Exhaust aftertreatment system

Abstract

The invention relates to an exhaust gas aftertreatment system (10) for an internal combustion engine, comprising an inlet (12) for receiving exhaust gas of the internal combustion engine, and comprising at least one exhaust gas channel (14), wherein a first three-way catalytic converter (16) is arranged in the exhaust gas channel (14) downstream of the inlet (12), and wherein at least one second three-way catalytic converter (18) is arranged in the exhaust gas channel (14) downstream of the first three-way catalytic converter (16) close to the engine, and wherein at least one turbine (20) is arranged in the exhaust gas channel (14) between the inlet (12) and the first three-way catalytic converter (16). In the exhaust gas aftertreatment system (10), in which the structural space is designed as efficiently as possible, a first deflection portion (22) of the exhaust gas channel (14) is arranged downstream of the turbine (20), and a second deflection portion (24) of the exhaust gas channel (14) is arranged downstream of the second three-way catalytic converter (18) in the same direction of curvature as the first deflection portion (22).

Description

Technical Field

[0001] The present invention relates to an exhaust gas aftertreatment system (or exhaust gas aftertreatment system, i.e., Abgasnachbehandlungssystem) for an internal combustion engine, which has an inlet for receiving the exhaust gas of the internal combustion engine; and has at least one exhaust passage, wherein a first three-way catalytic converter is arranged in the exhaust passage downstream of the inlet. At least one second three-way catalytic converter is arranged in the exhaust passage downstream of the first three-way catalytic converter close to the engine. In addition, at least one turbine is arranged in the exhaust passage between the inlet and the first three-way catalytic converter. Background Art

[0002] Due to the development of exhaust gas regulations, automobile manufacturers are faced with the following challenges: reducing the original emissions of the engine and purifying the exhaust gas that is still produced by appropriate exhaust gas aftertreatment. Regulation level EU7 makes it necessary that gasoline engines often require a particle filter in order not to exceed the number of particles permitted by regulations during emission. Such gasoline particle filters are loaded with soot during driving. In order to prevent the exhaust back pressure from increasing too much, the gasoline particle filter must be restored continuously or periodically. The increase in exhaust back pressure will lead to additional consumption of the internal combustion engine, power loss and affect the running smoothness until the ignition is interrupted.

[0003] For example, DE 10 2019 109 442 A1 shows an exhaust gas aftertreatment system that can receive and at least partially purify the exhaust gas of an internal combustion engine. The particle filter is subject to high thermal aging near the engine. The particle filter is only difficult to regenerate far from the engine. For this purpose, it is provided that a first three-way catalytic converter is placed in front of a four-way catalytic converter, i.e. a particle filter with a three-way catalytic converter coating, in the exhaust channel.

[0004] Another technical solution is to reduce the cold start emissions of gasoline engines, because the cold start emissions add up to a large proportion of the emissions in the entire driving cycle. This need becomes increasingly important if the effective distance of the RDE journey in the city (i.e. the emission of emissions during actual driving operation) is further reduced, because the proportion of cold starts is becoming increasingly heavy. As a solution, either the original emissions can be reduced or the conversion performance of the exhaust aftertreatment can be improved. This can be achieved in the following way, that is, the three-way catalytic converter is heated to its operating temperature more quickly. For this purpose, measures inside the engine and outside the engine can be used. Here, the measures outside the engine must be purposefully integrated into the exhaust system solution. A possible heating measure outside the engine is the electrical heating of the catalyst.

[0005] However, in addition to these additional measures, the three-way catalytic converter still has to provide the necessary conversion performance, so it often has to be designed to be relatively large. This can lead to installation space problems, especially in a narrow engine compartment, especially when additional components are required for heating. Summary of the invention

[0006] It is therefore an object of the present invention to specify an exhaust gas aftertreatment system in which the installation space is designed to be as compact and efficient as possible.

[0007] This object is achieved according to the invention in that a first deflection of the exhaust duct is provided downstream of the turbine and a second deflection of the exhaust duct is provided downstream of the second three-way catalytic converter in the same direction of curvature as the first deflection.

[0008] In this context, a position close to the engine is understood to be a position in the exhaust gas aftertreatment system with an exhaust gas path length of the end inlet of the three-way catalytic converter from the outlet of the internal combustion engine of less than 80 cm, preferably less than 50 cm.

[0009] In the context of the present invention, a three-way catalytic converter is understood to include materials that are able to at least partially convert carbon monoxide (CO), nitrogen oxides (NO X ) and unburned hydrocarbons (HC) are converted into carbon dioxide (CO2), nitrogen (N2) and water (H2O).

[0010] The exhaust gas aftertreatment system can be connected with the outlet of the internal combustion engine by an inlet, so that the exhaust gas discharged by the engine is directly guided into the exhaust gas aftertreatment system. Preferably, the exhaust gas channel is designed as a pipeline, through which the exhaust gas can flow. Various internal parts, such as the first three-way catalytic converter and / or the second three-way catalytic converter, can be arranged in the pipeline or are part of the pipeline itself.

[0011] A deflection is understood to be a bend in the exhaust gas channel. In principle, the bend can be oriented both horizontally and vertically. However, a horizontal bend is preferably provided. If the direction of curvature (i.e. the orientation of the bend) is approximately the same at both bends, the exhaust gas is deflected overall by the two bends and is not directed back to the inlet in the original flow direction.

[0012] For example, the turbine can be part of a turbocharger. A turbocharger is a component for generating engine supercharging. It increases the engine power or the efficiency of the internal combustion engine. Its working method is that part of the energy of the engine exhaust gas is used to drive the compressor in the exhaust system by means of the turbine.

[0013] By means of the embodiment of the exhaust gas device according to the invention, many functions of the exhaust gas aftertreatment system are simultaneously implemented in a minimal installation space.

[0014] Further preferred embodiments of the invention result from the remaining contents mentioned according to the invention.

[0015] In a first design of the exhaust gas aftertreatment system according to the invention, it is provided that the first deflection portion and / or the second deflection portion has a curvature angle between 70° and 110°, preferably 90°. The curvature angle describes the curvature of the deflection portion. A curvature angle of 90° corresponds to a deflection of the exhaust gas flowing through the exhaust gas aftertreatment system by 90°. Since the two deflection portions have the same direction of curvature, the exhaust gas is deflected by 180° when the curvature angle of the first deflection portion is 90° and when the curvature angle of the second deflection portion is 90°. This type of deflection portion can achieve a structure of the exhaust gas aftertreatment system that is as compact as possible.

[0016] In a particularly preferred embodiment of the exhaust gas aftertreatment system according to the present invention, an electric heating device is arranged downstream of the first three-way catalytic converter and upstream of the second three-way catalytic converter. The electric heating device is therefore arranged between the first three-way catalytic converter and the second three-way catalytic converter with respect to the flow path in the exhaust gas channel. In this way, the electric heating device can transport heat not only in the direction of the first three-way catalytic converter, but also in the direction of the second three-way catalytic converter.

[0017] In addition, in a further advantageous embodiment of the invention, it is provided that the electric heating device is designed as an electric heating disk through which flow can flow. By designing the electric heating device as an electric heating disk through which flow can flow, the electric heating device can be arranged in the exhaust gas duct without significantly increasing the structural space of the exhaust gas aftertreatment system.

[0018] In order to protect the electric heating device, in a further design of the exhaust gas aftertreatment system according to the present invention, it is arranged that the electric heating plate abuts against the first three-way catalytic converter with a first contact surface, and abuts against the second three-way catalytic converter with a second contact surface. This design has multiple advantages. On the one hand, the various components are pressed closer to each other, so that the required structural space of the exhaust gas aftertreatment system is significantly reduced. On the other hand, the electric heating plate is protected due to the structure of the first three-way catalytic converter and the second three-way catalytic converter. This "sandwich structure" prevents the electric heating plate from being susceptible to external mechanical influences. In addition, the radiant heat of the electric heating device is coupled into the three-way catalytic converter in two directions.

[0019] In order to further improve the working principle of the exhaust gas aftertreatment system according to the present invention, it is provided in a further design that a first lambda probe, in particular a broadband probe, is arranged upstream of the first three-way catalytic converter, and a second lambda probe, in particular a jump probe, is arranged downstream of the second three-way catalytic converter. The lambda probe is designed to compare the residual oxygen content in the exhaust gas with a reference oxygen content. The oxygen content of the current atmospheric air is usually used as the reference oxygen content. With knowledge of the residual oxygen content, the air-fuel ratio lambda can be determined and adjusted accordingly.

[0020] The jump sensor emits a voltage signal depending on the residual oxygen content in the exhaust gas. The engine control unit determines the current mixture composition of fuel and oxygen from this voltage signal. In the case of a jump sensor, the sensor signal fluctuates between two values. Depending on the mixture composition, the fuel injection quantity is reduced (rich mixture) or increased (lean mixture).

[0021] The broadband probe consists of two units, a pump unit and a concentration unit. This probe (in contrast to the jump probe) continuously measures over a wide lambda range from rich (i.e. excess fuel over stoichiometry) to lean (i.e. excess oxygen over stoichiometry). The corresponding control is thus able to always establish any desired air ratio in the combustion chamber.

[0022] Advantageously, in a further design of the present invention, it is provided that the first three-way catalytic converter is designed in the form of a metal carrier substrate. Therefore, the first three-way catalytic converter can also be used as a support structure for the electric heating device.

[0023] Alternatively or additionally, in a further embodiment, it is provided that the second three-way catalytic converter is designed in the form of a ceramic carrier substrate. For reasons of cost and performance, the second three-way catalytic converter can be implemented as a ceramic substrate.

[0024] Other designs are also conceivable. The first three-way catalytic converter and the second three-way catalytic converter can also be configured in the form of a metal carrier substrate. Correspondingly, it is also conceivable that the first three-way catalytic converter and the second three-way catalytic converter are both configured in the form of a ceramic carrier substrate.

[0025] In order to further improve the exhaust gas purification, in a further embodiment of the exhaust gas purification system according to the invention, a particle filter is arranged downstream of the second deflector. The particle filter can be designed as a gasoline particle filter, in which highly porous, heat-resistant cordierite ceramic is used. The soot particles contained in the exhaust gas remain adhered to the rough ceramic surface.

[0026] In addition, in a further embodiment, it is further provided that the particle filter has a coating so that the particle filter is designed as a four-way catalytic converter. In this way, the functions of a three-way catalytic converter and a gasoline particle filter are combined in one component. In this case, a catalytically active coating is applied to the particle filter, which coating has a three-way catalytic effect.

[0027] The various embodiments of the invention mentioned in this application can advantageously be combined with one another, provided that they are not implemented otherwise in each case. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is described below with reference to the accompanying drawings by way of embodiments.

[0029] Figure 1 A preferred exemplary embodiment of an exhaust gas aftertreatment system according to the invention for an internal combustion engine is shown in a schematic diagram. DETAILED DESCRIPTION

[0030] Figure 1 An exhaust gas aftertreatment system 10 for purifying the exhaust gas of an internal combustion engine is shown. The exhaust gas aftertreatment system comprises an inlet 12 for receiving the exhaust gas of the internal combustion engine. The exhaust gas aftertreatment system 10 can be connected with the inlet 12 to an outlet of an internal combustion engine (not shown here), so that the exhaust gas discharged from the engine can be guided directly into the exhaust gas aftertreatment system 10. The exhaust gas is transported in an exhaust gas channel 14. The exhaust gas channel 14 is preferably designed as a pipeline through which the exhaust gas can flow.

[0031] A first three-way catalytic converter 16 is arranged in the exhaust passage 14 downstream of the inlet 12. A second three-way catalytic converter 18 is arranged in the exhaust passage 14 downstream of the first three-way catalytic converter 16. A turbine 20 is arranged downstream of the inlet 12 and upstream of the first three-way catalytic converter 16. In this embodiment, the turbine 20 is part of a turbocharger. The turbocharger is used to generate engine supercharging. It increases the engine power or the efficiency of the internal combustion engine. Its working method is that a part of the energy of the engine exhaust is used to drive a compressor not shown here in the exhaust device by means of the turbine 20.

[0032] In order to keep the exhaust gas aftertreatment system 10 compact, the exhaust gas channel 14 is bent in two sections. For this purpose, the exhaust gas channel 14 has a first deflection portion 22 and a second deflection portion 24. Both the first deflection portion 22 and the second deflection portion 24 have a curvature angle of approximately 90°. The two deflections 22, 24 bend the exhaust gas channel 14 in the same direction in terms of fluid technology. In this way, the exhaust gas is deflected by approximately 180° via the first deflection portion 22 and the second deflection portion 24.

[0033] The first three-way catalytic converter 16 is designed as a metal carrier substrate. The catalytic layer is applied to the support of the first three-way catalytic converter 16. The catalytic layer is capable of at least partially converting carbon monoxide (CO), nitrogen oxides (NO X) and unburned hydrocarbons (HC) are converted into carbon dioxide (CO2), nitrogen (N2) and water (H2O).

[0034] The second three-way catalytic converter 18 is designed in the form of a ceramic carrier substrate and is correspondingly provided with a catalytic layer, similar to the first three-way catalytic converter 16 .

[0035] In order for the first three-way catalytic converter 16 and the second three-way catalytic converter 18 to best exert their catalytic effect, they must be brought to their optimal operating temperature. In particular, the gasoline engine emits a large amount of gaseous harmful substances during the cold start phase. For this purpose, it is necessary to bring the first three-way catalytic converter 16 and the second three-way catalytic converter 18 to the corresponding operating temperature as quickly as possible.

[0036] The three-way catalytic converters 16, 18 are heated in particular by hot exhaust gas. In addition, an electric heating device 26 is provided between the first three-way catalytic converter 16 and the second three-way catalytic converter 18. The electric heating device 26 is designed as an electric heating disk through which flow can flow. By designing the electric heating device 26 as an electric heating disk through which flow can flow, the electric heating device can be arranged in the exhaust passage 14 without significantly increasing the structural space of the exhaust gas aftertreatment system 10.

[0037] In order to protect the electric heating device 26, the electric heating plate is arranged at the first three-way catalytic converter 16 with a first contact surface 28. The electric heating device 26 is arranged at the second three-way catalytic converter 18 with a second contact surface 30, thereby forming a "sandwich structure. This design has multiple advantages. On the one hand, the individual components are pressed closer to each other, so that the required structural space of the exhaust gas aftertreatment system 10 is significantly reduced. On the other hand, the electric heating plate is protected by the structure of the first three-way catalytic converter 16 and the second three-way catalytic converter 18. This "sandwich structure" prevents the electric heating plate from being susceptible to external mechanical influences. In addition, the radiant heat of the electric heating device 26 is coupled into the three-way catalytic converters 16 and 18 in two directions. The first three-way catalytic converter 16 is also used as a supporting structure for the electric heating device 26.

[0038] A first lambda probe 32 is arranged upstream of the first three-way catalytic converter 16. The first lambda probe 32 is designed as a broadband probe. A second lambda probe 34 is arranged downstream of the second three-way catalytic converter 18. The second lambda probe 34 is designed as a jump probe. The lambda probes 32 and 34 are designed to compare the residual oxygen content in the exhaust gas with a reference oxygen content. In this embodiment, the oxygen content of the current atmospheric air is used as the reference oxygen content. Under the condition of knowing the residual oxygen content, the air-fuel ratio lambda is determined and adjusted accordingly.

[0039] A particle filter 36 is arranged downstream of the second deflector 24. In this exemplary embodiment, the particle filter 36 is a gasoline particle filter. The particle filter 36 has a coating, so that the particle filter 36 is designed as a four-way catalytic converter. In this way, the functions of a three-way catalytic converter and a gasoline particle filter are combined in one component. For this purpose, a catalytically active coating is applied to the particle filter 36, which has a three-way catalytic effect.

[0040] Reference numerals list:

[0041] 10 Exhaust aftertreatment system

[0042] 12 Entrance

[0043] 14 Exhaust channel

[0044] 16 First three-way catalytic converter

[0045] 18 Second three-way catalytic converter

[0046] 20 Turbine

[0047] 22. First deflection unit

[0048] 24 Second deflection unit

[0049] 26 Electric heating device

[0050] 28 First contact surface

[0051] 30 Second contact surface

[0052] 32 First lambda detector

[0053] 34 Second lambda detector

[0054] 36 Particle filter.

Claims

1. An exhaust gas aftertreatment system (10) for an internal combustion engine, comprising an inlet (12) for receiving exhaust gas from the internal combustion engine; and at least one exhaust gas passage (14), wherein: A first three-way catalytic converter (16) is arranged in the exhaust passage (14) downstream of the inlet (12) and at least one second three-way catalytic converter (18) is arranged in the exhaust passage (14) downstream of the first three-way catalytic converter (16) close to the engine, and at least one turbine (20) is arranged in the exhaust passage (14) between the inlet (12) and the first three-way catalytic converter (16), It is characterized in that A first deflection portion (22) of the exhaust passage (14) is arranged downstream of the turbine (20), and a second deflection portion (24) of the exhaust passage (14) is arranged downstream of the second three-way catalytic converter (18) and is in the same curvature direction as the first deflection portion (22). An electric heating device (26) is arranged downstream of the first three-way catalytic converter (16) and upstream of the second three-way catalytic converter (18), and A particle filter (36) is arranged downstream of the second deflector (24).

2. The exhaust gas aftertreatment system (10) according to claim 1, characterized in that: The first deflection portion (22) and / or the second deflection portion (24) has a curvature angle between 70° and 110°.

3. The exhaust gas aftertreatment system (10) according to claim 2, characterized in that: The first deflection portion (22) and / or the second deflection portion (24) has a curvature angle of 90°.

4. The exhaust gas aftertreatment system (10) according to claim 1, characterized in that: The electric heating device (26) is designed as an electric heating plate through which water can flow.

5. The exhaust gas aftertreatment system (10) according to claim 4, characterized in that: The electric heating plate abuts against the first three-way catalytic converter (16) with a first contact surface (28), and abuts against the second three-way catalytic converter (18) with a second contact surface (30).

6. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, characterized in that: A first lambda probe (32) is arranged upstream of the first three-way catalytic converter (16), and a second lambda probe (34) is arranged downstream of the second three-way catalytic converter (18).

7. The exhaust gas aftertreatment system (10) according to claim 6, characterized in that: The first lambda detector (32) is a broadband detector.

8. The exhaust gas aftertreatment system (10) according to claim 6, characterized in that: The second lambda detector (34) is a jump detector.

9. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, characterized in that: The first three-way catalytic converter (16) is designed in the form of a metal carrier substrate.

10. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, characterized in that: The second three-way catalytic converter (18) is designed in the form of a ceramic carrier substrate.

11. The exhaust gas aftertreatment system (10) according to claim 1, characterized in that: The particle filter (36) has a coating, so that the particle filter (36) is designed as a four-way catalytic converter.

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