DE102015110319A1 - Device for introducing a fluid into a gas stream - Google Patents

Abstract

The present invention relates to a device for introducing a fluid into a gas stream, in particular a reducing agent in an exhaust stream of an internal combustion engine. The device has a mixing chamber and a metering device, by means of which the fluid can be introduced by means of a metering tip into an injection space defined by a protective sleeve, which is arranged in the interior of the chamber and which is in fluid communication therewith. The protective sleeve has an intermediate chamber extending in the circumferential direction of the protective sleeve, which is bounded radially on the inside by an inner wall and radially on the outside by an outer wall, wherein the intermediate chamber with the injection space formed by the inner wall and formed at this gap, in particular annular gap Fluid connection is. The intermediate chamber is also in fluid communication with the mixing chamber via at least one opening in the outer wall.

Description

The present invention relates to an arrangement for introducing a fluid into a gas stream, in particular a reducing agent in an exhaust stream of an internal combustion engine.

The problem of reliably distributing a liquid additive in a suitable form in a gas stream, for example to allow a chemical reaction of components of the gas stream with components of the introduced fluid, arises in many fields of application. In exhaust gas technology, this problem arises, for example, in connection with the SCR process, in which an aqueous urea solution is introduced into the exhaust gas line of a motor vehicle, for example by means of a metering device. Thermolysis and hydrolysis produce ammonia and CO ₂ from the urea solution. The ammonia thus produced can react in a suitable catalyst with the nitrogen oxides contained in the exhaust gas, which are removed so efficiently from the exhaust gas.

In this process, it is of particular relevance that the urea solution is introduced into the exhaust gas stream in a well-defined form. In addition, it is of great importance that the introduced into the exhaust stream urea solution is evaporated as completely as possible and evenly distributed in the exhaust gas stream.

In many cases, the urea solution is injected or sprayed through a metering device into the exhaust gas line, which is flowed obliquely or laterally from the exhaust gas flow. This can lead to the sprayed-on reducing agent being blown away. Often the introduced additive forms a spray cone. Due to the exhaust gas flow this is deformed and may even be pressed against the walls of the exhaust system. As a result, the injected fluid is distributed less well, resulting in a reduction in the efficiency of catalysis. In addition, unwanted deposits of the fluid may form inside the device, especially in the area around the metering device, which may also lead to a reduction in the efficiency or even failure of the device or the exhaust gas cleaning system.

It is therefore an object of the present invention to provide a device of the type mentioned above with improved introduction and distribution efficiency of the fluid.

This object is achieved by a device having the features of claim 1.

According to the invention, the device has a mixing chamber and a metering device. The fluid can be introduced by the metering device by means of a metering tip into an injection space defined by a protective sleeve. The injection space is located inside the chamber and is in fluid communication therewith. The protective sleeve has a circumferentially extending intermediate chamber, which is bounded radially on the inside by an inner wall and radially on the outside by an outer wall. The intermediate chamber is in fluid communication with the injection space via a gap formed by or formed on the inner wall, in particular an annular gap. On the other hand, the intermediate chamber is in fluid communication with the mixing chamber via at least one opening, in particular a plurality of openings, in the outer wall.

In other words, the fluid is introduced by means of the metering tip of the metering device into the injection space defined by the protective sleeve. The injection space is open to the mixing chamber. The protective sleeve thus forms a kind of shield, which prevents the gas from flowing directly to the dosing tip. The protective sleeve also protects - at least initially - the injection cone, which leads to a better distribution of the fluid in the gas stream.

In addition, the protective sleeve acts as a kind of "flushing device" to protect the dosing tip by a flow of gas around the formation of deposits. Part of the gas flowing against the protective sleeve can in fact penetrate through the openings in the outer wall of the protective sleeve into the intermediate chamber. From there, the gas flows through the gap forming a constriction into the injection space. The exhaust gas flowing through the gap into the injection space can be guided in such a way that it at least largely prevents the formation of deposits in the area of the injection space and in particular of the metering tip.

Further embodiments of the invention are indicated in the description, the claims and the attached drawings.

According to one embodiment, the gap surrounds the dosing tip in the circumferential direction at least partially, preferably completely. In particular, the gap is arranged such that at least a portion of the gas flow flowing through it backwashes the metering tip. For this purpose, the gap may be shaped in the axial direction, i. in the direction of introduction of the fluid, seen - be approximately at the level of the dosing or even arranged in front of it.

In the gap, at least one guide element may be arranged, through which a swirl component is impressed on at least part of the gas flow flowing through it. Such a vortex can help to prevent the formation of deposits even more efficiently. In addition, the swirl ensures that the flow of a contour of the inner wall defining the injection space better follows, so that flow separation is minimized.

According to a further embodiment of the device according to the invention, a part of a wall of the mixing chamber limits the intermediate chamber at least in sections. In particular, it limits these in the area around the dosing tip. The protective sleeve may for example be attached to the wall of the mixing chamber, in particular via its outer wall, so that the wall of the mixing chamber and the inner and outer walls of the protective sleeve together define the intermediate chamber. However, it is also possible for an end of the intermediate chamber facing the dosing tip to be bounded, at least in sections, by a bottom section of the protective sleeve. In particular, the bottom portion of the protective sleeve is connected to the outer wall or formed integrally therewith. The bottom portion may be spaced from the wall of the mixing chamber. This provides a flow path between the protective sleeve and the mixing chamber wall which contributes to (additional) backwashing of the dosing tip to further reduce the formation of deposits.

The gap can be bounded by an end portion of the inner wall facing the metering tip, a part of a wall of the mixing chamber which partially delimits the intermediate chamber and / or, if provided, the bottom portion of the protective sleeve. In particular, the inner wall is provided at its end facing the dosing tip with a collar which projects into the intermediate chamber in order to efficiently guide the gas flow through the gap. That in one embodiment of the device according to the invention, the end portion of the inner wall of the sleeve - with or without collar - from the wall of the mixing chamber or the bottom portion spaced to form the gap.

The at least one opening in the outer wall may be a bore, a slot and / or a slot. In particular, a plurality of openings are provided, which are preferably distributed uniformly in the circumferential direction. For certain applications, however, provision may also be made for larger, differently shaped and / or more openings to be provided in certain areas of the outer wall, for example in order to compensate for uneven flow of the protective sleeve through the gas flow. It can also be combined openings with different shapes.

According to one embodiment, the inner wall has a funnel-shaped or conical section which opens in a direction away from the metering tip. That said portion diverges in the direction of introduction of the fluid to accommodate its "unfolding". In particular, the inner wall is formed without interruption, so that the gas can only pass through the gap from the intermediate chamber into the injection space.

Alternatively or additionally, the outer wall can also have a funnel-shaped or conical section which opens in a direction towards the metering tip. That In this embodiment, said portion converges in the direction of introduction of the fluid.

According to one embodiment of the protective sleeve, this is integrally formed. Alternatively, the inner wall and the outer wall of the protective sleeve may be separately manufactured elements which are connected to each other, in particular welded or soldered together. The connection between the inner wall and the outer wall may, for example, be provided at the ends facing away from the dosing tip.

According to a cost-effective embodiment of the protective sleeve, which is also suitable for many applications, the protective sleeve is formed substantially rotationally symmetrical. In order to take into account special flow conditions, however, an asymmetrical design can also be provided.

The mixing chamber may have at least one inlet opening, which is arranged and designed such that the protective sleeve, in particular its outer wall, is flowed by at least part of the gas flow flowing into the mixing chamber. In particular, there may be an at least partially radial, oblique and / or lateral flow of the protective sleeve.

However, it can also be provided a plurality of inlet openings, which are arranged around the protective sleeve. Each of the inlet openings may be associated with at least one, in particular exactly one opening in the outer wall of the protective sleeve.

In the mixing chamber, a gas guide element may be arranged, which feeds at least a part of the gas flow of the protective sleeve. The gas-conducting element can be connected to the protective sleeve and protrude into the gas flow flowing to the protective sleeve. In particular, an upstream end of the gas guide element is arranged substantially parallel to the gas flow to prevent the generation of unnecessary turbulence.

In principle, the gas-conducting element can be a separate component which, as mentioned above, is or is not connected to the protective sleeve. However, the gas-conducting element can also be formed by a section of the outer wall of the protective sleeve. According to one embodiment, the gas guiding element is associated with the at least one opening in the outer wall of the protective sleeve in order to direct a part of the gas flow in or through the opening, so that it passes into the intermediate chamber. In particular, the gas guide element is arranged in the region of the opening. For example, the gas guide is at least partially formed by a portion of the outer wall of the protective sleeve, which has been bent out, for example, to form the at least one opening in the outer wall.

The gas guiding element may have a section which is U-shaped or has the shape of an incomplete U. It is e.g. conceivable that the gas guide is bent out of the outer wall, so that it merges in a bend in the outer wall. In the further course, the gas-conducting element can be shaped accordingly in order to direct a desired subset of the gas flow into the intermediate chamber.

The gas guiding element may have openings, e.g. Holes have. In particular, the openings are arranged in a region which is arranged adjacent to the protective sleeve.

The gas-conducting element can protrude into an inlet opening of the mixing chamber or even through it in order to optimize the gas flow.

According to a further embodiment of the present invention, the mixing chamber has a bypass flow path through which at least part of the gas flow flows into or through the mixing chamber, without flowing into the protective sleeve or even through the protective sleeve, in particular its intermediate chamber to flow. For example, the bypass flow path is defined at least in sections by a wall of the mixing chamber and an end of the protective sleeve facing away from the metering tip.

To optimize the flow of the protective sleeve, the wall of the mixing chamber may have an inwardly directed bead, which is arranged in the axial direction of the mixing chamber approximately at the level of the protective sleeve.

For additional protection of the Einsprühkegels - also differing from a cone shape Einsprühgeometrien are conceivable - may be arranged in the mixing chamber, a Gasleitrohr whose outer periphery is spaced from the wall of the mixing chamber. The wall of the mixer chamber and the outer circumference of the Gasleitrohrs thus define sections a gap through which gas can flow. The Gasleitrohr is arranged in particular downstream of the metering device.

In the gap between the wall of the mixer chamber and the Gasleitrohr at least one flow guide may be arranged to impart a well-defined flow pattern to the gas flowing through the gap. In particular, a swirl is imparted to the gas flow by one or preferably a plurality of flow guide elements arranged distributed in the circumferential direction of the gap. The one or more flow guide elements are arranged in particular on the input side of the gap.

According to one embodiment, at least one flow guide element is arranged in the gas guide tube. This means that in this embodiment, at least one flow guide at least partially projects into the Gasleitrohr or completely disposed therein. In particular, a flow-guiding element is provided at the inlet-side end of the gas-conducting tube, which at least partially projects into the gas-conducting tube and / or is in communication with the inner circumference of the gas-conducting tube. Preferably, a plurality of flow guide elements are provided.

The at least one flow guide element can be arranged between the protective sleeve and the gas guide tube. In other words, the at least one flow-guiding element is arranged at least in sections in a gap or gap between the protective sleeve and the gas-conducting tube. Preferably, a plurality of flow directing elements are provided which impart a twist to the gas flow which flows through the intermediate space or gap between the protective sleeve and the gas guide tube in the latter. In particular, the at least one flow guide element is arranged between a downstream section of the protective sleeve and an upstream section of the gas guide tube. The flow guide can be in contact with the gas guide tube and / or the protective sleeve or even connected.

The protective sleeve can protrude in the axial direction at least partially into the Gasleitrohr. Side flowing gas can therefore not directly flow the injected fluid.

The Gasleitrohr may have a portion which widens in the flow direction of the gas stream. According to one embodiment, the gas guide tube has a funnel-shaped inlet region and / or a constriction with a reduced cross-section. The funnel-shaped inlet region efficiently "traps" the gas flowing into the gas conduit and the injected fluid. The optionally provided constriction produces an advantageous nozzle effect, which increases the efficiency of the device according to the invention. In order to take into account the space requirements, the Gasleitrohr may also have a curved portion.

In particular, the Gasleitrohr is arranged coaxially with the mixing chamber and / or protective sleeve.

The mixing chamber is in particular a tubular section of an exhaust system.

The invention will be explained purely by way of example with reference to advantageous embodiments with reference to the accompanying drawings. Show it:

1 a first embodiment of the device according to the invention,

2 to 5 an embodiment of the protective sleeve,

6 and 6a a sectional or side view of another embodiment of the device according to the invention,

7 a sectional view of another embodiment of the device according to the invention,

8th to 11 different views of the protective sleeve with a gas guide attached thereto in the 6 and 6a shown embodiment of the device according to the invention,

12 to 15 further embodiments of the protective sleeve,

16 a further embodiment of the device according to the invention in a sectional view,

17 another embodiment of the protective sleeve and

18 and 19 a sectional view and top view of the protective sleeve according to 17 in their installation position.

1 shows a first embodiment 10 of the device according to the invention for introducing a fluid into a gas stream. In the specific application, the device is integrated in an exhaust system of a motor vehicle. The exhaust gas discharged from the engine thereof flows through an exhaust pipe 12 through an inlet opening 14 in a mixer tube 16 , The mixer tube 16 is in turn connected to downstream components of the exhaust system, but not shown. At a bottom section 18 of the mixer tube 16 a metering device for introducing the reducing agent is fixed in the exhaust gas flow. In 1 is just a dosing tip 20 to recognize the metering device in the mixer tube 16 protrudes. The dosing tip 20 is through a protective sleeve 22 prevented from directly from the through the inlet opening 14 flowing exhaust gas to be flowed. Would be the protective sleeve 22 not present, so would a dashed line indicated Einsprühkegel 24 the reducing agent practically immediately after exiting the metering tip 20 through that into the mixer tube 16 inflowing exhaust gas are deformed. In other words, the sprayed fluid would be against the in 1 left side of the mixer tube 16 be forced, whereby the fluid would be distributed unevenly in the exhaust stream and even unwanted deposits of the reducing agent on the inner wall of the mixer tube 16 could occur.

The protective sleeve 22 includes an outer wall 26 that with the bottom section 18 (eg deflection shell) of the mixer tube 16 is connected, in particular welded or soldered. The outer wall 26 has openings 28 on, through which part of the protective sleeve 22 inflowing exhaust gas into an intermediate chamber 30 can pass through the outer wall 26 and one in one direction from the dosing tip 20 away cone-shaped inner wall opening 32 is limited. The inner wall 32 and the outer wall 26 stand over a forehead section 34 in indirect connection with each other. A direct connection of the walls 26 . 32 is also possible. In particular, the inner wall 32 and the outer wall 26 and - if available - the forehead section 34 integrally formed. However, it may also be provided, the inner wall 32 and to produce the outer wall separately from each other and then connect to each other, in particular to the dosing tip 20 opposite ends.

The essentially funnel-shaped inner wall 32 defines one to the interior of the mixer tube 16 towards open injection space 36 in which the injection cone 24 passing through the dosing tip 20 is generated, is protected from direct flow against the exhaust gas.

To the formation of reducing agent deposits in the dosing tip 20 It is intended to prevent them from being backwashed in a well-defined way. On the one hand, backwashing has to be sufficiently efficient, on the other hand it is intended to impair the development of the spray cone 24 be avoided as much as possible.

For this purpose, that is in the intermediate chamber 30 used incoming gas. Between the bottom section 18 and the dosing tip 20 facing the end of the inner wall 32 is an annular gap 38 formed, which is a bottleneck for out of the intermediate chamber 30 in the injection room 36 represents flowing exhaust gas.

As by flow paths 40 is indicated, flows at least part of the protective sleeve 22 side flowing exhaust gas through the openings 28 into the intermediate chamber 30 , Part of the exhaust gas also flows around the protective sleeve 22 around and does not enter the inlet opening 14 facing sides of the protective sleeve 22 into the intermediate chamber 30 one. In the intermediate chamber 30 In an operation of the exhaust system, substantially homogeneous pressure conditions prevail. From the intermediate chamber 30 the exhaust gas passes through the gap 38 in the injection room 36 , Due to the homogeneous pressure conditions in the chamber 30 Also forms a circumferentially substantially homogeneous flow through the gap 38 out. The positioning of the gap 38 Make sure the dosing tip 20 is lapped by exhaust gas, so that can not form deposits of the reducing agent here.

The protective sleeve 22 - functionally speaking - acts like a two-stage throttle device. The first throttling takes place as the exhaust gas flows in through the openings 28 into the intermediate chamber 30 instead of. The second throttling is through the gap 38 achieved. This will ensure that in the area around the dosing tip 20 well-defined flow conditions and pressure conditions prevail that reliably prevent the formation of deposits. Because the inner wall 32 is formed without interruption, is also the Einsprühkegel 24 not by radially inflowing gas except for the area around the gap 38 - disturbed. That through the gap 38 passing exhaust follows in the injection space 36 the geometry of the inner wall 32 and therefore has mainly axial flow components.

To the inflow of the exhaust gas from the intermediate chamber 30 in the injection room 36 designed as possible without turbulence, that is the metering tip 20 facing end of the inner wall 32 with a curved collar 42 provided, which is in the intermediate chamber 30 extends.

However, not all the exhaust gas flowing through the inlet opening 14 into the mixer tube 16 enters, flows around the protective sleeve 22 around or even through them. Part of the exhaust gas - characterized by flow paths 40 ' - flows between the dosing tip 20 opposite end of the protective sleeve 22 and the lower right outer wall of the mixer tube 16 directly into this one. The flow paths 40 ' thus symbolize a bypass flow. It is understood that the bypass flow, inter alia, of the dimensioning of the protective sleeve 22 and the mixer tube 16 depends. It is quite conceivable that the protective sleeve 22 a smaller axial extent than in 1 dargstellt or even deeper into the mixer tube 16 extends what gives a less or more protection for the Einsprühkegel 24 means. By dimensioning the components mentioned 22 . 16 the conditions for the best possible distribution of the reducing agent can be set. The same applies to the geometric design of the walls 26 . 32 the protective sleeve 22 , as well as the openings 28 and the gap 38 taking into account the geometry of the injection characteristic / geometry of the metering device.

The 2 to 5 show various views of another embodiment 22a the protective sleeve (side view, sectional view, top view or perspective view). Unlike the protective sleeve 22 which has a substantially cylindrical outer wall 26 has, is the outer wall 26 the protective sleeve 22a slightly conical shaped. The outer wall 26 is with oblong holes 44 provided, which are evenly distributed in the circumferential direction. At the in the installation position of the metering tip 20 facing the end of the outer wall 26 this is with a flange section 46 provided to the attachment of the protective sleeve 22a at the bottom section 18 of the mixer tube 16 to facilitate.

The inner wall 32 the protective sleeve 22a is funnel-shaped (see in particular 3 ) and has a curved shape, the meterierspitzenseitig in a flow through the gap 38 optimizing collar 42 passes. At the dosing tip 20 the opposite side is the inner wall 32 by a curvature in the outer wall 26 above. It can be clearly seen (see in particular 3 ) that the protective sleeve 22a a one-piece sheet metal component is.

The 6 and 6a show a further embodiment 10 ' the device according to the invention. The device 10 ' is integral with an inlet nozzle 48 and an outlet 50 connected, which allow the connection to the other components of the exhaust system.

To that through the inlet opening 14 into the mixer tube 16 entering exhaust gas of the protective sleeve, here as another embodiment 22b is designed to feed in well-defined form, this includes a gas guide 52 , The gas guide 52 is in different views also in the 8th to 11 shown. It essentially comprises a tongue-shaped plate, which is at about half height with the outer wall 26 the protective sleeve 22b connected is. The gas guide 52 protrudes into the installation position through the inlet opening 14 through the inlet pipe 48 , An upstream end 54 of gas guide element 52 is arranged and formed so that it is aligned substantially parallel to the inflowing gas flow. Thus, adverse swirling will occur at the upstream end 54 avoided.

Through the gas guide 52 that will be the device 10 ' inflowing gas stream is divided into two partial streams. A first partial flow flows below the gas guide element 52 on the protective sleeve 22b to. The outer wall 26 the protective sleeve 22b is in the flowed by the first partial flow area with circular holes 44 ' provided so that this part of the gas flow into the intermediate chamber 30 can get. From there, the exhaust gas flows through the gap 38 in the injection room 36 and backwash the dosing tip 20 the dosing device (not shown), which via a mounting flange 55 gas-tight at the bottom section 18 is attached.

The second partial flow flows above the gas guide element 52 on a section of the protective sleeve 22b to, which is formed without interruption. Ie this part of the exhaust gas can not enter the intermediate chamber 30 arrive, but flows through an annular gap 56 between one in the mixer tube 16 arranged Gasleitrohr 58 and the dose of the tip facing away from the protective sleeve 22b in the pipe 58 one. Because the protective sleeve 22b in the axial direction in the dosing tip 20 facing end of Gasleitrohrs 58 protrudes, no exhaust gas can directly into the Gasleitrohr 58 but it has to get through the gap 56 "Squeeze". This causes the originally inclined or laterally flowing exhaust gas inside the Gasleitrohrs 58 has a substantially axial flow direction, resulting in a further protection of the spray cone 24 contributes and so supports the uniform distribution of the reducing agent in the exhaust stream.

The not the protective sleeve 22b inflowing part of the second partial flow strikes the outer wall of the protective sleeve 22 " facing end of Gasleitrohrs 58 and flows through a bypass gap 60 passing through the outer wall of the Gasleitrohrs 58 and the spaced therefrom inner wall of the mixer tube 16 is formed. This part of the exhaust stream thus does not occur with the protective sleeve 22b in contact.

The protective sleeve 22b and the gas conduit 58 are coaxial with the mixer tube 16 aligned.

6a shows a side view of the device 10 ' , causing the mounting flange 55 can be clearly seen for the metering device.

7 shows an embodiment 10 ''' the device according to the invention, which in most points of the device 10 ' of the 6 and 6a equivalent. To optimize the gas flow through the device 10 ''' However, additional flow guide elements 59 . 59 ' intended.

The flow guide elements 59 are in the bypass gap 60 arranged, more precisely in its entrance area. The flow guide elements 59 , which have in particular opposite the main flow direction employed, curved and / or planar surface portions, shape this in the bypass gap 60 inflowing gas flow in the embodiment 10 ''' a swirling flow pattern. This will achieve that the Gasleitrohr 58 - Simplified said - flows around spirally. It is understood that the number, arrangement and / or configuration of the flow guide elements 59 is freely selectable to produce the appropriate flow pattern for the particular application (with or without swirl component).

The flow guide elements 59 ' span the annular gap 56 between the gas guide tube 58 and the dose of the tip facing away from the protective sleeve 22b , Also the flow guide elements 59 ' are at the device 10 ''' provided for generating a swirl-shaped flow pattern. That is through the annular gap 56 in the gas pipe 58 incoming exhaust gas has a spin-loaded flow pattern. Again, that the number, configuration and / or arrangement of the flow guide 59 ' can be adapted to the prevailing conditions in each case to produce the respectively desired flow pattern. In the exemplified device 10 ''' extend the flow guide 59 ' over the entire annular gap 56 , But they only partially protrude into the pipe 58 , The flow guide elements 59 ' on the one hand with the upstream end portion of Gasleitrohrs 58 and on the other hand with a downstream portion of the protective sleeve 22b in contact. The flow guide elements 59 ' can with the components 58 . 22b be firmly connected. However, it is also possible that the flow guide 59 ' only over part of the annular gap 56 extend. Of course, the same applies to the flow guide elements 59 ,

8th shows a cross section through the protective sleeve 22b with the gas guide 52 , Both components 22b . 52 are sheet metal components. It has been joined together, for example by welding or soldering. The protective sleeve 22b has a more conically shaped outer wall 26 on as the protective sleeve 22a , The inner wall 32 the protective sleeve 22b forms a slightly longer stretched funnel than the inner wall 32 the protective sleeve 22a , The inner wall 32 but is also slightly curved. The collar 42 the protective sleeve 22b points contrary to the collar 42 the protective sleeve 22a a weaker curvature. This makes it clear that the geometry of the protective sleeve can be widely varied to meet the respective requirements.

Through a synopsis of 6 to 11 it becomes clear that the gas baffle 52 one of the metering device facing end portion of the mixer tube 16 virtually complete to ensure that the flowing into this section of the exhaust gas as completely as possible to the backwashing of the metering tip 20 provided. Through the gas guide 52 , ie its arrangement and training, can thus be precisely determined, which exhaust gas quantities are available for backwashing the dosing.

12 shows an embodiment 22c the protective sleeve. It points, however, in addition to the walls 26 . 32 a base section 62 on, in one piece with the wall 26 is formed or made separately from this and then connected to her. The base section 62 has one of the dosing tip 20 associated opening to the injection of the reducing agent into the injection space 36 to enable. By means of spacers 64 will ensure that the base section 62 spaced from the bottom section 18 of the mixer tube 16 is arranged. This will create a backflushing gap 66 generated, through which a flow path 40 " leads. That through the gap 66 flowing exhaust gas contributes to backwashing the dosing tip 20 at. A purpose of this embodiment of the backwash is to divert a suitably large mass flow, on the one hand ensures a good flush, but on the other hand, on the other hand, is not too large. The heat input in the area of the dosing tip 20 namely, should not exceed a certain limit.

13 shows a further embodiment 22d the protective sleeve. It has both a curved inner wall 32 as well as a curved outer wall 26 to produce the desired flow pattern. At the right part of the outer wall are openings 28 provided to the entry of exhaust gas into the intermediate chamber 30 to enable. On the left side of the protective sleeve 22d has the outer wall 26 no openings 28 on. It is, however, with an outer wall section 68 provided, which - similar to the gas guide 52 the protective sleeve 22b - through the inlet opening 14 in the inlet pipe 48 protrudes. A part of the exhaust gas can thus directly into the intermediate chamber 30 arrive (see flow path 40 '' ).

To optimize the flow conditions, is the wall of the mixer tube 16 in the protective sleeve 22d with a bead 70 provided, whose configuration varies in the circumferential direction. Depending on the axial position - especially if the bead 70 in the axial direction above the inlet opening 14 is - this may also have a constant configuration in the circumferential direction.

14 and 15 show a further embodiment 22e the protective sleeve (only one opening 28 in 15 shown). It has conical inner and outer walls 32 . 26 on. In the gap 38 between the dosing tip side collar 42 the inner wall 32 and the bottom section 18 of the mixer tube 16 are guiding elements 72 arranged through which through the gap 38 flowing swirling gas is imparted a swirl component, as the flow path 40 "" by way of example. This measure also leads to a better backwashing of the dosing tip 20 and to a more efficient distribution of the reducing agent in the exhaust stream. In addition, this measure allows larger angles on the cone, without a release of the flow is to be feared.

The 16 shows a further embodiment 10 " the device according to the invention. The device 10 " shows in terms of the design of the mixer tube 16 a pretty similar structure to how the device 10 ' (see. 6 and 7 ). However, the protective sleeve differs 22f from the protective sleeve 22b in that guiding elements 72 are provided, which in the intermediate chamber 30 Exhaust gas located the gap 38 and impose a swirl on the exhaust gas. In contrast to the guiding elements 72 of the 14 and 15 are the guiding elements 72 the protective sleeve 22f bent outwards, leaving them in the intermediate chamber 30 protrude.

The in the 6 and 7 shown mounting flange 55 was to increase clarity in 16 Not shown. However, it is clear that the attachment of the metering device can be carried out in the same or similar manner as in the device 10 ' ,

Another difference between the devices 10 ' and 10 " is that a Gasleitrohr 58 ' the device 10 " constructed something different than the Gasleitrohr 58 , The gas pipe 58 ' has a funnel-shaped inlet area 74 in which the dosing tip 20 opposite end (forehead section 34 ) of the protective sleeve 26f protrudes. An opening plane of the funnel-shaped inlet area 74 is not parallel to one of the dosing tip 20 opposite edge of the protective sleeve 26f defined level.

To the funnel-shaped inlet area 74 closes a constriction 76 which unfolds a nozzle effect, by the efficiency of the device 10 " is increased.

The gas pipe 58 ' also extends deeper into the mixer tube 16 as the mixer tube 58 , It essentially follows a downstream geometry of the mixer tube 16 , which is why it has a curved section 78 having.

A gas conducting element 52 ' the device 10 " is also designed something different than the gas guide 52 the device 10 ' , It does not just stick in the inlet 48 into it, but even extends into one with the inlet nozzle 48 connected pipe 80 , The gas guide 52 ' follows the geometry of the tube 80 so that the upstream end 54 of the gas conducting element 52 ' parallel to the main flow direction of the exhaust gas in the pipe 80 is arranged. The gas guide 52 . 52 ' can also be made in several pieces, eg nested or cohesively connected components include.

In contrast to the gas guide 52 has the gas guide element 52 ' also holes 44 " on. They are in an area adjacent to the protective sleeve 22f arranged and allow passage of exhaust gas in this area.

The embodiment of the gas-conducting element 52 ' ensures early separation of the exhaust flow into a part of a lower portion of the protective sleeve 22f is fed, and in a part of the upper part of the protective sleeve 22f or the bypass gap 60 is forwarded. By the constriction 76 and the geometry of the funnel-shaped inlet area 74 indicates the bypass gap 60 a flow-mechanically favorable embodiment of the inlet region as the gap 60 the device 10 ' ,

17 shows a protective sleeve 22g , the flow guide elements forming tabs 82 having. The tabs 82 are each a gap opening 84 assigned. That means every flap 82 directs the inflowing gas of a certain gap opening 84 to. The tabs 82 can be obtained, for example, by cutting into the outer wall 26 are introduced and the tabs 82 then be bent out.

The 18 and 19 show the protective sleeve 22g in their installation position. The protective sleeve 22g points - as in the section of the 18 good to see - a non-disruptive inner wall 32 on, the Dosierspitzenseitig in one in the intermediate chamber 30 protruding collar 42 empties. The collar 42 defined together with the bottom section 18 the gap 38 , The bottom section 18 is relative to inlet nozzle 48 in the mixer tube 16 open, arranged slightly lowered. He is one of the pipe 16 separate, but gas-tight connected to this component.

To that through the respective inlet opening 14 the stub 48 flowing exhaust gas at least partially the stomata 84 to forward, are the tabs 82 correspondingly curved or bent. 18 shows that four with exhaust pipes 12 connected sockets 48 into the mixer tube 16 lead. Every neck 48 , and with it every inlet opening 14 , is in each case a gap opening 84 assigned. Each gap opening 84 again is a tab 82 assigned by a precisely defined portion of the in the mixer tube 16 flowing exhaust gas into the intermediate chamber 30 can be directed.

It is understood that individual features which have been described in connection with certain embodiments of the protective sleeve can be freely combined in order to obtain an optimal configuration of the protective sleeve for the respective prevailing conditions. In principle, it is also possible to provide openings on the side of the protective sleeve facing away from the dosing tip, so that exhaust gas can also flow out of the intermediate chamber in the axial direction. The throttle sleeve can be actively heated to even faster vaporize reducing agent occurring on it, in particular if the exhaust gas flow has not yet led to the heating of the components of the device according to the invention (for example, shortly after starting the engine). The surface of the protective sleeve can also be catalytically coated.

The throat forming gap for establishing fluid communication between the intermediate chamber and the injection space may have a circumferentially varying configuration (e.g., varying gap width). However, it is preferred to form the gap in the circumferential direction as constant as possible in order to allow a homogeneous flow of the gas in the circumferential direction into the injection space.

The concept according to the invention of firstly allowing an inlet of the exhaust gas through openings in the outer wall of the protective sleeve into an intermediate chamber and then using the exhaust gas for backwashing the dosing tip leads to significantly lower deposits than with previously known concepts. Namely, a substantially uniform pressure level is formed in the intermediate chamber, so that the flow through the gap and thus the backwashing of the dosing tip are also comparatively homogeneous. The exhaust gas flowing through the gap also flushes the reducing agent out of the injection space. Overall, a more homogeneous distribution of the reducing agent in the exhaust gas flow results.

LIST OF REFERENCE NUMBERS

10, 10 ', 10' ', 10' ''

contraption

12

exhaust pipe

14

inlet port

16

mixer tube

18

bottom section

20

Dosierspitze

22, 22a, 22b, 22c, 22d, 22e, 22f, 22g

protective sleeve

24

Einsprühkegel

26

outer wall

28

opening

30

intermediate chamber

32

inner wall

34

front section

36

injection room

38

gap

40, 40 ', 40 ", 40"', 40 ""

 flow path

42

collar

44, 44 ', 44' '

hole

46

flange

48

inlet port

50

outlet

52, 52 '

gas guide

54

upstream end

55

mounting flange

56

annular gap

58, 58 '

gas conduit pipe

59, 59 '

flow guide

60

Bypass gap

62

base section

64

spacer

66

Backflushing gap

68

Outer wall section

70

bead

72

vane

74

funnel-shaped inlet area

76

constriction

78

curved section

80

pipe

82

flap

84

gap opening

Claims (35)

Device for introducing a fluid into a gas stream, in particular into an exhaust gas stream of an internal combustion engine, with a mixing chamber ( 16 ) and with a metering device, through which the fluid by means of a metering tip ( 20 ) in a radial direction of a protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) defined injection space ( 36 ) can be introduced, which in the interior of the mixing chamber ( 16 ) and which is in fluid communication therewith, the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) in the circumferential direction of the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) extending intermediate chamber ( 30 ), the radially innseitig by an inner wall ( 32 ) and radially on the outside by an outer wall ( 26 ), the intermediate chamber ( 30 ) over one of the inner wall ( 32 ) formed or formed at this gap ( 38 ), in particular annular gap, with the injection space ( 36 ) is in fluid communication and via at least one opening ( 28 . 44 . 44 ' . 84 ) in the outer wall ( 26 ) with the mixing chamber ( 16 ) is in fluid communication. Device according to claim 1, characterized in that the gap ( 38 ) the dosing tip ( 20 ) at least partially, preferably completely surrounds in the circumferential direction. Device according to claim 1 or 2, characterized in that the gap ( 38 ) is arranged such that at least a part of the gas flow flowing through it, the dosing tip ( 20 ) backwashed. Device according to at least one of the preceding claims, characterized in that in the gap ( 38 ) at least one guiding element ( 72 ) is arranged, through which at least a portion of the gas flow flowing through it, a swirl component can be impressed. Device according to at least one of the preceding claims, characterized in that a part of a wall of the mixing chamber ( 16 ) the intermediate chamber ( 30 ) is limited at least in sections, in particular in an area around the dosing tip ( 20 ). Device according to at least one of claims 1 to 4, characterized in that one of the dosing tip ( 20 ) facing the end of the intermediate chamber ( 30 ) at least in sections through a bottom section ( 62 ) of the protective sleeve ( 22d ), in particular with the outer wall ( 26 ) is connected or integrally formed therewith. Apparatus according to claim 6, characterized in that the bottom section ( 62 ) spaced from a wall of the mixing chamber ( 16 ) is arranged. Device according to at least one of the preceding claims, characterized in that the gap ( 38 ) through one of the dosing tip ( 20 ) facing end portion of the inner wall ( 32 ), one the intermediate chamber ( 30 ) sectionally limiting part of a wall of the mixing chamber ( 16 ) and / or the bottom section ( 62 ) is limited. Device according to at least one of the preceding claims, characterized in that the inner wall ( 32 ) at its the dosing tip ( 20 ) facing end with a collar ( 42 ), which enters the intermediate chamber ( 30 protrudes. Device according to at least one of the preceding claims, characterized in that the at least one opening ( 28 ) in the outer wall ( 26 ) a hole ( 44 ' ), a slot ( 44 ) and / or a slot. Device according to at least one of the preceding claims, characterized in that the inner wall ( 32 ) has a funnel-shaped or conical section which extends in a direction from the metering tip (FIG. 20 ) opens away. Device according to at least one of the preceding claims, characterized in that the inner wall ( 32 ) is formed without interruption. Device according to at least one of the preceding claims, characterized in that the outer wall ( 26 ) has a funnel-shaped or conical section extending in a direction to the dosing tip ( 20 ) opens. Device according to at least one of the preceding claims, characterized in that the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) is integrally formed. Device according to at least one of claims 1 to 13, characterized in that the outer wall ( 26 ) and the inner wall ( 32 ) of the protective sleeve are separate elements which are connected to each other, in particular welded or soldered together. Device according to at least one of the preceding claims, characterized in that the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22f . 22g ) is formed substantially rotationally symmetrical. Device according to at least one of the preceding claims, characterized in that the mixing chamber ( 16 ) at least one inlet opening ( 14 ) which is arranged and formed such that the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ), in particular its outer wall ( 26 ), of at least part of it into the mixing chamber ( 16 ) flowing gas stream is flowed. Apparatus according to claim 17, characterized in that each inlet opening ( 14 ) at least one, in particular exactly one opening ( 28 . 44 . 44 ' . 44 '' ) in the outer wall ( 26 ) assigned. Device according to at least one of the preceding claims, characterized in that in the mixing chamber ( 16 ) a gas conducting element ( 52 . 52 ' . 68 . 82 ) is arranged, the at least part of the gas flow of the protective sleeve ( 22b . 22d . 22f . 22g ). Device according to claim 19, characterized in that the gas guiding element ( 52 . 52 ' . 68 . 82 ) with the protective sleeve ( 22b . 22d . 22f . 22g ) and in which the protective sleeve inflowing gas stream protrudes, in particular wherein an upstream end ( 54 ) of the gas guiding element ( 52 . 52 ' . 68 . 82 ) is arranged substantially parallel to the gas flow. Device according to claim 20, characterized in that the gas guiding element ( 52 . 52 ' . 68 . 82 ) of the at least one opening ( 28 . 44 . 44 ' . 84 ) is assigned to a portion of the gas flow in the opening ( 28 . 44 . 44 ' . 82 ), in particular wherein the gas guiding element ( 52 . 52 ' . 68 . 82 ) in the region of the opening ( 28 . 44 . 44 ' . 84 ) assigned. Device according to at least one of claims 19 to 21, characterized in that the gas guiding element ( 52 . 52 ' . 68 . 82 ) has a portion which is U-shaped or has the shape of an incomplete U. Device according to at least one of claims 19 to 22, characterized in that the gas guiding element ( 68 . 82 ) at least partially through a portion of the outer wall ( 26 ) of the protective sleeve ( 22d . 22g ) is formed. Device according to at least one of claims 19 to 23, characterized in that the gas guide element ( 52 . 52 ' . 68 . 82 ) in an inlet opening ( 14 ) of the mixing chamber ( 16 ) or protrudes through it. Device according to at least one of the preceding claims, characterized in that the mixing chamber ( 16 ) a bypass flow path ( 40 ' ), through which at least part of the gas flow into or through the mixing chamber ( 16 ) flows without the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) or through the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ), in particular its intermediate chamber ( 30 ) to flow. Apparatus according to claim 25, characterized in that the bypass flow path ( 40 ' ) at least in sections through a wall of the mixing chamber ( 16 ) and one of the dosing tip ( 20 ) facing away from the protective sleeve ( 22 . 22a . 22b . 22c . 22d . 22e . 22f . 22g ) is defined. Device according to at least one of the preceding claims, characterized in that the wall of the mixing chamber ( 16 ) an inwardly directed bead ( 70 ), which in the axial direction of the mixing chamber ( 16 ) approximately at the level of the protective sleeve ( 22d ) is arranged. Device according to at least one of the preceding claims, characterized in that in the mixing chamber ( 16 ) a gas conduit ( 58 . 58 ' ) whose outer circumference is spaced from the wall of the mixing chamber ( 16 ) is arranged. Apparatus according to claim 28, characterized in that between the outer periphery of the Gasleitrohrs ( 58 . 58 ' ) and the wall of the mixer chamber ( 16 ) at least one flow guide ( 59 ) is arranged. Apparatus according to claim 28 or 29, characterized in that at least one flow guide ( 59 ' ) provided in the Gasleitrohr ( 58 . 58 ' ) is arranged or at least partially in the Gasleitrohr ( 58 . 58 ' ), wherein the flow guide ( 59 ' ) in particular at the input end of the Gasleitrohrs ( 58 . 58 ' ) is provided. Apparatus according to claim 30, characterized in that the flow guide ( 59 ' ) between the protective sleeve ( 22b ) and the Gasleitrohr ( 58 . 58 ' ) is arranged, in particular between a strömabwärtigen portion of the protective sleeve ( 22b ) and an upstream portion of the Gasleitrohrs ( 58 . 58 ' ). Device according to at least one of claims 28 to 31, characterized in that the protective sleeve ( 22b . 22f ) in the axial direction at least partially into the Gasleitrohr ( 58 . 58 ' protrudes. Device according to at least one of claims 28 to 32, characterized in that the Gasleitrohr ( 58 . 58 ' ) has a portion which widens in the flow direction of the gas flow. Device according to at least one of claims 28 to 33, characterized in that the Gasleitrohr ( 58 . 58 ' ) a funnel-shaped inlet area ( 74 ) and / or a constriction ( 76 ) having a reduced cross section and / or a curved section ( 78 ) having. Device according to at least one of claims 28 to 34, characterized in that the Gasleitrohr ( 58 . 58 ' ) coaxial with the mixing chamber ( 16 ) and / or the protective sleeve ( 22b . 22f ) is arranged.

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