Post-treatment urea mixing structure

Abstract

The utility model relates to a post-treatment urea mixing structure. The post-treatment urea mixing structure is characterized in that the outer edge of a Z-shaped plate is welded with the inner wall of a mixing cylinder in the circumferential direction; the stainless steel corrugated weaving structure is welded in the outer-layer pipe, the outer-layer pipe is located in the interval of the Z-shaped plate and fixedly connected with the Z-shaped plate, and the upper edge of the outer-layer pipe is higher than the transverse plate; the mixing barrel is divided into an upper front cavity and a lower rear cavity by the outer-layer pipe and the Z-shaped plate; vertical through holes are distributed in the finned tubes, the through holes are connected with blades expanding outwards, and gaps are formed in the lower side edges of the finned tubes at intervals. The upper part of the finned tube is welded with the mixing cylinder body, and the finned tube is communicated with a urea nozzle seat welded on the mixing cylinder body; the finned tube is located above the outer-layer tube, and a gap is formed between the lower end of the finned tube and the upper end of the outer-layer tube; and the special-shaped mixing plate with a plurality of through holes is positioned at the rear end of the mixing barrel. The utility model has the advantages of low back pressure, compact structure, small occupied space, better flow field uniformity and strong crystallization resistance.

Description

Technical Field

[0001] The utility model belongs to the technical fields of vehicle engine exhaust emission purification technology and energy conservation and consumption reduction technology, and particularly relates to a post-treatment urea mixing structure. Background Art

[0002] The current technical routes of the National VI heavy-duty diesel engines are all composed of a series combination of an oxidation catalytic unit (DOC) / a particulate trap unit (DPF) / a selective catalytic reduction conversion unit (SCR) and an ammonia oxidation catalytic unit (ASC). The cumulative back pressure of each carrier is already relatively high. Coupled with a complex urea mixing structure, it will lead to a high back pressure in the post-treatment and poor fuel economy. In order to meet the requirement of a low exhaust system back pressure and at the same time be able to meet the mixing structure of emissions and anti-crystallization ability, a urea mixing structure with a more compact structure, a lower back pressure, less urea crystallization, and good flow field uniformity is designed. Summary of the Invention

[0003] The utility model provides a post-treatment urea mixing structure, the purpose of which is to solve the disadvantages of the existing technology and achieve a low back pressure, a compact structure, a small occupied space, a good flow field uniformity, and a strong anti-crystallization ability.

[0004] The solution of the utility model to solve its technical problems lies in:

[0005] A post-treatment urea mixing structure, the Z-shaped plate includes an upper vertical plate, the bottom edge of the upper vertical plate extends laterally to two transverse plates, and the ends of the two transverse plates extend downward to two lower vertical plates. There is a gap between the combinations of the two groups of transverse plates and lower vertical plates;

[0006] The outer edge of the Z-shaped plate is welded to the inner wall of the mixing cylinder in the circumferential direction;

[0007] The stainless steel corrugated braided structure is welded inside the outer tube. The outer tube is located within the gap of the Z-shaped plate and is fixedly connected to the Z-shaped plate. The upper edge of the outer tube is higher than the transverse plate;

[0008] The outer tube and the Z-shaped plate divide the mixing cylinder into an upper front cavity and a lower rear cavity;

[0009] The finned tube is distributed with vertical through holes, the through holes are connected with outwardly expanding blades, and spaced notches are opened on the lower side of the finned tube;

[0010] The upper part of the finned tube is welded to the mixing cylinder, and the finned tube is communicated with the urea nozzle seat welded on the mixing cylinder;

[0011] The finned tube is located above the outer tube;

[0012] The special-shaped mixing plate with multiple through holes is located at the rear end of the mixing cylinder.

[0013] The outer tube and the finned tube are of a disconnected structure, and there is a gap between the lower end of the finned tube and the upper end of the outer tube.

[0014] The stainless steel wound mesh is woven from cylindrical stainless steel wires into a shape with wave crests and wave troughs, and then wound layer by layer.

[0015] The outer wall of the outer tube is welded to two groups of horizontal plates and the lower vertical plate.

[0016] The notch opened on the lower side of the finned tube is rectangular.

[0017] The special-shaped mixing plate is located at the rear end of the mixing cylinder, and the through holes on the special-shaped mixing plate are irregular mesh holes and special-shaped holes.

[0018] The diameter of the finned tube is smaller than that of the outer tube. Beneficial effects

[0019] 1. When the tail gas enters the mixing structure, part of it accelerates the air flow through the finned tube, and part of it enters the stainless steel corrugated woven structure through the channel between the finned tube and the outer tube. The tail gas enters the stainless steel corrugated woven structure through the above two channels, and the diameter of the outer tube is larger than that of the finned tube, so the gas resistance generated by the mixing structure is small;

[0020] 2. The diameter of the finned tube is small and the diameter of the outer tube is large. When the tail gas enters the stainless steel corrugated woven structure through the channel between the finned tube and the outer tube, an air flow will be formed downward along the inner wall surface of the outer tube, purging the inner wall surface of the outer tube and reducing the risk of crystallization on the inner wall surface of the outer tube;

[0021] 3. The lower part of the finned tube is provided with intermittent rectangular openings, which can increase the air flow velocity outside the tube wall at the openings, form air flow disturbance, and reduce the risk of crystallization inside and outside the finned tube.

[0022] 4. The mixing structure adopts a Z-shaped plate structure to separate the inlet and outlet air of the urea mixing structure, making the structure more compact and occupying less space. Description of the drawings

[0023] Figure 1 It is an explosion schematic diagram of the urea mixing structure;

[0024] Figure 2 It is an overall schematic diagram of the air inlet direction of the urea mixing structure;

[0025] Figure 3 It is an overall schematic diagram of the air outlet direction of the urea mixing structure;

[0026] Figure 4 It is a sectional view of the urea mixing structure;

[0027] Figure 5 It is a schematic diagram of the stainless steel corrugated woven structure and the outer tube. Detailed implementation mode

[0028] The following further describes the present utility model in conjunction with the accompanying drawings and specific embodiments.

[0029] To more clearly illustrate the technical solution of the present utility model, the accompanying drawings required in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings. To facilitate the understanding of the present utility model, the present utility model will be described in more detail below in conjunction with the accompanying drawings and specific embodiments.

[0030] The present utility model is a post-treatment urea mixing structure. The flared cylinder of the mixing structure cooperates with the hump pipe at the rear end of the particulate trap, and the rear end is welded to the front end of the selective catalytic reduction converter.

[0031] As Figure 1 , Figure 2 , Figure 3 , Figure 4 shown:

[0032] The present utility model provides a post-treatment urea mixing structure, which is arranged at the front end of the SCR. The urea mixing structure includes a mixing cylinder 1, a urea nozzle seat 2, a finned tube 3, a Z-shaped plate 4, a stainless steel corrugated braided structure 5, an outer tube 6, and a special-shaped mixing plate 7.

[0033] As Figure 5 shown:

[0034] The stainless steel corrugated braided structure 5 is located inside the outer tube 6, and the two are combined together by brazing. The stainless steel corrugated braided structure 5 is woven from cylindrical stainless steel wires into a shape of wave crests and wave troughs, and then wound layer by layer.

[0035] The Z-shaped plate 4 includes an upper vertical plate 41. The bottom edge of the upper vertical plate 41 extends laterally to form two horizontal plates 42. The ends of the two horizontal plates 42 extend downward to form two lower vertical plates 43. There is a gap 40 between the combinations of the two groups of horizontal plates 42 and lower vertical plates 43. The upper vertical plate 41, the horizontal plates 42, and the lower vertical plates 43 form a Z shape, so it becomes the Z-shaped plate 4.

[0036] The outer edge of the Z-shaped plate 4 is welded to the inner wall of the mixing cylinder 1 in the circumferential direction.

[0037] The outer tube 6 is located in the gap 40 between the combinations of the two groups of horizontal plates 42 and lower vertical plates 43 of the Z-shaped plate 4. The upper edge of the outer tube 6 is higher than the horizontal plates 42, and the outer wall of the outer tube 6 is welded to the two groups of horizontal plates 42 and lower vertical plates 43.

[0038] In this way, the outer tube 6 and the Z-shaped plate 4 divide the mixing cylinder 1 into two cavities, namely the upper front cavity 11 and the lower rear cavity 12.

[0039] The finned tube 3 is a stainless steel tube with a certain diameter, on which a certain number of vertical through holes 31 are distributed. The through holes 31 are connected with blades 32, and the blades 32 are outwardly extended at a certain angle. The lower side of the finned tube 3 is provided with spaced rectangular or other shaped notches 33.

[0040] The diameter of the finned tube 3 is smaller than that of the outer tube 6. The finned tube 3 is located directly above the outer tube 6, and the outer tube 6 and the finned tube 3 are of a disconnected structure, and there is a gap 36 between the lower end of the finned tube 3 and the upper end of the outer tube 6.

[0041] The upper part of the finned tube 3 is welded to the mixing cylinder 1, and the finned tube 3 is communicated with the urea nozzle seat 2 welded to the mixing cylinder 1.

[0042] The special-shaped mixing plate 7 with a plurality of through holes 71 (the through holes 71 can be irregular mesh holes and special-shaped holes) is located at the rear end of the mixing cylinder 1.

[0043] During use:

[0044] After the tail gas enters the urea mixing structure, it passes through the upper front cavity 11 separated from the mixing cylinder 1 by the outer tube 6 and the Z-shaped plate 4.

[0045] A part of the tail gas enters the finned tube 3 through the vertical through holes 31 of the finned tube 3 to accelerate the air flow.

[0046] A part of the tail gas enters the gap 36 between the finned tube 3 and the outer tube 6.

[0047] The tail gas enters the stainless steel corrugated braided structure 5 through the above two channels, which can reduce the gas resistance generated by the mixing structure.

[0048] The size of the gap 36 between the finned tube 3 and the outer tube 6 can be adjusted to adjust the sizes of the two parts of the air flow, so as to adjust the back pressure and the gas flow rate in the finned tube 3.

[0049] At this time, the tail gas entering the finned tube 3 is mixed with the urea solution sprayed from the nozzle seat 2.

[0050] The tail gas passing through the channel between the finned tube 3 and the outer tube 6 is mixed with the urea for secondary turbulent mixing and enters the outer tube 6 and passes through the stainless steel corrugated braided structure 5. The diameter of the finned tube 3 is small and the diameter of the outer tube 6 is large. When the tail gas passes through the gap 36 between the finned tube 3 and the outer tube 6 and enters the outer tube 6 and passes through the stainless steel corrugated braided structure 5, an air flow downward along the inner wall surface of the outer tube 6 will be formed to blow the inner wall surface of the outer tube 6 and reduce the crystallization risk of the inner wall surface of the outer tube 6.

[0051] The lower part of the finned tube 3 is provided with spaced rectangular notches 33. When the tail gas passes through the rectangular notches 33, the air flow velocity on the outer side of the tube wall at the notches 33 can be increased, forming air flow disturbance and reducing the crystallization risk inside and outside the finned tube 3.

[0052] When the mixed gas passes through the stainless steel corrugated braided structure 5, the urea mixed gas is further broken, pyrolyzed and hydrolyzed into ammonia. After the tail gas and ammonia enter the lower rear cavity 12 separated from the mixing cylinder 1 by the outer tube 6 and the Z-shaped plate 4, they are secondarily mixed and rectified by the special-shaped mixing plate 7, improving the velocity distribution of the air flow and the ammonia distribution.

[0053] Finally, the mixed gas passes through the through holes 71 of the special-shaped mixing plate 7 and enters the SCR carrier.

[0054] The outer tube 6 and the Z-shaped plate 4 divide the mixing cylinder 1 into two cavities, namely the upper front cavity 11 and the lower rear cavity 12. The upper front cavity 11 is used for the mixing of gas and urea and the crushing, pyrolysis and hydrolysis of urea, and the lower rear cavity 12 is used for the secondary mixing and rectification of the mixed urea and gas. This structure can shorten the length of the mixing structure and reduce the space occupied by the mixing structure.

[0055] The utility model uses the finned tube 3 to increase the air flow velocity to crush urea, and then uses the stainless steel corrugated braided structure 5 for secondary crushing and evaporation, so that NH3 generated after the hydrolysis and pyrolysis of urea is fully mixed with the tail gas, improving the ammonia concentration uniformity in front of the catalyst, thereby enhancing the NOx conversion efficiency of the SCR catalyst; using the disconnection structure of the finned tube 3 and the outer tube 6, and the diameter of the finned tube 3 is smaller than that of the outer tube 6 to reduce the resistance of the mixing structure, thereby achieving the purpose of reducing the back pressure of the mixing structure; using the disconnection structure of the finned tube 3 and the outer tube 6, and the lower part of the finned tube 3 is intermittently provided with rectangular notches 33 to increase the gas disturbance at the tube walls of the finned tube 3 and the outer tube 4, reducing the crystallization risk.

[0056] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. The above description of the disclosed embodiments enables those skilled in the art to implement or use the utility model. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the utility model. Therefore, the utility model will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A post-treatment urea mixing structure, characterized in that: The Z-shaped plate includes an upper vertical plate. The bottom edge of the upper vertical plate extends laterally to form two horizontal plates. The ends of the two horizontal plates extend downward to form two lower vertical plates. There is a gap between the combinations of the two sets of horizontal plates and lower vertical plates. The outer edge of the Z-shaped plate is welded to the inner wall of the mixing cylinder in the circumferential direction. The stainless steel corrugated braided structure is welded inside the outer tube. The outer tube is located within the gap of the Z-shaped plate and is fixedly connected to the Z-shaped plate. The upper edge of the outer tube is higher than the horizontal plate. The outer tube and the Z-shaped plate divide the mixing cylinder into a front upper chamber and a rear lower chamber. The finned tube is distributed with vertical through holes, and the through holes are connected with outwardly expanding blades. The lower side of the finned tube is provided with spaced notches. The upper part of the finned tube is welded to the mixing cylinder, and the finned tube communicates with the urea nozzle seat welded to the mixing cylinder. The finned tube is located above the outer tube, and there is a gap between the lower end of the finned tube and the upper end of the outer tube. The special-shaped mixing plate with multiple through holes is located at the rear end of the mixing cylinder.

2. The post-treatment urea mixing structure according to claim 1, characterized in that: The outer tube and the finned tube are of a disconnected structure, and there is a gap between the lower end of the finned tube and the upper end of the outer tube.

3. The post-treatment urea mixing structure according to claim 1, characterized in that: The stainless steel wound mesh is woven into the shape of wave crests and wave troughs by cylindrical stainless steel wires and then wound layer by layer.

4. The post-treatment urea mixing structure according to claim 1, wherein: The outer wall of the outer tube is welded to the two sets of horizontal plates and lower vertical plates.

5. A post-treatment urea mixing structure according to claim 1, characterized in that: The notches provided on the lower side of the finned tube are rectangular.

6. The post-treatment urea mixing structure according to claim 1, characterized in that: The special-shaped mixing plate is located at the rear end of the mixing cylinder, and the through holes on the special-shaped mixing plate are irregular mesh holes and special-shaped holes.

7. The post-treatment urea mixing structure according to claim 1, characterized in that: The diameter of the finned tube is smaller than the diameter of the outer tube.

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