate 221, and the position of the speaker 231 when installed corresponds to the position of the circular hole, ensuring that the sound source emitted by the speaker 231 is smoothly transmitted to reduce noise. Rectangular holes are provided on the trapezoidal porous plate 221 so that the vertical sound-absorbing cotton sheet 24 can fully absorb the noise.

[0054] In this embodiment, the preferred thickness of the sound-absorbing cotton is 30 mm, the thickness of the porous plate is 1.5 mm-3 mm, preferably 2 mm in this embodiment, the opening rate of the porous plate is not less than 20%, and circular holes or square holes can be used. In this embodiment, preferably, 7 mm × 7 mm rectangular holes are used on the vertical porous portion 22, and the hole spacing is 2 mm, and the inner cavity porous portion 25 uses 10 mm × 10 mm rectangular holes, and the hole spacing is 5 mm.

[0055] A noise reduction method for an active noise reduction intake muffler utilizes the active noise reduction intake muffler and includes the following steps:

[0056] S1: Extract two groups of fan signals and obtain corresponding noise signals. One group is the signal at high speed of the fan, and the other group is the signal at low speed of the fan. The high speed is 2840r / min-2970r / min, and the low speed is 1420r / min-1485r / min. The sound frequency of the noise signal is k times the product of the number of fan blades and the speed, f=kzn / 60, where z is the number of blades, n is the operating speed in r / min, and k=1, 2;

[0057] S2: Generate reverse noise signals of corresponding frequencies according to the extracted noise signals, and pre-store the reverse noise signals in the speakers 231 as the frequencies of the reverse sound sources.

[0058] Specifically, the cooling fan on an EMU typically operates at a power supply frequency of 50Hz and 25Hz, employing a three-phase asynchronous motor. The fan has both high and low speeds, with the high speed range being 2840r / min-2970r / min and the low speed range being 1420r / min-1485r / min. In this embodiment, the EMU cooling fan has nine blades, a high speed of 2960r / min and a low speed of 1480r / min. The high speed corresponds to main frequencies of 888Hz and 444Hz, while the low speed corresponds to main frequencies of 444Hz and 222Hz. Therefore, reverse noise signals corresponding to 888Hz, 444Hz, and 222Hz are generated and pre-stored in speaker 231, which then responds to the actual cooling fan speed.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An active noise reduction intake muffler, characterized in that: The muffler shell (1) comprises a muffler housing (1) and a muffler assembly (2), wherein the muffler shell (1) is provided with a housing cavity, the muffler assembly (2) is arranged in the housing cavity, the muffler shell (1) is further provided with an air inlet (11) and an air outlet (12), and the cross section of the housing cavity gradually increases in a direction from the air inlet (11) to the air outlet (12); The muffler assembly (2) includes a muffler plate (21); The muffler plate (21) comprises a plate-shaped vertical porous portion (22), the ends of which are fixedly connected to the muffler housing (1) and divide the accommodating cavity into a plurality of muffler cavities. The vertical porous portion (22) is provided with a filling cavity, in which a sound-speaking component (23) and a vertical sound-absorbing cotton sheet (24) are provided. The vertical sound-absorbing cotton sheet (24) is provided with a through hole, and the sound-speaking component (23) is provided in the through hole.

2. The active noise reduction intake muffler according to claim 1, characterized in that: The muffler housing (1) is composed of four isosceles trapezoidal plates whose oblique sides are connected in pairs.

3. The active noise reduction intake muffler according to claim 2, characterized in that: One end of the muffler housing (1) close to the air outlet (12) is externally connected to a square flange (13) corresponding to the flange structure of the inlet filter (3), and the muffler housing (1) and the inlet filter (3) are fixedly connected by bolts; One end of the muffler housing (1) close to the air inlet (11) is externally connected to a circular flange (14) corresponding to the threaded hole of the fan volute (4), and the muffler housing (1) and the fan volute (4) are fixedly connected by bolts.

4. The active noise reduction intake muffler according to claim 3, characterized in that: The vertical porous portion (22) is perpendicular to the plane where the square flange (13) is located and the plane where the circular flange (14) is located.

5. The active noise reduction intake muffler according to claim 4, characterized in that: Several groups of the speaker assemblies (23) are evenly spaced within the vertical porous portion (22), each group of the speaker assemblies (23) comprising two speakers (231) in opposite directions, and each speaker (231) is capable of eliminating noise for the adjacent muffler cavity.

6. The active noise reduction intake muffler according to claim 5, characterized in that: The vertical porous portion (22) comprises two identical trapezoidal porous plates (221) and two rectangular connecting plates (222) of the same width and different lengths. The parallel and opposite sides of the two trapezoidal porous plates (221) are of equal length. The parallel ends of one trapezoidal porous plate (221) are fixedly connected to the parallel ends of the other trapezoidal porous plate (221) via the connecting plates (222) of corresponding lengths.

7. The active noise reduction intake muffler according to claim 6, characterized in that: The muffler assembly (2) further includes an inner cavity porous portion (25) and an inner cavity sound-absorbing cotton sheet (26); The inner cavity porous part (25) is composed of four isosceles trapezoidal porous plates whose oblique sides are connected in pairs, and a corresponding flange is provided at the end close to the square flange (13). The muffler shell (1) and the inner cavity porous part (25) are fixedly connected by bolts, and the inner cavity sound-absorbing cotton sheet (26) is arranged between the outer wall of the inner cavity porous part (25) and the inner wall of the muffler shell (1).

8. The active noise reduction intake muffler according to claim 7, characterized in that: The vertical porous portion (22) further includes a mounting portion (223), the two oblique ends of the trapezoidal porous plate (221) are provided with the mounting portion (223), the mounting portion (223) is provided with a mounting hole, the inner cavity porous portion (25) is provided with a threaded hole corresponding to the mounting hole, the mounting hole and the threaded hole of the inner cavity porous portion (25) are fixedly connected by bolts, thereby fixing the vertical porous portion (22) and the inner cavity porous portion (25) in connection.

9. The active noise reduction intake muffler according to claim 8, characterized in that: The trapezoidal porous plate (221) is provided with a plurality of circular holes arranged in a ring shape and a plurality of rectangular holes arranged at even intervals.

10. A noise reduction method for an active noise reduction intake muffler, characterized in that: The active noise reduction intake muffler according to any one of claims 1 to 9 is used, and the steps include: S1: Extract two groups of fan signals and obtain corresponding noise signals. One group is the signal at high speed of the fan, and the other group is the signal at low speed of the fan. The high speed is 2840r / min-2970r / min, and the low speed is 1420r / min-1485r / min. The sound frequency of the noise signal is k times the product of the number of fan blades and the speed, f=kzn / 60, where z is the number of blades, n is the operating speed in r / min, and k=1, 2; S2: Generate reverse noise signals of corresponding frequencies according to the extracted noise signals, and pre-store the reverse noise signals in the speakers (231) as the frequencies of the reverse sound sources.

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