EP3752721A1

EP3752721A1 - Exhaust aftertreatment device for dosing a liquid exhaust aftertreatment agent

Info

Publication number: EP3752721A1
Application number: EP19700042.5A
Authority: EP
Inventors: Kamran Khani
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-02-15
Filing date: 2019-01-03
Publication date: 2020-12-23
Anticipated expiration: 2039-01-03
Also published as: EP3752721B1; WO2019158269A1; DE102018202298A1; CN111742123B; CN111742123A

Abstract

The invention relates to an exhaust aftertreatment device (7) for metering a liquid aftertreatment agent into an exhaust stream of an internal combustion engine, comprising a mixing chamber (22), in which the exhaust aftertreatment agent is mixed with the exhaust stream, a mixing chamber (22) having a circularly cylindrical mixing pipe (8), which has a funnel-shaped end section (9) widening the periphery toward a free end, having a funnel element (17) opening at least partly conically in the direction of the mixing pipe (8), which has a plurality of passage openings (18) in the lateral wall (19) of the funnel element, and wherein an injection valve (21) for the exhaust aftertreatment agent is arranged at the end of the funnel element (17) that faces away from the mixing tube (8), in order to inject the exhaust aftertreatment agent into the funnel element (17). According to the invention, the funnel element (17) is located at least substantially within the end section (9), coaxially with respect to the end section, and at least some of the passage openings (18) are each assigned a flow element (20) rising up from the lateral wall (19) to produce a swirling flow in the mixing pipe (8).

Description

description

title

Exhaust after-treatment device for dosing a liquid

Mitel exhaust aftertreatment

The invention relates to an exhaust aftertreatment device for metering a liquid exhaust aftertreatment agent into an exhaust stream of an internal combustion engine, with a mixing chamber, in which the

Exhaust aftertreatment agent is mixed with the exhaust gas stream, wherein the mixing chamber has a circular cylindrical mixing tube having a funnel-shaped end portion which widens towards a free end with a funnel element which opens conically at least in sections in the direction of the mixing tube and which has a plurality of funnels

Having flow openings in its jacket wall, and with an injection valve, which at the end facing away from the mixing tube of the

Funnel element is arranged to inject the exhaust aftertreatment agent into the T judge element.

Furthermore, the invention relates to an exhaust aftertreatment system with the above-mentioned exhaust aftertreatment device.

State of the art

Exhaust gas aftertreatment devices of the type mentioned are known from the prior art. In order to comply with the stricter legislation on permissible discharge levels of pollutants in the exhaust gas of

To meet internal combustion engines of motor vehicles, it is known to use exhaust aftertreatment devices, which ensure a reduction of pollutants by using an additional exhaust aftertreatment agent. So it is known, for example, by the so-called SCR Method (SCR = selective catalytic reduction) to first mix an exhaust gas with an exhaust aftertreatment agent, and then to supply an SCR catalyst in which the exhaust gas together with the

Exhaust aftertreatment agent reacts and pollutant emissions are reduced. As exhaust aftertreatment agent is an aqueous

Urea solution by means of suitable metering systems, in particular

Injectors, is injected into the exhaust gas or the exhaust pipe. From the aqueous urea solution, which during operation of the

Internal combustion engine is supplied to the exhaust gas, the reducing agent ammonia is obtained by means of thermolysis and hydrolysis. In the treatment of the urea solution in the exhaust gas, there is the difficulty that in addition to the desired chemical reaction of the thermolysis, in which the ammonia is released, crystalline by-products can arise.

From the publication WO 2015/197145 Al, for example, an exhaust aftertreatment device of the type mentioned is known. In order to improve the mixing of the exhaust aftertreatment agent and exhaust gas, the exhaust gas is introduced radially into a mixing chamber, so that a swirl occurs even before the exhaust gas and the exhaust aftertreatment agent are mixed together. As a result, the mixture preparation is improved. By means of a funnel-shaped element, it is ensured that the injected exhaust gas aftertreatment agent can initially expand substantially undisturbed through the exhaust gas flow over a predetermined length, before it is mixed with the exhaust gas flow. In this case, the exhaust gas regardless of the

Exhaust aftertreatment agent flow into the mixing tube.

Disclosure of the invention

The exhaust aftertreatment device according to the invention with the features of claim 1 has the advantage that despite a small space volume optimum mixing of exhaust gas and exhaust aftertreatment agent takes place, and crystalline by-products are avoided during operation. According to the invention this is achieved in that the funnel element is at least substantially within the end portion coaxial with the end portion, and that at least some of the flow openings each one of the Mantle wall is assigned in particular outwardly uplifting flow guide for generating a swirl flow in the mixing tube. The

Funnel element is substantially free in the mixing chamber, but ends in a funnel-shaped widened end portion of the in the

Mixing chamber also protruding mixing tube. By doing that

Funnel element is at least substantially within the end portion, it is achieved that an admission of the funnel element is ensured with the inflowing into the mixing tube exhaust gas. In this case, the exhaust gas at least partially flows through the through-flow openings through the jacket wall of the funnel element in order to be already mixed with the exhaust-gas aftertreatment agent within the funnel element. The flow guide elements assigned to the respective throughflow openings ensure that the exhaust gas flowing in or flowing through the jacket is directed into a swirling motion, which additionally improves the mixing of the exhaust aftertreatment agent with the exhaust gas. Characterized in that the swirl flow is achieved by the funnel element, the swirl flow is independent of how the exhaust gas of the exhaust gas aftertreatment device is supplied. The mixing chamber is thus completely in the mixing tube. This makes it possible to make the exhaust aftertreatment device much more space-saving than was previously possible and at the same time to avoid the aforementioned disadvantages.

According to a preferred embodiment of the invention it is provided that the flow openings in an injection valve near area

Flow guide-free. This means that the flow-through opening in the injection-valve-near region represent simple openings which are not

Swirl effect on the exhaust gas and / or the exhaust aftertreatment agent exercise. On the contrary, the simple passage openings allow the exhaust gas to flow into the funnel element without serious recirculation areas.

Preference is given to all flow openings, with the exception of

Throughflow openings in the injection valve near each area

Associated flow guide. In the injector remote area thus the flow guide elements are present to the swirl flow through the through Mantle wall of the funnel element to produce flowing exhaust gas. Due to the late swirl generation is also achieved that the

Exhaust aftertreatment agent spray can first expand more or less undisturbed and atomized before it is mixed with the exhaust gas, whereby an optimized mixing is achieved. By doing that all

Injector valves flow openings are provided with flow guide, a swirl generation is ensured with high efficiency.

According to a preferred embodiment of the invention, the funnel element is arranged on a cup-shaped flow element, wherein the

Flow element is located in an exhaust gas supply passage, in which the free end of the mixing tube opens. The funnel element is thus held by a separate flow element, wherein the flow element in a

Abgaszuführkanal is located, and in particular attached to this. Through the cup-shaped element of the air flow is directed from the feed channel in the direction of the mixing tube. Due to the cup-shaped design, the arrangement of the injection valve is ensured particularly close to the top of the funnel element in a simple manner. In particular, the center axes of the cup-shaped flow element and of the mixing tube are aligned with one another in order to achieve an advantageous flow effect.

Furthermore, it is preferably provided that the flow element has a tapered in the direction of the mixing tube and formed closed cone wall. Due to the conical shape of the cup-shaped

Flow element, the exhaust gas flow from the Abgaszuführkanal is optimized in the mixing tube, in particular by avoiding turbulence in the transition from the feed channel into the mixing tube. In addition, an annular gap is defined by the flow element to the mixing tube or its orifice, through which the exhaust gas flowing into the mixing tube is compressed and / or accelerated, whereby the mixing with the exhaust aftertreatment agent is further improved.

This is according to a preferred embodiment of the invention

Flow element partially in the end portion of the mixing tube into it. As a result, the formation of the annular gap and a defined leadership of the Exhaust gas flow ensured in the mixing tube. In addition, this results in a compact embodiment of the exhaust aftertreatment device.

Furthermore, the injection valve is preferably fastened or arranged on the flow element and / or on the funnel element in such a way that a central axis of the conically ejected exhaust gas aftertreatment means and a spin axis generated by the flow guide elements are at least substantially aligned with one another. As a result, the exhaust gas aftertreatment agent is injected into the exhaust gas particularly close to the eye of the swirl flow, resulting in advantageous mixing.

Furthermore, it is preferably provided that the flow guide elements are designed or oriented such that at least part of the injected exhaust gas aftertreatment agent encounters an inner wall of the mixing tube.

This ensures that the exhaust aftertreatment agent is evenly distributed on the inside of the mixing tube wall and there at least largely evaporated in the further operation of the internal combustion engine. Due to the swirl flow, the thermal energy input into the wall, which increases the

Evaporation of the exhaust aftertreatment agent is used. The swirl flow prevents larger amounts of the exhaust aftertreatment agent from passing the mixing tube without contact with the inner wall.

According to a preferred development, the funnel element bears radially on the mixing tube. At its free end, on which the funnel element has its greatest outer circumference, the funnel element thus rests radially on the inner wall of the mixing tube, whereby it is achieved that all the exhaust gas has to flow through throughflow openings of the funnel element in order to reach the mixing tube. As a result, the swirl flow is set particularly secure and ensures the advantageous mixing.

According to an alternative embodiment of the invention, it is preferably provided that a particularly annular bypass gap for the exhaust gas is present radially between the funnel element and the mixing tube. In this case, therefore, there remains a radial distance between the funnel element and the mixing tube or its inner wall. This leaves the gap also on the largest outer circumference of the funnel element. Through the bypass gap, the exhaust gas can be transferred without passing into the swirl flow past the funnel element into the mixing tube. Here, for example, an advantage that the dynamic pressure of the exhaust gas aftertreatment device is reduced to the exhaust gas. The bypass channel may extend annularly or ring segment-shaped over the circumference of the funnel element. Thus, the possibility remains that the funnel element is radially positioned by one or more webs or spacers arranged on its outer circumference in the mixing tube, which abut against the inner wall of the mixing tube.

Advantageously, the funnel element opens funnel-shaped along its entire longitudinal extent. Thus, the funnel element is overall funnel-shaped, so that it optimally to the shape of the

Exhaust aftertreatment agent sprays of the injector is adjustable.

Alternatively, the funnel element is funnel-shaped only in one end region and in an area close to the injection valve in particular

cylindrical, wherein preferred only in this area

Throughflow openings are formed. Also in this case, the or at least most of the flow openings is preferably one each

Flow guide, as described above, assigned to the

To generate hydraulic flow. On the one hand, it is achieved by means of the funnel-shaped end region that the exhaust gas aftertreatment agent spray can expand to the end of the funnel section, and on the other hand that advantageous mixing also takes place downstream of the funnel element in the funnel

Mixing tube takes place.

Furthermore, it is preferably provided that the Abgaszuführkanal extends transversely, in particular perpendicular to the central axis of the mixing tube. This results in a deflection of the exhaust gas into the mixing tube, which is for example 90 °. This ensures a compact design, due to the advantageous embodiment of the exhaust aftertreatment device the

Deflection has no adverse effect on the flow behavior. In particular, the exhaust gas supply passage causes exhaust gas diversion of the exhaust gas into the mixing pipe of 180 ° or less. As a result, particularly compact designs of the exhaust aftertreatment device can be achieved.

Preferably, the flow guide elements have a straight transverse and / or longitudinal section, or alternatively have a curvature in the cross section and / or longitudinal section, through which the preferred swirl flow is achieved.

The exhaust aftertreatment system according to the invention with the features of claim 15 is characterized by the inventive

Exhaust after-treatment device off. This results in the already mentioned advantages.

Further advantages and preferred features and combinations of features result from the previously described and from the claims.

In the following, the invention will be explained in more detail with reference to the drawing. Show this

Figure 1 shows an exhaust aftertreatment system in a simplified

Longitudinal view,

Figure 2 shows an exhaust aftertreatment device of

Exhaust aftertreatment system in an enlarged sectional view,

Figures 3A and 3B show a first embodiment of an advantageous

Funnel element of the exhaust aftertreatment device,

FIGS. 4A and 4B show a second embodiment of the funnel element,

Figures 5A and 5B, a third embodiment of the advantageous

Funnel element and FIGS. 6A and 6B show a fourth embodiment of the funnel element, in each case in a side view and in a plan view.

FIG. 1 shows a simplified sectional view

Exhaust after-treatment system 1 for an internal combustion engine

Motor vehicle. The exhaust aftertreatment system 1 has an exhaust pipe 2, which adjoins the internal combustion engine and has an exhaust gas inlet 3. In the exhaust pipe 2, for example, a first catalyst 4 and a particle filter 5 downstream of the catalyst 4 are arranged, which treat the exhaust gas flowing into the exhaust pipe 2 in a known manner. The exhaust pipe 2 is in an exhaust gas supply channel 6 for a

Exhaust after-treatment device 7, which will be described in more detail below.

Figure 2 shows an enlarged sectional view of the

Exhaust gas aftertreatment device 7. This has a mixing tube 8 opening into the exhaust gas supply duct 6. A the Abgaszuführkanal 6 facing

End portion 9 of the mixing tube widens in the direction of the Abgaszuführkanals 6 conically. The end portion 9 terminates at a first side wall 10 of the Abgaszuführkanals 6. On one of the side wall 10 disposed opposite side wall 11 of the Abgaszuführkanals 6 a cup-shaped flow element 12 is fixed, which projects into the Abgaszuführkanal 6 in the direction of the mixing tube 8, so that it the Abgaszuführkanal. 6 in this case penetrates completely from the side wall 11 to the side wall 10. At the side wall 10, the flow element 12 protrudes into a mouth opening of the end section 9 in the side wall 10.

In this case, the flow element 12 has an end section 13 facing the mixing tube 8, which tapers in the direction of the mixing tube 8. The end portion 13 extends in the longitudinal direction of the

A shell wall 14 of the flow element 12, which seen in longitudinal section has the conical shape, is closed and ends in a the mixing tube 8 facing bottom portion 15, the flow element 12, or in axial extension, over more than half of the entire longitudinal extent essentially extends parallel to the side walls 10 and 11 of the Abgaszuführkanals 6. In the bottom portion 15, an opening 16 is formed centrally. This opening 16 is associated with a funnel 17. According to the present exemplary embodiment, the funnel element 17 is funnel-shaped in such a way that it widens from the flow element 12 in the direction of the mixing tube 8, a central axis of the funnel element 17 and the mixing tube 8 being aligned with one another, at least in the end section 9. The funnel element 17 or its jacket wall 19 protrudes from the flow element 12 through the entire conical end section 9 through into the mixing tube 8. As a result, the funnel element 17 lies overall in the end section 9. Its maximum outer circumference corresponds at its free end substantially or almost to the inner circumference of the mixing tube 8.

The funnel element 17 has a multiplicity of flow openings 18 which are uniformly distributed in a jacket wall 19 of the funnel element 17. For reasons of clarity, only some of the flow openings 18 are provided with a reference symbol in the present case.

According to the present exemplary embodiment, each flow-through opening is assigned a flow-guiding element 20, which extends radially in sections over the respective through-flow opening, so that the

Flow guide 20 a flow direction for through

Flow opening 18 specify flowing exhaust gas, which is in the circumferential direction or at least substantially in the circumferential direction of the funnel 17, so that a swirl flow through the funnel 17 for the exhaust gas, which flows axially into the mixing tube 8, is generated. Because the funnel element 17 extends almost to the inner wall of the mixing tube 8, the exhaust gas is forced to pass through the through-flow openings 18 or the funnel element 17. By the flow guide 20 ensures that the entering into the mixing tube 8 exhaust gas in a

Swirl flow is passed through the mixing tube 8. These are the

Flow guide 20 all aligned in the same direction. In the flow element 12, an injection valve 21 is also arranged, which is connected by a conveyor not shown here with a tank, which provides liquid exhaust aftertreatment agent. By actuating the injection valve 21, the liquid exhaust aftertreatment agent is mixed with the exhaust gas flow, which enters the mixing tube 8. Thus, the mixing tube 8 is a mixing chamber 22. In this case, the injection valve 21 is arranged centrally on the flow element 12 such that a central axis of a spray cone of the injection valve 21 is aligned with the central axis of the funnel element 17 (dash-dot line in FIG. 2). Vorzugsweist the funnel element 17 is formed such that the mixing tube axially facing funnel opening is larger than the spray cone of the injection valve 21, so that wetting of the funnel member 17 is prevented with the exhaust aftertreatment agent.

In normal operation, the exhaust gas flows through the Abgaszuführkanal 6 in the direction of the exhaust aftertreatment device 7 and is passed through the advantageous flow part 12 in the end portion 9 of the mixing tube 8. Because the flow part 12 projects in regions into the mixing tube 8, an annular gap is formed, through which the exhaust gas flow flows, causing it to be compressed and accelerated. When passing through the flow openings 18 of the funnel 17, the exhaust gas flow is forced into a swirling motion and mixed with the injected exhaust gas aftertreatment agent.

The flow part 12 may be formed symmetrically or asymmetrically in order to ensure an optimal exhaust gas flow. Preferably, the outer interior of the flow part 12 is formed such that the injection valve 21 finds place including necessary insulation elements in the recess. In particular, the flow part 12 is formed from sheet metal.

Due to the advantageous flow element 12, the exhaust gas is the

Funnel 17 fed particularly evenly. Optionally, an upstream of the funnel 17 attached

flow-complimenting geometry are supplemented to ensure the most homogeneous possible supply of the exhaust gas to the funnel 17. The funnel element 17 is expediently attached to the flow part 12 and optionally laterally or radially supported on the mixing tube 8. For this purpose, radial spacers or spacers can be present on the funnel element 17 at the end, which rest against the inside of the mixing tube 8. The advantageous swirl flow ensures that the introduced exhaust gas aftertreatment agent is uniformly distributed to the inner wall of the mixing tube 8 and largely evaporated from there. Due to the swirl flow, the thermal energy input into the mixing tube 8, which can be used for evaporation of the exhaust gas aftertreatment agent, is increased. Depending on the design of the funnel element 17, this may also be so

be configured that a portion of the exhaust gas is passed through an annular gap as a bypass channel 23 at the transition or radially between funnel 17 and mixing tube 8.

Also in the embodiment of Figure 2, such a bypass channel 23 is formed radially between the free end of the funnel member 17 and the mixing tube 8. As a result, for example, a dynamic pressure acting on the exhaust system is reduced.

While in the present embodiment, the exhaust gas is deflected by the exhaust system 1 by 180 °, other

Exhaust gas supplies may be conceivable, for example, have a deflection of only 90 ° or less.

Figures 3A and 3B show the funnel element 17 according to the first

Embodiment of Figure 2 in a side view (Figure 3A) and in a plan view (Figure 3B). It can be seen that the flow guide elements 20 have a torbogenförmige contour to produce an optimum swirl flow. The openings of the flow guide elements 20 are always aligned in the same direction, to a clear swirl flow to

guarantee.

FIGS. 4A and 4B show a second embodiment of the funnel element 17, in a side view and in a plan view, wherein the funnel element 17 according to this exemplary embodiment differs from the preceding one Distinguishes embodiment in that a plurality of flow openings 18 are formed free of flow in a near the injection valve end, ie at the end with the smaller diameter, multiple flow openings.

As a result, the penetration of the spray of the injection valve 21 into the mixing tube 8 is initially uninfluenced by the exhaust gas, at least without a swirl being generated. Only after the spray has already been fanned out sufficiently far in the funnel element 17, is it made clear by the

Injection valve remove portion of the funnel 17 by the

Flow guide 20 generates the swirl flow and causes the mixing of the exhaust aftertreatment agent with the exhaust gas. As a result of the advantageous embodiment, it is also achieved that no serious recirculation areas arise in the area close to the meter, which can act to promote deposition with regard to crystalline by-products.

Figures 5A and 5B show a third embodiment of the funnel 17, which differs from the embodiment of Figures 4A and 4B, characterized in that the flow guide 20 are not arched, but in cross section and longitudinal section each have a straight contour, so are plate-shaped. As a result, a particularly cost-effective implementation of the funnel 17 is possible. Also in the embodiment of Figure 3A and 3B, the

Flow guide 20 may be plate-shaped. In this case, the flow guide elements 20 are preferably designed as outwardly bent air ducts of the jacket wall 19.

The fourth embodiment of the funnel member 17, which is shown in FIGS. 6A and 6B in a side view and a plan view, differs from the previous embodiments in that the funnel-shaped portion of the funnel member 17 is particularly short axially. Otherwise, the funnel 17 is formed circular cylindrical. In the circular cylindrical portion while the flow openings 18 with the

Flow guide 20 arranged / formed. This also achieves an advantageous mixing of exhaust gas and exhaust gas aftertreatment agent and the prevention of crystal formation.

Claims

claims

An exhaust after-treatment device (7) for dosing a liquid exhaust aftertreatment agent in an exhaust stream of an internal combustion engine, with a mixing chamber (22) in which the exhaust aftertreatment agent is mixed with the exhaust gas stream, wherein the mixing chamber (22) a

having a circular cylindrical mixing tube (8), which has a funnel-shaped end section (9), which widens toward a free end toward the periphery, at least in sections in the direction of the mixing tube (8)

cone-shaped opening funnel element (17), the more

Throughflow openings (18) in its jacket wall (19), and wherein at the end remote from the mixing tube (8) of the funnel element (17) an injection valve (21) for the exhaust aftertreatment agent is arranged to inject the exhaust aftertreatment agent into the funnel element (17) , characterized in that the funnel element (17) at least in

Substantially within the end portion (9) is coaxial with the end portion, and that at least some of the flow openings (18) each one of the jacket wall (19) elevating flow guide (20) for generating a swirl flow in the mixing tube (8) is associated.

2. exhaust gas aftertreatment device according to claim 1, characterized in that the flow openings (18) in one

near the injection valve area are free of flow guides.

3. Exhaust after-treatment device according to one of the preceding claims, characterized in that all flow openings (18) with the exception of the flow openings (18) in the injection valve near area or all flow openings (18) each one

Flow control element (20) is assigned.

4. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the funnel element (17) on a cup-shaped flow element (12) is arranged, which in a

Abgaszuführkanal (6), in which the free end of the mixing tube (8) opens.

5. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the flow element (12) has a tapered in the direction of the mixing tube (8) and formed closed cone wall (14).

6. exhaust aftertreatment device according to one of the preceding claims, characterized in that the flow element (12) projects in regions in the end portion (9) of the mixing tube (8).

7. Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the injection valve (21) on the flow element (12) and / or on the funnel element (17) is fixed or arranged such that a central axis of the conically ejected exhaust aftertreatment agent and one through the Flow guide elements (20) generated swirl axis at least substantially aligned with each other.

8. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the flow guide elements (20) are formed or aligned such that at least a portion of the injected exhaust aftertreatment agent on an inner wall of the

Mixing tube (8) hits.

9. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the funnel element (17) rests radially on the mixing tube (8).

10. Exhaust after-treatment device according to one of the preceding claims, characterized in that radially between the Funnel element (17) and the mixing tube (8) a particular annular bypass channel (23) for the exhaust gas is present.

11. Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the funnel element (17) opens like a funnel along its entire longitudinal extent.

12. Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the funnel element (17) opens in a funnel shape only in one end region, and that the throughflow openings (18) are formed only in a cylindrical region of the funnel element (17).

13. exhaust gas aftertreatment device according to one of the preceding claims, characterized in that extending the Abgaszuführkanal (6) transversely, in particular perpendicular to the central axis of the mixing tube (8).

14. exhaust aftertreatment device according to one of the preceding claims, characterized in that the Abgaszuführkanal (6) causes an exhaust gas deflection into the mixing tube (8) of 180 ° or less.

15. exhaust aftertreatment system (1) for reducing

Pollutant emissions in the exhaust gas of an internal combustion engine of a motor vehicle, with an exhaust gas aftertreatment device (7) according to one of claims 1 to 14.