DE102012014528A1 - Mixing- or evaporation device for exhaust system of internal combustion engine, particularly of motor vehicle, has guide blade that protrudes in direction towards long side wall, where additional guide blade protrudes in acute angle - Google Patents

Abstract

The mixing- or evaporation device has a supporting body, which encloses a cross-section of an equipment in a peripheral direction. two small side walls (23,24) connect both long side walls (21,22) with each other, where multiple guide blades (25) are arranged on an axial end (26) on one long side wall The guide blade protrudes in direction towards another long side wall, and is engaged against an axial direction (20). An additional guide blade (29) protrudes from the long side wall in an acute angle (alpha), and is inclined around an axis extending parallel to axial direction. Independent claims are included for the following: (1) an exhaust system for an internal combustion engine, particularly of a motor vehicle; and (2) a silicon controlled rectifier-catalytic converter for an exhaust system of an internal combustion engine, particularly of a motor vehicle.

Description

The present invention relates to a mixing and / or evaporation device for an exhaust system of an internal combustion engine, in particular of a motor vehicle. The invention also relates to an exhaust system equipped with such a device and to an SCR catalytic converter equipped with such a device.

Usually, an exhaust system of an internal combustion engine is equipped with devices for cleaning or after-treatment of the exhaust gases carried away by the internal combustion engine. It may be necessary to introduce a liquid educt into the exhaust gas stream, to evaporate therein and to mix with the exhaust gas. For example, it may be necessary to mix a fuel upstream of an oxidation catalyst to the exhaust gas to cause heating of the exhaust gas stream by an exothermic reaction of the fuel in the oxidation catalyst. The heated exhaust stream can then be used downstream of the oxidation catalyst to heat another exhaust aftertreatment device to operating temperature or to regeneration temperature, for example, another catalyst or a particulate filter. Furthermore, SCR systems are known which operate with selective catalytic reaction and are equipped with an SCR catalyst, which receives NO _x from the exhaust gas stream. Upstream of the SCR catalyst, a suitable reducing agent is supplied to the exhaust gas stream, for example ammonia or urea, preferably an aqueous urea solution. In the SCR catalytic converter, the ammonia then converts the stored nitrogen oxides into nitrogen and water.

For all educts supplied to the exhaust gas stream in liquid form, the desired effect can only be satisfactorily achieved if sufficient vaporization of the starting material and adequate mixing of the gaseous educt with the exhaust gas stream can take place between the point of introduction of the liquid starting material and a point of consumption of the educt , For this purpose, the mixing and / or evaporation devices mentioned above are used, which are arranged in the flow path of the exhaust gas between the point of introduction of the educt and the point of consumption of the educt.

The present invention is concerned with the problem of providing an improved or at least another embodiment for a device of the type mentioned at the outset or for an SCR catalytic converter equipped therewith, which is characterized by a simpler and thus cheaper construction , wherein also a lower flow resistance or back pressure and an improved mixing of the reactant with the exhaust gas is desired. In addition, liquid educt, which accumulates on walls of the exhaust system to form a wall film, can be returned to the exhaust gas stream.

This problem is solved in the present invention, in particular by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea to equip the mixing and / or evaporation device with a support body which encloses a transversely extending to the axial direction of the device, the flat, flow-through cross-section of the device in the circumferential direction. The carrier body thus does not define a circular cross section, but an elongated or flat cross section, such that the carrier body has two opposite long side walls and two opposite short side walls, wherein the short side walls connect the two long side walls together. The inventively proposed embodiment of the support body with a flat cross-section, it is possible to arrange at least on a long side wall a plurality of vanes which protrude in the direction of the other long side wall and which are employed with respect to the axial direction at an angle.

By this construction, the vanes extend transversely to the axial direction and are also arranged both transversely to the axial direction and transversely to their longitudinal direction side by side. The axial direction of the device corresponds to a main flow direction of the exhaust gas through the device. This main flow direction does not take into account flow deflections, crossflows, backflows, turbulences and the like within the flow-through cross section. At the respective axial end of the respective long side wall there is thus provided a row of guide vanes arranged side by side, in particular running parallel to one another, each of which causes a flow deflection in the direction of a short side wall.

On the one hand, the guide vanes of the respective rectilinear guide blade row provide a comparatively large impact surface for liquid educt introduced into the exhaust gas stream upstream therefrom, so that the liquid can impinge on the guide vanes and vaporize, or can be divided by the impact into smaller liquid droplets. On the other hand, the vanes cause an intensive flow deflection, which promotes the mixing of the vaporized reactant with the exhaust stream.

In order to reduce the backpressure of the above-described mixing and / or evaporation device and to achieve a better mixing of the educt with the exhaust gas, a plurality of guide vanes or rows of guide vanes may be arranged in the axial direction of the device. Thus, at the respective axial ends of the long side walls Leitschaufelreihen and in addition between these, ie, for example, in the axial direction in the middle between the two axial ends Zusatzleitschaufelreihen be arranged. These can be bent about an axis extending parallel to the axial direction or employed with respect to the axial direction at an angle of attack.

By this arrangement of additional guide vanes between the arranged at the axial ends vanes, an additional process stage is created in which the already evaporated liquid or existing liquid droplets are swirled once more and mixed more strongly with the exhaust stream. In addition, the not yet vaporized liquid droplets can impinge on the auxiliary vanes and evaporate at this. In this way, the efficiency of the entire assembly is improved, thereby enabling a total reduction of the number of vanes or a reduction of the total projecting into the exhaust stream impingement surface of the vanes with constant mixing. Thus, a further reduction of the back pressure can be achieved.

A "flat" flow-through cross section as described above is characterized in that, in a first direction perpendicular to the axial direction, it has a diameter which is greater than a diameter in a second direction perpendicular to the axial direction and perpendicular to the first direction. In particular, the diameter in one direction may be at least twice as large as in the other direction. Excluded are thereby circular cross-sections, while oval and elliptical cross sections are also flat or can be. The terms "long" and "short" are not to be understood here as absolute, but relative to each other, so that the long side walls in the circumferential direction are longer than the short side walls. Depending on the geometry of the flow-through cross-section of the device, the long side walls are expediently flat, while the short side walls can be curved.

According to a particularly advantageous embodiment, the additional guide vanes are at an acute angle from the side wall on which they are arranged and are bent about an axis extending parallel to the axial direction.

As a result of this embodiment, the exhaust gas flow within the carrier body is set in rotation or swirled, whereby a particularly intensive mixing of the educt with the exhaust gas takes place. Furthermore, not yet vaporized liquid droplets can impinge on the auxiliary vanes and evaporate at this.

According to a further advantageous embodiment, the length of the auxiliary guide vanes is selected such that a free end of the auxiliary guide vanes protrudes beyond a central longitudinal center plane extending between the long side walls.

In this way, with a small number of additional guide vanes, a large flow transverse vessel of the exhaust gas flow can be detected and good mixing of the educt with the exhaust gas can be achieved in the region between the guide vanes arranged at the axial ends.

According to another advantageous embodiment, in each case two arranged on opposite side walls auxiliary vanes are arranged so that they are arranged in the axial direction at the same distance from the axial end of the respective side walls.

In this way, in each case two guide vanes, which are not arranged on the same side wall, in the flow direction at the same height opposite and can thus form a pair of guide vanes, which cooperates in the formation of certain flow conditions and in particular of rotating flow portions or vortices.

In a further advantageous embodiment, at least one pliers side wall at an axial end transverse to the axial direction a plurality of guide vanes arranged to each other so that the short side walls of the nearest guide vanes in the axial direction a greater distance from the opposite axial end than the transverse to the axial direction respectively closer to a center of the carrier body arranged vanes.

The guide blade surfaces which are transverse to the flow direction thus form on the upstream side of the carrier body a concave outer surface of the carrier body which is permeable to the exhaust gas. With a constant flow-through cross section of the carrier body thus more vanes or a larger impact surface can be arranged in the exhaust stream.

According to another advantageous embodiment, the additional guide vanes are of the long side wall substantially orthogonal and extend in the direction of the respective opposite wall, wherein they are employed with respect to the axial direction.

Due to the rectilinear design of the guide vanes and the additional vanes, the exhaust gas flow within the carrier body is not set in rotation, but good mixing can nevertheless be achieved by the successive stages of the vanes. By avoiding a rotation of the exhaust gas stream within the carrier body of the flow resistance or the back pressure of the mixing and / or evaporation device can be reduced.

In a further advantageous embodiment, a further vane is arranged on at least one short side wall, wherein the further vane protrudes at an acute angle from the short side wall and is bent around an axis orthogonal to the central longitudinal center plane extending between the long side walls.

Centrifugal forces, which act on liquid droplets introduced into or entrained in the exhaust gas stream, when the exhaust gas is deflected from a rectilinear movement, may cause the liquid droplets to be thrown against walls of the exhaust system and form a wall film of liquid educt there. The further vanes on the short side walls of the carrier body can lead liquid from such a wall film away from the wall and reintroduce it into the exhaust gas flow. In addition, the further guide vanes introduced into the exhaust gas stream bring about a reorientation of the flow course in this area, whereby a better mixing and an optimization of the flow distribution can be achieved. In this way, the effectiveness of the mixing and / or evaporation device is increased.

According to another advantageous embodiment, all vanes are formed integrally on the respective side wall. In this way, the guide vanes and the side walls can be made particularly simple and inexpensive, for example as a stamped and formed part of a sheet metal part.

In a further advantageous embodiment, all side walls are integrally formed on the carrier body. In this way, the entire device can be made particularly simple and inexpensive from a stamped and formed part of a sheet metal part.

An exhaust system according to the invention comprises at least one SCR catalyst, a Reduktionsmittelzuführeinrichtung having at least one injector for supplying a reducing agent to the exhaust gas upstream of the SCR catalyst, and at least one mixing and / or evaporation device of the type described above, between the at least one injector and the at least one SCR catalyst is arranged.

By contrast, an SCR catalytic converter according to the invention comprises a housing in which at least one SCR catalytic converter element is arranged, and at least one mixing and / or evaporating device of the type described above, which is arranged in the housing of the SCR catalytic converter upstream of the at least one SCR element.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Show, in each case schematically,

1 a greatly simplified, schematics-like schematic diagram of an internal combustion engine with an exhaust system,

2 a simplified, schematic view of an SCR catalyst,

3 each a cross section of the SCR catalyst according to section lines III in 2 in different embodiments A and B,

4 an isometric view of an embodiment of the mixing and / or evaporation device,

5 a supervision of the in 4 shown embodiment,

6 a sectional view taken along section line IV in 5 .

7 an isometric view of another embodiment of the mixing and / or evaporation device, and

8th an isometric view of another embodiment of the mixing and / or evaporation device.

Corresponding 1 includes an internal combustion engine 1 in the usual way an engine block 2 , the several cylinders 3 having. A fresh air system 4 supplies the cylinders 3 of the engine block 2 with fresh air. A corresponding fresh air flow is indicated by an arrow 11 indicated. An exhaust system 5 leads during operation of the internal combustion engine 1 Combustion gases from the cylinders 3 of the engine block 2 from. Furthermore, the exhaust system causes 5 an exhaust gas purification or exhaust aftertreatment. This is the exhaust system 5 with at least one SCR catalyst 6 fitted in a suitable way in an exhaust line 7 the exhaust system 5 is involved. The SCR catalyst can also be designed as a particle filter or diesel particle filter, which is provided with a corresponding coating. Furthermore, the exhaust system includes 5 a reducing agent supply device 8th that has at least one injector 9 or a pipe 9 having, with the aid of a reducing agent in an exhaust gas stream 10 can be introduced, in the operation of the internal combustion engine 1 in the exhaust system 7 flows and is indicated by arrows. The injection of the liquid reducing agent in the exhaust stream 10 takes place upstream of the SCR catalyst 6 ,

Furthermore, the exhaust system includes 5 at least one mixing and / or evaporation device 12 , which in the following shortened with device 12 referred to as. The device 12 is in the exhaust system 7 between the injector 9 and the SCR catalyst 6 arranged so that the exhaust gas with the supplied reducing agent first the device 12 must flow through before the mixture to the SCR-In contrast shows 2 an embodiment in which the SCR catalyst 6 and the device 12 form an integral unit. This is in the case 15 of the SCR catalyst 6 at least one SCR catalyst element 16 arranged, being in the housing 15 upstream of this SCR catalyst element 16 as well as the furnishings 12 is arranged. Thus, the device 12 and the SCR catalyst element 16 in a common housing 15 arranged.

In the example of 2 includes the housing 15 an inlet funnel 17 and an outlet funnel 18 , where the device 12 and the SCR catalyst element 16 between the two funnels 17 . 18 are arranged.

According to the 3A and 3B can the case 15 at least in the area of the institution 12 have a flat cross-section, to which the respective device 12 is adjusted. 3A shows an embodiment in which the durchströmbare cross section of the housing 15 with the help of a single device 12 is filled. In contrast, shows 3B an embodiment in which the flow-through cross-section of the housing 15 with the help of two juxtaposed facilities 12 is filled. The same then applies to the arrangement of the device 12 in the exhaust system 7 so that there too at least two facilities 12 next to each other in the area 13 can be arranged to the flow-through cross-section of the exhaust line 7 fill.

Since the flow-through cross-section of the device 12 flat, owns the support body 19 two long side walls 21 . 22 facing each other and two short side walls 23 . 24 which are also opposite each other. The short side walls 23 . 24 connect each of the two long side walls 21 . 22 ,

Furthermore, the device 12 with several vanes 25 each equipped with one of the long side walls 21 . 22 towards the other long side wall 21 . 22 stand out while holding it at one axial end 26 or 27 the device 12 or the supporting body 19 or the respective long side wall 21 . 22 protrude. If the exhaust flow according to the arrow 10 is oriented, forms the one, first flowed axial end 26 an inflow side, which in the following also with 26 is designated, while the other axial end 27 then forms a downstream side, which in the following also with 27 referred to as.

The vanes 25 each extend straight and parallel to each other. Further, the vanes 25 each configured just in the embodiments shown here. In addition, they are opposite to the axial direction 20 hired. In the examples shown, an angle of incidence of the guide vanes is 25 opposite to the axial direction 20 each 45 ° within the usual manufacturing tolerances.

The vanes 25 extend transversely to the axial direction 20 and are also transverse to their longitudinal extent and transverse to the axial direction 20 arranged side by side in a row, also called a row of blades 28 can be designated.

In the embodiments of the 4 - 8th is provided that on both long side walls 21 . 22 at least at one axial end 26 . 27 each guide vanes 25 which are directed towards the other long side wall 21 . 22 protrude. In the embodiments shown here are characterized at the respective axial end 26 . 27 , so on the upstream side 26 or on the downstream side 27 in each case two juxtaposed blade rows running parallel to each other 28 intended. Exemplary here are themselves opposite vanes 25 dimensioned so that they are starting from the associated long side wall 21 . 22 extend to a median longitudinal plane midway between the two long sidewalls 21 . 22 runs. Alternatively, embodiments are conceivable in which only at one long side wall 21 or only at one axial end 26 stator blade 28 can be arranged.

In a further alternative embodiment, the vanes may 25 the two long side walls 21 . 22 as far as the other side wall 21 . 22 extend that to the vanes 25 the one long side wall 21 into the gaps between adjacent vanes 25 the other side wall 22 into it, so that ultimately a common row of guide vanes 28 is formed by the vanes 25 the two long side walls 21 . 22 is formed, being within this common vane row 28 the vanes 25 the two long side walls 21 . 22 alternate.

In the embodiments shown here, the vanes are 25 each arranged and dimensioned so as to be spaced from the respective long side wall 21 . 22 from which they emanate, free-standing end or a free end 31 exhibit. So are the vanes 25 the embodiments shown in particular contactless to each opposite long side wall 21 . 22 and non-contact to the other vanes 25 ,

As in the embodiments of the 4 - 8th recognizable at both axial ends 26 . 27 vanes 25 are provided, they can either in the same direction or opposite to the axial direction 20 be employed. The vanes 25 that are at the same axial end 26 . 27 but on opposite long side walls 21 . 22 are arranged, are in the embodiments shown opposite to the axial direction 20 hired. In other words, on the upstream side 26 and / or on the downstream side 27 are the vanes 25 the one row of blades 28 on the one long side wall 21 is formed, opposite to the vanes 25 the other row of blades 28 on the other long side wall 22 are formed, to the axial direction 20 hired.

In one in the 4 - 6 illustrated embodiment are on both long side walls 21 . 22 at a distance s in the axial direction 20 to an axial end 26 Zusatzleitschaufeln 29 arranged. These are at an acute angle α from the respective long side wall 21 . 22 from and are parallel to the axial direction 20 extending axis so bent that its free end 31 essentially allocates to the opposite long side wall. In this embodiment, the auxiliary vanes are 29 not to the axial direction 20 employed, since the deflection of the exhaust gas flow through the curved course of the auxiliary vanes 29 he follows. Due to the employment of the vanes 25 the exhaust gas stream flows inside the carrier body 19 not laminar parallel to the axial direction 20 but at different angles or swirls to it. Therefore, individual portions of the exhaust gas flow so hit the curved surfaces of the auxiliary vanes 29 that two around parallel to the axial direction 20 extending axes rotating flows are formed. In this way, a very good mixing of the gaseous starting material with the exhaust gas flow can take place.

In the in the 4 - 6 illustrated embodiment are also more vanes 30 on the short side walls 23 . 24 arranged. These are at an acute angle β from the short side walls 23 . 24 and are in the flow direction about an orthogonal to the axial direction ( 20 ) and orthogonal to the center between the long side walls ( 21 . 22 ) extending longitudinal central plane extending axis bent so that they are in the direction of the opposite short side wall 23 . 24 protrude. Through these further vanes 30 For example, a wall film of liquid starting material, which can be formed on walls of the exhaust system by adhering droplets, can be returned to the exhaust gas flow.

In an in 7 illustrated embodiment, the auxiliary vanes 29 not bent but just executed, according to the vanes 25 essentially orthogonal to the long sidewalls 21 . 22 protrude and opposite to the axial direction 20 are employed. The angle of attack of the respective additional guide vane 29 is in each case opposite to the respective upstream vane 25 , In this way, an additional mixing step within the carrier body 19 created, wherein in addition not yet vaporized liquid droplets impinge on the staffed vane surfaces and divided into these are divided into smaller droplets or vaporized.

In the 8th a further embodiment is shown, in which the guide blade rows 28 at the upstream axial ends 26 . 27 concave to the carrier body 19 run. In other words, the vanes 25 attached to the outer sides of the carrier body 19 ie closest to the short side walls 23 . 24 are arranged, have the shortest distance to the Reduktionsmittelzuführeinrichtung in the exhaust stream 8th on. The further inside, ie further from the short side walls 23 . 24 remote arranged vanes 25 , On the other hand, are at a greater distance from the Reduktionsmittelzuführeinrichtung 8th arranged. With this arrangement, it is possible, with a constant flow-through cross section of the carrier body more vanes or a larger impact surface of the vanes 25 to arrange in the exhaust stream.

In the described embodiments, the support body 19 a sheet metal part that integrally forms the four side walls 21 . 22 . 23 . 24 includes. Further, the vanes 25 on the respective long side wall 21 . 22 integrally formed, so that ultimately the complete device 12 is made of a single sheet metal part. The preparation can be carried out from an elongated strip-shaped sheet metal blank, in which initially the guide vanes 25 be cut free. Subsequently, the vanes can 25 be angled. Finally, the metal strip according to the flat permeable cross section of the device 12 be bent to the long and short side walls 21 . 22 . 23 . 24 of the supporting body 19 train. The longitudinal ends of the blank may be on the one short side wall 23 according to a connecting seam 31 be attached to each other.

Claims (11)

Mixing and / or evaporating device for an exhaust system ( 5 ) an internal combustion engine ( 1 ), in particular a motor vehicle, with a supporting body ( 19 ), one transverse to the axial direction ( 20 ) of the institution ( 12 ), flat, flow-through cross-section of the device ( 12 ) encloses in the circumferential direction, wherein the supporting body ( 19 ) two opposing long side walls ( 21 . 22 ) and two opposite short side walls ( 23 . 24 ), wherein the short side walls ( 23 . 24 ) each have the two long side walls ( 21 . 22 ), at least on a long side wall ( 21 . 22 ) at least at one axial end ( 26 . 27 ) several vanes ( 25 ) which are directed towards the other long side wall ( 21 . 22 ) and opposite the axial direction ( 20 ) are employed, wherein at least one long side wall ( 21 . 22 ) in the axial direction ( 20 ) at a distance (s) to an axial end (s) ( 26 ) Additional guide vanes ( 29 ) are arranged. Mixing and / or evaporating device according to claim 1, characterized in that the auxiliary guide vanes ( 29 ) from the long side wall ( 21 . 22 ) protrude at an acute angle (α) and about a parallel to the axial direction ( 20 ) extending axis are bent. Mixing and / or evaporating device according to one of claims 1 to 2, characterized in that the length of the auxiliary guide vanes ( 29 ) is selected so that a free end of the auxiliary guide vanes over a centrally between the long side walls ( 21 . 22 ) extending longitudinal median plane protrudes. Mixing and / or evaporating device according to one of claims 1 to 3, characterized in that in each case two on opposite side walls ( 21 . 22 ) arranged additional guide vanes ( 29 ) are arranged so that they are in the axial direction ( 20 ) at the same distance (s) to the axial end (s) ( 26 . 27 ) of the respective side wall are arranged. Mixing and / or evaporating device according to one of claims 1 to 4, characterized in that along at least one long side wall ( 21 . 22 ) at an axial end ( 26 . 27 ) transverse to the axial direction ( 20 ) several vanes ( 25 ) are arranged so that the short side walls ( 23 . 24 ) closest to the axial direction of the guide vanes ( 20 ) a greater distance to the opposite axial end ( 26 . 27 ) than the transverse to the axial direction ( 20 ) each closer to a center of the carrier body ( 19 ) arranged guide vanes ( 25 ). Mixing and / or evaporating device according to claim 1, characterized in that the auxiliary guide vanes ( 29 ) from the long side wall ( 21 . 22 ) protrude substantially orthogonal and extend in the direction of the respective opposite wall, with respect to the axial direction ( 20 ) are employed. Mixing and / or evaporating device according to one of the preceding claims, characterized in that on at least one short side wall ( 23 . 24 ) another vane ( 30 ), wherein the further guide vane ( 30 ) at an acute angle (β) from the short side wall (FIG. 23 . 24 ) and bent around an axis orthogonal to the longitudinal center plane. Mixing and / or evaporating device according to one of the preceding claims, characterized in that all guide vanes ( 25 . 29 . 30 ) integral to the respective side wall ( 21 . 22 . 23 . 24 ) are formed. Mixing and / or evaporating device according to one of the preceding claims, characterized in that all side walls ( 21 . 22 . 23 . 24 ) integral to the carrier body ( 19 ) are formed. Exhaust system for an internal combustion engine ( 1 ), in particular of a motor vehicle, with at least one SCR catalytic converter ( 6 ) with a reducing agent supply device ( 8th ), the at least one injector ( 9 ) for supplying a reducing agent to the exhaust gas flow ( 10 ) upstream of the SCR catalyst ( 6 ), with at least one mixing and / or evaporation unit ( 12 ) according to one of claims 1 to 9, which between the least one injector ( 9 ) and the at least one SCR catalyst ( 6 ) is arranged. SCR catalytic converter for an exhaust system ( 5 ) an internal combustion engine ( 1 ), in particular a motor vehicle, with a housing ( 15 ), in which at least one SCR catalyst element ( 16 ) is arranged with at least one mixing and / or evaporation unit ( 12 ) according to one of claims 1 to 9, in the housing ( 15 ) upstream of the at least one SCR catalyst element ( 16 ) is arranged.

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