Exhaust system and method for manufacturing such a

Abstract

Exhaust system (12) with an exhaust channel (20) for guiding an exhaust gas flow (24), a wall (22) which encloses the exhaust channel (20), and a mixer (10) for mixing a means (26) supplied to the exhaust gas flow (24) with the exhaust gas flow (24), wherein the mixer (10) is arranged in the exhaust channel (20) and has a base body (32) and exhaust gas guide elements (34) which cantilever out from the base body (32), characterized in that the exhaust gas guide elements (34) extend to a region (50) of the wall (22) opposite the base body (32).

Description

[0001] The invention relates to an exhaust system with an exhaust duct for guiding an exhaust gas flow, a wall which encloses the exhaust duct, and a mixer for mixing a medium supplied to the exhaust gas flow with the exhaust gas flow, wherein the mixer is arranged in the exhaust duct and has a base body and exhaust gas guide elements which cantilever out from the base body.

[0002] To reduce emissions from internal combustion engines and comply with current emissions regulations, exhaust systems with multiple aftertreatment components are used. For example, an exhaust system for reducing emissions from a diesel-powered internal combustion engine can include an oxidation catalyst, a particulate filter, and an SCR catalyst (selective catalytic reduction). Selective catalytic reduction removes nitrogen oxides (NOx). XThe reaction reduces the amount of CO2 emitted by the exhaust gas. Ammonia (NH3) is used as the reducing agent in the reaction; it is added to the exhaust gas in the form of an aqueous urea solution. Ammonia and CO2 are formed from the urea solution through a hydrolysis reaction.

[0003] To achieve low ammonia consumption while simultaneously reducing NOx emissions sufficiently, thorough mixing of the urea solution with the exhaust gas is essential, which also prevents ammonia slip. For this reason, mixers are installed in the exhaust systems to create turbulent flow conditions and thus ensure good mixing of the exhaust gas.

[0004] Currently used mixers are assembled from many individual parts, often soldered together. This involves first soldering blades (exhaust gas guide elements) to halves of a surrounding cage that encloses the blades, and then snapping the two halves together. The disadvantages of this method are the costly soldering process and the additional work required to snap the two halves together.

[0005] DE 20 2012 011 764 U1 describes an exhaust system with a mixer comprising an annular body and a row of several blades projecting radially inwards from the annular body. The blades are manufactured by bending and stamping.

[0006] Documents DE 10 2011 083 636 A1 and DE 10 2007 028 449 A1 show devices of the generic type.

[0007] The invention is based on the objective of providing a more cost-effective exhaust system and a method for manufacturing the exhaust system.

[0008] According to the invention, an exhaust system is provided with an exhaust duct for guiding an exhaust gas flow, a wall enclosing the exhaust duct, and a mixer for mixing a substance supplied to the exhaust gas flow with the exhaust gas flow. The mixer is arranged in the exhaust duct and has a base body and exhaust gas guide elements that project from the base body. A characteristic feature is that the exhaust gas guide elements extend to a region of the wall opposite the base body.

[0009] Because the exhaust gas guide elements cantilever (project) freely from the base body and extend to the area of ​​the wall opposite the base body, the mixer does not require a surrounding cage or ring body. This makes the mixer, and therefore the exhaust system, simpler and more cost-effective to manufacture.

[0010] A mixer is typically understood to be a device that, through one or more flow deflectors, causes turbulence or vortex formation (increased turbulence) in the exhaust gas stream. A substance, preferably supplied upstream of the mixer, is better distributed in the exhaust gas stream due to the increased turbulence, thereby aiding its evaporation in the case of a liquid substance.

[0011] The exhaust gas stream typically originates from an internal combustion engine. The added agent is primarily a reducing agent, for example, an aqueous urea solution for selective catalytic reduction (SCR). Mixing with the mixer thus reduces the consumption of urea solution and any ammonia slip that might otherwise occur.

[0012] The exhaust gas guide elements can also be described as blades or vanes, analogous to turbines. The wall enclosing the exhaust gas channel is typically an exhaust pipe of the exhaust system. The area of ​​the wall opposite the main body is the section located on the side of the exhaust gas guide elements facing away from the main body (i.e., at a free end of the exhaust gas guide elements). The exhaust gas guide elements extending to the wall do not necessarily have to contact it. A relatively small gap may also exist between the exhaust gas guide elements and this area. This prevents noise from the exhaust gas guide elements striking the area during operation. The width of the gap is, in particular, less than 10%, preferably less than 5%, and preferably less than 3% of the length of the respective exhaust gas guide element.This reduces the bypass of the exhaust gas guide elements between the exhaust gas guide elements and the wall area. Alternatively, the exhaust gas guide elements can also contact the wall area. To prevent noise, the exhaust gas guide elements can be pressed elastically against the wall.

[0013] Preferably, the exhaust system upstream of the mixer includes a metering module for adding the agent to the exhaust stream, thus making it easy to add the agent to the exhaust stream.

[0014] Preferably, the mixer is manufactured in one piece. In particular, the mixer is made from the same sheet metal. This eliminates time-consuming and costly assembly steps during the manufacturing process.

[0015] Preferably, the base body is designed to be flat, which means that no further processing steps are required to manufacture the base body from a (typically flat) sheet of metal.

[0016] According to a preferred embodiment of the invention, the base body is arranged on the wall surrounding the exhaust duct, in particular in abutting it. This allows the base body to be easily connected to the wall, for example by welding.

[0017] Preferably, the exhaust gas guide elements are arranged in at least one row, with the at least one row extending transversely to a predetermined flow direction through the mixer. This divides the exhaust gas channel into several sub-channels, thereby improving the deflection of the exhaust gas flow by means of the exhaust gas guide elements and thus the mixing of the agent with the exhaust gas flow.

[0018] Preferably, the exhaust gas guide elements on one side of the row and the exhaust gas guide elements on the opposite side of the row point in different directions. This directs the exhaust gas flow towards the center of the exhaust duct or from the center towards the wall of the exhaust system, further improving mixing.

[0019] According to a preferred embodiment of the invention, the at least one row comprises two rows arranged one behind the other in the direction of flow. This results in multiple, successive deflections of the exhaust gas flow, thereby optimizing mixing.

[0020] Preferably, successive exhaust gas guide elements in the rows arranged one behind the other in the flow direction point in opposite directions. This creates an alternating deflection of the exhaust gas flow, thereby optimizing mixing.

[0021] Furthermore, a method for manufacturing an exhaust system according to the invention is provided, wherein the method comprises the following steps: - Making the mixer using: a) Manufacturing a flat blank of the mixer from a sheet of metal, by means of material separation and / or material removal, wherein the blank has an outer contour which defines the base body together with the exhaust gas guide elements, and b) Bending of the exhaust guide elements, whereby the exhaust guide elements are pivoted out of a plane of the sheet metal; - Inserting the mixer into the exhaust duct.

[0022] The inventive method produces a particularly cost-effective mixer and a particularly cost-effective exhaust system in just a few steps.

[0023] To manufacture the mixer, the flat mixer blank is first produced from a sheet of metal, in particular a steel sheet (step a)). This involves creating an outer contour of the blank by material separation (e.g., punching) and / or material removal (e.g., laser cutting), which defines the base body including the exhaust gas guide elements. The exhaust gas guide elements are then bent so that they are pivoted out of a plane of the sheet metal, i.e., out of a plane of the flat extent of the sheet (step b)), causing the exhaust gas guide elements to protrude from the mixer base body.

[0024] Preferably, the base body of the mixer is welded to the wall to create a permanent connection between the mixer and the wall.

[0025] Preferably, the exhaust gas guide elements have connections by which they are linked to the base body, each connection forming a reduction in cross-section. In this context, a connection is understood to be a (mechanical) joint designed to integrally join the exhaust gas guide elements to the base body. Because each connection has a reduction in cross-section, i.e., a smaller cross-section than the respective exhaust gas guide element, bending the exhaust gas guide elements is facilitated.

[0026] Preferably, the bending of the exhaust gas guide elements includes or is a bending of the connections of the exhaust gas guide elements. By having the connections each have a reduction in cross-section, the bending of the exhaust gas guide elements is essentially a bending of the connections of the exhaust gas guide elements, resulting in exhaust gas guide elements that are essentially straight outside the connections.

[0027] According to a preferred embodiment of the invention, the manufacture of the mixer includes step c) of twisting the exhaust gas guide elements. Twisting the exhaust gas guide elements can also be described as torsion, i.e., a (plastic) twisting of the exhaust gas guide elements. By twisting the exhaust gas guide elements, a deflection angle of the exhaust gas flow predetermined by the exhaust gas guide elements can be defined.

[0028] Preferably, the reduction in cross-section of the connection is achieved through material constriction, and the twisting of the exhaust gas guide elements includes or is a twisting of the connections of the exhaust gas guide elements. The material constriction reduces not only the cross-section of the connection but also its torsional moment of inertia. The twisting of the exhaust gas guide elements is therefore essentially a twisting of the connections of the exhaust gas guide elements, resulting in straight exhaust gas guide elements despite the twisting.

[0029] Furthermore, a motor vehicle equipped with the exhaust system according to the invention is provided. The motor vehicle is characterized in particular by reduced manufacturing costs. Alternatively, the exhaust system according to the invention can also be used for exhaust aftertreatment of ships, power plants, etc.

[0030] Further preferred embodiments of the invention result from the other features mentioned in the dependent claims.

[0031] Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another.

[0032] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1. A mixer according to the state of the art in a first perspective view, Fig. 2. the mixer in a second perspective view according to the state of the art, Fig. 3. An exhaust system with the mixer in accordance with the state of the art in a sectional view, Fig. Four steps of a manufacturing process according to a preferred embodiment of the invention, Fig. 5 a twisting of a single stop element, and Fig. 6 A representation of the exhaust system in one flow direction through the mixer.

[0033] Fig. 1 and Fig. Figure 2 shows a mixer 10 according to the state of the art in perspective views. Fig. Figure 3 shows this mixer 10 in an exhaust system 12 in a sectional view.

[0034] The mixer 10 comprises a plurality of exhaust gas guide elements 14, which are individually soldered to two halves 16 of a cage 18. After the exhaust gas guide elements 14 are soldered to their respective halves 16, the halves 16 are locked together. The disadvantages of this method are the costly soldering process and the additional work step required to lock the two halves 16 together.

[0035] After the mixer 10 has been manufactured, it is inserted into an exhaust duct 20 of the exhaust system 12 (see Fig. 3) and welded to a wall 22 which borders the exhaust duct 20 all around.

[0036] During operation of the exhaust system 12, an exhaust gas stream 24 flows through the exhaust duct 20 (the arrow of the exhaust gas stream also symbolizes a flow direction 25 of the mixer 10), whereby an agent 26 is added to the exhaust gas stream 24 upstream of the mixer 10. The added agent 26 is, in particular, a reducing agent, for example, an aqueous urea solution for selective catalytic reduction (SCR). The exhaust gas guide elements deflect the exhaust gas stream 24 multiple times, thereby increasing turbulence and improving the mixing of the agent 26 with the exhaust gas stream 24.

[0037] In Fig. Figure 4 shows a method 29 according to the invention for manufacturing a mixer 10 according to a preferred embodiment of the invention. The hatching of the exhaust gas guide elements 34 serves to facilitate the visual differentiation of the individual exhaust gas guide elements 34 from one another and to assign the exhaust gas guide elements 34 during individual manufacturing steps a), b) and c). In the areas a), b) and c) of the Fig. Figure 4 shows the results of the respective manufacturing steps a), b) and c).

[0038] In step a), a flat blank 28 of the mixer 10 is first produced from a sheet 35 by material separation and / or material removal. After material separation and / or material removal, the flat blank 28 has an outer contour 30, which defines a base body 32 of the mixer 10 including exhaust gas guide elements 34 of the mixer 10. In particular, the material separation is carried out by stamping (the flat blank 28 is therefore a stamped part), which allows for the cost-effective production of high quantities.

[0039] In step b), the exhaust gas guide elements 34 are bent (folded), whereby the exhaust gas guide elements 34 are pivoted out of a plane of the sheet 35. This results in a bent blank 36. Depending on the shape of the outer contour 30, a finished mixer may be produced immediately after bending instead of the bent blank 36. In the example shown, the exhaust gas guide elements 34 are at a right angle to the base body 32.

[0040] The exhaust gas guide elements 34 each have a connection 38 (in Fig. Figure 4 shows an example of a connection 38 (circled) by which the exhaust guide elements 34 are connected to the base body 32, with each connection 38 forming a reduction in cross-section. A cross-section 40 of the exhaust guide elements 34 in the area of ​​the connections 38 is therefore smaller than a cross-section 42 in the rest of the exhaust guide element 34. This simplifies the bending of the exhaust guide elements 34, and essentially only the connections 38 need to be bent, resulting in a straight extension of the exhaust guide elements 34 away from the base body 32.

[0041] According to the illustrated variant, the manufacture of the mixer 10 according to step c) can include twisting (torturing) the exhaust gas guide elements 34. This results in the [missing information] described in part c) of the Fig. The final geometry of mixer 10 shown in section 4 has been achieved.

[0042] The twisting of the exhaust guide elements 34 is optimized by the fact that the cross-sectional reduction of the connection 38, as shown, constitutes a material constriction. This essentially limits the twisting of the exhaust guide elements 34 to the twisting of the connections 38 of the exhaust guide elements 34. Thus, essentially only the connections 38 of the exhaust guide elements 34 are twisted.

[0043] Once the mixer 10 has been manufactured, the mixer is inserted into the exhaust duct 20 - see Fig. 6. The base body 32 of the mixer 10 can then be welded to the wall 22 of the exhaust system 12. Fig. Figure 6 shows only the sectioned wall 22. The hatching of the exhaust gas guide elements 34 and the base body 32 serves as shown in Fig. 4 for easier visual identification.

[0044] In Fig. Figure 5 simplifies the basic principle of twisting according to step c) on a single exhaust guide element 34 and shows it from a different perspective. Section 44 shows a top view of a flat side of a single exhaust guide element 34, which is punched from a sheet 35. Section 46 shows a view along a longitudinal extension of the exhaust guide element 46, i.e., looking at the connection 38. The base body 32 and the step of bending the connection 38 are not shown for clarity. However, it is clearly visible how, during twisting, the (planar) cross-section 40 of the connection 38 remains undeformed at the visible end of the connection 38, while the (previously also planar) cross-section 42 in the rest of the exhaust guide element 34 changes its shape and position. The cross-sections 40 and 42 are each shown as (differently oriented) hatching.

[0045] An exhaust system 12 according to the invention, in a preferred embodiment of the invention, is in Fig. 6 shown. The exhaust system 12 exhibits (as already shown) Fig. 3 known) an exhaust gas channel 20 for guiding an exhaust gas flow 24 and a wall 22 enclosing the exhaust gas channel 20. In addition, the exhaust gas system 12 has the mixer 10 according to the invention. Fig. 4. The mixer 10 is located in the exhaust duct 20. It features (as already shown in Fig. 4 is known) a base body 32 and exhaust gas guide elements 34, which cantilever freely from the base body 32. In contrast to the exhaust system according to Fig. 3 the exhaust gas guiding elements 34 now extend to a region 50 of the wall 22 opposite the base body 32.

[0046] The exhaust gas guide elements 34 are arranged in rows 52, the rows 52 extending transversely to a provided flow direction 25 of the mixer 10. The exhaust gas guide elements 34 on one side of the respective row 52 and the exhaust gas guide elements 34 on the other side of the row 52 face in different directions (see Fig. 4).

[0047] The two rows 52 are arranged one behind the other in the flow direction 25, with successive exhaust gas guide elements 34 pointing in opposite directions in the flow direction 25 (see Fig. 4).

[0048] In the operation of the exhaust system 12 according to the preferred embodiment of the invention, as already described in the description of the Fig. 1, Fig. 2 to Fig. 3 is known, the exhaust duct 20 is traversed by the exhaust gas flow 24 in the flow direction 25 (in Fig. Figure 6 shows the flow direction 25 into the plane of the image) and a reducing agent 26 is added to the exhaust gas stream 24 upstream of the mixer 10. The exhaust gas guide elements 34 deflect the exhaust gas stream 24 several times, thereby improving the mixing of the reducing agent 26 with the exhaust gas stream 24.

[0049] The base body 32 is arranged in abutting the wall 22, so that at most a negligible fraction of the exhaust gas flow 24 flows between the base body 32 and the wall 22 against which the base body 32 rests. Even through a possible gap (not shown) between the exhaust gas guide elements 34 and the area 50, typically only a very small fraction (if any) of the exhaust gas flow 24 flows.

[0050] Since the mixer 10 is manufactured in one piece from a single sheet of metal, its durability during operation is increased. It also does not require a surrounding cage 18, as is the case with the Fig. 1, Fig. 2 to Fig.As is known, the base body 32 is arranged only on one side of the exhaust gas guide elements 34, and the exhaust gas guide elements 34 (guide plates) cantilever freely from the base body 32; they are therefore freestanding. The mixer 10 is also attached only on one side (to the base body 32) to the wall 22 of the exhaust system 12 (especially an exhaust gas purification system located close to the engine). This reduces the amount of material required and allows for a more precise representation of the desired geometry of the mixer 10. Bending (and possibly twisting) eliminates the costly steps of soldering and snapping. Reference symbol list 10 mixers 12 Exhaust system 14 Exhaust guide element 16 halves of a cage 18 cage 20 Exhaust duct 22 wall 24 Exhaust gas flow 26 means 29 Methods for manufacturing the mixer 28 flat blank of the mixer 30 Outer contour 32 basic shapes 34 Exhaust guide element 35 sheet metal 36 curved blank of the mixer 38 Connection 40 Cross-section in the area of ​​the connection 42 Cross-section in the remaining exhaust gas guide element 44 Top view of an exhaust gas guide element 46 View along a longitudinal extension of the exhaust guide element 50 Area of ​​the wall opposite the base body

Claims

[1] Exhaust system (12) with an exhaust duct (20) for guiding an exhaust gas flow (24), a wall (22) which encloses the exhaust duct (20), and a mixer (10) for mixing a medium (26) supplied to the exhaust gas flow (24) with the exhaust gas flow (24), wherein the mixer (10) is arranged in the exhaust duct (20) and has a base body (32) and exhaust gas guide elements (34) which project from the base body (32), characterized by , that the exhaust gas guiding elements (34) extend to an area (50) of the wall (22) opposite the base body (32). [2] Exhaust system (12) according to claim 1, characterized by , that the mixer (10) is formed in one piece. [3] Exhaust system (12) according to one of the preceding claims, characterized by , that the base body (32) is arranged on the wall (22) enclosing the exhaust duct (20), in particular adjacent to it. [4] Exhaust system (12) according to any one of the preceding claims, characterized by, that the exhaust gas guide elements (34) are arranged in at least one row (52), wherein the at least one row (52) extends transversely to a provided flow direction (25) of the mixer (10). [5] Exhaust system (12) according to claim 4, characterized by , that at least one row (52) comprises two rows (52) which are arranged one behind the other in the direction of flow (25). [6] Method (29) for manufacturing an exhaust system (12) according to one of the preceding claims, wherein the method (29) comprises the following steps: - Making the mixer (10) using: a) Manufacturing a flat blank (28) of the mixer (10) from a sheet metal part by means of material separation and / or material removal, wherein the flat blank (28) has an outer contour (30) which defines the base body (32) together with the exhaust gas guide elements (34), and b) Bending the exhaust guide elements (34), wherein the exhaust guide elements (34) are pivoted out of a plane of the sheet metal; - Inserting the mixer (10) into the exhaust duct (20). [7] Method (29) according to claim 6, characterized by , that the exhaust gas guide elements (34) have connections (38) with which the exhaust gas guide elements (34) are connected to the base body (32), wherein the connections (38) each form a reduction in cross-section. [8] Method (29) according to claim 7, characterized by , that the bending of the exhaust guide elements (34) includes or is a bending of the connections (38) of the exhaust guide elements (34). [9] Method (29) according to any one of claims 6 to 8, characterized by , that the manufacture of the mixer (10) includes step c) of twisting the exhaust gas guide elements (34). [10] Method (29) according to claims 7 and 9, characterized by, that the reduction in cross-section of the respective connection (38) is a material constriction and the twisting of the exhaust guide elements (34) includes or is a twisting of the connections (38) of the exhaust guide elements (34).

Images