Exhaust Aftertreatment System

Abstract

An exhaust gas treatment system for the purpose of reducing the harmful substances present in the exhaust gas of combustion engines, particularly diesel engines, has a gas- and liquid-tight housing with at least one inlet and at least one outlet. Gas guide elements are arranged in the housing, and the housing encloses at least one chamber in which is contained a catalyst material and/or a particle filter material. The gas guide elements have spark-catching and/or spark-extinguishing elements.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an exhaust gas treatment system for the purpose of reducing the harmful substances in the exhaust gas of combustion engines, and particularly diesel engines.

Exhaust gas treatment systems for diesel engines are currently very well known. In automotive technology, the SCR method—that is, selective catalytic reduction method—is frequently used in exhaust gas treatment systems, in order to reduce nitrogen oxide emissions. By means of a selective catalytic reduction, nitrogen oxides are removed with a high degree of efficacy from the exhaust gas. The installation of an SCR system for nitrogen oxide reduction makes it possible to operate the engine at economical operating points.

The exhaust gas treatment system typically consists of a housing which is gas- and liquid-tight, having an inlet and an outlet, with gas guide elements arranged in the housing. The housing encloses at least one chamber which contains a catalyst material. Other exhaust gas treatment systems have corresponding construction; such a system contains a particle filter material in place of the catalyst material. In addition, the exhaust gas treatment system can be constructed in two-stages. In a first stage, the exhaust gas is guided over a catalyst material. Next, the exhaust gas enters a particle filter contained in the exhaust gas treatment system. Single-stage exhaust gas treatment systems are also known wherein only particle filters are used.

In known exhaust gas treatment systems, it has been necessary to date to additionally attach a spark catcher behind the exhaust gas treatment system. This additional spark catcher is a component which must be included additionally, through which the exhaust gas flow must be guided after passing through the exhaust gas treatment system. This guidance through the additionally configured spark catcher leads to a high back-pressure, and therefore to higher consumption of fuel. In addition, the weight of the entire exhaust gas treatment system is increased.

SUMMARY OF THE INVENTION

The problem addressed by the present invention is that of improving an exhaust gas treatment system for the purpose of reducing the harmful substances present in the exhaust gas of combustion engines, in such a manner that it is not necessary to include an additional spark catcher.

According to the invention, this problem is addressed in an exhaust gas treatment system with gas guide elements that have turbulence generating elements. By means of the turbulence generating elements, a spark-extinguishing optimization of the flow of the exhaust gases guided through the exhaust gas treatment system is achieved inside the exhaust gas treatment system. As a result of the increased turbulence, the spark particles in the exhaust gas flow are brought into contact with the respective walls in order that they are reduced in size and cooled down. The sparks are therefore reduced in size by means of at least one impact. As a result of the impact, the sparks cool down even more. Moreover, due to the turbulent flow, the duration for which the sparks remain in the exhaust gas treatment system is increased. During the duration of flow through the exhaust gas treatment system, the sparks come into contact with colder exhaust gas and the colder separation wall, and burn out. Preferred embodiments of the invention are defined by the dependent claims of this application.

According to certain claims, the gas guide elements are formed by separation walls running in parallel, which divide the exhaust gas into multiple partial flows.

The turbulence generating elements can advantageously be passages or cavities included in the separation wall, or baffles, impact points, or additional deflectors arranged between the separation walls. The deflectors can serve the purpose of guiding the exhaust gas flow carrying the sparks into the walls, in order to specifically reduce the size of the solid particles and cool them down.

The catalyst material can advantageously consist of a catalyst carrier material with a catalytic/chemical surface or coating.

According to a particularly advantageous embodiment of the invention, multiple chambers with catalysts can be connected one behind the other for the purpose of selective catalytic reduction.

Due to the high temperatures which arise, the separation wall advantageously consists of sheet metal or metal foil, and/or ceramic elements, or combinations of these materials.

According to a further advantage of the invention, at least one sound damping element can additionally be integrated into the housing of the exhaust gas treatment system.

In a further advantageous solution of the invention, in a particle filter included in the exhaust gas treatment system, the porosity of the walls through which the exhaust gas is guided is selected in such a manner that spark particles potentially present in the flow are filtered out.

According to an alternative solution of the invention, the exhaust gas treatment system is constructed in a single stage, wherein only one particle filter is included, wherein the porosity of the walls thereof, through which the exhaust gas is guided, is selected in such a manner that the spark particles entering the exhaust gas treatment system are filtered out. In this embodiment, therefore, all spark particles entering into the exhaust gas treatment system are completely filtered out by the particle filter.

Additional features, details, and advantages of the invention are explained in greater detail with reference to an embodiment which is illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cutaway illustration of an exhaust gas treatment system according to the present invention,

FIG. 2 shows a detail of the exhaust gas treatment system according to FIG. 1,

FIG. 3 shows an illustration corresponding to FIG. 2, with a direction of flow of the exhaust gases added to the drawing,

FIG. 4 shows a perspective illustration of a part of the exhaust gas treatment system according to FIG. 1,

FIG. 5 shows a schematic illustration of a further exhaust gas treatment system according to the present invention,

FIG. 6 shows a detail of the exhaust gas treatment system according to FIG. 5, and

FIG. 7 shows a schematic illustration of a further detail of the exhaust gas treatment system according to FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exhaust gas treatment system 1 for the purpose of reducing the harmful substances present in the exhaust gas of diesel engines. This exhaust gas treatment system 1 has a housing 5 which has an inlet 2 and an outlet 3. The diesel engine exhaust gases being cleaned are fed into the inlet 2. The cleaned exhaust gas exits from the outlet 3. Multiple chambers 6, 6′, and 6″ are constructed in the housing 5, wherein multiple chambers 6, 6′, and 6″ can each form a segment. In addition, gas guide elements 4 are arranged in the housing, as is seen in Detail A illustrated in FIG. 2. The gas guide elements 4 have separation walls 8, 8′, 8″ which divide the exhaust gas flow into partial flows 7, 7′, 7″. The separation walls 8, 8′, 8″ typically consist of metal. However, they can also consist of ceramic, because ceramic also withstands the high exhaust gas temperatures.

The cleaning of the exhaust gases themselves takes place in at least one element 9, 9′, the same consisting of one or multiple chambers 6, 6′, 6″. In each element 9 and/or 9′, the cleaning of the exhaust gases can take place by means of a chemical conversion and/or by filters. In one segment in the embodiment illustrated here, the exhaust gas flow comes into contact with a catalytically/chemically active surface or coating (the so-called wash coat 10). This surface can constitute a reducing or oxidizing catalyst.

The assurance that the gases exiting from the outlet 3 are free of sparks can be given by means of methods which extinguish sparks or separate out sparks. For this purpose, it is possible to utilize spark-extinguishing and/or spark-catching properties of the elements 9, 9′.

According to the present invention, the partial streams 7, 7′, and 7″ are turbulently whirled by suitable measures. This generation of turbulence is carried out by means of turbulence generating elements 11. The turbulence generating elements 11 can be passages, cavities, or impact points, as illustrated in FIGS. 2 and 3. Also, curved channels, structured channel walls, and flow deflectors can optionally be included. The flow line of the exhaust gas flow is indicated in FIG. 3, wherein the turbulence generated is indicated by the course of the flow lines. In order to generate turbulent flows here as early as possible, the highest possible flow velocity is generated (high Reynolds number).

One embodiment is shown in FIG. 4, in which the separation walls 8 consist of a core and/or base material 15 and are coated with a surface coating—a so-called wash coat 10. This constitutes an advantageous embodiment variant of the invention.

A second embodiment of the exhaust gas treatment system 1 for reducing the harmful substances present in the exhaust gases of diesel engines is shown in FIGS. 5 to 7.

FIG. 5 likewise shows a housing 5 in which, again, an inlet 2 and an outlet 3 are included. The diesel engine exhaust gas being cleaned is fed into the inlet 2, while the cleaned exhaust gas exits from the outlet 3. The embodiment variant illustrated here contains two regions. In the first region 20, an oxidative diesel catalyst is accommodated which contains a Metalit substrate.

The second region contains a diesel particle filter 30 and consists substantially of a ceramic substrate.

The first region in this embodiment variant of the exhaust gas treatment system 1 has turbulence generating elements as have already been explained in the context of the first embodiment. This is shown here in the perspective detail illustration according to FIG. 6. In this case, walls 22 which contain turbulence generating elements 24 are illustrated, via which the entire flow is made turbulent. In this way, it is possible for the spark particles 26 to be deposited on the wall, thereby reducing the size thereof and cooling the same, and therefore extinguishing them.

If spark particles are still contained in the treated exhaust gas flow exiting from region 20, these enter the region 30 together with the exhaust gas flow, said region 30 being constructed in principle according to FIG. 7. There, the exhaust gas flows into the closed channels 32 and passes through the porous walls 34. Upon passing through the porous walls, the soot particles, which typically have a diameter up to 23 nm, are filtered out. As a result of this filtration effect, spark particles which are potentially still present are also filtered out, such that at this point it is reliably assured that no spark particles are carried along with the exhaust gas exiting from the channels 36. Detail A in FIG. 7 shows schematically how a spark particle 26 is deposited on the porous wall 34.

Claims

1. An exhaust gas treatment system for reducing harmful substances present in exhaust gas of diesel engines, comprising:

a gas- and liquid-tight housing with at least one inlet and at least one outlet,

gas guide elements arranged in the housing, and

a catalyst material and/or a particle filter material contained in at least one chamber enclosed by the housing,

wherein the gas guide elements have spark-catching and/or spark-extinguishing elements.

2. An exhaust gas treatment system according to claim 1, wherein the gas guide elements are formed by separation walls, which run in parallel, and which divide the exhaust gas into multiple partial flows.

3. An exhaust gas treatment system according to claim 2, wherein the turbulence generating elements are passages or cavities included in the separation walls, baffles, impact points, or additional deflector plates arranged between the separation walls.

4. An exhaust gas treatment system according to claim 1, wherein the catalyst material consists of a catalyst carrier material having a catalytic chemical surface or coating.

5. An exhaust gas treatment system according to claim 1, wherein the at least one chamber contains a particle filter.

6. An exhaust gas treatment system according to claim 4, wherein the at least one chamber is one of multiple chambers with catalysts that are connected one behind the other for the purpose of selective catalytic reduction.

7. An exhaust gas treatment system according to claim 5, wherein the at least one chamber is one of multiple chambers with filters that are connected one behind the other.

8. An exhaust gas treatment system according to claim 2, wherein the separation walls are made of sheet metal or metal foil, or ceramic elements, or combinations of these materials.

9. An exhaust gas treatment system according to claim 1, further comprising at least one sound damper element that is additionally integrated into the system.

10. An exhaust gas treatment system according to claim 1, wherein the at least one chamber contains a first region in which is contained an oxidative catalyst, and a second region in which is contained a particle filter.

11. An exhaust gas treatment system according to claim 5, wherein, in the particle filter, a porosity of the walls through which the exhaust gas is guided is selected in such a manner that spark particles which are potentially present are filtered out.

12. An exhaust gas treatment system according to claim 4, wherein the at least one chamber contains a particle filter.

13. An exhaust gas treatment system according claim 2, wherein the catalyst material consists of a catalyst carrier material having a catalytic chemical surface or coating.

14. An exhaust gas treatment system according claim 3, wherein the catalyst material consists of a catalyst carrier material having a catalytic chemical surface or coating.

15. An exhaust gas treatment system according to claim 2, wherein the at least one chamber contains a particle filter.

16. An exhaust gas treatment system according to claim 3, wherein the at least one chamber contains a particle filter.

17. An exhaust gas treatment system according to claim 2, wherein the at least one chamber contains a first region in which is contained an oxidative catalyst, and a second region in which is contained a particle filter.

18. An exhaust gas treatment system according to claim 3, wherein the at least one chamber contains a first region in which is contained an oxidative catalyst, and a second region in which is contained a particle filter.

19. An exhaust gas treatment system according to claim 4, wherein the at least one chamber contains a first region in which is contained an oxidative catalyst, and a second region in which is contained a particle filter.

20. An exhaust gas treatment system according to claim 5, wherein the at least one chamber contains a first region in which is contained an oxidative catalyst, and a second region in which is contained a particle filter.