Title of Invention

EXHAUST SYSTEM HAVING AN EXHAUST GAS TREATMENT UNIT AND A HEAT EXCHANGER IN AN EXHAUST RECYCLE LINE

Abstract

The invention relates to exhaust system (1) on an internal combustion engine (2), comprising an inlet system (3) and an exhaust outlet (4), whereby the exhaust outlet (4) and the inlet system(3) are connected by means of an exhaust recycle line (5) in which an exhaust treatment unit (6) and a heat exchanger (7) are embodied. The heat exchanger (7) has a first back pressure and the exhaust treatment unit (6) has a second back pressure smaller than the first back pressure, characterised in that the exhaust treatment unit (6) is embodied at such a first separation (8) from the heat exchanger (7) in the direction of flow that, during operation, a gas flow (14) entering the exhaust treatment unit (6) is equilibrated. Said exhaust system permits an advantageous embodiment of a heat exchanger (7) and an exhaust treatment un it (6), such as for example a honeycomb body in the exhaust recycle line (5), whereby both the heat exchanger (7) and the exhaust treatment unit (6) can have a smaller embodiment than in conventional system. The above reduces the costs considerably on equipping such a system.

Full Text

WO 2006/100090 PCT/EP2006/002702 - 1 - Exhaust system having an exhaust gas treatment unit and a heat exchanger in an exhaust gas recirculation line The subject matter of the present invention is an exhaust system for internal combustion engines having a heat exchanger and an exhaust gas treatment unit in an exhaust gas recirculation line. Exhaust systems of internal combustion engine are often formed with heat exchangers which are used to cool the exhaust gas, in particular when the exhaust gas is recirculated into the air inlet region of the internal combustion engine. Contamination of the heat exchanger by pollutants present in the exhaust gas reduces its effectiveness so that when the heat exchanger is configured it has to be basically overdimensioned in order to ensure that the heat exchanger has at least the reference effectiveness over a relatively long time period. In order to reduce the contamination of the heat exchanger, it is known from the prior art to form a catalytic converter upstream of the heat exchanger by means of which at least long-chained hydrocarbons, which can lead to sticky deposits in the heat exchanger, are removed. Such systems have the disadvantage that either insufficient conversion of the exhaust gas occurs due to the catalytic converter being arranged upstream, so that contamination of the heat exchanger still occurs, or that the catalytic converter has to be given very large dimensions in order to effectively prevent the contamination of the heat exchanger. Taking this as a starting point, the invention is based on the object of proposing a system which is to be used WO 2006/100090 PCT/EP2006/002702 - 2 - in the exhaust gas recirculation line and which comprises a heat exchanger and a catalytic converter in which effective reduction of the contamination of the heat exchanger and at the same time a smallest possible overall volume of the heat exchanger and of the catalytic converter are obtained. This object is achieved by means of an exhaust system having the features of claim 1. Advantageous developments are the subject matter of the dependent claims. The inventive exhaust system of an internal combustion engine which comprises an intake system and an exhaust outlet, wherein the exhaust outlet and intake system are connected via an exhaust gas recirculation line in which an exhaust gas treatment unit and a heat exchanger are formed, wherein the heat exchanger has a first backpressure and the exhaust gas treatment unit has a second backpressure which is lower than the first backpressure, is defined by the fact that the exhaust gas treatment unit is formed at such a first distance upstream of the heat exchanger in the direction of flow that during operation a gas flow which enters the exhaust gas treatment unit is homogenized. This means in particular that the backpressure upstream of the exhaust gas treatment unit in the direction of flow is influenced by the first backpressure of the heat exchanger. The heat exchanger is to be understood here in particular also as referring to an exhaust cooler with which the fed-back exhaust gas is cooled. The internal combustion engine is, in particular a diesel engine, for example a diesel engine of a motor vehicle (for example of a passenger car, of a lorry, of an engine- operated two wheeled vehicle, boat or aircraft) or a WO 2006/100090 PCT/EP2006/002702 - 3 - diesel engine in a stationary application. Homogenization is also to be understood in particular as referring to widening of the probability distribution of the speeds which occur. The design of the heat exchanger gives rise to the raised backpressure compared to the exhaust gas treatment unit. In particular, a heat exchanger which has a plurality of pipes through which the exhaust gas flows is advantageous. A cooling medium which flows through the housing of the heat exchanger and is extracted from a cooling circuit (not illustrated) of the internal combustion engine preferably flows around these pipes. In particular honeycomb bodies, for example ceramic or metallic honeycomb bodies, or else wire mesh bodies, bodies made of metal foam or the like, are suitable as exhaust gas treatment units. Metallic honeycomb bodies can be constructed, in particular, from at least one at least partially structured, metallic layer and, if appropriate, at least one essentially smooth layer which are wound or stacked and twisted together. The layers which are twisted or wound together form cavities through which a fluid can flow and which are bounded by the layers. The layers are in particular formed from a material which is resistant to high temperature corrosion, such as Al or Cr steel. The layers can be connected to one another, in particular in a materially joined fashion, such as for example by means of a high temperature soldering method. Both the layers which are essentially smooth and the at least partially structured layers can have, at least in certain areas, microstructures, baffle faces, breakthroughs and/or perforations which promote the mixing of the gas flow even further. The homogenization of the gas flow before it enters the exhaust gas treatment unit advantageous occurs by WO 2006/100090 PCT/EP2006/002702 - 4 - virtue of the fact that the exhaust gas treatment unit is formed relatively close upstream of the heat exchanger. This leads to homogenization of the gas flow already in the exhaust gas treatment unit so that here the conversion rate is improved since exhaust gas is applied more uniformly to the cross section of the exhaust gas treatment unit. The volume of the exhaust gas treatment unit can thus be reduced compared to a customary design with the same conversion rate of the pollutants in the exhaust gas. The significantly more efficient conversion rate of the pollutants also reduces the contamination of the heat exchanger so that it can also be given smaller dimensions compared to conventional heat exchangers. In order to form an exhaust gas treatment unit which has only a low backpressure, it is possible to use a honeycomb body which has a relatively low number of cells, for example less than 400 cpsi (cells per square inch), preferably less than 3 00 cpsi, particularly preferably 200 cpsi and less, in particular even 100 cpsi. According to one advantageous configuration of the exhaust system according to the invention, the first distance is selected such that the effect of the first backpressure and of the second backpressure accumulate. Accumulation is understood here in particular to refer to the fact that backpressure which is present upstream of the exhaust gas treatment unit is higher than the second backpressure which the exhaust gas treatment unit would have as such. The backpressure upstream of a component in a flow brings about a type of pressure cushion which causes the flow to change. In an extreme case, the present invention brings about a situation in which only one pressure cushion is formed in front of WO 2006/100090 PCT/EP2006/002702 - 5 - the exhaust gas treatment unit instead of two areas with a pressure cushion, one in front of the heat exchanger and one in front of the exhaust gas treatment unit, respectively. The accumulation of the backpressures advantageously leads to a situation in which before the exhaust gas flows into the exhaust gas treatment unit it has to overcome a backpressure which is higher than the second backpressure of the exhaust gas treatment unit. Depending on the configuration of the heat exchanger and of the exhaust gas treatment unit, the backpressure is even significantly higher than the second backpressure. Raising the backpressure brings about homogenization of the flow of the exhaust gas treatment unit, and thus of the gas flow through the exhaust gas treatment unit and heat exchanger. According to a further advantageous configuration,a second distance of a gas inlet end side of the exhaust gas treatment unit from a gas inlet end side of the heat exchanger is less than 60 mm, preferably less than 45 mm, particularly less than 30 mm. These values have proven particularly advantageous. In particular, under customary operating conditions the effects of the first and of the second backpressure accumulate. According to a further advantageous configuration of the exhaust system according to the invention, the extent of the exhaust gas treatment unit in the direction of flow is less than 100 mm, preferably less than 50 mm, particularly preferably 25 mm or less. Owing to the very homogenous and effective conversion of the corresponding substances in the exhaust gas, in WO 2006/100090 PCT/EP2006/002702 - 6 - particular of hydrocarbons, relatively small exhaust gas treatment units can be used. According to a further advantageous configuration of the exhaust system according to the invention, the exhaust gas treatment unit comprises a honeycomb body. With a honeycomb body it is possible to provide an exhaust gas treatment unit whose properties, such as surface, backpressure etc., can be set very precisely. In particular metallic or ceramic honeycomb bodies are suitable as honeycomb bodies. In particular, honeycomb bodies such as are described, for example in DE 197 55 703 A1, WO 90/13736 A1 and WO 99/11911 A1 can advantageously be used. Reference is made to the entire contents of these applications with respect to the attachment of the honeycomb body. According to a further advantageous configuration of the exhaust system according to the invention, the first distance between the exhaust gas treatment unit and the heat exchanger is less than 15 mm, preferably less than 10 mm, particularly less than 5 mm. In particular it is also advantageous to provide the heat exchanger and exhaust gas treatment unit in a common housing. In this context, the exhaust gas treatment unit can be held in a corresponding bead of the housing by means of beading or the like. It is also possible to fit the exhaust gas treatment unit flush onto an end side of the heat exchanger. According to a further advantageous configuration of the exhaust system according to the invention, the exhaust gas treatment unit comprises a catalytically active coating, in particular an oxidation catalyst coating. WO 2006/100090 PCT/EP2006/002702 - 7 - The catalytically active coating comprises, for example, a ceramic wash coat which contains materials which catalyze the desired reactions, that is to say in particular reduce the reaction temperature of these reactions to such an extent that they occur to an appreciable extent at the temperatures in the exhaust gas recirculation line. In particular noble metals such as platinum, rhodium or the like are suitable as catalytic converters. The oxidation catalyst coating catalyzes, in particular, the oxidation of hydrocarbons since they are also responsible for the contamination of the heat exchanger. The hydrocarbons form a sticky substance which condenses on the cold areas of the heat exchanger and which can also cause soot particles contained in the exhaust gas to stick to the walls of the heat exchanger. The oxidation of hydrocarbons therefore leads in a particularly advantageous way to a significant reduction in the contamination of the heat exchanger. In particular in exhaust systems of diesel engines, very wide ranging up to complete oxidation of the hydrocarbons occurs owing to the relatively high proportion of oxygen in the exhaust gas. In order to achieve the maximum possible conversion efficiency of the oxidation of the hydrocarbons, the exhaust gas treatment unit is in particular formed in such a way that the dwell time is as long as possible and the surface available for the reaction is as large as possible. According to a further advantageous configuration of the exhaust system according to the invention, the ratio of the first backpressure to the second backpressure is greater than 2, preferably greater than 10. WO 2006/100090 PCT/EP2006/002702 - 8 - In particular under these backpressure conditions, that is to say when the backpressure of the heat exchanger as such is greater than the backpressure of the exhaust gas treatment unit as such by a factor of 2 or even 10, the effects of the first backpressure of the heat exchanger and of the second backpressure of the exhaust gas treatment unit accumulate in a particularly advantageous way, even at first distances of 15 mm or less. The present invention will be explained in more detail with reference to the appended figures, without said invention being restricted to the exemplary embodiments and advantages shown as described there. In the drawings: figure 1 is a schematic view of a first exemplary embodiment of an exhaust system according to the invention; figure 2 is a schematic view of a detail of the first exemplary embodiment of an exhaust system according to the invention; figure 3 is a schematic view of a detail of a second exemplary embodiment of an exhaust system according to the invention; and figure 4 is a schematic view of two probability distributions of a the flow speed. Figure 1 is a schematic view of a first exemplary embodiment of an inventive exhaust system 1 of an internal combustion engine 2. The internal combustion engine 2 comprises an intake system 3 and an exhaust outlet 4, when the exhaust outlet 4 and intake system 3 are connected via an exhaust gas recirculation line 5 WO 2006/100090 PCT/EP2006/002702 - 9 - in which an exhaust gas treatment unit 6 and a heat exchanger 7 are formed. The heat exchanger 7 has a first backpressure, and the exhaust gas treatment unit 6 has a second backpressure which is lower than the first backpressure. The customary direction of flow of the exhaust gas has been symbolized by corresponding arrows. The quantity of exhaust gas which flows through the exhaust gas recirculation line 5 can be regulated, for example by means of corresponding valves (not shown) . The exhaust gas recirculation line 5 can branch off on the exhaust gas side, either upstream or downstream of an exhaust gas turbocharger (not shown). According to the invention, the exhaust gas treatment unit 6 is formed at such a first distance 8 upstream of the heat exchanger 7 in the direction of flow that during operation a gas flow 14 which enters the exhaust gas treatment unit 6 is homogenized. The first distance 8 is in particular less than 15 mm, preferably less than 10 mm, particularly preferably less than 5 mm. The heat exchanger 7 and exhaust gas treatment unit 6 are embodied in such a way that at this first distance 8 the effects of the first backpressure and of the second backpressure are accumulated so that the exhaust gas flowing into the exhaust gas treatment unit 6 has to overcome a backpressure which is higher than the second backpressure of the exhaust gas treatment unit 6 as such. This leads to a situation, as explained above, in which the gas flow 14 which flows into the exhaust gas treatment unit 6 is homogenized. Figure 2 is a schematic view of a detail of the exhaust gas recirculation line 5, including the exhaust gas treatment unit 6 and the heat exchanger 7. A second distance 9 between a gas inlet end side 10 of the heat exchanger 7 and a gas inlet end side 11 of the exhaust gas treatment unit 6 is selected according to the WO 2006/100090 PCT/EP2006/002702 - 10 - invention in such a way that the flow in the exhaust gas treatment unit 6 is homogenized. In particular, the second distance 9 is less than 60 mm, preferably less than 45 mm, particularly less than 3 0 mm. In particular short honeycomb bodies, in particular with an extent 12 in the direction of flow of approximately 20 to 40 mm, can be used as the exhaust gas treatment unit 6. The first distance 8 is, for example, less than 15 mm or else 5 mm or less. In particular, the first distance 8 is selected such that the effect of the first backpressure of the heat exchanger 7 and of the second backpressure of the exhaust gas treatment unit 6 accumulate so that the exhaust gas which flows into the exhaust gas treatment unit 6 has to overcome a backpressure which is higher, preferably significantly higher, than the second backpressure of the exhaust gas treatment unit 6. Figure 3 is a schematic view of a detail of a further exemplary embodiment of an exhaust system 1 according to the invention. Here, a cone 13 which comprises the exhaust treatment unit 6 which is embodied as a honeycomb body 17 with passages 18 which are conical here, is formed in the exhaust gas recirculation line 5. The gas flow 14 which passes through the exhaust gas recirculation line 5 is directed to the heat exchanger 7 by the cone 13. The heat exchanger 7 comprises exhaust pipes 15 in a housing 16. The gas flow 14 passes through the exhaust pipes 15, the coolant which is part of the cooling circuit of the internal combustion engine 2 flowing around said exhaust pipes 15 in the housing 16. The first distance 8 between the heat exchanger 7 and the exhaust gas treatment unit 6 is selected according to the invention in such a way that during operation a gas flow 14 which enters the exhaust gas treatment unit 6 is homogenized. WO 2006/100090 PCT/EP2006/002702 - 11 - Figure 4 is a schematic view of a first probability- distribution 19 of the speed v and a second probability distribution 20 of the speed v. The first probability distribution 19 is obtained if gas flows only through the exhaust gas treatment unit 6, that is to say without a heat exchanger 7 being formed downstream of said exhaust gas treatment unit 6 in the direction of flow. The probability of a certain speed being present in the gas is plotted for both distributions. Both the probability and the speed are given in relative units. The second probability distribution 20 is the probability distribution in a system according to the invention. It relates therefore to an exhaust system 1 with a heat exchanger 7 and an exhaust gas treatment unit 6 in an exhaust gas recirculation line 5. The second probability distribution 2 0 is wider, has in particular a greater width with half the maximum height (full width half maximum) than the first probability distribution 19. This is due to the inventive homogenization of the flow. The exhaust system according to the invention advantageously permits a heat exchanger 7 and an exhaust gas treatment unit 6, such as for example a honeycomb body, to be formed in the exhaust gas recirculation line 5, and at the same time both the heat exchanger 7 and the exhaust gas treatment unit 6 can be made smaller than is customary. This provides considerable cost savings when configuring such systems. 2006/100090 PCT/EP2006/002702 - 12 - List of reference numerals exhaust system internal combustion engine intake system exhaust outlet exhaust gas recirculation line exhaust gas treatment unit heat exchanger first distance second distance gas inlet end side of the heat exchanger gas inlet end side of the exhaust gas treatment unit extent cone gas flow exhaust pipe housing honeycomb body passage first probability distribution second probability distribution WO 2006/100090 PCT/EP2006/002702 - 13 - Patent Claims 1. An exhaust system (1) of an internal combustion engine (2), which comprises an intake system (3) and an exhaust outlet (4) , wherein the exhaust outlet (4) and the intake system (3) are connected via an exhaust gas recirculation line (5) in which an exhaust gas treatment unit (6) and a heat exchanger (7) are formed, wherein the heat exchanger (7) has a first backpressure and the exhaust gas treatment unit (6) has a second backpressure which is lower than the first backpressure, characterized in that the exhaust gas treatment unit (6) is formed at such a first distance (8) upstream of the heat exchanger (7) in the direction of flow that during operation a gas flow (14) which enters the exhaust gas treatment unit (6) is homogenized. 2. The exhaust system (1) as claimed in claim 1, in which the first distance (8) is selected such that the effect of the first backpressure and of the second backpressure accumulate. 3. The exhaust system (1) as claimed in claim 1 or 2, in which a second distance (9) of a gas inlet end side (11) of the exhaust gas treatment unit (6) from a gas inlet end side (10) of heat exchanger (7) is less than 60 mm, preferably less than 45 mm, particularly preferably less than 3 0 mm. 4. The exhaust system (1) as claimed in one of the preceding claims, in which the extent (12) of the exhaust gas treatment unit (6) in the direction of flow is less than 100 mm, preferably less than 50 mm, particularly preferably 25 mm or less. WO 2006/100090 PCT/EP2006/002702 - 14 - 5. The exhaust system (1) as claimed in one of the preceding claims, in which the first distance (8) between the exhaust gas treatment unit (6) and the heat exchanger (7) is less than 15 mm, preferably less than 10 mm, particularly preferably less than 5 mm. 6. The exhaust system (1) as claimed in one of the preceding claims, in which the exhaust gas treatment unit (6) comprises a honeycomb body (17). 7. The exhaust system (1) as claimed in one of the preceding claims, in which the exhaust gas treatment unit (6) comprises a catalytically active coating, in particular an oxidation catalyst coating. 8. The exhaust system (1) as claimed in one of the preceding claims, in which the ratio of the first backpressure to the second backpressure is greater than 2, preferably greater than 10. The invention relates to exhaust system (1) on an internal combustion engine (2), comprising an inlet system (3) and an exhaust outlet (4), whereby the exhaust outlet (4) and the inlet system(3) are connected by means of an exhaust recycle line (5) in which an exhaust treatment unit (6) and a heat exchanger (7) are embodied. The heat exchanger (7) has a first back pressure and the exhaust treatment unit (6) has a second back pressure smaller than the first back pressure, characterised in that the exhaust treatment unit (6) is embodied at such a first separation (8) from the heat exchanger (7) in the direction of flow that, during operation, a gas flow (14) entering the exhaust treatment unit (6) is equilibrated. Said exhaust system permits an advantageous embodiment of a heat exchanger (7) and an exhaust treatment un it (6), such as for example a honeycomb body in the exhaust recycle line (5), whereby both the heat exchanger (7) and the exhaust treatment unit (6) can have a smaller embodiment than in conventional system. The above reduces the costs considerably on equipping such a system.

Documents:

03518-kolnp-2007-abstract.pdf

03518-kolnp-2007-claims.pdf

03518-kolnp-2007-correspondence others 1.1.pdf

03518-kolnp-2007-correspondence others.pdf

03518-kolnp-2007-description complete.pdf

03518-kolnp-2007-drawings.pdf

03518-kolnp-2007-form 1.pdf

03518-kolnp-2007-form 18.pdf

03518-kolnp-2007-form 2.pdf

03518-kolnp-2007-form 3.pdf

03518-kolnp-2007-form 5.pdf

03518-kolnp-2007-gpa.pdf

03518-kolnp-2007-international publication.pdf

03518-kolnp-2007-international search report.pdf

03518-kolnp-2007-others pct form.pdf

03518-kolnp-2007-pct request form.pdf

03518-kolnp-2007-translated copy of priority document.pdf

3518-KOLNP-2007-CLAIMS-1.1.pdf

3518-KOLNP-2007-CORRESPONDENCE OTHERS 1.2.pdf

3518-KOLNP-2007-CORRESPONDENCE-1.3.pdf

3518-KOLNP-2007-CORRESPONDENCE-1.4.pdf

3518-KOLNP-2007-FORM 26.pdf

3518-KOLNP-2007-FORM 27.pdf

3518-KOLNP-2007-FORM-27.pdf

3518-KOLNP-2007-OTHERS-1.1.pdf

3518-KOLNP-2007-OTHERS.pdf

3518-KOLNP-2007-PETITION UNDER RULE 137.pdf

3518-KOLNP-2007-REPLY TO EXAMINATION REPORT.pdf

3518-KOLNP-2007-TRANSLATED COPY OF PRIORITY DOCUMENT 1.1.pdf

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