DE112011101199T5 - Ring-shaped reducing agent mixer - Google Patents

Abstract

An engine exhaust aftertreatment system having a ring disposed in an exhaust conduit and the ring assists in the introduction and conversion of a reductant introduced through an injector.

Description

Technical area

The present disclosure relates to engine exhaust aftertreatment systems, and more particularly to exhaust aftertreatment systems that use reductant (also referred to as reductant or reductant) for NOx reduction technologies.

background

Selective catalytic reduction (SCR) systems may be used in exhaust treatment or in a power system after-treatment system to reduce nitrogen oxide (NOx or NO) emissions from engine exhaust. SCR systems use reducing agents, such as uric acid, that are introduced into the exhaust stream.

U.S. Patent 7,581,387 discloses a mixing system including mixing blades for mixing urea with the exhaust stream.

Summary

The present disclosure provides an engine exhaust aftertreatment system having an injector or injector configured to introduce a reductant into an exhaust conduit, and further, a ring is disposed in the exhaust stream.

Brief description of the drawings

1 Figure 3 is a schematic view of a power system including an engine and a post-treatment system with a mixer.

2 is a front view of the mixer.

3 is a front view of another embodiment of the mixer.

4 is a front view of another embodiment of the mixer.

5 is a front view of another embodiment of the mixer.

6 is a front view of another embodiment of the mixer.

7 is a schematic view of a two-legged aftertreatment system including the mixer.

Detailed description

A performance system 10 , see. 1 , has a motor 12 and an aftertreatment system 14 on to an exhaust flow 16 , produced by the engine 12 , to treat. The motor 12 may further include features not shown, such as control devices, fuel systems, air systems, cooling systems, peripheral devices, powertrain components, turbochargers, exhaust gas recirculation systems, etc.

The motor 12 may be any type of engine (internal combustion engine, gas, diesel, gaseous fuel, natural gas, propane, etc.) and may be of any size, with any number of cylinders or in any configuration ("V", "in-line", radial, etc.). The engine may be used to power any machine or other device, including trucks or vehicles to be used on-road, such as off-highway trucks or machines, earthmoving equipment, generators, space applications, locomotive applications, marine applications, pumps, stationary equipment, or other applications. which use a motor power.

The aftertreatment system 14 has an exhaust pipe 18 and further a selective catalytic reduction (SCR) system 20 , The SCR system 20 includes an SCR catalyst 22 , a mixed line 24 , a mixer 26 and a reductant supply system 28 ,

The SCR catalyst 22 has a catalyst material disposed on a substrate. The substrate may be made of cordierite, silicon carbide, other ceramics or metal. The substrate may have a plurality of passing channels and may form a honeycomb structure.

The reductant supply system 28 can be a reducing agent 30 have a reducing agent source 32 , a pump 34 , a valve 36 , a reducing agent line 38 and an injection device (injector) 40 , The reducing agent 30 is over the pump 34 from the reducing agent source 32 withdrawn and to the injector 40 delivered, controlled by the valve 36 , The flow of the reducing agent 30 may also be due to the operation of the pump 34 to be controlled.

The mixed line 24 is the section of the exhaust pipe 18 where the reducing agent 30 is introduced. The mixed line 24 has an inner wall 25 and an outer wall 27 on. The mixed line 24 is also characterized by an inner width 29 Are defined.

The reductant supply system 28 may also include a thermal management system for frozen reductant 30 Thaw to prevent reducing agent 30 freezes or to prevent reducing agent 30 is overheated. Components of the reducing agent supply system 28 may also be isolated to overheat the reducing agent 30 to prevent. The reductant supply system 28 may also include an air assist system to introduce compressed air to prevent the formation of small droplets in the reduction spray 44 to support. The air assist system may also be used to route the reductant lines 38 and other reductant supply system 28 -Components of reducing agent 30 to rinse if not in use.

The reducing agent 30 comes from a nozzle or an injector tip 42 of the injector 40 to form a reducing agent spray 44 or is otherwise in the exhaust stream 16 or the SCR catalyst 22 introduced. The position of the injector tip 42 may be such that the reducing agent spray 44 straight down to the centerline of the mixing pipe 24 and the mixer 26 is directed.

The aftertreatment system 14 Can also use a Diesel Oxidation Catalyst (DOC) 46 and a diesel particulate filter (DPF) 48 and a cleaning catalyst 50 exhibit. The DOC 46 and the DPF 48 may be in the same canister as shown, or they may be separate. The SCR catalyst 22 and the purification catalyst 50 may also be in the same canister as shown, located or separated.

The aftertreatment system 14 is configured to remove, collect, or convert unwanted components from the exhaust stream 16 , The DOC 46 oxidizes carbon monoxide (CO) and unburned hydrocarbons (HC) into carbon dioxide (CO2). The DPF 48 collects particulate matter or soot or soot (soot). The SCR catalyst 22 is configured to reduce an amount of NOx in the exhaust stream 16 in the presence of the reducing agent 30 ,

A heat source 52 can also be provided to remove the soot from the DPF 48 thermally remove the SCR catalyst 22 to manage, and the DOC 46 or the catalyst 50 to purify sulfur from the SCR catalyst 22 to remove or deposits of the reducing agent 30 to remove that have formed. The heat source 52 may include a burner, a hydrocarbon dosing system to provide an exothermic reaction on the DOC 46 , an electric heating element, a microwave device or another heat source. The heat source 52 can also be embodied by the operation of the engine 12 at conditions for generating an increased exhaust gas flow 16 in terms of temperatures. The heat source 52 may also embody a backpressure or backpressure valve or other restriction in the exhaust gas to cause the exhaust flow 16 reached elevated temperatures.

In the illustrated embodiment, the exhaust gas flow occurs 16 out of the engine 12 off, runs on the heat source 52 over or through them and runs through the DOC 46 , the DPF 48 and then passes through the SCR system 20 and then passes through the purifying catalyst 50 over the exhaust pipe 18 ,

Other exhaust treatment devices may also be upstream, downstream or within the SCR system 20 be arranged. In the illustrated embodiment, the SCR system is located 20 downstream from the DPF 48 and the DOC 46 lies upstream of the DPF 48 , The heat source 52 is upstream of the DOC 46 , The cleaning catalyst 50 is located downstream of the SCR system 20 , In other embodiments, these devices may be arranged in a variety of orders or may be combined with each other. In one embodiment, the SCR catalyst 22 with the DPF 48 combined with catalyst material deposited on the DPF 48 ,

Although other reducing agents 30 are possible, urea is the most common source of a reducing agent 30 , The urea reducing agent 30 decomposes or hydrolyzes in ammonia (NH3) and is then absorbed or otherwise in the SCR catalyst 22 saved. The mixed line 24 may be long to aid in the mixing or even the distribution of the reducing agent 30 in the exhaust stream 16 to give a residence time for the urea reducing agent 30 for conversion to NH3. The NH3 becomes in the SCR catalyst 22 consumed by a reduction of NOx in nitrogen gas (N2).

The cleaning catalyst 50 may be an ammonia oxidation catalyst (AMOR). The cleaning catalyst 50 is configured to contain NH3, that on the SCR catalyst 22 passes through or can trap, trap, store, oxidize, reduce, and / or convert. This cleaning catalyst 50 may also be configured to trap, store, oxidize, reduce, and / or convert other existing constituents.

The control and sensing systems may also be included to the engine 12 , the heat source 52 , the reductant supply system 28 and the other components in the power system 10 or to control its use case.

The mixer 26 includes an enclosing or orbiting member or ring 54 , The ring 54 is, as shown, even with a toroidal shape and with a rectangular cross section, like a disc. In other embodiments, the ring 54 have different cross sections, including the circular.

The ring 54 includes an end surface 55 , an inner surface 56 and an outer surface 57 , The ring 54 is through a thickness 58 in the direction of the flow of the exhaust stream 16 defined, further by an inner diameter 60 , an outer diameter 61 and a ring width 62 , The ring width 62 is the width of the ring 54 forming member and is half the difference between the inner diameter 60 and the outside diameter 61 , The inner diameter 60 of the ring 54 defines a central opening 64 ,

Because the ring 54 planar or planar, the surfaces of the ring can be constant across the thickness 58 be away and the same as face surface 55 , A transverse plane 65 passes through the mixer and cuts through the mixing line 24 , The transverse or transverse plane 65 includes a family of parallel planes. The transverse plane 65 can along the face surface 55 lie or can pass through another part of the mixer 26 extend. The transverse plane 65 can be perpendicular to the flow of exhaust gas 16 run as shown. The transverse plane 65 can also be perpendicular to the inner wall 25 the mixed line 24 run. In other embodiments, the transverse plane could 65 under a variety of angles to the flow of exhaust gas 16 and the inner wall 25 be arranged.

Although the ring 54 described and shown as a toroidal and circular and further having a "diameter", the ring could 54 rectangular, octagonal, triangular, or any other shape. The shape of the ring 54 can be the inner circumference of the mixing pipe 24 follow and be adapted accordingly at least to a part of the shape of the mixing pipe 24 where he is housed. The ring 54 can also have a different shape than the mixed line 24 and may be sized to enter the mixing duct 24 fits (for example, the ring 54 have a square shape, which in a circular mixing line 24 fits). The ring width 52 can be constant but does not need to be constant. The outer shape of the ring 54 may also be different from the inner mold (for example, the outer shape may be circular while the inner mold and the central opening 64 are rectangular).

The mixer 26 can also spacers 66 have the ring 54 from the inner wall 25 the mixed line 24 separate. The spacers 66 can also serve the ring 54 to install.

The separation between the outer surface 57 of the ring 54 and the inner wall 25 defines a gap 68 , The gap 68 may be annular or may have a different shape. The gap 68 can have a gap width 70 exhibit. The gap width 70 may, but does not have to be constant around the ring 54 run around. In some embodiments, there is no gap 68 at some parts of the ring 54 ,

The following are some dimensional aspects of the mixer 26 specified. These dimensional aspects can be dependent on a large number of variables that can vary between the different performance systems 10 , For example, the right mixers 26 Dimensions depend on the exhaust gas flow 16 Rates, the mixed line 24 Size, the cycle of the engine 12 and the backpressure requirements of the engine 12 , the drop size of the reduction spray 44 and the speed of the reduction spray 44 , To account for these variables, the dimensions defined below are expressed in terms of ratios and ranges.

The gap width 70 can be approximately 1/8 inch. In other embodiments, the gap width 70 between 1/16 and 1/4 of an inch. In other embodiments, the gap width 70 between 1/16 and ½ inches.

The size of the gap width 70 can also be a function of inner width 29 be. In one embodiment, the area of the gap is 68 along the transverse plane 65 approximately 1.3% of the area of the mixing pipe along the transverse plane 65 , In other embodiments, the area of the gap is 68 along the transverse plane 65 between 0.5% and 5%, between 0.1% and 10%, or between 0.7% and 2% of the area of the mixing duct along the transverse plane 65 ,

The ring width 62 can be approximately 2 inches. In other embodiments, the ring width 62 between 1 and 3 inches. In further embodiments, the ring width 62 between 0.5 and 5 inches.

The size of the ring width 62 can also be a function of inner width 29 be. In one embodiment, the ring width is 62 approximately 10% of the inside width 29 , In other embodiments, the ring width 62 between 5% and 15% or between 2% and 25% of the inside width 29 lie.

The gap width 70 and ring width 62 can also be chosen such that a given size of the central opening 64 is achieved, as a function of the inner width 29 , In one embodiment, the area of the central opening 64 along the transverse plane 65 approximately 62% of the area of the mixing line 24 along the transverse plane 65 , In other embodiments, the area of the central opening 64 along the transverse plane 65 between 50% and 70%, between 40% and 80%, between 30% and 80% or between 20% and 90%, of the area of the mixed line 24 along the transverse plane 65 ,

The ring 54 can be constructed of sheet metal and therefore a relatively small thickness 58 although he may have a variety of sizes. In one embodiment, the thickness may be less than 1 inch. In another embodiment, the thickness may be less than 1/4 inch. The fat 58 can also be smaller than the Ringbereite 62 ,

The 2 - 6 show various embodiments of the mixer 26 with different characteristics as described below. The mixer 26 may have any combination of features described herein. The 2 shows the ring 54 as a solid or solid surface. The 2 also shows that the spacers 66 as spot welds 72 can be formed, which the ring 54 from the inner wall 25 disconnect and attach or connect to this.

3 shows that the ring 54 one or more openings 73 through the face surface 55 can have. The openings 73 can be at different places on the ring 54 can be arranged and can form a variety of patterns. 3 also shows that the spacers 66 through approaches 74 can be formed, extending from the outer surface 57 of the ring 54 extend. A distant end of the approaches 74 can then contact the mixing line 24 be welded, be inserted into the mixing line 24 or otherwise with the mixing line 24 be connected to the ring 54 with the inner wall 25 to join, attach or disconnect, so the gap 68 to build.

4 shows the mixer 26 with center structures 76 that are in the middle opening 64 extend. These middle structures 76 can be different from the inside surface 56 of the ring 54 extend from or from another body or from another body. The middle structures 76 can use large links, small metal wires or a mesh of wires.

5 shows that baffles 78 the mixer 26 can be added. The baffles 78 include baffles 80 and a deflecting means 82 , The deflection means 82 are at an angle of more than 90 ° to the exhaust flow 16 arranged to thereby the exhaust gas flow 16 through the baffles 80 to guide at an angle. The baffles 78 can by bending a section 84 or by punching a shell element 86 be formed. 6 shows that deflection means (deflectors) 82 also from the spacer elements 66 or the central structures 76 can be formed.

1 shows the arrangement of the mixer 26 in the mixing pipe 24 , The mixer 26 is inside the inner wall 25 arranged, with a mixer distance 88 from the injection tip or nozzle 42 , The mixer distance 88 may be selected such that the size of the reduction spray 44 relatively expanded to the size of the central opening 64 then, if the spray 44 The ring 54 reached.

7 shows that the mixer 26 in a two-step aftertreatment system 90 can be used. The two-legged aftertreatment system 90 has first and second SCR legs 91 and 92 on, and indeed for receiving the exhaust stream 16 and the reducing agent 30 from the reductant supply system 28 ,

The exhaust gas flow 16 from the mixing pipe 24 is split or subdivided into a subdivision section 93 the exhaust pipe 18 , The subdivision section 93 can at a pitch 94 downstream of the mixer 26 be arranged. The part distance 94 can be longer than the mixer distance 88 , In one embodiment, the pitch is a function of the inside width 29 , The part distance 94 can be approximately 1.2 times the inside width 29 be. In other embodiments, the pitch or pitch may be 94 more than 1.2 times, between 1 and 2 times or between 1 and 3 times the inner width 29 ,

The two-legged aftertreatment system 90 can also have first and second entry legs 95 and 96 have, for the delivery of the exhaust stream 16 to the reductant supply system 28 , The exhaust gas flow 16 from the first and second entrance legs 95 and 96 becomes split or subdivided in a combination or combination section 97 the exhaust pipe 18 ,

The first and second entrance legs 95 and 96 is shown as the DPF 48 and the DOC 46 having, but need have neither of them or may have other components. In one embodiment, first and second entry legs 95 . 96 without DPF 48 intended. The first and second entrance leg 95 . 96 is also arranged as shown, at right angles with respect to the first and second SCR legs 91 . 92 , but also other angles can be provided or a linear arrangement. The two-legged aftertreatment system 90 may also be contained in a box structure with inner walls that divide the flow of exhaust gas.

The components of the mixer 26 can be made of steel or any other of a variety of materials. The mixer 26 may also be coated with materials used in the conversion or hydrolysis of the reducing agent 30 assist in NH3.

Industrial applicability

The mixer 26 Helps or assists in the even distribution or mixing of the reducing agent 30 in the exhaust stream 16 , promotes the conversion of the reducing agent 30 in NH3 and prevents the formation of deposits. The mixer 26 should be inexpensive, small and generating a minimum back pressure. However, these features often conflict with each other. For example, large and complex structures can be effective for even distribution of the reducing agent 30 in the exhaust stream 16 and to promote the conversion of the reducing agent 30 in NH3, but these are not cheap, take up too much space and often create a large back pressure.

Uniformly distributed reducing agent 30 in the exhaust stream 16 improves the efficiency of the SCR system 20 by uniform introduction of NH3 to all channels of the SCR catalyst, and therefore, a larger conversion amount or amount may occur. The uniform distribution of the reducing agent 30 in the exhaust stream 16 can also reduce the amount of reducing agent 30 which is needed to achieve greater efficiency. The uniform distribution of the reducing agent 30 in the exhaust stream 16 can also prevent too much NH3 from occurring in some areas of the SCR catalyst, which can cause NH3 slip.

Deposits can form when the reducing agent 30 is not rapidly decomposed into NH3 and thick layers of reducing agent 30 collect themselves. These layers can build up when more reducing agents 30 is sprayed or collected, which may have a cooling effect that prevents decomposition into NH3. As a result, the reducing agent sublimes 30 in crystals or otherwise transforms into solid or solid compositions to form a deposit. The deposition composition may consist of biuret (NH 2 CONHCONH 2) or cyanuric acid ((NHCO) 3) or another composition depending on the temperatures and other conditions. These deposits can form in areas or even surfaces where the reducing agent spray 44 hits, settles or stagnates.

These deposits can negatively impact the operation of the power system 10 to have. The deposits can change the flow of the exhaust stream 16 prevent what causes higher backpressure and a reduction in engine efficiency and efficiency 12 and aftertreatment system 14 , The deposits may be the flow and the mixture of the reducing agent 30 in the exhaust stream 16 which reduces decomposition into NH3 and reduces NOx reduction efficiency. The formation of deposits also consumes reducing agents 30 , makes control of injection more difficult and potentially reduces NOx reduction efficiency. The deposits can also be the components of the SCR system 20 corrode and degrade.

Limiting back pressure or back pressure increase is also important. High back pressure can increase engine efficiency 12 damage. A high backpressure can also cause deposits to form and the exhaust gas to leak.

The ring 54 can provide a limited back pressure while still allowing a high degree of mixing of the reductant 30 in the exhaust stream 16 is reached. The big size of the center opening 64 Limits limitations and also creates a tumbling or tumbling of the exhaust stream 16 , which is effective in mixing the reducing agent 30 in the exhaust stream 16 is. Many other mixer designs achieve mixing by vortexing or creating high levels of turbulence. These mixers have structures that are complicated and large and that tend to be expensive and create a back pressure. In contrast, that is through the ring 54 generated tumbling or tumbling recognized as effective in mixing, and it is also cheap to produce and does not produce large backpressure like other mixers. The flat shape of the ring 54 facilitates its manufacture by cutting simple Sheet metal, which is cheap. In addition, complicated mixers require more complicated cuts, bends and welds, which is expensive.

The gap 68 can be used to allow the exhaust flow 16 flows past, while still the above-described tumbling or tumbling effect is achieved. This secondary flow prevents the stagnant accumulation of reducing agent 30 that would otherwise form deposits. The secondary or secondary flow also helps to reduce the back pressure or back pressure. If the gap 68 would be too large, so the tumbling or tumbling effect described above would be prevented because a significant flow just around the ring 54 around goes through the middle opening 64 to stumble. If the gap 68 Too small, then the secondary flow may not be sufficient to prevent deposits and to produce significant reductions in the back pressure.

The gap 68 may be along the circumference along the outer surface 57 of the ring 54 be located, since this is the place where the reducing agent would collect. In some embodiments, the gap 68 only at the bottom of the ring 24 be provided where the reducing agent 30 otherwise accumulate.

The mixer distance 88 of the mixer 26 from the injector or injector tip 42 can influence the formation of the deposits and the mixing effectiveness. When the mixer distance 88 is too short, then the reducing agent spray 44 concentrated in a small volume because the spray did not expand. Accordingly, the reducing agent spray 44 only through the true center of the central opening 64 run. Because the spray 44 concentrated in a small volume and passing only through the center opening means, the tumbling or tumbling effect described above may not be effective and the mixture of the reducing agent 30 in the exhaust stream 16 can not be done to the extent desired. If the mixing distance 88 is too long, then the reducing agent spray 44 may have expanded to a larger volume and may be on the ring 54 or the inner wall 25 impinge before conversion to NH3. This impact can cause deposits as described above.

The used openings 73 can help to reduce back pressure and can also reduce weight. The openings 73 can also be used to generate by-pass and run-off areas where reducing agents 30 accumulates, preventing deposits.

The middle structures 76 can help, the reduction spray 44 break down and atomize, supporting the conversion to NH3. The middle structures 76 can cause turbulence in the exhaust gas streams 16 which may be helpful in converting to NH3. The middle structures 76 do not form deposits because they occur in a region that has high flow rates and high temperatures. The middle structures 76 can also increase the rigidity and the structural strength of the mixer 26 ,

The baffles 78 may be used to induce vortex formation, in addition to the tumbling or tumbling effect, in the exhaust stream 16 for an extra mix. In some embodiments, the baffles produce 78 counter-rotating vortices. Like the openings 73 can also use the baffles 78 help to reduce the back pressure and can also reduce the weight. The baffles 78 can also be used to create the by-pass and create areas where reducing agents 30 accumulates, whereby deposits are prevented.

The mixer 26 may also be suitable for the dual leg aftertreatment system 90 , Dual leg aftertreatment systems 90 are often used with large engine systems. The dual-leg aftertreatment systems 90 allow the use of smaller aftertreatment substrates. Since these substrates are often complex ceramic bodies, they can be produced economically in smaller sizes. The smaller sizes can also improve packaging options and improve fluid distribution across the face of the substrates.

Because the mixer 26 Introduces limited back pressure, it can uniformly the flows of the exhaust stream 16 from the first and second entry legs 95 and 96 combine. The one by the mixer 26 The tumbling or tumbling effect generated may also help to control the flows in the first and second exhaust legs 91 and 92 the exhaust stream 16 divide. Mixers that are highly dependent on vortex formation and turbulence can create a biased flow to either the first or second exit legs 91 and 92 ,

The pitch 94 can the uniform subdivision of the flow of exhaust gas flow 16 in the first and second exit legs 91 and 92 influence and prevent the formation of deposits.

The subdivision distance 94 can the uniform subdivision of the flow of exhaust gas flow 16 in the first and second exit legs 91 and 92 prevent. If the subdivision distance 94 is too short, then the reducing agent 30 not time have to convert to NH3 and the tumbling effect of the mixer 26 can be big. A bad conversion to NH3 before the subdivision section 93 may cause the deposits when the reducing agent impinges on the walls. The large tumbling can create a bias to the first and second exit legs 91 and 92 , If the pitch is too long, packaging challenges of the dual leg aftertreatment system may arise 90 cause and can cause heat is lost, which is needed to the SCR catalyst 22 to activate and prevent the formation of deposits.

The mixer 26 has been described above in supporting the introduction of a reducing agent into an exhaust stream and it has also been envisaged that the mixer 26 could be used to carry out the introduction of any variety of substances into any variety of flows. Although the disclosed embodiments as described herein may be embodied without departing from the scope of the claims, those skilled in the art will recognize that various modifications and variations can be made. Other embodiments will be apparent to those skilled in the art upon consideration of the specification and practice of the disclosure. It is intended that the specification and examples be regarded as exemplary and that the true scope of the invention be defined by the claims and their equivalents.

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

• US 7581387 [0003]

Claims (10)

An engine exhaust aftertreatment system ( 14 ) comprising: an injector ( 40 ) configured to introduce a reducing agent ( 30 ) in an exhaust pipe ( 24 ) of an engine ( 12 ) and a ring ( 54 ) arranged in the exhaust pipe ( 24 ) Engine exhaust aftertreatment system ( 14 ) according to claim 1, wherein the ring ( 54 ) is planar. Engine exhaust aftertreatment system ( 14 ) according to claims 1-2, wherein the ring ( 54 ) is toroidal and has a rectangular cross-section. Engine exhaust aftertreatment system ( 14 ) according to any one of claims 1-3, wherein the ring ( 54 ) a central opening ( 64 ) defined with an area along a transverse plane ( 65 ) of the exhaust pipe ( 24 ) between 50% and 70% of the area of the transverse plane ( 65 ) within the exhaust pipe ( 24 ). Engine exhaust aftertreatment system ( 14 ) according to any one of claims 1-4, wherein the ring ( 54 ) a gap ( 68 ) defined around the circumference of the ring ( 54 ) formed by spacers ( 66 ), wherein the spacer elements ( 66 ) between an outer surface ( 57 ) of the ring and an inner wall ( 25 ) of the exhaust pipe 24 extend. Engine exhaust aftertreatment system ( 14 ) according to claim 5, wherein the gap ( 68 ) a width ( 70 ), which is between 1/16 and ½ inches. Engine exhaust aftertreatment system ( 14 ) according to claim 5, wherein the gap ( 68 ) has an area along the transverse plane ( 65 ) of the exhaust pipe ( 24 ) between 0.5% and 5% of the area of the transverse plane ( 65 ) within the exhaust pipe ( 24 ) lies. Engine exhaust aftertreatment system ( 14 ) according to any one of claims 1-7, wherein the ring ( 54 ) with a distance ( 88 ) opposite the injector ( 40 ) is arranged so that a spray or jet ( 44 ) of the reducing agent ( 30 ) is not larger than a central opening ( 64 ), if the spray or jet ( 44 ) The ring ( 54 ) reached. Engine exhaust aftertreatment system ( 14 ) according to any one of claims 1-8, wherein the exhaust pipe ( 24 ) in two or more legs ( 91 . 92 ) is divided downstream of the ring ( 54 ) with a distance ( 94 ) from the ring ( 54 ), which is greater than a width ( 29 ) of the exhaust pipe ( 24 ). Engine exhaust aftertreatment system ( 14 ) according to any one of claims 1-9, wherein the ring ( 54 ) a plurality of openings ( 73 ), deflectors ( 82 ) and central structures ( 76 ) extending from a central opening ( 64 ) in the ring ( 54 )

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