CN113446088A - Composite frequency modulation silencer and tuning method thereof - Google Patents
Composite frequency modulation silencer and tuning method thereof Download PDFInfo
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- CN113446088A CN113446088A CN202110868339.3A CN202110868339A CN113446088A CN 113446088 A CN113446088 A CN 113446088A CN 202110868339 A CN202110868339 A CN 202110868339A CN 113446088 A CN113446088 A CN 113446088A
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- 230000003584 silencer Effects 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000002131 composite material Substances 0.000 title claims description 29
- 230000008030 elimination Effects 0.000 claims description 14
- 238000003379 elimination reaction Methods 0.000 claims description 14
- 230000000694 effects Effects 0.000 claims description 8
- 230000005540 biological transmission Effects 0.000 claims description 7
- 239000012528 membrane Substances 0.000 claims description 7
- 238000007789 sealing Methods 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- 238000012937 correction Methods 0.000 claims description 3
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- 230000001629 suppression Effects 0.000 abstract description 3
- 239000010408 film Substances 0.000 description 40
- 230000009467 reduction Effects 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 3
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- 230000030279 gene silencing Effects 0.000 description 2
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N1/00—Silencing apparatus characterised by method of silencing
- F01N1/08—Silencing apparatus characterised by method of silencing by reducing exhaust energy by throttling or whirling
- F01N1/082—Silencing apparatus characterised by method of silencing by reducing exhaust energy by throttling or whirling the gases passing through porous members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N1/00—Silencing apparatus characterised by method of silencing
- F01N1/02—Silencing apparatus characterised by method of silencing by using resonance
- F01N1/04—Silencing apparatus characterised by method of silencing by using resonance having sound-absorbing materials in resonance chambers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N1/00—Silencing apparatus characterised by method of silencing
- F01N1/08—Silencing apparatus characterised by method of silencing by reducing exhaust energy by throttling or whirling
- F01N1/10—Silencing apparatus characterised by method of silencing by reducing exhaust energy by throttling or whirling in combination with sound-absorbing materials
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/08—Other arrangements or adaptations of exhaust conduits
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/16—Selection of particular materials
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Exhaust Silencers (AREA)
Abstract
The invention provides a combined frequency modulation silencer and a tuning method thereof, wherein the combined frequency modulation silencer comprises: a fixing assembly; the micro-perforation assembly comprises micro-perforation pipes, at least two fixing plates and a baffle plate, the micro-perforation assembly is fixedly arranged in the fixing assembly, the fixing plates are oppositely arranged on the outer sides of the micro-perforation pipes and are integrally formed with the micro-perforation pipes, a plurality of rows of through holes are formed in the micro-perforation pipes between the fixing plates at equal intervals, and the baffle plate penetrates through the fixing plates and is slidably arranged on the outer sides of the micro-perforation pipes and covers the through holes; the adjusting assembly comprises an elastic film and a piezoelectric vibrator which are coated on the outer sides of the oppositely arranged fixed plates, a first resonant cavity is formed between the elastic film and the outer side of the micro-perforated pipe, a second resonant cavity is formed between the elastic film and the inner wall of the fixed assembly, and the piezoelectric vibrator of the sound attenuation system with two closed degrees of freedom is formed by the micro-perforated pipe, the first resonant cavity, the elastic film and the resonant cavity and is arranged on the outer side of the elastic film and electrically connected with a power supply. The invention can enlarge the noise control frequency band and realize the effective suppression of noise.
Description
Technical Field
The invention belongs to the technical field of silencers, and particularly relates to a combined frequency modulation silencer and a tuning method thereof.
Background
The composite muffler is a muffler formed by combining a resistive muffler and a reactive muffler in a certain mode for an airflow pipeline with noise transmission.
In the prior art, in the composite muffler, the muffler of the perforated pipe has a good muffling effect in a middle and high frequency range, but the perforated pipe needs an extremely low perforation rate or increases the volume of a resonant cavity in a low frequency range, so that the processing difficulty and the cost are increased, the occupied space is increased accordingly, the application occasions of the muffler structure of the perforated pipe are limited, the flexible film structure has a good absorbing effect on low-frequency noise, and the muffler has the advantages of simple structure, easiness in preparation, large deformation and the like, and application limitation is still realized, if the medium and high-frequency noise cannot be simultaneously and efficiently inhibited, the muffler is not suitable for strong vibration sound excitation, high temperature difference, extremely light additional mass and extremely small additional space requirements. For example, patent publication No. CN109139191A discloses a micro-perforated resonant cavity noise reduction structure and a noise reduction muffler for APU, which adopts a large resonant cavity structure form, greatly reduces the weight of the device, increases the structural rigidity, weakens the intensity of the noise propagated in the APU working state, but the noise control band is fixed, the noise reduction effect is fixed, and the maximum suppression of the noise cannot be realized through tuning.
Disclosure of Invention
The invention aims to provide a composite frequency modulation silencer and a tuning method thereof.
The invention provides the following technical scheme:
the application provides a combined type frequency modulation silencer includes:
the fixing assembly is used for ensuring the sealing performance of the coordination chamber;
the micro-perforation assembly comprises micro-perforation pipes, at least two fixing plates and a baffle plate, the micro-perforation assembly is fixedly arranged in the fixing assembly, the fixing plates are oppositely arranged on the outer sides of the micro-perforation pipes, a plurality of rows of through holes are formed in the micro-perforation pipes between the fixing plates at equal intervals, and the baffle plate penetrates through the fixing plates, is slidably arranged on the outer sides of the micro-perforation pipes and covers the through holes and is used for adjusting the perforation rate of the micro-perforation pipes;
the adjusting assembly comprises an elastic film and a piezoelectric vibrator which are coated on the outer sides of oppositely arranged fixed plates, the elastic film and the outer side of the micro-perforated pipe form a first resonant cavity, the elastic film and the inner wall of the fixed assembly form a second resonant cavity which is used for preventing sound leakage, the first resonant cavity and the second resonant cavity are filled with air, the micro-perforated pipe, the first resonant cavity, the elastic film and the resonant cavity form a closed two-degree-of-freedom noise elimination system, the two-degree-of-freedom noise elimination system comprises 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 with a power supply and used for controlling the rigidity of the elastic film by adjusting the driving voltage and achieving tunable frequency.
Preferentially, fixed subassembly includes two shells through flange joint, the shell is the halfcylinder, and the relative recess that is equipped with in surface about the shell, be equipped with the cavity in the shell, the cavity is located to the micro-perforation subassembly.
Preferably, the microperforated tube is integrally formed with the fixation plate, and the microperforated tube includes an inlet and an outlet.
Preferably, the fixing plate is inserted into the groove, the side wall of the groove compresses the elastic membrane, and the fixing plate close to the inlet side is provided with a plurality of jacks.
Preferably, the baffle is equipped with a plurality of strip of paper used for sealing along the microperforated tube axial towards one side of export, the strip of paper used for sealing cooperatees with the through-hole.
Preferentially, 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.
Preferably, the interior of the cavity is relatively incompressible.
Based on the composite frequency modulation silencer, the application also provides a tuning method using the composite frequency modulation silencer, which comprises the following steps:
s1, air in a resonant cavity I is equivalent to a spring, air in a through hole part is equivalent to a mass block, and the mass block is converted into a first spring mass resonance unit and serves as a main vibration system;
s2, the mass of the elastic film is equivalent to a mass block, the tension of the elastic film and the elastic coupling acting force of an air layer in the second resonance cavity are equivalent to springs, and the springs are converted into a second spring mass resonance unit and serve as an additional system;
s3, both the main vibration system and the additional system have natural frequency and are only related to the equivalent mass of the system and the rigidity of the spring, and the expressions of the main vibration system and the additional system are
Wherein M ismFor elastic film quality, kaIs the stiffness of the air spring in the first resonant cavitymFor the rigidity of the elastic film, MhIs the through-hole air equivalent mass, omegahIs the natural frequency, omega, of the primary vibration systemmIs the natural frequency of the additional system;
s4, the equivalent mass of the air of the through hole and the equivalent rigidity of the film are
Wherein, t'h＝th+δ，thIs the hole depth, delta 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 first resonant cavity, l1Is the cavity depth, ρ is the air density;
s5, the equivalent mass of the air of the through hole in the step S4 can be adjusted by pushing the baffle to adjust the perforation rate, and the equivalent stiffness of the film in the step S4 can be adjusted by adjusting the driving voltage of the piezoelectric vibrator, so that the noise elimination frequency is controlled, namely the transmission loss of the combined tuned silencer is controlled;
s6, the transmission loss of the composite tuned silencer can be controlled by adjusting the total acoustic impedance ratio of the surface of the composite tuned silencer, the total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio of two sides of the micro-perforated pipe, the acoustic impedance ratio between the micro-perforated pipe and the elastic film and the acoustic impedance ratio of two sides of the elastic film, and the total acoustic impedance ratio of the composite tuned silencer is as follows:
wherein m is s ρ t'hThe mass of air in the via, c the viscous drag of the inner surface of the via, and ω the frequency of the incident angle of the planar acoustic wave, ω2Natural angular frequency, omega, of the membrane and the additional cavityfNatural frequency of the membrane, air spring stiffness in the first resonant cavity
l1Is the length of the resonant cavity I2The length of the resonant cavity II and the equivalent mass of air are Ma1＝ρl1s, elastic film mass of
The opening ratio epsilon is the ratio of the sectional area S of the chamber to the inner area S of the micro-perforated pipe, and eta is a loss factor.
Preferably, the combined tuned muffler muffling effect includes the structural dimensions of the microperforated pipe, the material and structural properties of the elastomeric film, and the distance between the elastomeric film and the microperforated pipe.
The invention has the beneficial effects that:
1. the light elastic film structure is combined with the perforated pipe silencer, so that the silencing performance of the perforated pipe silencer structure in a low frequency domain and the silencing performance of the elastic film on high-frequency noise are improved, the noise control frequency band is expanded, the effective suppression of the noise is realized, and the composite spectrum noise control structure has important engineering practical value on controlling the composite spectrum noise in the low frequency domain;
2. the damping device has two frequency tuning modes, the rigidity of the elastic film is adjusted by adjusting the perforation rate through the baffle and controlling the driving voltage, and the damping frequency can be flexibly controlled;
3. the adopted raw materials are cheap and easy to obtain, the synthesis method is simple, no dangerous and virulent reagent or noble metal catalyst is used, the operation is simple and convenient, and the yield of the final product is relatively high.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic view of the adjustment assembly connection of the present invention;
FIG. 3 is a schematic view of the housing connection of the present invention;
FIG. 4 is a schematic view of the microperforation assembly attachment of the present invention;
FIG. 5 is a schematic view of the perforation rate effect of the present invention;
fig. 6 is a schematic diagram of the muffling effect of the present invention at different voltages.
Labeled as: 1. the piezoelectric resonator comprises a fixed assembly, 11, a shell, 2, a micro-perforation assembly, 21, a micro-perforation tube, 211, a through hole, 212, an inlet, 213, an outlet, 22, a fixed plate, 221, a jack, 23, a baffle, 231, a seal, 3, an adjusting assembly, 31, an elastic film, 32, a piezoelectric vibrator, 33, a first resonant cavity and 34, and a second resonant cavity.
Detailed Description
Example one
The application provides a combined type frequency modulation silencer includes:
and the fixing assembly 1 is used for ensuring the tightness of the co-integration chamber. Fixed subassembly 1 includes two shells 11 through flange joint, and shell 11 is the halfcylinder, and 11 upper and lower surfaces of shell are equipped with the recess relatively, are equipped with the cavity in the shell 11, and the cavity is located to micro-perforation subassembly 2.
The micro-perforation assembly 2 comprises a micro-perforation tube 21, at least two fixing plates 22 and a baffle plate 23, the micro-perforation assembly 2 is fixedly arranged in the fixing assembly 1, the fixing plates 22 are arranged on the outer side of the micro-perforation tube 21 relatively, a plurality of rows of through holes 211 are formed in the micro-perforation tube 21 between the fixing plates 22 at equal intervals, and the baffle plate 23 penetrates through the fixing plates 22 to be arranged on the outer side of the micro-perforation tube 21 in a sliding mode and covers the through holes 211 and is used for adjusting the perforation rate of the micro-perforation tube 21. The microperforated tube 21 is integrally formed with the fixing plate 22, and the microperforated tube 21 includes an inlet 212 and an outlet 213. The fixing plate 22 is inserted into the groove, the side wall of the groove presses the elastic membrane 31, and a plurality of insertion holes 221 are formed on the fixing plate 22 near the inlet 212. The baffle 23 is provided with a plurality of seals 231 along the axial direction of the microperforated tube 21 on the side facing the outlet 213, and the seals 231 are fitted into the through holes 211.
The adjusting component 3 comprises an elastic film 31 and a piezoelectric vibrator 32 which are coated on the outer side of the fixing plate 22 which is oppositely arranged, the piezoelectric vibrator 32 comprises a copper sheet and a zinc sheet, and the piezoelectric vibrator 32 is adhered on the outer side of the elastic film 31 through silica gel. The elastic membrane 31 and the outer side of the micro-perforated pipe 21 form a first resonant cavity 33, and the inside of the first resonant cavity 33 is relatively incompressible. The elastic film 31 and the inner wall of the fixed component 1 form a second resonant cavity 34 for preventing sound leakage, the first resonant cavity 33 and the second resonant cavity 34 are filled with air, the micro perforated pipe 21, the first resonant cavity 33, the elastic film 31 and the second resonant cavity 34 form a closed two-degree-of-freedom noise elimination system, the two-degree-of-freedom noise elimination system comprises a main vibration system and an additional system, and the piezoelectric vibrator 32 is arranged on the outer side of the elastic film 31 and is electrically connected with a power supply for controlling the rigidity of the elastic film 31 by adjusting the magnitude of driving voltage and realizing tunable frequency.
Based on the composite frequency modulation silencer, the application also provides a tuning method using the composite frequency modulation silencer, which comprises the following steps:
s1, air in a resonant cavity I33 is equivalent to a spring, air in a through hole 211 is equivalent to a mass block, the mass block is converted into a first spring mass resonant unit, and the first spring mass resonant unit serves as a main vibration system;
s2, the mass of the elastic film 31 is equivalent to a mass block, the tension of the elastic film 31 and the elastic coupling acting force of the air layer in the second resonance cavity 34 are equivalent to springs, and the springs are converted into a second spring mass resonance unit and used as an additional system;
s3. Master vibration System and AccessoriesThe systems have natural frequency and are only related to the equivalent mass and the spring stiffness of the system, and the expressions of the two are
Wherein M ismIs the mass, k, of the elastic film 31aIs the air spring stiffness, k, in the resonant cavity one 33mFor the rigidity of the elastic film 31, MhIs the air equivalent mass, omega, of the through-hole 211hIs the natural frequency, omega, of the primary vibration systemmIs the natural frequency of the additional system;
s4, the equivalent air mass and the equivalent film stiffness of the through hole 211 are
Wherein, t'h＝th+δ，thIs the hole depth, delta 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 first resonant cavity 33, l1Is the cavity depth, ρ is the air density;
s5, detecting noise generated by the micro perforated pipe 21 at the outlet 213 of the micro perforated pipe 21 by using a sound level meter, screening out noise frequency with larger sound pressure level, namely noise frequency needing noise reduction according to the noise spectrum characteristic, adjusting the perforation rate by pushing the baffle plate 23, controlling the neck area of the system, adjusting the air equivalent mass of the through hole 211 in the step S4, and realizing tunable frequency, namely controlling 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 surface of the composite tuned muffler, wherein the total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio of two sides of the micro-perforated pipe 21, the acoustic impedance ratio between the micro-perforated pipe 21 and the elastic film 31 and the acoustic impedance ratio of two sides of the elastic film 31, and the influence factors of the noise elimination effect of the composite tuned muffler comprise the structural size of the micro-perforated pipe 21, the material property and the structural property of the elastic film 31 and the distance between the elastic film 31 and the micro-perforated pipe 21. The total acoustic impedance ratio of the composite tuned muffler is as follows:
wherein m is s ρ t'hMass of air in the through-hole 211, c viscous drag of the inner surface of the through-hole 211, and ω planar acoustic wave incident angular frequency, ω2Natural angular frequency, omega, of the membrane and the additional cavityfNatural frequency of the diaphragm, air spring stiffness in the first resonant cavity 33 is
l1Is the length of the resonant cavity one 33,/2The length of the second resonant cavity 34 and the equivalent mass of air are Ma1＝ρl1s, elastic film 31 mass of
The opening ratio epsilon is the ratio of the chamber sectional area S to the inner area S of the micro-perforated pipe 21, and eta is a loss factor.
As shown in fig. 5, the hole depth t of the single-layer perforated pipehWhen the thickness σ is 0.5mm, the first-order peak value f is 178Hz, and the second-order peak frequency f is 865 Hz. The perforation rate of the perforated pipe can be increased from 0 gradient to 1%, the increase step length is 0.1%, the baffle pipe is continuously drawn out of the chamber, the perforation rate is gradually increased, when the baffle pipe is completely drawn out, the maximum perforation rate is 1%, and the generated resonance frequency is also maximum.
Example two
The present embodiment is different from the first embodiment in that: in step S5 of the tuning method, the equivalent stiffness of the thin film in step S4 is adjusted by adjusting the magnitude of the driving voltage of the piezoelectric vibrator 32, and frequency tuning is realized. As shown in FIG. 6, when the voltage is increased from 0V to 300V, the rigidity of the film is increased, the anti-resonance point moves to a high-frequency domain, the coupling effect of the structural resonance and the acoustic resonance is weakened, the first-order noise elimination peak is shifted from 180Hz to 275Hz, the shift is 95Hz, and the noise elimination amount is increased. The second-order noise elimination peak is shifted to 655Hz from 520Hz, the shift is 135Hz, and the noise elimination amount is greatly reduced. Other technical features and working principles of the embodiment are the same as those of the first embodiment.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The utility model provides a combined type frequency modulation silencer which characterized in that: the method comprises the following steps:
the fixing assembly is used for ensuring the sealing performance of the coordination chamber;
the micro-perforation assembly comprises micro-perforation pipes, at least two fixing plates and a baffle plate, the micro-perforation assembly is fixedly arranged in the fixing assembly, the fixing plates are oppositely arranged on the outer sides of the micro-perforation pipes, a plurality of rows of through holes are formed in the micro-perforation pipes between the fixing plates at equal intervals, and the baffle plate penetrates through the fixing plates, is slidably arranged on the outer sides of the micro-perforation pipes and covers the through holes and is used for adjusting the perforation rate of the micro-perforation pipes;
the adjusting assembly comprises an elastic film and a piezoelectric vibrator which are coated on the outer sides of oppositely arranged fixed plates, the elastic film and the outer side of the micro-perforated pipe form a first resonant cavity, the elastic film and the inner wall of the fixed assembly form a second resonant cavity which is used for preventing sound leakage, the first resonant cavity and the second resonant cavity are filled with air, the micro-perforated pipe, the first resonant cavity, the elastic film and the resonant cavity form a closed two-degree-of-freedom noise elimination system, the two-degree-of-freedom noise elimination system comprises 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 with a power supply and used for controlling the rigidity of the elastic film by adjusting the driving voltage and achieving tunable frequency.
2. The composite fm silencer of claim 1, wherein: the fixed assembly comprises two shells connected through flanges, each shell is a semi-cylinder, grooves are oppositely formed in the upper surface and the lower surface of each shell, a cavity is formed in each shell, and the micro-perforation assemblies are arranged in the cavities.
3. The composite fm silencer of claim 1, wherein: the micro-perforated pipe and the fixing plate are integrally formed, and the micro-perforated pipe comprises an inlet and an outlet.
4. The composite fm silencer of claim 3, wherein: the fixing plate is inserted in the groove, the side wall of the groove compresses the elastic film, and a plurality of jacks are arranged on the fixing plate close to the inlet side.
5. The composite fm silencer of claim 3, wherein: the baffle is equipped with a plurality of strip of paper used for sealing along the microperforated tube axial towards export one side, the strip of paper used for sealing cooperatees with the through-hole.
6. The composite fm silencer of claim 1, wherein: the piezoelectric vibrator comprises a copper sheet and a zinc sheet, and the piezoelectric vibrator is arranged on the outer side of the elastic film through silica gel adhesion.
7. The composite fm silencer of claim 1, wherein: the interior of the resonant cavity one is relatively incompressible.
8. A tuning method using a compound fm silencer according to any of claims 1-7, characterized by: the method comprises the following steps:
s1, air in a resonant cavity I is equivalent to a spring, air in a through hole part is equivalent to a mass block, and the mass block is converted into a first spring mass resonance unit and serves as a main vibration system;
s2, the mass of the elastic film is equivalent to a mass block, the tension of the elastic film and the elastic coupling acting force of an air layer in the second resonance cavity are equivalent to springs, and the springs are converted into a second spring mass resonance unit and serve as an additional system;
s3. both the main vibration system and the additional system have natural frequency, andonly the equivalent mass and the spring stiffness of the system are related, and the expressions of the equivalent mass and the spring stiffness are
Wherein M ismFor elastic film quality, kaIs the stiffness of the air spring in the first resonant cavitymFor the rigidity of the elastic film, MhIs the through-hole air equivalent mass, omegahIs the natural frequency, omega, of the primary vibration systemmIs the natural frequency of the additional system;
s4, the equivalent mass of the air of the through hole and the equivalent rigidity of the film are
Wherein, th′＝th+δ，thIs the hole depth, delta 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 first resonant cavity, l1Is the cavity depth, ρ is the air density;
s5, the equivalent mass of the air of the through hole in the step S4 can be adjusted by pushing the baffle to adjust the perforation rate, and the equivalent stiffness of the film in the step S4 can be adjusted by adjusting the driving voltage of the piezoelectric vibrator, so that the noise elimination frequency is controlled, namely the transmission loss of the combined tuned silencer is controlled;
s6, the transmission loss of the composite tuned silencer can be controlled by adjusting the total acoustic impedance ratio of the surface of the composite tuned silencer, the total acoustic impedance ratio is the synergistic effect of the acoustic impedance ratio of two sides of the micro-perforated pipe, the acoustic impedance ratio between the micro-perforated pipe and the elastic film and the acoustic impedance ratio of two sides of the elastic film, and the total acoustic impedance ratio of the composite tuned silencer is as follows:
wherein m is s ρ t'hThe mass of air in the via, c the viscous drag of the inner surface of the via, and ω the frequency of the incident angle of the planar acoustic wave, ω2Natural angular frequency, omega, of the membrane and the additional cavityfNatural frequency of filmRate, air spring stiffness in resonator one is
l1Is the length of the resonant cavity I2The length of the resonant cavity II and the equivalent mass of air are Ma1＝ρl1s, elastic film mass of
The opening ratio epsilon is the ratio of the sectional area S of the chamber to the inner area S of the micro-perforated pipe, and eta is a loss factor.
9. The tuning method of a compound fm muffler according to claim 8, wherein: the influence factors of the noise elimination effect of the composite tuning silencer comprise the structural size of the micro-perforated pipe, the material property and the structural property of the elastic film and the distance between the elastic film and the micro-perforated pipe.
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