MUFFLER FOR AN EXHAUST SYSTEM

Abstract

A muffler for an exhaust system has a muffler housing with an inlet chamber fluidically connected an outlet chamber. The inlet chamber has an inlet pipe for supplying an exhaust gas stream into the inlet chamber, and the outlet chamber has an outlet pipe for discharging the exhaust gas stream from the outlet chamber, wherein the inlet pipe and the outlet pipe each have a first pipe portion and a second pipe portion. The inlet pipe and the outlet pipe in the respective first pipe portions are circumferentially impermeable to the exhaust gas stream and are circumferentially porous in the respective second pipe portions. The first pipe portions each have a predetermined length, such that a ?/4 resonator is formed between the respective first pipe portions and walls of the muffler housing associated with the respective first pipe portions.

Claims

1. A muffler for an exhaust system, comprising: a muffler housing having an inlet chamber fluidically connected to an outlet chamber; wherein the inlet chamber has an inlet pipe to supply an exhaust gas stream into the inlet chamber, and the outlet chamber has an outlet pipe to discharge the exhaust gas stream from the outlet chamber; wherein the inlet pipe and the outlet pipe each have a first pipe portion a second pipe portion; wherein the inlet pipe and the outlet pipe are impermeable to the exhaust gas stream in respective first pipe portions and are porous in respective second pipe portions; and wherein the first pipe portions each have a predetermined length such that a ?/4 resonator is formed between the respective first pipe portion and an inner wall of the muffler housing associated with the respective first pipe portion.

2. The muffler according to claim 1, wherein a ratio of a porosity in the second pipe portion of the inlet pipe is three to six times a porosity in the second pipe portion of the outlet pipe.

3. The muffler of claim 1, wherein a ratio of a length of the second pipe portion of the inlet pipe to a length of the second pipe portion of the outlet pipe is in a range of 1 to 2.

4. The muffler according to claim 1, wherein the inlet pipe and/or the outlet pipe have an axial end associated with the inlet chamber or the outlet chamber, which axial end is at least partially sealed.

5. The muffler according to claim 1, wherein an exhaust gas aftertreatment element that treats at least one pollutant contained in the exhaust gas stream is arranged between the inlet chamber and the outlet chamber.

6. The muffler according to claim 5, wherein the inlet pipe is a mixing pipe that mixes the exhaust gas stream with a treatment chemical.

7. The muffler according to claim 1, wherein the inlet chamber and/or the outlet chamber have multiple partial chambers which are delimited from one another by a partition wall through which the exhaust gas stream can flow.

8. The muffler according to claim 7, wherein the partition wall has one or more connecting pipes which fluidically connect the partial chambers to one another.

9. The muffler according claim 4, wherein the axial end of the outlet pipe associated with the outlet chamber is tulip-shaped.

10. The muffler according to claim 1, wherein at least one inner wall of the muffler housing is lined at least partially with a sound-absorbing material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features and properties of the disclosure result from the following description of exemplary embodiments, which are not to be understood in a limiting sense, and from the drawings. In the figures:

[0035] FIG. 1 shows a first embodiment of a muffler according to the disclosure;

[0036] FIG. 2 shows a second embodiment of the muffler from FIG. 1; and

[0037] FIG. 3 shows a third embodiment of the muffler from FIG. 2.

DETAILED DESCRIPTION

[0038] FIG. 1 schematically shows a cross-sectional view of a first embodiment of a muffler 10 according to the disclosure. The muffler 10 is a component of an exhaust system of a vehicle (not shown), so that an exhaust gas stream flows through the muffler 10 during operation of the vehicle, which exhaust gas flow was generated by an internal combustion engine of the vehicle. The muffler 10 serves to damp the sound emissions which are produced by the combustion process running in the internal combustion engine or by the design of the entire exhaust system, in particular the pipe routing and the lengths of pipes used in the exhaust system.

[0039] The muffler 10 can also be used in principle for other devices. For example, the muffler 10 can be a component of an exhaust system of a stationary motor (not shown), for example a stationary motor of a power generating device.

[0040] The muffler 10 has a gas-tight muffler housing 12 which is formed by a jacket 14 comprising an upper side 16 and an underside 18 and a first end floor 20, e.g. first end cap, and a second end floor 22, e.g. second end cap.

[0041] The muffler housing 12 shown in FIG. 1 has a substantially rectangular cross section. However, it is understood that the muffler housing 12 can also be designed differently. In general, the muffler housing 12 can be box-shaped or cylindrical, for example.

[0042] In the interior of the muffler housing 12, said housing has an inlet chamber 24 and an outlet chamber 26, which are in fluid communication with one another, i.e., are fluidically connected. Both the inlet chamber 24 and the outlet chamber 26 comprise multiple partial chambers 28 and 30 or 32 and 34, which are each delimited from one another by a partition wall 36.

[0043] The inlet chamber 24 has an associated inlet pipe 38 which is configured to conduct the exhaust gas stream of the exhaust system into the interior of the muffler housing 12, as indicated by the arrow P.sub.1 FIG. 1.

[0044] Analogously thereto, the outlet chamber 26 has an associated outlet pipe 40 which is configured to divert the exhaust gas flow from the interior of the muffler housing 12, as indicated by the arrow P.sub.2 in FIG. 1, for example into downstream components of the exhaust system of the vehicle.

[0045] The inlet pipe 38 comprises a first pipe portion 42 and a second pipe portion 44 along its axial extension direction, wherein the first pipe portion 42 extends from an inner wall 46 associated with the upper side 16 of the muffler housing 12 up to the second pipe portion 44. The second pipe portion 44 in turn runs from the connection point at the first pipe portion 42 up to an axial end 48 of the inlet pipe 38.

[0046] The first pipe portion 42 of the inlet pipe 38 has a length L.sub.1 in the axial direction of the inlet pipe 38 and the second pipe portion 44 of the inlet pipe 38 has a length I.sub.1 in the axial direction of the inlet pipe 38. The total length of the inlet pipe 38 thus results from the sum of the lengths L.sub.1 and I.sub.1.

[0047] Thus, the total length means only that length of the inlet pipe 38 with which the inlet pipe 38 extends into the muffler housing 12. It goes without saying that the inlet pipe 38 can additionally extend further from the muffler housing 12 to the outside.

[0048] In the first pipe portion 42, the inlet pipe 38 is designed to be solid, i.e., impermeable to the exhaust gas stream. In contrast, in the second pipe portion 44, the inlet pipe 38 has a plurality of openings 50 on the circumference side, so that the inlet pipe 38 is porous on the circumference. The porosity of the second pipe portion 44 is also designated as porosity x.sub.1 and is determined via the ratio of the sum of the area of all openings 50 in the circumferential surface of the second pipe portion 44 to the total surface of the circumferential surface of the second pipe portion 44.

[0049] Accordingly, in the embodiment shown, the exhaust gas stream can flow from the inlet pipe 38 into the inlet chamber 24, namely into the partial chamber 28, via the axial end 48 and via the openings 50.

[0050] A ?/4 resonator 54 is formed between the inner wall 46, an inner wall 52 associated with the first end floor 20, and the first pipe portion 42, wherein the frequency at which the ?/4 resonator 54 has a damping maximum is defined by the length L.sub.1.

[0051] Accordingly, by selecting the inlet pipe 38 used, the damping behavior of the muffler 10 can be adapted in a targeted manner.

[0052] Similarly to the inlet pipe 38, the outlet pipe 40 comprises a first pipe portion 56 and a second pipe portion 58 along its axial extension direction, wherein the first pipe portion 56 extends from an inner wall 60 associated with the underside 18 of the muffler housing 12 up to the second pipe portion 58. The second pipe portion 58 in turn runs from the connection point for the first pipe portion 56 up to an axial end 62 of the outlet pipe 40.

[0053] The first pipe portion 56 of the outlet pipe 40 has a length L.sub.2 in the axial direction of the outlet pipe 40, and the second pipe portion 58 of the outlet pipe 40 has a length l.sub.2 in the axial direction of the outlet pipe 40. The total length of the outlet pipe 40 thus results from the sum of the lengths L.sub.2 and l.sub.2.

[0054] Thus, the total length of the outlet pipe 40 means only that length of the outlet pipe 40 with which the outlet pipe 40 extends into the muffler housing 12. It goes without saying that the outlet pipe 40, analogously to the inlet pipe 38, can additionally extend from the muffler housing 12 further to the outside.

[0055] In the first pipe portion 56, the outlet pipe 40 is solid, i.e., impermeable to the exhaust gas stream. By contrast, in the second pipe portion 58, the outlet pipe 40 has a plurality of openings 64 on the circumferential side, so that the outlet pipe 40 is porous on the circumferential side. The porosity of the second pipe portion 58 is also referred to as porosity x.sub.2 and is determined via the ratio of the sum of the surface of all openings 64 in the circumferential surface of the second pipe portion 58 to the total surface of the circumferential surface of the second pipe portion 58.

[0056] Accordingly, in the embodiment shown, the exhaust gas stream can flow into the outlet pipe 40 both via the axial end 62 and via the openings 64 from the outlet chamber 26, namely the partial chamber 32.

[0057] A ?/4 resonator 68 is formed between the inner wall 60, an inner wall 66 associated with the second end floor 22, and the first pipe portion 56, wherein the frequency at which the ?/4 resonator 68 has a damping maximum is defined by the length L.sub.2.

[0058] The lengths L.sub.1 and L.sub.2 can be the same or different. Preferably, the ratio L.sub.1/L.sub.2 is in a range from 1 to 2.

[0059] The porosity x.sub.1 is preferably three to six times the porosity x.sub.2. That is to say, the inlet pipe 38 preferably has a higher porosity than the outlet pipe 40, as shown schematically in FIG. 1.

[0060] The tuning of the lengths L.sub.1 and L.sub.2 to particularly relevant sound frequencies in the inlet chamber 24 or the outlet chamber 26, the use of an inlet pipe 38 and outlet pipe 40 which are porous only over a partial region, and the selected ratio of the porosities x.sub.1 and x.sub.2 provide an ideal compromise between the achieved noise dampening effect and the backpressure generated in the exhaust gas stream.

[0061] In addition, the resonance behavior of sound waves in the inlet chamber 24 and the outlet chamber 26 can be influenced via the positioning of the partition walls 36 along the upper side 14 and underside 16 and via their porosity.

[0062] The partition walls 36 also have connecting pipes 70 which fluidically connect each of the partial chambers 28 and 30 or 34 and 32 to one another. The flow and damping behavior of the muffler 10 can further be adapted to the intended application scenario via the positioning of the connecting pipes 70 relative to the inlet pipe 38 or to the outlet pipe 40 and via the length of the connecting pipes 70.

[0063] In the embodiment shown in FIG. 1, an exhaust gas aftertreatment element 72 is arranged downstream of the inlet chamber 24 and upstream of the outlet chamber 26. The exhaust gas aftertreatment element 72 serves to at least partially remove one or more pollutants from the exhaust gas stream flowing through the muffler 10. Accordingly, the muffler 10 shown is a coupled muffler exhaust gas aftertreatment device.

[0064] The type of exhaust gas aftertreatment element 72 is not further limited and is only to be tuned to the intended place of use and the expected composition of the exhaust gas stream. For example, the exhaust gas aftertreatment element 72 is or comprises an active or passive SCR (selective catalytic reduction) catalytic converter, a filter element, and/or an oxidation catalytic converter.

[0065] A sound-absorbing material 74, which in particular serves to damp high-frequency components of the noise spectrum, is also attached to the inner wall 66 of the outlet chamber 26 associated with the end floor 22. The sound-absorbing material 74 is fixed to the inner wall 66 by a perforated retaining element 76, in particular by a micro-perforated retaining element 76.

[0066] It is also conceivable that the (micro-)perforated retaining element 76 is used without the sound-absorbing material 74 being present. In this case, the acoustic damping is accomplished by friction in the (micro-)perforation and by the volume situated between the respective inner wall and the holding element 76, which volume is selected via the distance between the respective inner wall and the holding element 76.

[0067] FIG. 2 schematically shows a second embodiment of the muffler 10 according to the disclosure.

[0068] The second embodiment substantially corresponds to the first embodiment so that only differences will be discussed below. Identical reference signs designate identical or functionally identical components, and reference can be made to the explanations provided above.

[0069] In the second embodiment, the inlet pipe 38 runs completely through the muffler housing 12, so that the inlet pipe 38 extends from the inner wall 46 associated with the upper side 16 up to the inner wall 60 associated with the underside 18.

[0070] The axial end 48 is thus completely sealed off by the inner wall 60, so that an exhaust gas stream flowing through the inlet pipe 38 can only pass into the inlet chamber 24 through the openings 50 in the second pipe portion 44 of the inlet pipe 38.

[0071] In addition, in the second embodiment the inlet pipe 38 is designed as a mixing pipe. This means that at least one treatment chemical 78 which mixes with the exhaust gas stream is supplied to the exhaust gas stream and is transported together with the exhaust gas stream into the inlet chamber 24 and from there to the exhaust gas aftertreatment element 72. The treatment chemical 78 is, for example, a urea solution which is converted with nitrogen oxides contained in the exhaust gas stream in the exhaust gas aftertreatment element 72.

[0072] Furthermore, in the second embodiment, the partition walls 36 have a first sub-region 80 and a second sub-region 82, wherein the partition wall 36 is gas-impermeable in the first sub-region 80 and is porous in the second sub-region 82 and thus the exhaust gas stream can flow through it.

[0073] A further ?/4 resonator 84 is formed between the first pipe portion 42, the inner wall 46, and the first subregion 80 of the partition wall 36 arranged in the inlet chamber 24, the resonant frequency of such resonator, analogously to the ?/4 resonator 54, depending on the length L.sub.1 of the first pipe portion 42.

[0074] Analogously, a further ?/4 resonator 84 is formed between the first pipe portion 56, the inner wall 60, and the first subregion 80 of the partition wall 36 arranged in the outlet chamber 26.

[0075] It goes without saying that in all embodiments the partition walls 36 of the inlet chamber 24 and the outlet chamber 26 can also be designed differently.

[0076] In the second embodiment, the outlet pipe 40 has a tulip-shaped axial end 62 in order to even better prevent additional flow noises.

[0077] In the second embodiment, the sound-absorbing material 74 is likewise attached to the inner wall 66. However, the sound-absorbing material 74 does not completely cover the inner wall 66 as in the first embodiment, but only partially and exclusively in the region of the inner wall 66 which is at the height of the second partial region 82 of the partition wall 36 associated with the outlet chamber 26.

[0078] FIG. 3 schematically shows a third embodiment of the muffler 10 according to the disclosure.

[0079] The third embodiment substantially corresponds to the first and second embodiments, so that only differences will be discussed below. Identical reference signs designate identical or functionally identical components, and reference can be made to the explanations provided above.

[0080] In the third embodiment, the inlet pipe 38 is not routed through the upper side 16 but through the first end floor 20 into the inlet chamber 24 and extends parallel to the upper side 16 and to the underside 18, i.e., in the direction of the outlet chamber 26.

[0081] Likewise, the outlet pipe 40 is not routed through the underside 18, but through the second end floor 22 out of the outlet chamber 26 and extends parallel to the upper side 16 and to the underside 18.

[0082] It is clear that a combination of the orientations of inlet pipe 38 and outlet pipe 40 according to the designs shown in the first to third embodiments is also possible.

[0083] The orientations of the inlet pipe 38 and the outlet pipe 40, which are changed compared to the first and second embodiment, also change the point at which the ?/4 resonators are formed. Specifically, in the third embodiment, the ?/4 resonators 54 and 68 are formed between the inner walls 46, 52 and 60 and the first pipe portion 42 of the inlet pipe 38 or between the inner walls 46, 66 and 60 and the first pipe portion 56 of the outlet pipe 40.

[0084] In the third embodiment, the sound-absorbing material 74 is additionally attached to the inner walls 46 or 60 associated with the upper side 16 and the underside 18.

[0085] Furthermore, the outlet pipe 40 has at its axial end 62 a gas-impermeable cap element 86 which completely closes the axial end 62. The exhaust gas stream from the outlet chamber 26 can thus only pass through the openings 64 in the second pipe portion 58 into the outlet pipe 40. Of course, the inlet pipe 38 can also have such a cap element 86.

[0086] It is clear that the features and embodiments described only in connection with one of the embodiments can also be used in further embodiments, as long as this does not contradict the basic mode of operation of the muffler 10 according to the disclosure.

[0087] Overall, the muffler 10 is characterized by the possibility of being able to be optimally tuned to the relevant frequency ranges in the noise spectrum without adaptations relating to the required installation space becoming necessary. In addition, an optimal compromise between the damping effect and the backpressure that occurs can be found.

[0088] The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims