DE102020106544A1 - Exhaust gas recirculation device for an internal combustion engine, internal combustion engine with an exhaust gas recirculation device, motor vehicle with an internal combustion engine and method for operating an internal combustion engine - Google Patents

Abstract

The invention relates to an exhaust gas recirculation device for an internal combustion engine, comprising at least one duct arrangement which is designed to guide an exhaust gas flow from an exhaust tract of the internal combustion engine to an intake tract of the internal combustion engine and an inlet area for coupling the duct arrangement to the exhaust tract and an outlet area arranged downstream of the inlet area Coupling of the channel arrangement with the intake tract includes. The exhaust gas recirculation device comprises an introduction device which is connected to the duct arrangement and by means of which fuel can be introduced into a duct interior of the duct arrangement downstream of the inlet region and thereby an exhaust gas flow-fuel mixture can be generated. In addition, the exhaust gas recirculation device comprises a catalytic converter device which is connected to the duct arrangement and which is designed for thermo-catalytic reforming of the exhaust gas flow-fuel mixture. Further aspects of the invention relate to an internal combustion engine with an exhaust gas recirculation device and a method for operating an internal combustion engine with an exhaust gas recirculation device.

Description

With exhaust gas recirculation, also called EGR for short, exhaust gas is fed to the respective combustion chambers of an internal combustion engine, which acts as a so-called drag gas and enables an effective reduction of a peak temperature in the combustion chambers that is decisive for nitrogen oxide emissions. To set so-called exhaust gas recirculation rates, also known as EGR rates, exhaust gas recirculation devices are used which include, for example, pivotable exhaust gas flaps or so-called exhaust gas recirculation valves with height-adjustable valve bodies.

The object of the present invention is to create an exhaust gas recirculation device, an internal combustion engine, a motor vehicle and a method for operating an internal combustion engine of the type mentioned above, by means of which a particularly favorable use of energy contained in an exhaust gas flow is made possible.

This object is achieved by an exhaust gas recirculation device with the features of claim 1, by an internal combustion engine with the features of claim 7, by a motor vehicle with the features of claim 8 and by a method with the features of claim 9. Advantageous configurations with expedient developments of the invention are specified in the subclaims.

A first aspect of the invention relates to an exhaust gas recirculation device for an internal combustion engine, with at least one duct arrangement which is designed to guide an exhaust gas flow from an exhaust tract of the internal combustion engine to an intake tract of the internal combustion engine and an inlet area for coupling the duct arrangement to the exhaust tract and a downstream of the inlet area comprises arranged outlet area for coupling the channel arrangement with the intake tract. The inlet area can have at least one inlet opening via which the exhaust gas flow can enter the exhaust gas duct arrangement. The outlet region can have at least one outlet opening through which the exhaust gas flow can exit from the exhaust gas duct arrangement. The term “downstream” means an arrangement when the exhaust gas recirculation device is used as intended in the direction of flow behind a corresponding element or area (here: inlet area). In other words, the term “downstream” is to be understood as an arrangement that is connected downstream in the direction of flow. The intended use is to be understood as the use of the exhaust gas recirculation device for recirculating the exhaust gas flow, the exhaust gas flow flowing from the inlet area to the outlet area when used as intended.

According to the invention it is provided that the exhaust gas recirculation device comprises an introduction device connected to the duct arrangement, by means of which fuel can be introduced downstream of the inlet region into a duct interior of the duct arrangement and thereby an exhaust gas flow-fuel mixture can be generated, as well as a catalytic converter device connected to the duct arrangement, which is used for Thermo-catalytic reforming of the exhaust gas flow-fuel mixture is formed. This is advantageous because thermo-catalytic reforming, which is also abbreviated as TCR in the following, at least part of an otherwise unused thermal exhaust gas energy can be converted into chemical energy, which in turn can be used by the internal combustion engine. _{Hydrogen (H 2} ), for example, can be formed by the TCR, which can be supplied to the respective combustion chambers of the internal combustion engine via the intake tract. Due to the high reaction speed or detonation speed of hydrogen, particularly high values of a laminar burning speed can be achieved when the internal combustion engine is operating. Further advantages are that the TCR enables the internal combustion engine to be operated with increased knock resistance, provided the internal combustion engine is designed as a gasoline engine, which enables an improved center of gravity of a combustion center of gravity in a characteristic map of the internal combustion engine. The increased knock resistance in turn makes it possible to operate the internal combustion engine with a compression ratio that is more favorable in terms of its efficiency. The exhaust gas recirculation device thus enables a particularly favorable use of the energy contained in the exhaust gas flow.

In an advantageous development of the invention, the exhaust gas recirculation device comprises at least one heat exchanger for heating the catalytic converter device at least to a predetermined operating temperature. This is advantageous because the predetermined operating temperature, which can be a so-called light-off temperature of the catalytic converter device, is particularly rapid as a result of the heating and regardless of whether the exhaust gas recirculation device is operated and the exhaust gas flow flows through the duct arrangement, can be adjusted.

In a further advantageous development of the invention, the heat exchanger is for the exhaust-gas-conducting connection with the exhaust gas tract Internal combustion engine formed. This is advantageous because it allows exhaust gas carried in the exhaust gas tract to be used via the heat exchanger to heat the catalytic converter device. A particularly rapid heating of the catalytic converter device can thereby be brought about. Thus, exhaust gas can be conducted from the exhaust gas tract via the heat exchanger in order to heat the catalytic converter device by means of the heat exchanger on the basis of the heat contained in the exhaust gas.

In a further advantageous development of the invention, the exhaust gas recirculation device comprises at least one exhaust gas cooler connected to the duct arrangement for cooling the exhaust gas flow. This is advantageous because the cooling of the exhaust gas flow enables so-called cooled exhaust gas recirculation with a higher degree of efficiency than would be the case with uncooled exhaust gas recirculation. In addition, by cooling the exhaust gas flow, it can be prevented in a particularly simple manner that an undesired ignition of hydrogen formed by the TCR occurs.

In a further advantageous development of the invention, the exhaust gas cooler is connected to the duct arrangement downstream of the catalytic converter device. This is advantageous because the exhaust gas flow downstream of the catalytic converter device already has a significantly lower exhaust gas temperature than when the exhaust gas flow enters via the inlet area, whereby the exhaust gas cooler provides a particularly effective, further cooling of the exhaust gas flow to a particularly low exhaust gas temperature before it enters via the outlet area allows the intake tract.

In a further advantageous development of the invention, the exhaust gas recirculation device comprises at least one cooling device for cooling the introduction device. This is advantageous since it can thereby be ensured, for example, in an effective and simple manner, that there is no thermal conversion of the fuel carried in the introduction device.

A second aspect of the invention relates to an internal combustion engine with an exhaust gas recirculation device according to the first aspect of the invention. The internal combustion engine enables particularly favorable use of the energy contained in the exhaust gas flow.

A third aspect of the invention relates to a motor vehicle with an internal combustion engine according to the second aspect of the invention. The motor vehicle with the internal combustion engine, which in turn includes the exhaust gas recirculation device, enables the energy contained in the exhaust gas flow to be used particularly advantageously.

A fourth aspect of the invention relates to a method for operating an internal combustion engine with an exhaust gas recirculation device, in which an exhaust gas flow is guided via a duct arrangement of the exhaust gas recirculation device from an exhaust tract of the internal combustion engine to an intake tract of the internal combustion engine, the duct arrangement having an inlet area coupled to the exhaust tract and a downstream the inlet area, which is arranged and the outlet area is coupled to the intake tract. According to the invention, it is provided that fuel is introduced into a duct interior of the duct arrangement by means of an introduction device of the exhaust gas recirculation device downstream of the inlet region, thereby generating an exhaust gas flow-fuel mixture and thermo-catalytic reforming of the exhaust gas flow-fuel mixture by means of a duct arrangement connected catalyst device of the exhaust gas recirculation device takes place. The method allows a particularly favorable use of the energy contained in the exhaust gas flow.

In an advantageous development of the invention, high pressure exhaust gas recirculation, low pressure exhaust gas recirculation and / or donor cylinder exhaust gas recirculation takes place via the exhaust gas recirculation device. This is advantageous because these types of exhaust gas recirculation make it possible, for example, to lower nitrogen oxide emissions in a particularly effective manner.

The preferred embodiments presented in relation to one aspect of the invention and their advantages apply correspondingly to the other aspects of the invention and vice versa.

The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination specified, but also in other combinations or on their own, without the scope of the Invention to leave.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and on the basis of the drawings.

The invention is explained again below using a specific exemplary embodiment. For this purpose, the single FIGURE shows a schematic representation of a motor vehicle with an internal combustion engine which comprises an exhaust gas recirculation device via which a Exhaust gas flow can be guided from an exhaust gas tract to an intake tract of the internal combustion engine.

The single figure shows a schematic representation of a motor vehicle K , which is an internal combustion engine 100 includes. The internal combustion engine 100 is designed here as a gasoline engine. However, an embodiment of the internal combustion engine is also conceivable, for example 100 as a diesel engine. The internal combustion engine 100 includes a plurality of cylinders 102 . Via an intake duct 80 the internal combustion engine 100 fresh air is sucked in during their operation, in a flow direction indicated by an arrow 104 through at least one intake duct 82 of the intake tract 80 up to an intake manifold 84 of the intake tract 80 flows. The intake tract can be used to set a desired amount of fresh air 80 a throttle element designed, for example, as a throttle valve 87 include.

In the direction of flow 104 upstream of the intake manifold 84 shows the intake tract 80 an intercooler 86 on, by means of which the fresh air before it enters the intake manifold 84 can be cooled. Via the intake manifold 84 can the cooled fresh air for combustion with fuel in the respective cylinders 102 assigned combustion chambers, not shown here, are initiated. The respective cylinders 102 Several gas exchange valves are assigned to each, which are opened and closed intermittently, on the one hand to allow fresh air to be introduced into the respective combustion chambers and, on the other hand, after combustion has taken place, to allow exhaust gas to be discharged from the respective combustion chambers. The exhaust gas exiting the combustion chambers intermittently passes through an exhaust manifold 74 an exhaust tract 70 into an exhaust duct 72 of the exhaust tract 70 . The exhaust gas flows in a flow direction indicated by a further arrow 114 of the exhaust gas through the exhaust duct 72 .

The internal combustion engine 100 includes an exhaust gas turbocharger 106 , which one with the exhaust duct 72 coupled turbine 108 and one with the intake port 82 coupled compressor 110 having. The turbine 108 and the compressor 110 are mechanically via a shaft 109 coupled together so that the turbine driven by exhaust gas 108 turn the compressor 110 can drive to compress the fresh air. The fresh air can therefore using the compressor 110 compressed and thus a so-called boost pressure of the fresh air can be set. The exhaust tract is used to regulate the boost pressure 70 a bypass channel 76 and one in the bypass duct 76 integrated, adjustable throttle element 77 . The bypass channel 76 opens for this on the one hand in the direction of flow 114 upstream and on the other hand in the direction of flow 114 downstream of the turbine 108 in the exhaust duct 72 . The throttle element 77 can also be referred to as a bypass valve or a "wastegate".

In the direction of flow 114 downstream of the turbine 108 as well as downstream of the bypass channel 76 is in the present case an exhaust gas aftertreatment device 78 of the exhaust tract 70 with the exhaust duct 72 coupled. The exhaust aftertreatment device 78 can - depending on the design of the internal combustion engine 100 as a diesel engine or as a gasoline engine - for example, an oxidation catalytic converter, a particle filter and / or a three-way catalytic converter, to name just a few examples.

The internal combustion engine 100 comprises an exhaust gas recirculation device for reducing nitrogen oxide emissions contained in the exhaust gas 10 , with a channel arrangement 20th . The channel arrangement 20th serves to guide an exhaust gas flow 12th from the exhaust tract 70 to the intake tract 80 .

The channel arrangement 20th includes an inlet area 22nd with an inlet port 24 . Via the inlet opening 24 is the exhaust gas recirculation device 10 present in the direction of flow 114 of the exhaust gas downstream of the exhaust gas aftertreatment device 78 with the exhaust duct 72 tied together. In other words, the inlet area opens 22nd with the inlet port 24 downstream of the exhaust aftertreatment device 78 in the exhaust duct 72 . The exhaust tract 70 can be one, in the direction of flow 114 downstream of the inlet port 24 in the exhaust duct 72 integrated exhaust throttle 79 include, via which a desired exhaust gas back pressure in the exhaust gas duct as required 72 can be adjusted. This exhaust gas back pressure causes the flow of exhaust gas to flow in 12th via the inlet port 24 into the channel arrangement 20th causes.

If the internal combustion engine 100 is designed as a gasoline engine, it is advantageous if the inlet opening 24 in the direction of flow 114 of the exhaust gas upstream of the exhaust gas aftertreatment device 78 and additionally or alternatively downstream of the turbine 108 with the exhaust duct 72 connected is. This can result in an operation of the internal combustion engine 100 effective range in which there is a combustion air ratio with the value "1" (λ = 1) can be expanded. In addition, a greater degree of efficiency of the internal combustion engine can be achieved if the inlet opening 24 in the direction of flow 114 of the exhaust gas upstream of the exhaust gas aftertreatment device 78 with the exhaust duct 72 is connected, as this results in unburned hydrocarbons via the exhaust gas recirculation device 10 can be traced back. The previously unburned hydrocarbons get there again for combustion in the respective combustion chambers.

The channel arrangement 20th further comprises an outlet area 26th with an outlet port 28 . Via the outlet opening 28 is the exhaust gas recirculation device 10 in the direction of flow 104 the fresh air in the present case downstream of the throttle element 87 (Throttle valve) and upstream of the compressor 110 with the intake duct 82 tied together. In other words, the outlet area opens 26th with the outlet port 28 downstream of the throttle element 87 as well as upstream of the compressor 110 in the intake duct 82 . This allows the recirculated exhaust gas flow 12th together with the fresh air from the compressor 110 be condensed.

Using the exhaust gas recirculation device 10 In the present case, what is known as low-pressure exhaust gas recirculation takes place. By means of the exhaust gas recirculation device 10 However, a so-called high-pressure exhaust gas recirculation and additionally or alternatively a donor cylinder exhaust gas recirculation could alternatively also take place, although this is not further shown here.

The exhaust gas recirculation device 10 includes one with the channel arrangement 20th connected delivery device 30th , by means of which fuel downstream of the inlet area 22nd into a channel interior of the channel arrangement 20th can be initiated. As a result, an exhaust gas flow / fuel mixture can be generated. The exhaust gas recirculation device 10 further comprises a cooling device 60 , by means of which the introduction device 30th can be cooled as required. The cooler 60 can for example be flowed through with cooling water to thereby the introduction device 30th to cool.

In addition, the exhaust gas recirculation device comprises 10 one with the channel arrangement 20th connected catalyst device 40 , which is designed for TCR, i.e. for thermal catalytic reforming, of the exhaust gas flow-fuel mixture. The catalyst device 40 can at least one catalyst 44 include, which is designed for TCR.

The exhaust gas recirculation device 10 also includes a heat exchanger 42 for heating the catalyst device 40 to a predetermined operating temperature. The heat exchanger 42 In the present case, it conducts exhaust gas with the exhaust tract 70 connected so that at least part of the exhaust gas through the heat exchanger 42 can be performed, and thereby a heat transfer from this part of the exhaust gas to the catalyst device 40 can be done. The heat exchanger 42 can in the catalyst 44 the catalyst device 40 be integrated. The catalyst device 40 is the exhaust gas flow in the direction of the arrow 12th Illustrative arrow downstream of the introduction device 30th arranged. Downstream of the catalyst device 40 and upstream of the outlet port 28 are an exhaust gas cooler in this order 50 and an exhaust gas recirculation valve 90 arranged and each with the channel arrangement 20th tied together. The downstream of the catalytic converter 40 with the channel arrangement 20th connected exhaust gas cooler 50 serves to cool the exhaust gas flow as required 12th . The adjustable exhaust gas recirculation valve 90 on the other hand, it is used to set a via the outlet opening 28 in the intake duct 82 the amount of exhaust gas to be introduced in the exhaust gas mass flow 12th .

The following briefly describes the use of the exhaust gas recirculation device 10 when operating the internal combustion engine 100 be summarized. When operating the exhaust gas recirculation device 10 for high-pressure exhaust gas recirculation or for the low-pressure exhaust gas recirculation shown in the figure here, via the introduction device 30th , which can be referred to as an injection unit, fuel into the channel arrangement 20th and thus introduced into the channel interior, in particular injected and thus added. The fuel is thus with the hot exhaust gas flow 12th mixed and thereby the hot exhaust gas flow 12th so to speak added, whereby the fuel is not unused or unburned in an environment of the internal combustion engine 100 or the motor vehicle K got. Instead, this is done from the fuel and the exhaust gas flow 12th formed exhaust gas flow-fuel mixture, which can also be referred to as a fuel-exhaust gas mixture, by the catalyst device 40 and thus through their catalyst 44 guided by the help of in the exhaust tract 70 exhaust gas based on the heat exchanger 42 , which can also be referred to as a heat exchanger, is heated to the predetermined operating temperature. Then, in particular after the TCR has taken place, the hot exhaust gas flow / fuel mixture is measured using the exhaust gas cooler 50 cooled down before using the exhaust port 28 in the intake duct 82 of the intake tract 80 and is mixed there with the fresh air. By cooling down, a so-called cooled exhaust gas recirculation can be achieved on the one hand and, on the other hand, premature ignition of the exhaust gas flow-fuel mixture before it enters the respective combustion chambers of the cylinders together with the fresh air 102 be prevented. The delivery device 30th (Injection unit) can advantageously be based on the cooling device 60 be cooled to avoid overheating of the delivery device 30th to avoid.

When using the exhaust gas recirculation device 10 for donor cylinder exhaust gas recirculation could be used as a delivery device 30th for example an existing one Direct injection injector can be used. In this case, fuel can be fed into a corresponding combustion chamber of a cylinder designed as the dispenser cylinder 102 are introduced shortly before respective gas exchange valves designed as outlet valves are opened. Here, a predetermined maximum amount of fuel can be introduced until shortly before the outlet valves close. In donor cylinder exhaust gas recirculation, the donor cylinder is the exhaust gas recirculation device 10 upstream, the introduction device in this case as well 30th ideally should be chilled. The catalyst device 40 can likewise be connected downstream of the donor cylinder, that is to say introduced into the path of the donor cylinder, and can through respective exhaust gas lines of the cylinders which are different from the donor cylinder and therefore different 102 using the heat exchanger 42 be heated. Before it is mixed with the fresh air, the exhaust gas flow-fuel mixture chemically converted by the TCR is processed using the exhaust gas cooler 50 , which can also be referred to as an EGR cooler, is cooled down.

To the catalytic device 40 or their catalyst 44 To be able to clean if necessary, the fuel can preferably be used immediately after a cold start of the internal combustion engine 100 be used as a solvent or cleaning agent. In the case of warm or hot boundary conditions, the catalytic converter device can 40 or their catalyst 44 be burned free when cleaning is required, which can also be referred to as regeneration. This can be done after the compressor 110 Fresh air branched off and in front of the catalytic converter device 40 into the channel arrangement 20th and thus introduced into the duct interior. This can be done with activated or deactivated injection of the fuel (by means of the introduction device 30th ) take place. Provided an exhaust gas temperature of the exhaust gas flow 12th big enough to burn free the catalyst 44 or the catalyst device 40 is, the injection of fuel by the introduction device 30th remain under. If the exhaust gas temperature is too low to burn free, the fuel can be fed with the aid of the introduction device 30th can also be injected in order to achieve a temperature value of the exhaust gas temperature required for burning free.

In all described variants of exhaust gas recirculation (high pressure exhaust gas recirculation, low pressure exhaust gas recirculation, donor cylinder exhaust gas recirculation) it is advantageous to use direct injection (injection of the fuel directly into the respective combustion chambers of the respective cylinder 102 ) or with an intake manifold injection that is at least close to the cylinder (in which the fuel is injected into the intake manifold, for example 84 can be injected), in order to achieve the most exact possible regulation to a stoichiometric combustion air ratio and thereby a desired dynamic behavior of the internal combustion engine 100 as well as showing their engine start as well as possible. By using the exhaust gas recirculation device 10 possible wall wetting of the combustion chambers of the cylinders 102 especially when starting the internal combustion engine from cold 100 be reduced.

List of reference symbols

10

Exhaust gas recirculation device

12th

Exhaust gas flow

20th

Channel arrangement

22nd

Inlet area

24

Inlet opening

26th

Outlet area

28

Outlet opening

30th

Delivery device

40

Catalyst device

42

Heat exchanger

44

catalyst

50

Exhaust gas cooler

60

Cooling device

70

Exhaust tract

72

Exhaust duct

74

Exhaust manifold

76

Bypass duct

77

Throttle element

78

Exhaust aftertreatment device

79

Exhaust throttle

80

Intake tract

82

Intake duct

84

Intake manifold

86

Intercooler

87

Throttle element

90

Exhaust gas recirculation valve

100

Internal combustion engine

102

cylinder

104

Direction of flow

106

Exhaust gas turbocharger

108

turbine

109

wave

110

compressor

114

Direction of flow

K

Motor vehicle

Claims (10)

Exhaust gas recirculation device (10) for an internal combustion engine (100), with at least one duct arrangement (20) which is designed to guide an exhaust gas flow (12) from an exhaust gas tract (70) of the internal combustion engine (100) to an intake tract (80) of the internal combustion engine (100) and an inlet area (22) for coupling the duct arrangement (10) to the exhaust gas tract (70) and an outlet area (26) arranged downstream of the inlet area (22) for coupling the duct arrangement (20) to the intake tract (80), thereby characterized in that the exhaust gas recirculation device (10) has an introduction device (30) connected to the duct arrangement (20), by means of which fuel can be introduced into a duct interior of the duct arrangement (20) downstream of the inlet region (22) and thereby an exhaust gas flow-fuel mixture can be generated, as well as a catalyst device (40) connected to the channel arrangement (20), which catalytic converter for thermo-catalytic reforming of the exhaust asstrom-fuel mixture is formed. Exhaust gas recirculation device (10) according to Claim 1 , characterized in that the exhaust gas recirculation device (10) comprises at least one heat exchanger (42) for heating the catalyst device (40) at least to a predetermined operating temperature. Exhaust gas recirculation device (10) according to Claim 2 , characterized in that the heat exchanger (42) is designed for the exhaust-conducting connection with the exhaust tract (70) of the internal combustion engine (100). Exhaust gas recirculation device (10) according to one of the preceding claims, characterized in that the exhaust gas recirculation device (10) comprises at least one exhaust gas cooler (50) connected to the duct arrangement (20) for cooling the exhaust gas flow (12). Exhaust gas recirculation device (10) according to Claim 4 , characterized in that the exhaust gas cooler (50) is connected to the duct arrangement (20) downstream of the catalyst device (40). The exhaust gas recirculation device (10) according to any one of the preceding claims, characterized in that the exhaust gas recirculation device (10) comprises at least one cooling device (60) for cooling the introduction device (30). Internal combustion engine (100) with an exhaust gas recirculation device (10) according to one of the Claims 1 until 6th . Motor vehicle (K) with an internal combustion engine (100) Claim 7 . Method for operating an internal combustion engine (100) with an exhaust gas recirculation device (10), in which an exhaust gas flow (12) via a duct arrangement (20) of the exhaust gas recirculation device (10) from an exhaust gas tract (70) of the internal combustion engine (100) to an intake tract (80) of the internal combustion engine (100), the duct arrangement (20) comprising an inlet area (22) coupled to the exhaust gas tract (70) and an outlet area (26) arranged downstream of the inlet area (22) and coupled to the intake tract (80), thereby characterized in that fuel is introduced into a duct interior of the duct arrangement (20) by means of an introduction device (30) of the exhaust gas recirculation device (10) downstream of the inlet region (22) and thereby an exhaust gas flow-fuel mixture is generated and a thermo-catalytic reforming of the exhaust gas flow Fuel mixture through a catalyst device (40) of the exhaust gas connected to the duct arrangement (20) feedback device (10) takes place. Procedure according to Claim 9 , characterized in that a high pressure exhaust gas recirculation, a low pressure exhaust gas recirculation and / or a donor cylinder exhaust gas recirculation takes place via the exhaust gas recirculation device (10).

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