DE10321105A1 - Regeneration of a particle trap - Google Patents

Abstract

It is an exhaust system (1) for cleaning a gas stream (2) Pollutants (3) are proposed which are in the flow direction (4) of the gas stream (2) through the exhaust system (1) at least means for supplying a Reducing agent, a first catalytic converter (5) and has a particle trap (8), at least one further exhaust gas cleaning component and / or a distance of at least 0.5 meters between the first catalytic converter (5) and the particle trap (8) are provided are in which a mixer (6) and a second catalytic converter (7) the particle trap (8) are placed directly in front. Further concerns the invention a method for the regeneration of a particle trap (8), which is arranged in the exhaust system (1), in which a reducing agent (23) Upstream (only) of the turbocharger (6) for implementation a regeneration process of the particle trap (8) into the exhaust system (1) is initiated.

Description

The The present invention relates to an exhaust system for cleaning an Gas flow of pollutants, which includes a particle trap, which is discontinuous is regenerated using a reducing agent. Farther describes a method for regenerating a particle trap.

by virtue of legal regulations, which make ever higher demands on the exhaust systems in the automotive industry, the exhaust systems were in the past constantly evolving. There are a variety of components used, each with different functions within the Exhaust system. For example, starting catalytic converters or pre-turbo catalytic converters are known, which have a particularly small volume and therefore quickly after one Cold start of the internal combustion engine for catalytic conversion reach the required start temperature. Furthermore, are electrical heatable catalysts known, which is also an improved Enable cold start behavior of the exhaust system. So-called adsorbers have the task in the exhaust system of an internal combustion engine, certain pollutants contained in the exhaust gas for a certain period of time adsorb, which are preferably stored as long as until a downstream catalytic converter reaches its operating temperature Has. Especially in the exhaust system of diesel engines Particle traps or particle filters used, which contained in the exhaust gas Soot particles and / or collect other solid contaminants. The collected particles can basically be continuous or implemented discontinuously, for example by supply high thermal energy.

to Reduction of particle emissions in the exhaust gas, especially in diesel engines, particle traps are known which are made of a ceramic substrate are built up. These have channels so that the exhaust gas to be cleaned can flow into the particle trap. The neighboring canals are alternately closed, so that the exhaust gas on the inlet side flows into the channel, through at least one ceramic wall and through the neighboring channel on the outlet side escapes again. such Particle traps are known as "closed" particle filters. You achieve effectiveness of about 95% above the entire range of particle sizes.

Another type of particle trap that can withstand high thermal loads and has a significantly lower pressure drop is derived from the unpublished German patent application DE 101 53 283 out. In this document, a particle trap is described, which is referred to as an “open” filter system. In such an open system, the filter channels are not structurally and mutually closed. The channel walls consist at least partially of porous or highly porous material. The flow channels of the open filter point Deflecting or guiding structures that direct the exhaust gas with the particles contained therein to the areas made of porous or highly porous material A particle filter is said to be open if it can basically be completely traversed by particles, including particles that Such a filter cannot clog even during agglomeration of particles during operation. A suitable method for measuring the openness of a particle filter is, for example, checking to what diameter the spheres are shaped particles can still trickle through such a filter. In the present applications, a filter is particularly open when balls with a diameter greater than or equal to 0.1 mm can still trickle through, preferably balls with a diameter above 0.2 mm.

Independent of The particle trap used must be safe and secure Possibility of complete regeneration the particle filter in the exhaust system of an automobile ensures his. Such regeneration of the particle trap is necessary because the increasing accumulation of particle particles in the channel wall to be flowed through has a steadily increasing pressure loss, the negative Effects on engine performance. The regeneration essentially involves briefly heating the particle trap or the particles accumulated therein, so that the soot particles in gaseous Components are implemented.

Have been such particle traps heated directly, for example by a ohmic resistance heating. It was also known to have a separate one Burner the soot particles implement. Subsequent devices for the regeneration of the particle filter are characterized in that upstream of such a particle trap a reducing agent supplied which is ultimately a chemical implementation of the in the particle trap soot particles causes. There are essentially two different ones Systems crystallized: the discontinuous and the continuous Regeneration.

The system for the continuous regeneration of filters is called CRT (Continuous Regeneration Trap) and for example in the US 4,902,487 described. In such a system, the particles are at temperatures above 200 ° C implemented by oxidation by contacting with nitrogen dioxide (NO ₂ ). The nitrogen dioxide required for this is often generated by an oxidation catalyst which is arranged upstream of the filter. However, this poses the problem, particularly with regard to the use in motor vehicles with diesel fuel, that there is only an insufficient proportion of nitrogen monoxide (NO) in the exhaust gas, which can be converted into the desired nitrogen dioxide. As a result, it has not yet been possible to ensure that the particle trap in the exhaust system is continuously regenerated. For this reason, it is also common to feed urea or similar reducing agents into the exhaust system, which enable the filters to be continuously regenerated. A disadvantage of such systems is the high level of technical complexity and the fact that separate consumables or operating resources must be carried in the motor vehicle.

at the discontinuous regeneration of particle traps it is known the particle trap upstream of an oxidation catalyst unsaturated or unburned hydrocarbons (HC) are supplied. When contacting the unsaturated A hydrocarbon with the oxidation catalyst creates a special one exothermic reaction resulting in a significant increase in the temperature of the exhaust gas Consequence. Temperatures are reached in a range lie that an implementation of the stored in the particle traps Particle agglomerations possible is. Here you have to frequently Temperatures above 600 ° C can be achieved. The supply of reducing agent can take place separately, but it is also known to burn unburned fuel from the Introduce internal combustion engine directly into the exhaust pipe, so that they hit the oxidation catalyst.

The Desired at the beginning, immediately after the cold start the internal combustion engine a catalytic conversion of the exhaust gas to cause are achieved through the use of catalytic converters that a small volume (e.g. less than 20% of the displacement of the internal combustion engine) and distinguish their proximity to the engine. This poses the technical problem of an unsaturated feed Hydrocarbons located in a downstream, distinct from a regeneration of the particle trap located away from the starting catalyst is no longer possible is. The fuel acting as a reducing agent would be on hit the starting catalyst and cause an exothermic reaction to lead. by virtue of the fact that the particle trap is very far from the starting catalyst is remote or additional Components for exhaust gas purification between the catalytic converters and the particle trap are not arranged in the particle trap the required temperature increase causes.

Therefore it is an object of the present invention, the technical described Eliminate problems, particularly an exhaust system and process for the regeneration of a particle trap, so that a discontinuous Regeneration of the particle trap can also be guaranteed if size Distances between the starting catalyst and the particle trap for the Exhaust gas or temperature-sensitive components for the implementation of certain Exhaust gas components between the starting catalytic converter and the particle trap are arranged. The exhaust system should also be simple and the regeneration is easy to carry out his.

This Tasks are solved by an exhaust system with the features of claim 1 and a method for the regeneration of a particle trap with the features of claim 11. Further advantageous refinements are in the respective dependent Claims described. The further developments shown there are also arbitrary can be combined with one another in a sensible manner.

The Exhaust system for cleaning a gas stream with pollutants includes in the direction of flow of the gas flow through the exhaust system at least means for feed of the reducing agent, a first catalytic converter and a particle trap, with at least one further exhaust gas cleaning component and / or a distance of at least 0.5 m between the first catalytic converter's and the particle trap is provided. According to the invention a mixer and a second catalytic converter of the particle trap immediately preceding.

To clarify the terms used here, the meaning is explained in more detail below. The "flow direction of the gas flow" is to be understood as the direction of the gas flow which the flow takes from an internal combustion engine to the exhaust or outlet into the atmosphere. This means a main flow direction, so local flow turbulence or the like is particularly disregarded Arrangement of the individual means in the direction of flow through the exhaust system means that the gas flow first comes into contact with the means for supplying a reducing agent, then with the first catalytic converter and finally with the particle trap. This does not affect the fact that the gas flow between these individual components comes into contact with other components of the exhaust system, such as Further adsorbers, exhaust pipes, etc. Furthermore, with reference to the fact that “at least” the listed devices are provided, it is also included that the devices can be arranged several times, directly or indirectly, one after the other.

Under a “catalytic Converters "are one Many known carrier bodies for catalytic understand active material. The carrier body can be made predominantly of metal and / or ceramic be constructed. As is known, at least in the case of metallic catalyst carrier bodies partially structured metal foils are wound together so that for a Fluid can flow through Channels formed are. It is also known to produce metallic carrier bodies by extrusion. Ceramic carrier bodies are also known, the honeycomb shape also through an extrusion and sintering process receive. Such a honeycomb shape has therefore proven to be particularly advantageous proven because this provides a particularly large surface area which results in intimate contact with the gas flow.

Under the term "particle trap" are both classic Filter systems with mutually closed channels as the “open” filter systems described above are also meant.

The The term “exhaust gas cleaning component” represents a generic term for one Numerous different components for exhaust gas treatment in particular honeycomb bodies, Water traps, heating elements, silencers, adsorbers, storage devices, etc.

Under a "distance" between the first catalytic converter and the particle trap is especially theirs Distance along the flow path to understand the gas flow. That means doing this distance along the exhaust pipe to determine which is the first catalytic Converter and the particle trap, by the shortest route, connects.

A “mixer” in the sense of this disclosure describes a device which causes a swirling or a significant flow deflection of partial gas flows. In particular, the proportion of redirected partial gas flows is above 50%, in particular 80%, preferably above 95%. It is particularly advantageous here that the partial exhaust gas flows are not deflected essentially parallel to one another, but rather move at least partially towards one another, so that mixing takes place. As an example, a mixing element of the type mentioned in FIG DE 199 38 840 is described. Of course, all other known mixers can also be used as long as they meet the above criteria.

Concerning the second catalytic converter, it should be noted that this in turn is an exhaust treatment component acts as it relates to the first catalytic converter has been described. However, this second catalytic converter is not designed as a starting catalyst, d. H. it is not in the vicinity of the engine.

With the exhaust system according to the invention Is it possible, as will be explained in more detail below with reference to the method, Fuel as a reducing agent for the regeneration of the particle trap use the fuel essentially without a complete exothermic Reaction passes the first catalytic converter. Then it will be this fuel-gas mixture is processed by the mixer so that the one you want exothermic reaction takes place in the second catalytic converter, which the for the regeneration of the particle trap causes the required temperature increase. An essential aspect of the invention is that the fuel required for regeneration concentrated in a section or partial volume flow of the exhaust gas flow is passed through the first catalytic converter, so that for a significant proportion of the fuel carried is insufficient Oxygen available stands, which is required for catalytic conversion. So kick only in the edge areas of the high-fuel partial gas flow catalytically motivated reactions to, a large part of the additionally injected However, fuel quantity passes the first catalytic one without conversion Converter.

The Mixer now causes this fuel-enriched partial gas flow mixes with the remaining exhaust gas, which is particularly the case with diesel engines especially lean, d. H. is oxygen-rich. Through this mixing process there is a resolution of the high-fuel partial gas flow, so that the fuel finely dispersed with the exhaust gas flow to the downstream particle trap flows. In this context, it does not matter whether the mixed exhaust gas flow on the way to the second catalytic converter flows through further (non-oxidizing) exhaust gas cleaning components or Not. Ultimately, the mixed exhaust gas flow meets the second catalytic converter, which in turn has a catalytically active surface and now brings about implementation of the exhaust gas fuel dispersion.

Since this second catalytic converter is connected directly (or immediately, that is, without further exhaust gas purification components being arranged in between) upstream of the particle trap, the temperature increase due to the exothermic reaction is passed on directly to the particle trap. This now ensures complete regeneration of the Particulate trap. It is particularly advantageous that the second catalytic converter and the particle trap are arranged with respect to one another in such a way that the exhaust gas can deliver the greatest possible amount of energy to the particle trap. This can be ensured, for example, by the catalytic converter and the particle trap being only a short distance from one another, in particular this distance is less than 10 cm, in particular less than 5 cm and preferably less than 2 cm. The distance describes the distance that the exhaust gas travels after exiting the second catalytic converter until it enters the particle trap. In particular, it is advantageous if the exhaust pipe between the second catalytic converter and the particle trap is thermally insulated or has no additional components such as flaps, baffles, probes or the like, or also curved sections.

According to one In another embodiment of the invention, the mixer is a turbocharger. Especially with the newer diesel engines, which operate on the principle of Working direct injection has been the use of an exhaust gas turbocharger proven for compression of the intake air. Such a compressor for the Intake air is generated by the exhaust gas flowing through the turbocharger operated. When flowing through the turbocharger learns the exhaust gas swirls so that the criteria from the turbocharger that were presented above with reference to the mixer are fully satisfied. I.e. for example, that now the first catalytic converter only a turbocharger can be connected downstream, which in turn a second catalytic converter and the particle trap downstream are. Especially with such an arrangement of the exhaust gas cleaning components or the turbocharger, the method described below is advantageous, since it prevents the first catalytic converter, which is preferably designed as a starting catalyst, such high temperatures are generated in the exhaust gas that the directly downstream turbocharger damaged becomes. So it is possible the exhaust with for tolerable the turbocharger Passing temperatures and then it to such a temperature by means of the second catalytic converter to ensure that regeneration of the particle trap is ensured is.

According to one A further embodiment of the exhaust system includes the means for supplying the reducing agent at least one injector for providing fuel in the combustion chamber of a mobile internal combustion engine. This means in particular that only one or more injection nozzles that destined for supplying the internal combustion engine with fuel are to provide reducing agents for the regeneration of the particle trap be used. I.e. in other words that at least an injector injects fuel into the cylinders of the internal combustion engine, which leaves the cylinder essentially unburned, the first catalytic converter (and possibly also the turbocharger) happens and finally only by contact with the second catalytic converter exothermic reaction to convert the fuel takes place. On this makes the exhaust system particularly simple possible, finally can on additional Pipes or nozzles u. The like. For the introduction of the reducing agent.

Further it is proposed that the injection nozzle be arranged such that the fuel can be introduced into an outlet channel of the internal combustion engine is. Here is for the specialist clear that this may require additional funds are. So it has to be considered that the injector is usually is designed so that a particularly good compression or Combustion behavior of the fuel-air mixture in the cylinder the internal combustion engine is guaranteed. To ensure, that the fuel reaches the outlet channel, may be predetermined Piston or valve positions required.

Around for example, an easily retrofittable design of the exhaust system to obtain a modification of the cylinder or the combustion chamber does not require, it is proposed that at least a separate feed line in or on an outlet duct of the internal combustion engine and / or the exhaust system is provided. This means that, for example an additional line is provided from the fuel supply to the engine and the fuel between the combustion chamber or the engine cylinder and the first catalytic converter is supplied to the exhaust gas stream. It should be noted that this is done in such a way that it is relatively narrow Part gas stream is generated, which has a particularly high concentration of fuel. This ensures that the to perform a exothermic reaction required oxygen is displaced and the high-fuel partial gas stream both the first catalytic Converters and any downstream components flow through without to experience a significant chemical conversion.

According to a further embodiment, it is proposed that the means for supplying a reducing agent are connected to a reducing agent reservoir and a control unit, so that an intermittent supply of reducing agent can be carried out. With regard to the reducing agent reservoir, separate containers or storage spaces can be provided, but it is also possible that this is directly the fuel tank. The control unit takes over the task, the opening time as required to regulate or control the pressures at the injection nozzle or other nozzles. This has to be done in particular as a function of the piston or exhaust valve position of the cylinder of the internal combustion engine.

Further it is advantageous that the first catalytic converter is a Oxidation of at least one pollutant contained in the gas stream promotional first contact area Has. I.e. especially that with the first catalytic converter unsaturated Hydrocarbons are converted into less harmful components become. Precisely because there is always something special in this context Public interest is present, it is proposed that the second catalytic Converter an the oxidation of at least one contained in the gas stream Pollutant-promoting second contact area Has. It is u. May be possible that both the first catalytic converter and the second catalytic converter to the same catalytically active material or in the contact area exhibit. This is surprising in that since with the device proposed here and the following explained Procedure guaranteed is that the reducing agent has the same coating on the one hand happens, but on the other hand with an exothermic reaction a significant increase in temperature of the exhaust gas is implemented.

According to one more Another embodiment of the exhaust system form the second catalytic Converter and the particle trap a structural unit. This means in particular that the second catalytic converter and the particle trap are not only over the exhaust pipe surrounding them are connected. For example possible, that the second catalytic converter and the particle trap in a common casing pipe are arranged, which with the exhaust pipe is in contact. However, it is also possible that the second catalytic Converters and the particle trap don't just span each other are connected, but this is possibly a contact via the end faces takes place, for example via Pens, metal foils, or the like. Furthermore, it is also possible, for example, with regard to the structural unit to provide thermal insulation acting in the circumferential direction, so that the exothermic generated in the second catalytic converter Energy almost completely is delivered to the particle trap.

According to one Another advantageous embodiment of the exhaust system form the second catalytic converter and the particle trap together one for a fluid through which Body, the in the direction of flow first a catalytically active coating and subsequently means for Has attachment of particles. I.e. for example, that the second Catalytic converter and the particle trap are designed with the same carrier body. I.e. in other words, that for example the channel walls, which usually formed by ceramic material or metal sheets be about a whole length in the direction of flow of the second catalytic converter and the particle trap together extend. A subdivision of the carrier body itself then does not have to available. However, it can Cutouts, deformations, material accumulations or the like in partial sections of the body or the canal walls be made so that the section of the body to the particular function, Catalyst on the one hand and particle trap on the other, adjusted is. in principle but is possible that these sections of the carrier body or body (only or additionally) differentiate by different coatings. It can also an overlap area the section constituting the second catalytic converter and the section that forms the particle trap.

According to one Another aspect of the invention is a method for regeneration proposed a particle trap arranged in an exhaust system is, the exhaust system (in the direction of flow of a gas stream seen) at least a first catalytic converter, a turbocharger, has a second catalytic converter and the particle trap. A reducing agent is used upstream of the turbocharger to carry out a Regeneration process of the particle trap initiated in the exhaust system. For this purpose, the reducing agent is concentrated in a partial gas stream fed to the exhaust system, that when flowing through of the first catalytic converter no or only a very small one exothermic reaction takes place. This one, still high in fuel Part gas flow is now led through the turbocharger, with a particularly intensive one Mix with the partial exhaust gas streams other cylinders of the internal combustion engine takes place. There these partial exhaust gas flows from the other cylinders essentially a particularly lean one represent (oxygen-rich) mixture, the partial gas flow is now which still has a high fuel content, enriched with oxygen. This has the consequence that when the partial gas flow subsequently hits the desired exothermic reaction takes place on an oxidation catalyst. The thermal energy that is released thereby burns off the soot particles used, which accumulated in the downstream particle trap to have. This prevents flow paths (which the exhaust gas through the particle trap), which leads to an increase in the flow resistance the particle trap leads. The resulting pressure drop in the exhaust gas flow above the Particle trap has a negative impact on engine performance can be safely avoided with the method described here.

there it is particularly advantageous that the supply of reducing agent is intermittent he follows. This is especially true when the supply of reducing agent by means of at least one injection nozzle, fuel introduced into a combustion chamber of a mobile internal combustion engine becomes. The main focus here is on diesel engines.

According to one Another, advantageous embodiment of the method takes place post injection of the fuel into the combustion chamber, so that unburned partial volume flows of the fuel get into an exhaust port of the internal combustion engine. Afterwards means in this sense, that the injector during a working cycle of the piston in the cylinder fuel at two different times injects. At the first point in time, that is for self-ignition or combustion the required amount of fuel is injected into the combustion chamber of the cylinder, compressed and burned. While the upward movement the flue gas is generated by the combustion an open one Exhaust valve into the exhaust duct and on to the exhaust pipe pushed out. At this point, especially after the combustion has been completed in the combustion chamber, a predeterminable or calculable amount of fuel (or another reducing agent) through the injector into the Combustion chamber introduced, the one with or after the exhaust gas partial flow is pushed out through the exhaust duct or the exhaust pipe flows.

at Internal combustion engines with a plurality of cylinders one combustion chamber, it is particularly advantageous that the injection of the Reducing agent takes place alternately in the cylinder. That includes on the one hand that the individual cylinders one after the other Take over injection of the reducing agent, but it is also possible that individual cylinders skipped individual injectors take over the injection of the reducing agent several times in succession and / or no rigidly specified change with regard to the cylinders is made. The latter is particularly the case if the injection into the respective cylinders depending of measured values that determine the operating state of the internal combustion engine or reflect the exhaust system. On the one hand, this ensures that in a single cylinder after the reductant injection any remaining amounts of fuel burned again and again become. So there is even combustion in all cylinders.

According to one The triggering time is a further embodiment of the method for one Injection of the reducing agent depending on a detected and / or calculated parameter determines which characterizes the functionality of the particle trap. This means that means (sensors, probes, etc.) are provided which the functionality of the Monitor particle trap. Suitable measured values represent the pressure drop over the Particle trap, the temperature in the particle trap, the concentration of at least one pollutant in the exhaust gas after the particle trap has escaped, etc. If the pressure drop reaches a predetermined level, for example Limit value, this can be an indication of the initiation of a regeneration cycle be used. Here u. U. also take into account the length of time which the amount of fuel injected close to the engine needs to to reach the particle trap. This must be done in such a way that a temperature increase the particle trap is caused before it has a noticeable negative For example, it has an effect on engine performance.

According to one more A further embodiment of the method is the location of the injection of the reducing agent depending of a detected and / or calculated parameter, which the Characterized temperature of the gas stream in a portion of the exhaust system. This means, for example, that the choice of the injection nozzle of the several Cylinders of certain temperatures of the gas flow or the exhaust system and / or the internal combustion engine is selected. For example, performs a remaining one The remaining amount of fuel in the cylinder after the next combustion to an elevated thermal load, it may be advantageous when reached an injection of the reducing agent at a predetermined limit temperature just about the other injectors make. In certain circumstances is it also possible that by designing the flow paths in the exhaust pipe dependent on different areas of the emission control components from the injection site reinforced be flown to so that in these areas especially the temperature of the exhaust gas flow represents as thermal load. Again, an adjustment can be made to guarantee of functionality of the exhaust gas treatment components are provided.

The The invention is explained in more detail below with reference to the figures. there it should be clarified that the figures are shown schematically, especially preferred embodiments show, however, the invention can not be limited.

It demonstrate:

1 : Schematic of the structure of an exhaust system;

2 : schematic of the structure of a direct-injection diesel internal combustion engine;

3 : schematically a subsequent injection of reducing agent;

4 : An embodiment of a first catalytic converter;

5 : An embodiment relating to a structural unit from a second catalytic converter and a particle trap; and

6 : schematically and in perspective a detail of a particle trap as shown in 5 is shown.

1 shows schematically and in perspective an exhaust system 1 for cleaning a gas stream 2 of pollutants 3 , This exhaust system 1 includes in the direction of flow 4 of the gas flow 2 through the exhaust system 1 through at least a first catalytic converter 5 , a mixer 6 , a second catalytic converter 7 and a particle trap 8th , Means for supplying a reducing agent are also provided, which are only upstream of the mixer 6 are arranged. This is done in the internal combustion engine 12 , which is preferably a diesel engine for a car, fuel 10 into the combustion chambers 11 of the different cylinders 24 injected. That fuel 10 is burned with highly compressed intake air and then via the exhaust pipe 26 expelled to the environment.

Immediately near the internal combustion engine 12 , in particular at a distance of less than 70 cm, are a plurality of first catalytic converters 5 provided, each with a first catalytic converter 5 is integrated in a pipe of the exhaust manifold. In the illustrated embodiment, a reducing agent 23 via a separate supply line 14 upstream of a mixer 6 , which is designed here as a turbocharger, supplied to the exhaust gas stream. The reducing agent 23 flows through the mixer 6 or the turbocharger and then meets a second catalytic converter 7 , This second catalytic converter 7 is designed conical and in an extension of the exhaust pipe 26 arranged. The particle trap is immediately after the second catalytic converter 8th at a distance 44 positioned, which is preferably less than 5 cm. The particle trap downstream is a three-way catalyst 27 the known type. Between the first catalytic converter 5 and the particle trap 8th is a distance 43 given that is at least 0.5 m, preferably even more than 1 m. The is with 43 marked arrow only to understand schematically the actual distance 43 is determined by the flow path of the gas stream 2 from the exit of the first catalytic converter 5 until entry into the particle trap 8th ,

2 shows a combustion chamber schematically and obviously not to scale 11 , as it can be found, for example, in a direct-injection diesel internal combustion engine. The cylinder 24 includes a piston 32 , the cylinder 24 and the piston 32 at least partially a combustion chamber 11 , also called displacement, limit. In the engine block of the internal combustion engine 12 is still an injector 9 arranged the one hand with a fuel reservoir 15 as well as with a control unit 16 connected is. Injector task 9 it is, as required, a predefined or predetermined amount of fuel 10 in the combustion chamber 11 inject, which then ignites with highly compressed intake air. The ignition of the air-fuel mixture causes the gas mixture to expand, causing the piston to expand 32 is pressed down. After the combustion the valve 33 move upwards in the combustion chamber 11 Exhaust gas located through an exhaust duct 13 in the direction of flow 4 pushed out. In the form shown is the exhaust valve 33 closed, the injector 9 spray finely dispersed the required amount of fuel 10 one that is required for actual combustion or performance development.

3 shows schematically and with a partial section the subsequent injection of fuel as a reducing agent. Again, the cylinder is schematic 24 and the piston 32 hinted at the combustion chamber 11 limit. The valve is in the snapshot shown here 33 in a position that the exhaust flow from the combustion chamber 11 into the exhaust duct 13 can flow. This is caused by the piston 32 moved up. Now through the injector 9 the desired amount of fuel is injected into the combustion chamber, which is required to reduce the particle trap. That fuel 10 is in the exhaust duct if possible 13 introduced that a “fat disk” is formed. This is preferably a partial volume flow 25 meant that has a particularly high concentration of hydrocarbons. This partial volume flow is low in oxygen, a condition that is usually not present in diesel exhaust gases due to the lean combustion. In the enlarged section in 3 is indicated schematically that the gas flow 2 or the exhaust gas flow pollutants 3 as well as particles 22 includes, which is in the direction of flow 4 through the outlet duct 13 procreate. While in the indicated sub-area, in which there are pollutants 3 and particles 22 have accumulated, a relatively high concentration of oxygen is provided for a catalytic reaction are in the partial volume flow 25 almost no oxygen molecules or a proportion well below 50%, preferably less than 30%. This ensures that this partial volume flow 25 the first catalytic converter 5 flows through, without causing already strongly exothermic reactions there, which could result in damage to the downstream turbocharger.

4 shows schematically and in a perspective view an embodiment of a first catalytic converter 5 such as can be found for example in a pipe of an exhaust manifold. The first catalytic converter 5 includes a housing 31 , in which several metal foils 28 are arranged so that for the gas flow 2 flowable channels 29 are formed. Thus, despite the small volume, there is a relatively large first contact area 17 educated. The tin foils 28 are partly structured and arranged in such a way that channels running essentially parallel to one another are formed. Inside the case 31 a kind of honeycomb body is formed by the fact that smooth and corrugated metal foils 28 first stacked and then S-shaped (or involute-shaped) and wound into the housing 31 be introduced. For fixing the metal foils 28 on the housing 31 or for fastening the metal foils 28 mainly a soldering technique is used with each other.

5 shows schematically and in a perspective view an embodiment of a second catalytic converter 7 and a particle trap 8th that together form a structural unit 19 form. The unit 19 is also characterized by the fact that the second catalytic converter 7 and the particle trap 8th in a common casing tube 34 are arranged. In the variant shown are the second catalytic converter 7 and the particle trap 8th through a body 20 formed of a plurality of metal foils 28 comprises, which are at least partially structured such that channels through which a fluid can flow 29 are formed. This also means, for example, that as such a unit 19 basically specially designed metallic honeycomb bodies can be used, the general design of which is already known.

A distinction is made primarily between two typical designs for metallic honeycomb bodies. An earlier design for which the DE 29 02 776 A1 shows typical examples is the spiral design, in which essentially a smooth and a corrugated sheet metal layer are placed on top of one another and wound in a spiral, as is also the case in 5 is shown. In another design, the honeycomb body is built up from a multiplicity of alternatingly arranged smooth and corrugated or differently corrugated sheet metal layers, the sheet metal layers initially forming one or more stacks which are intertwined with one another. The ends of all sheet metal layers come to the outside and can be connected to a housing or casing tube, which creates numerous connections that increase the durability of the honeycomb body. Typical examples of these designs are in the EP 0 245 737 B1 or WO 90/03220. It has also been known for a long time to provide the sheet metal layers with additional structures in order to influence the flow and / or to achieve cross-mixing between the individual flow channels. Typical examples of such configurations are WO 91/01178, WO 91/01807 and WO 90/08249. Finally, there are also honeycomb bodies in a conical design, possibly also with additional structures for influencing the flow. Such a honeycomb body is described, for example, in WO 97/49905. In addition, it is also known to leave a recess in a honeycomb body for a sensor, in particular for accommodating a lambda probe. An example of this is in the DE 88 16 154 U1 described.

On the gas inlet side, which in 5 Shown on the left is the body 20 a catalytically active coating 21 on. This catalytically active coating 21 in connection with the second contact surface 18 which is partly due to the catalytic coating 21 is formed, ensure an effective implementation of the amounts of reducing agent, generating a thermal energy that the entire body 20 or the exhaust gas contained therein increased significantly, for example to temperatures above 600 ° C. The sheet metal foils shown here 28 are with a thickness 35 provided, which is in the range of 0.02 to 0.11 mm.

6 shows an embodiment of a particle trap 8th , as for example in the in 5 shown unit 19 can be present. The metal foil is corrugated here 36 called because of this corrugated area 36 has additional structures for collecting solid components in the exhaust gas flow. Basically, however, the sheet metal foil 29 at the same time the corrugation 36 his. The arrows are in the 6 the direction of flow 4 and illustrate which flow paths the exhaust gas in the particle 22 are included. At least in the part of the body 20 that the particle trap 8th represents is a fiber layer 37 in the immediate vicinity of the corrugated area 36 arranged the pores 38 has to take up the particles 22 , The corrugated area 36 forms a variety of channels 29 that a free flow through the particle trap 20 makes possible for the exhaust gas (the principle: "open filter") 36 baffles 40 on that at least partially from openings 39 are limited. Through the openings 39 become adjacent channels 29 interconnected so that an exchange of partial gas flows in neighboring channels 29 he is possible. The guiding surfaces 40 form calming points 41 and swirling points 42 that ensure that the particles 22 on the one hand towards the fiber layer 37 can be directed, on the other hand can collect in parts until the regeneration takes place.

The The device described here and the method explained here also allow simple means a safe regeneration of a particle filter with fuel, even if in the flow path the fuel to the particle trap or the one positioned directly in front of it Oxidation catalytic converter further components or exhaust gas cleaning components are positioned. Especially in connection with exhaust systems, the one Having exhaust gas turbochargers, the proposed method is special effectively.

1

exhaust system

2

gas flow

3

pollutant

4

flow direction

5

first catalytic converter

6

mixer

7

second catalytic converter

8th

particulate trap

9

injection

10

fuel

11

combustion chamber

12

Internal combustion engine

13

exhaust port

14

supply

15

Reducing agent reservoir

16

Control unit

17

First contact area

18

Second contact area

19

unit

20

body

21

coating

22

particle

23

reducing agent

24

cylinder

25

Partial volume flow

26

exhaust pipe

27

3-way catalyst

28

metal sheets

29

channel

30

collar

31

casing

32

piston

33

Valve

34

casing pipe

35

thickness

36

Well location

37

fiber layer

38

pore

39

opening

40

baffle

41

calming place

42

Verwirbelungsstelle

43

distance

44

distance

Claims (17)

Exhaust system ( 1 ) for cleaning a gas stream ( 2 ) with pollutants ( 3 ) comprehensive in the direction of flow ( 4 ) of the gas flow ( 2 ) through the exhaust system ( 1 ) at least means for supplying a reducing agent, a first catalytic converter ( 5 ) and a particle trap ( 8th ), at least one further exhaust gas purification component and / or a distance of at least 0.5 meters between the first catalytic converter ( 5 ) and the particle trap ( 8th ) is provided, characterized in that a mixer ( 6 ) and a second catalytic converter ( 7 ) the particle trap ( 8th ) are placed directly in front. Exhaust system ( 1 ) according to claim 1, characterized in that the mixer ( 6 ) is a turbocharger. Exhaust system ( 1 ) according to claim 1 or 2, characterized in that the means for supplying the reducing agent at least one injection nozzle ( 9 ) to provide fuel ( 10 ) in the combustion chamber ( 11 ) a mobile internal combustion engine ( 12 ) is. Exhaust system ( 1 ) according to claim 3, characterized in that the injection nozzle ( 9 ) is arranged so that the fuel ( 10 ) into an outlet duct ( 13 ) of the internal combustion engine ( 12 ) can be initiated. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that at least one separate feed line ( 14 ) into an outlet duct ( 13 ) of the internal combustion engine ( 12 ) and / or the exhaust system ( 1 ) is provided. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the means for supplying a reducing agent with a reducing agent reservoir ( 15 ) and a control unit ( 16 ) are connected so that an intermittent supply of reducing agent can be carried out. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the first catalytic converter ( 5 ) the oxidation of at least one in the gas stream ( 2 ) contained pollutant ( 3 ) promoting first contact surface ( 17 ) Has. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the second catalytic converter ( 7 ) the oxidation of at least one in the gas stream ( 2 ) contained pollutant ( 3 ) promoting second contact surface ( 18 ) Has. Exhaust system ( 1 ) according to one of the preceding claims, characterized in that the second catalytic converter ( 7 ) and the particle trap ( 8th ) one unit ( 9 ) represent. Exhaust system ( 1 ) according to claim 9, characterized in that the second catalytic converter ( 7 ) and the particle trap ( 8th ) with a body through which a fluid can flow ( 20 ) are formed in the direction of flow ( 4 ) first a catalytically active coating ( 21 ) and subsequently means for the attachment of particles ( 22 ) having. Particle trap regeneration process ( 8th ) in exhaust system ( 1 ) is arranged, the exhaust system ( 1 ) in the direction of flow ( 4 ) a gas stream ( 2 ) at least a first catalytic converter ( 5 ), a turbola, a second catalytic converter ( 7 ) and the particle trap ( 8th ) in which a reducing agent ( 23 ) upstream of the turbocharger to carry out a regeneration process for the particle trap ( 8th ) in the exhaust system ( 1 ) is initiated. The method of claim 11, wherein the reducing agent supply intermittent. A method according to claim 11 or 12, wherein the reducing agent supply by means of at least one injection nozzle ( 9 ) takes place, where fuel ( 10 ) into a combustion chamber ( 11 ) a mobile internal combustion engine ( 12 ) is initiated. Method according to Claim 13, in which a subsequent injection of the fuel ( 10 ) in the combustion chamber ( 11 ) takes place so that unburned partial volume flows ( 25 ) of fuel ( 10 ) into an outlet duct ( 13 ) of the internal combustion engine ( 12 ) reach. The method of claim 13 or 14, wherein the internal combustion engine ( 12 ) a plurality of cylinders ( 24 ) each with a combustion chamber ( 23 ) in which the injection of the reducing agent into the cylinders ( 24 ) takes place alternately. Method according to one of Claims 11 to 15, in which the triggering time for an injection of the reducing agent takes place as a function of a detected and / or calculated parameter which determines the functionality of the particle trap ( 8th ) characterized. Method according to one of claims 11 to 16, in which the location of the injection of the reducing agent is selected as a function of a detected and / or calculated parameter which determines the temperature of the gas stream ( 2 ) in a section of the exhaust system ( 1 ) characterized.