Acoustically damping device for a charged internal combustion engine

Description

[0001] The present invention relates to an acoustic attenuation device for an intake line of a thermal combustion engine equipped with one or more turbochargers.

[0002] Internal combustion engines exhibit a low-frequency acoustic component ranging from 30Hz to 1kHz. This component is generated by the opening and closing of the valves, as well as by the resonance of the various cavities of the engine (combustion chambers, ducts, etc.).

[0003] Furthermore, in the case of turbocharged engines, there is a high-frequency acoustic component ranging from 800 Hz to 15 kHz. This acoustic component is generated by the turbocharger and can propagate and radiate through the air intake ducts.

[0004] Conventional solutions for mitigating turbocharger noise along the air intake ducts include the use of resonators, silencers, quarter-wave devices, and expansion chambers. However, these solutions are insufficient to reduce the noise generated by the turbocharger.

[0005] Document FR 2 824 383 describes a sound attenuation device using open cavities in a main duct through which the gaseous fluid flows. These open cavities can be filled completely or partially with a porous or fibrous material to modify their noise attenuation characteristics. Because these cavities are open, the porous or fibrous material they contain is exposed to the flow of gaseous fluid circulating in the main duct. It can therefore deteriorate over time due to the erosive effect of the gaseous fluid. The solution considered so far to prevent this deterioration involves using materials that are more resistant to erosion. In particular, materials such as metallic foam have proven especially effective in this regard.However, these materials have the disadvantage of being expensive and having relatively low sound absorption capacity.

[0006] Document WO 2017 / 068264 A1 presents another example of a known device.

[0007] Consequently, the invention aims to provide a noise attenuation device that effectively reduces noise propagated in air intake ducts while limiting the manufacturing cost of said ducts.

[0008] In general terms, the invention relates to a noise attenuation device for the intake line of a thermal combustion engine equipped with a turbocharger. The noise attenuation device is defined in claim 1.

[0009] Thus configured, the acoustic attenuation device of the invention separates the interior space of the peripheral chamber, in which the acoustic absorption element is housed, from the interior space of the duct, through which the gaseous fluid flows. The acoustic absorption element is therefore no longer in contact with the gaseous fluid. This results in less erosion, allowing the use of less expensive fibrous or porous materials with superior acoustic absorption compared to metallic foam materials.

[0010] The acoustic attenuation device of the invention may also include the following features, taken individually or in combination: The sound-absorbing element is made of a material selected from polymer foams, including polyurethane foams or polyurethane foams covered with a laminated polypropylene or polyethylene film, and materials comprising polymer fibers, including polypropylene and polyethylene fibers, and preferably comprising 30% polypropylene fibers and 70% polyethylene fibers. The separating element is made of a porous material comprising polymer fibers. The separating element is made of a porous material comprising metallic fibers. The peripheral chamber is completely filled with the sound-absorbing element. The peripheral chamber is partially filled with the sound-absorbing element.

[0011] According to a second aspect, the invention relates to a vehicle air intake assembly, comprising a turbocharger having an air inlet and an air outlet and a sound attenuation device as described above.

[0012] In an advantageous configuration, the acoustic attenuation device is positioned upstream of the turbocharger.

[0013] Other features and advantages of the present invention will become clear from the following detailed description of several embodiments of a sound attenuation device according to the invention, given by way of non-limiting examples, with reference to the attached drawings, in which: THE figures 1 et 2 are schematic cross-sectional views of two acoustic attenuation devices according to the prior art; figures 3 à 6 present schematic cross-sectional views of a sound attenuation device different from that of the invention; the figure 7 is a schematic cross-sectional view of a sound attenuation device according to an embodiment of a sound attenuation device according to the invention; the figure 8 represents Attenuation / Frequency curves of the devices shown on the figures 1 à 3 ; there figure 9 represents Attenuation / Frequency curves of the devices shown on the figures 1, 3 And 4 .

[0014] In reference to the figure 1 A known configuration of a sound attenuation device for the intake line of a thermal combustion engine equipped with a turbocharger is shown. This device 1 includes, in particular, a main duct 2 through which air or the gas mixture flows in the direction of flow S, said duct 2 extending along a guide axis ZZ'. The duct 2 has a substantially cylindrical geometry. It is defined by a peripheral wall 3 having an internal diameter D1. The peripheral wall 3 is provided with a through opening 4, said through opening 4 opening into an annular peripheral chamber 5. The peripheral chamber 5 is delimited by the internal walls of a cylindrical bell 6 which is arranged coaxially around the duct 2 so as to completely cover the through opening 4. The bell 6 is defined, in particular, by an external diameter D2 and a length L.

[0015] With reference to the figure 2 Figure 1 shows another known configuration of a noise attenuation device for the intake line of a thermal combustion engine equipped with a turbocharger. This device 1' differs from device 1 shown in the figure. figure 1 by the presence of a separating wall 7 at the through opening 4. This separating wall 7 is formed by a strip of porous material arranged in line with the peripheral wall 3 so as to close the peripheral chamber 5. The strip constituting the wall 7 has a certain permeability, specifically between 650 l / m² / s and 1200 l / m² / s, and is generally made of a textile of polymer or metallic fibers. The wall 7 thus ensures a flow with virtually no pressure loss while also providing acoustic attenuation.

[0016] With reference to the figure 3 A different acoustic attenuation device 10 of the invention is shown. This device 10 differs from the device 1' shown in the figure 2 by the presence of a sound-absorbing element 8 inside the peripheral chamber 5. The sound-absorbing element 8 has an annular profile and partially fills, in particular half, the peripheral chamber 5. It may advantageously be fixed to the bell 6, for example by welding or clipping, so as to leave a free space between the separating wall 7 and the sound-absorbing element 8. The sound-absorbing element 8 may advantageously be formed from a material chosen from polymer foams, in particular polyurethane foams or polyurethane foams covered with a laminated film of polypropylene or polyethylene, the foams preferably having a density between 8 and 55 kg / m³, or from materials comprising polymer fibers, in particular comprising 30% polypropylene fibers and 70% polyethylene fibers.

[0017] With reference to the figure 8 A graph is shown comparing the acoustic performance of device 10 according to the invention with that of devices 1 and 1' of the prior art. This graph is derived from acoustic attenuation measurements (expressed in dB and measured on the y-axis) by varying the frequency (expressed in Hz and measured on the x-axis) of the acoustic wave passing through the main duct 2. Example 1 corresponds to the configuration shown in the figure 1 , in which the diameter D1 is 56 mm, the diameter D2 is 90 mm and the length L is 90 mm. Example 2 corresponds to the configuration shown on the figure 2 , wherein the diameter D1 is 56 mm, the diameter D2 is 90 mm and the length L is 90 mm, and wherein the separating wall 7 is formed from a textile material of polymer fibers comprising 30% polypropylene fibers and 70% polyethylene fibers and has a permeability of 850 l / m² / s. Example 3 corresponds to the configuration shown in the figure 3 , wherein the diameter D1 is 56 mm, the diameter D2 is 90 mm and the length L is 90 mm, wherein the separating wall 7 is formed in a textile material of polymer fibers comprising 30% polypropylene fibers and 70% polyethylene fibers and has a permeability of 850 l / m 2< / s and wherein the sound absorption element 8 is formed in a trench open-cell polyurethane foam material covered with a laminated film of polypropylene or polyethylene and having a density of 25 kg / m 3< . The acoustic absorption element 8 is arranged so that the laminated film is directed towards the main duct 2. It can therefore be seen that the acoustic attenuation of the device in example 3 is at least 5 dB greater than that of the devices in examples 1 and 2, particularly in the frequency range between 1500 and 2500 Hz, which corresponds to the frequencies generally associated with turbocharged engines.

[0018] In reference to the figure 4 A different acoustic attenuation device 11 of the invention is shown. This device 11 differs from the device 10 shown in the figure 3 by the fact that the sound-absorbing element 8 completely fills the peripheral chamber 5, so that the sound-absorbing element 8 and the separating wall 7 are in contact.

[0019] In reference to the figure 9 A graph is shown comparing the acoustic performance of device 11 with that of prior art device 1 and device 10. Examples 1 and 3 correspond to those defined previously for the figure 8 and example 4 corresponds to the configuration shown on the figure 4 in which the diameter D1 is 56 mm, the diameter D2 is 90 mm, and the length L is 90 mm, in which the separating wall 7 is made of a textile material of polymer fibers comprising 30% polypropylene fibers and 70% polyethylene fibers and has a permeability of 850 l / m² / s, and in which the sound-absorbing element 8 is made of a polyurethane foam material. It can therefore be seen that the sound attenuation of the device in Example 4 is greater than that of the devices in Examples 1 and 3 in the frequency range between 2000 and 2500 Hz. The device in Example 4 can therefore be used preferentially when the frequencies emitted by the turbocharged engine are within this specific range.

[0020] With reference to figures 5 et 6 Several embodiments of the acoustic attenuation device not conforming to the invention are shown. In these embodiments, the acoustic absorption element 8 is formed from a material comprising polypropylene fibers and polyethylene fibers, preferably in the proportion of 30% polypropylene fibers and 70% polyethylene fibers. This type of material has the advantage of being easily compressible, as illustrated in the figure. figure 7 .

[0021] Device 12 shown on the figure 5 differs from device 10 shown on the figure 3 by the fact that the sound-absorbing element 8 comprises a first part 81 and a second part 82 contiguous to the first part 81. The first and second parts 81 and 82 both have an annular shape defined by an external diameter d1 and d2, respectively, and an internal diameter d1' and d2', respectively. The external diameters d1 and d2 are equal, while the internal diameter d1' of the first part 81 is greater than the internal diameter d2' of the second part 82, such that, in the first part 81, a free space exists between the separating wall 7 and the sound-absorbing element 8, and in the second part 82, the sound-absorbing element 8 and the separating wall 7 are in contact. This device 12 will therefore exhibit different sound attenuation characteristics from those of the device 10.

[0022] Device 13 shown on the figure 6 differs from device 10 shown on the figure 3 by the fact that the acoustic absorption element 8 has an annular shape defined by a constant external diameter d and an internal diameter d' decreasing continuously along its length, according to the direction of circulation S, such that, at at least one first end, the acoustic absorption element 8 and the separating wall 7 are in contact, and, at at least one second end, a free space is present between the separating wall 7 and the acoustic absorption element 8. This device 13 will therefore have different acoustic attenuation characteristics from those of the device 10.

[0023] The device 14 according to the invention shown in the figure 7 differs from device 10 shown on the figure 3by the fact that the bell 6 has a cross-section increasing in the direction of circulation S, the external diameter D2 increasing in steps. The acoustic absorption element 8 also has a cross-section increasing in the direction of circulation S so as to completely fill the peripheral chamber 5. In particular, it has three contiguous parts 83, 84 and 85, whose internal diameters d3', d4' and d5' are equal and whose external diameters d3, d4 and d5 are defined by the relation d3

Claims

1. A sound attenuation device (10) for an intake line of a heat combustion engine equipped with a turbocharger, the device comprising: - a pipe (2) for conveying gas having a peripheral wall (3) provided with at least one through opening (4), said through opening (4) serving as a housing for a separation element (7), and - at least one peripheral chamber (5) disposed around the pipe (2) so as to totally or partially surround the separation element (7), wherein the separation element (7) is formed from a fibrous material so as to allow gas to circulate between the pipe (2) and the peripheral chamber (5), the fibrous material having a permeability comprised between 650 l / m2 / s and 1200 l / m2 / s, characterized in that the peripheral chamber (5) is at least partially filled with a sound absorption element (8), in that the sound absorption element (8) has an annular or substantially annular profile, and in that the sound absorption element (8) comprises at least two adjacent parts, namely a first part (83) and a second part (84), the first part (83) having an external diameter (d3) smaller than the external diameter (d4) of the second part (84).

2. The sound attenuation device (10) according to claim 1, characterized in that the sound absorption element (8) is formed from a material chosen from polymer foams, in particular polyurethane foams or polyurethane foams covered with a laminated polypropylene or polyethylene film, and the materials comprising polymer fibers, in particular comprising polypropylene fibers and polyethylene fibers, and preferably comprising 30% polypropylene fibers and 70% polyethylene fibers.

3. The sound attenuation device (10) according to claim 1 or 2, characterized in that the separation element (7) is formed from a fibrous material comprising polymer fibers.

4. The sound attenuation device (10) according to claim 1 or 2, characterized in that the separation element (7) is formed from a fibrous material comprising metal fibers.

5. The sound attenuation device (10) according to any of claims 1 to 4, characterized in that the peripheral chamber (5) is completely filled with the sound absorption element (8).

6. The sound attenuation device (10) according to any of claims 1 to 4, characterized in that the peripheral chamber (5) is partially filled with the sound absorption element (8).

7. The sound attenuation device (10) according to any of claims 1 to 6, characterized in that the sound absorption element (10) comprises at least two adjacent parts, namely a first part (81) and a second part (82), the first part (81) having an internal diameter (d1') greater than the internal diameter (d2') of the second part (82).

8. An air intake assembly of a vehicle, characterized in that it comprises a turbocharger having an air inlet and an air outlet and a sound attenuation device (10) according to any of claims 1 to 7.

9. The intake assembly according to claim 8, characterized in that the sound attenuation device (10) is positioned upstream of the turbocharger.