Mixer and exhaust gas aftertreatment system

Abstract

This application relates to a mixer and an exhaust gas aftertreatment system. The mixer includes: a cover with a spray nozzle through which a reducing agent spray enters the mixer; a base surrounding and defining a receiving space, the base including an inlet opening and an outlet opening, the receiving space including an inlet area corresponding to the inlet opening, an outlet area corresponding to the outlet opening, and an intermediate area between the two; a pipe assembly extending in its extending direction from one end of the pipe assembly located in the inlet area to the other end of the pipe assembly located in the outlet area; the pipe assembly including an inner pipe and an outer pipe, the outer pipe being radially outside the inner pipe, the inner pipe providing a mixing space for mixing the reducing agent and exhaust gas, and the radial space between the outer pipe and the inner pipe providing a bypass channel for exhaust gas flow; wherein the outer pipe includes a body portion and a protruding portion.

Description

Technical Field

[0001] This application relates to the field of waste gas treatment, and more particularly to a mixer and a waste gas after-treatment system. Background Technology

[0002] Exhaust gas aftertreatment systems treat the hot exhaust gases generated by the engine through various upstream exhaust components to reduce pollutant emissions. These upstream components may include one or more of the following: pipes, filters, valves, catalytic converters, mufflers, etc. For example, the upstream exhaust components guide the exhaust gases into a diesel oxidation catalytic converter (DOC) with inlets and outlets. Downstream of the DOC may be a diesel particulate filter (DPF). Downstream of the DOC and optional DPF is a selective catalytic reduction (SCR) reactor with inlets and outlets. The outlet leads the exhaust gases to the downstream exhaust components. A mixer is located downstream of the DOC outlet or DPF and upstream of the SCR inlet. Within the mixer, the exhaust gases undergo swirling or rotational motion. The injector is used to inject a reducing agent, such as an aqueous solution of urea, from upstream of the SCR into the exhaust gas stream, allowing the mixer to thoroughly mix the urea and exhaust gas together before being discharged into the SCR for a reduction reaction to produce nitrogen and water, thereby reducing the engine's nitrogen oxide emissions.

[0003] However, existing mixers still have room for improvement. For example, it is necessary to further balance the relationship between the uniformity of the mixture of exhaust gas and reducing agent (such as urea) and the exhaust back pressure, and to minimize the exhaust back pressure while ensuring the uniformity of the mixture of exhaust gas and urea. Utility Model Content

[0004] One object of this application is to provide a mixer.

[0005] Another objective of this application is to provide an exhaust gas aftertreatment system.

[0006] A mixer according to a first aspect of this application, used in an exhaust gas aftertreatment system, includes: a cover having an injection port through which a reducing agent spray enters the mixer; a base surrounding and defining a receiving space, the base including an air inlet and an air outlet, the receiving space including an air inlet area corresponding to the air inlet, an air outlet area corresponding to the air outlet, and an intermediate area between the two; and a pipe assembly extending in the extending direction of the pipe assembly from one end located in the air inlet area to the other end located in the air outlet area; the pipe assembly including an inner pipe and an outer pipe, the outer pipe being located within the inner pipe. Radially outward, the inner tube provides a mixing space for the reducing agent and exhaust gas, and the radial space between the outer tube and the inner tube provides a bypass channel for the exhaust gas flow; wherein, the outer tube includes a body portion and a protrusion portion, the protrusion portion protruding from the body portion beyond one axial end of the inner tube, such that the protrusion portion provides one end of the tube assembly; wherein, the protrusion portion has a plurality of uniformly distributed swirl blades, each swirl blade being configured such that, on an axially protruding cylindrical side, one circumferential end is pressed inward or outward toward the center of the tube assembly, and the other circumferential end extends axially or is also pressed inward or outward toward the center of the tube assembly, forming the swirl blade.

[0007] In one or more embodiments of the mixer, the protrusion has one or more uniformly distributed swirl blades; the swirl blades are integrally connected to the body portion.

[0008] In one or more embodiments of the mixer, for each swirl blade, the circumferential end is squeezed inward or outward toward the center of the tube assembly at an angle of 30° to 60°.

[0009] In one or more embodiments of the mixer, a heat exchange element is further included, disposed in the bypass channel, the heat exchange element being axially located downstream of the protrusion.

[0010] In one or more embodiments of the mixer, the body of the outer tube has a first through hole penetrating the tube wall, the first through hole being located upstream of the heat exchange element, and the axial distance between the first through hole and the heat exchange element being 8 mm to 20 mm; the heat exchange element has a first axial length range and a second axial length range, the first axial length range being located in the air inlet area and the second axial length range being located in the air outlet area, the axial length of the first axial length range being greater than the axial length of the second axial length range; the heat exchange element comprises foamed metal material, or a corrugated structure extending axially on the outer wall of the inner tube.

[0011] In one or more embodiments of the mixer, the body portions of both the inner and outer tubes are straight tubes, and at the other end of the tube assembly, the inner tube protrudes axially from the body portion to provide the other end.

[0012] In one or more embodiments of the mixer, a flow guiding element is further included, disposed in the outlet region and adjacent downstream of the other end, the flow guiding element covering a radial dimension larger than that of the other end, the flow guiding element providing a flow guiding surface, the extension of the flow guiding surface enabling airflow output from the other end to be guided along the flow guiding surface, the provided flow guiding path including: airflow output from the other end flowing along the flow guiding surface in a first direction, then flowing along a flow boundary defined by a cover, and then flowing in a second direction to the outlet opening; the first direction is opposite to the second direction; the minimum distance between the flow guiding surface and the other end is at least 10 mm; the flow guiding surface has a structure symmetrical about the axis of the tube assembly; or, the mixer does not have a flow guiding element in the outlet region.

[0013] In one or more embodiments of the mixer, a partition is further included to separate the air inlet zone and the air outlet zone, and the pipe assembly passes through the partition such that the pipe assembly is the only or main channel connecting the air inlet zone and the air outlet zone.

[0014] According to a second aspect of this application, an exhaust gas aftertreatment system includes a mixer as described in the first aspect, and an injector capable of spraying a reducing agent liquid into the pipe assembly of the mixer to form a reducing agent spray, thereby mixing the exhaust gas with the reducing agent in the mixing space.

[0015] In one or more embodiments of the exhaust gas aftertreatment system, the exhaust gas aftertreatment system further includes a first exhaust gas treatment unit and a second exhaust gas treatment unit. The first exhaust gas treatment unit is connected to the air inlet of the mixer to provide exhaust gas to enter the mixer from the air inlet. The second exhaust gas treatment unit is connected to the air outlet of the mixer so that the mixed gas flow in the mixer flows out to the second exhaust gas treatment unit. The diesel particulate filter or diesel oxidation catalyst of the first exhaust gas treatment unit is connected to the mixer, and the selective catalytic reduction reactor of the second exhaust gas treatment unit is connected to the mixer. The reducing agent is a urea solution.

[0016] The advantages of this application include, but are not limited to, the inventor's discovery that it is possible to minimize exhaust back pressure while ensuring the uniformity of the mixture of exhaust gas and urea. The principle likely lies in the fact that the main body protrudes beyond one axial end of the inner tube, providing one end of the pipe assembly. This protrusion has multiple uniformly distributed swirl blades, each configured such that one circumferential end of the axially protruding cylindrical side is pressed inward or outward toward the center of the pipe assembly, and the other circumferential end extends axially or is also pressed inward or outward toward the center of the pipe assembly, forming the swirl blade structure. This allows as much exhaust gas as possible to enter the pipe assembly, and the opening formed by the swirl blades is relatively large. While meeting the swirl requirements, the exhaust back pressure can be minimized, eliminating the need for structures with high exhaust back pressure, such as swirl cones or swirl porous structures. Attached Figure Description

[0017] The above and other features, properties and advantages of this application will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments. It should be noted that the drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of protection actually claimed by this application, wherein:

[0018] Figure 1 This is a schematic diagram of the structure of an exhaust gas after-treatment system according to one embodiment;

[0019] Figure 2 This is a schematic diagram of the mixer from an external perspective of one embodiment.

[0020] Figure 3 This is a structural schematic diagram of a mixer from an internal perspective of one embodiment.

[0021] Figure 4 This is a structural schematic diagram of the mixer from another internal perspective of one embodiment.

[0022] Figure 5 This is a structural schematic diagram of a mixer from another cross-sectional perspective of one embodiment.

[0023] Figure 6 This is a structural schematic diagram of the outer tube of a mixer according to an embodiment, viewed from the front.

[0024] Figure 7 This is a schematic diagram of the structure of the outer tube of a mixer according to one embodiment, viewed from an external perspective.

[0025] Figure 8 This is a schematic diagram of the structure of the outer tube of a mixer in one embodiment from another external perspective.

[0026] Figure 9 This is a side view of the outer tube of a mixer according to one embodiment.

[0027] Figure label:

[0028] 100-Exhaust Gas Aftertreatment System

[0029] 101-First Exhaust Gas Treatment Department

[0030] 102-Second Exhaust Gas Treatment Department

[0031] 10-Mixer

[0032] 20-Injector

[0033] 1-Lid

[0034] 11-Injection port

[0035] 2-Base

[0036] 21-Intake opening

[0037] 22-Exhaust opening

[0038] 3-Accommodation space

[0039] 31-Intake Area

[0040] 32-Vent Zone

[0041] 33-Middle Zone

[0042] 4-pipe assembly

[0043] 40-Mixed Space

[0044] The center of the O-tube assembly

[0045] 41-Inner tube

[0046] 42-Outer tube

[0047] 420-Ontology Department

[0048] 421-Protrusion

[0049] 422-Swirl Blade

[0050] 4221-Cylindrical side surface

[0051] 4222 - One end of the circumference

[0052] 4223 - The other end of the circumference

[0053] a-Extrusion Angle

[0054] 43-Bypass Channel

[0055] 44-Connecting bracket

[0056] One end of the 401-pipe assembly

[0057] The other end of the 402-pipe assembly

[0058] 5-Heat exchange element

[0059] 51-First axial length range

[0060] 52 - Second axial length range

[0061] 6-Flow guiding element

[0062] 61-Guide surface

[0063] 8-partition

[0064] 91-Temperature Sensor

[0065] 92 - Pressure sensor. Detailed Implementation

[0066] The following discloses various implementation methods or embodiments of the subject matter technical solutions. To simplify the disclosure, specific examples of the various elements and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of protection of this application.

[0067] It should be noted that in the following description, terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "one or more embodiments" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0068] The mixer and exhaust aftertreatment system described in this application are based on an automotive exhaust aftertreatment system, but other applications are not excluded. For example, they can be used in other vehicles or machinery, such as agricultural machinery, marine internal combustion engines, and train internal combustion engines. Any equipment that needs to treat nitrogen oxides may be able to use the mixer and exhaust aftertreatment system described in this application.

[0069] refer to Figure 1 As shown, in one embodiment, the exhaust gas aftertreatment system 100 can be a U-shaped structure, such as... Figure 1As shown, a first exhaust gas treatment unit 101 and a second exhaust gas treatment unit 102 are arranged in a generally parallel manner, and a mixer 10 is located between the first exhaust gas treatment unit 101 and the second exhaust gas treatment unit 102, connecting the two. The first exhaust gas treatment unit 101 is connected to the air inlet opening of the mixer 10 to provide exhaust gas into the mixer 10 from the air inlet opening 21. The second exhaust gas treatment unit 102 is connected to the air outlet opening 22 of the mixer 10, so that the mixed gas flow in the mixer 10 flows out to the second exhaust gas treatment unit 102. The component connected between the first exhaust gas treatment unit 101 and the mixer 10 can be a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), or a selective catalytic reduction reactor (SCR). The diesel oxidation catalyst and diesel particulate filter described above are conventional terms in this field, but are not limited to DOC and DPF, which are only applicable to diesel engine exhaust aftertreatment systems. Exhaust gas from the internal combustion engine sequentially passes through the diesel oxidation catalyst to treat unburned hydrocarbons and carbon monoxide, and the diesel particulate filter to treat particulate pollutants. It then enters the mixer 10, where it mixes with a reducing agent liquid sprayed by the injector 20, typically a urea solution. The mixed gas flow exits the mixer 10 to the second exhaust gas treatment section 102, and then enters the selective catalytic reduction reactor to undergo a reduction reaction, generating nitrogen and water to treat nitrogen oxides in the exhaust gas. It is understood that exhaust gas components are not limited to those described above; for example, in some exhaust aftertreatment systems, the particulate filter may be omitted.

[0070] refer to Figures 2 to 9 As shown, in some embodiments, the mixer 10 includes a cover 1, a base 2, and a tube assembly 4.

[0071] The cover 1 is provided with a spray nozzle 11, through which the reducing agent spray enters the mixer 10. The spray nozzle 11 can be provided with an injector mounting base 111 for mounting an injector 20. In some embodiments, such as... Figure 4 As shown, a sensor mounting base 90 can be installed on the cover 1, and a temperature sensor 91 and a pressure sensor 92 can be installed on the sensor mounting base 90. The collected data can be fed back to the control unit to better monitor the operation of the mixer and the exhaust gas system. The cover 1 generally also has a heat insulation cover 112 to further ensure the temperature inside the mixer 10. The cover 1 may also have a jet protector to protect the jet from interference from the exhaust gas swirling flow in the initial stage.

[0072] The cover 1 and the base 2 surround and define the accommodating space 3. The base 2 includes an air inlet 21 and an air outlet 22. The accommodating space 3 includes an air inlet area 31 corresponding to the air inlet 21, an air outlet area 32 corresponding to the air outlet 22, and an intermediate area 33 located between the two.

[0073] like Figure 5 As shown, in the extension direction of the pipe assembly 4, it extends from one end 401 of the pipe assembly located in the air intake zone 31 to the other end 402 of the pipe assembly located in the air outlet zone 32; the pipe assembly 4 includes an inner pipe 41 and an outer pipe 42, the outer pipe 42 being located radially outside the inner pipe 41, the inner pipe 41 providing a mixing space 40 for mixing the reducing agent and the exhaust gas, and the radial space between the outer pipe 42 and the inner pipe 41 providing a bypass channel 43 for the exhaust gas flow.

[0074] The inner tube 41 and the outer tube 42 can be connected by welding through the connecting bracket 44, but this is not a limitation.

[0075] like Figures 6 to 9 As shown, the outer tube 42 includes a body portion 420 and a protrusion 421. The protrusion 421 protrudes from the body portion 420 beyond one axial end of the inner tube 41, such that the protrusion 421 provides one end 401 of the tube assembly. The protrusion 421 has a plurality of evenly distributed swirl blades 422, each swirl blade 422 being configured such that one circumferential end 4222 of the axially protruding cylindrical side 4221 is pressed inward toward the center O of the tube assembly, and the other circumferential end 4223 extends axially or is also pressed inward toward the center O of the tube assembly, forming the swirl blade 422. It can be understood that... Figures 6 to 9 In the embodiment shown, the swirl blade 422 is structured such that one circumferential end 4222 is pressed inward toward the center O of the tube assembly, and the other circumferential end 4223 extends along the axial direction. This process is relatively simple. However, for different swirl effects and exhaust back pressure requirements, the circumferential end 4222 can be pressed outward toward the center O of the tube assembly, or the other circumferential end 4223 can be pressed inward or outward toward the center O of the tube assembly. This is not a limitation.

[0076] like Figures 5 to 9 As shown, in some embodiments, the protrusion 421 has 2 to 8 evenly distributed swirl blades 422, i.e., not... Figures 6 to 8 The four swirling blades 422 shown are circumferentially evenly distributed and can be adjusted according to the requirements of back pressure and swirling mixing effect (airflow uniformity, ammonia uniformity). The inventors found that too many swirling blades would make the swirling effect too strong and the back pressure too large.

[0077] Furthermore, it can be understood that the swirl blades formed by the axially protruding cylindrical side 4221, one circumferential end 4222 pressing inward or outward toward the center O of the tube assembly, and the other circumferential end 4223 extending axially or also pressing inward or outward toward the center O of the tube assembly, are generally integrally formed with the body 420. This avoids the welding process required by using a separate swirl cone to set the swirl blades in some comparative solutions, as well as the need to consider the machining error and assembly error of the swirl cone, further simplifying the processing and manufacturing of the mixer.

[0078] like Figure 6 As shown, in some embodiments, for each swirl vane 422, the circumferential end 4223 is pressed inward or outward at an angle α toward the tube assembly 4 of 30° to 60°. The inventors have found that within the above angle range of 30° to 60°, the reduction effect on exhaust back pressure is significant. Outside this angle range, whether less than 30° or greater than 60°, the reduction effect on exhaust back pressure is weakened, which is unfavorable for applications with stringent requirements for exhaust back pressure.

[0079] Continue to refer to Figure 5 As shown, in some embodiments, the specific structure of the pipe assembly 4 may be that both the inner pipe 41 and the body portion 420 of the outer pipe are straight pipes. At the other end 402 of the pipe assembly, the inner pipe 41 protrudes axially from the body portion 420 to provide the other end 402. This allows the exhaust gas flowing out from the bypass channel 43 to have more space to fully mix and contact with the mixed airflow of exhaust gas and reducing agent discharged from the inner pipe 41, further improving the mixing uniformity of the airflow.

[0080] The beneficial effect of this is that it allows as much exhaust gas as possible to enter the pipe assembly, and the opening formed by the swirl blades is relatively large. Under the premise of meeting the swirl requirements, the exhaust back pressure can be reduced as much as possible. In addition, there is no need to use structures with high exhaust back pressure, such as swirl cones and swirl porous structures.

[0081] like Figure 5As shown, in some embodiments, a heat exchange element 5 is provided in the bypass channel 43, and the heat exchange element 5 is axially located downstream of the protrusion 421. Preferably, the heat exchange element 5 has a first axial length range 51 and a second axial length range 52, the first axial length range 51 being located in the inlet zone 31 and the second axial length range 52 being located in the outlet zone 32, and the axial length of the first axial length range 51 being greater than that of the second axial length range 52. In some embodiments, the heat exchange element 5 comprises a foamed metal material. This allows the heat of the exhaust gas to heat the urea droplets on the inner wall of the pipe assembly 4, causing them to decompose in a timely manner and reducing urea crystallization. The heat exchange element 5 can be made of foamed metal, which can further optimize the effect of reducing urea crystallization. The material can be common foamed metal materials such as foamed aluminum, foamed nickel, foamed titanium, and foamed stainless steel, and is not limited thereto. By using foamed metal, more heat from the waste gas in the bypass channel 43 is retained, thus allowing droplets of reducing agent spray, such as urea spray, adhering to the inner wall of the pipe assembly 4 to be decomposed in a timely manner, preventing droplet accumulation or even liquid film formation, thereby reducing the risk of urea crystallization. In some embodiments, a wavy structure extending axially can also be used on the outer wall of the inner pipe 41, allowing the heat exchange element 5 to be directly machined on the outer wall of the inner pipe 41, resulting in lower costs.

[0082] Continue to refer to Figure 5 As shown, in some embodiments, the body portion 420 of the outer tube has a first through hole 423 penetrating the tube wall. The first through hole 423 is located upstream of the heat exchange element 5, and the axial distance between the first through hole 423 and the heat exchange element 5 is 8 mm to 20 mm. This can further improve the heating effect of the bypass channel 43 and the heat exchange element 5 on the inner tube 41, and further reduce the risk of urea crystallization. Alternatively, a second through hole 424 penetrating the tube wall can be opened in the body portion 420 at the position of the gas outlet zone 32. The second through hole 424 can be close to the other end 402, which can further optimize the uniformity of the mixed gas flow.

[0083] refer to Figures 2 to 5As shown, in some embodiments, the mixer 10 may further include a baffle 8 separating the intake zone 31 and the exhaust zone 32, and the pipe assembly 4 passes through the baffle 8, making the pipe assembly 4 the only or main channel connecting the intake zone 31 and the exhaust zone 32. Here, "main channel" means that the vast majority of exhaust gas passes through the pipe assembly 4 from the intake zone 31 to the exhaust zone 32. However, in some cases, small holes may be made in the baffle 8 to reduce exhaust back pressure, but the area of ​​the holes is much smaller than the area of ​​the baffle 8 itself, so the vast majority of exhaust gas still passes through the pipe assembly. "Only channel" means that except for a very small percentage of exhaust gas flowing through the connection gaps of the baffle 8, the remaining exhaust gas passes through the pipe assembly 4 from the intake zone 31 to the exhaust zone 32.

[0084] Additionally, please continue to refer to Figure 5 As shown, in some embodiments, the mixer 10 may further include a flow guiding element 6 disposed in the air outlet region 32 and adjacent to the downstream end 402. The radial dimension covered by the flow guiding element 6 is larger than the radial dimension of the other end 402. The flow guiding element 6 provides a flow guiding surface 61, the extension of which allows the airflow output from the other end 402 to be guided along the flow guiding surface 61. The provided flow guiding path includes: the airflow output from the other end 402 flowing along the flow guiding surface 61 in a first direction, then flowing along the flow boundary defined by the cover 1, and then flowing in a second direction to the air outlet opening 22; the first direction and the second direction are opposite, for example, the first direction is upward and the second direction is downward, but this is not a limitation. The minimum distance W between the flow guiding surface 61 and the other end 402 is at least 10 mm, that is, the distance between the end of the flow guiding surface 61 near the other end 402 and the other end 402 is at least 10 mm. The flow guiding surface 61 has a structure symmetrical about the axis of the tube assembly 4. The inventors discovered that if the minimum spacing W is less than 10 mm, the ammonia uniformity will not meet the requirements. For example, in the comparative example, the minimum spacing W between the guide surface 61 and the other end 402 is almost zero, resulting in unsatisfactory ammonia uniformity. Alternatively, the guide element 6 can be omitted. Although this is not as efficient as using the guide element 6, it can reduce exhaust back pressure and meet different needs. It is understood that this has the advantage of further extending the mixing path of the mixed airflow discharged from the other end 402, further optimizing the mixing effect. In some embodiments, the guide element 6 is a structure symmetrical about the axis of the pipe assembly 4, such as the "ω"-shaped structure shown in the figure. This allows the mixed airflow to be divided into two more uniform swirling streams, further optimizing the mixing effect.

[0085] In summary, the beneficial effects of the mixer and exhaust gas aftertreatment system described in the above embodiments include, but are not limited to, minimizing exhaust back pressure while ensuring the uniformity of the mixture of exhaust gas and urea. The principle likely lies in the fact that the main body 420 protrudes beyond one axial end of the inner tube 41, providing one end 401 of the pipe assembly. The protruding part 421 has multiple evenly distributed swirl blades 422. Each swirl blade 422 is configured such that one circumferential end 4222 of the axially protruding cylindrical side 4221 is pressed inward or outward toward the center of the pipe assembly, and the other circumferential end 4223 extends axially or is also pressed inward or outward toward the center of the pipe assembly, forming a swirl blade 422 structure. This allows as much exhaust gas as possible to enter the pipe assembly, and the opening formed by the swirl blades is relatively large. While meeting the swirl requirements, the exhaust back pressure can be minimized, eliminating the need for structures with high exhaust back pressure, such as swirl cones or swirl porous structures.

[0086] While this application discloses the above embodiments, it is not intended to limit the scope of this application. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this application. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall fall within the protection scope defined by the claims of this application.

Claims

1. A mixer (10) for an exhaust gas aftertreatment system (100), characterized in that, include: The cover (1) is provided with a spray nozzle (11), and the reducing agent spray enters the mixer (10) from the spray nozzle (11); The base (2) and the cover (1) surround and define the accommodating space (3). The base (2) includes an air inlet (21) and an air outlet (22). The accommodating space (3) includes an air inlet area (31) corresponding to the air inlet (21), an air outlet area (32) corresponding to the air outlet (22), and an intermediate area (33) located between the two. The pipe assembly (4) extends in the extending direction from one end (401) of the pipe assembly located in the air intake area (31) to the other end (402) of the pipe assembly located in the air outlet area (32); the pipe assembly (4) includes an inner pipe (41) and an outer pipe (42), the outer pipe (42) being located radially outside the inner pipe (41), the inner pipe (41) providing a mixing space (40) for mixing the reducing agent and the exhaust gas, and the radial space between the outer pipe (42) and the inner pipe (41) providing a bypass channel (43) for the exhaust gas flow. The outer tube (42) includes a body portion (420) and a protruding portion (421), the protruding portion (421) protruding from the body portion (420) beyond one axial end of the inner tube (41), such that the protruding portion (421) provides one end (401) of the tube assembly; wherein the protruding portion (421) has a plurality of uniformly distributed swirl blades (422), each swirl blade (422) being configured such that one circumferential end (4222) of the axially protruding cylindrical side surface (4221) is pressed inward or outward toward the center (O) of the tube assembly, and the other circumferential end (4223) extends axially or is also pressed inward or outward toward the center (O) of the tube assembly, forming the swirl blade (422).

2. The mixer (10) of claim 1, wherein The protrusion (421) has 2 to 8 evenly distributed swirl blades (422); The swirl blade (422) is integrally connected to the body (420).

3. The mixer (10) of claim 1, wherein, For each swirl blade (422), the circumferential end (4223) is squeezed inward or outward at an angle (a) of 30° to 60° toward the center (O) of the tube assembly.

4. The mixer (10) of claim 1, wherein, It also includes a heat exchange element (5) disposed in the bypass channel (43), the heat exchange element (5) being located axially downstream of the protrusion (421).

5. The mixer (10) as claimed in claim 4, characterized in that The body part (420) of the outer tube has a first through hole (423) that penetrates the tube wall. The first through hole (423) is located upstream of the heat exchange element (5). The axial distance between the first through hole (423) and the heat exchange element (5) is 8 mm to 20 mm. The heat exchange element (5) has a first axial length range (51) and a second axial length range (52). The first axial length range (51) is located in the air inlet area (31), and the second axial length range (52) is located in the air outlet area (32). The axial length of the first axial length range (51) is greater than that of the second axial length range (52). The heat exchange element (5) includes foamed metal material or a wavy structure extending axially on the outer wall of the inner tube (41).

6. The mixer (10) of claim 1, wherein, Both the inner tube (41) and the body portion (420) of the outer tube are straight tubes. At the other end (402) of the tube assembly, the inner tube (41) protrudes axially from the body portion (420) to provide the other end (402).

7. The mixer (10) of claim 1, wherein, It also includes a flow guiding element (6) disposed in the air outlet area (32) and adjacent to the other end (402) downstream. The radial dimension covered by the flow guiding element (6) is larger than the radial dimension of the other end (402). The flow guiding element (6) provides a flow guiding surface (61). The extension of the flow guiding surface (61) allows the airflow output from the other end (402) to be guided along the flow guiding surface (61). The provided flow guiding path includes: the airflow output from the other end (402) flowing along the flow guiding surface (61) in a first direction, then flowing along a flow boundary defined by the cover (1), and then flowing in a second direction to the air outlet opening (22); the first direction is opposite to the second direction; the minimum distance (W) between the flow guiding surface (61) and the other end (402) is at least 10 mm; the flow guiding surface (61) has a structure symmetrical about the axis of the tube assembly (4). Alternatively, the mixer may not have a flow guide element (6) in the outlet zone (32).

8. The mixer (10) of claim 1, wherein, It also includes a partition (8) that separates the air intake area (31) and the air outlet area (32), and the pipe assembly (4) passes through the partition (8), so that the pipe assembly (4) is the only or main channel connecting the air intake area (31) and the air outlet area (32).

9. An exhaust gas aftertreatment system (100), characterized by include: The mixer (10) as described in any one of claims 1-8, and the injector (20), the injector (20) being capable of spraying a reducing agent liquid into the pipe assembly (4) of the mixer (10) to form a reducing agent spray, so that the exhaust gas and the reducing agent are mixed in the mixing space (40).

10. The exhaust gas aftertreatment system (100) of claim 9, characterized in that The exhaust gas aftertreatment system (100) further includes a first exhaust gas treatment unit (101) and a second exhaust gas treatment unit (102). The first exhaust gas treatment unit (101) is connected to the air inlet (21) of the mixer (10) to provide exhaust gas to enter the mixer (10) from the air inlet (21). The second exhaust gas treatment unit (102) is connected to the air outlet (22) of the mixer (10) so that the gas flow mixed in the mixer (10) flows out to the second exhaust gas treatment unit (102). The diesel particulate filter or diesel oxidation catalyst of the first exhaust gas treatment unit (101) is connected to the mixer (10), and the selective catalytic reduction reactor of the second exhaust gas treatment unit (102) is connected to the mixer (10). The reducing agent is a urea solution.

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