EP1639241A1

EP1639241A1 - Exhaust gas aftertreatment installation comprising a reverse flow housing, and corresponding exhaust gas aftertreatment method

Info

Publication number: EP1639241A1
Application number: EP04739722A
Authority: EP
Inventors: Rolf BRÜCK
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH
Current assignee: Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 2003-06-27
Filing date: 2004-06-09
Publication date: 2006-03-29
Also published as: JP2007506893A; US20060107656A1; WO2005001252A1; DE10329000A1; TW200508480A; CN1809688A

Abstract

The invention relates to an exhaust gas aftertreatment installation (1), especially for use near the internal combustion engine of an automobile. Said installation comprises a housing (2), having a catalytic converter (3), surrounded by at least one return flow area (6) through which the fluid can flow in a substantially free manner. Said catalytic converter (3) has a first face (14), a second face (16) and cavities (10) through which a fluid can flow in a forward flow direction (15). The first face (14) of the at least one catalytic converter (3) is linked with at least one gas supply pipe (13) and at least one gas discharge pipe (25) is linked with the at least one return flow area (6) in a substantially gas-tight manner. At least one flow deflection means (17) effects deflection (20) of the fluid from the catalytic converter (3) to the return flow area (6) of the housing (2) through which the fluid can flow in a substantially free manner. The inventive exhaust gas aftertreatment installation (1) is compact in design, has a better light-off performance and reduced alternating thermal stresses as compared to conventional exhaust gas aftertreatment installations.

Description

Exhaust gas aftertreatment system with a counterflow housing, as well as corresponding method for exhaust gas aftertreatment

The invention relates to an exhaust gas aftertreatment system with a counterflow housing and a corresponding method for exhaust gas aftertreatment. Due to the steadily increasing volume of automobile traffic, legal limit values have been enacted in numerous countries worldwide, which must not exceed the pollutant pollution of automobile exhaust gases. These limit values are lowered regularly, so that an increased effort in the implementation of pollutants in the exhaust gas has to be carried out to meet these limit values. Here it has prevailed to subject the exhaust gas to a catalytic conversion, in which the harmful portions of the exhaust gas are converted into harmless portions. Such a catalytic conversion requires a reaction surface that is as large as possible, but the component used for this purpose must not be so large that it blows up the space normally available in an automobile. The Merfür solution is provided by honeycomb bodies as catalyst support bodies. Honeycomb bodies have cavities for the exhaust gas to flow through, for example channels. By forming the cavities separating walls with a layer containing a catalyst, for example a noble metal catalyst, e.g. B. a washcoat layer can be provided, a large reaction surface can be provided for the catalytic reaction.

Such honeycomb bodies or catalytic converters can be constructed, for example, from ceramic materials, from metallic layers or as an extruded component. A distinction is made primarily between two typical designs for metallic honeycomb bodies. An early design, for which DE 29 02 779 AI shows typical examples, is the spiral design, in which essentially one smooth and a corrugated sheet layer are placed on top of each other and wound in a spiral. In another design, the honeycomb body is built up from a multiplicity of alternatingly arranged smooth and corrugated or differently corrugated sheet metal layers, the sheet metal layers initially forming one or more stacks which are intertwined with one another. The ends of all sheet metal layers come to the outside and can be connected to a housing or casing tube, which creates numerous connections that increase the durability of the honeycomb body. Typical examples of these designs are described in EP 0 245 737 B1 or WO 90/03220. It has also been known for a long time to provide the sheet metal layers with additional structures in order to influence the flow and / or to achieve cross-mixing between the individual flow channels. Typical examples of such configurations are WO 91/01178, WO 91/01807 and WO 90/08249. Finally, there are also honeycomb bodies in a conical design, possibly also with additional structures for influencing the flow. Such a honeycomb body is described, for example, in WO 97/49905. In addition, it is also known to leave a recess in a honeycomb body for a sensor, in particular for accommodating a lambda probe. An example of this is described in DE 88 16 154 Ul. Furthermore, honeycomb bodies are known which flow a fluid in a radial direction

Allow direction from inside to outside. An example of this is in WO

96/09893, which is formed from adjacent disks, one

Have a macro structure that forms channels running outward from a central channel in an arc shape. A further possibility for the construction of honeycomb bodies which are flowed through radially from the inside to the outside is described in WO 98/57050.

In order to achieve the highest possible conversion rate, as well as a quick start of the catalytic conversion, it is advantageous to charge the honeycomb body with the hotest possible exhaust gas, since this reaches the start-up temperature from which the catalytic conversion takes place relatively quickly on cold start. This can be achieved by installing the catalytic converter as close to the engine as possible. However, the spaces available for forming a catalytic converter are often very limited, especially in the area close to the engine. On the other hand, installation close to the engine places a high thermal load on the catalytic converter, due to the thermal gradients that arise and the strongly pulsatile gas flow. It is therefore the object of the present invention to propose an exhaust gas aftertreatment system and a method for exhaust gas aftertreatment in which the exhaust gas aftertreatment can be carried out in a compact manner and a rapid light-off behavior is ensured, with a long service life of the exhaust gas aftertreatment system.

This object is achieved by an exhaust gas aftertreatment system with the features of claim 1 and a method for exhaust gas aftertreatment with the features of claim 18. Advantageous further developments and refinements are the subject of the respective dependent claims.

An exhaust gas aftertreatment system according to the invention is particularly suitable for use close to the engine in an internal combustion engine of an automobile and comprises a housing which surrounds a catalytic converter surrounded by at least one essentially freely flowable

Has backflow area, the catalytic. Converter (3) a first

End face (14), a second end face (16) and cavities (10) through which a fluid can flow in a direction of flow (15), the first end face of the at least one catalytic converter being connected to at least one gas supply line and at least one gas discharge line essentially is connected in a gastight manner to the at least one backflow region, and at least one flow deflecting means redirecting the fluid from the catalytic converter into the essentially freely flowable one

Backflow area of the housing causes. An essentially freely flow-through backflow region is understood here in particular to mean that the backflow region is not designed as a honeycomb structure, that is to say is essentially not divided into channels or cavities through which flow can pass. In particular, it is possible and according to the invention that the backflow region can be flowed through freely in the housing, with the possible exception of the fastening means for fastening the catalytic converter, which, for example, consists of a honeycomb structure in a casing tube. In this case, the backflow region in the case of an internal cylindrical catalytic converter in a cylindrical housing is designed as a circular annular cylindrical gap between the casing tube of the catalytic converter and the inner wall of the housing. The exhaust gas aftertreatment system according to the invention has the advantage that, by redirecting the direction of flow, blind holes in the vicinity of the engine, for example, can be used to accommodate the exhaust gas aftertreatment system, which could not be used in catalytic converters in a classic design - that is, without a redirection of flow. Since the catalytic conversion is usually exothermic, the exhaust gas heats up after the catalytic conversion has started or started. In the case of conventional catalytic converters, this requires strong thermal gradients via the catalytic converter. Since, in an exhaust gas aftertreatment system according to the invention, the converted exhaust gas flow is deflected in its flow direction, inverted in the case of a catalytic converter which can be flowed through in the axial direction, and flows back in the backflow region of the housing, but this housing also contains the catalytic converter, the catalytic converter is heated uniformly, so that thermal gradients are avoided and the service life of the catalytic converter is increased. Furthermore, the heating of the catalytic converter with the help of the hot exhaust gas leads to a faster start of the catalytic conversion in the catalytic converter in the Cold start phase and thus a significantly accelerated light-off behavior compared to conventional exhaust gas aftertreatment systems without a counterflow housing.

According to an advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the gas supply line and the gas discharge line are formed in the region of the first end face of the catalytic converter.

The formation of the gas supply line and the gas discharge line on only one side of the housing and the catalytic converter allows a space-saving design of the exhaust gas aftertreatment system according to the invention. In particular, the gas supply and discharge lines are not designed in parallel, especially not coaxially. In the case of a catalytic converter through which the exhaust gas flows essentially radially, there is a deflection of the exhaust gas when it emerges from the catalytic converter, while in the case of an axially flowed catalyst the deflection of the gas flow represents an inversion of the gas flow, i.e. a deflection of essentially 180 ° (degrees).

According to an advantageous embodiment of the exhaust gas aftertreatment system, the housing is designed as a manifold. Another advantageous embodiment of the exhaust gas aftertreatment system is aimed at designing the housing as a collector. Both when the housing is designed as a manifold and as a collector, it is possible to use the exhaust gas aftertreatment system as close as possible to the engine.

According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the gas discharge line and / or the gas supply line is connected to a turbocharger.

A turbocharger is used for charging, that is, a method for increasing the performance of an internal combustion engine, which is particularly useful in Connection with diesel engines is used. During charging, a working machine compresses the air required for the engine combustion process, so that a larger air mass gets into the cylinder or combustion chamber per work cycle of the internal combustion engine. For this purpose, the compressor is driven by a turbocharger, for example, which uses the exhaust gas energy. The coupling to the engine is not mechanical, but is purely thermal, with the principle of accumulation charging mainly being used in automobile construction. The arrangement of the exhaust gas aftertreatment system upstream of such a turbocharger ensures that the operating temperature of the catalytic converter contained in it is reached very quickly, since heat dissipation of the exhaust gas due to contact with components of the turbocharger is avoided in this way.

However, the arrangement of the turbocharger is particularly preferably connected directly to the feed line or upstream. In this embodiment, it is particularly advantageous to provide the feed line with a cone, which leads the exhaust gas directly to the first end face of the honeycomb body. This cone advantageously has an opening angle of at least 20 °, in particular of at least 30 ° and particularly preferably of at least 40 °. Advantageously, only a very short or no tubular supply line section to the turbocharger is connected upstream of the cone, but the cone is then possibly directly connected to the turbocharger. However, should a tubular supply line section be provided, for example in order to provide a sufficiently large backflow area for the exhaust gas with a dome-shaped component, this section should not exceed a length of 20 mm [millimeters], in particular not longer than 10 mm or even just 8 mm. With such a configuration, the exhaust gas flow generated by the turbocharger is used to an effective extent to the honeycomb body. The turbocharger generates a type of swirl flow, which is advantageously maintained and thus results in intensive contact of the uniformly mixed exhaust gas flow. According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the housing and the at least one catalytic converter are concentric, preferably coaxial. The concentric or coaxial construction of the catalytic converter and housing advantageously allows the exhaust gas aftertreatment system to be constructed in a particularly simple manner; in particular, conventional catalytic converters in cylindrical construction can thus be used. The coaxial structure advantageously offers only low pressure losses in the backflow area with a simple structure of the exhaust gas aftertreatment system at the same time. Furthermore, the concentric or coaxial construction of the catalytic converter and housing simplifies the design of the flow deflecting means. If the housing and catalytic converter have essentially cylindrical geometry and if the exhaust gas flows axially through the catalytic converter, the flow deflecting means can be formed in a particularly simple manner by forming a torus with the smallest possible inner radius, ideally zero. If the catalytic converter flows essentially radially through the exhaust gas, the housing itself forms the flow deflecting means which ensures the deflection of the exhaust gas from the radial flow direction into the backflow direction.

According to a further advantageous embodiment of the

Exhaust gas aftertreatment system, the at least one backflow region is formed outside the at least one catalytic converter. The formation of the backflow region outside of the at least one catalytic converter advantageously ensures a rapid starting behavior of the catalytic converter, a uniform heating of the catalytic converter while preventing the formation of thermal gradients and a simple structural design of both the catalytic converter and the housing, because a conventional catalytic converter with a honeycomb structure made of ceramic or metal, optionally an extruded honeycomb structure, can be used inside the housing. In advantageous It is possible to fasten the catalytic converter with holding means, for example thin webs, which point radially outward from the catalytic converter in the direction of the housing, without the pressure loss in the backflow region being increased significantly. Other holding means are also possible and according to the invention, in particular it is also advantageous to fix the catalytic converter only by means of the gas supply line.

According to a further advantageous embodiment of an exhaust gas aftertreatment system according to the invention, the cavities of the at least one catalytic converter each have a first cross-section through which a flow can pass, an inner area with a second cross-section through which the flow can flow being formed as a backflow section within the catalytic converter. Here, the second cross-section through which flow can flow is significantly larger than the first cross-section through which flow can pass. This allows, for example, the use of hollow-cylindrical catalytic converters, the cross section of which represents a circular ring with cavities through which a first cross section can be flowed.

According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the cross-section of the return flow area through which flow can flow is essentially the same as the sum of the cross-sections of the catalytic converter through which the flow can pass. This advantageously prevents pressure loss during flow deflection. It is equally advantageous, however, to make the second cross-section through which flow can be greater than the sum of the first cross-sections through which flow can occur, in order to slow down the flow in the return flow region and to increase the heat transfer to the catalytic converter in the cold start phase.

According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the housing has a first length L1 and the catalytic converter has a second length L2, the first length of the Housing and the second length of the catalytic converter are essentially identical. The design of the catalytic converter of identical length to the length of the housing allows the catalytic converter to be held in the housing in a simple manner and the flow deflecting means and the gas discharge and supply line to be constructed in a simple manner.

According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the housing has a diameter D, the quotient of the first length L1 and the diameter D of the housing being greater than or equal to 0.3 and less than or equal to 1.5, preferably greater than or equal to 0, 3 and less than or equal to 1, particularly preferably approximately 0.5. This means that the following equation applies to the first length L1 and the diameter D of the housing: 0.3 <L1 / D <1.5

According to a further advantageous embodiment of an exhaust gas aftertreatment system according to the invention, the return flow region has a pressure loss which is less than or equal to the pressure loss of the forward flow region, in particular less than or equal to the pressure loss of a pipe of the first length and a diameter which corresponds to the diameter of the feed line.

According to another advantageous _. Embodiment of an exhaust gas aftertreatment system, the at least one gas supply line has a first longitudinal axis and the at least one gas discharge line has a second longitudinal axis, wherein the projection of the first and the second longitudinal axis onto a plane that includes the first end face of the catalytic converter includes an angle that is larger than 60 ° (degrees). Such an angular constellation between the gas discharge line and the gas supply line advantageously allows the use of even the smallest free cavities when installing near the engine, for example of very narrow blind holes. According to a further advantageous embodiment of an exhaust gas aftertreatment system according to the invention, the gas supply line and the first end face of the at least one catalytic converter are connected to one another in the form of a sliding seat. The formation of the connection between the gas supply line and the first end face in the form of a sliding seat advantageously allows the formation of an essentially gas-tight connection, while at the same time allowing a different thermal expansion, which in the case of a simple welded connection can easily lead to the connection breaking. In this way, an essentially gas-tight connection between the gas line and the first end face of the at least one catalytic converter can be ensured in an advantageous manner even with different thermal expansion behavior. According to a further advantageous embodiment of the exhaust gas aftertreatment system according to the invention, the catalytic converter is made of ceramic. It is also advantageous to design the catalytic converter as an extruded component. According to a further advantageous embodiment, the catalytic converter can also be formed from at least one metallic layer. In this context, it is particularly advantageous that the catalytic converter

a) by winding at least one at least partially structured metallic layer or at least one essentially smooth and at least one at least partially structured metallic layer or

b) by stacking a plurality of essentially smooth and at least partially stabilized metallic layers and then twisting a plurality of stacks is trained. This allows both the construction of spiral honeycomb bodies and of metallic honeycomb bodies with stacks which are intertwined in an S-shape or involute shape. In particular, in the case of metallic catalytic converters, it is advantageous and according to the invention that these with structures that are transverse to the cavity extension or longitudinally to the cavity expansion, holes in the metallic layers or also the formation of at least some of the metallic layers by at least partially permeable material for a fluid are possible and according to the invention.

According to a further aspect of the invention, a method for exhaust gas aftertreatment, in particular the exhaust gases of an internal combustion engine of an automobile in an exhaust gas aftertreatment system, preferably an exhaust gas aftertreatment system according to the invention, is proposed. The method according to the invention comprises the following steps: a) flowing through a flow area in a flow direction and catalytic conversion of at least parts of the exhaust gas in this flow area;

b) deflection of the flow direction of the exhaust gas from the forward flow direction into a return flow direction; and

c) flowing through an essentially freely flowable backflow region in the backflow direction.

The advantages and details listed above for the exhaust gas aftertreatment system according to the invention can be applied in the same way to the method for exhaust gas aftertreatment according to the invention. Further advantages and details of the invention will be explained in more detail below with reference to the drawings, but the invention is not restricted to the exemplary embodiments shown there. 1 schematically shows a longitudinal section through an exhaust gas aftertreatment system according to the invention;

Fig. 2 shows schematically a honeycomb body; 3 schematically shows a housing with a built-in honeycomb body;

4 schematically shows a further exemplary embodiment of an exhaust gas aftertreatment system according to the invention; 5 schematically shows a section through the second exemplary embodiment of the exhaust gas aftertreatment system; and

6 schematically shows a section through a third exemplary embodiment of an exhaust gas aftertreatment system according to the invention.

FIG. 1 schematically shows a longitudinal section through a first exemplary embodiment of an exhaust gas aftertreatment system 1 according to the invention. The exhaust gas aftertreatment system 1 has a housing 2 with a honeycomb body 3, which serves as a catalytic converter. The honeycomb body 3 is surrounded by a tubular casing 4 and is fastened in the housing 2 with holding means 5. These holding means 5 are predominantly designed as webs which do not significantly reduce the cross-section of the backflow region 6 through which the flow can flow freely. Cross-section through which flow is free means in particular that no honeycomb structure is formed in the backflow region. The honeycomb body 3 can be designed both as a ceramic and as a metallic honeycomb body 3. An example of a metallic honeycomb body can be seen in FIG. 2. The Feed line 13 is provided with a cone 35, which leads the exhaust gas directly to the first end face 14 of the honeycomb body 3. This cone 35 has an opening angle 33 of at least 20 °. A very short tubular feed line section leading to a turbocharger (not shown) is connected upstream of the cone 35, this section not exceeding a length 34 of 20 mm [millimeters].

FIG. 2 shows a honeycomb body 3 which has a tubular casing 4. A honeycomb structure 7 is fastened in this casing tube 4. This is made up of metallic layers 8, 9. To build the honeycomb structure 7, essentially smooth metallic layers 8 and at least partially structured metallic layers 9 are alternately stacked and several stacks are connected to one another in the same direction. For the sake of clarity, the at least partially structured metallic layers 9 are only shown in a partial area. The essentially smooth metallic layers 8 and the at least partially stiuldurized metallic layers 9 form channels 10.

Sheet metal layers with a thickness of less than 80 μm, preferably less than 40 μm, particularly preferably less than 25 μm can be used as metallic layers. It is just as well possible for the substantially smooth metallic layers 8 and / or the at least partially stagnated metallic layers 9 to be at least partially made of a material that can be flowed through by a fluid, for example one. metallic sintered fleece. Furthermore, it is possible and according to the invention to introduce holes and / or structures of any kind into the substantially smooth metallic layers 8 and / or the at least partially structured metallic layers 9. In particular, it is also possible to close some of the channels 10. The introduction of holes, the dimensions of which are greater than the repeat length of the at least partially stagnated metallic layers 9, is also possible and according to the invention. FIG. 1 shows that the housing 2 of the exhaust gas aftertreatment system 1 according to the invention has two flow areas. The channels 10 of the honeycomb body 3 form a forward flow area 11, while the area of the housing between the casing tube 4 and the wall of the housing 2 forms a return flow area 6. The honeycomb body 3 serves as a catalytic converter, ie it is usually provided with a catalytically active coating, for example a washcoat, which contains, for example, noble metal catalyst particles such as platinum or rhodium. In the present exemplary embodiment, the exhaust gas flows axially through the honeycomb body 3. An exhaust gas flow flowing through the honeycomb body 3 is at least partially converted catalytically in the honeycomb body 3. In contrast to this, an exhaust gas flow flowing through the backflow region 6 is not converted catalytically.

Each of the channels 10 has a first cross-section through which flow can flow, while the backflow region 6 has a second cross-section through which flow can pass. Free-flowing means that the second flow-through cross-section of the return flow region 6 is significantly larger than the first flow-through cross-section of a channel 10.

In the operation of the exhaust gas aftertreatment system 1, an exhaust gas stream 12 is introduced into the exhaust gas aftertreatment system 1 via a gas supply line 13. The gas supply line 13 is connected in a substantially gas-tight manner to the casing tube 4 of the honeycomb body 3 in the region of the first end face 14 of the honeycomb body, so that there is an essentially gas-tight connection between the gas supply line 13 and the inflow region 11. The exhaust gas flow 12 thus essentially passes completely into the honeycomb body 3. The exhaust gas flow 12 flows through this honeycomb body 3 in the direction of the flow 15. In this case, at least partial conversion of the exhaust gas flow 12 takes place. The exhaust gas flow 12 leaves the honeycomb body 3 through a second end face 16. In the region of the second end face 16, a flow deflecting means 17 connects in a downward direction 15. This is in the essentially gas-tightly connected to the housing 2. The flow deflecting means 17 has a depression 18 and a toroidal elevation 19. The greatest increase lies in the axial direction of the honeycomb body 3 in each case opposite the center of the return flow region 6, while the depression 18 lies opposite the center of the cylindrical honeycomb body 3 in the axial direction. Other designs of the flow deflecting means 17 are also possible and according to the invention. The flow deflecting means 17 leads to a deflection 20 of the exhaust gas flow 12 from the forward flow direction 15 into a return flow direction 21. In the present case it is even an inversion of the exhaust gas flow, that is to say a deflection by essentially 180 °. In this case, the exhaust gas flow 12 is deflected from the inflow region 11 into the return flow region 6. The flow deflecting means 17 can optionally have thermal insulation 22. Furthermore, a collecting means 23 is connected to the housing 2. The connection is essentially gas-tight. The collecting means 23 consists of a dome-shaped component 24 and a gas discharge line 25. The at least partially converted gas stream leaves the exhaust gas aftertreatment system 1 through the gas discharge line 25.

In operation, the exhaust gas flow 12 flows through the gas supply line 13 into the honeycomb body 3. At least a part of the exhaust gas flow 12 is at least partially catalytically converted therein. After the honeycomb body 3 has been flowed through in the upstream direction 15, a deflection 20 takes place in the flow direction in the flow deflection means 17 The exhaust gas stream 12 then flows through the backflow region 6 in the backflow direction 21. No catalytic conversion takes place in the backflow region 6, essentially it is a non-subdivided flow space. The gas stream flowing through the backflow region 6 is generally heated in comparison to the inflowing exhaust gas stream 12, since the catalytic conversion in the honeycomb body 3 is generally exothermic. The through the reverse flow area 6 flowing gas stream is thus advantageously used for tempering the honeycomb body 3. Even in the cold start phase, in which there is no heating of the gas flow in the honeycomb body 3 due to the exothermic reaction which has not yet started, the recirculation of the exhaust gas flow can advantageously be used for heating the honeycomb body 3, since elevated temperatures are quickly reached when a combustion engine is cold started, which are below the light-off temperature of the catalytic conversion in the catalytic converter 3, but above the ambient temperature of the surroundings of the honeycomb body 3. This leads to significantly shorter light-off times of the catalytic reaction in the honeycomb body 3. The optional thermal insulation 22 of the flow deflecting means 17 also prevents heat losses and improves thus the light-off behavior of the honeycomb body 3. Furthermore, the backflow of the hot exhaust gas leads to the fact that, compared to conventional exhaust gas aftertreatment systems, lower thermal gradients build up over the honeycomb body 3. This requires an improved service life of the honeycomb body.

In the connection between the gas supply line 13 and the casing tube 4, a sliding seat can advantageously be used. This enables a gas-tight connection even in the event of different thermal expansions of the two components.

The backflow principle, in particular in that gas supply line 13 and gas discharge line 25 are both formed in the area of the first end face 14 of the honeycomb body 3, makes it possible to utilize even small free spaces in the area of the engine compartment of an automobile, for example blind holes. In this way, the exhaust gas aftertreatment system 1 can be installed as close as possible to the engine. As a result, higher temperatures are present in the exhaust gas more quickly, so that the light-off behavior of the honeycomb body 3 is also improved as a result. The gas supply line 13 has a first longitudinal axis 27. The gas discharge line 25 has a second longitudinal axis 28. In order to enable the exhaust aftertreatment system 1 to be installed as space-saving as possible, it is advantageous if the angle of the projections of the first longitudinal axis 27 and the second longitudinal axis 28 on a plane that includes the first end face 14 is greater than 60 degrees.

In the case of a honeycomb body 3 according to the invention, the return flow region 6 has a pressure loss which is less than or equal to the pressure loss in the forward flow region 11. It is preferred here that the pressure loss in the backflow region 6 is less than or equal to the pressure loss that a pipe of the first length L1 and a diameter that corresponds to the diameter 32 of the feed line 31 has.

FIG. 3 shows a housing 2 according to the invention with a honeycomb body 3 inserted. The honeycomb body 3 is designed coaxially with the housing 2. The casing tube 4 of the honeycomb body 3 is connected to the housing 2 via holding means 5. The channels 10 of the honeycomb body 3, which are not shown for the sake of clarity, form the forward region 11, while the housing region between the housing wall and casing tube 4 forms the return flow region 6. The housing 2 has a first length L1 and a diameter D. The honeycomb body 3 has a second length L2. In the present exemplary embodiment, the first length L1 is identical to the second length L2. The so-called pancake shape is preferred for the exhaust gas aftertreatment system according to the invention; H. the ratio L1 / D is preferably 0.3 <Ll / D <1. It is particularly preferred here if the ratio Ll / D is approximately 0.5. However, other ratios L1 / D are also possible and according to the invention.

FIG. 4 schematically shows another exemplary embodiment of an exhaust gas aftertreatment system 1 according to the invention. In this case, four honeycomb bodies 3 are fastened in the housing 2 of the exhaust gas aftertreatment system 1 and are supplied with exhaust gas via four gas supply lines 13. Furthermore, a gas discharge line 25 is formed, so that this exemplary embodiment is a Exhaust aftertreatment system according to the invention can be used as a collector. It is also possible and according to the invention to form two or more gas discharge lines 25 instead of one gas discharge line 25 in order to be able to implement, for example, multi-purpose exhaust systems. The dome-shaped components 24 are connected to one another accordingly. The flow deflecting element 17 is designed in such a way that in this exemplary embodiment, too, an effective deflection 20 takes place from the inflow regions 11 into the respective backflow regions 6. In this case too, the flow deflecting means 17 is formed with depressions 18 and elevations 19, the depressions 18 being formed in each case centered on the honeycomb bodies 3.

Figure 5 shows schematically a section through the exemplary embodiment shown in Figure 4 along the line V-V. This cross section shows the housing 2 with the four honeycomb bodies 3 attached to it. In this cross section, the casing tubes 4 form the boundary between the inflow regions 11 and the backflow region 6.

FIG. 6 shows a further exemplary embodiment of an exhaust gas aftertreatment system 1 according to the invention, which has a honeycomb body 3 through which radial flow is possible. As is known from the prior art, this is constructed by disks 29 with macrostructures (not shown) which form channels 10 leading from a central flow region 30 to the backflow region 6. The exhaust gas flow 12 to be converted flows axially through the gas supply line 13 through the first end face 14 into the central flow region 30. Because the second end face 16 of the honeycomb body 3 is closed, the gas flow is deflected into the radial flow channels 10 as indicated by the arrows. The flow direction 15 of the flow region 11 formed by the channels 10 is thus directed radially from the inside to the outside. The housing 2 serves as the flow deflecting means 17 which, after the gas has exited the channels 10, deflects the gas flow 20 in the backflow direction 21 effected in the backflow region 6. In contrast to an axially flowable honeycomb body, in which there is a deflection of, for example, essentially 180 °, the gas flow is deflected by approximately 90 ° in the case of a honeycomb body 3 through which there is a radial flow.

From the return flow region 6, the exhaust gas flows into the dome-shaped component 24. From there, the converted gas stream 26 leaves the exhaust gas aftertreatment system 1 through the gas discharge line 25. Also in this exemplary embodiment, the gas supply line 13 and gas discharge line 25 are in the region of the first end face 14 of the honeycomb body 3.

With an exhaust gas aftertreatment system 1 according to the invention, the at least partially catalytic conversion of exhaust gases can advantageously take place even with a very limited free receiving space for an exhaust gas aftertreatment system 1. This is possible due to the countercurrent principle in the housing 2. Furthermore, an exhaust gas aftertreatment system 1 according to the invention is distinguished by an improved light-off behavior and lower thermal alternating loads in comparison to conventional exhaust gas aftertreatment systems.

LIST OF REFERENCE NUMBERS

Exhaust gas aftertreatment system housing honeycomb body casing tube retaining means backflow area honeycomb structure essentially smooth metallic layer at least partially structured metallic layer channel downflow area exhaust gas flow gas supply line first end face

Hinsfrömrichtung

Second face

Sfrömungsumlenkmittel

deepening

increase

redirection

return flow direction

thermal insulation

mopping-up

Dome-shaped component

Gas discharge line

Converted gas flow

First longitudinal axis

Second longitudinal axis 29 disc

30 central flow area

31 supply line

32 diameter of the feed line

33 opening angle

34 Length of the supply line

35 cone

D diameter

Ll first length of the case

L2 second length of the honeycomb body

Claims

claims

1. Exhaust gas aftertreatment system (1), in particular for use close to the engine in an internal combustion engine of a motor vehicle, with a housing (2) which has a catalytic converter (3) surrounded by at least one essentially freely flowable backflow area (6), the catalytic converter ( 3) comprises a first end face (14), a second end face (16) and cavities (10) through which a fluid can flow in a flow direction (15), the first end face (14) of the at least one catalytic converter (3) having at least one a gas supply line (13) is connected and at least one gas discharge line (25) is connected in an essentially gas-tight manner to the at least one return flow region (6) and at least one flow deflection means (17) deflects (20) the fluid from the catalytic converter (3) in causes the backflow region (6) of the housing (2) to flow through freely.

2. exhaust gas aftertreatment system (1) according to claim 1, characterized in that the gas supply line (13) and the gas discharge line (25) in the region of the first end face (14) of the catalytic converter (3) are formed.

3. exhaust gas aftertreatment system (1) according to claim 1 or 2, characterized in that the housing (2) is designed as a manifold.

4. exhaust gas aftertreatment system (1) according to claim 1 or 2, characterized in that the housing (2) is designed as a collector.

5. exhaust gas aftertreatment system (1) according to any one of the preceding claims, characterized in that the gas discharge line (25) and / or the gas supply line (13) is connected to a turbocharger.

6. exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the housing (2) and the at least one catalytic converter (3) are concentric, preferably coaxial.

7. exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the at least one backflow region (6) is formed outside the at least one catalytic converter (3).

8. exhaust gas aftertreatment system (1) according to one of claims 1 to 6, characterized in that the cavities (10) of the at least one catalytic converter (3) each have a first cross-section through which flow and that within the catalytic converter (3) an inner area with a second cross section through which flow can take place is designed as a backflow region (6), the second cross section being significantly larger than the first cross section.

9. exhaust gas aftertreatment system (1) according to any one of the preceding claims, characterized in that the second flow-through cross section of the return flow area (6) is substantially the same size as the sum of the first flow-through cross sections of the catalytic converter (3).

10. exhaust gas aftertreatment system (1) according to any one of the preceding claims, characterized in that the housing (2) has a first length (Ll) and the catalytic converter (3) has a second length (L2), the first length (Ll) of Housing (2) and the second length (L2) of the catalytic converter (3) are essentially identical.

11. Exhaust aftertreatment system (1) according to one of the preceding claims, characterized in that the housing (2) has a diameter (D), the quotient of the first length (L1) and the diameter (D) of the housing (2) being larger or 0.3 and less than or equal to 1.5, preferably greater than or equal to 0.3 and less than or equal to 1, particularly preferably approximately 0.5.

12. Exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the return flow region (6) has a pressure loss which is less than or equal to the pressure loss of the forward flow region (11), in particular less than or equal to the pressure loss of a pipe of the first length ( Ll) and a diameter that corresponds to the diameter (32) of the feed line (31).

13. Exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the at least one gas supply line (13) has a first longitudinal axis (27) and the at least one gas discharge line (25) has a second longitudinal axis (28) and that the projection of first (27) and the second longitudinal axis (28) on a plane which comprises the first end face (14) of the catalytic converter (3), an angle which is greater than 60 ° (degrees).

14. exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the gas supply line (13) and the first end face (14) of the at least one catalytic converter (3) are connected to one another in the form of a sliding seat.

15. Exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the catalytic converter (3) is made of ceramic.

16. Exhaust gas aftertreatment system (1) according to one of the preceding claims, characterized in that the catalytic converter (3) is extruded.

17. Exhaust gas aftertreatment system (1) according to one of claims 1 to 14, characterized in that the catalytic converter (3) is formed from at least one metallic layer (8, 9).

18. Exhaust gas aftertreatment system (1) according to claim 16, characterized in that the catalytic converter (3) a) by winding up at least one - at least partially structured metallic layer (9) or at least one essentially smooth (8) and at least one at least partially stagnated metallic layer (9) or b) is formed by stacking a plurality of substantially smooth (8) and at least partially structured metallic layers (9) and then twisting at least one stack.

9. A method for exhaust gas aftertreatment, in particular the exhaust gases of an internal combustion engine of a motor vehicle, in an exhaust gas aftertreatment system (1), in particular an exhaust gas aftertreatment system (1) according to one of claims 1 to 18, comprising the following steps: a) flowing through a Hinfrömbereich (11) in one Direction of flow (15) and catalytic conversion of at least parts of the exhaust gas in this area (15); b) deflection (20) of the flow direction of the exhaust gas from the forward flow direction (11) into a return flow direction (21); and c) flowing through a substantially freely flowable backflow region (6) in the backflow direction (21).