DE102019120234B4 - Exhaust gas recirculation arrangement of an internal combustion engine and method for operating such an exhaust gas recirculation arrangement - Google Patents

Abstract

Exhaust gas recirculation arrangement (1) of an internal combustion engine (100), comprising an exhaust gas recirculation (2), wherein an exhaust gas treatment device (23) for reducing nitrogen oxides in exhaust gas flowing through the exhaust gas recirculation (2) is arranged, characterized in that the Exhaust gas recirculation (2) comprises a cooler line (20) with an exhaust gas recirculation cooler (21) and a bypass line (22), the exhaust gas treatment device (23) being arranged in the bypass line (22) and the bypass line (22) for bypassing the exhaust gas recirculation cooler (21) is arranged parallel to the cooler line (20).

Description

The present invention relates to an exhaust gas recirculation system of an internal combustion engine and a method for operating such an exhaust gas recirculation system.

It is known from the prior art to feed the exhaust gases, which are produced during the combustion of fuel in an internal combustion engine, to the combustion again. The exhaust gases do not take part in the combustion. The recirculation of the exhaust gases lowers the combustion temperature, which leads to a reduction in nitrogen oxide emissions.

From the DE 10 2017 100 217 A1 an engine assembly is known with an exhaust gas recirculation arrangement having a first exhaust gas recirculation loop and a second exhaust gas recirculation loop. Two recirculation treatment devices are arranged in the first exhaust gas recirculation loop. A recirculation treatment device is arranged in the second exhaust gas recirculation loop.

The pamphlets JP H10 196 462 A and U.S. 2006/0137665 A1 further examples of exhaust gas recirculation arrangements of a respective internal combustion engine can be found as known.

It is the object of the invention to propose an exhaust gas recirculation arrangement of an internal combustion engine and a method for operating an exhaust gas recirculation arrangement of an internal combustion engine, through which a further reduction of nitrogen oxides, in particular during warm-up or low-load operation of the internal combustion engine, is made possible.

This problem is solved by the combination of features of the independent claims.

In particular, this object is achieved by an exhaust gas recirculation arrangement of an internal combustion engine, the exhaust gas recirculation arrangement comprising an exhaust gas recirculation and an exhaust gas treatment device arranged in the exhaust gas recirculation. The exhaust gas treatment device is set up to bring about a reduction in nitrogen oxides in the exhaust gas flowing through the exhaust gas recirculation.

According to the invention, the exhaust gas recirculation includes a cooler line with an exhaust gas recirculation cooler and a bypass line. The bypass line is arranged parallel to the cooler line to bypass the exhaust gas recirculation cooler. Furthermore, the exhaust gas treatment device is arranged in the bypass line. By arranging the exhaust gas treatment device in the bypass line, the exhaust gas can be recirculated without active cooling. This is particularly advantageous when the internal combustion engine is being operated in the engine warm-up range or in the low-load range. Cooling of the exhaust gas is not required in these operating modes of the internal combustion engine. Furthermore, an exhaust gas temperature can thus more quickly reach a temperature threshold of the exhaust gas treatment device at which the exhaust gas treatment device is fully functional.

The exhaust gas recirculation cooler is used to cool the exhaust gas that is routed through the cooler line.

Furthermore, the aforementioned object is achieved by a method for operating an exhaust gas recirculation system of an internal combustion engine, in particular the exhaust gas recirculation system described above. In this case, exhaust gas from a combustion chamber of the internal combustion engine is routed through an exhaust gas treatment device in a recirculation system to reduce nitrogen oxides in the exhaust gas.

Through the proposed exhaust gas recirculation arrangement and the proposed method for operating an exhaust gas recirculation arrangement, exhaust gas from a combustion cycle is recirculated to the new combustion cycle virtually free of nitrogen oxides or with a reduced nitrogen oxide content. This results in a reduction in raw emissions.

The exhaust gas recirculation connects in particular an exhaust gas area with a fresh air area of the internal combustion engine. The exhaust gas area can in particular be an exhaust manifold or an exhaust pipe. The fresh air area is advantageously an area of an intake tract of the internal combustion engine, in particular an intake duct, an intake manifold or an intake duct.

The exhaust gas treatment device preferably has a catalytic converter.

In particular, the catalyst can be used to bring about a chemical reduction of nitrogen oxides.

The exhaust gas treatment device particularly preferably has a nitrogen oxide storage catalytic converter and/or an SCR catalytic converter.

A nitrogen oxide storage catalytic converter extracts the nitrogen oxides from the exhaust gas and stores them until its absorption capacity is reached. To regenerate it, the internal combustion engine control adjusts a rich combustion mixture with more fuel. This will restore the saved Nitrogen oxides are converted into the neutral components "nitrogen", "water" and "carbon dioxide" and the nitrogen oxide storage catalytic converter starts working again.

An SCR catalytic converter is operated according to the principle of selective catalytic reduction. The nitrogen oxide emissions are reduced by adding a reducing agent, in particular a urea solution. The reducing agent is sprayed into the exhaust flow as required and converts the nitrogen oxide emissions into the neutral components "nitrogen", "water" and "carbon dioxide" in the SCR catalytic converter.

Preferably, the exhaust gas recirculation also includes a first line and a second line. The first line can be connected to the exhaust gas area of the internal combustion engine. Furthermore, the first line is connected to the bypass line and the cooler line. The second line is correspondingly connected to the bypass line and the cooler line and can be connected to the fresh air area of the internal combustion engine.

Furthermore, the exhaust gas recirculation arrangement preferably comprises an exhaust gas recirculation valve for controlling an exhaust gas quantity in the exhaust gas recirculation of the exhaust gas recirculation arrangement and/or a cooler bypass valve for selectively conducting the exhaust gas through the exhaust gas treatment device. As a result, a reduction in the emissions of nitrogen oxides can be achieved independently of the operating range of the internal combustion engine.

Furthermore, the present invention relates to an internal combustion engine with an exhaust gas recirculation arrangement as described above.

The internal combustion engine advantageously also has a turbocharger device with at least one turbine. In this case, the exhaust gas recirculation or the bypass line with the exhaust gas treatment device is arranged in front of the turbine in a flow direction of the exhaust gas from a combustion chamber of the internal combustion engine. In other words, an extraction point for extracting exhaust gas from an exhaust gas region of the internal combustion engine is preferably located in front of the turbine in the direction of flow of the exhaust gas. Thus, the exhaust gas arrives at the exhaust treatment device at a substantially higher temperature compared to the temperature at which the exhaust gas would reach a post-turbine exhaust treatment device. A temperature threshold of the exhaust gas treatment device at which the exhaust gas treatment device is fully functional can thus be reached more quickly.

In particular, if the exhaust gas treatment device has a nitrogen oxide storage catalytic converter and/or an SCR catalytic converter, these are activated earlier, especially when the internal combustion engine is warming up, due to the higher temperature of the exhaust gas.

In particular, the exhaust gas recirculation is arranged directly on an exhaust pipe or an exhaust manifold.

The exhaust gas is preferably routed through the exhaust gas treatment device during warm-up operation or low-load operation of the internal combustion engine. An internal combustion engine is operated in particular in a warm-up range when it has a temperature of up to 80 degrees to 90 degrees Celsius.

Low-load operation is, in particular, operation in the lower third of the maximum possible load on the internal combustion engine at the respective speed.

Further preferably, a maximum of 60% of the exhaust gas is routed through the exhaust gas treatment device.

• 1 eine Brennkraftmaschine mit einer Abgasrückführungsanordnung gemäß einem bevorzugten Ausführungsbeispiel der vorliegenden Erfindung.

Further details, features and advantages of the invention result from the following description and 1 . It shows:

• 1 an internal combustion engine with an exhaust gas recirculation arrangement according to a preferred embodiment of the present invention.

Below, with reference to 1 an exhaust gas recirculation system 1 according to a preferred embodiment of the present invention is described in detail.

1 shows schematically an internal combustion engine 100 with a plurality of combustion chambers 101, a fresh air area 102 and an exhaust gas area 103. The internal combustion engine 100 is operated in particular with diesel.

The fresh air area 102 includes in particular an intake manifold 106 via which fresh air can be supplied to the combustion chambers 101 . The exhaust gas area 103 accordingly comprises an exhaust gas manifold 107 through which the exhaust gas produced during the combustion can be discharged.

A plurality of swirl flaps 104, in particular one swirl flap 104 per cylinder or combustion chamber 101, is provided in the intake ducts of intake manifold 106. The swirl flaps 104 are configured to create a vortex along the ent to generate speaking cylinder axis in order to improve the mixing of the fuel-air mixture at low speeds. Better mixing reduces fuel consumption and pollutant emissions.

The fresh air area 102 also includes an intake duct 108 in which a throttle valve 105 is arranged.

The internal combustion engine 100 here includes a turbocharger device 109 which has a first turbocharger 110 and a second turbocharger 120 . However, the invention can also be applied to an internal combustion engine 100 with simple supercharging or without supercharging.

The first turbocharger 110, which has a first compressor 111 and a first turbine 112 mechanically connected thereto, forms a high-pressure stage of the supercharging of the internal combustion engine 100. In particular, the first turbine 112 (high-pressure turbine) is a variable turbine.

The second turbocharger 120, which accordingly has a second compressor 121 and a second turbine 122 mechanically connected thereto, forms a low-pressure stage of the supercharging of the internal combustion engine 100. In particular, the second turbine 122 (low-pressure turbine) is designed as a variable turbine.

However, it is also possible for the internal combustion engine to have only one turbocharger. In this case, charging occurs in only one stage.

A compressor bypass valve 115 for bypassing the first compressor 111 is arranged on a compressor bypass line 116 . Furthermore, a turbine bypass valve 113 is arranged in a turbine bypass line 114 to bypass the first turbine 112 .

In order to cool the compressed fresh air, an intercooler 117 is provided in the intake duct after the first compressor 111 in the flow direction of the air.

The exhaust gas recirculation arrangement 1 of the internal combustion engine 100 has an exhaust gas recirculation system 2 which connects the exhaust gas area 103 to the fresh air area 102 of the internal combustion engine 100 . The exhaust gas recirculation 2 includes a cooler line 20 in which an exhaust gas recirculation cooler 21 is arranged, and a bypass line 22 for bypassing the exhaust gas recirculation cooler 21. For this purpose, the bypass line 22 is arranged parallel to the cooler line 20.

According to the invention, an exhaust gas treatment device 23 for reducing nitrogen oxides in the exhaust gas flowing through the exhaust gas recirculation system 2 is provided in the exhaust gas recirculation system 2 .

In particular, the exhaust gas treatment device 23 is arranged in the bypass line 22 of the exhaust gas recirculation system 2 .

The exhaust gas treatment device 23 has in particular a nitrogen oxide storage catalytic converter and/or an SCR catalytic converter.

Furthermore, the exhaust gas recirculation 2 includes a first line 24 and a second line 25 . The first line 24 is connected to the bypass line 22 and the cooler line 20 via a cooler bypass valve 26 . Exhaust gas may be routed through exhaust gas treatment device 23 through cooler bypass valve 26 .

Furthermore, the first line 24 communicates via an exhaust gas recirculation valve 27 with the exhaust gas region 103 of the internal combustion engine 100. In particular, the first line 24 is directly connected to the exhaust manifold 107. A quantity of exhaust gas in the recirculation system 2 of the exhaust gas recirculation arrangement 1 can be controlled by the exhaust gas recirculation valve 27 .

The exhaust gas recirculation valve 27 is arranged upstream of the cooler bypass valve 26 .

How out 1 As can be seen, the exhaust gas recirculation system 2, in particular the first line 24 and the bypass line 22, is arranged in front of the first turbine 112 with respect to a flow direction of the exhaust gas. In other words, the extraction point for extracting exhaust gas from the exhaust gas region 103 of the internal combustion engine 100 is in the direction of flow of the exhaust gas in front of the first turbine 112. The exhaust gas is thus routed directly from the exhaust gas manifold 107 into the exhaust gas recirculation system 2 and is therefore at a significantly higher temperature compared to the exhaust gas which is passed through the first turbine 2. The exhaust gas treatment device 23 can thus be activated earlier, since the temperature of the exhaust gas more quickly reaches or exceeds a temperature threshold of the exhaust gas treatment device 23 at which the full functionality of the exhaust gas treatment device 23 is achieved.

The exhaust gas treated by the exhaust gas treatment device 23 reaches the combustion chambers 101 virtually free of nitrogen oxides, which leads to a strong reduction in raw emissions.

Exhaust gas is discharged through the bypass line 22, in particular during engine warm-up or Low-load operation of the internal combustion engine 100 passed.

Since the exhaust gas is routed directly from the exhaust manifold 107 in the direction of the exhaust gas treatment device 23, the temperature threshold of the exhaust gas treatment device 23 is also reached relatively quickly in these operating modes of the internal combustion engine 100.

As a result, the raw emissions can also be greatly reduced in the warm-up range or in the low-load range of internal combustion engine 100 . In this way, the constantly tightening legal emission requirements can be met.

Reference List

1

exhaust gas recirculation arrangement

2

exhaust gas recirculation

20

cooler line

21

exhaust gas recirculation cooler

22

bypass line

23

exhaust treatment device

24

first line

25

second line

26

cooler bypass valve

27

exhaust gas recirculation valve

100

internal combustion engine

101

combustion chamber

102

fresh air area

103

exhaust area

104

swirl flap

105

throttle

106

intake manifold

107

exhaust manifold

108

intake duct

109

turbocharger device

110

first turbocharger

111

first compressor

112

first turbine

113

turbine bypass valve

114

turbine bypass line

115

compressor bypass valve

116

compressor bypass line

117

intercooler

120

second turbocharger

121

second compressor

122

second turbine

Claims (8)

Exhaust gas recirculation arrangement (1) of an internal combustion engine (100), comprising an exhaust gas recirculation (2), wherein an exhaust gas treatment device (23) for reducing nitrogen oxides in the exhaust gas flowing through the exhaust gas recirculation (2) is arranged, characterized in that the Exhaust gas recirculation (2) comprises a cooler line (20) with an exhaust gas recirculation cooler (21) and a bypass line (22), the exhaust gas treatment device (23) being arranged in the bypass line (22) and the bypass line (22) for bypassing the exhaust gas recirculation cooler (21) is arranged parallel to the cooler line (20). Exhaust gas recirculation arrangement (1) after claim 1 , wherein the exhaust gas treatment device (23) has a nitrogen oxide storage catalyst and / or an SCR catalyst. Exhaust gas recirculation arrangement (1) according to one of the preceding claims, further comprising an exhaust gas recirculation valve (27) for controlling an exhaust gas quantity in the exhaust gas recirculation (2) and/or a cooler bypass valve (26) for selectively directing the exhaust gas through the exhaust gas treatment device (23). Internal combustion engine (100) comprising an exhaust gas recirculation arrangement (1) according to one of the preceding claims. Internal combustion engine (100) after claim 4 Further comprising a turbocharger device (109) with at least one turbine (112, 122), wherein the exhaust gas recirculation (2) is arranged in front of the turbine (112, 122) with respect to a flow direction of the exhaust gas. Method for operating an exhaust gas recirculation arrangement (1) according to one of Claims 1 until 3 , wherein exhaust gas from a combustion chamber (101) of an internal combustion engine (100) through the exhaust gas treatment device (23) in an exhaust gas recirculation system (2) for reducing nitrogen oxides in the exhaust gas is guided. procedure after claim 6 , wherein the routing of the exhaust gas through the exhaust gas treatment device (23) takes place in a warm-up range or low load range of the internal combustion engine (100). procedure after claim 6 or 7 , wherein a maximum of 60% of the volume of the exhaust gas is passed through the exhaust gas treatment device (23) during a combustion cycle.

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