Mixing path for an exhaust system of an internal combustion engine

Abstract

In a mixing section for an exhaust system of an internal combustion engine, comprising a mixing section housing (16) through which exhaust gas (A) can flow in a main exhaust gas flow direction (H) and a tubular mixing body (18) arranged in the mixing section housing (16) and extending in the direction of a longitudinal axis (L) of the mixing body, wherein the mixing body (18) defines a first flow volume (24) through which exhaust gas (A) can flow radially outwards and defines a second flow volume (26) through which exhaust gas (A) can flow radially inwards, wherein the mixing body (18) comprises a tubular first mixing body part (20) extending in the direction of the longitudinal axis (L) of the mixing body and at least one tubular second mixing body part (34) extending in the direction of the longitudinal axis (L) of the mixing body on an outer surface (32) of the first mixing body part (20) facing the second flow volume (26),The mixing body (18) is radially supported in a first radial support area (50) by means of a plurality of first radial support elements (58) with respect to the mixing section housing (16) and radially supported in a second radial support area (52) arranged at a distance from the first radial support area (50) in the direction of the longitudinal axis (L) of the mixing body by means of a plurality of second radial support elements (66) with respect to the mixing section housing (16). The first radial support elements (58) radially support the first mixing body part (20) on the mixing section housing (16), and the second radial support elements (66) radially support the second mixing body part (34) on the mixing section housing (16).

Description

[0001] The present invention relates to a mixing section for an exhaust system of an internal combustion engine, comprising a mixing section housing through which exhaust gas flows in a main exhaust gas flow direction and a tubular mixing element arranged in the mixing section housing and extending in the direction of a longitudinal axis of the mixing element. The mixing element defines a first flow volume through which exhaust gas flows radially outwards and defines a second flow volume through which exhaust gas flows radially inwards. The mixing element comprises a tubular first mixing element part extending in the direction of the longitudinal axis of the mixing element and, on an outer surface of the first mixing element part facing the second flow volume, at least one tubular second mixing element part extending in the direction of the longitudinal axis of the mixing element, wherein the second mixing element part is radially supported on the first mixing element part at a plurality of mixing element support areas.

[0002] Such a mixing section for an exhaust system is known from the subsequently published German patent application 10 2024 119 108.2. Since, in such a mixing section, the mixing element, which is surrounded by exhaust gas on its outer and inner sides, can be heated more than the mixing section housing, which is generally surrounded by ambient air on its outer side, different thermally induced expansions of the mixing section housing on the one hand and the mixing element on the other can occur during operation.

[0003] The object of the present invention is to provide a mixing section for an exhaust system of an internal combustion engine which ensures efficient mixing of exhaust gas and the reactant injected into it while simultaneously compensating for different thermally induced expansions of mixing section components.

[0004] According to the invention, this problem is solved by a mixing section for an exhaust system of an internal combustion engine, comprising: a mixing section housing through which exhaust gas flows in a main exhaust gas flow direction, a tubular mixing body arranged in the mixing section housing and extending in the direction of a longitudinal axis of the mixing body, wherein the mixing body defines a first flow volume through which exhaust gas flows radially outwards and defines a second flow volume through which exhaust gas flows radially inwards, wherein the mixing body comprises a tubular first mixing body part extending in the direction of the longitudinal axis of the mixing body and at least one tubular second mixing body part extending in the direction of the longitudinal axis of the mixing body on an outer side of the first mixing body part facing the second flow volume, wherein the second mixing body part is radially supported on the first mixing body part at a plurality of mixing body part support areas.

[0005] The mixing section according to the invention is characterized in that the mixing body is radially supported in a first radial support area by means of a plurality of first radial support elements with respect to the mixing section housing and in a second radial support area arranged at a distance from the first radial support area in the direction of the longitudinal axis of the mixing body by means of a plurality of second radial support elements with respect to the mixing section housing, and that the first mixing body part is radially supported on the mixing section housing by the first radial support elements and the second mixing body part is radially supported on the mixing section housing by the second radial support elements.

[0006] In the mixing section according to the invention, the support functions to be implemented in the two axially spaced radial support areas are distributed between the first mixing body part of the mixing body, which is arranged further radially inwards, and the second mixing body part, which surrounds the first mixing body part on its outer surface. This makes it possible to optimally distribute the support functionalities to be implemented in the various radial support areas, some of which are intended to allow relative movement, while others are intended to ensure a defined fixed position, over the entire mixing body. At the same time, the second mixing body part, around which exhaust gas flows on its inner and outer surfaces, provides the function of a heat exchanger, which absorbs heat from the exhaust gas and transfers it to the first mixing body part through the contact with the first mixing body part in the area of ​​the support areas of the mixing body parts.Since the two mixing body parts are surrounded by exhaust gas on their outer and inner sides, they essentially have the same temperature during operation, so that even taking into account the fact that the two mixing body parts may be made of the same material, in particular metal material, different thermally induced dimensional changes of the mixing body parts will essentially not occur.

[0007] In order to ensure, on the one hand, a defined positioning of the mixing body with respect to the mixing section housing, but on the other hand to avoid stresses induced by different thermal expansions, it is proposed that the first radial support elements hold the first mixing body part firmly against movement in the direction of the mixing body longitudinal axis and / or movement in the circumferential direction around the mixing body longitudinal axis, and that the second radial support elements radially support the second mixing body part on the mixing section housing so that it is movable in the direction of the mixing body longitudinal axis and / or in the circumferential direction around the mixing body longitudinal axis.

[0008] A defined support function can be further supported by providing a plurality of first radial support elements with circumferential spacing around the longitudinal axis of the mixing body, or / and by providing a plurality of second radial support elements with circumferential spacing around the longitudinal axis of the mixing body.

[0009] The structural integration of the support function to be implemented at the second radial support area into the components of the mixing section can be achieved by having at least some of the second radial support elements, preferably all of them, include support features of the second mixing element directed away from the first mixing element and / or support features of the mixing element housing directed towards the second mixing element. This eliminates the need for additional components to implement this support function.

[0010] By providing radial support elements as projections of, for example, the second mixing body part or the mixing section housing, i.e., as convex protrusions directed towards the other component, a radial elasticity exists in the area of ​​such projections, which also enables the compensation of different thermally induced radial expansions of the mixing section housing on the one hand and the mixing body on the other.

[0011] To ensure the relative mobility of the mixing element with respect to the mixing section housing, the support projections of the second mixing element part may be movably supported on an inner surface of the mixing section housing in the direction of the mixing element's longitudinal axis and / or circumferentially around the mixing element's longitudinal axis, or / and the support projections of the mixing section housing may be movably supported on an outer surface of the second mixing element part in the direction of the mixing element's longitudinal axis and / or circumferentially around the mixing element's longitudinal axis. If such projections, directed towards the other component, are provided on both components—in this case, the mixing section housing and the second mixing element part—they may be arranged in pairs, so that projections of the second mixing element part are radially supported on these respective projections of the mixing section housing.

[0012] For axially and / or circumferentially fixed support of the mixing body in the first radial support area, at least a part of the first radial support elements, preferably all first radial support elements, can comprise support elements fixed to the mixing section housing and the first mixing body part, preferably by material connection, for example by welding or brazing.

[0013] Alternatively or additionally, to obtain a design with as few components as possible, at least a part of the first radial support elements, preferably all first radial support elements, can comprise support forms of the first mixing body part directed towards the mixing section housing and preferably fixed to the mixing section housing by material connection, for example by welding or brazing, and / or support forms of the mixing section housing directed towards the first mixing body part and preferably fixed to the first mixing body part by material connection, for example by welding or brazing.

[0014] In order to ensure a defined positioning of the mixing body in the mixing section, particularly in an upstream region of the mixing body where the injection of a reaction agent generally takes place, it is proposed that the first radial support area be provided in an upstream end region of the mixing body, preferably upstream of the second mixing body part, and / or that the second radial support area be provided in a downstream end region of the mixing body.

[0015] For a defined positioning of the radially inner, first mixing body part with respect to the mixing section housing, at least a part of the second radial support elements, preferably all second radial support elements, can axially overlap with a part of the mixing body part support areas.

[0016] To provide the mixer body support areas, the second mixer body can have a plurality of first projections arranged adjacent to one another in the direction of the mixer body longitudinal axis and in the circumferential direction around the mixer body longitudinal axis, directed towards the first mixer body, wherein at least one first projection, preferably each first projection, forms a mixer body support area.

[0017] To obtain a substantially regular shape pattern and thus a substantially uniform heat transfer between the two mixing bodies, it is proposed that the first shapes be arranged in a plurality of rows of first shapes arranged successively in the circumferential direction around the longitudinal axis of the mixing bodies, preferably extending substantially in the direction of the longitudinal axis of the mixing bodies, or / and that the first shapes be arranged in a plurality of rings of first shapes arranged successively in the direction of the longitudinal axis of the mixing bodies, preferably extending substantially in the circumferential direction around the longitudinal axis of the mixing bodies.

[0018] For particularly efficient heat transfer between the second mixing body part and the first mixing body part, it is proposed that at least a part of the first shapings, preferably each first shaping, is designed as a closed shaping, and / or that at least a part of the first shapings, preferably each first shaping, is designed with a shaping circumferential wall and a shaping base abutting the first mixing body part, preferably substantially planar or curved to substantially conform to a curvature of the first mixing body part, and / or that at least a part of the first shapings, preferably each first shaping, is circular.

[0019] A further intensified thermal interaction with the exhaust gas can be achieved by the second mixing body part having a plurality of second forms arranged adjacent to each other in the direction of the mixing body longitudinal axis and in the circumferential direction around the mixing body longitudinal axis, and directed away from the first mixing body part.

[0020] If it is further provided that at least one opening is provided in the second mixing body part adjacent to at least a part of the second shapings, preferably every second shaping, preferably wherein in each pair of mutually associated second shaping and opening the second shaping and the opening overlap each other in some areas, it is possible that exhaust gas flowing into the space between the two mixing body parts flows out of this space again and that even warmer exhaust gas enters this space and transfers heat to the mixing body parts.

[0021] The outflow and inflow of exhaust gas from and into the space formed between the two mixing body parts can be further supported by the fact that, in some of the pairs of mutually associated second shape and opening, the opening is arranged on a first side, preferably the first axial side, of the associated second shape, and in other of the pairs of mutually associated second shape and opening, the opening is arranged on a second side, preferably the second axial side, of the associated second shape that is substantially opposite the first side.

[0022] In connection with the second shapes, a regular shape pattern that supports uniform heat transfer can also be provided by arranging the second shapes in a plurality of rows of second shapes arranged successively in the circumferential direction around the longitudinal axis of the mixing body, preferably extending substantially in the direction of the longitudinal axis of the mixing body, or / and by arranging the second shapes in a plurality of rings of second shapes arranged successively in the direction of the longitudinal axis of the mixing body, preferably extending substantially in the circumferential direction around the longitudinal axis of the mixing body.

[0023] To introduce a reactant, a reactant discharge device can be arranged upstream of the mixing body in the main exhaust gas flow direction, essentially only into the first flow volume. Since essentially no reactant thus enters the space formed between the two mixing body parts, there is no risk of reactant deposits forming in this space.

[0024] A stable connection between the two mixing body parts, which supports heat transfer, can be achieved, for example, by fixing the second mixing body part to the first mixing body part in the area of ​​at least a portion of the mixing body part support areas, preferably all mixing body part support areas, preferably by material bonding, for example by welding or brazing. Since the two mixing body parts essentially have the same temperature during operation and are preferably made of the same material or of materials with essentially the same coefficient of thermal expansion, there is no risk of stresses arising from fixing the two mixing body parts to each other.

[0025] The present invention further relates to an exhaust system for an internal combustion engine, comprising a mixing section constructed according to the invention and an exhaust gas treatment unit, preferably an SCR catalyst, downstream of the mixing section.

[0026] The present invention is described in detail below with reference to the accompanying figures. These show: Fig. 1 a basic representation of an exhaust system for an internal combustion engine with a mixing section; Fig. 2 in its representation a) a cross-sectional view of the exhaust system of the Fig. 1 , cut along a line IIa) - IIa) in Fig.1 , and in their representation b) a cross-sectional view of the exhaust system of the Fig. 1 , cut along a line IIb)-IIb) in Fig. 1 ; Fig. 3 a perspective view of a mixing body constructed with two tube-like mixing body parts; Fig. 4 a detailed longitudinal section view of the mixing body; Fig. 5 a cross-sectional view of the mixing body in a section plane corresponding to section plane IIb)-IIb); Fig. 6 in its representations a) to d) different designs of radial support elements.

[0027] In Fig. 1 Figure 10 represents a section of an exhaust system for an internal combustion engine, generally designated as 10, in a schematic representation. The exhaust system 10 comprises a mixing section, generally designated as 12, and, downstream of the mixing section 12, an exhaust gas treatment unit 14. In the illustrated example, the exhaust gas treatment unit 14 includes an SCR catalyst.

[0028] The mixing section 12 comprises a mixing section housing 16 in which a substantially tubular mixing element 18, elongated in the direction of a mixing element longitudinal axis L, is arranged. Exhaust gas emitted from an internal combustion engine, in particular a diesel internal combustion engine, flows into the mixing section housing 16 or towards the mixing element 18 in a main exhaust gas flow direction H that corresponds substantially to the orientation of the mixing element longitudinal axis L.

[0029] The mixing body 18 comprises a tubular first mixing body part 20 with a closed circumferential wall 22, for example, having a substantially cylindrical cross-section and a circular cross-section. The first mixing body 20, or its circumferential wall 22, divides the internal volume of the mixing section housing 16 in the axial extent of the mixing body 18 into a first flow volume 24, formed inside the first mixing body part 20 or its circumferential wall 22 and surrounded by the circumferential wall 22 or bounded radially outwards by it, and a second flow volume 26, which is formed between the mixing section housing 16 and the first mixing body part 20 or bounded radially inwards by it.

[0030] The exhaust system 10, or the mixing section 12, further comprises a reactant dispensing device 28, also commonly referred to as an injector, which injects a reactant R, for example a urea / water solution, in the form of a spray mist, i.e., in the form of fine droplets, into the exhaust gas A flowing in the mixing section housing 16. The reactant dispensing device 28 is designed such that it dispenses the reactant R into the first flow volume 24 and thus into a partial flow T1 of the exhaust gas A flowing in the first flow volume 24. Therefore, essentially no reactant R is injected into the second flow volume 26 and into a second partial flow T2 of the exhaust gas A flowing in the second flow volume 26. The second flow volume 26 is thus only traversed by the exhaust gas A, i.e., the second partial flow T2, and, as explained in detail below, primarily serves to transfer heat transported in the exhaust gas A to the mixing body 18.to transfer the first mixing body part 20. The increased heating of the first mixing body part 20 results in the evaporation of the reaction agent R coming into contact with an inner surface 30 of the circumferential wall 22, and thus improved mixing of reaction agent R and exhaust gas A, without the need for system areas leading to increased flow resistance, such as a mixer or the like.

[0031] A second mixing body part 34, shaped like a tube, is arranged on an outer surface 32 of the circumferential wall 22 of the first mixing body part 20, facing the second flow volume 26. This second mixing body part preferably surrounds the first mixing body part 20 completely, essentially over its entire axial extent and in the circumferential direction, and essentially fulfills the function of a heat exchanger, through which heat transported in the second partial flow T 2 of the exhaust gas A can be introduced into the mixing body 18 in a more concentrated manner.

[0032] Before the mounting of the mixing element 18 in the mixing section housing 16, realized according to the principles of the present invention, is described primarily with reference to the Fig. 1, 2 , 5 und 6 The detailed description begins with a description of the basic structure of the mixing body 18, known from the subsequently published German patent application DE 10 2024 119 108.2, comprising the tubular first mixing body part 20 and its circumferentially closed circumferential wall 22, and the tubular second mixing body part 34 surrounding the first mixing body part 20 or its circumferential wall 22. Fig. 3 und 4 described.

[0033] The second mixing body part 34, which, like the first mixing body part 22, is designed, for example, as a sheet metal part, has a plurality of, for example, essentially cup-shaped first projections 36 arranged along the axial length of the second mixing body part 34 and circumferentially around the longitudinal axis L of the mixing body. The cup-shaped first projections 36 are formed on the second mixing body part 34 such that they extend from a base level of the second mixing body part 34, located at an essentially constant distance from the outer surface 32 of the first mixing body part 20, to the outer surface 32 of the first mixing body part 20 and bear against it. Each first projection 36 bearing against the outer surface 32 of the first mixing body part 20 forms a mixing body support area 37, by which the second mixing body part 34 is radially supported on the first mixing body part 20.

[0034] The recesses 36 are formed with a recess circumferential wall 38 and a recess base 40 abutting the outer surface 32 of the first mixing body part 20, and have a circular shape in plan view. The recess base 40 is essentially planar or adapted to the curvature of the outer surface 32 of the first mixing body part 20, so that there is a planar contact between the second mixing body part 34 and the first mixing body part 20 in the area of ​​the recess base 40. Preferably, in the area of ​​all first recesses 36, a material-bonded connection is created between the two mixing body parts 20, 34, for example by welding or brazing, to generate good heat transfer contact.

[0035] One can recognize in Fig. 3 that a plurality of rows of first forms 36 extending substantially in the direction of the longitudinal axis L of the mixing body are formed on the second mixing body part 34. In the case of circumferentially adjacent rows of first forms 36, the first forms 36 are offset from one another in the direction of the longitudinal axis L of the mixing body, such that a first form 36 of the other row is positioned between two first forms 36 of one row in the direction of the longitudinal axis L of the mixing body. For uniform heat transfer contact, the first forms 36 in the rows of first forms 36, which follow one another in the direction of the longitudinal axis L of the mixing body, are preferably arranged with substantially uniform spacing from one another.

[0036] Similarly, on the second mixing body part 34, rings of first forms 36 extending circumferentially around the mixing body longitudinal axis L are formed. In these rings of first forms 36, the first forms 36 also have a substantially uniform distance from each other, and in rings of first forms 36 that are immediately adjacent to each other in the direction of the mixing body longitudinal axis L, the first forms 36 are offset from each other circumferentially, so that between two first forms 36 of one of the two rings, a first form of the other ring is positioned circumferentially.

[0037] A substantially uniform pattern of first features 36 extending over the entire axial extent and circumference of the second mixing body part 34 creates a substantially uniform heat transfer contact between the two mixing body parts 34, 20. The exhaust gas A of the second partial flow T 2, flowing along the second mixing body part 34 in the second flow volume 26, can thus flow around the second mixing body part 34 on its outer surface 42 facing away from the first mixing body part 20 and on its inner surface 44 facing the first mixing body part 20, thereby transferring heat to it. The heat absorbed in the second mixing body part 34 is transferred to the first mixing body part 20 via the contact between the two mixing body parts 34, 20 in the region of the first features 36.It is particularly advantageous that, due to the provision of the numerous first forms 36 in the area of ​​the inside 44 and the outside 42 of the second mixing body part 34, turbulences are created which improve the thermal interaction of the exhaust gas A in the second partial flow T 2 with the second mixing body part 34.

[0038] To further improve thermal interaction and increase heat input into the first mixing body part 20, the second mixing body part 20 has a plurality of second projections 46. Each second projection 46 is associated with an opening 48, so that pairs of second projections 46 and openings 48 are formed. The second projections 46 are oriented radially outward with respect to the longitudinal axis L of the mixing body, i.e., in the direction away from the first mixing body part 20, and are positioned with respect to their respective associated openings 48 such that in each pair of second projection 46 and opening 48, they overlap, meaning that the opening 48 extends into the area of ​​the projection 46. This results in the Fig. 4 recognizable structure in which each such second form 46 is formed in the manner of a section of a spherical cap or similarly shaped cap and is open in the direction of the respective associated opening 48.

[0039] One can recognize in Fig. 3 und 4 Furthermore, in each pair of second shaping 46 and opening 48, these are arranged axially consecutively in the direction of the longitudinal axis L of the mixing body. The second shapings 46 or openings 48, or pairs of second shapings 46 and openings 48, are also arranged in rows extending essentially in the direction of the longitudinal axis L of the mixing body, wherein the arrangement is such that the second shapings 46 or openings 48, or pairs of second shapings 46 and openings 48, are offset from each other in the circumferential direction of immediately adjacent rows of second shapings 46 in the direction of the longitudinal axis L of the mixing body. Likewise, the second shapings 46 or the associated openings 48 orPairs of second forms 46 and openings 48 are circumferentially extending rings, wherein even in the case of rings immediately adjacent to one another in the direction of the longitudinal axis L of the mixing body, the second forms 46, which are positioned at a uniform distance from one another both circumferentially and in the direction of the longitudinal axis L of the mixing body, are offset from one another. In particular, a structure is provided in which the second forms 46 or openings 48 are integrated between two first forms 36 in both the axial and circumferential directions, so that an alternating sequence of first forms 36 and second forms 46 with each associated opening 48 results in both the axial and circumferential directions, and thus the rows and rings of first forms 36 correspond to the rows or rings of second forms 46.

[0040] One can recognize in Fig. 3 Furthermore, in each pair of circumferentially adjacent rows of second forms 46, the openings 48 are positioned on different sides of the second forms 46. In one of the two circumferentially adjacent rows of second forms 46, the corresponding openings 48 are arranged on a first side, in particular a first axial side, of the second forms 46, while in the other row of two circumferentially adjacent rows of second forms 46, the corresponding openings 48 are positioned on the other side, in particular the other axial side, of the second forms 46.Thus, both circumferentially and axially, an alternating pattern of the axial opening direction of the second forms 46 results for immediately adjacent rings of second forms. This facilitates the inflow of exhaust gas A into and out of a space 50 formed between the two mixing body parts 20, 34. The second forms 46 therefore not only contribute to intensifying the turbulence in the near-surface region of the second mixing body part 34, but also support the exhaust gas exchange in the space 50. This improves the heat transfer between the two mixing body parts 34, 20 and also the thermal contact between the first mixing body part 20 and the second partial flow T 2 flowing in the second flow volume 26.

[0041] Various configurations of the mixing body 18 shown in the figures can be implemented. For example, the rows of first and second forms 36, 46 can have an orientation that deviates from the parallel orientation to the longitudinal axis L of the mixing body, i.e., they can have a circumferential extension component, resulting in a helical pattern of the circumferentially adjacent rows of first and second forms 36, 46. In a further embodiment, the second mixing body part 34 could be arranged on the inner side 30 of the first mixing body part 20, while the reaction agent discharge arrangement 28 could then be configured to introduce the reaction agent R into the second flow volume 26, so that the first flow volume 24 is essentially only permeated by exhaust gas A.It is also possible to arrange several such second mixing body parts 34 consecutively in the direction of the mixing body longitudinal axis L, for example with axial distances to each other, whereby, for example, the rows of the first or second forms 36, 46 can be offset from each other in the circumferential direction when the second mixing body parts 34 follow each other in the axial direction.

[0042] The number of first forms 36 or second forms 46 can also be changed. For example, in the axial direction and / or in the circumferential direction, two second forms 46 with each associated opening 48 could be positioned between any two first forms 36, or two or more first forms 36 could be provided between two second forms 46 with associated opening 48.

[0043] In a further alternative embodiment, at least one part of the second shapings 46 may have two openings 48 on opposite sides of each second shaping 46. Each of these openings 48 may then extend into the associated second shaping 46 or overlap with it, for example axially, so that the second shaping 46 forms a bridge between the two openings 48, directed away from the first mixing body part 20.

[0044] Finally, it may be provided that at least in a partial area of ​​the mixing body 18, or at least a part of the first forms 36 and / or a part of the second forms 46 with their respective associated openings 48 are not arranged in the symmetrical or ordered structure shown in the figures, but rather that a statistical or disordered distribution of these forms 36, 46 with uneven mutual distances in the circumferential and axial directions and without a defined orientation to each other in the circumferential and axial directions is provided.

[0045] The following describes the mounting of the mixing body 18 in the mixing section housing 16, realized according to the principles of the present invention.

[0046] The mixing element 18 is held in the mixing section housing by two radial support areas 50 and 52, which are spaced apart from each other in the direction of the mixing element's longitudinal axis L. The first radial support area 50 is located at an upstream end region 54 of the mixing element 18 and, as explained below, serves to firmly support the mixing element 18 axially on the mixing section housing 16. The second radial support area 52 is located at a downstream end region 56 of the mixing element 18 and, as explained below, serves to radially support the mixing element 18 on the mixing section housing 16, while still allowing relative movement between the mixing element 18 and the mixing section housing 16.

[0047] The first radial support area 50 comprises a plurality of first radial support elements 58, which, for example, are located in the same axial area with respect to the longitudinal axis L of the mixing body and can be arranged circumferentially at uniform intervals from one another. In the Fig. 2a In the embodiment examples shown, three such first radial support elements 58 are provided, which may, for example, have an angular distance of about 120° from each other.

[0048] Each of the first radial support elements 58 radially supports the first mixing body part 20 with respect to the mixing section housing 16 in the first radial support area 50, or holds it in the mixing section housing 16 in the direction of the mixing body longitudinal axis L and also circumferentially around the mixing body longitudinal axis L. For this purpose, the first radial support elements 58 can be connected between a Fig. 3 The first radial support area 50, or its first radial support elements 58, is thus located upstream of the second mixing body part 34 with respect to the main exhaust gas flow direction H.

[0049] For example, as shown in Fig. 6a ) is illustrated, the first radial support elements are provided as separately designed, for example bolt-like, support elements 60, which can be fixed to the first mixing body part 20 in the area of ​​section 59 of the same by material connection, for example by welding or brazing, at their radially inner area and can be fixed to the mixing section housing 16 by material connection, for example by welding or brazing, at their radially outer area.

[0050] The support elements thus ensure a defined positioning of the mixing body 18 in the mixing section housing 16 in the upstream end region of the mixing body 18, in the direction of the mixing body's longitudinal axis L, in the circumferential direction around the mixing body's longitudinal axis L, and in the radial direction. Such a defined positioning of the mixing body 18 in its upstream end region 54 is particularly advantageous because the reaction agent R is also injected into the mixing section 12 in this region, and a defined positioning of the mixing body 18 can ensure that essentially no reaction agent R enters the second flow volume 26.

[0051] In the Fig. 6b), 6c) und 6d ) are alternative designs of such first radial support elements 58 shown.

[0052] The Fig. 6b Figure 1 shows an embodiment in which the radial support elements 58 are formed by support projections 62 on section 59 of the first mixing body part 20, which are directed radially outwards, i.e., towards the mixing section housing 16. The support projections 62, which are designed as convex bulges, bear against the inside of the mixing section housing 16 at their apex and are fixed to the mixing section housing 16 in this area by a material connection, for example by welding or brazing.

[0053] These support features 62 can have an essentially spherical cap shape, but alternatively they can also have a pot-like or cup-like shape, as described above with reference to the first features 36 of the second mixing body part 34.

[0054] At the in Fig. 6c In the embodiment shown, the first radial support elements 58 are provided by support projections 64 on the mixing section housing 16, which are directed radially inwards towards the first mixing body part 20 or its section 59. These support projections can also have the shape described above with reference to the support projections 62 and can be fixed to the first mixing body part 20 in their apex or base area by material connection, preferably by welding or brazing.

[0055] The Fig. 6d Figure 1 shows an embodiment in which such support forms 62, 64 are provided both on the first mixing body part 20 and on the mixing section housing 16. These are preferably arranged such that pairs of support forms 62, 64 are formed, so that support forms 62 of the first mixing body part 20 bear against their respective associated support forms 64 of the mixing section housing 16 in their apex and bottom regions, respectively, and are connected to them by material bonding, for example by welding or brazing.

[0056] The design of the first radial support elements 58 as integral components of the first mixing body part 20 or the mixing section housing avoids the need for additional components and, due to the fact that the mixing section housing 16 or the first mixing body part 20 has radial elasticity in the area of ​​such support features 62, 64, provides the possibility of compensating for different thermally induced radial expansions of the mixing section housing 16 on the one hand and the first mixing body part 20 on the other.

[0057] In the second radial support area 52, the mixing body 18 is radially supported in the region of its downstream end area 56 by a plurality of second radial support elements 66 with respect to the mixing section housing 16. The second radial support elements 66 act between the second mixing body part 34 and the mixing section housing 16 and can be configured as shown in Fig. 2b ) illustrated, preferably lying in the same axial region around the longitudinal axis L of the mixing body, and arranged at a uniform distance from each other. In the case of the Fig. 2b ) In the illustrated embodiment with three such second radial support elements 66, these can have an angular distance of 120° to each other.

[0058] The second radial support elements 66 are provided at a downstream end region 68 of the second mixing body part 34 and are, for example, formed by Fig. 5 Recognizable support projections 70 of the second mixing body part 34, oriented radially outwards, i.e., towards the mixing section housing 16, are provided. For example, such a support projection 70 can be arranged between two first projections 36 of the second mixing body part 34 that follow one another in the circumferential direction. To enable this, a second projection 46 with an associated opening 48 can be provided, for example, in such a region of the second mixing body part 34 between the two affected first projections 36. Instead of such a second projection 46 or opening 48, an outwardly directed support projection 70 can be formed at such a location, which, as shown in Fig. 5 illustrated, for example, may have the shape of a spherical cap or the like, or may have a similar shape to the first forms 36.

[0059] The second radial support area 52, or its second radial support elements 66, is thus located essentially in the same axial region as a portion of the first projections 36 provided on the second mixing body part 34, each forming a mixing body part support area 37, so that at least a portion, preferably all, of the second radial support areas 66 overlap axially in the axial direction, i.e., in the direction of the main exhaust gas flow direction H, with a portion of the first projections 36 or the mixing body part support areas 37. For example, the second radial support areas 66 can be arranged in the same axial region as, or axially overlapping with, the first projections 36 of the ring of first projections positioned furthest downstream with respect to the main exhaust gas flow direction H.

[0060] With these support features 70, the mixing body 18 is supported radially at its downstream end region 56 against the mixing section housing 16, but is not fundamentally fixed to the mixing section housing 16. If different thermal expansions occur between the mixing body 18 and the mixing section housing 16, the mixing body 18 can move with the support features 70 along the inner surface of the mixing section housing 16, particularly in the axial direction, thus avoiding stresses caused by differing thermal expansions. At the same time, the support features 70 of the second radial support elements 66, which are formed as an integral part of the second mixing body section 34, are deformable in the radial direction, so that different radial dimensional changes can be compensated for by deformation of the second mixing body section 34 in the area of ​​the support features 70.

[0061] It should be noted that alternatively, the second support elements 66, located in the Fig. 6c) und 6d ) can exhibit the structure shown. This means that the second support elements 66 could alternatively be provided by radially inwardly directed support forms on the mixing section housing 16, which bear against the second mixing body part 34. The interaction of radially supported support forms of the mixing section housing 16 on the one hand and the second mixing body part 34 on the other hand in the structure shown in Fig. 6d ) as depicted, but without specifying such support forms against each other, is possible.

[0062] By supporting the mixing body 18 in its downstream end region 56 on the mixing section housing 16 via the second mixing body part 18, it becomes possible, particularly in this region of the mixing body 18 where the reaction agent R injected into the first flow volume 24 also flows, to design the first mixing body part 20, through which the reaction agent R or a mixture of reaction agent R and exhaust gas A flows, with a substantially smooth, unstructured surface. This prevents cavities in which deposits of the reaction agent R can form.

[0063] Finally, it should be noted that the design and positioning of the first and second radial support elements 58, 66 can be varied in a wide range of aspects. For example, the second radial support elements 66 or the second radial support area 52 can also be positioned further upstream, so that, for instance, the mixing body 18 can be supported in its mid-length region, or additionally in its mid-length region, by the second radial support area 52 on the mixing section housing 16. The various radial support elements 58, 66 can also be provided in different numbers and offset from each other circumferentially.In the first radial support area 50, for example, a ring-shaped support element could be positioned between the first mixing body part 20 and the mixing section housing 16, wherein this support element can have a plurality of openings allowing the passage of exhaust gas into the second flow volume 26. The web areas limiting these openings in the circumferential direction then form radial support elements within the meaning of the present invention.

[0064] The assignment of the first radial support area 50 and the second radial support area 52 to the two end regions 54, 56 of the mixing body 18 could also be reversed. Thus, the mixing body 18 could be radially supported and fixed to the mixing section housing 16 in its downstream end region 56 via the first radial support elements 58, which can then act between an axially projecting section 72 of the first mixing body part 20 and the mixing section housing 16, while the second radial support elements 66, acting between the second mixing body part 34 and the mixing section housing 16, could then, for example, be provided at the upstream end region 54 of the mixing body 18.

[0065] Regardless of their positioning and design, the various radial support elements not only compensate for dimensional variations and tolerances, but also, particularly when formed as contours, dampen vibrations in the radial direction and, through friction with each other, in the axial and circumferential directions. These contours also act as centering aids when the mixing element 18 is mounted in the mixing section housing 16. Since, during operation of such a mixing section 12, the mixing element 18 is only in contact with the mixing section housing 16 via the various radial support elements 58 and 66, heat dissipation to the outside through the mixing section housing 16 is minimized.

Claims

1. Mixing section for an exhaust system of an internal combustion engine, comprising: - a mixing section housing (16) through which exhaust gas (A) can flow in a main exhaust gas flow direction (H), - a tubular mixing body (18) arranged in the mixing section housing (16) and extending in the direction of a longitudinal axis (L) of the mixing body, wherein the mixing body (18) defines a first flow volume (24) through which exhaust gas (A) can flow radially outwards and defines a second flow volume (26) through which exhaust gas (A) can flow radially inwards, wherein the mixing body (18) comprises a tubular first mixing body part (20) extending in the direction of the longitudinal axis (L) of the mixing body and, on an outer surface (32) of the first mixing body part (20) facing the second flow volume (26), at least one tubular second mixing body part (34) extending in the direction of the longitudinal axis (L) of the mixing body.wherein the second mixing body part (34) is radially supported on a plurality of mixing body part support areas (37) on the first mixing body part (20), characterized by the fact that the mixing body (18) is radially supported in a first radial support area (50) by means of a plurality of first radial support elements (58) with respect to the mixing section housing (16) and is radially supported in a second radial support area (52) arranged in the direction of the longitudinal axis (L) of the mixing body at a distance from the first radial support area (50) by means of a plurality of second radial support elements (66) with respect to the mixing section housing (16), and that the first mixing body part (20) is radially supported on the mixing section housing (16) by the first radial support elements (58) and the second mixing body part (34) is radially supported on the mixing section housing (16) by the second radial support elements (66).

2. Mixing section according to claim 1, characterized by the fact thatby means of the first radial support elements (58) the first mixing body part (20) is held firmly against movement in the direction of the mixing body longitudinal axis (L) and / or movement in the circumferential direction around the mixing body longitudinal axis (L), and that by means of the second radial support elements (66) the second mixing body part (34) is radially supported on the mixing body housing (16) in a manner movable in the direction of the mixing body longitudinal axis (L) and / or in the circumferential direction around the mixing body longitudinal axis (L).

3. Mixing section according to claim 1 or 2, characterized by the fact that a plurality of first radial support elements (58) are provided in the circumferential direction around the longitudinal axis (L) of the mixing body with a circumferential distance to each other, or / and a plurality of second radial support elements (66) are provided in the circumferential direction around the longitudinal axis (L) of the mixing body with a circumferential distance to each other.

4. Mixing section according to one of claims 1-3, characterized by the fact thatat least a part of the second radial support elements (66), preferably all second radial support elements (66), comprise support forms (70) of the second mixing body part (34) directed away from the first mixing body part (20) and / or support forms of the mixing section housing (16) directed towards the second mixing body part (34), preferably wherein the support forms (70) of the second mixing body part (34) are supported on an inner surface of the mixing section housing (16) in the direction of the longitudinal axis (L) of the mixing body and / or circumferentially about the longitudinal axis (L) of the mixing body, and / or wherein the support forms of the mixing section housing (16) are supported on an outer surface of the second mixing body part (34) in the direction of the longitudinal axis (L) of the mixing body and / or circumferentially about the longitudinal axis (L) of the mixing body.

5. Mixing section according to one of claims 1-4, characterized by - thatat least a part of the first radial support elements (58), preferably all first radial support elements (58), comprise support elements (60) preferably fixed by material interlocking on the mixing section housing (16) and the first mixing body part (20), or / and - that at least a part of the first radial support elements (58), preferably all first radial support elements (58), support forms (62) of the first mixing body part (20) directed towards the mixing section housing (16) and preferably fixed to the mixing section housing (16) by material interlocking, or / and support forms (64) of the mixing section housing (16) directed towards the first mixing body part (20) and preferably fixed to the first mixing body part (20) by material interlocking.

6. Mixing section according to one of claims 1-5, characterized by - thatthe first radial support area (50) is provided in an upstream end area (54) of the mixing body (18), preferably upstream of the second mixing body part (34) with respect to the main exhaust gas flow direction (H), and / or that the second radial support area (52) is provided in a downstream end area (56) of the mixing body (18), and / or - that at least a part of the second radial support elements (66), preferably all second radial support elements (66), overlap axially with a part of the mixing body part support areas (37).

7. Mixing section according to one of claims 1-6, characterized by the fact thatthe second mixing body part (34) has a plurality of first forms (36) arranged adjacent to each other in the direction of the mixing body longitudinal axis (L) and in the circumferential direction around the mixing body longitudinal axis (L) and directed towards the first mixing body part (20), and that at least one first form (36), preferably each first form (36), forms a mixing body part support area (37).

8. Mixing section according to claim 7, characterized by the fact thatthe first forms (36) are arranged in a plurality of rows of first forms (36) arranged successively in the circumferential direction around the longitudinal axis (L) of the mixing body, preferably extending substantially in the direction of the longitudinal axis (L) of the mixing body, or / and that the first forms (36) are arranged in a plurality of rings of first forms (36) arranged successively in the direction of the longitudinal axis (L) of the mixing body, preferably extending substantially in the circumferential direction around the longitudinal axis (L) of the mixing body.

9. Mixing section according to claim 7 or 8, characterized by the fact thatat least a part of the first forming (36), preferably each first forming (36), is designed as a closed forming, and / or that at least a part of the first forming (36), preferably each first forming (36), is formed with a forming circumferential wall (38) and a forming base (40) abutting the first mixing body part (26), preferably substantially planar or substantially curved to match a curvature of the first mixing body part (20), and / or that at least a part of the first forming (36), preferably each first forming (36), is circular.

10. Mixing section according to one of claims 1-9, characterized by the fact that the second mixing body part has a plurality of second forms (46) arranged adjacent to each other in the direction of the mixing body longitudinal axis (L) and in the circumferential direction around the mixing body longitudinal axis (L), directed away from the first mixing body part (20).

11. Mixing section according to claim 10, characterized by the fact that Adjacent to at least a part of the second forms (46), preferably every second form (46), at least one opening (48) is provided in the second mixing body part (34), preferably wherein in each pair of mutually associated second forms (46) and openings (48) the second forms (46) and the opening (48) overlap each other in certain areas, preferably wherein in some part of the pairs of mutually associated second forms (46) and openings (48) the opening (48) is arranged on a first side, preferably first axial side, of the associated second form (46) and in another part of the pairs of mutually associated second forms (46) and openings (48) the opening (48) is arranged on a second side, preferably second axial side, of the associated second form (46) that is substantially opposite the first side.

12. Mixing section according to one of claims 10 or 11, characterized by the fact that the second forms (46) are arranged in a plurality of rows of second forms (46) arranged consecutively in the circumferential direction around the longitudinal axis (L) of the mixing body, preferably extending substantially in the direction of the longitudinal axis (L) of the mixing body, or / and that the second forms (46) are arranged in a plurality of rings of second forms (46) arranged consecutively in the direction of the longitudinal axis (L) of the mixing body, preferably extending substantially in the circumferential direction around the longitudinal axis (L) of the mixing body.

13. Mixing section according to one of claims 1-12, characterized by the fact that In the main exhaust gas flow direction (H) upstream of the mixing body (18) a reaction agent delivery arrangement (28) is arranged for the delivery of reaction agent (R) essentially only into the first flow volume (24).

14. Mixing section according to one of claims 1-13, characterized by the fact that the second mixing body part (34) is preferably fixed to the first mixing body part (20) by material interlocking in the area of ​​at least a part of the mixing body part support areas (37), preferably all mixing body part support areas (37).

15. Exhaust system for an internal combustion engine, comprising a mixing section (12) according to one of claims 1-14 and downstream of the mixing section (12) an exhaust gas treatment unit (14), preferably an SCR catalyst.

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