An exhaust gas aftertreatment device

Abstract

The application discloses a tail gas aftertreatment device, which comprises a selective catalytic oxidizer, a particle trap, a mixer and a selective catalytic reducer arranged in sequence along an axial direction, wherein the mixer comprises a mixing cylinder and a flow guide plate, and an inside of the mixing cylinder is formed with a mixing cavity; a rear air inlet part of the mixing cylinder is inwardly recessed, two sides of the rear air inlet part are symmetrical arc-shaped cylinder walls, the rear air inlet part is provided with a rear air inlet hole, and the two arc-shaped cylinder walls are respectively provided with a left air inlet hole and a right air inlet hole; the flow guide plate is arc-shaped and located at a rear side of the rear air inlet hole, and an arc-shaped channel is formed between the flow guide plate and the mixing cylinder and leads to the left air inlet hole, the right air inlet hole and the rear air inlet hole from a front side. The device can make the reducing agent and the exhaust gas fully mix, evaporate and decompose, and improve the mixing uniformity and the anti-crystallization performance.

Description

Technical Field

[0001] This invention relates to the field of diesel engine technology, and in particular to exhaust aftertreatment devices in diesel engine exhaust systems. Background Technology

[0002] The basic principle of SCR (Selective Catalytic Reduction) technology is to inject fuel or add other reducing agents into the exhaust gas, select a suitable catalyst, promote the reaction between the reducing agent and NOx, and at the same time inhibit the oxidation of the reducing agent by oxygen in the exhaust gas. In practice, urea is often chosen as the reducing agent.

[0003] During vehicle operation, due to poor urea atomization, uneven mixing, or insufficient decomposition, the sprayed urea droplets cannot be converted into NH3 in real time, but instead generate byproducts, leading to unstable reduction reactions and affecting the consistency and conversion efficiency of NOx emissions.

[0004] Urea deposits can be classified into urea crystals and urea stones based on their formation process. Urea crystals are formed when the urea solution becomes supersaturated due to the loss of water from the urea solution, resulting in the precipitation of urea. They are products of a physical reaction process and can continue to decompose as the temperature rises. Urea stones, on the other hand, are byproducts of side reactions during the decomposition of urea. They are products of a chemical reaction and require higher temperatures to decompose.

[0005] Because urea droplets are much larger than gas, crystals formed in areas where airflow is stagnant will continue to grow as nuclei if they cannot be completely decomposed in time. Due to the incomplete decomposition, they eventually form urea crystal stones, which may block the urea flow channels if they accumulate to a certain extent.

[0006] Currently, most SCR system mixing devices are of the non-swirling or single-swirling type, such as the exhaust gas aftertreatment device disclosed in CN 110056414A, which includes a first aftertreatment carrier assembly, a second aftertreatment carrier assembly, and a mixer assembly. The mixer assembly includes a housing, a mixing pipe located inside the housing, and a partition. The partition divides the housing into a first space and a second space. The mixing pipe includes a first pipe section located in the first space and a second pipe section located in the second space. The first pipe section has at least two first openings located on its two sides. The exhaust gas aftertreatment device also covers the front end of the first opening with a first shield and a second shield.

[0007] When airflow passes through such a mixing device, multiple airflows mix and concentrate in a local area, which can easily lead to urea crystallization and poor uniformity, while also resulting in high pressure loss. Summary of the Invention

[0008] The purpose of this invention is to provide an exhaust gas aftertreatment device. The mixer of this treatment device can fully mix, evaporate, and decompose the reducing agent with the exhaust gas, and improve the mixing uniformity and anti-crystallization performance.

[0009] To achieve the above objectives, the present invention provides an exhaust gas aftertreatment device, comprising a selective catalytic oxidizer, a particulate filter, a mixer, and a selective catalytic reducer arranged sequentially along the axial direction. The mixer includes a mixing cylinder and a guide plate, and the interior of the mixing cylinder forms a mixing chamber. The rear side of the mixing cylinder has an inwardly recessed rear air intake portion, and the two sides of the rear air intake portion are symmetrical arc-shaped cylinder walls. The rear air intake portion is provided with a rear air intake hole, and the two arc-shaped cylinder walls are respectively provided with a left air intake hole and a right air intake hole. The guide plate is arc-shaped and located behind the rear air intake hole, and an arc-shaped channel is formed between the guide plate and the mixing cylinder, leading from the front side to the left and right air intake holes and the rear air intake hole.

[0010] Optionally, the mixing cylinder is provided with an inlet vent on its front side.

[0011] Optionally, the bottom of the mixing cylinder and the flow guide plate is provided with a hollow partition, and a flow guide plate is provided below the hollow partition. The flow guide plate has an arc-shaped part that arches in the direction of the incoming airflow and side wing parts located on both sides of the arc-shaped part.

[0012] Optionally, a flow equalization plate is arranged on the rear side of the flow diversion plate, and the flow equalization plate is provided with a Y-shaped rectification structure.

[0013] Optionally, the flow equalization plate is circular, and the Y-shaped rectification structure includes a Y-shaped non-conducting region located in the center, with multiple concentric arc-shaped elongated holes symmetrically distributed on both sides of the Y-shaped non-conducting region.

[0014] Optionally, the front air inlet of the mixing cylinder is a plurality of vertical elongated holes or a dot-matrix distributed circular holes; and / or, the rear air inlet of the mixing cylinder is a vertical planar part, and the rear air inlet thereon is a plurality of vertical elongated holes, and the left air inlet and right air inlet are dot-matrix distributed circular holes.

[0015] Optionally, it also includes a gas sampling component, which is disposed in the conical section of the gas outlet end of the selective catalytic reducer.

[0016] Optionally, the gas intake assembly includes a gas mixing section and a gas intake pipe. The gas mixing section is located on the side wall of the conical section. The gas intake pipe includes a main gas intake pipe and at least two branch gas intake pipes. The main gas intake pipe extends radially from the gas mixing section to the central region of the conical section. The branch gas intake pipes extend radially from the central region to the side wall. Both the main gas intake pipe and the branch gas intake pipes are provided with gas intake holes.

[0017] Optionally, the main air intake tube and the branch air intake tubes are evenly distributed in the circumferential direction, and the end of each branch air intake tube is supported by a support foot on the side wall of the conical section.

[0018] Optionally, an arc-shaped air intake pipe is provided between every two adjacent branch air intake pipes, and the arc-shaped air intake pipe is provided with the air intake hole.

[0019] When the exhaust gas aftertreatment device provided by this invention is in operation, part of the airflow enters the mixing chamber from the inlet of the mixing cylinder, and the other part of the airflow enters the mixing chamber from the rear inlet, left inlet and right inlet through the arc-shaped channel formed by the mixing cylinder and the guide plate. They converge to generate two opposing vortices. At the same time, urea enters the mixing chamber from the urea nozzle in the direction perpendicular to the airflow. After being fully mixed with the exhaust gas, it enters the evaporator. The evaporator further mixes the urea droplets and exhaust gas, and accelerates the breaking and evaporation of the urea droplets to form NH3. Compared with the single swirling structure, by forming two opposing swirling flow fields in the direction perpendicular to the airflow, the problem of urea being blown off course can be greatly reduced, ensuring that the urea jet falls centered on the surface of the evaporator, thereby achieving the purpose of resisting urea crystallization. Compared with similar products, the mixing effect is higher, the anti-crystallization ability is stronger, and the uniformity of ammonia distribution is greatly improved, which can effectively reduce pressure loss.

[0020] In a preferred embodiment, the gas sampling component is located in the conical section of the selective catalytic reducer outlet. Compared to arranging it in the straight section, the entire device occupies less space and is more compact in the axial direction. Moreover, the gas sampling component with a multi-branch gas sampling structure increases the gas sampling area. By distributing different gas sampling holes in the gas sampling pipe, NOx at most locations of the cross-section can be extracted in a reasonable manner, effectively improving the measurement accuracy of the NOx sensor. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an exhaust gas aftertreatment device provided in an embodiment of the present invention.

[0022] Figure 2 for Figure 1 A schematic diagram of the mixer described in the figure;

[0023] Figure 3 This is a schematic diagram of another type of mixer;

[0024] Figure 4 for Figure 1 The diagram shows the structure of the gas extraction component.

[0025] In the picture:

[0026] 10. Selective catalytic oxidizer 20. Particulate trap 30. Mixer 31. Mixing cylinder 311. Rear air inlet section 312. Arc-shaped cylinder wall 313. Rear air inlet port 314. Left air inlet port 315. Right air inlet port 316. Front air inlet port 32. Flow guide plate 33. Guide plate 331. Arc-shaped section 332. Side wing section 34. Flow equalization plate 341. Y-shaped non-conducting area 342. Arc-shaped elongated hole 35. Hollow partition 40. Selective catalytic reduction unit 41. SCR carrier 42. Conical section 50. Gas intake assembly 51. Gas intake mixing section 52. Main gas intake pipe 53. Branch gas intake pipe 54. Arc-shaped gas intake pipe 55. Support leg 56. Gas intake port Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] In this document, terms such as "upper," "lower," "inner," and "outer" are established based on the positional relationships shown in the accompanying drawings. Depending on the drawings, the corresponding positional relationships may also change. Therefore, they should not be interpreted as an absolute limitation on the scope of protection. Moreover, relational terms such as "first" and "second" are only used to distinguish one component from another that has the same name, and do not necessarily require or imply any such actual relationship or order between these components.

[0029] Please refer to Figure 1 , Figure 2 , Figure 1 This is a schematic diagram of the structure of an exhaust gas aftertreatment device provided in an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the mixer described in the figure.

[0030] As shown in the figure, in one specific embodiment, the exhaust gas aftertreatment device provided by the present invention mainly consists of a selective catalytic oxidizer 10, a particulate filter 20, a mixer 30, and a selective catalytic reducer 40. The above components are arranged sequentially along the axial direction. During operation, the engine exhaust gas flows sequentially through the selective catalytic oxidizer 10, the particulate filter 20, the mixer 30, and the selective catalytic reducer 40 to complete the treatment of the exhaust gas and make the exhaust gas emissions meet environmental protection requirements.

[0031] Specifically, the mixer 30 is mainly composed of a mixing cylinder 31, a flow guide plate 32, a flow guide plate 33, and a flow equalization plate 34. The mixing cylinder 31 is a circumferentially closed sleeve shape, and a mixing chamber is formed inside it. The rear side of the mixing cylinder 31 has an inwardly recessed rear air intake part 311. The rear air intake part 311 is a vertical planar part. The two sides of the rear air intake part 311 are symmetrical arc-shaped cylinder walls 312. The rear air intake part 311 is provided with a rear air intake hole 313. The two arc-shaped cylinder walls 312 are respectively provided with a left air intake hole 314 and a right air intake hole 315.

[0032] The rear air intake 313 consists of several vertical elongated holes, with two sets of elongated holes located on the upper and lower halves of the rear side of the mixing cylinder 31, respectively.

[0033] The mixing cylinder 31 has a front air inlet 316, which can be a vertical elongated hole or a dot-matrix of circular holes. The rear air inlet 313 on the rear air inlet 311 can be a vertical elongated hole, and the left air inlet 314 and right air inlet 315 are dot-matrix of circular holes. By combining different hole types, multiple different embodiments can be obtained. For example, the front air inlet 316 is an elongated hole, the rear air inlet 313 is an elongated hole, and the left air inlet 314 and right air inlet 315 are circular holes; or, the front air inlet 316 is a circular hole, the rear air inlet 313 is an elongated hole, and the left air inlet 314 and right air inlet 315 are circular holes, and so on.

[0034] In this embodiment, the rear air inlet 313 is a number of vertical elongated holes, and the two sets of elongated holes are located in the upper and lower parts of the rear side of the mixing cylinder 31, respectively.

[0035] The left air inlet 314 and the right air inlet 315 are circular holes distributed in a dot matrix, and the front air inlet 316 is a number of vertical elongated holes. The two sets of elongated holes are located in the upper and lower parts of the front side of the mixing cylinder 31, respectively.

[0036] The inlet vent 316 consists of several vertical elongated holes, with two sets of elongated holes located in the upper and lower halves of the front side of the mixing cylinder 31, respectively.

[0037] The guide plate 32 is arc-shaped and located behind the rear air inlet 313. The guide plate 32 and the mixing cylinder 31 form an arc-shaped channel from the front to the left and right air inlets 314, 315 and 313. The airflow can enter the mixing chamber through the front air inlet 316, 314 and 315 and the rear air inlet 313. When the airflow passes through the mixing chamber, it can rotate at high speed under the action of the two arc-shaped cylinder walls 312 of the mixing cylinder 31, generating two opposing vortices.

[0038] This special flow guiding structure can rationally distribute the airflow to ensure that the airflow forms two symmetrically distributed vortices after passing through the flow channel, ensuring that the urea jet falls centered on the surface of the evaporator (e.g., steel wool), significantly enhancing the mixing ability of urea with waste gas and its anti-crystallization ability.

[0039] The bottom of the mixing cylinder 31 and the guide plate 32 is provided with a hollow baffle 35, and a guide plate 33 is provided below the hollow baffle 35. An evaporator, such as steel wool, can be installed below the hollow baffle 35 and located behind the guide plate.

[0040] The deflector 33 has an arc-shaped portion 331 that arches in the direction of the airflow and side wing portions 332 located on both sides of the arc-shaped portion.

[0041] The front edge of the guide plate 32 is flared outwards, corresponding to the side wing portion 332 of the guide plate 33. The projections of the mixing cylinder 31, the guide plate 32, and the guide plate 33 in the axial direction have a circular outer contour as a whole, which facilitates encapsulation inside the cylindrical component. After encapsulation, it is more compact in the axial length direction, requires less space, and has a more compact structure. Of course, it can also be designed into other shapes depending on the external components.

[0042] A flow equalization plate 34 is arranged on the rear side of the flow guide plate 32. The flow equalization plate 34 is circular and has a Y-shaped rectification structure on it. The Y-shaped rectification structure has a Y-shaped non-conducting area 341 located in the center, and multiple concentric arc-shaped elongated holes 342 symmetrically distributed on both sides of the Y-shaped non-conducting area 341.

[0043] The Y-shaped rectification structure of the flow equalization plate 34 can improve the uniformity of urea and exhaust gas distribution after SCR. By controlling the gas flow rate through different opening forms and sizes, the NOx and urea distribution can be made more uniform, thereby improving the post-treatment conversion efficiency.

[0044] Please refer to this as well. Figure 4 , Figure 4 for Figure 1 The diagram shows the structure of the gas extraction component.

[0045] As shown in the figure, the gas intake assembly 50 is located in the conical section 42 at the gas outlet of the selective catalytic reducer 40, and mainly consists of a gas intake mixing section 51 and a gas intake pipe.

[0046] The gas mixing section 51 is fixed to the side wall of the conical section 42. The gas intake pipe is divided into a main gas intake pipe 52 and at least two branch gas intake pipes 53. The main gas intake pipe 52 extends radially from the gas mixing section 51 to the central region, and the branch gas intake pipes 53 extend radially from the central region to the side wall. The main gas intake pipe 52 and the branch gas intake pipes 53 are evenly distributed in the circumferential direction. An arc-shaped gas intake pipe 54 is provided between the branch gas intake pipes 53. The end of the branch gas intake pipe 53 is supported on the inner wall of the conical section 42 by a support foot 55. The main gas intake pipe 52, the branch gas intake pipe 53 and the arc-shaped gas intake pipe 54 are provided with gas intake holes 56.

[0047] By placing the gas sampling assembly 50 in the conical section 42 at the outlet of the selective catalytic reducer 40, the entire device occupies less space and is more compact in the axial direction compared to arranging it in the straight section. Moreover, the gas sampling assembly with a multi-branch gas sampling structure increases the gas sampling area. Through the distribution of different gas sampling holes 56 in the gas sampling pipe, NOx at most locations of the cross section can be reasonably extracted, effectively improving the measurement accuracy of the NOx sensor.

[0048] During operation, after the airflow reaches the mixer 30, part of the airflow enters the mixing chamber through the inlet 316 of the mixing cylinder 31, while the other part flows along the arc-shaped channels on both sides of the mixing cylinder 31 to the rear, and then enters the mixing chamber through the rear inlet 313, the left inlet 314, and the right inlet 315. Under the combined action of the mixing cylinder 31, the guide plate 32, and the guide plate 33, the mixture can rotate at high speed, forming two opposing swirling flows. Under the action of the swirling flows, the reducing agent droplets have sufficient time and conditions to fully mix with the waste gas in the mixing space. After the airflow passes downward through the evaporator, the urea and waste gas mixture undergoes further turbulence and evaporation. To further increase the mixing degree of various gases, improve the efficiency of urea gasification and conversion, and enhance the uniformity of airflow mixing, the mixed gas after being mixed in the evaporator enters the lower space of the hollow partition 35 and is then introduced downstream into the flow equalization plate 34. The flow equalization plate 34 is adjusted according to the different displacements of the engine to maintain its distance from the mixing pipe. After passing through different holes in the flow equalization plate 34, the mixed gas can be evenly distributed in front of the SCR carrier, improving the uniformity of NH3 mixing before SCR and preventing engine emissions from exceeding limits. Since the urea jet will not be blown off course and cause liquid film accumulation, it can effectively reduce crystallization and improve the uniformity of ammonia distribution. After the mixed gas passes through the SCR carrier, the remaining unreacted NOx gas enters the gas intake pipe through the gas intake hole 56 and then converges into the gas intake mixing section 51, where the NOx sensor further measures the concentration of NO / NO2 and other nitrogen oxides in the exhaust gas.

[0049] The above embodiments are merely preferred embodiments of the present invention and are not limited thereto. Based on these, targeted adjustments can be made according to actual needs to obtain different implementation methods. For example, the inlet vent 316 of the mixing cylinder 31 is a dot-matrix distributed circular vent (see...). Figure 3 Alternatively, air vents can be made in the arc-shaped portion 331 and the side wing portion 332 of the deflector 33, etc. Since there are many possible ways to achieve this, they will not be listed here.

[0050] The exhaust gas aftertreatment device provided by this invention enables the exhaust gas emitted by the engine to be fully mixed with the ammonia generated from the decomposition of urea in a mixing device. Under the high temperature of the exhaust gas, catalytic conversion occurs in the SCR chamber, thus purifying the exhaust gas. The mixing cylinder 31, the guide plate 32, the deflector plate 33, and the flow equalization plate 34 work together to achieve a much greater effect than each component alone, maximizing their respective functions. This ensures thorough mixing and rotation of the passing airflow, improving conversion efficiency and reducing the risk of urea crystallization. Furthermore, the uniformity of ammonia distribution is significantly improved. In addition, it has advantages such as compact structure, convenient manufacturing process, and lower cost.

[0051] The exhaust gas aftertreatment device provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A tail gas aftertreatment device, comprising a selective catalytic oxidizer (10), a particulate filter (20), a mixer (30), and a selective catalytic reducer (40) arranged sequentially along the axial direction, characterized in that, The mixer (30) includes a mixing cylinder (31) and a guide plate (32). The mixing cylinder (31) forms a mixing chamber inside. The mixing cylinder (31) has an inwardly recessed rear air intake portion (311) on its rear side. The two sides of the rear air intake portion (311) are symmetrical arc-shaped cylinder walls (312). The rear air intake portion (311) is provided with a rear air intake hole (313). The two arc-shaped cylinder walls (312) are respectively provided with a left air intake hole (314) and a right air intake hole (315). The guide plate (32) is arc-shaped and located behind the rear air intake hole (313). 2) An arc-shaped channel is formed between the mixing cylinder (31) and the mixing cylinder (31), leading from the front side to the left air inlet (314), the right air inlet (315) and the rear air inlet (313); the mixing cylinder (31) is provided with a front air inlet (316) on the front side. When the airflow reaches the mixer (30), part of the airflow enters the mixing chamber from the front air inlet (316) of the mixing cylinder (31), and the other part flows from both sides of the mixing cylinder (31) along the arc-shaped channel to the rear side, and then enters the mixing chamber from the rear air inlet (313), the left air inlet (314) and the right air inlet (315), forming two opposing swirling flows.

2. The exhaust gas aftertreatment device according to claim 1, characterized in that, The bottom of the mixing cylinder (31) and the flow guide plate (32) is provided with a hollow partition plate (35), and a flow guide plate (33) is provided below the hollow partition plate (35). The flow guide plate (33) has an arc-shaped part (331) that arches in the direction of the airflow and side wing parts (332) located on both sides of the arc-shaped part.

3. The exhaust gas aftertreatment device according to claim 1, characterized in that, A flow equalization plate (34) is arranged on the rear side of the flow equalization plate (32), and a Y-shaped rectification structure is provided on the flow equalization plate (34).

4. The exhaust gas aftertreatment device according to claim 3, characterized in that, The flow equalization plate (34) is circular, and the Y-shaped rectification structure includes a Y-shaped non-conducting region (341) located in the center. On both sides of the Y-shaped non-conducting region (341) are multiple concentric arc-shaped elongated holes (342) symmetrically distributed.

5. The exhaust gas aftertreatment device according to claim 1, characterized in that, The front air inlet (316) of the mixing cylinder (31) is a plurality of vertical elongated holes or dot-matrix distributed circular holes; and / or, the rear air inlet (311) of the mixing cylinder (31) is a vertical planar part, and the rear air inlet (313) thereon is a plurality of vertical elongated holes, and the left air inlet (314) and right air inlet (315) are dot-matrix distributed circular holes.

6. The exhaust gas aftertreatment device according to any one of claims 1 to 5, characterized in that, It also includes a gas intake assembly (50), which is located at the conical section (42) of the gas outlet of the selective catalytic reducer (40).

7. The exhaust gas aftertreatment device according to claim 6, characterized in that, The gas intake assembly (50) includes a gas intake mixing section (51) and a gas intake pipe. The gas intake mixing section (51) is located on the side wall of the conical section (42). The gas intake pipe includes a main gas intake pipe (52) and at least two branch gas intake pipes (53). The main gas intake pipe (52) extends radially from the gas intake mixing section (51) to the central region of the conical section (42). The branch gas intake pipes (53) extend radially from the central region to the side wall. Both the main gas intake pipe (52) and the branch gas intake pipes (53) are provided with gas intake holes (56).

8. The exhaust gas aftertreatment device according to claim 7, characterized in that, The main air intake tube (52) and the branch air intake tubes (53) are evenly distributed in the circumferential direction, and the end of each branch air intake tube (53) is supported by a foot (55) on the inner wall of the conical section (42).

9. The exhaust gas aftertreatment device according to claim 8, characterized in that, An arc-shaped air intake pipe (54) is provided between every two adjacent branch air intake pipes (53), and the arc-shaped air intake pipe (54) is provided with the air intake hole (56).

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