DE102015201378A1 - Mixer and exhaust system with such - Google Patents

Abstract

The invention relates to a mixer (10) for an exhaust system (20), for mixing an exhaust gas flow (AG) supplied means (M) with the exhaust stream (AG), wherein the mixer (10) comprises at least one exhaust gas guide element (14). It is provided that the mixer is designed such that the at least one exhaust gas guide element (14) with an increasing exhaust flow (AG) of - a mixing position (Sm) with a mixing resistance to - a passage position (Sd) is adjustable with an on-resistance, wherein the mixing resistance is greater than the on-resistance. Furthermore, the invention relates to an exhaust system with such a mixer.

Description

The invention relates to a mixer for an exhaust system for mixing a means supplied to an exhaust gas flow with the exhaust gas flow, wherein the mixer comprises at least one exhaust gas guide. Furthermore, the invention relates to an exhaust system with the mixer according to the invention.

To reduce the emission of internal combustion engines and to comply with current emissions legislation exhaust systems with multiple exhaust aftertreatment components are used. For example, an exhaust system for reducing emissions of a diesel fueled internal combustion engine may include an oxidation catalyst, a particulate filter, and an SCR (Selective Catalytic Reduction) catalyst. In selective catalytic reduction, nitrogen oxides (NO _x ) are reduced, thus reducing their emission. At the end of the reaction, ammonia (NH ₃ ), which is supplied to the exhaust gas in the form of an aqueous urea solution, is used as the reducing agent. From the urea solution, ammonia and CO _{2 are} formed in a hydrolysis reaction.

In order to achieve low ammonia consumption with simultaneous sufficient NO _x reduction, good mixing of the urea solution with the exhaust gas is required, which at the same time also serves to avoid ammonia slip. For this reason, mixers are installed in the exhaust system, which ensure turbulent flow conditions and thus good mixing in the exhaust gas.

That's how it describes DE 10 2011 112 988 A1 an exhaust system with an evaporator body and a mixer. As evaporation body sheets may be provided. A surface of the evaporation body may also be optimized by scooping for the evaporation of the liquid urea solution.

Furthermore, the describes DE 10 2011 077 645 A1 an exhaust system with a static mixer, which has an annular body and at least one row of blades with a plurality of radially projecting from the annular body inwardly projecting vanes. The DE 20 2012 011 764 U1 describes a similarly constructed mixer, which can be electrically heated.

With a relatively low exhaust gas flow (in particular exhaust gas mass flow and / or exhaust gas volumetric flow), a sufficient uniform distribution of the reducing agent within the exhaust gas flow is much more difficult to produce than with a relatively high exhaust gas flow. The mixers are therefore shaped such that they ensure a sufficient uniform distribution of the reducing agent within the exhaust gas flow even with a relatively small exhaust gas flow. However, this also means that they represent a relatively large flow resistance at a relatively high exhaust flow and thus increase the exhaust back pressure unnecessarily. This higher exhaust backpressure was previously accepted and compensated by a higher CO ₂ emissions. Furthermore, already adjustable mixers are known:

In the document DE 10 2012 205 680 A1 a reconfigurable bimetallic mixer for an exhaust aftertreatment system is described. The mixer includes a plurality of blade sections which are reversibly movable between extended and retracted positions, having a greater resistance to exhaust flow in the extended position than in the retracted position. By means of a bimetallic pair or a shape memory metal element, which is connected to the mixer, the wing sections are reversibly extended and retracted.

The in the document DE 10 2009 420 A1 The mixing device shown has mixing elements, which from a rest position, in which they provide the lowest possible flow resistance for an exhaust gas flow, in a mixing position in which they cause turbulence in the exhaust gas flow, by deformation of a bimetallic element due to a change in the temperature of the exhaust gas the exhaust gas flow can be brought.

The document US 2011/0258983 A1 relates to a reconfigurable mixer whose flow-influencing parts are adjustable from a first to a second position under the effect of a shape-memory metal. The invention is based on the object of providing a mixer by means of which, on the one hand, with relatively low exhaust gas flows, a higher uniform distribution of the reducing agent in the exhaust gas and, on the other hand, with relatively high exhaust gas flows, a low exhaust back pressure can be achieved.

• – einem zunehmenden Abgasstrom von
• – einer Mischungsstellung mit einem Mischungswiderstand zu
• – einer Durchlassstellung mit einem Durchlasswiderstand verstellbar ist oder verstellt wird, wobei der Mischungswiderstand größer als der Durchlasswiderstand ist.

According to the invention, a mixer for an exhaust system, for mixing an exhaust gas flow, in particular in the exhaust system, supplied with the exhaust gas flow provided. The mixer comprises at least one exhaust gas guide element. Characteristic is provided that the mixer is designed such that the at least one exhaust gas guide with

• - An increasing flow of exhaust gas from
• - To a mixing position with a mixing resistance
• - A passage position is adjustable with an on-resistance or is adjusted, wherein the mixing resistance is greater than the on-resistance.

The mixing resistance and the forward resistance are each a flow resistance. They may therefore also be referred to as mixing flow resistance and transmission flow resistance.

As a result, a higher uniform distribution of the reducing agent in the exhaust gas and, on the other hand, with a relatively high exhaust gas flow, a lower exhaust backpressure is achieved compared with static (non-adjustable) mixers with a relatively low exhaust gas flow (in particular exhaust gas mass flow and / or exhaust gas volumetric flow).

The mixer can be adjusted directly by the exhaust gas flow and / or the exhaust gas temperature. This means that the adjustment is brought about by an exhaust gas back pressure resulting from the exhaust gas flow through the flow resistance of the mixer.

In addition, in concrete embodiments, the at least one exhaust gas guide element can be adjustable with an increasing exhaust gas temperature from the mixing position into the passage position. That is, the adjustment may be enhanced or assisted or facilitated by a heat input into the mixer caused by the increasing temperature.

The adjustment is reversible, so reversible. With a decreasing exhaust gas flow and possibly a decreasing exhaust gas temperature, the at least one exhaust gas guide element is thus adjusted from the passage position to the mixing position.

Furthermore, the adjustment can be continuous or erratic. The preferred, continuous adjustment thus takes place continuously with an increasing exhaust gas flow and / or with an increasing exhaust gas temperature, while the abrupt adjustment takes place in discrete partial steps, in particular in a single step (eg by means of a snap mechanism) between the two positions. Due to the continuous adjustment, a more precise adaptation of the mixer to the instantaneous exhaust gas flow and / or to the instantaneous exhaust gas temperature is achieved.

As a result of the adjustment according to the invention of the at least one exhaust gas guide element, a better uniform distribution of the agent in the exhaust gas flow can be ensured even at relatively low exhaust gas flows, which are critical for adequate mixing. In this case, the at least one exhaust gas guide element of the mixer is in the mixing position, which can be regarded as a first end position. Although in the mixing position the mixer ensures an improved uniform distribution, at the same time this results in a relatively high flow resistance. In this application, the flow resistance of the mixer in the mixing position is referred to as a mixing resistor. The mixer thus has the mixing position at an exhaust gas flow less than a predetermined exhaust gas flow and / or at an exhaust gas temperature less than a predetermined exhaust gas temperature.

With increasing exhaust gas flows, a sufficient uniform distribution is less problematical, so that the at least one exhaust gas guide is adjusted except for the passage position, which can be regarded as a second end position. As a result, the flow resistance drops to a value which in this application is referred to as an on-resistance. The at least one exhaust gas guide thus has the passage position at an exhaust gas flow greater than a predetermined exhaust gas flow and / or at an exhaust gas temperature greater than a predetermined exhaust gas temperature.

In the present case, a mixer is understood to mean a device which causes turbulence or vortex formation (turbulence increase) of an exhaust gas stream, in particular originating from an internal combustion engine, through one or more flow deflections. An agent preferably fed upstream of the mixer is better distributed in the exhaust gas flow by the increased turbulence and thereby assisted in a liquid supply during evaporation.

Of particular advantage is the invention, when the supplied agent is a reducing agent, for. B. is an aqueous urea solution for selective catalytic reduction (SCR, selective catalytic reduction). As a result of the improved mixing, consumption of urea solution and otherwise possibly occurring ammonia slip can be reduced.

The at least one exhaust gas guide can also be referred to as a blade or else as a wing, based on turbines.

It is preferably provided that the mixer comprises a particular circumferential main body, from which protrudes the at least one exhaust gas guide. The main body is preferably a circumferential basic body, that is to say a basic body with a circumferential (or at least for the most part circulating) form, z. B. with a circular cross-section (a ring) or polygonal cross-section. As a result, the mixer can be easily inserted into a corresponding pipe of an exhaust system. The mixer preferably comprises a plurality of exhaust gas guide elements according to the invention. Due to the increased number of exhaust gas elements, a better mixing of the agent with the exhaust gas flow is effected. In particular, the at least one exhaust gas guide is inwardly from. Thus, the at least one exhaust gas guide, in particular in the mixing position, extend substantially radially inwards and, in particular, end approximately in the center.

Preferably, a portion of the at least one Abgasleitelements between the mixing position and the passage position on an offset of at least 1%, in particular at least 5%, preferably at least 10% of a largest clear width of a passage opening of the body. The passage opening is an opening of the main body through which the exhaust gas flow flows during operation. With a largest clear width (that is to say, for example, a diameter of the main body) of, for example, 90 mm, the offset of the part (ie of the partial area) between the two positions is thus at least 0.9 mm, in particular at least 4.5 mm, preferably at least 9 mm.

Preferably, the part is an inner end of the at least one exhaust gas guide. Thus, a free cross-section increases in the middle of the mixer and the exhaust gas back pressure decreases. This is especially true when the offset is aligned in a main flow direction of the exhaust stream.

According to a preferred embodiment of the invention, it is provided that the mixer is designed such that the adjustment from the mixing position to the passage position by means of a caused by an exhaust gas backpressure of the exhaust gas flow elastic deformation of the mixer. Thus, the exhaust back pressure is used directly to adjust the mixer, whereby a component and cost savings is achieved. It is preferably provided that the elastic deformation of the mixer comprises an elastic deformation of the at least one exhaust gas guide element and / or a connection of the at least one exhaust gas guide element. Thus, the adjustment can be effected by an elastic deformation of the exhaust gas guide. Additionally or alternatively, the adjustment can be effected by an elastic deformation of a connection of the at least one exhaust gas guide element.

In the present case, a connection is understood as meaning a mechanical connection (eg a suspension) which is designed to connect the at least one exhaust gas guide element to the environment. In particular, the connection of the at least one exhaust gas guide element is a connection to the main body. Thus, the at least one exhaust gas guide is connected via the connection to the base body. By adjusting the connection thus the at least one exhaust gas guide is mitverstellt.

In order to enable an elastic deformation with an increasing exhaust gas flow, the at least one exhaust gas guide element and / or the at least one connection can be made of a metal sheet, in particular a steel sheet or an alternative, temperature-resistant material (eg a composite material, in particular carbon fiber-reinforced plastic). be formed with a thickness of at most 2 mm, in particular of at most 1 mm, preferably of at most 0.5 mm, further preferably of at most 0.3 mm, more preferably of at most 0.1 mm, or have this. Thus, the wall thickness of the at least one Abgasleitelements and / or the at least one connection is low enough to allow significant elastic deformation.

Furthermore, it can preferably be provided that a wall thickness of the at least one exhaust gas guide element is smaller at its side intended for fastening, that is to say in the region of the at least one connection or the main body than in the remaining exhaust gas guide element. This can positively influence a vibration behavior, in particular a stronger flutter at full load can be effected, which benefits the mixing.

If an internal combustion engine provides the exhaust gas flow, and if the increasing exhaust gas flow is the result of an increased load, the exhaust gas flow also increases the exhaust gas temperature. According to the invention, the increasing exhaust gas temperature (additionally or alternatively) can cause the adjustment of the exhaust gas guide.

It is preferably provided that the mixer has at least one bimetallic element which is connected to the at least one exhaust gas guide element and / or to a connection of the at least one exhaust gas guide element. Bimetallic elements (often referred to as bimetal strips) are well known in the art. They typically have two juxtaposed metals with different thermal expansion coefficients. When the temperature of the bimetal element changes, the thermal expansions of the two metals thus differ, as a result of which the bimetal element reversibly deforms. Deformation of the bimetallic element thus causes a deformation or movement of these mixer parts due to the connection to the exhaust gas guide element and / or to the connection. Thus, an adjustment of the mixer is effected by the material properties.

It is preferably provided that the at least one exhaust gas guide element and / or a connection of the at least one exhaust gas guide element is designed as a bimetallic element. Thus, the at least one adjustable exhaust gas guide or the connection itself is the bimetal element, whereby a simple and inexpensive construction is given.

The adjustment of the mixer can also by means of a servomotor, for. B. done electrically. However, for cost reasons and for increased reliability, the above-mentioned adjustment mechanisms are preferred.

Furthermore, an exhaust system (an exhaust gas purification system) for a motor vehicle with a mixer according to the invention (with features or feature combinations according to this representation) is provided. The exhaust system already has a good mixing of the exhaust gas flow with the means supplied to it at relatively low exhaust gas flows. At relatively high exhaust gas flows, the exhaust system is characterized by a reduced exhaust back pressure.

It is preferably provided that the means is a reducing agent and the exhaust system comprises, in particular upstream of the mixer, a preferred metering module for metering the agent into the exhaust stream. Thus, an exhaust system is provided, which is characterized by a reduced exhaust gas back pressure improved mixing of the reducing agent with the exhaust stream.

Furthermore, a motor vehicle with the exhaust system according to the invention is provided. The motor vehicle is characterized in particular by a reduced fuel consumption and thus by a reduced CO ₂ emissions.

An analogous (similar) constructed mixer can in principle be used anywhere where different media are to be mixed by an adjustable mixer, z. B. in the chemical or food industry.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a mixer in a perspective view,

2 a part of an exhaust system in a perspective view,

3 the part of the exhaust system in a side view,

4 the part of the exhaust system in a view opposite to the main flow direction of an exhaust gas flow,

5 a representation of the uniform distribution index of the mixer, and

6 a representation of the exhaust back pressure of the mixer.

1 shows a mixer 10 according to a preferred embodiment of the invention in a perspective view. The mixer 10 can be a rotating body 12 and a plurality of exhaust gas guide elements 14 include. The main body 12 It can be designed in various forms (eg round, oval, quadrangular, in particular rectangular) and wall thicknesses. The exhaust gas guide elements 14 can be connected as shown 16 with the main body 12 be connected. In addition, the exhaust gas guide elements 14 starting from the main body 12 radially inward from the main body 12 protrude. The exhaust gas guide elements 14 can be realized as a metal strip as shown and around a radial axis of the body 12 be inclined.

The mixer is designed such that it has a mixing position S _m with a mixing resistance at a relatively low exhaust gas flow AG (an exhaust gas mass flow m and / or an exhaust gas volumetric flow) and / or at a relatively low exhaust gas temperature. At a relatively high exhaust gas flow AG and / or at a relatively high exhaust gas temperature, the mixer has 10 However, a passage position S _d with an on resistance. An adjustment of the mixer 10 from the mixing position S _m to the passage position S _d takes place either continuously or suddenly with an increasing exhaust gas flow AG and / or with an increasing exhaust gas temperature. The mixing position S _m and the passage position S _d are in the 5 and 6 seen.

For adjustment, the mixer 10 be formed such that the adjustment of the mixing position S _m to the passage position S _d by means of a caused by an exhaust gas back pressure p of the exhaust stream AG elastic deformation of the mixer 10 he follows. The elastic deformation of the mixer 10 may be an elastic deformation of the at least one exhaust gas guide 14 and / or an elastic deformation of the respective connection 16 be.

For adjustment, the mixer 10 also bimetallic elements 18 having, which with the exhaust gas guide elements 14 are connected. Furthermore, the connections 16 bimetallic 18 exhibit. For clarity, the bimetallic elements 18 only in 1 located. In addition, the exhaust gas guide elements 14 and / or the connections 16 as bimetal elements 18 be formed, so have a bimetallic structure.

In the 2 to 6 is part of an exhaust system 20 for a motor vehicle, with the off 1 known mixer 10 seen. The exhaust system 20 can be upstream of the mixer 10 a dosing module 22 for metering a medium M into the exhaust stream AG. The dosing module 22 can by means of a junction 24 in an exhaust pipe 26 the exhaust system 20 fluidically with the mixer 10 be connected (cf. 2 ).

The following is with reference to the 5 and 6 the operation of the mixer 10 and the exhaust system 20 be clarified. This is in 5 a dimensionless uniform distribution index GV of a static (non-adjustable) mixer according to the prior art (curve 100 ) and a mixer 10 according to a preferred embodiment of the invention (curve 200 ) is plotted above the exhaust gas mass flow m (at high point) in kg / h (kilograms per hour). A DC distribution index of 1 denotes complete mixing, while a DC distribution index of 0 denotes a non-mixed state. In 6 is an exhaust back pressure p in mbar (millibars) of a static (non-adjustable) mixer according to the prior art (curve 110 ) and a mixer 10 according to a preferred embodiment of the invention (curve 220 ) is plotted against the exhaust gas mass flow m in kg / h (kilograms per hour). In the figures, the exhaust gas mass flow m is correctly designated as an m with a superscript point above the m, for reasons of printability the point above the m in the description is omitted. Furthermore, the diagrams of the 5 and 6 are divided into regions of the exhaust gas mass flow m and thereby comprise a lower part load range uTL, an upper part load range oTL and a full load range VL. The arrows 30 point in the direction of better, ie more preferred values.

The in the 5 and 6 numerical values and curves are only examples of illustration, but of importance are the qualitative differences of the curves 100 and 110 to the curves 200 and 220 , The exhaust gas temperature is not explicitly shown in the figures. However, it correlates with the exhaust gas mass flow m, which is why it is shown in the diagrams of the 5 and 6 increases with increasing exhaust gas mass flows m (ie from left to right). As exemplary numerical values can be found in 5 at a mass flow of 150 kg / h, an exhaust gas temperature of 200 ° C and at a mass flow of 950 kg / h, an exhaust gas temperature of 900 ° C are assumed. Furthermore, in 6 at a mass flow of 100 kg / h, an exhaust gas temperature of 150 ° C and at a mass flow of 900 kg / h, an exhaust gas temperature of 900 ° C are assumed.

An internal combustion engine, not shown, produced in their operation, for. B. in a motor vehicle, the exhaust stream AG. As raw emissions, this contains pollutants, including nitrogen oxides (NO _x ). So that they do not get into the environment, is by the dosing 22 a means M, which in this case is a reducing agent, upstream of the mixer 10 in the exhaust system 20 injected. The agent M may, for. Example, be an aqueous urea solution or a gaseous ammonia mixture, which by means of the mixer 10 should be mixed as evenly as possible with the exhaust stream AG to develop its optimal effect.

At a relatively low exhaust gas flow AG, however, the mixing can be problematic. For this reason, static mixers according to the prior art have hitherto been designed such that they ensure, even in a lower partial load range uTL, a uniform distribution index GV of the mean M in the exhaust gas flow AG considered sufficient (cf. 100 ). Increasing the uniform distribution index GV in the lower part load range uTL, however, would further improve NO _x reduction.

In 6 is another disadvantage of the previously known, static mixer can be seen. Thus, in a prior art mixer, exhaust back pressure p increases approximately exponentially (or according to a similar function) along the line 110 , The increased exhaust back pressure p is compensated by an increased fuel consumption compared to an operation without a static mixer with a constant mechanical output of the internal combustion engine.

According to the invention, however, an adjustment of the mixer takes place as a function of the exhaust gas flow AG and / or the exhaust gas temperature 10 instead of. The adjustment takes place from a mixing position S _m with an increasing exhaust gas flow AG and / or with an increasing exhaust gas temperature towards a passage position S _d . A particularly simple and at the same time effective adjustment is achieved when the exhaust gas guide 14 and / or the connections 16 are formed from a relatively thin sheet metal. As a metal sheet is z. B. a Suitable steel sheet, which has a thickness of, for example, at most 0.5 mm. Thus, the exhaust back pressure p causes an elastic (ie reversible) deformation of the exhaust gas guide elements 14 and / or the connections 16 , The exhaust gas guide elements 14 are thus pressed in the flow direction of the exhaust stream AG, resulting in a free cross section in the middle of the body 12 extended.

A comparable effect can also be achieved if the exhaust gas guide elements 14 and / or the connections 16 with bimetal elements 18 connected, or are formed as such. The mode of operation of such a configuration is beneficial in that the exhaust-gas temperature T increases as the load increases, ie as the exhaust-gas flow AG increases. The increasing exhaust gas temperature thus causes heating of the bimetallic elements 18 , which in turn cause an adjustment from the mixing position S _m to the passage position S _d .

The adjustment can be an offset 310 of parts of the exhaust gas guide elements 14 between the mixing position S _m and the passage position S _d of at least 5% of a largest clear width 300 a passage opening of the main body 12 (in this case, the inner diameter of the main body 12 ) cause. In the example, the part of the at least one exhaust gas guide element 14 an inner end 28 of the at least one exhaust gas guide element 14 , The offset 310 is aligned in a main flow direction (see arrow of the exhaust stream AG) of the exhaust stream AG. As an example, an offset 310 the inner ends 28 of 10 mm in the main flow direction at a clear width 300 of the basic body 12 of 90 mm.

As in 5 can be seen, thanks to the trained according to a preferred embodiment of the invention mixer 10 the uniform distribution index GV in the critical lower part load range uTL can be improved (compare curve 200 ). Owing to the adjustment towards smaller flow resistances, in the upper part load range oTL and in the full load range VL the uniform distribution index GV also increases compared with the curve known from the prior art 100 from. However, this is not relevant in practice since a DC distribution index of 0.9 or higher can be considered sufficient.

In 6 is another advantage of the designed according to a preferred embodiment of the invention mixer 10 seen. So is according to curve 220 of the mixer 10 the exhaust back pressure p compared to a conventional mixer with the curve 110 lowered to about half. An increase in the exhaust back pressure p, which is to be expected due to the better mixing in the lower part-load range uTL, lies within the line thickness.

Thus, in a cost effective manner, a mixer 10 and a comprehensive exhaust system 20 provided, which allow at the same time a reduced fuel and thus a fuel and thus CO ₂ savings. In particular, as shown in the figures, there is no complex adjustment mechanism for geometry change. The adjustment responds directly to the exhaust gas flow AG (in particular to the exhaust gas mass flow m), the exhaust gas temperature and / or thus to the resulting from these two variables exhaust gas energy, whereby the adjustment is more accurate and reliable, for example by means of a servomotor.

LIST OF REFERENCE NUMBERS

10

mixer

12

body

14

Exhaust component

16

connection

18

bimetallic

20

exhaust system

22

dosing

24

junction

26

exhaust pipe

28

Part of the exhaust guide / inner end

30

Arrow towards better values

100

Curve of the uniform distribution index of a mixer according to the prior art

200

Curve of the uniform distribution index of a mixer according to a preferred embodiment of the invention

110

Curve of the exhaust back pressure of a mixer according to the prior art

220

Curve of the exhaust back pressure of a mixer according to a preferred embodiment of the invention

300

largest clear width of the main body

310

offset

AG

exhaust gas flow

m

 Exhaust gas mass flow

M

 the exhaust gas mass flow supplied means

S _m

mix position

S _d

Passage position

GV

Equal distribution index

p

 Exhaust backpressure

UTL

lower part load range

OTL

upper part load range

VL

Full load range

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011112988 A1 [0004]
• DE 102011077645 A1 [0005]
• DE 202012011764 U1 [0005]
• DE 102012205680 A1 [0007]
• DE 102009420 A1 [0008]
• US 2011/0258983 A1 [0009]

Claims (10)

Mixer ( 10 ) for an exhaust system ( 20 ) for mixing an exhaust gas flow (AG) supplied means (M) with the exhaust gas stream (AG), wherein the mixer ( 10 ) at least one exhaust gas guide element ( 14 ), characterized in that the mixer is designed such that the at least one exhaust gas guide element ( 14 ) with - an increasing exhaust gas flow (AG) from - a mixing position (S _m ) with a mixing resistance to - a passage position (S _d ) is adjustable with an on resistance, wherein the mixing resistance is greater than the on-resistance. Mixer ( 10 ) according to claim 1, characterized in that the mixer ( 10 ) is designed such that the adjustment from the mixing position (S _m ) to the passage position (S _d ) by means of a by an exhaust back pressure (p) of the exhaust gas flow (AG) caused elastic deformation of the mixer ( 10 ) he follows. Mixer ( 10 ) according to claim 2, characterized in that the elastic deformation of the mixer ( 10 ) an elastic deformation of the at least one exhaust gas guide element ( 14 ) and / or a connection ( 16 ) of the at least one exhaust gas guide element ( 14 ). Mixer ( 10 ) according to one of the preceding claims, characterized in that the at least one exhaust gas guide element ( 14 ) _is adjustable with an increasing exhaust gas temperature of the mixing position (S _m ) in the passage position (S _d ). Mixer ( 10 ) according to one of the preceding claims, characterized in that the mixer ( 10 ) at least one bimetallic element ( 18 ), which with the at least one exhaust gas guide ( 14 ) and / or with a connection ( 16 ) of the at least one exhaust gas guide element ( 14 ), and / or that the at least one exhaust gas guide element ( 14 ) and / or a connection ( 16 ) of the at least one exhaust gas guide element ( 14 ) is formed as a bimetallic element. Mixer ( 10 ) according to one of the preceding claims, characterized in that the mixer ( 10 ) a particular circulating basic body ( 12 ), from which the at least one exhaust gas guide element ( 14 ) protrudes. Mixer ( 10 ) according to claim 6, characterized in that a part ( 28 ) of the at least one exhaust gas guide element ( 14 ) between the mixing position (S _m ) and the passage position (S _d ) an offset ( 310 ) of at least 1%, in particular of at least 5%, preferably of at least 10% of a largest clearance ( 300 ) a passage opening of the base body ( 12 ) having. Mixer ( 10 ) according to claim 7, characterized in that the part ( 28 ) of the at least one exhaust gas guide element ( 14 ) an inner end ( 28 ) of the at least one exhaust gas guide element ( 14 ). Exhaust system ( 20 ) for a motor vehicle, with a mixer ( 10 ) according to any one of the preceding claims. Exhaust system ( 20 ) according to claim 9, characterized in that the means (M) is a reducing agent and the exhaust system ( 20 ) upstream of the mixer ( 10 ) a dosing module ( 22 ) for metering the agent (M) into the exhaust stream (AG).

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