Mixer device, exhaust gas aftertreatment system and motor vehicle

Abstract

A mixer device for an exhaust gas aftertreatment system of a motor vehicle comprises a housing, a peripheral wall, a first end wall and a second end wall, an injection opening being constructed in the peripheral wall; at least one curved guide element is arranged in the housing, the guide element guides the exhaust gas flow from at least one inlet to an outlet constructed in the second end wall, the at least one inlet is constructed in the first end wall, the injection opening is configured to fix a metering module, such as a metering valve, a straight metering axis that imaginarily extends longitudinally through the metering module tangentially contacts a theoretical cylinder arranged in the housing at a contact point, the metering axis corresponds to the injection direction of the exhaust gas aftertreatment agent injected into the housing, the theoretical cylinder has a variable radius and a cylinder axis that coincides with the central axis of the housing, and at least one region of the metering axis extending from the injection opening to the contact point is located in the leeward area of ​​the non-opening region of the first end wall with respect to the inflowing exhaust gas.

Description

Technical Field

[0001] The invention relates to a mixer device for an exhaust gas aftertreatment system of a motor vehicle, the mixer device having a housing, for example cylindrical, with a peripheral wall, a first end wall and a second end wall, wherein an injection opening for an exhaust gas aftertreatment agent is formed in the peripheral wall, and wherein at least one curved flow guide element is arranged in the housing, which guides the exhaust gas flow from at least one inlet to an outlet formed in the second end wall.

[0002] Furthermore, the invention relates to an exhaust gas aftertreatment system having such a mixer device and to a motor vehicle having a corresponding exhaust gas aftertreatment system. Background Art

[0003] Different methods and devices are known for the aftertreatment of exhaust gases, in particular diesel engines, which are used to reduce harmful components of the exhaust gas. A frequently used method is the so-called selective catalytic reduction (SCR), which is used to reduce the nitrogen oxide components in the exhaust gas. Here, an aqueous urea solution is injected into the exhaust gas flow as an exhaust gas aftertreatment agent, the urea solution is mixed with the exhaust gas and acts with the exhaust gas downstream in a catalytic converter to reduce nitrogen oxides. The result of the exhaust gas aftertreatment is hereby optimizable by improved mixing of the exhaust gas aftertreatment agent and the exhaust gas. Therefore, it is known that a mixer device is provided for mixing, as has been described, for example, in the publication DE 10 2013005 206 B3. The mixer device has a helically extending flow guide element in the housing, which causes: the exhaust gas flow to acquire a swirl (Drall); and provides a mixing section that is as long as possible with only a small structural space. The guide element guides the exhaust gas flow from the inlet to the outlet in the second end wall, where the exhaust gas flow-exhaust gas aftertreatment agent mixture flows out of the mixer device and is supplied to the SCR catalyst. Due to increasingly stringent exhaust gas regulation, the greatest efforts are made to improve fuel efficiency and at the same time reduce emissions, especially the nitrogen oxide content in the exhaust gas. In addition, this leads to a drop in the temperature of the exhaust gas flow. This has the following disadvantages for the SCR catalyst: it is more difficult to achieve the necessary reaction temperature for reducing the nitrogen oxide component. Normally, the SCR catalyst is arranged away from the internal combustion engine, which results in additional temperature losses. The closer the catalyst is arranged to the internal combustion engine, or the shorter the path that the exhaust gas flow must overcome from the internal combustion engine to the catalyst, the better the multiple operating states for the exhaust gas aftertreatment results.

[0004] From document DE 10 2016 211 703 A1, the disclosure of which is expressly included in the description of the present invention, a mixer device for an exhaust gas aftertreatment system of a motor vehicle is known, the mixer device having a cylindrical housing with a peripheral wall, a first end wall and a second end wall, wherein injection openings for an exhaust gas aftertreatment agent are formed in the peripheral wall. Exhaust gas flows from at least one inlet in the first end wall to an outlet in the second end wall, wherein the at least one inlet allows a majority of the exhaust gas flowing through to flow into the mixer device. Summary of the invention

[0005] The mixer device according to the invention has the following advantages: a further improved mixing of the exhaust gas and the exhaust gas aftertreatment agent is achieved in a small space, wherein the mixer device and the subsequent catalytic converter can be arranged close to the internal combustion engine and still ensure a sufficient mixing path for thorough mixing. It is particularly advantageous here that at least one important region of the metering axis is located in the leeward area of ​​the opening-free region of the first end wall starting from the injection opening with respect to the inflowing exhaust gas, so that the reducing agent jet diffuses in a protected manner and can still be closely mixed with the exhaust gas in the narrowest space. In this case, the suitable arrangement of the opening-free region simultaneously enables an improved fixing of the guide element to the first end wall, especially in terms of thermomechanics, which fixing is close to the inlet or in the region of the inlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present invention will be described in detail below with reference to the accompanying drawings. It is shown here:

[0007] Figure 1 A top view of a mixing device known from the prior art for an exhaust gas aftertreatment system of a motor vehicle;

[0008] Figure 2 A perspective view of a mixing device known from the prior art;

[0009] Figure 3 A top view of a mixing device for an exhaust gas aftertreatment system of a motor vehicle; and

[0010] Figure 4 A perspective view of another mixing device for an exhaust gas aftertreatment system of a motor vehicle. DETAILED DESCRIPTION

[0011] Figure 1 A simplified top view of a mixer device 1 for an exhaust gas aftertreatment system (not shown in detail here) of a motor vehicle is shown. The mixer device 1 can be arranged downstream of an internal combustion engine, in particular in terms of flow technology, between an oxidation catalytic converter and an SCR catalytic converter or an SCR-coated particle filter, and serves to optimally mix an exhaust gas aftertreatment agent with the exhaust gas flow of the internal combustion engine, so that an advantageous reduction of nitrogen oxides can be achieved in the downstream SCR catalytic converter.

[0012] Figure 2 A perspective view of the mixer device 1 is shown, wherein the upstream oxidation catalytic converter 2 and the downstream SCR catalytic converter or SCR-coated particle filter are indicated by dashed lines.

[0013] The mixer device 1 has a housing 4, which has a circular peripheral wall 5 and a first end wall 6 and a second end wall 7. The end walls 6 and 7 are oriented parallel to each other and are arranged at a distance from each other, wherein the peripheral wall preferably protrudes beyond the end walls. The housing 4 is cylindrical in this respect.

[0014] The first end wall 6 has a plurality of inlets 8, 9 and 10. Inlet 8 can optionally be circular, inlet 9 can be wedge-shaped and inlet 10 can be circular segment-shaped. The arrangement and construction of inlets 8, 9 and 10 will be discussed further below.

[0015] The peripheral wall 5 has an injection opening 11 for a liquid exhaust gas aftertreatment agent, wherein the injection opening 11 is formed at the end of an injection connection 12. The injection connection 12 is used, for example, to receive an injection valve or a metering module so that a metered injection of the exhaust gas aftertreatment agent is achieved directly at the mixer device 1 by means of the injection valve or the metering module. The connection 12 is designed in this case so that the liquid exhaust gas aftertreatment agent is injected into the housing 4 in the direction of a secant.

[0016] The first inlet 8 is arranged here, for example, upstream of the injection opening 11, and the inlet 9 begins, for example, at the level of the injection opening 11 and extends substantially parallel to the injection direction, wherein the clear width of the inlet 9 is widened here, thereby producing the wedge shape already described above. The two inlets 9 are arranged here in a mirror-symmetrical manner to each other, so that there is a section 13 between the two inlets, which is designed to be without openings. The section 13 extends from the injection opening 11 to the inlet 10 in the end wall 6. The section 13 ensures that in this area the exhaust gas flow does not directly reach the injected exhaust gas aftertreatment agent vertically, as a result of which the exhaust gas flow would displace the injection agent flow or deflect the injection agent flow toward the end wall 7 of the housing 4.

[0017] In addition, a guide element 14 is arranged in the housing 4, which extends semicircularly or spirally and eccentrically in the housing 4, so that the exhaust gas flow and the injected exhaust gas aftertreatment agent are guided to an outlet 15 eccentrically configured in the end wall 7. The flow path in the housing 4 is extended by the guide element. The guide element 14 extends semicircularly or spirally along the outer contour of the circular outlet 15. Here, the guide element 14 starts on the peripheral wall 5, thereby generating a semicircular or spiral trend. The exhaust gas aftertreatment agent and the exhaust gas flow first reach the outside of the guide element 14 and are then supplied to the inside of the guide element 14 through the peripheral wall 5, and the guide element supplies the flow to the outlet 15. Here, a swirl is generated in the exhaust gas-exhaust gas aftertreatment agent mixture, as shown by the arrow 16.

[0018] Arranged parallel to the air guide element 14 are two further air guide elements 17 and 18 , which are shorter than the air guide element 14 and extend along a circumference whose radius has the same origin as the radius of the air guide element 14 .

[0019] The further air guide elements 17, 18 each have a plurality of laterally protruding collision elements 19 (Aufprallelemente). The collision elements 19 each form a collision surface 20 facing the injection opening 11. The collision elements 19 are oriented in this case so that the collision surface 20 is substantially perpendicular to the injection direction of the exhaust gas aftertreatment agent. Here, the collision elements 19 are configured as collision tongues bent out from the further air guide elements 17, 18. The further air guide elements 17, 18 are configured in this respect in one piece with the respective collision elements 19. The further air guide elements 17, 18 can be manufactured, for example, as sheet metal stamping bent parts.

[0020] The further air guidance elements 17 , 18 are arranged, for example, at the level of the inlet 10 , so that the exhaust gas flowing into the inlet 10 can directly reach the air guidance elements 17 , 18 .

[0021] During operation, the exhaust gas flow is thus introduced into the housing 4 through the inlets 8, 9 and 10, while the exhaust gas aftertreatment agent is injected into the housing 4 through the injection opening 11. Due to the section 13, the injected exhaust gas aftertreatment agent reaches the collision surface 20 and is atomized there and advantageously mixed with the exhaust gas flow that is also flowing in. The exhaust gas flow-exhaust gas aftertreatment agent-mixture is supplied to the outlet 15 along the peripheral wall 5 and the flow guide element 14 through the extension of the flow guide element 14 and the flow guide element 17, 18, thereby generating a swirl 16. The swirl 16 causes the mixing of the exhaust gas aftertreatment agent with the exhaust gas and causes the SCR catalytic converter or SCR-coated particle filter located downstream to be uniformly loaded with the exhaust gas aftertreatment agent, so that an advantageous exhaust gas aftertreatment occurs.

[0022] The mixer device 1 has the advantage of a space-saving design with a long flow path, which allows for advantageous mixing. In addition, an advantageous atomization of the exhaust gas aftertreatment agent is ensured. It is possible without any problems to arrange one or more sensors on the mixer device, in particular upstream of the mixing region, in order to monitor the exhaust gas aftertreatment. The injection valve can be arranged simply and cost-effectively on the housing 4 or on the mixer device 1. The mixer device 1 allows for a high degree of utilization of the thermal energy of the exhaust gas flow on the collision surface or other flow-guiding elements 17, 18, thereby increasing the stability of the mixer device with respect to the exhaust gas aftertreatment agent.

[0023] Figure 3 A mixer device 50 is shown with an alternative design of the mixing section, which is determined by an alternative design of the first end wall 6. This is a compact reducing agent mixing section with an improved exhaust gas inlet area. Figure 1 and 2 The arrangement according to 6 and 7 comprises a cross-sectional cylindrical or alternatively oval region in the exhaust gas path, which is limited in length by the inlet and outlet planes in the configuration of the inlet and outlet plates (end walls 6 and 7). Figure 1 and 2 The main opening for the main exhaust gas flow is realized in the configuration of the inlet plate (first end wall 6) in the arrangement mode of Figure 1 and 2 In the arrangement of , further smaller openings, so-called side flow openings or auxiliary openings (inlet 8 and 9) are optionally present in the inlet plate. Figure 1 and 2 The configuration of the main openings of the mixer device results in that the exhaust gas flow in the interior of the mixer device can influence the spray diffusion in an undesirable manner, especially in the region of the surfaces interacting with the spray, in the region of the reducing agent-spray-wall interaction. Unfavorable influences can occur, especially in dynamic engine operation, due to typical and very strong variations in the exhaust gas flow conditions (especially pressure, temperature, exhaust gas mass flow). This can have unfavorable consequences for mixing and evaporation, and even for undesirable deposition of auxiliary materials in the exhaust system.

[0024] according to Figure 3 The alternative configuration of 4 now shows a change in the entry area, which leads to a reduction in the influence of the normally existing variations in the exhaust gas flow conditions and thus to an improved and more robust operating mode of the mixing section. Figure 1 Identical or similar components in FIG. 1 or 2 are provided with the same reference numerals and are not described again.

[0025] Figure 3The mixer device 50 is shown in a top view 51 from the outside toward the first end wall 6. The inlet 8 or 9 already described, which is arranged close to the injection nozzle, is a so-called auxiliary opening, which is mainly used to form a backpressure compensation bypass by providing an orientation predetermined by the injection direction 60 for the mixing section. The injection direction 60 corresponds to an imaginary metering axis of a metering module or metering valve (not shown further) which is mounted on the injection nozzle 12 and injects through the injection opening 11. In the area of ​​the injection direction, but not directly connected to the injection nozzle 12, that is, away from the injector or metering valve outlet, there are inlets 52, 53 and 54, which are also called main openings and are preferably close to the desired spray-wall contact between the reducing agent and the mixer wall. Different from Figure 1 and 2 The arrangement of Figure 3 The arrangement of the mixer 52 and 54 has a plurality of main openings. These main openings are arranged in the first end wall 6 in such a way that they are located next to the metering axis in the top view shown, i.e. surround the metering axis, so that the end wall 6 has areas that cover the metering axis, at least starting from the injection nozzle to the point 62 at which the metering axis is tangential to an imaginary, i.e. theoretical, cylinder 61, which has a central axis 65 of the mixer device or housing perpendicular to the drawing plane and consisting of the measured radius R. In the exemplary embodiment shown, the main openings 52 and 54 arranged in this way on both sides of the metering axis or injection direction result in so-called jet stabilizing webs 63 as components of the end wall 6, which is preferably designed as a two-dimensionally shaped, i.e. flat sheet metal, like the end wall 7 arranged downstream. In the case of jet stabilizing webs with a width b, the introduction of reducing agent can be diffused in a protected manner, i.e. in the leeward area of ​​the end wall or its jet stabilizing web. The further main opening 53 is produced in the transverse web 64 which mechanically stabilizes the beam stabilizing web 63 due to its proximity to the main opening 52. Figure 3 The fixing area 140 of the guide element 14 can also be seen, which has been combined with Figure 1 and 2 Described.

[0026] exist Figure 3 In the example shown, no inlet opening is provided in the first end wall 6 which has 60% or more of the total free cross section of the end wall 6. Preferably, no inlet opening is provided in the first end wall which has 50% or more of the total free cross section of the end wall 6. An arrangement with three main openings is shown. However, it is also possible to provide only two main openings which are separated from one another at the height of the metering axis by a jet stabilizing web of the end wall.

[0027] As a single main opening or as one of a plurality of main openings, a main opening can alternatively be provided which comprises at least 50% or even more than 60% of the free cross section, i.e. the surface through which the exhaust gas can flow into the mixer device. In any case, it is ensured that the injection direction in the region of the injection nozzle is preferably covered by the first end wall 6 until the imaginary contact point 62 with the theoretical cylinder described is covered. The injection direction can also extend beyond the first end wall, in particular continuously, until the circumferential wall 5 opposite the injection nozzle is covered by the end wall.

[0028] Even in the case of only one main opening, the spray direction or metering axis 60 should be covered by the end wall 6. Preferably, a main opening close to the peripheral wall can be provided, which is located between the peripheral wall and the metering axis, wherein the metering axis preferably extends close to the single main opening, in particular parallel to the edge of the single main opening close to the central axis of the mixer device, but covered by the end wall 6.

[0029] By following Figure 3 Or according to the described alternative it is ensured that the reducing agent jet is influenced as little as possible by the exhaust gas flow (“blown off”) and that the jet reaches precisely the desired preparation region for an optimized function.

[0030] The further air guidance elements 17 , 18 are arranged partially at the level of the main openings 52 , 53 and 54 , in particular 53 and 54 , so that the exhaust gas flowing in, in particular through the inlets 53 and 54 , can directly reach the air guidance elements 17 , 18 .

[0031] For according to Figure 3 Other alternatives to the arrangement include eliminating Figure 3 , the right-hand side opening 9 shown in the figure and / or the main opening 54 can be omitted. Alternatively, the main openings 52 and / or 53 can also be omitted. In particular, only the right-hand auxiliary opening 9 can also be reduced, in particular reduced to half, wherein the part oriented toward the center of the mixer device is preferably omitted, for example, so that the reduced right-hand opening 9 is not closer to the center than the left-hand opening 9 and / or the opening 8 which remain unchanged in size.

[0032] In contrast, it is preferred that the openings are arranged as symmetrically as possible on the right and left of the spray axis or metering axis or spray direction. The formed section 13 or jet stabilizing web 63 can vary in width along its extension from the injection nozzle to its end remote from the injection nozzle, for example, in a trend to form a diverging spray cone in order to provide the best possible leeward area for the spray cone, or if the exhaust gas back pressure is to be kept as low as possible, the width of the jet stabilizing web decreases in the direction of its end remote from the injection nozzle.

[0033] Figure 4In the perspective view 501 (only) towards the first end wall 6, a part of another alternative mixer device 500 is shown. Figure 3 The arrangement of the right-hand opening 9 has three main openings and three auxiliary openings, but the geometry of these openings is slightly changed. That is, the right-hand opening 9 has a rounding 99 on the side facing the middle of the mixer device, which reduces the right-hand opening 9. In addition, the alternative beam stabilizing tab 630 has an angular region 631 that protrudes into the main opening 53.

[0034] In a further variant, the first end wall can be shaped such that the metering axis along its entire course (ie not only up to the contact point 62 ) through the mixer device is located in the leeward region of the first end wall without openings with respect to the inflowing exhaust gas.

[0035] In another variant, the first end wall can be formed in such a way that, in addition to the measure of moving at least one area of ​​the metering axis extending from the injection opening to the contact point 62 in the leeward area of ​​the opening-free area of ​​the first end wall, the entire theoretical cylinder, at least the theoretical cylinder downstream of the contact point 62, is located in the leeward area of ​​the opening-free area of ​​the first end wall, that is, the theoretical cylinder or the relevant part of the theoretical cylinder (as viewed from the entry side of the mixer device) is covered by one or more opening-free areas of the first end wall.

[0036] In the case of a cylindrical mixer device, the diameter of the mixer device is typically 5 to 15 inches (Zoll).

[0037] If a jet stabilizing web is provided, it preferably has a width b of 1 to 2 centimeters transversely to the metering axis 60 .

[0038] The radius R of the theoretical cylinder is preferably of such a size that the metering axis contacts the theoretical cylinder approximately halfway between the peripheral wall and the central axis of the mixer device. In this case, the radius R can be 0.25 to 0.65 times the half diameter of the mixer device. Particularly preferably, a value range of between 0.4 and 0.5 times the half diameter of the mixer device is used.

[0039] A preferred ratio R / b of the radius of the theoretical cylinder to the width b of the beam-stabilizing web lies in a value range between 0.55 and 9, particularly preferably in a value range between 0.9 and 4.5.

Claims

1. A mixer device (50, 500) for an exhaust gas aftertreatment system of a motor vehicle, the mixer device having a housing (4) having a peripheral wall (5), a first end wall (6) and a second end wall (7), wherein: An injection opening (11) for an exhaust gas aftertreatment agent is constructed in the peripheral wall (5); and at least one curved guide element (14) is arranged in the housing (4), which guides the exhaust gas flow from at least one inlet to an outlet (15) constructed in the second end wall (7), wherein the at least one inlet is constructed in the first end wall (6), wherein the injection opening is provided for fixing a metering module, wherein a straight metering axis (60) extending longitudinally through the metering module imaginarily contacts a theoretical circular axis (60) arranged in the housing tangentially at a contact point (62). A cylinder (61), wherein the metering axis corresponds to the injection direction of the exhaust gas aftertreatment agent injected into the shell, and the theoretical cylinder has a variable radius (R) and a cylinder axis coinciding with the central axis (65) of the shell, characterized in that at least one area of ​​the metering axis (60) extending from the injection opening (11) to the contact point (62) is located in the leeward area of ​​the non-opening area of ​​the first end wall (6) with respect to the inflowing exhaust gas, wherein the entire theoretical cylinder (61) is located in the leeward area of ​​the non-opening area of ​​the first end wall (6) downstream of the contact point (62).

2. The mixer device according to claim 1, characterized in that The first end wall (6) has at least two inlets separated from one another by beam stabilizing webs (63, 630).

3. The mixer device according to claim 2, characterized in that The variable radius (R) is determined in accordance with the width (b) of the beam stabilizing web (63, 630) so that the contact point (62) is located in the leeward region of the beam stabilizing web.

4. The mixer device according to claim 3, characterized in that A ratio of the variable radius to the width of the beam-stabilizing web has a value between 0.55 and 9.

5. The mixer device according to claim 4, characterized in that A ratio of the variable radius to the width of the beam-stabilizing web has a value between 0.9 and 4.

5.

6. The mixer device according to any one of claims 1 to 5, characterized in that The outlet (15) is arranged / configured eccentrically in the second end wall (7).

7. The mixer device according to any one of claims 1 to 5, characterized in that The housing is cylindrical, oval or elliptical in shape.

8. The mixer device according to any one of claims 1 to 5, characterized in that The first end wall (6) and the second end wall (7) are respectively located in one plane, that is, are formed two-dimensionally.

9. The mixer device according to any one of claims 1 to 5, characterized in that The first end wall (6) and the second end wall (7) are arranged parallel to each other.

10. The mixer device according to claim 1, characterized in that The metering module is designed as a metering valve.

11. An exhaust gas aftertreatment system for a motor vehicle, comprising at least one mixer device (50, 500) for an exhaust gas flow of an internal combustion engine, wherein: A liquid exhaust gas aftertreatment agent can be supplied to an exhaust gas flow via the mixer device (50, 500), characterized in that the mixer device is a mixer device (50, 500) according to any one of claims 1 to 10.

12. The exhaust gas aftertreatment system according to claim 11, characterized in that: A first exhaust gas aftertreatment component is arranged upstream of the mixer device (50, 500) and thus upstream of the first end wall (6), and a second exhaust gas aftertreatment component is arranged downstream of the mixer device (50, 500) and thus downstream of the second end wall (7).

13. The exhaust gas aftertreatment system according to claim 12, characterized in that: The first exhaust gas aftertreatment component is designed as an oxidation catalytic converter (2), and the second exhaust gas aftertreatment component is designed as a selectively catalytic reduction catalytic converter (3) and / or a selectively catalytically coated particle filter.

14. A motor vehicle having an internal combustion engine and an exhaust gas aftertreatment system for the internal combustion engine, characterized in that The exhaust gas aftertreatment system constitutes the exhaust gas aftertreatment system according to any one of claims 11 to 13.

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