AT520786A1 - Mixing device for an exhaust aftertreatment device - Google Patents

Abstract

The invention relates to a mixing device (1) for an exhaust aftertreatment device of an internal combustion engine, comprising a hollow cylindrical mixing tube (2) with a constant free diameter (D), wherein within the mixing tube (2) two deflection elements (3, 4) are arranged extending at least in a z-direction over the entire free diameter (D) of the mixing tube (2) and are connected to an inner wall (8) of the mixing tube (2), wherein a first deflecting element (3) and a second deflecting element (4) in a x-direction (X) and a y-direction are arranged spaced from each other, wherein a profile of the deflecting elements (3, 4) along the free diameter (D) to form at least one edge (5) varies such that the at least one Edge (5) forms the deflecting elements (3, 4) kinked, wherein at least the first deflecting element (3) and the second deflecting element (4) with respect to the x-direction (X) oppositely kinked s ind. Furthermore, the invention relates to a use of such a mixing device (1) and an exhaust gas aftertreatment device with such a mixing device (1).

Description

Summary

The invention relates to a mixing device (1) for an exhaust gas aftertreatment device of an internal combustion engine, comprising a hollow cylindrical mixing tube (2) with a constant free diameter (D), two deflection elements (3, 4) being arranged within the mixing tube (2) extend at least in a z direction over the entire free diameter (D) of the mixing tube (2) and are connected to an inner wall (8) of the mixing tube (2), a first deflecting element (3) and a second deflecting element (4) are arranged at a distance from each other in an x-direction (X) and a y-direction, the course of the deflection elements (3, 4) along the free diameter (D) varying to form at least one edge (5) such that the at least one Edge (5) forms the deflection elements (3, 4) in a bent manner, at least the first deflection element (3) and the second deflection element (4) being bent in the opposite direction with respect to the x direction (X) ind.

The invention further relates to the use of such a mixing device (1) and an exhaust gas aftertreatment device with such a mixing device (1).

Fig. 2

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Mixing device for an exhaust gas aftertreatment device

The invention relates to a mixing device for a

Exhaust gas aftertreatment device of an internal combustion engine, in particular for an exhaust gas aftertreatment device for carrying out a selective catalytic reduction in an exhaust gas stream, comprising a hollow cylindrical mixing tube with a free diameter that at least in sections runs constantly, at least two deflection elements being arranged within the mixing tube, which are at least in a z-direction Extend over the entire free diameter of the mixing tube and are connected to an inner wall of the mixing tube, at least one first deflecting element and at least one second deflecting element in an x-direction normal to the z-direction, parallel to a main flow direction of the exhaust gas flow and one to the x -Direction and the z-direction normal direction are spaced from each other.

Furthermore, the invention relates to the use of such a mixing device.

The invention further relates to an exhaust gas aftertreatment device.

Mixing devices for an exhaust gas aftertreatment device are known from the prior art, these being generally designed to add a reducing agent to an exhaust gas stream and to produce a homogeneous mixture, so that harmful exhaust gases are at least partially reduced or converted in an exhaust gas aftertreatment element.

DE 100 60 808 A1 describes, for example, an exhaust gas purification system of an internal combustion engine for aftertreatment of exhaust gases by means of catalytic reduction of nitrogen oxides, in which a metering device for supplying an auxiliary or additive for aftertreatment of the exhaust gas is arranged downstream of an exhaust gas mixer. The mixing device has an orifice arrangement with a large number of guide vanes. It is disadvantageous here that relatively high flow losses occur.

Mixing devices are known from the prior art which partially avoid these flow losses. Such mixing devices, however, comprise complex deflection elements which are additionally designed

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Positions in a mixing tube must be arranged at a predetermined distance from each other.

Known mixing devices are consequently designed either with geometrically simple deflection elements, with which flow losses are associated, or with complex and complex to produce deflection elements.

The object of the invention is to overcome the disadvantages mentioned above. In particular, the object is to specify a mixing device which enables simple and efficient mixing of an exhaust gas with an additive and which at the same time is easy to manufacture.

It is also an aim to specify the use of such a mixing device.

Another goal is to provide an efficient exhaust gas aftertreatment device.

The object is achieved in that, in a mixing device of the type mentioned, a course of the deflection elements varies along the free diameter with the formation of at least one edge such that the at least one edge forms the deflection elements in a bent manner, at least the first deflection element and the second deflection element are bent in the opposite direction with respect to the x direction.

According to the invention, a z direction can be understood as a first direction, an x direction as a second direction and a y direction as a third direction.

In other words, the first deflecting element and the second deflecting element are therefore bent in an opposite second direction or x-direction.

By designing the mixing device with the deflection elements according to the invention, the exhaust gas flow can be deflected and subsequently swirled, so that when an additive is added to the exhaust gas flow, a rapid and almost complete mixing of the additive and the exhaust gas is made possible. The additive can be, for example, a reducing agent such as an aqueous urea solution, as is used in SCR catalysts. Furthermore, undesirable pressure changes are avoided by the solution according to the invention, which is why no back pressure is generated. In addition, through the

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The deflection elements extend from a first side of an inner wall to a side of an inner wall approximately opposite this or from a first inner wall to a second inner wall of the mixing tube, these being connected to the inner wall at both ends thereof. Exactly two deflection elements are particularly preferably provided. According to the invention, the mixing tube is hollow, the exhaust gas stream being guided within it and mixed with the additive. Although the mixing tube can have any cross-section, such as circular, it is advantageously designed with a square, in particular rectangular cross-section. The free diameter of the mixing tube has a constant length over an entire length of the mixing tube. If the mixing tube is designed with a rectangular or square cross section or base area, the free diameter means a side length of this cross section. If the hollow cylinder is designed with a rectangular base surface with different lengths of side length, a free side is to be understood as a first side length of the base surface in the z direction. The second side length then runs orthogonally to it in the y direction. Within the scope of the invention, side lengths are to be understood as the lengths of a cross section of the mixing tube. The side lengths form the inner walls of the mixing tube, the deflection elements being connected at least to a first and a second inner wall, the first and the second inner wall being opposite one another. The first and second inner walls are each connected to a third and fourth inner wall in such a way that a mixing tube with a rectangular cross section is formed.

The fact that a first deflecting element and a second deflecting element in a y direction are arranged at a distance from one another means in the context of the invention that a flow cross section of the exhaust gas stream flows through the deflecting elements (in the y direction) that extend radially into the mixing tube (in x Direction) can. The deflection elements are also arranged at a distance from one another in the x direction, that is to say one after the other downstream or upstream. In a longitudinal section (along the x-direction, orthogonal to the z-axis) through the

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Mixing tube, a flow area of the exhaust gas flow is thus reduced in the area of the deflection elements. It is advantageous if a first deflection element is arranged in a lower or first third (in the y direction) and a second deflection element in an upper or third third (in the y direction) of the mixing tube, so that a third of the mixing tube is in between , the third third, remains as the flow cross section for the exhaust gas flow. The lower or upper third does not restrict a geometrical arrangement of the same in the exhaust pipe or a design of the exhaust pipe.

According to the invention, the deflection elements can also be connected to a further inner wall of the mixing tube, which are each arranged orthogonally to the two sides of the inner wall mentioned above. In a cross section through the mixing tube (orthogonal to the x-axis), the deflection elements are each connected to a further side of the inner wall thereof. For example, a first deflection element can be connected to a first and a second and a third inner wall of the mixing tube and a second deflection element can be connected to a first and a second and a fourth inner wall of the mixing tube. Consequently, the deflection elements each protrude from the third or fourth inner wall of the mixing tube, the width of this inner wall being oriented in the z direction, and extend in the y direction towards a center of the mixing tube. However, the deflection elements are not connected to one another in the y direction, but are arranged at a distance from one another. The less they reach into the mixing tube in the y direction, i.e. the shorter their height in the y direction, the lower the pressure loss in the mixing tube. However, it should be noted that deflection elements in the y direction should be dimensioned sufficiently to achieve a sufficiently large deflection of the exhaust gas flow. This compromise can be achieved if the deflection elements each occupy a range of approximately 1/4 to 1/3 of the second side length of the base of the mixing tube.

The fact that a course of the deflection elements varies along the free diameter with the formation of at least one edge is to be understood within the scope of the invention that the deflection elements each include (indirectly or directly) an angle different from 90 ° with the inner wall of the mixing tube. Since the deflection elements each form an edge, the included angles between a first and a second inner wall opposite this are either both greater than 0 ° and less than 90 ° or both greater than 90 ° and

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It is provided according to the invention that the kink of the first or second deflecting element which arises as a result is arranged in the flow direction and the kink of the second or first deflecting element is arranged counter to the flow direction. The deflection elements are consequently each formed with a curvature or kinked. It is advantageous if the deflection elements are free of arcuate sections, ie - apart from the edge - are formed exclusively by straight lines.

In one embodiment variant of the invention, the first deflecting element is concave and the second deflecting element is convexly buckled against a flow direction of the exhaust gas flow, the second deflecting element being arranged downstream of the first deflecting element. This means that the exhaust gas flow hits the concave side of a first deflection element first, and this hits the convex side of the second deflection element downstream of the first deflection element. As a result, the exhaust gas flow is deflected satisfactorily in order to mix efficiently with an additive.

In an alternative embodiment, it is advantageously provided that the first deflection element is concave and the second deflection element is convexly buckled against a flow direction of the exhaust gas flow, the second deflection element being arranged upstream of the first deflection element. In this variant, too, the parameters that are important for a mixed assessment, such as ratios of the kinetic energies, a gradient of these ratios and a pressure loss, are optimized in comparison with the prior art. In comparison to the variant described above, an arrangement of the deflection elements is therefore reversed in the x direction or flow direction. The exhaust gas flow hits the convex side of the second deflection element first and the concave side of the first deflection element downstream of the second deflection element.

A concave kink is understood here to mean that the kink is designed in the flow direction of the exhaust gas stream. In the case of a convex kink, the kink is oriented counter to the direction of flow.

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The deflection elements are each designed with a curvature or curvature, in particular free of arcuate elements, the curvature being designed or aligned either in the flow direction or counter to the flow direction of the exhaust gas flow. The shape of the deflection elements therefore deviates from a straight line in a sectional view. It can always be favorable for the deflection of the exhaust gas flow if the deflection elements in each case directly adjoin one another in an x direction, these being spaced apart from one another in the y direction and z direction.

In any case, it is expedient if a thickness of the deflection elements is essentially constant. This ensures simple manufacture and manufacture of the same. Within the scope of the invention, a thickness of the deflection elements is to be understood as the smallest length or height thereof, that is to say the constant extension of the deflection elements in the x direction. It is particularly advantageous if the length of the other two dimensions is also constant and has no tapering or widening regions. The deflection elements are in particular designed as thin-walled baffles, which can be integrally connected to the inner wall of the mixing tube. For example, they are welded to the inner walls. Alternatively, a non-positive connection can also be provided between the deflection elements and the mixing tube. For this purpose, the deflection elements can be inserted from the outside through corresponding openings in the mixing tube.

According to an embodiment variant of the invention, it is provided that exactly two deflection elements of essentially identical construction are provided, these being arranged in the mixing tube rotated relative to one another by approximately 180 ° in the y direction. Consequently, only one type of deflection element has to be produced when manufacturing the deflection elements. These are then only arranged in the opposite direction and / or at another location in the mixing tube. According to the two variants described above, an order of arrangement is changed to implement the same. Basically, according to the invention, more than two deflection elements can also be provided, all of which are of identical construction and are arranged differently in the mixing tube.

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It is advantageous if the deflection elements each have at least two partial areas, a first partial area each from a first inner wall of the mixing tube with a constant slope Δχ / Δζ to in particular approximately a center of the mixing tube and a second partial area in particular with the same slope of in particular approximately the middle of the mixing tube runs to a second inner wall of the mixing tube which is approximately opposite the first inner wall. The subareas are in particular all rectilinear. A center of the mixing tube is essentially to be understood here as a central plane which is spanned by the second or x direction and third or y direction. This design enables an optimal flow deflection of the exhaust gas flowing through the mixing tube. An optimal geometry of the mixing device is achieved, through which the exhaust gas flow is swirled sufficiently to mix efficiently with the additive. At the same time, the geometry according to the invention allows flow losses to be kept as low as possible. The first and second sections can each be connected indirectly or directly to an inner wall of the mixing tube. Transitions between the partial areas are preferably carried out in leaps and bounds, which allows the same to be produced easily. Both sections are formed in particular by straight lines.

It is particularly preferred in the manufacture and for the stable arrangement of the deflection elements if they each have five subregions. A short partial area is provided between the respective inner wall of the mixing tube and the first partial area or the second partial area. The two short partial areas per deflection element have a shorter length than the first and second partial areas and enclose an angle of preferably approximately 90 ° with the respective inner wall. This means that the short sections run in the z direction. Furthermore, a connecting partial area is provided between the first and second partial area, approximately in the middle of the mixing tube, which connects the first to the second partial area. The connecting sub-area is also shorter than the first and the second sub-area, which has approximately the same length as the short sub-areas and also runs in the z-direction, but parallel to the short sub-areas in the x-direction. This geometry further improves the advantages mentioned above. These advantages occur equally in the two arrangements of the deflection elements mentioned. In the formation of the deflection elements with three or

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AVL List GmbH more sub-areas, these are advantageously arranged in the mixing tube in such a way that the x-axis running through the geometric center of the mixing tube is designed as a plane of symmetry. This means that the deflection elements are mirrored in the z-direction around the x-axis. In principle, however, it can also be provided that the partial areas, in particular the first and second partial areas, have a different length or slope. There is no longer any such symmetry. It is advantageous if there is a sudden transition between the respective sub-areas, with inclusive angles between the sub-areas being predetermined. The deflection elements are advantageously made in one piece and exclusively with straight-line sections. However, it can also be favorable if at least in particular only the short partial areas and the connecting partial area are rounded or designed with a curvature.

It is expedient in all embodiment variants if at least one metering device is provided for feeding an additive into the exhaust gas stream, the at least one metering device being arranged in particular in a flow direction of the exhaust gas stream downstream of the deflection elements. In principle, it is possible to arrange the metering device upstream of the deflection elements or between them, but optimal mixing of the exhaust gas with the additive seems to be achievable with a downstream arrangement of the metering device with respect to the deflection elements. It is expedient if the at least one metering device is arranged in a position with z = 0, that is to say in the plane of symmetry mentioned above, in order to achieve an optimal supply of the additive to the exhaust gas flow and subsequently a satisfactory mixing of the two. It is particularly expedient if two, three, four or more metering devices are provided, which are arranged along the x-axis or a longitudinal axis of the mixing tube, in particular at equidistant distances from one another. It is advantageous if the at least one metering device supplies the additive to the exhaust gas flow in or with a flow direction of the exhaust gas. The exhaust gas stream is advantageously already swirled at the point at which the additive is supplied, so that the additive is mixed as directly as possible. In the context of the invention, it was determined by corresponding simulations that an arrangement of the metering device at a predetermined position along the x-axis is important for mixing the exhaust gas with the

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Is additive. The mixing is also influenced by the speed of the exhaust gas flow and the additive. The additive is either sprayed into the exhaust gas flow via the metering devices or supplied dropwise to it. The amount and speed of the additive can advantageously be determined and changed by the metering device. A respective mouth of the metering device is in particular arranged at a distance from the inner walls of the mixing tube.

A mixing device according to the invention is advantageously used when deflecting and / or swirling an exhaust gas flow in a mixing pipe of an exhaust gas aftertreatment device of a marine diesel engine.

The further goal is achieved if an exhaust gas aftertreatment device comprises a mixing device according to the invention.

Further advantages, features and effects result from the non-restrictive exemplary embodiments shown below. In the drawings, to which reference is made, show:

Fig. 1 section of an engine with an exhaust gas aftertreatment device according to the invention;

2 shows a perspective illustration of a section of a mixing device according to the invention;

FIG. 3 shows a side view of the mixing device according to FIG. 2;

4 shows a section through a mixing device according to FIG. 2 along the line IVIV according to FIG. 3;

Fig. 5 shows a section of a further mixing device according to the invention;

FIG. 6 shows a side view of a mixing device according to FIG. 5;

7 shows a section through a mixing device according to FIG. 5 along the line VIIVII according to FIG. 6;

8 shows a further section through a mixing device according to FIG. 2 or FIG. 5.

1 shows a section of an engine 200 with an exhaust gas aftertreatment device 100 according to the invention, the engine 200 being designed in particular as a marine diesel engine. A mixing device 1 according to the invention

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2 shows a section of the mixing device 1 according to the invention in accordance with a first embodiment. This is designed to be arranged in an exhaust gas aftertreatment device of an internal combustion engine according to FIG. 1 for carrying out a selective catalytic reduction in an exhaust gas stream S. The mixing device 1 comprises a hollow cylindrical mixing tube 2 with two deflection elements 3 arranged inside the mixing tube 2,

4. For a better overview, the mixing tube 2 is shown transparently in the figures.

The mixing tube 2 has a rectangular base with two different lengths of side. The exhaust gas flow S, which flows through the mixing tube 2, is therefore delimited from four sides by inner walls 8, 9, 14, 15 of the mixing tube 2. A free diameter D of the mixing tube 2 has a constant length over an entire length of the mixing tube, is formed by a width of a third inner wall 14, and runs in the first or z direction Z. A fourth inner wall 15 runs parallel to the third inner wall 14 and orthogonal to a first inner wall and a second inner wall 9.

The deflection elements 3, 4 are arranged at a distance from one another in the third or y-direction Y and are traversed by an exhaust gas flow S, the deflection elements 3, 4 generating vortices in the exhaust gas flow S. A second deflection element 4 is arranged downstream of a first deflection element 3 with respect to a flow direction of the exhaust gas flow S. The first deflection element is arranged in a lower third of the volume of the mixing tube 2 and the second deflection element 4 in an upper third of the volume of the mixing tube 2. This is shown in Figure 3. The first deflecting element 3 is integrally connected to the third inner wall 14 and the first inner wall 8 and the second inner wall 9, whereas the second deflecting element 4 is integrally connected to the fourth inner wall 15 and the first inner wall 8 and the second inner wall.

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It can be seen from FIG. 2 that a course of the deflection elements 3, 4 varies in the second or x-direction X and the deflection elements 3, 4 each have edges 5 curved in the x-direction X. The edges 5 of the two deflecting elements 3, 4 point in a different x-direction X, the edges 5 being aligned with one another, so that the exhaust gas flow S first meets the essentially concave first deflecting element 3 and then downstream to the essentially convex one second deflecting element 4 meets or is deflected by the deflecting elements.

FIG. 4 shows that the deflection elements 2, 3 each have five partial areas 6, 7, 10, 11, 12. A first partial area 6 and a second partial area 7 each have a constant slope Δ Ste / Δζ in the direction of the center of the mixing tube 2 and are indirectly connected to the first inner wall 8 and the second inner wall 9 of the mixing tube 2 via a short partial area 10, 11, respectively , The two short sections 10, 11 per deflection element 3, 4 have a shorter length than the first and second sections 6, 7 and enclose an angle of approximately 90 ° with the respective inner wall. The short sections 10, 11 thus run in the z-direction Z. Between the first and second sections 6, 7, a connecting section 12 is provided approximately centrally in the mixing tube 2, which connects the first to the second section 6, 7. The connecting sub-area 12 is also shorter than the first and second sub-areas 6, 7, which has approximately the same length as the short sub-areas 10, 11 and is also offset in the z-direction Z, but parallel in the x-direction X. the short sections 10, 11. The deflection elements 3, 4 or the respective partial areas 6, 7, 10, 11 are integrally connected to the respective inner wall 8, 9. All partial areas 6, 7, 10, 11, 12 of the first deflecting element 3 are integrally connected to the third inner wall 14 and all partial areas 6, 7, 10, 11, 12 of the second deflecting element 4 are connected to the fourth inner wall 14 of the mixing tube 3. All sub-areas 6, 7, 10, 11, 12 of the deflection elements 3, 4 are straight.

5 to 7 show a second variant of a mixing device according to the invention

1. This differs from the variant according to FIGS. 2 to 4 in that the first deflection element 3 and the second deflection element 4 are arranged at a different position in the x-direction X. This time, the first deflection element 3 is arranged downstream of the second deflection element 4. The edges 5 of the two deflection elements 3, 4 again show a different one

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AVL List GmbH x-direction X, the edges 5 pointing away from each other this time, so that the exhaust gas flow S first hits the essentially convex second deflecting element 4 and downstream then the essentially concave first deflecting element 3 or deflects it from the deflecting elements becomes. 4 and 7, a plane of symmetry E is shown, the deflection elements 3, 4 being designed such that they are mirrored about the plane of symmetry E. The plane of symmetry E is spanned by the second or x direction and the third or y direction.

In both exemplary embodiments, the deflection elements 3, 4 are each constructed identically, with these being arranged differently in the mixing tube 2.

A mixing device 1 with four possible positions for metering devices 13 is shown in FIG. 8. The positions of the metering devices 13 are provided along the x-axis X or the mixing tube 2, in particular at equidistant distances from one another. The position of the metering devices 13 along the other axes is z = 0 and y = 0. It can be seen that all metering devices 13 are arranged downstream of the two deflection elements 3, 4, with a metering device 13 arranged most upstream in the x-direction X directly connects to the second deflecting element 4. The metering devices 13 are each designed to introduce or spray an additive into the exhaust gas stream S. An injection direction corresponds to the flow direction of the exhaust gas stream S, because an optimal mixing is achieved.

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Claims (10)

claims 1. Mixing device (1) for an exhaust gas aftertreatment device (100) of an internal combustion engine (200), in particular for an exhaust gas aftertreatment device (100) for carrying out a selective catalytic reduction in an exhaust gas stream (S), comprising a hollow cylindrical mixing tube (2) with an at least sectionally constant free diameter (D), at least two deflection elements (3, 4) being arranged within the mixing tube (2), which are at least in a z-direction (Z) over the entire free diameter (D) of the mixing tube (2) extend and are connected to an inner wall (8, 9) of the mixing tube (2), at least one first deflection element (3) and at least one second deflection element (4) running parallel to a main flow direction in a direction normal to the z direction (Z) the x direction (X) of the exhaust gas flow (S) and a y direction (Y) which is normal to the x direction (X) and the z direction (Z) det are arranged, characterized in that a course of the deflection elements (3, 4) along the free diameter (D) with formation of at least one edge (5) varies such that the at least one edge (5) the deflection elements (3, 4) forms kinked, at least the first deflecting element (3) and the second deflecting element (4) being kinked in opposite directions with respect to the x direction (X). 2. Mixing device (1) according to claim 1, characterized in that the first deflecting element (3) is concave and the second deflecting element (4) is convexly buckled against a flow direction of the exhaust gas stream (S), the second deflecting element (4) downstream of the first Deflection element (3) is arranged. 3. Mixing device (1) according to claim 1, characterized in that the first deflecting element (3) is concave and the second deflecting element (4) is convexly buckled against a flow direction of the exhaust gas stream (S), the second deflecting element (4) upstream of the first Deflection element (3) is arranged. 4. Mixing device (1) according to one of claims 1 to 3, characterized in that a thickness of the deflection elements (3, 4) is substantially constant. 5. Mixing device (1) according to one of claims 1 to 4, characterized in that exactly two substantially identical designs 14/20 PP31637AT AVL List GmbH Deflection elements (3, 4) are provided, these being arranged in the mixing tube (2) rotated relative to one another by approximately 180 ° about the y direction (Y). 6. Mixing device (1) according to one of claims 1 to 5, characterized in that the deflecting elements (3, 4) each have at least two partial areas (6, 7), with a first partial area (6) each from a first inner wall (8 ) of the mixing tube (2) with a constant slope Δχ / Δζ up to in particular approximately a center of the mixing tube (2) and a second partial area (7) in particular with the same slope from in particular approximately the center of the mixing tube (2) to a second inner wall ( 9) of the mixing tube (2), the first inner wall (8) being arranged approximately opposite the second inner wall (9). 7. Mixing device (1) according to claim 6, characterized in that the deflecting elements (3, 4) each have five partial areas (6, 7, 10, 11, 12). 8. Mixing device (1) according to one of claims 1 to 7, characterized in that at least one metering device (13) is provided for supplying an additive in the exhaust gas stream (S), the at least one metering device (13) in particular in a flow direction of the Exhaust gas flow (S) is arranged downstream of the deflection elements (3, 4). 9. Use of a mixing device (1) according to one of claims 1 to 8 for deflecting and / or swirling an exhaust gas flow in a mixing tube (2) of an exhaust gas aftertreatment device (100) of a marine diesel engine. 10. exhaust gas aftertreatment device (100) with a mixing device (1) according to one of claims 1 to 8. 15/20 PP31637AT AVL List GmbH 1.4

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