Abstract
A mixer arrangement for mixing an additive with an exhaust-gas flow, having an exhaust-gas line, an exhaust gas flowing through the exhaust-gas line in a main flow direction, and having at least one exhaust-gas purification element which is arranged in the exhaust-gas line and which has a casing and, arranged within the casing, a flow-over surface for the exhaust gas. Here, the casing of the at least one exhaust-gas purification element has a guide structure.
Claims
1. A mixer arrangement for mixing an additive with an exhaust-gas flow, comprising: an exhaust-gas line; at least one exhaust-gas purification element which is arranged in the exhaust-gas line; a casing; a flow-over surface for the exhaust gas, the flow-over surface arranged within the casing; a guide structure connected to the casing of the at least one exhaust-gas purification element; wherein an exhaust gas flows through the exhaust-gas line in a main flow direction.
2. The mixer arrangement of claim 1, the guide structure further comprising multiple guide elements.
3. The mixer apparatus of claim 2, wherein the multiple guide elements are at least partially bent radially inward.
4. The mixer apparatus of claim 2, further comprising an unwound casing, wherein the multiple guide elements are, in the unwound casing, arranged at an angle with respect to the axial extent of the casing.
5. The mixer apparatus of claim 2, wherein each of the multiple guide elements further comprising the same shape.
6. The mixer apparatus of claim 2, wherein the multiple guide elements are of asymmetrical design.
7. The mixer apparatus of claim 2, wherein two adjacent multiple guide elements have different areas.
8. The mixer apparatus of claim 2, the multiple guide elements further comprising substructures.
9. The mixer apparatus of claim 8, the substructures in the guide elements further comprising embossments.
10. The mixer apparatus of claim 8, the substructures in the guide elements further comprising perforations.
11. The mixer apparatus of claim 8, the substructures further comprising incisions in the end regions of the respective guide element.
12. The mixer apparatus of claim 11, wherein, in the case of the incisions in the end regions, the individual regions may be additionally bent.
13. The mixer arrangement of claim 1, wherein the guide structure is formed in one piece with the casing.
14. The mixer arrangement of claim 1, wherein the guide structure is connected to the casing.
15. The mixer arrangement of claim 1, wherein the guide structure is connected to the casing using inductive welding.
16. The mixer apparatus of claim 1, wherein the guide structure is arranged on the downstream-facing side of the casing of the exhaust-gas purification element.
17. The mixer apparatus of claim 1, wherein the guide structure is arranged on the upstream-facing side of the casing of the exhaust-gas purification element.
18. The mixer apparatus of claim 1, the at least one exhaust-gas purification element further comprising multiple exhaust-gas purification elements, wherein the multiple exhaust-gas purification elements are arranged in the exhaust-gas line.
19. The mixer apparatus of claim 18, wherein the guide structure is arranged on at least one of the multiple exhaust-gas purification elements which is positioned upstream of another of the multiple exhaust-gas purification elements as viewed in the flow direction.
20. The mixer arrangement of claim 1, the honeycomb body further comprising a hollow cylinder with a radially internally situated cylindrical recess.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention will be discussed in more detail on the basis of multiple exemplary embodiments. In the figures:
[0030] FIG. 1 is a schematic illustration of a mixer arrangement;
[0031] FIG. 2-4 show further arrangements of a mixer arrangement as per FIG. 1,
[0032] FIG. 5 shows an exhaust-gas purification element with a flow-over surface,
[0033] FIG. 6 shows the casing of an exhaust-gas purification element,
[0034] FIG. 7-9 show guide elements of the guide structure,
[0035] FIG. 10 shows a further embodiment of a mixer arrangement.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
[0037] FIG. 1 shows a mixer arrangement having an exhaust-gas line 1 in a motor vehicle (not illustrated in any more detail). The arrow indicates the main flow direction of the exhaust gas flowing through the exhaust-gas line 1. By means of an injector 2 arranged on the exhaust-gas line 1, urea solution is injected into the exhaust-gas flow at an angle with respect to the main flow direction, such that the jet 3 strikes an exhaust-gas purification element 4 approximately centrally. The exhaust-gas purification element is an SCR catalytic converter 4. The SCR catalytic converter 4 is composed of a schematically illustrated honeycomb body 5, which forms a flow-over surface for the exhaust gas, and a casing 6, which fully encloses the honeycomb body 5. On the downstream-facing side 7 of the casing 6, a guide structure 8 is fastened to the casing 6. The construction of the guide structure 8 is described in the following figures. During the operation of the mixer arrangement, the injected urea solution is sprayed onto the honeycomb body 5 and is transported through the honeycomb body 5 by the exhaust gas. Owing to the structure of the flow-over surface, the exhaust gas and the droplets of urea solution still contained therein emerge from the honeycomb body 5 on the side 7 substantially as a laminar flow. The guide structure 8 disrupts the laminar flow, such that, downstream of the guide structure 8 in the flow direction, the laminar flow is caused to swirl and thus changes into a turbulent flow. As a result of this swirling, more exhaust gas comes into contact with the droplets of the urea solution, whereby the efficiency of the exhaust-gas after treatment is increased.
[0038] The mixer arrangement in FIG. 2 is composed of the exhaust-gas line 1 and two SCR catalytic converters 4, 4 as exhaust-gas purification elements. Both SCR catalytic converters 4, 4 have in each case one honeycomb body 5 and one casing 6 surrounding the honeycomb body. The SCR catalytic converter 4 arranged upstream of the final SCR catalytic converter 4 as viewed in the flow direction has a guide structure 8 on its downstream-facing side 7. By means of the guide structure 8, the flow emerging from the SCR catalytic converter 4 is caused to swirl, such that a thoroughly mixed exhaust-gas flow enters the downstream SCR catalytic converter 4. As a result of this swirling, hot exhaust gas from the center of the SCR catalytic converter 4 is mixed with the less hot exhaust gas from the regions in the vicinity of the casing 6, such that exhaust gas entering the SCR catalytic converter 4 exhibits greater temperature homogeneity in relation to the cross section, which increases the efficiency of the second SCR catalytic converter 4.
[0039] The mixer arrangement as per FIG. 3 may be regarded as a combination of the mixing arrangements from FIGS. 1 and 2. The guide structure 8 causes swirling of the exhaust-gas flow emerging from the SCR catalytic converter 4, whereby the exhaust-gas flow entering the SCR catalytic converter 4 exhibits a more uniform distribution both with regard to the temperature distribution but also with regard to the droplet distribution of the injected urea solution. In particular in the case of the distribution of the urea solution, the guide structure 8 assists the jet 3 in order to distribute the urea solution more uniformly over the entire cross section.
[0040] The mixer arrangement shown in FIG. 4 differs with regard to the exhaust-gas purification element 4. The latter has a guide structure 8 on the upstream-facing side 9 of the casing 6. Thus, the impinging exhaust-gas flow is influenced with a swirling action by the exhaust-gas purification element 4 to which the exhaust-gas flow is supplied.
[0041] FIG. 5 shows a plan view of an exhaust-gas purification element 4, in particular an SCR catalytic converter. The exhaust-gas purification element is composed of a casing 6 in which a honeycomb body 5 is arranged. The honeycomb body 5 is composed of a multiplicity of interconnected foil layers, which form the flow-over surface for the exhaust gas. The casing 6 has a greater length than the honeycomb body 5. The guide structure 8 is fastened to the inner side of the free casing surface by means of induction welding. The guide structure 8 is composed of an encircling ring 10 which bears against the inner side of the casing 6. Guide elements 11 extend in an axial direction from the ring 10. The guide elements 11 all have the same area and shape and are bent radially inward by virtue of the guide elements 11 being kinked in discontinuous fashion along an edge, such that they project at an angle of between 0 and 90 into the exhaust-gas flow.
[0042] In FIG. 6, the guide structure 8 with the guide elements 11 is formed in one piece with the casing 6 of the SCR catalytic converter 4. The casing tube 6 is illustrated in unwound form. For the production of the casing 6, the casing tube is rolled up, such that the two outer edges 13, 14 abut against one another. The casing 6 may subsequently be welded. Along the edges 12, the guide elements 11 are bent at the desired angle. To intensify the mixing and to avoid partial swirling patterns, adjacent guide elements 11 have different shapes. This is achieved through variation of the lengths and widths of the guide elements 11 but also by means of bends at different angles.
[0043] The following figures show different guide elements 11. The guide element in FIG. 7 has a multiplicity of apertures 15, such that, as a result of the passage from one side of the guide element 11 to the other side, the exhaust gas intensifies the thorough mixing of the exhaust-gas flow. Thorough mixing is also realized even if, in this arrangement, depressions 15 are arranged in place of the apertures, which depressions project as protuberances on the opposite side of the guide element 11. These substructures effect additional swirling and thus improve the thorough mixing.
[0044] FIG. 8 shows a guide element 11 that has not yet been bent in a side view, which guide element has incisions on the circumference as a substructure, and individual regions 16 are bent in the manner of tongues out of the plane of the guide element 11.
[0045] The guide element 11 in FIG. 9 has a first region 17, in which the guide element 11 has been bent radially inward. In a second region 18, the guide element has been bent in the opposite direction thereto. By means of both regions 17, 18, the guide element 11 has a twist about its longitudinal axis 19.
[0046] FIG. 10 shows a further embodiment of a mixer arrangement, which is directed substantially to the embodiment of the honeycomb body 5 of the exhaust-gas purification element 4. The honeycomb body 5 is formed as a hollow cylinder with a cylindrical recess 20 situated in the center. The guide structure 8 is arranged in the cylindrical recess 20, preferably on the wall, which delimits the honeycomb body 5 in a radially inward direction, of the casing 6. In the illustration shown, the guide structure 8 is arranged at the downstream-facing end of the exhaust-gas purification element 4. It is however also conceivable for the exemplary embodiments described in the above figures to be applied to a honeycomb body 5 as per FIG. 10.
[0047] The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
