Urea mixing structure and urea mixer

Abstract

The utility model relates to the technical field of diesel engine tail gas treatment, in particular to a urea mixing structure and a urea mixer. The inner fixing pipe is arranged on the inner side of the outer fixing pipe, a first channel is formed between the outer fixing pipe and the inner fixing pipe, and a second channel is formed on the inner side of the inner fixing pipe; and the outer-layer blade is arranged in the first channel. The urea mixing structure comprises the annular first channel located on the outer layer and the circular second channel located on the inner layer, a rotational flow structure is arranged in the first channel, and the guide vanes in the second channel increase the area of a front contact part, so that airflow can stably pass through, the risks of backflow, liquid film formation and crystallization are reduced, and the service life of the urea mixing structure is prolonged. The urea crushing and decomposing effect is improved, the urea mixing path is increased, liquid urea is prevented from being accumulated on the mixer and the downflow pipe wall of the mixer, urea crystallization is effectively eliminated, and the carrier conversion efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of diesel engine tail gas treatment, in particular to a urea mixing structure and a urea mixer. Background Art

[0002] At present, the main countermeasure to solve the excessive emission of nitrogen oxides in internal combustion engines is to use the selective catalytic reduction technology SCR after-treatment system. Urea aqueous solution is sprayed into the exhaust pipe by the nozzle, and after pyrolysis and hydrolysis under specific conditions, ammonia is generated, and ammonia reacts with nitrogen oxides in the exhaust gas to generate nitrogen and water to achieve the purpose of exhaust gas purification.

[0003] The uniformity of ammonia distribution in the SCR post-treatment system pipeline has an important impact on the overall performance and durability of the system. If the ammonia distribution is uneven, it will lead to excessive ammonia in local areas, which is easy to cause ammonia leakage, and in other areas where the ammonia is thin, the nitrogen oxide (NOx) conversion efficiency will be too low. Long-term uneven distribution of ammonia will cause uneven aging of the catalyst, thereby reducing the conversion efficiency of the SCR post-treatment system. In addition, the uneven distribution of urea droplets will cause the temperature of the local pipe wall or mixing structure to be too low, forming crystals, which will block the exhaust pipe in severe cases and cause the engine power performance to decrease.

[0004] In order to improve the conversion efficiency and reduce the risk of crystallization, the applicant has recently proposed a mixer solution. For example, a mixer proposed in publication number CN220395806U includes a fixed ring located at the periphery and a plurality of partition plates fixed in the fixed ring. Each partition plate includes inclined blades extending along the exhaust direction and protruding from the fixed ring. These inclined blades are used to mix the exhaust gas with the atomized urea solution. However, a mixer of this structure has certain disadvantages. For example, this mixer has a small direct contact area and a single mixing structure. When a large amount of urea is sprayed under high flow conditions, some urea aqueous solution will not be able to be hydrolyzed and pyrolyzed in time, which further leads to uneven distribution of ammonia and urea crystallization.

[0005] Therefore, it is still necessary to propose a new mixer to solve the above technical problems. Summary of the invention

[0006] In view of the technical problems existing in the mixer in the prior art, the first aspect of the utility model proposes a urea mixing structure, comprising:

[0007] an external fixed tube connected to the mixing pipe;

[0008] An inner fixing tube is arranged inside the outer fixing tube, a first passage is formed between the outer fixing tube and the inner fixing tube, and a second passage is formed inside the inner fixing tube;

[0009] Outer blades are arranged in the first channel and form a plurality of swirl chambers inclined to the axis of the first channel;

[0010] A plurality of inner blades are arranged in the second channel to divide the second channel into a plurality of parallel channels at different height layers;

[0011] Wherein, the inner blade includes a front contact part and a rear contact part, the length of the front contact part is greater than the length of the rear contact part, the front contact part is used to guide the airflow to contact the rear contact part, and the rear contact part is used to disperse the wake to the tail of the parallel channel of the adjacent upper or lower layer.

[0012] Preferably, the plurality of inner blades include two groups, the first group includes a plurality of first blades, and the second group includes at least one second blade, and the first blades and the second blades are arranged in parallel, so that the second channel is separated by the first blades and the second blades to form a plurality of parallel channels with similar thickness at different height layers.

[0013] Preferably, the second blade is located on a side of the plurality of first blades away from the urea pump.

[0014] Preferably, each of the first blades includes a first front contact portion and a first rear contact portion, wherein the first front contact portion is configured to have a length greater than a length of the second channel, and the first rear contact portion is configured to include an upwardly inclined first upper fin and a downwardly inclined first lower fin, so as to disperse the airflow passing through the current altitude layer to the tail of the parallel channel of the adjacent upper layer or lower layer;

[0015] The second blade includes a second front contact portion and a second rear contact portion, the second front contact portion has a size greater than that of the first front contact portion, the second front contact portion extends to the first channel, and the second rear contact portion includes a second upper fin inclined upward.

[0016] Preferably, the first upper fin and the second upper fin each include two upper folding plates connected together at a middle position, and the first lower fin includes lower folding plates located on both sides of the two folding plates, and the upper folding plates form an angle of forty-five degrees with the front contact portion.

[0017] Preferably, the front contact portion is constructed in a plate shape and is provided with upwardly tilted fins, and the fins are used to guide the airflow to disperse from the parallel channels of the current altitude layer to the parallel channels of the adjacent upper layer or lower layer.

[0018] Preferably, the fins are arranged in two or three rows along the exhaust direction, and the opening direction of the fins is along the exhaust direction or opposite to the exhaust direction.

[0019] Preferably, the second front contact portion comprises a main board body, and extension plates extending outward are provided on both sides of the main board body, the extension plates extend into the range of the first channel, and the extension plates have an inclination angle with the main board body.

[0020] Preferably, the outer fixing tube and the inner fixing tube have the same length, the first channel is an annular channel, the second channel is a circular channel, and the first channel and the second channel have the same length.

[0021] The second aspect of the utility model provides a technical solution, a urea mixer, comprising:

[0022] Mixing pipeline;

[0023] The above-mentioned urea mixing structure is arranged in the mixing pipe;

[0024] A mixing chamber connected to the mixing pipe and located at the inlet side of the urea mixing structure, wherein a urea nozzle mounting seat is provided on the mixing chamber, and the axial direction of the urea nozzle mounting seat intersects with the center of the urea mixing structure;

[0025] The urea mixing structure is arranged so that the front contact portion of the inner blade faces the exhaust gas flow direction.

[0026] Compared with the prior art, the advantages of the utility model are:

[0027] The urea mixing structure of the utility model comprises an annular first channel in an outer layer and a circular second channel in an inner layer, a swirl structure is provided in the first channel, and the guide vanes in the second channel increase the area of ​​the front contact part, so that the airflow can pass smoothly, reduce the risk of backflow and formation of liquid film and crystallization, and also improve the urea crushing and decomposition effect, and at the same time, the swirl structure is added to make the airflow turbulent in a spiral manner, accelerate the airflow speed, increase the urea mixing path, avoid the accumulation of liquid urea in the mixer and the downstream pipe wall of the mixer, effectively eliminate urea crystallization and improve the carrier conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the utility model will be described by way of example and with reference to the accompanying drawings, in which:

[0029] Figure 1 It is a structural schematic diagram of a urea mixer shown in the utility model;

[0030] Figure 2 It is a structural schematic diagram of the urea mixing structure shown in the utility model;

[0031] Figure 3 It is a three-dimensional diagram of the urea mixing structure shown in the utility model;

[0032] Figure 4 It is a stereogram of the urea mixing structure shown in the utility model from another perspective;

[0033] Figure 5 It is a schematic diagram of the structure of multiple inner blades shown in the utility model;

[0034] Figure 6 It is a right side view of the urea mixing structure shown in the utility model;

[0035] Figure 7 It is a left view of the urea mixing structure shown in the utility model;

[0036] Figure 8 It is a front view of the urea mixing structure shown in the utility model;

[0037] Fig. 9 It is a dynamic schematic diagram of the flue gas flowing through the urea mixing structure shown in the utility model;

[0038] Fig.10 It is a dynamic schematic diagram of urea flowing through a urea mixing structure shown in the utility model. DETAILED DESCRIPTION

[0039] In order to better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0040] Combination Figure 1-2 As shown, the first aspect of the utility model proposes a urea mixing structure, comprising an outer fixed tube 20, an inner fixed tube 21, an outer blade 22 and a plurality of inner blades, the outer fixed tube 20 is connected to the inner wall of the mixing pipe 1, the inner fixed tube 21 is arranged on the inner side of the outer fixed tube 20, a first channel is formed between the outer fixed tube 20 and the inner fixed tube 21, and a second channel is formed on the inner side of the inner fixed tube 21.

[0041] Optionally, the outer fixing tube 20 and the inner fixing tube 21 have the same length, wherein the first channel is an annular channel, the second channel is a circular channel, and the first channel and the second channel have the same length.

[0042] When the flue gas flows through the urea mixing structure, it is divided into two parts, one part flows through the annular first channel, and the second part flows through the circular first channel.

[0043] Furthermore, the outer blades 22 are arranged in the first channel, and form a plurality of swirl chambers 23 inclined to the axis of the first channel. Thus, when the airflow flows through the first channel, the airflow is guided by the plurality of swirl chambers 23 to form a spiral flow adhering to the inner wall of the mixing pipe 1, especially avoiding the accumulation of urea droplets on the pipe wall, and not easily forming urea crystals.

[0044] Furthermore, a plurality of inner blades are arranged in the second channel to divide the second channel into a plurality of parallel channels at different height layers; wherein the inner blades include a front contact portion and a rear contact portion, the length of the front contact portion is greater than the length of the rear contact portion, the front contact portion is used to guide the airflow to contact the rear contact portion, and the rear contact portion is used to disperse the wake to the tail of the parallel channels of the adjacent upper or lower layers.

[0045] In this way, the airflow through the second channel first flows through the front contact part of each inner blade, and then flows through the rear contact part. Since the front contact part is set longer, it can play a good guiding role, especially prolonging the contact time between urea, flue gas and inner blades, reducing the risk of forming a liquid film on the blade surface, and not easily forming urea crystals, so that the flue gas can flow smoothly through the front contact part and the rear contact part in turn, avoiding flue gas backflow.

[0046] Combination Figure 3-4 As shown, in an optional embodiment, the multiple inner blades include two groups, the first group includes multiple first blades 2a, and the second group includes at least one second blade 2b. The first blades 2a and the second blades 2b are arranged in parallel, so that the second channel is separated by the first blades 2a and the second blades 2b to form multiple parallel channels with similar thickness at different height layers.

[0047] In this way, after the airflow flows through the second channel with a circular cross-section, it can be separated by a plurality of blades arranged in parallel, so that the mixed airflow of the flue gas and urea is mixed in relatively independent areas.

[0048] Optionally, the first blade 2a includes blade A24, blade B25, blade C26, blade D27 and blade E28, and the second blade 2b includes blade H29.

[0049] Furthermore, the second blade 2b is located on a side of the plurality of first blades 2a away from the urea pump. By arranging the second blade 2b below the plurality of first blades 2a, it is possible to prevent the urea solution from adhering to the inner wall of the mixing pipe 1 and causing urea crystallization when the urea pump sprays a large amount of urea solution.

[0050] Further, such as Figure 4As shown, each first blade 2a includes a first front contact portion and a first rear contact portion, the first front contact portion is set to have a length greater than the length of the second channel, and the first rear contact portion is set to include an upwardly inclined first upper fin 2a1 and a downwardly inclined first lower fin 2a2, so as to disperse the airflow passing through the current altitude layer to the tail of the parallel channel of the adjacent upper layer or lower layer;

[0051] The second blade 2b includes a second front contact portion and a second rear contact portion, the second front contact portion has a size greater than that of the first front contact portion, the second front contact portion extends to the first channel, and the second rear contact portion includes a second upper fin 2b1 inclined upward.

[0052] It should be understood that the length of the first front contact portion is greater than that of the second channel, and it extends to the front end of the mixing structure. The mixed airflow of the flue gas and the urea solution first contacts this portion, and the size of the second front contact portion is greater than that of the first front contact portion, which can play a protective role when a large flow of urea is injected. The mixed airflow is divided into multiple independent areas after passing through the first front contact portion and then contacts the first rear contact portion, so that the mixed airflows of the two adjacent areas are again mixed for the second time, thereby enhancing the crushing and decomposition effect of the urea.

[0053] Optional, such as Figure 4-8 As shown, the first upper fin 2a1 and the second upper fin 2b1 each include two upper folding plates connected together in the middle position, and the first lower fin 2a2 includes lower folding plates on both sides of the two folding plates, and the upper folding plates form an angle of forty-five degrees with the front contact portion.

[0054] In this way, a part of the mixed gas flowing out from the parallel channel of a certain height layer flows upward through the guiding effect of the two upper folding plates, and the other part of the gas flows downward through the guiding effect of the two lower folding plates. Since the positions of the upper folding plates and the lower folding plates of each layer correspond, the fluid flows smoothly and without disorder, and turbulence and backflow are not easily formed. The tail flow flowing out through the lower folding plates and the upper folding plates collides and mixes with the spiral airflow flowing out of the first channel, thereby increasing the mixing effect. At the same time, the airflow can be constrained within the annular area of ​​the first channel to avoid contact with the inner wall of the mixing pipe 1.

[0055] Furthermore, the front contact portion is constructed in a plate shape and is provided with upwardly tilted fins, which are used to guide the airflow to disperse from the parallel channels of the current altitude layer to the parallel channels of the adjacent upper layer or lower layer.

[0056] The fins are arranged in two or three rows along the exhaust direction, and the opening direction of the fins is along the exhaust direction or opposite to the exhaust direction.

[0057] In this way, when the airflow flows over the surface of the front contact part, due to the effect of the fins, part of the airflow can enter the parallel channels of the adjacent upper or lower layers for premixing, thereby achieving a better mixing effect.

[0058] Combination Figure 5 As shown, the blade A24 includes a plate body A241, a fin A244, an upper folding plate A242 and a lower folding plate A243, and the fin A244, the upper folding plate A242 and the lower folding plate A243 are all formed by stamping and bending the plate body A241.

[0059] The blade B25 includes a plate body B251, fins B254, an upper folding plate B252 and a lower folding plate B253. The fins B254, the upper folding plate B252 and the lower folding plate B253 are all formed by stamping and bending the plate body B251.

[0060] The blade C26 includes a plate body C261, fins C264, an upper folding plate C262 and a lower folding plate C263. The fins C264, the upper folding plate C262 and the lower folding plate C263 are all formed by stamping and bending the plate body C261.

[0061] The blade D27 includes a plate body D271, fins D274, an upper folding plate D272 and a lower folding plate D273. The fins D274, the upper folding plate D272 and the lower folding plate D273 are all formed by stamping and bending the plate body D271.

[0062] The blade E28 includes a plate body E281, fins E284, an upper folding plate E282 and a lower folding plate E283. The fins E284, the upper folding plate E282 and the lower folding plate E283 are all formed by stamping and bending the plate body E281.

[0063] Among them, the flow directions of the airflow when flowing through the surfaces of blades A24, blade B25, blade C26, blade D27 and blade E28 are similar. Taking blade D27 as an example, when the mixed airflow flows through the surface of the plate body D271, part of the airflow flows from the fin D274 to the lower layer (the space between blades D27 and blade E28, and is pre-mixed with the airflow in this layer of space), and most of the airflow is guided by the plate body D271 and is divided into three airflows, one flows upward from the upper folding plate D272, and two flows downward from the two lower folding plates D273 to mix with the airflow of the adjacent layers, and then mix again with the swirl airflow of the first channel.

[0064] Furthermore, the blade H29 includes a main body E291, fins E295, and an upper folding plate H292. A first extension plate H293 and a second extension plate H294 extending outward are provided on both sides of the main body, wherein the extension plate extends into the range of the first channel, and the extension plate has an inclination angle with the main body.

[0065] like Figure 5 As shown, the inclination direction of the fin E295 on the main body E291 is different from that of the other fins, the first extension plate H293 and the second extension plate H294 provide a larger contact area, and the main body E291 is designed to provide an upward rebound for the large flow of urea sprayed downward, so that most of the urea is more inclined to contact and mix with the flue gas in the middle area.

[0066] The second aspect of the utility model proposes a technical solution, a urea mixer, comprising:

[0067] Mixing pipeline 1;

[0068] The above-mentioned urea mixing structure 2 is arranged in the mixing pipe 1;

[0069] A mixing chamber 3 is connected to the mixing pipe 1 and is located at the inlet side of the urea mixing structure 2. A urea nozzle mounting seat 4 is provided on the mixing chamber 3. The axial direction of the urea nozzle mounting seat 4 intersects with the center of the urea mixing structure 2.

[0070] The urea mixing structure 2 is arranged such that the front contact portion of the inner blades faces the exhaust gas flow direction.

[0071] It should be understood that when the urea mixing structure 2 is installed in the exhaust aftertreatment system, an oxidation catalyst (DOC) or a diesel particulate filter (DPF) may be installed upstream of the mixing pipe 1, and a selective reduction catalyst (SCR) may be provided downstream of the mixing pipe 1.

[0072] During operation, the urea nozzle installed on the urea nozzle mounting seat 4 sprays atomized urea solution into the mixing chamber 3 , and the exhaust gas discharged by the engine is mixed with the urea solution through the urea mixing structure 2 .

[0073] Optionally, the homogeneous mixed gas flow after mixing flows through a selective reduction catalyst (SCR) to react so as to reduce the content of nitrogen oxides.

[0074] Combination Fig. 9 mix in Fig.10 As shown, the fluid flowing out of the mixing structure flows smoothly and without disorder, and turbulence and backflow are not easily formed. The tail flow flowing out through the lower folding plate and the upper folding plate collides and mixes with the spiral airflow flowing out of the first channel, so that the airflow is disordered in a spiral manner, thereby increasing the mixing effect, accelerating the airflow speed, increasing the urea mixing path, and avoiding the accumulation of liquid urea in the mixer and the downstream pipe wall of the mixer.

[0075] In combination with the above embodiments, the urea mixing structure of the utility model includes an annular first channel in an outer layer and a circular second channel in an inner layer. A swirl structure is provided in the first channel. The guide blades in the second channel increase the area of ​​the front contact part, so that the airflow can pass smoothly, reduce the risk of backflow and formation of liquid film and crystallization, and improve the urea crushing and decomposition effect. At the same time, the swirl structure is added to make the airflow turbulent in a spiral manner, accelerate the airflow speed, increase the urea mixing path, avoid the accumulation of liquid urea in the mixer and the downstream pipe wall of the mixer, effectively eliminate urea crystallization and improve the carrier conversion efficiency.

[0076] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A urea mixing structure, characterized in that: include: An external fixed pipe (20) connected to the mixing pipe (1); An inner fixing tube (21) is arranged inside the outer fixing tube (20), a first passage is formed between the outer fixing tube (20) and the inner fixing tube (21), and a second passage is formed inside the inner fixing tube (21); Outer blades (22) are arranged in the first channel and form a plurality of swirl chambers (23) inclined to the axis of the first channel; A plurality of inner blades are arranged in the second channel to divide the second channel into a plurality of parallel channels at different height layers; Wherein, the inner blade includes a front contact part and a rear contact part, the length of the front contact part is greater than the length of the rear contact part, the front contact part is used to guide the airflow to contact the rear contact part, and the rear contact part is used to disperse the wake to the tail of the parallel channel of the adjacent upper or lower layer.

2. The urea mixing structure according to claim 1, characterized in that: The plurality of inner blades include two groups, the first group includes a plurality of first blades (2a), and the second group includes at least one second blade (2b), the first blades (2a) and the second blades (2b) are arranged in parallel, so that the second channel is separated by the first blades (2a) and the second blades (2b) to form a plurality of parallel channels with similar thickness and at different height layers.

3. The urea mixing structure according to claim 2, characterized in that: The second blade (2b) is located on a side of the plurality of first blades (2a) away from the urea pump.

4. The urea mixing structure according to claim 2, characterized in that: Each of the first blades (2a) comprises a first front contact portion and a first rear contact portion, wherein the first front contact portion is configured to have a length greater than a length of the second channel, and the first rear contact portion is configured to include an upwardly inclined first upper fin (2a1) and a downwardly inclined first lower fin (2a2), so as to disperse the airflow passing through the current altitude layer to the tail of the parallel channel of the adjacent upper layer or lower layer; The second blade (2b) comprises a second front contact portion and a second rear contact portion, the second front contact portion is larger than the first front contact portion, the second front contact portion extends to the first channel, and the second rear contact portion comprises a second upper fin (2b1) inclined upward.

5. The urea mixing structure according to claim 4, characterized in that: The first upper fin (2a1) and the second upper fin (2b1) both comprise two upper folding plates connected together at a middle position, and the first lower fin (2a2) comprises lower folding plates located on both sides of the two folding plates, and the upper folding plates form an angle of forty-five degrees with the front contact portion.

6. The urea mixing structure according to any one of claims 1 to 5, characterized in that: The front contact portion is constructed in a plate shape and is provided with upwardly tilted fins, and the fins are used to guide the airflow to disperse from the parallel channels of the current altitude layer to the parallel channels of the adjacent upper layer or lower layer.

7. The urea mixing structure according to claim 6, characterized in that: The fins are arranged in two or three rows along the exhaust direction, and the opening direction of the fins is along the exhaust direction or opposite to the exhaust direction.

8. The urea mixing structure according to claim 4, characterized in that: The second front contact portion includes a main board body, and extension plates extending outward are provided on both sides of the main board body. The extension plates extend into the range of the first channel, and the extension plates have an inclination angle with the main board body.

9. The urea mixing structure according to claim 1, characterized in that: The outer fixing tube (20) and the inner fixing tube (21) have the same length, the first channel is an annular channel, the second channel is a circular channel, and the first channel and the second channel have the same length.

10. A urea mixer, characterized in that: include: Mixing pipeline (1); The urea mixing structure (2) according to any one of claims 1 to 9, arranged in the mixing pipe (1); A mixing chamber (3) connected to the mixing pipe (1) and located at the inlet side of the urea mixing structure (2); a urea nozzle mounting seat (4) is provided on the mixing chamber (3); the axial direction of the urea nozzle mounting seat (4) intersects with the center of the urea mixing structure (2); The urea mixing structure (2) is arranged so that the front contact portion of the inner blade faces the exhaust gas flow direction.

Images