DE102015208421A1 - R2S charging system with intermediate exhaust aftertreatment - Google Patents

Abstract

An arrangement is provided for operating an internal combustion engine with two turbochargers arranged in series, with a device for exhaust gas aftertreatment arranged between the turbines of the turbocharger and a fluid connection between the exhaust gas and intake tract for exhaust gas recirculation. Furthermore, a method for operating an internal combustion engine with a corresponding arrangement is provided.

Description

The invention relates to an arrangement for operating an internal combustion engine with two turbochargers arranged in series, with an exhaust gas aftertreatment device between the turbines and a fluid connection between exhaust and intake for exhaust gas recirculation.

Turbochargers are used to charge the cylinders of internal combustion engines with pressurized combustion air. A turbocharger consists of a turbine and a compressor, which may be similarly constructed and mounted on a common shaft. The mass flow of the exhaust gas causes the turbine wheel in the exhaust tract in rotation. Via the common shaft, the torque is transmitted to the compressor wheel in the intake tract, whereby the compressor compresses combustion air. In serially arranged turbochargers for supercharging internal combustion engines, exhaust gas first flows through the turbine of a first turbocharger and subsequently the turbine of a second turbocharger arranged downstream of the turbine of the first turbocharger. The turbine of the second turbocharger can also be switched on only if necessary, if sufficient exhaust gas is available for their operation.

An advantage of serially arranged turbochargers is the high efficiency with which corresponding internal combustion engines operate. A disadvantage is significant heat losses, which is extracted from the exhaust gas in the flow through the turbine much heat energy. As a result, less heat energy is available to an exhaust gas aftertreatment device arranged behind the turbines. This leads to a delayed start of the exhaust aftertreatment device and thus to a higher emission of exhaust gas pollutants.

A reduction especially of emission of nitrogen oxides in the exhaust gas can be achieved by exhaust gas recirculation. For this purpose, exhaust gas is added to the charge air and thus circulated by an internal combustion engine. In motor vehicles with a diesel engine and a low-pressure exhaust gas recirculation (ND-EGR), the exhaust gas or a portion of the exhaust gas is discharged via a downstream in the flow direction of the exhaust gas behind a diesel particulate filter (DPF) return valve in the direction of a compressor. Owing to the low temperatures of the exhaust gas after passing through two turbines, especially at low engine loads, additional high pressure exhaust gas recirculation (HD-EGR) is usually necessary to avoid too low charge air inlet temperatures, as these lead to excessive carbon monoxide and hydrocarbon emissions. Emissions. A disadvantage of HD-EGR, however, that the supplied exhaust gas causes higher temperatures than desired and that is reduced by discharging exhaust gas of the exhaust gas mass flow before reaching the turbine of a turbocharger.

It is therefore the object to provide a device that allows efficient use of exhaust heat.

This object is achieved by an arrangement having the features of the main claim. Further advantageous embodiments and embodiments of the invention will become apparent from the dependent claims, the subclaims, the figure and the embodiments.

A first aspect of the invention relates to an arrangement for operating an internal combustion engine comprising an exhaust tract, an intake tract and a two-stage supercharger with a first turbocharger and a second turbocharger arranged serially to the first, wherein downstream of the turbine of the first turbocharger, a first exhaust aftertreatment device in an exhaust pipe of the first turbocharger Exhaust tract is arranged.

The arrangement according to the invention thus comprises, in addition to the serially arranged turbochargers, an intermediate exhaust aftertreatment device behind the turbine of the first turbocharger. This arrangement advantageously makes it possible to start the exhaust aftertreatment device quickly, since exhaust gas at this point was removed from exhaust heat only in a turbine.

The first turbocharger is also referred to as a high-pressure turbocharger, and its turbine and compressor as a high-pressure turbine or compressor. The second turbocharger is also referred to as a low-pressure turbocharger, and its turbine and compressor as a low-pressure turbine or compressor. The first exhaust aftertreatment device is also referred to as an intermediate exhaust aftertreatment device.

The internal combustion engine is particularly a self-igniting internal combustion engine, but can also be another internal combustion engine. The high-pressure turbine is especially designed as a turbine with variable turbine geometry (variable nozzle turbine, VNT turbine), but can also be designed differently.

"Downstream" refers to the direction of the exhaust or charge air flow provided in the arrangement. "Upstream" corresponds to a corresponding opposite direction.

Intake air that has been mixed with recirculated exhaust gas is also referred to as a gas mixture.

In the arrangement according to the invention, in the downstream of the first exhaust gas aftertreatment device, at least one line of exhaust gas recirculation branches off from the exhaust gas line, which produces a fluid connection to an intake line of the exhaust gas tract. The exhaust gas recirculation is thus a LP EGR. Advantageously, the discharged exhaust gas is still sufficiently warm in the LP EGR branching off behind the first exhaust gas aftertreatment device, so that no exhaust gas has to be discharged via an HP EGR.

Preferably, the exhaust gas recirculation line is connected to the intake line by means of a combination valve. As a result, the exhaust gas recirculation can advantageously be regulated or switched on or off.

Preferably, the exhaust gas recirculation line downstream of the compressor of the second turbocharger is connected to the intake line. By mixing the supplied exhaust gas with already heated compressed air from the low pressure compressor, condensation of water contained in the recirculated exhaust gas, which may damage the subsequent compressor, is restricted.

Preferably, in the arrangement according to the invention, downstream of the combination valve, a first charge air cooler is additionally arranged in the intake line. The first intercooler is due to the exhaust gas recirculation flowing into the intake tract upstream equally a cooler for the charge air and the introduced recirculated exhaust gas. A special intercooler for the exhaust gas is thus not needed.

Preferably, in the arrangement according to the invention, upstream of the first charge air cooler, a first bypass line with a cooler bypass valve branches off from the intake line, which opens into the intake line downstream of the first charge air cooler. At low load of the internal combustion engine, with the radiator bypass valve open, exhaust gas can advantageously be conducted past the first intercooler, as a result of which a higher inlet temperature of charge air into the cylinders of the internal combustion engine can be achieved. As a result, the emission of carbon monoxide and unburned hydrocarbons can advantageously be kept low.

Furthermore, in the arrangement according to the invention downstream of the first charge air cooler and upstream of the compressor of the first turbocharger, it is preferable for a second bypass line to branch off from the intake line with a compressor bypass valve and to open into the intake line downstream of the compressor of the first turbocharger.

Preferably, in the arrangement according to the invention, a third bypass line with a condensate drain valve connects the first charge air cooler and the intake manifold of the internal combustion engine fluid. The condensate drain valve allows z. B. advantageous the discharge of condensate from the first intercooler.

Furthermore, in the arrangement according to the invention, a fourth bypass line is arranged with a turbine bypass valve in the exhaust tract, which branches off from the exhaust line downstream of the internal combustion engine and opens into the exhaust pipe upstream of the turbine of the second turbocharger. Advantageously, the fourth bypass passage allows the passage of exhaust gas past the high pressure turbine such that it may be introduced into the exhaust passage upstream of the low pressure turbine and used to drive the low pressure turbine. Downstream of the low-pressure turbine, a second exhaust gas aftertreatment device is preferably arranged in the exhaust gas line, which advantageously enables the aftertreatment of exhaust gas not fed back as well as via the fourth bypass line.

A second aspect of the invention relates to a motor vehicle having an arrangement according to the invention. Thus, according to the invention, the motor vehicle comprises an arrangement for operating an internal combustion engine comprising an exhaust tract, an intake tract and a two-stage turbocharger with a first turbocharger and a second turbocharger arranged serially to the first turbocharger, and downstream of turbine of the first turbocharger a first exhaust aftertreatment device an exhaust pipe of the exhaust tract is arranged.

A third aspect of the invention relates to a method for operating an internal combustion engine having an arrangement according to the invention, wherein the internal combustion engine is charged in two stages by the serially arranged turbocharger, the exhaust gas flow from the turbine of the first turbocharger is supplied to a first exhaust gas treatment device, and at least a part of the exhaust gas flow in the turbine of the second turbocharger is passed. The advantages of the method correspond to those of the device according to the invention.

In the method according to the invention, part of the exhaust gas stream downstream of the first exhaust gas aftertreatment device is particularly preferably fed via a line branching off from the exhaust tract to the intake tract upstream of the first charge air cooler.

Preferably, in the method at low load of the internal combustion engine, the radiator bypass valve in the first bypass line is opened.

Preferably, in the method at high load of the internal combustion engine, the turbine bypass valve in the fourth bypass line is opened.

Furthermore, in the method, the condensate drain valve is opened when the pressure of the intake air in the first charge air cooler becomes larger than the allowable intake pressure when condensate has formed in the first charge air cooler.

The invention will be explained in more detail with reference to FIG. It shows:

1 an inventive arrangement.

In the presentation of 1 has the arrangement 1 an internal combustion engine 2 with four cylinders 2a in a row arrangement. The number of cylinders 2a can also 2 . 3 . 5 . 6 or 8th be. The cylinders can also be arranged differently, for example in a V-shaped arrangement. From the outlet openings of the cylinders 2 B exhaust gas flows into an exhaust tract 3 , The exhaust tract 3 has an exhaust pipe 3a but may also include multiple exhaust pipes. About an intake tract 4 Charge air flows to the engine 2 , In the exhaust tract 3 is one to a first turbocharger 5 belonging turbine 5a arranged, also as a high-pressure turbine 5a referred to over a wave 5b with a compressor 5c connected is. The turbine is located above the exhaust tract 5a with one to a second turbocharger 6 belonging turbine 6a , also referred to as low-pressure turbine, in a fluid connection. The turbine 6a is about a wave 6b with a compressor 6c connected. Between the turbines 5a . 6a is downstream of the high-pressure turbine 5a is a first exhaust aftertreatment device 7 arranged. This has, for example, a NOx storage catalytic converter, a diesel oxidation catalytic converter and / or a diesel particle filter.

Downstream of the first exhaust aftertreatment device 7 branches to an exhaust gas recirculation valve 8a a line 8th which represents the beginning of a LP EGR. Via a combination valve 9 leads the line 8th in a line 4a the intake tract 4 ,

Downstream of the combination valve 9 is a first intercooler 10 in the intake tract 4 arranged. The first intercooler 10 is both for the cooling of compressed charge air from the compressor 6c of the second turbocharger 6 as well as supplied exhaust gas. Via a first bypass line 11 can charge air, especially with exhaust gas mixed charge air, to the first intercooler 10 be diverted by the radiator bypass valve 12 is opened. The first bypass line 11 branches at one point 11a from the intake pipe 4a and ends at the point 11b back into the intake pipe 4a ,

Downstream of the intercooler 10 is the compressor 5c , as high pressure compressor 5c designated arranged. Via a second bypass line 13 can charge air to the high pressure compressor 5c be diverted if one in the second bypass line 13 arranged compressor bypass valve 14 is opened. The second bypass line 11 branches at one point 13 from the intake pipe 4a and ends at the point 13b back into the intake pipe 4a ,

Downstream of the high pressure compressor 5c is a second intercooler 15 arranged in the intake tract. From the second intercooler 15 leads the intake pipe 4b to the intake manifold 16 , From the first intercooler 10 performs a third bypass line 17 to the intake manifold 16 , About the third bypass line 17 can when the condensate drain valve is open 18 condensed water from the first intercooler 10 directly to the intake manifold 16 be directed.

A fourth bypass line 19 with a turbine bypass valve 20 is downstream of the internal combustion engine 2 in the exhaust tract 3 arranged. The fourth bypass line 19 branches in the area of the exhaust manifold 21 at the point 19a from the exhaust pipe 3a from and flows upstream of the low-pressure turbine 6a at the point 19b back into the exhaust pipe 3a ,

Downstream of the low-pressure turbine 6a is a second exhaust post-treatment device 22 arranged. This has z. B. a NOx storage catalyst, a diesel oxidation catalyst and / or a diesel particulate filter on. Downstream of the turbine 6a the exhaust is through an exhaust 23 derived.

In operation of the internal combustion engine 2 exhaust flows from the cylinders 2a through the exhaust tract 4 in the direction of the exhaust 23 , From the internal combustion engine 2 exhaust gas reaches the high-pressure turbine 5a to power these. By means of the wave 5b drives the turbine 5a the compressor 5c at. From the high-pressure turbine 5a exhaust flows to the first exhaust aftertreatment device 7 , From there, the post-treated and purified exhaust gas flows on to the exhaust gas recirculation valve 8a , In this case, the exhaust gas recirculation valve 8a designed to be at least partially opened. Via an opened exhaust gas recirculation valve 8a Depending on the degree of opening, a certain part of the exhaust gas is passed through the line 8th in the intake pipe 4a directed. At least partially open combination valve 9 the exhaust gas enters the suction line 4a and is doing with the low-pressure compressor 6c flowing intake air mixed. Opening and closing the valves 8a and 9 may be done by a signal from a controller (not shown) when exhaust is to be recycled.

The charge air mixed with the supplied exhaust gas passes downstream from the combination valve 9 in the first intercooler 10 , From there, the cooled gas mixture becomes a high-pressure compressor 5c directed. At very low loads of the internal combustion engine 2 becomes the radiator bypass valve 12 open. As a result, the gas mixture flows on the first intercooler 10 over and thus gets its temperature. This is mainly due to a higher inlet temperature of the gas mixture at the cylinders 2a aimed at controlling the emission of carbon monoxide and unburned hydrocarbons. At higher load is the operation of the internal combustion engine 2 however, more efficient when the gas mixture in the first intercooler 10 is cooled.

Via the second bypass line 13 becomes charge air or the gas mixture at the high pressure compressor 5c passed by, for example, if this is not needed. About the third bypass line 17 condensate from the first intercooler 10 in the intake manifold 16 passed when condensate has formed.

At high load of the internal combustion engine 2 is via a fourth bypass line 19 a part of the exhaust gas at the high-pressure turbine 5a bypassed to avoid exhaust backflow. For this purpose, a part of the exhaust gas in the region of the exhaust manifold 21 at a branch 19a from the exhaust pipe 3a derived. This is at the junction 19a ideally, a valve is arranged which is opened to exhaust gas through the fourth bypass line 19 to lead.

LIST OF REFERENCE NUMBERS

1

 arrangement

2

 Internal combustion engine

2a

cylinder

3

 exhaust tract

3a

 exhaust pipe

4

 intake system

4a

 suction

5

 first turbocharger

5a

 Turbine of the first turbocharger

5b

 Wave of the first turbocharger

5c

 Compressor of the first turbocharger

6

 second turbocharger

6a

 Turbine of the second turbocharger

6b

 Wave of the second turbocharger

6c

 Compressor of the second turbocharger

7

 first exhaust aftertreatment device

8th

 Management of exhaust gas recirculation

8a

 Exhaust gas recirculation valve

9

 combination valve

10

 first intercooler

11

 first bypass line

11a

 Branch of the first bypass line

11b

 Mouth of the first bypass line

12

 Cooler bypass valve

13

 second bypass line

13a

 Compressor bypass valve

13b

 Branch of the second bypass line

14

 Mouth of the second bypass line

15

 second intercooler

16

 intake manifold

17

 third bypass line

18

 Condensate drain valve

19

 fourth bypass line

19a

 Branch of the fourth bypass line

19b

 Mouth of the fourth bypass line

20

 Turbine bypass valve

21

 exhaust manifold

22

 second exhaust aftertreatment device

23

 Exhaust

Claims (16)

Arrangement ( 1 ) for operating an internal combustion engine ( 2 ) comprising an exhaust gas tract ( 3 ), an intake tract ( 4 ) and a two-stage supercharging system with a first turbocharger ( 5 ) and a second turbocharger arranged in series with the first one ( 6 ), characterized in that downstream of the turbine of the first turbocharger ( 5a ) a first exhaust aftertreatment device ( 7 ) in an exhaust pipe of the exhaust tract ( 3a ) is arranged. Arrangement ( 1 ) according to claim 1, in which downstream of the first exhaust aftertreatment device ( 7 ) at least one line of exhaust gas recirculation ( 8th ) from the exhaust pipe ( 3a ), which is a fluid connection to a suction line of the intake ( 4a ). Arrangement ( 1 ) according to claim 1 or 2, wherein the line of exhaust gas recirculation ( 3a ) by means of a combination valve ( 9 ) with the suction line ( 4a ) connected is. Arrangement ( 1 ) according to one of the preceding claims, in which the line of exhaust gas recirculation ( 8th ) downstream of the compressor of the second turbocharger ( 6c ) with the suction line ( 4a ) connected is. Arrangement ( 1 ) according to one of the preceding claims, in which downstream of the combination valve ( 9 ) additionally a first intercooler ( 10 ) in the intake tract ( 4 ) is arranged. Arrangement ( 1 ) according to claim 5, in which upstream of the first intercooler ( 10 ) a first bypass line ( 11 ) with a radiator bypass valve ( 12 ) of the Intake pipe ( 4a ) branches off and downstream of the first intercooler ( 10 ) back into the suction line ( 4a ) opens. Arrangement ( 1 ) according to one of the preceding claims, in which upstream of the compressor of the first turbocharger ( 5c ) a second bypass line ( 13 ) with a compressor bypass valve ( 14 ) from the suction line ( 4a ) branches off and downstream of the compressor of the first turbocharger ( 5c ) back into the suction line ( 4a ) opens. Arrangement ( 1 ) according to one of the preceding claims, in which a third bypass line ( 17 ) with a condensate drain valve ( 18 ) the first intercooler ( 10 ) and the intake manifold of the internal combustion engine ( 16 ) fluid connects. Arrangement ( 1 ) according to one of the preceding claims, in which a fourth bypass line ( 19 ) with a turbine bypass valve ( 20 ) in the exhaust tract ( 3 ) arranged downstream of the internal combustion engine ( 2 ) from the exhaust pipe ( 3a ) branches off and upstream of the turbine of the second turbocharger ( 6a ) in the exhaust pipe ( 3a ) opens. Arrangement ( 1 ) according to one of the preceding claims, in which downstream of the turbine of the second turbocharger ( 6a ) a second exhaust aftertreatment device ( 22 ) in the exhaust pipe ( 3a ) is arranged. Motor vehicle with an arrangement according to one of claims 1-10. Method for operating an internal combustion engine with an arrangement according to one of claims 1-10, wherein the internal combustion engine ( 2 ) is charged in two stages by the serially arranged turbocharger, the exhaust gas flow from the turbine of the first turbocharger ( 5a ) a first exhaust aftertreatment device ( 7 ) and at least part of the exhaust gas flow into the turbine of the second turbocharger ( 6a ). The method of claim 12, wherein a portion of the exhaust stream downstream of the first exhaust aftertreatment device (10). 7 ) via a line branching off from the exhaust gas tract ( 8th ) the intake tract ( 4 ) upstream of the first intercooler ( 10 ) is supplied. Method according to claim 12 or 13, wherein at low load of the internal combustion engine ( 2 ) the radiator bypass valve ( 12 ) in the first bypass line ( 11 ) is opened. A method according to claim 12 or 13, wherein at high load of the internal combustion engine ( 2 ) the turbine bypass valve ( 20 ) in the fourth bypass line ( 19 ) is opened. Method according to one of the preceding claims, wherein the condensate drain valve ( 18 ) in the third bypass line ( 17 ) is opened when in the first intercooler ( 10 ) Condensate has formed.

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