Title of Invention	"EXHAUST-GAS SECONDARY TREATMENT PRECEDING A TURBOCHARGER"
Abstract	Exhaust-gas aftertreatment system (1) for an internal combustion engine (2) of a vehicle (3) having at least one exhaust line (4) and at least one turbocharger (5) and at least one exhaust-gas converter (6), with the catalytic converter (6) being provided between the internal combustion engine (2) and the at least one turbocharger (5) that having a first volume (7) of at least 0.6 liters. Figure 1

Title of Invention

"EXHAUST-GAS SECONDARY TREATMENT PRECEDING A TURBOCHARGER"

Abstract

Exhaust-gas aftertreatment system (1) for an internal combustion engine (2) of a vehicle (3) having at least one exhaust line (4) and at least one turbocharger (5) and at least one exhaust-gas converter (6), with the catalytic converter (6) being provided between the internal combustion engine (2) and the at least one turbocharger (5) that having a first volume (7) of at least 0.6 liters. Figure 1

Full Text	The present invention relates to an exhaust-gas aftertreatment system for an internal combustion engine of a vehicle, which exhaust-gas aftertreatment system has at least one exhaust line and at least one turbocharger and at least one exhaust-gas converter. Said exhaust-gas aftertreatment system is in particular a system for the aftertreatment of exhaust gas of a lean-burn engine of a passenger motor vehicle. In past years, the focus has been on adhering to exhaust-gas legislation for spark-ignition engines, though this situation has recently changed. There is an increased public awareness of the significance of the environmental impact of diesel engines. The reasons for this are firstly the discussion of a particular health risk posed by the particle emissions of this engine type, and secondly the drastically rising numbers of diesel vehicles registered in Europe. Decisive factors in this development are not only reasons of economy but also the driving behaviour of vehicles with modern diesel engines, which is characterized by high torque at low engine speeds. In order to keep the pollutant emissions as low as possible, a plurality of different systems have already been developed and brought into use, such as for example improved injection systems (common rail systems with relatively high injection pressures), advanced exhaust-gas turbocharger and exhaust-gas recirculation technologies and model-based combustion processes for control or regulation. Furthermore, in certain operating ranges, despite compression ignition being maintained in principle, newer diesel engines are characterized to a greater or lesser extent by homogeneous combustion processes (HCCI: Homogeneous Charge Compression Ignition). Engines of said type have extremely low nitrogen oxide emissions and soot emissions in said operating mode. The carbon monoxide and hydrocarbon emissions are however possibly increased. Although tried and tested technologies in the form of oxidation catalytic converters are available for the elimination of these pollutants, the level of the emissions in connection with the low exhaust-gas temperatures typical of diesel engines pose considerable difficulties. With regard to this situation in particular, it is intended to specify an exhaust-gas treatment system which at least partially solves the technical difficulties and problem specified above. Here, the exhaust-gas aftertreatment system should in particular operate with uniform effectiveness over the different operating states of the diesel engine or lean-burn engine, and should nevertheless be cost-effective to produce. These objects are achieved by means of an exhaust-gas aftertreatment system as per the features of Patent Claim 1 and by means of a method as per the features of Patent Claim 7. Further advantageous embodiments of the invention are specified in the dependent patent claims. It should be noted that the features specified individually in the patent claims can be combined in any desired technologically meaningful way and highlight further embodiments of the invention. The description, in particular in connection with the figures, describes further exemplary embodiments of the invention. The exhaust-gas aftertreatment system according to the invention for an internal combustion engine of a vehicle has at least one exhaust line and at least one turbocharger and at least one exhaust-gas converter, with the exhaust-gas converter being provided between the internal combustion engine and the at least one turbocharger and having a first volume of at least 0.6 litres [1] . The exhaust system can, for example, be of initially multi-strand design proceeding from the internal combustion engine, such that for example a separate exhaust line is provided for each outlet of the combustion chamber. Said exhaust line sections, also referred to overall as a fan-type manifold, can subsequently be merged to form a common exhaust line. An exhaust line (or plurality of exhaust lines) of said type can be formed with an exhaust-gas turbocharger. A turbocharger of said type serves to increase the power of the internal combustion engine by increasing the air quantity throughput and fuel throughput per working stroke. The turbocharger is driven here by the exhaust-gas pressure, with it also being possible for the turbocharger to utilize the exhaust-gas speed as an energy source (impulse supercharging). A turbocharger is composed of an exhaust-gas turbine in the exhaust-gas flow, which exhaust-gas turbine is connected by means of a shaft to a compressor in the intake tract for the internal combustion engine. The turbine is set in rotation by the exhaust-gas flow of the internal combustion engine and thereby drives the compressor. The compressor increases the pressure in the intake tract of the internal combustion engine such that a greater quantity of air passes into the combustion chamber during the intake stroke. More oxygen is therefore available for the combustion of a correspondingly greater fuel quantity. It is thereby possible to obtain a considerable increase in power of the internal combustion engine (in particular of the diesel engine). In order to provide sufficient energy in the turbocharger for this purpose, use has hitherto been made of the concept of introducing the exhaust-gas flow into the turbocharger with high energy. This has also been the reason that, only very small exhaust-gas treatment units have been inserted into the region between the internal combustion engine and turbocharger in order to prevent a pressure drop and therefore a reduced compression action of the exhaust-gas turbocharger. For example, so-called pre-turbocharger catalytic converters ("PTC", pre-turbocharger-catalyst) are known which are positioned either in the exhaust line directly downstream of the outlet valves in a cylinder head of the internal combustion engine, in the manifold upstream of the exhaust-gas turbocharger or directly upstream or even in the exhaust-gas turbocharger. By positioning an oxidation catalytic converter at this point close to the engine, said oxidation catalytic converter (in particular having a surface which generates a turbulent flow) can further increase the exhaust-gas temperature as a result of an exothermic reaction, and thereby "heat up" subsequent exhaust-gas purification components. The invention now departs from this path for the first time and proposes that the exhaust-gas converter positioned upstream of the turbocharger has a first volume of at least 0.6 1. Here, the in particular catalytically active exhaust-gas converter now no longer serves simply to provide a temperature increase for the downstream exhaust-gas treatment units, but also ensures significant conversion of the pollutants contained in the exhaust gas, in particular hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides, particles, etc. Exhaust-gas converters of said type are often designed in the form of a honeycomb body, with the latter being formed with ceramic or (preferably) with metallic walls. For this purpose, said walls can be formed at least partially with corresponding coatings: oxidation catalyst, 3-way catalyst, adsorber coating. Furthermore, the design can also be correspondingly adapted, for example as a so-called secondary flow filter or wall-flow filter. Here, the volume is formed by the sum of the walls and ducts. Under some circumstances, in particular very large internal combustion engines, it can even be advantageous to provide an even larger first volume of the exhaust-gas converter upstream of the turbocharger, such as for example a first volume of at least 1.0 1 or even 1.5 1. This is a departure, for the first time, from the concept of the exhaust-gas treatment taking place primarily in the underbody region of the vehicle, which has been followed for decades. Here, it is proposed to provide such a large volume of the exhaust-gas converter upstream of the turbocharger despite the extremely restricted space conditions in the engine bay of vehicles and despite the pressure drop of the exhaust gas which increases with volume. Although it is fundamentally possible for the first volume specified here to be formed by a plurality of exhaust-gas converters positioned between the internal combustion engine and the at least one turbocharger, it is preferable to provide a single exhaust-gas converter with the first volume specified here. According to one refinement of the exhaust-gas aftertreatment system, it is proposed that the at least one exhaust-gas converter has a first volume which is larger than a second volume of at least one exhaust-gas aftertreatment unit which is situated opposite the at least one turbocharger. This means in particular that the exhaust-gas aftertreatment system is formed with an (in particular catalytically active) exhaust-gas converter upstream of the turbocharger and an exhaust-gas aftertreatment unit which (also) has the same function as the exhaust-gas converter, with the larger reaction volume being provided upstream of the turbocharger. In this way, for example on account of the larger catalytically active surface in the exhaust-gas converter and the relatively high temperatures which prevail there on account of the proximity to the engine, a significantly greater proportion of the relevant pollutants are converted. In this way, the exhaust-gas aftertreatment system can be of more cost-effective design overall, in particular if the exhaust-gas converter upstream of the turbocharger is provided with turbulence-generating structures in or on the walls (holes, flow constrictions, flow deflections etc.). Here, the invention very particularly envisages that the at least one exhaust-gas converter comprises an oxidation catalytic converter. This means in particular that said exhaust-gas converter is designed in the form of a honeycomb body, preferably with at least partially structured metallic sheet-metal foils on which are provided a substrate substance (for example washcoat) and a corresponding catalyst such as a noble metal (platinum, rhodium etc.). With the size of the oxidation catalytic converter proposed here, it is possible under some circumstances to combine several functions. It is, for example, possible for nitrogen dioxide to also be produced in addition to the conversion of hydrocarbons and carbon monoxides, for example in order to be able to continuously regenerate a downstream particle separator. Accordingly, an exhaust-gas aftertreatment system is also preferable in which the at least one exhaust-gas converter comprises an oxidation catalytic converter and a particle separator. Here, the particle separator can be constructed as a so-called wall-flow filter with alternately closed-off flow paths and porous walls, though open particle separators are preferable which have no flow dead-ends and which are in particular constructed with metallic components comprising at least sheet-metal foils, wire cloth, fibrous nonwovens or the like. For the particle separation, it is also possible for at least one of the following effects to be used: electrostatic charging of the particles, agglomeration of the particles, thermophoresis, diffusion, convection etc. In one very particularly preferable refinement of the exhaust-gas aftertreatment system according to the invention, the at least one exhaust-gas converter is positioned in a collecting space for a plurality of exhaust line sections. This means in particular that the exhaust-gas converter is formed as one component, and that the exhaust-gas converter is arranged in the region of the junction of the individual manifold tubes to form a common exhaust line. Here, it is possible in particular to make use of non-cylindrical exhaust-gas converters and/or exhaust-gas converters which are traversed by flow radially. The invention is particularly suitable for an exhaust-gas aftertreatment system in which the at least one turbocharger is designed with two stages. A two-stage turbocharger is therefore provided in particular, which two-stage turbocharger has a low-pressure stage and a high-pressure stage which each comprise one compressor and one turbine. The respective turbines and compressors are connected to one another by means of a common shaft. Two turbochargers of different size are therefore used in particular; a small turbocharger for the low engine-speed range and a larger turbocharger for the upper rotational speed range with large amounts of air throughput. The two turbochargers are connected to one another in series on the exhaust-gas side and on the air side and are adapted to the respective speed and load range of the engine by means of bypass flaps. One to two charge-air coolers may be necessary depending on the charge-pressure level. According to a further aspect of the invention, a method is proposed for purifying an exhaust gas of an internal combustion engine with an exhaust-gas aftertreatment system in which at least one turbocharger is provided, with all of the exhaust gas being converted by oxidation to a greater degree between the internal combustion engine and the turbocharger than in a region downstream of the turbocharger. Said method can be realized in particular with the exhaust-gas aftertreatment system explained here according to the invention. Here, conversion "to a greater degree" means for example that, in a reproducible standard test, the (mass) proportion of hydrocarbons (HC) and/or carbon monoxide (CO) which is converted upstream of the turbocharger is greater than the (mass) proportion converted by the subsequent exhaust-gas aftertreatment units. On account of the increased temperature in the vicinity of the engine, this can also be achieved with a first volume of the exhaust-gas converter which is smaller than the exhaust-gas. aftertreatment units, though it is preferable for the greater degree to be associated with a larger first volume. With regard to this method, reference is otherwise made to the above-specified effects of the device. It is particularly preferable for a vehicle having an exhaust-gas aftertreatment system as described here according to the invention to be operated with a method which is likewise described here according to the invention, with these lending themselves to use in internal combustion engines in the form of a lean-burn engine. Here, a "lean-burn engine" is an internal combustion engine which is regularly operated with an excess of air, such as for example a diesel engine. The invention and the technical field are now explained in more detail on the basis of the figures. It should be noted that the exemplary embodiments illustrated in the figures are not intended to restrict the invention. In the figures: Figure 1 schematically shows a first embodiment variant of an exhaust-gas aftertreatment system of a vehicle, and Figure 2 schematically shows a further embodiment variant of an exhaust-gas aftertreatment system according to the invention. Figure 1 schematically illustrates a vehicle 3 which has an internal combustion engine 2 in the form of a diesel engine, with the exhaust gas generated in the internal combustion engine being conducted through an exhaust-gas aftertreatment system 1. In the example shown here, the exhaust gas flows in the flow direction 13 firstly through an exhaust-gas converter 6, then through a turbocharger 5 (which is designed with two stages 16) , before the exhaust gas flows on through the exhaust line 4, for example into an underfloor region of the vehicle 3, where further exhaust-gas aftertreatment units 9, in this case for example an oxidation catalytic converter 10, a particle separator 14 and an SCR catalytic converter 15 are provided. Here, the exhaust-gas converter 6, which is provided between the internal combustion engine 2 and the turbocharger 5, has a first volume 7 which is larger than a second volume 8 of the exhaust-gas aftertreatment units 9 which perform the same functions. Here, the exhaust-gas converter 6 is formed by a combination of an oxidation catalytic converter 10 and an oxidatively coated particle separator 14. In the embodiment variant shown here, the exhaust-gas converter 6 is, for example, provided, like the oxidation catalytic converter 10 and the particle separator 14, with an oxidation coating. The SCR catalytic converter (SCR = selective catalytic reaction) has a reduction coating and therefore a different function. Consequently, the first volume 7 here is larger than the second volume 8 formed by the oxidation catalytic converter 10 and the particle separator 14 (with the intermediate space being neglected), though this is not strictly necessary. Figure 2 is, by way of example, a plan view of part of an internal combustion engine 2 with the subsequent exhaust line sections 12, also referred to as a manifold. The individual exhaust line sections 12 open out into a common collecting space 11 in which an oxidation catalytic converter 10 is again provided here as a first catalytic converter 6. The exhaust gas flowing into the exhaust-gas converter 6 through the exhaust line sections 12 is correspondingly catalytically treated and thereafter leaves the exhaust-gas converter 6 (together) in the flow direction 13 and flows further towards the turbocharger 5 arranged downstream. Obvious modifications can of course also be carried out. It is for example possible for the exhaust-gas treatment system 1 to have exhaust lines 4 which remain separate until downstream of a plurality of exhaust-gas turbochargers 5. It is also possible for a plurality of exhaust-gas converters 6 to be provided between the internal combustion engine 2 and the at least one turbocharger 5. Furthermore, the exhaust-gas converter 6 can also comprise another exhaust-gas aftertreatment unit 9, such as for example a particle separator, in addition to an oxidation catalytic converter 10. Furthermore, it is also possible for devices for introducing liquid and/or gaseous reducing agents to be provided in connection specifically with an SCR catalytic converter. In addition, the exhaust-gas converter 6 can be formed with openings in the duct walls and/or guide blades and/or flow constrictions and/or turbulence-generating points in order to realize a turbulent flow in the interior and to thereby improve the contact between the pollutants to be converted and the catalytically active coating of the exhaust-gas converter. This is proposed in particular in the knowledge of the associated pressure loss which has a corresponding influence on the downstream turbocharger 5. If appropriate, a plurality of turbochargers 5 can then also be provided in series in the flow direction of the exhaust gas in order to slightly compensate said effect. List of reference symbols 1 Exhaust-gas aftertreatment system 2 Internal combustion engine 3 Vehicle 4 Exhaust line 5 Turbocharger 6 Exhaust-gas converter 7 First volume 8 Second volume 9 Exhaust-gas aftertreatment unit 10 Oxidation catalytic converter 11 Collecting space 12 Exhaust line section 13 Flow direction 14 Particle separator 15 SCR catalytic converter 16 Stage We Claim: 1. Exhaust-gas aftertreatment system (1) for an internal combustion engine (2) of a vehicle (3) having at least one exhaust line (4) and at least one turbocharger (5) and at least one exhaust-gas converter (6), with the catalytic converter (6) being provided between the internal combustion engine (2) and the at least one turbocharger (5) and having a first volume (7) of at least 0.6 litres. 2. Exhaust-gas aftertreatment system (1) according to Patent Claim 1, in which the at least one exhaust-gas converter (6) has a first volume (7) which is larger than a second volume (8) of at least one exhaust-gas aftertreatment unit (9) which is situated opposite the at least one turbocharger (5). 3. Exhaust-gas aftertreatment system (1) according to Patent Claim 1 or 2, in which the at least one exhaust-gas converter (6) comprises an oxidation catalytic converter (10). 4. Exhaust-gas aftertreatment system (1) according to Patent Claim 3, in which the at least one exhaust-gas converter (6) comprises an oxidation catalytic converter (10) and a particle separator (14) . 5. Exhaust-gas aftertreatment system (1) according to one of the preceding patent claims, in which the at least one exhaust-gas converter (6) is positioned in a collecting space (11) for a plurality of exhaust line sections (12). 6. Exhaust-gas aftertreatment system (1) according to one of the preceding patent claims, in which at least one turbocharger (5) is designed with two stages. 7. Method for purifying an exhaust gas of an internal combustion engine (2) with an exhaust-gas aftertreatment system (1) in which at least one turbocharger (5) is provided, with all of the exhaust gas being converted by oxidation to a greater degree between the internal combustion engine (2) and the turbocharger (5) than in a region downstream of the turbocharger (5). 8. Vehicle (3) having an exhaust-gas aftertreatment system (1) according to one of Patent Claims 1 to 6, with the internal combustion engine (2) being a lean-burn engine.

Full Text

The present invention relates to an exhaust-gas aftertreatment system for an internal combustion engine of a vehicle, which exhaust-gas aftertreatment system has at least one exhaust line and at least one turbocharger and at least one exhaust-gas converter. Said exhaust-gas aftertreatment system is in particular a system for the aftertreatment of exhaust gas of a lean-burn engine of a passenger motor vehicle.
In past years, the focus has been on adhering to exhaust-gas legislation for spark-ignition engines, though this situation has recently changed. There is an increased public awareness of the significance of the environmental impact of diesel engines. The reasons for this are firstly the discussion of a particular health risk posed by the particle emissions of this engine type, and secondly the drastically rising numbers of diesel vehicles registered in Europe. Decisive factors in this development are not only reasons of economy but also the driving behaviour of vehicles with modern diesel engines, which is characterized by high torque at low engine speeds. In order to keep the pollutant emissions as low as possible, a plurality of different systems have already been developed and brought into use, such as for example improved injection systems (common rail systems with relatively high injection pressures), advanced exhaust-gas turbocharger and exhaust-gas recirculation technologies and model-based combustion processes for control or regulation. Furthermore, in certain operating ranges, despite compression ignition being maintained in principle, newer diesel engines are characterized to a greater or lesser extent by homogeneous combustion processes (HCCI: Homogeneous Charge Compression Ignition). Engines of said type have extremely low nitrogen oxide emissions and soot emissions in said operating mode. The carbon monoxide and hydrocarbon emissions are
however possibly increased. Although tried and tested technologies in the form of oxidation catalytic converters are available for the elimination of these pollutants, the level of the emissions in connection with the low exhaust-gas temperatures typical of diesel engines pose considerable difficulties.
With regard to this situation in particular, it is intended to specify an exhaust-gas treatment system which at least partially solves the technical difficulties and problem specified above. Here, the exhaust-gas aftertreatment system should in particular operate with uniform effectiveness over the different operating states of the diesel engine or lean-burn engine, and should nevertheless be cost-effective to produce.
These objects are achieved by means of an exhaust-gas aftertreatment system as per the features of Patent Claim 1 and by means of a method as per the features of Patent Claim 7. Further advantageous embodiments of the invention are specified in the dependent patent claims. It should be noted that the features specified individually in the patent claims can be combined in any desired technologically meaningful way and highlight further embodiments of the invention. The description, in particular in connection with the figures, describes further exemplary embodiments of the invention.
The exhaust-gas aftertreatment system according to the invention for an internal combustion engine of a vehicle has at least one exhaust line and at least one turbocharger and at least one exhaust-gas converter, with the exhaust-gas converter being provided between the internal combustion engine and the at least one turbocharger and having a first volume of at least 0.6 litres [1] .
The exhaust system can, for example, be of initially multi-strand design proceeding from the internal combustion engine, such that for example a separate exhaust line is provided for each outlet of the combustion chamber. Said exhaust line sections, also referred to overall as a fan-type manifold, can subsequently be merged to form a common exhaust line. An exhaust line (or plurality of exhaust lines) of said type can be formed with an exhaust-gas turbocharger. A turbocharger of said type serves to increase the power of the internal combustion engine by increasing the air quantity throughput and fuel throughput per working stroke. The turbocharger is driven here by the exhaust-gas pressure, with it also being possible for the turbocharger to utilize the exhaust-gas speed as an energy source (impulse supercharging). A turbocharger is composed of an exhaust-gas turbine in the exhaust-gas flow, which exhaust-gas turbine is connected by means of a shaft to a compressor in the intake tract for the internal combustion engine. The turbine is set in rotation by the exhaust-gas flow of the internal combustion engine and thereby drives the compressor. The compressor increases the pressure in the intake tract of the internal combustion engine such that a greater quantity of air passes into the combustion chamber during the intake stroke. More oxygen is therefore available for the combustion of a correspondingly greater fuel quantity. It is thereby possible to obtain a considerable increase in power of the internal combustion engine (in particular of the diesel engine).
In order to provide sufficient energy in the turbocharger for this purpose, use has hitherto been made of the concept of introducing the exhaust-gas flow into the turbocharger with high energy. This has also been the reason that, only very small exhaust-gas treatment units have been inserted into the region between the internal combustion engine and turbocharger
in order to prevent a pressure drop and therefore a reduced compression action of the exhaust-gas turbocharger. For example, so-called pre-turbocharger catalytic converters ("PTC", pre-turbocharger-catalyst) are known which are positioned either in the exhaust line directly downstream of the outlet valves in a cylinder head of the internal combustion engine, in the manifold upstream of the exhaust-gas turbocharger or directly upstream or even in the exhaust-gas turbocharger. By positioning an oxidation catalytic converter at this point close to the engine, said oxidation catalytic converter (in particular having a surface which generates a turbulent flow) can further increase the exhaust-gas temperature as a result of an exothermic reaction, and thereby "heat up" subsequent exhaust-gas purification components.
The invention now departs from this path for the first time and proposes that the exhaust-gas converter positioned upstream of the turbocharger has a first volume of at least 0.6 1. Here, the in particular catalytically active exhaust-gas converter now no longer serves simply to provide a temperature increase for the downstream exhaust-gas treatment units, but also ensures significant conversion of the pollutants contained in the exhaust gas, in particular hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides, particles, etc. Exhaust-gas converters of said type are often designed in the form of a honeycomb body, with the latter being formed with ceramic or (preferably) with metallic walls. For this purpose, said walls can be formed at least partially with corresponding coatings: oxidation catalyst, 3-way catalyst, adsorber coating. Furthermore, the design can also be correspondingly adapted, for example as a so-called secondary flow filter or wall-flow filter. Here, the volume is formed by the sum of the walls and ducts. Under some circumstances, in particular very large internal combustion engines, it can even be
advantageous to provide an even larger first volume of the exhaust-gas converter upstream of the turbocharger, such as for example a first volume of at least 1.0 1 or even 1.5 1.
This is a departure, for the first time, from the concept of the exhaust-gas treatment taking place primarily in the underbody region of the vehicle, which has been followed for decades. Here, it is proposed to provide such a large volume of the exhaust-gas converter upstream of the turbocharger despite the extremely restricted space conditions in the engine bay of vehicles and despite the pressure drop of the exhaust gas which increases with volume. Although it is fundamentally possible for the first volume specified here to be formed by a plurality of exhaust-gas converters positioned between the internal combustion engine and the at least one turbocharger, it is preferable to provide a single exhaust-gas converter with the first volume specified here.
According to one refinement of the exhaust-gas aftertreatment system, it is proposed that the at least one exhaust-gas converter has a first volume which is larger than a second volume of at least one exhaust-gas aftertreatment unit which is situated opposite the at least one turbocharger. This means in particular that the exhaust-gas aftertreatment system is formed with an (in particular catalytically active) exhaust-gas converter upstream of the turbocharger and an exhaust-gas aftertreatment unit which (also) has the same function as the exhaust-gas converter, with the larger reaction volume being provided upstream of the turbocharger. In this way, for example on account of the larger catalytically active surface in the exhaust-gas converter and the relatively high temperatures which prevail there on account of the proximity to the engine, a significantly greater proportion of the relevant pollutants are converted. In this way, the
exhaust-gas aftertreatment system can be of more cost-effective design overall, in particular if the exhaust-gas converter upstream of the turbocharger is provided with turbulence-generating structures in or on the walls (holes, flow constrictions, flow deflections etc.).
Here, the invention very particularly envisages that the at least one exhaust-gas converter comprises an oxidation catalytic converter. This means in particular that said exhaust-gas converter is designed in the form of a honeycomb body, preferably with at least partially structured metallic sheet-metal foils on which are provided a substrate substance (for example washcoat) and a corresponding catalyst such as a noble metal (platinum, rhodium etc.). With the size of the oxidation catalytic converter proposed here, it is possible under some circumstances to combine several functions. It is, for example, possible for nitrogen dioxide to also be produced in addition to the conversion of hydrocarbons and carbon monoxides, for example in order to be able to continuously regenerate a downstream particle separator.
Accordingly, an exhaust-gas aftertreatment system is also preferable in which the at least one exhaust-gas converter comprises an oxidation catalytic converter and a particle separator. Here, the particle separator can be constructed as a so-called wall-flow filter with alternately closed-off flow paths and porous walls, though open particle separators are preferable which have no flow dead-ends and which are in particular constructed with metallic components comprising at least sheet-metal foils, wire cloth, fibrous nonwovens or the like. For the particle separation, it is also possible for at least one of the following effects to be used: electrostatic charging of the particles, agglomeration of the particles, thermophoresis, diffusion, convection etc.
In one very particularly preferable refinement of the exhaust-gas aftertreatment system according to the invention, the at least one exhaust-gas converter is positioned in a collecting space for a plurality of exhaust line sections. This means in particular that the exhaust-gas converter is formed as one component, and that the exhaust-gas converter is arranged in the region of the junction of the individual manifold tubes to form a common exhaust line. Here, it is possible in particular to make use of non-cylindrical exhaust-gas converters and/or exhaust-gas converters which are traversed by flow radially.
The invention is particularly suitable for an exhaust-gas aftertreatment system in which the at least one turbocharger is designed with two stages. A two-stage turbocharger is therefore provided in particular, which two-stage turbocharger has a low-pressure stage and a high-pressure stage which each comprise one compressor and one turbine. The respective turbines and compressors are connected to one another by means of a common shaft. Two turbochargers of different size are therefore used in particular; a small turbocharger for the low engine-speed range and a larger turbocharger for the upper rotational speed range with large amounts of air throughput. The two turbochargers are connected to one another in series on the exhaust-gas side and on the air side and are adapted to the respective speed and load range of the engine by means of bypass flaps. One to two charge-air coolers may be necessary depending on the charge-pressure level.
According to a further aspect of the invention, a method is proposed for purifying an exhaust gas of an internal combustion engine with an exhaust-gas aftertreatment system in which at least one turbocharger is provided, with all of the exhaust gas being converted by oxidation to a greater degree
between the internal combustion engine and the turbocharger than in a region downstream of the turbocharger.
Said method can be realized in particular with the exhaust-gas aftertreatment system explained here according to the invention.
Here, conversion "to a greater degree" means for example that, in a reproducible standard test, the (mass) proportion of hydrocarbons (HC) and/or carbon monoxide (CO) which is converted upstream of the turbocharger is greater than the (mass) proportion converted by the subsequent exhaust-gas aftertreatment units. On account of the increased temperature in the vicinity of the engine, this can also be achieved with a first volume of the exhaust-gas converter which is smaller than the exhaust-gas. aftertreatment units, though it is preferable for the greater degree to be associated with a larger first volume. With regard to this method, reference is otherwise made to the above-specified effects of the device.
It is particularly preferable for a vehicle having an exhaust-gas aftertreatment system as described here according to the invention to be operated with a method which is likewise described here according to the invention, with these lending themselves to use in internal combustion engines in the form of a lean-burn engine. Here, a "lean-burn engine" is an internal combustion engine which is regularly operated with an excess of air, such as for example a diesel engine.
The invention and the technical field are now explained in more detail on the basis of the figures. It should be noted that the exemplary embodiments illustrated in the figures are not intended to restrict the invention. In the figures:
Figure 1 schematically shows a first embodiment variant of an exhaust-gas aftertreatment system of a vehicle, and
Figure 2 schematically shows a further embodiment variant of an exhaust-gas aftertreatment system according to the invention.
Figure 1 schematically illustrates a vehicle 3 which has an internal combustion engine 2 in the form of a diesel engine, with the exhaust gas generated in the internal combustion engine being conducted through an exhaust-gas aftertreatment system 1. In the example shown here, the exhaust gas flows in the flow direction
13 firstly through an exhaust-gas converter 6, then
through a turbocharger 5 (which is designed with two
stages 16) , before the exhaust gas flows on through the
exhaust line 4, for example into an underfloor region
of the vehicle 3, where further exhaust-gas
aftertreatment units 9, in this case for example an
oxidation catalytic converter 10, a particle separator
14 and an SCR catalytic converter 15 are provided.
Here, the exhaust-gas converter 6, which is provided between the internal combustion engine 2 and the turbocharger 5, has a first volume 7 which is larger than a second volume 8 of the exhaust-gas aftertreatment units 9 which perform the same functions. Here, the exhaust-gas converter 6 is formed by a combination of an oxidation catalytic converter 10 and an oxidatively coated particle separator 14. In the embodiment variant shown here, the exhaust-gas converter 6 is, for example, provided, like the oxidation catalytic converter 10 and the particle separator 14, with an oxidation coating. The SCR catalytic converter (SCR = selective catalytic reaction) has a reduction coating and therefore a different function. Consequently, the first volume 7 here is larger than the second volume 8 formed by the
oxidation catalytic converter 10 and the particle separator 14 (with the intermediate space being neglected), though this is not strictly necessary.
Figure 2 is, by way of example, a plan view of part of an internal combustion engine 2 with the subsequent exhaust line sections 12, also referred to as a manifold. The individual exhaust line sections 12 open out into a common collecting space 11 in which an oxidation catalytic converter 10 is again provided here as a first catalytic converter 6. The exhaust gas flowing into the exhaust-gas converter 6 through the exhaust line sections 12 is correspondingly catalytically treated and thereafter leaves the exhaust-gas converter 6 (together) in the flow direction 13 and flows further towards the turbocharger
5 arranged downstream.
Obvious modifications can of course also be carried out. It is for example possible for the exhaust-gas treatment system 1 to have exhaust lines 4 which remain separate until downstream of a plurality of exhaust-gas turbochargers 5. It is also possible for a plurality of exhaust-gas converters 6 to be provided between the internal combustion engine 2 and the at least one turbocharger 5. Furthermore, the exhaust-gas converter
6 can also comprise another exhaust-gas aftertreatment
unit 9, such as for example a particle separator, in
addition to an oxidation catalytic converter 10.
Furthermore, it is also possible for devices for
introducing liquid and/or gaseous reducing agents to be
provided in connection specifically with an SCR
catalytic converter. In addition, the exhaust-gas
converter 6 can be formed with openings in the duct
walls and/or guide blades and/or flow constrictions
and/or turbulence-generating points in order to realize
a turbulent flow in the interior and to thereby improve
the contact between the pollutants to be converted and
the catalytically active coating of the exhaust-gas
converter. This is proposed in particular in the knowledge of the associated pressure loss which has a corresponding influence on the downstream turbocharger 5. If appropriate, a plurality of turbochargers 5 can then also be provided in series in the flow direction of the exhaust gas in order to slightly compensate said effect.
List of reference symbols
1 Exhaust-gas aftertreatment system
2 Internal combustion engine
3 Vehicle
4 Exhaust line
5 Turbocharger
6 Exhaust-gas converter
7 First volume
8 Second volume
9 Exhaust-gas aftertreatment unit
10 Oxidation catalytic converter
11 Collecting space
12 Exhaust line section
13 Flow direction
14 Particle separator
15 SCR catalytic converter
16 Stage

We Claim:
1. Exhaust-gas aftertreatment system (1) for an internal combustion engine (2) of a vehicle (3) having at least one exhaust line (4) and at least one turbocharger (5) and at least one exhaust-gas converter (6), with the catalytic converter (6) being provided between the internal combustion engine (2) and the at least one turbocharger (5) and having a first volume (7) of at least 0.6 litres.
2. Exhaust-gas aftertreatment system (1) according to Patent Claim 1, in which the at least one exhaust-gas converter (6) has a first volume (7) which is larger than a second volume (8) of at least one exhaust-gas aftertreatment unit (9) which is situated opposite the at least one turbocharger (5).
3. Exhaust-gas aftertreatment system (1) according to Patent Claim 1 or 2, in which the at least one exhaust-gas converter (6) comprises an oxidation catalytic converter (10).
4. Exhaust-gas aftertreatment system (1) according to Patent Claim 3, in which the at least one exhaust-gas converter (6) comprises an oxidation catalytic converter (10) and a particle separator (14) .
5. Exhaust-gas aftertreatment system (1) according to one of the preceding patent claims, in which the at least one exhaust-gas converter (6) is positioned in a collecting space (11) for a plurality of exhaust line sections (12).
6. Exhaust-gas aftertreatment system (1) according to one of the preceding patent claims, in which at
least one turbocharger (5) is designed with two stages.
7. Method for purifying an exhaust gas of an internal combustion engine (2) with an exhaust-gas aftertreatment system (1) in which at least one turbocharger (5) is provided, with all of the exhaust gas being converted by oxidation to a greater degree between the internal combustion engine (2) and the turbocharger (5) than in a region downstream of the turbocharger (5).
8. Vehicle (3) having an exhaust-gas aftertreatment system (1) according to one of Patent Claims 1 to 6, with the internal combustion engine (2) being a lean-burn engine.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=nd/FiRBl4Rv2xNuLTb7UQw==&loc=+mN2fYxnTC4l0fUd8W4CAA==

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Patent Number

277266

Indian Patent Application Number

390/DELNP/2010

PG Journal Number

48/2016

Publication Date

18-Nov-2016

Grant Date

16-Nov-2016

Date of Filing

19-Jan-2010

Name of Patentee

BORG WARNER INC.

Applicant Address

3800 AUTOMATION AVENUE, SUITE 400, AUBURN HILLLS, MI 48326-1785, U.S.A

Inventors:

#	Inventor's Name	Inventor's Address
1	BRÜCK, ROLF	FROBELSTRASSE 12, 51429 BERGISCH GLADBACH (DE)
2	JOERGL, VOLKER	PRIMELWEG 6, A-2384 BREITENFURT (AT)

PCT International Classification Number

F01N 3/023

PCT International Application Number

PCT/EP2008/057037

PCT International Filing date

2008-06-05

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2007 032 736.8	2007-07-13	Germany