AT414295B - EXHAUST GUIDING ON A COMBUSTION ENGINE - Google Patents

Description

2

AT 414 295 B

The invention relates to the exhaust system in an internal combustion engine with cylinder banks arranged in a V-shape, wherein the exhaust ducts each lead to a cylinder bank in a common exhaust manifold and the exhaust duct downstream of an exhaust aftertreatment system for reducing at least NOX) consisting of at least one hydrolysis catalyst and at least one SCR -Catalyst contains.

In today's conventional diesel internal combustion engines for commercial vehicles, it is necessary for reasons of environmental compatibility to limit the proportions of nitrogen oxides to a minimum. For this purpose, exhaust aftertreatment systems are provided in which urea solution can be metered into the hot exhaust gas by means of a metering device upstream of a hydrolysis catalytic converter arranged in the exhaust gas line, the ammonia solution then being converted into ammonia in the hydrolysis catalytic converter. Downstream of the hydrolysis catalyst, an SCR catalyst is provided which, with the aid of the ammonia produced in the hydrolysis catalyst, effects the actual reduction of the nitrogen oxides (NO x). Such systems are e.g. known from DE 40 38 054 A1. 15

In replacement of the freezing at temperatures below -11.5 degrees Celsius and thus problematic in the use of aqueous urea solution, it is also known ammonia carrier in solid form z. B. solid urea, which is the upstream of a corresponding hydrolysis catalyst fed to the exhaust gas stream. Such a device is known for example from the 20 DE 102 52 734 A1.

Finally, it is known from DE 101 23 359 A1 to arrange the hydrolysis catalytic converter in the front silencer and the SCR catalytic converter in the main silencer of an internal combustion engine. 25

For thermal reasons, such exhaust aftertreatment systems are placed as close as possible to the exhaust manifold of the internal combustion engine.

For driving commercial vehicles often Brennkraftmaschi-nen 30 are used with V-shaped cylinder banks in the upper power range. In these internal combustion engines usually two exhaust manifolds each extend on the outer sides parallel to the cylinder banks, it is therefore advisable to arrange in each case a hydrolysis catalyst in the shortest possible distance downstream of the respective exhaust manifold. However, such an arrangement raises the problem that on the one hand the cost of exhaust aftertreatment for the elimination of NOx shares, especially for legislatures in connection with the EURO 4 or EURO 5 emission standard required electronic monitoring of the functionality of the exhaust aftertreatment system, almost doubled and on the other hand in commercial vehicles such as trucks in the area in question the available space is small. 40

It is therefore an object of the invention to provide for internal combustion engines with V-shaped arrangement of the cylinder banks an exhaust system, which avoids the disadvantages described above. The problem is solved by the characterizing features of claim 1, advantageous embodiments of the invention are characterized in the dependent claims.

In the solution of the problem, it is assumed that the exhaust manifolds are connected via a respective turbine of an exhaust gas turbocharger with exhaust pipes, which open into a pre-muffler common to the cylinder banks, into which a hydrolysis catalytic converter and an oxidation catalytic converter are integrated. The downstream of the front silencer is followed by a main silencer with integrated SCR catalytic converter.

In such a construction, the effort for the Abgasnachbe-55 is treatment system and in particular the associated control, monitoring and 3 in an advantageous manner

AT 414 295 B

Control devices are kept to a minimum. At the same time, the space required for the arrangement is advantageously minimized by the fact that the exhaust lines are grouped together after the turbines of the exhaust gas turbocharger and form the hydrolysis and oxidation catalyst or SCR catalyst integral components of the pre-muffler and the main muffler 5.

To reduce the production costs of the catalysts, it is possible to construct these advantageously from several identical modules. In order to optimize the thermal connection, in particular of the hydrolysis catalyst, it may be advantageous to equip the exhaust pipes at least partially with a heat insulation, which in addition to the thermal benefits for the hydrolysis at the same time necessary in the engine compartment of a commercial vehicle thermal shielding sensitive components is achieved, so that separate Shielding measures can be omitted. 15

An example of the invention and advantageous embodiments are explained in more detail with reference to the drawing.

The illustration shows a schematic representation of an internal combustion engine with Abgasnachbe-20 treatment system.

Basis of the arrangement shown is a for driving commercial vehicles, especially those with high performance, frequently used internal combustion engines 1 with V-shaped cylinder banks 2.1, 2.2. In such internal combustion engines in the cylinder banks 25 2.1, 2.2 released during the combustion process exhaust gases through outlet channels (not illustrated sets) and exhaust manifold 3.1, 3.2 exhaust manifolds 4.1, 4.2, respectively. The exhaust manifolds 4.1, 4.2 are parallel to the cylinder banks 2.1, 2.2 and are connected in the example shown with their ends to the inlet of a respective turbine 5.1, 5.2 each of an exhaust gas turbocharger 6.1, 6.2. From the outputs of the turbines 5.1, 5.2 each leads an exhaust pipe 30 7.1, 7.2 to a two exhaust pipes 7.1, 7.2 and thus both cylinder banks 2.1, 2.2 common muffler 8. In the front muffler 8 are located next to the necessary arrangements for the sound attenuation (not shown), an existing two modules oxidation catalyst 9, a hydrolysis catalyst 10 and upstream of the hydrolysis catalyst, a feed 11, which is connected to a device 12 arranged outside of the pre-silencer 8 metering. The output of the pre-silencer 8 is connected to a main silencer 13, in which, in addition to the not shown for the sound damping arrangements, an example of five modules existing SCR catalyst 14 is integrated. The exhaust duct ends after the skin muffler 13 in the surrounding atmosphere. 40

The oxidation catalyst 9 mentioned in the above description of the exhaust gas guide can consist of several modules flowed through in parallel or in succession, in the example two modules through which flow is made in parallel. As known from the prior art, the object of the oxidation catalyst (9) is to convert the NO contained in the exhaust gas into NO 2 45 in order to positively influence the subsequent conversion into nitrogen.

The object of the hydrolysis catalyst, which could also consist of several modules flowed through in parallel or in succession, but in the example embodied as a component, is, as is also known, therein the reducing agent so supplied via the feed 11 from the metering device 12 - usually aqueous urea solution or urea in solid form - to convert as completely as possible into NH3 and CO2.

The dosage of the reducing agent, as usual in such arrangements, accomplished via an acting on the metering device 12 electronic control unit 15, which is connected via its 55 inputs with sensors 16, 17.1, 17.2, 18, 19, the one hand operating parameters

Claims (3)

4 AT 414 295 B of the internal combustion engine such as speed, accelerator pedal position, temperature, etc. (sensor 16) and on the other hand, at various points of the exhaust system, operating parameters in the exhaust system of the internal combustion engine, such as pressure, exhaust gas temperature and NOx content (sensors 17.1, 17.2, 18, 19). The amount of reducing agent to be metered into the exhaust gas is determined from FIG. 5 by the operating parameters determined by the electronic control unit 15 and by the maps stored in the electronic control unit 15. The enriched with ammonia exhaust gas is supplied from the front silencer 8 to the main muffler 13, where the reduction of the NOx contained in the exhaust gas using the SCR catalyst takes place in a known manner. Reference is made to the publications mentioned in the introduction to the known chemical processes taking place in the exhaust gas aftertreatment. The monitoring of the functionality of the emission control system is also carried out by means of the electronic control unit 15 z. B. by the sensors 17.1, 17.2, 18, 19 detected 15 NOx content of the exhaust gas before and after the catalysts is compared by the control unit 15. For the sake of completeness, it should be mentioned that the control unit 15 may be part of the engine control unit, so that the mixture formation of the internal combustion engine can be controlled by taking into account the operating parameters determined in the exhaust gas tract by means of the sensors 17.1, 17.2, 18, 19. To shield the exhaust gas against heat loss, the exhaust pipes 7.1, 7.2, as indicated in the drawing by the exhaust pipes 7.1, 7.2, parallel lines, be provided with an insulation 20.1, 20.2. The shielding of the exhaust pipes 7.1, 7.2 against heat loss may therefore be necessary because the exhaust gas on the route between the turbines 5.1, 5.2 25 and the hydrolysis catalyst 10 would cool too much and so the implementation of z. As aqueous urea solution in ammonia, for which high exhaust gas temperatures are required, could not be done in the necessary manner. By the chosen construction, on the one hand, the shielding of heat-sensitive areas 30 of the vehicle and on the other hand, the protection of the exhaust gas from excessive heat loss on the way to the hydrolysis, achieved in an ideal manner. Of course, the example described above can be embodied in a variety of ways with specialist knowledge available to the person skilled in the art, without departing from the basic inventive concept; thus, these exemplary embodiments are exemplary in nature. 1. Exhaust system in an internal combustion engine with V-shaped arranged cylinder banks, the exhaust ports each a cylinder bank (2.1, 2.2) into a common exhaust manifold (4.1, 4.2) open and the exhaust system downstream of an exhaust aftertreatment system for reducing at least NOx consisting of at least one hydrolysis catalytic converter (10) and at least one SCR catalytic converter (14), characterized in that each exhaust gas manifold (4.1, 4.2) is connected at its end to the inlet of at least one turbine (5.1, 5.2) of at least one exhaust gas turbocharger ( 6.1, 6.2), the turbine (5.1, 5.2) is connected downstream to an exhaust pipe (7.1, 7.2) and the two exhaust pipes (7.1, 7.2) in a, two cylinder banks (2.1, 2.2) common pre-silencer (8). open, internally a hydrolysis catalyst (10) and we-50 least one oxidation catalyst (9) and the downstream of a Hauptschalldämp fer (13) with least ens integrated SCR catalyst (14). 2. Exhaust system according to claim 1, characterized in that the hydrolysis catalyst (10) and / or the oxidation catalyst (9) and / or the SCR catalyst (14) consists of a plurality of parallel or successively flowed through modules. 55 5 AT 414 295 B 3. Exhaust duct according to one of the preceding claims, characterized in that the exhaust pipes (7.1, 7.2) at least in part, a heat insulation (20.1, 20.2). 5 1 sheet of drawings 10 15 20 25 30 35 40 45 50 55