Mixer assembly and exhaust gas aftertreatment device

Abstract

A mixer assembly, comprising a housing (31), a blocking wall (61), a first connecting wall (71), a second connecting wall (72), and a mixing tube assembly (8). The housing comprises an internal cavity (30), and the internal cavity comprises a first gas flow cavity (301) and a second gas flow cavity (302). The mixer assembly comprises a gas flow mixing cavity (70) at least defined together by the blocking wall, the first connecting wall, and the second connecting wall. The mixing tube assembly is provided with first gas flow inlets (801) and an inner cavity (80) for receiving a urea spray. The second connecting wall is provided with second gas flow inlets (721). Gas flow flowing into the gas flow mixing cavity from the first gas flow inlets impinges against gas flow flowing into the gas flow mixing cavity from the second gas flow inlets, thereby improving a mixing effect and enhancing resistance to urea crystallization. An exhaust gas aftertreatment device having the mixer assembly is also disclosed.

Description

Mixer assembly and exhaust gas aftertreatment device

[0001] The present application claims priority to the Chinese patent application No. 202411354026.6, filed on September 26, 2024, entitled “Mixer assembly and exhaust gas aftertreatment device”, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a mixer assembly and an exhaust gas aftertreatment device, and belongs to the technical field of engine exhaust gas aftertreatment. BACKGROUND

[0003] With the continuous upgrading of emission regulations, higher requirements are put forward for the concentration of harmful substances in engine exhaust gas. In order to reduce the concentration of harmful substances, the exhaust gas aftertreatment system correspondingly increases the injection amount of urea. However, with the increase of urea injection amount, the risk of urea crystallization is also increasing.

[0004] However, the technical solutions in the related art still have room for improvement. SUMMARY

[0005] The purpose of the present application is to provide a mixer assembly and an exhaust gas aftertreatment device with good anti-urea crystallization performance.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: a mixer assembly, comprising: a housing, a blocking wall located in the housing, a first connecting wall connected with the blocking wall, a second connecting wall connected with the blocking wall and spaced apart from the first connecting wall, and a mixing pipe assembly at least partially fixed on the first connecting wall, the housing comprising an internal cavity, the internal cavity comprising a first airflow cavity located on one side of the first connecting wall and away from the second connecting wall, and a second airflow cavity located on one side of the second connecting wall and away from the first connecting wall, the mixer assembly further comprising an airflow mixing cavity surrounded by the blocking wall, the first connecting wall and the second connecting wall together; the mixing pipe assembly is provided with an inner cavity for receiving a urea jet and a first airflow inlet in communication with the first airflow cavity and guiding at least part of the airflow into the inner cavity, the inner cavity is in communication with the airflow mixing cavity, and the second connecting wall is provided with a second airflow inlet communicating the second airflow cavity and the airflow mixing cavity, wherein the airflow flowing into the airflow mixing cavity from the first airflow inlet collides with the airflow flowing into the airflow mixing cavity from the second airflow inlet.

[0007] As a further improved technical solution of the present application, the mixer assembly further comprises a first blocking portion located downstream of the first airflow cavity in the direction of airflow flow, the first blocking portion being used to force the airflow flowing into the first airflow cavity to enter the inner cavity of the mixing tube assembly.

[0008] As a further improved technical solution of the present application, the mixing tube assembly comprises a mixing tube, wherein the mixing tube is provided with a plurality of fins located at least partially in the first airflow cavity, and the first airflow inlet is located between adjacent fins; the mixing tube comprises a first inner cavity in communication with the first airflow inlet, and the inner cavity comprises the first inner cavity.

[0009] As a further improved technical solution of the present application, the mixing tube assembly comprises an outer tube at least partially sleeved outside the mixing tube, the outer tube is fixed to the first connecting wall, the outer tube comprises a second inner cavity in communication with the first inner cavity, and the inner cavity comprises the second inner cavity.

[0010] As a further improved technical solution of the present application, the first connecting wall is provided with a mounting hole, and the outer tube is at least partially located in the mounting hole and is welded and fixed to the first connecting wall.

[0011] As a further improved technical solution of the present application, the mixing tube assembly comprises an annular space located between the outer tube and the mixing tube, and the annular space is in communication with the first airflow cavity.

[0012] As a further improved technical solution of the present application, the mixing tube assembly further comprises a fixing ring located in the annular space and fixing the mixing tube to the outer tube.

[0013] The fixing ring comprises an annular portion sleeved and fixed on the mixing tube, and a claw portion extending from the annular portion, and the claw portion is welded and fixed to the inner wall of the outer tube.

[0014] As a further improved technical solution of the present application, the outer tube is provided with a first extension portion protruding into the first airflow cavity and a second extension portion protruding into the airflow mixing cavity, and the second extension portion is provided with a plurality of airflow perforations in communication with the second inner cavity and the airflow mixing cavity.

[0015] As a further improved technical solution of the present application, the first connecting wall comprises a first wall portion integrally extended with the blocking wall and a second wall portion integrally extended with the first blocking portion, the first wall portion is provided with a first mounting recess, the second wall portion is provided with a second mounting recess, and the first mounting recess and the second mounting recess are combined to form the mounting hole.

[0016] As a further improved technical solution of the present application, the blocking wall is provided with a plurality of first perforations communicating the internal cavity and the airflow mixing cavity.

[0017] The second connecting wall is integrally extended with the blocking wall, and the second airflow inlet includes a plurality of second perforations penetrating through the second connecting wall.

[0018] As a further improved technical solution of the present application, the mixer assembly further includes a third connecting wall fixed to the blocking wall and spaced apart from the second connecting wall, and the third connecting wall is provided with a plurality of third perforations communicating the second airflow cavity and the airflow mixing cavity.

[0019] As a further improved technical solution of the present application, the mixer assembly includes a first plate downstream of the blocking wall in the airflow flow direction, and the first plate is provided with a second blocking portion downstream of the second airflow cavity, and the second blocking portion is used to force the airflow flowing into the second airflow cavity to enter the airflow mixing cavity.

[0020] As a further improved technical solution of the present application, the second connecting wall is fixed to the first plate.

[0021] As a further improved technical solution of the present application, the first plate is provided with a first main body portion at the rear end of the airflow mixing cavity, and the first main body portion includes a first fixed portion fixed to the inner wall of the shell and a first arc-shaped protruding portion protruding forward from the middle portion of the first fixed portion into the airflow mixing cavity; the first fixed portion is located on both sides of the first arc-shaped protruding portion, and the first arc-shaped protruding portion is provided with a plurality of first airflow perforations; and the first fixed portion is provided with a plurality of first airflow through holes for airflow to pass through.

[0022] As a further improved technical solution of the present application, the mixer assembly further includes a second plate downstream of the first plate in the airflow flow direction, and the first plate is provided with a first recessed space located rearward of the first arc-shaped protruding portion; and the second plate is provided with a second fixed portion fixed to the inner wall of the shell and a second arc-shaped protruding portion at least partially protruding forward from the middle portion of the second fixed portion into the first recessed space, and the second arc-shaped protruding portion is provided with a plurality of second airflow perforations, and the second fixed portion is provided with a plurality of second airflow through holes for airflow to pass through.

[0023] As a further improved technical solution of the present application, the mixer assembly further includes a urea crystallization baffle downstream of the second plate in the airflow flow direction, and the urea crystallization baffle is configured to prevent urea crystals from flowing downstream in the airflow flow direction.

[0024] The present application also discloses an exhaust gas aftertreatment device comprising a diesel oxidation catalyst assembly, a diesel particulate filter assembly located downstream of and connected to the diesel oxidation catalyst assembly, a mixer assembly located downstream of and connected to the diesel particulate filter assembly, and a selective catalytic reducer assembly located downstream of and connected to the mixer assembly, the mixer assembly being the aforementioned mixer assembly.

[0025] Compared with the prior art, the present application is provided with the first gas flow cavity and the second gas flow cavity, the gas flow flowing into the gas flow mixing cavity from the first gas flow inlet collides with the gas flow flowing into the gas flow mixing cavity from the second gas flow inlet, thereby improving the mixing effect and improving the ability of resisting urea crystallization. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a perspective view of the exhaust gas aftertreatment device in an embodiment of the present application.

[0027] Fig. 2 is a perspective view of Fig. 1 from another angle.

[0028] Fig. 3 is a perspective view of the mixer assembly of the present application.

[0029] Fig. 4 is a top view of Fig. 3.

[0030] Fig. 5 is a sectional view along line A-A of Fig. 4.

[0031] Fig. 6 is a partially exploded view of Fig. 3.

[0032] Fig. 7 is a partially exploded view of Fig. 6 from another angle.

[0033] Fig. 8 is a perspective view of the first plate, the second plate and the urea crystallization baffle in Fig. 6. DETAILED DESCRIPTION

[0034] The exemplary embodiments will be described in detail below with reference to the attached drawings. The following description is with reference to the drawings, in which like numerals indicate like elements, unless otherwise described in the following description. The embodiments described in the following exemplary embodiments are not meant to represent all embodiments consistent with the present application. Rather, they are merely examples that can be embodied within the scope of the present application as detailed in the appended claims.

[0035] The term used in the present application is merely for the purpose of describing particular embodiments and is not intended to limit the present application. In addition, the terms "first", "second", "third", etc. are used to describe various components, but these components must not be understood as being of relative importance or implying the number of the technical features indicated. Thus, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0036] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "over" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is horizontally higher than the second feature. "Under", "below" and "underneath" of a first feature to a second feature includes that the first feature is directly below and obliquely below the second feature, or only means that the first feature is horizontally lower than the second feature. The exemplary embodiments of the present application are described in detail below with reference to the accompanying drawings. In the case of no conflict, the embodiments described below and the features in the embodiments can be complementary or combined with each other.

[0037] The term used in the present application is merely for the purpose of describing particular embodiments and is not intended to limit the present application. In the present application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0038] Please refer to FIG. 1 and FIG. 2, the present application discloses a tail gas aftertreatment device 100 for treating the tail gas of an engine to reduce the emission of harmful substances. The tail gas aftertreatment device 100 comprises an oxidation catalyst assembly (DOC) 1, a diesel particulate filter assembly 2 (DPF) located downstream of and connected with the oxidation catalyst assembly 1, a mixer assembly 3 located downstream of and connected with the diesel particulate filter assembly 2, and a selective catalytic reduction assembly (SCR) 4 located downstream of and connected with the mixer assembly 3. In the embodiment shown in the present application, the oxidation catalyst assembly 1, the diesel particulate filter assembly 2 and the mixer assembly 3 are detachably connected by a clamp for maintenance and replacement. In the embodiment shown in the present application, the oxidation catalyst assembly 1, the diesel particulate filter assembly 2, the mixer assembly 3 and the selective catalytic reduction assembly 4 are arranged in a straight line.

[0039] Please refer to FIGS. 3-8, the mixer assembly 3 comprises a housing 31, a blocking wall 61 located in the housing 31, a first connecting wall 71 connected with the blocking wall 61, a second connecting wall 72 connected with the blocking wall 61 and spaced apart from the first connecting wall 71, and a mixing tube assembly 8 fixed at least partially on the first connecting wall 71. In the embodiment shown in the present application, the blocking wall 61 extends substantially in the vertical direction, the first connecting wall 71 and the second connecting wall 72 both extend substantially in the horizontal direction. The first connecting wall 71 and the second connecting wall 72 are both perpendicular to the blocking wall 61.

[0040] In the embodiment shown in the present application, the housing 31 comprises a first flange 32 at one end thereof and a second flange 33 at the other end thereof, wherein the first flange 32 is used to be detachably connected with the diesel particulate filter assembly 2, and the second flange 33 is used to be detachably connected with the selective catalytic reduction assembly 4.

[0041] In the embodiment shown in the present application, the housing 31 is cylindrical and made of metal material; of course, in other embodiments, the housing 31 can also be other shapes, such as oval, etc. The housing 31 comprises an internal cavity 30. The internal cavity 30 comprises a first airflow cavity 301 located at one side of the first connecting wall 71 and away from the second connecting wall 72, and a second airflow cavity 302 located at one side of the second connecting wall 72 and away from the first connecting wall 71. In the embodiment shown in the present application, the first airflow cavity 301 is located above the first connecting wall 71, and the second airflow cavity 302 is located below the second connecting wall 72.

[0042] In the embodiment shown in the present application, the mixer assembly 3 further comprises a first blocking portion 73 located downstream of the first airflow cavity 301 in the airflow flow direction, which is used to force the airflow flowing into the first airflow cavity 301 to enter the internal cavity 80 of the mixing tube assembly 8. In the embodiment shown in the present application, the first blocking portion 73 is located at the rear end of the first airflow cavity 301 in the airflow flow direction.

[0043] In the embodiment shown in the present application, the first blocking portion 73 is welded and fixed to the inner wall of the housing 31. The first blocking portion 73 is provided with an inclined portion 731 located at the rear end of the first airflow cavity 301.

[0044] In the embodiment shown in the present application, the first connecting wall 71 comprises a first wall portion 711 integrally extended from the blocking wall 61 and a second wall portion 712 integrally extended from the first blocking portion 73, the first wall portion 711 is provided with a first mounting notch 7111, and the second wall portion 712 is provided with a second mounting notch 7121, the first mounting notch 7111 and the second mounting notch 7121 are combined into a circular mounting hole.

[0045] In the embodiment shown in the present application, the mixer assembly 3 further comprises an airflow mixing cavity 70 which is jointly surrounded by at least the blocking wall 61, the first connecting wall 71 and the second connecting wall 72.

[0046] The mixing pipe assembly 8 is provided with an inner cavity 80 for receiving a urea jet and a first airflow inlet 801 which is in communication with the first airflow cavity 301 and guides at least part of the airflow into the inner cavity 80, and the inner cavity 80 is in communication with the airflow mixing cavity 70. The second connecting wall 72 is provided with a second airflow inlet 721 which is in communication with the second airflow cavity 302 and the airflow mixing cavity 70, wherein the airflow flowing into the airflow mixing cavity 70 from the first airflow inlet 801 collides with the airflow flowing into the airflow mixing cavity 70 from the second airflow inlet 721, thereby improving the mixing effect and increasing the ability to resist urea crystallization.

[0047] In the embodiment shown in the present application, the second connecting wall 72 is integrally extended from the blocking wall 61, and the second airflow inlet 721 comprises a plurality of second perforations penetrating through the second connecting wall 72.

[0048] In the embodiment shown in the present application, the mixing pipe assembly 8 comprises a mixing pipe 81, an outer pipe 82 which is at least partially sleeved outside the mixing pipe 81, and a fixing ring 83 which is fixed between the mixing pipe 81 and the outer pipe 82. The mixing pipe 81 has a tapered portion 811 which is provided with a plurality of fins 812 which are at least partially located in the first airflow cavity 301, and the first airflow inlet 801 is located between adjacent fins 812; the mixing pipe 81 comprises a first inner cavity 810 which is in communication with the first airflow inlet 801, and the inner cavity 80 comprises the first inner cavity 810.

[0049] In the embodiment shown in the present application, the outer pipe 82 is fixed to the first connecting wall 71, and the outer pipe 82 comprises a second inner cavity 820 which is in communication with the first inner cavity 810, and the inner cavity 80 comprises the second inner cavity 820. The outer pipe 82 is at least partially located in the mounting hole and is welded and fixed to the first connecting wall 71.

[0050] In the embodiment illustrated in the present application, the mixing pipe assembly 3 comprises an annular space 84 between the outer pipe 82 and the mixing pipe 81, which is in communication with the first gas flow cavity 301. Part of the gas flow flowing into the first gas flow cavity 301 can directly flow into the second inner cavity 820 through the annular space 84. The fixing ring 83 is located in the annular space 84 and fixes the mixing pipe 81 to the outer pipe 82.

[0051] Specifically, in the embodiment illustrated in the present application, the fixing ring 83 comprises an annular portion 831 sleeved and fixed on the mixing pipe 81 and a plurality of claw portions 832 extending from the annular portion 831, which are welded to the inner wall of the outer pipe 82.

[0052] The outer pipe 82 is provided with a first extension portion 821 protruding into the first gas flow cavity 301 and a second extension portion 822 protruding into the gas flow mixing cavity 70, which is provided with a plurality of gas flow perforations 8221 communicating the second inner cavity 820 and the gas flow mixing cavity 70.

[0053] The shell 31 comprises a mounting portion 34 for mounting a urea nozzle 5 for spraying urea droplets into the gas flow mixing cavity 70, the tail gas entering the gas flow mixing cavity 70 and the urea droplets having at least a main component in the opposite direction (for example, an upward component) in the respective flow direction, the tail gas and the urea droplets with the main component colliding and mixing with each other in the gas flow mixing cavity 70. It can be understood by those skilled in the art that in the embodiment illustrated in the present application, the urea spray jet sprayed from the urea nozzle 5 can also hit the second connecting wall 72, which can also play a role in further breaking the urea droplets.

[0054] In the embodiment illustrated in the present application, the blocking wall 61 is provided with a plurality of first perforations 611 communicating the inner cavity 30 and the gas flow mixing cavity 70. Part of the gas flow entering the inner cavity 30 can directly enter the gas flow mixing cavity 70 through the first perforations 611 to adjust the back pressure.

[0055] In the embodiment shown in the present application, the mixer assembly 3 further comprises a third connecting wall 74 fixed to the blocking wall 61 and spaced apart from the second connecting wall 72, and the third connecting wall 74 is provided with a plurality of third perforations 741 communicating the second airflow cavity 302 and the airflow mixing cavity 70. In the embodiment shown in the present application, the third connecting wall 74 is located below the second connecting wall 72. In other embodiments of the present application, the third connecting wall 74 can also be located above the second connecting wall 72.

[0056] In the embodiment shown in the present application, the mixer assembly 3 comprises a first plate 41 located downstream of the blocking wall 61 along the airflow flow direction, a second plate 42 located downstream of the first plate 41 along the airflow flow direction, and a urea crystallization baffle 43 located downstream of the second plate 42 along the airflow flow direction.

[0057] The first plate 41 is provided with a second blocking portion 411 located downstream of the second airflow cavity 302, and the second blocking portion 411 is used to force the airflow flowing into the second airflow cavity 302 to enter the airflow mixing cavity 70.

[0058] In the embodiment shown in the present application, the second connecting wall 72 and the third connecting wall 74 are both fixed to the first plate 41. Specifically, the first plate 41 is provided with a first insertion slot 4111 and a second insertion slot 4112, and the second connecting wall 72 and the third connecting wall 74 are respectively inserted into the first insertion slot 4111 and the second insertion slot 4112 and fixed by welding.

[0059] The first plate 41 is provided with a first fixed portion 412 fixed to the inner wall of the shell 31 and a first arc-shaped protruding portion 413 protruding into the airflow mixing cavity 70 from the middle of the first fixed portion 412. The first fixed portion 412 is located on both sides of the first arc-shaped protruding portion 413. The first arc-shaped protruding portion 413 is provided with a plurality of first airflow perforations 4131. The first fixed portion 412 is provided with a plurality of first airflow through holes 4121 allowing airflow to pass through. The first plate 41 is further provided with a first recessed space 414 located behind the first arc-shaped protruding portion 413.

[0060] The second plate 42 is provided with a second fixed part 421 fixed to the inner wall of the shell 31 and a second arc-shaped protruding part 422 protruding at least partially into the first recessed space 414 from the middle part of the second fixed part 421. The second arc-shaped protruding part 422 is provided with a plurality of second airflow perforations 4221. The second fixed part 421 is provided with a plurality of second airflow through holes 4211 for airflow. The second fixed part 421 is located around the second arc-shaped protruding part 422. In the embodiment shown in the present application, the second arc-shaped protruding part 422 is punched from the middle part of the second plate 42, and the second plate 42 is provided with a first tearing opening 423 corresponding to the upper edge of the second arc-shaped protruding part 422 and a second tearing opening 424 corresponding to the lower edge of the second arc-shaped protruding part 422.

[0061] The urea crystal baffle 43 is configured to prevent the urea crystals that may be generated from flowing downstream along the airflow direction, i.e., flowing to the selective catalytic reduction device assembly 4 along the airflow direction to cause blockage. The urea crystal baffle 43 is provided with a plurality of airflow holes 431 and airflow gaps 432 located on one side of the airflow holes 431, which are used to allow airflow to pass through to adjust uniformity. The solid part of the urea crystal baffle 43, in particular the solid part located at the bottom thereof, can block the urea crystals that may be generated.

[0062] In operation, exhaust gas flows into the left internal cavity 30, most of which flows into the first gas flow cavity 301 and the second gas flow cavity 302 on both sides (e.g., upper and lower sides) under the blockage of the block wall 61, and a small amount of exhaust gas directly enters the gas flow mixing cavity 70 through the first perforation 611. Then, most of the exhaust gas entering the first gas flow cavity 301 flows into the gas flow mixing cavity 70 in a spiral flow from the first gas flow inlet 801. A portion of the exhaust gas directly flows into the second internal cavity 820 through the annular space 84. The exhaust gas entering the second gas flow cavity 302 flows into the gas flow mixing cavity 70 from the third perforation 741 and the second gas flow inlet 721. When the injection condition is reached, the urea nozzle 5 located in the internal cavity 80 sprays atomized urea droplets into the internal cavity 80. The mixed gas flow formed by the exhaust gas flowing into the gas flow mixing cavity 70 from the first gas flow inlet 801 and the urea droplets flows downward together, collides with the exhaust gas flowing upward into the gas flow mixing cavity 70 from the second gas flow inlet 721, thereby improving the mixing effect and increasing the ability to resist urea crystallization. During the downward flow of the mixed gas flow, part of the gas flow passes through the gas flow perforation 822, and at the same time, the urea droplets collide with the second extension 822 to further break the urea droplets, further increasing the ability to resist urea crystallization. Of course, those skilled in the art can understand that the mixed gas flow can also further break the urea droplets under the action of the first plate 41 and the second plate 42 after flowing out of the gas flow mixing cavity 70, further increasing the ability to resist urea crystallization.

[0063] Compared with the prior art, the present application has a first gas flow cavity 301 and a second gas flow cavity 302. The gas flow flowing into the gas flow mixing cavity 70 from the first gas flow inlet 801 collides with the gas flow flowing into the gas flow mixing cavity 70 from the second gas flow inlet 721, thereby improving the mixing effect and increasing the ability to resist urea crystallization.

[0064] In addition, the above embodiments are only used to illustrate the technical solutions described in the present application and are not intended to limit the technical solutions described in the present application. The understanding of the specification should be based on the skilled person in the art. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the skilled person in the art can still modify or equivalently replace the present application, and all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered within the scope of the claims of the present application.

Claims

1. A mixer assembly characterized by, The mixer assembly comprises a housing, a blocking wall located in the housing, a first connecting wall connected to the blocking wall, a second connecting wall connected to the blocking wall and spaced apart from the first connecting wall, and a mixing tube assembly at least partially fixed to the first connecting wall, the housing comprising an internal cavity, the internal cavity comprising a first airflow cavity located on one side of the first connecting wall and away from the second connecting wall, and a second airflow cavity located on one side of the second connecting wall and away from the first connecting wall, the mixing tube assembly further comprising an airflow mixing cavity jointly formed by the blocking wall, the first connecting wall and the second connecting wall; the mixing tube assembly is provided with an inner cavity for receiving a urea jet and a first airflow inlet in communication with the first airflow cavity and guiding at least part of the airflow into the inner cavity, the inner cavity being in communication with the airflow mixing cavity, the second connecting wall being provided with a second airflow inlet in communication with the second airflow cavity and the airflow mixing cavity, wherein the airflow flowing into the airflow mixing cavity from the first airflow inlet collides with the airflow flowing into the airflow mixing cavity from the second airflow inlet. The mixer assembly further comprises a first blocking portion located downstream of the first airflow cavity in the direction of airflow flow, the first blocking portion being used to force the airflow flowing into the first airflow cavity to enter the inner cavity of the mixing tube assembly.

2. The mixer assembly of claim 1, wherein: The mixing tube assembly comprises a mixing tube, wherein the mixing tube is provided with a plurality of fins located at least partially in the first airflow cavity, the first airflow inlet being located between adjacent fins; the mixing tube comprises a first inner cavity in communication with the first airflow inlet, the inner cavity comprising the first inner cavity.

3. The mixer assembly of claim 2, wherein: The mixing tube assembly comprises an outer tube at least partially sleeved outside the mixing tube, the outer tube being fixed to the first connecting wall, the outer tube comprising a second inner cavity in communication with the first inner cavity, the inner cavity comprising the second inner cavity.

4. The mixer assembly of claim 3, wherein: The first connecting wall is provided with a mounting hole, the outer tube being at least partially located in the mounting hole and being welded and fixed to the first connecting wall.

5. The mixer assembly of claim 4, wherein: The mixing tube assembly comprises an annular space located between the outer tube and the mixing tube, the annular space being in communication with the first airflow cavity.

6. The mixer assembly of claim 4, wherein: The mixing tube assembly further comprises a fixing ring located in the annular space and fixing the mixing tube to the outer tube; 7. The mixer assembly of claim 6, wherein: The fixing ring comprises an annular portion sleeved and fixed on the mixing tube, and a claw portion extending from the annular portion, the claw portion being welded and fixed to the inner wall of the outer tube. The outer tube is provided with a first extension portion protruding into the first airflow cavity and a second extension portion protruding into the airflow mixing cavity, the second extension portion being provided with a plurality of airflow perforations in communication with the second inner cavity and the airflow mixing cavity.

8. The mixer assembly of claim 4, wherein: ​ 9. The mixer assembly of claim 4, wherein: The first connecting wall comprises a first wall portion integrally extended from the blocking wall and a second wall portion integrally extended from the first blocking portion, the first wall portion is provided with a first mounting notch, the second wall portion is provided with a second mounting notch, and the first mounting notch and the second mounting notch are combined to form the mounting hole.

10. The mixer assembly of claim 1, wherein: The blocking wall is provided with a plurality of first perforations communicating the internal cavity and the airflow mixing cavity; The second connecting wall is integrally extended from the blocking wall, and the second airflow inlet comprises a plurality of second perforations penetrating through the second connecting wall.

11. The mixer assembly of claim 1, wherein: The mixer assembly further comprises a third connecting wall fixed to the blocking wall and spaced apart from the second connecting wall, and the third connecting wall is provided with a plurality of third perforations communicating the second airflow cavity and the airflow mixing cavity.

12. The mixer assembly of claim 1, wherein: The mixer assembly comprises a first plate downstream of the blocking wall in the airflow flow direction, and the first plate is provided with a second blocking portion downstream of the second airflow cavity, and the second blocking portion is used to force the airflow flowing into the second airflow cavity to enter the airflow mixing cavity.

13. The mixer assembly of claim 12, wherein: The second connecting wall is fixed to the first plate.

14. The mixer assembly of claim 12, wherein: The first plate is provided with a first main body portion at the rear end of the airflow mixing cavity, and the first main body portion comprises a first fixed portion fixed to the inner wall of the shell and a first arc-shaped protruding portion protruding forward from the middle portion of the first fixed portion into the airflow mixing cavity; the first fixed portion is located on both sides of the first arc-shaped protruding portion, the first arc-shaped protruding portion is provided with a plurality of first airflow perforations, and the first fixed portion is provided with a plurality of first airflow through holes allowing airflow to pass through.

15. The mixer assembly of claim 14, wherein: The mixer assembly further comprises a second plate downstream of the first plate in the airflow flow direction, and the first plate is provided with a first recessed space rearward of the first arc-shaped protruding portion; the second plate is provided with a second fixed portion fixed to the inner wall of the shell and a second arc-shaped protruding portion at least partially protruding forward from the middle portion of the second fixed portion into the first recessed space, the second arc-shaped protruding portion is provided with a plurality of second airflow perforations, and the second fixed portion is provided with a plurality of second airflow through holes allowing airflow to pass through.

16. The mixer assembly of claim 15, wherein: The mixer assembly further comprises a urea crystallization baffle downstream of the second plate in the airflow flow direction, and the urea crystallization baffle is configured to prevent urea crystals from flowing downstream in the airflow flow direction.

17. An exhaust gas aftertreatment device, characterized by A diesel oxidation catalyst assembly, a diesel particulate filter assembly downstream of and connected to the diesel oxidation catalyst assembly, a mixer assembly downstream of and connected to the diesel particulate filter assembly, and a selective catalytic reduction assembly downstream of and connected to the mixer assembly, the mixer assembly being any one of claims 1 to 16.

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