A pneumatic silencer based on a helical secondary flow channel

Abstract

This invention proposes a pneumatic silencer based on a helical secondary flow channel, comprising a shell and a mixing chamber and an expansion chamber located within it. The mixing chamber and the expansion chamber are internally connected to form a main flow channel. Several helical structures are evenly distributed between the sidewalls of the mixing chamber and the expansion chamber and the sidewall of the shell, forming a helical secondary flow channel. A sub-flow channel is formed between adjacent helical structures. The mixing chamber is divided into a primary mixing chamber and a secondary mixing chamber located downstream of it. The expansion chamber is connected downstream of the mixing chamber. Several vent holes for connecting the main flow channel and the helical secondary flow channel are respectively provided on the sidewalls of the primary mixing chamber, the secondary mixing chamber, and the expansion chamber. This pneumatic silencer can effectively balance the resistance between the main and secondary flow channels, avoid gas blockage, and maintain flow stability.

Description

Technical Field

[0001] This utility model belongs to the field of acoustic engineering technology, and specifically proposes a pneumatic silencer based on a spiral secondary flow channel. Background Technology

[0002] Noise has a negative impact on human physical and mental health as well as the environment. In the engineering field, when the noise generated during the normal operation of equipment exceeds the tolerance limits of relevant laws and standards, silencers need to be installed to suppress the noise.

[0003] For construction machinery, common noises include mechanical noise and exhaust noise. Mechanical noise typically originates inside the equipment, and noise reduction methods usually involve suppressing noise propagation. Exhaust noise is aerodynamic noise, and its source is generally located outside the equipment, requiring suppression of the noise source's intensity. The two types of noise have different generation principles and suppression methods, corresponding to different silencer structures.

[0004] The installation of silencers should not excessively affect equipment performance. For equipment with airflow, the minimum diameter of the silencer and the flow resistance need to be kept within a reasonable range to ensure normal operation of the equipment.

[0005] Traditional pneumatic silencers typically employ a multi-layered throttling structure. While they offer a compact size and good noise reduction, they often exhibit significant flow resistance, limiting their application. Classic expansion cavity silencers ensure airflow and provide some noise reduction, but they are primarily designed for linear noise and exhibit lower noise reduction efficiency when applied to aerodynamic noise.

[0006] Traditional pneumatic silencers are typically designed for noise reduction in stable flow conditions, where the flow state remains constant over time and noise levels are low. However, in some operating conditions, noise reduction is required for intermittent, impact, and ultra-high-pressure jets. The design principles and mechanical strength of traditional pneumatic silencers are inadequate for these conditions. Traditional pneumatic silencers are mostly small-hole, multi-hole design silencers with a fine internal structure and high flow resistance. The impact of the jet can easily damage this type of silencer structure. Furthermore, the multiple side holes on the surface of traditional pneumatic silencers mean that even after the ultra-high-pressure impact jet has been reduced by the silencer, it still possesses a certain degree of destructive force and may cause environmental pollution; therefore, it cannot be allowed to exit in all directions. Thus, a silencer with airflow primarily directed in one direction needs to be designed. Utility Model Content

[0007] This utility model aims to at least partially solve one of the technical problems in the related art.

[0008] Therefore, this utility model proposes a pneumatic silencer based on a spiral secondary flow channel. By combining a main flow channel with an expansion cavity structure located at the center of the axis and a spiral secondary flow channel located at the edge of the axis and divided into multiple sub-flow channels, the resistance between the main and secondary flow channels can be better balanced, gas blockage can be avoided, and flow stability can be maintained. This allows the silencer to achieve a good effect of reducing aerodynamic noise within a limited volume. At the same time, its flow structure and central aperture can reduce internal flow resistance, and the retention of the central aperture can also meet the material transport needs in practical applications. It is suitable for noise suppression of high-speed flowing gas.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This utility model provides a pneumatic silencer based on a spiral secondary flow channel, including a shell and a mixing chamber and an expansion chamber located therein. The mixing chamber and the expansion chamber are internally connected to form a main flow channel. Several spiral structures are arranged between the sidewalls of the mixing chamber and the expansion chamber and the sidewall of the shell to form a spiral secondary flow channel. A sub-flow channel of the spiral secondary flow channel is formed between two adjacent spiral structures.

[0011] The outer casing has two ends that serve as the air inlet and air outlet of the pneumatic silencer, respectively.

[0012] The mixing chamber is divided into two sections: a primary mixing chamber and a secondary mixing chamber located downstream of it. The side walls of the primary mixing chamber and the secondary mixing chamber are respectively provided with a number of first vent holes and second vent holes for connecting the main flow channel and the spiral secondary flow channel.

[0013] The expansion chamber is connected downstream of the mixing chamber. The sidewall of the expansion chamber has the same diameter as the sidewall of the secondary mixing chamber. The sidewall of the expansion chamber is provided with several third vent holes for connecting the main flow channel and the spiral secondary flow channel.

[0014] In some embodiments, the primary mixing chamber adopts a hollow structure, and a second air inlet concentric with the first air inlet of the air inlet end of the housing is provided at the center of the upstream end of the primary mixing chamber. The outer diameter of the upstream end facing the air inlet end is equal to the inner diameter of the housing.

[0015] In some embodiments, the secondary mixing cavity is a thin-walled rotating body with a uniform cross-section, and its diameter is the same as the diameter at the widest point of the expansion cavity. The inner diameter of the secondary mixing cavity remains unchanged along the airflow direction.

[0016] In some embodiments, the dividing end between the secondary mixing chamber and the primary mixing chamber is a cylinder with a central through hole, the inner diameter of the through hole increases sequentially in the direction of airflow, and the minimum diameter of the through hole is the minimum diameter in the pneumatic silencer.

[0017] In some embodiments, the expansion chamber includes a plurality of bowl-shaped frustum-shaped thin-walled rotating bodies of the same shape, which are equally spaced along the airflow direction. The smallest diameter end of each bowl-shaped frustum-shaped thin-walled rotating body is positioned closer to the mixing chamber than the largest diameter end. Adjacent bowl-shaped frustum-shaped thin-walled rotating bodies are connected by a third sleeve on their respective outer sides. Each third sleeve has a plurality of third vent holes. The air inlet end of the bowl-shaped frustum-shaped thin-walled rotating body located on the upstream side extends into the secondary mixing chamber and is connected to the air outlet end of the secondary mixing chamber. The downstream side of the bowl-shaped frustum-shaped thin-walled rotating body located on the downstream side is provided with a converging structure connected to the third sleeve, and the diameter of the converging structure is slightly smaller than the diameter of the third sleeve.

[0018] In some embodiments, the height of the spiral structure is equal to the net distance between the sidewalls of the mixing chamber and the expansion chamber and the sidewall of the outer shell.

[0019] In some embodiments, the inclination angle of the sub-channel is 15° to 30°, the diameters of the second vent and the third vent are equal, and the radius r of the second vent and the width L of the sub-channel satisfy the condition: 0.25L ≤ r ≤ 0.5L. The sum of the areas of the second vents opened on the sidewall of the secondary mixing chamber accounts for 5% to 20% of the unfolded area of ​​the sidewall of the secondary mixing chamber. Similarly, the sum of the areas of the third vents opened on the sidewall of the expansion chamber accounts for 5% to 20% of the unfolded area of ​​the sidewall of the expansion chamber.

[0020] In some embodiments, the sub-flow is provided with a resistance structure.

[0021] In some embodiments, the resistance structure is a triangular wedge of the same height as the spiral structure, disposed between two adjacent vents within the sub-flow.

[0022] In some embodiments, the outlet end of the housing is provided with an end cap to encapsulate the downstream end of the expansion chamber. The end cap is a blind hole end cap or a multi-hole end cap. The blind hole end cap is provided with only a central hole communicating with the main flow channel, and the multi-hole end cap is provided with a central hole communicating with the main flow channel and a plurality of edge holes evenly arranged around the central hole and communicating with the spiral secondary flow channel.

[0023] Features and beneficial effects of this utility model:

[0024] 1. The main and secondary flow channels have balanced resistance. The outer wall of the main flow channel has enough side holes to connect with the spiral secondary flow channel. When the gas resistance of the main flow channel is too high and the flow is blocked, the gas in the main flow channel can be discharged to the spiral secondary flow channel, and vice versa. This adjusts the gas flow resistance of the main and secondary flow channels to be equal, avoids gas blockage, and maintains flow stability.

[0025] 2. Under suitable operating conditions, the main channel in the form of an expansion cavity can induce a strong shock wave at the outlet, consume airflow energy, reduce airflow speed, and thus effectively suppress aerodynamic noise.

[0026] 3. The spiral secondary flow channel structure is closely attached to the outer wall of the main flow channel, making full use of the limited space inside the muffler, making the overall structural design more compact and improving the noise reduction efficiency of the muffler.

[0027] 4. The addition of the secondary flow channel improves the overall mechanical strength and facilitates processing. During processing, especially 3D printing, the spiral secondary flow channel structure serves as a positioning, guiding, and supporting bracket; at the same time, the guide protrusions of the secondary flow channel can act as fasteners connecting the main flow channel cylinder and the outer wall, improving the structural strength and overall rigidity of the muffler when subjected to airflow impact during operation.

[0028] 5. The secondary flow channel and spiral guide groove, which complement the main flow channel, increase the airflow path and induce the airflow to change direction. This increases the flow path, creates a direction change and generates vortices, thereby improving the overall energy consumption of the silencer and reducing aerodynamic noise.

[0029] 6. The secondary flow channel can guide the airflow to generate vortex flow. When the silencer is connected to other equipment by threads, by controlling the direction of the vortex flow to be consistent with the thread installation, it can play a self-tightening function to prevent vibration from causing the fastening connection to loosen.

[0030] 7. Flow-through design, mainly including: (1) the main channel retains the minimum diameter, (2) the secondary channel maintains a certain flowability (unlike using only the expansion chamber which causes gas to enter the blind end, forcing it to be pressurized and causing the subsequent gas to deflect), the gas can be discharged directly through the secondary channel by replacing the downstream end cap of the silencer. (The application of these two structures) can reduce flow resistance, suppress gas backflow, reduce the maximum working pressure, and help improve the life and working stability of the equipment. At the same time, it plays a role in material transport. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the outer contour of a pneumatic silencer based on a spiral secondary flow channel provided in an embodiment of this utility model;

[0032] Figure 2 yes Figure 1 The diagram shows a cross-sectional view of the pneumatic silencer.

[0033] Figure 3 yes Figure 1 A schematic diagram of the internal noise reduction structure of the pneumatic silencer shown;

[0034] Figure 4 yes Figure 1The diagram shows the structure of the mixing chamber in the pneumatic silencer.

[0035] Figure 5-1 , Figure 5-2 They are Figure 1 The expansion chamber and its cross-sectional view in the pneumatic silencer shown;

[0036] Figure 6-1 , Figure 6-2 , Figure 6-3 They are Figure 1 The diagram shows the unfolded view of the outer wall of the main flow channel, the schematic diagram of the sub-flow channel structural parameters, and the schematic diagram of the resistance structure installed in the sub-flow channel in the pneumatic silencer.

[0037] Figure 7-1 , Figure 7-2 They are set in Figure 1 A perspective view and a cross-sectional view of the blind hole end cap on the downstream side of the pneumatic silencer;

[0038] Figure 7-3 , Figure 7-4 , Figure 7-5 They are set in Figure 1 The diagram shows a perspective view, a cross-sectional view, and an assembly schematic of the porous end cap on the downstream side of the pneumatic silencer with the outer shell and the converging structure.

[0039] In the picture:

[0040] 100. Outer shell; 110. Air inlet end; 111. First air inlet; 120. Air outlet end; 130. End cap; 131. Center hole; 132. Edge hole.

[0041] 200. Mixing chamber; I. ​​Primary mixing chamber; 211. First vent hole; 212. Upstream end; 213. Second air inlet; II. Secondary mixing chamber; 221. Second vent hole; 222. Boundary end; 223. Through hole; 224. Protruding frustum.

[0042] 300, Expansion chamber; 310, Bowl-shaped frustum-shaped thin-walled rotating body; 311, Air inlet end of bowl-shaped frustum-shaped thin-walled rotating body; 320, Third sleeve; 321, Third vent hole; 330, Convergence structure.

[0043] 400. Spiral structure;

[0044] A. Main flow channel, B. Spiral secondary flow channel, B1. Resistance structure. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0046] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0047] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the foundation or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0048] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0049] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] See Figures 1-3 This utility model embodiment provides a pneumatic silencer based on a spiral secondary flow channel, including an outermost shell 100 and a mixing chamber 200 and an expansion chamber 300 arranged sequentially within the shell 100 in the direction of airflow (in this embodiment, the airflow direction is from right to left). The mixing chamber 200 and the expansion chamber 300 are internally connected, forming the main flow channel A of the pneumatic silencer of this embodiment. A plurality of spiral structures 400 are evenly distributed between the sidewalls of the mixing chamber 200 and the expansion chamber 300 and the sidewall of the shell 100, forming the spiral secondary flow channel B of the pneumatic silencer of this embodiment. The space between two adjacent spiral structures 400 is a sub-flow channel of the spiral secondary flow channel B; wherein,

[0051] The outer casing 100 has two ends that serve as the air inlet 110 and air outlet 120 of the pneumatic silencer, respectively.

[0052] The mixing chamber 200 is divided into two sections: a primary mixing chamber I and a secondary mixing chamber II located downstream of it. The primary mixing chamber I adopts a hollow structure, and its side wall is provided with several first vent holes 211. The airflow in the primary mixing chamber I flows into the spiral secondary flow channel B near the air inlet end 110 through the first vent holes 211. The side wall of the secondary mixing chamber II is provided with several second vent holes 221, and the second vent holes 221 are evenly distributed in each sub-flow channel. The main flow channel A located in the secondary mixing chamber II region is connected to the spiral secondary flow channel B through the second vent holes 221.

[0053] An expansion chamber 300 has a sidewall of equal diameter to the sidewall of the secondary mixing chamber II, which is fixedly connected at the joint. The sidewall of the expansion chamber 300 is provided with several third vent holes 321, which are evenly distributed within each sub-channel. These third vent holes 321 connect the main flow channel A and the spiral secondary flow channel B located in the expansion chamber 300 region. The downstream side of the expansion chamber 300 is connected by an end cap 130 located at the outlet end 120. Figure 1 , Figure 2 The end cap 130 is not shown in the diagram. The end cap 130 has an air vent.

[0054] In some embodiments, the housing 100 is a cylindrical first sleeve, the cross-section of which is a concentric circle with equal inner and outer diameters at any position. The air inlet end 110 and the air outlet end 120 of the housing 100 are respectively threaded for connection with other equipment. The air inlet end 110 is provided with a first air inlet 111 at the center, which serves as the main air inlet of the pneumatic silencer in this embodiment.

[0055] In some embodiments, see Figures 1-4The primary mixing chamber I within the mixing chamber 200 is a cylindrical frame with a hollow interior. To ensure mechanical strength, a large enough through-hole (i.e., the sidewall of the frame) is formed on the outer circumference of this frame as a first vent 211. At the center of the upstream end 212 of the primary mixing chamber I, a second air inlet 213 is provided, concentric with the first air inlet 111 of the air inlet end 110 of the outer casing 100. The outer diameter of the upstream end 212 facing the air inlet end 110 is equal to the inner diameter of the outer casing 100, ensuring that all gas delivered by the first air inlet 111 enters the primary mixing chamber I and its downstream components through the second air inlet 213. The gas entering the silencer from the upstream device has a high velocity and energy, and its flow is unstable. The hollow primary mixing chamber I first allows the airflow to expand (after expansion, the pressure and impact force decrease), while simultaneously stabilizing the flow, allowing the downstream silencer components to operate in a better state and achieve better noise reduction. In addition, the primary mixing chamber I also serves as a pre-diversion function. The gas that is squeezed to the outermost part of the cylinder due to expansion will directly enter the secondary flow channel, while the gas that enters the connecting hole between the primary mixing chamber I and the secondary mixing chamber II will enter the main flow channel.

[0056] In some embodiments, see Figures 1-4 The secondary mixing chamber II within the mixing chamber 200 is a thin-walled rotating body with a uniform cross-section. Its diameter is the same as the widest diameter of the expansion chamber 300, manifested as a cylindrical thin-walled second sleeve. The inner and outer diameters of the sidewalls of this second sleeve remain constant along its axial direction. Several circular second vent holes 221 are densely arranged on the second sleeve to connect the main flow channel A and the spiral secondary flow channel B. The boundary 222 between the secondary mixing chamber II and the primary mixing chamber I is a cylinder with a central through hole 223. Considering that the gas pressure in the silencer is the highest in the primary mixing chamber I range, and the primary mixing chamber I experiences the most severe impact, the inner diameter of the through hole 223 is gradually increased in the direction of airflow. That is, the boundary 222 adopts a gradually expanding design, which helps to extend the life of the secondary mixing chamber II. In addition, the gradually expanding design of the boundary 222 helps to force more gas into the spiral secondary flow channel B, and from an aerodynamic point of view, the gradually expanding structure can induce the formation of shock waves, which can dissipate more airflow energy. The minimum diameter of the through-hole 223 is the smallest diameter in the entire silencer, and this minimum diameter is determined by the gas flow rate and velocity entering the silencer. A raised frustum 224 is provided on the upstream side of the through-hole 223 to facilitate positioning of the through-hole 223 during machining. The secondary mixing chamber II, as the upstream of the main flow channel A, primarily serves to further expand and stabilize the airflow, ensuring that the downstream expansion chamber 300 operates in a more stable state to maximize the noise reduction effect. Simultaneously, further outward expansion forces a large amount of gas from the main flow channel A into the spiral secondary flow channel B, acting as a diversion to alleviate blockage in the main flow channel A and improve the noise reduction effect.

[0057] In some embodiments, see Figure 5-1 , Figure 5-2 The expansion chamber 300 includes several bowl-shaped frustum-shaped thin-walled rotating bodies 310 that are equally spaced and identical in shape along the airflow direction. The smallest diameter end of each bowl-shaped frustum-shaped thin-walled rotating body 310 is positioned closer to the mixing chamber 200 than the largest diameter end. Adjacent bowl-shaped frustum-shaped thin-walled rotating bodies 310 are connected by their respective outer third sleeves 320. Each third sleeve 320 has several third vent holes 321 evenly distributed on it for connecting the main flow channel A and the spiral secondary flow channel B. The air inlet end 311 of the bowl-shaped frustum-shaped thin-walled rotating body located on the upstream side extends into the secondary mixing chamber II and is connected to the air outlet end of the secondary mixing chamber II. The downstream side of the bowl-shaped frustum-shaped thin-walled rotating body 310 located on the downstream side is provided with a converging structure 330 connected to the third sleeve 320, and the diameter of the converging structure 330 is slightly smaller than the diameter of the third sleeve 320.

[0058] Furthermore, the inner side of the expansion cavity 300 consists of several equally spaced, equally inclined, and identically shaped bowl-shaped frustum-shaped thin-walled rotating bodies 310. The inner diameter of each bowl-shaped frustum-shaped thin-walled rotating body 310 increases from upstream to downstream, which can better consume gas energy. In this embodiment, the expansion cavity 300 is provided with 5 bowl-shaped frustum-shaped thin-walled rotating bodies 310, which are the main force for exerting the noise reduction effect of the main flow channel A. The third sleeve 320 connected to the outer side of two adjacent bowl-shaped frustum-shaped thin-walled rotating bodies 310 is a cylindrical thin-walled sleeve. The diameter of the third vent hole 321 on the side wall of the third sleeve 320 is the same as the diameter of the second vent hole 221 on the side wall of the secondary mixing cavity II. The third vent hole 321 is used to connect the main flow channel A and the spiral secondary flow channel B, while ensuring the uniformity of the downstream gas. The leftmost cylindrical shell of the expansion cavity 300 is a converging structure 330, which is directly connected to the third sleeve 320. The diameter of the converging structure 330 is slightly smaller than that of the third sleeve 320, so that the gas enters the next device in a converging rather than diffused manner.

[0059] In some embodiments, see Figure 6-1 , Figure 6-2The concentric circular space located inside the outer shell 100 and outside the second and third sleeves 320 is divided by several spiral structures 400 to form a spiral secondary flow channel B. The height of the spiral structure 400 is equal to the inner diameter of the first sleeve minus the outer diameter of the second sleeve. A sub-flow channel is formed within the spiral secondary flow channel B between two adjacent spiral structures 400. The sub-flow channels are not directly connected but are connected through the main flow channel A. The side holes on the second and third sleeves, namely the second vent hole 221 and the third vent hole 321, are all used to connect the main flow channel A and the sub-flow channel, and none are opened on the spiral structure 400. If the walls of the second and third sleeves 320 are unfolded into planar rectangles, the sub-flow channels on the spiral secondary flow channel B are parallelogram-shaped flow channels formed by a series of parallel lines. Given a fixed outer diameter of the second sleeve and a fixed axis length of the helical secondary flow channel B, the sub-flow channel can be fully described by the following parameters: number of strands n, inclination angle θ (i.e., the helix angle of the helical structure), width L, and the radius r and spacing d of the second / third vent holes. The selection range of each parameter is determined by processing capability and precision, and the values ​​are determined by their actual performance. The helical secondary flow channel B reduces airflow energy by changing the airflow direction, increasing the airflow stroke, and inducing vortices. Simultaneously, it generates axial torque as airflow passes through, functioning as a self-spinning tightening mechanism. When the main flow channel A is blocked, the flow resistance increases, creating resistance to downstream gas. Simultaneously, the gas flow is also affected by the upstream pressure differential thrust, resulting in increased gas pressure. The second vent hole 221 and the third vent hole 321 allow gas from the main flow channel A to overflow laterally into the helical secondary flow channel B under the combined action of downstream resistance and upstream thrust; when gas in the helical secondary flow channel B is blocked, it also enters the main flow channel A through a similar path. This maintains the pressure and flow resistance of both the main and secondary flow channels at reasonable levels, thereby improving noise reduction and extending structural lifespan.

[0060] Preferably, θ is taken as 15° to 30°, and r and L satisfy: 0.25L≤r≤0.5L. The sum of the areas of the vent holes opened on the side walls of the second sleeve and the third sleeve accounts for 5% to 20% of the unfolded area of ​​the side walls of the second sleeve and the third sleeve, respectively.

[0061] Optionally, see Figure 6-3 A resistance structure B1 is provided in each sub-channel of the spiral secondary channel B. The resistance structure B1 can be located between two adjacent vent holes of the sub-channel and adopts a triangular wedge with the same height as the spiral structure. It is used to regulate and increase the resistance of the spiral secondary channel B, so as to avoid the spiral secondary channel B having too little resistance, which would cause a large amount of gas from the main channel A to enter the spiral secondary channel B and reduce the noise reduction effect.

[0062] In some embodiments, the downstream end of the housing 100 may be provided with an end cap 130, which includes a blind end cap with a central hole 131 communicating only with the main flow channel A (meaning the spiral secondary flow channel B is a blind hole, see [reference]). Figure 7-1 and Figure 7-2) and a porous end cap containing a central hole 131 and edge holes 132 arranged in a circular array along the axis and connected to the secondary flow channel (see Figure 7-3 , Figure 7-4 and Figure 7-5 When a blind end cap is selected, the airflow passing through the spiral secondary flow channel B is ultimately forced into the main flow channel A via the convergence structure 330. When a multi-hole end cap is selected, the gas flowing through the spiral secondary flow channel B is mainly discharged through the edge hole 132 to control the directionality of noise. The multi-hole end cap and the outer shell 100 are connected by threads, with the threads located on the outer wall of the outer shell 100 and the inner wall of the multi-hole end cap. During assembly, the downstream end of the convergence structure 330 and the outer shell 100 abuts against the limiting part of the multi-hole end cap, and the internal structure can just close the hole of the convergence structure 330 to achieve separate discharge of gas from the main and secondary flow channels.

[0063] The following describes the installation and operation process of the pneumatic silencer provided in the embodiments of this utility model:

[0064] (1) Installation: The pneumatic silencer in this embodiment is connected to the upstream and downstream equipment by tightening the threads at both ends of the housing 100. The leftmost thread can also be directly connected to the atmosphere without being connected to other equipment.

[0065] (2) Working process: After the pneumatic silencer in this embodiment is connected to the upstream equipment, when the upstream equipment is working normally, the incoming flow enters the mixing chamber 200 from the right side. The mixing chamber 200 plays a role in stabilizing the flow, so that the airflow entering the pneumatic silencer but not reaching the downstream structure for silencing is pre-mixed and flows smoothly, preventing it from impacting the subsequent narrower and denser structure. The mixing chamber 200 also plays a role in diverting the flow, so that the gas is divided into two streams that enter the main flow channel A and the spiral secondary flow channel B respectively.

[0066] When this pneumatic silencer is working, the gas flow path of the main flow channel A is as follows: the airflow entering the main flow channel A flows in the "contraction-expansion" structure formed by five rotating bodies, losing energy during compression and expansion; the second and third sleeves are respectively opened with a second vent hole and a third vent hole, which further diverts the high-pressure airflow in the main flow channel A to the spiral secondary flow channel B. (The basis for diverting the gas in the main flow channel A to the spiral secondary flow channel B is based on theoretical calculations and engineering practice. The noise reduction effect of the spiral secondary flow channel B is better than that of the main flow channel A because the main flow channel A has a minimum diameter limitation under operating conditions, while the spiral secondary flow channel B does not have this limitation). The gas in the main flow channel A is directly discharged through the converging structure 330.

[0067] When this pneumatic silencer is working, the gas flow path in the spiral secondary flow channel B is as follows: the gas diverted through the mixing chamber 200 is redirected, compressed, and enters each sub-channel of the spiral secondary flow channel B, vortexing forward along the axis of the sub-channel. Energy is consumed by friction with the wall, vortexing, compression, and the additional resistance structure B1. When the airflow in the spiral secondary flow channel B is blocked due to pressure, it can enter the main flow channel A through the second vent 221 or the third vent 321 to balance the flow resistance and ensure the flow matching relationship between the main and secondary flow channels, thereby maximizing the noise reduction effect. Depending on the selection of the end cap 130, when no end cap is installed or a through-hole end cap is installed, the spiral secondary flow channel B is connected to the atmosphere, and the gas is directly introduced into the atmosphere; when a blind-hole end cap is used, the gas in the spiral secondary flow channel B is forced into the main flow channel A and discharged through the converging structure 330.

[0068] In one specific embodiment of this application, the key parameters are as follows:

[0069] The cylinder has a diameter of 46mm and a length of approximately 170mm.

[0070] The narrowest aperture of the main channel A is 9mm, and the widest aperture is 28mm.

[0071] The number of bowl-shaped frustum-shaped thin-walled rotating bodies in the main channel is 5, with an angle of 35° to the axis.

[0072] The outer diameter of the main flow channel is 34mm, the inner diameter of the cylinder is 42mm, and the corresponding height (or diameter) of the secondary flow channel is 4mm.

[0073] The spiral secondary flow channel B has 4 strands, an angle of 30°, a width L = 4 mm, and a hole spacing of 4 mm.

[0074] Actual measurements showed that when the upstream equipment generates a jet with a total pressure of 100 MPa and the outlet environment is at atmospheric pressure, the embodiment using a 30° spiral secondary flow channel and blind hole end caps can reduce noise by an average of 33 dB in the 90° axial direction, achieving a significant noise reduction effect. Compared with the control group without any structure in the secondary flow channel, the noise reduction performance is improved by more than 8 dB.

[0075] Therefore, by adding a spiral structure to the secondary flow channel to increase the resistance of the secondary flow channel, the resistance matching relationship between the main and secondary flow channels can be adjusted, and the main and secondary flow channels can be connected, which helps to further improve the noise reduction performance of the pneumatic silencer.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application.

Claims

1. A helix-vice-flow-channel-based pneumatic muffler, characterized in that, It includes an outer shell and a mixing chamber and an expansion chamber located therein. The interiors of the mixing chamber and the expansion chamber are connected to form a main flow channel. Several spiral structures are arranged between the sidewalls of the mixing chamber and the expansion chamber and the sidewall of the outer shell to form a spiral secondary flow channel. A sub-flow channel of the spiral secondary flow channel is formed between two adjacent spiral structures. The outer casing has two ends that serve as the air inlet and air outlet of the pneumatic silencer, respectively. The mixing chamber is divided into two sections: a primary mixing chamber and a secondary mixing chamber located downstream of it. The side walls of the primary mixing chamber and the secondary mixing chamber are respectively provided with a number of first vent holes and second vent holes for connecting the main flow channel and the spiral secondary flow channel. The expansion chamber is connected downstream of the mixing chamber. The sidewall of the expansion chamber has the same diameter as the sidewall of the secondary mixing chamber. The sidewall of the expansion chamber is provided with several third vent holes for connecting the main flow channel and the spiral secondary flow channel.

2. The pneumatic muffler of claim 1, wherein, The primary mixing chamber adopts a hollow structure. At the center of the upstream end of the primary mixing chamber, there is a second air inlet concentric with the first air inlet of the air inlet end of the outer shell. The outer diameter of the upstream end facing the air inlet end is equal to the inner diameter of the outer shell.

3. The pneumatic muffler of claim 1, wherein, The secondary mixing chamber is a thin-walled rotating body with a uniform cross-section, and its diameter is the same as the widest diameter of the expansion chamber. The inner diameter of the secondary mixing chamber remains unchanged along the airflow direction.

4. The pneumatic muffler of claim 1, wherein, The boundary between the secondary mixing chamber and the primary mixing chamber is a cylinder with a central through hole. The inner diameter of the through hole increases sequentially in the direction of airflow, and the minimum diameter of the through hole is the minimum diameter in the pneumatic silencer.

5. The pneumatic muffler of claim 1, wherein, The expansion chamber includes several bowl-shaped frustum-shaped thin-walled rotating bodies of the same shape, evenly spaced along the airflow direction. The smallest diameter end of each bowl-shaped frustum-shaped thin-walled rotating body is positioned closer to the mixing chamber than the largest diameter end. Adjacent bowl-shaped frustum-shaped thin-walled rotating bodies are connected by a third sleeve on their outer sides. Each third sleeve has several third vent holes. The air inlet end of the bowl-shaped frustum-shaped thin-walled rotating body located on the upstream side extends into the secondary mixing chamber and connects to the air outlet end of the secondary mixing chamber. The downstream side of the bowl-shaped frustum-shaped thin-walled rotating body located on the downstream side is provided with a converging structure connected to the third sleeve, and the diameter of the converging structure is slightly smaller than the diameter of the third sleeve.

6. The pneumatic muffler of claim 1, wherein, The height of the spiral structure is equal to the net distance between the sidewalls of the mixing chamber and the expansion chamber and the sidewall of the outer shell.

7. The pneumatic muffler of claim 1, wherein, The inclination angle of the sub-channel is 15° to 30°. The diameters of the second and third vents are equal. The radius r of the second vent and the width L of the sub-channel satisfy the condition: 0.25L ≤ r ≤ 0.5L. The sum of the areas of the second vents on the sidewall of the secondary mixing chamber accounts for 5% to 20% of the unfolded area of ​​the sidewall of the secondary mixing chamber. Similarly, the sum of the areas of the third vents on the sidewall of the expansion chamber accounts for 5% to 20% of the unfolded area of ​​the sidewall of the expansion chamber.

8. The pneumatic muffler of claim 1, wherein, The sub-flow is equipped with a resistance structure.

9. The pneumatic muffler of claim 8, wherein, The resistance structure is a triangular wedge with the same height as the spiral structure, and is positioned between two adjacent vents within the sub-flow.

10. The pneumatic muffler of claim 1, wherein, The outlet end of the outer shell is provided with an end cap to encapsulate the downstream end of the expansion chamber. The end cap is either a blind hole end cap or a multi-hole end cap. The blind hole end cap is provided with only a central hole communicating with the main flow channel. The multi-hole end cap is provided with a central hole communicating with the main flow channel and several edge holes evenly arranged around the central hole and communicating with the spiral secondary flow channel.

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