Composite impedance exhaust silencer

Abstract

The invention relates to the field of airflow silencers of engines, in particular to a composite impedance exhaust silencer. The composite impedance exhaust silencer comprises a silencer cavity, an air inlet pipe is arranged at one end of the silencer cavity, an air outlet pipe is arranged at the other end of the silencer cavity, at least two partition plates are arranged in the silencer cavity, and the partition plates are sequentially arranged in the silencer cavity in the length direction of the silencer cavity. The partition plates are arranged in the silencer cavity and divide the silencer cavity into a plurality of cavities, the partition plates are provided with inner insertion pipes used for communicating every two adjacent cavities, sound absorption materials are arranged on the inner walls of the inner insertion pipes, and axial through airflow channels are formed in the sound absorption materials. Air flow flows in from the air inlet of the silencer cavity and flows into the air flow channel with the contracted section under the guidance of the inner insertion pipe, sound waves are reflected, interfered and refracted in the flow channel, meanwhile, the porous sound absorption materials in the flow channel are combined to absorb noise, and the effect of efficiently absorbing the noise is achieved.

Description

Technical Field

[0001] The invention relates to the field of airflow silencers of engines, and in particular to a composite impedance exhaust silencer. Background Art

[0002] Exhaust noise is the main noise source of diesel engines. To obtain good silencer performance, it is necessary to rely on the structure of the muffler and the matching of the diesel engine. Existing mufflers are mainly divided into three types: resistive muffler, reactive muffler and impedance composite muffler. Resistive muffler absorbs noise by installing porous sound-absorbing materials on the inner wall of the pipe where the air flows. It can effectively control medium and high frequency noise, but has poor control effect on low frequency noise. Resistive muffler is to suddenly increase, reduce or change the impedance of the resonance cavity next to the muffler cavity by the pipe cross-section to make the sound waves reflect and interfere, thereby reducing the medium and low frequency noise in the pipe. Impedance composite muffler refers to a muffler that combines the resistive unit structure and the reactive unit structure according to the demand for silencer to obtain a wider silencer frequency band. Since the diesel engine used in the emergency power supply vehicle has a large power, the muffler not only needs to have a high broadband silencer performance, but also needs to have good aerodynamic performance to ensure smooth exhaust. At present, the exhaust muffler used in diesel engines of power supply vehicles is mainly a resistive muffler, which has a narrow muffler frequency band, is difficult to control high-frequency noise, and has a large pressure loss, resulting in a large power loss in the diesel engine.

[0003] The Chinese invention patent application with application publication number CN117167116A and application publication date 2023 / 12 / 05 discloses an impedance composite muffler with multi-frequency noise reduction, including a muffler body, the outer shell part of the muffler body is a double-layer structure, and a sandwich cavity is formed between the outer layer and the inner layer, and a sound-absorbing structure is arranged in the sandwich cavity, and a through hole is arranged in the inner layer; a muffler cavity is formed inside the inner layer of the muffler body, and a barrier structure is provided in the length direction of the muffler cavity, the barrier structure divides the muffler cavity into multiple chambers, and a plurality of inner tubes connecting two adjacent chambers are provided on the barrier structure; an air inlet pipe and an air outlet pipe are provided at both ends of the muffler body. When the airflow enters different chambers through the air inlet pipe and the inner tube, the sound-absorbing structure in the sandwich cavity constitutes a resistive structure that can reduce the medium and high frequency noise in the airflow; the air inlet pipe, the air outlet pipe and the barrier structure form an expanding and contracting gas flow channel, which effectively reduces the medium and low frequency noise; multiple inner tubes are used to connect the chambers, so that the airflow flows smoothly and the pressure loss is small. The acoustic performance and aerodynamic performance of the muffler are simulated and analyzed using simulation software, and it is concluded that the muffler can cover the full frequency band of noise with low pressure loss. The muffler solves the above-mentioned problems of narrow muffler frequency band, difficulty in controlling high-frequency noise, and large pressure loss.

[0004] The muffler is provided with a resistive sound-absorbing structure in the interlayer cavity of the muffler body, and the purpose of noise elimination is achieved through the contact between sound waves and the sound-absorbing structure. However, the inner tube arranged in the muffler cavity extends from the air inlet pipe to the air outlet pipe in the length direction of the muffler cavity. Therefore, when the air flow enters from the air inlet pipe, the air flow will mainly pass through the inner tube due to the guiding effect of the inner tube, and the contact time with the sound-absorbing structure in the interlayer cavity in each chamber is short. Therefore, the utilization rate of the sound-absorbing structure in the interlayer cavity is low, resulting in low sound absorption efficiency in the entire muffler cavity. Summary of the invention

[0005] The object of the present invention is to provide a composite impedance exhaust muffler to solve the problem of low utilization rate of the sound absorption structure in the existing multi-frequency noise reduction impedance composite muffler.

[0006] To achieve the above purpose, the composite impedance exhaust muffler of the present invention adopts the following technical solutions: A composite impedance exhaust silencer comprises a silencer cavity, one end of the silencer cavity is provided with an air inlet pipe, the other end is provided with an air outlet pipe, at least two partitions are provided in the silencer cavity, each of the partitions is arranged in sequence inside the silencer cavity along the length direction of the silencer cavity, and the silencer cavity is divided into different chambers, an inner insert pipe for connecting two adjacent chambers is provided on the partition, the inner wall of the inner insert pipe is provided with sound absorbing material, and the sound absorbing material has an axially through-going airflow channel inside.

[0007] Furthermore, the inner insert tube adopts a double-layer structure, including an inner tube and an outer tube, the outer tube is sleeved outside the inner tube, and an interlayer cavity is formed between the inner and outer tubes, the sound-absorbing material is arranged in the interlayer cavity, and a plurality of through holes are provided on the tube wall of the inner tube, so that the interlayer cavity is connected with the inner cavity of the inner tube through the through holes, and the inner cavity of the inner tube forms the airflow channel.

[0008] Furthermore, the number of inner insert tubes installed on each partition is equal, and the distribution positions of the inner insert tubes on each partition correspond in the axial direction.

[0009] Furthermore, the diameters of the inner insert pipes installed at corresponding positions on each partition are equal.

[0010] Furthermore, a single-layer perforated tube is provided in the chamber between two adjacent partitions, and the single-layer perforated tube connects the inner tubes on the two adjacent partitions to form a resonance cavity sound absorption structure in the chamber where the single-layer perforated tube is located.

[0011] Furthermore, the single-layer perforated tube connects the outer tubes of the inner tubes on two adjacent partitions.

[0012] Furthermore, there are two partitions, which divide the muffler cavity from one end close to the air inlet pipe to the other end to form a first chamber, a second chamber and a third chamber in sequence. The length of the inner tube connecting the first chamber and the second chamber is not equal to the length of the inner tube connecting the second chamber and the third chamber.

[0013] Furthermore, the length of the inner tube connecting the first chamber and the second chamber is greater than the length of the inner tube connecting the second chamber and the third chamber.

[0014] Furthermore, the composite impedance exhaust muffler is a horizontal muffler, and the air inlet pipe and the air outlet pipe are respectively arranged perpendicular to the axis of the muffler cavity.

[0015] Furthermore, a perforated plate is provided at at least one end of the muffler cavity, and a sound absorbing material is provided in the interlayer between the perforated plate and the end plate of the muffler cavity.

[0016] Beneficial effects: The impedance horizontal superstructure exhaust silencer of the present invention is a pioneering invention. Specifically, it includes a silencer cavity, in which at least two partitions are provided, and each partition is sequentially arranged inside the silencer cavity along the length direction of the silencer cavity, so as to divide the silencer cavity into a plurality of chambers, and an inner insert pipe for connecting two adjacent chambers is provided on the partition, and the inner wall of the inner insert pipe is provided with a sound-absorbing material, and an axially through-going airflow channel is formed inside the sound-absorbing material. The airflow flows in from the air inlet of the silencer cavity, and under the guidance of the inner insert pipe, it flows into the gas flow channel with a contracted cross section, and the sound waves are reflected, interfered and refracted in the flow channel, and at the same time, the sound waves are combined with the sound-absorbing material in the flow channel to absorb the noise, which increases the contact time between the sound-absorbing material and the noise compared with the prior art, and achieves the effect of efficient noise absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an embodiment of the impedance horizontal super-structure exhaust muffler of the present invention; Figure 2 for Figure 1 A graph of the transmission loss of noise in the embodiment.

[0018] In the figure: 1. Inlet pipe flange; 2. Inlet pipe; 3. Muffler cavity; 4. Outer pipe; 41. Inner pipe; 5. Sound-absorbing material; 6. Inner pipe; 7. Single-layer perforated pipe; 8. Partition; 9. Perforated plate; 10. Outlet pipe flange; 11. Outlet pipe; 12. First chamber; 13. Second chamber; 14. Third chamber. DETAILED DESCRIPTION

[0019] The present invention sets the inner insert tube as a double-layer structure, and arranges sound-absorbing material in the double-layer structure. Under the guidance of the inner insert tube, the airflow flows into the gas flow channel with a contracted cross-section. While the sound waves are reflected, interfered and refracted in the flow channel, the sound-absorbing material filled between the pipe walls in the flow channel absorbs the noise, thereby achieving an efficient noise reduction effect.

[0020] Based on the above-mentioned inventive concept, the present invention provides a composite impedance exhaust silencer. As a basic solution, the silencer of the present invention includes a silencer cavity 3, one end of the silencer cavity 3 is provided with an air inlet pipe 2, and the other end is provided with an air outlet pipe 11, and at least two partitions 8 are provided in the silencer cavity, and each partition 8 is sequentially arranged inside the silencer cavity 3 along the length direction of the silencer cavity 3, and the silencer cavity 3 is divided into a plurality of chambers, and an inner insert pipe 41 for connecting two adjacent chambers is provided on the partition 8, and the inner wall of the inner insert pipe 41 is provided with a sound absorbing material 5, and an axially through air flow channel is formed inside the sound absorbing material 5. The length, number and aperture of the inner insert pipe 41 may be different on each partition 8, which shall be determined according to the design objectives and acoustic principles of different silencers.

[0021] Because impurities or particulate matter that may be carried in the exhaust airflow of the engine can easily clog and damage the sound-absorbing material 5, a protective barrier is provided on the surface of the sound-absorbing material. Preferably, the inner insert tube 41 adopts a double-layer structure, including an inner tube 6 and an outer tube 4. The outer tube 4 is sleeved on the inner tube 6, and an interlayer cavity is formed between the inner and outer tubes. The sound-absorbing material 5 is arranged in the interlayer cavity. A plurality of through holes are provided on the tube wall of the inner tube 6, so that the interlayer cavity is connected with the inner cavity of the inner tube 6 through the through holes. The inner cavity of the inner tube 6 forms an airflow channel for airflow to pass through. When the airflow passes through the airflow channel, the sound waves are reflected, interfered and refracted in the flow channel, and at the same time, they contact the sound-absorbing material 5 in the interlayer cavity through the through holes in the tube wall of the inner tube 6, thereby achieving the purpose of reducing noise.

[0022] In some embodiments, in order to further reduce the mid- and low-frequency noise, preferably, as Figure 1 As shown, a single-layer perforated pipe 7 is also provided in the muffler cavity 3, and the single-layer perforated pipe 7 is connected to the inner pipe 41 on the two adjacent partitions 8. The inner pipe 41 connects the inner pipes 41 of the two adjacent partitions 8, which is conducive to smooth gas flow and reduces the pressure loss during engine exhaust. The cavity surrounded by the two adjacent partitions 8 and the single-layer perforated pipe 7 form a resonance cavity sound absorption structure, which further reduces the medium and low frequency noise of the airflow.

[0023] The single-layer perforated plate 7 can be connected to the inner tube 6 of the inner tube 41, or to the outer tube 4. Both connection methods can form a resonance cavity sound absorption structure between the cavity surrounded by the two adjacent partitions 8 and the single-layer perforated plate 7 to eliminate medium and low frequency noise. In order to make the gas exhaust of the inner tube 4 smoother and reduce the pressure loss during exhaust, preferably, the single-layer perforated tube 7 connects the outer tube 4 of the inner tube 41 on the two adjacent partitions 8. Under the condition of satisfying the muffler performance, in order to facilitate the installation of the single-layer perforated tube 7, preferably, an equal number of inner tubes 41 are set on each partition 8, and the distribution positions of the inner tubes 41 on each partition 8 correspond in the axial direction. The diameters of the inner tubes 41 corresponding to each other in the axial direction may be equal or unequal. When the diameters of the inner tubes 41 corresponding to each other in the axial direction are unequal, the single-layer perforated tube 7 is installed corresponding to the inner tubes using a tapered tube with different diameters at both ends. However, while satisfying the muffler performance, preferably, the diameters of the inner tubes 41 installed at corresponding positions on each partition 8 are equal. In this case, the single-layer perforated tube 7 is an equal-diameter perforated tube with the same diameter at both ends.

[0024] According to different requirements for muffler performance, the number of baffles 8 can be more than two, and they are arranged in parallel from one end of the air intake pipe 2 to the other end. However, too many baffles 8 will increase the airflow resistance and affect the exhaust efficiency. Preferably, two baffles 8 are provided, and the two baffles 8 divide the muffler cavity 3 from one end close to the air intake pipe 2 to the other end to form the first chamber 12, the second chamber 13 and the third chamber 14, and the chambers are connected by the inner insert tube 41. In some embodiments, the length of the inner insert tube connecting the first chamber 12 and the second chamber 13 is 350mm-400mm, and the length of the inner insert tube connecting the second chamber 13 and the third chamber 14 is 200mm-250mm. In the second chamber 13, the length of the single-layer perforated tube 7 connecting the outer tube wall 4 of the inner insert tube is 50mm-100mm. The length and number of the inner insert tube 41 and the single-layer perforated tube 7 have an important influence on the acoustic performance of the muffler. Preferably, the first chamber 12 and the second chamber 13 are connected by 4 inner tubes 41 with a length of 380 mm, the second chamber 13 and the third chamber 14 are connected by 4 inner tubes 41 with a length of 240 mm, and in the second chamber 13, 4 single-layer perforated tubes 7 with a length of 130 mm are connected to the outer tube wall of the double-layer inner tubes 41 on both sides. The length and number of the inner tubes 41 and the single-layer perforated tubes 7 are set to meet the noise reduction requirements of the 400KW emergency power supply vehicle. In other application scenarios, the number and length of the inner tubes are not limited to this, and can be reasonably selected according to the noise control requirements and the pressure loss limit.

[0025] The positions of the air inlet pipe 2 and the air outlet pipe 11 of the muffler cavity 3 should comprehensively consider the exhaust efficiency and the muffler effect of the muffler. In some embodiments, the air inlet pipe 2 and the air outlet pipe 11 are located on the center line of the muffler cavity 3. Such a position can make the noise and air flow faster. In another embodiment, the air inlet pipe 2 and the air outlet pipe 11 are respectively arranged at the two ends of the muffler cavity 3, and are placed perpendicular to the muffler cavity 3. For the convenience of installation, they are arranged on the same side of the muffler cavity 3. The extended end of the air inlet pipe 2 is equipped with an air inlet pipe flange 1, and the extended end of the air outlet pipe 11 is equipped with an air outlet pipe flange 10. The air inlet pipe flange 1 is used to connect the air inlet pipe 2 with the air outlet pipe of the first-stage exhaust muffler of the diesel generator set, that is, the muffler is a horizontal muffler, so that the airflow can change its flow direction when passing through the muffler, which is helpful for muffler.

[0026] In order to further increase the contact area between the sound wave and the sound absorbing material and improve the noise reduction performance of the muffler, perforated plates 9 are also provided at both ends of the muffler cavity 3, and sound absorbing material 5 is provided in the interlayer between the perforated plate 9 and the end plate of the muffler cavity 3, and the perforated plate 9 is used to support and protect the sound absorbing material 5. The muffler cavity 3 can be set to a structure such as a square tube, but in the high frequency band of noise, the muffler effect of the square muffler may not be as good as that of the circular muffler. Preferably, the muffler cavity 3 is a cylindrical structure, and the perforated plates 9 corresponding to the two ends of the cavity are circular plates.

[0027] In some embodiments, the perforation rate of the inner tube wall of the inner tube 41, the single-layer perforated tube 7 and the perforated plate 9 is 25%-35%, and the perforation diameter is 4mm-6mm. After comprehensively considering the acoustic performance and structural strength of the perforated plate, preferably, the perforation rate of the inner tube 6 of the inner tube, the single-layer perforated tube 7 and the perforated plate 9 is set to 25%, and the perforation diameter is 5mm.

[0028] The sound absorbing material 5 can be a fibrous porous sound absorbing material, such as glass fiber needle felt, rock wool, ultrafine glass wool and other commonly used sound absorbing materials. Of course, the sound absorbing material 5 can also be other new sound absorbing materials. According to different acoustic performance requirements, different types, bulk densities and thicknesses of sound absorbing materials are used.

[0029] In the above preferred embodiment, the through pipe composed of the inner tube 41 inside the muffler cavity 3 and the single-layer perforated plate 7 forms an expanding and contracting gas flow channel with other cavity parts inside the muffler cavity 3. When the airflow flows in the expanding and contracting flow channel, the sound waves will be reflected, interfered and refracted in the flow channel, thereby effectively reducing the medium and low frequency noise; the inner tube 41 adopts a double-layer structure, and the double-layer tube wall is filled with porous sound-absorbing material. The inner tube 6 of the inner tube and the porous sound-absorbing material constitute a resistive structure. When the noise flows through the resistive structure under the guidance of the inner tube 41, the sound waves oscillate back and forth in the gaps of the porous sound-absorbing material 5 and continuously rub against the pore walls of the material to generate heat energy. The heat energy gradually diffuses away from the outer tube wall 4 of the inner tube, and the noise is in the inner tube 41 as the propagation distance increases. And it is constantly attenuated, thus having a good mid- and high-frequency sound-absorbing effect; at the same time, porous sound-absorbing materials 5 are arranged at both ends of the muffler cavity 3, which effectively weaken the regenerated noise generated by the high-speed airflow, and increase the contact area between the sound wave and the sound-absorbing material, so that more sound energy is converted into heat energy and dissipated, further improving the noise reduction performance of the muffler; the second chamber 13 adopts a single-layer perforated tube 7 to connect the inner tube outer tube wall 6, which not only forms a resonant cavity sound-absorbing structure in the second chamber 13, so that the mid- and low-frequency noise is further reduced, but also the airflow flows smoothly under the guidance of the pipeline, reducing the pressure loss; the muffler cavity 3 also has a more complex geometric structure, such as a partition, a perforated plate, an inner tube and its edges and corners, etc. These geometric structures can achieve the sound absorption effect by reflecting, refracting, scattering and absorbing sound waves.

[0030] Based on the above preferred embodiment, COMSOL Multiphysics is used to perform numerical simulation analysis on the acoustic performance and aerodynamic performance of a composite impedance exhaust muffler of the present invention. Figure 2 As shown, the anechoic frequency band can cover the full frequency band of noise, and the transmission loss between 20Hz and 3000Hz is about 40 dB on average, which has excellent anechoic performance; the pressure loss is about 632 Pa, which has good aerodynamic performance.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A composite impedance exhaust muffler, characterized in that: The utility model comprises a muffler cavity, one end of which is provided with an air inlet pipe, and the other end of which is provided with an air outlet pipe. At least two partitions are provided in the muffler cavity, and each of the partitions is sequentially arranged inside the muffler cavity along the length direction of the muffler cavity to divide the muffler cavity into different chambers. An inner tube for connecting two adjacent chambers is provided on the partition, and a sound absorbing material is provided on the inner wall of the inner tube, and an axially through-going airflow channel is provided inside the sound absorbing material.

2. The composite impedance exhaust muffler according to claim 1, characterized in that: The inner insert tube adopts a double-layer structure, including an inner tube and an outer tube. The outer tube is sleeved outside the inner tube to form an interlayer cavity between the inner and outer tubes. The sound-absorbing material is arranged in the interlayer cavity. A plurality of through holes are provided on the tube wall of the inner tube so that the interlayer cavity can communicate with the inner cavity of the inner tube through the through holes. The inner cavity of the inner tube forms the airflow channel.

3. The composite impedance exhaust muffler according to claim 2, characterized in that: The number of the inner insert tubes installed on each partition is equal, and the distribution positions of the inner insert tubes on each partition correspond in the axial direction.

4. The composite impedance exhaust muffler according to claim 3, characterized in that: The diameters of the inner insert pipes installed at corresponding positions on each partition are equal.

5. The composite impedance exhaust muffler according to claim 3 or 4, characterized in that: A single-layer perforated tube is also provided in the chamber between two adjacent partitions, and the single-layer perforated tube is connected to the inner insert tubes on the two adjacent partitions to form a resonance cavity sound absorption structure in the chamber where the single-layer perforated tube is located.

6. The composite impedance exhaust muffler according to claim 5, characterized in that: The single-layer perforated tube is connected to the outer tube of the inner tube on two adjacent partitions.

7. The composite impedance exhaust muffler according to any one of claims 1 to 4, characterized in that: There are two partitions, which divide the muffler cavity from one end close to the air inlet pipe to the other end to form a first chamber, a second chamber and a third chamber. The length of the inner tube connecting the first chamber and the second chamber is different from the length of the inner tube connecting the second chamber and the third chamber.

8. The composite impedance exhaust muffler according to claim 7, characterized in that: The length of the inner tube connecting the first chamber and the second chamber is greater than the length of the inner tube connecting the second chamber and the third chamber.

9. The composite impedance exhaust muffler according to any one of claims 1 to 4, characterized in that: The composite impedance exhaust muffler is a horizontal muffler, and the air inlet pipe and the air outlet pipe are respectively arranged perpendicular to the axis of the muffler cavity.

10. The composite impedance exhaust muffler according to claim 9, characterized in that: At least one end of the muffler cavity is provided with a perforated plate, and a sound absorbing material is provided in the interlayer between the perforated plate and the end plate of the muffler cavity.

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