DE102018202298A1 - Exhaust gas aftertreatment device for metering in a liquid exhaust aftertreatment agent - Google Patents

Abstract

The invention relates to an exhaust aftertreatment device (7) for dosing a liquid exhaust aftertreatment agent into an exhaust gas stream of an internal combustion engine, comprising a mixing chamber (22) in which the exhaust gas aftertreatment agent is mixed with the exhaust gas stream, the mixing chamber (22) having a circular cylindrical mixing tube (8), which has a funnel-shaped end section (9) which increases in size towards a free end, with a funnel element (17) which opens conically at least in sections in the direction of the mixing tube (8) and which has a plurality of flow-through 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). It is provided that the funnel element (17) lies coaxially with the end section at least substantially within the end section (9), and that at least some of the throughflow openings (18) each have a flow guide element (20) which rises from the jacket wall (19) associated with a swirl flow in the mixing tube (8).

Description

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 stream, wherein the mixing chamber has a circular cylindrical mixing tube, the funnel-shaped, to a free end to the periphery having an enlarging end portion, with an opening in the direction of the mixing tube at least partially cone-shaped funnel element having a plurality of flow openings in its jacket wall, and with an injection valve which is arranged at the end remote from the mixing tube end of the funnel element to inject the exhaust aftertreatment agent into the funnel 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 meet the stricter legislation regarding permissible discharge quantities of pollutants in the exhaust gas of internal combustion engines of motor vehicles, it is known to use exhaust aftertreatment devices, which ensure a pollutant reduction by using an additional exhaust aftertreatment agent. For example, it is known to mix an exhaust gas with an exhaust aftertreatment agent by the so-called SCR process (SCR = Selective Catalytic Reduction) and then supply it to an SCR catalyst, in which the exhaust gas reacts together with the exhaust aftertreatment agent and pollutant emissions are lowered. Suitable as exhaust aftertreatment agent is an aqueous urea solution, which is injected into the exhaust gas or the exhaust pipe by means of suitable metering systems, in particular injection valves. From the aqueous urea solution, which is supplied to the exhaust gas during operation of the internal combustion engine, 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 A1 For example, an exhaust aftertreatment device of the type mentioned above is known. In order to improve the mixing of 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 can flow into the mixing tube independently of the exhaust aftertreatment agent.

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 is assigned in each case one of the shell wall in particular outwardly uplifting flow for generating a swirl flow in the mixing tube. The funnel element lies substantially freely in the mixing chamber, but ends in a funnel-shaped widened end portion of the mixing tube likewise projecting into the mixing chamber. Characterized in that the funnel element is at least substantially within the end portion, it is achieved that an admission of the funnel element is ensured with the flowing 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 through-flow openings in a region near the injection valve are free of flow guide elements. This means that the through-flow opening in the region near the injection valve represents simple openings which exert no swirl effect on the exhaust gas and / or the exhaust gas aftertreatment agent. On the contrary, the simple passage openings allow the exhaust gas to flow into the funnel element without serious recirculation areas.

Preferably, all the flow openings, with the exception of the through-flow openings in the region near the injection valve, are each assigned a flow-guiding element. In the injection valve remote region, the flow guide elements are thus present in order to generate the swirl flow through the exhaust gas flowing through the jacket wall of the funnel element. 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. Characterized in that all injection valve remote flow openings are provided with flow guide elements, 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 channel, 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 is located in an exhaust gas supply channel, and in particular is attached thereto. 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 design of the cup-shaped flow element, the exhaust gas flow is optimized by the Abgaszuführkanal in the mixing tube, in particular by turbulence in the transition from the feed channel are avoided in 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.

According to a preferred embodiment of the invention, the flow element projects in regions into the end portion of the mixing tube. This ensures the formation of the annular gap and a defined guidance of the exhaust gas flow into 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. The swirl flow increases the thermal energy input into the wall, which is used for the evaporation of the exhaust gas aftertreatment agent. 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, a radial distance between the funnel element and the mixing tube or its inner wall. Thus, the distance also remains at 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 funnel-shaped as a whole, so that it can be optimally adapted to the shape of the exhaust aftertreatment agent spray of the injection valve.

Alternatively, the funnel element is funnel-shaped only in one end region and is cylindrical in a region close in particular to the injection valve, wherein the through-flow openings are preferably formed only in this region. Also in this case, the flow passage element, as described above, is preferably assigned to the or at least most of the flow openings in order to generate the hydraulic flow. On the one hand, it is achieved by 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, advantageous mixing also takes place downstream of the funnel element in the mixing tube.

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 °. As a result, a compact design is ensured, 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 exhaust aftertreatment device according to the invention. 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.

• 1 ein Abgasnachbehandlungssystem in einer vereinfachten Längsschn ittdarstell ung,
• 2 eine Abgasnachbehandlungseinrichtung des Abgasnachbehandlungssystems in einer vergrößerten Schnittdarstellung,
• 3A und 3B ein erstes Ausführungsbeispiel eines vorteilhaften Trichterelements der Abgasnachbehandlungseinrichtung,
• 4A und 4B ein zweites Ausführungsbeispiel des Trichterelements,
• 5A und 5B ein drittes Ausführungsbeispiel des vorteilhaften Trichterelements und
• 6A und 6B ein viertes Ausführungsbeispiel des Trichterelements, jeweils in einer Seitenansicht und in einer Draufsicht.

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

• 1 an exhaust aftertreatment system in a simplified longitudinal representation,
• 2 an exhaust aftertreatment device of the exhaust aftertreatment system in an enlarged sectional view,
• 3A and 3B A first embodiment of an advantageous funnel element of the exhaust aftertreatment device,
• 4A and 4B A second embodiment of the funnel element,
• 5A and 5B a third embodiment of the advantageous funnel element and
• 6A and 6B A fourth embodiment of the funnel element, in each case in a side view and in a plan view.

1 shows in a simplified sectional view of an exhaust aftertreatment system 1 for an internal combustion engine of a motor vehicle. The exhaust aftertreatment system 1 has an exhaust pipe 2 on, which connects to the internal combustion engine and an exhaust inlet 3 having. In the exhaust pipe 2 is for example a first catalyst 4 as well as a particle filter 5 downstream of the catalyst 4 arranged, which in the exhaust pipe 2 treat incoming exhaust gas in a known manner. The exhaust pipe 2 goes in a Abgaszuführkanal 6 for an exhaust aftertreatment device 7 about, which will be described in more detail below.

2 shows an enlarged sectional view of the exhaust aftertreatment device 7 , This has a in the Abgaszuführkanal 6 opening mixing pipe 8th on. A the Abgaszuführkanal 6 facing end portion 9 of the mixing tube widens in the direction of the Abgaszuführkanals 6 cone-shaped. The end section 9 ends on a first side wall 10 the Abgaszuführkanals 6 , On one of the side wall 10 opposite side wall 11 the Abgaszuführkanals 6 is a cup-shaped flow element 12 fixed in the exhaust gas supply duct 6 in the direction of the mixing tube 8th protrudes so that it the Abgaszuführkanal 6 in the present case completely from the side wall 11 up to the side wall 10 penetrates. On the side wall 10 protrudes the flow element 12 in a mouth opening of the end portion 9 in the sidewall 10 into it.

The flow element 12 has a the mixing tube 8th facing end portion 13 on, moving in the direction of the mixing tube 8th rejuvenated. The end section 13 extends in the longitudinal extension of the flow element 12 seen, or in axial extent, over more than half of the total longitudinal extent of the flow element 12 , A jacket wall 14 of the flow element 12 , which has the conical shape seen in longitudinal section, is formed closed and ends in a mixing tube 8th facing floor section 15 which is essentially parallel to the sidewalls 10 and 11 the Abgaszuführkanals 6 extends. In the bottom section 15 is an opening 16 centrally formed. This opening 16 is a funnel element 17 assigned. The funnel element 17 is in accordance with the present embodiment, a total of funnel shape formed such that it from the flow element 12 starting in the direction of the mixing tube 8th widens, wherein a center axis of the funnel element 17 and the mixing tube 8th at least in the end section 9 , get along with each other. The funnel element 17 or his mantle wall 19 protrudes from the flow element 12 through the entire conical end portion 9 through to the mixing tube 8th into it. This is the funnel element 17 in total 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 8th ,

The funnel element 17 has a plurality of flow openings 18 on, evenly in a jacket wall 19 of the funnel element 17 are formed distributed. For clarity, only a few of the flow openings are present 18 provided with a reference numeral.

According to the present embodiment, each flow opening is a flow guide 20 assigned, which extends radially in sections over the respective flow opening, so that the flow guide 20 a flow direction for through the flow opening 18 pouring exhaust gas, in the circumferential direction or at least substantially in the circumferential direction of the funnel element 17 lies, so that a swirl flow through the funnel element 17 for the exhaust gas, which is axial in the mixing tube 8th flows in, is generated. Because the funnel element 17 almost to the inner wall of the mixing tube 8th extends, the exhaust gas is forced through the flow openings 18 or the funnel element 17 to step through. Through the flow guide elements 20 This will ensure that in the mixing tube 8th entering exhaust gas in a swirling flow through the mixing tube 8th is guided. For this purpose, the flow guide elements 20 all aligned in the same direction.

In the flow element 12 is also an injection valve 21 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 For example, the liquid exhaust aftertreatment agent is the exhaust stream that flows into the mixing tube 8th penetrates, mixed. Thus, the mixing tube 8th a mixing chamber 22 This is the injection valve 21 on the flow element 12 arranged centrally such that a central axis of a spray cone of the injection valve 21 with the center axis of the funnel element 17 is aligned (dash-dot line in 2 ). The preferred embodiment is the funnel element 17 designed such that the mixing tube axially facing funnel opening is larger than the spray cone of the injection valve 21 , allowing wetting of the funnel element 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 due to the advantageous flow part 12 in the end section 9 of the mixing tube 8th directed. Because the flow part 12 partially into the mixing tube 8th protrudes, creates an annular gap through which the exhaust gas flow, causing it to be compressed and accelerated. When passing through the flow openings 18 of the funnel element 17 the exhaust stream is forced into a swirling motion and mixed with the injected exhaust aftertreatment agent.

The flow part 12 can be symmetrical or asymmetrical in order to ensure an optimal exhaust gas flow. Preferably, the outer interior of the flow part 12 formed such that the injection valve 21 including necessary isolation elements in the recess. In particular, the flow part 12 formed from sheet metal.

Due to the advantageous flow element 12 the exhaust gas is the funnel element 17 fed particularly evenly. Optionally, an upstream of the funnel element 17 attached Strömungsvergleichmäßende geometry are supplemented to a homogeneous supply of the exhaust gas to the funnel element 17 to ensure.

The funnel element 17 is suitably on the flow part 12 fixed and optional on the mixing tube 8th supported laterally or radially. This can be done on the funnel element 17 Radial spacers or spacers may be present at the end, which are on the inside of the mixing tube 8th issue. The advantageous swirl flow ensures that the introduced exhaust gas aftertreatment agent uniformly on the inner wall of the mixing tube 8th is distributed and evaporated from there largely. The swirl flow increases the thermal energy input into the mixing tube 8th which is further usable for the vaporization of the exhaust aftertreatment agent. Depending on the version of the funnel element 17 this can also be designed so that a part of the exhaust gas through an annular gap as a bypass channel 23 at the transition or radially between funnel element 17 and mixing tube 8th is passed.

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

While in the present embodiment, the exhaust gas through the exhaust system 1 is deflected by 180 °, other exhaust gas supplies may be conceivable, for example, have a deflection of only 90 ° or less.

3A and 3B show the funnel element 17 according to the first embodiment of 2 in a side view ( 3A) and in a plan view ( 3B) , It can be seen that the flow guide 20 have an arched contour to produce an optimal swirl flow. The openings of the flow guide elements 20 are always aligned in the same direction to ensure a clear swirl flow.

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 differs according to this embodiment of the previous embodiment in that in a near the injection valve end, ie at the end with the smaller diameter, a plurality of flow openings 18 are formed free of flow guides. This results in the penetration of the spray of the injection valve 21 into the mixing tube 8th initially unaffected by the exhaust gas, at least without a swirl being generated. Only after the spray already sufficiently fanned out in the funnel element 17 is through the in the subsequent, injection valve remote section of the funnel element 17 through the flow guide elements 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.

5A and 5B show a third embodiment of the funnel element 17 that differs from the embodiment of 4A and 4B characterized in that the flow guide elements 20 are not arched, but in cross section and longitudinal section each have a straight contour, so are plate-shaped. This is a particularly cost-effective implementation of the funnel element 17 possible. Also in the embodiment of 3A and 3B can the flow guide 20 be plate-shaped. In this case, the flow guide elements 20 preferably as outwardly bent air ducts of the jacket wall 19 educated.

The fourth embodiment of the funnel element 17 that in the 6A and 6B is shown in a side view and a plan view, differs from the previous embodiments, that the funnel-shaped portion of the funnel element 17 axially is particularly short. Otherwise, the funnel element 17 formed circular cylindrical. In the circular cylindrical portion are the flow openings 18 with the flow guide elements 20 arranged / formed. This also achieves an advantageous mixing of exhaust gas and exhaust gas aftertreatment agent and the prevention of crystal formation.

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

• WO 2015/197145 A1 [0004]

Claims (15)

Exhaust aftertreatment device (7) for metering a liquid exhaust 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, the mixing chamber (22) having a circular cylindrical mixing tube (8) having a funnel-shaped, extending to a free end towards the perimeter end portion (9), with a in the direction of the mixing tube (8) at least partially cone-shaped opening funnel element (17) having a plurality of flow openings (18) in its jacket wall (19), and wherein on the end of the funnel element (17) facing away from the mixing tube (8) 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) is at least substantially inside the end portion (9) coaxial with d Em end portion is located, 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. Exhaust after-treatment device according to Claim 1 , characterized in that the flow openings (18) in a region close to the injection valve are free of flow guides. 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) is associated with a respective flow guide (20). Exhaust after-treatment device according to one of the preceding claims, characterized in that the funnel element (17) is arranged on a cup-shaped flow element (12) which lies in an exhaust gas supply channel (6), in which the free end of the mixing tube (8) opens. Exhaust gas aftertreatment device according to one of the preceding claims, characterized in that the flow element (12) has a conical wall (14) which tapers in the direction of the mixing tube (8) and has a closed design. Exhaust after-treatment device according to one of the preceding claims, characterized in that the flow element (12) projects in regions into the end section (9) of the mixing tube (8). Exhaust after-treatment device according to one of the preceding claims, characterized in that the injection valve (21) is fastened or arranged on the flow element (12) and / or on the funnel element (17) in such a way that a central axis of the conically ejected exhaust gas aftertreatment means and one through the flow guide elements ( 20) generated swirl axis at least substantially aligned with each other. Exhaust after-treatment device according to one of the preceding claims, characterized in that the flow-guiding elements (20) are designed or oriented in such a way that at least part of the injected exhaust-gas treatment means impinges on an inner wall of the mixing tube (8). Exhaust after-treatment device according to one of the preceding claims, characterized in that the funnel element (17) rests radially on the mixing tube (8). Exhaust after-treatment device according to one of the preceding claims, characterized in that a particularly annular bypass channel (23) for the exhaust gas is present radially between the funnel element (17) and the mixing tube (8). Exhaust after-treatment device according to one of the preceding claims, characterized in that the funnel element (17) opens in a funnel shape along its entire longitudinal extent. Exhaust after-treatment 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 in that the throughflow openings (18) are formed only in a cylindrical region of the funnel element (17). Exhaust after-treatment device according to one of the preceding claims, characterized in that the exhaust gas supply channel (6) extends transversely, in particular perpendicular to the central axis of the mixing tube (8). Exhaust after-treatment 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. Aftertreatment system (1) for reducing pollutant emissions in the exhaust gas of an internal combustion engine of a motor vehicle, with a Exhaust after-treatment device (7) according to one of Claims 1 to 14 ,

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