DE102019203938A1 - Exhaust gas aftertreatment system and method - Google Patents

Abstract

An exhaust gas aftertreatment system includes an exhaust gas recirculation subsystem, EGR subsystem; a device for selective catalytic reduction, SCR device, with an entry surface, an exit surface and a catalytically active substrate, which is arranged between the entry surface and the exit surface and is designed to guide exhaust gas from the entry surface to the exit surface for catalytic treatment, wherein the catalytically active substrate comprises a return channel and a catalytic reduction channel, the channels being fluidly separated from one another; a first flow separation device, which is arranged on the inlet surface and is designed to guide the exhaust gas into the return duct and the catalytic reduction duct; an injector which is designed to inject reducing agent into the exhaust gas which is conducted into the catalytic reduction channel; and a second flow separation device which is arranged on the outlet surface and is designed to guide at least a portion of the exhaust gas from the return duct to the EGR subsystem and the remaining exhaust gas from the return duct together with the exhaust gas from the catalytic reduction duct to an exhaust outlet.

Description

Technical field

The present invention relates to a system for exhaust gas aftertreatment, in particular during the operation of an internal combustion engine of an automobile, e.g. of a diesel engine. The present invention further relates to a method for exhaust gas aftertreatment.

background

A catalytic converter is an exhaust gas purification device that converts toxic gases and pollutants in the exhaust gas of an internal combustion engine into less toxic or non-toxic substances by catalysing a redox reaction (a reduction process and a complementary oxidation process). Catalysts are used particularly in internal combustion engines that run on either gasoline or diesel, including lean burn engines, but also in kerosene heaters and stoves and so on. Other uses of catalysts are known for gas engines, e.g. LPG engines or compressed gas engines.

Selective catalytic reduction (SCR) is a known technique that is used in catalytic converters in which nitrogen oxides, so-called NOx, are converted into diatomic nitrogen and water with the help of a catalytic converter. A gaseous and / or liquid reducing agent, e.g. anhydrous ammonia, aqueous ammonia or urea is added to an exhaust gas stream and adsorbed on the catalyst. SCR converters require a certain temperature in order to function properly, so that the catalytic reaction is typically only initiated above temperatures between 200 ° C and 250 ° C. The SCR is normally heated by the exhaust gases flowing through it. It takes a relatively long time for SCR converters to heat up, especially during a cold start, and thus until NOx emissions are effectively reduced.

One approach that is often used with SCR devices is called exhaust gas recirculation (EGR), where NOx emissions are further reduced by returning some of the exhaust gas to the engine. The recirculated exhaust gas dilutes the oxygen coming from an inflowing air flow, which leads to a reduction in the peak temperatures in the cylinder and the NOx emission. However, since the reducing agent of the SCR must not reach the engine, the EGR gas is normally discharged upstream of the SCR with respect to the engine. This reduces the amount of exhaust gas used to heat the SCR, which further slows down the heating process of the SCR.

Efforts are being made to improve the warm-up phase of catalysts for efficient operation, especially during cold starts.

The publication US 8,402,747 B2 refer to a method of heating a catalyst. At least one chemical heating measure, which causes an increase in the catalyst temperature by essentially introducing additional chemical energy into the exhaust gas flow beyond the energy provided in a first engine operating point, is combined with at least one thermal heating measure, which causes an increase in the catalyst temperature, by: essentially introduces additional thermal energy beyond the energy provided at a first engine operating point into the exhaust gas stream, so that a large part of the chemical energy is introduced before a large part of the thermal energy is introduced.

The document US 8,931,265 B2 describes an exhaust gas aftertreatment system for a diesel engine having a selective catalytic reduction (SCR) device and a diesel oxidation catalyst upstream of the SCR device. One method of warming up the SCR device includes monitoring a plurality of combustion input parameters during an SCR warm-up strategy, monitoring a first temperature and a second temperature within the aftertreatment system, providing a feedback adjustment parameter as a function of a deviation of the first temperature from a desired temperature only when the monitored first and second temperatures are within a predetermined setting range, and initiating an adjusted SCR warm-up strategy based on the feedback adjustment parameter to converge the first temperature toward the desired temperature.

Summary of the invention

Thus, there is a need to find solutions to heat SCR devices more effectively.

To this end, the present invention provides a system according to claim 1 and a method according to claim 11.

According to one aspect of the invention, an exhaust gas aftertreatment system includes an exhaust gas recirculation subsystem, EGR subsystem; a Selective catalytic reduction device, SCR device, having an entry surface, an exit surface and a catalytically active substrate, which is arranged between the entry surface and the exit surface and is designed to conduct exhaust gas from the entry surface to the exit surface for catalytic treatment, the catalytically active substrate comprises a return channel and a catalytic reduction channel, the channels being fluidly separated from one another; a first flow separation device which is arranged on the entry surface and is designed to guide the exhaust gas into the return duct and the catalytic reduction duct; an injector which is designed to inject reducing agent into the exhaust gas which is conducted into the catalytic reduction channel; and a second flow separation device which is arranged on the exit surface and is designed to conduct at least a portion of the exhaust gas from the return duct to the EGR subsystem and the remaining exhaust gas from the return duct together with the exhaust gas from the catalytic reduction duct to an exhaust outlet.

According to a further aspect of the invention, a method comprises routing exhaust gas into a return channel and a catalytic reduction channel of a catalytically active substrate of a device for selective catalytic reduction, SCR device, the catalytically active substrate being designed to guide exhaust gas for catalytic treatment , wherein the channels are fluidly separated from each other; and directing at least a portion of the exhaust gas from the recirculation channel to an exhaust gas recirculation subsystem, EGR subsystem, and any remaining exhaust gas from the recirculation channel together with the exhaust gas from the catalytic reduction channel to an exhaust gas outlet.

According to a further aspect of the invention, a motor vehicle with an internal combustion engine and a system for exhaust gas aftertreatment according to the invention is provided.

An idea of the present invention is to use the heat contained in the EGR exhaust gas to heat the SCR catalyst more quickly so that the starting temperature, i.e. the temperature at which the catalytic reaction is initiated in the catalyst is reached earlier. Therefore, the catalytic chemical reactions in the present invention proceed more efficiently. As a result, emissions, especially during the cold start phase of an engine, can be significantly reduced.

This is achieved by dividing the catalyst into two separate channels, one for exhaust gas recirculation and one for catalytic reduction. The two channels are fluidly separated from each other, which means that no exhaust gas is exchanged between the two channels. The exhaust gas routed through the recirculation channel heats the SCR device before it is partially or fully released to the EGR subsystem. The exhaust gas flowing through the catalytic reduction channel, on the other hand, is mixed with reducing agent, e.g. gaseous and / or liquid reducing agent, mixed and released at an exhaust gas outlet so that reducing agent cannot enter the engine via the EGR subsystem.

Advantageous refinements and developments result from the subclaims.

According to a development of the invention, the method can further comprise injecting reducing agent into the exhaust gas, which is led into the catalytic reduction channel.

According to a development of the invention, the channels can be thermally coupled to one another. Therefore, the temperature provided by the exhaust gas can be used to heat sections of the catalytically active substrate that adjoin the sections through which the exhaust gas flows. For example, the substrate can be a ceramic monolith that is interspersed with a plurality of subchannels that are fluidly separated from one another, each channel being designed to guide exhaust gas from the inlet surface to the outlet surface. The substrate can in particular be structured such that a large surface is provided. A first subset of the subchannels can serve as a return channel, while another subset can be used for the catalytic reduction channel. The individual subchannels can be fluidly decoupled from one another. Nevertheless, the heat can be exchanged via adjacent or adjacent subchannels using heat conduction. Therefore, the catalytic reduction channel can heat the return channel and vice versa. As a result, the heating of the SCR device is further improved.

According to a development of the invention, the catalytically active substrate can thus comprise a multiplicity of catalytically active subchannels which are fluidly separated from one another, each subchannel being designed to conduct exhaust gas from the entry surface to the exit surface. A first subset of the subchannels can serve as a return channel, while another subset can be used for the catalytic reduction channel. In a special development of the invention, the assignment of each subchannel to the return duct or the catalytic reduction duct can be predetermined by the first flow separation device, for example by a first one Butterfly valve, possibly in connection with the second flow separation device, for example a second butterfly valve. In such a further development, the first flow separation device and / or the second flow separation device can thus be designed to change the assignment of the subchannels and thus the relative size of the return channel and the catalytic reduction channel, in incremental and / or discrete steps, for example by moving adjusting flaps in discrete steps.

According to a development of the invention, the entry surface can be subdivided into a first entry surface, which serves as an inlet for the return duct, and a second entry surface, which serves as an inlet for the catalytic reduction duct. The first flow separation device can be designed to vary the subdivision of the entry area into the first entry area and the second entry area. Accordingly, the method can furthermore vary the subdivision of the entry area into the first entry area and the second entry area with the first flow separation device.

In this development, the active surface of the SCR used for the catalytic reduction can be varied continuously or in steps by varying the division of the entry surface accordingly. The SCR device can (almost continuously) be divided into a part in which the use of reducing agent is possible and a part which is used for gas recirculation. By selecting the surface areas depending on the specific driving situation and / or the current operating temperatures of the engine, the SCR device and / or the EGR subsystem, an optimal combination of catalytic reduction and gas recirculation can be set. A selected configuration can be used between successive phases of a driving process, e.g. with a cold start, can be varied quickly.

According to a development of the invention, the first flow separation device can comprise a first adjusting flap which is adjustable in order to subdivide the entry area into the first entry area and the second entry area. A flap is a very simple, yet robust solution for changing the cross-section of two areas divided by the flap continuously or step by step. In a specific example, the substrate may have a plurality of adjacent catalytically active subchannels that run from the entry surface to the exit surface of the SCR device. The flap can, for example, be articulated on at least one edge of the entry surface and / or be designed such that it can be pushed along on at least one edge of the entry surface. The flap can be arranged in such a way that it can gradually change the number of catalytically active subchannels assigned to the return channel or the catalytic reduction channel. In a concrete example, the first control flap can be used to gradually reduce the entrance area of the catalytic reduction channel, e.g. in situations where only a small cross section of the catalyst is required.

According to a development of the invention, the second flow separation device can be designed to vary the proportion of the exhaust gas which is conducted from the return duct to the EGR subsystem. Accordingly, the method may further include varying the portion of the exhaust gas with the second flow separation device that is routed from the return duct to the EGR subsystem. The amount of exhaust gas can thus be selected in accordance with current driving conditions and / or working temperatures of the system. In this sense, it should be noted that the exhaust gas from the catalytic reduction channel is always directed completely to the exhaust gas outlet, so that the reducing agent cannot reach the engine. However, a portion of the exhaust gas from the return duct can also be directed to the exhaust outlet.

According to a development of the invention, the second flow separation device can be designed to conduct the entire exhaust gas from the return duct to the EGR subsystem.

According to a development of the invention, the second flow separation device can comprise a second control flap, which is adjustable in order to divide the exit surface into a first exit surface, which serves as an outlet for the return duct and as an inlet for the EGR subsystem, and a second outlet surface, which as Inlet for the exhaust outlet serves. In a specific development, the first flow separation device and the second flow separation device can each comprise a flap, which can be designed for simultaneous movement in order to assign the input and output areas of the return duct and the catalytic reduction duct.

According to a development of the invention, the system can further comprise a flow control element which is designed to at least partially open and close the return duct. Accordingly, the method can include at least partially closing and opening the return duct with the flow control element. The flow control element can be designed as a valve and / or as a flap or the like. For example, the flow control element can be a valve which is used to control the exhaust gas mass flow can be used for exhaust gas recirculation. In this development, the return channel can be switched off completely depending on the current phase of the catalytic process. For example, the return duct can be closed during a first phase of a cold start of a motor vehicle until the operating temperature is high enough for efficient gas return. During this phase, the entry area of the catalytic reduction channel can be set relatively small in order to heat only a selected part of the SCR device, which can then be brought to operating temperature much faster than would be necessary to heat the entire substrate of the SCR device. The SCR device can then be operated in a partial operating mode in which the active surface of the SCR device only makes up a fraction of the maximum active surface.

According to a development of the invention, the first flow separation device, the second flow separation device and / or the flow control element can be designed to be operated by the SCR device and / or the EGR subsystem depending on a driving state and / or an operating temperature. For example, the catalytic reduction channel can be opened as much as possible in the event that high power is required from the engine. The temperature can be measured with temperature sensors, which can be arranged on the entry surface, the exit surface and / or within the SCR device. It would also be conceivable for temperature models for the system to be developed and / or simulated on the basis of temperature sensors, it being possible for the temperature sensors to be used for test phases. Corresponding results of the test phases can be used for temperature models depending on different driving conditions, the temperature models being a function of different input parameters such as time, exhaust gas temperature and exhaust gas mass flow, ambient temperature, engine shutdown time, positions of the at least one cover element and / or thermal conductivity (based on the thermal inertia of the Systems) and engine operating status (e.g. regeneration or engine brake).

The present invention is explained in more detail below with reference to the exemplary embodiments given in the schematic figures.

Figure list

• 1 zeigt schematisch ein beispielhaftes System zur Abgasnachbehandlung während einer ersten Phase eines Motoraufheizprozesses.
• 2 zeigt schematisch das System aus 1 während einer zweiten Phase des Motoraufheizprozesses.
• 3 zeigt schematisch das System aus 1 während einer dritten Phase des Motoraufheizprozesses.
• 4 zeigt ein Flussdiagramm eines Verfahrens zur Abgasnachbehandlung gemäß einer Ausführungsform der Erfindung.
• 5 zeigt schematisch ein Kraftfahrzeug mit einem System zur Abgasnachbehandlung gemäß einer Ausführungsform der Erfindung.
• 6 ist eine perspektivische Ansicht einer SCR-Vorrichtung des Systems aus 5.
• 7 ist eine Querschnittsansicht der SCR-Vorrichtung aus 6.
• 8 bis 11 zeigen schematisch das System aus 5 während vier unterschiedlichen Phasen eines Motoraufheizprozesses.

The accompanying figures are intended to convey a further understanding of the invention and form part of the present disclosure. They illustrate embodiments of the invention and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments of the invention and many of the stated advantages of the invention will become apparent in view of the following detailed description. The elements of the drawings are not necessarily shown to scale with respect to one another. In the figures, the same reference numerals designate the same or functionally identical elements, unless stated otherwise.

• 1 shows schematically an exemplary system for exhaust gas aftertreatment during a first phase of an engine warm-up process.
• 2nd shows the system schematically 1 during a second phase of the engine warm-up process.
• 3rd shows the system schematically 1 during a third phase of the engine warm-up process.
• 4th shows a flow diagram of a method for exhaust gas aftertreatment according to an embodiment of the invention.
• 5 schematically shows a motor vehicle with a system for exhaust gas aftertreatment according to an embodiment of the invention.
• 6 Figure 3 is a perspective view of an SCR device of the system 5 .
• 7 13 is a cross-sectional view of the SCR device of FIG 6 .
• 8th to 11 show the system schematically 5 during four different phases of an engine warm-up process.

Although specific embodiments are illustrated and described herein, it will be apparent to those skilled in the art that a variety of alternative and / or equivalent implementations may replace the specific embodiments shown and described without departing from the scope of the present invention. In general, the application covers any adaptations or variations of the specific embodiments described herein.

Detailed description of the exemplary embodiments

1 to 3rd schematically show an exemplary system 10 for exhaust gas aftertreatment during three phases of an engine warm-up process, in particular a cold start process.

The system 10 is designed to exhaust 20 to clean which is from an internal combustion engine 101 , for example a diesel engine, a motor vehicle 100 , like like that in 5 pictured, is expelled. For this purpose, this includes system 10 a chain of exhaust aftertreatment devices including a diesel oxidation catalyst and a diesel particulate filter (both of which are referred to by reference numerals 23 in 1 to 3rd are summarized) and a device 2nd for selective catalytic reduction (SCR). The SCR device 2nd is the oxidation catalyst / particle filter 23 related to the engine 101 downstream.

The motor 101 bumps exhaust gas 20 through a gas pipe 25th , which is then from the oxidation catalyst / particle filter 23 is treated. Next the exhaust gas flows 20 to the SCR device 2nd and from there to a gas outlet 13 , for example an exhaust pipe of the vehicle 100 where a gas sensor 22 is designed to the exhaust gas 20 check for NOx emissions. An injection 11 is the SCR device 2nd upstream to reducing agents in the flow of exhaust gas 20 to inject, which acts as a reducing agent in the catalytic process within the SCR device 2nd serves in the usual way.

The system 10 also includes a subsystem 1 for exhaust gas recirculation (EGR), which is via a low-pressure EGR valve 24th between the oxidation catalyst / particle filter 23 and the SCR device 2nd to the gas pipe 25th is coupled. The EGR valve 24th is designed to activate a portion of the exhaust gas 20 to branch into the EGR subsystem. This proportion of the exhaust gas 20 then with fresh air 21st from an air intake 19th mixed and then to the engine 101 returned.

The basic sequence during a cold start of the engine 101 is in 1 to 3rd illustrated. First is the EGR subsystem 1 immediately after starting the engine 101 deactivated and the EGR valve 24th is closed, see 1 . The injector 11 is also disabled because of the SCR device 2nd a certain minimum temperature is required to work properly, which is called the start temperature and is typically in the range of 200 ° C to 250 ° C. The EGR subsystem 1 also requires a certain minimum temperature, which, however, is significantly lower than the start temperature of the SCR device 2nd is, for example around 100 ° C. So the NOx emissions of the engine 101 at the exhaust outlet 13 during this first in 1 phase shown relatively. The SCR device 2nd is from the exhaust 20 heated up, which however takes a certain time to reach the start temperature. A typical SCR device 2nd has a significant temperature inertia, ie the heating up of the SCR is slow.

In a second phase, the EGR subsystem 1 activated, the EGR valve opened and a certain proportion of the exhaust gas 20 to the engine 101 returned so that this no longer through the SCR device 2nd flows. So there is a reduced amount of exhaust gas 20 for heating the SCR device 2nd available, which further increases the amount of time until the SCR device 2nd their working temperature can be reached and activated.

Once the start temperature of the SCR device 2nd the injector starts 11 with reducing agents 12th to inject into the exhaust gas flow as in 3rd will be shown.

A disadvantage of the conventional system 10 in 1 to 3rd can be seen in that the NOx emissions during the second in 2nd phase shown are relatively high while the SCR device 2nd has not yet reached its working temperature. This disadvantage is overcome by the embodiment of the present invention as described below with reference to 4th to 11 is described.

4th shows a flow diagram of a method M for exhaust gas aftertreatment according to an embodiment of the invention. The associated system 10 is in 5 to 11 shown.

The system 10 for exhaust gas aftertreatment includes an EGR subsystem 1 along with a chain of exhaust aftertreatment devices including an oxidation catalyst / particulate filter 23 and an SCR device 2nd further downstream with respect to an internal combustion engine 101 of a motor vehicle 100 .

The SCR device 2nd as detailed in 6 and 7 is shown has an entry surface 3rd , an exit surface 4th and a catalytically active substrate 5 on which is between the entry surface 3rd and the exit surface 4th is arranged and which is designed to exhaust 20 from the entrance area 3rd to the exit surface 4th to lead to catalytic treatment. The substrate 5 can comprise a ceramic monolith in the usual manner, for example with a honeycomb structure, which has a multiplicity of catalytically active subchannels 17th provides.

However, the catalytically active substrate 5 In the present embodiment, unlike in conventional systems, it is divided into a return channel 6 and a catalytic reduction channel 7 , which are fluidly separated from each other. This is done by a first flow separation device 8th reached which at the entrance surface 3rd arranged and designed to exhaust 20 separately in the return duct 6 on the one hand and into the catalytic reduction channel 7 to lead on the other side. The substrate 5 can have a variety of catalytically active subchannels 17th have, both for the return channel 6 , as well as for the catalytic reduction channel 7 through which the Exhaust gas 20 then further from the entrance area 3rd to the exit surface 4th is transported. A second river separation device 9 is on the exit surface 4th arranged and designed to at least a portion of the exhaust gas 20 from the return duct 6 to the EGR subsystem 1 to lead (cf. 8th to 11 ) and any remaining exhaust gas 20 from the return duct 6 along with the exhaust 20 from the catalytic reduction channel 7 to an exhaust outlet 13 of the system 10 to lead.

Thus, the SCR device 2nd basically divided into two separate segments, one for catalytic reduction and one for transporting the exhaust gas 20 to the EGR subsystem 1 . Hence is an injector 11 on the catalytic reduction channel 7 for the injection of reducing agents 12th into the exhaust 20 trained, which in the catalytic reduction channel 7 is directed. Both segments, ie the return channel 6 and the catalytic reduction channel 7 , are thermally coupled to one another, so that, for example, heat which is emitted by the catalytic reduction channel 7 flowing exhaust gas 20 is transported to adjacent sections of the substrate 5 is ultimately conducted over the entire substrate 5 is distributed (see curved arrows in 7 ). In particular, the exhaust gas 20 in the return channel 6 for heating the SCR device 2nd be used so that the start temperature of the SCR device 2nd can be achieved much earlier than in the conventional system 10 out 1 to 3rd .

The size of the two channels 6 , 7 the SCR device 2nd can be adjusted to the amount of exhaust gas 20 to vary, which is passed through both channels.

In particular, the cross sections of both channels 6 , 7 can be varied. For this purpose, the first flow separation device comprises 8th a first valve 14 which is adjustable to the entry area 3rd in a first entrance area 3a (which serves as the inlet for the return duct 6 serves) and a second entrance area 3b to subdivide (which is used as the inlet for the catalytic reduction channel 7 serves), the size of the first and second entry surfaces 3a , 3b can be varied by the first valve 14 along the entrance area 3rd is moved (see the arrow at the top left in 6 and 7 ). This has the effect that the inlet cross-section of both channels 6 , 7 can be varied. Because the individual subchannels 17th inside the substrate 5 are fluidally separated from each other, the first valve 14 be moved in discrete steps to specific subchannels 17th to one of the two channels 6 , 7 assign.

Correspondingly, the second flow separation device comprises 9 a second valve 15 , which can be adjusted accordingly to the amount of exhaust gas 20 to vary which over the return channel 6 to the EGR subsystem 1 is redirected. It will be clear to the person skilled in the art that both flaps 14 , 15 must be checked together to ensure that no reducing agent 12th the EGR subsystem 1 can reach. So the second valve 15 regarding 7 either right to the first valve 14 be open, which means that everything is in the return channel 6 flowing exhaust gas 20 to the EGR subsystem 1 is directed, or at least less open than the first valve 14 be, ie only a portion of the exhaust gas 20 in the return channel 6 becomes the EGR subsystem 1 passed while the remaining portion of the exhaust gas 20 from the return duct 6 along with the exhaust 20 from the catalytic reduction channel 7 to the exhaust outlet 13 is branched off. In principle it is possible to use both butterfly valves 14 , 15 close completely so that the full cross section of the substrate 5 and thus its complete active surface to the catalytic reduction channel 7 is assigned.

The system 10 further includes a flow control element 15 (see. 8th to 11 ), which is designed for the return channel 6 at least partially open or close. Thus the return channel 6 are fully opened and / or closed regardless of the setting of the flow separation devices 8th , 9 , ie regardless of the currently set inlet cross-section of the return duct 6 . For example, all of the exhaust gas 20 due to a reduced entry area of the SCR device 2nd (ie the catalytic reduction channel 7 allocated entrance area share) by the return channel 6 by means of the flow control device 16 is closed. The associated subsection of the SCR device 2nd can thus be heated more efficiently and thus start working earlier. The SCR device 2nd can thus be operated in a partial operating mode with a reduced active area, which can be sufficient for many driving situations.

The procedure M out 4th can accordingly at least partially close and open the return duct under M0 6 with the flow control element 16 include. The procedure M can also go to M1 Vary the subdivision of the entrance area 3rd in the first entrance area 3a and the second entrance area 3b with the first flow separation device 8th include. The procedure M can also go to M2 Varying the proportion of the exhaust gas 20 with the second flow separation device 9 include which of the return channel 6 to the EGR subsystem 1 is directed. The procedure M can also go to M3 Passing exhaust gas 20 in the Return channel 6 and the catalytic reduction channel 7 include. The procedure M can also go to M4 Injecting reducing agent 12th into the exhaust 20 include which in the catalytic reduction channel 7 is directed. The procedure M can also go to M5 Guiding at least a portion of the exhaust gas 20 from the return duct 6 to the EGR subsystem 1 and any remaining exhaust gas 20 from the return duct 6 along with the exhaust 20 from the catalytic reduction channel 7 to the exhaust outlet 13 include. It goes without saying that the order of the individual method steps is not fixed and that the steps can be carried out in different orders and / or simultaneously.

The system described above 10 offers several advantages over the system 1 to 3rd , for example in the case of a cold start scenario of the motor vehicle 100 as below with reference to 8th to 11 is described.

During a first phase after starting the internal combustion engine 101 , is the flow control element 16 closed so no exhaust 20 in the return channel 6 the SCR device 2nd reached. Instead, all of the exhaust gas 20 through the catalytic reduction channel 7 and from there to the exhaust outlet 13 directed. As in the conventional system 1 to 3rd the temperature of the system is not yet high enough that neither the EGR nor the SCR can work properly. Thus, no reducing agent 12th from the injector 11 injected. However, the entry surface is the catalytic reduction channel 7 and thus the active surface of the SCR device 2nd different from the conventional system 1 to 3rd reduced. Thus, initially only part of the SCR device 2nd heated up. This part will thus reach its working temperature much earlier than would be required for the entire SCR device 2nd heat up with their significant temperature inertia.

9 and 10 show a second phase of the cold start process corresponding to the second phase in FIG 2nd , the temperature of the system 10 has risen to the point where the EGR subsystem 1 is activated. In a first step of the second phase, the flow control element 16 opened and the exhaust 20 through the return duct 6 the SCR device 2nd to the EGR subsystem 1 headed. In this first step of the second phase is the temperature of the SCR device 2nd not high enough to work properly. However, it will heat up the SCR device 2nd still from the total amount of exhaust gas available in the system 20 driven, of which now a portion through the return channel 6 flows (the latter is in thermal communication with the other parts of the SCR device 2nd ). Once the operating temperature (of the part) of the SCR device 2nd in the catalytic reduction channel 7 is high enough for proper operation, a second step of the second phase is initiated, where reductants enter the gas stream within the catalytic reduction channel 7 is injected (cf. 10 ). As in 10 is visible, the exhaust outlet 13 achieve no NOx emissions because the exhaust gas 20 either back to the engine 101 steered or by the partially working SCR device 2nd is treated.

In a third in 11 phase shown, the system is fully functional. The first and second flow separation devices 8th , 9 as well as the flow control element 16 can depend on a driving state and / or an operating temperature of the SCR device 2nd and / or the EGR subsystem 1 operate. For example, the catalytic reduction channel 7 with increasing temperature relative to the return duct 6 be enlarged as soon as larger parts of the substrate 5 of the SCR 2nd Reach operating temperature. The input cross section of the catalytic reduction channel 7 can thus gradually heat up the SCR device 2nd be enlarged. In principle, it is even possible to determine the relative size of the return channel 6 reduce to zero. In any case, the system 10 however, by operating the flow separation devices together 8th , 9 and the flow control element 16 be brought into an optimal configuration depending on the current driving situation.

The system 10 of the 4th to 11 represents an SCR device 2nd available, which heats up faster than conventional EGR-based systems, since the fully available amount of exhaust gas is used to gradually heat up the SCR. So the system offers 10 Advantages with regard to emission values, especially during cold starting phases of an engine, and thus new and stricter requirements for diesel engines can be met.

Although the system and method described here have each been described in connection with automobiles, it is clear to a person skilled in the art that the system and method described here can be used for various exhaust gas aftertreatment purposes.

In the foregoing detailed description, various features to improve the stringency of the presentation have been summarized in one or more examples. However, it should be understood that the above description is merely illustrative, not restrictive. It serves to cover everyone Alternatives, modifications and equivalents. Many other examples will be immediately apparent to those skilled in the art based on their technical knowledge in light of the above description.

The exemplary embodiments were selected and described in order to be able to best represent the principles on which the invention is based and their possible uses in practice. As a result, experts can optimally modify and use the invention and its various exemplary embodiments in relation to the intended purpose. Many other examples will be immediately apparent to those skilled in the art based on their technical knowledge in light of the above description.

Reference list

1

Exhaust gas recirculation subsystem (EGR)

2nd

Selective catalytic reduction (SCR) device

3rd

Entrance area

3a

first entrance area

3b

second entrance area

4th

Exit surface

4a

first exit surface

4b

second exit surface

5

catalytically active substrate

6

Return channel

7

catalytic reduction channel

8th

first flow separation device

9

second flow separation device

10th

Exhaust gas treatment system

11

Injector

12th

Reducing agent

13

Exhaust outlet

14

first valve

15

second valve

16

Flow control element

17th

catalytically active subchannels

18th

turbocharger

19th

Air intake

20

Exhaust gas

21

fresh air

22

Gas sensor

23

Oxidation catalyst / particle filter

24th

EGR valve

25th

Gas pipe

100

Motor vehicle

101

Internal combustion engine

M

Procedure

M0-M5

Procedural step

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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

• US 8402747 B2 [0006]
• US 8931265 B2 [0007]

Claims (16)

System (10) for exhaust gas aftertreatment comprising: an exhaust gas recirculation subsystem, EGR subsystem, (1); a device for selective catalytic reduction, SCR device, (2) with an entry surface (3), an exit surface (4) and a catalytically active substrate (5) which is arranged between the entry surface (3) and the exit surface (4) and is designed to guide exhaust gas (20) from the inlet surface (3) to the outlet surface (4) for catalytic treatment, the catalytically active substrate (5) comprising a return duct (6) and a catalytic reduction duct (7), the Channels (6, 7) are fluidly separated from each other; a first flow separation device (8) which is arranged on the entry surface (3) and is designed to guide the exhaust gas (20) into the return duct (6) and the catalytic reduction duct (7); an injector (11) which is designed to inject reducing agent (12) into the exhaust gas (20) which is passed into the catalytic reduction channel (7), and a second flow separation device (9) which is arranged on the outlet surface (4) and is designed to remove at least a portion of the exhaust gas (20) from the return duct (6) to the EGR subsystem (1) and the remaining exhaust gas (20) from to lead the return duct (6) together with the exhaust gas (20) from the catalytic reduction duct (7) to an exhaust gas outlet (13). System (10) according to Claim 1 , wherein the channels (6, 7) are thermally coupled to one another. System (10) according to Claim 1 or 2nd , wherein the entry surface (3) is divided into a first entry surface (3a), which serves as an inlet for the return channel (6), and a second entry surface (3b), which serves as an inlet for the catalytic reduction channel (7), the first flow separation device (8) is designed to vary the subdivision of the entry surface (3) into the first entry surface (3a) and the second entry surface (3b). System (10) according to Claim 3 , wherein the first flow separation device (8) comprises a first control flap (14) which is adjustable in order to subdivide the entry surface (3) into the first entry surface (3a) and the second entry surface (3b). System (10) according to one of the Claims 1 to 4th , wherein the second flow separation device (9) is designed to vary the proportion of the exhaust gas (20) which is directed from the return duct (6) to the EGR subsystem (1). System (10) according to Claim 5 , wherein the second flow separation device (9) is designed to direct all of the exhaust gas (20) from the return duct (6) to the EGR subsystem (1). System (10) according to one of the Claims 1 to 6 , wherein the second flow separation device (9) comprises a second control flap (15) which is adjustable in order to divide the outlet surface (4) into a first outlet surface (4a), which serves as an outlet for the return duct (6) and as an inlet for the EGR -Subsystem (1), and a second exit surface (4b), which serves as an inlet for the exhaust gas outlet (13). System (10) according to one of the Claims 1 to 7 , further comprising a flow control element (16) which is designed to at least partially open and close the return duct (6). System (10) according to one of the Claims 1 to 8th , at least one of the first flow separation device (8), the second flow separation device (9) and the flow control element (16) being designed, depending on a driving state and / or an operating temperature, of at least one of the SCR device (2) and the EGR subsystem (1). Motor vehicle (100) with an internal combustion engine (101) and a system (10) for aftertreatment of exhaust gas (20) according to one of the Claims 1 to 9 . A method (M) for the aftertreatment of exhaust gas (20), comprising: Passing (M3) of exhaust gas (20) into a return channel (6) and a catalytic reduction channel (7) of a catalytically active substrate (5) of a device for selective catalytic reduction, SCR device, (2), the catalytically active substrate ( 5) is designed to conduct exhaust gas (20) for catalytic treatment, the channels (6, 7) being fluidly separated from one another; and Directing (M5) at least a portion of the exhaust gas (20) from the return duct (6) to an exhaust gas recirculation subsystem, EGR subsystem, (1) and any remaining exhaust gas (20) from the return duct (6) together with the exhaust gas ( 20) from the catalytic reduction channel (7) to an exhaust gas outlet (13). Method (M) according to Claim 11 , further comprising: injecting (M4) reducing agent (12) into the exhaust gas (20) which is passed into the catalytic reduction channel (7). Method (M) according to Claim 11 or 12th , wherein the exhaust gas (20) is guided into the return duct (6) and the catalytic reduction duct (7) with a first flow separation device (8) which is arranged on an entry surface (3) of the SCR device (2), the entry surface (3) is divided into a first entry surface (3a), which serves as an inlet for the return duct (6), and a second entry surface (3b), which serves as an inlet for the catalytic reduction duct (7), the method (M) further comprises: varying (M1) the subdivision of the entry surface (3) into the first entry surface (3a) and the second entry surface (3b) with the first flow separation device (8). Method (M) according to one of the Claims 11 to 13 , wherein the exhaust gas (20) is directed to the EGR subsystem (1) and the exhaust gas outlet (13) with a second flow separation device (9), the method (M) further comprising: varying (M2) the proportion of the exhaust gas (20 ), which is routed from the return duct (6) to the EGR subsystem (1) with the second flow separation device (9). Method (M) according to one of the Claims 11 to 14 , further comprising: at least partially closing and opening (M0) the return duct (6) with a flow control element (16). Method (M) according to one of the Claims 11 to 15 , at least one of the first flow separation device (8), the second flow separation device (9) and the flow control element (16) depending on a driving state and / or an operating temperature of at least one of the SCR device (2) and the EGR subsystem (1) is operated.

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