Catalyst assembly with injection section

Abstract

Injection section of an exhaust system for an internal combustion engine, - with a channel (13) for guiding an exhaust gas flow (3), - with an injector connection (14) arranged laterally on the channel (13), to which an injector (15) can be connected for introducing a liquid or a gas into the exhaust gas flow (3), - with an injection chamber (16) formed in the channel (13) in the area of ​​the injector connection (14), which is bounded on the one hand by a perforated first partition (17) arranged upstream of the injector connection (14) in the channel (13) with respect to the exhaust gas flow (3) and through which the exhaust gas flow (3) can flow, and on the other hand by a perforated second partition (18) arranged downstream of the injector connection (14) in the channel (13) with respect to the exhaust gas flow (3) and through which the exhaust gas flow (3) can flow, characterized in that - that a perforation of the first partition (17) is designed such that, when flowing through the first partition (17) within the injection chamber (16), it generates at least two exhaust gas partial flows (20, 21) which form two opposing flow vortices (22, 23), - that the two exhaust gas partial flows (20, 21) flow separately proximal to a channel wall (24) which laterally limits the injection chamber (16) and flow together distally to the channel wall (24).

Description

[0001] The present invention relates to an injection section of an exhaust system for an internal combustion engine. The invention also relates to a catalyst system for an exhaust system of an internal combustion engine equipped with such an injection section.

[0002] From WO 2010 / 146285 A1, a catalyst arrangement is known which comprises a tubular housing for guiding an exhaust gas flow and contains an SCR catalyst in an outlet section, where SCR stands for Selective Catalytic Reduction. The housing also has an inlet section, which is arranged upstream of the outlet section with respect to the exhaust gas flow and which contains an oxidation catalyst. An injection section is arranged axially between the inlet section and the outlet section, wherein a further housing section, integrally formed on the inlet section, defines a channel of the injection section, which also serves to guide the exhaust gas flow. An injector connection is arranged laterally on the channel in the injection section, to which an injector for laterally injecting or jetting a liquid or gas into the exhaust gas flow is connected.This results in a lateral injection of the liquid, i.e., an injection in which a main injection direction is inclined relative to an axial direction of the channel, preferably in an angular range of 60° to 120°, particularly in an angular range of 85° to 95°, and expediently by about 90°. In the channel of the injection chamber, an injection chamber is formed in the region of the injector connection. This chamber is bounded on the one hand by a perforated first partition wall arranged upstream of the injector connection with respect to the exhaust gas flow, and through which the exhaust gas flow can flow. On the other hand, it is bounded by a perforated second partition wall arranged downstream of the injection connection with respect to the exhaust gas flow. In the known catalyst arrangement, the two partition walls, in conjunction with their perforations, are designed as follows:The design ensures that during operation of the exhaust system, a swirl, vortex, or rotational flow is created in the injection chamber, in which the entire exhaust gas flow rotates around the longitudinal center axis of the channel. This results in a flow path in the injection chamber, which the exhaust gas flow follows from the first partition to the second partition, being at least 20% longer than the axial distance between the inlet and outlet sections. This creates a mixing zone in which the injected liquid can vaporize and mix with the exhaust gas flow.

[0003] In an SCR system, the injected liquid is a reducing agent. Currently, an aqueous urea solution is preferred, which is ultimately converted to ammonia and carbon dioxide via thermolysis and hydrolysis to convert nitrogen oxides deposited in the SCR catalyst into nitrogen and water. Crucial for the efficiency of such an SCR system is, on the one hand, the most complete possible vaporization of the reducing agent introduced in liquid form. On the other hand, the most intensive possible mixing of the vaporized reducing agent with the exhaust gas stream must also be achieved.

[0004] Alternatively, modern SCR systems can also inject a gaseous reducing agent, such as gaseous ammonia. In this case, the ammonia can be stored in the form of solid particles, which are vaporized using heat, for example, electrically supplied, to generate the gaseous ammonia. With these so-called Amminex systems, the ammonia is therefore immediately available in the exhaust gas stream, so that only thorough mixing with the exhaust gas stream is required, since the vaporization takes place beforehand, outside the exhaust gas stream.

[0005] The present invention addresses the problem of providing an improved embodiment for an injection section of the aforementioned type or for a catalyst arrangement equipped therewith, as well as for a method for introducing a liquid into an exhaust gas flow, which is characterized in particular by an efficient evaporation effect and mixing of the injected liquid with the exhaust gas flow.

[0006] This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0007] The invention is based on the general concept of generating two counter-rotating flow vortices in the injection chamber, each formed by a partial exhaust gas stream. The two flow vortices are generated in the injection chamber such that the two exhaust gas streams flow separately proximal to a channel wall that laterally delimits the injection chamber, and together distal to the channel wall. The liquid or gas is injected laterally into this system of counter-rotating flow vortices, resulting in intensive mixing between the reducing agent and the exhaust gas. In the case of a liquid reducing agent, this also leads to efficient vaporization of the liquid. The flow vortices create targeted turbulence within the injection chamber, which improves the mixing between the introduced reducing agent and the exhaust gas flow.On the other hand, the flow vortices lengthen an exhaust gas path that the exhaust gas flow follows within the injection chamber. This increases the residence time of the exhaust gas flow, thus providing more time for the injected liquid or gas to evaporate and / or mix.

[0008] Specifically, for the injection section according to the invention, it is proposed to design a perforation of the first partition wall in such a way that, when flowing through the first partition wall within the injection chamber, it generates at least the two aforementioned exhaust gas partial flows, which form two separate and counter-rotating flow vortices, such that the two partial flows flow separately along the channel wall, i.e., along separate channel wall sections, while distal to the channel wall, i.e., in a central region of the injection chamber, they flow together or combined.

[0009] The generation of such a vortex system is supported by a substantially cylindrical shape for the channel, resulting in a curved channel wall in the circumferential direction. The exhaust gas partial flows thus converge proximal to the channel wall along its surface until they meet in a stagnation zone and are deflected into the interior of the injection chamber, where they then flow together distal to the channel wall. Furthermore, the flow vortices preferentially rotate around separate vortex axes that run parallel to the longitudinal center axis of the channel.

[0010] A preferred embodiment is one in which the perforation of the first partition is designed symmetrically to a longitudinal median plane of the channel, so that when fluid flows through the first partition, the two flow vortices can form symmetrically to said longitudinal median plane. A symmetrical vortex system allows for a symmetrical injection jet, which can be produced particularly easily with the aid of a suitable injector.

[0011] The injector connection is advantageously arranged in this longitudinal center plane according to a further development. In the assembled state, one of the main injection directions of the injector then lies in the longitudinal center plane. Such a symmetrical arrangement improves the efficiency of evaporation and / or mixing.

[0012] In another embodiment, the two exhaust gas partial flows can flow away from the injector connection proximal to the channel wall, while distal to the channel wall they flow together towards the injector connection. This means that the combined exhaust gas partial flows in the center of the injection chamber flow against the injection jet, which significantly improves mixing and, if applicable, vaporization.

[0013] In another embodiment, the perforation of the first partition wall for generating the flow vortices can have first openings that are arranged proximally to the channel wall and that each have an outlet surface facing away from the injector connection in the injection chamber. Thus, the separate exhaust gas partial flows exit the first openings in a direction away from the injector connection, thereby already determining the flow direction for inducing the flow vortices.

[0014] According to a further development, the exit surfaces can be formed by integral wall sections of the first partition wall that project from the rest of the first partition wall into the injection chamber. This shields the exit surfaces from an injection jet, preventing the injection jet from escaping the injection chamber through the first openings.

[0015] In another further development, the first openings on the upstream side of the first partition, facing away from the injection chamber, can each have an inlet surface facing the injector connection. This ensures that the exhaust gas partial flows can only enter the respective first opening through the inlet surface in a direction away from the injector connection, thus defining a preferred flow direction required for vortex formation.

[0016] Advantageously, the inlet surfaces can be formed by integral wall sections of the first partition wall, which project from the rest of the first partition wall on the upstream side. The wall sections at the inlet and outlet surfaces can channel the exhaust gas partial flows passing through them, thus promoting vortex formation. Furthermore, integral wall sections can be particularly easily fabricated from a sheet metal body, preferably a flat one, thereby simultaneously forming the desired first openings.

[0017] The first openings of the perforation in the first partition are advantageously located proximal to the channel wall within the first partition. They are advantageously spaced apart from one another in the circumferential direction. Furthermore, the perforation of the first partition can have several second openings located distal to the channel wall. These second openings can also have outlet surfaces facing away from the injector connection and inlet surfaces facing the injector connection. These inlet surfaces can be associated with wall sections integrally formed on the first partition, some of which project into the injection chamber, while others project away from the first partition on the upstream side.

[0018] Furthermore, in another embodiment, the second partition wall may have perforations with openings that are shielded by guide surfaces projecting into the injection chamber. These shielded openings prevent direct flow through the second partition wall, as additional flow deflections are required, each contributing to the mixing of the vaporized liquid or the gas and exhaust gas flow.

[0019] According to a further development, the perforation openings of the second partition wall can have first openings that are arranged proximally to the channel wall, are elongated, extend essentially in the circumferential direction, and are shielded radially inwards by the respective guide surface. This ensures that the flow vortices flowing proximally to the channel wall cannot pass directly through the first openings.

[0020] In another refinement, the perforation openings of the second partition wall can have secondary openings located distal to the channel wall and shielded from the injector connection by the respective guide surface. Furthermore, these secondary openings are preferably also elongated, but extending parallel to each other. By shielding the secondary openings towards the injector connection, the combined flow of the two vortices, flowing distal to the channel wall, can pass through these secondary openings particularly easily. This is desirable at the end of the vortex movement and reduces the overall flow resistance of the injection section.

[0021] The shielding of the perforated openings in the second partition also prevents the injection jet from passing directly through the second partition. This promotes turbulence and mixing. The guide surfaces can also serve as impact surfaces against which the injected liquid can strike, thus aiding its evaporation.

[0022] According to another advantageous embodiment, the first partition wall can extend essentially perpendicular to a longitudinal central axis of the channel. This results in a comparatively compact injection section in the axial direction.

[0023] In another embodiment, the second partition can be inclined relative to the first partition such that the injection chamber tapers with increasing distance from the injector connection. In contrast, the injection jet widens with increasing distance from the injector connection, particularly in a conical shape, resulting in intensive mixing and, if applicable, improved vaporization.

[0024] According to a particularly advantageous embodiment, a perforated third partition, through which the exhaust gas flow can pass, can optionally be provided, which is arranged downstream of the second partition with respect to the exhaust gas flow. This additional third partition can be used, on the one hand, to reduce the risk of unvaporized liquid escaping from the injection section. On the other hand, with appropriate perforation design of the third partition, flow stabilization and homogenization can be achieved, which, particularly within a catalyst assembly, leads to improved flow to a potentially downstream catalyst. For example, the third partition can be formed by a simple perforated sheet in which a large number of relatively small openings are provided, uniformly distributed over the entire surface of the third partition.In particular, the third partition wall does not have any guide surfaces or similar features at the perforation openings. Alternatively, the third partition wall can be equipped with guide surfaces to direct the flow through its perforations. Advantageously, the third partition wall extends in a plane perpendicular to the longitudinal center axis of the channel. The openings for the passages are also located in this plane.

[0025] A catalyst arrangement according to the invention comprises a tubular housing for guiding an exhaust gas flow, which contains an SCR catalyst in an outlet section. Furthermore, the catalyst arrangement is equipped with an injection section of the type described above, which connects upstream to the outlet section with respect to the exhaust gas flow. The injection section forms a completely pre-assembled, separate unit that can be attached to or installed in the housing of the catalyst arrangement. For example, the channel of the injection section can be inserted into a designated housing section of the housing, such that the housing and channel overlap axially and are radially adjacent.

[0026] A preferred embodiment, however, is one in which the channel of the injection section itself forms a section of the housing of the catalyst assembly. In this case, the channel and the outlet section connect axially to each other.

[0027] In another embodiment, the housing can have an inlet section that connects upstream of the injection section with respect to the outlet section and that contains an oxidation catalyst. A preferred design is also one in which the common housing of the catalyst assembly has at least three housing sections that connect axially to one another, namely the inlet section, the outlet section, and the housing section formed by the channel of the injection section located between them.

[0028] Another conceivable embodiment is one in which the channel of the injection section has a different, preferably larger, flowable cross-section than the outlet section and / or the inlet section of the housing. This allows for the creation of vortices with particularly large diameters, which promotes intensive mixing.

[0029] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0030] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0031] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0032] They show, schematically, Fig. 1 an isometric view of a catalyst arrangement with transparent components, Fig. 2 an isometric view of an injection section of the catalyst assembly, but showing only partitions of the injection section, Fig. 3 a side view of the injection section, showing only the partitions and an injector connection, Fig. 4 An axial view of a first partition wall of the injection section with flow arrows.

[0033] Accordingly Fig. 1 comprises a catalyst arrangement 1, which is intended for use in an exhaust system of an internal combustion engine, preferably of a motor vehicle, a tubular, preferably cylindrical housing 2, which is designed to guide a Fig. The housing 2 serves the exhaust gas flow 3 indicated by arrows. The housing 2 has an inlet section 4, an outlet section 5, and a central housing section 6, which is arranged axially between the inlet section 4 and the outlet section 5 with respect to a longitudinal center axis 7 of the housing 2. The inlet section 4 is fluidically connected to a housing inlet 8 and contains, for example, an oxidation catalyst 9. The inlet section 4 could also contain a mixer, for example, to mix additionally injected or sprayed hydrocarbons with the exhaust gas flow 3. The outlet section 5 is fluidically connected to a housing outlet 10 and contains an SCR catalyst 11.In the middle housing section 6 an injection section 12 is formed, with the aid of which a liquid reducing agent, preferably an aqueous urea solution, or a gaseous reducing agent, preferably ammonia gas, can be introduced into the housing 2 upstream of the SCR catalyst 11 and downstream of the oxidation catalyst 9.

[0034] According to the Fig. In sections 1 to 4, such an injection section 12 comprises a channel 13 for guiding the exhaust gas flow 3. The channel 13 is designed here as a cylindrical pipe section, which simultaneously forms the central housing section 6 of the housing 2 of the catalyst assembly 1. The injection section 12 further comprises an injector connection 14 arranged laterally on the channel 13, to which an injector is connected. Fig. 1 and Fig. Injector 15, indicated by a broken line, is connected to in order to inject the respective liquid into the exhaust gas flow 3.

[0035] The channel 13 contains an injection chamber 16 in the region of the injector connection 14, into which the injector 15 injects the reducing agent during operation. The injection chamber 16 is bounded upstream of the injector connection 14 by a first partition 17 and downstream of the injector connection 14 by a second partition 18, relative to the exhaust gas flow 3. In the preferred embodiment shown here, a third partition 19 is also provided, purely optionally, which is arranged downstream of the second partition 18 in the channel 13. The partitions 17, 18, 19 are separate components, each expediently designed as a sheet metal forming. The partitions 17, 18, 19 each extend over the entire cross-section of the channel 13; they are perforated and thus allow the exhaust gas flow 3 to pass through them.

[0036] An unspecified perforation of the first partition wall 17 is designed such that, when flow passes through the first partition wall 17, it generates at least two exhaust gas partial flows 20, 21, which in Fig. 4 are indicated by arrows. These exhaust gas partial flows 20, 21 are generated such that they form two separate and counter-rotating flow vortices 22 and 23, respectively, in the injection chamber 16. In a region 25 proximal to a channel wall 24, the two exhaust gas partial flows 20, 21 flow separately through the flow vortices 22, 23, while in a region 26 distal to the channel wall 24 they flow largely together. The channel wall 24 laterally delimits the injection chamber 16, extends circumferentially, and thus forms the channel 13. The two flow vortices 22, 23 rotate about separate vortex axes 42, 43, which run parallel to each other.

[0037] The perforation of the first partition 17 is symmetrical, in particular mirror-symmetrical, with respect to a longitudinal median plane 27 of the channel 13. The longitudinal median plane 27 contains a longitudinal median axis 28 of the channel 13, which coincides with the longitudinal median axis 7 of the housing 2 within the catalyst assembly 1. Due to the symmetry of the perforation of the first partition 17, the two flow vortices 22, 23 are also formed symmetrically with respect to the longitudinal median plane 27. Preferably, the vortex axes 42, 43 extend parallel to the longitudinal median axis 28 of the channel 13. The first partition 17 is preferably arranged in the channel 13 such that the injector connection 14 is located in the longitudinal median plane 27, i.e., in the plane of symmetry of the first partition 17. For illustration, see in Fig. 4 The position of the injector connection 14 is indicated by a dashed line. Preferably, there is a Fig. Figure 3 indicates the main injection direction 29 of an injection jet 30 of the injector 15 in the longitudinal center plane 27. The injection jet 30 is designed here in a conical shape, so that it can also be referred to as an injection cone. It is clear that any other geometries are also possible for the injection jet 30.

[0038] Furthermore, the symmetrical first partition 17 in the channel 13 is positioned such that the two exhaust gas partial flows 20, 21 flow away from the injector connection 14 proximal to the channel wall 24, i.e. in the proximal areas 25, while in distal areas 26 they flow together towards the injector connection 14.

[0039] How in particular the Fig. The perforation of the first partition 17, which can be extracted from the first partition 17, has openings 31 for generating the flow vortices 22, 23. These openings are arranged proximally to the channel wall 24 and each has an outlet surface 32 facing away from the injector connection 14 in the injection chamber 16, i.e., on an outflow side of the first partition 17. The outlet surfaces 32 are formed by means of wall sections 33 integrally formed on the first partition 17, which project from the rest of the first partition 17 into the injection chamber 16. Furthermore, these first openings 31 each have an inlet surface 34 facing the injector connection 14 on an upstream side of the first partition 17 facing away from the injection chamber 16. These can advantageously be formed by means of wall sections 35, which are also integrally formed on the first partition 17 and which project from the rest of the first partition 17 on the upstream side.

[0040] How to Fig. 2 and Fig. As can be seen from Figure 4, the perforation of the first partition 17 also has second openings 36, which likewise have inlet surfaces facing the injector connection 14 and outlet surfaces facing away from the injector connection 14. Here too, the inlet surfaces are located on the side facing away from the injection chamber 16, while the outlet surfaces are arranged within the injection chamber 16. While the first openings 31 extend proximal to the channel wall 13 in the circumferential direction, the second openings 36 are arranged distal to the channel wall 24 in a straight line, preferably in the longitudinal median plane 27.

[0041] How to Fig. 2 and Fig. 4 furthermore, the perforation of the first partition 17 can also have third openings 37 which lie in the plane of the first partition 17.

[0042] According to the Fig. 2 and Fig.3 can comprise the unspecified perforation of the second partition 18, comprising first and second openings 38 and 39, each shielded by guide surfaces 40. The guide surfaces 40 project into the injection chamber 16. The first openings 38 are arranged proximal to the channel wall 24. They are elongated and extend essentially circumferentially. They are shielded inwards by the guide surfaces 40. In contrast, the second openings 40 are arranged distal to the channel wall 24 and shielded by the guide surfaces 40 on a side facing the injector connection 14. The second openings 39 are also elongated, but straight and parallel to each other. The straight, elongated second openings 39 extend transversely to the longitudinal median plane 27. The second partition 18 is also designed symmetrically to the longitudinal median plane 27. However, it differs from the first partition 17.

[0043] The optional third partition 19 contains only one type of opening 41, each lying in the plane of the third partition 19 and defining a uniform perforation in the example shown. The third partition 19 is expediently a simple perforated sheet. The third partition 19 is thus designed differently from the first partition 17 and the second partition 18. Here, too, it is conceivable to provide a non-uniform perforation, i.e., a perforation with various openings with and / or without covers and / or guide surfaces.

[0044] The three partition walls 17, 18, 19 are each basically configured as flat, whereby integral sections of the respective partition wall 17, 18 can be reshaped and flared in the first partition wall 17 and in the second partition wall 18 to form the individual openings or the flow guide contours.

[0045] The first partition 17 extends essentially perpendicular to the longitudinal center axis 28 of the channel 13. The third partition 19 also extends expediently transversely to the longitudinal center axis 28 and thus parallel to the first partition 17. In contrast, the second partition 18 is inclined relative to the first partition 17 and thus also relative to the third partition 19. The inclination of the first partition 17 to the second partition 18 is such that the injection chamber 17 tapers with increasing distance from the injector connection 14.

Claims

[1] Injection section of an exhaust system for an internal combustion engine, - with a channel (13) for guiding an exhaust gas flow (3), - with an injector connection (14) arranged laterally on the channel (13), to which an injector (15) can be connected for introducing a liquid or a gas into the exhaust gas flow (3), - with an injection chamber (16) formed in the channel (13) in the area of ​​the injector connection (14), which is bounded on the one hand by a perforated first partition (17) arranged upstream of the injector connection (14) in the channel (13) with respect to the exhaust gas flow (3) and through which the exhaust gas flow (3) can flow, and on the other hand by a perforated second partition (18) arranged downstream of the injector connection (14) in the channel (13) with respect to the exhaust gas flow (3) and through which the exhaust gas flow (3) can flow, characterized by , - that a perforation of the first partition (17) is designed such that, when flowing through the first partition (17) within the injection chamber (16), it generates at least two exhaust gas partial flows (20, 21) which form two opposing flow vortices (22, 23), - that the two exhaust gas partial flows (20, 21) flow separately proximal to a channel wall (24) which laterally limits the injection chamber (16) and flow together distally to the channel wall (24). [2] Injection section according to claim 1, characterized by , that the perforation of the first partition (17) is designed symmetrically to a longitudinal median plane (27) of the channel (13), so that when flow passes through the first partition (17) the two flow vortices (22, 23) are formed symmetrically to the longitudinal median plane (27). [3] Injection section according to claim 2, characterized by , that the injector connection (14) is arranged in this longitudinal median plane (27). [4] Injection section according to any one of claims 1 to 3, characterized by , that the two exhaust gas partial flows (20, 21) flow away from the injector connection (14) proximal to the channel wall (24) and flow together towards the injector connection (14) distal to the channel wall (24). [5] Injection section according to any one of claims 1 to 4, characterized by , that the perforation of the first partition wall (17) for generating the flow vortices (22, 23) has first openings (31) which are arranged proximal to the channel wall (24) and which each have an outlet surface (32) in the injection chamber (16) facing away from the injector connection (14). [6] Injection section according to claim 5, characterized by , that the exit surfaces (32) are formed by means of wall sections (33) of the first partition wall (17) which project from the rest of the first partition wall (17) into the injection chamber (16). [7] Injection section according to claim 5 or 6, characterized by, that the first openings (31) on an upstream side of the first partition (17) facing away from the injection chamber (16) each have an inlet surface (34) facing the injector connection (14). [8] Injection section according to any one of claims 1 to 7, characterized by , that a perforation of the second partition (18) has openings (38, 39) which are shielded by guide surfaces (40) which project into the injection chamber (16). [9] Injection section according to claim 8, characterized by , that the openings of the perforation of the second partition wall (18) have first openings (38) which are arranged proximal to the channel wall (24), which are elongated, which extend substantially in the circumferential direction and which are shielded radially inwards by the respective guide surface (40). [10] Injection section according to claim 8 or 9, characterized by, that the openings of the perforation of the second partition wall (18) have second openings (39) which are arranged distal to the channel wall (24) and which are shielded to the injector connection (14) with the respective guide surface (40). [11] Injection section according to any one of claims 1 to 10, characterized by , that the first partition wall (17) extends substantially perpendicular to a longitudinal central axis (28) of the channel (13). [12] Injection section according to any one of claims 1 to 11, characterized by , that the second partition (18) is inclined relative to the first partition (17) such that the injection chamber (16) tapers with increasing distance from the injector connection (14). [13] Injection section according to any one of claims 1 to 12, characterized by , that a perforated third partition (19) through which the exhaust gas flow (3) can flow is provided, which is arranged downstream of the second partition (18) with respect to the exhaust gas flow (3). [14] Catalyst arrangement for an exhaust system of an internal combustion engine, - with a tubular housing (2) for guiding an exhaust gas flow (3), which contains an SCR catalyst (11) in an outlet section (5), - with an injection section (12) according to one of claims 1 to 13, which is arranged upstream of the SCR catalyst (11) with respect to the exhaust gas flow (3). [15] Catalyst arrangement according to claim 14, characterized by , that the channel (13) of the injection section (12) forms a separate section (6) of the housing (2) of the catalyst assembly (1). [16] Catalyst arrangement according to claim 14 or 15, characterized by , that the housing (2) has an inlet section (4) which contains an oxidation catalyst (9) upstream of the injection section (12) with respect to the exhaust gas flow (3).

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