CN1813120A - Method for regenerating a particle trap - Google Patents

Abstract

The invention relates to an exhaust system (1) for purifying a gas flow (2) of harmful substances (3), said exhaust system comprising at least means for supplying a reducing agent, a first catalytic converter (5), and a particle trap (8), in the direction of flow (4) of the gas flow (2) through the exhaust system (1). According to the invention, at least one other exhaust purification component is provided and/or there is a distance of at least 0.5 metres between the first catalytic converter (5) and the particle trap (8), and a mixer (6) and a second catalytic converter (7) are positioned directly upstream of the particle trap (8). The invention also relates to a method for regenerating a particle trap (8) arranged in the exhaust system (1), whereby a reducing agent (23) is introduced into the exhaust gas system (1), (only) upstream of the turbocharger (6), for carrying out a regeneration process of the particle trap (8).

Description

Regeneration of the Particulate Filter

technical field

The invention relates to an exhaust gas treatment system for purifying a gas flow of harmful substances, which has a particle trap which can be regenerated discontinuously using a reducing agent. Furthermore, it also relates to a method for regenerating a particle trap.

Background technique

Exhaust systems have been continuously developed in the past due to legal regulations that place ever higher demands on exhaust systems in vehicle construction. In the process, many components are used which fulfill different functions in the exhaust system. For this purpose, for example, starter catalytic converters and pre-turbo catalytic converters (Vorturbo-Katalysators) are known, which have a particularly small volume so that after a cold start of the internal combustion engine the starting temperature required for the catalytic conversion can be reached quickly. Furthermore, electrically heatable catalytic converters are known which likewise make it possible to improve the cold-start behavior of the exhaust system. The task of so-called adsorbers in the exhaust gas system of an internal combustion engine is to adsorb harmful substances contained in the exhaust gas for a certain period of time, wherein the harmful substances are preferably stored until the downstream catalytic converter has reached its operating temperature. Particularly in exhaust systems of diesel engines, particle traps or particle filters are also used which trap black soot particles and/or other solid pollutants contained in the exhaust gas. The trapped particle accumulations can in principle be transformed continuously or discontinuously, for example by supplying them with high thermal energy.

In order to reduce particulate emissions in the exhaust gas, particulate traps consisting of a ceramic matrix are known, in particular in diesel engines. The particle trap has channels so that the exhaust gas to be cleaned can flow into the particle trap. Adjacent channels are closed alternately, so that exhaust gas flows into the channels on the inlet side, passes through at least one ceramic wall, and is discharged again on the outlet side through adjacent channels. Particulate traps of this type are known as "closed" particulate filters. The particle trap can achieve an efficiency of about 95% over the entire range of particle sizes present.

Another type of particle trap is known from the unpublished German patent application DE 10153283, which can withstand high thermal loads and has a significantly lower pressure loss. This document describes a so-called "open" filter system for particulate traps. In such an open system, an alternate closing of the filter channels is dispensed with. The channel walls consist at least partially of a porous or highly porous material. The flow channels of the open filter have deflecting or guiding structures which direct the exhaust gas, together with the particles contained therein, to the region of porous or highly porous material. A particle filter is referred to as open here if it is substantially completely permeable to particles, and even particles that are much larger than the particles that are intended to be filtered out. As a result, such filters cannot become clogged during operation in the event of particle accumulations. A suitable method of measuring the degree of opening of a particle filter is, for example, to detect the largest diameter of spherical particles that can flow through such a filter. In existing applications, especially when spherical particles with a diameter greater than or equal to 0.1 mm, especially spherical particles with a diameter greater than 0.2 mm can still pass through, the filter is open.

Regardless of the type of particle filter used, a reliable and as complete as possible regeneration of the particle filter in the exhaust system of the vehicle must be ensured. Regeneration of such particle traps is necessary, since the increasing accumulation of particles in the walls of the flow-through channels leads to a continuously increasing pressure loss, which has a negative effect on the engine performance. This regeneration essentially involves brief heating of the particle trap or of the particles accumulated therein in order to convert the carbon black particles into gaseous constituents.

Such particle traps have previously been directly heated, for example by means of ohmic resistance heating. It is also known to convert accumulated carbon black particulates using a separate burner. The latter device for regenerating a particle filter is characterized in that a reducing agent is supplied upstream of such a particle trap, said reducing agent finally being able to chemically convert the soot particles accumulated in the particle trap. Here, two different systems are mainly distinguished: discontinuous and continuous regeneration.

A system for continuously regenerating filters is known as CRT (Continuously Regenerating Filters) and is described in US 4,902,487. In such systems the particles are converted at temperatures above 200° C. by means of an oxidation reaction by contact with nitrogen dioxide (NO ₂ ). The nitrogen dioxide required for this is usually generated by an oxidation catalyst arranged upstream of the filter. Here, however, the problem arises, especially with regard to use in motor vehicles using diesel fuel, that only insufficient nitrogen monoxide (NO) is present in the exhaust gas, which can be converted into the desired nitrogen dioxide. So far it has not been possible to ensure continuous regeneration of the particle traps in the exhaust system. Therefore, it is often more common to also supply a reducing agent such as urea to the exhaust system, said reducing agent allowing continuous regeneration of the filter. Disadvantages of such systems are the high technical costs and the fact that separate consumer and operating devices have to be carried in such motor vehicles at the same time.

For discontinuous regeneration of the particle trap, it is known to connect an oxidation catalyst upstream of the particle trap, which is supplied with unsaturated or unburned hydrocarbons (HC). When the unsaturated hydrocarbons come into contact with the oxidation catalyst, a particularly exothermic reaction takes place which significantly increases the temperature of the exhaust gas. Here the temperature is in a range in which the particle aggregates accumulated in the particle trap can be transformed. Here the temperature usually has to reach above 600°C. The reducing agent can be supplied separately, but it is also known to supply the unburned fuel fraction from the internal combustion engine directly into the exhaust gas line so that it reaches the oxidation catalyst.

The wish stated at the outset, namely the catalytic conversion of the exhaust gases immediately after a cold start of the internal combustion engine, can be achieved by using a starter catalytic converter which is characterized by a small volume (for example, smaller than the exhaust gas of the internal combustion engine). 20% of the amount) and located close to the engine. Here, the technical problem arises that the unsaturated hydrocarbons that are intended to regenerate the upstream particle trap, which is arranged at a considerable distance from the starter catalytic converter, cannot be supplied. This propellant, which acts as a reducing agent, reaches the starter catalyst and causes an exothermic reaction. Due to the remote arrangement of the particle trap from the starter catalytic converter or the arrangement of additional components for exhaust gas purification between the starter catalytic converter and the particle trap, the required temperatures cannot be achieved in the particulate trap raised.

Contents of the invention

It is therefore the object of the present invention to eliminate the stated technical problem and in particular to provide an exhaust system and a method for regenerating a particle trap in such a way that even if there is a large gap between the starter catalyst and the particle trap The distance to be traveled by the exhaust gas, or the arrangement of a temperature-sensitive component between the starter catalyst and the particle trap for the conversion of the determined exhaust gas composition, can also ensure a discontinuous regeneration of the particle trap. In addition, such an exhaust gas system should also have a simple structure and regeneration should also be carried out easily.

This object is achieved by an exhaust system having the features of claim 1 and by a method for regenerating a particle trap having the features of claim 11 . Further advantageous configurations are specified in the subclaims. The improvements shown here can also be combined with one another in any reasonable manner.

An exhaust system for purifying a gas flow with pollutants comprises, in the flow direction of the gas flow through the exhaust system, at least a structure for supplying a reducing agent, a first catalytic converter and a particle trap, wherein the first catalytic converter At least one further exhaust gas cleaning component and/or a distance of at least 0.5 meters are arranged to the particle trap. According to the invention, a mixer and a second catalytic converter are installed directly in front of the particle trap.

To illustrate the concepts used here, their meanings will be explained separately below in detail. "Flow direction of the airflow" means the direction that the airflow has from the internal combustion engine towards the exhaust pipe or outlet into the atmosphere. Here, the main airflow direction is meant, ie in particular local turbulences etc. are not taken into account. The arrangement of the devices in the direction of flow through the exhaust system means that the gas flow first comes into contact with the structure for supplying the reducing agent, then with the first catalytic converter and finally with the particle trap. What remains unchanged here is that the gas flow comes into contact with other components of the exhaust gas system, such as further adsorbers, exhaust gas lines, etc., between the individual components. In addition, it should be pointed out that "at least" setting the listed devices also includes that the devices can be arranged sequentially multiple times, directly or indirectly.

"Catalytic converter" refers to a number of known supports for catalytically active materials. Wherein the carrier is mainly made of metal and/or ceramics. For metal catalyst supports, it is known to wind at least partially structured sheets around one another in such a way that channels through which fluid can flow are formed. Metal supports produced by extrusion are also known. In addition, ceramic supports are known whose honeycomb shape is likewise obtained by extrusion and sintering processes. This honeycomb shape has proven to be particularly advantageous, since this provides a particularly large surface area, which enables intimate contact with the air flow.

The term "particulate trap" means both conventional filter systems with alternately closed channels and also the aforementioned "open" filter systems.

The term "exhaust gas purification component" is a generic term for a large number of different components for exhaust gas treatment, in particular honeycomb bodies, water separators, heating elements, silencers, adsorbers, storages, etc.

The "distance" between the first catalytic converter and the particulate trap means in particular the distance between them along the flow path of the gas flow. That is to say, for this purpose the distance along the exhaust gas line connecting the first catalytic converter and the particle trap along the shortest path is determined.

"Mixer" in the sense of the present disclosure describes a device which causes a vortex or a pronounced flow deflection of the partial airflows. In particular, the proportion of deflected sub-flows is above 50%, in particular above 80%, preferably above 95%. It is particularly advantageous here if the partial exhaust gas flows are not deflected essentially parallel to each other, but are at least partially displaced towards each other in order to mix. The mixing element described in DE19938840 is used here as an example of this type of mixing element. It is of course also possible to use all other known mixers, provided they meet the aforementioned criteria.

With regard to the second catalytic converter, it should be pointed out that it is also an exhaust gas treatment component here, like the exhaust gas treatment component described for the first reactor. But the second catalytic converter is not designed as a starter catalytic converter, that is, it is not located near the engine.

With the exhaust system according to the invention, it is possible to use fuel as reducing agent for regenerating the particulate trap, as explained in detail below for the method, wherein the fuel is passed through the first catalytic converter substantially without a complete exothermic reaction . The fuel-gas mixture is then prepared by means of the mixer in such a way that the desired exothermic reaction takes place in the second catalytic converter, which produces the temperature rise necessary to regenerate the particle trap. An essential aspect of the invention is that the fuel necessary for regeneration is guided through the first catalytic converter in a concentrated state in a part of the exhaust gas flow or in a sub-volume flow, so that sufficient fuel is not provided for the majority of the entrained fuel Oxygen necessary for catalytic conversion. Catalyst-promoted reactions therefore occur only in the marginal region of the high-fuel-content partial flow, while the majority of the additionally injected fuel passes through the first catalytic converter unconverted.

The mixer now mixes the fuel-rich partial flow with the rest of the exhaust gas, which is particularly lean, ie rich in oxygen, in particular for diesel engines. As a result of this mixing process, the fuel-rich partial flow dissolves, so that the fuel flows in a finely divided manner together with the exhaust gas flow to the downstream particle filter. In this case, it is not important whether the mixed exhaust gas flow flows through other (non-oxidizing) exhaust gas purification components on the way to the second catalytic converter. The finally mixed exhaust gas flow reaches the second catalytic converter, which also has catalytically active surfaces, where the conversion of exhaust gas-fuel-dispersion now takes place.

Since the second catalytic converter is connected directly (or immediately, ie no further exhaust gas purification components are arranged therebetween) upstream of the particle trap, the temperature increase due to the exothermic reaction is directly conducted to the particle trap. This now ensures a complete regeneration of the particle trap. At the same time, it is particularly advantageous to arrange the second catalytic converter and the particle trap relative to each other in such a way that the exhaust gas can transfer as much energy as possible to the particle trap. This can be ensured, for example, by having only a small distance between the catalytic converter and the particles, in particular less than 10 cm, in particular less than 5 cm, and preferably less than 2 cm. The distance described here describes the travel length of the exhaust gas from the second catalytic converter to the particle trap. It is particularly advantageous if the exhaust gas line between the second catalytic converter and the particle trap is thermally insulated or does not have any additional components, such as flaps, deflectors, detectors, etc., or bends.

According to another embodiment of the invention, the mixer is a vortex booster. In particular, the use of exhaust gas turbochargers for the compression of the intake air has proven itself in new diesel engines operating on the direct injection principle. This compressor for intake air operates with exhaust gas flowing through the turbocharger. The exhaust gas undergoes a strong swirl as it flows through the turbocharger, so that the turbocharger fully meets the criteria stated above for the mixer, ie it is now possible, for example, after the first catalytic converter Only one turbocharger is connected, while the second catalytic converter and particulate filter are connected after the turbocharger. In particular for such an arrangement of the exhaust gas purification component and the turbocharger, the method described below is advantageous because it prevents the build-up of high temperatures in the exhaust gas via the first catalytic converter, which is preferably designed as a starter catalytic converter, This can damage the directly downstream turbocharger. It is thus possible to introduce exhaust gas at a temperature that can be tolerated by the turbocharger and to subsequently heat the exhaust gas by means of the second catalytic converter to a temperature that ensures regeneration of the particle trap.

According to a further embodiment of the exhaust gas system, the means for supplying the reducing agent comprises at least one injection nozzle for supplying fuel to the combustion chamber of the internal combustion engine of the vehicle. This means in particular that only one or more injection nozzles intended for supplying fuel to the internal combustion engine are used for supplying regeneration reducing agent for the particle trap. In other words, at least one injection nozzle injects fuel into the cylinder of the internal combustion engine, the fuel emerges from the cylinder essentially unburned, passes through the first catalytic converter (and possibly also the turbocharger) and finally passes through the The exothermic reaction for fuel conversion occurs due to the contact of the two catalysts. In this way, a particularly simple construction of the exhaust gas system can be achieved, ultimately omitting the use of additional lines or nozzles or the like for introducing the reducing agent.

Furthermore, it is proposed to arrange the injection nozzles in such a way that fuel can be introduced into the exhaust tract of the internal combustion engine. It is clear to the person skilled in the art that other structures must be used for this if necessary. It must be taken into consideration here that the injection nozzles are generally oriented in such a way as to ensure excellent compression and combustion behavior of the fuel-air mixture in the cylinder of the internal combustion engine. In order to ensure that the fuel can reach the exhaust pipe, it is required in some cases to have pistons or valves in predetermined positions.

For example, in order to obtain an easily retrofittable embodiment of the exhaust system, which does not require changes to the cylinders or combustion chambers, it is proposed to provide at least one separate input in or on the exhaust duct of the internal combustion engine and/or the exhaust system pipeline. This means, for example, that an additional line is provided from the fuel supply to the engine and feeds the exhaust gas flow with fuel between the combustion chamber or engine cylinder and the first catalytic converter. It should be noted here that this results in a relatively narrowly defined partial flow with a particularly high fuel concentration. This ensures that the oxygen necessary for the exothermic reaction is removed, while the high-fuel-content part-stream flows through the first catalytic converter and, in some cases, also through subsequent components without significant chemical conversion.

According to another embodiment, it is proposed that the means for supplying reducing agent are connected to a reducing agent store and a control unit, so that an intermittent supply of reducing agent can be realized. A separate container and storage space can be provided for the reducing agent storage, but here the storage can also simply be the fuel tank. The task of the control unit is to adjust or control the opening time and the pressure prevailing as required during the operation of the injection nozzle and other nozzles. This takes place in particular as a function of the piston position or the exhaust valve position of the cylinders of the internal combustion engine.

Furthermore, it is advantageous for the first catalytic converter to have a first contact surface which promotes the oxidation of at least one harmful substance contained in the gas flow. This means that in particular unsaturated hydrocarbons are converted into less harmful components by means of the first catalytic converter. Especially since there is always a special interest of the public in this case, it is proposed that the second catalytic converter also has a second contact surface which promotes the oxidation of at least one pollutant contained in the gas flow. In some cases it is possible here for the first catalytic converter and the second catalytic converter to have the same catalytically active material on or in the contact surfaces. Surprisingly here, with the device proposed here or the method described below it is ensured that the reducing agent passes through the same coating on the one hand, but on the other hand is converted by an exothermic reaction due to the considerable temperature rise of the exhaust gas.

According to yet another embodiment of the exhaust gas system, the second catalytic converter and the particle trap form a structural unit. This means in particular that the second catalytic converter and the particle trap are not only connected to the exhaust gas line surrounding them. This makes it possible, for example, to arrange the second catalytic converter and the particle trap in a common casing which is in contact with the exhaust gas line. However, it is also possible for the second catalytic converter and the particle trap to be connected not only via the periphery, but in some cases also come into contact on the end faces, for example via pins, lamellae or the like. Furthermore, in the case of the structural unit, for example, a heat insulation acting in the circumferential direction can also be provided, so that the exothermic energy generated in the second catalytic converter is almost completely transferred to the particle trap.

According to another advantageous embodiment of the exhaust gas system, the second catalytic converter and the particle trap together form a fluid-permeable body, which firstly has a catalytically active coating in the direction of flow. , and then have structures for accumulating particles. That is to say, for example, that the second catalytic converter and the particle trap are made of the same carrier. In other words, the channel walls, for example usually made of ceramic material and metal plates, extend in the direction of flow over the common overall length of the second catalytic converter and the particle trap. In this way it is not necessary to divide the carrier. However, recesses, deformations, material deposits or the like can be provided in subsections of the body or in the channel walls, so that the sections of the body can correspond to the corresponding functions of the catalytic converter and the particle trap. match. In principle, the carrier or the sections of the body can be distinguished (only or additionally) by different coatings. Here, too, there may be overlapping regions of the section forming the second catalytic converter and the section forming the particle trap.

According to a further aspect of the invention, a method is proposed for regenerating a particle trap arranged in an exhaust gas system, wherein the exhaust gas system (in the flow direction of the gas flow) comprises at least one first catalytic converter , a turbocharger, a second catalytic converter and the particulate trap. Here, a reducing agent is introduced into the exhaust gas system upstream of the turbocharger for the regeneration process of the particle trap. For this purpose, the reducing agent is fed into a partial flow of the exhaust system in a concentrated manner, so that no or only slightly exothermic reactions take place when flowing through the first catalytic converter. The partial flow, which still has a high fuel content, is now guided through the turbocharger, where it is mixed particularly intensively with the exhaust gas partial flow from other cylinders of the internal combustion engine. Since the partial flow from the other cylinders is predominantly a particularly lean (oxygen-rich) mixture, the oxygen concentration of the partial flow, which still has a high fuel ratio, increases. This leads to the desired exothermic reaction when the partial flow subsequently reaches the oxidation catalyst. The heat released here is used to burn off the soot particles accumulated in the downstream particle trap. This prevents blockage of the flow path (the path that the exhaust gas takes through the particle trap), which would lead to an increase in the flow resistance of the particle trap. The resulting reduction in the pressure of the exhaust gas flow at the particle trap has a negative effect on the engine performance, which can be reliably avoided with the method described here.

It is particularly advantageous here that the reducing agent feed takes place intermittently. This is the case in particular when the reducing agent is supplied via at least one injection nozzle, wherein the fuel is introduced into the combustion chamber of the internal combustion engine of the vehicle. This is in particular a diesel engine.

According to a further advantageous embodiment of the method, the post-injection of fuel into the combustion chamber takes place, so that an unburned fractional volume flow of fuel can enter the exhaust tract of the internal combustion engine. Subsequent in this sense means that the injection nozzle injects fuel at two different times during the working cycle of the piston in the cylinder. At the first moment, the amount of fuel required for self-ignition or combustion is injected into the combustion chamber of the cylinder, compressed and combusted. During the upward movement of the piston, the exhaust gases produced during the combustion process are expelled through the open exhaust valve into the exhaust tract and further into the exhaust pipe. At this moment, in particular after the combustion in the combustion chamber is complete, a predeterminable or calculable amount of fuel (or other reducing agent) is introduced into the combustion chamber via the injection nozzle, said fuel being separated from the discharged exhaust gas. The gas flow flows with or after it through this exhaust duct or exhaust pipe.

For internal combustion engines with a plurality of cylinders each having a combustion chamber, it is particularly advantageous to alternately inject reducing agent into the cylinders. On the one hand, this includes one injection of reducing agent in succession to each cylinder, however, it is also possible to skip several individual cylinders, to perform multiple successive injections of reducing agent from the injection nozzles and/or not to The cylinders are injected in a fixed alternating manner. The latter type of injection is used in particular when the injection into the corresponding cylinder is carried out as a function of measured values which reflect the operating state of the internal combustion engine or the exhaust gas system. This ensures, on the one hand, that residual fuel which may still be present in an individual cylinder after the injection of the reducing agent is always reburned. In this way there is uniform combustion in all cylinders.

According to a further variant of the method, the start point of the injection of the reducing agent is determined on the basis of measured and/or calculated parameters describing the functionality of the particle trap. This means that there are no means (sensors, probes, etc.) for monitoring the functionality of the particle trap. Here, the pressure drop of the particle trap, the temperature in the particle trap, the concentration of at least one harmful substance in the exhaust gas after leaving the particle trap etc. are specified by suitable measured values. For example, if the pressure drop reaches a defined limit value, this can be used as an indicator to start a regeneration cycle. Here, in some cases also the duration required for the fuel injected close to the engine to reach the particle trap is taken into account. This has to be done in order to warm up the particle trap before it has a perceptibly negative effect on engine power, for example.

According to a further embodiment of the method, the injection points of the reducing agent are selected as a function of measured and/or calculated parameters which describe the temperature profile of the gas flow in a subregion of the exhaust gas system. This means, for example, that the injection nozzles of a plurality of cylinders are selected as a function of a specific temperature of the air flow or of the exhaust gas system and/or of the internal combustion engine. For example, if a residual fuel quantity remaining in the cylinder subsequently leads to an increased thermal load during the next combustion, it may be advantageous to only perform reducing agent injection via other injection nozzles when a defined limit temperature is reached. In some cases, depending on the design of the gas flow path in the exhaust gas line depending on the injection position, the respectively different areas of the exhaust gas cleaning component can be subjected to an intensified inflow, so that the flow temperature of the exhaust gas in these areas is especially hot. load. Of course, adjustments are also conceivable here to ensure the functionality of the exhaust gas treatment component.

Description of drawings

The present invention will be described in detail below with reference to the accompanying drawings. It should be noted here that the figures show schematically particularly preferred exemplary embodiments, but the invention is not restricted thereto.

in:

Fig. 1 schematically shows the structure of exhaust equipment;

Fig. 2 schematically shows the structure of a direct-injection diesel internal combustion engine;

Figure 3 schematically shows the subsequent injection of reducing agent;

Figure 4 shows an embodiment of a first catalytic converter;

Figure 5 shows an embodiment of a structural unit consisting of a second catalytic converter and a particulate trap; and

FIG. 6 schematically shows a detailed perspective view of the particle trap as shown in FIG. 5 .

Detailed ways

FIG. 1 schematically shows a perspective view of an exhaust system 1 for cleaning a gas flow 2 of pollutants 3 . In flow direction 4 of gas flow 2 , exhaust system 1 comprises at least a first catalytic converter 5 , a mixer 6 , a second catalytic converter 7 and a particle trap 8 . Furthermore, means are provided for supplying the reducing agent, which are arranged only upstream of the mixer 6 . Here in an internal combustion engine 12 , preferably a diesel engine for a passenger vehicle, fuel 10 is injected into the combustion chamber 11 of the individual cylinders 24 . The fuel 10 is combusted with highly compressed intake air and is then exhausted through exhaust duct 26 into the surrounding environment.

In the immediate vicinity of the internal combustion engine 12 , in particular at a distance of less than 70 cm, a plurality of first catalytic converters 5 are arranged, one of each first catalytic converter 5 being integrated in a tube of the exhaust gas manifold. In the embodiment shown, reducing agent 23 is fed into the exhaust gas flow via a separate feed line 14 upstream of mixer 6 designed as a turbocharger. The reducing agent 23 flows through the mixer 6 or the turbocharger and then reaches the second catalytic converter 7 . The second catalytic converter 7 is of conical design and is arranged in the widening of the exhaust gas line 26 . A particle trap 8 is arranged directly adjoining the second catalytic converter at a distance 44 , preferably less than 5 cm. A three-way catalytic converter 27 of known construction is connected downstream of the particle trap. The distance 43 between the first catalytic converter 5 and the particle trap 8 is at least 0.5 meters, preferably even more than 1 meter. In this case, the arrows indicated by 43 are to be understood as only schematic, the actual distance 43 being determined by the flow path of the gas stream 2 from the outlet of the first catalytic converter 5 to the inlet of the particle trap 8 .

FIG. 2 shows the combustion chamber 11 schematically and not to scale, and shows, for example, its use in a direct-injection diesel internal combustion engine. The cylinder 24 includes a piston 32 , wherein the cylinder 24 and the piston 32 at least partially delimit the combustion chamber 11 , also referred to as cylinder displacement. Furthermore, an injection nozzle 9 is arranged in the block of the internal combustion engine 12 , which is connected to a fuel store 15 and also to a control unit 16 . The task of this injection nozzle 9 is to inject, as required, a predefined or predetermined quantity of fuel 10 into the combustion chamber 11 , which is then ignited with the highly compressed intake air. Ignition of the fuel-air mixture expands the gas mixture, through which expansion displaces piston 32 downward. After combustion, the valve 33 is moved upwards and the exhaust gases in the combustion chamber 11 are discharged in the flow direction 4 via the exhaust duct 13 . In the form shown, the exhaust valve 33 is closed, so that the injection nozzle 9 injects the quantity of fuel 10 required for actual combustion or power generation in a finely divided manner.

FIG. 3 shows schematically and in partial view the subsequent injection of fuel as reducing agent. Also shown schematically is cylinder 24 and piston 32 delimiting combustion chamber 1 . In the momentary state shown here, the valve 33 is in a position where the exhaust gas flow from the combustion chamber 11 can flow into the exhaust tract 13 . This is accomplished by the piston 32 moving upwards. The combustion chamber is now injected into the combustion chamber via the injection nozzle 9 with the desired amount of fuel required to restore the particle trap. The fuel 10 is guided as far as possible into the exhaust gas channel 13 in such a way that a "rich layer" is formed. This preferably refers to a sub-volume flow 25 with a particularly high hydrocarbon concentration. There is a high oxygen deficiency in the fractional airflow, a state which is not normally present in diesel exhaust due to insufficient combustion. The enlarged detail in FIG. 3 shows schematically that gas flow 2 or exhaust gas flow contains pollutants 3 and particles 22 , which flow forward in flow direction 4 through exhaust duct 13 . In the subregions shown where the harmful substances 3 and particles 22 accumulate, a relatively high concentration of oxygen is provided for the catalytic reaction, while in the partial volume flow 25 there are hardly any oxygen molecules or the proportion of oxygen molecules is clearly below 50%, preferably below 50%. 30%. This ensures that the partial volume flow 25 passes through the first catalytic converter 5 without causing strong exothermic reactions therein which could damage the downstream turbocharger.

FIG. 4 shows a schematic perspective view of an embodiment of the first catalytic converter 5 , where it is shown as it occurs in a pipe of an exhaust gas manifold. The first catalytic converter 5 comprises a housing 31 in which a plurality of lamellae 28 are arranged in such a way that channels 29 through which the gas flow 2 can flow are formed. This results in a relatively large first contact surface 17 despite its small volume. Said sheets 28 partially form a (surface) structure and are arranged to form channels extending substantially parallel to one another. The smooth and corrugated sheets 28 are first stacked, then S-shaped (or involute) wound and installed in the housing 31 , whereby a kind of honeycomb body is formed inside the housing 31 . Soldering techniques are mainly used to fasten the thin plates 28 to the housing 31 or to fasten the thin plates 28 to one another.

FIG. 5 shows a schematic perspective view of an exemplary embodiment of the second catalytic converter 7 and the particle trap 8 , which together form a structural unit 19 . The structural unit 19 is also characterized in that the second catalytic converter 7 and the particle trap 8 are arranged together in a sleeve 34 . In said variant, the second catalytic converter 7 and the particles 8 are formed by an integral part 20 comprising a plurality of thin plates 28 at least partially structured to form passages 29 through which fluid can flow. . This also means, for example, that in principle a specially designed metal honeycomb body, whose general construction is known, can be used as such structural unit 19 .

Metal honeycombs are mainly divided into two structural forms. A DE 29 02 776 A1 shows a typical example of the previous structural form of the helical structural form, in which mainly a smooth and a corrugated sheet layer is stacked on top of each other and wound helically, as in FIG. 5 as shown. In another configuration, the honeycomb body is formed from a plurality of alternately arranged smooth and corrugated or differently corrugated sheet metal layers, wherein the sheet metal layers first form one or more intertwined stacks. In this case, the ends of all the laminates are located on the outside and can be connected to the shell or sleeve, thereby forming a large number of connections which increase the durability of the honeycomb body. Typical examples of such structural forms are described in EP0245737B1 or WO90/03220. It has also been known for a long time to provide the thin plates with additional structures in order to control the flow and/or to achieve lateral mixing between the individual flow channels. Typical examples of such designs are WO91/01178, WO91/01807 and WO90/08249. Finally, there are also honeycomb bodies in the form of conical structures, optionally with additional structures for controlling the flow. Such a honeycomb body is described, for example, in WO 97/49905. It is also known to provide recesses in the honeycomb body for detectors, in particular for accommodating lambda detectors. An example of this is described in DE8816154 U1.

On the gas inlet side shown on the left in FIG. 5 , the body 20 has a catalytically active coating 21 . The catalytically active coating 21 in combination with the second contact surface 18 partly formed by the catalytic coating 21 ensures an efficient conversion of the reducing agent species, wherein thermal energy is generated which significantly increases the overall body 20 or is located therein. The temperature of the exhaust gas is raised, for example, to a temperature higher than 600 °C. The sheet metal 28 shown here has a thickness 35 in the range of 0.02 to 0.11 mm.

FIG. 6 shows the design of the particle trap 8 , which is, for example, the same as the particle trap in the structural unit 19 shown in FIG. 5 . The sheet metal is here referred to as the corrugated layer 36 because it has an additional structure for trapping solid components in the exhaust gas flow. In principle, however, the sheet metal 29 can also be a corrugated layer 36 at the same time. In FIG. 6 the arrows indicate the flow direction 4 and indicate the flow path through which the exhaust gas containing the particles 22 can travel. At least in the partial region of the body 20 with the particle trap 8 , a fiber layer 37 is arranged directly adjacent to the corrugated layer 36 , said fiber layer having openings 38 for receiving the particles 22 . The corrugated layer 36 forms a plurality of channels 29 which allow the exhaust gas to flow freely through the particle trap 20 (principle: “open filter”). To control the flow, the corrugated layer 36 has guide surfaces 40 at least partially defined by openings 39 . Adjacent channels 29 are communicated with each other via openings 39 , so that the partial flows in adjacent channels 29 can be exchanged. The guide plate 40 forms a stabilizing point 41 and a swirl point 42 which ensure on the one hand that the particles 22 are guided to the fiber layer 37 and on the other hand allow the particles to accumulate in subregions until regeneration takes place.

The device described here or the method described here makes it possible to regenerate the particle filter with fuel in a simple manner, even in the flow path to the particle trap or to an oxidation catalyst directly upstream of the particle trap Other components or exhaust gas purification components are arranged on it. The method is particularly effective in connection with an exhaust gas system with an exhaust gas turbocharger.

List of reference signs 12345678910111213141516171819202122 Exhaust equipment Airflow Harmful substances Airflow direction 1st catalytic converter Mixer 2nd catalytic converter Particulate filter Injection nozzle Fuel Combustion Engine Exhaust pipe Inlet pipe Reductant storage unit Control unit 1st contact surface 2nd contact surface Structural unit body layer particles 23242526272829303132333435363738394041424344 Partial volume of reducing agent cylinder air flow exhaust pipe three-way catalytic converter thin plate passage protruding part housing piston valve bushing thickness corrugated layer fiber layer hole opening guide plate stable position vortex position distance

Claims (17)

1. An exhaust gas installation (1) for purifying an airflow (2) containing harmful substances (3), said exhaust installation along the flow direction (4) of the airflow (2) through said exhaust installation (1) comprising at least The structure for inputting the reducing agent, a first catalytic converter (5) and a particle trap (8), wherein at least A further exhaust gas purification unit and/or a distance of at least 0.5 m, characterized in that a mixer (6) and a second catalytic converter (7) are arranged directly upstream of the particle trap (8). 2. Exhaust gas system (1) according to claim (1), characterized in that the mixer (6) is a swirl intensifier. 3. The exhaust system (1) according to claim 1 or 2, characterized in that the means for supplying reducing agent is at least one for supplying fuel (10) in the combustion chamber (11) of the internal combustion engine (12) of the vehicle ) of the nozzle (9). 4. Exhaust gas system (1) according to claim 3, characterized in that the injection nozzle (9) is arranged such that fuel (10) can be introduced into the exhaust gas line (13) of the internal combustion engine (12). 5. Exhaust gas system (1) according to any one of the preceding claims, characterized in that at least one separate inlet line (14) is arranged to the exhaust gas of the internal combustion engine (12) and/or the exhaust gas system (1) Among the pipelines (13). 6. Exhaust gas system (1) according to any one of the preceding claims, characterized in that the means for supplying reducing agent is connected to a reducing agent storage (15) and to a control unit (16), so that Intermittent reductant input is possible. 7. The exhaust gas system (1) according to any one of the preceding claims, characterized in that the first catalytic converter (5) has a function which promotes the oxidation of at least one harmful substance (3) contained in the gas flow (2) The first contact surface (17). 8. The exhaust gas system (1) according to any one of the preceding claims, characterized in that the second catalytic converter (7) has a function which promotes the oxidation of at least one harmful substance (3) contained in the gas flow (2) The second contact surface (18). 9 . The exhaust system ( 1 ) as claimed in claim 1 , characterized in that the second catalytic converter ( 7 ) and the particle trap ( 8 ) form a structural unit ( 9 ). 10. The exhaust gas system (1) according to claim 9, characterized in that the second catalytic converter (7) and the particle trap (8) are formed by a fluid-permeable body (20), so that In the direction of flow (4), the body firstly has a catalytically active coating (21) and then has structures for accumulating particles (22). 11. Method for regenerating a particle trap (8) arranged in an exhaust gas system (1), wherein the exhaust gas system (1) is in the direction of flow (4) of a gas flow (2) comprises at least a first catalytic converter (5), a turbocharger, a second catalytic converter (7) and the particulate trap (8), in the method, in the turbocharger Upstream of , the reducing agent (23) is introduced into the exhaust system (1) for the regeneration process of the particulate trap (8). 12. The method according to claim 11, characterized in that the input of the reducing agent is performed intermittently. 13. The method as claimed in claim 11 or 12, characterized in that the reducing agent is supplied via at least one injection nozzle (9), wherein the fuel (10) is introduced into the combustion chamber (11) of the internal combustion engine (12) of the vehicle. 14. The method according to claim 13, characterized in that a subsequent injection of the fuel (10) into the combustion chamber (11) causes the unburned fractional volume flow (25) of the fuel (10) to enter the internal combustion engine (12 ) exhaust duct (13). 15. The method according to claim 13 or 14, wherein the internal combustion engine (12) has a plurality of cylinders (24) each having a combustion chamber (23), characterized in that the reducing agent is carried out alternately in the cylinders (24) of the jet. 16. The method according to any one of claims 11 to 15, characterized in that the starting moment of the reducing agent injection is carried out on the basis of measured and/or calculated parameters describing the functionality of the particle trap (8) Sure. 17. The method according to any one of claims 11 to 16, characterized in that, based on the measured and/or calculated description of the temperature of the gas flow (2) in a partial area of the exhaust gas installation (1) parameter to select the injection position of the reducing agent.

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