Low temperature gas silencer

Abstract

The object of the present invention is to provide a silencer that does not become brittle at low temperatures even with low-temperature gases, does not cause clogging, and has low resistance. [Solution] The silencer (A1, A2) comprises a gas inlet (4) through which low-temperature gas is introduced, a gas outlet (5) through which the low-temperature gas is discharged, and a gas passage (6) through which the low-temperature gas flows, and is provided with a passage-forming member (1) whose wall surface is made of mesh-like metal, a sound-absorbing material (2) that covers the outer periphery of the passage-forming member, and an exterior material (3) that covers the outer periphery of the sound-absorbing material, thereby reducing the sound emitted from the gas outlet.

Description

[Technical Field]

[0001] This invention relates to a silencer that can be used for low-temperature gas (0°C to -40°C). [Background technology]

[0002] Gas supply equipment such as cold evaporators is known as equipment for storing liquefied gas and supplying vaporized gas, but the noise (release noise) generated when low-temperature gases such as nitrogen and oxygen are released from the gas supply equipment has become a noise problem. As a countermeasure, it is known to install a silencer to reduce the noise of gases emitted from the vehicle (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-80820 Summary of the Invention [Problem to be solved by the invention]

[0004] Gases emitted from automobiles, motorcycles, etc. range from room temperature to high temperature, and vehicle silencers are designed for use in these temperature ranges, so the metal plates used for the exterior of the silencers are not designed in thickness or structure to be used in low temperature ranges. Therefore, if low-temperature gas (0°C to -40°C) or trace amounts of liquefied gas are mixed in, there is a concern that the metal plates may deform due to low-temperature contraction or break due to low-temperature brittleness. Furthermore, conventional silencers for low-temperature applications use containers filled with stainless steel mesh or sintered metal. However, if air gets inside the silencer, the moisture on the stainless steel mesh or sintered metal may freeze and block the gas flow path. This means that the silencer must be constantly monitored while in use, making unmanned operation difficult. Furthermore, these mufflers increase the exhaust pressure upstream of the muffler due to the resistance of the stainless steel mesh or sintered metal inside the muffler, which may affect gas supply equipment (e.g., cold evaporators or other gas supply equipment) and gas supply destination equipment (e.g., vaporizers) located upstream of the muffler. Therefore, an object of the present invention is to provide a silencer that does not become brittle at low temperatures even with low-temperature gases, does not cause clogging, and has low resistance. [Means for solving the problem]

[0005] The silencers (A1, A2) of the present disclosure include: a passage forming member (1) that forms a gas passage (6) having a gas inlet (4) at one end through which a low-temperature gas is introduced and a gas outlet (5) at the other end through which the low-temperature gas is discharged; a sound-absorbing material (2) covering the outer periphery of the passage-forming member; An exterior material (3) that covers the outer periphery of the sound absorbing material; The silencer may include: The shape of the passage-forming member (1) along the gas flow direction may be, for example, one or a combination of one or more of a cylinder, a triangular prism, a square prism, a polygonal prism, a sphere, a cone, a polygonal pyramid, a truncated cone, etc. In other words, the gas passage (6) formed by the passage-forming member (1) also has a similar shape.

[0006] The silencer (A2) of the present disclosure may include at least one bypass wall extending from one wall surface to the other wall surface of the gas passage (6). The shape of the bypass wall may be, for example, one of a rectangular parallelepiped, a cylinder, a triangular prism, a square prism, a polygonal prism, a sphere, a cone, a polygonal pyramid, or a truncated cone, or a combination of one or more of these shapes. The overall shape of the gas passage (6), when viewed from above or from the side along the gas flow direction, may be, for example, one of a linear, U-shaped, Z-shaped, L-shaped, convex, concave, curved, zigzag, and spiral shape, or a combination of one or more of these shapes.

[0007] The silencer (A2) of the present disclosure may further include a decompression chamber (7) therein for reducing the pressure of the low-temperature gas.

[0008] The decompression chamber (7) may include a diffusion plate (11) extending toward the gas inlet (4).

[0009] The passage forming member (1) may be a mesh-like metal material that is resistant to low temperatures caused by the low-temperature gas.

[0010] The sound absorbing material (2) may be rock wool or glass wool, or a mixture of these materials, which are resistant to low temperatures caused by the low-temperature gas.

[0011] The exterior material (3) may be a metal material that strikes or reflects the sound that has passed through the sound absorbing material (2).

[0012] The low temperature gas may be nitrogen gas, oxygen gas, or argon gas.

[0013] The low-temperature gas may have a temperature of 0°C to -40°C. (effect)

[0014] (1) The noise emitted when low-temperature gas is released to the outside can be reduced. In addition, even when low-temperature gas is introduced, damage due to low-temperature brittleness does not occur. (2) The cross-sectional area of ​​the gas passage is large enough, and the gas inlet and outlet are designed to penetrate through the gas passage, so the gas passage is not clogged. In addition, the resistance inside the silencer is small, so there is no impact on the gas supply equipment or gas user equipment located upstream of the silencer. (3) The passage-forming member that forms the gas passage maintains the shape of the sound-absorbing material that surrounds the periphery and prevents the sound-absorbing material from scattering. In addition, because the mesh-like structure has large pores, sound is easily absorbed by the sound-absorbing material. (4) By providing multiple bypass walls in the gas passage, the number of collisions between the generated sound and the sound-absorbing material can be increased, further reducing the emitted sound. (5) By providing a decompression chamber and reducing the pressure of the low-temperature gas, the flow rate of the low-temperature gas can be reduced, and the scattering of sound-absorbing material by the low-temperature gas can be suppressed. (6) The low-temperature gas collides with the diffusion plate in the decompression chamber and diffuses, reducing the flow rate of the low-temperature gas, thereby preventing the sound-absorbing material from scattering due to the low-temperature gas. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a side view of the silencer of the first embodiment. [Figure 2A] FIG. 10 is a top view of the silencer of the second embodiment. [Figure 2B] FIG. 10 is a side view of a silencer according to a second embodiment. [Figure 3] This is a reference example when a gas supply facility, a gas supply destination facility, and a silencer are connected. DETAILED DESCRIPTION OF THE INVENTION

[0016] Several embodiments of the present disclosure are described below. The embodiments described below are examples of the present disclosure. The present disclosure is not limited to the following embodiments and includes various modified forms implemented within the scope of the present disclosure. Note that not all of the configurations described below are essential configurations of the present disclosure. Upstream and downstream are based on the flow direction of fluid (liquid, gas). In the drawings below, the "X direction" refers to the linear direction connecting the gas inlet and gas outlet, the "Y direction" refers to the direction perpendicular to the X direction on the same plane, and the "Z direction" refers to the direction perpendicular to the Y direction on the same plane.

[0017] Silencers A1 and A2 are installed to silence the sound propagating through the gas pipes. Here, "silencing" includes both sound insulation and sound absorption. Also, "sound absorption" means absorbing sound or reducing reflected sound.

[0018] (Embodiment 1) The silencer A1 of the first embodiment will be described with reference to FIG. The silencer A1 includes a passage-forming member 1, a sound-absorbing material 2, an exterior material 3, a gas inlet 4, a gas outlet 5, and a gas passage 6.

[0019] The silencer A1 is installed on the piping on the outlet side of an automatic release valve V1 connected to a gas supply facility such as a cold evaporator (CE). The low-temperature gas obtained by vaporizing the liquefied gas stored in the cold evaporator (CE) passes through the automatic release valve V1 and is introduced into the silencer A1 from the gas inlet 4. At this time, the temperature of the low-temperature gas is about -20°C. The low-temperature gas may be oxygen gas or argon gas, in addition to nitrogen gas, or any other low-temperature gas with a temperature of up to -40°C.

[0020] The passage-forming member 1 penetrates in a straight line from the gas inlet 4 to the gas outlet 5, forming a gas passage 6. The low-temperature gas introduced into the gas inlet 4 flows downstream (toward the gas outlet 5) through the gas passage 6, and is then discharged through the gas outlet 5 to the outside of the silencer A1.

[0021] The gas passage 6 may have one or a combination of two or more of the following shapes: a cylinder, a triangular prism, a square prism, a polygonal prism, a sphere, a cone, a polygonal pyramid, a truncated cone, etc. The cross-sectional shape of the gas passage 6 may be circular or polygonal.

[0022] The passageway forming member 1 may be a mesh-like metal material such as stainless steel. Alternatively, one or more wires may be combined to form a gas passageway in the shape of, for example, a cylinder, triangular prism, square prism, polygonal prism, sphere, cone, polygonal pyramid, or truncated cone. The mesh-like metal material and the wire may be made of stainless steel (e.g., SUS304). When the low-temperature gas is oxygen, copper may be used.

[0023] The sound-absorbing material 2 covers the outer periphery of the passage-forming member 1. The material may be rock wool, glass wool, or a mixture of these. Rock wool and glass wool are porous inorganic materials that have the property of converting the kinetic energy of sound generated by the flow of low-temperature gas into thermal energy and absorbing it. Sound generated by the low-temperature gas passing through the gas passage 6 formed by the passage-forming member 1 enters the pores of the sound-absorbing material 2 through the mesh in the wall of the gas passage 6 and is absorbed.

[0024] The exterior material 3 covers the outer periphery of the sound-absorbing material 2. Sound that passes through the sound-absorbing material 2 is reflected by hitting the inner wall of the exterior material 3, thereby preventing sound from leaking outside. The exterior material 3, which is the outermost part of the silencer (A1, A2), is preferably made of a rust-resistant metal (e.g., stainless steel SUS304) in consideration of being installed outdoors. The sound reflected by the exterior material 3 is again incident on the sound-absorbing material 2 and is absorbed. To reduce the weight of the exterior material 3, the thickness of the metal may be reduced and combined with a polymer material such as rubber to form a two-layer structure. Furthermore, to improve sound-deadening performance, a space may be provided between the sound-absorbing material 2 and the exterior material 3.

[0025] The cross-sectional area of ​​the gas passage 6 is adjusted appropriately according to the flow rate and flow velocity of the low-temperature gas. The cross-sectional area of ​​the gas passage 6 may be the same as or larger than the cross-sectional area of ​​the gas inlet 4. The longer the gas passage 6, the more times the sound comes into contact with the sound-absorbing material, and the more the sound is absorbed, thereby reducing the sound emitted at the gas outlet. Here, the length of the gas passage 6 means the distance the gas flows from the gas inlet 4 to the gas outlet 5. The length of the gas passage 6 is adjusted appropriately according to the required sound-deadening performance.

[0026] In the mesh-like metal material that forms the wall of the passage forming member 1, i.e., the gas passage 6, the larger the mesh pore diameter and the smaller the surface area, the greater the contact area between the sound generated when the low-temperature gas passes through the gas passage 6 and the sound-absorbing material 2 on the periphery, and the easier it is for the sound to be absorbed by the sound-absorbing material 2. In addition, the mesh-like metal material supports the sound-absorbing material 2 on the periphery and prevents the sound-absorbing material 2 from scattering. Therefore, it has sufficient strength to support the sound-absorbing material 2. When the silencer A1 is not operating, moisture in the air may adhere to the surface of the mesh-like metal material on the wall of the gas passage. If a metal with small pores and a large surface area, such as a punched plate, is used, when operation is resumed, the mesh is likely to become clogged due to frozen moisture, which will likely hinder sound absorption by the sound-absorbing material. Therefore, it is preferable that the mesh-like metal material have large pores and a small surface area.

[0027] The sound-absorbing material 2 is placed on the outside of the passage-forming member 1. The greater the flow rate and flow velocity of the low-temperature gas passing through the gas passage 6, the greater the sound (sound pressure) generated. Since the sound-absorbing effect increases as the thickness of the sound-absorbing material 2 increases, the thickness of the sound-absorbing material 2 is adjusted appropriately depending on the frequency to be silenced and the sound pressure. Generally, the wavelength of the sound to be silenced divided by 4 is used as the thickness of the sound-absorbing material 2. For example, if the target sound is 500 Hz, the speed of sound is 343 m / s, and 343÷500÷4=170mm Therefore, the required thickness of the sound-absorbing material 2 is calculated to be 170 mm or more. However, if the exterior material 3 is installed, the number of times the sound comes into contact with the sound-absorbing material increases due to sound reflection, so the thickness can be made thinner than this calculated thickness. Also, by extending the length of the gas passage 6, the number of times the sound is reflected increases, making it possible to further reduce the thickness of the sound-absorbing material 2.

[0028] In order to reliably reflect the sound transmitted through the sound-absorbing material 2, the exterior material 3 is preferably made of a material having sufficient sound insulation properties, such as metal, high-density rubber, or concrete. In addition, in consideration of the fact that it will be installed in an external environment, it is preferable to cover the entire outer periphery of the silencer 1 with the exterior material 3 to create a sealed structure that prevents rainwater from entering from the outside. The silencer A1 may be installed vertically or horizontally with respect to the ground.

[0029] In this embodiment, it is possible to effectively reduce the sound generated by the low-temperature gas flowing through the gas passage 6. In addition, the mesh-like metal material that forms the wall of the gas passage 6 is less likely to become clogged due to freezing of moisture in the air, so contact between the sound and the sound-absorbing material 2 is maintained, and the sound-absorbing function is continuously exerted. By appropriately setting the cross-sectional area of ​​the gas passage, the length of the gas passage, the thickness of the sound-absorbing material 2, and the thickness of the exterior material 3 according to the pressure and flow rate of the low-temperature gas, it is possible to reduce the sound from the gas outlet port 5 to a level (60 dB) equivalent to the surrounding environmental noise. Furthermore, since the low-temperature gas inlet 4 and low-temperature gas outlet 5 of the gas passage 6 pass straight through, resistance is small and there is no effect on the gas supply equipment or gas destination equipment upstream of the silencer.

[0030] In this embodiment, the cross-sectional area of ​​the gas passage 6, the length of the gas passage 6 and the thickness of the sound absorbing material 2 are adjusted in accordance with the flow rate and pressure of the low-temperature gas within a range in which the sound absorbing effect is exhibited.

[0031] (Embodiment 2) The silencer A2 of the second embodiment will be described with reference to Figures 2A and 2B. Figure 2A is a top view of the silencer A2, and Figure 2B is a side view of the silencer A2. The same reference numerals as those in the first embodiment have the same functions, and therefore their description may be omitted. The silencer A2 includes a passage-forming member 1, a sound-absorbing material 2, an exterior material 3, a gas inlet 4, a gas outlet 5, a gas passage 6, a decompression chamber 7, a first detour wall 8, a second detour wall 9, a third detour wall 10, and a diffusion plate 11. The silencer A2 is configured to be able to handle low-temperature gas with a large flow rate and high flow velocity.

[0032] The silencer A2 is installed in the piping downstream of the gas supply destination equipment (for example, a vaporizer) that is connected to a cold evaporator (CE) or the like. The liquefied gas is vaporized in the vaporizer to become a low-temperature gas, which is then introduced into the silencer A2. The temperature of the low-temperature gas when introduced into the silencer A2 is about -20°C. The low-temperature gas may be nitrogen gas, oxygen gas, or argon gas. Other low-temperature gases ranging from 0°C to 40°C may also be used.

[0033] The silencer A2 is provided with a decompression chamber 7 between the gas inlet 4 and the gas outlet 5, which reduces the flow rate of the low-temperature gas and reduces its pressure. The decompression chamber 7 can be provided by dividing the gas passage 6 with a first detour wall 8, which will be described later. The low-temperature gas introduced into the gas inlet 4 is then introduced into the decompression chamber 7, where it is decompressed, passes through the inside of the gas passage 6, and is discharged to the outside through the gas outlet 5. (decompression chamber)

[0034] The cross-sectional area of ​​the decompression chamber 7 is adjusted appropriately according to the flow rate and flow velocity of the low-temperature gas. The cross-sectional area of ​​the decompression chamber 7 may be larger than that of the gas inlet 4. The low-temperature gas introduced from the gas inlet 4 is then released into a larger space, thereby reducing the flow velocity of the low-temperature gas and reducing the pressure. The cross-sectional shape of the decompression chamber 7 may be circular, rectangular, or polygonal. Here, by making the distance from the gas inlet 4 to the first detouring wall 8 sufficiently large, the volume of the decompression chamber 7 increases, creating a large space, which further reduces the flow rate of the low-temperature gas and reduces the pressure. The wall surface of the decompression chamber 7 is formed by the passage forming member 1. The outer periphery of the decompression chamber 7 is covered with a sound absorbing material 2 and an exterior material 3. (Detour wall)

[0035] The low-temperature gas introduced into the decompression chamber 7 has its flow velocity reduced and its pressure reduced, and then collides with the detour wall, changing its direction of travel as it flows through the gas passage 6. The gas passage 6 includes at least one detour wall, and may include multiple detour walls as appropriate. 2A , the first bypass wall 8 extends from one wall surface of the gas passage 6 to the other wall surface. The second bypass wall 9 is provided downstream of the first bypass wall 8 and extends from the other wall surface of the gas passage 6 to one wall surface, and the third bypass wall 10 is provided downstream of the second bypass wall 9 and extends from one wall surface to the other wall surface. The low-temperature gas collides with these bypass walls, changes its direction of travel, and flows downstream of the gas passage 6, and is then discharged to the outside of the silencer A2 through the gas outlet port 5. By providing the gas passage 6 with at least one bypass wall, the distance the low-temperature gas flows becomes longer than in a straight passage, and the area where the low-temperature gas comes into contact with the sound-absorbing material 2 becomes larger, thereby increasing the sound absorption effect and reducing the sound emitted from the gas outlet. The number of detour walls and the length of the gas passage 6 may be adjusted as appropriate depending on the frequency and sound pressure to be silenced. The detour wall is made of the same metal material as the passage-forming member 1, and the sound-absorbing material 2 is installed on its outer periphery. The shape of the detour wall may be, for example, one of a rectangular parallelepiped, a cylinder, a triangular prism, a square prism, a polygonal prism, a sphere, a cone, a polygonal pyramid, or a truncated pyramid, or a combination of one or more of these. The cross-sectional shape of the detour wall on the XY plane may be a circle, a triangle, a rectangle, or any other shape. (diffuser plate)

[0036] The decompression chamber 7 may be provided with a diffusion plate (baffle plate) 11 that extends toward the gas inlet 4 and reduces the flow velocity of the low-temperature gas. The shape of the diffusion plate 11 may be a flat plate or an L-shape. When the low-temperature gas collides with the diffusion plate 11, the flow velocity of the low-temperature gas is reduced and the low-temperature gas is diffused, thereby preventing scattering and deterioration of the sound-absorbing material.

[0037] In this embodiment, the flow velocity of the low-temperature gas introduced into the silencer A2 is reduced in the decompression chamber 7, thereby effectively reducing the noise of the low-temperature gas flowing inside. In addition, by providing at least one bypass wall in the gas passage 6, the number of collisions with the sound-absorbing material increases, reducing the noise at the gas outlet. Furthermore, the low-temperature gas collides with the diffusion plate 11 of the decompression chamber 7, thereby reducing the flow rate of the low-temperature gas, and scattering and deterioration of the sound-absorbing material 2 can be suppressed.

[0038] In this embodiment, the cross-sectional area of ​​the gas passage 6, the volume of the decompression chamber 7, the number of bypass walls, the length of the gas passage 6, and the thickness of the sound-absorbing material 2 are appropriately adjusted within the range in which the sound-absorbing effect is exerted, depending on the flow rate and pressure of the low-temperature gas.

[0039] Example 1 In the configuration of embodiment 1 (FIG. 1), the performance of silencer A1 was confirmed using low-temperature (about -20°C) nitrogen gas. The cross section of gas passage 6 of silencer A1 was circular, and the appearance was cylindrical when the outer periphery was covered with sound-absorbing material 2 and exterior material 3. The passage-forming member 1 forming gas passage 6 was a mesh-like wire mesh with a wire diameter of 0.29 mm and a mesh size (pitch) of 0.98 mm, and was made of SUS304 (stainless steel). Rock wool was used as the sound absorbing material 2, and SUS304 (stainless steel) with a thickness of 2-3 mm was used as the exterior material 3.

[0040] In a cold evaporator storing liquefied nitrogen, the sound pressure was compared before and after a silencer was installed downstream of the automatic release valve. The ambient noise around the silencer installation location was about 54 dB. Before the installation of the silencer, the emitted noise was 96.8 dB, but after the installation of the silencer, the sound pressure was reduced to 60.3 dB, a reduction of about 38%. It was also confirmed that the installation of the silencer did not affect the gas supply equipment upstream of the silencer (for example, a cold evaporator). As the silencer maintained the same silencing performance even after more than a year had passed since its installation, it is believed that the silencer has sufficient durability against low-temperature gases of around -20°C.

[0041] Example 2 In the configuration of embodiment 2 (FIGS. 2A and 2B), the performance of the silencer A2 was confirmed using low-temperature (approximately -20°C) nitrogen gas. The cross-sectional shape of the gas passage 6 of the silencer A2 was rectangular, and the appearance was box-like when the outer periphery was covered with the sound-absorbing material 2 and the exterior material 3. The sound pressure was compared before and after the silencer was installed downstream of the vaporizer connected to the cold evaporator storing liquefied nitrogen. The ambient noise around the installation location of the silencer was approximately 67 dB. Before the silencer was installed, the maximum sound pressure measured was 105.7 dB, but after the silencer was installed, the sound pressure was reduced to 79 dB or less at all frequencies, confirming a reduction of approximately 26% in the maximum sound pressure. It was also confirmed that the installation of the silencer did not affect the gas supply equipment upstream of the silencer (for example, a vaporizer). As the silencer maintained the same silencing performance even more than a year after installation, it is believed that the silencer has sufficient durability against low-temperature gases of around -20°C. [Explanation of symbols]

[0042] 1 Passage forming parts 2. Sound-absorbing material 3. Exterior materials 4 Gas inlet 5 Gas outlet 6 Gas passage 7. Decompression Chamber 8 First detour wall 9 Second detour wall 10 Third detour wall 11 Diffuser CE Cold Evaporator A1 Silencer A2 Silencer

Claims

1. a passage forming member that forms a gas passage having a gas inlet port at one end through which a low-temperature gas is introduced and a gas outlet port at the other end through which the low-temperature gas is discharged; a sound absorbing material covering the outer periphery of the passage forming member; an exterior material that covers the outer periphery of the sound-absorbing material; A silencer comprising:

2. The gas passage is characterized in that it has at least one bypass wall extending from one wall surface to the other wall surface.

2. The silencer of claim 1.

3. 2. The silencer according to claim 1, further comprising a pressure reducing chamber therein for reducing the pressure of said low temperature gas.

4. The silencer of claim 3 , wherein the vacuum chamber includes a diffuser plate extending toward the gas inlet.

5. 2. The silencer according to claim 1, wherein the passage forming member is made of a mesh-like metal material.

6. 2. The silencer according to claim 1, wherein the sound absorbing material is rock wool, glass wool, or a mixture thereof.

7. 2. The silencer according to claim 1, wherein the exterior material is a material that strikes or reflects sound that has passed through the sound-absorbing material.

8. 2. The silencer according to claim 1, wherein the low temperature gas is nitrogen gas, oxygen gas, or argon gas.

9. 2. The silencer according to claim 1, wherein the temperature of the low temperature gas is 0°C to -40°C.

10. 2. The silencer according to claim 1, wherein the silencer reduces the sound pressure at the gas outlet to 79 dB or less when the sound pressure of the ambient sound is 50 dB to 70 dB at a frequency of 250 Hz to 8 kHz.

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