DE102022000400A1 - Device for exhaust aftertreatment with mass flow control - Google Patents

Abstract

The invention relates to a device for heating the exhaust gases of an internal combustion engine (1) with a pyrolysis reactor (4) into which at least a partial mass flow of the exhaust gas of the internal combustion engine (1) is introduced, the pyrolysis reactor (4) having at least one fleece (14), which is charged with fuel, the fuel evaporating and at least partially reacting exothermally in the pyrolysis reactor (4) with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor (4) by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis, the pyrolysis reactor (4) is arranged in a bypass (3) parallel to a main exhaust line (2) of an internal combustion engine (1), the main exhaust line (2) having a controllable throttle point (5) downstream of a branch to the exhaust gas inlet (11) of the pyrolysis reactor (4). , by means of which the back pressure in the main exhaust line (2) can be regulated. Furthermore, the invention relates to a method for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor.

Description

The invention relates to a device for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor into which at least part of the exhaust gas of the internal combustion engine is introduced, the pyrolysis reactor having at least one fleece which is impinged with fuel, the fuel evaporating and at least partly in the Pyrolysis reactor reacts exothermally with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis.

Furthermore, the invention relates to a method for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor.

Such devices are known from the prior art. From the DE 10 2010 049 957 A1 a device is known by means of which fuel can be broken down into shorter carbon chains by pyrolysis and the exhaust gases can be heated by their subsequent oxidation in order to provide the exhaust gas temperature level required for effective nitrogen oxide reduction during a cold start of the internal combustion engine. Devices of this type are usually arranged in a bypass parallel to the exhaust line of the internal combustion engine, and a partial mass flow of the exhaust gas is routed via the device.

A disadvantage of the known devices is that the entire reaction chamber is first electrically heated in order to heat the catalytic converter located therein to a temperature level from which oxidation of the fuel introduced can take place automatically. This requires a very high electrical power. The very high currents flowing through the honeycomb structure of the catalytic converter can damage the honeycomb structure and the electrical connection of the metal catalytic converter in the reaction chamber.

Another disadvantage of the prior art is that it is not possible or only insufficiently possible to keep the partial mass flow of the exhaust gas, which is passed through the device, constant by means of the throttle valve commonly used in the bypass accommodating the device effective use of the device is required.

Catalysts for selective catalytic reduction (English: selective catalytic reduction, abbreviated: SCR), so-called SCR catalysts, are used to reduce the nitrogen oxide emissions from diesel engines, furnaces, waste incineration plants, industrial plants and the like. For this purpose, a reducing agent is injected into the exhaust system with a dosing device. Ammonia or an ammonia solution or another reducing agent is used as the reducing agent.

Since the carriage of ammonia in vehicles is safety-critical, urea is used in an aqueous solution, usually with a urea content of 32.5%, in particular in accordance with DIN 70070. In the exhaust gas, the urea decomposes at temperatures above 150° Celsius into gaseous ammonia and CO ₂ . The main parameters for the decomposition of the urea are time (evaporation and reaction time), temperature and droplet size of the injected urea solution. In these SCR catalytic converters, the emission of nitrogen oxides is reduced by around 90% through selective catalytic reduction.

The term reducing agent solution or reducing agent includes any reducing agent suitable for selective catalytic reduction; a urea solution according to DIN 70070 is preferably used for this purpose. However, the invention is not limited to this.

In the known exhaust aftertreatment systems for selective catalytic reduction, the relatively low temperatures of the exhaust gases z. B. at a cold start of the combustion engine, i.e. before the operating temperature of the combustion engine is reached, have an unfavorable effect on the functioning of an SCR catalytic converter.

After the urea has been injected into the exhaust system in an aqueous solution, ammonia (NH ₃ ) must first be formed for the SCR reaction. Here, the reducing ammonia is released through the thermal decomposition of urea (thermolysis) and the hydrolysis of the resulting isocyanic acid.

In the first reaction, thermolysis, urea is converted into ammonia (NH ₃ ) and isocyanic acid (HNCO) due to the influence of temperature. In the second step, hydrolysis follows in the presence of water, in which the isocyanic acid is also converted into ammonia with the formation of carbon dioxide (CO ₂ ). Relatively low temperatures, such as when the combustion engine is started cold, can slow down these reactions.

In order to ensure the effectiveness of the selective catalytic reduction in the exhaust system, the temperature level of the exhaust gas must therefore be reduced to a certain level as quickly as possible during a cold start catalyst coating-specific temperature level, for example about 230 ° C, are raised.

The object of the invention is therefore to develop a device for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor in such a way that the disadvantages mentioned are overcome and rapid and effective commissioning of the pyrolysis reactor is made possible with a mass flow of the partial mass flow of the exhaust gas conducted via the pyrolysis reactor that is as constant as possible becomes.

According to the invention, this object is achieved by a device according to claim 1 and a method according to claim 13 . Advantageous developments of the invention are specified in the dependent claims.

Particularly advantageous in the device for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor, into which at least a partial mass flow of the exhaust gas of the internal combustion engine is introduced, the pyrolysis reactor having at least one fleece which is impinged with fuel, the fuel evaporating and at least partially in the pyrolysis reactor reacts exothermally with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis, the pyrolysis reactor is arranged in a bypass parallel to a main exhaust line of an internal combustion engine, with the main exhaust line downstream of a branch to the exhaust gas inlet of the pyrolysis reactor has a controllable throttle point, by means of which the back pressure in the main exhaust line can be controlled.

This controllable throttle point can in particular be an adjustable throttle valve.

By arranging the pyrolysis reactor in a bypass parallel to a main exhaust system of an internal combustion engine, the pyrolysis reactor is thus integrated into an exhaust system of an internal combustion engine. The back pressure in the main exhaust line can be regulated by arranging a throttle point in the main exhaust line downstream of a branch to the exhaust gas inlet of the pyrolysis reactor. This regulation of the counter-pressure in the main exhaust line can thus simultaneously regulate the pressure present at the branch to the exhaust gas inlet of the pyrolysis reactor. The partial mass flow of the exhaust gas of the internal combustion engine conducted via the pyrolysis reactor arranged in the bypass is dependent on the pressure difference between the pressure at the branch to the exhaust gas inlet of the pyrolysis reactor and the pressure at the outlet of the pyrolysis reactor to the main exhaust line. In other words: By controlling the back pressure in the main exhaust line, the partial mass flow of the exhaust gas of the internal combustion engine that is routed via the bypass and thus via the pyrolysis reactor can be adjusted to the desired level and kept constant.

The branch from the exhaust tract to the exhaust gas inlet of the pyrolysis reactor can have guide elements for flow control. The branch to the exhaust gas inlet of the pyrolysis reactor can be aligned in such a way that the flow to the branch or into the bypass takes place in the opposite direction to the main flow direction in the exhaust tract. In particular, a ring plate and/or a pipe bend can be arranged for this purpose, which protrudes into the exhaust tract and opens into the exhaust gas inlet of the pyrolysis reactor.

Alternatively or cumulatively, the heated exhaust gas can be introduced from the pyrolysis reactor back into the exhaust gas section from the bypass with or counter to the main flow direction in the exhaust gas section. The branch from the exhaust tract to the exhaust gas outlet of the pyrolysis reactor can have guide elements for guiding the flow. In particular, a ring plate and/or a pipe bend can be arranged for this purpose, starting from the exhaust gas outlet of the pyrolysis reactor, which projects into the exhaust gas tract and opens into the exhaust gas tract.

The controllable throttle point is preferably an adjustable baffle plate, in particular it can be an adjustable baffle plate with a diaphragm actuator. Furthermore, it can be a magnetically adjustable baffle plate.

With a throttling point using a baffle plate, a force acts on the adjustable baffle plate due to the flow velocity (dynamic pressure) and the dynamic pressure (static pressure). The flapper can be adjusted via a membrane, which can be adjusted by means of negative pressure or positive pressure using compressed air. In particular, the compressed air system that is usually present in a commercial vehicle can be used for this purpose.

The adjustable baffle plate has an exponential function via the stroke/diameter ratio. The force on the flapper over the stroke is not linear. With increasing flow resistance, the force also increases, so that a force-providing or force-regulating actuator counteracts this and can adjust it. This adjustment takes place without delay and thus helps directly to regulate the differential pressure and thus the regulation of the Pyrolysis reactor conducted partial mass flow of the exhaust gas of the internal combustion engine.

Furthermore, the controllable throttle point can be a pipe outlet with an adjustable closing flap, in particular an adjustable closing flap with a servomotor for positioning the closing flap over the pipe outlet.

In the case of a throttle point by means of a closing flap, in which, for example, a pivot axis is arranged on one side of the main exhaust line, a force also acts on the flap due to the flow velocity and the dynamic pressure.

The drive can take place here via a servomotor, by means of which the closing flap is positioned.

In the pressure range required for the pyrolysis reactor, the static pressure is much higher than the dynamic pressure achieved by the flow rate. The static pressure is therefore decisive for the magnitude of the force that counteracts the servomotor. In this case, a drive is preferably chosen that does not output the position, but a controlled force. This means that the correction for changes in the exhaust gas mass flow is immediate and automatic.

The focus here is not on the geometry of the throttle device as a closing cap or baffle plate, but on the fact that the static pressure acts as a counterforce on the actuator and can change its position and an immediate correction is made. As a result, the set mass flow can be kept constant via the bypass. In particular, it is possible to regulate the mass flow to zero via the bypass by regulating the pressure difference across the bypass to zero.

In a preferred embodiment, the device has at least one heating source, by means of which the fuel introduced into the pyrolysis reactor can be at least partially vaporized locally and/or by means of which the exhaust gas mass flow introduced into the pyrolysis reactor can be heated to a temperature above the evaporation temperature of the fuel introduced into the pyrolysis reactor .

For the reduction of nitrogen oxides in exhaust gases from internal combustion engines by means of an exhaust gas aftertreatment system for selective catalytic reduction, the SCR catalytic converter must be brought to a certain temperature level specific to the catalytic converter coating, for example approx good efficiency range works. As a result, nitrogen oxides can be reduced to a large extent and the requirements of strict emission standards can also be met.

The invention enables this temperature level, which is required for an effective selective catalytic reduction of nitrogen oxides, to be reached particularly quickly, since it is no longer necessary, as in the prior art, to heat the pyrolysis reactor completely by applying a high level of electrical power, which is energy-intensive on the one hand on the other hand, takes a considerable amount of time. In contrast, in the case of the invention, by arranging at least one heating source, only the fuel introduced into the pyrolysis reactor is at least partially vaporized locally and/or the exhaust gas mass flow introduced into the pyrolysis reactor is heated to a temperature above the vaporization temperature of the fuel introduced into the pyrolysis reactor. Both options can be used alternatively or cumulatively.

Since the entire pyrolysis reactor no longer has to be heated electrically, the complex and cost-intensive electrical installation and electronics can largely be omitted.

Since the electrical current no longer has to flow through a metallic catalyst in the reaction space for heating, this support for the catalytic coating can also consist of non-metallic material. A ceramic carrier or silicon carbide carrier, for example, is suitable for this. These carriers do not have to be installed in a cost-intensive and complex manner with electrical insulation, but can be fixed in the reaction space more simply and cost-effectively.

Due to the at least partial evaporation of the fuel introduced into the pyrolysis reactor, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor begins and the device thereby continues to heat up automatically.

At least one heating source is preferably an electric glow plug.

In a preferred embodiment, the pyrolysis reactor has a reaction chamber with a catalyst with an oxidation-promoting coating, the glow plug being arranged in such a way that the glow plug can be used to heat the reaction chamber locally to a temperature that is above the coating-specific temperature for the start of oxidation.

The term "coating-specific temperature" for the start of oxidation refers to the temperature that is required in the reaction chamber, depending on the material of the oxidation-promoting coating of the catalytic converter, in order to initiate the oxidation of the fuel introduced.

The glow plug is preferably arranged in such a way that the fleece can be heated locally to a temperature above the evaporation temperature of the fuel introduced by means of the glow plug. In particular, the glow plug can be arranged upstream or downstream of the fleece in the flow direction of the fuel.

This results in local heating of the fleece in the immediate spatial vicinity of the glow plug. At this point of the fleece, the evaporation of the fuel begins and the onset of oxidation in the reaction chamber, which is also locally heated, causes the fleece and the entire pyrolysis reactor to be heated further until automatic evaporation, oxidation and pyrolysis begin without further heating by the heating source required. The power requirement of such a glow plug is very low. The reaction chamber has a catalyst with an oxidation-promoting coating and denotes that part of the pyrolysis reactor in which the oxidation of the fuel takes place and the pyrolysis of the fuel is started and continued in the pyrolysis reactor (chamber).

In a preferred embodiment, at least one heat source is a flame glow plug. Such a flame glow plug can be operated with or without additional combustion air. This means that the flame glow plug can be operated with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor. Alternatively or cumulatively, additional combustion air can be supplied from outside.

At least one heating source is preferably arranged upstream of the pyrolysis reactor in the flow direction of the exhaust gas mass flow; in particular, a flame glow plug can be arranged in the flow direction of the exhaust gas mass flow upstream of the pyrolysis reactor.

The exhaust gas diverted to the pyrolysis reactor is preferably heated by means of a flame glow plug before the exhaust gas mass flow is introduced into the pyrolysis reactor.

The heating of the exhaust gas to a temperature above the vaporization temperature of the fuel thus causes the fuel to vaporize; the subsequent oxidation causes the entire pyrolysis reactor to be heated further until automatic evaporation, oxidation and pyrolysis begins without the exhaust gas being heated any further required by the heating source.

The flame glow plug is preferably arranged in such a way that the exhaust gas mass flow introduced into the pyrolysis reactor can be heated upstream of the pyrolysis reactor to a temperature which is above the evaporation temperature of the fuel introduced into the pyrolysis reactor.

At least one heating source in the form of an electric glow plug, in particular at the fuel inlet of the pyrolysis reactor, and at least one heating source in the form of a flame glow plug, in particular at the exhaust gas inlet of the pyrolysis reactor, can be arranged alternatively or cumulatively.

The pyrolysis reactor preferably has a reaction chamber with a catalyst with an oxidation-promoting coating, the carrier material of the catalyst for oxidizing the fuel being made of an electrically non-conductive material, in particular ceramic or silicon carbide.

The catalyst is particularly preferably fixed in the reaction chamber by means of an expanded mat or by other simple means.

In a preferred embodiment, the pyrolysis reactor has an orifice plate with a plurality of passage bores downstream of the exhaust gas inlet.

This orifice serves to direct the exhaust gas mass flow in the direction of the fleece and to bring about a uniform velocity distribution over the cross section of the pyrolysis reactor.

Particularly preferably, the pyrolysis reactor downstream of the exhaust gas inlet has an orifice plate with a plurality of through-holes, with at least some of the through-holes being followed by a tapering flow channel or a Laval nozzle.

The exhaust gas is accelerated in the direction of the fleece through such nozzles on the bores of the orifice. The nozzles thus serve to direct the exhaust gas mass flow in the direction of the fleece and to accelerate it locally.

On its way to the fleece, the admitted exhaust gas flows through the hot reaction space between the orifice plate and the fleece, absorbing it in the process heat generated by combustion and transports it to the fleece.

The pyrolysis reactor is particularly preferably arranged concentrically to an exhaust line of the internal combustion engine, the exhaust gas inlet to the pyrolysis reactor being formed by a plurality of openings, in particular deep-drawn openings, over the circumference of the exhaust line.

The pyrolysis reactor is preferably arranged concentrically to an exhaust line of the internal combustion engine, the exhaust gas outlet of the pyrolysis reactor being formed by a plurality of openings, in particular deep-drawn openings, over the circumference of the exhaust line.

This plurality of particularly deep-drawn openings, which form the exhaust gas inlet to the pyrolysis reactor and/or the exhaust gas outlet of the pyrolysis reactor, can each be formed in one or more cross-sectional planes along the flow channel of the exhaust line.

By designing these openings in the form of deep-drawn openings over the circumference of the main exhaust line, these openings can be given a geometry that influences the bypass flow in order to form a particularly homogeneous bypass flow and to compensate for the differential pressure of an open throttle device.

In a preferred embodiment, the main exhaust system has an adjustable throttle valve downstream of a branch to the exhaust gas inlet of the pyrolysis reactor, which can be rotated and adjusted from a closed position to an open position parallel to the direction of flow in the exhaust system and beyond.

Preferably, the main exhaust line has an adjustable throttle valve downstream of a branch to the exhaust gas inlet of the pyrolysis reactor, which is positioned in relation to a branch, in particular a plurality of openings, which form/form the exhaust gas inlet to the pyrolysis reactor, such that the branch/openings pass through turning the throttle valve beyond the open position will be in the slipstream of the throttle valve.

In the open position, the throttle valve is aligned parallel to the main flow direction of the exhaust gas in the exhaust tract. By turning the throttle valve further beyond this open position, the throttle valve can be rotated so far that the branch to the exhaust gas inlet of the pyrolysis reactor, in particular several openings to the exhaust gas inlet of the pyrolysis reactor, are in the slipstream of the throttle valve. As a result, the local pressure conditions at the throttle valve in the exhaust tract can be used in an advantageous manner to bring about a pressure equalization over the pyrolysis reactor and thereby regulate the partial mass flow of the exhaust gas flowing through the pyrolysis reactor down to zero.

An oxidation catalytic converter and/or a catalytic converter for the selective catalytic reduction of nitrogen oxides is/are preferably arranged downstream of the pyrolysis reactor in an exhaust system of the internal combustion engine. By means of such an oxidation catalytic converter and/or by means of a catalytic converter for the selective catalytic reduction of nitrogen oxides, the exhaust gas is further treated to reduce pollutants in the exhaust gas, with the upstream pyrolysis reactor raising the temperature level in the exhaust gas, especially in cold start phases, to the level required for an optimal working range of the Oxidation catalyst and / or the catalyst for the selective catalytic reduction of nitrogen oxides takes place.

Particularly advantageous in the method for heating the exhaust gases of an internal combustion engine with a pyrolysis reactor, into which at least a partial mass flow of the exhaust gas of the internal combustion engine is introduced, the pyrolysis reactor having at least one fleece which is impinged with fuel, the fuel evaporating and at least partially in the pyrolysis reactor reacts exothermally with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis, the pyrolysis reactor is arranged in a bypass parallel to a main exhaust line of an internal combustion engine, with the main exhaust line downstream of a branch has a throttle point for the exhaust gas inlet of the pyrolysis reactor, by means of which the back pressure in the main exhaust line is regulated.

By controlling the back pressure in the main exhaust line, the pressure at the exhaust gas inlet to the pyrolysis reactor and thus the resulting partial mass flow of the exhaust gas from the internal combustion engine, which is routed via the pyrolysis reactor, are adjusted at the same time. As a result, this exhaust gas mass flow introduced into the pyrolysis reactor can be kept constant.

Preferably, the fuel introduced into the pyrolysis reactor is at least partially vaporized locally by means of at least one heating source and/or the exhaust gas mass flow introduced into the pyrolysis reactor is reduced to a Temperature heated above the evaporation temperature of the fuel introduced into the pyrolysis reactor.

Due to the at least partial evaporation of the fuel introduced into the pyrolysis reactor, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor begins and the device thereby continues to heat up automatically.

In this case, for example, the fleece and a reaction chamber of the pyrolysis reactor are locally heated by means of a glow plug as the heat source. At this point of the fleece, the evaporation of the fuel begins. Due to the oxidation in the reaction space of the pyrolysis reactor that starts directly at this position, the fleece, the reaction space and the entire pyrolysis reactor are heated further until automatic evaporation, oxidation and pyrolysis start without the need for further heating by the heat source. The power requirement of such a glow plug is very low. The reaction chamber has a catalyst with an oxidation-promoting coating and denotes that part of the pyrolysis reactor in which the oxidation of the fuel takes place and the pyrolysis of the fuel is started and continued in the pyrolysis reactor (chamber).

Alternatively or cumulatively, the exhaust gas is heated to a temperature above the vaporization temperature of the fuel and thus causes the vaporization of the fuel. The oxidation that then begins causes the entire pyrolysis reactor to be heated further until automatic evaporation, oxidation and pyrolysis begins, without the need for further heating of the exhaust gas by the heat source.

The throttle point is preferably formed by a rotatable throttle valve, with the geometric positioning of the throttle valve in relation to the inlet openings of the pyrolysis reactor bringing these inlet openings into their slipstream by rotating the throttle valve beyond the open position of the throttle valve and/or with the geometric positioning of the Throttle valve in relation to the outlet openings of the pyrolysis reactor, these outlet openings are brought into the slipstream by rotating the throttle valve beyond the open position of the throttle valve, in order to bring the differential pressure across the pyrolysis reactor to zero.

In the open position, the throttle valve is aligned parallel to the main flow direction of the exhaust gas in the exhaust tract. By turning the throttle valve further beyond this open position, the throttle valve can be rotated so far that the branch to the exhaust gas inlet of the pyrolysis reactor, in particular several openings to the exhaust gas inlet of the pyrolysis reactor, are in the slipstream of the throttle valve. Alternatively or cumulatively, the outlet openings from the exhaust gas outlet of the pyrolysis reactor can be positioned in such a way that these outlet openings lie in the slipstream of the throttle valve when the throttle valve is twisted beyond the open position.

As a result, the local pressure conditions at the throttle valve in the exhaust tract can be used in an advantageous manner to bring about a pressure equalization over the pyrolysis reactor and thereby regulate the partial mass flow of the exhaust gas flowing through the pyrolysis reactor down to zero.

• 1 Ein Anlagenschema eines Verbrennungsmotors mit Abgasstrang und Komponenten zur Abgasnachbearbeitung;
• 2 eine erste Ausführungsform eines Pyrolysereaktors;
• 3 eine zweite Ausführungsform eines Pyrolysereaktors;
• 4 eine dritte Ausführungsform eines Pyrolysereaktors;
• 5 einen Ausschnitt des Anlagenschemas nach 1;
• 6 eine erste Ausführungsform einer Drosselstelle im Abgasstrang;
• 6a die erste Ausführungsform einer Drosselstelle im Abgasstrang mit alternativ positionierten Abzweigstellen;
• 7 eine zweite Ausführungsform einer Drosselstelle im Abgasstrang;
• 8 eine dritte Ausführungsform einer Drosselstelle im Abgasstrang;
• 9 eine erste Ausführungsform eines konzentrisch zum Abgasstrang angeordneten Pyrolysereaktors;
• 10 eine zweite Ausführungsform eines konzentrisch zum Abgasstrang angeordneten Pyrolysereaktors;

Several exemplary embodiments of the invention are shown in the figures and are explained below. Show it:

• 1 A system diagram of a combustion engine with exhaust system and components for exhaust aftertreatment;
• 2 a first embodiment of a pyrolysis reactor;
• 3 a second embodiment of a pyrolysis reactor;
• 4 a third embodiment of a pyrolysis reactor;
• 5 a section of the system diagram 1 ;
• 6 a first embodiment of a throttle point in the exhaust system;
• 6a the first embodiment of a throttle point in the exhaust line with alternatively positioned branch points;
• 7 a second embodiment of a throttle point in the exhaust system;
• 8th a third embodiment of a throttle point in the exhaust system;
• 9 a first embodiment of a pyrolysis reactor arranged concentrically to the exhaust line;
• 10 a second embodiment of a pyrolysis reactor arranged concentrically to the exhaust line;

In the figures, identical components are marked with identical reference symbols. The illustrations are each schematic.

1 shows a system diagram of an internal combustion engine 1 with an exhaust line 2 and components 4, 6, 7 for exhaust gas post-processing. The exhaust line 2 has a bypass 3 with a pyrolysis reactor 4, via which a partial mass flow of the exhaust gas from the internal combustion engine is conducted. The mode of operation of the pyrolysis reactor 4 is explained below using various exemplary embodiments. Downstream of the branch to the pyrolysis reactor, the exhaust line has an adjustable throttle point 5, by means of which the back pressure in the exhaust line can be regulated and adjusted to a desired level.

Downstream of the bypass 3 with the pyrolysis reactor 4, the exhaust line 2 of the internal combustion engine 1 has an oxidation catalytic converter 6 and an SCR catalytic converter 7 for the selective catalytic reduction of nitrogen oxides. In an alternative that is not shown, the exhaust line also has a diesel particle filter (DPF).

As is known, the relatively low temperatures of the exhaust gases can have an unfavorable effect on the functioning of the SCR catalytic converter 7, e.g.

In order to ensure the effectiveness of the selective catalytic reduction in the exhaust system, the temperature level of the exhaust gas must be raised as quickly as possible during a cold start. For the reduction of nitrogen oxides in exhaust gases from internal combustion engines by means of an exhaust gas aftertreatment system for selective catalytic reduction, the SCR catalytic converter must be brought to a certain temperature level specific to the catalytic converter coating, for example 230°C, and maintained at least at this level during engine operation so that the SCR catalytic converter is in a good efficiency range is working. As a result, nitrogen oxides can be reduced to a large extent and the requirements of strict emission standards can also be met.

For this purpose, a partial mass flow of the exhaust gas of the internal combustion engine 1 is passed via the bypass 3 of the exhaust line 2 via the pyrolysis reactor 4 and is heated in the pyrolysis reactor. The partial mass flow of the exhaust gas heated in the pyrolysis reactor 4 is then introduced back into the exhaust line 2 and mixed with the remaining exhaust gas mass flow. In lean operation with lambda > 1, this partial mass flow from the pyrolysis reactor 4 can contain the exhaust gases of the fuel that has been completely burned (oxidized) therein or, in addition, the pyrolysis products of the fuel portion that has not been burned in it with lambda < 1. First, the oxidation catalytic converter 6 with the complete combustion of the fuel brought to a sufficiently high temperature. Later, the pyrolysis products are then transported at lambda <1 with the remaining exhaust gas mass flow to the oxidation catalytic converter 6 in order to oxidize them there. This sets the required temperature level. Below are several embodiments of such a pyrolysis reactor 4 based on the 2 until 4 explained.

2 shows a section through a pyrolysis reactor 4 in a first embodiment. The pyrolysis reactor 4 has a housing 10 with an input 11 for the supply of oxygen-rich exhaust gas via the in 2 Bypass from the exhaust line to the pyrolysis reactor 4, not shown. Furthermore, the housing has an outlet 12 for discharging the exhaust gas heated in the pyrolysis reactor 4 back into the exhaust line 2 . The pyrolysis reactor 4 with the housing 10 has a rotationally symmetrical structure, as indicated by the radius r.

The housing also has a feed 13 for introducing fuel into the housing 10 of the pyrolysis reactor. A fleece 14, in which the introduced fuel is distributed, is arranged immediately downstream of the fuel supply line in the housing 10.

Directly next to the fleece 14 is an electrically controlled glow plug 15 as a heat source, by means of which the fleece 14 is heated locally during a cold start of the internal combustion engine 1, so that part of the fuel introduced into the pyrolysis reactor 4 evaporates.

When the internal combustion engine 1 is started from cold, only a small central part of the fleece 14 and the reaction space 19 is initially heated by means of the glow plug 15 as the heat source.
This part of the fleece 14 is then filled with a little fuel, which vaporizes at this position and reacts in the reaction chamber 19 with the oxygen in the exhaust gas introduced. There, the heat in the reaction chamber 19 is transported from the inside to the outside over the radius and more fuel can be metered in until the entire reaction chamber 19 and the pyrolysis reactor 4 are heated and the full heating output can be used.

Due to the at least partial evaporation of the fuel introduced into the pyrolysis reactor 4, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor 4 begins and the device thereby continues to heat up automatically.

The glow plug 15 is arranged in such a way that the fleece 14 can be locally heated to a temperature which is above the evaporation temperature of the introduced fuel, the glow plug 15 in the illustrated embodiment 2 is arranged downstream of the fleece in the flow direction of the fuel.

As explained, this results in local heating of the fleece 14 in the immediate vicinity of the glow plug 15. At this point on the fleece 14, the evaporation of the fuel begins and the onset of oxidation in the reaction chamber 19, which is also locally heated, causes the fleece 14 and of the entire pyrolysis reactor 4 until automatic evaporation, oxidation and pyrolysis begins without the need for further heating by the heat source. The power requirement of such a glow plug 15 is very low. The reaction chamber 19 has a catalyst with an oxidation-promoting coating and designates that part of the pyrolysis reactor 4 in which the oxidation of the fuel takes place and the pyrolysis of the fuel is started and continued in the pyrolysis reactor (chamber).

The introduced oxygen-rich exhaust gases flow along the arrows 16 into the space 17 in which the vaporization of the fuel and the orientation of the return flow along the arrows 18 takes place. The oxidation takes place within the reaction space 19 . The exhaust gas heated in this way is then routed back into the exhaust line via the collection chamber 20 and the outlet 12 .

The exhaust gas introduced into the housing 10 via the inlet 11 is first calmed in a calming chamber 21 for pressure equal distribution and then directed and accelerated towards the reaction chamber 19 via a partition 22 with evenly distributed bores. The holes in the partition wall 22 thus result in the targeted generation of locally increased flow velocities in the exhaust gas introduced, in order to increase the pyrolysis reaction speed in the pyrolysis reactor and to increase the quality of the pyrolysis reaction.

At the start of operation, in this exemplary embodiment, a partial area of fleece 14 is locally heated to a temperature above the evaporation temperature of the fuel introduced, as a result of which the oxidation or pyrolysis reactions begin and the entire device continues to be heated automatically.

The second embodiment of a pyrolysis reactor 4 according to 3 has a fundamentally similar structure to that of the first embodiment 2 .

The pyrolysis reactor 4 in turn has a housing 10 with an input 11 for the supply of oxygen-rich exhaust gas via the in 3 Bypass from the exhaust line to the pyrolysis reactor 4, not shown. Furthermore, the housing has an outlet 12 for discharging the exhaust gas heated in the pyrolysis reactor 4 back into the exhaust line 2 . The pyrolysis reactor 4 with the housing 10 has a rotationally symmetrical structure, as indicated by the radius r.

The housing also has a feed 13 for introducing fuel into the housing 10 of the pyrolysis reactor. A fleece 14, in which the introduced fuel is distributed, is arranged immediately downstream of the fuel supply line in the housing 10.

In the second embodiment of the pyrolysis reactor 4 according to 3 a flame glow plug 23 is arranged in the input 11 instead of a glow plug as the heat source. Oxygen-rich exhaust gas from the exhaust line 2 (not shown) is introduced into the pyrolysis reactor 4 via the bypass 3 via the input 11 . The flame glow plug 23 is operated with the same fuel as the internal combustion engine 1 and has a corresponding fuel supply and activation of the flame plug operation.

When the internal combustion engine 1 is started cold, the flame glow plug 23 is used to heat the introduced exhaust gas to a temperature level above the vaporization temperature of the fuel. As a result, the fuel introduced into the pyrolysis reactor 4 evaporates and oxidation begins in the reaction chamber 19, which is also heated.

The fuel introduced is distributed over the fleece 14, evaporates as a result of the heating due to the application of heated exhaust gas and reacts in the pyrolysis reactor 4 with the oxygen in the exhaust gas introduced. There, the heat in the pyrolysis reactor 4 is transported from the inside to the outside over the radius and more fuel can be metered in turn until the entire pyrolysis reactor 4 is heated and the full heating capacity can be used.

Due to the evaporation of the fuel introduced into the pyrolysis reactor 4, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor 4 begins and the device thereby continues to heat up automatically.

In contrast to the first embodiment according to 2 is in accordance with the second embodiment of a pyrolysis reactor 4 3 instead of a glow plug 15 ( 2 ) A flame glow plug 23 is arranged in the input 11 as a heat source.

The introduced oxygen-rich exhaust gases flow along the arrows 16 into the space 17 in which the vaporization of the fuel and the orientation of the return flow along the arrows 18 takes place. The oxidation takes place within the reaction space 19 . The exhaust gas heated in this way is then routed back into the exhaust line via the collection chamber 20 and the outlet 12 .

The special feature of this embodiment according to 3 is the flame glow plug 23, which is only heated by the internal glow plug. Then fuel is supplied to the flame glow plug 23 via a line, not shown here, and the inflowing, oxygen-rich exhaust gas is heated with high power. Here, compared to the previously explained embodiment 2 the entire pyrolysis reactor 4 is heated directly with the glow plug 15 . If the pyrolysis reactor 4 is heated, a large amount of fuel can be metered into the fleece 14 immediately, so that the full heat output is available.

The exhaust gas introduced into the housing 10 via the inlet 11 is in turn first settled in a calming chamber 21 for pressure equal distribution and then directed and accelerated in the direction of the reaction chamber 19 via a partition wall 22 with evenly distributed bores. The holes in the partition 22 thus result in the targeted generation of locally increased flow velocities in the introduced exhaust gas in order to convey the oxygen-rich exhaust gas to the fleece 14, at least as far as the reaction chamber 19, so that there is always enough oxygen for oxidation. This ensures a sufficiently high temperature to increase the quality of the pyrolysis reaction.

At the beginning of the operation is thus carried out in accordance with this embodiment 3 heating of the exhaust gas introduced via the input 11 by means of the flame glow plug 23 to a temperature which is above the evaporation temperature of the introduced fuel, as a result of which the oxidation begins in the reaction chamber 19 and the entire device is automatically further heated.

At the in 4 In the illustrated third exemplary embodiment of a pyrolysis reactor 4, both the electric glow plug 15 for local heating of the fleece 14 and the flame glow plug 23 are arranged cumulatively in the inlet 11 for heating the introduced exhaust gas. The basic structure of the pyrolysis reactor according to the third embodiment 4 again has basically the same structure as the previously explained exemplary embodiments.

The pyrolysis reactor 4 has a housing 10 with an input 11 for the supply of oxygen-rich exhaust gas via the in 4 Bypass from the exhaust line to the pyrolysis reactor 4, not shown. Furthermore, the housing has an outlet 12 for discharging the exhaust gas heated in the pyrolysis reactor 4 back into the exhaust line 2 . The pyrolysis reactor 4 with the housing 10 has a rotationally symmetrical structure, as indicated by the radius r.

The housing also has a feed 13 for introducing fuel into the housing 10 of the pyrolysis reactor. A fleece 14, in which the introduced fuel is distributed, is arranged immediately downstream of the fuel supply line in the housing 10.

Directly next to the fleece 14 is an electrically controlled glow plug 15 as a heat source, by means of which the fleece 14 is heated locally during a cold start of the internal combustion engine 1, so that part of the fuel introduced into the pyrolysis reactor 4 evaporates.

When the internal combustion engine 1 is started from cold, only a small central part of the fleece 14 and the reaction space 19 is initially heated by means of the glow plug 15 as the heat source. This part of the fleece 14 is then filled with a little fuel, which vaporizes at this position and reacts in the reaction chamber 19 with the oxygen in the exhaust gas introduced. There, the heat in the reaction chamber 19 is transported from the inside to the outside over the radius and more fuel can be dosed until the reaction chamber 19 and also the entire pyrolysis reactor 4 is heated and the full heating capacity can be used.

Due to the at least partial evaporation of the fuel introduced into the pyrolysis reactor 4, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor 4 begins and the device thereby continues to heat up automatically.

The glow plug 15 is arranged in such a way that the fleece 14 can be heated locally to a temperature which is above the evaporation temperature of the introduced fuel by means of the glow plug 15, the glow plug 15 in the exemplary embodiment shown 4 is arranged downstream of the fleece in the flow direction of the fuel.

As explained, this results in local heating of the fleece 14 in the immediate vicinity of the glow plug 15. At this point on the fleece 14, the evaporation of the fuel begins and the onset of oxidation causes further heating of the fleece 14 and the entire pyrolysis reactor 4 until a self-evaporation, oxidation and pyrolysis without the need for further heating by the heat source. The power requirement of such a glow plug 15 is very low.

The introduced oxygen-rich exhaust gases flow along the arrows 16 into the space 17 in which the vaporization of the fuel and the orientation of the return flow along the arrows 18 takes place. The oxidation takes place within the reaction space 19 . The exhaust gas heated in this way is then routed back into the exhaust line via the collection chamber 20 and the outlet 12 .

The rapid onset of oxidation after a cold start is supported by heating the introduced exhaust gas using the flame glow plug 23 in inlet 11.

Oxygen-rich exhaust gas from the exhaust line 2 (not shown) is introduced into the pyrolysis reactor 4 via the bypass 3 via the input 11 . The flame glow plug 23 is operated with the same fuel as the internal combustion engine 1 and has a corresponding fuel supply line and control of the flame plug operation, not shown here.

When the internal combustion engine 1 is started cold, the flame glow plug 23 is used to heat the introduced exhaust gas to a temperature level above the vaporization temperature of the fuel. As a result, the fuel introduced into the pyrolysis reactor 4 evaporates more quickly and oxidation begins in the reaction chamber 19, which is also heated.

The introduced fuel is distributed over the fleece 14, evaporates much more quickly as a result of the heating due to the application of heated exhaust gas and reacts in the pyrolysis reactor 4 with the oxygen in the introduced exhaust gas. There, the heat in the pyrolysis reactor 4 is transported from the inside to the outside over the radius and more fuel can be metered in turn until the entire pyrolysis reactor 4 is heated and the full heating capacity can be used.

The simultaneous local heating of the fleece 14 by means of the glow plug 15 and the heating of the introduced exhaust gas by means of the flame glow plug 23 result in faster evaporation of the fuel introduced into the pyrolysis reactor 4 and thus an even faster onset of oxidation of the fuel with the oxygen content of the Pyrolysis reactor 4 introduced exhaust gas mass flow at a cold start. After the onset of oxidation in the reaction chamber 19, the device continues to heat up automatically.

The exhaust gas introduced into the housing 10 via the inlet 11 is first calmed in a calming chamber 21 for pressure equal distribution and then directed and accelerated towards the reaction chamber 19 via a partition 22 with evenly distributed bores. The holes in the partition 22 thus result in the targeted generation of locally increased flow velocities in the introduced exhaust gas in order to convey the oxygen-rich exhaust gas to the fleece 14, at least as far as the reaction chamber 19, so that there is always enough oxygen for oxidation. This ensures a sufficiently high temperature to increase the quality of the pyrolysis reaction.

Downstream of the bores in the dividing wall are tapered nozzles 24 for further accelerating the flow of the exhaust gas in the direction of the reaction space 19 .

The small nozzles 24 of the partition wall 22 are particularly advantageous here. Due to the reduced contact with the return flow, a lower flow rate at the nozzle outlet can be used here without reducing the flow rate through the catalytic converter.

Since the flow rate is largely dependent on the differential pressure across the nozzles 24, the pressure in front of the partition wall can be reduced. The maximum required exhaust gas mass flow through the pyrolysis reactor 4 is thus achieved with a lower pressure. As a result, the exhaust gas pressure required at the inlet 11 in front of the pyrolysis reactor 4 is reduced, which means that the entire exhaust gas back pressure opposing the engine is reduced. This results in fuel savings. This is independent of whether a glow plug 15, flame glow plug 23 or a combination of different heat sources is used.

Deviating from the exemplary embodiments explained, the heat sources can be arranged in the form of one or more glow plugs 15 and/or one or more flame glow plugs 23 or other heat sources at other suitable points of the pyrolysis reactor 4 .

At the beginning, the pyrolysis reactor 4 is operated lean in the cold start phase, ie without excess fuel. After reaching the coating spe zific temperature for the oxidation with a high degree of conversion of the pyrolysis products in the oxidation catalytic converter 6 can and is ramped up to rich operation in the pyrolysis reactor 4 . After reaching the temperature level of the SCR catalytic converter 7 required for an effective catalytic reduction of nitrogen oxides, the operation of the pyrolysis reactor 4 is repeatedly switched between rich and lean operation in order to keep the temperature in the SCR catalytic converter 7 at the required temperature level for an effective catalytic reduction to keep from nitrogen oxides. That is, there is always a transition from rich to lean operation, ie operation with high excess air.

In order to avoid overheating in the pyrolysis reactor 4 when switching from rich to lean operation, the combustion output must approximately correspond to the heat-dissipating output of the gas not involved in the combustion, so that the temperature does not rise any further.

Since there is an excess of fuel in fleece 14, it is not enough to simply turn off the fuel supply, because then, coming from rich operation, the stoichiometric range with lambda=1 is slowly reached and the cooling effect of evaporation and its further vapor heating is missing for cooling still the same power of combustion.

Sending more exhaust gas through the pyrolysis reactor 4 also means more oxygen, and the heat output is correspondingly higher, which leads to an increase in temperature.

A safe method is therefore to stop the fuel supply and reduce the oxygen content to such an extent that the combustion performance is kept below the performance via heat loss through radiation and conduction. This prevents an increase in temperature. This is achieved in that the back pressure in the exhaust line 2 downstream of the branch to the bypass 3 is adjusted by means of the throttle point 5 such that the pressure difference across the pyrolysis reactor 4 is zero or almost zero. As a result of the pressure difference across the pyrolysis reactor 4 being zero or almost zero, the exhaust gas flow across the pyrolysis reactor 4 collapses. This means that no more oxygen-rich exhaust gas is introduced into the pyrolysis reactor 4 . As a result, pyrolysis of the remaining fuel ends and heat release ends.

It is irrelevant in which direction the small gas volume flow flows through the pyrolysis reactor 4, it can also be backwards. Because now the fuel is almost only vaporized and where the combustible fuel vapor is conveyed out at the pyrolysis reactor4, i.e. via the inlet 11 or the outlet 12, is irrelevant, because both sides lead the fuel vapor with the other engine exhaust gas to the downstream oxidation catalytic converter 6, which is in the rich operation of the pyrolysis reactor 4 with excess fuel has oxidized the fuel vapor or the combustible gas of the pyrolysis all the time. The downstream oxidation catalytic converter 6 was already at a sufficiently high temperature before the rich/lean changeover of the pyrolysis reactor 4 in order to convert all unburned components in the exhaust gas.

5 shows a section of the system diagram 1 . A section of the exhaust line 2 with the bypass 3 , which accommodates the pyrolysis reactor 4 , is shown enlarged. The partial mass flow of the exhaust gas conducted via the pyrolysis reactor 4 is introduced via the inlet 11 into the pyrolysis reactor 4 and via the outlet 12 further into the inlet chamber 27 of the exhaust gas aftertreatment system. The main line of the exhaust system 2 also opens out via the throttle point 5 into the inlet chamber 27 of the exhaust gas aftertreatment system. In the inlet chamber 27 of the exhaust gas aftertreatment system, the partial mass flow of the exhaust gas heated by means of the pyrolysis reactor 4 is mixed with the main mass flow of the exhaust gas. Then, as indicated by the arrow 28, the exhaust gas is passed on to the oxidation catalytic converter 6 arranged downstream in the exhaust line 2 and to the SCR catalytic converter 7.

In order to reduce the oxygen supply to the pyrolysis reactor 4 when switching over from rich to lean operation of the pyrolysis reactor 4, as explained above, the back pressure in the exhaust system 2 is adjusted so that the pressure difference across the pyrolysis reactor 4 is zero or almost zero.

To this end, it is helpful or even necessary to make it more difficult for the gas to enter the bypass 3 into the inlet 11, shown here with the baffle plate 40. This baffle plate 40 can also be designed as a pipe bend. The direction of flow, shown with the arrow 41 at the inlet 11, is therefore opposite to the exhaust gas flow in the exhaust line 2. The same applies to the gas outlet 12. This is to be positioned, shown with the pipe bend 42, so that the gas outlet 12 is subject to the flow from the open Throttle point coming, here flap 5, is directed in the opposite direction, shown by the arrow 43. This arrangement generates 4 small differential pressures at the entry point and exit point of the pyrolysis reactor, which approximately correspond to the pressure drop across the open flap 5, but in the opposite direction. There is therefore no or hardly any differential pressure directly on the pyrolysis reactor 4 and the exhaust gas flow through it is almost zero.

For this purpose, the back pressure in the exhaust line 2 is controlled by means of the throttle point 5 with an actuator 25 via the actuator 26 and adjusted accordingly.

In the following 6 , 7 and 8th and their descriptions, these detailed illustrations and descriptions of items 40 to 43 are omitted to improve clarity. This does not mean that their positive effects and functions are dispensed with there.

In the 6 until 8th Various embodiments of such actuators 25 and actuators 26 are shown and explained below.

In the embodiment according to 6 the throttle point 5 is formed by a throttle flap 29 which can be adjusted by means of a servomotor 30 . In 6 two different positions of the throttle valve 29 are shown.

In the case of the throttle valve 29, the angle is fixed by the drive 30 and the adjustment angle is not influenced by the flow or the pressure drop. The throttle valve 29 has a very exponential function over the setting angle. Regulating the differential pressure across the throttle valve 29 is correspondingly difficult, since both the flat part and the steep part of the flow resistance must be used for both the different exhaust gas mass flows and different differential pressure target values.

An adjustable baffle plate or an adjustable flap at a pipe outlet has a significantly more advantageous profile of the pressure drop over the adjustment path of the actuator compared to such a throttle flap 29 .

In the embodiment of 6a the flap position is rotated beyond the direction of flow to obtain some negative pressure at inlet 11 and some positive pressure at outlet 12. The guide sheets 40 and 42 are optional. They are only necessary if the pressure drop across the open flap 29 cannot be compensated by simply turning the throttle valve 29 further, so that the differential pressure at the pyrolysis reactor 4 drops to zero. There is no oxygen supply here. In this exemplary embodiment, the pyrolysis reactor 4 is located to the side next to the exhaust line 2.

At the in 7 illustrated embodiment of an actuator of a throttle 5 downstream of the bypass 3 in the exhaust line 2, the actuator is formed by an adjustable baffle plate 31 at a pipe outlet. The baffle plate 31 is actuated by means of the diaphragm actuator 32. The diaphragm actuator 32 is actuated by controlling the positive pressure p+ at a constant negative pressure p- on the other side of the diaphragm and acts directly on the baffle plate. To regulate the overpressure p+ of the diaphragm actuator, it is coupled to a compressed air supply, which is usually present in commercial vehicles. Impact plate 31 and membrane actuator 32 are directly kinematically coupled.

In the case of this throttle point by means of a baffle plate 31, a force acts on the adjustable baffle plate as a result of the flow velocity (dynamic pressure) and the back pressure (static pressure).

The baffle plate 31 also has an exponential function via the stroke/diameter ratio h/d. However, the force on the impact plate 31 is not linear over the stroke h either. With increasing flow resistance, the force also increases, so that a force-providing/force-regulating actuator counteracts this and can adjust it. This adjustment takes place without delay and thus helps directly to regulate the differential pressure.

In an alternative that is not shown, the adjustment of the baffle plate 31 takes place magnetically by means of an electromagnet.

At the in 8th illustrated further embodiment of an actuator of a throttle 5 downstream of the bypass 3 in the exhaust line 2, the actuator is formed by an adjustable flap 33 at a pipe outlet.

In the case of a throttling point by means of a flap 33, with the pivot axis of the flap 33 being arranged on one side, a force also acts on the flap 33 due to the flow velocity and the dynamic pressure. The drive takes place here via a servomotor 34, which applies a certain force to bring the flap 33 into position.

In the pressure range required for the pyrolysis reactor 4, the static pressure is much higher than the dynamic pressure achieved by the flow rate. The static pressure is therefore decisive for the magnitude of the force that counteracts the servomotor 34 . Therefore, a drive was chosen that does not output the position, but a controlled force. This means that the correction for changes in the exhaust gas mass flow is immediate and automatic.

The focus here is not on the geometry of the throttle device as a flap or baffle plate, but on the fact that the static pressure exerts a counterforce on the actuator and can change its position, and this positioning is corrected immediately.

the 9 shows a first embodiment of a pyrolysis reactor 4 arranged concentrically to the exhaust line. The housing 10 of the pyrolysis reactor 4 is formed by a sleeve arranged concentrically to the exhaust line 2 . The input 11, via which a partial mass flow of the exhaust gas is conducted to the pyrolysis reactor 4, is formed by deep-drawn holes over the circumference of the exhaust line 2. The deep-drawn holes forming the entrance 11 indicate those with the positions 40 and 41 5 functions shown. The deep-drawn holes forming the outlet 12 indicate those with the positions 42 and 43 5 functions shown.

The entry takes place in the slipstream against the direction of flow in the exhaust line 2. The exit also occurs against the direction of flow in the exhaust line 2. This arrangement allows a pressure equalization via the inlet 11 and the outlet 12 of the pyrolysis reactor 4 by means of the downstream of the inlet 11 in the exhaust line 2 arranged throttle point 5 to regulate the differential pressure at the pyrolysis reactor 4 to almost zero, i.e. to drive down the oxygen supply to the pyrolysis reactor when switching from rich to lean operation, as explained above. In the exemplary embodiment shown, the throttle point 5 is formed by an adjustable throttle valve in the exhaust line 2 .

The partial mass flow of the exhaust gas diverted to the pyrolysis reactor 4 is heated by the flame glow plug 23 . The screen 22 is arranged concentrically to the exhaust line 2 . The reaction space 19 is arranged concentrically to the exhaust line 2 . A fleece 14 is also arranged concentrically between the concentric housing 10 of the pyrolysis reactor 4 and the reaction chamber 19 arranged concentrically to the exhaust line 2 , and is charged with fuel via the fuel supply line 13 .

The reaction chamber 19 has a honeycomb catalyst with pressed-in channel crossings, it being possible for a fleece to be arranged between the jacket layers in order to catch droplets.

When the internal combustion engine 1 is started cold, the flame glow plug 23 is used to heat the introduced exhaust gas to a temperature level above the vaporization temperature of the fuel. As a result, the fuel introduced into the pyrolysis reactor 4 vaporizes and oxidation starts.

The fuel introduced is distributed over the fleece 14, evaporates as a result of the heating due to the application of heated exhaust gas and reacts in the pyrolysis reactor 4 with the oxygen in the exhaust gas introduced. Due to the evaporation of the fuel introduced into the pyrolysis reactor 4, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor 4 begins and the device thereby continues to heat up automatically.

The exhaust gas heated by means of the pyrolysis reactor 4 is introduced back into the exhaust line 2 via a plurality of deep-drawn holes which are arranged in several axial planes and form the outlet 12 . The stamped holes forming the outlet 12 are opposite in orientation with respect to the stamped holes forming the inlet 11 . This orientation supports near-zero pressure equalization across pyrolysis reactor 4.

In the 10 The illustrated second embodiment of a pyrolysis reactor 4 arranged concentrically to the exhaust line has a basically identical structure. The housing 10 of the pyrolysis reactor 4 is formed by a sleeve arranged concentrically with the exhaust line 2 . The input 11, via which a partial mass flow of the exhaust gas is conducted to the pyrolysis reactor 4, is formed by deep-drawn holes on the circumference of the exhaust line 2. The deep-drawn holes forming the entrance 11 lie in a plane above the circumference of the exhaust line 2 and, in contrast to the embodiment according to FIG 9 only arranged in the upper storage area of the downstream throttle valve. The axis of rotation of the throttle valve is arranged directly downstream of the openings 11 .

The entry takes place in the lee against the direction of flow in the exhaust system 2. This arrangement allows pressure equalization across the inlet 11 and the outlet 12 of the pyrolysis reactor 4 by means of the throttle point 5 arranged downstream of the inlet 11 in the exhaust system 2 in order to increase the oxygen supply to the pyrolysis reactor to ramp down when switching from rich to lean operation. In the illustrated embodiment according to 10 the throttle point 5 is in turn formed by an adjustable throttle flap in the exhaust line 2 .

It is advantageous here that the throttle valve of the throttle point 5 can not only be aligned with the flow, i.e. fully opened, but can also be rotated further, as is the case with the dashed position of the throttle valve in 10 is shown. This means that most of the entry holes in the slipstream of the Dros brought sellapp and thereby learns the entrance 11 a controllable negative pressure. With this geometric arrangement of the inlet holes, throttle valve and the rotatability of the throttle valve, the differential pressure across the pyrolysis reactor 4 can be controlled from the positive to the negative range. This transition through zero allows the exhaust gas mass flow and thus the oxygen supply to the reaction chamber 19 to be regulated to zero.

The partial mass flow of the exhaust gas diverted to the pyrolysis reactor 4 is heated by the flame glow plug 23 . The screen 22 is arranged concentrically to the exhaust line 2 . The reaction space 19 is arranged concentrically to the exhaust line 2 . A fleece 14 is also arranged concentrically between the concentric housing 10 of the pyrolysis reactor 4 and the reaction chamber 19 arranged concentrically to the exhaust line 2 , and is charged with fuel via the fuel supply line 13 .

The reaction chamber 19 has a honeycomb catalyst with pressed-in channel crossings, it being possible for a fleece to be arranged between the jacket layers in order to catch droplets.

When the internal combustion engine 1 is started cold, the flame glow plug 23 is used to heat the introduced exhaust gas to a temperature level above the vaporization temperature of the fuel. As a result, the fuel introduced into the pyrolysis reactor 4 vaporizes and oxidation starts.

The fuel introduced is distributed over the fleece 14, evaporates as a result of the heating due to the application of heated exhaust gas and reacts in the pyrolysis reactor 4 with the oxygen in the exhaust gas introduced. Due to the evaporation of the fuel introduced into the pyrolysis reactor 4, the oxidation of the fuel with the oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor 4 begins and the device thereby continues to heat up automatically.

The exhaust gas heated by means of the pyrolysis reactor 4 is introduced back into the exhaust line 2 via a plurality of deep-drawn holes which are arranged in several axial planes and form the outlet 12 . The deep-drawn holes forming the outlet 12 are in turn oppositely oriented in their orientation in relation to the deep-drawn holes forming the inlet 11 . This orientation supports near-zero pressure equalization across pyrolysis reactor 4.

Through the two embodiments according to 9 and 10 a system is thus realized which has a particularly simple structure and can easily be integrated into the pipeline of the exhaust system 2 in front of a complex exhaust system. By positioning the inlet holes forming the inlet 11 with a deep-drawn trough shape, the positioning of the throttle point and the oppositely directed trough shape of the outlet holes forming the outlet 12, the differential pressure across the pyrolysis reactor 4 can be brought to zero when the throttle valve is fully open or beyond, so that no Partial mass flow of the exhaust gas is passed more over the pyrolysis reactor 4 when the throttle valve is fully open or beyond. Thus, at the moment of switching from rich to lean operation, no more oxygen is introduced and overheating is avoided.

By appropriately positioning the inlet 11 and the outlet 12 relative to the throttle valve 29, the local pressure conditions at the throttle valve 29 can be used in an advantageous manner. The guide elements 40, 42, which can be used optionally, are helpful here for guiding the flow. It is particularly advantageous that an overall inexpensive arrangement can also be selected since, as a result of the utilization of the local pressure conditions, it is no longer absolutely necessary for the throttle valve 29 to seal precisely in the closed position. By arranging the pyrolysis reactor 4 to the side of the exhaust tract 2 instead of the previously used arrangement on the exhaust tract, the installation space required is significantly reduced.

QUOTES INCLUDED IN DESCRIPTION

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

Patent Literature Cited

• DE 102010049957 A1 [0003]

Claims (15)

Device for heating the exhaust gases of an internal combustion engine (1) with a pyrolysis reactor (4) into which at least a partial mass flow of the exhaust gas of the internal combustion engine (1) is introduced, the pyrolysis reactor (4) having at least one fleece (14) which is charged with fuel is evaporated and at least partially reacts exothermally in the pyrolysis reactor (4) with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor (4) by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis, characterized in that the pyrolysis reactor ( 4) is arranged in a bypass (3) parallel to a main exhaust line (2) of an internal combustion engine (1), the main exhaust line (2) having a controllable throttle point (5) downstream of a branch to the exhaust gas inlet (11) of the pyrolysis reactor (4), by means of which the back pressure in the main exhaust line (2) can be regulated. device after claim 1 , characterized in that the controllable throttle point (5) is an adjustable baffle plate (31), in particular an adjustable baffle plate (31) with a diaphragm actuator (32) and/or a magnetically adjustable baffle plate (31). device after claim 1 , characterized in that the controllable throttle point (5) is a pipe outlet with an adjustable closing flap (33), in particular an adjustable closing flap (33) with a servomotor (34). Device according to one of the preceding claims, characterized in that the device has at least one heating source, by means of which the fuel introduced into the pyrolysis reactor (4) can be vaporized at least partially locally and/or by means of which the exhaust gas mass flow introduced into the pyrolysis reactor (4) can be Temperature can be heated above the vaporization temperature of the fuel introduced into the pyrolysis reactor (4). device after claim 4 , characterized in that at least one heating source is an electric glow plug (15), in particular that the pyrolysis reactor (4) has a reaction chamber (19) with a catalyst with an oxidation-promoting coating, the glow plug (15) being arranged in such a way that by means of the glow plug (15) the reaction chamber (19) can be heated locally to a temperature which is above the coating-specific temperature for the start of oxidation. device after claim 4 or 5 , characterized in that at least one heating source is an electric glow plug (15), the glow plug (15) being arranged in such a way that the fleece (14) can be heated locally to a temperature by means of the glow plug (15), which is above the evaporation temperature of the fuel introduced, in particular that the glow plug (15) is arranged upstream or downstream of the fleece (14) in the flow direction of the fuel. Device according to one of the preceding claims, characterized in that at least one heating source is arranged upstream of the pyrolysis reactor (4) in the flow direction of the exhaust gas mass flow, in particular that a flame glow plug (23) is arranged in the flow direction of the exhaust gas mass flow upstream of the pyrolysis reactor (4). Device according to one of the preceding claims, characterized in that the pyrolysis reactor (4) has an orifice plate (22) with a plurality of passage bores downstream of the exhaust gas inlet (11). Device according to one of the preceding claims, characterized in that the pyrolysis reactor (4) is arranged concentrically to an exhaust line (2) of the internal combustion engine (1), the exhaust gas inlet (11) to the pyrolysis reactor (4) through a plurality of openings, in particular deep-drawn openings, is formed over the circumference of the exhaust line (2). Device according to one of the preceding claims, characterized in that the pyrolysis reactor (4) is arranged concentrically to an exhaust line (2) of the internal combustion engine (1), the exhaust gas outlet (12) of the pyrolysis reactor (4) being formed by a plurality of openings, in particular deep-drawn ones Openings, is formed over the circumference of the exhaust line (2). Device according to one of the preceding claims, characterized in that the main exhaust line (2) downstream of a branch to the exhaust gas inlet (11) of the pyrolysis reactor (4) has an adjustable throttle valve (29) which can be moved from a closed position to an open position parallel to the flow direction in the exhaust line and is also further rotatable and adjustable. Device according to one of the preceding claims, characterized in that the main exhaust line (2) downstream of a branch for the exhaust gas inlet (11) of the pyrolysis reactor (4) has an adjustable throttle valve (29) which is positioned in relation to a branch, in particular a plurality of openings, which form/form the exhaust gas inlet (11) to the pyrolysis reactor (4). that the branch/openings are in the slipstream of the throttle valve (29) by turning the throttle valve (29) further beyond the open position. Method for heating the exhaust gases of an internal combustion engine (1) with a pyrolysis reactor (4) into which at least a partial mass flow of the exhaust gas of the internal combustion engine (1) is introduced, the pyrolysis reactor (4) having at least one fleece (14) which is charged with fuel is evaporated and at least partially reacts exothermally in the pyrolysis reactor (4) with an oxygen content of the exhaust gas mass flow introduced into the pyrolysis reactor (4) by oxidation, in particular in order to provide a sufficiently high temperature for pyrolysis, characterized in that the pyrolysis reactor ( 4) is arranged in a bypass (3) parallel to a main exhaust line (2) of an internal combustion engine (1), the main exhaust line (2) having a throttle point (5) downstream of a branch to the exhaust gas inlet (11) of the pyrolysis reactor (4), by means of which regulates the back pressure in the main exhaust line (2). procedure after Claim 13 , characterized in that the fuel introduced into the pyrolysis reactor (4) is at least partially vaporized locally by means of at least one heating source and/or the exhaust gas mass flow introduced into the pyrolysis reactor (4) is raised to a temperature above the vaporization temperature of the gas introduced into the pyrolysis reactor (4 ) introduced fuel is heated. procedure after Claim 13 or 14 , characterized in that the throttle point (5) is formed by a rotatable throttle valve (29), the geometric positioning of the throttle valve (29) in relation to the inlet openings of the pyrolysis reactor (4) opening these inlet openings by rotating the throttle valve via the open position of the Throttle valve (29) are brought out into their slipstream and/or through the geometric positioning of the throttle valve (29) in relation to the outlet openings of the pyrolysis reactor (4) these outlet openings by rotating the throttle valve beyond the open position of the throttle valve (29) in their slipstream be brought to bring the differential pressure across the pyrolysis reactor (4) to zero

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