Exhaust gas aftertreatment system

Abstract

An exhaust gas aftertreatment system comprising a first branch comprising an oxidation catalyst and a particulate filter, a second branch comprising a selective catalytic reduction device, a mixing chamber connected between the first branch and the second branch, a reductant injector arranged facing the mixing chamber on a side close to the first branch for injecting reductant into the mixing chamber, and a mixer fixed in the mixing chamber, the mixer comprising a plate body having a plurality of openings for the exhaust gas flow mixed with reductant to flow through, wherein at least some of the openings are provided with fins extending obliquely from the plate body, the fins being configured to disturb the exhaust gas flow through the openings.

Description

TECHNICAL FIELD

[0001] The present application relates to an exhaust gas aftertreatment system for treating exhaust gas emitted by an engine, in particular a diesel engine. BACKGROUND

[0002] Engine exhaust gas contains harmful components. In order to reduce the amount of harmful components emitted in the exhaust gas, various aftertreatment techniques have been developed. A typical exhaust gas aftertreatment system for a diesel engine comprises a diesel oxidation catalyst (DOC), a selective catalytic reducer (SCR) and a diesel particulate filter (DPF). The DOC, the SCR and the DPF are arranged in series along the flow direction of the exhaust gas.

[0003] For small diesel vehicles, such an exhaust gas aftertreatment system can be constructed in the form of an exhaust gas aftertreatment box. In order to reduce the size of the exhaust gas aftertreatment box, the SCRoF technique has been proposed, in which the SCR is integrated in the DPF. For large diesel vehicles, the exhaust gas aftertreatment system is large in size and it is difficult to construct in the form of an exhaust gas aftertreatment box. For this reason, the U-shaped exhaust gas aftertreatment system has been proposed. Such an exhaust gas aftertreatment system is smaller in size than the exhaust gas aftertreatment box and it is more flexible in arrangement.

[0004] In the exhaust gas aftertreatment system, there is a mixing chamber between the DOC and the SCR, and urea solution is injected into the exhaust gas flowing through the mixing chamber. It is desirable that the urea is fully evaporated and uniformly mixed in the exhaust gas, so as to ensure that the exhaust gas is fully catalytically reduced in the SCR. SUMMARY

[0005] It is an object of the present application to provide an exhaust gas aftertreatment system for treating exhaust gas of an engine, which is capable of improving the uniformity of mixing of a reducing agent in the exhaust gas.

[0006] To this end, the present application provides, in one of its aspects, an exhaust gas aftertreatment system for treating exhaust gas of an engine, comprising:

[0007] a first branch comprising an oxidation catalyst and a particulate filter;

[0008] a second branch comprising a selective catalytic reducer;

[0009] a mixing chamber connected between the first branch and the second branch;

[0010] a reducing agent injector arranged facing the mixing chamber on the side of the first branch, for injecting a reducing agent into the mixing chamber; and

[0011] a mixer fixed in the mixing chamber, the mixer comprising a plate body having a plurality of openings for allowing the exhaust gas mixed with the reducing agent to flow through the openings;

[0012] At least some of the openings have fins extending obliquely from the plate body, the fins being configured to interfere with the flow of exhaust gas through the openings.

[0013] According to an optional embodiment, the mixing chamber comprises a first portion facing substantially the outlet of the first branch and a second portion facing substantially the inlet of the second branch; the mixer is arranged in the mixing chamber at a position corresponding to the portion of the first branch facing the second branch; or, the mixer is arranged at a position between the first portion and the second portion of the mixing chamber.

[0014] According to an optional embodiment, the fins comprise fins extending obliquely from the plate body toward the side of the reductant injector; and / or, the fins comprise fins extending obliquely from the plate body away from the side of the reductant injector.

[0015] According to an optional embodiment, the fins have the same oblique angle; or, some fins have different oblique angles from other fins.

[0016] According to an optional embodiment, the fins comprise two groups of fins arranged symmetrically with respect to each other on the lateral side portions of the plate body.

[0017] According to an optional embodiment, the plate body is curved substantially corresponding to the portion of the first branch facing the second branch, with the concave surface facing the side of the reductant injector.

[0018] According to an optional embodiment, the mixer further comprises a portion extending from the plate body for being secured to the inner side of the mixing chamber.

[0019] According to an optional embodiment, the exhaust gas aftertreatment system further comprises a flow guide plate installed in the mixing chamber facing substantially the outlet of the first branch, the flow guide plate comprising a plate body having a plurality of discrete through holes formed therein, one or more of the through holes having fins for guiding the flow.

[0020] According to an optional embodiment, at least one portion of the flow guide plate is inserted into a slit formed in the plate body of the mixer to facilitate the positioning between the flow guide plate and the mixer.

[0021] According to an optional embodiment, the exhaust gas aftertreatment system further comprises a mixing plate installed in the mixing chamber facing substantially the inlet of the second branch, the mixing plate having a plurality of evenly distributed openings formed therein.

[0022] According to an optional implementation, the mixer is a first mixer, and the exhaust gas aftertreatment system further comprises a second mixer fixed in the mixing chamber downstream of the first mixer relative to the direction of exhaust gas flow in the mixing chamber, the second mixer comprising a plate body having a plurality of openings formed therein.

[0023] According to an optional implementation, at least some of the openings of the second mixer are provided with fins configured to interfere with the flow of exhaust gas through the openings.

[0024] According to an optional implementation, the fins of the second mixer include fins that extend obliquely from the plate body of the second mixer toward the side of the second mixer facing the reductant injector; and / or the fins of the second mixer include fins that extend obliquely from the plate body of the second mixer away from the side of the second mixer facing the reductant injector.

[0025] According to an optional implementation, the fins of the second mixer have the same oblique angle; or, some fins have different oblique angles than other fins.

[0026] According to an optional implementation, the fins of the second mixer include two groups of fins disposed symmetrically with respect to each other on opposite sides of the plate body of the second mixer.

[0027] According to an optional implementation, the plate body of the second mixer has a curved shape corresponding to the portion of the second branch facing the first branch, with the convex side of the curved shape facing the side of the second mixer facing the reductant injector.

[0028] According to an optional implementation, each opening of the second mixer is aligned with a corresponding opening of the first mixer as viewed in the direction of exhaust gas flow in the mixing chamber; or, at least some of the openings of the second mixer are not fully aligned with any opening of the first mixer as viewed in the direction of exhaust gas flow in the mixing chamber.

[0029] According to an optional implementation, the first branch, the second branch and the mixing chamber are configured such that exhaust gas enters the mixing chamber from the first branch in a first direction, flows in the mixing chamber in a second direction different from the first direction, and then enters the second branch from the mixing chamber in a third direction different from the second direction.

[0030] According to the present application, a mixer is arranged in the mixing chamber for dividing the exhaust gas flow into multiple gas streams, so that the mixing of the reducing agent in the exhaust gas is more uniform, and thus a more sufficient catalytic reduction reaction occurs in the selective catalytic reduction device. In addition, the oxidation catalyst and the particulate trap occupy one branch of the exhaust gas aftertreatment system, while the selective catalytic reduction device itself occupies another branch of the exhaust gas aftertreatment system, so that the selective catalytic reduction device can be designed to have a larger size, so that the catalytic reduction reaction is more sufficient. The present application can more efficiently remove harmful components in the exhaust gas to meet higher exhaust emission standards. BRIEF DESCRIPTION OF DRAWINGS

[0031] The foregoing and other aspects of the present application will be more fully understood and appreciated by referring to the following detailed description in conjunction with the accompanying drawings, in which:

[0032] Figure 1 is a sectional view of an exhaust gas aftertreatment system according to an embodiment of the present application;

[0033] Figure 2 is a perspective view of the exhaust gas aftertreatment system in Figure 1 ;

[0034] Figure 3 , 4 are a perspective view and an elevation view of a deflector in the exhaust gas aftertreatment system, respectively;

[0035] Figure 5 , 6 are a perspective view and an elevation view of a mixing plate in the exhaust gas aftertreatment system, respectively;

[0036] Figure 7 , 8 are a perspective view and an elevation view of a mixer in the exhaust gas aftertreatment system, respectively;

[0037] Figure 9 is a sectional view of an exhaust gas aftertreatment system according to another embodiment of the present application;

[0038] Figure 10 is a perspective view of an additional mixer in the exhaust gas aftertreatment system in Figure 9 ; DETAILED DESCRIPTION

[0039] The present application generally relates to an exhaust gas aftertreatment system, which is typically suitable for treating exhaust gas of a diesel engine; however, the exhaust gas aftertreatment system can also be applicable to other types of engines (some components in the system can need to be modified accordingly).

[0040] Figure 1 , 2An exhaust gas aftertreatment system according to an embodiment of the present application is shown in Fig. 1. The exhaust gas aftertreatment system mainly comprises a first branch 1 and a second branch 2, which are connected by a mixing chamber 3. A reductant injector 4 is arranged facing the mixing chamber 3 close to the side of the first branch 1 for injecting a reductant (e.g. an aqueous urea solution) into the mixing chamber 3. The reductant is atomized in the mixing chamber 3 and mixed into the exhaust gas flow.

[0041] The first branch 1 and the second branch 2 can be arranged on the same side of the mixing chamber 3 and have substantially parallel central axes, as shown in Fig. 1. Such an exhaust gas aftertreatment system can be referred to as a U-shaped exhaust gas aftertreatment system. Of course, depending on the layout of the elements upstream and downstream of the exhaust gas aftertreatment system, the central axes of the first branch 1 and the second branch 2 can not be parallel to each other but can be arranged at an angle to each other. According to one possible configuration, the first branch 1 and the second branch 2 can extend on opposite sides of the mixing chamber 3 towards each other in opposite directions, wherein the central axes of the first branch 1 and the second branch 2 can be parallel to each other or at an angle to each other. Figure 1 、 2

[0042] The first branch 1 comprises an oxidation catalyst 5 and a particulate filter 6 arranged in series, the particulate filter 6 being located downstream of the oxidation catalyst 5.

[0043] The first branch 1 is further provided with an inlet 7 for introducing exhaust gas into the exhaust gas aftertreatment system. The first branch 1 can be arranged in any direction that is convenient for connection to elements located on the upstream side of the exhaust gas aftertreatment system.

[0044] The second branch 2 comprises a selective catalytic reduction device 8. The length of the second branch 2 in the axial direction can be substantially equal to or slightly smaller than the axial length of the first branch 1.

[0045] In contrast to the conventional art, in which the oxidation catalyst is arranged in the first branch of the exhaust gas aftertreatment system and the particulate filter and the selective catalytic reduction device are arranged in the second branch, in the present application only the selective catalytic reduction device 8 needs to be arranged in the second branch 2, so that the selective catalytic reduction device 8 can have an increased axial dimension, thereby providing a greater selective catalytic reduction capacity. At the same time, since the selective catalytic reduction device 8 has a sufficiently large axial dimension, its radial dimension can be reduced.

[0046] The second branch 2 is further provided with an outlet 9 for discharging exhaust gas treated by the exhaust gas aftertreatment system. The outlet 9 can be arranged in any direction that is convenient for connection to elements located on the downstream side of the exhaust gas aftertreatment system.

[0047] ​The mixing chamber 3 is connected between the first branch 1 and the second branch 2 and can extend substantially in a direction (longitudinal direction) that intersects, for example, is perpendicular to the central axes of the first branch 1 and the second branch 2. The structure constituting the mixing chamber 3 mainly includes a side wall 10, an end cover 11, and a bottom wall 12. The side wall 10 and the bottom wall 12 can be integrally formed. The end cover 11 is fixed to the side wall 10. The first branch 1 and the second branch 2 are fixed to the bottom wall 12, and the bottom wall 12 is provided with corresponding first and second openings through which the first branch 1 and the second branch 2 respectively communicate with the inside of the mixing chamber 3.

[0048] The mixing chamber 3 is divided into a first portion substantially facing the outlet of the first branch 1 and a second portion substantially facing the inlet of the second branch 2 in the longitudinal direction. As shown in FIG. 1, the profile of the side wall 10 at the first portion and the second portion substantially corresponds to the first branch 1 and the second branch 2, and is narrowed at the transition portion between the first portion and the second portion. Of course, the side wall 10 can also have other profiles. Figure 2

[0049] According to one possible way, the exhaust gas introduced from the inlet 7 flows in the first direction (axial direction) through the oxidation catalyst 5 and the particulate trap 6 in turn. The hydrocarbons and carbon monoxide in the exhaust gas react with oxygen in the oxidation catalyst 5 to generate water and carbon dioxide. Then, the particulate matter or soot in the exhaust gas is trapped in the particulate trap 6. Then, the exhaust gas enters the first portion of the mixing chamber 3 of the mixing chamber 3. Then the flow direction of the exhaust gas is substantially turned by 90 degrees to flow in the second direction (longitudinal direction) toward the second portion of the mixing chamber 3. In the second portion, the flow direction of the exhaust gas is again substantially turned by 90 degrees to flow into the selective catalytic reducer 8 in the third direction (axial direction).

[0050] It should be noted that although in the example described above the first direction is substantially perpendicular to the second direction, and the second direction is substantially perpendicular to the third direction, the angle between the first direction and the second direction, and the angle between the second direction and the third direction, do not have to be about 90 degrees, but can be other angles, so that the configuration of the exhaust gas aftertreatment system is adapted to the requirements of its installation space and the layout relationship with other related elements.

[0051] The reductant injector 4 can be substantially arranged at the center of the longitudinal end of the side wall 10, and the injection direction is substantially directed to the longitudinal direction of the longitudinal mixing chamber 3, so that the central axis of the reductant injected into the mixing chamber 3 is substantially consistent with the flow direction of the exhaust gas in the mixing chamber. Of course, the reductant injector 4 can also be arranged so that the central axis of the reductant injected into the mixing chamber 3 is at an angle to the flow direction of the exhaust gas in the mixing chamber.

[0052] ​The reducing agent is atomized and mixed in the exhaust gas stream, and the exhaust gas mixed with the reducing agent flows into the selective catalytic reducer 8. In the selective catalytic reducer 8, the reducing agent is catalytically reduced with nitrogen oxides and oxygen in the presence of a catalyst to form harmless nitrogen and water. The exhaust gas is then discharged from the outlet 9.

[0053] In order to make the selective catalytic reducer 8 have a higher exhaust gas reduction capacity, it is desirable to improve the uniformity of mixing of the reducing agent with the exhaust gas, and to improve the uniformity of the speed of the exhaust gas flowing into the selective catalytic reducer 8. To this end, a flow guide plate 20 is installed at the first opening of the bottom wall 12, a mixing plate 30 is installed at the second opening of the bottom wall 12, and a mixer 40 (first mixer) is installed in the mixing chamber, as described below.

[0054] The flow guide plate 20 is arranged between the outlet of the first branch 1 and the mixing chamber 3 substantially transversely to the central axis of the first branch 1, for dispersing the exhaust gas flowing through the first branch 1 and more easily achieving a change in the flow direction of the exhaust gas in the first part of the mixing chamber 3. To this end, the flow guide plate 20 is provided with a plurality of discrete apertures for dispersing the exhaust gas stream into a plurality of gas streams, and one or more flow guide vanes for directing the exhaust gas stream longitudinally.

[0055] According to an embodiment shown in Figure 3 , 4 The flow guide plate 20 is an integral element stamped from sheet metal, comprising a substantially disc-shaped plate body 21 and an outer rim 22 extending substantially perpendicularly from a portion of the outer circumference of the plate body 21. The outer rim 22 is used to be fixed to the inner side of the side wall 10, and the plate body 21 is transverse to the central axis of the first branch 1, such that the plate body 21 faces the outlet of the first branch 1. The portion of the plate body 21 in the installed position facing the second part of the mixing chamber 3 is free of the outer rim 22.

[0056] In the lower portion of the plate body 21 in the longitudinal direction, a plurality of discrete through-holes 23 are provided. The shape of these through-holes 23 can be different, but they are generally symmetrically distributed with respect to the longitudinal center axis of the flow guide plate 20. In addition, in the middle portion of the plate body 21 in the longitudinal direction, a plurality of transversely extending through-holes 24 are provided, each of which is formed by stamping the material of the plate body 21 without separation, such that each through-hole 24 has a corresponding vane 25. Each vane 25 is connected to the plate body 21 by a transverse edge 26, which is located on the longitudinal side further away from the second branch 2 (i.e. closer to the longitudinal side of the reducing agent injector 4). Each vane 25 is inclinedly open with respect to the plate body 21, and the angle of opening is suitable for directing the exhaust gas flowing through the through-hole 24 towards the direction of the second branch 2.

[0057] Optionally, one or more tab portions 27 are formed on the portion of the plate body 21 that is free of the outer rim 22, as described below.

[0058] It is noted that in the illustrated example, the through-holes 24 are longitudinally distributed and each extend continuously transversely across a substantial portion of the transverse width of the plate body 21. However, it is also possible to provide a plurality of through-holes and corresponding fins in a matrix form on the plate body 21.

[0059] Furthermore, in the illustrated example, there are through-holes without fins. However, it is also possible to eliminate these through-holes without fins and instead provide through-holes with corresponding fins throughout the plate body 21.

[0060] Through the respective through-holes in the flow guide plate 20, the exhaust gas flowing through the first branch 1 can be dispersed into a plurality of streams. Furthermore, through the fins, the exhaust gas can be guided to turn in the mixing chamber towards the direction of the second branch. Thus, by providing the flow guide plate 20, the uniform mixing of the exhaust gas with the reducing agent and the uniformization of the velocity of the exhaust gas portions can be facilitated.

[0061] It is understood that other forms of the flow guide plate 20 can be conceived under the concept of the present application.

[0062] The mixing plate 30 is described next.

[0063] According to an example implementation shown in Figure 5 , 6 , the mixing plate 30 is an integral element made of sheet metal stamping, comprising a substantially disc-shaped plate body 31 and a mounting flange 32 extending from the outer periphery of the plate body 31. The mounting flange 32 is configured to be adapted to be mounted at its end to the inlet of the second branch 2 (i.e. the inlet of the selective catalytic reducer 8); alternatively, the mounting flange 32 can also be configured to be mounted on the inner side of the side wall 10. The plate body 31 faces the inlet of the second branch 2.

[0064] A plurality of openings 33 are provided on the plate body 31, which are circumferentially distributed around the middle portion of the plate body 31 and on the outer portion of the plate body 31. The openings 33 can be in the form of sectors or other suitable shapes, so that the exhaust gas in the mixing chamber 3 can be dispersedly introduced into the selective catalytic reducer 8. In addition, other auxiliary openings 34 can also be provided on the plate body 31.

[0065] Through the respective openings in the mixing plate 30, the exhaust gas in the mixing chamber 3 can be introduced into the selective catalytic reducer 8 in the form of a plurality of streams. Thus, the uniformization of the velocity of the exhaust gas mixed with the reducing agent entering the selective catalytic reducer 8 can be facilitated.

[0066] It is understood that other forms of the mixing plate 30 can be conceived under the concept of the present application.

[0067] The mixer 40 is described next.

[0068] According to an example implementation shown in Figure 7 ,8 In one possible embodiment shown in the drawings, the mixer 40 is a one-piece member stamped from sheet metal, comprising a curved plate body 41 having lateral ends 42 and lateral curved edges 43 extending between the lateral ends 42. The mixer 40 further comprises edge flanges 44 extending from the curved edges 43 of the plate body 41 and end flanges 45 extending from the lateral ends 42 of the plate body 41. The edge flanges 44 are adapted to be secured to the end caps 11 and the bottom wall 12, respectively, and the end flanges 45 are adapted to be secured to the inner sides of the side walls 10 at locations laterally opposite each other. The edge flanges 44 and the end flanges 45 are not particularly limited with respect to their extension from the plate body 41, as long as they facilitate mounting of the mixer 40 in the mixing chamber 3.

[0069] The mixer 40 is mounted in the mixing chamber 3 in a position and orientation generally corresponding to the portion of the particulate trap 6 facing the selective catalytic reducer 8, with the concave surface of the plate body 41 generally facing the direction of the reductant injector 4. The curvature of the plate body 41 is generally the same as the curvature at the outlet of the particulate trap 6.

[0070] Optionally, one or more slits 46 are formed in the plate body 41, near one of the lateral curved edges 43. The slits 46 correspond to the optional tab portions 27 of the flow guide 20. In mounting, the tab portions 27 are inserted into the corresponding slits 46 to facilitate the relative positioning of the flow guide 20 and the mixer 40. Of course, the tab portions 27 and the slits 46 are not essential.

[0071] Furthermore, the plate body 41 of the mixer 40 is formed with an array of openings 47 formed by integrally stamping the material of the plate body 41, such that each opening 47 is provided with a corresponding flap 48. The edge of each flap 48 connecting to the plate body 41 can be perpendicular to the curved edge 43. Each opening 47 is adapted to be flowed through by the exhaust gas and the reductant in the mixing chamber 3 to disperse the exhaust gas and the reductant. Each flap 48 extends obliquely towards the side of the concave surface of the plate body 41 facing the other, so as to interfere with the flow of the exhaust gas mixed with the reductant directly into the corresponding opening 47.

[0072] Furthermore, the flaps 48 are divided into a first lateral group of flaps 48 and a second lateral group of flaps 48. The first lateral group of flaps 48 is generally symmetrical to the second lateral group of flaps 48. The flaps 48 in each group can have the same or different obliquity with respect to the mixer 40.

[0073] It will be appreciated that the structure of the mixer 40 is not limited to the form shown in the drawings, but can be designed as required. For example, the edge flanges 44 can be omitted, or the end flanges 45 can be omitted, provided that the strength is sufficient; or two end flanges 45 and one lateral edge flange 44 can be used.

[0074] Furthermore, in the illustrated example, the plate 41 of the mixer 40 has a curved shape, but the plate 41 can also be roughly flat, a combination of multiple plate segments, etc.

[0075] Furthermore, in the illustrated example, each opening 47 is rectangular; however, each opening 47 may also have other shapes; and the shape and / or size of each opening 47 may be the same or different. Moreover, it is not necessary for every opening 47 to have a fin 48, but some fins 48 at some openings 47 may be omitted.

[0076] In addition, each wing 48 can also be configured to extend obliquely toward the side facing the convex surface of the plate 41, so as to interfere with the exhaust gas mixed with reducing agent flowing directly out of the corresponding opening 47. Alternatively, some wing 48 can be designed to face the side facing the concave surface of the plate 41, and other wing 48 can be designed to face the side facing the convex surface of the plate 41.

[0077] Furthermore, the edges of each wing 48 that are connected to the plate 41 are not necessarily perpendicular to the curved edge 43 as shown in the figure, but can be located in other directions; and the edges of each wing 48 that are connected to the plate 41 do not have to be parallel to each other. For example, the edges of some wing 48 that are connected to the plate 41 are located in one direction, while the edges of other wing 48 that are connected to the plate 41 are located in another direction.

[0078] Furthermore, depending primarily on the injection force of the reducing agent injector 4, the mixer 40 can be positioned at other longitudinal locations within the mixing chamber 3. For example, it could be located closer to the second part of the mixing chamber 3 than the position shown in the diagram, such as between the first and second parts of the mixing chamber 3.

[0079] The specific structure and installation method of the mixer 40 can be optimized through experiments or simulations to achieve the expected interference and dispersion effects on the exhaust gas and reducing agent.

[0080] As can be seen, the exhaust gas and reducing agent in the mixing chamber 3 flow through the openings 47 and the vanes 48 of the mixer 40 to disperse the exhaust gas and reducing agent, thereby promoting the mixing of the exhaust gas and reducing agent and homogenizing the velocity of the exhaust gas flow at different locations. Therefore, by employing the mixer 40, it is possible to further contribute to the uniform mixing of the exhaust gas and reducing agent and the homogenization of the velocity of each part of the exhaust gas.

[0081] If a single mixer 40 is insufficient to achieve adequate and uniform mixing of the exhaust gas and reducing agent, as well as uniform velocity of different parts of the exhaust gas, an additional mixer can be added to the mixing chamber 3. For example, in Figure 9 In the embodiment shown, in addition to the mixer 40, the mixing chamber 3 is also equipped with an auxiliary mixer 50 (second mixer).

[0082] With the additional mixer 50, the mixer 40 can be identical or similar to the mixer 40 shown in Figure 7 , 8 . For example, in the example shown in Figure 9 , the mixer 40 is not provided with edge flanges, but is secured to the inside of the side wall 10 of the mixing chamber 3 only by end flanges. In this case, the end flanges have a greater dimension in the axial direction than the end flanges 45 shown in Figure 7 .

[0083] Furthermore, in the example shown in Figure 9 , the side wall 10 of the mixing chamber 3 does not have a narrowing as in the example shown in Figure 2 .

[0084] The additional mixer 50 is a one-piece element made of sheet metal stamping, comprising a curved plate 51 having lateral ends 52 and two lateral curved edges 53 extending between the lateral ends 52. The additional mixer 50 further comprises end flanges 54 extending from the lateral ends 52 of the plate 51. The two end flanges 54 are adapted to be secured to the inside of the side wall 10 at locations laterally opposite each other. The end flanges 54 are not particularly limited with respect to their extension direction relative to the plate 51, as long as they facilitate mounting of the additional mixer 50 on the side wall 10.

[0085] It will be appreciated that, if necessary, edge flanges similar to the edge flanges 44 shown in Figure 7 , 8 may also be formed along one or both lateral curved edges 53. Alternatively, two edge flanges can be employed instead of the end flanges 54 described above.

[0086] Furthermore, the plate 51 of the additional mixer 50 is provided with a plurality of openings 55 in an array, which openings 55 are formed by stamping the material of the plate 51 without separation, such that each opening 55 is provided with a respective flap 56. The edge of each flap 56 which is connected to the plate 41 is perpendicular to the curved edge 53. Each opening 55 is adapted to be flowed through by exhaust gas and reducing agent in the mixing chamber 3, in order to disperse the exhaust gas and the reducing agent. The shape of each opening 55 can be rectangular as shown, or another shape. Also, the shape of each opening 55 can be different.

[0087] Each flap 56 extends obliquely towards the side of the plate 41 which faces the convex surface, so as to interfere with a direct flow of exhaust gas mixed with reducing agent into the respective opening 55.

[0088] Furthermore, the flaps 56 are divided into a first lateral group of flaps 56 and a second lateral group of flaps 56. The first lateral group of flaps 56 is substantially symmetrical to the second lateral group of flaps 56. The flaps 56 in each group can have the same or different obliquity with respect to the additional mixer 50.

[0089] The edges of the fins 56 that are connected to the plate body 41 do not necessarily have to be perpendicular to the curved edge 53 as shown in the figure, but can be in other directions; and the edges of the fins 56 that are connected to the plate body 41 can not be parallel to each other, for example, the edges of some fins 56 that are connected to the plate body 41 are in one direction, and the edges of the other fins 56 that are connected to the plate body 41 are in another direction.

[0090] The additional mixer 50 is installed close to the part of the mixing plate 30 that faces the first part of the mixing chamber 3, and the convex surface of the additional mixer 50 faces the convex surface of the mixer 40 in the longitudinal direction. In the installed state, the fins 48 of the mixer 40 and the fins 56 of the additional mixer 50 are respectively located on the side of the mixer 40 and the additional mixer 50 that faces the reductant injector 4. The inclination of the fins 56 of the additional mixer 50 can be substantially the same as or different from the inclination of the fins 48 of the mixer 40.

[0091] Optionally, each opening 55 on the additional mixer 50 is aligned with each opening 47 on the mixer 40 as seen in the direction of the exhaust gas flow in the mixing chamber 3. Alternatively, at least some of the openings 55 on the additional mixer 50 are not completely aligned with any of the openings 47 on the mixer 40 as seen in the direction of the exhaust gas flow in the mixing chamber 3, i.e. at least partially staggered, or completely staggered.

[0092] In the example shown, the exhaust gas flow mixed with reductant in the mixing chamber 3 will successively flow through each opening 47 of the mixer 40 and each opening 55 of the additional mixer 50 to disperse the exhaust gas flow, thereby promoting mixing of the reductant with the exhaust gas and homogenizing the velocity of the exhaust gas flow at different locations. Therefore, by using the mixer 40 and the additional mixer 50, the degree of uniform mixing of the exhaust gas with the reductant and the homogenization of the velocity of the exhaust gas flow at different parts of the exhaust gas flow can be improved. Figure 9 It can be understood that the form of the additional mixer 50 is not limited to the form shown in the figure, but can be designed according to specific needs. The specific structure and installation method of the additional mixer 50 and the mixer 40 can be optimized through experiments or simulations so that the combination of the two achieves the expected interference and dispersion effect on the exhaust gas and the reductant.

[0093] It should be noted that although in the example shown, the plate body 51 of the additional mixer 50 has a curved shape, the plate body 51 can have a substantially flat shape, a combined shape of multiple flat segments, etc.

[0094] In addition, it is not necessary for each opening 55 to have a fin 56, but some fins 56 at some openings 55 can be removed.

[0095]

[0096] ​In addition, the wings 56 can also be arranged to extend obliquely towards the side of the plate body 51 facing the concave surface, so as to interfere with the exhaust gas flow mixed with the reducing agent directly flowing out of the corresponding opening 55.

[0097] Alternatively, some wings 56 can be designed to extend obliquely towards the side of the plate body 51 facing the convex surface, and the other wings 56 can be designed to extend obliquely towards the side of the plate body 51 facing the concave surface.

[0098] According to the present application, by using at least one mixer in the mixing chamber, the exhaust gas flow mixed with the reducing agent flowing through the mixer is dispersed, so as to improve the uniformity of the velocity of each part at the mixed degree, thereby improving the efficiency of the catalytic reduction reaction of the selective catalytic reduction device, reducing the content of nitrogen oxides in the exhaust gas, and making the exhaust gas treated by the exhaust gas aftertreatment system meet higher emission requirements.

[0099] In addition, according to the present application, the selective catalytic reduction device is arranged only in the second branch of the exhaust gas aftertreatment system, so that the selective catalytic reduction device can have an increased axial dimension, thereby increasing the selective catalytic reduction capacity. At the same time, the radial dimension of the selective catalytic reduction device can be reduced. Overall, the configuration of the present application is easier to realize the miniaturization of the exhaust gas aftertreatment system while ensuring the exhaust gas treatment capacity of the exhaust gas aftertreatment system. This makes the exhaust gas aftertreatment system of the present application more easily applied to large vehicles.

[0100] Although the present application is described herein with reference to specific embodiments, the scope of the present application is not limited to the details shown. Various modifications can be made to the details without departing from the essential principles of the present application.

Claims

1. An exhaust aftertreatment system for treating engine exhaust gas, comprising: The first branch (1) includes an oxidation catalyst (5) and a particulate trap (6); The second branch (2) contains a selective catalytic reducer (8); A mixing chamber (3) is connected between the first branch and the second branch; A reducing agent injector (4), which is arranged facing the mixing chamber on the side closer to the first branch, is used to inject a reducing agent into the mixing chamber; A first mixer (40) is fixed in a mixing chamber. The mixer includes a plate (41) with multiple openings (47) for allowing the exhaust gas mixed with reducing agent to flow through these openings. The plate of the first mixer is curved, with its concave surface facing the side of the reducing agent injector. At least some of the openings have winglets (48) extending obliquely from the plate, the winglets being configured to interfere with the exhaust flow through these openings; The exhaust gas aftertreatment system also includes a second mixer (50), which is fixed in the mixing chamber downstream of the first mixer relative to the exhaust gas flow direction in the mixing chamber. The second mixer includes a plate (51) with multiple openings (55) on the plate. The plate of the second mixer is curved, with its convex surface facing the side of the reducing agent injector.

2. The exhaust gas aftertreatment system as described in claim 1, wherein, The mixing chamber includes a first portion facing the outlet of the first branch and a second portion facing the inlet of the second branch; The mixer is arranged in the mixing chamber at a position corresponding to the portion of the first branch facing the second branch; or, the mixer is arranged between the first and second portions of the mixing chamber.

3. The exhaust gas aftertreatment system as described in claim 1, wherein, The blades on the plate of the first mixer include blades that extend obliquely from the plate of the first mixer toward the side of the reducing agent injector; and / or The blades on the plate of the first mixer include blades that extend obliquely from the plate of the first mixer on the side opposite to the reducing agent injector.

4. The exhaust gas aftertreatment system as described in claim 3, wherein, The blades on the plates of each first mixer have the same slope; or, the slope of the blades on some plates of the first mixer is different from that of others.

5. The exhaust gas aftertreatment system as described in claim 3, wherein, The blades on the plate of the first mixer include two sets of blades symmetrically arranged on both sides of the plate of the first mixer.

6. The exhaust gas aftertreatment system as described in any one of claims 1 to 5, wherein, It also includes a flow deflector (20), which is installed in the mixing chamber facing the outlet of the first branch. The flow deflector includes a plate body (21) with a plurality of discrete through holes, one or more of which have flow deflecting blades.

7. The exhaust gas aftertreatment system as described in any one of claims 1 to 5, wherein, It also includes a mixing plate (30) installed in the mixing chamber facing the inlet of the second branch, wherein a plurality of evenly distributed openings (33) are formed in the mixing plate.

8. The exhaust gas aftertreatment system as described in claim 1, wherein, At least some of the openings in the second mixer have blades (56) configured to interfere with the flow of exhaust gas through these openings.

9. The exhaust gas aftertreatment system as described in claim 8, wherein, The blades of the second mixer include blades that extend obliquely from the plate of the second mixer toward the side facing the reducing agent injector; and / or the blades of the second mixer include blades that extend obliquely from the plate of the second mixer away from the side facing the reducing agent injector.

10. The exhaust gas aftertreatment system as described in claim 8, wherein, The blades of the second mixer have the same angle; or, some blades of the second mixer have a different angle than others.

11. The exhaust gas aftertreatment system as described in claim 8, wherein, The blades of the second mixer include two sets of blades symmetrically arranged on both sides of the plate of the second mixer.

12. The exhaust gas aftertreatment system as described in claim 1, wherein, Viewed along the exhaust gas flow direction in the mixing chamber, each opening on the second mixer is aligned with the corresponding opening on the first mixer; or, viewed along the exhaust gas flow direction in the mixing chamber, at least some of the openings on the second mixer are not completely aligned with any opening on the first mixer.

13. The exhaust gas aftertreatment system as described in any one of claims 1 to 5, wherein, The first branch, the second branch, and the mixing chamber are configured such that exhaust gas enters the mixing chamber from the first branch in a first direction, flows in the mixing chamber in a second direction different from the first direction, and then enters the second branch from the mixing chamber in a third direction different from the second direction.

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