Patent Publication Number: US-11384671-B2

Title: Gas/gas mixer for introducing gas into the exhaust gas stream of an internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2020 101 134.2, filed Jan. 20, 2020, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention pertains to a gas/gas mixer, with which gas can be introduced into the exhaust gas stream of an internal combustion engine. 
     TECHNICAL BACKGROUND 
     A gas/gas mixer in which a mixer body with a drop-like cross section protrudes into an exhaust gas flow duct formed in a tubular exhaust gas carrying element is known from DE 10 2018 108 592 A1. Exhaust gas flowing in the exhaust gas flow duct can flow around the mixer body in the manner of a support surface, and the mixer body has a plurality of gas release openings, via which a gas feed volume of gas flowing in the interior of the mixer body is released into the exhaust gas stream that is flowing around the mixer body. 
     SUMMARY 
     An object of the present invention is to provide a gas/gas mixer for introducing gas into the exhaust gas stream of an internal combustion engine, with which an improved mixing of exhaust gas with a gas to be introduced into the exhaust gas stream can be achieved. 
     This object is accomplished according to the present invention by a gas/gas mixer for introducing gas, especially air or burner exhaust gas, into the exhaust gas stream of an internal combustion engine, comprising an exhaust gas flow duct in an exhaust gas carrying element, through which exhaust gas can flow, a mixer body arranged in the exhaust gas carrying element with a plurality of exhaust gas flow openings, through which exhaust gas flowing in the exhaust gas flow duct can flow, wherein a gas feed volume, through which gas to be introduced into the exhaust gas stream can flow, is formed in the mixer body, and wherein the gas feed volume is open towards the exhaust gas flow duct via a plurality of gas release openings. 
     In the configuration according to the present invention, the gas/gas mixer has not only gas release openings, through which the exhaust gas to be introduced into the exhaust gas stream is released, but also has exhaust gas flow openings, through which the exhaust gas or at least a substantial part thereof flowing in the exhaust gas flow duct flows. As a result, when the exhaust gas flows through the exhaust gas flow openings on the downstream side of the mixer body, a swirling is generated, which brings about an efficient mixing of the gas that is released from the gas release openings of the mixer body and carried along by the exhaust gas stream. 
     For a configuration which can be embodied in a simple manner and which brings about an efficient flow of exhaust gas through the mixer body, it is proposed that the mixer body have a plate-shaped configuration and be arranged in the exhaust gas carrying element obliquely to an exhaust gas main flow direction of the exhaust gas flowing through the exhaust gas flow duct. 
     The gas feed volume can be provided in the mixer body, for example, by the mixer body comprising a first mixer body part that is arranged oriented in the upstream direction in the exhaust gas carrying element and a second mixer body part that is arranged in the downstream direction in the exhaust gas carrying element, wherein the gas feed volume is formed essentially between the first mixer body part and the second mixer body part. 
     In this connection, to obtain the plate-shaped configuration of the mixer body, the first mixer body part may have an essentially plate-shaped configuration and the second mixer body part may have an essentially plate-shaped configuration. 
     It should be pointed out in this connection that a structure of the mixer body and of the mixer body parts, in which these mixer body or mixer body parts have a markedly smaller thickness than their extension obliquely to the thickness direction, is addressed with the term “plate-shaped” in the sense of the present invention. 
     For fixing the mixer body to the exhaust gas carrying element. which fixing can be embodied in a simple manner, it is proposed that a fastening area fixed to the exhaust gas carrying element be provided at one of the mixer body parts, preferably at the second mixer body part, and that a second fastening area fixed to the one mixer body part be provided at the other mixer body part, preferably at the first mixer body part. 
     In this case, for example, the first fastening area may comprise a preferably essentially cylindrical fastening edge that is fixed to an inner circumferential surface of the exhaust gas carrying element in an outer circumferential area of the one mixer body part, or/and that the second fastening area may comprise a preferably essentially cylindrical fastening edge, which is fixed to the one mixer body part, in an outer circumferential area of the other mixer body part. 
     A plurality of flow-through holes may be provided for providing the exhaust gas flow openings in the second mixer body part, and a preferably tubular or funnel-shaped flow-through bulge, which extends to the second mixer body part, carries exhaust gas in the direction of the associated flow-through hole and provides a flow duct of the first mixer body part, may then be provided in the first mixer body part in association with each flow-through hole of the second mixer body part. 
     An efficient mixing of exhaust gas and gas to be introduced into same can be further supported by in at least one, preferably in each exhaust gas flow opening, a gas release opening being formed between a flow-through hole edge area of the second mixer body part, which flow-through hole edge area encloses the flow-through hole in the second mixer body part, and the flow-through bulge of the first mixer body part. The gas release openings have thus a ring-like structure and bypass, with this ring-like structure, each an area, in which exhaust gas flowing through a respective exhaust gas flow opening is carried. 
     As an alternative or in addition, at least one gas release opening may be provided in the second mixer body part between the flow-through holes provided in the second mixer body part. Further, at least one gas release opening may be provided in the first mixer body part, preferably in the area of at least one flow-through bulge. 
     Here, for a defined introduction of the gas into the exhaust gas stream between the exhaust gas flow openings, in at least one, preferably in each exhaust gas flow opening, the flow-through bulge may be in contact with a flow-through hole edge area of the second mixer body part, which flow-through hole edge area encloses the flow-through hole in the second mixer body part, preferably such that the gas feed volume is essentially closed against the discharge of gas in the area of this exhaust gas flow opening. 
     For a thermally stable configuration that can be embodied in a simple and cost-effective manner, it is proposed that the first mixer body part be a shaped sheet metal part, or/and that the second mixer body part be a shaped sheet metal part. 
     For feeding the gas to be introduced into the exhaust gas stream, at an outer circumferential area of the mixer body, a gas feed duct, which is passed through a wall of the exhaust gas carrying element, may be open towards the gas feed volume. 
     Efficient mixing of gas and exhaust gas can be further guaranteed by the mixer body being arranged in the exhaust gas carrying element such that exhaust gas essentially only flows through the exhaust gas flow openings in the exhaust gas flow duct in the area of the mixer body. It is thus guaranteed that the entire exhaust gas flowing in the exhaust gas flow duct flows through the exhaust gas flow openings provided in the mixer body and is thus sent into an area, in which the gas to be introduced into the exhaust gas is discharged from the mixer body. 
     The present invention further pertains to an exhaust system for an internal combustion engine of a vehicle, comprising a gas/gas mixer having the configuration according to the present invention. 
     The present invention will be described 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a partial longitudinal sectional view of a gas/gas mixer in an exhaust system of an internal combustion engine; 
         FIG. 2  is a view corresponding to  FIG. 1  of an alternative type of configuration of the gas/gas mixer; and 
         FIG. 3  is a view of an alternative type of configuration of a gas/gas mixer in the area of an exhaust gas flow opening. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings,  FIG. 1  shows a gas/gas mixer  12  arranged in an exhaust system  10  of an internal combustion engine. The gas/gas mixer  12  comprises a tubular, for example, essentially cylindrical exhaust gas carrying element  14 , which encloses an exhaust gas flow duct  18  with a tubular wall  16 . In the exhaust gas flow duct  18 , exhaust gas A flows essentially in an exhaust gas main flow direction H along the exhaust gas carrying element  14 . It should be pointed out that flow directions deviating from the exhaust gas main flow direction H may be present locally. In principle, the exhaust gas main flow direction H may essentially also correspond to the longitudinal extension direction or to a longitudinal central axis L of the tubular exhaust gas carrying element  14 . 
     The gas/gas mixer  12  comprises a mixer body  20  in the exhaust gas carrying element  14 . The mixer body  20  has, in principle, a plate-shaped configuration, which means that its extension, for example, obliquely to the exhaust gas main flow direction H or to the longitudinal central axis L is markedly greater than its extension in the exhaust gas main flow direction H. The mixer body  20  is arranged in the exhaust gas carrying element  14  or in the exhaust gas flow duct  18  essentially obliquely to or at right angles to the exhaust gas main flow direction H, which means that the mixer body  20  with its direction of thickness or thickness extension is oriented essentially in the exhaust gas main flow direction H or in the direction of the longitudinal central axis L. 
     The mixer body  20  comprises two mixer body parts  22 ,  24 . The first mixer body part  22  is arranged, in principle, in the exhaust gas flow duct  18  such that it is oriented in the upstream direction, so that the exhaust gas A flowing towards the mixer body  20  in the exhaust gas main flow direction H at first impinges on the first mixer body part  22 . The second mixer body part  24  is oriented in the downstream direction in the exhaust gas flow duct  18  and is thus positioned essentially on the downstream side of the first mixer body part  22 . The two mixer body parts  22 ,  24  also have a plate-shaped configuration and are provided, for example, as shaped sheet metal parts. 
     The second mixer body part  24  is adapted in its outer circumferential contour to the inner circumferential contour of the wall  16  of the tubular exhaust gas carrying element  14 . If the exhaust gas carrying element  14  has, for example, a circular inner circumferential contour in the area, in which the mixer body  20  is positioned, then the outer circumferential contour of the second mixer body part is advantageously likewise circular. 
     For fixing to the wall  16  of the exhaust gas carrying element  14 , the second mixer body part  24  has in an outer circumferential area  26  of same a fastening edge  28 , which is bent in the exhaust gas main flow direction H and preferably extends completely circularly in the circumferential direction. In an end area, the fastening edge  28  is fixed by welding  30  to the inner surface of the wall  16  of the exhaust gas carrying element  14 , so that when the fastening edge  28  is configured as extending completely circularly in the circumferential direction, the passage of exhaust gas between the wall  16  of the exhaust gas carrying element  14  and the second mixer body part  24  is not possible. 
     It should be pointed out that, in principle, the fastening edge  28  could also be configured with a plurality of fastening edge straps, which are deflected in the exhaust gas main flow direction H and provided at spaced locations to one another and fixed, for example, each by welding to the exhaust gas carrying element  14 . 
     The first mixer body part  22  is fixed on the side of the plate-shaped second mixer body part  24 , which side is oriented in the upstream direction. The first mixer body part  22  has an outer circumferential contour, which corresponds approximately to the outer circumferential contour of the second mixer body part  24  or to the inner circumferential contour of the exhaust gas carrying element, but has smaller dimensions than the second mixer body part  24 . The first mixer body part  22  has, in its outer circumferential area  32 , a fastening edge  34  that is deflected in the exhaust gas main flow direction H and preferably extends completely circularly in the circumferential direction. This fastening edge is fixed by welding  36  to the side of the second mixer body part  24 , which side is oriented in the upstream direction. 
     It should be pointed out that the two mixer body parts  22 ,  24  could also be configured such that the first mixer body part  22  has somewhat larger dimensions than the second mixer body part  24  and has a fastening edge  34  extending to a greater extent in the exhaust gas main flow direction H. This fastening edge may then extend around the fastening edge  28  of the second mixer body part  24  on its outer side, so that the second mixer body part  24  can be inserted into the first mixer body part  22 . The fastening edge  34  of the first mixer body part  22  is fixed by welding to the wall  16  of the exhaust gas carrying element  14 , and the fastening edge  28  of the second mixer body part  24  is fixed by welding to the fastening edge  34  of the first mixer body part  22  or/and to the wall  16  of the exhaust gas carrying element  14 . For example, the dimensions of the two fastening edge areas  34 ,  28  may be such that they end approximately in the same area in the exhaust gas main flow direction H and are connected by joint welding to the wall  16  of the exhaust gas carrying element  14 . 
     A gas feed volume  38  is formed between the two mixer body parts  22 ,  24 . In a circumferential area a gas feed line  40  is passed through the wall  16  of the exhaust gas carrying element  14  and through the fastening edge  34  of the first mixer body part  22  and is thus connected, for example, to each by welding permanently and in a gastight manner (gastight). A gas feed duct  42 , which opens into the gas feed volume  38  and through which gas G to be introduced into the exhaust gas A is sent into the gas feed volume  38 , is provided in the exhaust gas feed line  40 . 
     The mixer body  20  has a plurality of exhaust gas flow openings  44 , through which the exhaust gas A flowing in the exhaust gas main flow direction H towards the mixer body  20  or towards the first mixer body part  22  can flow through the mixer body  20 . To provide the exhaust gas flow openings  44 , which can be arranged distributed, for example, in a regular pattern, the second mixer body part  24  has a plurality of flow-through holes  48  surrounded by a flow-through hole edge area  46 . For example, the flow-through holes  48  may have a circular contour. 
     A flow-through bulge  50  is provided at the first mixer body part  22  in association with each flow-through hole  48  in the second mixer body part  24 . This flow-through bulge  50  may be provided, for example, as a flanged hole and with its tubular or funnel-shaped structure provides a flow duct  52  for the exhaust gas A. Because of the constriction of the flow cross section occurring in the area of the exhaust gas flow openings  44 , the exhaust gas A flowing through the exhaust gas flow openings  44  is accelerated during the passage through the exhaust gas flow openings  44 , so that the flow velocity increases. 
     The first mixer body part  22  is dimensioned or shaped in the area of its flow-through bulges  50  such that a ring-like intermediate space, which provides a gas release opening  56 , is formed in each case between the downstream end areas  54  of the flow-through bulges  50  and the corresponding flow-through hole edge areas  46 . The gas G introduced into the gas feed volume  38  is discharged from the gas feed volume  38  via these gas release openings  56  having a ring-like configuration and thus reaches the stream of the exhaust gas A flowing through the flow-through bulges  50  or in the flow ducts  52 . Because of the fact that the exhaust gas A is accelerated in the area of the exhaust gas flow openings  44  and a swirling is generated during the passage through the flow-through holes  48  or downstream thereof, the gas G introduced into the exhaust gas stream in these areas is efficiently mixed with the exhaust gas A. Since the flow-through bulges  50  are dimensioned or coordinated with the flow-through holes  48  such that these flow-through bulges have a smaller dimension especially in the area of their downstream edges  54  than the flow-through holes  48 , it is guaranteed that the exhaust gas A flowing through the flow ducts  52  is sent through the flow-through holes  48  such that no exhaust gas A can reach the gas feed volume  38  via the gas release openings  56 , even if, as shown in  FIG. 1 , the flow-through bulges  50  end in the exhaust gas main flow direction H in front of the second mixer body part  24  and thus already in front of the flow-through holes  48 . Rather, because of the comparatively high flow velocity of the exhaust gas A in the area of the flow ducts  52 , a suction pump effect is generated, which suctions the gas G present in the exhaust gas feed volume  38  independently of a possibly present gas overpressure into the stream of the exhaust gas flowing through the flow ducts  52 . 
       FIG. 2  shows a modified type of embodiment of the exhaust gas mixer  12 . In regard to the basic configuration of the mixer body  20  with its two mixer body parts  22 ,  24 , the configuration in this case corresponds to the configuration described above. In this embodiment, the two mixer body parts  22 ,  24  also have a plate-shaped configuration, for example, as shaped sheet metal parts. The second mixer body part  24  is with its fastening edge  28  fixed by welding  30  to the wall  16  of the exhaust gas carrying element  14 , and the first mixer body part  22  is fixed with its fastening edge  34  by welding  36  to the second mixer body part  24 , so that the gas feed volume  38  is formed between the two mixer body parts  22 ,  24 . 
     In the embodiment shown in  FIG. 2 , the flow-through bulges  50  are shaped or coordinated with the flow-through holes  48  associated with each of these bulges  50  such that the downstream end areas  54  of the flow-through bulges  50  are in contact with the flow-through hole edge areas  46  of each of the associated flow-through holes  48 . Thus, essentially no intermediate space is formed in the area, in which the flow-through bulges  50  adjoin the associated flow-through hole edge areas  46 , so that a discharge of gas G from the gas feed volume  38  directly in the area of the exhaust gas flow openings  44  is essentially not intended. For example, the flow-through bulges  50  with their downstream end areas  54  can be pressed against the associated flow-through edge areas  46  when the first mixer body part  22  is connected to the second mixer body part  24 , so that an essentially gastight closing forms. Gas leaks in these areas caused by manufacturing tolerances are, however, in principle, harmless, since, on the one hand, the gas/gas mixer  12  is intended anyway for introducing the gas G into the exhaust gas A, and since, on the other hand, a substantial gas leak in these areas will not occur. A connection in substance of the two mixer body parts  22 ,  24  in the area of the downstream end areas  54  of the flow-through bulges  50  to the flow-through hole edge areas  46  of the second mixer body part  24  can, in principle, be provided, but is not necessary. 
     In the second mixer body part  24 , the gas release openings  56 , which have a hole-like configuration here as well, are provided in areas between the flow-through holes  48 . These gas release openings  56  may, just as the flow-through holes  48 , be provided in a regular pattern to achieve an approximately uniform introduction of the gas G into the exhaust gas A over the entire cross section. Considering the fact that the flow velocity and thus the throughput close to the wall  16  will be smaller than in the central area of the exhaust gas flow duct  18 , provisions may be made in all embodiments according to the present invention that the density of the exhaust gas flow openings  44  or the total passage cross-sectional area provided by the exhaust gas flow openings  44  in the central area of the exhaust gas flow duct  18  is greater than in an area close to the wall  16  or increases from the wall  16  to the central area. This may also be provided in the gas release openings  56  so that where an especially greater portion of the exhaust gas A flows, a greater portion of the gas G is also introduced into the exhaust gas A. 
     It should be pointed out that, what a comparison of  FIGS. 1 and 2  clearly shows, the dimensions of the mixer body  20  may also be influenced substantially by the configuration of the two mixer body parts  22 ,  24 . Thus, the size of the gas feed volume  38  can be influenced, for example, by the length of the flow-through bulges  50  or of the fastening edge  34  of the first mixer body part  22 . While the gas feed volume  38  has a greater extension in the exhaust gas main flow direction H in the exemplary embodiment shown in  FIG. 1 , the mixer body  20  in the embodiment according to  FIG. 2  has a flatter configuration due to a corresponding configuration of the first mixer body part  22 . 
     Further, it should be pointed out that the embodiments shown in  FIGS. 1 and 2  may obviously be combined with each other. Thus, both gas release openings  56  with the ring-like structure shown in  FIG. 1  can be provided in the area of the exhaust gas flow openings  44  and gas release openings  56  with the hole-like structure shown in  FIG. 2  may be provided in the area between the exhaust gas flow openings  44 . In this embodiment, for example, some of the exhaust gas flow openings  44  may have such a configuration, as shown in  FIG. 1 , i.e., with gas release opening  56  provided in association with it, while other exhaust gas flow openings  44  may have such a configuration, as shown in  FIG. 2 , i.e., without associated gas release opening. 
     A variant of the gas/gas mixer especially in regard to the configuration in the area of the exhaust gas flow openings  44  is shown in  FIG. 3 . In the area of the exhaust gas flow opening  44  which can be seen in  FIG. 3 , the second mixer body part  24  is shaped such that the flow-through hole edge area  46  enclosing the flow-through hole  48  is deflected against the exhaust gas main flow direction H, for example, is provided as a flanged hole. The flow-through hole edge area  46  is shaped or dimensioned such that it provides a larger opening cross section than the flow-through bulge  50  at the first mixer body part  22 . In particular, the dimensioning is such that the flow-through bulge  50  extends in the area of the flow-through hole  48  into the volume enclosed by the flow-through hole edge area  46  and overlaps with the flow-through hole edge area  46  in the exhaust gas main flow direction H. 
     The ring-like intermediate space formed between the flow-through hole edge area  46  deflected against the exhaust gas main flow direction H and the flow-through bulge  50  provides a gas release opening  56 , which, as in the exemplary embodiment of  FIG. 1 , has, in principle, a ring-like configuration and via which the gas G fed via the gas feed volume  38  is introduced into the exhaust gas A flowing through the exhaust gas flow duct  52  in the first mixer body part  22 . Also, in this embodiment, because of the fact that the flow-through bulge  50  extending in the exhaust gas main flow direction H meshes with the flow-through hole edge area  46  extending opposite the exhaust gas main flow direction H or the volume enclosed by this flow-through hole edge area  46 , an entry of exhaust gas A into the gas feed volume  38  is ruled out. 
     It should be noted that the gas/gas mixer  12  shown in the figures can be varied in many different aspects, without deviating from the principles of the present invention. Thus, for example, in the embodiment shown in  FIG. 1 , the flow-through bulges  50  may also be dimensioned such that they extend into the flow-through holes  48  or they extend through them. In all embodiments, as an alternative or in addition, one or more gas release openings  56  may also each be provided in the area of the flow-through bulges  50 , as this is suggested in  FIG. 2 . 
     The exhaust gas flow openings  44  may have, for example, a circular opening cross section, but may also be provided with an elliptical, oval or other cross-sectional geometry. The same also applies to the gas release openings  56 . Further, the two mixer body parts  22 ,  24  may be provided as integral components of a component provided by shaping a sheet metal blank, which can be folded over and then fixed to one another, e.g., by welding in some areas. 
     With the mixer according to the present invention, it is possible to introduce gas G into the exhaust gas stream over the entire cross section of the exhaust gas flow duct  18  and to mix same efficiently together with the exhaust gas flowing in the exhaust gas flow duct  18 . In this case, the gas G to be mixed with the exhaust gas A may be, for example, the exhaust gas provided by a burner, which in a start phase of the combustion operation of an internal combustion engine can ensure a more rapid heating in case of a still cold catalytic converter device positioned downstream of the gas/gas mixer. In principle, any other type of gas, for example, air, could be mixed with the exhaust gas stream in order to obtain an improved operating characteristic in system areas following downstream of the gas/gas mixer  12 . 
     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.