CN107633838B - Silencer with through hole-containing acoustic metamaterial baffle plate and manufacturing and assembling method thereof - Google Patents

Abstract

The invention relates to a silencer, which comprises an inlet pipe, an outlet pipe, a hollow expansion cavity between the inlet pipe and the outlet pipe, and an acoustic metamaterial baffle plate which is vertically or obliquely provided with a through hole on the inner section of the hollow expansion cavity. The through hole-containing acoustic metamaterial baffle plate comprises a frame, a restraint body rigidly connected with the frame is arranged in the frame, a film covers the surface of the frame, and through holes are formed in the restraint body and the film. The silencer has the characteristics of compact structure, simple process, stable performance and long service life.

Description

Silencer with through hole-containing acoustic metamaterial baffle plate and manufacturing and assembling method thereof

Technical Field

The invention relates to a silencer with a through hole-containing acoustic metamaterial baffle plate, which can customize an effective silencing frequency band, expand low-frequency silencing bandwidth, has small fluid passing resistance and can enhance the fluid heat transfer efficiency, and belongs to the field of acoustic devices.

Background

For the noise generated by gas or liquid medium through the pipeline, such as industrial through-flow pipeline, building fresh air system pipeline, air inlet and outlet pipes of fluid mechanical power equipment, refrigerant conveying pipes of refrigeration appliances such as air conditioners and refrigerators, various high-pressure, high-temperature and high-speed exhaust emptying terminals, and the like, the common solution is to install a silencer device, so that the passing noise level is effectively reduced while sufficient fluid is ensured to pass smoothly.

At present, mufflers are mainly classified into three categories according to the working principle and the structural form: reactive mufflers, resistive mufflers and resistive composite mufflers. The reactive muffler mainly rebounds part of sound waves to achieve the purpose of sound elimination through sudden changes of acoustic characteristics of the pipeline, such as expansion, contraction or bypass branches; the resistive muffler usually adopts sound-absorbing materials lined on the inner wall of the pipeline, such as foam, fiber cotton and other porous materials, and continuously absorbs the noise in the pipeline in the transmission process; the impedance composite muffler has the structural characteristics of both resistance and impedance mufflers, wherein the most widely studied and applied structural form is to install a perforated or micro-perforated pipe in the expansion cavity along the axial direction, and fill a sound absorption material in a gap between the perforated pipe and the wall surface of the muffler. The silencer can simultaneously utilize the sudden change structure to rebound sound waves, utilize the cavity resonance characteristic formed by the perforated pipe and the wall surface of the silencer to absorb noise in a specific frequency band, and utilize the filled sound absorption material to absorb transmitted high-frequency sound waves.

Because the effective noise elimination frequency band of the reactive muffler has an inverse relation with the structural size of the reactive muffler, the structural size of the corresponding reactive muffler needs to be large enough for low-frequency noise with large wavelength scale and long propagation distance. For example, a simple expansion cavity reactive muffler designed for airborne 100 hz noise has an expansion cavity length of at least one quarter of the desired noise rejection wavelength, i.e., about 85 cm, to effectively muffle the noise. In addition, in order to compensate the standing wave noise elimination valley problem of the single-section reactive muffler, namely, when the length of the expansion cavity is one half of the noise wavelength and integral multiple thereof, the noise elimination amount is close to zero, the prior art is to connect an insert pipe inside the expansion cavity or connect a plurality of sections of expansion cavities in series. Therefore, the silencer is huge in size and heavy in structure, and is difficult to meet the situation that the actual engineering has high requirements on installation space (Chinese published patents: CN202707196U, CN105569775A, CN105518269A and CN103382874A, and U.S. published patents: US7497301B2, US7798286B2, US7942239B2 and US8617454B 2). The resistive muffler adopts the sound absorption material, so that the effective noise elimination frequency band is limited to high frequency, and the sound absorption material is in direct contact with the passing fluid, so that the sound absorption material inevitably absorbs moisture, sticks together or falls off in the working process, and the service life of the sound absorption material is influenced. Although the impedance composite muffler has the characteristics of resistance and resistance, the problem that sound absorption materials are exposed in pipeline fluid cannot be avoided, the application of the impedance composite muffler in occasions with high temperature, humidity, large flow rate and high cleaning requirements is limited, the internal structure is complex, and the production, manufacture, overhaul and maintenance costs are high (Chinese published patents: CN204921097U and CN104564285A, U.S. published patents: US6332511B1 and US8146574B 2).

In the last two decades, the research results of the Acoustic field with subversive breakthrough first pushed local resonance type Acoustic metamaterials (acoustics metal material.2000, Zhengyou L iu, etc., L Acoustic resonance materials, Science 289,1734.) as an artificially designed Acoustic microstructure that exhibits a specific state of "negative dynamic mass" and/or "negative bulk modulus" under Acoustic excitation of specific frequencies, so that one can effectively manipulate the propagation of low-frequency Acoustic waves with a light and thin structure having a structure size much smaller than the Acoustic wavelength. in 2015, chinese patent application CN105090670A combines the Acoustic metamaterial concept with specific silencer components, discloses a thin film Acoustic metamaterial silencer.

In summary, in the field of pipeline silencing engineering, a silencer with a compact structure, good low-frequency broadband silencing, accurate and convenient silencing frequency regulation, small through-flow obstruction, stable working performance and long service time is urgently needed to be created.

Disclosure of Invention

The invention provides a technical scheme capable of overcoming the problem of narrow low-frequency silencing bandwidth of the existing thin-film Acoustic Metamaterial Silencer, and provides a Silencer (BAFFled Acoustic Metamaterial muffler for short) with through-hole Acoustic Metamaterial baffle plates, which is vertically or obliquely arranged along the flow direction section of a pipeline, wherein the low-frequency silencing effect of the Silencer is better than that of a perforated baffle plate with the same aperture and a micro perforated baffle plate Silencer with the same total perforated area. In addition, the size of the through hole on the Acoustic Metamaterial Baffle plate (hereinafter referred to as PAMB) containing the through hole can be designed according to the through flow requirement and the requirement of the sound attenuation frequency band, and the noise level can be effectively reduced while sufficient heat flow, air flow or liquid flow can smoothly pass through the through hole.

The invention also provides an improved reactive muffler technical scheme, and the working frequency band of the PAMB arranged on the internal section of the traditional reactive muffler covers the standing wave low-valley frequency band of the original muffler, so that the sound transmission loss performance of the frequency band is obviously improved, and the muffling bandwidth is widened. Because the silencing principle that the structural size of the silencer is matched with the silencing wavelength is not relied on, but the local resonance mechanism based on PAMB is used, the excellent low-frequency silencing effect can be still obtained on the premise that the structure of the silencer is compact enough.

The invention also provides an improved resistive muffler technical scheme, which adopts a thicker layer (more than 5mm in thickness) or a plurality of layers of PAMB to seal the sound absorption material, transmits sound energy through a film matched with the impedance of the sound absorption material, and further converts the sound energy into heat energy consumption, thereby effectively solving the problem that the sound absorption material of the traditional resistive muffler is directly contacted with the passing fluid.

The invention also provides a technical scheme of the silencer for enhancing the heat transfer efficiency of the fluid, which improves the temperature difference and the heat transfer rate of the media at two sides of the through hole on one hand through the vibration generated by PAMB under the excitation of sound waves; on the other hand, when fluid passes through, the flow-induced vibration generated by the PAMB film can increase the fluid turbulence at the position where the heat source adheres to the wall, hinder the formation of a heat boundary layer and a speed boundary layer, and accelerate the heat exchange efficiency.

The invention also provides a PAMB frequency modulation method, a PAMB manufacturing method and a silencer assembling method. The working frequency band of the PAMB is adjusted by changing the structural sizes and materials of the PAMB frame, the restraint body and the film; the PAMB is prepared by adopting an integral forming or prefabricated part assembling method, and the silencer is assembled by utilizing technological methods such as rolling assembly, interference fit, gap welding, combined splicing and the like.

The technical scheme of the invention is as follows:

a silencer comprises an inlet pipe, an outlet pipe, a hollow expansion cavity between the inlet pipe and the outlet pipe, and PAMB arranged in the hollow expansion cavity in a vertical or inclined mode on at least one section. It is preferable to install PAMB on the cross section along the flow direction of the pipe.

The PAMB comprises a frame, wherein at least one restraint body is arranged in the frame, a film covers at least one surface of the two side surfaces of the frame, and at least one through hole is formed in each of the restraint body and the film.

The section shape of the hollow expansion cavity is determined according to the parameter requirements of the installation space of the silencer, the expansion ratio of the silencer and the like; preferably, the cross-sectional shape of the hollow expansion chamber is circular, elliptical, rectangular, or regular polygonal, and the longitudinal cross-sectional shape of the hollow expansion chamber is rectangular, tapered, or wavy.

The frame is of a hollow structure, and the shape of the outer contour of the frame is consistent with the shape of the cross section of the hollow expansion cavity; the restraint body is arranged inside the frame, and the restraint body and the frame are rigidly connected through at least one connecting rod; the peripheral area of the film is attached to the surface of the frame, and the inner area of the film is restrained by the restraint body; preferably, the constraining body and the connecting rod are flush with the frame, and the connecting rod becomes a part of the constraining body and is used for constraining the vibration of the film.

The sizes of the through holes of the constraint body and the film are jointly determined according to through-flow requirements (the area of the through hole is equal to flow/flow speed) and a silencing frequency band; preferably, the aperture of the through holes on the constraining body and the thin film is larger than 2 mm.

The through hole area of the constraining body is determined according to the following modes: selecting large through hole area of the restraint body on occasions with higher requirements on the through-flow efficiency; on the occasion that the silencing frequency band tends to be low frequency, the small-size through hole aperture is selected on the premise that the geometric size and material parameters of the frame and the film are not changed.

The shape, position and size of the holes on the restraining body and the film are the same or different; preferably, the shape, position and size of the through holes are the same; preferably, the shape of the through hole is any geometric shape; more preferably, the geometric shape is a symmetrical regular shape, and still more preferably a circle, an ellipse, or a regular polygon.

The contact area of the constraint body and the film is a line or a plane; preferably the contact shape is a symmetrical regular geometric shape; more preferably, the geometric shape is a circle, an ellipse, or a regular polygon.

The number of the constraining bodies is mainly determined according to the noise elimination frequency band, and the larger the number of the constraining bodies is, the smaller the vibratable area of the film is, and the noise elimination frequency band of the silencer tends to be higher.

An improved reactive muffler, characterized in that at least one PAMB is provided on the internal cross-section of a conventional reactive muffler, preferably the operating band of PAMB covers the standing wave muffling valley band of said conventional reactive muffler; more preferably, the peak operating frequency of the PAMB coincides with the standing wave frequency of each order.

An improved resistive muffler is characterized in that the sound absorbing material is sealed by one or more layers of PAMB to avoid the sound absorbing material from directly contacting the passing fluid; preferably the thickness of the said layer of PAMB is greater than 5 mm; preferably, the surfaces of two sides of the frame of the PAMB layer are covered with films, and porous materials matched with the film impedance are filled in the two layers of films; preferably, the two films differ in thickness and/or material. When the thicknesses and/or materials are different, the two layers of films show different characteristic vibration frequencies, and the working bandwidth is favorably expanded. Preferably, the multilayer PAMB is positioned by a bracket, a layer of impermeable film is coated on the periphery of the bracket, and a porous material matched with the impedance of the film is filled in a cavity between the impermeable film and the wall surface of the expansion cavity or between two layers of films; preferably the material of the impermeable film is the same as that of the PAMB; preferably, the porous material is glass fiber cotton or open and closed cell foam.

A muffler for enhancing heat transfer efficiency of fluid is characterized in that on one hand, the temperature difference and the heat transfer rate of media on two sides of a through hole are improved through vibration generated by PAMB under the excitation of sound waves; on the other hand, when fluid passes through, the flow-induced vibration generated by the PAMB film can increase the fluid turbulence at the position of the heat source adherence, hinder the formation of a heat boundary layer and a speed boundary layer and accelerate the heat exchange efficiency; which serves to enhance the heat transfer efficiency of the fluid.

An array baffle plate containing the PAMB, which is formed by combining and splicing a plurality of PAMB in an in-plane direction; when broadband sound attenuation is required, it is preferable that the geometric dimensions and material parameters of each PAMB forming the array baffles be different, and when narrowband sound attenuation is required, it is preferable that the geometric dimensions and material parameters of each PAMB forming the array baffles be the same.

The frame and the restraint body of the PAMB are made of metal materials or nonmetal materials, preferably, the metal materials are aluminum, iron, steel and copper, and preferably, the nonmetal materials are wood, ceramics, rubber, glass, gypsum, cement, high polymer or composite fiber materials; the film is made of a high-molecular polymer film material, a metal film material or an elastic film material, the polymer film material is preferably a polyetherimide film, a polyvinyl chloride film or a polyethylene film, the metal film material is preferably an aluminum and aluminum alloy film or a titanium and titanium alloy film, and the elastic film material is preferably a rubber film, a silica gel film or an emulsion film.

A method of canceling standing wave canceling valleys of a conventional reactive muffler, the method comprising the steps of: mounting the acoustic metamaterial baffle plate with the through hole on the inner cross section of the traditional reactive muffler, and enabling the working frequency band of the acoustic metamaterial baffle plate with the through hole to cover the standing wave silencing valley frequency band of the traditional reactive muffler; preferably, the working frequency band of the acoustic metamaterial baffle plate with the through holes is consistent with the first-order standing wave frequency of low frequency.

On the premise of no change of the shape and size of an expansion cavity of the muffler, the effective working frequency band of the PAMB is adjusted by changing the structural sizes and material parameters of a frame, a restraint body and a film of the PAMB, and the muffling performance of the muffler in the frequency band is improved.

The method for assembling the PAMB is characterized in that the holed constraining body and the frame are prepared by adopting an integral forming technology, or a holed constraining body prefabricated part and a frame prefabricated part are manufactured, the holed constraining body prefabricated part is rigidly connected to the frame prefabricated part through a connecting rod to form a frame, then a film is covered on the frame in a free stretching state and is fixedly connected, and finally holes are punched on the film; furthermore, in order to ensure the working stability of the PAMB, the film is clamped between two layers of frames and fixedly connected; machining the frame into an integrally formed frame preferably by milling, casting, stamping, laser cutting or 3D printing technology, or manufacturing a perforated constraining body prefabricated part and a frame prefabricated part by milling, casting, stamping, laser cutting or 3D printing technology; preferably the fixed connection is an adhesive, a thermal weld or a mechanical rivet.

A method for assembling the silencer is characterized in that PAMB is sent to a set position in a hollow pipe through a positioning tool, then a roller cutter head is moved to a position corresponding to the outer wall surface of the hollow pipe and certain pressure is applied, and the PAMB is embedded in the hollow pipe; and closing up the two ends of the hollow tube to form the hollow tube.

The method for assembling the silencer is characterized in that PAMB is installed in the hollow pipe by a stamping or hot assembling method, and the acoustic metamaterial baffle plate with the through hole is fixed at a set position of the hollow pipe by using the constraint force of interference fit; and closing up the two ends of the hollow tube to form the hollow tube.

A method for assembling the silencer is characterized in that PAMB is arranged at a set position in a hollow pipe through a positioning clamp, and then the PAMB is fixed by spot welding through the processes of ultrasonic wave, laser, argon arc welding and the like, or the PAMB is positioned by adopting structures such as a sleeve, a spring and the like; and closing up the two ends of the hollow tube to form the hollow tube.

Wherein the closing-in forming preferably adopts die forming, spinning forming and inlet and outlet pipe welding forming.

The method for assembling the silencer is characterized in that two or more silencer splices are manufactured through casting, turning and stamping processes, the silencer splices are preferably in a shaft-cutting half-and-half mode, and after PAMB is fixedly installed at the set position of one half of the silencer splices, the other half of the silencer splices are buckled and seamed; the preferable method for installing and fixing the PAMB comprises welding, groove tightening and sleeve positioning, and the preferable seaming mode is welding, riveting, hinging and gluing.

Compared with the prior art, the invention has the beneficial effects that:

1) the PAMB is vertically or obliquely arranged in the silencer along the flow direction section of the pipeline, and the low-frequency silencing bandwidth and the silencing quantity of the PAMB are superior to those of a perforated baffle silencer with the same aperture, a micro-perforated baffle silencer with the same total perforated area, an existing thin film acoustic metamaterial silencer attached to the wall surface in parallel and the like.

2) The PAMB is different from the traditional film local resonance type acoustic metamaterial, a counterweight mass block does not need to be installed, the situation that the counterweight mass block accidentally falls off in the working process can not occur, and the working stability of the silencer is enhanced.

3) The size of the through hole of the PAMB can be designed according to the through-flow requirement and the requirement of the noise elimination frequency band, and the noise level is effectively reduced while sufficient heat flow, air flow or liquid flow is ensured to smoothly pass through. By designing the working frequency band of PAMB inserted into the cross section of the traditional reactive muffler to be consistent with the standing wave muffling valley of the original muffler, the muffling performance at the standing wave frequency is obviously improved, and the muffling bandwidth is widened. The technical scheme that an insert pipe is installed inside the expansion cavity or a plurality of expansion cavities are connected in series is replaced, and the standing wave silencing valley problem of the traditional reactive silencer is thoroughly solved on the premise of not changing the overall structure size of the expansion cavity.

4) The silencer adopts a thicker or multilayer PAMB layer to seal the sound absorption material, and sound energy is transmitted to the sound absorption material through the film so as to be converted into heat energy for consumption. The problem of sound absorbing material and through fluid direct contact in the traditional hindering nature silencer effectively solved, avoid sound absorbing material's moisture absorption, become to stick together and the appearance of the phenomenon that drops, show increase of service life.

5) The vibration of the PAMB self structure under the excitation of sound waves is utilized in the silencer, the cold and hot air exchange process at the wall attaching position is accelerated, the temperature difference of media at two sides of the hole is ensured to be maintained at a higher magnitude, and a larger heat conduction rate is ensured for a long time; when fluid passes through the heat exchanger, the PAMB film vibration can increase the fluid turbulence at the position of the heat source adherence, hinder the formation of a heat boundary layer and a speed boundary layer and accelerate the heat convection efficiency.

6) The PAMB is simple in structural form and mature in batch processing technology. The silencer has the advantages of simple internal structure, small processing and assembling difficulty and compact structure, and is suitable for various installation spaces.

Drawings

Fig. 1 is a structural schematic diagram of a general configuration of an acoustic metamaterial baffle muffler and a PAMB included in the acoustic metamaterial baffle muffler.

Fig. 2 is a schematic structural diagram of a basic acoustic metamaterial baffle muffler according to embodiment 1 of the present invention.

Fig. 3 is a structural cross-sectional view of a basic acoustic metamaterial baffle muffler, a perforated baffle muffler with the same aperture, and a micro-perforated baffle muffler with the same total perforated area according to embodiment 1 of the present invention.

Fig. 4 is a comparison graph of the sound transmission loss finite element simulation calculation results of the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area and the non-baffle muffler in embodiment 1 of the present invention.

FIG. 5 is a schematic view of a system for testing an acoustic impedance tube for measuring acoustic transmission loss of a muffler sample by a four-microphone single-load method.

Fig. 6 is a comparison graph of the sound transmission loss test measurement result and the finite element simulation calculation result of the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area and the non-baffle muffler according to embodiment 1 of the present invention.

Fig. 7 is a velocity direction distribution diagram of the intracavity air particles of the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area, and the non-baffle muffler according to embodiment 1 of the present invention.

Fig. 8 is a pressure loss comparison graph of different inlet air flow rates for the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area, and the non-baffle muffler according to embodiment 1 of the present invention.

Fig. 9 is a comparison graph of heat transfer efficiency of the basic acoustic metamaterial baffle muffler and the perforated baffle muffler with the same aperture according to embodiment 1 of the present invention.

Fig. 10 is a schematic structural view of a muffler containing two PAMBs according to embodiment 2 of the present invention.

Fig. 11 is a sectional view of the structure of a muffler containing two groups of PAMBs and a muffler containing two groups of perforated baffles with the same aperture according to embodiment 2 of the present invention.

Fig. 12 is a comparison graph of the sound transmission loss finite element simulation results of the muffler containing two groups of PAMBs and the muffler containing two groups of perforated baffles with the same aperture according to embodiment 2 of the present invention.

Fig. 13 is a schematic structural view of a sound-absorbing material closed impedance composite muffler formed by filling sound-absorbing material between two layers of PAMB according to embodiment 3 of the present invention.

Fig. 14 is a comparison graph of the sound transmission loss test results of the sound-absorbing material closed impedance composite muffler formed by filling the sound-absorbing material between two layers of PAMB and the muffler formed by not filling the sound-absorbing material between two layers of PAMB according to example 3 of the present invention.

Fig. 15 is a schematic structural diagram of a three-dimensional acoustic metamaterial baffle muffler according to embodiment 4 of the present invention.

Fig. 16 is a comparison graph of the sound transmission loss finite element simulation calculation results of the three-dimensional acoustic metamaterial baffle muffler and the baffle-free muffler according to embodiment 4 of the present invention.

Fig. 17 is a schematic structural diagram of the sandwich-type PAMB according to embodiment 5 of the present invention.

Fig. 18 is a schematic structural diagram of an inclined acoustic metamaterial baffle muffler according to embodiment 6 of the present invention.

Fig. 19 is a comparison graph of the sound transmission loss test results of the inclined type acoustic metamaterial baffle muffler containing different inclined angles PAMB according to embodiment 6 of the present invention.

Fig. 20 is a schematic structural diagram of a PAMB array baffle muffler composed of a plurality of PAMB in-plane arrays according to embodiment 7 of the present invention.

Fig. 21 is an assembly structure diagram of a flange-mounted, thread-mounted, and welded acoustic metamaterial baffle muffler according to embodiment 8 of the present invention.

Fig. 22 is a process flow of rolling a baffle muffler made of an acoustic metamaterial according to embodiment 9 of the present invention.

Wherein, 1-inlet pipe, 2-expansion chamber, 3-outlet pipe, 4-acoustic metamaterial baffle (PAMB), 5-frame, 6-film, 7-film hole, 8-frame, 9-constraining body, 10-constraining body hole, 11-inlet pipe described in example 1, 12-expansion chamber described in example 1, 13-outlet pipe described in example 1, 14-basic PAMB described in example 1, 15-perforation baffle with same aperture as basic PAMB described in example 1, 16-micro perforation baffle with same total perforation area as basic PAMB described in example 1, 17-sound source, 18-incident sound pipe, 19-sound absorbing transmission sound pipe, 20-end wedge, 21-inlet transition pipe, 22-outlet transition pipe, 23-muffler to be tested, 24-microphone fixing terminal, 25-microphone, 26-leg, 27-inlet pipe described in example 2, 28-expansion chamber described in example 2, 29-outlet pipe described in example 2, 30-group 1 PAMB described in example 2, 31-group 2 PAMB described in example 2, 32-group 1 perforated baffle described in example 2, 33-group 2 perforated baffle described in example 2, 34-muffler external cavity described in example 3, 35-sound absorbing material closed impedance composite baffle described in example 3, 36-perforated film of layer 1 PAMB described in example 3, 37-frame of layer 1 PAMB described in example 3, 38-sound absorbing material described in example 3, 39-annular wrapping film described in example 3, 40-a stent between 2 PAMBs as described in example 3, 41-a frame of 2 PAMBs as described in example 3, 42-a perforated film of 2 PAMBs as described in example 3, 43-a muffler outer cavity as described in example 4, 44-a three-dimensional PAMB as described in example 4, 45-a frame of three-dimensional PAMB as described in example 4, 46-a perforated restraint for three-dimensional PAMB as described in example 4, 47-an inclined connecting bar for three-dimensional PAMB as described in example 4, 48-a perforated film of three-dimensional PAMB as described in example 4, 49-a sandwich PAMB as described in example 5, 50-a 1 st frame of sandwich PAMB as described in example 5, 51-a 2 nd frame of sandwich PAMB as described in example 5, 52-a perforated film of sandwich PAMB as described in example 5, 53-muffler external cavity as described in example 6, 54-tilted PAMB as described in example 6. 55-an external cavity of the muffler according to embodiment 7, 56-the PAMB array baffle according to embodiment 7, 57-the frame of the PAMB array baffle according to embodiment 7, 58-the perforated film of the PAMB array baffle according to embodiment 7, 59-the 1 st splice of the flange-mounted acoustic metamaterial baffle muffler according to embodiment 8, 60-the 2 nd splice of the flange-mounted acoustic metamaterial baffle muffler according to embodiment 8, 61-the 1 st splice end flange according to embodiment 8, 62-the 2 nd splice end flange according to embodiment 8, 63-bolts, 64-nuts, 65-the female end splice of the screw-mounted acoustic metamaterial baffle muffler according to embodiment 8, 66-the male end splice of the screw-mounted acoustic metamaterial baffle muffler according to embodiment 8, 67-the female end splice of the screw-mounted acoustic metamaterial baffle according to embodiment 8, 68-male end splice male threaded end of example 8, 69-female end splice of weld-assembled acoustical metamaterial baffle mufflers of example 8, 70-male end splice of weld-assembled acoustical metamaterial baffle mufflers of example 8, 71-weld zone of male end splice of example 8, 72-PAMB of example 9, 73-positioning tool of example 9, 74-hollow tube of example 9, 75-roller knife of example 9, 76-semi-finished muffler of example 9 with multiple sets of acoustical metamaterial baffles rolled, 77-necking device of example 9, and 78-finished muffler of example 9 with multiple sets of acoustical metamaterial baffles rolled.

Detailed Description

The following describes embodiments of the present invention with reference to the drawings.

Fig. 1 is a general configuration of the acoustic metamaterial baffle muffler of the present invention, which includes an external cavity of the muffler and a plurality of internal acoustic metamaterial baffles (PAMB) vertically or obliquely disposed therein. The external cavity of the silencer comprises an inlet pipe (1), an outlet pipe (3) and a hollow expansion cavity (2), and PAMB is vertically or obliquely arranged on a plurality of sections in the hollow expansion cavity. Taking a PAMB (4) as an example, the PAMB comprises a frame (8), a restraint body (9) which is rigidly connected with the frame is arranged in the frame, a thin film (6) is covered on the surface of one side of the frame and is restrained by the internal restraint body (9), and through holes (10) and (7) are respectively arranged on the restraint body (9) and the thin film (6).

Fig. 2 shows a basic acoustic metamaterial baffle muffler according to embodiment 1 of the present invention, which only contains a group of vertically placed basic PAMBs (14) inside, and the external cavity of the muffler contains an inlet pipe (11), an expansion cavity (12) and an outlet pipe (13).

Fig. 3 is a structural cross-sectional view of a basic acoustic metamaterial baffle muffler, a perforated baffle muffler with the same aperture, and a micro-perforated baffle muffler with the same total perforated area according to embodiment 1 of the present invention.

The three kinds of silencer have the same external cavity structure and size, the length L of expansion cavity is 250mm, the internal diameter D is 46mm, and the length L of inlet pipe₁15mm, inner diameter d₁10mm, outlet tube length L₂15mm, inner diameter d ₂10 mm; the wall thickness of the silencer is uniform, and the thickness h is 3 mm; the distance between each baffle plate and the incident port of the expansion cavity is l₁150 mm. The material of the outer cavity of the silencer is 6063 aluminum alloy.

The frame of the basic PAMB (14) is circular, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame, the holed constraint body and the double-arm connecting rod are made of the same material and are made of SPCC cold-rolled steel; the material of the perforated film is polyetherimide.

The perforation baffle plate (15) is in a ring shape, the outer diameter is 46mm, the inner diameter is 10mm, and the thickness is 0.75 mm; the material is SPCC cold rolled steel.

The outer diameter of the micro-perforation baffle plate (16) is 46mm, the thickness is 0.75mm, 25 micro-holes with the diameter of 2mm are distributed in the inner central area, and the center distance of the micro-holes is 7 mm; the material is SPCC cold rolled steel.

The surface density of the three baffle plates is 5.67kg/m³The perforation rate (area of through-hole/total area of baffle) was 4.73%.

FIG. 4 is a comparison graph of finite element simulation results of sound transmission losses for a basic acoustic metamaterial baffle muffler, a perforated baffle muffler with the same aperture diameter, a micro-perforated baffle muffler with the same total perforated area, and a non-baffle muffler according to example 1 of the present invention, wherein the dashed line corresponds to the result of the non-baffle muffler, the dotted line corresponds to the result of the perforated baffle muffler, the dashed line corresponds to the result of the micro-perforated baffle muffler, and the solid line corresponds to the result of the basic acoustic metamaterial baffle muffler, for the non-baffle muffler, the sound transmission loss spectrum appears as significant valleys around 700Hz and 1400Hz, and the amount of sound absorption is almost zero, since the longitudinal dimension L of the expansion cavity is just equal to an integer multiple of the half wavelength of the incident sound wave, for the non-baffle muffler, the perforated baffle is placed inside the expansion cavity so that the two valleys of sound transmission losses move to around 460Hz and 1250Hz, respectively, for the micro-perforated muffler, the corresponding frequencies of the valleys of sound transmission losses are around 600Hz and 1300Hz, for the basic acoustic metamaterial muffler according to example 1 of the present invention, the first order of the low valley of sound transmission losses, the acoustic baffle muffler, the high efficiency of the baffle muffler is significantly higher than that of the baffle muffler, the total reflection losses of the baffle muffler are about 10dB, and the total reflection losses of the acoustic baffle muffler are all of the acoustic losses are as shown.

FIG. 5 is a schematic diagram of an acoustic impedance tube testing system for measuring sound transmission loss of a silencer sample by using a four-microphone single-load method, wherein the acoustic impedance tube mainly comprises an incident sound tube (18) and a transmission sound tube (19), a sound source (17) is arranged at the end of the incident sound tube (18), broadband white noise excitation sound waves generated by the acoustic impedance tube are developed into plane sound waves with consistent wave front amplitude before reaching a microphone (25) on an inlet transition tube (21), the sound waves pass through a silencer to be tested (23), then enter an outlet transition tube (22) and finally enter the transmission sound tube (19), a sound absorption wedge (20) which is long enough is arranged at the rear end of the transmission sound tube (19) to reduce the influence of multiple reflections of the sound waves on a test result as much as possible, and the acoustic impedance tube testing system is positioned on two sides of the silencer to be tested (23) and has four microphone fixing terminals (24) in which the microphones (25) (&

) Two by two are arranged on the inlet transition pipe (21) and the outlet transition pipe (22). The effective test frequency band of the test system is 50 Hz-1600 Hz, and the cut-off frequency is 1720 Hz.

Fig. 6 is a comparison graph of the sound transmission loss test measurement result and the finite element simulation calculation result of the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area and the non-baffle muffler according to embodiment 1 of the present invention. Wherein, fig. 6(a) corresponds to the no-baffle muffler result, wherein the solid line is the simulation result, and the hollow circle is the test result; FIG. 6(b) corresponds to the perforated baffle muffler results, wherein the solid line is the simulation result and the hollow circle is the test result; FIG. 6(c) corresponds to the microperforated baffle muffler results, where the solid line is the simulation result and the open circle is the test result; fig. 6(d) corresponds to the basic acoustic metamaterial baffle muffler result, wherein the solid line is the simulation result, and the hollow circle is the test result. According to the figure, the coincidence degree of the simulation result and the test result is good, which shows that the simulation model is correctly calculated and can be used for analyzing the micro mechanism of the sound transmission loss characteristic of the silencer, and also shows that the simulation model is suitable for the noise elimination frequency band design of the acoustic metamaterial baffle silencer.

Fig. 7 shows velocity distribution of air particles in an internal cavity of a basic acoustic metamaterial baffle muffler, a perforated baffle muffler with the same aperture, a micro-perforated baffle muffler with the same total perforated area, and a non-baffle muffler according to embodiment 1 of the present invention under a 460Hz acoustic wave excitation condition. Wherein FIG. 7(a) corresponds to the no flap muffler result; FIG. 7(b) corresponds to the perforated baffle muffler result; FIG. 7(c) corresponds to the microperforated baffle muffler result; fig. 7(d) corresponds to the basic acoustic metamaterial baffle muffler result. Black arrows indicate the direction of incidence of the acoustic waves. It can be obviously seen that the front and back areas of the baffle of the basic acoustic metamaterial baffle muffler have obvious acoustic wave vortex, which is obviously different from other types of mufflers. Specifically, for a baffle-free silencer, an obvious sound wave reflection phenomenon only occurs in a near-wall surface area of an outlet end, the sound wave reflection area of a perforated baffle silencer is advanced, and compared with the perforated baffle silencer, the sound wave reflection area of the micro-perforated baffle silencer is closer to the outlet end. The sound wave reflection area of the acoustic metamaterial baffle plate silencer is arranged at the upstream end of the acoustic metamaterial baffle plate, and the whole silencer cavity is mainly provided with the backward-propagating sound wave.

Fig. 8 is a comparison of pressure loss at different inlet air flow rates for the basic acoustic metamaterial baffle muffler, the perforated baffle muffler with the same aperture, the micro-perforated baffle muffler with the same total perforated area, and the non-baffle muffler according to example 1 of the present invention. Wherein the circle mark corresponds to a non-baffle silencer result, the square mark corresponds to a perforated baffle silencer result, the triangle mark corresponds to a micro-perforated baffle silencer result, and the asterisk mark corresponds to a basic acoustic metamaterial baffle silencer result. The pressure loss of the micro-perforated baffle plate silencer is the largest of four under different incident flow speed input conditions, the basic acoustic metamaterial baffle plate silencer is the second best, and the pressure loss of the baffle plate-free silencer is the smallest. The inlet flow velocity of the airflow pipeline system is usually below 10m/s, and the pressure loss difference of the four mufflers is small and is below 200 Pa.

Fig. 9 is a comparison graph of heat transfer efficiency of the basic acoustic metamaterial baffle muffler and the perforated baffle muffler with the same aperture according to embodiment 1 of the present invention. Wherein the dotted line corresponds to the perforated baffle muffler result and the solid line corresponds to the basic acoustic metamaterial baffle muffler result. It can be obviously seen that the heat transfer efficiency of the basic acoustic metamaterial baffle muffler is higher than that of a perforated baffle muffler with the same aperture, and the outlet temperature of the basic acoustic metamaterial baffle muffler reaches a steady-state value in a shorter time.

It is worth pointing out that the diameter of the through hole of the internal baffle of the basic acoustic metamaterial baffle muffler and the perforated baffle muffler with the same aperture as that of the inlet pipe and the outlet pipe in the embodiment 1 of the invention are the same and 10mm respectively. Under the condition of such large-size through holes, the through-flow heat dissipation effect of the common perforated baffle plate muffler is ideal enough, so that the heat transfer efficiency of the acoustic metamaterial baffle plate muffler adopting PAMB is not obviously different from that of the conventional perforated baffle plate muffler. However, with the further reduction of the size of the baffle through hole or the further reduction of the inlet flow velocity, the vibration amplitude of the PAMB placed in the acoustic metamaterial baffle muffler is increased, the exchange rate of media on two sides of the through hole can be increased more effectively, and the advantage of the PAMB in the aspect of enhancing heat transfer can be reflected more.

Fig. 10 is a schematic structural view of a muffler containing two PAMBs according to embodiment 2 of the present invention. The external cavity of the silencer comprises an inlet pipe (27), an expansion cavity (28) and an outlet pipe (29), two groups of PAMB (30) and PAMB (31) which are vertically arranged in the expansion cavity (28) at a certain distance are arranged, the structural size and the material composition of the PAMB are not completely the same, and the PAMB is respectively used for different silencing low-valley frequency bands.

FIG. 11 is a sectional view of the muffler of embodiment 2 of the present invention with two PAMB groups and two perforated baffle mufflers with the same aperture diameter, wherein the black arrows indicate the sound wave incident direction, the external cavity of the two mufflers has the same structure and size, the expansion cavity length L is 250mm, the internal diameter D is 46mm, and the inlet pipe length L is equal to the inlet pipe length L₁15mm, inner diameter d₁10mm, outlet tube length L₂15mm, inner diameter d ₂10 mm; the wall thickness of the silencer is uniform, and the thickness h is 3 mm; distance l between the group 1 PAMB (30) and the entrance port of the expansion chamber₁L/3, distance l between the 2 nd group PAMB (31) and the exit port of the expansion cavity₂L/3. the material of the outer cavity of the silencer is 6063 aluminum alloy.

For the silencer containing two groups of PAMB, the structural size and the material composition of the two groups of PAMB inside the silencer are not completely the same. Wherein, the frame of the 1 st group of PAMB (30) is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 18mm, and the diameter of the restraining body hole is 12 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 12 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame of the 2 nd group of PAMB (31) is also in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frames, the holed constraint bodies and the double-arm connecting rods of the two groups of PAMB are made of the same material and are made of SPCC cold-rolled steel; the materials of the perforated film are all polyetherimide.

For the muffler comprising two sets of perforated baffles with the same aperture corresponding to the two sets of PAMB, the through holes of the two sets of perforated baffles (32) and (33) inside the muffler respectively correspond to the two sets of PAMB (30) and (31).

Wherein, the perforation baffle plate (32) is in a ring shape, the outer diameter is 46mm, the inner diameter is 12mm, and the thickness is 0.75 mm; the perforation baffle plate (33) is also in a ring shape, the outer diameter is 46mm, the inner diameter is 10mm, and the thickness is 0.75 mm; the two groups of perforated separation blades are made of SPCC cold-rolled steel.

The surface density of the baffle plates (30) and (32) of the 1 st group is 5.49kg/m³The perforation rate is 6.81%; the surface density of the baffle plates (31) and (33) of the 2 nd group is 5.67kg/m³The perforation rates were all 4.73%.

Fig. 12 is a comparison graph of sound transmission loss simulation results of the muffler containing two sets of PAMBs and the muffler containing two sets of perforated baffle plates with the same aperture according to embodiment 2 of the present invention. Wherein the solid line corresponds to the muffler result with two sets of PAMBs and the dashed line corresponds to the muffler result with two sets of perforated baffles. It can be obviously seen that the silencer containing two groups of PAMB effectively makes up two standing wave silencing valleys respectively located at 400Hz and 760Hz of the silencer containing two groups of perforated baffle plates, so that the effective low-frequency silencing bandwidth and silencing magnitude are obviously improved.

Fig. 13 is a schematic structural diagram of a sound-absorbing material closed impedance composite muffler formed by filling sound-absorbing material between two layers of PAMB according to embodiment 3 of the present invention. The sound absorption material sealing impedance composite baffle (35) is formed by clamping sound absorption materials between two layers of PAMB. Wherein, the 1 st layer PAMB (comprising a frame (37) and a perforated film (36)) and the 2 nd layer PAMB (comprising a frame (41) and a perforated film (42)) are connected through a bracket (40), an annular coating film (39) is laid on the periphery of the bracket (40), and a sound absorption material (38) is filled between the annular coating film (39) and the inner wall surface of the silencer cavity (34).

The structural size and material composition of the muffler external cavity (34) are the same as those of embodiment 1. The frame of the PAMB layer 1 is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame of the 2 nd layer PAMB is also in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 11mm, and the diameter of the restraining body hole is 5 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole is 5 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. Frame, apertured restraint and dual layer PAMBThe arm connecting rods are made of the same material and are made of SPCC cold-rolled steel; the materials of the perforated film are all polyetherimide. The support (40) consists of two support rods, and the support rods are 50mm long, 3mm wide and 2mm thick. The thickness of the annular coating film (39) is 0.038mm, and the material is polyetherimide. The sound absorption material (38) is glass fiber cotton with the volume weight of 9.6kg/m³A flow resistivity of 19000Nsm^-4The filling length was 50 mm.

Fig. 14 is a comparison graph of the sound transmission loss test results of the sound-absorbing material closed impedance composite muffler formed by filling the sound-absorbing material between two layers of PAMB and the muffler formed by not filling the sound-absorbing material between two layers of PAMB according to example 3 of the present invention. Wherein, the solid line corresponds to the sound absorbing material closed impedance composite muffler result, and the dotted line corresponds to the muffler result of the sound absorbing material not filled between the two PAMB layers. Compared with a silencer without sound absorption materials filled between two PAMB layers, the sound absorption material closed impedance composite silencer has no obvious silencing collapse in full frequency bands, and the integral silencing effect is excellent.

Fig. 15 is a schematic structural diagram of a three-dimensional acoustic metamaterial baffle muffler according to embodiment 4 of the present invention. The frame (45) and the hole restraint body (46) are not in the same plane, a certain distance is reserved between the frame (45) and the hole restraint body, the frame and the hole restraint body are rigidly connected through an inclined connecting rod (47), and the film (48) wraps the side faces of the frame (45) and the restraint body (46) in a round table shape.

The structural size and material composition of the muffler external cavity (43) are the same as those of embodiment 1. The frame (45) of the three-dimensional PAMB is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body (46) with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film (48) is 0.05mm, and the diameter of the through hole on the perforated film is also 10 mm; the double-arm inclined connecting rod between the hole constraint body and the frame is of a rectangular section, the width of the double-arm inclined connecting rod is 3mm, the thickness of the double-arm inclined connecting rod is 2mm, and the axial vertical height of the double-arm inclined connecting rod is 20 mm. The frame (45), the hole constraint body (46) and the inclined connecting rod (47) are made of the same material and are made of SPCC cold rolled steel; the material of the film (48) is polyetherimide.

Fig. 16 is a comparison graph of the simulation results of the sound transmission loss of the baffle muffler and the baffle-free muffler made of the three-dimensional acoustic metamaterial according to embodiment 4 of the present invention. Wherein, the solid line corresponds to the result of the baffle plate silencer made of the three-dimensional acoustic metamaterial, and the dotted line corresponds to the result of the silencer without the baffle plate. According to the graph, the effective noise elimination frequency of the three-dimensional acoustic metamaterial baffle plate silencer is near 400Hz, and compared with a silencer without the baffle plate, the sound transmission loss is improved by about 3-5 dB. The embodiment is particularly suitable for silencing pipelines with small pipe diameters, and the three-dimensional PAMB can remarkably improve the vibration area of the film and ensure good low-frequency silencing effect.

Fig. 17 is a schematic structural diagram of the sandwich-type PAMB according to embodiment 5 of the present invention. The structure is that two layers of frames (50) and (51) are attached to the left and right sides of a perforated film (52) and the perforated film (52) is clamped. The configuration described in this example improves the operational stability of the PAMB, making it adequate for high flow rates, high impact flows, and the like.

Fig. 18 is a schematic structural diagram of an inclined acoustic metamaterial baffle muffler according to embodiment 6 of the present invention, wherein the inclined PAMB (54) is obliquely disposed at an angle α on an inner wall surface of an external cavity (53) of the muffler.

The structural size and the material of the external cavity (53) of the silencer are the same as those of the external cavity (53) of the silencer in embodiment 1, the installation inclination angle of the inclined PAMB (54) is α, the projection size of the axial cross section of the inclined PAMB (54) is the same as that of the basic PAMB (14) shown in embodiment 1, the materials of the frame, the hole constraint body and the connecting rod of the inclined PAMB (54) are the same as those of the basic PAMB (14), the frame, the hole constraint body and the connecting rod are all SPCC cold-rolled steel, the thickness.

Fig. 19 is a comparison graph of sound transmission loss test results of the inclined type acoustic metamaterial baffle muffler comprising different inclination angles PAMB according to embodiment 6 of the present invention, wherein the solid line corresponds to the result of the muffler installed at α -30 °, and the dotted line corresponds to the result of the muffler installed at α -45 °, it can be seen that the smaller the installation inclination angle α is, the more the sound attenuation peak acted by PAMB is biased to low frequency, that is, when the installation inclination angle α is reduced from 45 ° to 30 °, the sound attenuation peak is shifted from 600Hz to 450Hz, and the sound transmission loss change in other frequency bands is not large.

Fig. 20 is a schematic structural diagram of a PAMB array baffle muffler composed of a plurality of PAMB in-plane arrays according to embodiment 7 of the present invention. The configuration of the embodiment can ensure that the PAMB array baffle has enough bending rigidity, and is convenient for installing the baffle in the hollow expansion cavity with a large-size section.

Fig. 21 is an assembly structure diagram of a flange-mounted, thread-mounted, and welded acoustic metamaterial baffle muffler according to embodiment 8 of the present invention. Wherein fig. 21(a) corresponds to a flange assembly method; FIG. 21(b) corresponds to a thread make-up method; fig. 21(c) corresponds to the welding assembly method.

The flange assembling method comprises the steps of butting two end face flanges (61) and (62) of two splicing pieces (59) and (60) of the silencer, and matching and screwing the two end face flanges through bolts (63) and nuts (64). The thread assembling method is that a female end splicing piece (65) of the silencer is butted with a male end splicing piece (66), and the female end splicing piece is matched with an external thread end (68) of the male end splicing piece through an internal thread end (67) of the female end splicing piece and is screwed and connected. The welding assembly method is that the female end splicing piece (69) of the silencer is butted with the male end splicing piece (70), and the female end splicing piece and the male end splicing piece are welded and connected through a welding area (71) of the male end splicing piece.

Fig. 22 shows a process flow of a rolling processing acoustic metamaterial baffle muffler according to embodiment 9 of the present invention, step ①, an annular groove is processed in the entire outer contour of a frame of the PAMB (72), the annular groove is implemented by casting, turning, and the like, step ②, the PAMB (72) is clamped inside the hollow tube (74) by a positioning tool (73), and a scale of the positioning tool (73) is used to determine a fixed position, step ③, a tool bit of the roller knife (75) is moved to a position on the outer wall surface of the hollow tube (74) corresponding to the groove of the PAMB (72) and a certain pressure is applied, meanwhile, the positioning tool (73) clamps the PAMB (72) and the hollow tube (74) to rotate circumferentially together, so that an inward protrusion formed on the hollow tube (74) and the groove of the frame of the PAMB (72) inside are in tight fit, wherein for a thin-wall hollow tube, a plurality of rolling processing grooves can be performed by one-time rolling processing, for a hollow tube, a plurality of rolling processing of the hollow tube can be performed by a plurality of rolling processing, or only a plurality of extrusion processing of extrusion at a plurality of extrusion points, and a plurality of acoustic metamaterial baffle muffler semi-finished product (76) can be assembled, and a plurality of groups of finished product of the baffle muffler (76) can be processed by a plurality of finished product of the finished product (76) can be rolled and a plurality of the finished product.

Examples

The following describes the simulation method, test method and material source in the examples of the present invention.

A finite element simulation calculation method for sound transmission loss of a silencer is characterized by establishing a finite element simulation calculation model for sound transmission loss of the silencer based on an acoustic-solid coupling frequency domain analysis module of commercial finite element software COMSO L Multiphysics 5.2, wherein the simulation model comprises a solid mechanics physical field formed by an external cavity structure of the silencer and different types of baffle structures and a pressure acoustic physical field formed by an air cavity in the silencer, the two physical field regions are mutually coupled and associated through an acoustic-solid interface continuity condition, a boundary condition of the different types of baffle structures is defined as a fixed support, incident sound waves are arranged on the end face of an inlet pipe and are planar sound waves (20-2000 Hz frequency band, sweep step length is 10Hz), the end faces of the inlet pipe and the outlet pipe are defined as planar wave radiation boundary conditions, and the sound transmission loss of the silencer is calculated according to sound pressure amplitudes of the end faces of the inlet pipe and the outlet pipe (Sourandtsis L oss, written as ST L):

STL＝20log₁₀|P_I/P_T|

in the formula, P_IIs inlet pipe sound pressure amplitude, P_TTransmitting the sound pressure amplitude for the outlet pipe.

A finite element simulation calculation method of silencer pressure loss is characterized in that a finite element simulation calculation model of the silencer pressure loss is established based on a fluid-solid coupling steady-state analysis module of commercial finite element software COMSO L Multiphysics 5.2, the simulation model comprises a linear elastic material domain formed by an outer cavity structure of a silencer and different types of baffle plate structures and a fluid domain formed by an air cavity in the silencer, the two domains are mutually coupled and associated through a flow-solid interface continuity condition, the boundary condition of the different types of baffle plate structures is defined as a solid support, different inlet flow rates are arranged on the end face of an inlet pipe, the end face of an outlet pipe is defined as an outlet boundary condition, and the pressure loss (PressurDrop, abbreviated as PD) of the silencer is calculated according to the total pressure of the end faces of the inlet pipe and the outlet pipe:

PD＝P_in-P_out

in the formula, P_inFor inlet full pressure, P_outIs the outlet full pressure.

A finite element simulation calculation method of silencer heat transfer efficiency includes the steps of based on sound-solid coupling, fluid-solid coupling and fluid heat transfer physical fields of commercial finite element software COMSO L Multiphysics 5.2, using flow velocity distribution obtained through calculation of the sound-solid coupling and the fluid-solid coupling physical fields as flow field input conditions of the fluid heat transfer physical fields, setting the temperature of the outer cavity wall of a silencer to be a constant value as a heat source, setting the initial temperature value inside the silencer to be 293.15K (room temperature), setting other wall surfaces to be heat insulation boundaries, applying planar sound wave excitation of specific inlet flow velocity, specific frequency and specific amplitude to the section of an inlet pipe of the silencer, setting the section of the outlet pipe of the silencer to be a backflow-free boundary, and calculating the average temperature value of the section of the outlet.

A test method for acoustic impedance tube of sound transmission loss of silencer includes measuring sound transmission loss of silencer by four-microphone single-load method in acoustic impedance tube, connecting silencer to incident sound tube and transmission sound tube separately through inlet transition tube and outlet transition tube, placing sound source at one side of incident sound tube and placing sound-absorbing wedge at end of transmission sound tube, decomposing incident sound wave, reflected sound wave and transmitted sound wave by two pairs of microphones separately placed on inlet transition tube and outlet transition tube, obtaining sound transmission loss of silencer according to transmission matrix equation of silencer (Munjal M L, Acoustics of products and muscles, Wiley, 1987.).

The materials used in the following examples, such as SPCC cold rolled steel, 6063 aluminum alloy, polyetherimide film, and glass fiber cotton, were all commercially available.

EXAMPLE 1 basic type Acoustic metamaterial baffle muffler

The structural parameters, the preparation method, the performance calculation and determination and the mechanism analysis of the basic acoustic metamaterial baffle muffler are explained in the following by combining the attached drawings 2 to 8.

1. Structural parameters and preparation method

A frame of a basic PAMB (14) as shown in fig. 2 was integrally formed by laser cutting using an SPCC cold-rolled steel sheet, a film was adhered to one side thereof and a punching operation was performed, the basic PAMB was positioned inside an expansion chamber (12) through a sleeve, and an outer cavity of a muffler was assembled by a flange connection manner. Wherein the length of the expansion cavity (12) is 250mm, and the inner diameter is 46 mm; the length of the inlet pipe (11) is 15mm, and the inner diameter is 10 mm; the length of the outlet pipe (13) is 15mm, and the inner diameter is 10 mm; the wall thickness of the silencer is uniform and is 3 mm; the distance between the basic PAMB and the entrance port of the expansion chamber is 150 mm. The material of the outer cavity of the silencer is 6063 aluminum alloy. The frame of the basic PAMB (14) is circular, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame, the holed constraint body and the double-arm connecting rod are made of the same material and are made of SPCC cold-rolled steel; the material of the perforated film is polyetherimide.

2. Performance calculations and measurements

As shown in fig. 3, the muffler external cavity and the basic PAMB (14) were set to "solid mechanics physical field" and the muffler internal air cavity was set to "pressure acoustic physical field" in the finite element model. The boundary condition of the basic PAMB (14) is defined as the solid branch. Incident sound waves are set on the end face of the inlet pipe (11) and are plane sound waves, the end faces of the inlet pipe (11) and the outlet pipe (13) are defined as plane wave radiation boundary conditions, and the calculation result is prevented from being influenced by multiple reflection of the sound waves. Incident sound wave P_IExciting PAMB to produce reflected acoustic wave P_RAnd a transmitted sound wave P_TThe sound transmission loss of the muffler is 20log by ST L₁₀|P_I/P_TAnd | is obtained by calculation.

The sound transmission loss of the basic acoustic metamaterial baffle plate silencer is tested by adopting a four-microphone single-load method, and a schematic diagram of a testing system is shown in fig. 5. The acoustic impedance tube mainly comprises an incident sound tube (18) and a transmission sound tube(19) The acoustic testing device is characterized in that a sound source (17) is arranged at the end part of an incident sound pipe (18), broadband white noise excitation sound waves generated by the sound source are developed into plane sound waves with consistent wave front amplitude before reaching a microphone (25) on an inlet transition pipe (21), the sound waves pass through a silencer to be tested (23), enter an outlet transition pipe (22) and finally enter a transmission sound pipe (19), a sound absorption wedge (20) which is long enough is arranged at the rear end of the transmission sound pipe (19) to reduce the influence of multiple reflections of the sound waves on a test result to the greatest extent, four microphone fixing terminals (24) are arranged on two sides of the silencer to be tested (23), and the microphone (25) (model 4187, Br ü el) is inserted into the microphone fixing terminals&

) Two by two are arranged on the inlet transition pipe (21) and the outlet transition pipe (22). Incident sound waves, reflected sound waves and transmitted sound waves are decomposed through the two pairs of microphones, and sound transmission loss of the silencer is obtained according to a transmission matrix equation of the silencer.

As shown in FIG. 3a, a fluid-solid coupling computational finite element simulation model was created that included a "linear elastic material domain" consisting of the exterior cavity of the muffler and the base model PAMB (14), and a "fluid domain" consisting of the interior air cavity of the muffler. The boundary condition of the basic PAMB (14) is defined as the solid branch. The inlet flow velocities are respectively 1m/s, 2m/s, 5m/s, 10m/s, 15m/s, 20m/s, 25m/s and 30m/s at the end face of the inlet pipe (11), and the end face of the outlet pipe (13) is defined as an outlet boundary condition according to the total pressure P of the end faces of the inlet pipe and the outlet pipe_inAnd P_outCalculating the pressure loss of the silencer as PD ═ P_in-P_out。

On the basis of the silencer pressure loss calculation model, an acoustic-solid coupling physical field and a fluid heat transfer physical field are added, and the flow velocity distribution obtained by calculating the acoustic-solid coupling physical field and the fluid-solid coupling physical field is used as the flow field input condition of the fluid heat transfer physical field. The temperature of the wall surface of the cavity outside the silencer is set to 303.15K, the initial temperature value inside the silencer is set to 293.15K, and other wall surfaces are set as heat insulation boundaries. The inlet flow velocity applied to the cross section of the inlet pipe of the muffler was 5cm/s, the amplitude of the incident plane acoustic wave was 1Pa, the frequency was 200Hz, and the cross section of the outlet pipe of the muffler was set to have no backflow boundary. And calculating the average temperature value of the section of the outlet pipe of the silencer by adopting a time history solver.

3. Comparison with the prior art

Three mufflers, namely, a perforated baffle muffler with the same aperture, a micro-perforated baffle muffler with the same total perforated area and a non-baffle muffler were prepared by using the basic acoustic metamaterial baffle muffler method described in example 1, and two performance indexes, namely, sound transmission loss and pressure loss, were measured.

Referring to fig. 3(a), 3(b) and 3(c), the structural dimensions and material composition of the external cavity of the four types of mufflers are the same, except for the internally installed baffle. Wherein, the perforation baffle plate (15) is in a ring shape, the outer diameter is 46mm, the inner diameter is 10mm, and the thickness is 0.75 mm; the material is SPCC cold rolled steel; the outer diameter of the micro-perforation baffle plate (16) is 46mm, the thickness is 0.75mm, 25 micro-holes with the diameter of 2mm are distributed in the inner central area, and the center distance of the micro-holes is 7 mm; the material is also SPCC cold rolled steel. The surface densities of the three baffle plates are all 5.67kg/m³The perforation rate (area of through-hole/total area of baffle) was 4.73%.

Fig. 4 is a comparison graph of the sound transmission loss finite element simulation calculation results of the above-described muffler. Wherein the dotted line corresponds to a non-baffle muffler result, the dotted line corresponds to a perforated baffle muffler result, the dash-dot line corresponds to a micro-perforated baffle muffler result, and the solid line corresponds to a basic acoustic metamaterial baffle muffler result. Aiming at the first-order sound transmission loss valley of low frequency, the basic acoustic metamaterial baffle plate silencer in embodiment 1 of the invention utilizes the total reflection vibration mode generated by sound wave excitation of PAMB at the frequency corresponding to the valley to efficiently reflect sound waves, so that the sound transmission loss value near the frequency is obviously improved, the sound transmission loss is higher than 10dB in the continuous low and middle frequency bands of 50-1300 Hz, and is especially higher than that of a perforated baffle plate by about 30dB at 460 Hz.

In order to verify the effectiveness of the finite element sound transmission loss calculation model, fig. 6 shows the comparison between the sound transmission loss test measurement result of the silencer and the finite element simulation calculation result. Wherein FIG. 6(a) corresponds to the no flap muffler result; FIG. 6(b) corresponds to the perforated baffle muffler result; FIG. 6(c) corresponds to the microperforated baffle muffler result; fig. 6(d) corresponds to the basic acoustic metamaterial baffle muffler result. According to the figure, the coincidence degree of the simulation result and the test result is good, which shows that the simulation model is correctly calculated and can be used for analyzing the micro mechanism of the sound transmission loss characteristic of the silencer, and also shows that the simulation model is suitable for the noise elimination frequency band design of the acoustic metamaterial baffle silencer.

Fig. 8 is a comparison of the pressure loss at different inlet air flow rates of the above-described muffler. Wherein the circle mark corresponds to a non-baffle silencer result, the square mark corresponds to a perforated baffle silencer result, the triangle mark corresponds to a micro-perforated baffle silencer result, and the asterisk mark corresponds to a basic acoustic metamaterial baffle silencer result. The pressure loss of the micro-perforated baffle plate silencer is the largest of four under different incident flow speed input conditions, the basic acoustic metamaterial baffle plate silencer is the second best, and the pressure loss of the baffle plate-free silencer is the smallest. The inlet flow velocity of the airflow pipeline system is usually below 10m/s, and the pressure loss difference of the four mufflers is small and is below 200 Pa.

Fig. 9 shows a comparison of the heat transfer efficiency of the basic acoustic metamaterial baffle muffler of embodiment 1 of the present invention and a perforated baffle muffler with the same aperture. Wherein the dotted line corresponds to the perforated baffle muffler result and the solid line corresponds to the basic acoustic metamaterial baffle muffler result. Under the condition of the same external heat source temperature and the same inlet flow rate, the heat transfer efficiency of the basic acoustic metamaterial baffle muffler is obviously higher than that of a perforated baffle muffler with the same aperture, and the outlet temperature of the basic acoustic metamaterial baffle muffler reaches a steady-state value in a shorter time.

4. Analysis of mechanism of operation

Fig. 7 shows the velocity distribution of the air particles in the internal chamber of the muffler. Wherein FIG. 7(a) corresponds to the no flap muffler result; FIG. 7(b) corresponds to the perforated baffle muffler result; FIG. 7(c) corresponds to the microperforated baffle muffler result; fig. 7(d) corresponds to the basic acoustic metamaterial baffle muffler result. Black arrows indicate the direction of incidence of the acoustic waves. It can be obviously seen that the front and back areas of the baffle of the basic acoustic metamaterial baffle muffler have obvious acoustic wave vortex, which is obviously different from other types of mufflers. Specifically, for a baffle-free silencer, an obvious sound wave reflection phenomenon only occurs in a near-wall surface area of an outlet end, the sound wave reflection area of a perforated baffle silencer is advanced, and compared with the perforated baffle silencer, the sound wave reflection area of the micro-perforated baffle silencer is closer to the outlet end. The sound wave reflection area of the acoustic metamaterial baffle plate silencer is arranged at the upstream end of the acoustic metamaterial baffle plate, and the whole silencer cavity is mainly provided with the backward-propagating sound wave.

Example 2 muffler with two sets of acoustic metamaterial baffle plates

1. Structural parameters

As shown in fig. 10, the muffler containing two groups of PAMBs according to embodiment 2 of the present invention is formed by mounting one group of PAMBs on the basic acoustic metamaterial baffle muffler according to embodiment 1. The two groups of PAMB (30) and (31) are not identical in structural size and material composition and respectively aim at different sound attenuation valley frequency bands. Wherein, the frame of the 1 st group of PAMB (30) is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 18mm, and the diameter of the restraining body hole is 12 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 12 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame of the 2 nd group of PAMB (31) is also in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole on the perforated film is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frames, the holed constraint bodies and the double-arm connecting rods of the two groups of PAMB are made of the same material and are made of SPCC cold-rolled steel; the materials of the perforated film are all polyetherimide.

By way of comparison, FIG. 11 shows a cross-sectional view of a muffler having two sets of perforated baffle mufflers of equal aperture size corresponding to the muffler of the present invention, example 2, which includes two sets of PAMB. The through holes of the two groups of perforation baffles (32) and (33) inside the cylinder body respectively correspond to the two groups of PAMB (30) and (31). Wherein the perforation baffle plate (32) is in a ring shape, the outer diameter is 46mm, the inner diameter is 12mm,the thickness is 0.75 mm; the perforation baffle plate (33) is also in a ring shape, the outer diameter is 46mm, the inner diameter is 10mm, and the thickness is 0.75 mm; the two groups of perforated separation blades are made of SPCC cold-rolled steel. The surface density of the baffle plates (30) and (32) of the 1 st group is 5.49kg/m³The perforation rate is 6.81%; the surface density of the baffle plates (31) and (33) of the 2 nd group is 5.67kg/m³The perforation rate is 4.73%, the structures and the sizes of the external cavities of the two types of silencers are the same, the length L of the expansion cavity is 250mm, the inner diameter D is 46mm, and the length L of the inlet pipe₁15mm, inner diameter d₁10mm, outlet tube length L₂15mm, inner diameter d ₂10 mm; the wall thickness of the silencer is uniform, and the thickness h is 3 mm; distance l between the 1 st set of baffles (30) and (32) and the entrance port of the expansion chamber₁L/3, distance l between the 2 nd group of baffle plates (31) and (33) and the exit port of the expansion cavity₂L/3. the material of the outer cavity of the silencer is 6063 aluminum alloy.

2. Performance analysis

Fig. 12 is a comparison graph of sound transmission loss simulation results of the muffler containing two sets of PAMBs and the muffler containing two sets of perforated baffle plates with the same aperture according to embodiment 2 of the present invention. Wherein the solid line corresponds to the muffler result with two sets of PAMBs and the dashed line corresponds to the muffler result with two sets of perforated baffles. It can be obviously seen that the silencer containing two groups of PAMB effectively makes up two standing wave silencing valleys respectively located at 400Hz and 760Hz of the silencer containing two groups of perforated baffle plates, so that the effective low-frequency silencing bandwidth and silencing magnitude are obviously improved.

EXAMPLE 3 Sound-absorbing Material Enclosed impedance composite muffler

1. Structural parameters

As shown in fig. 13, the sound-absorbing material sealed impedance composite muffler formed by filling sound-absorbing material between two layers of PAMB according to embodiment 2 of the present invention includes a group of sound-absorbing material sealed impedance composite baffle plates (35) formed by sandwiching sound-absorbing material between two layers of PAMB. Wherein, the 1 st layer PAMB (comprising a frame (37) and a perforated film (36)) and the 2 nd layer PAMB (comprising a frame (41) and a perforated film (42)) are connected through a bracket (40), an annular coating film (39) is laid on the periphery of the bracket (40), and a sound absorption material (38) is filled between the annular coating film (39) and the inner wall surface of the silencer cavity (34). It is composed ofThe structural dimensions and material composition of the muffler outer cavity (34) are the same as those of embodiment 1. The frame of the PAMB layer 1 is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole is 10 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frame of the 2 nd layer PAMB is also in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body with the hole is 11mm, and the diameter of the restraining body hole is 5 mm; the thickness of the perforated film is 0.05mm, and the diameter of the through hole is 5 mm; the double-arm connecting rod between the hole constraint body and the frame is of a rectangular section, 3mm wide and 2mm thick. The frames, the holed constraint bodies and the double-arm connecting rods of the two layers of PAMB are made of the same material and are made of SPCC cold rolled steel; the materials of the perforated film are all polyetherimide. The support (40) consists of two support rods, and the support rods are 50mm long, 3mm wide and 2mm thick. The thickness of the annular coating film (39) is 0.038mm, and the material is polyetherimide. The sound absorption material (38) is glass fiber cotton with the volume weight of 9.6kg/m³The flow resistivity is 19000Nsm-⁴The filling length was 50 mm.

2. Performance analysis

Fig. 14 is a comparison graph of the sound transmission loss test results of the sound-absorbing material closed impedance composite muffler formed by filling the sound-absorbing material between two layers of PAMB and the muffler formed by not filling the sound-absorbing material between two layers of PAMB according to example 3 of the present invention. Wherein, the solid line corresponds to the sound absorbing material closed impedance composite muffler result, and the dotted line corresponds to the muffler result of the sound absorbing material not filled between the two PAMB layers. Compared with a silencer without sound absorption materials filled between two PAMB layers, the sound absorption material closed impedance composite silencer has no obvious silencing collapse in full frequency bands, and the integral silencing effect is excellent.

Embodiment 4 three-dimensional stereo type learning metamaterial baffle plate silencer

1. Structural parameters

As shown in fig. 15, a frame (45) of the three-dimensional acoustic metamaterial baffle muffler according to embodiment 4 of the present invention and the holed constraining body (46) are not in the same plane, but are separated by a certain distance and rigidly connected by an inclined connecting rod (47), and a film (48) is wrapped around the frame (45) and the constraining body (46) in a circular truncated cone shape. The structural size and material composition of the muffler external cavity (43) are the same as those of embodiment 1. The frame (45) of the three-dimensional PAMB is in a ring shape, the outer diameter is 46mm, the inner diameter is 40mm, and the thickness is 2 mm; the outer diameter of the restraining body (46) with the hole is 16mm, and the diameter of the restraining body hole is 10 mm; the thickness of the perforated film (48) is 0.05mm, and the diameter of the through hole on the perforated film is also 10 mm; the double-arm inclined connecting rod between the hole constraint body and the frame is of a rectangular section, the width of the double-arm inclined connecting rod is 3mm, the thickness of the double-arm inclined connecting rod is 2mm, and the axial vertical height of the double-arm inclined connecting rod is 20 mm. The frame (45), the hole constraint body (46) and the inclined connecting rod (47) are made of the same material and are made of SPCC cold rolled steel; the material of the film (48) is polyetherimide.

2. Performance analysis

Fig. 16 is a comparison graph of the simulation results of the sound transmission loss of the baffle muffler and the baffle-free muffler made of the three-dimensional acoustic metamaterial according to embodiment 4 of the present invention. Wherein, the solid line corresponds to the result of the baffle plate silencer made of the three-dimensional acoustic metamaterial, and the dotted line corresponds to the result of the silencer without the baffle plate. According to the graph, the effective noise elimination frequency of the three-dimensional acoustic metamaterial baffle plate silencer is near 400Hz, and compared with a silencer without the baffle plate, the sound transmission loss is improved by about 3-5 dB. The embodiment is particularly suitable for silencing pipelines with small pipe diameters, and the three-dimensional PAMB can remarkably improve the vibration area of the film and ensure good low-frequency silencing effect.

EXAMPLE 5 Sandwich-type Acoustic metamaterial baffle

As shown in fig. 17, the sandwich PAMB according to example 5 of the present invention is formed by attaching two frames (50) and (51) to the left and right sides of a perforated film (52) and clamping the perforated film (52). The configuration of this embodiment can improve the operational stability of PAMB due to the fastening of the perforated film on both sides, making it suitable for high flow rate, strong impact flow, etc., such as handling of transient impulse noise generated by the switch of a pneumatic valve.

EXAMPLE 6 inclined Acoustic metamaterial baffle muffler

1. Structural parameters

As shown in fig. 18, the inclined PAMB (54) inside the inclined acoustic metamaterial baffle muffler according to embodiment 6 of the present invention is obliquely disposed at a certain angle α on the inner wall surface of the external cavity (53) of the muffler, wherein the structural dimensions and the material of the external cavity (53) of the muffler are the same as those of the external cavity (53) of the muffler in embodiment 1, the installation inclination angle of the inclined PAMB (54) is α, the projection dimensions of the axial cross section of the inclined PAMB (54) are the same as those of the frame, the hole-containing constraining body and the connecting rod of the basic PAMB (14) of embodiment 1, all are SPCC cold rolled steel, the thickness of the thin film is 0.05mm, and the material is polyetherimide.

2. Performance analysis

Fig. 19 is a comparison graph of sound transmission loss test results of the inclined type acoustic metamaterial baffle muffler comprising different inclination angles PAMB according to embodiment 6 of the present invention, wherein the solid line corresponds to the result of the muffler installed at α -30 °, and the dotted line corresponds to the result of the muffler installed at α -45 °, it can be seen that the smaller the installation inclination angle α is, the more the sound attenuation peak acted by PAMB is biased to low frequency, that is, when the installation inclination angle α is reduced from 45 ° to 30 °, the sound attenuation peak is shifted from 600Hz to 450Hz, and the sound transmission loss change in other frequency bands is not large.

EXAMPLE 7PAMB array baffle muffler

Fig. 20 is a schematic structural diagram of a PAMB array baffle muffler composed of a plurality of PAMB in-plane arrays according to embodiment 7 of the present invention. The PAMB array baffle plate (56) comprises a plurality of PAMB units with the same or different structure sizes and a perforated film (58) corresponding to the PAMB units. The configuration of the embodiment can ensure that the PAMB array baffle has enough bending rigidity, and is convenient for installing the baffle in the hollow expansion cavity with a large-size section.

Embodiment 8 assembling method of three acoustic metamaterial baffle plate silencers

Fig. 21 is an assembly structure diagram of a flange-mounted, thread-mounted, and welded acoustic metamaterial baffle muffler according to embodiment 8 of the present invention. Wherein fig. 21(a) corresponds to a flange assembly method; FIG. 21(b) corresponds to a thread make-up method; fig. 21(c) corresponds to the welding assembly method.

The flange assembling method comprises the steps of butting two end face flanges (61) and (62) of two splicing pieces (59) and (60) of the silencer, and matching and screwing the two end face flanges through bolts (63) and nuts (64). The thread assembling method is that a female end splicing piece (65) of the silencer is butted with a male end splicing piece (66), and the female end splicing piece is matched with an external thread end (68) of the male end splicing piece through an internal thread end (67) of the female end splicing piece and is screwed and connected. The welding assembly method is that the female end splicing piece (69) of the silencer is butted with the male end splicing piece (70), and the female end splicing piece and the male end splicing piece are welded and connected through a welding area (71) of the male end splicing piece.

Embodiment 9 Process flow for rolling acoustic metamaterial baffle plate muffler

The technological process of the rolling processing acoustic metamaterial baffle silencer in embodiment 9 of the invention is as shown in fig. 22, and includes five steps, step ①, processing an annular groove in the whole outer contour of a frame of the PAMB (72), wherein the annular groove is formed by casting, turning and other processing manners, step ②, clamping the PAMB (72) to the inside of the hollow tube (74) through a positioning tool (73), and determining a fixed position by using a graduated scale of the positioning tool (73), step ③, moving a cutter head of a roller cutter (75) to the position of the outer wall surface of the hollow tube (74) corresponding to the groove of the PAMB (72) and applying certain pressure, and meanwhile, the positioning tool (73) clamps the PAMB (72) and the hollow tube (74) to rotate circumferentially together, so that a protrusion formed inwards of the hollow tube (74) and the groove of the frame of the internal PAMB (72) are tightly fastened and matched, wherein, for a hollow tube, for a single-time, multiple-time feeding spinning processing is needed for a thicker hollow tube, or only multiple-point extrusion and compression processing is suitable for a plurality of finished products of the rolled acoustic metamaterial baffle silencer (76) are obtained, and a plurality of the finished products are fixed by a plurality of rolling processing of the finished products of the rolled products (36) by using a plurality of rolling processing of the finished products of the rolled acoustic metamaterial silencer (76) and a plurality of the finished products of.

Finally, it is noted that: the above-mentioned embodiments are only examples of the present invention, and it is a matter of course that those skilled in the art can make modifications and variations to the present invention, and it is considered that the present invention is protected by the modifications and variations if they are within the scope of the claims of the present invention and their equivalents.

Claims (35)

1. The silencer is characterized by comprising an inlet pipe, an outlet pipe, a hollow expansion cavity between the inlet pipe and the outlet pipe, and an acoustic metamaterial baffle plate with a through hole, wherein the acoustic metamaterial baffle plate is vertically or obliquely arranged on at least one section in the hollow expansion cavity; the through hole-containing acoustic metamaterial baffle plate comprises a frame, at least one constraint body is arranged in the frame, a thin film covers at least one of the two side surfaces of the frame, and at least one through hole is formed in each of the constraint body and the thin film; the shape, position and size of the through holes on the constraint body and the thin film are the same; the sizes of the through holes of the restraint body and the thin film are determined according to the through-flow requirement and the noise elimination frequency band.

2. The muffler of claim 1, wherein the sectional shape of the hollow expansion chamber is determined according to the installation space of the muffler and the expansion ratio of the muffler.

3. The muffler of claim 2, wherein the cross-sectional shape of the hollow expansion chamber is circular, elliptical, rectangular, regular polygonal, conical, or undulating.

4. The muffler of claim 1, wherein said rim is a hollow structure having an outer contour conforming to the cross-sectional shape of the hollow expansion chamber; the restraint body is arranged inside the frame, and the restraint body and the frame are rigidly connected through at least one connecting rod; the peripheral area of the film is attached to the surface of the frame, and the inner area of the film is restrained by the restraint body.

5. The muffler of claim 4, wherein the restraints and the connecting bar are flush with the rim.

6. The muffler of claim 1, wherein the through holes in the restriction and the membrane have a diameter greater than 2 mm.

7. The muffler of claim 1, wherein the shape of the through-hole is a symmetrical regular shape.

8. The muffler of claim 7, wherein the through-hole has a shape of a circle, an ellipse, or a regular polygon.

9. The muffler of claim 1, wherein the contact area of the constraining body with the membrane is a line or a plane; the contact shape of the constraining body and the thin film is a symmetrical regular geometric shape.

10. The muffler of claim 9, wherein said geometry is circular, elliptical or regular polygonal.

11. The muffler of claim 1, adapted to enhance fluid heat transfer efficiency.

12. The muffler of any one of claims 1-11, wherein the material of the border and the restraint body of the baffle plate of the acoustic metamaterial with through holes is a metal material or a non-metal material.

13. The muffler of claim 12, wherein the metallic material is aluminum, iron, steel, or copper; the non-metallic material is wood, ceramic, rubber, glass, gypsum, cement, high molecular polymer or composite fiber material; the film is made of a high-molecular polymer film material, a metal film material or an elastic film material.

14. The muffler of claim 13, wherein the polymeric film material is a polyetherimide film, a polyvinyl chloride film, or a polyethylene film; the metal film material is one of an aluminum and aluminum alloy film and a titanium and titanium alloy film; the elastic film material is a rubber film, a silica gel film or an emulsion film.

15. An improved reactive muffler is characterized in that at least one through hole-containing acoustic metamaterial baffle is arranged on the inner section of a traditional reactive muffler, the through hole-containing acoustic metamaterial baffle comprises a frame, at least one constraint body is arranged in the frame, a thin film covers at least one surface of two side surfaces of the frame, and at least one through hole is formed in each of the constraint body and the thin film; the shape, position and size of the through holes on the constraint body and the thin film are the same; the sizes of the through holes of the restraint body and the thin film are determined according to the through-flow requirement and the noise elimination frequency band.

16. The improved reactive muffler of claim 15, wherein the operating band of the acoustic metamaterial baffle with through-holes covers the standing wave muffling valley band of the conventional reactive muffler.

17. The improved reactive muffler of claim 16, wherein the through-hole containing acoustic metamaterial baffle has a peak operating frequency consistent with the standing wave frequency of each step.

18. An improved resistive muffler is characterized in that a sound absorption material is sealed by one or more layers of acoustic metamaterial baffle plates with through holes, so that the sound absorption material is prevented from being in direct contact with a passing fluid; the through hole-containing acoustic metamaterial baffle plate comprises a frame, at least one constraint body is arranged in the frame, a thin film covers at least one of the two side surfaces of the frame, and at least one through hole is formed in each of the constraint body and the thin film; the shape, position and size of the through holes on the constraint body and the thin film are the same; the sizes of the through holes of the restraint body and the thin film are determined according to the through-flow requirement and the noise elimination frequency band.

19. The improved resistive muffler of claim 18, wherein a thickness of the baffle of acoustic metamaterial having through holes is greater than 5 mm.

20. The improved resistive muffler of claim 18, wherein the side surfaces of the rim of one of the layers of the acoustic metamaterial baffle with the through holes are covered with a film, and the two layers of the film are filled with a porous material matching the impedance of the film.

21. The improved resistive muffler of claim 18, wherein the plurality of layers of acoustic metamaterial baffles with through holes are positioned by a support, a layer of impermeable membrane is wrapped around the support, and a porous material matched with the impedance of the membrane is filled in a cavity between the impermeable membrane and the wall surface of the expansion cavity or between the two layers of membranes.

22. The improved resistive muffler of claim 21, wherein the impermeable membrane is made of the same material as the membrane of the acoustic metamaterial baffle with the through-holes.

23. The improved resistive muffler of claim 20, wherein the porous material is fiberglass wool or open and closed cell foam.

24. A method of canceling standing wave canceling valleys of a conventional reactive muffler, the method comprising the steps of: mounting the acoustic metamaterial baffle plate with the through hole on the inner cross section of the traditional reactive muffler, and enabling the working frequency band of the acoustic metamaterial baffle plate with the through hole to cover the standing wave silencing valley frequency band of the traditional reactive muffler; the through hole-containing acoustic metamaterial baffle plate comprises a frame, at least one constraint body is arranged in the frame, a thin film covers at least one of the two side surfaces of the frame, and at least one through hole is formed in each of the constraint body and the thin film; the shape, position and size of the through holes on the constraint body and the thin film are the same; the sizes of the through holes of the restraint body and the thin film are determined according to the through-flow requirement and the noise elimination frequency band.

25. The method of canceling standing wave canceling low dip of a conventional reactive muffler of claim 24, wherein the acoustic metamaterial baffle with through holes has an operating band that coincides with the first order standing wave frequency of low frequencies.

26. The method for adjusting the muffling frequency band of the muffler according to any one of claims 1 to 14, wherein the effective working frequency band of the acoustic metamaterial baffle plate with the through hole is adjusted by changing the structural dimensions and material parameters of the frame, the constraining body and the thin film of the acoustic metamaterial baffle plate with the through hole under the premise that the shape and the size of the expansion cavity of the muffler are not changed, so that the muffling performance of the muffler in the frequency band is improved.

27. A method for assembling the muffler according to any one of claims 1 to 14, wherein the acoustic metamaterial baffle plate with the through hole is inserted into the hollow pipe by feeding the acoustic metamaterial baffle plate with the through hole to a predetermined position inside the hollow pipe through a positioning tool, moving a roller cutter head to a position corresponding to the outer wall surface of the hollow pipe and applying a certain pressure; and closing up the two ends of the hollow tube to form the hollow tube.

28. The method of claim 27, wherein the necking is performed by die forming, spin forming, or welding of the inlet and outlet tubes.

29. A method for assembling the muffler according to any one of claims 1 to 14, wherein the acoustic metamaterial baffle plate with the through hole is installed in the hollow pipe by a stamping or hot assembling method, and the acoustic metamaterial baffle plate with the through hole is fixed at a given position of the hollow pipe by using the restraining force of interference fit; and closing up the two ends of the hollow tube to form the hollow tube.

30. The method of claim 29, wherein the necking is performed by die forming, spin forming, or welding of the inlet and outlet tubes.

31. A method for assembling the muffler according to any one of claims 1 to 14, wherein the acoustic metamaterial baffle plate with the through hole is installed at a predetermined position in the hollow tube through a positioning fixture, and then the acoustic metamaterial baffle plate with the through hole is fixed by using an ultrasonic welding process, a laser welding process or an argon arc welding process, or the acoustic metamaterial baffle plate with the through hole is positioned by using a sleeve or a spring structure to perform closing-up forming on two ends of the hollow tube.

32. The method of claim 31, wherein the necking is performed by die forming, spin forming, or welding of the inlet and outlet tubes.

33. A method for assembling the muffler according to any one of claims 1 to 14, wherein two or more muffler splices are manufactured by casting, turning or punching, the muffler splices are in axial cut and half type, and after an acoustic metamaterial baffle plate containing a through hole is installed and fixed at a predetermined position of one half of the muffler splices, the other half of the muffler splices are fastened and seamed.

34. The method of assembling a muffler of claim 33, wherein the method of installing and securing the baffle of acoustic metamaterial including through holes comprises welding, groove clinching, and sleeve positioning.

35. The method of assembling a muffler of claim 33, wherein the seaming is by welding, riveting, hinging, or gluing.

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