Exhaust gas aftertreatment system for an internal combustion engine

Abstract

The invention relates to an exhaust gas aftertreatment system for an internal combustion engine comprising a first catalytic converter that has a first exhaust gas inlet to admit the exhaust gas into the first catalytic converter and has an exhaust gas outlet positioned on the opposite side, also comprising a second catalytic converter that is arranged downstream from the first catalytic converter and that is flow-connected to the first catalytic converter in order to allow the exhaust gas to pass from the first catalytic converter into the second catalytic converter and that likewise has a second exhaust gas inlet that is at a physical distance from the exhaust gas outlet of the first catalytic converter. The exhaust gas aftertreatment system also comprises a particulate filter that is arranged downstream from the second catalytic converter and that is flow-connected to the second catalytic converter in order to allow the exhaust gas to pass from the second catalytic converter into the particulate filter. A flow-around area is formed adjacent to an outer surface of the first catalytic converter in which the exhaust gas flows from the exhaust gas outlet to the second exhaust gas inlet into the second catalytic converter.

Claims

1. An exhaust gas aftertreatment system for an internal combustion engine, comprising: a first catalytic converter that has an exhaust gas inlet to admit exhaust gas into the first catalytic converter and an exhaust gas outlet positioned on an opposite side of the first catalytic converter therefrom, wherein the first catalytic converter is installed in a housing and is configured to be cylindrical; a second catalytic converter that is arranged downstream from the first catalytic converter and that is flow-connected to the first catalytic converter in order to allow the exhaust gas to pass from the first catalytic converter into the second catalytic converter, and that has an exhaust gas inlet that is at a physical distance from the exhaust gas outlet of the first catalytic converter; a particulate filter that is arranged downstream from the second catalytic converter and that is flow-connected to the second catalytic converter in order to allow the exhaust gas to pass from the second catalytic converter into the particulate filter; a flow-around area formed adjacent to an outer surface of the first catalytic converter in which the exhaust gas flows from the exhaust gas outlet to the exhaust gas inlet of the second catalytic converter, wherein the flow-around area is formed by a space between the housing and the first catalytic converter and surrounds the first catalytic converter; and a first exhaust gas conveying direction distance that is created between the housing and the first catalytic converter on a side facing away from the second catalytic converter, wherein this first exhaust gas conveying direction distance widens in the first exhaust gas conveying direction.

2. The exhaust gas aftertreatment system according to claim 1, wherein the flow-around area is formed adjacently around a lateral surface of the first catalytic converter.

3. The exhaust gas aftertreatment system according to claim 1, further comprising a deflection device being positioned at an outlet side of the first catalytic converter, said deflection device being configured to feed the exhaust gas from the outlet side of the first catalytic converter to the flow-around area of the first catalytic converter.

4. The exhaust gas aftertreatment system according to claim 1, wherein the first catalytic converter has a first exhaust gas conveying direction to allow the exhaust gas to pass through, wherein the second catalytic converter has a second exhaust gas conveying direction to allow the exhaust gas to pass through, and wherein the first catalytic converter is oriented relative to the second catalytic converter in such a way that the first and the second exhaust gas conveying directions are oriented between 45° and 135° relative to each other.

5. The exhaust gas aftertreatment system according to claim 4, wherein the first catalytic converter is oriented relative to the second catalytic converter in such a way that the first and the second exhaust gas conveying directions are oriented between 60° and 120° relative to each other.

6. The exhaust gas aftertreatment system according to claim 5, wherein the first catalytic converter is oriented relative to the second catalytic converter in such a way that the first and the second exhaust gas conveying directions are oriented perpendicular to each other.

7. The exhaust gas aftertreatment system according to claim 1, wherein the flow-around area is configured above and/or below the first catalytic converter, as seen from the first exhaust gas conveying direction in a cross sectional view of the first catalytic converter.

8. The exhaust gas aftertreatment system according to claim 1, further comprising a second exhaust gas conveying direction distance that is created between the housing and the first catalytic converter on the outlet side, wherein this second exhaust gas conveying direction distance tapers in the second exhaust gas conveying direction.

9. The exhaust gas aftertreatment system according to claim 1, wherein the first catalytic converter is configured as a metal catalytic converter, and wherein the second catalytic converter is configured as a metal catalytic converter or as a ceramic catalytic converter.

10. The exhaust gas aftertreatment system according to claim 1, wherein the first catalytic converter and/or the second catalytic converter is/are provided with a washcoat layer with or without a precious metal.

11. The exhaust gas aftertreatment system according to claim 1, wherein the particulate filter is provided with a washcoat layer with or without a precious metal.

12. A motor vehicle, comprising an internal combustion engine with an exhaust gas aftertreatment system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained below on the basis of embodiments making reference to the accompanying drawings. The following is shown:

(2) FIG. 1 is an embodiment of an exhaust gas aftertreatment system according to the invention; and

(3) FIG. 2 is a cross sectional view of the first catalytic converter in the configuration according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an exemplary embodiment of an exhaust gas aftertreatment system 1 according to the invention. Other additional components are shown in the present depiction in which the exhaust gas aftertreatment system 1 has been installed, whereby the technical depiction serves merely for illustration purposes and the invention is not limited to such an implementation. Exhaust gas from an internal combustion engine 70 is fed to the exhaust gas aftertreatment system 1. In this context, the internal combustion engine 70, preferably a gasoline engine, is shown schematically. Moreover, a turbocharger having a compressor 72 and a turbine 90 is shown by way of example. Via a connecting flange 92, for example, an inlet funnel 94 adjoins the turbine 90. In this embodiment, by way of example, the exhaust gas is fed to the exhaust gas aftertreatment system 1 via the inlet funnel 94. In this exemplary embodiment, the inlet funnel 94 is slanted on the outlet side and it deflects the exhaust gas stream away through the tilted funnel opening, as can be seen in FIG. 1, whereby this, too, is only a structurally suitable implementation by way of an example, although the invention is not limited to this.

(5) The exhaust gas aftertreatment system 1 also comprises a first catalytic converter 10. The first catalytic converter 10 also has an exhaust gas outlet 11 to admit the exhaust gas into the first catalytic converter 10. In this exemplary arrangement, a feed side 24 of the first catalytic converter 10 adjoins the funnel opening of the inlet funnel 94. The exhaust gas flows through the first catalytic converter 10 and is discharged again at an exhaust gas outlet 12 situated opposite from the first exhaust gas inlet 11. Moreover, a second catalytic converter 30 is positioned downstream from the first catalytic converter 10.

(6) This second catalytic converter 30 is flow-connected to the first catalytic converter 10 in order to allow the exhaust gas to pass from the first catalytic converter 10 into the second catalytic converter 30. In this preferred embodiment, the second catalytic converter 30 adjoins the first catalytic converter 10 in a compact manner. The second catalytic converter 30 also has an exhaust gas inlet 31 that is at a physical distance from the exhaust gas outlet 12 of the first catalytic converter 10.

(7) The first catalytic converter 10 as well as the second catalytic converter 30 can preferably be configured as three-way catalytic converters that consequently convert carbon monoxide (CO), nitrogen oxides (NO.sub.x) and unburned hydrocarbons (HC) into carbon dioxide (CO.sub.2), nitrogen (N.sub.2) and water (H.sub.2O). The first catalytic converter 10 or the second catalytic converter 30 can also be provided with a washcoat layer, especially in the form of suitable metal oxides. The first catalytic converter 10 is preferably configured as a metal catalytic converter because of the faster light-off, while the second catalytic converter 30 can be configured as a metal catalytic converter or as a ceramic catalytic converter.

(8) Moreover, the exhaust gas aftertreatment system 1 comprises a particulate filter 50 arranged downstream from the second catalytic converter 30. This particulate filter 50 is flow-connected to the second catalytic converter 30 in order to allow the exhaust gas to pass from the second catalytic converter 30 into the particulate filter 50. Here, too, by way of example, the particulate filter 50 immediately or directly adjoins the second catalytic converter 30, although the invention is not limited to this. In other embodiments, when yet another, third catalytic converter adjoins the second catalytic converter 30, the particulate filter 50 can also be positioned in the undercarriage of a motor vehicle, that is to say, far away from the engine, and not near the engine as shown in FIG. 1 by way of example. Therefore, in FIG. 1, the first catalytic converter 10, the second catalytic converter 30 as well as the particulate filter 50 are all positioned near the engine. As a result, the waste heat from the catalytic converters 10, 20 as well as from the particulate filter 50 generated in the internal combustion engine 70 is advantageously absorbed, thereby bringing about an improvement of the performance of the catalytic properties. In this context, the particulate filter 50 is preferably a gasoline particulate filter. Preferably, this gasoline particulate filter is configured without a coating in this embodiment, but in other embodiments, appropriate coatings can be provided. By way of example, an outlet 52 leading out of the exhaust gas aftertreatment system 1 is shown behind the particulate filter 50.

(9) A flow-around area 20 is formed adjacently around an outer surface 14 of the first catalytic converter 10. The exhaust gas flows in the flow-around area 20 from the exhaust gas outlet 12 of the first catalytic converter 10 to the exhaust gas inlet 31 into the second catalytic converter 30. In this context, the flow-around area 20 constitutes a flow volume that is in physical contact with the outer surface 14 of the first catalytic converter 10. The flow-around area surrounds or sheathes the first catalytic converter 10 at least partially or else almost completely. The catalytic converters are usually configured to be cylindrical. Then the flow-around area is preferably formed adjacently around a lateral surface of the first catalytic converter 10. As a result, an especially uniform heating of the first catalytic converter or of its catalytic converter substrate is achieved. An exemplary schematic depiction of the flow-around area 20 can be seen in FIG. 2 in a cross sectional view.

(10) Therefore, the exhaust gas flows around the first catalytic converter 10 or around its outer surface 14 after the exhaust gas stream has passed through the first catalytic converter 10. The exhaust gas stream then flows all the way to the second exhaust gas outlet 31 from the exhaust gas outlet 12 of the first catalytic converter 10. Only then is the exhaust gas stream coupled or introduced into the second catalytic converter 30 via the second exhaust gas inlet 31, so that as a result, a catalytic effect is brought about by the second catalytic converter 30.

(11) Purely schematic flow lines have been drawn in FIG. 1 for this purpose, and these lines describe an exemplary flow path. From the exhaust gas outlet 11 of the first catalytic converter, a first catalytic exhaust gas stream 17 flows in a first exhaust gas conveying direction 13 all the way to the exhaust gas outlet 12 of the first catalytic converter 10. A catalytic effect already takes place in this section. Starting from the exhaust gas outlet 12, the exhaust gas stream is deflected and fed to the flow-around area 20. Then the exhaust gas stream forms a heat-exchanging exhaust gas stream 22 that describes an exhaust gas flow path—which is only indicated schematically here due to the cross sectional view—from the exhaust gas outlet 12 through the flow-around area 20 and to a discharge side 25 and then to the exhaust gas inlet 31 of the second catalytic converter 30. In this flow section, heat is transmitted to the first catalytic converter 10. Subsequently, the exhaust gas penetrates into the second catalytic converter 30 via the exhaust gas inlet 31 of the second catalytic converter 30 and forms a second catalytic exhaust gas stream 37 that flows in a second exhaust gas conveying direction 33. A catalytic effect takes place once again in this section.

(12) In this preferred embodiment, the first catalytic converter 10 is accommodated in a housing 16. In this embodiment, the housing 16 surrounds at least the first catalytic converter 10. By virtue of the housing 16, the flow-around area 20 is formed by a space 15 between the housing 16 and the first catalytic converter 10.

(13) Moreover, in this exemplary embodiment, a deflection device 18 is positioned on an outlet side 26 of the first catalytic converter 10 where the exhaust gas outlet 12 is positioned. This deflection device 18 is configured to feed the exhaust gas from the outlet side 26 of the first catalytic converter 10 to the flow-around area 20 of the first catalytic converter 10. Such a deflection device can be, for example, a metal plate or a baffle plate that imparts the exhaust gas with a desired flow direction. For example, the deflection device 18 can have an opening that is oriented in the deflection direction. In this context, the opening can have various orientations so that the flow optimally strikes the first catalytic converter 10 in a certain manner, depending on the geometry and on the arrangement. In particular, this yields a suitable flow towards the first catalytic converter 10 so that the exhaust gas flows uniformly through the flow-around area.

(14) In this embodiment, the first catalytic converter 10 is oriented vertically relative to the second catalytic converter 30. In other words, this means that the first exhaust gas conveying direction 13 is oriented perpendicular to the second exhaust gas conveying direction 33. As a result, the exhaust gas stream is deflected by effectively 90° inside the housing 16 from the first exhaust gas conveying direction 13 in the direction of the second exhaust gas conveying direction 33. In other embodiments of the invention, the first and the second exhaust gas conveying directions 13, 33 can be oriented between 45° and 135° relative to each other, more preferably between 60° and 120°.

(15) In this exemplary embodiment, the first catalytic converter 10 and the second catalytic converter 30 have a linear arrangement. Here, in particular, the first catalytic converter 10, the second catalytic converter 30 and the particulate filter 50 even form a linear arrangement, which translates into a compact structure.

(16) The exhaust gas stream from the outlet side 26 of the first catalytic converter 10 is deflected by the housing 16 and/or deflected with the assistance of the deflection device 18 positioned in-between.

(17) For this purpose, the housing 16 is oriented on the outlet side 26 in such a way that the outgoing exhaust gas stream is deflected, here initially from the first exhaust gas conveying direction 13 in the opposite direction to the second exhaust gas conveying direction 33. Here, the housing 16 forms a bulging rounded segment 19 on the outlet side 26. In this case, by way of example, the rounded segment 19 extends towards the outside in order to assist the deflection of the exhaust gas stream away from the second catalytic converter 30.

(18) For example, a first distance d1 between the housing 16 and the first catalytic converter 10 on the outlet side 26 can taper in the second exhaust gas conveying direction 33 so that the incoming exhaust gas stream is deflected away from the second catalytic converter 30. Moreover, in this embodiment, the housing 16 has a rounded segment 19 in order to improve the flow-around properties. Furthermore, as shown by way of example in FIG. 1, a second distance d2 between the housing 16 and the first catalytic converter 10 can widen in the first exhaust gas conveying direction 13 on the side facing away from the second catalytic converter 30. As a result, the entry into the flow-around area 20 adjacent to the outer surface 14 can be improved in the direction of the second catalytic converter 30.

(19) FIG. 2 shows a cross sectional view of the first catalytic converter 10—as seen in the first exhaust gas conveying direction 13; in this context, also see the sectional view references shown in FIG. 1.

(20) Here, the cross section of the first catalytic converter 10 is configured cylindrically purely by way of example. The flow-around area 20 is adjacent to the outer surface 14 of the first catalytic converter 10. The outer surface 14 forms a lateral surface of the first catalytic converter 10. Purely by way of example, a flow-around area 20 is shown schematically as a space 15 between the first catalytic converter 10 and the housing 16.

(21) The flow-around area 20 in the cross sectional view of the first catalytic converter 10—as seen from the first exhaust gas conveying direction 13—is formed by way of example above and below the first catalytic converter 10. This means that the lateral surface—as seen in the cross section—divides the exhaust gas stream into two flow components that flow in opposite rotational directions in the flow-around area 20 around the first catalytic converter 10; in this context, see the drawn arrows. In this manner, a particularly uniform heating is achieved, whereby the invention is not restricted to this. However, the invention is not limited to such a flow-around course.

(22) After the exhaust gas stream has flowed around the first catalytic converter 10, it enters the second catalytic converter 30 where the catalytic reactions then take place. The exhaust gas then follows the catalytic exhaust gas stream 37 as shown in FIG. 1.

LIST OF REFERENCE NUMERALS

(23) 1 exhaust gas aftertreatment system 10 first catalytic converter 11 exhaust gas inlet 12 exhaust gas outlet 13 first exhaust gas conveying direction 14 outer surface 15 space 16 housing 17 first catalytic exhaust gas stream 18 deflection direction 19 rounded segment 20 flow-around area 22 heat-exchanging exhaust gas stream 24 feed side 25 discharge side 26 outlet side 30 second catalytic converter 31 exhaust gas inlet 33 second exhaust gas conveying direction 37 second catalytic exhaust gas stream 50 particulate filter 52 outlet 70 internal combustion engine 72 compressor 90 turbine 92 flange 94 inlet funnel d1 first distance d2 second distance