RU2098652C1 - Intake system of internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering; internal combustion engines with noise suppressors in intake and fuel feed systems. SUBSTANCE: system has air cleaner 1 to which intake pipe and air supply branch pipe are connected. Air supply branch pipe has inlet portion 3 accommodating coaxially arranged noise suppressor forming through ring clearance 4. Suppressor is made in form of quarter-wave resonator 7 located in inlet portion 3 of branch pipe. Length of resonator is equal to half the length of branch pipe, neck 8 of resonator 7 is located in middle of branch pipe, and bottom 9 of resonator is furnished with fairing 10 projecting beyond the plane of cross section of branch pipe entry cut 5. Coupling portion 6 of branch pipe is connected to chamber of air cleaner 1. Second quarter-wave resonator can be placed inside resonator 7, length of second resonator being equal to quarter of branch pipe length. Different design versions are available. EFFECT: improved efficiency and reliability of noise suppression. 9 cl, 11 dwg

Description

 The invention relates to engine building, in particular to multi-cylinder internal combustion engines with fuel injection into cylinders.

 In the intake systems of carburetor internal combustion engines (ICE), the presence of diffuser elements provides a weakening of the resonant properties of the system as a whole, because due to the significant active resistances of these elements, the system becomes less “sound” (i.e., the resonant frequencies are damped). This is to some extent a positive factor, as on the one hand, cylinder filling losses (loss of effective power, improved engine efficiency) are compensated for due to a decrease in the resonant amplitudes of the pulsations of the volumetric air flow (and the increase in the hydraulic resistance of the system, as is known, is proportional to the square of the amplitudes of the pulsations of the gas flow), on the other hand, the suppression of resonant gas pulsations in the ICE intake system it is favorable from the point of view of sound (noise) radiation into the environment produced as open ends of the air intake pipes cleaner (aerodynamic noise), and vibrating walls of the intake system elements (structural noise, body noise).

 Thus, the elimination of the carburetor as a conservative device that does not provide high environmental characteristics of the internal combustion engine and the vehicle as a whole (“rough” fuel dosage, evaporation of fuel vapor from the carburetor, etc.), and the use of electronic fuel injection systems necessitate the use of devices in the internal combustion engine designs weakening or eliminating the above adverse events. For this purpose, the use of a wide variety of devices is currently known.

 So, for example, the Japanese company Yamaha Motor in the application N 61-244824, F 02 B 27/00, 10/31/86, to reduce ripple and noise, suggests using two receivers connected in parallel and in series to the intake manifold route.

 Japanese company Honda Motor in the application N 63-219866, F 02 M 35 / 10,13.09.88 suggests to use two separate air pipes connecting the air purifier and the receiver with two controlled throttle valves to close the auxiliary valve to reduce noise during suction channel at low speeds and the open state of both connecting pipelines at high speeds. The same company in the application N 61-190159, F 02 M 35/12, 01/14/87, in order to ensure sound attenuation in a wide range of frequencies, proposes to connect two 1/4 dead-end wave resonator and a resonant chamber to the inlet pipe.

 In EPO N 0278117, F 02 B 27 / 00.17.08.88, to use the effects of increasing the filling of the cylinders, by suppressing resonant gas pulsations by adding them in antiphase, it is proposed to use mutually agreed additional resonant tubes and an additional receiver.

 The Austrian company "AVL" in the application of Germany N 3820607, F 01 B 25/00, 12.29.88, to expand the frequency range of the effective operation of the additional resonator offers to carry out its design of variable volume depending on the rotation of the crankshaft.

 The Japanese company "Nippon Radzieta" in Japan's application N 62-48047, F 01 N 1/02, 10.10.87, proposes to use an anti-resonant inlet pipe, including a controlled noise source or to use large-sized complex silencers, to increase the effect of damping vibration, solenoid valve, receiving acoustic sensors, controlled processor.

 Japanese company "Hitachi seisakuse" in Japanese application N 2-4840, F 16 L 55/04, 01/30/90, to reduce ripple in the piping system, proposes to branch the pipeline into at least two channels, at different distances from the branch point to place expansion cameras reflecting direct incident waves back to the source of pulsations (engine cylinder), and the distance between the walls of the cameras is selected in a certain way.

 The English branch of the Ford Motor company in the application of Great Britain N 2203488, F 02 B 29/00, publ. 10.19.88 g to suppress pulsations of gas and noise in the intake manifold provides for the installation of anti-sound in the form of a special loudspeaker or a special reservoir with an electrovalve.

 The Japanese company Nissan Jidosia in Japanese application N 51-23656, F 02 B 37/00, 05/08/89, to reduce the intake noise of the internal combustion engine and increase the power due to lower reverse charge air flow, proposes to use a special silencer design in the form of an expansion chamber with internal tubes of a certain ratio of diameters and a certain distance of pipe sections between themselves.

 The Siemens Bendix Canada branch in US Pat. No. 4,934,343, F 02 M 35/00, for suppressing gas flow noise without significantly affecting the hydraulic resistance of the inlet tract, provides for the use of two special diffuser sections in a bifurcated section of the gas pipeline that provides phase shift and amplitude compensation pulsations when they are added in the connection zone.

 The French company Peugeot in French patent N 2536792, publ. 06/22/84, declares the use of narrowing the bore of the inlet pipe of the throttle washer or diffuser insert to reduce the noise of the intake of ICE with direct fuel injection. The throttle washer or diffuser insert to ensure the required efficiency is located in the antinode wave of the vibrational velocity of the gas stream at some given speed mode of operation of the internal combustion engine. An obvious drawback of the device is the increase in hydraulic resistance of the intake system due to narrowing of the bore and, as a consequence, the deterioration of power, economic and environmental (toxic) parameters of the internal combustion engine. Also, the location of the throttle washer of the diffuser insert in one specific place of the inlet path allows you to effectively act on only one resonant frequency and multiple odd harmonics, i.e. there is a limited impact on individual high-speed engine operation modes.

 The American branch of the company Siemens Bendix in US patent N 4907547, F 02 M 35/10, publ. 03/13/90 to suppress noise and pulsations in the intake system of the engine, it is proposed to use a special wave reflector located across the intake pipe of one of the cylinders and a pair of cylinders on a rotating roller, which, when turned, provides an inventive opening of one of the adjacent intake pipes of the engine cylinder.

 The Japanese company Mazda-Motor in EPO N 0376299, F 02 M 35/12, publ. 07/04/90, to suppress gas pulsations and noise in the intake system of the internal combustion engine, the use of a special device is provided for suppressing each of the resonant harmonics of pulsations that are multiples of (0.5 + h) the lengths of the resonant pulsation waves, where h is a number equal to zero or more than zero.

 In the application of Germany N 3742322, F 02 M 35/10, 07.07.88, the German company Volkswagen provides for damping the fluctuations in the intake air flow in the internal combustion engine due to the inclusion of an additional "soothing" receiver with elastic walls in the intake duct, in which elastic deformation of the walls of the receiver, due to the pulsating effect of the gas flow, the pulsation energy will be converted into thermal energy in the elastic wall material with high internal friction of the material (rubber). The obvious disadvantages of such a system include the relative high cost of the device, the instability of the characteristics, low durability, the risk of untreated air entering the ICE cylinders when the elastic wall is damaged, significant sound emission from the “pulsating” elastic wall, etc.

 Analyzing and summarizing the results of the above patent review, it should be concluded that all of the above devices to improve acoustic performance and reduce gas-dynamic pulsations in the intake systems of ICEs and, accordingly, improve their power, economic and environmental performance are associated with the use of additional expansion or resonance chambers connected in parallel, and sequentially to the intake tract, using electronic systems for the formation of artificial anti basic signals to compensate for real pulsation and noise signals, using additional receivers, additional controlled air ducts and chambers with variable volume, branched gas ducts with phase-controlled diffuser sections.

 Known engine company "Mazda Motor" described in the application EPO N 0379926, F 02 M 35/12, publ. 08/01/90, containing a cylinder head with inlet openings in which inlet valves are installed, inlet nozzles extending directly from the inlet openings and exiting into the gas collection receiver, the side wall of which is provided with connecting holes for the said nozzles, and mounted along the receiver cavity, mounted on its end wall is a fitting. Three resonant silencers are connected to the engine intake system (between the throttle and the air cleaner), which are directly connected to the receiver volume, the pipe between the receiver and the air cleaner chamber and the volume of the air cleaner chamber, respectively.

 The effectiveness of this type of ICE intake systems is acceptable only in a narrow frequency (speed) range, which necessitates the use of three silencers simultaneously.

 But given the wide speed mode of the engine, the presence of a large number of natural frequencies of vibrations of individual elements of the gas ducts, resonating when they coincide with the frequencies (or their multiple harmonics) of forced vibrations (gas pulsations during the opening and closing of intake valves and at the time of phase overlap in the intake processes and gas release in the internal combustion engine), the use of even several sharply tuned parallel-connected resonators cannot provide the required efficiency over the entire operating range in and load, and can only suppress or more correct the most pronounced "acoustic defects" on a separate system (separate) regime, as evidenced by the illustrations given in the application of experimental evaluations.

 The engine’s disadvantages are also obvious from the point of view of material consumption, limited layout options in the cramped space of the car’s engine compartment, as well as the adverse effect on the change in the coefficient of excess air during the intake during intensive engine acceleration.

 As a prototype, the intake system of the internal combustion engine, described in PCT (E) N 91/00958, class. F 02 M 35/12, 01/24/91, containing an air purifier to which an inlet pipe with a fuel supply source to the engine cylinders and an air supply pipe are connected, including an inlet part made in the form of a chamber bounded by an inlet shear, in which the noise suppression device is coaxially placed , and a connecting part connected to the air cleaner chamber. The sound attenuation device is made in the form of a plastic insert having a confuser-diffuser shape, with a streamlined entry part and side slots for air to enter the insert. The confuser-diffuser section serves to drown out the noise.

 The principle of noise suppression in the prototype is based on creating a mismatch in the wave impedances of the pipeline in which sound waves propagate. The mismatch of wave impedances provides reflection of sound waves in the opposite direction to the location of the source of sound waves - the cylinder of the engine at the moments of opening and closing of the intake valves. In the prototype, a mismatch of wave impedances is provided in zones of change in its flow area in the diffuser element, i.e. it is in this zone that the sound reflected in the direction of the free cut of the air purifier is reflected back back to the inlet valve. Such processes of forward and backward propagation of waves occur continuously (like the processes of filling the cylinders when the engine is running) and in this section of the pipeline there is a partial conversion of the energy of sound waves into thermal energy (energy dissipation due to friction losses during repeated passage of reflected elastic waves with corresponding friction about the heterogeneity of the walls of the pipeline).

 However, the negative impact of the introduction of such narrowed (diffuser) zones in the pipeline on cylinder filling processes and the power, economic and toxic parameters of internal combustion engines associated with the throttling of the air (suction) flow and the growth of hydraulic resistance of the tract is well known.

 In addition, lateral air intake eliminates the possibility of using high-speed pressure of air moving at high speed of the car. Since the insert is “recessed” inside the nozzle, snow, dust, leaves, etc. may get into the annular gap for the outboard air intake, which interferes with the normal intake of air, increases the hydraulic resistance, and reduces the effectiveness of the insert as a noise muffler.

 The insert itself is a rather complicated part from the point of view of design and technology.

 Ultimately, the gain due to the aerodynamic shape of the insert is nullified due to the presence of significant back pressures in the intake stroke caused by a sharp turn of the air flow and other design features of the insert.

 It should be noted and the limited functionality of the prototype, which will be discussed in detail below. In particular, it means that the complex of modern requirements for the design of elements of internal combustion engines provides for communication, in particular, with air intake pipes of intake systems, of multifunctional qualities, for example, additional functions of aesthetic, load-bearing, heating, deflecting, and other character that contribute to the creation of compact and optimal designs.

 The objective of the invention is to increase the efficiency and reliability of the noise suppression device while improving the technical and operational qualities of the engine.

 The essence of the invention lies in the fact that in the known intake system of an internal combustion engine comprising an air purifier, to which an intake pipe with a fuel supply source to the engine cylinders and an air supply pipe are connected, including an input part bounded by an inlet cut, in which the noise suppression device is coaxially placed, and the connecting part connected to the chamber of the air purifier, the said noise suppression device is made in the form of a 1/4-wave resonator located in the input part of the pa cutting to form the through annular gap, wherein the resonator length is 1 / 2l, throat cavity taken in the middle of the air supply pipe and the bottom cavity is provided with a fairing, projecting beyond the cross-sectional plane of the lead-in pipe section.

 It is preferable when the cavity walls are made of porous, gas-permeable, sound-absorbing material, for example, metal wool, metal rubber, cathode copper, etc., which allows minimizing the hydraulic resistance in the inlet tract and increasing the noise attenuation efficiency.

However, if the cavity walls are made of a gas-permeable material, then the minimum cross-sectional area of the annular gap formed by the outer cavity wall and the inner wall of the inlet of the nozzle should be determined from the dependence
π (r ₂ -r ₁ ) ² ≥ πr $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ ,
where l is the length of the air inlet;
r _{1 is the} maximum outer radius of the resonator;
r _{2 is the} minimum radius of the inlet of the nozzle;
r ₃ minimum radius of the connecting part of the pipe.

 In this case, the resonator can be made of steel, plastic, etc.

 The efficiency of the intake system will increase if, coaxially with the aforementioned 1/4-wave resonator, with the formation of a through annular gap, a second 1/4-wave resonator is placed, the throat of which is located at a distance of 1 / 4l from the middle of the air inlet pipe and the length is 1 / 4l.

 The internal cavities of at least one of the resonators can be filled with a porous, sound-absorbing, gas-permeable material, and the walls of the resonators (sound attenuation device) can be single-layer, or have a sandwich (multilayer) structure, with the material of each layer taking into account certain functions, selected with specific physical and mechanical properties.

 In particular, the noise suppression device, at least in part, can be made of high-resistance material and connected to a power source in a certain way. Or the cavity walls can be made three-layer, the outermost layers are made of high-resistance, gas-permeable material, and the inner layer is an absorbent material that traps fuel vapor. Similarly, the annular gap between the resonators can be filled with absorbent material, for example, activated carbon.

 The sound attenuation device itself can be technologically made in the form of a single part, for example, from plastic, but in this case the bottom of the resonators should be made of a rigid, sound-reflecting material, for example, in the form of metal washers.

 With this design, in contrast to the prototype, the proposed device allows you to use the high-pressure air pressure of a fast moving car, while a cowl located outside the inlet section of the nozzle acts as an element of the reducing hydraulic resistance of the engine intake tract and at the same time prevents dirt and snow from entering the nozzle, leaves, etc. located in the oncoming air stream into the cavity of the nozzle. A sufficiently simple design of the noise suppression device is also effective, since the bottom of the resonator is located in the inlet section, and the throat is in the middle of the nozzle, which allows the construction of a 1/4-wave resonator without increasing the dimensions of the intake system device.

 It should be emphasized the versatility of the proposed device, because along with the sound attenuation that occurs in the prototype, additional exposure to the intake air with heat is also possible, which improves the starting and operational qualities of the engine, especially in the cold season, using the adsorption phenomenon, which reduces the toxicity of the engine , eliminates the possibility of icing or ingress of water into the engine cylinders (this excludes water hammer and, as a result, engine failure).

 In FIG. 1 shows an embodiment of an internal combustion engine intake system design; in FIG. 2, 3, 4 and 6 possible options for the design of noise suppression devices; in FIG. 5 a section along AA in FIG. 4; in FIG. 7 a section along BB in FIG. 6; in FIG. 8 a section along BB in FIG. 2 (increased).

 The intake system of the internal combustion engine includes an air cleaner 1, to which an intake pipe 2 is connected with a source of fuel supply to the engine cylinders (not shown) and an air supply pipe including an inlet part 3, in which a noise suppression device is arranged coaxially with the formation of a through annular gap 4. The inlet part 3 of the pipe is limited by the inlet slice 5, and the connecting part 6 of the pipe is connected to the chamber of the air cleaner 1.

The noise suppression device is made in the form of a 1/4-wave resonator 7 located in the inlet part 3 of the pipe with the formation of a through annular gap 4, the length of the resonator 7 being 1 / 2l, the neck 8 of the resonator 7 is placed in the middle of the air supply pipe, and the bottom 9 of the resonator 7 equipped with a fairing 10 protruding beyond the plane of the cross section of the inlet slice 5 of the pipe. The minimum cross-sectional area of the annular gap 4 is determined from the dependence
π (r ₂ -r ₁ ) ² ≥ πr $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ ,
where l is the length of the air inlet;
r _{1 the} maximum outer radius of the resonator 7;
r ₂ minimum radius of the inlet part 3 of the pipe;
r ₃ minimum radius of the connecting part 6 of the pipe.

 Inside the 1/4-wave resonator 7, coaxially with the formation of a through annular gap 11 is placed the second 1/4-wave resonator 12, the bottom of which 13 is located in the throat plane 8 of the first 1/4-wave resonator 7, and the length is 1 / 4l.

 The internal cavity of at least one of the 1/4-wave resonators 7 and 12 may be filled with porous, sound-absorbing, gas-permeable material. The shells of the resonators 7 and 12 can also be made of such material, however, in this case, their bottom 9 and 14 is made of hard, sound-reflecting material.

 The sound attenuation device, at least in part, can be made of high-impedance material and connected to a power source (Fig. 8).

 The walls of the resonators 7 and 12 can have a multilayer structure, and each of the layers is made of a material with certain physical and mechanical properties, for example, the walls of the resonator are made of three layers, while the extreme walls are made of high resistance material connected to a power source (to the battery through a control device) and the middle layer is an absorbent substance, for example, activated carbon.

 Similarly, in the annular gap 11, between the resonators 7 and 12 (Fig. 2.8) can be placed a layer of activated carbon.

 In FIG. 1, 4, 5 and 8 show a possible installation option of a noise attenuation device in the input part 3 of the pipe by means of mounting ribs 15, although the installation and fixing methods may be very different.

 Additionally, a static description of the object is illustrated (Fig. 9) by a diagram of the air supply pipe with integrated 1/4 wave resonators; in FIG. 10 plot of the sound pressure distribution in the pipe on the lowest intrinsic form of air vibrations in the pipe cavity, when 1/2 of the sound wavelength is laid along the pipe length; in FIG. 11 is a diagram of the distribution of sound pressure in a pipe on the second lowest intrinsic form of air vibrations in the pipe cavity, when the length of the sound wave is laid along the pipe length. Below is a diagram of the options for the placement of the throat of a 1/4 wave resonator with a length of 1 / 4l.

 The device operates as follows. The reciprocating movement of the engine pistons creates gas vibrations and elastic waves in the intake pipe 2 that are transmitted to the cavity of the air cleaner 1. Due to these oscillations, the gas in the chamber of the air cleaner 1 is periodically excited at the frequency of the intake processes, the density and amount of gas in the volume of the chamber of the air cleaner 1 continuously changes periodically. In this case, part of the gas in the form of a pulsating component included in the cavity of the air cleaner 1 is consumed both to increase the amount of gas in its chamber and to transfer it to the connecting part 6, then to the inlet part 3 of the air supply pipe and through the inlet section 5 is discharged into the atmosphere. The variable flow of gas into the air inlet creates gas velocity fluctuations in it. It is these vibrations and elastic waves that cause the emission of sound by the entry cut 5 into the environment.

 The installation in the inlet part 3 of the air supply pipe 1/4 wave acoustic resonator, in antiphase tuned to the most energy-intensive lower intrinsic resonance waveform of the air volume enclosed in the pipe (half the wavelength fits along the pipe length), allows for maximum gas compression in the pipe and at the same time maximum vacuum in the cavity of the resonator 7 to provide the maximum suction of gas from the cavity of the pipe into the cavity of the resonator 7, i.e. significantly “calm” the gas pulsations in the nozzle at this frequency and thereby minimize the sound emission at this frequency by the entry cut-off 5. The second 1/4-wave resonator 12 works in a similar way, suppressing resonant acoustic phenomena in the air inlet to the second, as well a sufficiently energy-consuming frequency of the intrinsic resonance waveform of the air volume enclosed in the nozzle cavity (the full wavelength is laid along the nozzle length), due to the placement of the neck of the resonator 12 in the zone of maximum pressure Nia (FIG. 11, a-d) for this form of oscillation.

The presence of the fairing 10, on the one hand, makes it possible to reduce the hydraulic resistance in the engine intake tract, and the location of the fairing outside the plane of the cross section of the inlet cut 5 of the nozzle helps to prevent the entry of a wide variety of implants in the oncoming air flow, in particular, it can be insects, leaves, soil particles, snow, etc. The presence of a through gap in the form of a direct flow channel 4 between the resonator 7 and the walls of the inlet part 3 of the pipe allows you to use the effect and ertsionnogo boost when driving a car, that is excluded in the prior art, because there is sucked in air flow suddenly changes direction (twice at 90 ^o). It should be noted here that in the case when the walls of the resonator 7 are made of gas-permeable material, for example, when the resonator is made in the form of a metal or plastic sleeve, the cross section of the annular gap in the inlet part of the nozzle should not be less than the cross section of the connecting part 6 of the nozzle, because otherwise In case of increased hydraulic resistance of the intake tract. In practice (FIGS. 1-5) this is achieved by making the input part 3 of the pipe in the form of an expanded chamber.

 If the casing of the resonator 7 is made of a gas-permeable material (Fig. 6-7), then the pipe can be made straight or smoothly conical, since in this case the presence of the resonator 7 inside the inlet part 3 of the pipe does not affect the hydraulic resistance in the engine inlet.

 Filling the internal cavities of the resonators 7 and / or 12 with a porous, gas-permeable, sound-absorbing material, for example, metal wool, cathode copper, fibrous or foamy polymeric material, allows to increase the efficiency of the noise-attenuation device not only in individual modes, but also in the entire operating range, due to the expansion frequency range of noise attenuation.

 In contrast to the prototype, the proposed noise suppression device is multifunctional, in particular, the walls of the resonators 7 and / or 12, or the packing of their internal cavities, can be made of high-resistance material, which makes it possible to heat the intake air during engine start-up and warm-up, or constant heating air intake when operating in low ambient temperatures. In this case, the noise attenuation device can also be used as a water evaporator in traffic conditions with a significant amount of snow or rain falling in the oncoming air stream, for example, when driving on a snowy road near a large truck in front.

 The cavities of the resonators 7 and / or 12 can be filled with a special adsorbent of gasoline vapors, for example, a substance obtained by burning coconut (activated carbon). In this case, with the carburetor version in the engine power system, when the engine is stopped, fuel vapors from the carburetor are not able to directly enter the atmosphere through section 5, since they are retained by the adsorbing substance. Thus, the ecology of the engine is improved by reducing the ingress of fuel vapor through cut 5 into the atmosphere.

The specific placement inside the air inlet of the resonator 12 is explained in detail in FIG. 11, a-d. In particular, in the embodiment, the resonator can be double, with a common hard bottom 14, while the throat 13 of the resonator is placed in the “antinodes” of the pressure diagram “P ₂ ”.

 Currently, AvtoVAZ JSC has developed technical documentation for the new engine, where the intake system design shown in FIG. one.

Claims (9)

 1. The intake system of an internal combustion engine containing an air cleaner to which an intake pipe is connected with a source for supplying fuel to the engine cylinders and an air supply pipe including an inlet portion bounded by an inlet slice in which a noise absorption device is coaxially located and a connecting portion connected to the air cleaner chamber characterized in that the noise suppression device is made in the form of a 1/4 wave resonator located in the input part of the pipe with the formation of an annular through of the gap, the cavity length being 1/2 l, the neck of the resonator is located in the middle of the air inlet pipe, and the bottom of the resonator is equipped with a fairing protruding beyond the cross-sectional plane of the inlet section of the pipe. 2. The system according to claim 1, characterized in that the minimum cross-sectional area of the annular gap is determined from the dependence
π (r ₂ -r ₁ ) ² ≥ πr $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ ,
where l is the length of the air inlet pipe, m;
r _{1 the} maximum outer radius of the resonator, m;
r ₂ minimum radius of the inlet of the pipe, m;
r ₃ minimum radius of the connecting part of the pipe, m  3. The system according to claims 1 and 2, characterized in that coaxially to the 1/4-wave resonator, with the formation of a through annular gap, a second 1/4-wave resonator is placed, the throat of which is located at a distance of 1/4 l from the middle of the air supply pipe and the length is 1/4 l.  4. The system according to claims 1 to 3, characterized in that the internal cavity of at least one of the resonators is filled with porous, sound-absorbing, gas-permeable material.  5. The system according to claims 1 to 3, characterized in that the noise suppression device is made as a single part of a porous, sound-absorbing, gas-permeable material, while the bottom of the resonators is made of hard, sound-reflecting material.  6. The system according to PP.1 to 5, characterized in that the noise suppression device is at least partially made of high resistance material and is connected to a power source.  7. The system according to claims 1 to 6, characterized in that the walls of the noise suppression device have a multilayer structure, each of the layers being made of a material with certain physical and mechanical properties.  8. The system according to PP.6 and 7, characterized in that the walls of at least one of the 1/4-wave resonators are made of three layers, while the extreme layers are made of high resistance, gas permeable material, and the inner layer is made of absorbent material, for example, activated carbon.  9. The system according to PP.3 to 7, characterized in that the annular gap between the resonators is filled with absorbent material.

Images