DE102010005814A1 - Exhaust gas system for internal combustion engine of passenger car, has exhaust manifold which is connected with exhaust tract in gas guiding manner, in which exhaust turbocharger is arranged - Google Patents

Abstract

The exhaust gas system (1) has an exhaust manifold (3) which is connected with an exhaust tract (4) in a gas guiding manner, in which an exhaust turbocharger (5) is arranged. The exhaust turbocharger is flow-throughable by exhaust gas of an internal combustion engine (2). The exhaust gas flows through the exhaust manifold and then the exhaust turbocharger. An exhaust gas cleaning equipment (6) is arranged in the exhaust tract between the exhaust manifold and the exhaust turbocharger. The exhaust gas cleaning equipment has passive storage properties for nitrogen oxide or hydrocarbon.

Description

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

It is based on the not yet published German disclosure DE 10 2008 057 572.0 out. For this purpose, a generic exhaust system for an internal combustion engine is known. This consists at least of an exhaust manifold, which is connected exhaust gas leading to an exhaust line, in which an exhaust gas of the internal combustion engine durchflutbarer exhaust gas turbocharger is arranged. In this case, the exhaust gas first flows through the exhaust manifold and then through the exhaust gas turbocharger, wherein a first exhaust gas purification system is arranged in the exhaust gas line in front of the exhaust gas turbocharger. A flow cross section of the first exhaust gas purification system is in the region of the first exhaust gas purification system a partial flow cross section of the exhaust gas line. In this case, the partial flow cross section of the exhaust gas line and the flow cross section of the first exhaust gas purification system can be closed alternately by a closing element. Behind the exhaust gas turbocharger is a particulate filter and behind the particulate filter another emission control system, an SCR catalyst, arranged in the exhaust system. By using the generic exhaust system, the hydrocarbon (HC) and carbon monoxide (CO) emissions can be significantly reduced. When the exhaust system is new, it is thus able to fall below the legal emission limit values with a sufficient safety margin and to pass the type test positively.

A disadvantage of this prior art, however, is that after a cold start of the internal combustion engine, the SCR catalyst to reduce the nitrogen oxides (NO _x ) downstream of the particulate filter reaches its operating temperature only very slowly and in some operating cycles only towards the end. The released from the internal combustion engine nitrogen oxides can be converted very late and cause relatively high emissions of nitrogen oxides of the vehicle.

Object of the present invention is to avoid the above-mentioned disadvantages.

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

What is new is that the catalytic components with the previously known oxidation function are replaced by catalytic components with completely new functionality. Instead of the oxidation catalysts, catalysts with passive storage properties for NO _x and / or HC are used. In contrast to the NO _x storage catalytic converter (NSC), these do not require a rich exhaust gas (stoichiometric mixture composition) for their regeneration. The removal of pollutants depends essentially on the parameters of exhaust gas temperature and exhaust gas mass flow rate. The previously known oxidation function can essentially be retained. This results in a new emission control system with completely new properties. During the warm-up phase of the internal combustion engine, the nitrogen oxide and / or HC emissions are cached by the catalysts with passive storage characteristics until the downstream SCR system has reached its operating temperature downstream of the particulate filter. Thereafter, the cached emission components are accumulated as described above and converted from the downstream components (nitrogen oxides are reacted by the SCR catalyst, HC emissions from the coated diesel particulate filter). The withdrawal is controlled by raising the exhaust gas temperature and / or the exhaust gas mass flow. This can be implemented either by increased load of the internal combustion engine due to the driving profile or by internal combustion engine intervention.

Further advantageous developments of the invention can be found in the dependent claims.

In a further variant, either only the first emission control system with passive NO _x / HC storage properties and the second emission control system can be equipped with a known oxidation coating or vice versa.

In yet another variant, the coating with passive NO _x / HC storage properties can be integrated into the particulate filter.

In a further variant, the SCR catalyst arranged downstream of the particulate filter can also be integrated into the coating of the particulate filter and does not necessarily have to be applied to a separate catalyst support. In this case, the reducing agent introduction point is located in front of the particle filter.

In a further variant, the operation of the system can be configured such that the removal of pollutants from the first emission control system with passive NO _x / HC storage properties by temporarily opening the bypass valve in operating conditions of the internal combustion engine with sufficiently high exhaust gas temperatures.

In a further variant, the operation of the system can be configured such that immediately after the cold start of the internal combustion engine and in operating states with low NO _x - Emission (low-load operating points, close to idling or quasi-stationary operation, ...) with conventional engine settings, the NO _x and HC emissions in the exhaust gas purification systems with passive NO _x / HC storage properties are cached and in operating conditions with high NO _x emissions in switched to stoichiometric operation and converted by 3-way catalysis.

With the proposed inventive design of the exhaust system for an internal combustion engine thus the above-mentioned functional disadvantages of the known prior art can be completely bypassed.

• 1. NO_x-Speicherkatalysator (NSC) und
• 2. SCR-System (selective catalytic reduction).

So far, two known from the prior art technologies at hand, for example, to reduce nitrogen oxides in the lean exhaust gas in the diesel engine:

• 1. NO _x storage catalytic converter (NSC) and
• 2. SCR system (selective catalytic reduction).

Both systems have so far had fundamental disadvantages: The NO _x storage catalytic converter only works in a very limited operating range of the internal combustion engine, is very complicated to apply and has an increased consumption.

The SCR system operates in a much wider operating range, but so far has been reluctant to reach operating temperature and will not convert nitrogen oxides during warm-up.

• – Leichte Fahrzeuge
• – NO_x-unkritische aber HC/CO-kritische Fahrzeug/Brennkraftmaschinenkombinationen
• – Testzyklen mit niedriger Dynamik, moderaten Lasten bzw. NO_x-Grenzwerten.

The invention provides the following advantages over the prior art:
With the present invention, a system is described which is particularly suitable for low-load car applications, such. B .:

• - Light vehicles
• - NO _x -uncritical but HC / CO-critical vehicle / engine combinations
• - Test cycles with low dynamics, moderate loads or NO _x limits.

• – Stickoxidemissionen unmittelbar nach dem Brennkraftmaschinenstart zwischenspeichert und konvertiert;
• – sehr strenge Emissionsgesetze (EU6 und ff., US-SULEV (ultra low emissions vehicle),...) schafft;
• – im gesamten Betriebsbereich der Brennkraftmaschine funktioniert;
• – ohne zusätzlichen Kraftstoffmehrverbrauch auskommt;
• – die Dynamik des Fahrzeuges nicht einschränkt;
• – alterungsstabil ist;
• – aufgrund der kleinen Abmessungen geringe Zusatzkosten verursacht und
• – mit überschaubaren Änderungen im bestehendes Package unterzubringen ist.

Thus, according to the invention, a system is available which:

• Nitrogen emissions cached and converted immediately after the engine start;
• - creates very stringent emissions legislation (EU6 and ff., US ultra low emission vehicle (SULEV), ...);
• - works in the entire operating range of the internal combustion engine;
• - manages without additional fuel consumption;
• - does not restrict the dynamics of the vehicle;
• - aging stable;
• - caused small additional costs due to the small dimensions and
• - accommodate with manageable changes in the existing package is.

In the following, the invention is explained in more detail with reference to two particularly preferred embodiments in three figures.

1 schematically shows a first preferred embodiment of an exhaust system according to the invention for an internal combustion engine.

2 schematically shows a second preferred embodiment of an exhaust system according to the invention for an internal combustion engine.

3 shows a diagram of a pollutant emissions of an internal combustion engine with an exhaust system according to the invention.

1 schematically shows an exhaust system according to the invention 1 for an internal combustion engine 2 , The internal combustion engine 2 has in this embodiment 6 cylinders, which are symbolically represented by circles with injectors. To the internal combustion engine 2 is an exhaust manifold 3 arranged for the discharge of exhaust gases. To the exhaust manifold 3 is an exhaust system 4 Flanged, in which an exhaust gas turbocharger 5 is arranged, wherein an unspecified figured turbine housing is flowed through by the exhaust gas.

Between the exhaust manifold 3 and the exhaust gas turbocharger 5 is the exhaust system 4 twin-flow, with a flood in a first emission control system 6 is arranged. The floods are alternately from an actuator 12 switchable, designated with DDE (digital diesel electronics). The actuator 7 This can be controlled or regulated operated to either the conversion properties of the first emission control system 6 to use or to protect them from overheating.

Next in the flow direction of the exhaust gas are in the exhaust system 4 a second emission control system 8th as well as a particle filter 11 arranged. Downstream of the particulate filter is a reducing agent introduction point for a reducing agent, such. B. aqueous urea solution, which is for an SCR catalyst 10 in the flow direction of the exhaust gas behind the reducing agent introduction point 9 is provided.

On the intake side, the exhaust gas turbocharger 5 an unnumbered compressor housing that with an intake air line 13 Gas leading is connected. The compressor is driven by the turbine during operation of the internal combustion engine and first conveys an intake air into a charge air cooler 14 and then on in an intake air collector 15 , From there, the intake air enters the cylinder mentioned above.

According to the invention, the first and / or the second emission control system 6 . 8th passive storage properties for NO _x and / or HC (nitrogen oxides and / or hydrocarbons).

2 schematically shows a second preferred embodiment of an exhaust system according to the invention 1 for an internal combustion engine 2 , Compared to the first embodiment, in this second preferred embodiment, a second exhaust gas turbocharger 16 provided between the first exhaust gas turbocharger 5 and the second emission control system 8th in the exhaust system 4 is arranged. Intake air side, the intake air line 13 compared to the first embodiment, an actuating element 21 on to the intake air depending on the operating condition of the internal combustion engine 2 to be able to lead. Next points the first exhaust gas turbocharger 5 a bypass 17 on with a first throttle element 18 which may be a flap, for example. Also the second exhaust gas turbocharger 16 has a second bypass 19 in which a second throttle element 20 , which may also be a flap, is arranged.

3 shows a diagram of a pollutant emissions of an internal combustion engine with an exhaust system according to the invention 1 , A X-axis the time is shown in [s], via a Y-axis provides a measure of NO _x upstream of the catalyst (Cat), NO _x on the catalyst, HC before catalyst, HC on the catalyst, exhaust gas temperature before the catalyst and the lambda upstream of the catalyst shown. Time phases are designated phase 1, 2, 3, 4, 5 and 6.

NO _x : In phase 1, "Loaded tank", the measured variable "NO _x after cat" initially shows a lower value than "NO _x before cat", ie a part of the raw emission is stored and only a remainder is slipped. This is the case until either the NO _x storage tank is full or, as shown, the exhaust gas temperature / exhaust gas mass flow is increased, see Phase 3 "Draining the storage tank". In this phase, the stored NO _{x is} expelled and converted by a downstream SCR system, which in the meantime is at operating temperature. Thus, the storage can start again, z. B. Phase 4.

HC: In the example shown, only a very small part of HC is stored in phase 1 ("HC after Cat" is only slightly lower than "HC before Cat"). However, due to its oxidation function, the catalyst almost completely converts the HC emission once it has reached its HC Light Off temperature (50% conversion), see Phase 2 "Achieving Light Off Temperature for" HC ""). If the catalyst is exposed to an exhaust gas temperature below the light-off temperature, then the catalyst cools down again (phase 4 "store loaded") and HC will slip again.

TWC function: in stage 5 "Emptying storage by stoichiometric operation" the reaction of the catalyst is shown, which optionally has a three-way conversion characteristic (TWC) integrated. If this catalyst is charged with stoichiometric exhaust gas (lambda = 1), then it works as a three-way catalyst and converts not only CO but also HC and NO _x .

• – Stickoxidemissionen unmittelbar nach dem Brennkraftmaschinenstart zwischenspeichert und konvertiert;
• – sehr strenge Emissionsgesetze (EU6 und ff. US-SULEV (super ultra low emissions vehicle,...) schafft;
• – im gesamten Betriebsbereich der Brennkraftmaschine funktioniert;
• – ohne zusätzlichen Kraftstoffmehrverbrauch auskommt;
• – die Dynamik des Fahrzeuges nicht einschränkt;
• – alterungsstabil ist;
• – aufgrund der kleinen Abmessungen geringe Zusatzkosten verursacht und
• – mit überschaubaren Änderungen in bestehendes Package unterzubringen ist.

Thus, according to the invention, a system is available which:

• Nitrogen emissions cached and converted immediately after the engine start;
• - creates very stringent emissions legislation (EU6 and ff. US SULEV (super ultra low emission vehicle, ...);
• - works in the entire operating range of the internal combustion engine;
• - manages without additional fuel consumption;
• - does not restrict the dynamics of the vehicle;
• - aging stable;
• - caused small additional costs due to the small dimensions and
• - to accommodate with manageable changes in existing package is.

LIST OF REFERENCE NUMBERS

1

exhaust system

2

Internal combustion engine

3

exhaust manifold

4

exhaust gas line

5

turbocharger

6

first emission control system

7

closing element

8th

second emission control system

9

Reduktionsmitteleinbringstelle

10

SCR catalyst

11

particulate Filter

12

actuator

13

intake air line

14

Intercooler

15

plenum chamber

16

second exhaust gas turbocharger

17

first bypass

18

first throttle element

19

second bypass

20

second throttle element

21

actuator

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008057572 A [0002]

Claims (7)

Exhaust system ( 1 ) for an internal combustion engine ( 2 ), consisting at least of an exhaust manifold ( 3 ), the gas-conducting with an exhaust line ( 4 ) in which one of an exhaust gas of the internal combustion engine ( 2 ) flooded exhaust gas turbocharger ( 5 ), wherein the exhaust gas first the exhaust manifold ( 3 ) and then the exhaust gas turbocharger ( 5 ) and between the exhaust manifold ( 3 ) and the exhaust gas turbocharger ( 5 ) a first emission control system ( 6 ) in the exhaust gas line ( 4 ) is arranged and wherein a flow cross-section of the first emission control system ( 6 ) in the area of the first emission control system ( 6 ) a partial flow cross section of the exhaust line ( 4 ) and wherein the flow cross-section of the first emission control system ( 6 ) of a closing element ( 7 ) and behind the exhaust gas turbocharger ( 5 ) a second emission control system ( 8th ) and behind this a SCR (Selective Catalytic Reduction) catalyst ( 10 ), characterized in that the first and / or the second emission control system ( 6 . 8th ) has passive storage properties for NO _x and / or HC (nitrogen oxides and / or hydrocarbons). Exhaust system according to claim 1, characterized in that in the flow direction of an exhaust gas behind the second emission control system ( 8th ) a reducing agent introduction site ( 9 ) is provided. Exhaust system according to claim 1 or 2, characterized in that between the second emission control system ( 8th ) and the reducing agent introduction site ( 9 ) a particle filter ( 11 ) in the exhaust system ( 1 ) is arranged. Exhaust system according to one of the claims 1 to 3, characterized in that with the closing element ( 7 ) the flow cross-section of the emission control system ( 6 ) and the partial flow cross section of the exhaust line ( 4 ) can be closed alternately. Exhaust system according to one of the claims 1 to 4, characterized in that in the flow direction of the exhaust gas to the exhaust gas turbocharger ( 5 ) in the exhaust gas line ( 4 ) a second exhaust gas turbocharger ( 16 ) is arranged. Exhaust system according to one of the claims 1 to 5, characterized in that the first and / or the second emission control system ( 6 . 8th ) is carried out as an oxidation component. Exhaust system according to one of the claims 1 to 6, characterized in that the first and / or the second emission control system ( 6 . 8th ) has a three-way conversion function.

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