DE102017209483A1 - Optimized exhaust gas purification - Google Patents

Abstract

The present invention relates to an exhaust gas purification system for a motor vehicle and a method for operating the exhaust gas purification system.

Description

The present invention relates to an exhaust gas purification system for a motor vehicle and a method for operating the exhaust gas purification system.

The exhaust gases from internal combustion engines are now cleaned in multiple stages. The exhaust gas flows through different monoliths. These include catalysts and filters. To optimize the cleaning, the exhaust gases are mixed with reactants. This mixture of exhaust gas and reactant can then react optimally in a monolith (which often also has a coating).

The exhaust gas generated by the internal combustion engine initially flows laminar through a pipe of the exhaust gas purification system and is swirled in a first step by a mixer. In the turbulent exhaust gas, a reactant is introduced into the exhaust gas flow through an injector arranged after the mixer. The resulting turbulent fluid mixture may then be reacted with the reactant in a monolith, such as a catalyst.

The series connection of the components of the system results in a long exhaust gas purification path. This means a large space requirement, more weight and increased back pressure. The increased back pressure is due to the long distance of the exhaust gas cleaning system to conditions and leads to a loss of power.

It would therefore be desirable to provide an exhaust gas purification system which allows a more compact design. Proposals have already been made to more spatially merge the mixing element and the reactant injector.

EP 2 796 684 A1 discloses a mixing device for an exhaust gas purification system. The mixing device serves to swirl an exhaust gas and has an integrated injection device for a reducing agent, for. As a urea solution, on. Herein, the reactant is first added to the exhaust gas flow through a metering unit, and then the exhaust gas is fluidized by a mixer and the already added reactant is distributed in the exhaust gas flow.

Out EP 2 314 837 A1 For example, an exhaust gas mixing module for turbulence of exhaust gases, which comprises an integrated injection for a reducing agent, emerges. Through a tubular intake, exhaust gas from a chamber of an exhaust gas purification system is sucked into a second chamber. In this tubular aspiration, a reactant is injected through an external dosing module. This two-stage system with turbulence of the exhaust stream and subsequent addition of the reactant has a strong back pressure increase result.

DE 10 2011 018 569 A1 teaches an exhaust system with a metering valve for injecting a reducing agent. A metering valve injects a reducing agent laterally into an exhaust gas flow led to a catalytic converter in an exhaust gas duct. The injection device of the metering valve is directed to a baffle arranged in the exhaust device.

Against this background, the object of the invention was to provide an exhaust gas purification system with reduced space requirement and reduced pressure build-up.

An object of the invention is an exhaust gas purification system for a motor vehicle, comprising a tubular housing with an inlet for an exhaust gas stream to be cleaned and an outlet for a purified exhaust gas stream. In the tubular housing, a loaded with a reactant mixing element for generating a turbulent fluid mixture containing exhaust gas and reactant is arranged. Downstream of the mixing element loaded with a reactant is disposed a honeycomb body loaded with a catalyst for reacting the turbulent fluid mixture.

In one embodiment of the exhaust gas purification system according to the invention, the mixing element loaded with a reactant fills the entire cross section of the tubular housing. In one embodiment, the mixing element loaded with a reactant is a static mixer.

The mixing element of the exhaust gas purification system according to the invention is loaded with a reactant. In one embodiment, the surface of the mixing element is coated with a reactant, for example in the form of a suspension or a solution, which wets and adheres to the surface of the mixing element.

The term "reactant" is used in the context of the present invention for substances which can react with pollutants contained in the exhaust gas to form less toxic or less harmful reaction products. In one embodiment of the invention, the reactant comprises urea. In a specific embodiment, the reactant is an aqueous urea solution.

In one embodiment, the exhaust gas purification system comprises a supply to the mixing element, via which the mixing element can be fed with a reactant. In a Embodiment, the reactant is supplied from an external reservoir to the mixing element.

An advantage of the exhaust gas purification system according to the invention is that the reactant is introduced into the exhaust gas flow via the mixing element. In this case, the mixing element may be loaded or wetted with a reactant and / or fed via an external inflow with the reactant. This makes a separate injection of the reactant and the associated injector dispensable.

In the exhaust gas purification system according to the invention, by combining the swirling of the laminar exhaust gas flow and the mixing of the exhaust gas with a reactant at one point, the distance of the exhaust gas purification is shortened. This offers the advantages of reducing the installation space and weight of the exhaust gas purification system and reducing the backpressure. Both have a positive effect on the cleaning of the exhaust gases.

Another object of the invention is a method for purifying an exhaust gas stream of a motor vehicle. In this case, an exhaust gas stream to be purified is passed through a mixing element loaded with a reactant. The mixing element swirls the exhaust stream and simultaneously releases the reactant. This creates a turbulent fluid mixture containing exhaust gas and reactant. Subsequently, the turbulent, exhaust gas and reactant-containing fluid mixture is passed through a honeycomb body loaded with a catalyst, brought in the exhaust gas and reactant for implementation and thereby pollutants are removed from the exhaust gas.

• 1 in einer schematischen Darstellung ein Abgasreinigungssystem des Standes der Technik;
• 2 in einer schematischen Darstellung eine Ausführungsform des erfindungsgemäßen Abgasreinigungssystems.

The invention is schematically illustrated by means of embodiments in the drawings and will be further described with reference to the drawings. It shows:

• 1 in a schematic representation of an exhaust gas purification system of the prior art;
• 2 in a schematic representation of an embodiment of the emission control system according to the invention.

In 1 is schematically an emission control system 10 of the prior art. In a tubular housing 12 are a mixing element 13 and a catalyst carrier 14 loaded with a catalyst. Between the mixing element 13 and the catalyst carrier 14 there is an injector 16 , Through the exhaust inlet 11 becomes a laminar exhaust flow 1 in the emission control system 10 directed. The laminar exhaust gas flow 1 flows through the mixing element 13 that swirls it and a turbulent exhaust flow 4 generated. About the injector 16 becomes a reactant 5 , For example, an aqueous urea solution, in the turbulent exhaust gas stream 4 sprayed, creating a turbulent fluid mixture 6 arises, the exhaust gas and the reactants 5 contains. This fluid mixture flows through the catalyst support loaded with a catalyst 14 , There react exhaust and reactant 5 each other and pollutants contained in the exhaust gas, z. As nitrogen oxides are converted into non-toxic reaction products. The exhaust gas flow leaves the exhaust gas purification system 10 over the exhaust outlet 15 ,

In 2 is schematically an embodiment 20 of the exhaust gas purification system according to the invention. In a tubular housing 22 are one with a reactant 5 , z. As urea, loaded mixing element 23 and a catalyst carrier 24 loaded with a catalyst 1 the system shown is the mixing element 23 already with a reactant 5 , z. As urea loaded. Through the exhaust inlet 21 becomes a laminar exhaust flow 1 in the emission control system 20 passed and flows through with a reactant 5 loaded mixing element 23 , When flowing through the mixing element 23 gets out of the laminar exhaust stream 1 directly a turbulent fluid mixture 6 generated, the exhaust gas and the reactants 5 contains. Therefore, there is no additional injector for the reactant 5 more required. How out 2 becomes clear, therefore, the distance between the mixing element can be 23 and the catalyst carrier loaded with a catalyst 24 significantly shorten what a considerable space savings for the entire emission control system 20 allows. Due to the shorter design, the weight of the exhaust gas cleaning system 20 is reduced and there is a lower back pressure in the system. The turbulent fluid mixture 6 flows through the catalyst support loaded with a catalyst 24 , There react exhaust and reactant 5 each other and pollutants contained in the exhaust gas, z. As nitrogen oxides are converted into non-toxic reaction products. The purified exhaust gas flow leaves the exhaust gas purification system 20 over the exhaust outlet 25 ,

LIST OF REFERENCE NUMBERS

1

Exhaust stream (laminar)

4

Exhaust gas flow (turbulent)

5

reactant

6

Turbulent fluid mixture

10

emission Control system

11

exhaust inlet

12

casing

13

mixing element

14

Catalyst / particulate filter

15

exhaust outlet

16

injector

20

emission Control system

21

exhaust inlet

22

casing

23

mixing element

24

Catalyst / particulate filter

25

exhaust outlet

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2796684 A1 [0006]
• EP 2314837 A1 [0007]
• DE 102011018569 A1 [0008]

Claims (10)

An exhaust gas purification system (20) for a motor vehicle, comprising a tubular housing (22) with an inlet (21) for an exhaust gas stream to be cleaned and an outlet (25) for a purified exhaust gas stream, containing therein a mixing element (23) loaded with a reactant (5) ) for generating a turbulent fluid mixture (6) containing exhaust gas and reactant (5) and a downstream of the mixing element (23) arranged, loaded with a catalyst honeycomb body (24) for the implementation of the turbulent fluid mixture (6). Emission control system (20) according to Claim 1 in which the mixing element (23) fills the entire cross section of the tube (22). Emission control system (20) according to Claim 1 or 2 in which the mixing element (23) is a static mixer. Emission control system (20) according to one of Claims 1 to 3 in which the surface of the mixing element (23) is coated with a reactant (5). Emission control system (20) according to one of Claims 1 to 3 in which the surface of the mixing element (23) is wetted by a liquid containing a reactant (5). An exhaust gas purification system (20) according to any one of the preceding claims, which has a feed to the mixing element (23) via which the mixing element (23) can be fed with a reactant (5). An exhaust gas purification system (20) according to any one of the preceding claims, wherein the reactant (5) comprises urea. A method of purifying an exhaust gas stream of a motor vehicle, wherein a laminar exhaust gas stream (1) to be purified is passed through a mixing element (23) loaded with a reactant (5), thereby producing a turbulent fluid mixture (6) containing exhaust gas and reactant (5); and then the turbulent fluid mixture (6) containing the exhaust gas and reactant (5) is passed through a honeycomb body (24) loaded with a catalyst, in which the exhaust gas and reactant (5) are reacted and thereby pollutants are removed from the exhaust gas. Method according to Claim 8 in which the mixing element (23) is a static mixer. Method according to Claim 8 or 9 in which the reactant (5) comprises urea.

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