DE102019102013A1 - Exhaust system and method for operating an exhaust system - Google Patents

Abstract

An exhaust gas system (10) for a motor vehicle is provided, with an exhaust manifold (16) for collecting exhaust gases generated in an internal combustion engine, a turbine (20) of an exhaust gas turbocharger (22) connected downstream to the exhaust manifold (16) and a downstream one to the turbine Connected exhaust gas aftertreatment device (28), in particular exhaust gas catalytic converter for converting CO and / or NOX and / or HC, the exhaust gas turbocharger (22) having a bypass duct which can be actuated with the aid of a wastegate valve for regulating the charge pressure of the exhaust gas turbocharger (22), one with the exhaust manifold (16) and the short-circuit line (34) connected to the exhaust-gas after-treatment device (28) and operable with the aid of a short-circuit valve (36) is provided. Due to the lower heat sink effect of the short-circuit line (34) compared to the exhaust gas turbocharger (22), the exhaust gas aftertreatment device (28) can be heated up more quickly to its light-off temperature, so that an exhaust gas system (10) with good exhaust gas purification is made possible.

Description

The invention relates to an exhaust gas system and a method for operating such an exhaust gas system, in which exhaust gases from a chargeable exhaust gas system can be cleaned with the aid of an exhaust gas aftertreatment device.

Out DE 2010 029 109 A1 it is known in a rechargeable exhaust system of a motor vehicle with the aid of a wastegate valve of an exhaust gas turbocharger to guide an exhaust gas stream coming from an internal combustion engine past a turbine of the exhaust gas turbocharger in order to heat up an exhaust gas catalytic converter connected downstream of the exhaust gas turbocharger as quickly as possible.

There is a constant need to improve the exhaust gas purification of an exhaust system.

It is the object of the invention to enable an exhaust system with good exhaust gas purification.

The object is achieved according to the invention by an exhaust system with the features of claim 1, a method with the features of claim 8, a method with the features of claim 9 and a method with the features of claim 10. Preferred embodiments of the invention are in the Subclaims and the following description are given, each of which may represent an aspect of the invention individually or in combination.

A first aspect of the invention relates to an exhaust system for a motor vehicle with an exhaust manifold for collecting exhaust gases generated in an internal combustion engine, a turbine of an exhaust gas turbocharger connected downstream of the exhaust manifold and an exhaust gas aftertreatment device connected downstream of the turbine, in particular exhaust gas catalytic converter for converting CO and / or NOx and / or HC, the exhaust gas turbocharger having a bypass duct which can be actuated with the aid of a wastegate valve for regulating the charge pressure of the exhaust gas turbocharger, a short-circuit line which is connected to the exhaust manifold and to the exhaust gas aftertreatment device and can be actuated with the aid of a short-circuit valve.

For good exhaust gas purification of the exhaust gas contained in the exhaust system, the exhaust gas aftertreatment device should reach its operating temperature as quickly as possible when the motor vehicle is cold started. For this purpose, the exhaust gas aftertreatment device must be heated up at least to its light-off temperature, which is, for example, in the range of approximately 300 ° C. For this purpose, in a situation when the temperature of the exhaust gas aftertreatment device is below the light-off temperature, as is the case in particular when the motor vehicle is cold started, the short-circuit valve can be opened so that the exhaust gas is directed past the exhaust gas turbocharger via the short-circuit line and reaches the exhaust gas aftertreatment device directly . Here, the knowledge is exploited that the exhaust gas turbocharger, including the turbine and the bypass duct, can act as a heat sink for the exhaust gas conducted through the exhaust gas turbocharger. Due to a temperature difference between the exhaust gas and the exhaust gas turbocharger, part of the enthalpy of the exhaust gas is used to heat the exhaust gas turbocharger, so that the exhaust gas would arrive at the exhaust gas aftertreatment device with a correspondingly lower enthalpy and a correspondingly lower temperature. The heating of the exhaust gas aftertreatment device would be delayed in this case.

Although the bypass duct can connect the exhaust manifold to the exhaust gas aftertreatment device bypassing the turbine, it would nevertheless lead to a significant cooling of the exhaust gas if the exhaust gas were passed through the bypass duct of the exhaust gas turbocharger, since the bypass duct switched with the wastegate valve is usually in one Exhaust gas turbocharger housing is integrated. The bypass duct is therefore connected to other components of the exhaust gas turbocharger in a heat-conducting manner, so that the entire thermal capacity (“thermal mass”) of the exhaust gas turbocharger may act as a heat sink on the exhaust gas to a somewhat lesser extent.

However, the short-circuit line only has the function of guiding the exhaust gas from the exhaust manifold to the exhaust-gas aftertreatment device, so that the short-circuit line can be provided with a correspondingly smaller wall thickness and / or thermal insulation, as a result of which the effect of the short-circuit line as a heat sink can be minimized. At least the short-circuit line has a significantly lower heat sink effect than the turbine and / or the bypass duct, so that the exhaust gas can arrive at the exhaust gas aftertreatment device with a higher temperature and higher enthalpy and the exhaust gas aftertreatment device can thereby heat up more quickly to the light-off temperature. The full functionality of the exhaust gas aftertreatment device to purify the exhaust gas is therefore available earlier, so that more exhaust gas can be cleaned effectively and an emission of harmful gases and / or exhaust gas components and / or soot and / or exhaust gas particles can be reduced. Due to the lower heat sink effect of the short-circuit line compared to the exhaust gas turbocharger, the exhaust gas aftertreatment device can react more quickly to it Starting temperature are heated so that an exhaust system with a good exhaust gas cleaning is possible.

In particular, the exhaust manifold is connected to the turbine and the bypass duct via a shut-off valve. With the help of the shut-off valve, the volume flow of the exhaust gas coming from the exhaust manifold can at least be throttled, preferably essentially completely interrupted. When the exhaust gas aftertreatment device is heated up, essentially the entire volume flow of the exhaust gas coming from the exhaust manifold can be conducted via the short-circuit line. An enthalpy loss of the exhaust gas due to heat sink effects in the exhaust system can be minimized.

The exhaust gas at the input of the exhaust gas aftertreatment device preferably has a higher enthalpy in a flow path via the short-circuit line than in the case of a flow path via the turbine and / or the bypass duct. Since the short-circuit line only has to fulfill the function of guiding the exhaust gas from the exhaust manifold to the exhaust-gas aftertreatment device, the short-circuit line can be optimized to avoid heat sink effects. At least the short-circuit line has a lower heat sink effect than if the exhaust gas is conducted via the exhaust gas turbocharger to the exhaust gas aftertreatment device. As a result, a faster heating of the exhaust gas aftertreatment device can be ensured in comparison with a flow path of the exhaust gas leading via the exhaust gas turbocharger.

A flow length from the exhaust manifold to the exhaust gas aftertreatment device via the short-circuit line is particularly preferably shorter than via the bypass channel. As a result, contact of the exhaust gas with surfaces of components of the exhaust system that are still cold can be minimized, so that a heat sink effect can be minimized. In addition, a pressure loss can be reduced over the flow length of the short-circuit line, so that the exhaust gas can enter the exhaust gas aftertreatment device with a correspondingly high enthalpy. The exhaust gas aftertreatment device is preferably arranged as close as possible to the exhaust manifold, so that the flow length of the short-circuit line can be minimized due to the spatial proximity of the exhaust gas aftertreatment device to the exhaust manifold. In particular, the minimum distance between the exhaust gas aftertreatment device and the exhaust manifold can be less than the minimum distance between the exhaust gas turbocharger and the exhaust manifold.

In particular, when the short-circuit valve is fully open, the short-circuit line has a lower flow resistance than a flow path from the exhaust manifold to the exhaust gas aftertreatment device via the bypass channel when the wastegate valve is fully open. Due to the lower flow resistance along the short-circuit line, a pressure loss can be minimized, so that the exhaust gas can flow through the short-circuit line with the lowest possible flow velocity and / or reduced turbulence.

The turbine and the bypass duct are preferably connected to the exhaust gas aftertreatment device via a connecting line, the connecting line being able to be cooled with the aid of a cooling device, in particular a headwind cooler. Since the exhaust gas aftertreatment device can essentially be heated by the exhaust gas conducted via the short-circuit line, it is possible to provide no heating function for the exhaust gas leaving the exhaust gas turbocharger via the turbine and / or the bypass duct. Instead, a conscious cooling of the exhaust gas can be provided, which leaves the exhaust gas turbocharger via the connection line. Here, the knowledge is exploited that after the exhaust gas aftertreatment device has been heated to a temperature above the light-off temperature, the exhaust gas is generally conducted via the exhaust gas turbocharger. The short-circuit valve can be closed after the exhaust gas aftertreatment device has been heated up. In this situation, the exhaust gas aftertreatment device may overheat, particularly with a high engine output of the internal combustion engine, which could chemically age or even damage the exhaust gas aftertreatment device. By cooling the connecting line, the exhaust gas can be cooled to a temperature that is more suitable for the exhaust gas aftertreatment device, so that the service life of the exhaust gas aftertreatment device and the chemical exhaust gas cleaning ability of the exhaust gas aftertreatment device are improved. A temperature window for the operation of the exhaust gas aftertreatment device can thereby be kept small and be particularly close to the optimal operating temperature. For this purpose, the cooling device provided for cooling the connecting line can, for example, provide air cooling with the help of airflow.

A further exhaust manifold for collecting exhaust gases generated in the internal combustion engine is particularly preferred, a turbine of a further exhaust gas turbocharger connected to the further exhaust manifold downstream via a further shut-off valve, a further exhaust gas aftertreatment device connected downstream to the turbine, in particular an exhaust gas catalytic converter for converting CO and / or NOx and / or HC, and one with the other exhaust manifold and with the other Exhaust aftertreatment device connected and operable with the aid of a further short-circuit valve, further short-circuit line is provided, the further exhaust-gas turbocharger having a further by-pass channel, which can be actuated with the aid of a further wastegate valve, for boost pressure regulation of the further exhaust-gas turbocharger, the further exhaust-gas manifold being connectable to the exhaust-gas manifold via a connecting line which can be actuated by a connecting valve is. The internal combustion engine can, for example, have two different cylinder banks, the first cylinder bank being connected to the exhaust manifold and the second cylinder bank being connected to the further exhaust manifold. The exhaust system can in particular be configured symmetrically. The above statements apply in particular analogously to the other corresponding components of the exhaust system. Both sides of the exhaust system can act essentially independently of one another when the connecting valve is closed. If the connecting valve is opened completely or partially, the exhaust gases can be exchanged between the two sides, which results in different modes of operation of the exhaust system, which are suitable for different operating situations. The connecting line and the connecting valve provided in the connecting line allow increased flexibility in the operation of the exhaust system. In addition, the volume of the exhaust manifold and the further exhaust manifold can be connected to one another when the connecting valve is open, as a result of which pressure fluctuations can be damped, for example.

A further aspect of the invention relates to a method for operating an exhaust gas system, which can be designed and developed as described above, in which, in order to heat up the exhaust gas aftertreatment device, the exhaust gas from the exhaust manifold is wholly or partially fed directly past the turbine and the bycass duct to the exhaust gas aftertreatment device . Due to the lower heat sink effect of the short-circuit line compared to the exhaust gas turbocharger, the exhaust gas aftertreatment device can be heated to its light-off temperature more quickly, so that an exhaust gas system with good exhaust gas purification is made possible.

Another aspect of the invention relates to a method for operating an exhaust system, which can be designed and further developed as described above, in which the connecting valve is open, the further shut-off valve and the further short-circuit valve are closed in a first period, and the shut-off valve and / or the Short-circuit valve are open and in a second period the shut-off valve and the short-circuit valve are closed and the further shut-off valve and / or the further short-circuit valve are open, with both the exhaust gas aftertreatment device and the further exhaust gas aftertreatment device and / or for carrying out an operating temperature to be heated and / or maintained Register charging of the internal combustion engine of the first period and the second period can be provided alternately in succession. Due to the lower heat sink effect of the short-circuit line compared to the exhaust gas turbocharger, the exhaust gas aftertreatment device can be kept warm better, so that an exhaust gas system with good exhaust gas purification is made possible. In particular with a low engine output and / or a cylinder deactivation, there is only a small total volume flow of exhaust gas. The exhaust gas which is brought together from both sides can either be passed over one side or over the other side and supply thermal energy to the exhaust gas aftertreatment device in the first period and to the further exhaust gas aftertreatment device in the second period. As a result, both exhaust gas aftertreatment devices can be heated to the light-off temperature and / or can be kept at a sufficiently high temperature even when the engine power is low.

Another aspect of the invention relates to a method for operating an exhaust system, which can be designed and developed as described above, in which the damping of a dynamic exhaust gas back pressure on the turbine and on the other turbine and / or for damping pressure pulsations in the exhaust system Connection valve is at least partially opened. If the engine output is low, the connecting valve can be closed, so that pressure surges of the exhaust gas that occur when the exhaust valve is opened on the internal combustion engine can consciously attack the turbine of the exhaust gas turbocharger in order to carry out a shock charging. Charger operation can thus be averted and register charging can be achieved. When the engine power increases, the average pressure acting on the turbine can be high enough to drive the turbocharger compressor without problems via the turbine. In this situation, pressure surges at the inlet of the turbine are generally not desired, since these can lead to a loss of efficiency in the turbine. However, the volume of the exhaust manifold and of the further exhaust manifold can be connected to one another by the opened connecting valve, so that pressure surges can be damped via the two volumes of the exhaust manifold and a high efficiency can be achieved in the exhaust gas turbocharger.

• 1: eine schematische Prinzipdarstellung eines Abgassystems.

In the following, the invention is explained by way of example with reference to the accompanying drawing using preferred exemplary embodiments, the features shown below can represent an aspect of the invention both individually and in combination. It shows:

• 1 : a schematic diagram of an exhaust system.

This in 1 Exhaust system shown 10th has a first page 12th and one to the first page 12th essentially symmetrical second side 14 on. The first page 12th has an exhaust manifold connected to a first cylinder bank of an internal combustion engine on the exhaust gas side 16 on that via a shut-off valve 18th with a turbine 20 of an exhaust gas turbocharger 22 connected is. The turbine 20 is with a compressor 24th coupled, which can charge fresh air drawn in and deliver it to the internal combustion engine. The turbine 20 is via a connection line, in particular cooled by a cooling device 26 with an exhaust gas aftertreatment device 28 connected. In the illustrated embodiment, the exhaust gas aftertreatment device 28 be designed as an exhaust gas catalytic converter, the output side with an additional exhaust gas aftertreatment device 30th , which is designed, for example, as a particle filter. Via a silencer 32 the cleaned exhaust gas can be released into the environment. The exhaust gas turbocharger 22 has in the usual way a bypass channel provided with a wastegate valve, which bypasses the turbine 20 at least partially the exhaust gas downstream of the shut-off valve 18th to the connection line 26 can lead. In addition, the exhaust manifold 16 via a short-circuit line 34 with the exhaust gas aftertreatment device 28 connected, the short circuit line 34 optionally from a short-circuit valve 36 can be opened and closed. Preferably the shut-off valve 18th and the short circuit valve 36 combined in a common valve, for example a 3/2-way valve to form a common structural unit.

The second page shows the same 14 a further exhaust manifold connected to a second cylinder bank of the internal combustion engine 38 on that via another shut-off valve 40 with another turbine 42 of another exhaust gas turbocharger 44 connected is. The other turbine 42 is with another compressor 46 coupled, which can charge fresh air drawn in and deliver it to the internal combustion engine. The other turbine 42 is via a further connection line, in particular cooled by a cooling device 48 with another exhaust gas aftertreatment device 50 connected. In the exemplary embodiment shown, the further exhaust gas aftertreatment device can 50 be designed as an exhaust gas catalytic converter, the output side with a further additional exhaust gas aftertreatment device 52 , which is designed, for example, as a particle filter. Another silencer 54 the cleaned exhaust gas can be released into the environment. The further exhaust gas turbocharger 44 has in the usual way a further bypass duct provided with a further wastegate valve, which bypasses the further turbine 42 at least partially the exhaust gas downstream of the further shut-off valve 40 to the other connection line 48 can lead. In addition, the other exhaust manifold 38 via another short-circuit line 56 with the further exhaust gas aftertreatment device 50 connected, the further short-circuit line 56 optionally from another short-circuit valve 58 can be opened and closed. These are preferably the further shut-off valve 40 and the other short circuit valve 58 combined in a common valve, for example a 3/2-way valve to form a common structural unit.

The first page 12th and the second page 14 of the exhaust system 10th are via a connecting line 60 interconnected, the connecting line 60 optionally from a connection valve 62 can be opened and closed. Here is the connecting line 60 on the one hand with the exhaust manifold 16 and on the other hand with the other exhaust manifold 38 connected.

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

• DE 2010029109 A1 [0002]

Claims (10)

Exhaust system for a motor vehicle, having an exhaust manifold (16) for collecting exhaust gases generated in an internal combustion engine, a turbine (20) of an exhaust gas turbocharger (22) connected downstream to the exhaust manifold (16) and an exhaust gas aftertreatment device (28) connected downstream of the turbine, In particular an exhaust gas catalytic converter for converting CO and / or NOx and / or HC, the exhaust gas turbocharger (22) having a bypass duct which can be actuated with the aid of a wastegate valve for regulating the charge pressure of the exhaust gas turbocharger (22), characterized in that one with the exhaust manifold (16) and a short-circuit line (34) connected to the exhaust-gas after-treatment device (28) and operable with the aid of a short-circuit valve (36) is provided. Exhaust system after Claim 1 characterized in that the exhaust manifold (16) is connected to the turbine (20) and the bypass duct via a shut-off valve (18). Exhaust system after Claim 1 or 2nd characterized in that the exhaust gas at the input of the exhaust gas aftertreatment device (28) has a higher enthalpy in a flow path via the short-circuit line (34) than in the case of a flow path via the turbine (20) and / or the bypass duct. Exhaust system according to one of the Claims 1 to 3rd characterized in that a flow length from the exhaust manifold (16) to the exhaust gas aftertreatment device (28) via the short-circuit line (34) is shorter than via the bypass duct. Exhaust system according to one of the Claims 1 to 4th characterized in that, when the short-circuit valve (36) is fully open, the short-circuit line (34) has a lower flow resistance than a flow path from the exhaust manifold (16) to the exhaust-gas aftertreatment device (28) via the bypass channel when the wastegate valve is fully open. Exhaust system according to one of the Claims 1 to 5 characterized in that the turbine (20) and the bypass duct are connected to the exhaust gas aftertreatment device (28) via a connecting line (26), the connecting line (26) being able to be cooled with the aid of a cooling device, in particular a headwind cooler. Exhaust system according to one of the Claims 1 to 5 characterized in that a further exhaust manifold (38) for collecting exhaust gases generated in the internal combustion engine, a further turbine (42) of a further exhaust gas turbocharger (44) connected downstream of the further exhaust manifold (38) via a further shutoff valve (40), a downstream further exhaust gas aftertreatment device (50) connected to the further turbine (42), in particular exhaust gas catalytic converter for converting CO and / or NOx and / or HC, and one connected to the further exhaust manifold (38) and to the further exhaust gas aftertreatment device (50) and with the aid A further short-circuit valve (58) which can be actuated is provided, the further exhaust gas turbocharger (44) having a further bypass duct which can be actuated with the aid of a further wastegate valve for regulating the boost pressure of the further exhaust gas turbocharger (44), the further exhaust manifold (38) Via a connecting line (60) which can be actuated with a connecting valve (62) it is connectable to the exhaust manifold (16). Method for operating an exhaust system (10) according to one of the Claims 1 to 7 , in which, in order to heat up the exhaust gas aftertreatment device (28), all or part of the exhaust gas from the exhaust manifold (16) is fed directly past the turbine (20) and the bypass duct to the exhaust gas aftertreatment device (28). Method for operating an exhaust system (10) according to Claim 7 , in which the connecting valve (62) is open, the further shut-off valve (40) and the further short-circuit valve (58) are closed in a first period and the shut-off valve (18) and / or the short-circuit valve (36) are open and in a second period the shut-off valve (18) and the short-circuit valve (36) are closed and the further shut-off valve (40) and / or the further short-circuit valve (58) are open, both the exhaust gas aftertreatment device (28) and the further one being used to heat and / or maintain an operating temperature Exhaust gas aftertreatment device (50) and / or for carrying out register charging of the internal combustion engine, the first period and the second period are provided alternately in succession. Exhaust system operation method according to Claim 7 , in which the connection valve (62) is at least partially opened to dampen a dynamic exhaust gas back pressure on the turbine (20) and on the further turbine (42) and / or to dampen pressure pulsations in the exhaust system (10).

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