DE102008043487A1 - Internal combustion engine with turbocharger and oxidation catalyst - Google Patents

Abstract

The invention relates to an internal combustion engine (1) of a motor vehicle, having an exhaust system (2) which has at least one first turbine (5) of at least one turbocharger (4) for charging the internal combustion engine (1) and at least one first oxidation catalytic converter (21). It is provided that the first oxidation catalytic converter (21) is arranged upstream of the turbine (5) and that the exhaust system (2) has at least one denitrification device (23), which is arranged downstream of the first oxidation catalytic converter (21). Furthermore, the invention relates to a corresponding method.

Description

The The invention relates to an internal combustion engine of a motor vehicle with an exhaust system that has at least one, first turbine at least a turbocharger for charging the internal combustion engine and at least having a first oxidation catalyst.

State of the art

Internal combustion engines achieve their maximum efficiency in an operation with an excess of air in a fuel-air mixture at an air ratio λ> 1. It is necessary to reduce a nitrogen oxide content with exhaust gas of the internal combustion engine, a special exhaust aftertreatment system. A nitrogen oxide reduction (NO _x reduction) can only be carried out in the case of excess fuel, ie for λ <1 or in a catalytic manner with a stoichiometric mixture, that is to say for λ = 1. For this reason, both in a diesel internal combustion engine and in an Otto internal combustion engine, nitrogen oxide storage catalysts are used. These internal combustion engines also use selective catalytic reduction (SCR). Furthermore, an after-combustion of partially oxidized or unburned hydrocarbons additionally usually requires an oxidation catalyst and possibly a particle filter for particle reduction.

One Nitrogen oxide storage catalyst stores nitrogen oxides during a lean operation, that is for λ> 1, and is regularly included Presence of a fuel surplus regenerated in order to always ensure a sufficient storage capacity. During regeneration, nitrogen oxides are released, which with unburned Fuel or carbon monoxide to nitrogen, carbon dioxide and / or Water reacts. When exceeding the memory would that Nitrogen oxides pass the nitrogen oxide storage catalyst and from the vehicle as Pollutants ejected become. The nitrogen oxide storage catalysts operate in a temperature range the exhaust gases from about 250 to 500 ° C. Due to the fact that engine efficiencies continue to improve and so that temperatures of the exhaust gas are always lowered, is a low temperature activity the nitrogen oxide storage catalysts very relevant.

Becomes a motor vehicle operated with sulfur-containing fuel, so can form and store sulfates in the nitrogen oxide storage catalyst, resulting in a loss of storage capacity in the nitrogen oxide catalyst leads. To ensure the storage capacity the nitrogen oxide storage catalyst must occasionally desulfate become. For this purpose, have temperatures the exhaust gas of at least 650 ° C in Nitrogen oxide storage catalyst present.

Denitrification of exhaust gas by means of a system based on selective catalytic reduction requires the addition of ammonia (NH ₃ ) or precursors to form ammonia, which are introduced into the exhaust gas. In the catalytic reduction catalyst (SCR catalyst), the ammonia reacts via different reaction paths with the nitrogen oxides. It can come to the standard reaction with nitrogen monoxide and oxygen, a slow reaction with nitrogen dioxide or for rapid reaction with nitrogen monoxide and nitrogen dioxide. Such SCR catalysts generally operate in a temperature range of about 230 to 450 ° C. Nitrogen dioxide in particular can also be converted at temperatures below 230 ° C. If the SCR catalyst is preceded by an oxidation catalyst, a proportion of nitrogen dioxide in the inlet of the SCR catalyst increases, which increases the low-temperature activity of the SCR catalyst.

Basically, the effectiveness of the mentioned denitrification processes are influenced by the temperature of the exhaust gas. In particular, during a warm-up phase of the internal combustion engine after a cold start a Denitrifikationsvorrichtung (DeNO _x system) as well as the oxidation catalyst must be brought quickly to an operating temperature, so in a short driving cycle, such as a short certification driving cycle (new European driving cycle NEDC) sufficient Gesamtkonvertierungsphasen Denitrification can be achieved.

The Temperature of the exhaust gas at the denitrification depends mainly on Type of internal combustion engine and a structural design of the Exhaust system off. Charging systems, such as two-stage turbochargers allow high specific engine power of internal combustion engines, withdraw but the exhaust usually more heat than, for example, a single-stage turbocharger. This reduces the one hand for a heating the exhaust aftertreatment system required heat flow in the warm-up phase, On the other hand, the inlet temperatures for the exhaust aftertreatment decrease.

It is a device needed which is an increase of exhaust gas temperatures in the exhaust aftertreatment and thus a Improvement of pollutant conversion rates achieved.

Disclosure of the invention

According to the invention, it is provided that the first oxidation catalyst is arranged in terms of flow in front of the turbine and that the Abgasanla ge has at least one denitrification device, which is arranged in terms of flow after the first oxidation catalyst. This arrangement of the oxidation catalyst ensures that it is arranged close to the combustion chambers - cylinder - of the internal combustion engine and is supplied with exhaust gas, which has a high exhaust gas temperature, whereby the oxidation catalyst is heated very quickly to its operating temperature. Thus, it is achieved that an exhaust gas aftertreatment by the oxidation catalyst is carried out very quickly effectively and is very effective even at low load and / or speed of the internal combustion engine and / or despite high engine efficiencies. The use of the denitrification device (DeNOx system) in the exhaust system leads to nitrogen oxides in the exhaust gas being reduced by denitrification. The application of the first oxidation catalyst before the denitrification device further provides the advantage of increasing a nitrogen dioxide concentration within the exhaust gas to the denitrification device, which improves denitrification during a partial load operation of the internal combustion engine.

To A development of the invention provides that the denitrification device fluidically is arranged before or after the turbine. The turbine works due their mass as a heat sink, which reduces the exhaust gas temperature. This is especially true transient operation the internal combustion engine of the case. By an arrangement of the denitrification device before the turbine is achieved that the denitrification device in the same way as the first oxidation catalyst with a high exhaust gas temperature is applied and thus very fast reaches its operating temperature, causing emissions of the internal combustion engine quickly can be effectively reduced. Next is a urea evaporation for ammonia generation in the denitrification improved by higher exhaust gas temperatures (For example, Ad Blue evaporation). Particularly advantageous is the arrangement of the denitrification device between the first oxidation catalyst and the turbine since the Denitrification at a cold start of the internal combustion engine earlier reaches its operating temperature and also in one operation of Internal combustion engine at low loads a very good exhaust aftertreatment he follows. An arrangement of the denitrification device according to the Turbine leads causing the denitrification device to heat up more slowly and thus counteracted aging of the denitrification becomes.

To a development of the invention is a second oxidation catalyst intended. The second oxidation catalyst is preferably after arranged first oxidation catalyst and leads to a particularly good Exhaust gas aftertreatment, which is characterized by low emissions at delivery of the exhaust gas. Dependent on the execution of the first oxidation catalyst, that is, depending on its dimensions, Cell density and / or type of precious metal coating is the second Oxidation catalyst required to complete as possible a full hydrocarbon coals to achieve monoxide oxidation.

To a development of the invention, it is provided that the second Oxidation catalyst fluidically is arranged after the turbine. Because of this arrangement will the second oxidation catalyst protected from rapid aging.

To a development of the invention, it is provided that the second Oxidation catalyst fluidically is arranged before or after the Denitrifikationsvorrichtung. Advantageous is in particular the arrangement according to the denitrification device, as a possible Ammonia slip, that is Ammonia exiting the denitrification device, can be reacted on the second oxidation catalyst.

To a development of the invention is provided that the first and / or second oxidation catalyst, a three-way catalyst is. This is particularly advantageous if the otherwise lean operated Internal combustion engine with a higher fuel content, stoichiometric, is operated. This stoichiometric Operation is characterized by an air ratio λ = 1. In this case, the leads Use of the three-way catalytic converter for exhaust aftertreatment, which include both nitrogen oxides and hydrocarbons and carbon monoxide can implement.

To a development of the invention is provided that the exhaust system has a particle filter, which - fluidically seen - as the last Building member is disposed within the exhaust system. Under construction songs In the course of this application, particulate filters, denitrification devices, oxidation catalysts and turbines understood. Members do not designate exhaust gas Systems such as exhaust pipes and exhaust pots. The use of the particulate filter is preferably provided in diesel internal combustion engines.

To a development of the invention, a bypass is provided. Of the Bypass allows Pass exhaust past at least one of the members. This leads to, that the corresponding members are less stressed and thus aging of the members is prevented. Furthermore, by the bypass on the bypassed members a pressure within the Exhaust system can be reduced.

To a development of the invention is provided that the bypass fluidically parallel is switched to the first oxidation catalyst. Thus, will achieved that the first oxidation catalyst with a lower Amount of exhaust gas is applied, whereby the above-described Benefits arise.

To a development of the invention is provided that the bypass fluidically parallel for series connection of oxidation catalyst and Denitrifikationsvorrichtung is switched. Thus, it is achieved that the oxidation catalyst, and applied to the denitrification with less exhaust gas which gives the advantages described above.

To a development of the invention is provided that the bypass having a controllable valve. This ensures that the Amount of the bypassed exhaust gas can be controlled. The controllable Valve is preferably designed so that it depends the need at least partially open and partially closed again can be. By controlling the valve, preferably by a control of the exhaust gas flow controlled by the valve, by means of the valve is allowed Pressure losses in the exhaust system at a rated power and / or a Keep thermal stress of the members low. This is special then the case when the particulate filter is present and regenerates shall be. In this way it is achieved that the aging of the Structural elements is further reduced and thus a component protection for the members is present. It is especially provided, the bypass in a full load operation the internal combustion engine completely to open, To prevent the aging of the members and the component protection cause.

To a development of the invention is provided that the turbocharger a two-stage turbocharger with the first turbine and a second turbine is. By using the two-stage turbocharger is the Exhaust gas in the second turbine in addition Heat withdrawn, whereby the exhaust gas temperature decreases further. Therefore, an arrangement the oxidation catalyst and preferably also the denitrification device especially useful in front of the turbine. That way they can continue to be brought to an operating temperature very quickly, thereby giving the advantages described above.

To a development of the invention, it is provided that the second Turbine of the first turbine fluidically is downstream.

To a development of the invention, it is provided that the first Turbine a high pressure turbine and the second turbine a low pressure turbine is.

To a development of the invention is provided that the bypass fluidically parallel for series connection of oxidation catalyst, denitrification device and the first turbine is switched. In this way it is achieved if necessary, exhaust gas with high exhaust gas temperature to that of the turbine Downstream members can be forwarded and simultaneously at least a part of the performance of the turbocharger maintained becomes. This procedure is especially for a regeneration of the particulate filter advantageous. If it is intended that the denitrification device aerodynamically arranged after the high-pressure turbine and behind the bypass line is, can by change the exhaust gas flow within the bypass a nitrogen dioxide is controlled to nitric oxide ratio and / or regulated. If the denitrification device fluidic For example, the regeneration can be arranged parallel to the bypass of the particulate filter without unwanted Temperature drop at the Denitrifikationsvorrichtung done.

Further The invention relates to a method for operating an internal combustion engine of a motor vehicle, in particular according to the preceding description, with an exhaust system for guiding of exhaust gas, which is at least a first turbine of at least one turbocharger for charging the internal combustion engine and at least one first oxidation catalyst wherein the exhaust gas first the oxidation catalyst and then the first turbine and a denitrification device flows through. By the flow through the oxidation catalyst before the turbine and the denitrification device is achieved that the oxidation catalyst very quickly to a Operating temperature is brought, since the exhaust gas temperature before the Turbine and the denitrification device is higher than after the turbine and the denitrification device. This leads to a very good exhaust aftertreatment, in that the oxidation catalyst starts very quickly after commissioning, such as starting the engine, emissions are effective can treat.

According to a development of the method according to the invention, it is provided that at high load, in particular full load of the internal combustion engine, at least a portion of the exhaust gas of the internal combustion engine is bypassed at least on the oxidation catalyst or on the oxidation catalyst and on the denitrification device or on the oxidation catalyst, a denitrification device and on the first turbine. By passing the exhaust gas past the members ensures that the members are protected from aging and excessive stress. Depending on which Structural elements, the exhaust gas is conducted past, downstream members can be subjected to high exhaust gas temperatures to perform, for example, regenerations without burdening the members.

To a development of the invention is provided that by at least Partial passing of the exhaust gas, a Stickstoffoxidkonvertierung in the denitrification apparatus, a nitrogen dioxide to nitrogen monoxide ratio in the denitrification device, a temperature of the denitrification device and / or a temperature of the oxidation catalyst is / are regulated. The possibility, which of the mentioned sizes are regulated becomes dependent of which components of the exhaust system bypasses the exhaust gas becomes. Furthermore, for a Regulation a corresponding sensing necessary and the scheme can be carried out in an advantageous manner by a control unit, in particular engine control unit.

The Drawings illustrate the invention with reference to exemplary embodiments, and that shows:

1 an internal combustion engine with an exhaust system in a first embodiment,

2 an internal combustion engine with an exhaust system in a second embodiment, and

3 an internal combustion engine with an exhaust system in a third embodiment.

The 1 shows an internal combustion engine 1 a motor vehicle, not shown, with an exhaust system 2 in a first embodiment 3 that a turbocharger 4 with a turbine 5 having. Furthermore, the internal combustion engine has 1 an air intake system 6 , The air intake system 6 has an air intake 7 on which one over a pipeline 8th Air to a first compressor 9 of the turbocharger 4 leads, with the compressor 9 over a wave 9 ' with the turbine 5 connected is. The air will continue through a pipeline 10 in air ducts 11 brought. The air channels 11 lead to cylinders 12 the internal combustion engine 1 , from which exhaust gas into the exhaust manifold 13 and thus in the exhaust system 2 is directed. Starting from the manifolds 13 additionally runs an exhaust gas recirculation 14 which exhaust from the exhaust manifolds 13 over a pipeline 15 to a cooling element 16 and continue via a pipeline 17 to a return valve 18 leads. After the return valve 18 is recirculated exhaust gas via a pipeline 19 into the pipeline 10 brought. The exhaust gas recirculation 14 serves to exhaust gas into the air of the pipeline 10 to influence the combustion process and thereby reduce nitrogen oxide emissions. Starting from the exhaust manifolds 13 runs a pipeline 20 to a first oxidation catalyst 21 , From the first oxidation catalyst 21 runs a pipeline 22 to a denitrification device 23 , which have a pipeline 24 with the turbine 5 fluidically connected. About a pipeline 25 the exhaust gas gets out of the turbine 5 to a second oxidation catalyst 26 passed, which via another pipeline 27 with a particle filter 28 connected is. The particle filter 28 leads the exhaust gas through a pipeline 29 and an exhaust outlet 30 from. At the pipeline 20 begins a bypass 31 which is in the pipeline 24 empties. The bypass 31 has a controllable valve 32 on, which one through the bypass 31 can change the guided exhaust gas quantity. As building songs 33 become here the first oxidation catalyst 21 , the denitrification device 23 , the first turbine 5 , the second oxidation catalyst 26 as well as the particle filter 28 considered.

The in the 1 illustrated first embodiment 3 the exhaust system 2 allows, at least partially, the exhaust gas at the first oxidation catalyst 21 and the denitrification device 23 over the bypass 31 pass route. This allows the particle filter 28 can be acted upon by very high exhaust gas temperatures, without the first oxidation catalyst 21 and the denitrification device 23 to be heated unnecessarily. Thus, an aging of the first oxidation catalyst 21 and the denitrification device 23 prevented. It is envisaged that in a full load operation of the internal combustion engine 1 the valve 32 is fully opened, so as much as possible exhaust gas on the first oxidation catalyst 21 and at the denitrification device 23 is passed to obtain a component protection, by an unnecessary aging of the relevant members 33 is avoided. In the illustrated arrangement, it follows that the exhaust gas close to the engine, that is in the vicinity of the cylinder 12 with a high exhaust gas temperature in the first oxidation catalyst 21 occurs and this heated very quickly to its operating temperature. With the remaining, after the first oxidation catalyst 21 The present exhaust gas temperature then becomes the denitrification device 23 heated quickly to its operating temperature. Thus it is achieved that the two relevant members 33 very fast after a start of the engine 1 be put into operation and perform an optimal exhaust aftertreatment.

The 2 shows the internal combustion engine 1 of the 1 with all its features. The 2 is different from the 1 in that the exhaust system 2 in a second embodiment 34 is present. In the second embodiment 34 the exhaust system 2 is the denitrification device 23 fluidically after the turbine 5 arranged. Thus, it follows that the first Oxidationskatalysa gate 21 directly with the pipeline 24 is connected, whereas the pipeline 25 in the denitrification device 23 which leads via an additional pipeline 35 with the second oxidation catalyst 26 connected is. The pipeline 22 not applicable to the 1 Completely. In the illustrated second embodiment 34 the exhaust system 2 runs the bypass 31 also from the pipeline 20 to the pipeline 24 , whereby the exhaust gas on the first oxidation catalyst 21 is bypassed. The amount of bypassed exhaust gas is via the valve 32 controlled or regulated.

Due to the second embodiment 34 the exhaust system 2 The advantages mentioned above with regard to rapid heating and the component protection against aging result for the oxidation catalytic converter 21 , In addition, a nitrogen dioxide can be regulated to nitrogen monoxide ratio in the exhaust gas by, as infinitely as possible, exhaust gas through the bypass 31 on the oxidation catalyst 21 is bypassed. In this way, it is possible to carry out a nitrogen oxide (NO _x ) conversion in the denitrification apparatus 23 to optimize.

The 3 shows the internal combustion engine 1 with the exhaust system 2 in a third embodiment 35 , The internal combustion engine 1 in 3 has all the features of 1 on. In contrast to 1 points the turbocharger 4 the first turbine 5 and a second turbine 36 on. The first turbine 5 is a high pressure turbine 37 while the second turbine 36 as a low-pressure turbine 38 is trained. Further differences arise as follows. The pipeline 8th goes to a compressor 39 the second turbine 36 , which compressed air through a pipeline 40 to the compressor 9 of the turbocharger 4 leads. Thus, the turbocharger 4 as a two-stage turbocharger 40 educated. The compressor 9 is about the wave 9 ' with the turbine 5 operatively connected and the compressor 39 is about a wave 43 with the turbine 36 connected. The third embodiment 35 the exhaust system 2 starts with the exhaust manifolds 13 and runs over the pipeline 20 to the first oxidation catalyst 21 and continue over the pipeline 22 to the denitrification device 23 , From the denitrification device 23 runs a pipeline 44 leading to the first turbine 5 leads. The first turbine 5 is over a pipeline 45 with the second turbine 36 connected, what the pipeline 25 followed. The further course of the third embodiment 35 the exhaust system 2 to the exhaust outlet 30 corresponds to the 1 , The bypass 31 starts in the pipeline 20 and flows into the pipeline 45 so that the exhaust gas around the oxidation catalyst 21 , the denitrification device 43 and the first turbine 5 can be diverted. About the valve 32 it is possible to set the amount of exhaust gas to be bypassed.

The illustrated third embodiment 35 the exhaust system 2 makes it possible, in addition to the already mentioned advantages with respect to rapid reaching of the operating temperatures and the component protection against aging, the first turbine 5 , the high-pressure turbine 37 to get around. This is advantageous when high loads on the internal combustion engine 1 present, so the high-pressure turbine 5 of the turbocharger 4 if possible can be spared. The embodiment 35 allows the particle filter 28 to apply high exhaust gas temperatures for regeneration without the denitrification device 23 be exposed to thermal loads.

In another, not shown embodiment of the exhaust system 2 it is conceivable starting from the embodiment 35 the denitrification device 23 after the first turbine 5 and after the bypass 31 to arrange. This embodiment allows the nitrogen dioxide to nitrogen monoxide ratio across the valve 32 to control or regulate.

Furthermore, in all embodiments 3 . 24 and 35 conceivable that the oxidation catalysts 21 and or 26 are designed as three-way catalysts. This is advantageous when the internal combustion engine 1 at least temporarily in a stoichiometric operation with an air ratio λ = 1 is operated.

Claims (18)

Internal combustion engine ( 1 ) of a motor vehicle, with an exhaust system ( 2 ), the at least one, first turbine ( 5 ) at least one turbocharger ( 4 ) for charging the internal combustion engine ( 1 ) and at least one, first oxidation catalyst ( 21 ), characterized in that the first oxidation catalyst ( 21 ) fluidically in front of the turbine ( 5 ) and that the exhaust system ( 2 ) at least one denitrification device ( 23 ), which are fluidically after the first oxidation catalyst ( 21 ) is arranged. Internal combustion engine ( 1 ) according to claim 1, characterized in that the denitrification device ( 23 ) fluidically before or after the turbine ( 5 ) is arranged. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized by a second oxidation catalyst ( 26 ). Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second oxidation catalyst ( 26 ) fluidically after the turbine ( 5 ) is arranged. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second oxidation catalyst ( 26 ) fluidically before or after the denitrification device ( 23 ) is arranged. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the first and / or second oxidation catalyst ( 21 . 26 ) is a three-way catalyst. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the exhaust system ( 2 ) a particle filter ( 28 ), which - fluidically speaking - as the last member ( 33 ) within the exhaust system ( 2 ) is arranged. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized by a bypass ( 31 ). Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the bypass ( 31 ) fluidically parallel to the first oxidation catalyst ( 21 ) is switched. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the bypass ( 31 ) fluidically parallel to the series connection of oxidation catalyst ( 21 ) and denitrification device ( 23 ) is switched. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the bypass ( 31 ) a controllable valve ( 32 ) having. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the turbocharger ( 4 ) a two-stage turbocharger ( 40 ) with the first turbine ( 5 ) and a second turbine ( 36 ). Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second turbine ( 36 ) of the first turbine ( 5 ) downstream of the flow. Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the first turbine ( 5 ) a high-pressure turbine ( 37 ) and the second turbine ( 36 ) a low-pressure turbine ( 38 ). Internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the bypass ( 31 ) fluidically parallel to the series connection of oxidation catalyst ( 21 ), Denitrification device ( 23 ) and the first turbine ( 5 ) is switched. Method for operating an internal combustion engine ( 1 ) of a motor vehicle, in particular according to one or more of the preceding claims, with an exhaust system ( 2 ) for guiding exhaust gas, the at least one first turbine ( 5 ) at least one turbocharger ( 4 ) for charging the internal combustion engine ( 1 ) and at least one first oxidation catalyst ( 21 ), characterized in that the exhaust gas only the oxidation catalyst ( 21 ) and then the first turbine ( 5 ) and a denitrification device ( 23 ) flows through. A method according to claim 15, characterized in that at high load, in particular full load of the internal combustion engine ( 1 ), at least a portion of the exhaust gas of the internal combustion engine ( 1 ) at least on the oxidation catalyst ( 21 ) or on the oxidation catalyst ( 21 ) and at the denitrification device ( 23 ) or on the oxidation catalyst ( 21 ), at the denitrification device ( 23 ) and at the first turbine ( 5 ) is bypassed. Method according to one of the preceding claims, characterized in that by at least partially bypassing the exhaust gas, a nitrogen oxide conversion in the denitrification device ( 23 ), a nitrogen dioxide to nitrogen monoxide ratio in the denitrification apparatus ( 23 ), a temperature of the denitrification device ( 23 ) and / or a temperature of the oxidation catalyst ( 21 . 26 ) is / are regulated.