A composite frequency modulation silencer and tuning method thereof

Abstract

The present invention provides a composite frequency modulation muffler and a tuning method thereof, the composite frequency modulation muffler comprises: a fixed component; a micro-perforated component, comprising a micro-perforated tube, at least two fixed plates and a baffle, the micro-perforated component is fixedly arranged in the fixed component, the fixed plate is relatively arranged on the outside of the micro-perforated tube, and is integrally formed with the micro-perforated tube, a plurality of rows of through holes are equidistantly arranged on the micro-perforated tube between the fixed plates, the baffle passes through the fixed plate and slides on the outside of the micro-perforated tube and covers the through holes; an adjustment component, comprising an elastic film and a piezoelectric vibrator coated on the outside of the relatively set fixed plates, the elastic film and the outside of the micro-perforated tube form a resonance cavity 1, the elastic film and the inner wall of the fixed component form a resonance cavity 2, the micro-perforated tube, the resonance cavity 1, the elastic film and the resonance cavity 2 form a closed double-degree-of-freedom muffler system, the piezoelectric vibrator is arranged on the outside of the elastic film, and is electrically connected to a power supply. The present invention can expand the noise control frequency band and achieve effective noise suppression.

Description

Technical Field

[0001] The invention belongs to the technical field of mufflers, and in particular relates to a composite frequency-modulated muffler and a tuning method thereof. Background Art

[0002] A composite silencer is a silencer that combines a resistive silencer and a reactive silencer in a certain way for an airflow duct that also transmits noise.

[0003] In the prior art, among the composite silencers, the perforated tube silencer has a good muffler effect in the medium and high frequency range, but in the low frequency range, the perforated tube requires an extremely low perforation rate or an increased resonance cavity volume, which not only increases the difficulty and cost of processing, but also increases the occupied space, limiting the applicable occasions of the perforated tube silencer structure. The flexible film structure has a better absorption effect on low-frequency noise, and has the advantages of simple structure, easy preparation, and large deformation, but it still has application limitations, such as not being able to efficiently suppress medium and high frequency noise at the same time, and not being suitable for strong vibration and sound excitation, high temperature difference, extremely light additional mass and extremely small additional space requirements. For example, the patent with patent announcement number CN109139191A discloses a micro-perforated resonance cavity muffler structure and a noise reduction muffler for APU, which adopts a large resonance cavity structure, greatly reduces the weight of the equipment, increases the structural rigidity, and weakens the noise intensity transmitted from the APU working state, but its noise control frequency band is fixed, the muffler effect is fixed, and it is impossible to achieve maximum noise suppression through tuning. Summary of the invention

[0004] The purpose of the present invention is to provide a composite frequency modulation silencer and a tuning method thereof, wherein a micro-perforated tube, a first resonance cavity, an elastic film and a second resonance cavity form a closed double-degree-of-freedom silencer system, thereby expanding the noise control frequency band and realizing effective noise suppression.

[0005] The present invention provides the following technical solutions:

[0006] The present application proposes a composite frequency modulation muffler, comprising:

[0007] A fixing assembly for ensuring the sealing of the cointegration chamber;

[0008] A micro-perforation assembly comprises a micro-perforation tube, at least two fixing plates and a baffle, wherein the micro-perforation assembly is fixedly arranged in the fixing assembly, the fixing plates are relatively arranged outside the micro-perforation tube, a plurality of rows of through holes are evenly arranged on the micro-perforation tube between the fixing plates, and the baffle passes through the fixing plates and is slidably arranged outside the micro-perforation tube and covers the through holes, so as to adjust the perforation rate of the micro-perforation tube;

[0009] The regulating component includes an elastic film and a piezoelectric vibrator coated on the outside of a relatively set fixed plate. The elastic film and the outside of a micro-perforated tube form a resonance cavity 1, and the elastic film and the inner wall of the fixed component form a resonance cavity 2 for preventing sound leakage. The resonance cavity 1 and the resonance cavity 2 are filled with air. The micro-perforated tube, the resonance cavity 1, the elastic film and the resonance cavity 2 form a closed double-degree-of-freedom silencer system. The double-degree-of-freedom silencer system includes a main vibration system and an additional system. The piezoelectric vibrator is arranged on the outside of the elastic film and is electrically connected to a power supply. It is used to control the stiffness of the elastic film by adjusting the driving voltage and realize frequency tunability.

[0010] Preferably, the fixing assembly includes two shells connected by flanges, the shells are semi-cylindrical, and grooves are provided on the upper and lower surfaces of the shells relative to each other. A cavity is provided in the shells, and the micro-perforation assembly is provided in the cavity.

[0011] Preferably, the micro-perforated tube is integrally formed with the fixing plate, and the micro-perforated tube comprises an inlet and an outlet.

[0012] Preferably, the fixing plate is inserted into the groove, and the side wall of the groove presses the elastic film, and a plurality of insertion holes are provided on the fixing plate near the inlet side.

[0013] Preferably, a plurality of seals are provided on the side of the baffle plate facing the outlet along the axial direction of the micro-perforated tube, and the seals are matched with the through holes.

[0014] Preferably, the piezoelectric vibrator includes a copper sheet and a zinc sheet, and the piezoelectric vibrator is attached to the outside of the elastic film through silicone.

[0015] Preferably, the air within the resonant cavity is relatively incompressible.

[0016] Based on the above-mentioned composite frequency modulation silencer, the present application also proposes a tuning method using the above-mentioned composite frequency modulation silencer, comprising the following steps:

[0017] S1. The air in the resonant cavity is equivalent to a spring, and the air in the through hole is equivalent to a mass block, which is converted into the first spring mass resonant unit and serves as the main vibration system;

[0018] S2. The mass of the elastic film is equivalent to a mass block, and the tension of the elastic film and the elastic coupling force of the air layer in the second resonance cavity are equivalent to a spring, which is converted into a second spring mass resonance unit and serves as an additional system;

[0019] S3. Both the main vibration system and the additional system have natural frequencies, which are only related to the system equivalent mass and spring stiffness. The expressions of the two are: Among them, M m is the mass of the elastic film, k a is the air spring stiffness in the resonance cavity 1, k mis the elastic membrane stiffness, M h is the equivalent mass of the air through the hole, ω h is the natural frequency of the main vibration system, ω m is the natural frequency of the additional system;

[0020] S4. The equivalent mass of the through-hole air and the equivalent stiffness of the film are: Among them, t′ h =t h +δ,t h is the hole depth, δ is the opening correction, C is the sound velocity, s is the hole cross-sectional area, S is the axial cross-sectional area of ​​the fixed plate in the resonance cavity 1, l1 is the cavity depth, and ρ is the air density;

[0021] S5. By pushing the baffle to adjust the perforation rate, the equivalent mass of the air through the hole in step S4 can be adjusted. By adjusting the driving voltage of the piezoelectric vibrator, the equivalent stiffness of the film in step S4 can be adjusted to control the silencing frequency, that is, to control the transmission loss of the composite tuned muffler;

[0022] S6. The transmission loss of the composite tuned muffler can be controlled by adjusting the total acoustic impedance ratio of the composite tuned muffler surface. The total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio on both sides of the micro-perforated tube, the acoustic impedance ratio between the micro-perforated tube and the elastic film, and the acoustic impedance ratio on both sides of the elastic film. The total acoustic impedance ratio of the composite tuned muffler is:

[0023]

[0024] Where m = sρt′ h is the mass of air in the through hole, c is the viscous resistance of the inner surface of the through hole, ω is the incident angular frequency of the plane acoustic wave, ω2 is the natural angular frequency of the film and the additional cavity, ω f The natural frequency of the film and the stiffness of the air spring in the resonance cavity are l1 is the length of resonant cavity 1, l2 is the length of resonant cavity 2, and the equivalent mass of air is M a1 =ρl1s, the mass of the elastic film is The opening ratio ε is the ratio of the chamber cross-sectional area s to the inner area S of the micro-perforated tube, and η is the loss factor.

[0025] Preferably, the factors affecting the muffler effect of the composite tuned muffler include the structural dimensions of the micro-perforated tube, the material properties and structural properties of the elastic film, and the distance between the elastic film and the micro-perforated tube.

[0026] The beneficial effects of the present invention are:

[0027] 1. Combine the lightweight elastic film structure with the perforated tube muffler to improve the muffler performance of the perforated tube muffler structure in the low frequency domain and the muffler performance of the elastic film on medium and high frequency noise, expand the noise control band, and achieve effective noise suppression, which has important engineering practical value for controlling the composite spectrum noise in the low frequency domain;

[0028] 2. It has two frequency tuning modes, which can flexibly control the silencing frequency by adjusting the perforation rate through the baffle and adjusting the stiffness of the elastic film by controlling the driving voltage;

[0029] 3. The raw materials used are relatively cheap and easy to obtain, the synthesis method is simple, no dangerous or highly toxic reagents or precious metal catalysts are used, the operation is simple and convenient, and the yield of the final product is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 It is a schematic diagram of the structure of the present invention;

[0032] Figure 2 is a schematic diagram of the connection of the regulating components of the present invention;

[0033] Figure 3 It is a schematic diagram of the shell connection of the present invention;

[0034] Figure 4 It is a schematic diagram of the connection of the micro-perforation assembly of the present invention;

[0035] Figure 5 It is a schematic diagram showing the effect of the perforation rate of the present invention;

[0036] Figure 6 It is a schematic diagram of the noise elimination effect under different voltages of the present invention.

[0037] Marked in the figure: 1. Fixed component, 11. Shell, 2. Micro-perforated component, 21. Micro-perforated tube, 211. Through hole, 212. Inlet, 213. Outlet, 22. Fixed plate, 221. Jack, 23. Baffle, 231. Seal, 3. Adjustment component, 31. Elastic film, 32. Piezoelectric vibrator, 33. Resonance cavity one, 34. Resonance cavity two. DETAILED DESCRIPTION

[0038] Embodiment 1

[0039] The present application proposes a composite frequency modulation muffler, comprising:

[0040] The fixing assembly 1 is used to ensure the sealing of the cointegration chamber. The fixing assembly 1 comprises two shells 11 connected by flanges, the shells 11 are semi-cylindrical, and grooves are arranged on the upper and lower surfaces of the shells 11. A cavity is arranged inside the shells 11, and the micro-perforation assembly 2 is arranged in the cavity.

[0041] The micro-perforation assembly 2 comprises a micro-perforation tube 21, at least two fixed plates 22 and a baffle 23. The micro-perforation assembly 2 is fixedly arranged in the fixed assembly 1, and the fixed plates 22 are relatively arranged on the outside of the micro-perforation tube 21. The micro-perforation tube 21 between the fixed plates 22 is provided with multiple rows of through holes 211 at equal intervals. The baffle 23 passes through the fixed plates 22 and is slidably arranged on the outside of the micro-perforation tube 21 and covers the through holes 211, which is used to adjust the perforation rate of the micro-perforation tube 21. The micro-perforation tube 21 and the fixed plates 22 are integrally formed, and the micro-perforation tube 21 comprises an inlet 212 and an outlet 213. The fixed plate 22 is inserted into the groove, and the side wall of the groove presses the elastic film 31. A plurality of jacks 221 are provided on the fixed plate 22 near the inlet 212. A plurality of seals 231 are provided along the axial direction of the micro-perforation tube 21 on the baffle 23 facing the outlet 213, and the seals 231 match the through holes 211.

[0042] The adjustment component 3 includes an elastic film 31 and a piezoelectric vibrator 32 which are coated on the outside of the fixed plate 22 which is relatively set up. The piezoelectric vibrator 32 includes a copper sheet and a zinc sheet, and the piezoelectric vibrator 32 is attached to the outside of the elastic film 31 through silicone. The elastic film 31 and the outside of the micro-perforated tube 21 form a resonance cavity 1 33, and the air in the resonance cavity 1 33 is relatively incompressible. The elastic film 31 and the inner wall of the fixed component 1 form a resonance cavity 2 34, which is used to prevent sound leakage. The resonance cavity 1 33 and the resonance cavity 2 34 are filled with air. The micro-perforated tube 21, the resonance cavity 1 33, the elastic film 31 and the resonance cavity 2 34 form a closed double-degree-of-freedom silencing system, which includes a main vibration system and an additional system. The piezoelectric vibrator 32 is arranged on the outside of the elastic film 31 and is electrically connected to the power supply, which is used to control the stiffness of the elastic film 31 by adjusting the driving voltage and realize frequency tunability.

[0043] Based on the above-mentioned composite frequency modulation silencer, the present application also proposes a tuning method using the above-mentioned composite frequency modulation silencer, comprising the following steps:

[0044] S1. The air in the resonant cavity 33 is equivalent to a spring, and the air in the through hole 211 is equivalent to a mass block, which is converted into a first spring mass resonant unit and serves as the main vibration system;

[0045] S2. The mass of the elastic film 31 is equivalent to a mass block, and the tension of the elastic film 31 and the elastic coupling force of the air layer in the resonant cavity 34 are equivalent to a spring, which is converted into a second spring mass resonance unit and serves as an additional system;

[0046] S3. Both the main vibration system and the additional system have natural frequencies, which are only related to the system equivalent mass and spring stiffness. The expressions of the two are: Among them, M m is the mass of the elastic film 31, k a is the air spring stiffness in the resonance cavity 33, k m is the stiffness of the elastic film 31, M h is the equivalent mass of air in the through hole 211, ω h is the natural frequency of the main vibration system, ω m is the natural frequency of the additional system;

[0047] S4. The equivalent mass of air and the equivalent stiffness of the film in the through hole 211 are: Among them, t′ h =t h +δ,t h is the hole depth, δ is the opening correction, C is the sound velocity, s is the hole cross-sectional area, S is the axial cross-sectional area of ​​the fixed plate 22 in the resonance cavity 33, l1 is the cavity depth, and ρ is the air density;

[0048] S5. At the outlet 213 of the micro-perforated tube 21, a sound level meter is used to detect the noise generated by the micro-perforated tube 21. According to the noise spectrum characteristics, the noise frequency with a larger sound pressure level is screened out, that is, the noise frequency that needs to be reduced. By pushing the baffle 23 to adjust the perforation rate and control the neck area of ​​the system, the air equivalent mass of the through hole 211 in step S4 can be adjusted to achieve frequency tunability, that is, to control the transmission loss of the composite tuned muffler;

[0049] S6. The transmission loss of the composite tuned silencer can be controlled by adjusting the total acoustic impedance ratio of the composite tuned silencer surface. The total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio on both sides of the micro-perforated tube 21, the acoustic impedance ratio between the micro-perforated tube 21 and the elastic film 31, and the acoustic impedance ratio on both sides of the elastic film 31. The factors affecting the silencing effect of the composite tuned silencer include the structural dimensions of the micro-perforated tube 21, the material properties and structural properties of the elastic film 31, and the distance between the elastic film 31 and the micro-perforated tube 21. The total acoustic impedance ratio of the composite tuned silencer is:

[0050]

[0051] Where m = sρt′ h is the mass of air in the through hole 211, c is the viscous resistance of the inner surface of the through hole 211, ω is the incident angular frequency of the plane sound wave, ω2 is the natural angular frequency of the film and the additional cavity, ω f The natural frequency of the film and the stiffness of the air spring in the resonance cavity 33 are l1 is the length of the resonance cavity 1 33, l2 is the length of the resonance cavity 2 34, and the equivalent mass of air is M a1=ρl1s, the mass of the elastic film 31 is The opening ratio ε is the ratio of the chamber cross-sectional area s to the inner area S of the micro-perforated tube 21, and η is the loss factor.

[0052] like Figure 5 As shown, in the single-layer perforated pipe, the hole depth t h =4mm, perforation rate P = 0.386%, film thickness σ = 0.5mm, at this time, the first-order peak f = 178Hz, the second-order peak frequency f = 865Hz. The perforation rate of the perforated tube can be increased from 0 gradient to 1%, with an increase step of 0.1%. The baffle tube is continuously withdrawn from the chamber, and the perforation rate gradually increases. When it is completely withdrawn, the perforation rate is the maximum of 1%, and the resonance frequency generated at this time is also the maximum.

[0053] Embodiment 2

[0054] The difference between this embodiment and the first embodiment is that in step S5 of the tuning method, by adjusting the driving voltage of the piezoelectric vibrator 32, the equivalent stiffness of the film in step S4 can be adjusted, and the frequency can be tuned. Figure 6 As shown, when the voltage increases from 0V to 300V, the film stiffness increases, the anti-resonance point moves to the high frequency domain, the coupling effect of structural resonance and acoustic resonance weakens, the first-order anechoic peak shifts from 180Hz to 275Hz, the shift is 95Hz, and the anechoic amount increases. The second-order anechoic peak shifts from 520Hz to 655Hz, the shift is 135Hz, and the anechoic amount decreases significantly. The other technical features and working principles of this embodiment are the same as those of Example 1.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite frequency modulation muffler, characterized in that: include: A fixing assembly for ensuring the sealing of the cointegration chamber; A micro-perforation assembly comprises a micro-perforation tube, at least two fixing plates and a baffle, wherein the micro-perforation assembly is fixedly arranged in the fixing assembly, the fixing plates are relatively arranged outside the micro-perforation tube, a plurality of rows of through holes are evenly arranged on the micro-perforation tube between the fixing plates, and the baffle passes through the fixing plates and is slidably arranged outside the micro-perforation tube and covers the through holes, so as to adjust the perforation rate of the micro-perforation tube; The regulating component includes an elastic film and a piezoelectric vibrator covering the outer side of a relatively set fixed plate, the elastic film and the outer side of the micro-perforated tube form a resonance cavity 1, and the elastic film and the inner wall of the fixed component form a resonance cavity 2, which is used to prevent sound leakage, the resonance cavity 1 and the resonance cavity 2 are filled with air, the micro-perforated tube, the resonance cavity 1, the elastic film and the resonance cavity 2 form a closed double-degree-of-freedom silencing system, the double-degree-of-freedom silencing system includes a main vibration system and an additional system, the piezoelectric vibrator is arranged on the outer side of the elastic film and is electrically connected to a power supply, and is used to control the stiffness of the elastic film by adjusting the driving voltage, and realize frequency tunability; The fixing assembly comprises two outer shells connected by flanges, the outer shells are semi-cylindrical, and grooves are arranged on the upper and lower surfaces of the outer shells. A cavity is arranged inside the outer shells, and the micro-perforation assembly is arranged in the cavity; The micro-perforated tube is integrally formed with the fixing plate, and the micro-perforated tube includes an inlet and an outlet; The fixing plate is inserted into the groove, and the side wall of the groove presses the elastic film tightly, and a plurality of insertion holes are provided on the fixing plate near the inlet side; The baffle is provided with a plurality of seals along the axial direction of the micro-perforated tube on one side facing the outlet, and the seals are matched with the through holes; The piezoelectric vibrator comprises a copper sheet and a zinc sheet, and the piezoelectric vibrator is attached to the outer side of the elastic film through silica gel; The air in the resonant cavity 1 is relatively incompressible.

2. A tuning method using the composite frequency modulation muffler as claimed in claim 1, comprising the following steps: S1. The air in the resonant cavity is equivalent to a spring, and the air in the through hole is equivalent to a mass block, which is converted into the first spring mass resonant unit and serves as the main vibration system; S2. The mass of the elastic film is equivalent to a mass block, and the tension of the elastic film and the elastic coupling force of the air layer in the second resonance cavity are equivalent to a spring, which is converted into a second spring mass resonance unit and serves as an additional system; S3. Both the main vibration system and the additional system have natural frequencies, which are only related to the system equivalent mass and spring stiffness. The expressions of the two are: in, M m is the mass of the elastic film, k a is the air spring stiffness in the resonance cavity 1, k m is the elastic membrane stiffness, M h is the equivalent mass of the air through the hole, ω h is the natural frequency of the main vibration system, ω m is the natural frequency of the additional system; S4. The equivalent mass of the through-hole air and the equivalent stiffness of the film are: Among them, t h ′=t h +δ,t h is the hole depth, δ is the opening correction, C is the sound velocity, s is the hole cross-sectional area, S is the axial cross-sectional area of ​​the fixed plate in the resonance cavity 1, l1 is the cavity depth, and ρ is the air density; S5. By pushing the baffle to adjust the perforation rate, the equivalent mass of the air through the hole in step S4 can be adjusted. By adjusting the driving voltage of the piezoelectric vibrator, the equivalent stiffness of the film in step S4 can be adjusted to control the silencing frequency, that is, to control the transmission loss of the composite tuned muffler; S6. The transmission loss of the composite tuned muffler can be controlled by adjusting the total acoustic impedance ratio of the composite tuned muffler surface. The total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio on both sides of the micro-perforated tube, the acoustic impedance ratio between the micro-perforated tube and the elastic film, and the acoustic impedance ratio on both sides of the elastic film. The total acoustic impedance ratio of the composite tuned muffler is: Where m = sρt h ′ is the mass of air in the through hole, c is the viscous resistance of the inner surface of the through hole, ω is the incident angular frequency of the plane acoustic wave, ω2 is the natural angular frequency of the film and the additional cavity, ω f The natural frequency of the film and the stiffness of the air spring in the resonance cavity are l1 is the length of resonant cavity 1, l2 is the length of resonant cavity 2, and the equivalent mass of air is M a1 =ρl1s, the mass of the elastic film is The opening ratio ε is the ratio of the chamber cross-sectional area s to the inner area S of the micro-perforated tube, and η is the loss factor.

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