RU2131519C1 - Power unit exhaust system - Google Patents

Abstract

FIELD: internal combustion engines primarily for motor cars. SUBSTANCE: exhaust system has gas intake line with gas-dynamic gas pulse and noise damper at its inlet connected to exhaust channel provided with at least one exhaust silencer; damper has hollow barrel with end plates whose volume equals at least four displacement volumes of engine; entrance and/or exit dynamic sections of gas-intake line pipes and those of outlet channel pipe are located inside barrel in vicinity of node surfaces of lower natural modes of gas volume inside damper. At least one gas- pulsation crosswise dissipater made in the form of perforated barrier may be placed in certain manner inside damper barrel. EFFECT: improved efficiency of noise suppression. 11 cl, 11 dwg

Description

 The invention relates to mechanical engineering, mainly to the automotive industry, and can find application in the design of exhaust systems with increased noise reduction efficiency.

 The classic model of the exhaust system, in the case when the engine is located in the front of the car, such as the widespread VAZ-2108, see V.A. Vershigora et al. "VAZ-2108 Car", M., DOSAAF USSR, 1986, pp. 79-80, Fig. 39, includes the following, in the direction of the exhaust gas (OG) flow, sequentially placed elements: a two-pipe (two-channel) gas receiving device fixed to the exhaust manifold, bounded by a tee welded to the tips named pipes. On the other hand, the tee is equipped with a gas outlet pipe, by means of which the gas intake device is connected to the end part of the exhaust tract, including the additional and main exhaust silencers. The entire system described, the length of which is comparable with the length of the car, is rigidly fixed to the engine on one side and suspended elastically (on five rubber cushions) to the underbody.

 A common drawback of such classical models of the exhaust system is that acoustic energy in the form of an intense noise stream, caused by both a gas-dynamic noisy gas stream in the path, and a dynamically excited thin-walled structure of the gas receiving device and part of the exhaust path (to an additional silencer), propagates without significant attenuation on the tract section from the exhaust valves of the engine to the silencing elements, since the concentration of sound energy in this section is tsya maximum - adversely affects the overall acoustic climate in the passenger compartment, and the acoustic pollution of the environment (outside the car). At the same time, in accordance with the order of operation of the engine cylinders, during the implementation of work processes in the village of with. one or the other pipe (channel) of the gas receiving device alternately exhausts the exhaust gases from the cylinders, with the attendant intense gas pulsations in this dual system of channels of the gas receiving pipes. At the same time, backpressure waves in each channel of the pipeline at the moments of opening the corresponding exhaust valve prevent the exhaust gas from exhausting from the corresponding cylinder of the engine operating in the exhaust stroke mode, and this prevents the exhaust gas from cleaning the cylinder well, impairing the process of filling the cylinder with fresh working mixture, with a corresponding deterioration in economic and toxic indicators

 The analysis of the prior art shows the presence of various technical methods that allow, to one degree or another, quite effectively solve the above problems that occur in the described classical exhaust system.

 In particular, in Russian patent N 2043511, class. F 01 N 7/14, publ. 09/10/95, Bull. No. 25, a technical solution is described that makes it possible to effectively reduce the noise level from the walls of the surface of the engine exhaust system, due to partial vacuuming with special sealed casings of the surfaces of the gas intake and exhaust routes of the system.

 In US patent N 4537278, CL. F 01 N 7/08, publ. 08.27.85, an exhaust system is described in which the tee of the gas receiving device is provided with a longitudinal perforated baffle partially separating the output sections of the gas receiving pipes. Here, the energy of gas pulsations, due to multiple forcing the exhaust gas flow through rather small perforation holes, or the porous structure of which the partition is made, is significantly weakened and converted into heat, which significantly reduces the noise levels transported along the final section of the exhaust route, as well as reduces the effect of backpressure of exhaust gases generated in the second channel and directed towards the cylinder of the engine with the exhaust valve ajar, and with another The first side reduces the amount of gas pulsations of the flow directed to the exhaust tract, which leads to a decrease in the aerodynamic and structural components of the exhaust noise level.

 A similar device of the exhaust system of a power plant, in particular an internal combustion engine, adopted as a prototype, is described in USSR author's certificate N 886539, class. F 01 N 7/08, publ. 05.30.84, Bull. N 20. The exhaust system contains exhaust pipes connected to a gas receiver (tee), along the axis of which a separation plate is installed, and a pipe for removing gases from the gas receiver. A distinctive feature is that the plate is perforated.

 In accordance with the order of operation of the cylinders, the exhaust gases enter the cavity of the gas receiver alternately through one or another pipe (channel) of the gas receiving device and gas pulsations with a certain resistance are forced through the perforation holes in the partition towards the free pipe (channel). At high engine speeds and, correspondingly, a higher pulsation frequency of gas flows due to the inertial and elastic properties of the oscillating mass of gas in the pipes of the gas receiving device, a diffuse state of elastic sound and gas-dynamic components of the gas stream is created on both sides of the plate, which leads to a process of partial field alignment pressure in the pipes of the gas receiver on both sides of the perforated plate of the gas receiver. At the same time, when the pulsating component of the gas stream passes from the cavity with high pressure to the cavity with lower pressure through the small perforation holes in the partition, due to friction in these perforation holes, part of the acoustic energy is dissipated due to its conversion into heat.

 However, in the prototype, the problems indicated above are only partially solved. In particular, the sound waves behind the exhaust valve are high-amplitude (essentially hypersonic), transforming acoustic energy along the exhaust tract in the direction of free exhaust, they strongly excite the system walls and generate sound on various inhomogeneities (washers, partitions, crevices, etc. .), along the gas intake line and part of the exhaust tract, and primarily on the first (along the gas flow) preliminary muffler of the exhaust system. At the same time, at the resonant frequencies (coincidence), the structure (walls) of this part of the tract of the exhaust system is intensely excited, with corresponding increased emission of noise into the environment. Moreover, the insignificant volume of the chamber of the gas receiving device, and hence the weak expansion of the gases entering this volume through the gas receiving pipes, and the weak reflection of sound back in the direction of the source also cause weak damping of gas pulsations in this volume, as a result of which the level of pulsations is not sufficiently attenuated and noise energy is transmitted to the final exhaust path in the direction of its free exhaust.

 The claimed technical solution proposes to a large extent to prevent the propagation of sound energy through the exhaust tract and reduce the levels of gas pulsations and sound generation on the inhomogeneities of the tract directly at the entrance to the path of the silencers of the exhaust system, due to the location in the immediate vicinity (due to approximation) from the source excitation (exhaust clone) of an effective damper of gas-dynamic pulsations and sound waves.

 The technical problem is solved by improving the design of the gas receiving device and giving it additional functions of an acoustically tuned preliminary silencer of exhaust noise and a separator (receiver) of wave phenomena in individual channels of the gas receiving device.

 The essence of the invention lies in the fact that in the known exhaust system of a power plant, in particular an internal combustion engine containing a gas intake line, the output of which is equipped with a gas-dynamic damper of gas pulsations and noise connected to an exhaust duct equipped with at least one exhaust silencer, called a gas damper pulsations are made in the form of a hollow cylindrical body bounded by end walls, while the volume of the internal cavity of the gas-dynamic damper is not m its four working volume of the engine cylinder, and the output and / or input dynamic gas inlet pipe sections of the pipe line and the exhaust duct placed inside the cavity of the cylindrical body, in the areas of nodal surfaces lowest natural oscillation forms gas volume enclosed in a cavity of the gas-dynamic damper.

 For this, the input dynamic section of the exhaust pipe is placed coaxially with the body of the gas-dynamic damper and is located in the center of the cavity of its chamber, and the internal sections of the pipes of the gas intake line are placed axially to the axis of the body of the gas-dynamic damper, at equal distances from the cylindrical walls of the body and its axis, and are located at a distance of 3 / 4 L from the end wall on which they are fixed, where L is the length of the body of the gas-dynamic damper of gas pulsations and noise.

 This arrangement of the dynamic sections of pipes in the space of the cylindrical body corresponds to their location in the nodal zones (where the pressure value approaches zero, which will be discussed in detail and illustrated below) of the first and second lower eigenmodes of the vibration mode of the gas volume located in the damper cavity, which minimizes the excitation of the second intrinsic resonance form, which is the second most energy intensive after the first and excludes the transfer of the first, most energy intensive water (and all odd) idents resonant vibration modes in the final exhaust tract, with the corresponding acoustic radiation by minimizing the free energy of the system to cut the environment.

 The internal outlet sections of at least one of the pipes of the gas intake line and / or exhaust tract are perforated, for example in the form of grouped through-hole belts. The latter can be made in the form of stampings with visors directed along the gas flow.

 The inner sections of the pipes of the gas intake line are provided with an additional output dynamic cut made in the form of a perforation belt located at a distance of 1/4 L from the end wall on which they are fixed.

 Inside the casing of the gas pulsation and noise damper, at a distance of 1/8 L from the transverse plane passing through the geometric center of the cylindrical casing (the center of gravity of the cavity volume), at least one transverse gas pulsation diffuser is located.

 The diffuser can be made in the form of at least one perforated partition.

 The diffuser can be made in the form of partitions symmetrical with respect to the transverse plane, one of which is solid.

 The diffuser can be made in the form of two perforated partitions placed with a gap, the gap S being in the range (0.2 ... 0.8) D, where is the diameter of the perforation hole in the partitions. In this case, the diameter of the perforation holes in the first, along the flow, partition is larger than the diameter of the perforation holes in the second partition, while the gap S is in the range 0.2x ... 0.4 (x + y), where x is the diameter of the larger hole in the first partition, y is the diameter of the smaller hole in the second partition.

 Such an installation of diffusers (perforated partitions, one of which may be continuous) corresponds to their location in areas with a maximum (antinodes) of the velocity distribution on the fourth eigenfunction of gas in the cavity of the cylindrical body (or in the node of the fourth eigenfunction of pressure distribution), which It contributes to the effective dissipation of sound energy in this mode, which cannot be suppressed solely by the processes of the optimal arrangement of the slices due to its conversion into heat.

 On the inside, the end walls and at least the adjoining part of the damper body are lined with a corrugated perforated shell. Inside the damper body, between its end walls and the shell, heat-insulating gaskets are placed. Since the maximum pressure values occur in the immediate vicinity of the inner walls of the chamber, the presence of the above-mentioned elements can significantly reduce the vibrational excitability of the chamber structure and, accordingly, the level of excited structural noise of the surfaces of the exhaust system as a whole.

 Thus, in the proposed exhaust system, the gas receiving device, which is structurally placed as close as possible to the source of excitation of wave and gas-dynamic oscillations, effectively works both as a smoothing device for gas pulsations and as a resonant silencer of acoustic vibrations tuned to suppress noise of a wide spectrum of frequencies. At the same time, the most energy-intensive lower, first through fifth, intrinsic resonance forms of gas volume oscillations enclosed in the gas-dynamic pulsation and noise damper chamber are purposefully suppressed (or substantially weakened). Thus, the gas stream supplied from the gas intake device to the exhaust path carries a significantly weakened gas-dynamic sound energy, which eliminates (to a considerable extent, weaken) the processes of structural sound excitation of the walls of the exhaust system and the generation of high-frequency sound when a highly pulsating gas passes through local inhomogeneities a path (washers, partitions, and cracks, etc.).

 Figure 1 shows the exhaust system of a power plant; figure 2 shows a diagram of a gas-dynamic damper of gas pulsations and noise; Figures 3-5 show, respectively, the first, second, and fourth lower intrinsic resonance waveforms of sound pressure of the gas volume of the internal cavity of the cylindrical body of the gas-dynamic damper of gas pulsations and noise; figure 6 shows one embodiment of a gasdynamic damper of gas pulsations and noise; Fig.7 shows a section aa in Fig.6; on Fig shows another embodiment of the gasdynamic damper of gas pulsations and noise; FIG. 9 is a view I of FIG. eight; 10 and 11 show the mutual influence of dynamic slices of perforation holes in a twin sound energy diffuser.

 A description of the proposed system is given by the example of its use as part of an internal combustion engine.

 The exhaust system contains a gas intake line 1, the output of which is equipped with a gas-dynamic damper 2 of gas pulsations and noise connected to the exhaust tract 3, in which an additional 4 and main 5 exhaust silencers are installed. The gas-dynamic damper 2 of gas pulsations and noise is made in the form of a hollow cylindrical body 6, limited by the end walls 7 and 8, while the volume of the internal cavity 9 of the damper 2 of gas pulsations and noise is at least four working volumes of one cylinder 10 of the engine 11, and the output dynamic sections 12 and 13 of the pipes 14 and 15 of the gas intake line 1 and / or the inlet dynamic section 16 of the pipe 17 of the exhaust tract 3 are placed inside the cavity 9, in the zones of the nodal surfaces (Figs. 2-5), lower natural longitudinal modes of gas volume fluctuations enclosed in cavities 9. A pipe section 17 located inside the damper 2 is located coaxially to the cylindrical body 6 (O-O axis), and pipe sections 14 and 15 placed inside the body 6 are axially aligned with the body (their axes A-A and B -B are parallel to the O-O axis), and the A-A and B-B axes are located at equal distances from the O-O axis and the corresponding wall of the cylindrical body 6. The ends of the pipes 14, 15 and 17 can be perforated with belts, respectively, 18, 19 and 20, through holes 21. The inner sections of the pipes 14 and 15 may be provided with additional dynamic av 22 and 23, which are the belts 24 and 25 of the through holes of the perforation 26. Inside the housing 6 of the damper 2, at a distance of 1/8 L from the transverse plane passing through the center of the housing 6, transverse perforated partitions 27 and 28 are placed (diffusers of gas pulsations ) On Fig shows a variant of a double partition, the dynamic sections 29 and 30 of the holes 31 and 32 of which are in mutual influence. On the inner side of the end walls 7 and 8, the adjacent part of the housing 6 is lined with a corrugated perforated shell 33. In addition, between the shells 33 and the end walls 7 and 8, heat-insulating gaskets 34 can be placed.

 The exhaust system works in the usual way. In accordance with the order of operation of the cylinders 10 of the engine 11, at the exhaust cycle, through the corresponding pipe 14 or 15 of the gas intake device (damper 2), the exhaust gas flows into the cavity 9. Here they are expanded, throttled through perforation holes, damped and redistributed through pipes 14, 15 and 17, while the main part of the gas stream, through pipe 17, enters the exhaust tract 3 of the engine and is discharged into the environment.

 The volume of the cavity 9 of the gas receiving device in the proposed exhaust system, to ensure effective expansion of the gas flow and reflection of sound waves back to the exhaust valve, is at least four working volumes of the cylinder 10 of the engine 11. It is known that the volume of the cavity of the classical expansion chamber is doubled approximately corresponds to an increase in noise attenuation of 3 dB. In terms of sound energy, this is also two times. Accordingly, a four-fold increase in the volume of the cavity 9 will be 6 dB reduction in the level of sound energy. The value - 6 dB of reduction of sound energy, in practical problems of technical (applied) acoustics is already considered quite a significant value.

 At the same time, the gas receiving device, which in this case is characterized by the properties of a resonant silencer of exhaust noise and a separator and a damper of phenomena in separate tubes 14 and 15 of the gas receiving line 1, is located in the immediate vicinity of the exhaust valves, where the maximum sound energy is concentrated (near the antinodes of all energy-intensive acoustic modes), concentrated in the channels of the pipes 14 and 15, can significantly reduce the transmission of aerodynamic noise and gas pulsations, as well as and reduce the excitation and sound emission by the wall structures along the entire length of the exhaust tract 3.

 Thus, already at the very initial stage of the exhaust gas exhaust process, an effective effect is made on the emitting and exciting medium, which is exposed to pulsations and elastic sound waves and transforms acoustic energy into the environment in the form of aerodynamic noise of a free cut of the exhaust system and structural noise emitted by the wall surfaces exhaust system.

 Moreover, the gas receiving device performs the function of an acoustically tuned resonator muffler, which is achieved by optimal placement of dynamic sections 12, 13 and 16, pipes 14, 15 and 17, FIG. 2-5, in the nodes of the lower proper longitudinal acoustic modes of gas oscillations enclosed in cavity 9. Moreover, as can be seen from Fig. 3, the first mode (and all odd modes) is not attached to the exhaust tract 3 by the pipe 17, and the second mode 4, sections 12 and 13, 22 and 23 in the cavity 9 is not excited. At the same time, similar transverse (elevation) modes are not excited or transmitted, since the O-O, A-A, and B-B axes are directed to the nodes of the first (and all odd) and second intrinsic elevation forms of gas pressure oscillations in the cavity 9.

 The attenuation of gas pulsations and noise in the cavity 9 at the fourth lowest intrinsic longitudinal mode, FIG. 5, is carried out through the use of special diffusers located at the maximum (antinode) of the gas pressure oscillation velocity on this form (as is known, the damping efficiency is determined by the oscillation velocity). In this case, with repeated passage of sound waves through the perforation holes 29, 31 and 32 in the partitions 27 and 28, and friction against the edges of these holes, their acoustic energy is converted into heat.

 On Fig shows a double diffuser made in the form of two perforated transverse partitions 27 and 28 located at a distance (with a gap) -S- from one another. The effectiveness of such a double diffuser is achieved only with a certain amount of gas gap -S-. The size of this gap is selected with the obligatory calculation of the dynamic mutual influence of the holes 31 and 32 of the perforation. The dynamic cut of the holes 31 and 32 of the perforation is theoretically separated from the static cut (metal surface) by ≈ 0.3 of the diameter of the corresponding hole (in this case, 0.3x or 0.3y), FIGS. 10 and 11. In practice, this value depends on from a variety of structural, technological and operational factors is taken equal to 0.2 ... 0.4 of the diameter of the corresponding hole.

 Thus, if the diameters of the holes are equal, the gap -S- is in the range of 0.2 ... 0.8 of the diameter of the holes. In this range, the interaction of the oscillating attached masses 29 and 30 in the coaxial holes 31 and 32 of the corresponding partitions 27 and 28 is ensured. If the range exceeds the upper boundary limit, the diffuser begins to degenerate into an independent resonator chamber and vibrations in the holes begin to occur independently of each other, those. mass fluctuations in these holes occur independently, without interference with each other. At lower boundary values of the range, the diffuser practically degenerates into one partition. In this case, the oscillating mass is weakly held in the openings 31 and 32, i.e., the interaction (involving large gas masses in the oscillatory process) and the mutual influence of the adjacent nearby oscillating masses 29 and 30 concentrated in the perforation holes are poorly used.

 At the same time, the damping properties of the air gap -S- between the partitions 27 and 28 are poorly used. its mass is significantly less. In some cases, the holes 31 in the partition 27, 11, (in the first along the gas flow) it is advisable to make a larger diameter -x- than the holes with a diameter -y- in the second partition 28, which allows to increase the air gap -S-, and therefore to provide greater damping and sound-reflecting ability while maintaining (increasing) the effective dynamic interaction of the attached masses 29 and 30 in opposite holes.

 In FIG. 6, the end walls 7 and 8 and part of the housing 6 are lined with perforated shells 33 on the inside, which further reduces structural noise caused by excitation by the pulsating gas-dynamic flow of the housing 6 and its end walls 7 and 8, and the presence between the end walls 7 and 8 and the shell 33 thermally insulating gaskets 34, further reduces the high-frequency noise of the exhaust and weaken the heat removal from the cavity 9, which may be important when using a catalytic converter in the exhaust system.

Claims (11)

 1. The exhaust system of a power plant, mainly an internal combustion engine, containing a gas intake line, the output of which is equipped with a gas-dynamic damper of gas pulsations and noise, connected to the exhaust tract, equipped with at least one silencer of exhaust noise, characterized in that the damper of gas pulsations and noise is made in the form of a hollow cylindrical body bounded by end walls, while the volume of the internal cavity of the damper is at least four working volumes of the engine cylinder la, and the output AND / OR input dynamic sections of the gas intake pipe and the exhaust pipe are located inside the cavity of the cylindrical body, in the zones of the nodal surfaces of the lower eigenmodes of gas volume oscillations enclosed in the damper cavity.  2. The system according to claim 1, characterized in that the input dynamic section of the exhaust pipe is placed coaxially with the body of the gas-dynamic damper of gas pulsations and noise and is located in the center of the cavity of its chamber, and the inner sections of the pipes of the gas intake line are placed axially to the axis of the body of the gas-dynamic damper of gas pulsations and noise at equal distances from the cylindrical walls of the casing and its axis and are located at a distance of 3 / 4L from the end wall on which they are fixed, where L is the length of the gas-dynamic gas damper body s pulsations and noise.  3. The system according to claim 1 or 2, characterized in that the internal output sections of at least one of the pipes of the gas intake line AND / OR of the exhaust tract are perforated.  4. The system according to p. 1, 2 or 3, characterized in that the inner sections of the pipes of the gas intake line are equipped with an additional output dynamic section made in the form of a perforation belt located at a distance of 1 / 4L from the end wall on which they are fixed.  5. The system according to any one of claims 1 to 4, characterized in that at least one transverse diffuser of gas pulsations is placed inside the damper body of gas pulsations and noise, at a distance of 1 / 8L from the transverse plane passing through the center of the cylindrical body.  6. The system according to claim 5, characterized in that the diffuser is made in the form of at least one perforated partition.  7. The system according to claim 5, characterized in that the diffuser is made in the form of partitions symmetrical with respect to the transverse plane, one of which is solid.  8. The system according to claim 5, characterized in that the diffuser is made in the form of two perforated partitions placed with a gap, the gap value - S - being in the range (0.2 - 0.8) D, where D is the diameter of the perforation hole in partitions.  9. The system of claim 8, characterized in that the diameter of the perforation holes in the first, upstream partition, is larger than the diameter of the perforation holes in the second partition, while the gap S is in the range 0.2x - 0.4 (x + y ), where x is the diameter of the larger hole in the partition, y is the diameter of the smaller hole in the partition.  10. The system according to any one of claims 1 to 9, characterized in that the inner walls and at least the adjacent portion of the damper body are lined with corrugated perforated shell.  11. The system according to any one of claims 1 to 10, characterized in that heat-insulating gaskets are placed inside the damper body, between its end walls and the shell.

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