DE10357402A1 - Operating a multicylinder internal combustion engine with an ammonia-generating catalyst comprises throttling the air supply to the first cylinder and adding a reducing agent to its exhaust gas - Google Patents

Abstract

Operating an internal combustion engine with several cylinders and an exhaust gas treatment unit comprising an ammonia-generating catalyst that receives exhaust gas only from the first cylinder comprises throttling the air supply to the first cylinder so that its exhaust gas has a lower air/fuel ratio than that of the other cylinders, and adding a reducing agent to this exhaust gas to produce a low-oxygen ammonia-generating atmosphere. Operating an internal combustion engine (10) with several cylinders (12, 14, 16, 18) and an exhaust gas treatment unit (20) comprising an ammonia-generating catalyst (22) that receives exhaust gas only from the first cylinder (12) comprises throttling the air supply to the first cylinder so that its exhaust gas has a lower air/fuel ratio than that of the other cylinders, and adding a reducing agent to this exhaust gas to produce a low-oxygen ammonia-generating atmosphere. An independent claim is also included for an internal combustion engine (10) with several cylinders (12, 14, 16, 18) and an exhaust gas treatment unit (20) comprising an ammonia-generating catalyst (22) that receives exhaust gas only from the first cylinder (12), comprising a throttle valve (24) for reducing the air supply to the first cylinder and an injection valve (26) for injecting reducing agent into the exhaust gas from the first cylinder and/or an injection valve (28) for delayed injection of fuel into the first cylinder.

Description

The The invention relates to a method for operating an internal combustion engine with several combustion chambers and an exhaust gas purification system comprising an ammonia generation catalyst, the only receives exhaust gas from at least a first combustion chamber, with the Steps: Operating at least one second combustion chamber with a lean air / fuel mixture, operating the at least one first combustion chamber with a less lean combustion air / fuel mixture, and generating an ammonia-producing atmosphere by reduced oxygen content the exhaust gas of the at least one first combustion chamber.

Further the invention relates to an internal combustion engine with multiple combustion chambers and an emission control system containing an ammonia generation catalyst comprising only exhaust gas from at least a first combustion chamber, with at least a second combustion chamber, with a lean air / fuel mixture is operated, at least a first combustion chamber, with a less lean combustion air / fuel mixture, and with funds for generating an oxygen deficiency in the exhaust gas of the at least one first combustion chamber.

Such a method and such an internal combustion engine are from the DE 199 09 933 A1 known. According to this document, the first combustion chambers of the internal combustion engine are operated continuously or discontinuously with a rich air / fuel mixture, so that ammonia is generated in a downstream ammonia production catalyst. Second combustion chambers are continuously operated with lean air / fuel mixture and thus generate high nitrogen oxide emissions. The exhaust gases of the first and second combustion chambers are combined downstream of the ammonia production catalyst. In the total exhaust gas line, there is an SCR (selective catalytic reduction) catalyst in which the resulting ammonia-nitrogen oxide mixture is converted into harmless components such as nitrogen and water.

After DE 199 09 933 A1 The rich air / fuel mixture is already set in the combustion chamber of the engine through an early engine post-injection. This has the disadvantage that the metered with the post-injection fuel wholly or partially participates in the combustion and thus leads to undesirably high temperatures of the combustion chamber walls and pistons involved, which is unfavorable for the life of the internal combustion engine. In addition, the fuel consumption of the internal combustion engine increases relatively strongly, because the nacheingespritzte fuel is implemented in the internal combustion engine with a poor efficiency. Although a very late-stage engine injection of the fuel has the advantage that the fuel thus supplied no longer participates in the combustion, but it can lead to smearing film breaks in the engine and thus to a failure of the internal combustion engine. In addition, the cost of the application of such a system is very high, which proves to be particularly in a large vehicle variety with the same internal combustion engines as disadvantageous.

From the JP 04365920 is a motor "on-board" ammonia production known in which the ammonia synthesis, however, takes place only in rich phases of the entire internal combustion engine An intake-side throttle body is located in the air duct in front of all cylinders of the engine high fuel consumption, since the entire internal combustion engine is temporarily operated fat JP 04365920 adjusted exclusively with the help of the throttle body, resulting in particular in diesel engine combustion processes to unacceptable particulate emissions, carbon monoxide emissions and hydrocarbon emissions.

From the EP 0796 983 For example, onboard ammonia production is known in which a second group of combustion chambers of the internal combustion engine are continuously operated lean and ammonia is produced in an ammonia production catalyst by means of a first group of combustion chambers The exhaust gas strands of the first and second combustion chamber groups are combined and the nitrogen oxides contained in the exhaust gas are reduced in an SCR catalytic converter with the ammonia generated, and the rich state required in the ammonia generation catalyst is set by means of external measures. As an external measure for setting the rich operation in the exhaust gas of the first group of combustion chambers, a combustion chamber is mentioned in this document, which may be configured in the form of an additional engine operated in bold or a fat operated separate burner.

A disadvantage of this item is the additional high technical complexity of aggregates additional engine or burner. Here too, as a result of the possible throttling of the entire internal combustion engine in diesel engine combustion processes, disadvantages arise with regard to particulate emissions, carbon monoxide emissions and hydrocarbon emissions. An additional combustion chamber has the further disadvantage of he Increased cost in the implementation of the idea and increased operating costs (especially a fuel consumption), because the fuel used for the operation of the combustion chamber can not be optimally used in the reducing agent carbon monoxide and / or hydrocarbons for subsequent necessary oxidation of the substance in the ammonia production catalyst.

Under The combustion engine offers the diesel engine with its very good Efficiencies, compared to engine concepts with other combustion processes, currently the biggest potential to reduce carbon dioxide emissions. So far you could always with improved internal engine measures the required emission limit values for diesel vehicles comply.

The internal engine reduction of pollutant emissions is subject but certain limits. An important conflict of interests of the diesel engine Emission reduction is between the nitrogen oxide and the particle emission. The reduction of a component usually causes an increase in the other component.

Out these reasons have to In addition to the motor concepts, further concepts for improvement the exhaust quality be used.

If Pollutants in exhaust gases of an existing engine concept by internal engine activities can not be sustainably reduced exists with exhaust aftertreatment concepts the possibility to further reduce this. So today's diesel-powered Passenger cars with so-called passive exhaust aftertreatment systems, for example with oxidation catalysts, to reduce the carbon monoxide and hydrocarbon emissions.

Further Exhaust aftertreatment concepts include systems for reduction of particle or nitrogen oxide emissions.

to There are two important methods of exhaust aftertreatment to reduce nitrogen oxides in diesel engine exhaust gases in the Development. For the realization of these concepts in large series are catalytically supported procedures such as the periodic, catalytic storage of nitrogen oxides (storage catalysts) and Selective Catalytic Reduction (SCR) technology promising.

If Nitrogen oxide is emitted by lean-burn engines, this provides SCR process is an efficient method for reducing these emissions. Here, ammonia acts to reduce the nitrogen oxides at appropriate Catalysts.

Either the storage catalytic converter technology, as well as the SCR technology show individual consideration of the individual vehicle classes (passenger cars, light commercial vehicles, heavy vehicles) Commercial Vehicles) at the current stage of development weaknesses.

at the storage catalyst technology are the weaknesses in first and foremost in the poor implementation in series application. The intermittent lean / rich operation is in current storage catalyst concepts because of the complexity of this Technology in mass production difficult to implement.

The in the engine map limited NOx reduction performance of these systems results essentially from the fact that the storage capacity of the storage catalytic converters is severely limited at high exhaust gas temperatures. In addition, rises, under consideration the thermal load of the engine in rich operation phases, with increasing engine load the fuel demand, which for a Lambda <1 state (Lack of oxygen) in the storage catalytic converter is necessary.

Finally are the highly precious metal-containing storage catalysts very sensitive to sulfur and become faster with increasing sulfur content in the fuel inactivated, or must frequently be desulfated. Common Desulphations burden the system of engine and storage catalytic converter however, in addition.

Of the current disadvantage of SCR technology in car use is the additional Refueling the vehicle with the necessary NOx reducing agent.

So is the customer acceptance for refueling a car with a second Resources, namely the NOx reducing agent extremely limited. For this reason, it must be ensured in future that the respective SCR system its NOx reduction performance with a NOx reducing agent filling at least over tank intervals, better over Service intervals or the lifetime of the vehicle maintains.

A An alternative to circumventing this problem would be the introduction of a double taps for the simultaneous fueling of the vehicle both with fuel, as also with NOx reducing agent. The infrastructure to be built up However, distribution of the NOx reductant in passenger car applications is very costly and therefore difficult to implement at every gas station. For this reason, in the present invention, on-board production of ammonia becomes for one subsequent selective catalytic reduction is preferred.

In front This is the object of the invention in both the Specification of a method and an internal combustion engine of each the aforementioned type, each one by the ammonia production caused additional fuel consumption and the mentioned disadvantages with regard to particulate emissions, Reduce carbon monoxide and hydrocarbon emissions.

These Task is in a method of the type mentioned by the following additional steps are solved: Throttling an air supply to the at least one first combustion chamber such that in the at least one first combustion chamber a smaller one Combustion air / fuel ratio sets as in the at least one second combustion chamber, and generating the oxygen deficiency in the exhaust of the at least one combustion chamber by after burns successive feeding from reducing agent to the exhaust gas of the at least one first combustion chamber.

Further This object is achieved in an internal combustion engine of the aforementioned Sort of solved by that the internal combustion engine has an actuator, which is an air supply to the at least one first combustion chamber throttles so that in which at least one first combustion chamber sets a smaller combustion air / fuel ratio as in the at least one second combustion chamber, and that of the internal combustion engine Further, a reducing agent actuator having an ammonia-producing atmosphere, for example due to lack of oxygen, in the exhaust of the at least one combustion chamber by after burns successive feeding of Reducing agent to the exhaust gas of the at least one first combustion chamber generated.

Advantages of invention

By these features, the object of the invention is completely solved. Especially can they first combustion chambers operated continuously or discontinuously with a defined air / fuel ratio in which involved components are not overheated or due to an increased particle production wear out faster. This advantage is achieved by the oxygen supply in the at least one first combustion chamber reduced by the throttling becomes. The fact that the throttling only on the at least one first combustion chamber acts, at the same time the fuel consumption limited.

With Looking at embodiments of the method is preferred that the Throttling the air supply by closing a throttle valve a separate air supply to the at least one first combustion chamber takes place.

These Design allows a decoupling of the throttling of various combustion chambers with structurally easy-to-implement technical measures.

Further is preferred that the throttling taking into account the signal of a Lambda sensor in the exhaust of the at least one first combustion chamber, or considering an air mass flow and a fuel mass flow to the at least a first combustion chamber takes place.

When Result is a demand-based throttling possible, based on the oxygen demand of the ammonia generation catalyst and the metered amount of reducing agent oriented.

A Another preferred embodiment is characterized by an under consideration a signal of a downstream the ammonia-generating catalyst arranged lambda sensor takes place Supply of diesel fuel as a reducing agent.

These Design allows a demand-based throttling in a closed Loop. Too strong or too weak throttling can thereby be effectively limited.

Furthermore can three operating states in the ammonia generation catalyst be set in a defined manner. At lambda gets bigger no ammonia is produced and the nitrogen oxides emitted by the engine pass the ammonia generation catalyst. If lambda is greater than or equal 1 is set, although no ammonia, but it will the emitted by motor oxides of nitrogen according to the three-way catalyst principle reduced. If Lambda is set to less than or equal to 1, then reduces the nitrogen oxides emitted by the engine and produces ammonia.

Prefers is also that a nitrogen oxide emission of the at least one first Combustion chamber by means of an upstream of the ammonia-generating catalyst arranged nitrogen oxide sensor and / or an air mass meter, the air mass flowing into the at least one first combustion chamber measures, is recorded.

With This embodiment can quantitatively the amount of ammonia generated be estimated since the nitrogen oxide emissions of the at least one first combustion chamber a precursor for represent the ammonia production.

Further, it is preferable that ammonia emission is disposed downstream of the ammonia producing catalyst by means of a downstream of the ammonia producing catalyst Ammonia sensor and / or an air mass meter, which measures the air mass flowing into the at least one first combustion chamber, and / or with the aid of an air mass meter, which measures the flowing into the at least one second combustion chamber air mass is detected.

Prefers is also that a lot of one of the at least one second Combustion chamber emitted nitrogen oxides with the aid of an exhaust gas in the at least a second combustion chamber arranged nitrogen oxide sensor and an air mass meter, the air mass flowing into the at least one first combustion chamber measures, and / or with the aid of an air mass meter for measuring the is detected in the at least one second combustion chamber flowing air mass.

Further It is preferred that a nitrogen oxide emission downstream of a SCR catalyst using a nitrogen oxide sensor and optionally with at least one air mass meter for measuring one in the at least a first combustion chamber and the at least one second combustion chamber incoming Total mass air flow is detected.

A Another preferred embodiment is characterized in that an ammonia emission downstream an SCR catalyst with Help of an ammonia sensor and optionally additionally with at least one Air mass meter for measuring one in the at least one first combustion chamber and the at least one second combustion chamber inflowing total air mass flow is detected.

Also these measures wear both individually and in combination with each other to a needs-based control of ammonia production. The sensors mentioned provide signals about relative proportions and the Inclusion of air mass measurements allows a determination of absolute Sizes.

With View of embodiments of the internal combustion engine is preferred that the emission control system has a volume in which the Exhaust gases of the at least one first combustion chamber and at least a second combustion chamber are mixed and that the volume one SCR catalyst and a downstream of the SCR catalyst arranged oxidation catalyst having.

By the mixing becomes the hot one Exhaust gas cooled at least a first combustion chamber, so that a thermal Load of the subsequent emission control components is limited. The oxidation catalyst prevents leakage of ammonia (Ammonia slip) from the entire emission control system in case that the amount of ammonia produced exceeds the needs of the SCR catalyst.

Prefers is also that the emission control system is a structural unit a particulate filter with SCR catalyst having.

By Such a combination can with a small footprint high cleaning effect with regard to the particle emissions and the NOx emissions are achieved. As a structural unit comes to Example of an integrated particle filter with an SCR coating in question.

Further it is preferred that the exhaust gas purification system upstream of the SCR catalyst arranged heat exchanger for cooling the exhaust gases of the at least one first combustion chamber.

These measure reduces the thermal load of subsequent exhaust gas cleaning components.

Prefers is also that the heat exchanger designed as a structural unit with the ammonia-generating catalyst is.

By This measure is the number of separate components of the emission control system and reduced the installation space requirement.

Further For example, the turbine of an exhaust gas turbocharger may be downstream of the ammonia generation catalyst is arranged in the volume, and the compressor of the exhaust gas turbocharger compresses the entire intake air flow of the engine, or a compressor the turbocharger one in the at least one second combustion chamber flowing Intake air flow compressed.

Further For example, the turbine of the exhaust gas turbocharger may be downstream of the ammonia generation catalyst be arranged in the exhaust gas of the at least one second combustion chamber, wherein a compressor of the exhaust gas turbocharger the entire intake air flow the engine or the flowing into the at least one second combustion chamber intake air flow compressed.

For the efficiency The engine is in each case an arrangement of the turbine in the total exhaust gas flow as well an arrangement of the compressor in the total flow of air supply preferred. The other alternatives can for constructional reasons Have advantages.

In further embodiments, the internal combustion engine is charged without an exhaust gas turbocharger the, for example, electrically or mechanically via a coupling of an intake air compressor with the crankshaft of the engine.

A Another preferred embodiment is characterized by an exhaust gas recirculation, the exhaust downstream of the ammonia production catalyst takes from the volume and the in the at least one second combustion chamber flowing intake air flow, or the flowing into the at least one first combustion chamber intake air flow and the flowing into the at least one second combustion chamber intake air flow supplies.

Prefers is also that exhaust gas recirculation exhaust the at least one second combustion chamber in the least one second combustion chamber flowing Intake air flow feeds, or the intake airflow flowing into the at least one first combustion chamber and the total intake airflow flowing into the at least one second combustion chamber supplies.

Further is preferred that the emission control system individually controllable flow barriers (For example, controllable flow cross sections such as valves) for Distribution of a recirculated exhaust gas quantity on in the at least one second combustion chamber or in the at least one second combustion chamber and the at least one first Combustion chamber flowing Has intake air flow.

These Embodiments show that an exhaust gas recirculation with great structural freedom can be integrated into the present invention.

Prefers is also that means of generating a lack of oxygen in the Exhaust gas of the at least one first combustion chamber in the at least a first combustion chamber injection injector, and / or a arranged in the exhaust gas of the at least one first combustion chamber separate metering valve, and / or an additional, separate combustion chamber, which is operated with a rich air / fuel mixture, as Have reducing agent actuator.

Also These designs prove large constructive degrees of freedom in the realization of the invention. Although preferred is oxygen deficiency generation with a throttle body in the intake air in conjunction with a separate dosing valve for Fuel to be adjusted are in some operating points Variants such as a late in-engine post-injection of the fuel in this method makes sense.

Further Advantages will be apparent from the description and the attached figures.

It it is understood that the above and the following yet to be explained features not only in the specified combination, but also in other combinations or alone, without to leave the scope of the present invention.

drawings

embodiments The invention are illustrated in the drawings and in the following description explained. Show it:

1 schematically an embodiment of an internal combustion engine according to the invention;

2 a further embodiment with an integrated in the ammonia-generating catalyst heat exchanger and various configurations of arrangements of an exhaust gas turbocharger;

3 various arrangements for integration of exhaust gas recirculation;

4 an embodiment with a sensor for controlling and monitoring the emission control, and

5 a flowchart as an embodiment of a method according to the invention.

1 shows an internal combustion engine 10 with several combustion chambers 12 . 14 . 16 . 18 and an emission control system 20 containing an ammonia generation catalyst 22 having. The ammonia generation catalyst 22 only takes exhaust from at least one first combustion chamber 12 on. At least a second combustion chamber 14 . 16 . 18 is operated with a lean air / fuel mixture Lambda_1> 1. The at least one first combustion chamber 12 is operated with a less lean combustion air / fuel mixture lambda_2 of, for example, lambda_2 = 1.1 <lambda_1.

As a means for generating an oxygen deficiency (Lambda_3 <Lambda_2) in the exhaust gas of the at least one first combustion chamber 12 points the internal combustion engine 10 an actuator 24 on, which is an air supply to the at least one first combustion chamber 12 so throttles that in the least a first combustion chamber 12 a smaller combustion air / fuel ratio lambda sets than in the at least one second combustion chamber 14 . 16 . 18 , Furthermore, the internal combustion engine 10 at least one reducing agent actuator 26 . 28 on the an oxygen deficiency in the exhaust gas of the at least one combustion chamber 12 by after combustion, supplying reducing agent, preferably fuel (gasoline or diesel fuel) to the exhaust gas of the at least one first combustion chamber 12 generated.

The reducing agent actuator 26 For example, an injector that is in an exhaust branch 30 between the at least one first combustion chamber 12 and the ammonia generation catalyst 22 injects. Alternatively or additionally, an injection valve, the fuel in the at least one combustion chamber 12 injected, as a reducing agent actuator 28 be used. In this case, after combustion of a main injection quantity that determines the power, fuel additionally becomes the residual gas charge of the combustion chamber 12 injected as a very late engine internal post fuel injection. However, preference is given to an off-engine metering via the reducing agent actuator 26 ,

In the case of in-engine post fuel injection, to maintain the upper temperature limits of the engine components, the injection timing should be chosen so that the subsequently injected fuel is not involved in the engine combustion. The so set oxygen deficiency can with a lambda sensor 32 be monitored in a control loop in combination with the previously explained fuel supply.

In the downstream, noble metal-containing ammonia production catalyst 22 Ammonia is produced by the combustion engine 10 emitted nitrogen oxides (NOx) and either carbon monoxide (CO), and / or hydrocarbons (HC) according to the following chemical reactions:
First, hydrocarbons and residual oxygen produce hydrogen according to the gross reaction (CH ₂ ) _n + n O = n CO + n H2 and from CO and water according to the water gas reaction CO + H ₂ O = CO ₂ + H ₂ .

Subsequently, the hydrogen and nitrogen oxides produce ammonia according to the example of the following gross reactions: NO + 5/2 H ₂ = NH ₃ + H ₂ O and NO ₂ + 7/2 H ₂ = NH ₃ + 2 H ₂ O.

As ammonia generation catalyst 22 For example, a noble metal-containing oxidation catalyst, a three-way catalyst or a NOx storage catalyst can be used.

The emission control system 20 has a volume 34 in which the exhaust gases of the at least one first combustion chamber 12 and the at least one second combustion chamber 14 . 16 . 18 be mixed and in which an SCR catalyst 36 is arranged. In the flowed through by the mixed exhaust SCR catalyst 36 The ammonia reacts out of the ammonia production catalyst 22 with nitrogen oxides from the exhaust gas of the at least one second combustion chamber 14 . 16 . 18 to molecular nitrogen and water. Here is the SCR catalyst 36 formed in one embodiment as a structural unit of a particulate filter with SCR catalyst or as an integrated particulate filter with SCR coating.

A control unit 38 controls said and optionally further actuators in response to a plurality of input signal generators, of which in the 1 a lambda sensor 32 and a driver's desire 40 are also represented on behalf of other donors.

Due to the rich operation, this method of "on-board" ammonia production in the ammonia production catalyst can 22 set high temperatures. As a result, oxidation of the reducing agent may occur. Therefore, in certain operating situations of the engine, the ammonia selectivity in the ammonia production in the designated catalyst 22 be reduced due to high exhaust gas temperatures with the measure described below. A poor ammonia selectivity, or a poor ammonia yield leads to a low NOx conversion rate in the downstream SCR catalyst 36 ,

In 2 is the optional integration of a heat exchanger for reducing the exhaust gas temperature of the exhaust gas in the ammonia generation catalyst 22 shown. In this case, the hot exhaust gas from the at least one first combustion chamber 12 containing the ammonia generation catalyst 22 flows through, with the exhaust gas flow of the lean-burned and therefore cooler exhaust gas of the at least one second combustion chamber 14 . 16 . 18 cooled. In this way, in particular at high-load engine operating points, which usually have a high exhaust gas temperature in the ammonia-generating catalyst 22 adjusted, the ammonia selectivity and thus the ammonia yield of the process can be increased. Typical heat exchangers, which heat from the hot exhaust gas flow from the exhaust system 30 to the cooler oxygen-containing exhaust stream from an exhaust line 42 and / or transmitted to the environment are, for example, pipe bundle heat exchangers, plate heat exchangers or fin heat exchangers incorporated in the ammonia generation catalyst 22 are integrated.

In another embodiment, the heat flow through the at least one first combustion chamber 12 is generated, in addition or exclusively to other media, such as the ambient air or the cooling water of the internal combustion engine 10 be coupled.

With reference to the integration of an exhaust gas turbocharger 44 in an internal combustion engine system with ammonia production catalyst 22 offer a total of four variants that in the 2a . 2 B . 2c and 2d are shown. In the variant a of 2a becomes the exhaust gas turbocharger 44 arranged so that the ammonia generating catalyst 22 in the flow direction of the exhaust gas between the internal combustion engine 10 and the turbine 46 the exhaust gas turbocharger 44 located. In this variant, the compressor compresses 48 the exhaust gas turbocharger 44 the entire intake air flow of the internal combustion engine 10 ,

In variant b, the in 2 B is shown, the compressor 48 the exhaust gas turbocharger 44 arranged so that it only the intake air flow to the at least one second combustion chamber 14 . 16 . 18 compacted. The intake air flow for the at least one first combustion chamber 12 will have a bypass 50 guided and therefore not compressed, so that this engine part sucks the intake air freely. As a result, the reduced in the combustion chamber 12 incoming air mass, which reduces the amount of fuel required to lower the lambda value.

The variant c after the 2c is designed so that with the help of the exhaust gas turbocharger 44 the entire intake air flow of the internal combustion engine 10 Motors is compressed. The energy for compressing this intake air receives the compressor 48 from the turbine 46 the exhaust gas turbocharger 44 , the exhaust side only of the exhaust gas of the lean-operated engine part with the at least one second combustion chamber 14 . 16 . 18 is flowed through. The turbine is therefore in the exhaust system 42 arranged, the only exhaust gas of the at least one second combustion chamber 14 . 16 . 18 leads.

The fourth variant d after the 2d sees an arrangement of the exhaust gas turbocharger 44 before, the latter only for the lean-operated engine part with the at least one second combustion chamber 14 . 16 . 18 uses. The at least first combustion chamber 12 is on the intake air side with an air duct bypass 50 , in the flow direction of the intake air in front of the compressor 48 Air from the suction tube takes, supplies. The exhaust gas flow of the at least one first combustion chamber is the exhaust gas flow of the at least one second combustion chamber on the exhaust gas side 14 . 16 . 18 only downstream of the turbine 46 allocated.

In further variants charging takes place without an exhaust gas turbine, for example electrically or mechanically over a coupling of energy with the crankshaft of the engine.

3 shows four different variants of the integration of exhaust gas recirculation 54 , In variants a and b after the 3a and 3b Exhaust gas, which is due to the intake region, immediately downstream of the ammonia-generating catalyst 22 taken. In these variants, a part of the previously produced ammonia gets back into the engine and is in the combustion engine during the combustion process 10 decomposed again. In variant a, the recirculated exhaust gas passes via a first exhaust gas recirculation valve 56 both in the at least one first combustion chamber 12 as well as a second exhaust gas recirculation valve 58 in the at least one second combustion chamber 14 . 16 . 18 , Motorteilselektiv different amounts of exhaust gas in the least a first combustion chamber 12 and the at least one second combustion chamber 14 . 16 . 18 to be led back. So must next to the second exhaust gas recirculation valve 58 for the allocation of the exhaust gas in the at least one second combustion chamber 14 . 16 . 18 yet another exhaust gas recirculation valve 56 be used, which is separate from the exhaust gas recirculation valve 58 is controlled. Optionally, for this measure instead of the first exhaust gas recirculation valve 56 also a static choke can be used. With this measure name, the exhaust gas recirculation quantities for the at least one first combustion chamber 12 and the at least one second combustion chamber 14 . 16 . 18 be brought into a certain relationship. The actual adjustment of the exhaust gas recirculation rates takes place only with an exhaust gas recirculation valve, which then in a common exhaust gas recirculation line 60 is arranged.

Compared to variant a is in the variant b after the 3b that to the internal combustion engine 10 recirculated exhaust gas exclusively via an exhaust gas recirculation valve 58 in the lean operated at least a second combustion chamber 14 . 16 . 18 directed. The at least one first combustion chamber 12 receives in this variant b no recirculated exhaust gas for the combustion of the fuel.

With two further variants c and d, which in the 3c and 3 d is shown, the exhaust line 42 the lean operated at least one second combustion chamber 14 . 16 . 18 taken. In this way, the ammonia previously produced in the ammonia production catalyst does not re-enter the internal combustion engine 10 but only in the SCR catalyst 36 ,

In the variant of 3c the recirculated exhaust gas according to the variant after 3a on the at least one first combustion chamber 12 and the at least one second combustion chamber 14 . 16 . 18 distributed. In contrast, the recirculated exhaust gas in the variant of 3d according to the variant of the 3b only the lean operated at least a second combustion chamber 14 . 16 . 18 made available.

4 shows an overview of an entire system with a first sensor. The monitoring of the on-board ammonia production process can be controlled and / or regulated 24 in the intake air region of the at least one first combustion chamber can with the help of one in the control unit 38 stored engine map are controlled or regulated to a defined lambda value between lambda <1 and an unthrottled state. When using a closed loop, an oxygen-sensitive exhaust gas sensor 32 between the at least one first combustion chamber 12 and the ammonia generation catalyst 22 is arranged to capture the current lambda value and with the control unit 38 as a controller and, for example, with a throttle valve as an actuator 24 form a closed loop.

Another way to capture the current lambda value is to use an air mass meter 62 in the intake air duct 64 the at least one first combustion chamber 12 in combination with the before the ammonia generation catalyst 22 injected fuel quantity. The respective current lambda value can be determined in this way from the air mass and fuel mass flows and the lambda sensor 32 replace. Finally, a variant of the lambda determination, in which the lambda value with the help of the signal of the driver request generator 40 in correlation with an opening degree of the actuator 24 , For example, a Drosselstellstellstellurg is determined, conceivable.

The adjustment of the oxygen deficiency in the ammonia generation catalyst 22 can with the help of an oxygen-sensitive lambda sensor 66 which is mounted downstream of the ammonia production catalyst, monitored and regulated. With the help of such an exhaust gas sensor 66 can the already mentioned three operating conditions (lambda <1, lambda = 1, lambda> 1) in the ammonia-generating catalyst 22 be set.

The detection of the amount of ammonia produced can be done both as ammonia content of the exhaust gas, as well as the absolute amount of ammonia produced. For this measure is a in the control unit 38 filed catalyst-specific map required in which the ammonia selectivity of ammonia production from nitrogen oxides is stored as a function of the temperature and the oxygen content of the exhaust gas.

In addition to referring to the 4 explained procedure for determining the amount of ammonia produced in each case, the nitrogen oxide concentration in the exhaust gas of the at least one first combustion chamber 12 either measured or determined using a suitable nitrogen oxide map. Such an engine operating point specific map is usually in dependence on the parameters engine load and engine speed in the control unit 38 stored. Will be a nitric oxide sensor 68 used, it is between the at least one first combustion chamber 12 and the ammonia generation catalyst 22 in the exhaust system 30 arranged. In this way, in combination with the current detection of the ammonia selectivity of the ammonia-producing catalyst 22 the produced ammonia content can be determined.

The air mass meter 62 in the intake air duct 64 Here, too, the determination of the absolute amount of ammonia produced can be determined.

Alternatively or in addition to the previously described method for detecting the ammonia concentration in exhaust gas or for detecting the amount of ammonia produced, an ammonia sensor 70 between the ammonia production catalyst 22 and the SCR catalyst 36 be arranged in the total exhaust stream. This measure allows a functional check of the ammonia production catalyst 22 as part of an on-board diagnostic ability.

Another nitric oxide sensor 72 is either in the exhaust tract 42 the at least one second combustion chamber 14 . 16 . 18 or in the total exhaust stream upstream of the SCR catalyst 36 arranged. Since nitric oxide sensors are generally cross-sensitive to ammonia, the arrangement of such a nitrogen oxide sensor is 72 in the exhaust tract 42 recommended. Also in this application, the measured nitrogen oxide concentration using an air mass meter 74 in an absolute size, namely an emitted amount of nitrogen oxide to be converted. For this purpose, an arrangement of the air mass meter 74 in the intake of the lean operated at least a second combustion chamber 14 . 16 . 18 required. Alternatively, in each case an air mass meter 76 in the total intake air flow in conjunction with one of the air mass meters 62 . 74 be used. The unmeasured air mass results in this case by subtraction.

To monitor the tail pipe emissions of the entire system of the internal combustion engine 10 at the End of the emission control system 20 is optionally a nitrogen oxide sensor 78 and / or an ammonia sensor 80 downstream of the SCR catalyst 36 at. These sensors 78 . 80 can also be realized in combination as a structural unit.

For combined nitrogen oxide and ammonia emission monitoring downstream of the SCR catalyst 36 It is also possible to use nitrogen oxide sensors which react cross-sensitively to ammonia. Such sensors are for example from the EP 820 799 known.

Next optional is the emission control system 20 downstream of the SCR catalyst 36 a so-called ammonia barrier catalyst 82 in front of a nitric oxide sensor 78 exhibit. This noble metal-containing catalyst 82 works in the oxygen-containing exhaust gas and quantitatively converts ammonia into nitric oxide in the presence of oxygen. The advantage of this measure is that a downstream nitrogen oxide sensor 78 sufficient to control the NOx emission downstream of the SCR catalyst 36 to be able to monitor. Another advantage is that an ammonia slip can be avoided even with a non-excludable misconduct of the overall system.

Further Advantages of the above Arrangements consist in the low complexity as well as the associated Easy to use of the involved control circuits with regard to on a variety of engine concepts for the Series application. The control circuits can both independently, as also coupled, for example with a lambda probe (instead of two separate probes) downstream of the ammonia generation catalyst. As another Option is the construction of an exclusively controlled manipulated variable, for Example of a throttle in the air intake area, and a closed Control circuit for one late fuel injection with a lambda probe on.

5 shows an embodiment of a method according to the invention. This is done in one step 84 at least a second combustion chamber 14 . 16 . 18 with a lean air / fuel mixture and at least a first combustion chamber 12 operated with a less lean combustion air / fuel mixture. In a step sequence 86 . 88 is an oxygen deficiency in the exhaust gas of the at least one first combustion chamber 12 and thus in the ammonia production catalyst 22 generated. This includes the step 86 throttling an air supply to the at least one first combustion chamber 12 such that at least a first combustion chamber adjusts the smaller combustion air / fuel ratio and the step 88 comprises a post-combustion supply of reducing agent to the exhaust gas of the at least one first combustion chamber 12 ,

Claims (20)

Method for operating an internal combustion engine ( 10 ) with several combustion chambers ( 12 . 14 . 16 . 18 ) and an emission control system ( 20 ) containing an ammonia generation catalyst ( 22 ), which only exhaust gas from at least a first combustion chamber ( 12 ), comprising the steps of: operating at least one second combustion chamber ( 14 . 16 . 18 ) with a lean air / fuel mixture; Operating the at least one first combustion chamber ( 12 ) with a less lean combustion air / fuel mixture; and generating an ammonia-producing low-oxygen atmosphere in the exhaust gas of the at least one first combustion chamber ( 12 ); characterized by the following further steps: throttling an air supply to the at least one first combustion chamber ( 12 ) so that in the least a first combustion chamber ( 12 ) sets a smaller combustion air / fuel ratio than in the at least one second combustion chamber ( 14 . 16 . 18 ); and generating the ammonia-producing low-oxygen atmosphere in the exhaust gas of the at least one combustion chamber ( 12 by supplying reductant after combustion to the exhaust gas of the at least one first combustion chamber ( 12 ). A method according to claim 1, characterized in that the throttling of the air supply by closing driving a throttle valve in a separate air supply ( 64 ) to the at least one first combustion chamber ( 12 ) he follows. A method according to claim 2, characterized in that the throttling taking into account the signal of a lambda sensor ( 32 ) in the exhaust gas of the at least one first combustion chamber ( 12 ), or taking into account an air mass flow and a fuel mass flow to the at least one first combustion chamber ( 12 ) he follows. Method according to one of the preceding claims, characterized by taking into account a signal of a downstream of the ammonia-producing catalyst ( 22 ) arranged ammonia sensor ( 70 ) supply of diesel fuel as a reducing agent. Method according to at least one of the preceding claims, characterized in that a nitrogen oxide emission of the at least one first combustion chamber ( 12 ) by means of an upstream of the ammonia production catalyst ( 22 ) arranged nitrogen oxide sensor ( 68 ) and an air mass meter ( 64 ), which in the at least one first combustion chamber ( 12 ) measuring air mass, is detected. Method according to at least one of the preceding claims, characterized in that an ammonia emission downstream of the ammonia-producing catalyst ( 22 ) by means of a downstream of the ammonia production catalyst ( 22 ) arranged ammonia sensor ( 70 ) and / or an air mass meter ( 64 ), which in the at least one first combustion chamber ( 12 ) measuring air mass, and / or by means of an air mass meter ( 74 ), which in the at least one second combustion chamber ( 14 . 16 . 18 ) measuring air mass, is detected. Method according to at least one of the preceding claims, characterized in that a quantity of one of the at least one second combustion chamber ( 14 . 16 . 18 ) emitted nitrogen oxides using a in the exhaust gas of the at least one second combustion chamber ( 14 . 16 . 18 ) arranged nitrogen oxide sensor ( 72 ) and an air mass meter ( 62 ), which in the at least one first combustion chamber ( 12 ) measuring air mass, and / or by means of an air mass meter ( 74 ) for measuring the in the at least one second combustion chamber ( 14 . 16 . 18 ) flowing air mass is detected. Method according to at least one of the preceding claims, characterized in that a nitrogen oxide emission downstream of an SCR catalyst ( 36 ) with the aid of a nitrogen oxide sensor ( 78 ) and optionally additionally with at least one air mass meter ( 62 . 74 . 76 ) for measuring one in the at least one first combustion chamber ( 12 ) and the at least one second combustion chamber ( 14 . 16 . 18 ) is detected total incoming air mass flow. Method according to at least one of the preceding claims, characterized in that an ammonia emission downstream of an SCR catalyst ( 36 ) with the aid of an ammonia sensor ( 80 ) and optionally additionally with at least one air mass meter ( 62 . 74 . 76 ) for measuring one in the at least one first combustion chamber ( 12 ) and the at least one second combustion chamber ( 14 . 16 . 18 ) is detected total incoming air mass flow. Internal combustion engine ( 10 ) with several combustion chambers ( 12 . 14 . 16 . 18 ) and an emission control system ( 20 ) containing an ammonia generation catalyst ( 22 ), which only exhaust gas from at least a first combustion chamber ( 12 ), with at least one second combustion chamber ( 14 . 16 . 18 ), which is operated with a lean air / fuel mixture, wherein the at least one first combustion chamber ( 12 ) is operated with a less lean combustion air / fuel mixture, and with means ( 24 . 26 . 28 ) for generating an oxygen deficiency in the exhaust gas of the at least one first combustion chamber ( 12 ), characterized in that the means ( 24 . 26 . 28 ) an actuator ( 24 ) having an air supply to the at least one first combustion chamber ( 12 ) so throttles that in the least a first combustion chamber ( 12 ) sets a smaller combustion air / fuel ratio than in the at least one second combustion chamber ( 14 . 16 . 18 ), and that the funds ( 24 . 26 . 28 ) further comprises a reducing agent actuator ( 26 . 28 ), which has an oxygen deficiency in the exhaust gas of the at least one combustion chamber ( 12 by supplying reductant after combustion to the exhaust gas of the at least one first combustion chamber ( 12 ) generated. Internal combustion engine ( 10 ) according to claim 10, characterized in that the emission control system ( 20 ) a volume ( 34 ), in which the exhaust gases of the at least one first combustion chamber ( 12 ) and the at least one second combustion chamber ( 14 . 16 . 18 ) and that the volume ( 34 ) an SCR catalyst ( 36 ) and downstream of the SCR catalyst ( 36 ) arranged oxidation catalyst ( 82 ) having. Internal combustion engine ( 10 ) according to claim 10, characterized in that the emission control system ( 20 ) a structural unit of a particulate filter with SCR catalyst ( 36 ) having. Internal combustion engine ( 10 ) according to claim 10, characterized in that the emission control system ( 20 ) upstream of the SCR catalyst ( 36 ) arranged heat exchanger for cooling the exhaust gases of the at least one first combustion chamber ( 12 ) having. Internal combustion engine ( 10 ) according to claim 13, characterized in that the heat exchanger as a structural unit with the ammonia-generating catalyst ( 22 ) is trained. Internal combustion engine ( 10 ) according to claim 11, characterized in that a turbine ( 46 ) of an exhaust gas turbocharger ( 44 ) downstream of the ammonia production catalyst ( 22 ) in the volume ( 34 ), and a compressor ( 48 ) of the exhaust gas turbocharger ( 44 ) the entire intake air flow of the internal combustion engine ( 10 ), or a compressor ( 48 ) of the exhaust gas turbocharger ( 44 ) into the at least one second combustion chamber ( 14 . 16 . 18 ) compressed intake air stream. Internal combustion engine ( 10 ) according to claim 10, characterized by a turbine ( 46 ) of an exhaust gas turbocharger ( 44 ) downstream of the ammonia production catalyst ( 22 ) in the exhaust gas of the at least one second combustion chamber ( 14 . 16 . 18 ), wherein a compressor ( 48 ) of the exhaust gas turbocharger ( 44 ) the entire intake air flow of the Internal combustion engine ( 10 ) or in the at least one second combustion chamber ( 14 . 16 . 18 ) compressed intake air stream. Internal combustion engine ( 10 ) according to claim 11, characterized by exhaust gas recirculation ( 54 ), the exhaust gas downstream of the ammonia production catalyst ( 22 ) from the volume ( 34 ) and in the at least one second combustion chamber ( 14 . 16 . 18 ) flowing in the intake air flow, or in the at least one first combustion chamber ( 12 ) flowing in the intake air flow and in the at least one second combustion chamber ( 14 . 16 . 18 ) supplying intake air flow. Internal combustion engine ( 10 ) according to at least one of claims 10 to 16, characterized in that the exhaust gas recirculation ( 54 ) Exhaust gas of the at least one second combustion chamber ( 14 . 16 . 18 ) in which at least a second combustion chamber ( 14 . 16 . 18 ), or into the at least one first combustion chamber (FIG. 12 ) flowing in the intake air flow and in the at least one second combustion chamber ( 14 . 16 . 18 ) supplying total intake air flow. Internal combustion engine ( 10 ) according to at least one of claims 17 or 18, characterized in that the emission control system ( 20 ) individually controllable flow barriers ( 56 . 58 ) for distributing a recirculated exhaust gas amount into the at least one second combustion chamber ( 14 . 16 . 18 ) or in the at least one first combustion chamber ( 12 ) and the at least one second combustion chamber ( 14 . 16 . 18 ) has flowing intake air flow. Internal combustion engine ( 10 ) according to at least one of claims 10 to 19, characterized in that the means ( 14 . 26 . 28 ) for generating an ammonia-producing low-oxygen atmosphere in the exhaust gas of the at least one first combustion chamber ( 12 ), an injecting into the at least one first combustion chamber injection valve ( 28 ) and / or in the exhaust gas of the at least one first combustion chamber ( 12 ) arranged separate metering valve ( 26 ), and / or have an additional, separate combustion chamber, which is operated with a rich air / fuel mixture, as a reducing agent actuator.