DE102017118214A1 - Exhaust gas aftertreatment system and method for exhaust aftertreatment of an internal combustion engine - Google Patents

Abstract

The invention relates to an exhaust aftertreatment system for an internal combustion engine (10), in particular a diesel engine. In this case, in the exhaust system (22) of the internal combustion engine (10) downstream of an outlet (12) of the internal combustion engine (10), an exhaust gas turbocharger (18), downstream of the exhaust gas turbocharger (18) an open particulate filter (30) and downstream of the open particulate filter (30) a diesel particulate filter (34), which is preferably provided with a coating (38) for the selective, catalytic reduction of nitrogen oxides arranged. The open particle filter (30) is preferably designed as a continuously regenerating particle filter and is continuously loaded with the soot particles during operation of the internal combustion engine and regenerated. The diesel particulate filter (34) is designed as a closed filter and must be regenerated periodically. By connecting the open particulate filter (30), the intervals between two regeneration processes of the diesel particulate filter (34) can be extended, whereby the excess consumption caused by the regeneration can be reduced and emits fewer pollutants to the environment in connection with the regeneration of the diesel particulate filter (34) become.

Description

The invention relates to an exhaust aftertreatment system for an internal combustion engine and to a method for exhaust aftertreatment of an internal combustion engine according to the preamble of the independent claims.

The current and increasingly stringent future exhaust gas legislation places high demands on the engine raw emissions and the exhaust aftertreatment of internal combustion engines. The demands for a further reduction in consumption and the further tightening of emission standards with regard to permissible nitrogen oxide emissions pose a challenge to engine developers. In gasoline engines, exhaust gas purification takes place in a known manner via a three-way catalytic converter, as well as the three-way catalytic converter. Catalyst upstream and downstream further catalysts. For diesel engines exhaust gas aftertreatment systems are currently used, which have an oxidation catalyst or NOx storage catalyst, a catalyst for the selective catalytic reduction of nitrogen oxides (SCR catalyst) and a particulate filter for the separation of soot particles and optionally other catalysts. The reducing agent used is preferably ammonia. Because the handling of pure ammonia is complicated, in vehicles usually a synthetic, aqueous urea solution is used, which is mixed in a SCR catalyst upstream mixing device with the hot exhaust gas stream. By this mixing, the aqueous urea solution is heated, wherein the aqueous urea solution releases ammonia in the exhaust gas passage. A commercial aqueous urea solution generally consists of 32.5% urea and 67.5% water.

When operating a diesel engine, there is a trade-off between low levels of raw NOx emissions, low particulate emissions and long regeneration intervals for a diesel particulate filter. In known from the prior art interpretations of the combustion process of the diesel engine is usually chosen, knowing the very high filterability of the diesel particulate filter and the less efficient way to reduce nitrogen oxides by exhaust aftertreatment, an application in which the NOx raw emissions are low and comparatively many Soot particles are generated to meet the emission limits of the EU6 emissions standard as well as future even stricter limit values. This has the disadvantage that the diesel particulate filter must be regenerated correspondingly frequently, with the regeneration of the diesel particulate filter leading to an increase in consumption and pollutant emissions during regeneration. If the interval between two successive regeneration processes of the diesel particulate filter becomes longer, multiple emissions and additional pollutant emissions decrease.

A reduction in PM emissions is associated with an increase in nitrogen oxide emissions as described, which would inevitably lead to exceeding the limit values for nitrogen oxide emissions. Such a procedure is therefore eliminated in the effort to extend the regeneration intervals of the diesel particulate filter.

From the DE 20 2014 102 809 U1 an exhaust gas module for an internal combustion engine is known, wherein in the exhaust gas module, an oxidation catalyst and a particulate filter are formed with a coating for the selective, catalytic reduction of nitrogen oxides, which are arranged in a common housing. In this case, the housing is made divisible, wherein an exhaust pipe is provided, which connects the first housing part with the second housing part.

The EP 2 826 971 A1 discloses an exhaust aftertreatment system and a method for exhaust aftertreatment of an internal combustion engine. Here, in the exhaust system in the flow direction of an exhaust gas through the exhaust system, an SCR catalyst, downstream of the SCR catalyst, a particulate filter and further downstream, a second SCR catalyst arranged.

In addition, from the EP 2 907 564 A1 an exhaust aftertreatment system and a method for the exhaust aftertreatment of an internal combustion engine, in which in the flow direction of an exhaust gas through the exhaust system, an oxidation catalyst downstream of the oxidation catalyst, a particulate filter with an SCR coating and downstream of the coated particulate filter another SCR catalyst are arranged.

It is an object of the invention to make it possible to extend the regeneration intervals of the diesel particulate filter even with comparatively high particulate raw emissions.

According to the invention, this object is achieved by an exhaust aftertreatment system for an internal combustion engine in which a turbine of an exhaust gas turbocharger and downstream of the turbine a diesel particulate filter are arranged in an exhaust system of the internal combustion engine downstream of an outlet of the internal combustion engine. It is inventively provided that downstream of the turbine and upstream of the diesel particulate filter, a PM catalyst is arranged. Here, a PM catalyst is to be understood as meaning a continuously catalytically regenerating particle reduction system which is in a low-temperature range of less than 300 ° C is regenerable. Preferably, the PM catalyst is formed of a thin, corrugated steel foil with paddle-shaped sub-structures and deposited layers of sintered metal nonwoven therebetween, wherein the layers of sintered metal nonwoven serve as a storage medium for the soot particles. As a result, the loading of the diesel particulate filter with soot particles can be slowed down at the same particle raw emissions, so that longer intervals between two regenerations of the diesel particulate filter are possible with the same particle raw emissions of the internal combustion engine. As a result, the additional fuel consumption can be reduced and the secondary emissions occurring in the regeneration of the diesel particulate filter can also be reduced.

By the features listed in the dependent claims advantageous improvements and developments of the exhaust gas aftertreatment system given in the independent claim are possible.

In an advantageous embodiment of the exhaust aftertreatment system it is provided that the diesel particulate filter has a coating for the selective, catalytic reduction of nitrogen oxides (SCR coating) and provided in the exhaust system downstream of the PM catalyst and upstream of the diesel particulate filter, a metering module for metering of reducing agent into the exhaust system is. Through a diesel particulate filter with a coating for the selective, catalytic reduction of nitrogen oxides, not only the particulate emissions but also the nitrogen oxide emissions can be reduced, whereby the SCR coating of the diesel particulate filter converts up to 95% of the raw NOx emissions of the internal combustion engine into harmless molecular nitrogen N ₂ and water vapor can be. It can be dispensed with an additional SCR catalyst by an SCR coating on the diesel particulate filter, which weight, space and cost can be saved.

Alternatively, it is advantageously provided that the diesel particulate filter is preceded by an SCR catalytic converter, which is arranged in the exhaust system downstream of the PM catalyst and a metering module for metering in reducing agent into the exhaust gas system. The functionalities of selective, catalytic reduction and the retention of soot particles can be distributed over two components, whereby each of these components can be further optimized in its function.

Alternatively, the dosing module and the SCR catalyst can also be arranged downstream of the diesel particulate filter. In a less preferred embodiment, it is possible to arrange the metering module upstream of the diesel particulate filter and the SCR catalyst downstream of the diesel particulate filter. Although you can use the diesel particulate filter as an additional exhaust gas mixer to improve the uniform distribution of the reducing agent in this configuration, but drops of the reducing agent can lead to damage and / or malfunction of the diesel particulate filter.

According to a preferred embodiment of the invention, it is provided that the PM catalyst has a noble metal coating for the oxidation of carbon monoxide and / or unburned hydrocarbons. By means of a corresponding noble metal coating unburned exhaust gas components can be exothermically reacted on the PM catalyst, whereby the achievement of the temperature for continuous regeneration of the retained soot particles and the implementation of a CRT process is facilitated. In this case, the noble metal coating on platinum, rhodium and / or palladium, which act catalytically effective for an oxidation process of the unburned exhaust gas components.

It is particularly preferred if the noble metal coating has a noble metal content of 30-250 g / ft ³ , preferably 40-200 g / ft ³ , particularly preferably 60-150 g / ft ³ , the noble metal coating having a platinum content of at least 40%. , preferably of at least 70%. An appropriate noble metal coating can ensure optimal conversion of the unburned exhaust gas components.

The PM catalyst has a catalyst volume of at least 0.5 dm ³ , preferably of at least 0.8 dm ³ , more preferably of at least 1.2 dm ³ , ideally of at least 1.5 dm ³ . In order to achieve a sufficient cleaning effect and a corresponding degree of separation for soot particles, a corresponding catalyst volume of the PM catalyst is necessary. In this case, a catalyst volume of at least 1.5 dm ^{3 is} particularly advantageous in order to allow a sufficient uptake of soot particles.

In a further improvement of the invention it is provided that the PM catalyst is preceded by an oxidation catalyst. By an upstream oxidation catalyst, which is also referred to as a starting catalyst of the internal combustion engine, a particularly efficient reaction of unburned hydrocarbons and carbon monoxide is possible. Due to the arrangement close to the engine, the oxidation catalytic converter reaches its operating temperature as quickly as possible after a cold start of the internal combustion engine, so that an effective conversion of said pollutants is possible is. In this case, the starting catalyst preferably has a catalyst volume of from 0.2 to 0.7 dm ³ , particularly preferably from 0.4 to 0.6 dm ³ .

In a preferred embodiment of the exhaust gas aftertreatment system, it is provided that an electrically heatable catalyst is connected upstream or downstream of the PM catalyst. By an electrically heatable catalyst, the heating of the PM catalyst can be promoted. If the electrically heatable catalyst precedes the PM catalyst, the Rußabbrand on the PM catalyst at cold exhaust system, especially in short-haul traffic, can be effectively supported. If the electrically heatable catalyst downstream of the PM catalyst and has a hydrolysis on effective evaporation of the aqueous reducing agent solution, in particular an aqueous urea solution, and the release of a reducing agent contained therein can be supported.

In an advantageous improvement of the invention, it is provided that the electrically heatable catalyst has a noble metal coating for the oxidative conversion of unburned exhaust gas components or a hydrolysis coating for the improved preparation of a liquid reducing agent. By an appropriate coating, the catalytic effect of the electrically heated catalyst can be improved.

In an advantageous embodiment of the invention, a low-pressure exhaust gas recirculation is provided, wherein an exhaust gas recirculation channel of the low-pressure exhaust gas recirculation downstream of the PM catalyst and upstream of the diesel particulate filter branches off from an exhaust passage of the exhaust system and opens upstream of a compressor of the exhaust gas turbocharger in a fresh gas line of an intake manifold of the internal combustion engine. Low-pressure exhaust gas recirculation, which branches off downstream of the PM catalyst and upstream of the diesel particulate filter, can reduce the space velocity in the diesel particulate filter. As a result, the conversion rates of the SCR coating of the diesel particulate filter can be increased.

Alternatively, it is advantageously provided that a low-pressure exhaust gas recirculation is provided, wherein a first exhaust gas recirculation channel of the low-pressure exhaust gas recirculation downstream of the PM catalyst and upstream of the diesel particulate filter branches off an exhaust passage of the exhaust system and a second exhaust gas recirculation channel of the low-pressure exhaust gas recirculation downstream of the diesel particulate filter from the Exhaust duct of the exhaust system branches off and upstream of a compressor of an exhaust gas turbocharger flows into a fresh gas line of the internal combustion engine, wherein in the second exhaust gas recirculation passage, preferably only in the second exhaust gas recirculation passage, a low-pressure exhaust gas recirculation cooler is arranged. As a result, a first partial flow of the exhaust gas can be recirculated without cooling via the first exhaust gas recirculation passage and a second partial flow of the exhaust gas can be recirculated in a cooled manner. Furthermore, it is possible, depending on the operating parameters of the internal combustion engine optionally to realize a cooled or uncooled exhaust gas recirculation via the low-pressure exhaust gas recirculation channels, whereby a condense of liquid in one of the exhaust gas recirculation channels is avoided and the raw emissions of the engine in a timely manner after a cold start by an uncooled low pressure Exhaust gas recirculation can be improved.

According to a further improvement of the exhaust aftertreatment system is advantageously provided that the inlet of the PM catalyst with a Abgaslauflänge of less than 400 mm, preferably less than 300 mm, more preferably less than 200 mm, ideally less than 150 mm from a Turbine outlet of the turbine of the exhaust gas turbocharger is arranged in the exhaust system. By a corresponding close-coupled arrangement of the PM catalyst and a short distance to the outlet of the turbine can be ensured that the PM catalyst reaches its operating temperature promptly after a cold start of the engine and in particular the required for self-cleaning of the PM catalyst temperature of more than 200 ° C is reached or exceeded.

According to the invention, a method for exhaust aftertreatment of an internal combustion engine is proposed, wherein an exhaust gas stream of the internal combustion engine is first passed through a turbine of an exhaust gas turbocharger. Subsequently, the exhaust gas stream downstream of the turbine is first passed through a PM catalyst arranged close to the engine and then through a diesel particulate filter arranged downstream of the PM catalyst. An advantage of this method is that soot particles are deposited on both the PM catalyst and on the diesel particulate filter, so that the load of the diesel particulate filter is slowed at the same PM emissions of the internal combustion engine and longer intervals between two regenerations of the diesel particulate filter are possible.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 ein Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems für einen Verbrennungsmotor;
• 2 ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems für einen Verbrennungsmotor, wobei die Positionen des elektrisch beheizbaren Katalysators und des PM-Katalysators gegenüber dem Ausführungsbeispiel in 1 vertauscht sind;
• 3 ein alternatives Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems für einen Verbrennungsmotor;
• 4 ein weiteres alternatives Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems für einen Verbrennungsmotor;
• 5 ein weiteres, besonders einfaches Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems für einen Verbrennungsmotor;
• 6 ein weiteres, alternatives Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems, wobei die Niederdruck-Abgasrückführung stromabwärts des PM-Katalysators und stromaufwärts des Dieselpartikelfilters aus dem Abgaskanal abzweigt;
• 7 ein weiteres, alternatives Ausführungsbeispiel eines erfindungsgemäßen Abgasnachbehandlungssystems, wobei die Positionen des elektrisch beheizbaren Katalysators und des PM-Katalysators gegenüber dem Ausführungsbeispiel in 6 vertauscht sind; und
• 8 ein Diagramm zur Visualisierung des Temperaturverlaufs stromaufwärts und stromabwärts des PM-Katalysators sowie der Geschwindigkeit eines Kraftfahrzeuges mit einem erfindungsgemäßen Abgasnachbehandlungssystem bei einem Testzyklus.

The invention will be explained below in embodiments with reference to the accompanying drawings. Identical components or components with the same function are shown in the different figures with the same reference numerals. Show it:

• 1 an embodiment of an exhaust aftertreatment system according to the invention for an internal combustion engine;
• 2 a further embodiment of an exhaust aftertreatment system according to the invention for an internal combustion engine, wherein the positions of the electrically heatable catalyst and the PM catalyst over the embodiment in 1 are reversed;
• 3 an alternative embodiment of an exhaust gas aftertreatment system according to the invention for an internal combustion engine;
• 4 a further alternative embodiment of an exhaust gas aftertreatment system according to the invention for an internal combustion engine;
• 5 a further, particularly simple embodiment of an exhaust aftertreatment system according to the invention for an internal combustion engine;
• 6 another alternative embodiment of an exhaust aftertreatment system according to the invention, wherein the low-pressure exhaust gas recirculation branches off from the exhaust passage downstream of the PM catalyst and upstream of the diesel particulate filter;
• 7 a further alternative embodiment of an exhaust aftertreatment system according to the invention, wherein the positions of the electrically heatable catalyst and the PM catalyst with respect to the embodiment in 6 are reversed; and
• 8th a diagram for visualizing the temperature profile upstream and downstream of the PM catalyst and the speed of a motor vehicle with an exhaust aftertreatment system according to the invention in a test cycle.

1 shows an embodiment of an exhaust aftertreatment system according to the invention 20 an internal combustion engine 10 , The internal combustion engine 10 has an outlet 12 , in particular an exhaust manifold 14 on, which with an exhaust system 22 of the internal combustion engine 10 connected is. The internal combustion engine 10 is as a self-igniting internal combustion engine 10 executed according to the diesel principle. In the exhaust system 22 of the internal combustion engine 10 is downstream of the outlet 12 a turbine 18 an exhaust gas turbocharger 16 arranged, with which a compressor 66 for air supply of the internal combustion engine 10 is driven. The internal combustion engine 10 has an inlet 68 on which with an intake tract 60 of the internal combustion engine 10 connected is. The intake tract 60 includes a fresh gas line 62 in which an air filter 64 and downstream of the air filter 64 at least one compressor 66 an exhaust gas turbocharger 18 is arranged. Downstream of the compressor 66 and upstream of an inlet 68 of the internal combustion engine 10 is a charge air cooler 58 arranged to pass through the compressor 66 to cool compressed fresh air and thus the filling of the combustion chambers of the internal combustion engine 10 continue to improve. The internal combustion engine 10 also has an outlet 12 on, on which an exhaust manifold 14 is formed, which with an exhaust aftertreatment system 20 of the internal combustion engine 10 connected is.

The exhaust system 22 points downstream of the turbine 18 a near-engine start catalyst 24 which is preferably formed as an oxidation catalyst. Downstream of the starting catalyst 24 is a supporting catalyst 28 arranged, which as PM catalyst 30 preferably with a noble metal coating 32 is trained. Immediately downstream of the PM catalyst 30 is an electrically heatable catalyst 26 arranged. The electrically heatable catalyst 26 has an electrical heating element, in particular an electric heating disk, which preferably with the support catalyst 28 is connected to increase the mechanical stability via a pinning. In this case, the electrically heatable catalyst 26 and the PM catalyst 30 designed as metal catalysts to allow high mechanical stability and also a high heat transfer between the components. The PM catalyst 30 has thin, corrugated steel foils with paddle-shaped sub-structures and interposed layers of sintered metal fleece, which serve as a storage medium for the soot particles. In PM catalysts 30 At sufficiently high temperatures and NO2 concentrations, the particles deposited there are oxidized and thus the PM catalyst 30 according to the so-called CRT method ("Continuous Regeneration Trap") continuously during operation of the internal combustion engine 10 regenerated. The necessary for the regeneration of nitrogen dioxide is on the upstream oxidation catalyst 24 formed or at the noble metal coating 32 of the PM catalyst 30 educated. Under a close-coupled arrangement in this context is an arrangement with a Abgaslauflänge of a maximum of 60 cm, preferably of a maximum of 40 cm, from the outlet 12 of the internal combustion engine 10 to understand. This is the inlet of the PM catalyst 30 preferably less than 400 mm, in particular less than 300 mm, more preferably less than 200 mm, ideally less than 150 mm downstream of an outlet of the turbine 18 the exhaust gas turbocharger 16 arranged.

Downstream of the PM catalyst 30 is a diesel particulate filter 34 with a coating 38 for the selective, catalytic reduction of nitrogen oxides (SCR coating) arranged. Downstream of the particulate filter 34 is a branch 46 the exhaust system 22 provided, at which there is an exhaust duct 44 in a low-pressure exhaust gas recirculation 50 and a subfloor channel 70 branches, which the diesel particulate filter 34 with a tailpipe of the exhaust system 22 combines. The low pressure exhaust gas recirculation 50 has an exhaust gas recirculation passage 52 on which the exhaust duct 44 at the junction 46 downstream of the diesel particulate filter 34 with a junction 54 in the intake tract 60 downstream of the air filter 64 and upstream of the compressor 66 combines. The low pressure exhaust gas recirculation 50 has a low pressure exhaust gas recirculation cooler 56 on, with which the recirculated exhaust gas before admixing with the fresh air in the intake 60 is cooled.

Downstream of the PM catalyst 30 and upstream of the diesel particulate filter 34 with the SCR coating 38 is a dosing module 40 for dosing a reducing agent 42 , in particular aqueous urea solution provided. In this case, the exhaust duct 44 the exhaust system 22 in the area between the PM catalyst 30 and the diesel particulate filter 34 a deflecting element 48 on. By the deflection of the exhaust gas flow creates a turbulence, which is a mixing of the metered reducing agent 42 with the exhaust gas before entering the diesel particulate filter 34 favors and thus the evaporation of the reducing agent 42 and the uniform distribution over the cross section of the exhaust passage 44 improved. Instead of a diesel particulate filter 34 with an SCR coating 38 can also, as in 2 shown, an uncoated diesel particulate filter 34 and a separate SCR catalyst 36 in the exhaust system 22 downstream of the dosing module 40 be installed.

In 2 is an alternative embodiment of an exhaust aftertreatment system according to the invention 20 shown. With essentially the same structure as 1 executed in this embodiment, the positions of the electrically heatable catalyst 26 and the PM catalyst 30 reversed. The PM catalyst 30 is thus downstream of the starting catalyst 24 and upstream of the electrically heatable catalyst 26 arranged and quasi by these two catalysts 24 . 26 embedded. In this case, the electrically heatable catalyst 26 in interaction with the dosing module 40 occur and be designed as a hydrolysis catalyst to evaporation of the liquid reducing agent 42 to favor. Further, downstream of the metering element 40 and upstream of the diesel particulate filter 34 an SCR catalyst 36 arranged. This can be the diesel particulate filter 34 free from a coating 38 be executed. Alternatively, as in 1 a diesel particulate filter 34 with an SCR coating instead of a diesel particulate filter 34 and a separate SCR catalyst 36 be used.

In 3 is another, alternative embodiment of an exhaust aftertreatment system according to the invention 20 shown. With essentially the same structure as 1 executed, omitted in this embodiment, the electrically heated catalyst 26 so that downstream of a startup catalyst 24 the PM catalyst 30 is arranged and downstream of the PM catalyst 30 no additional oxidation catalyst is present.

In 4 is another, alternative embodiment of an exhaust aftertreatment system according to the invention 20 for an internal combustion engine 10 shown. With essentially the same structure as 1 executed, omitted in this embodiment, the starting catalyst 24 and is powered by an electrically heated catalyst 26 which is upstream of the PM catalyst 30 is arranged replaced. Downstream of the PM catalyst 30 is not another electrically heatable catalyst 26 provided so that a total of one less catalyst is needed.

In 5 is a particularly simple embodiment of an exhaust aftertreatment system according to the invention 20 for an internal combustion engine 10 shown. With essentially the same structure as 1 executed, omitted in this embodiment, both the starting catalyst 24 as well as the electrically heatable catalyst 26 so that the exhaust aftertreatment system 20 just a PM catalyst 30 with a precious metal coating 32 and one downstream of the PM catalyst 30 arranged diesel particulate filter 34 with an SCR coating 38 having. Such an arrangement is especially in internal combustion engines 10 possible, which have low HC and CO raw emissions.

In 6 is another embodiment of an exhaust aftertreatment system 20 for an internal combustion engine 10 shown. With essentially the same structure as 1 listed branches the low-pressure exhaust gas recirculation 50 at a junction 46 downstream of the PM catalyst 30 and upstream of the diesel particulate filter 34 , in particular upstream of the metering module 40 , from the exhaust duct 44 the exhaust system 22 from. It can be at a sufficient degree of filtration of the PM-catalyst 30 and rugged components in low-pressure exhaust gas recirculation 50 as well as in the intake tract 60 the exhaust gas mass flow already before the NOx reduction stage on the coating 38 of the diesel particulate filter 34 respectively. This reduces the space velocities occurring there and can the degree of conversion for nitrogen oxides on the SCR coating 38 of the diesel particulate filter 34 increase. This offers the advantage that a faster heating of the exhaust gas can take place after a cold start. The disadvantage here, however, that the residual particle content in the on the low-pressure exhaust gas recirculation 50 recirculated exhaust gas is higher and thus to increased wear in the low-pressure exhaust gas recirculation 50 and in the intake tract 60 , in particular on the compressor 66 leads. Alternatively, as in 7 represented only a first, uncooled partial flow of the low-pressure exhaust gas recirculation 50 downstream of the PM catalyst 30 and upstream of the diesel particulate filter 34 be removed and a second cooled partial flow via a second low-pressure exhaust gas recirculation 50 downstream of the diesel particulate filter 34 removed and the fresh gas line 62 upstream of the compressor 66 be supplied.

In 8th is the temperature profile in the exhaust system 22 at a first measuring point T ₁ upstream of the PM catalyst 30 and a second measuring point T ₂ downstream of the PM catalyst 30 shown during a driving cycle of a motor vehicle. The speed profile of the drive cycle is also in 8th shown. It can be seen that a minimum temperature required for the continuous regeneration of the soot retained in the PM catalyst T _min of about 200 ° C even at relatively low speeds v and engine performance is achieved. It reaches or exceeds a middle class vehicle with a weight of about 1600 kg and a drag coefficient of about 0.25 - 0.3 and a face of about 2.5 - 3 m ² in the NEDC cycle at speeds of more than 50 km / h the necessary for the regeneration of the PM catalyst exhaust gas temperature of more than 200 ° C, so that even in practical operation a safe operation of the exhaust aftertreatment system according to the invention 20 can be achieved.

In summary it can be stated that by an inventive exhaust aftertreatment system 20 Even with comparatively high particulate raw emissions, an efficient exhaust aftertreatment and an extension of the regeneration intervals of the diesel particulate filter 34 possible are.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

outlet

14

exhaust manifold

16

turbocharger

18

turbine

20

aftertreatment system

22

exhaust system

24

Oxidation Catalyst / Start Catalyst

26

electrically heated catalyst

28

supporting catalyst

30

PM catalyst

32

noble metal coating

34

diesel particulate Filter

36

SCR catalyst

38

SCR coating

40

dosing

42

reducing agent

44

exhaust duct

46

branch

48

deflecting

50

Low-pressure exhaust gas recirculation

52

Exhaust gas recirculation passage

54

junction

56

Low-pressure exhaust gas recirculation cooler

58

Intercooler

60

intake system

62

Fresh gas line

64

air filter

66

compressor

68

inlet

70

Underbody channel

T

temperature

T ₁

Temperature upstream of the PM catalyst

T ₂

Temperature downstream of the PM catalyst

T _min

Minimum temperature for continuous regeneration of the PM catalyst

t

Time

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202014102809 U1 [0005]
• EP 2826971 A1 [0006]
• EP 2907564 A1 [0007]

Claims (10)

Aftertreatment system (20) for an internal combustion engine (10), in which in an exhaust system (22) of the internal combustion engine (10) downstream of an outlet (12) of the internal combustion engine (10), a turbine (18) of an exhaust gas turbocharger (16) and downstream of the turbine ( 18) a diesel particulate filter (34) are arranged, characterized in that downstream of the turbine (18) and upstream of the diesel particulate filter (34), a PM catalyst (30) is arranged. Exhaust after-treatment system (20) according to Claim 1 , characterized in that the diesel particulate filter (34) has a coating for the selective, catalytic reduction of nitrogen oxides (38) and in the exhaust system (22) downstream of the PM catalyst (30) and upstream of the diesel particulate filter (34) is a metering module (40) for the metering of reducing agent (42) in the exhaust system (22) is provided. Exhaust after-treatment system (20) according to Claim 1 , characterized in that the diesel particulate filter (34) upstream of an SCR catalyst (36) which in the exhaust system (22) downstream of the PM catalyst (30) and a metering module (40) for metering reducing agent (42) in the Exhaust system (22) is arranged. Exhaust after-treatment system (20) according to Claim 1 or 2 , characterized in that the PM catalyst (30) comprises a noble metal coating (32) for the oxidation of carbon monoxide and / or unburned hydrocarbons. Exhaust after-treatment system (20) according to Claim 3 , characterized in that the noble metal coating (32) has a noble metal content of 30 - 250 g / ft ³ , wherein the noble metal coating (32) has a platinum content of at least 40%. Exhaust after-treatment system (20) according to one of Claims 1 to 4 , characterized in that the PM catalyst (30) upstream of an oxidation catalyst (24) or the PM catalyst (30) upstream of an electrically heatable catalyst (26) or downstream. Exhaust after-treatment system (20) according to one of Claims 1 to 6 characterized in that a low pressure exhaust gas recirculation (50) is provided, wherein an exhaust gas recirculation passage (52) of the low pressure exhaust gas recirculation (50) downstream of the PM catalyst (30) and upstream of the diesel particulate filter (34) from an exhaust passage (44) of the Exhaust system (22) branches off. Exhaust after-treatment system (20) according to one of Claims 1 to 7 characterized in that a low pressure exhaust gas recirculation (50) is provided, wherein a first exhaust gas recirculation passage (52) of the low pressure exhaust gas recirculation downstream of the PM catalyst (30) and upstream of the diesel particulate filter (34) from an exhaust passage (44) of the exhaust system (22). branches off and a second exhaust gas recirculation passage (52) of the low pressure exhaust gas recirculation (50) downstream of the diesel particulate filter (34) from the exhaust passage (44) of the exhaust system (22) branches off and upstream of a compressor (66) of an exhaust gas turbocharger (16) in a fresh gas line (62 ), wherein in the second exhaust gas recirculation passage (52), a low-pressure exhaust gas recirculation cooler (56) is arranged. Exhaust after-treatment system (20) according to one of Claims 1 to 8th , characterized in that the PM catalyst (30) with an exhaust gas flow length (L) of less than 400 mm from a turbine outlet of the turbine (18) of the exhaust gas turbocharger (16) in the exhaust system (22) is arranged. A method for exhaust aftertreatment of an internal combustion engine (10), wherein an exhaust gas stream of the internal combustion engine (10) is passed through a turbine (18) of an exhaust gas turbocharger, characterized in that the exhaust gas stream downstream of the turbine (18) initially by a PM catalyst arranged close to the engine (30 ) and then passed through a diesel particulate filter (34) disposed downstream of the PM catalyst (30).

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