DE102021004145A1 - Exhaust system for an internal combustion engine of a motor vehicle - Google Patents

Abstract

The invention relates to an exhaust system (10) for an internal combustion engine (12) of a motor vehicle, with a high-pressure exhaust gas recirculation system (16) which has a first exhaust gas recirculation line (18) for recirculating exhaust gas from the internal combustion engine (12) flowing through the exhaust system (10). with a first dosing element (34), by means of which a reducing agent for denitrating the exhaust gas can be introduced into the exhaust gas flowing through the exhaust system (10) at a first introduction point (EB1) arranged downstream of the first exhaust gas recirculation line (18), and with a downstream of the first Introduction point (EB1) arranged and driven by the exhaust gas turbine wheel (26) of a turbine (24) for an exhaust gas turbocharger (22).

Description

The invention relates to an exhaust system for an internal combustion engine of a motor vehicle, in particular a motor vehicle, according to the preamble of patent claim 1.

Such an exhaust system for an internal combustion engine of a motor vehicle, in particular a motor vehicle, is, for example, already DE 10 2010 063 425 A1 to be taken as known. The exhaust system has a high-pressure exhaust gas recirculation system (HP-EGR), which has a first exhaust gas recirculation line for recirculating exhaust gas flowing through the exhaust system. The exhaust system also has a first dosing element, by means of which a reducing agent for denitrating the exhaust gas can be introduced into the exhaust gas flowing through the exhaust system at a first introduction point arranged downstream of the first exhaust gas recirculation line. Furthermore, the exhaust system has a turbine wheel of a turbine for an exhaust gas turbocharger, which is arranged downstream of the introduction point and can be driven by the exhaust gas flowing through the exhaust system.

Furthermore, the DE 10 2015 016 986 A1 another exhaust system of an internal combustion engine

The object of the present invention is to improve an exhaust system of the type mentioned at the outset.

This problem is solved by an exhaust system with the features of patent claim 1 . Advantageous configurations with expedient developments of the invention are specified in the remaining claims. In order to improve an exhaust system of the type specified in the preamble of patent claim 1, the invention provides that the exhaust system has an exhaust gas aftertreatment device which is arranged downstream of the turbine wheel and has a particle filter. By means of the particle filter, particles contained in the exhaust gas flowing through the exhaust system, in particular soot particles, can be filtered out of the exhaust gas. The exhaust gas aftertreatment device also includes at least one catalytically effective catalyst coating for selective catalytic reduction (SCR) for denitrification of the exhaust gas. Denitrification of the exhaust gas means that nitrogen oxides (NOx) contained in the exhaust gas are at least partially removed from the exhaust gas. For this purpose, the nitrogen oxides contained in the exhaust gas react as part of the selective catalytic reduction with ammonia provided by the reducing agent, for example, to form nitrogen and water, as a result of which the nitrogen oxides participating in the selective catalytic reduction (SCR) are removed from the exhaust gas.

The exhaust system also includes a low-pressure exhaust gas recirculation system (LP-EGR), which has a second exhaust gas recirculation line, arranged downstream of the exhaust gas aftertreatment device, for recirculating exhaust gas flowing through the exhaust system. The exhaust system also includes a second dosing element, by means of which a reducing agent for denitrating the exhaust gas can be introduced into the exhaust gas flowing through the exhaust system at a second introduction point arranged downstream of the second exhaust gas recirculation line. The reducing agent that can be introduced into the exhaust gas at the second introduction point by means of the second dosing element can be the same reducing agent that can be introduced into the exhaust gas at the first introduction point by means of the first dosing element. For example, the reducing agent that can be introduced into the exhaust gas at the respective introduction point is an aqueous urea solution, which can provide the aforementioned ammonia.

The exhaust system also has an SCR catalytic converter which is arranged downstream of the second introduction point and is catalytically active for the previously described SCR for denitrification of the exhaust gas. Since the SCR catalytic converter is arranged downstream of the catalytic converter coating in the flow direction of the exhaust gas flowing through the exhaust system, the catalytic converter coating is a catalytic converter coating close to the engine, with the SCR catalytic converter being an SCR catalytic converter remote from the engine. For example, the internal combustion engine and the exhaust gas aftertreatment device and thus the catalyst coating are arranged in a common engine compartment of the motor vehicle, the engine compartment being at least partially delimited, for example, by a structure of the motor vehicle designed in particular as a self-supporting body. In this regard, the SCR catalytic converter is, for example, an underfloor catalytic converter (UB catalytic converter), which is arranged, for example, in the vehicle vertical direction below a floor of the body, in particular in such a way that the SCR catalytic converter is overlapped in the vehicle vertical direction upwards by the floor. The interior of the body, also referred to as the passenger cell or passenger compartment, and thus of the motor vehicle, is delimited downwards in the vertical direction of the vehicle by the floor.

• Aufgrund immer anspruchsvoller gestalteter Emissionsgrenzwerte einhergehend mit neuen Anforderungen bezüglich Realemission (RDE - Real Drive Emission) wird es immer entscheidender, dass Systeme zur Abgasreinigung sowohl bei tiefen Temperaturen und vor allem in einem Startfall maximale Reinigungseffizienz aufweisen. Deshalb gibt es den Trend, entsprechende Abgasnachbehandlungskonzepte möglichst motornah unterzubringen, um das dortige höhere Temperaturniveau zu nutzen. Zusätzlich werden Heizeinrichtungen wie Brennersysteme und/oder elektrisch beheizbare Komponenten vorgeschlagen. Prinzipiell lassen sich mithilfe dieser Maßnahmen deutliche Verbesserungen erzielen, aber die Komplexität dieser Systeme ist zunehmend schwieriger umsetzbar, die konstruktive Umsetzung ist oft entweder nicht oder nur mit großen Einschränkungen möglich, und die anfallenden Zusatzkosten reduzieren deutlich die Wirtschaftlichkeit dieser Antriebskonzepte. Auch die Aufbereitung des Reduktionsmittels insbesondere durch Thermolyse und/oder Hydrolyse benötigt ausreichend hohe Temperaturen für eine vorteilhafte Funktion und deshalb sollten die auch als Eindosierstellen bezeichneten Einbringstellen ebenfalls möglichst motornah angebracht sein. Dies kann durch die Erfindung realisiert werden. Um den oben beschriebenen Problemstellungen zu begegnen und ein gegenüber herkömmlichen Lösungen verbessertes Abgasnachbehandlungssystem zu realisieren, ist vorzugsweise die erste Einbringstelle besonders nahe an der Verbrennungskraftmaschine und insbesondere direkt an einem Motorauslass der Verbrennungskraftmaschine und dabei stromab der ersten Abgasrückführleitung angeordnet. Hierunter ist insbesondere zu verstehen, dass die erste Abgasrückführleitung an einer Abzweigstelle fluidisch mit einem von dem Abgas durchströmbaren Rohr der Abgasanlage verbunden ist, sodass an der Abzweigstelle mittels der ersten Abgasrückführleitung zumindest ein Teil des das Rohr durchströmenden Abgases aus dem Rohr abzweigbar und insbesondere zu einem Einlasstrakt der Verbrennungskraftmaschine rückführbar ist. Somit ist das erste Dosierelement stromab der Abzweigstelle angeordnet.

The exhaust gas can be post-treated particularly advantageously by means of the exhaust system, in particular during and/or shortly after a cold start of the internal combustion engine. A particularly advantageous cold start behavior can thus be achieved by means of the invention. The invention lies in particularly based on the following knowledge and considerations:

• Due to increasingly demanding emission limit values combined with new requirements regarding real emissions (RDE - Real Drive Emission), it is becoming increasingly important that systems for exhaust gas cleaning have maximum cleaning efficiency both at low temperatures and especially in a starting case. Therefore, there is a trend towards accommodating corresponding exhaust aftertreatment concepts as close as possible to the engine in order to use the higher temperature level there. In addition, heating devices such as burner systems and/or electrically heatable components are proposed. In principle, significant improvements can be achieved with the help of these measures, but the complexity of these systems is becoming increasingly difficult to implement, the constructive implementation is often either not possible or only possible with major restrictions, and the additional costs incurred significantly reduce the profitability of these drive concepts. The processing of the reducing agent, in particular by thermolysis and/or hydrolysis, also requires sufficiently high temperatures for an advantageous function and therefore the injection points, also referred to as metering points, should also be attached as close as possible to the engine. This can be realized by the invention. In order to address the problems described above and to implement an exhaust gas aftertreatment system that is improved compared to conventional solutions, the first introduction point is preferably arranged particularly close to the internal combustion engine and in particular directly at an engine outlet of the internal combustion engine and thereby downstream of the first exhaust gas recirculation line. This means in particular that the first exhaust gas recirculation line is fluidly connected at a branch point to a pipe of the exhaust system through which the exhaust gas can flow, so that at the branch point, at least part of the exhaust gas flowing through the pipe can be branched off from the pipe by means of the first exhaust gas recirculation line, and in particular to one Intake tract of the internal combustion engine is traceable. Thus, the first dosing element is arranged downstream of the branching point.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own, without going beyond the scope of the leave invention.

• 1 eine schematische Darstellung einer Abgasanlage für eine Verbrennungskraftmaschine eines Kraftfahrzeugs, insbesondere eines Kraftwagens; und
• 2 eine schematische Darstellung einer Abgasnachbehandlungseinrichtung der Abgasanlage.

The drawing shows in:

• 1 a schematic representation of an exhaust system for an internal combustion engine of a motor vehicle, in particular a motor vehicle; and
• 2 a schematic representation of an exhaust aftertreatment device of the exhaust system.

Elements that are the same or have the same function are provided with the same reference symbols in the figures.

1 shows a schematic representation of an exhaust system 10 for an internal combustion engine of a motor vehicle, in particular a motor vehicle, which is preferably designed as a reciprocating piston engine and is also referred to as an internal combustion engine. The internal combustion engine is preferably designed as a diesel engine. The internal combustion engine is in 1 shown schematically and designated 12. Internal combustion engine 12 has cylinders 14 in which combustion processes take place during fired operation of internal combustion engine 12 . Exhaust gas from internal combustion engine 12 results from the respective combustion process, the exhaust gas from which can flow through exhaust system 10 .

The exhaust system 10 has a high-pressure exhaust gas recirculation system 16 which has a first exhaust gas recirculation line 18 . The first exhaust gas recirculation line 18 is also referred to as the first recirculation line. The internal combustion engine 12 also has an intake tract 20 through which air can flow, by means of which the air flowing through the intake tract 20 is guided to and into the cylinders 14 . An exhaust gas turbocharger 22 is provided, which has a turbine 24 with a turbine wheel 26 and a compressor 28 with a compressor wheel 30 . The compressor 28 and thus the compressor wheel 30 are arranged in the intake section 20 so that the air flowing through the intake section 20 can be compressed by means of the compressor wheel 30 . The turbine 24 and thus the turbine wheel 26 are arranged in the exhaust system 10, in particular in an exhaust pipe 32 of the exhaust system 10 through which the exhaust gas can flow and which is also simply referred to as a pipe. The turbine wheel 26 can be driven by the exhaust gas flowing through the exhaust system 10 and thus the exhaust pipe 32 .

The first exhaust gas recirculation line 18 is fluidically connected to the exhaust pipe 32 at a first branch point A1. In addition, the first exhaust gas recirculation line 18 is fluidically connected to the intake tract 20 at a first introduction point E1. The introduction point E1 is arranged upstream of the cylinder 14 and downstream of the compressor wheel 30 in the flow direction of the air flowing through the intake tract 20 . The branching point A1 is arranged downstream of the cylinders 14 in the flow direction of the exhaust gas flowing through the exhaust system 10 and thus the exhaust pipe 32 . At the branching point A1 , at least part of the exhaust gas flowing through the exhaust pipe 32 can be branched off from the exhaust pipe 32 by means of the exhaust gas recirculation line 18 and introduced into the exhaust gas recirculation line 18 . The exhaust gas branched off at branch point A1 by means of the exhaust gas recirculation line 18 can flow through the exhaust gas recirculation line 18 . At the introduction point E1, the exhaust gas flowing through the exhaust gas recirculation line 18 can flow out of the exhaust gas recirculation line 18 and flow into the intake tract 20. The feature that the exhaust gas recirculation line 44 is arranged downstream of the exhaust gas aftertreatment device 36 is therefore to be understood as meaning that the branching point A1 is arranged upstream of the exhaust gas aftertreatment device 36 .

Exhaust system 10 has a first dosing element 34, by means of which a preferably liquid reducing agent can be introduced, in particular injected, into the exhaust gas flowing through exhaust system 10 and thus through exhaust pipe 32 at a first introduction point EB1. The reducing agent is preferably an aqueous urea solution. The reducing agent is designed to provide ammonia (NH ₃ ). It can be seen that the introduction point EB1 is arranged downstream of the first exhaust gas recirculation line 18 . This means that the insertion point EB1 is arranged downstream of the first branch point A1. Furthermore, it is off 1 recognizable that the turbine wheel 26 is arranged downstream of the insertion point EB1.

The exhaust system 10 also has an exhaust gas aftertreatment device 36 which is arranged downstream of the turbine wheel 26 . The exhaust aftertreatment device 36 includes a particle filter 38 and an in 1 Catalyst coating 40 shown particularly schematically, which is catalytically effective for a selective catalytic reduction (SCR) for denitrification of the exhaust gas flowing through the exhaust gas aftertreatment device 36 . As part of the selective catalytic reduction (SCR), nitrogen oxides (NOx) contained in the exhaust gas flowing through the exhaust gas aftertreatment device 36 react with the ammonia provided by the reducing agent to form nitrogen and water, whereby the nitrogen oxides participating in the SCR are removed from the exhaust gas. As a result, the exhaust gas is denitrified.

The exhaust system 10 also has a low-pressure exhaust gas recirculation system 42 which has a second exhaust gas recirculation line 44 . The second exhaust gas recirculation line 44 is also referred to as the second recirculation line. Out of 1 it can be seen that the second exhaust gas recirculation line 44 is arranged downstream of the exhaust gas aftertreatment device 36 . This means in particular the following: At a second branch point A2, the second exhaust gas recirculation line 44 is fluidically connected to the exhaust system 10 with a second exhaust pipe 46 of the exhaust system 10, also referred to simply as the second pipe, with the second exhaust pipe 46 from which the exhaust system 10 through-flowing exhaust gas can flow through. As a result, at branch point A2, which is arranged downstream of exhaust gas aftertreatment device 36, at least part of the exhaust gas flowing through exhaust gas pipe 46 and in particular denitrified can be branched off from exhaust gas pipe 46 by means of exhaust gas recirculation line 44 and returned to intake tract 20. Exhaust gas recirculation line 44 is fluidically connected to intake tract 20 at a second introduction point E2, so that the exhaust gas branched off by means of exhaust gas recirculation line 44 and flowing through exhaust gas recirculation line 44 can flow out of exhaust gas recirculation line 44 at introduction point E2 and flow into the intake tract. Out of 1 it can be seen that the entry point E2 is arranged upstream of the compressor wheel 30 and thus upstream of the entry point E1.

Exhaust system 10 also has a second dosing element 48, by means of which the previously described reducing agent is introduced into exhaust pipe 46 and thus into the exhaust gas flowing through exhaust pipe 46 or exhaust system 10 at a second introduction point EB2 arranged downstream of branch point A2 and downstream of exhaust gas recirculation line 44 can be introduced, in particular injected.

Furthermore, the exhaust system 10 has an SCR catalytic converter 50 arranged downstream of the introduction point EB2, which is catalytically active for the SCR described above and thus represents an additional SCR catalytic converter with regard to the catalytic converter coating 40 . For example, the internal combustion engine 12 and the exhaust gas aftertreatment device 36 are arranged in a common engine compartment of the motor vehicle. Since exhaust gas aftertreatment device 36 is arranged upstream of SCR catalytic converter 50 in the flow direction of the exhaust gas flowing through exhaust system 10, exhaust gas aftertreatment device 36 is close to the engine, with the SCR Catalyst 50 is remote from the engine. In particular, the SCR catalyst 50 is an underfloor catalyst.

At the in 1 The exemplary embodiment shown is formed by a further SCR catalytic converter 52 provided in addition to the SCR catalytic converter 50, the catalytically active catalytic converter coating 40 for selective catalytic reduction (SCR) for denitrification of the exhaust gas, with the SCR catalytic converter 52 and thus the catalytic converter coating 40 being upstream of the particle filter 38 are arranged. At the in 1 shown embodiment, the particulate filter 38 is a diesel particulate filter (DPF) since the internal combustion engine 12 is a diesel engine. In addition, the particulate filter has an additional catalyst coating that is catalytically effective for oxidizing unburned hydrocarbons (HC) contained in the exhaust gas and carbon monoxide (CO) contained in the exhaust gas, so that the particulate filter 38 is designed as a cDPF, for example.

2 shows exhaust gas aftertreatment device 36 in a schematic representation 2 it can be seen that in the flow direction of the exhaust gas flowing through exhaust system 10 between catalyst coating 40, in this case between SCR catalyst 52, and particle filter 38, i.e. upstream of particle filter 38 and downstream of catalyst coating 40, in particular SCR catalyst 52, an electrical Heating element 54 is arranged. For example, the electrical heating element 54 is designed as an electrically heatable catalytic converter (EHC), in particular as an electrically heatable oxidation catalytic converter.

In a further specific embodiment, provision can be made for the particulate filter 38 arranged in particular downstream of the catalytic converter coating 40 and in particular of the SCR catalytic converter 52 to have a storage coating designed for at least temporarily storing nitrogen oxide contained in the exhaust gas, so that the particulate filter 38 is designed as an NDPF, for example.

In a further configuration, it is conceivable that the catalyst coating 40 is a layer or coating of the particle filter 38, so that the particle filter 38 is embodied as an SDPF, for example. In this case, for example, the exhaust gas aftertreatment device 36 includes an oxidation catalytic converter, in particular a diesel oxidation catalytic converter (DOC), the oxidation catalytic converter preferably being arranged downstream of the particle filter 38, in particular the SDPF. Related to 2 this means, for example, that the particulate filter 38 having the catalytic converter coating 40 is arranged instead of the SCR catalytic converter 52, in which case the oxidation catalytic converter then takes the place of the in 2 shown particle filter 38 is arranged, which is then arranged upstream of the oxidation catalyst.

Furthermore, it is conceivable that the exhaust gas aftertreatment device 36 has a nitrogen oxide storage catalytic converter (NSK) arranged downstream of the particle filter 38 , in particular the SDPF, and thereby downstream of the catalytic converter coating 40 . Related to 2 this means that the particulate filter 38 having the catalytic converter coating 40, in particular the SDPF, is then arranged in place of the SCR catalytic converter 52, in which case the nitrogen oxide storage catalytic converter (NSK) then takes the place of the in 2 particle filter 38 shown would be arranged.

Due to the fact that the insertion point EB1 is arranged upstream of the turbine wheel 26, the insertion point EB1 is arranged particularly close to the engine. In particular, the entry point EB1, also referred to as metering, can be arranged directly at an engine outlet of internal combustion engine 12, but the entry point EB1 or the metering point is arranged downstream of junction point A1, which is also simply referred to as junction and in front of turbine wheel 26, in particular in front of turbine 24 is. For example, the metering element 34, also referred to as a metering valve or designed as a metering valve, is not only used to introduce the reducing agent into the exhaust gas, but also to introduce a particularly liquid fuel into the exhaust gas, particularly at the introduction point EB1. The fuel can be conveyed via a low-pressure fuel system. Switching from fuel to reducing agent or vice versa, i.e. switching from the introduction of fuel to the introduction of the reducing agent and vice versa at the introduction point EB1 by means of the dosing element 34, can be done, for example, by means of a 2/3-way switching valve, also simply referred to as a valve will be realized. The valve is preferably arranged very close to the metering element 34 designed as a reducing agent and fuel metering module, so that only a small volume is used here for both media in the form of the fuel and the reducing agent.

• - Nach Kaltstart kann ab einer Temperatur von ca. 130°C am cDPF beziehungsweise DOC oder EHC (elektrisch beheizbarer Katalysator) Kraftstoff über die Einbringstelle EB1 vor der Turbine 24 dosiert werden. Mithilfe des Katalysators (SCR-Katalysator 52 und/oder cDPF 38) kann der eindosierte Kraftstoff dann oxidiert werden, wodurch das motornahe Abgassystem in Form der Abgasnachbehandlungseinrichtung 36 schnell aufgeheizt werden kann. Optional kann dies begleitet werden durch innermotorische Heizstrategien. Ab einer Temperatur von größer als 150°C bis 160°C vor dem SDPF beziehungsweise vor dem SCR-Katalysator 52 kann auf das Einbringen des Reduktionsmittels umgeschaltet werden, insbesondere von dem Einbringen des Kraftstoffs aus.
• - Im dauerhaft niedriglastigen Bereich charakterisiert von Temperaturen vor dem motornahen Einheizen von kleiner als 150°C kann optional auch Kraftstoff und Reduktionsmittel alternierend eindosiert werden, um die maximale Emissionsreduktionsleistung zu gewährleisten.
• - Im Rahmen einer Partikelfilterregeneration, insbesondere DPF-Regeneration, kann die hierfür erforderliche Temperatur vor dem Partikelfilter 38, insbesondere DPF, wie beispielsweise SDPF beziehungsweise cDPF, durch eine kontinuierliche Kraftstoffdosierung (Dosiermenge wird über die Zieltemperatur vor DPF geregelt) an der Einbringstelle EB1 auch im Leerlauf beziehungsweise Niederlastbereich sichergestellt werden. Der erforderliche NOx-Umsatz findet dabei über den als Unterboden-SCR-Katalysator ausgebildeten SCR-Katalysator 50 mit dem Einbringen des Reduktionsmittels an der Einbringstelle EB2 statt.
• - Normalerweise müssten vor dem Abstellen aufgrund des Einfrierschutzes Leitungen zum Führen des Reduktionsmittels inklusive des Ventils leergesaugt werden. Diese Notwendigkeit entfällt bei dem in den Figuren gezeigten Ausführungsbeispiel für die Einbringstelle EB1, weil hier die Leitungen vor dem Abstellprozess immer mit Kraftstoff befüllt werden.
• - Die Dosiergenauigkeit des SCR-Systems wird durch den Entfall des Rücksaugens an der Einbringstelle EB1 dadurch gesteigert, da kein undefiniertes Gas-Volumen in das Dosiersystem eingebracht wird und so immer ein wenig kompressibles Medium vor dem Injektor (Dosierelement 34) steht.
• - Durch das regelmäßige Spülen der Leitungen des Ventils kann auch ein Reduktionsmittelablagerungsrisiko für diese Bauteile dadurch reduziert werden (alle Oberflächen sind mit hydrophobem Kraftstoff benetzt).
• - Für die Ausführungsform mit NSK-Komponenten im motornahen Bereich, das heißt für die Ausführungsform, bei welcher der zuvor genannte Stickoxid-Speicherkatalysator stromab des Partikelfilters 38 der Abgasnachbehandlungseinrichtung 36 angeordnet ist, kann der zur Stickoxid-Regeneration erforderliche, unterstöchiometrische Motorbetrieb durch die Eindosierung des Kraftstoffs an der Einbringstelle EB1 unterstützt und damit deutlich vereinfacht werden.
• - Durch die Kombination von Kraftstoffdosierung mit Reduktionsmitteldosierung vor der Turbine 24 entfällt ein auch als HC-Doser bezeichnetes Dosierventil, und der ansonsten notwendige Mischer zur Realisierung einer Ammoniak- und HC-Gleichverteilung. Diese Funktion wird hier durch einen Turbinendurchgang, das heißt dadurch sichergestellt, dass das Reduktionsmittel beziehungsweise der Kraftstoff durch die Turbine 24 hindurchströmen.
• - Die hydraulische Verbindung des Ventils und des Injektors (Dosierelement 34) wird zweckmäßig in Edelstahl ausgeführt, um die Materialverträglichkeit für beide Medien (Reduktionsmittel und Kraftstoff beziehungsweise Diesel) zu gewährleisten.
• - Stromauf des Ventils wird das Einbringen des anderen Mediums in beiden hydraulischen Zuleitungen durch ein Rückschlagventil verhindert.
• - Der Vordruck vor dem Ventil kann für beide Medien vergleichbar gewählt werden, um eine Mischung stromauf des Umschaltventils (Ventil) weiter auszuschließen.

Downstream of the turbine wheel 26, in particular downstream of the turbine 24, and in particular downstream of a turbine outlet of the turbine 24, the SCR catalytic converter 52 is present as the first component, followed by the particulate filter 38 (cDPF) embodied as a coated particulate filter. The further, catalytic catalyst coating of the particle filter 38 is catalytically effective for oxidizing unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen monoxide (NO) in the exhaust gas, so the additional catalyst coating should support the oxidation of hydrocarbons, CO and NO and thus take on the function of an oxidation catalyst. Because there is no separate mixer or evaporator for preparing the reducing agent upstream of the SCR catalytic converter 52, the exhaust gas aftertreatment device 36, which is designed to be catalytically active, for example, can be arranged particularly close to the internal combustion engine 12, also simply referred to as the engine. As a result, the energy from the combustion is used even more quickly to reach the necessary temperatures at the SCR catalytic converter 52 . The branching point A2 is also referred to as the outlet of the exhaust gas recirculation line 44, which is also referred to as the low-pressure EGR line, with the second dosing element 48 being arranged after the branching point A2 (outlet). This is followed by the SCR catalytic converter 50. In particular, at least the following advantages can be realized:

• After a cold start, fuel can be metered via the injection point EB1 in front of the turbine 24 from a temperature of approx. 130° C. at the cDPF or DOC or EHC (electrically heatable catalytic converter). The metered fuel can then be oxidized with the aid of the catalytic converter (SCR catalytic converter 52 and/or cDPF 38), as a result of which the exhaust gas system close to the engine in the form of the exhaust gas aftertreatment device 36 can be heated up quickly. Optionally, this can be accompanied by internal engine heating strategies. From a temperature of greater than 150° C. to 160° C. in front of the SDPF or in front of the SCR catalytic converter 52, it is possible to switch to introducing the reducing agent, in particular starting with the introduction of the fuel.
• - In the permanently low-load range, characterized by temperatures of less than 150°C before heating up close to the engine, fuel and reducing agent can optionally also be metered in alternately in order to ensure maximum emission reduction performance.
• - As part of a particle filter regeneration, in particular DPF regeneration, the temperature required for this in front of the particle filter 38, in particular DPF, such as SDPF or cDPF, can be achieved by continuous fuel metering (metering quantity is controlled via the target temperature in front of the DPF) at the introduction point EB1, also in the Idle or low-load range can be ensured. The required NOx conversion takes place via the SCR catalytic converter 50 designed as an underbody SCR catalytic converter with the introduction of the reducing agent at the introduction point EB2.
• - Normally, before switching off, due to the anti-freeze protection, the lines for guiding the reducing agent including the valve would have to be drained. This necessity does not apply to the embodiment shown in the figures for the introduction point EB1, because here the lines are always filled with fuel before the shutdown process.
• - The dosing accuracy of the SCR system is increased by the elimination of sucking back at the introduction point EB1, since no undefined gas volume is introduced into the dosing system and there is always a slightly compressible medium in front of the injector (dosing element 34).
• - Regular flushing of the valve lines can also reduce the risk of reducing agent deposits on these components (all surfaces are wetted with hydrophobic fuel).
• - For the embodiment with NSK components in the area close to the engine, i.e. for the embodiment in which the aforementioned nitrogen oxide storage catalytic converter is arranged downstream of the particle filter 38 of the exhaust gas aftertreatment device 36, the sub-stoichiometric engine operation required for nitrogen oxide regeneration can be achieved by metering in the Fuel supported at the injection point EB1 and thus significantly simplified.
• The combination of fuel metering with reducing agent metering upstream of the turbine 24 eliminates the need for a metering valve, also referred to as an HC meter, and the mixer that would otherwise be required to achieve equal distribution of ammonia and HC. This function is ensured here by a turbine passage, that is to say by the reducing agent or the fuel flowing through the turbine 24 .
• - The hydraulic connection of the valve and the injector (metering element 34) is suitably made of stainless steel to ensure material compatibility for both media (reducing agent and fuel or diesel).
• - Upstream of the valve, the introduction of the other medium in both hydraulic supply lines is prevented by a non-return valve.
• - The pre-pressure before the valve can be selected to be comparable for both media in order to further rule out a mixture upstream of the switching valve (valve).

Reference List

10

exhaust system

12

internal combustion engine

14

cylinder

16

High pressure exhaust gas recirculation

18

First exhaust gas recirculation line

20

admission tract

22

exhaust gas turbocharger

24

turbine

26

turbine wheel

28

compressor

30

compressor wheel

32

exhaust pipe

34

first dosing element

36

exhaust aftertreatment device

38

particle filter

40

catalyst coating

42

Low-pressure exhaust gas recirculation

44

second exhaust gas recirculation line

46

exhaust pipe

48

second dosing element

50

SCR catalytic converter

52

SCR catalytic converter

54

electric heating element

A1

first junction

A2

second junction

E1

first entry point

E2

second entry point

EB1

first entry point

EB2

second entry point

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• DE 102010063425 A1 [0002]
• DE 102015016986 A1 [0003]

Claims (9)

Exhaust system (10) for an internal combustion engine (12) of a motor vehicle, with a high-pressure exhaust gas recirculation system (16), which has a first exhaust gas recirculation line (18) for recirculating exhaust gas from the internal combustion engine (12) flowing through the exhaust system (10), with a first dosing element (34), by means of which a reducing agent for denitrating the exhaust gas can be introduced into the exhaust gas flowing through the exhaust system (10) at a first introduction point (EB1) arranged downstream of the first exhaust gas recirculation line (18), and with a downstream of the first introduction point (EB1) arranged and driven by the exhaust gas turbine wheel (26) of a turbine (24) for an exhaust gas turbocharger (22), characterized by : - an exhaust gas aftertreatment device (36) arranged downstream of the turbine wheel (26) which has a particle filter (38) and at least one for a selective catalytic reduction for denitrification of the exhaust gas has a catalytically active catalyst coating (40), - a e low-pressure exhaust gas recirculation (42), which has a second exhaust gas recirculation line (44) arranged downstream of the exhaust gas after-treatment device (36) for recirculating exhaust gas, second introduction point (EB2) a reducing agent for denitrification of the exhaust gas into which the exhaust gas flowing through the exhaust system (10) can be introduced, and - an SCR catalytic converter (50) arranged downstream of the second introduction point (EB2). Exhaust system (10) after claim 1 , characterized in that the catalyst coating (40) is formed by a further SCR catalyst (52). Exhaust system (10) after claim 2 , characterized in that the particulate filter (38) has a catalytically effective for an oxidation of unburned hydrocarbons contained in the exhaust gas and of carbon monoxide contained in the exhaust gas, further catalyst coating. Exhaust system (10) after claim 2 or 3 , characterized in that an electric heating element (54) is arranged upstream of the particle filter (38) and downstream of the further SCR catalytic converter (52). Exhaust system (10) after claim 2 , characterized in that the particle filter (38) has a storage coating designed for at least temporarily storing stock oxide contained in the exhaust gas. Exhaust system (10) after claim 1 , characterized in that the catalyst coating (40) is a layer of the particulate filter (38). Exhaust system (10) after claim 6 , characterized in that the exhaust gas after-treatment device (36) has an oxidation catalytic converter arranged downstream of the particle filter (38) and thereby downstream of the layer (40). Exhaust system (10) after claim 6 , characterized in that the exhaust gas after-treatment device (36) has a nitrogen oxide storage catalytic converter arranged downstream of the particle filter (38) and thereby downstream of the layer. Exhaust system (10) according to one of Claims 1 until 3 , characterized in that the first dosing element (34), in addition to the reducing agent, also introduces fuel into the exhaust gas at the introduction point (EB1).

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