Patent Application
20200408131
This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2019 117 459.7, filed Jun. 28, 2019, the entire contents of which are incorporated herein by reference.
The present invention pertains to a mixer for an exhaust system of an internal combustion engine, which mixer is used to bring about the mixing of reactant injected into the exhaust gas stream, for example, a urea/water solution, with the exhaust gas.
To reduce the nitrogen oxide content in the exhaust gas discharged by a diesel internal combustion engine, it is known that a reactant is injected into the exhaust gas stream to carry out a selective catalytic reduction (SCR) in order to bring about a catalytic reaction of the nitrogen oxide being transported in the exhaust gas on an SCR catalytic converter. Good mixing of the reactant with the exhaust gas is necessary to carry out this catalytic reaction efficiently.
An object of the present invention is to provide a mixer for an exhaust system of an internal combustion engine, which mixer brings about an efficient mixing of a reactant injected into the exhaust gas stream with the exhaust gas while generating a low flow resistance for the exhaust gas flowing in an exhaust system and has a compact configuration.
This object is accomplished according to the present invention by a mixer for an exhaust system of an internal combustion engine, comprising:
A compact configuration, which can be manufactured with a small number of components and can be manufactured in a simple and cost-effective manner, is obtained with the mixer configured according to the principles of the present invention. The mixer can easily be adapted to the mixing process to be provided for different types of injectors and is insensitive with respect to the different spray angles generated by different types of injectors.
It is further proposed for a configuration that can be manufactured in a simple manner that the plate shape body of the first mixer part and the bottom wall of the second mixer part be arranged essentially parallel to one another, or/and that the two side walls of the second mixer part be arranged essentially parallel with respect to one another, or/and that the two side walls of the second mixer part be arranged essentially at right angles with respect to the bottom wall of the second mixer part or/and to the plate shape body of the first mixer part.
A stable configuration that can, for example, easily be integrated into an exhaust gas pipe can be obtained by a circumferential edge extending from the plate shape body in a direction away from the incoming flow side being provided at an outer circumference of the first mixer part.
To receive reactant from an injector, which is arranged, for example, outside an exhaust gas pipe, the reactant injection duct may be open in a first area of the outer circumference of the first mixer part at a receiving end for receiving reactant.
In order to obtain a flush connection also of the bottom wall to the exhaust gas pipe, for example, in interaction with the wall of an exhaust gas pipe, it is proposed that an outer circumferential contour of the bottom wall of the second mixer part in the first area of the outer circumference of the first mixer part correspond essentially to an outer circumferential contour of the first mixer part.
In order to make it possible to pass on the reactant injected into the reactant injection duct or the mixture of reactant and exhaust gas, which mixture was generated already in the reactant injection duct, the reactant injection duct may be open at a release end for releasing reactant or/and exhaust gas.
An intensified mixing of exhaust gas and reactant at the releasing end of the reactant injection duct can be ensured, for example, by the bottom wall of the second mixer part extending with a bottom wall extension area beyond the side walls of the second mixer part.
In order to avoid leakage flows compromising the mixing, it is proposed that the bottom wall extension area extend essentially to a second area of the outer circumference of the first mixer part and that an outer circumferential contour of the bottom wall extension correspond in the second area of the outer circumference of the first mixer part essentially to an outer circumferential contour of the first mixer part.
The mixing of exhaust gas and reactant at the releasing end of the reactant injection duct can be further supported by a deflecting wall extending essentially at right angle to the reactant main injection direction being arranged between the bottom wall extension area of the second mixer part and the plate shape body of the first mixer part. In order to bring about a defined flow deflection in the process, it is proposed that the deflecting wall have an essentially W-shaped or V-shaped configuration.
The deflecting wall may define with the plate shape body of the first mixer part, with the bottom wall extension area of the second mixer part and with each of the side walls of the second mixer part a respective main discharge opening of the reactant injection duct. A defined flow guiding is thus guaranteed at the releasing end through this main discharge opening or main discharge openings.
An efficient inflow of exhaust gas into the reactant injection duct can be supported by the exhaust gas main passage opening having an increasing opening width with respect to the exhaust gas main flow direction and to a central area of the plate shape body of the first mixer part in a first radial extension area originating from a radially outer end of the exhaust gas main passage opening and a decreasing opening width in a second radial extension area leading to a radially inner end of the exhaust gas main passage opening, the length of the second radial extension area being greater than a length of the first radial extension area.
To also achieve a defined flow guiding for the exhaust gas in an area next to the reactant injection duct, which flow guiding supports the mixing of exhaust gas and reactant, it is proposed that the exhaust gas secondary passage openings comprise a plurality of first exhaust gas secondary passage openings having a hole-like (hole) configuration, or/and that the exhaust gas secondary passage openings comprise a plurality of second exhaust gas secondary passage openings, wherein a flow deflection element is provided at the first mixer part in association with each second exhaust gas secondary passage opening.
In association with each second exhaust gas secondary passage opening, a bulge projecting on the outflow side may be provided at the plate shape body of the first mixer part for providing the flow deflection element. The bulge may have, for example, essentially the form of a calotte shell segment or of a deflecting flap.
The mixing of exhaust gas and reactant especially where reactant is discharged from the reactant injection duct can be made efficient by a second exhaust gas secondary passage opening being provided at the first mixer part in the area of at least one and preferably each main discharge opening, the flow deflection element associated with this second exhaust gas secondary passage opening deflecting exhaust gas passing through this secondary passage opening in the direction away from the reactant injection duct.
A plurality of secondary passage openings may be provided in the second mixer part. The provision of such secondary passage openings also supports the mixing of exhaust gas and reactant.
For example, the secondary discharge openings may comprise a plurality of first secondary discharge openings having a hole configuration. As an alternative or in addition, the secondary discharge openings may comprise a plurality of second secondary discharge openings, and a flow deflection element is provided at the second mixer part in association with each second secondary discharge opening.
A bulge may also be provided in association with each second secondary discharge opening at the second mixer part for providing the flow deflection element, and the bulge has, for example, essentially the form of a calotte shell segment or a deflecting flap.
The defined flow guiding in the area of the main passage opening(s) may be supported by a flow deflection element oriented in the direction away from the reactant injection duct being provided at least one and preferably each of the side walls of the second mixer part. Such a flow deflection element may have, for example, the form of a deflecting flap.
It is proposed for a configuration that can be embodied in a simple manner and is especially resistant to thermal effects that the first mixer part or/and the second mixer part be configured as a shaped sheet metal part.
The present invention further pertains to an exhaust system for an internal combustion engine, comprising an exhaust gas duct, through which exhaust gas can flow, and a mixer, which is configured according to the present invention and is arranged in the exhaust gas duct such that the first mixer part with its incoming flow side is oriented with its incoming flow side essentially at right angles to the exhaust gas main flow direction in the area of the mixer.
A reactant injection device may be provided for injecting reactant into the reactant injection duct.
An especially efficient mixing of exhaust gas and reactant can be supported here by the reactant main injection direction being essentially at right angles to the exhaust gas main flow direction in the exhaust gas duct on the incoming flow side of the first mixer part.
Provisions may be made in a configuration that likewise ensures a very good mixing of reactant and exhaust gas for the reactant injection device to be arranged for injecting reactant into the reactant injection duct through the exhaust gas main passage opening.
The present invention will be explained in detail below with reference to the attached figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Referring to the drawings,
A second mixer part 24 likewise provided as a shaped sheet metal part is provided on the outflow side 22 of the first mixer part 12, which said outflow side is oriented opposite the incoming flow side 18. The second mixer part 24 is configured with a bottom wall 26 and with side walls 28, 30 bent off from this at lateral areas. The side walls 28, 30 extend, starting from the bottom wall 26, towards the outflow side 22 of the plate shape body 14 of the first mixer part 12 and are fixed thereto, for example, by welding.
The second mixer part 24 is arranged with its bottom wall 26 essentially parallel to the plate shape body 14 of the first mixer part 12. The two side walls 28, 30 extend essentially at right angles to the bottom wall 26 and the plate shape body 14 and are essentially parallel to one another. A reactant injection duct 32 having an approximately rectangular cross section is defined in this manner by the bottom wall 26 of the second mixer part 24 and the two side walls 28, 30 of the second mixer part 24.
A receiving end 34 of the reactant injection duct 32 is located in a first area 36 of the outer circumference 16 of the first mixer part 12. The bottom wall 26 of the second mixer part 24 is formed in the area of the receiving end 34 of the reactant injection duct 32 with an outer circumferential contour adapted to the outer circumferential contour of the first mixer part 12, so that the second mixer part 34 can also adjoin the inner surface of an exhaust gas pipe essentially flush and leakage flows can be extensively avoided in this area. In case an exhaust gas pipe receiving the mixer 10 has, for example, an essentially circular cross-sectional contour, the outer circumferential contour of the first mixer part may correspond essentially to a circular contour. The outer circumferential contour of the bottom wall 26 in the area of the receiving end 34 of the reactant injection duct 32 may accordingly also correspond to a circular shape or to the segment of a circle.
The second mixer part 24 extends with a bottom wall extension area 38 beyond the side walls 28, 30 to a second area 40 of the outer circumference 16 of the first mixer part 12. The second mixer part 24 ends with an outer circumferential contour, which corresponds essentially to the outer circumferential contour of the first mixer part 12, in the bottom wall extension area 38 as well in order to obtain an essentially flush connection of the first mixer part 12 to the inner surface of an exhaust gas pipe in this area as well.
A deflecting wall 42, which is provided, for example, likewise as a shaped sheet metal part, is provided between the bottom wall extension area 38 and the plate shape body 14 of the first mixer part 12. The deflecting wall 42 has a plurality of passage openings 43 and is configured in the exemplary embodiment shown with an approximately W-like shape and it deflects a stream of reactant and exhaust gas, which is formed in the reactant injection duct 32, to respective main discharge openings 46, 48 formed in the area of a releasing end 44 of the reactant injection duct 32. Each of these main discharge openings 46, 48 is defined by the plate shape body 14 of the first mixer part 12, by one of the two side walls 28, 30, by the deflecting wall 42 and by the bottom wall extension area 38. As is indicated by flow arrows in
To support the flow guiding in the area of the main discharge openings 46, 48, flow deflection elements 50, 52 are provided at the side walls 28, 30, said flow deflection elements 50, 52 having the form of deflecting flaps, which are oriented in the direction away from the reactant injection duct 32 or from the releasing end 44 thereof. A nozzle effect contributing to the flow acceleration and hence to improved mixing can be generated in this manner in the area of the main discharge openings 46, 48.
In order to make possible the entry of exhaust gas into the reactant injection duct 32, an exhaust gas main passage opening 54 is formed in the plate shape body 14 of the first mixer part 12. This main passage opening 54 is located opposite the bottom wall 26 of the second mixer part 24 and is enclosed by an edge 56 extending in the direction away from the incoming flow side 28. The exhaust gas main passage opening 54 has approximately a drop-like shape, in which, starting from an end that is a radially outer end with respect to a central area of the plate shape body 14 and with respect to the exhaust gas main flow direction A, the width, i.e., the extension in the circumferential direction, at first increases in a first radial extension area and then decreases again in a second extension area in the direction of a radially inner end of the exhaust gas main passage opening 54. The length of extension, in which the width decreases again, is greater here than the length of extension, in which the width increases at first, starting from the radially outer end of the exhaust gas main passage opening.
The exhaust gas stream or a part of it, which flows in the exhaust gas main flow direction A towards the incoming flow side 18 of the first mixer part 12, passes through the exhaust gas main passage opening 54 and into the reactant injection duct 32. Reactant, which is injected in a reactant main injection direction R into the reactant injection duct 32, is deflected at least partially by the exhaust gas flowing through the exhaust gas main passage opening 54 in the direction of the bottom wall 26, so that an area 58, shown in
The part of the exhaust gas stream entering into the reactant injection duct 32 through the exhaust gas main passage opening 54 is mixed already partially in the reactant injection duct 32 with the reactant injected into this injection duct and leaves the reactant injection duct 32, as was already described above, mostly via the two main discharge openings 46, 48 provided in association with the side walls 28, 30. Another part of the mixture of exhaust gas and reactant, which is formed in the reactant injection duct 32, leaves the reactant injection duct 32 via the passage openings 43 in the deflecting wall 42 and via hole first secondary discharge openings 60 formed in the bottom wall 26 and at the bottom wall extension area 38. These hole first secondary discharge openings 60 may be arranged in a plurality of groups at the bottom wall 26 and at the bottom wall extension area 38. A second secondary discharge opening 62 and 64, respectively, is provided in the area of each side wall 28, 30. While no flow deflection element is provided in association with the first secondary discharge openings 60, a flow deflection element 66, 68, which is provided by a configuration in the form of a deflecting flap, is provided in association with each of these second secondary discharge openings 62, 64. For example, each second secondary discharge opening 62, 64 may be provided with the flow deflection element 66, 68 associated with this secondary discharge opening 62, 64 by preparing a U-shaped incision in the associated side wall 28, 30 and by bulging or bending out the flow deflection element 66, 68 out of the plane of the respective side wall 28, 30.
As can be seen in
Such second secondary discharge openings 70, 72 with flow deflection elements 74, 76 associated with them are also provided in the bottom wall extension area 38. These flow deflection elements 74, 76 also ensure that the mixture of reactant and exhaust gas, which flows farther in this area, will be deflected in a direction differing from the exhaust gas main flow direction A, which contributes to the intensified mixing of exhaust gas and reactant.
First exhaust gas secondary passage openings 78 with an essentially hole shape are provided in the first mixer part 12 in areas next to the reactant injection duct 32. As can be seen in
Further, a plurality of second exhaust gas secondary passage openings 80, 82, 84, 86, 88, 90, 92 are provided in the plate shape body of the first mixer part 12. While no flow deflection element is associated with each first exhaust gas secondary passage opening 78 either, a respective flow deflection element 94 and 96 provided by bulging the plate shape body 14 is associated with each second exhaust gas secondary passage opening 80, 82, 84, 86, 88, 90, 92. While the flow deflection elements 94 provided in association with the second exhaust gas secondary passage openings 80, 82, 84, 86, 88, 90 formed with a semicircular contour have the form of a calotte shell segment, the flow deflection element 96, which is provided in association with the second exhaust gas secondary passage opening 92, is configured in the form of a deflecting flap.
The two second exhaust gas secondary passage openings 80, 82 are positioned at the plate shape body 14 of the first mixer part 12 such that they are located in the area of the main discharge openings 46, 48. The flow deflection elements 94 associated with these two second exhaust gas secondary passage openings 80, 82 are oriented such that they deflect the exhaust gas passing through these second exhaust gas secondary passage openings 80, 82 in a direction that corresponds essentially to the flow direction of the mixture leaving the reactant injection duct 32 in the area of the main discharge openings 46, 48, so that this flow is supported. The second exhaust gas secondary passage openings 84, 86, 88, 90 are also positioned such that the flow deflection elements 94 associated with these support the flow in the circumferential direction. The second exhaust gas secondary passage opening 92 with the flow deflection element 96 configured in the manner of a deflecting flap is positioned such that the exhaust gas stream passing through this exhaust gas secondary passage opening 92 flows through the flow deflection element 96 in the direction of the rear side of the deflecting wall 42, which rear side faces away from the reactant injection duct 32. This exhaust gas stream is also deflected in the circumferential direction by the deflecting wall 42 configured with a curved W shape and it thus likewise supports the swirling and hence the mixing of exhaust gas and reactant.
The majority of the exhaust gas stream impinging on the first mixer part 12 on the incoming flow side 18 passes through the exhaust gas main passage opening 54 in case of the above-described configuration of a mixer 10 and mixes with the reactant injected in the reactant main injection direction R. The part of the exhaust gas passing through the exhaust gas secondary passage openings 78, 80, 82, 84, 86, 88, 90, 92 supports the swirling on the outflow side 22 of the first mixer part 12. The deflection of the reactant injected into the reactant injection duct 32 in the reactant main injection direction R towards the bottom wall 26 of the second mixer part 24 leads to an intensified contact of the reactant with the heated bottom wall 26 and thus to an intensified evaporation. The mixture of reactant and exhaust gas, which is thus formed, is deflected at first, supported by the deflecting wall 42 configured with a curved W shape, essentially in the circumferential direction and is then deflected and carried along by the part of the exhaust gas passing through the exhaust gas secondary passage openings 78, 80, 82, 84, 86, 88, 90, 92 in the direction of the exhaust gas main flow direction A.
It should further be noted that the number of exhaust gas secondary passage openings in the first mixer part 12 and the number of secondary passage openings in the second mixer part 24 may, of course, be selected such that these numbers are different than in the exemplary embodiment shown. This also pertains to the positioning of these openings.
It is seen clearly in
In this arrangement as well, the exhaust gas flowing towards the incoming flow side 18 of the first mixer part 12 has an exhaust gas main flow direction A, which is approximately at right angles to the reactant main injection direction R, in the area in which exhaust gas impinges on the first mixer part 12 and passes through the exhaust gas main passage opening 54, the reactant being injected into the reactant injection duct 32 through the injector 97 acting as a reactant injection device in the area of the receiving end 34.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 117 459.7 | Jun 2019 | DE | national |
