WO2010149410A1

WO2010149410A1 - Metering device for after-treating exhaust gases

Info

Publication number: WO2010149410A1
Application number: PCT/EP2010/055492
Authority: WO
Inventors: Max Leonhard; Ulrich Meingast; Tobias Hoeffken
Original assignee: Robert Bosch Gmbh
Priority date: 2009-06-25
Filing date: 2010-04-26
Publication date: 2010-12-29
Also published as: DE102009027185A1

Abstract

The invention relates to a device (110) for introducing a liquid pollutant-reducing medium into an exhaust gas. The device (110) comprises at least one metering unit (114) for providing the pollutant-reducing medium and at least one connector (118), which can be connected to an exhaust gas pipe (112), for mounting the metering unit (114) to the exhaust gas pipe (112). At least one injection channel (130) is provided in the connector (118), which channel is designed such that at least one inner wall (142) of the injection channel (130) is at least partially covered by the pollutant-reducing medium flow during operation of the device (110).

Description

description

title

Dosing device for aftertreatment of exhaust gases

State of the art

The invention is based on known devices for introducing pollutant-reducing media into an exhaust gas, for example an exhaust gas of an internal combustion engine.

Such pollutant-reducing media may for example be designed as liquids and may for example comprise reducing agents which specifically convert certain pollutants in the exhaust gases. This process is also referred to as Selective Catalytic Reduction (SCR). A well-known example of such a selective catalytic reduction is the reduction of nitrogen oxides (NOx) in the exhaust stream, for example a diesel engine, by means of a liquid urea-water solution (HWL), which is commercially available, for example, under the trade name AdBlue.

Such liquid pollutant-reducing media are usually injected via a metering unit in the exhaust system of a passenger car or commercial vehicle. Such metering units are known from the prior art. For example, the metering unit may comprise one or more self-opening or actuator-controlled injection valves, which generate a jet or a spray of the liquid pollutant-reducing medium via one or more injection openings.

In known constructions, the metering unit is usually attached to an exhaust pipe. However, by the heat flow from the exhaust pipe into the metering unit, the metering unit can heat up strongly, which has a detrimental effect on the durability and the function of the metering units. As a result, tightness problems or a Mehrmengendosierung occur. In addition, plastics, which may be contained in the metering unit, melt at high temperatures, and the pollutant-reducing liquid media may come to a boil in the metering unit.

In order to avoid these phenomena, the metering unit, for example a metering module of the metering unit, usually has to be configured retracted from the exhaust pipe in order to reduce the harmful influence of temperature on the metering unit. However, the problem arises that can form deposits on cool pipe walls in the retracted part when they are wetted by pollutant medium, for example by urea-water solution. These deposits can in turn endanger the function of the entire system.

It would therefore be desirable to have a device for introducing a liquid pollutant-reducing medium into an exhaust gas, which on the one hand avoids the problems caused by the high temperatures and, on the other hand, persistent deposits which can settle in particular in the area of the metering unit and / or a connecting piece connecting the metering unit and an exhaust pipe , avoids.

Disclosure of the invention

Accordingly, an apparatus for introducing a liquid pollutant-reducing medium into an exhaust gas is proposed, which at least largely solves the problem set out above and at least largely avoids the disadvantages of known devices. The liquid pollutant-reducing medium may in particular be a liquid reducing agent, for example HWL. In principle, however, alternatively or additionally, other liquid pollutant-reducing media are possible.

The device holds at least one metering unit for providing the pollutant-reducing medium. In this case, a metering unit is to be understood as meaning a device which can selectively meter the pollutant-reducing medium so that it is introduced into an exhaust gas stream flowing through an exhaust pipe. For example, the metering unit may comprise a metering unit, for example a self-opening, pressure-controlled and / or an actuator-controlled metering valve with min. at least one injection opening. With respect to this, reference may be made to known prior art metering units.

Furthermore, the device comprises at least one nozzle connectable to the exhaust pipe for mounting the metering unit to the exhaust pipe. Under a nozzle can be understood, for example, a conical or cylindrical element, by means of which the metering unit with the exhaust pipe is connectable, so that the pollution reducing medium can pass through the nozzle into the exhaust pipe, the nozzle leakage of pollutant reducing medium in Can at least largely prevent areas outside of the exhaust pipe.

The nozzle may preferably be mounted at an angle to the exhaust pipe, which may in particular be smaller than 90 °, so that the pollutant reducing medium can be introduced with a speed component in the direction of the exhaust gas flow within the exhaust pipe into the exhaust pipe. The introduction can take place in the form of a single jet or in the form of a plurality of jets or in the form of individual drops or a mist of the pollutant-reducing medium or of a spray.

In the neck at least one shot channel is formed. Under a shot channel is a channel to understand, which limits a lateral spread of the pollutant reducing medium. The shot channel can occupy the entire interior of the nozzle, or, as will be explained in more detail below, only a portion of the nozzle.

One idea of the present invention resides in the realization that stubborn deposits, which can settle on cool neck walls in the area of the metering unit, can be avoided in particular in that the walls of the neck are not made as hot as possible and are wetted as little as possible this is the case with conventional devices, but by the walls of the nozzle are designed as cold as possible and instead wets defined or even washed over. By a defined wetting it can come to a leaching effect, which can effectively prevent the deposit formation.

Accordingly, it is proposed to design the firing channel in such a way that at least one inner wall of the firing channel at least during operation of the device is partially overwhelmed by the pollutant reducing medium. For this purpose, the firing channel can for example be dimensioned such that this condition is given. An orientation of the firing channel, for example an axis of the firing channel, relative to an injection direction of the metering unit into the firing channel can be selected accordingly, that the at least one inner wall is flushed. Furthermore, as will be explained in more detail below, a length, a maximum width and / or an opening of the firing channel can be selected accordingly. The firing channel can be carried out either as part of the nozzle or as part of the metering unit protruding into the nozzle.

The nozzle may in particular comprise at least one outer tube, wherein the metering unit may be connected to the outer tube. At least one inner shell can be introduced into the outer tube. The firing channel can then be wholly or partially formed in the nozzle or, alternatively or additionally, also wholly or partly as part of the metering unit. The inner shell may completely or partially cover an inner area of the outer tube. The inner shell may be connected to the outer tube in particular by a cohesive connection, for example a welded connection. In particular, at least one air gap may be provided between the inner shell and the outer tube. This air gap may completely or partially surround the inner shell and / or may be part of the inner shell. The air gap can also be used in particular to keep the outer tube of the nozzle and thus also the metering unit and the firing channel as cold as possible.

As shown above, the nozzle can be connectable to the exhaust pipe, in particular at an acute angle. The exhaust pipe may be part of the device or may be formed separately. The neck should, if this is connected at an acute angle with the exhaust pipe, have on its shorter side a rounding, wherein the rounding is designed such that it allows an inflow of exhaust gas from the exhaust pipe into the nozzle, in particular in the firing channel. In this way, as much flow of the exhaust gas as possible can be brought into the recessed region in which the metering unit is arranged, so that flushing of the firing channel by exhaust gas can be ensured. In this way, a rinsing and / or removal of the pollutant-reducing medium from the firing channel can be effectively ensured. Furthermore, the firing channel can be designed in such a way that pollutant-reducing medium can flow and / or drip from the inner wall of the firing channel into hotter regions of the device and / or the exhaust pipe. This can be combined, for example, with the rounded configuration on the shorter side of the nozzle, since such a rounding can promote a drainage and / or dripping liquid pollutant reducing medium from the firing channel. If liquid pollutant-reducing medium drips out of the firing channel, the droplets preferably fall as low as possible into the exhaust system, into a noncritical region.

As described above, it is advantageous for the described washout effect, in which the pollutant-reducing medium is easily flushed out of the firing channel, to design the firing channel as short and narrow as possible. Accordingly, it is particularly preferred if the firing channel has a half opening angle which is between 3 ° and 25 °, in particular between 8 ° and 15 ° and particularly preferably at 10 °.

In particular, the neck can have a narrowed area and an extended area, the narrowed area allocating the metering unit and comprising the firing channel. The extended area, however, can assign the exhaust pipe and ensure assembly on the exhaust pipe. For example, the nozzle and / or the extended portion may be connected to the exhaust pipe via a welded joint or other type of connection. The extended region is preferably configured such that, during operation of the device, the pollutant-reducing medium does not come into contact with the walls of the extended region. The inner shell shown above is preferably formed in the narrowed region, but may also protrude completely or partially into the extended region.

The firing channel may preferably have a maximum diameter which is between 5 mm and 30 mm, preferably between 10 mm and 15 mm. The firing channel may preferably have a length which is between 5 mm and 45 mm, preferably between 10 mm and 20 mm.

The device according to the invention has numerous advantages over known devices. In particular, stubborn deposits can be effectively avoided by means of the device described, since in particular the firing channel is flushed out regularly or continuously by the pollutant-reducing medium itself can be. For this purpose, the critical transition region from the metering unit to a hotter region of the exhaust system can be configured completely or partially by a narrowest possible firing channel.

The firing channel should be dimensioned such that during normal operation no or only a few drops precipitate on the inner wall of the firing channel. However, if a deposit grows on the firing channel, it is preferably immediately wetted, softened and washed off by further pollutant-reducing medium, for example in the form of a spray. In order to assist the washing process, the firing channel itself should be kept as cool as possible, so that there can take place, for example, no concentration of the pollutant reducing medium. This can be effectively achieved, for example, by the inner shell described above. Washed off residues should, as shown above, dripping from the firing channel as deep as possible into the exhaust system, ie in areas where already higher temperatures prevail and in which thus a setting of deposits is largely excluded.

Brief description of the drawings

An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description.

It shows:

1 shows an embodiment of a device according to the invention for introducing a liquid pollutant-reducing medium into an exhaust gas.

embodiment

1 shows an embodiment of an inventive device 1 10 for introducing a pollutant-reducing medium into an exhaust gas in a sectional view from the side. The device 110 is mounted on an exhaust pipe 112, in which exhaust gas flows in the illustration in Figure 1 from right to left. The device 110 comprises a metering unit 114, which may for example comprise a metering valve 116 and which can be acted upon by a pipeline system, not shown, with liquid pollutant-reducing medium. The metering unit 114 is connected via a connecting piece 1 18 with the exhaust pipe 1 12, wherein the nozzle 1 18 is formed in the illustrated embodiment is substantially conical. The metering unit 114 is arranged at an acute angle α relative to a tube axis 120 of the exhaust pipe 1 12, which may for example be between 20 ° and 60 °, in particular at 30 °. Other embodiments are possible.

In this case, the dashed line 122 in Figure 1 denotes an injection direction, which may represent, for example, an extension of an axis of the metering valve 116. The liquid pollutant-reducing medium, for example HWL, can be metered into the exhaust gas in one or more jets or, for example, in the form of a spray.

The nozzle comprises in the illustrated embodiment, an outer tube 124, ü- about which the metering unit 1 14 is mounted on the exhaust pipe 1 12. In this outer tube 124, an inner shell 126 is inserted and connected to the outer tube 124 via a welded joint 128. The welded connection is preferably to be executed on the side of the inner shell 126 facing away from the metering unit 114.

Furthermore, a shot channel 130 is formed on the side of the metering unit 1 14 in the socket 118. The shot channel 130 encloses a narrowed portion 132 of the nozzle 118, whereas the remaining portion of the nozzle 118 is formed as an extended portion 134. In another embodiment, the nozzle 1 18 may also be designed as part of the metering unit 1 14.

The shot channel 130 has a half opening angle, which is designated in Figure 1 with the letter ß. This half opening angle can be for example 12 °. The opening angle is preferably configured in such a way that the inner wall 142 of the weft channel 130 is wetted as completely or partially as possible by a spray and / or jet of the pollutant-reducing liquid medium emerging from the metering unit 114 in order to ensure the above-described washout effect. In this way, the advantages shown above can be achieved. Between the inner shell 126 and the outer tube 124 and between the inner shell 126 and the firing channel 130, an air gap 136 is preferably provided. This air gap 136 serves the purpose of making both the shot channel 130 as cold as possible, and the inner shell 126 as hot as possible.

Furthermore, the nozzle 118 is provided on its shorter side with a rounding 138. This rounding makes it possible for as much flow as possible to flow from the exhaust pipe 1 12 into the retracted region of the nozzle 1 18 and there, in particular, into the discharge channel 130. Furthermore, the shot channel 130 protrudes into the inner shell 126. If drops form inside the weft channel 130, which are designated by the reference numeral 140 in FIG. 1, these drops can not penetrate into the air gap 136. The geometry of the neck 1 18 is further configured as possible so that these drops 140 may fall as deep as possible in the exhaust system in a non-critical area, here in the exhaust pipe 112th

Claims

claims

1. Device (1 10) for introducing a liquid pollutant-reducing medium into an exhaust gas, comprising at least one metering unit (114) for providing the pollutant-reducing medium and at least one with an exhaust pipe (1 12) connectable nozzle (1 18) for mounting the metering unit ( 1 14) on the exhaust pipe (112), wherein in the neck (1 18) at least one firing channel (130) is formed, wherein the firing channel (130) is configured such that at least one inner wall (142) of the firing channel (130) in Operation of the device (1 10) is at least partially washed by the pollutant reducing medium.

2. Device (1 10) according to the preceding claim, wherein the nozzle (1 18) comprises at least one outer tube (124), wherein the metering unit (1 14) with the outer tube (124) is connected, wherein in the outer tube (124). at least one inner shell (126) is introduced, wherein the firing channel (130) in the neck (1 18) is formed.

3. Device (1 10) according to any one of the preceding claims, wherein the nozzle (1 18) comprises at least one outer tube (124), wherein the metering unit (114) is connected to the outer tube (124), wherein in the outer tube (124). at least one inner shell (126) is introduced, wherein the firing channel (130) is formed as part of the metering unit (114).

4. Device (1 10) according to one of the two preceding claims, wherein the inner shell (126) with the outer tube (124) by a material connection, in particular a welded connection (128) is connected.

5. Device (1 10) according to one of the three preceding claims, wherein between the inner shell (126) and the outer tube (124) at least one air gap (136) is introduced.

6. Device (1 10) according to any one of the preceding claims, wherein the nozzle (118) at an acute angle with the exhaust pipe (1 12) is connectable, wherein the nozzle (118) on its shorter side has a rounding (138), wherein the rounding (138) allows an inflow of exhaust gas from the exhaust pipe (112) in the nozzle (118), in particular in the firing channel (130).

7. Device (1 10) according to any one of the preceding claims, wherein the firing channel (130) is configured such that polluting medium from the inner wall (142) of the firing channel (130) in the exhaust pipe (1 12) can drip.

8. Device (1 10) according to any one of the preceding claims, wherein the firing channel (130) has a half opening angle which is between 3 ° and 25 °, in particular between 8 ° and 15 ° and particularly preferably at 10 °.

The apparatus (1 10) of any one of the preceding claims, wherein the stub (118) has a narrowed portion (132) and an enlarged portion (134), the narrowed portion (132) assigning the metering unit (114) and the firing channel (130).

10. Device (1 10) according to any one of the preceding claims, wherein the firing channel (130) has a maximum diameter which is between 5 mm and 30 mm, preferably between 10 mm and 15 mm.

1 1. A device (1 10) according to any one of the preceding claims, wherein the firing channel (130) has a length which is between 5 mm and 45 mm, preferably between 10 mm and 20 mm.