Mixing section for exhaust gas systems of internal combustion engines

Abstract

To provide a mixing section for an exhaust gas system of an internal combustion engine that ensures compensation for the expansion of the mixing section components. [Solution] A mixing section housing (16) through which exhaust gas can flow in the main exhaust gas flow direction (H), and a tubular mixing body (18) extending in the direction of the longitudinal axis (L) of the mixing body, wherein a first flow volume (24) through which exhaust gas can flow is defined radially outward, and a second flow volume (26) through which exhaust gas can flow is defined radially inward. The mixing body (18) includes a first mixing body portion (20) extending in the direction of the longitudinal axis of the mixing body, and the outer surface (32) of the first mixing body portion (20) facing the second flow volume (26) includes at least one tubular second mixing body portion (34) extending in the direction of the longitudinal axis of the mixing body. The mixing body is radially supported with respect to the mixing section housing via a plurality of first radial support mechanisms (58) in a first radial support region (50).

Description

Technical Field

[0001] The present invention relates to a mixing section for an exhaust gas device of an internal combustion engine, comprising a mixing section housing through which exhaust gas can flow in the direction of the exhaust gas main flow, and a tubular mixing body arranged in the mixing section housing and extending in the direction of the longitudinal axis of the mixing body. The mixing body defines a first flow volume through which the exhaust gas can flow radially outward and a second flow volume through which the exhaust gas can flow radially inward. 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 the outer surface of the first mixing body part facing the second flow volume. In this case, the second mixing body part is supported radially on the first mixing body part in a plurality of mixing body part support regions.

Background Art

[0002] Such a mixing section for an exhaust gas device is known from German Patent Application No. 102024119108.2 before publication. In such a mixing section, the mixing body through which the exhaust gas flows surrounding the outer and inner surfaces is heated more strongly than the mixing section housing which is generally surrounded by ambient air on the outer surface, so that during operation, on the one hand, thermally induced different expansions of the mixing section housing and on the other hand of the mixing body occur.

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0004] According to the present invention, this object is a mixing section for an exhaust gas device of an internal combustion engine, - A mixing section housing through which exhaust gas can flow in the direction of the main exhaust gas flow, -A tubular mixing body disposed within a mixing section housing and extending in the direction of the longitudinal axis of the mixing body, wherein the mixing body defines a first flow volume through which exhaust gas can flow with respect to the radially outward direction and a second flow volume through which exhaust gas can flow with respect to the radially inward direction, the mixing body comprises a tubular first mixing body portion extending in the direction of the longitudinal axis of the mixing body, the outer surface of the first mixing body portion facing the second flow volume comprises at least one tubular second mixing body portion extending in the direction of the longitudinal axis of the mixing body, the second mixing body portion is radially supported by the first mixing body portion in a plurality of mixing body portion support regions, and This is resolved by a mixed section that includes the following:

[0005] The mixing section according to the present invention is characterized in that the mixture is radially supported with respect to the mixing section housing via a plurality of first radial support mechanisms in a first radial support region, and radially supported with respect to the mixing section housing via a plurality of second radial support mechanisms in a second radial support region which is spaced apart from the first radial support region in the direction of the longitudinal axis of the mixture, the first mixture portion is radially supported by the first radial support mechanism to the mixing section housing, and the second mixture portion is radially supported by the second radial support mechanism to the mixing section housing.

[0006] In the mixing section according to the present invention, the support functions to be realized in both radial support regions, which are spaced apart from each other in the axial direction, are distributed between a first mixing portion located more radially inward and a second mixing portion surrounding the outer surface of the first mixing portion. This makes it possible to optimally distribute the support functions to be realized in the entire mixing portion, in which some require the possibility of relative motion, but in which some require the guarantee of a defined, immovable position. At the same time, the second mixing portion, through which exhaust gas flows so as to surround 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 portion through contact with the first mixing portion that occurs in the region of the mixing portion support region. Because the exhaust gas flows around the outer and inner surfaces of both mixture parts, both mixture parts have substantially equal temperatures during operation, and thus, even considering that both mixture parts may be formed from the same material, particularly a metallic material, there is substantially no thermally induced dimensional variation between the mixture parts.

[0007] On the one hand, to ensure the defined positioning of the mixture with respect to the mixing section housing, but on the other hand, to avoid different stresses induced by thermal expansion, it is proposed that a first portion of the mixture is held immovably in the mixture housing against motion in the direction of the longitudinal axis of the mixture and / or circumferential motion about the longitudinal axis of the mixture by a first radial support mechanism, and a second portion of the mixture is radially supported in the mixture housing so as to be movable in the direction of the longitudinal axis of the mixture and / or circumferential motion about the longitudinal axis of the mixture by a second radial support mechanism.

[0008] The defined support function can be further assisted by the provision of a plurality of first radial support mechanisms spaced apart from each other in the circumferential direction around the longitudinal axis of the mixture, and / or a plurality of second radial support mechanisms spaced apart from each other in the circumferential direction around the longitudinal axis of the mixture.

[0009] Structurally incorporating the support function to be realized in the second radial support region into the components of the mixing section can be achieved by having at least some of the second radial support mechanisms, preferably all of the second radial support mechanisms, provide a support molding portion of the second mixing portion facing away from the first mixing portion, and / or a support molding portion of the mixing section housing facing towards the second mixing portion. This avoids the need to provide additional components to realize the support function.

[0010] By providing the radial support mechanism, for example, as a molded portion of the second mixed body portion or mixed section housing, that is, as a convex bulge oriented toward the other component, radial elasticity is generated in the region of such molded portion. This elasticity makes it possible to compensate for the thermally induced, different radial expansions of the mixed section housing on the one hand and the mixed body on the other.

[0011] In this case, in order to ensure the relative mobility of the mixture with respect to the mixing section housing, it may be specified that the support molding of the second mixture portion is supported on the inner surface of the mixture housing so as to be movable in the direction of the longitudinal axis of the mixture and / or in the circumferential direction about the longitudinal axis of the mixture, or / or that the support molding of the mixing section housing is supported on the outer surface of the second mixture portion so as to be movable in the direction of the longitudinal axis of the mixture and / or in the circumferential direction about the longitudinal axis of the mixture. If both components, i.e., the mixing section housing and the second mixture portion in this example, are provided with such moldings oriented toward the other component, these moldings can be assigned to each other in pairs so that the moldings of the second mixture portion are radially supported by the respective assigned moldings of the mixing section housing.

[0012] To hold the mixture immovably in the axial and / or circumferential directions within the first radial support region, at least some of the first radial support mechanisms, preferably all of the first radial support mechanisms, may include support elements fixed to the mixing section housing and the first mixture portion, preferably by material connections, such as welding or brazing.

[0013] Alternatively or additionally, in order to obtain a configuration with as few components as possible, at least some of the first radial support mechanisms, preferably all of the first radial support mechanisms, are oriented toward the first mixture portion toward the mixing section housing and have a support molded portion fixed to the mixing section housing, preferably by material connection, such as welding or brazing, and / or the mixing section housing is oriented toward the first mixture portion and has a support molded portion fixed to the first mixture portion, preferably by material connection, such as welding or brazing.

[0014] In particular, in the upstream region of the mixture where the reactant is typically sprayed, it is proposed that a first radial support region be provided in the upstream end region of the mixture, preferably upstream of the second portion of the mixture, and / or a second radial support region be provided in the downstream end region of the mixture, in order to ensure the defined positioning of the mixture within the mixing section.

[0015] For defined positioning of the first mixture portion radially inward with respect to the mixing section housing, at least some of the second radial support mechanisms, preferably all of the second radial support mechanisms, may axially overlap a portion of the mixture portion support area.

[0016] To provide a support region for the mixed body portion, the second mixed body portion has a plurality of first molded parts that are arranged adjacent to each other in the direction of the longitudinal axis of the mixed body and in the circumferential direction about the longitudinal axis of the mixed body, and are oriented toward the first mixed body portion, and at least one of the first molded parts, preferably each first molded part, may form a support region for the mixed body portion.

[0017] To obtain a substantially regular molded portion pattern and consequently substantially uniform heat transfer between the two mixtures, it is proposed that the first molded portion be arranged in a plurality of rows, preferably substantially extending in the direction of the longitudinal axis of the mixture, and continuously arranged circumferentially around the longitudinal axis of the mixture, and / or that the first molded portion be arranged in a plurality of rings, preferably substantially extending in the direction of the longitudinal axis of the mixture, and continuously arranged in the direction of the longitudinal axis of the mixture.

[0018] For particularly efficient heat transfer between the second mixture portion and the first mixture portion, it is proposed that at least a portion of the first molded portion, preferably each first molded portion, be formed as a closed molded portion, or / and that at least a portion of the first molded portion, preferably each first molded portion, be formed comprising a molded portion periphery wall and a molded portion bottom that contacts the first mixture portion, preferably substantially planar or curved to substantially conform to the curvature of the first mixture portion, or / and that at least a portion of the first molded portion, preferably each first molded portion, be formed in a circular shape.

[0019] Enhanced thermal interaction with the exhaust gas can be achieved by having a plurality of second molded portions facing away from the first mixture portion, which are arranged adjacent to each other in the direction of the longitudinal axis of the mixture and in the circumferential direction about the longitudinal axis of the mixture.

[0020] In this case, further, if at least one opening is provided in the second mixed portion adjacent to at least a portion of the second molded portion, preferably adjacent to each second molded portion, and preferably, in each pair of second molded portions and openings assigned to each other, the second molded portion and opening are specified to partially overlap each other, then exhaust gas that has flowed into the intermediate chamber between the two mixed portions can flow out of the intermediate chamber again, thereby allowing the still-warm exhaust gas to flow into this intermediate chamber and transfer heat to the mixed portion.

[0021] The outflow of exhaust gas from the intermediate chamber formed between the two mixed portions and the inflow of exhaust gas into the intermediate chamber can be further assisted by the fact that in one portion of a pair of assigned second molded portions and openings, the opening is located on the first side of the assigned second molded portion, preferably on the first axial side, and in the other portion of a pair of assigned second molded portions and openings, the opening is located on the second side of the assigned second molded portion, substantially opposite to the first side, preferably on the second axial side.

[0022] Furthermore, relating to the second molded portion, a regular molded portion pattern that assists uniform heat transfer can be provided by the second molded portion being arranged in a plurality of rows that are continuously arranged in the circumferential direction around the longitudinal axis of the mixture, preferably substantially extending in the direction of the longitudinal axis of the mixture, and / or by the second molded portion being arranged in a plurality of rings that are continuously arranged in the direction of the longitudinal axis of the mixture, preferably substantially extending in the circumferential direction around the longitudinal axis of the mixture.

[0023] To introduce the reactant, a reactant delivery assembly may be positioned upstream of the mixture in the main flow direction of the exhaust gas, for delivering the reactant substantially only into a first flow volume. Thus, since the reactant does not substantially reach the intermediate chamber formed between the two parts of the mixture, the risk of reactant deposits forming in the intermediate chamber is eliminated.

[0024] A stable bond that assists heat transfer between both mixture parts can be achieved, for example, by fixing the second mixture part to the first mixture part in the region of at least a part of the mixture part support region, preferably in the region of all mixture part support regions, preferably by a material connection, such as welding or brazing. In this case, during operation, both mixture parts have substantially equal temperatures with respect to each other, and are preferably formed of the same material as each other or materials having substantially equal coefficients of thermal expansion with respect to each other, so that the risk of stress generation due to the fixation of both mixture parts to each other is eliminated.

[0025] The present invention further relates to an exhaust gas device for an internal combustion engine, which includes a mixing section formed according to the present invention and an exhaust gas treatment unit, preferably an SCR catalyst, downstream of this mixing section.

[0026] The present invention will be described in detail below with reference to the accompanying drawings.

Brief Description of the Drawings

[0027] [Figure 1] It is a schematic diagram of an exhaust gas device for an internal combustion engine including a mixing section. [Figure 2] a) is a cross-sectional view of the exhaust gas device of FIG. 1 cut along the line IIa)-IIa) shown in FIG. 1, and b) is a cross-sectional view of the exhaust gas device of FIG. 1 cut along the line IIb)-IIb) shown in FIG. 1. [Figure 3] It is a perspective view of a mixture formed by two tubular mixture parts. [Figure 4] It is a detailed longitudinal sectional view of the mixture. [Figure 5] It is a cross-sectional view of the mixture in a cutting plane corresponding to the cutting plane IIb)-IIb). [Figure 6] a) to d) are diagrams showing one configuration form of the radial support mechanism.

Modes for Carrying Out the Invention

[0028] Figure 1 shows in principle a part of an exhaust gas system for an internal combustion engine, with the entire component denoted by reference numeral 10. The exhaust gas system 10 includes a mixing section, the entire component denoted by reference numeral 12, and an exhaust gas treatment unit 14 located downstream of the mixing section 12. In the illustrated example, the exhaust gas treatment unit 14 is equipped with an SCR catalyst.

[0029] The mixing section 12 comprises a mixing section housing 16, within which a substantially tubular mixture 18 is arranged, elongated in the direction of the longitudinal axis L of the mixture. Exhaust gases emitted from an internal combustion engine, particularly a diesel internal combustion engine, flow into the mixing section housing 16 or towards the mixture 18 in the main exhaust gas flow direction H, which substantially corresponds to the direction of the longitudinal axis L of the mixture.

[0030] The mixing body 18 comprises a tubular first mixing body portion 20, which comprises a closed circumferential wall 22 formed, for example, substantially cylindrical and having a circular cross-section. The first mixing body 20 or its circumferential wall 22 divides the internal volume of the mixing section housing 16 into a first flow volume 24 formed inside the first mixing body portion 20 or its circumferential wall 22 in the axially extending region of the mixing body 18 and surrounded by or defined radially outward by the circumferential wall 22, and a second flow volume 26 formed between the mixing section housing 16 and the first mixing body portion 20 or defined radially inward by the first mixing body portion 20.

[0031] The exhaust gas device 10 or mixing section 12 further comprises a reactant delivery assembly 28, also commonly called an injector, which injects a reactant R, for example, urea / aqueous solution, in the form of a spray mist, i.e., fine droplets, into the exhaust gas A flowing within the mixing section housing 16. The reactant delivery assembly 28 is configured to deliver the reactant R into a first flow volume 24, and thereby into a sub-flow T1 of the exhaust gas A flowing within the first flow volume 24. Thus, the reactant R is not substantially injected into a second flow volume 26 and into a second sub-flow T2 of the exhaust gas A flowing within the second flow volume 26. Thus, the second flow volume 26 is only passed through by the exhaust gas A, i.e., by the second sub-flow T2, and serves primarily to transfer heat transported within the exhaust gas A to the mixture 18 or the first mixture portion 20, as will be explained in detail below. The enhanced heating of the first mixture portion 20 enables the evaporation of the reactant R in contact with the inner surface 30 of the peripheral wall 22, thereby achieving improved mixing of the reactant R and exhaust gas A without requiring system regions that would result in high flow resistance, such as a mixer or similar component.

[0032] A tubular second mixture portion 34 is positioned on the outer surface 32 of the peripheral wall 22 of the first mixture portion 20, facing the second flow volume 26. The second mixture portion 34 completely surrounds the first mixture portion 20 circumferentially, preferably substantially over its entire axially extending region, and substantially fulfills the function of a heat exchanger, which can enhance the heat transported in the second partial flow T2 of exhaust gas A and introduce it into the mixture 18.

[0033] Before describing in detail, primarily with reference to Figures 1, 2, 5, and 6, how the retention of the mixture 18 within the mixing section housing 16 is achieved by the principle of the present invention, we will first describe, with reference to Figures 3 and 4, the structure of the mixture 18, which comprises a tubular first mixture portion 20, a circumferential wall 22 closed in its circumferential direction, and a tubular second mixture portion 34 surrounding the first mixture portion 20 or its circumferential wall 22, a structure known under German Patent Application No. 102024119108.2, which has not yet been published.

[0034] Similar to the first mixed body portion 20, the second mixed body portion 34, formed, for example, as a metal sheet formed portion, has a number of substantially cellular first molded portions 36 distributed circumferentially around the longitudinal axis L of the mixed body along the axial length of the second mixed body portion 34. These cellular first molded portions 36 are configured on the second mixed body portion 34 so as to extend toward and contact the outer surface 32 of the first mixed body portion 20 from a base level located substantially at a constant distance from the outer surface 32 of the first mixed body portion 20. Each first molded portion 36 that contacts the outer surface 32 of the first mixed body portion 20 forms a mixed body portion support region 37 that radially supports the second mixed body portion 34 to the first mixed body portion 20.

[0035] The molded portion 36 is formed by a molded portion periphery wall 38 and a molded portion bottom 40 that contacts the outer surface 32 of the first mixed portion 20, and has a circular shape when viewed in plan. The molded portion bottom 40 is substantially planar or conforms to the curvature of the outer surface 32 of the first mixed portion 20, thereby creating surface contact between the second mixed portion 34 and the first mixed portion 20 in the region of the molded portion bottom 40. Preferably, in order to create good heat transfer contact, a material-connecting bond between both mixed portions 20 and 34 is formed in the entire region of the first molded portion 36, for example by welding or brazing.

[0036] As can be seen in Figure 3, the second mixture portion 34 has a number of rows of first molded portions 36 that extend substantially in the direction of the longitudinal axis L of the mixture. In rows of the first molded portions 36 that are directly adjacent to each other in the circumferential direction, the first molded portions 36 are offset from each other in the direction of the longitudinal axis L of the mixture, so that in the direction of the longitudinal axis L of the mixture, one first molded portion 36 of one row is positioned between two first molded portions 36 of one row. For uniform heat transfer contact, preferably, within the rows of first molded portions 36, the first molded portions 36 that are continuous in the direction of the longitudinal axis L of the mixture are arranged at substantially uniform intervals from each other.

[0037] Similarly, the second mixed body portion 34 has a ring formed thereon that extends circumferentially around the longitudinal axis L of the mixed body of the first molded portion 36. In this ring of the first molded portion 36, the first molded portions 36 are spaced substantially uniformly apart from each other, and in the rings of the first molded portion 36 that are directly adjacent to each other in the direction of the longitudinal axis L of the mixed body, the first molded portions 36 are offset from each other in the circumferential direction, thereby positioning one first molded portion 36 of the other ring between two first molded portions in the circumferential direction of one of the rings of each of the two rings.

[0038] The substantially uniform pattern of the first molded portion 36 over the entire axial length of the second mixture portion 34 and around the entire circumference of the second mixture portion 34 creates substantially uniform heat transfer contact between both mixture portions 34,20. Thus, the exhaust gas A of the second partial flow T2, flowing in the second flow volume 26 along the second mixture portion 34, flows around the outer surface 42 of the second mixture portion 34 opposite to the first mixture portion 20 and the inner surface 44 facing the first mixture portion 20, and in this case, can transfer heat to the second mixture portion 34. The heat absorbed by the second mixture portion 34 is transferred to the first mixture portion 20 through the contact between both mixture portions 34,20 in the region of the first molded portion 36. In this case, particularly advantageously, turbulence is generated based on the fact that a number of first molded portions 36 are provided in the inner surface 44 and outer surface 42 regions of the second mixed portion 34, and this turbulence improves the thermal interaction between the exhaust gas A in the second partial flow T2 and the second mixed portion 34.

[0039] To obtain further improved thermal interaction and enhanced heat introduction into the first mixture portion 20, the second mixture portion 20 has a number of second molded portions 46. Each second molded portion 46 is assigned one opening 48, thereby forming each pair of second molded portion 46 and opening 48. The second molded portions 46 are oriented radially outward with respect to the longitudinal axis L of the mixture, i.e., away from the first mixture portion 20, and are positioned such that, with respect to each assigned opening 48, the second molded portion 46 and opening 48 overlap each other in each pair, i.e., the opening 48 extends into the region of the molded portion 46. This results in the structure that can be seen in Figure 4, i.e., each of these second molded portions 46 is formed like a kind of spherical crown or part of a similarly molded crown, opening towards each assigned opening 48.

[0040] As can be further seen in Figures 3 and 4, in each pair of the second molded portion 46 and the opening 48, the second molded portion 46 and the opening 48 are arranged axially and continuously in the direction of the longitudinal axis L of the mixture. Furthermore, the second molded portion 46 or the opening 48, or the pair consisting of the second molded portion 46 and the opening 48, are arranged in rows that substantially extend in the direction of the longitudinal axis L of the mixture. In this case, even in the illustrated configuration, the second molded portion 46 or the opening 48, or the pair consisting of the second molded portion 46 and the opening 48, are arranged in such a way that they are offset from each other in the direction of the longitudinal axis L of the mixture in rows of the second molded portion 46 that are directly adjacent to each other in the circumferential direction. Similarly, the second molding portion 46 or the corresponding opening 48, or a pair consisting of the second molding portion 46 and the opening 48, each form a ring extending in the circumferential direction. In this case, even in rings that are directly adjacent to each other in the direction of the longitudinal axis L of the mixture, the second molding portions 46 are offset from each other, positioned at uniform intervals in both the circumferential and longitudinal axis L of the mixture. In particular, in this case, the second molding portion 46 or the opening 48 is incorporated between two first molding portions 36 in both the axial and circumferential directions. As a result, in both the axial and circumferential directions, the first molding portions 36 and the second molding portions 46, each with its assigned opening 48, are arranged alternately and continuously. Consequently, the rows and rings of the first molding portions 36 correspond to the rows or rings of the second molding portions 46.

[0041] As can be further seen in Figure 3, in the two rows of the second molded portion 46 that are directly adjacent to each other in the circumferential direction, the openings 48 are positioned on opposite sides of the second molded portion 46. In one of the two rows of the second molded portion 46 that are directly adjacent to each other in the circumferential direction, the corresponding opening 48 is located on the first side of the second molded portion 46, particularly the first axial side, while in the other row of the two rows of the second molded portion 46 that are directly adjacent to each other in the circumferential direction, the corresponding opening 48 is located on the other side of the second molded portion 46, particularly the other axial side. Thus, in both the circumferential and axial directions, in the rings of the second molded portion that are directly adjacent to each other, an alternating pattern of axial openings of the second molded portion 46 is created, which assists the inflow of exhaust gas A into the intermediate chamber 50 formed between the two mixed portions 20, 34 and the outflow of exhaust gas A from the intermediate chamber 50. Therefore, the second molding section 46 not only contributes to enhancing turbulence in the region near the surface of the second mixture section 34, but also assists in exhaust gas exchange within the intermediate chamber 50, thereby improving heat transfer between both mixture sections 34 and 20, as well as thermal contact between the first mixture section 20 and the second partial flow T2 flowing within the second flow volume 26.

[0042] Various variations can be realized in the structure of the mixture 18 shown in the drawings. For example, the rows of the first molding section 36 or the second molding section 46 may have orientations different from those parallel to the longitudinal axis L of the mixture, that is, they may have circumferentially extending components, thereby obtaining a spiral pattern of adjacent rows of the first molding section 36 or the second molding section 46 in the circumferential direction. In a further configuration, the second mixture section 34 may be located on the inner surface 30 of the first mixture section 20, in which case the reactant delivery assembly 28 may be configured to introduce the reactant R into the second flow volume 26, so that the first flow volume 24 is substantially only passed through by exhaust gas A. Furthermore, multiple such second mixed body portions 34 can be arranged continuously in the direction of the longitudinal axis L of the mixed body, for example, with axial spacing between them. In this case, for example, the rows of the first molded portion 36 or the second molded portion 46 may be offset from each other in the circumferential direction in the axially continuous second mixed body portions 34.

[0043] Furthermore, the number of first molding sections 36 or second molding sections 46 may be changed. For example, two second molding sections 46, each having an assigned opening 48, may be positioned between two first molding sections 36 in the axial direction and / or the circumferential direction, or two or more first molding sections 36 may be provided between two second molding sections 46, each having an assigned opening 48.

[0044] In a further alternative configuration, two openings 48 may be provided on opposite sides of the second molding portion 46, each assigned to one of the second molding portions 46, in at least a portion of the second molding portion 46. In this case, each opening 48 may extend into the assigned second molding portion 46 or overlap the second molding portion 46, for example, axially, so that the second molding portion 46 forms a bridge between the two assigned openings 48, oriented away from the first mixed portion 20.

[0045] Finally, it may be specified that in at least a portion of the mixture 18, or at least a portion of the first molded portion 36 and / or at least a portion of the second molded portion 46 having the respective assigned openings 48, the molded portions 36, 46 are not arranged in a symmetrical or orderly manner as shown in the drawings, but rather the molded portions 36, 46 are set to a statistical or disorderly distribution with non-uniform spacing between them in the circumferential and axial directions, without any specified relative positional adjustments in the circumferential and axial directions.

[0046] The following describes how the mixture 18 is held within the mixing section housing 16, as achieved by the principle of the present invention.

[0047] The mixture 18 is held in the mixing section housing 16 in two radial support regions 50, 52 located spaced apart from each other in the direction of the longitudinal axis L of the mixture within the mixing section housing. In this case, the first radial support region 50 is located at the upstream end region 54 of the mixture 18 and serves to support the mixture 18 immobilely in the axial direction as described below. The second radial support region 52 is located at the downstream end region 56 of the mixture 18 and serves to support the mixture 18 radially in the mixing section housing 16 as described below, but basically serves to allow relative motion between the mixture 18 and the mixing section housing 16.

[0048] The first radial support region 50 comprises a plurality of first radial support mechanisms 58, which may be located in the same axial region with respect to the longitudinal axis L of the mixture and distributed at uniform intervals from each other in the circumferential direction. In the configuration example shown in Figure 2a), for example, three such first radial support mechanisms 58 are provided, which may have an angular spacing of approximately 120° from each other.

[0049] Each first radial support mechanism 58 supports the first mixture portion 20 radially with respect to the mixing section housing 16 within the first radial support region 50, or fixes it within the mixing section housing 16 in the direction of the longitudinal axis L of the mixture, or in the circumferential direction around the longitudinal axis L of the mixture. For this purpose, the first radial support mechanism 58 may be provided or fixed between the sections 59 of the first mixture portion 20, as can be seen in Figure 3, which protrude axially beyond the second mixture portion 34 in the upstream end region 54 of the mixture 18. Thus, the first radial support region 50 or the first radial support mechanism 58 is located upstream of the second mixture portion 34 with respect to the exhaust gas main flow direction H.

[0050] For example, as shown in Figure 6a), the first radial support mechanism may be provided as a separately formed support element 60, for example, a pin-shaped support element 60, which may be fixed in its radially inner region to the first mixed body portion 20 in the region of its section 59 by material connection, i.e., welding or brazing, and in its radially outer region to the mixed section housing 16 by material connection, i.e., welding or brazing.

[0051] Therefore, the support elements ensure the defined positioning of the mixture 18 within the mixing section housing 16 in the upstream end region of the mixture 18, in the direction of the longitudinal axis L of the mixture, and in the circumferential and radial directions around the longitudinal axis L of the mixture. Such defined positioning of the mixture 18 in the upstream end region 54 is particularly advantageous because, in this region, the reactant R is also injected into the mixing section 12, and the defined positioning of the mixture 18 can be used to substantially prevent the reactant R from reaching the second flow volume 26.

[0052] Figures 6b), 6c), and 6d) show alternative configurations of such a first radial support mechanism 58.

[0053] Figure 6b) shows that the radial support mechanism 58 is formed by a support molding portion 62 provided in section 59 of the first mixed body portion 20, which faces radially outward, that is, toward the mixed section housing 16. The support molding portion 62, which is formed as a convex bulge, is supported on the inner surface of the mixed section housing 16 at its apex region and is fixed to the mixed section housing 16 in that region by material connection, such as welding or brazing.

[0054] The support molding portion 62 may have a substantially spherical crown-shaped structure, but alternatively, as described above with respect to the first molding portion 36 of the second mixed portion 34, it may have a pot-shaped or cell-shaped structure.

[0055] In the configuration shown in Figure 6c), the first radial support mechanism 58 is provided by a support molding portion 64 located in the mixing section housing 16, which is radially inward and oriented toward the first mixed body portion 20 or its section 59. The support molding portion 64 may also have the shape described above with respect to the support molding portion 62, and may be fixed to the first mixed body portion 20 at its top or bottom region by material connection, preferably by welding or brazing.

[0056] Figure 6d) shows a configuration in which such support molding portions 62, 64 are provided in both the first mixed body portion 20 and the mixed section housing 16. Preferably, these support molding portions 62, 64 are formed in pairs, so that the support molding portion 62 of the first mixed body portion 20 contacts the respective assigned support molding portion 64 of the mixed section housing 16 at its top or bottom region and is joined to the support molding portion 64 by material connection, such as welding or brazing.

[0057] By forming the first radial support mechanism 58 as an integral component of the first mixed body portion 20 or the mixed body housing, the provision of additional components is avoided, and based on the situation in which the mixed body housing 16 or the first mixed body portion 20 has radial elasticity in the region of such support molded portions 62, 64, the possibility is provided to compensate for thermally induced radial expansion of the mixed body housing 16 on the one hand and the first mixed body portion 20 on the other hand.

[0058] In the second radial support region 52, the mixture 18 is radially supported with respect to the mixing section housing 16 by a plurality of second radial support mechanisms 66 in the region of its downstream end region 56. The second radial support mechanisms 66 act between the second mixture portion 34 and the mixing section housing 16 and may be arranged at uniform intervals from one another, preferably located in the same axial region in the circumferential direction around the longitudinal axis L of the mixture, as shown in Figure 2b). In the configuration with three such second radial support mechanisms 66 shown in Figure 2b), these second radial support mechanisms 66 may be spaced 120° apart from each other.

[0059] The second radial support mechanism 66 is provided in the downstream end region 68 of the second mixed portion 34 and is provided, for example, by a radially outward-facing support molding portion 70 of the second mixed portion 34, as can be seen in Figure 5, that is, oriented toward the mixed section housing 16. For example, such a support molding portion 70 may be located between two circumferentially continuous first molding portions 36 of the second mixed portion 34. To enable this, for example, a second molding portion 46 having an allocated opening 48 may be provided in such a region of the second mixed portion 34 between the two corresponding first molding portions 36. Instead of such a second molding portion 46 or opening 48, an outward-facing support molding portion 70 may be formed at such a location, and the support molding portion 70 may have the shape of, for example, a spherical cap or similar, as shown in Figure 5, or it may be a similar shape to the first molding portion 36.

[0060] Therefore, the second radial support region 52 or the second radial support mechanism 66 is substantially located in the same axial region as a portion of the first molding section 36 that forms one mixture section support region 37, provided in the second mixture section 34. Preferably, at least a portion of all of the second radial support regions 66 axially overlaps a portion of the first molding section 36 or the mixture section support region 37 in the axial direction or the exhaust gas main flow direction H. For example, the second radial support region 66 may be located in the same axial region as the first molding section 36 of the ring positioned furthest downstream with respect to the exhaust gas main flow direction H of the first molding section, or it may be located axially overlapping the first molding section 36.

[0061] Although the mixed body 18 is supported radially by the mixing section housing 16 in its downstream end region 56 by the support molding section 70, it is not fundamentally fixed to the mixing section housing 16. When different thermal expansions occur in the mixed body 18 on one side and the mixing section housing 16 on the other, the mixed body 18 moves along the inner surface of the mixing section housing 16, particularly in the axial direction, by the support molding section 70, thereby avoiding stress caused by the different thermal expansions. At the same time, the support molding section 70, which is formed as an integral component of the second mixed body portion 34 of the second radial support mechanism 66, becomes moldable in the radial direction, thereby compensating for the different radial dimensional changes caused by the deformation of the second mixed body portion 34 within the area of ​​the support molding section 70.

[0062] It should be added that, alternatively, the second support mechanism 66 may also have the structure shown in Figures 6c) and 6d). In other words, the second support mechanism 66 may, alternatively, be provided by a support molding part that is provided in the mixing section housing 16, faces radially inward, and is supported by the second mixed body portion 34. Furthermore, in the sense shown in Figure 6d), however, cooperation is possible between the radially supported support molding parts of the mixing section housing 16 on one side and the second mixed body portion 34 on the other, without fixing such support molding parts to each other.

[0063] By supporting the mixture 18 in the mixing section housing 16 via a second mixture portion 18 at its downstream end region 56, it becomes possible to form a first mixture portion 20 with a substantially smooth, unstructured surface, through which the reactant R injected into the first flow volume 24 of the mixture 18 also flows, with the reactant R or a mixture of reactant R and exhaust gas A flowing on its inner surface. This avoids the formation of a hollow chamber where reactant R deposits can occur.

[0064] Finally, it should be noted that the configuration and positioning of the first and second radial support mechanisms 58, 66 can be varied in various ways. For example, the second radial support mechanism 66 or the second radial support region 52 may be positioned further upstream, or additionally further upstream, so that, for example, the mixture 18 can be supported in the mixing section housing 16 via the second radial support region 52 in its intermediate length region or additional intermediate length region. Various radial support mechanisms 58, 66 may be provided in different numbers, and may be offset from each other in the circumferential direction. In the first radial support region 50, for example, an annular support element may be positioned within the mixing section housing 16 between the first mixture portion 20 and the mixing section housing 16, in which case this support element may have a number of openings that allow the flow of exhaust gas into the second flow volume 26. In this case, the web region defining these openings in the circumferential direction constitutes a radial support mechanism in the sense of the present invention.

[0065] Furthermore, the assignment of the first radial support region 50 and the second radial support region 52 to both end regions 54 and 56 of the mixture 18 may be reversed. In other words, the mixture 18 may be radially supported and fixed to the mixing section housing 16 via a first radial support mechanism 58 that may act between the axially protruding section 72 of the first mixture portion 20 and the mixing section housing 16 in its downstream end region 56, while a second radial support mechanism 66 acting between the second mixture portion 34 and the mixing section housing 16 may be provided, for example, in the upstream end region 54 of the mixture 18.

[0066] Regardless of the positioning location and configuration of the different radial support mechanisms, the radial support mechanisms not only ensure the function of compensating for different dimensional changes and error compensation, but also, especially when formed as a molded part, contribute to vibration damping in the radial direction as well as in the axial or circumferential direction due to friction arising with respect to each of the other components. At the same time, the molded part acts as a centering aid when assembling the mixture 18 into the mixing section housing 16. During the operation of such a mixing section 12, the mixture 18 is in contact with the mixing section housing 16 only through different radial support mechanisms 58,66, and at the same time, heat outflow through the mixing section housing 16 is minimized.

Claims

1. A mixing section for the exhaust gas system of an internal combustion engine, - A mixing section housing (16) through which exhaust gas (A) can flow in the main exhaust gas flow direction (H), - A tubular mixing body (18) is disposed within the mixing section housing (16) and extends in the direction of the 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 with respect to the radially outward direction and a second flow volume (26) through which exhaust gas (A) can flow with respect to the radially inward direction, and the mixing body (18) is a tubular mixing body that extends in the direction of the longitudinal axis (L) of the mixing body The mixture (18) comprises a first mixture portion (20), the outer surface (32) of the first mixture portion (20) facing the second flow volume (26), and at least one tubular second mixture portion (34) extending in the direction of the longitudinal axis (L) of the mixture, the second mixture portion (34) being radially supported by the first mixture portion (20) in a plurality of mixture portion support regions (37), In a mixed section comprising, A mixed section characterized in that the mixed body (18) is radially supported with respect to the mixed section housing (16) via a plurality of first radial support mechanisms (58) in a first radial support region (50), and is radially supported with respect to the mixed section housing (16) via a plurality of second radial support mechanisms (66) in a second radial support region (52) which is spaced apart from the first radial support region (50) in the direction of the longitudinal axis (L) of the mixed body, the first mixed body portion (20) is radially supported by the mixed section housing (16) by the first radial support mechanism (58), and the second mixed body portion (34) is radially supported by the mixed section housing (16) by the second radial support mechanism (66).

2. The mixing section according to claim 1, characterized in that the first mixing portion (20) is held immovably in the mixing section housing (16) against movement in the direction of the longitudinal axis (L) of the mixing portion and / or movement in the circumferential direction about the longitudinal axis (L) of the mixing portion by the first radial support mechanism (58), and the second mixing portion (34) is supported radially in the mixing section housing (16) so as to be movable in the direction of the longitudinal axis (L) of the mixing portion and / or in the circumferential direction about the longitudinal axis (L) of the mixing portion by the second radial support mechanism (66).

3. The mixing section according to claim 1 or 2, characterized in that a plurality of first radial support mechanisms (58) are provided in the circumferential direction around the longitudinal axis (L) of the mixture, with a circumferential distance between them, and / or a plurality of second radial support mechanisms (66) are provided in the circumferential direction around the longitudinal axis (L) of the mixture, with a circumferential distance between them.

4. A mixing section according to any one of claims 1 to 3, characterized in that at least some of the second radial support mechanisms (66), preferably all of the second radial support mechanisms (66), comprises a support molding portion (70) of the second mixing portion (34) facing away from the first mixing portion (20), and / or a support molding portion of the mixing section housing (16) facing towards the second mixing portion (34).

5. The mixing section according to claim 4, characterized in that the support molding portion (70) of the second mixing portion (34) is supported on the inner surface of the mixing section housing (16) so as to be movable in the direction of the longitudinal axis (L) of the mixing portion and / or in the circumferential direction about the longitudinal axis (L) of the mixing portion, and / or the support molding portion of the mixing section housing (16) is supported on the outer surface of the second mixing portion (34) so ​​as to be movable in the direction of the longitudinal axis (L) of the mixing portion and / or in the circumferential direction about the longitudinal axis (L) of the mixing portion.

6. A mixed section according to any one of claims 1 to 5, characterized in that at least some of the first radial support mechanisms (58), preferably all of the first radial support mechanisms (58), comprises a support element (60) fixed to the mixed section housing (16) and the first mixed section (20), preferably by material connection.

7. A mixed section according to any one of claims 1 to 6, characterized in that at least some of the first radial support mechanisms (58), preferably all of the first radial support mechanisms (58), are oriented toward the first mixed portion (20) toward the mixed section housing (16), and the mixed section housing (16) is provided with a support molded portion (62) or / and the mixed section housing (16) is oriented toward the first mixed portion (20), and the first mixed portion (20) is provided with a support molded portion (64) preferably

8. The mixing section according to any one of claims 1 to 7, characterized in that the first radial support region (50) is provided in the upstream end region (54) of the mixture (18), preferably upstream of the second mixture portion (34) with respect to the main exhaust gas flow direction (H), and / or the second radial support region (52) is provided in the downstream end region (56) of the mixture (18).

9. The mixing section according to any one of claims 1 to 8, characterized in that at least some of the second radial support mechanisms (66), preferably all of the second radial support mechanisms (66), overlap in the axial direction with a portion of the mixing section support area (37).

10. The mixed section according to any one of claims 1 to 9, characterized in that the second mixed portion (34) has a plurality of first molded portions (36) facing toward the first mixed portion (20), which are arranged adjacent to each other in the direction of the longitudinal axis (L) of the mixed portion and in the circumferential direction centered on the longitudinal axis (L) of the mixed portion, and at least one of the first molded portions (36), preferably each first molded portion (36), forms a mixed portion support region (37).

11. The mixing section according to claim 10, characterized in that the first molding section (36) is arranged in a plurality of rows of the first molding section (36) that are continuously arranged in the circumferential direction around the longitudinal axis (L) of the mixture, preferably substantially extending in the direction of the longitudinal axis (L) of the mixture, and / or, the first molding section (36) is arranged in a plurality of rings of the first molding section (36) that are continuously arranged in the direction of the longitudinal axis (L) of the mixture, preferably substantially extending in the circumferential direction around the longitudinal axis (L) of the mixture.

12. The mixing section according to claim 10 or 11, characterized in that at least a portion of the first molded portion (36), preferably each first molded portion (36) is formed as a closed molded portion, and / or, at least a portion of the first molded portion (36), preferably each first molded portion (36) is formed comprising a molded portion periphery wall (38) and a molded portion bottom (40) that is in contact with the first mixed portion (20), preferably substantially planar or curved to substantially conform to the curvature of the first mixed portion (20), and / or, at least a portion of the first molded portion (36), preferably each first molded portion (36) is formed in a circular shape.

13. The mixing section according to any one of claims 1 to 12, characterized in that the second mixing portion has a plurality of second molded portions (46) that are arranged adjacent to each other in the direction of the longitudinal axis (L) of the mixing and in the circumferential direction centered on the longitudinal axis (L) of the mixing, and that are oriented away from the first mixing portion (20).

14. The mixing section according to claim 13, wherein at least one opening (48) is provided in the second mixed portion (34) adjacent to at least a portion of the second molded portion (46), preferably adjacent to each second molded portion (46), and preferably, in each pair of second molded portions (46) and openings (48) assigned to each other, the second molded portion (46) and the openings (48) partially overlap each other.

15. The mixing section according to claim 14, characterized in that in one portion of the pair consisting of a second molded portion (46) and an opening (48) assigned to each other, the opening (48) is located on the first side, preferably the first axial side, of the assigned second molded portion (46), and in the other portion of the pair consisting of a second molded portion (46) and an opening (48) assigned to each other, the opening (48) is located on the second side, preferably the second axial side, of the assigned second molded portion (46) substantially opposite to the first side.

16. The mixing section according to any one of claims 13 to 15, characterized in that the second molding section (46) is arranged in a plurality of rows that are continuously arranged in the circumferential direction about the longitudinal axis (L) of the mixture, preferably substantially extending in the direction of the longitudinal axis (L) of the mixture, and / or, the second molding section (46) is arranged in a plurality of rings that are continuously arranged in the direction of the longitudinal axis (L) of the mixture, preferably substantially extending in the circumferential direction about the longitudinal axis (L) of the mixture.

17. The mixing section according to any one of claims 1 to 16, characterized in that a reactant delivery assembly (28) for delivering the reactant (R) substantially only into the first flow volume (24) is located upstream of the mixture (18) in the main exhaust gas flow direction (H).

18. The mixed section according to any one of claims 1 to 17, characterized in that the second mixed portion (34) is fixed to the first mixed portion (20) preferably by material connection in at least a portion of the mixed portion support area (37), preferably in the entirety of the mixed portion support area (37).

19. An exhaust gas system for an internal combustion engine, comprising a mixing section (12) according to any one of claims 1 to 18, and an exhaust gas treatment unit (14), preferably an SCR catalyst, located downstream of the mixing section (12).

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