WO2019201546A1

WO2019201546A1 - Internal combustion engine with an exhaust gas system

Info

Publication number: WO2019201546A1
Application number: PCT/EP2019/057175
Authority: WO
Inventors: Christian Schwarz; Dirk Christian Leinhos
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2018-04-17
Filing date: 2019-03-22
Publication date: 2019-10-24
Also published as: DE102018205768B3

Abstract

Internal combustion engine with at least four cylinders and an exhaust gas system, wherein a turbine casing with a turbine of a turbocharger is arranged in the exhaust gas system, and an exhaust gas purification system is arranged downstream of the turbine casing, in the direction of flow of the exhaust gas, a first exhaust pipe carrying exhaust gas branches off between the internal combustion engine and the turbine casing and opens again into the exhaust pipe system after the exhaust gas purification system, the turbocharger is a twin scroll turbocharger, at least two cylinders form a cylinder group according to an ignition sequence of the internal combustion engine, a first cylinder group is linked to a first scroll through a second exhaust pipe and a second cylinder group is linked to a second scroll through a third exhaust pipe, both exhaust pipes carrying exhaust gas, and the first exhaust pipe can be linked to the second and third exhaust pipes so as to carry exhaust gas. The design according to the invention allows the internal combustion engine to achieve higher specific outputs, at the same time as the components are thermally protected.

Description

Internal combustion engine with an exhaust system

The invention relates to an internal combustion engine having an exhaust system with the features of the preamble of patent claim 1.

The technical environment is, for example, the German

Offenlegungsschrift DE 28 51 675 A1. From this

Offenlegungsschrift is a Nachverbrennungsvorrichtung for the exhaust gases of internal combustion engines known. A device is proposed for the afterburning of exhaust gases of internal combustion engines with a catalyst for the oxidation of CO (carbon monoxide) and HC

(Hydrocarbons), in which in the upper load range of

Internal combustion engine, a part of the exhaust gas bypassing a

Catalyst is passed through an exhaust passage, wherein the catalyst in the exhaust passage, a second catalyst is arranged downstream.

A development of known from DE 28 51 675 A1

Nachverbrennungsvorrichtung is described in the not yet published German patent application, with the official file number 10 2017 218 837.5. In this patent application, an internal combustion engine is described with an exhaust system having an exhaust manifold, which is connected to that of the internal combustion engine. In the exhaust system are a first and in the flow direction of the exhaust behind a second

Emission control system arranged. The first emission control system is bypassable by a bypass element with a closure element, wherein the closure element is arranged in the exhaust manifold.

In petrol engines is at high engine speeds and high power usual way, the fuel-air Gem enriched Enriched (lambda <1) to protect the exhaust gas components from thermal overload. This is especially true for supercharged internal combustion engines, in which the exhaust gas turbine and the catalyst could otherwise be destroyed by excessive exhaust gas temperatures.

The mixture enrichment leads to high CO concentrations in the exhaust gas and the CO is in the catalyst due to the prevailing in the exhaust gas

Oxygen deficiency disadvantageously not oxidized. The catalyst no longer works as a 3-way catalyst in this operating range because no stoichiometric mixture (lambda = 1) is set. This endangers the fulfillment of future approval requirements for motor vehicles.

Today's exhaust systems, in particular of turbocharged Otto internal combustion engines typically have a turbine bypass, also called waste gate, with adjustable exhaust gas mass flow through the waste gate. With this waste gate, the exhaust gas mass flow through the turbine and thus the turbine power and thus the desired

Boost pressure set. After the turbine and after the supply of the wastegate channel to the main flow of the exhaust gas is typically as close as possible to a rapid heating after the start of the

To ensure internal combustion engine, a catalyst (also called close-coupled catalyst). When starting the engine, the waste gate is also wide open to direct as much hot exhaust gas directly to the close-coupled catalyst for heating. In full load, at high power levels of the internal combustion engine, typically high exhaust gas mass flows (about 30-45%) must be routed past the turbine via the waste gate. Since this exhaust gas is not expanded in the turbine, it is very hot. This is the mean

Exhaust gas temperature after mixing turbine exhaust mass flow and wastegate exhaust mass flow higher than the

Turbine outlet temperature. It may exceed the maximum exhaust gas inlet temperature allowed for the catalyst. As a result, z. B. the performance of the internal combustion engine are throttled, which is not desirable.

The object of the present invention is to identify a measure with which higher specific powers of the internal combustion engine can be achieved without thermal damage to the catalyst close to the engine.

This object is solved by the features in the characterizing part of patent claim 1.

Advantageous developments of the invention are described in the subclaims.

Due to the inventive design of the internal combustion engine with the exhaust system significantly higher performance of the internal combustion engine can be achieved without thermal damage to the engine near catalyst.

With the embodiment according to claim 2, a controlled or regulated distribution of the exhaust gas mass flow can be represented by a

Overheating of the first emission control system after the turbine of the

Exhaust gas turbocharger to avoid. In order to ensure pollutant cleaning of the exhaust gas conducted through the waste gate, a second exhaust gas purification system is preferably provided in the first exhaust pipe according to claim 3.

In order to achieve the best possible emission control, is in accordance with

Claim 4 in the exhaust system in the flow direction of the exhaust gas behind a junction of the first exhaust pipe, a third

Emission control system provided.

In order to achieve the greatest possible variability in the heating behavior and with respect to the exhaust gas purification, a second shut-off element is preferably arranged in the first exhaust pipe in the flow direction of the exhaust gas behind the first shut-off element, wherein the first exhaust pipe between the first and the second shut-off element with the exhaust system between the turbine housing and the first emission control system is connected via a fourth exhaust pipe exhaust gas leading.

In a further particularly preferred embodiment, a cooling device is provided for the fourth exhaust pipe according to claim 6, with the overheating of the first exhaust gas purification device is safely avoided.

In a further particularly preferred embodiment, a third shut-off element 20 is provided in the fourth exhaust pipe according to claim 7, with which the second and the third exhaust pipe 8, 9 are shut off.

In the following the invention is explained in more detail with reference to six figures.

Figure 1 shows a first embodiment of an inventive

Internal combustion engine with an exhaust system. Figure 2 shows a second embodiment of an internal combustion engine according to the invention with an exhaust system.

Figure 3 shows a third embodiment of an inventive

Internal combustion engine with an exhaust system.

Figure 4 shows a fourth embodiment of a

Internal combustion engine according to the invention with an exhaust system.

Figure 5 shows a fifth embodiment of a

Internal combustion engine according to the invention with an exhaust system.

Figure 6 shows a sixth embodiment of a

Internal combustion engine according to the invention with an exhaust system.

In the following, the same reference numerals apply in the figures 1 to 6 for the same components.

FIG. 1 schematically shows an internal combustion engine 1 according to the invention with an exhaust system 3. As known from the prior art, FIG

Fresh air sucked in via an intake silencer 15. An influx of fresh air is shown symbolically by an arrow. Subsequently, the fresh air through an unnumbered suction line by a

Compressor 16 passed an exhaust gas turbocharger 5, and after the compressor 16 further cooled in a charge air cooler 17. After the intercooler 17, the fresh air flows through a throttle element 18, such as a throttle valve. After the throttle element 18, the fresh air enters an air collector 19, from which the fresh air in the present

Embodiment is divided into four cylinders 2. In these four

Cylinders 2, the fresh air is mixed with fuel and burned. The exhaust gas flows per cylinder 2 via two unnumbered, each symbolically represented by a gas cycle gas outlet valves in the exhaust system 3. Each two cylinders 2 are summarized according to a cylinder order of the internal combustion engine 1 in a cylinder group. A typical firing order for a present four-cylinder internal combustion engine is, for example, cylinder 1, cylinder 3, cylinder 4, cylinder 2. In this firing order, cylinders 1 and 4 and cylinders 2 and 3 each form a cylinder group. Another possible

Ignition order is cylinder 1, cylinder 2, cylinder 4, cylinder 3. Here, the first cylinder (cylinder 1) is the, the power output side / clutch

opposite cylinders.

The first cylinder group is connected to a second scroll via a second exhaust pipe 8 with a first scroll and the second cylinder group via third exhaust pipe 9 with a second scroll of the exhaust gas turbocharger 5. The exhaust gas turbocharger 5 is thus a so-called twin-scroll turbocharger or an exhaust gas turbocharger with a segment turbine. However, the exhaust gas turbocharger can also be designed with a mono-scroll turbine. Through the second and the third exhaust pipe 8, 9 a turbine 4 of the exhaust gas turbocharger 5 is driven, which is non-rotatably in operative connection with the compressor 16 and compresses the fresh air.

After the exhaust gas turbocharger 5, the exhaust gas flows through a first

Emission control system 6 (close-coupled catalyst) and leaves the

Exhaust system 3 in the present embodiment in the

Ambient air. In reality, this is a downstream

Exhaust system with optionally further emission control devices, such. B. catalysts may be provided. A leakage of the exhaust gas from the exhaust system 3 is shown symbolically by an arrow.

Between the internal combustion engine 1 and the exhaust gas turbocharger 5 are the second and the third exhaust pipe 8, 9 with a first exhaust pipe. 7 connected exhaust gas, wherein the first exhaust pipe 7 in the flow direction of the exhaust gas after the first emission control system 6 back into the

Exhaust system 3 opens. At the transition from the second exhaust pipe 3 and the third exhaust pipe 9 in the first exhaust pipe 7 is a first shut-off element 10, such. As an exhaust valve, provided with the passage of exhaust gas from the second exhaust pipe 8 and the third exhaust pipe 9 can be prevented in the first exhaust pipe 7. The shut-off element 10 is shown in a closed position.

At a full load of the internal combustion engine 1, the first shut-off element 10 is opened so that hot exhaust gas on the turbine wheel 4 of

Exhaust gas turbocharger 5 can flow past, so that the first

Emission control system 6, but also the turbine 4 itself, is thermally protected. Due to the design according to the invention, significantly higher full-load powers for the internal combustion engine 1 can now be represented, since the first exhaust-gas cleaning system 6 and also the turbine 4 are thermally protected by the exhaust-gas mass flow that has flowed past the turbine 4.

- Advantage: Temperature reduction before the first emission control system 6 at rated power compared to. the admixing of the waste gas exhaust gas mass flow before the first emission control system 6.

- Disadvantage: Catalyzing takes longer because the waste-gas exhaust gas mass flow can not contribute.

Figure 2 shows a second embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3. Figure 2 differs from Figure 1 in that in the first exhaust pipe 7, a second

Emission control system 11 is arranged. Because the second

Emission control system 11 is arranged far further away from the internal combustion engine 1 than the first emission control system 6, this is only flowed through by already cooled exhaust gas, so that thermal overheating is largely excluded. In an advantageous way cleaned in this way, the guided through the waste gate exhaust gases.

- Advantage: Temperature reduction before the first emission control system 6 at rated power compared to. the admixing of the waste-gas exhaust gas mass flow upstream of the first exhaust-gas purification system 6.

Figure 3 shows a third embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3. The internal combustion engine 1 in Figure 3 differs from the internal combustion engine in Figure 1, characterized in that in the exhaust system 3 behind the junction of the first

Exhaust pipe 7 in the exhaust system 3, a third emission control system 12 is arranged. Also in this configuration, the exhaust gases conducted through the waste gate are cleaned by the third emission control system 12, the exhaust gases having already cooled down again prior to entering the third emission control system 12 and thus also providing thermal protection for the third emission control system 12.

Figure 4 shows a fourth embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3. Figure 4 differs from the internal combustion engine 1 in Figures 1 to 3, characterized in that now both the first emission control system 6 and the second

Emission control system 11 and the third emission control system 12 are arranged in the exhaust system 3. In this configuration, the best possible exhaust gas purification is achieved, with simultaneous thermal protection for all emission control systems 6, 11, 12. The exhaust gas purification systems 6, 11,

12 may be in all embodiments, for example, three-way catalysts and / or particulate filter and / or coated particulate filter (four-way catalysts) and / or NOx storage catalysts and / or passive SCR catalysts or particulate filter with SCR coating. - Advantage: Temperature reduction before the first emission control system 6 at rated power compared to. the admixing of the waste-gas exhaust gas mass flow upstream of the first exhaust-gas purification system 6.

Figure 5 shows a fifth embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3. The exhaust system 3 in Figure 5 differs from the exhaust system in Figure 4, characterized in that in the first exhaust pipe 7 in the flow direction of the exhaust behind the first shut-off element 10, a second shut-off 13 is arranged and the first exhaust pipe 7 between the first and the second shut-off element 10, 13 is exhaust-connected with the exhaust system 3 between the turbine housing and the first emission control system 6 via a fourth exhaust pipe 14. Both shut-off elements 10, 13 are shown in a closed position. With this configuration shown in Figure 5 is now the best possible variability for a thermally best possible

Split of the hot exhaust gas shown.

In a particularly preferred embodiment, a cooling device, for example a connection to the fourth exhaust pipe 14

Coolant system of the internal combustion engine 1 is provided.

- Catalyzing is possible via the Waste Gate Canal.

- Disadvantage: second shut-off element 13 in the hot area (tightness must be ensured). 6 shows a sixth embodiment of the internal combustion engine 1 according to the invention with the exhaust system 3. The exhaust system 3 in Figure 6 differs from the exhaust systems in Figures 1 to 5, characterized in that a first partial exhaust gas mass flow from the second and the third exhaust pipe 8, 9 via the third shut-off element 20 and the fourth exhaust pipe 14 in the exhaust system 3 between the turbine 4 and the first

Exhaust gas purification system 6 can be introduced and a second partial exhaust gas mass flow from the second and the third exhaust pipe 8, 9 via the first shut-off element 10 and the first exhaust pipe 7 in the exhaust system 3 between the first emission control system 6 and the third

Exhaust gas purification system 12 can be introduced. Both shut-off elements 10, 20 are shown in a closed position.

The following operating modes are possible:

Partial load: second shut-off element 13 closed, boost pressure control via first shut-off element 10, catalyzing via first shut-off element 10.

Full load: first shut-off element 10 closed, boost pressure control via the second shut-off element 13.

- Catheying is possible via the first shut-off element 10.

- Disadvantage: more complicated exhaust manifold, two shut-off elements 10, 13, (tightness must be ensured).

LIST OF REFERENCE NUMBERS

1st internal combustion engine

2nd cylinder

3. exhaust system

4. turbine wheel

5. Exhaust gas turbocharger

6th first emission control system

7. first exhaust pipe

8. second exhaust pipe

9. third exhaust pipe

10. first shut-off element

11th second emission control system

12th third emission control system

13. second shut-off element

14. fourth exhaust pipe

15. Intake silencer

16th compressor

17. Intercooler

18. Throttle element

19th air collector

20. third shut-off element

Claims

Internal combustion engine with an exhaust system PATENT CLAIMS

1. internal combustion engine (1) with at least four cylinders (2) and with an exhaust system (3), wherein in the exhaust system (3) a turbine housing with a turbine wheel (4) of an exhaust gas turbocharger (5) and in

Flow direction of an exhaust gas behind the turbine housing, a first emission control system (6) is arranged, wherein between the internal combustion engine (1) and the turbine housing, a first

Exhaust pipe (7) leading exhaust branches and after the first

Emission control system (6) back into the exhaust system (3) opens, characterized in that the exhaust gas turbocharger (5) is a twin-scroll exhaust gas turbocharger or an exhaust gas turbocharger with a segmented turbine, wherein at least two cylinders (2) according to a firing order of the internal combustion engine (1) are combined to form a cylinder group and a first cylinder group via a second exhaust pipe (8) with a first scroll and a second cylinder group via a third exhaust pipe (9) leading to a second scroll exhaust gas is connected, wherein the first exhaust pipe (7 ) with the second and the third

Exhaust pipe (8, 9) exhaust leading is connectable.

2. Internal combustion engine according to claim 1,

characterized in that in the first exhaust pipe (7) a first shut-off element (10) is arranged, with which the second and the third exhaust pipe (8, 9) can be shut off.

3. Internal combustion engine according to claim 1 or 2,

characterized in that in the first exhaust pipe (7) a second emission control system (11) is arranged.

4. Internal combustion engine according to one of the claims 1 to 3,

characterized in that in the exhaust system (3) in

Flow direction of the exhaust gas behind a junction of the first exhaust pipe (7), a third emission control system (12) is arranged.

5. Bren n kraftmasch ine according to one of the claims 1 to 4,

characterized in that in the first exhaust pipe (7) in

Flow direction of the exhaust gas behind the first shut-off element (10) a second shut-off element (13) is arranged and the first exhaust pipe (7) between the first and the second shut-off element (10, 13) exhaust leading to the exhaust system (3) between the

Turbine housing and the first emission control system (6) via a fourth exhaust pipe (14) exhaust leading leader is connected.

6. Internal combustion engine according to claim 1,

characterized in that a cooling device is provided for the fourth exhaust pipe (14).

7. Internal combustion engine according to one of the claims 5 to 6,

characterized in that in the fourth exhaust pipe (14), a third shut-off element (20) is provided, with which the second and the third exhaust pipe (8, 9) can be shut off.