CN219366142U

CN219366142U - Mixing arrangement and SCR system

Info

Publication number: CN219366142U
Application number: CN202320850027.4U
Authority: CN
Inventors: 韩笑; 张成龙; 郑茜; 郑鹏
Original assignee: Weichai Power Co Ltd
Current assignee: Weichai Power Co Ltd
Priority date: 2023-04-17
Filing date: 2023-04-17
Publication date: 2023-07-18
Anticipated expiration: 2033-04-17

Abstract

The utility model discloses a mixing device and an SCR system, wherein the mixing device comprises a first arc-shaped baffle, a second arc-shaped baffle, a drainage plate and a flow equalizing plate; a mixing cavity is formed between the first arc-shaped baffle plate and the second arc-shaped baffle plate; a front opening is formed between the front side edges of the first arc-shaped baffle plate and the second arc-shaped baffle plate, and a rear opening is formed between the rear side edges of the first arc-shaped baffle plate and the second arc-shaped baffle plate; the drainage plate is arc-shaped and is positioned at the rear side of the rear opening, and a cavity which is led to the rear opening from the front side left and right is formed between the drainage plate and the first arc-shaped baffle plate and between the drainage plate and the second arc-shaped baffle plate; the flow equalizing plate is arranged at the rear side of the flow guiding plate, and is provided with air outlets for forming cyclone air flow, and the air outlets are distributed in an annular array with the circle center of the flow equalizing plate as the center. The mixing device can fully mix the reducing agent with the waste gas, evaporate and decompose the waste gas, and improve the mixing uniformity and crystallization resistance.

Description

Mixing arrangement and SCR system

Technical Field

The utility model relates to the technical field of diesel engines, in particular to a mixing device in an exhaust system of a diesel engine. The utility model also relates to an SCR system provided with said mixing device.

Background

The basic principle of SCR (i.e. selective catalytic reduction) technology is to inject fuel or add other reducing agent into the exhaust gas, select a suitable catalyst to promote the reaction of the reducing agent with NOx, and at the same time inhibit the oxidation of the reducing agent by oxygen in the exhaust gas, in practice, urea is used as the reducing agent in a large number.

In the running process of the vehicle, the injected urea liquid drops can not be converted into NH in real time due to poor atomization, uneven mixing or insufficient decomposition of the urea ₃ But by-products are formed, resulting in unstable reduction reactions, thereby affecting the consistency of NOx emissions and conversion efficiency.

Urea sediment can be divided into urea crystals and urea stones according to the formation process, wherein the urea crystals are generated by precipitation of supersaturated urea of a urea solution due to water loss in the urea solution, are products of a physical reaction process, and can be continuously decomposed along with the rise of temperature; the urea stones are by-products generated by side reactions in the urea decomposition process, belong to chemical reaction products, and can be decomposed at a higher temperature.

Since the mass of urea liquid drops is much larger than that of gas, crystals formed in the gas flow stagnation area remain, and if the crystals cannot be completely decomposed in time, the crystals can be used as prokaryotes to grow continuously, and urea crystal stones are finally formed due to the incomplete decomposition, and the urea crystal stones can be accumulated to a certain degree to possibly block a urea flow channel.

At present, most of mixing devices of an SCR system are in a single vortex mode, when airflow passes through, rotating vortex is formed at a urea injection center, waste gas and urea are mixed through the vortex, and urea liquid drops are promoted to rapidly complete evaporation and decomposition. However, the turbulence of the single rotation is too strong, which causes crystallization of the wall surface of the mixer near the gas outlet side, and also has high pressure loss.

Moreover, the gas flow directly enters the selective catalytic reducer after passing through the mixer, so that the flow uniformity of the front end face of the SCR carrier and the uniformity of ammonia distribution are poor, and the effect of selective catalytic reduction is affected.

Disclosure of Invention

The utility model aims to provide a mixing device. The mixing device can fully mix the reducing agent with the waste gas, evaporate and decompose the waste gas, and improve the mixing uniformity and crystallization resistance.

Another object of the utility model is to provide an SCR system provided with said mixing device.

In order to achieve the above object, the present utility model provides a mixing device, which includes a first arc baffle, a second arc baffle, a drainage plate and a flow equalizing plate, wherein the first arc baffle and the second arc baffle are symmetrically arranged in a manner that openings are opposite, and a mixing cavity is formed between the first arc baffle and the second arc baffle; a front opening which is communicated with the mixing cavity is formed between the front side edges of the first arc-shaped baffle plate and the second arc-shaped baffle plate, and a rear opening which is communicated with the mixing cavity is formed between the rear side edges of the first arc-shaped baffle plate and the second arc-shaped baffle plate; the flow guide plate is arc-shaped and is positioned at the rear side of the rear opening, a cavity which is led to the rear opening from the left side to the right side is formed between the flow guide plate and the first arc-shaped baffle plate and the second arc-shaped baffle plate, the flow equalization plate is arranged at the rear side of the flow guide plate, an air outlet hole for forming cyclone air flow is formed in the flow equalization plate, and the air outlet hole is used for separating air holes from an annular array with the center of the flow equalization plate as the center.

Optionally, the first arc-shaped baffle plate, the second arc-shaped baffle plate and the drainage plate are arranged to guide the airflow to enter the mixing cavity through the front opening and the rear opening, and four uniformly distributed rotational flows can be formed under the action of the first arc-shaped baffle plate and the second arc-shaped baffle plate when the airflow passes through the mixing cavity.

Optionally, each air outlet hole extends from the center region to the edge region of the flow equalizing plate.

Optionally, the air outlet holes are elongated holes, and extend along the radial direction of the flow equalization plate, or the air outlet holes are arc holes, and a plurality of air outlet holes are distributed in a vortex shape around the circle center of the flow equalization plate.

Optionally, each air outlet hole is provided with a cyclone drainage edge on the same side.

Optionally, the cyclone drainage edge protrudes towards the back surface of the flow equalizing plate, and is inclined or bent from the hole wall on one side to the hole wall on the other side.

Optionally, the central area of the flow equalizing plate is provided with a plurality of vent holes distributed in a lattice form.

Optionally, the bottom of first arc baffle the second arc baffle with the drainage board is equipped with hollow baffle, the below of hollow baffle is equipped with the guide plate of perpendicular to air current direction, the guide plate has the arc position that arches to the air current direction of coming and is located the flank position of arc position both sides.

Optionally, the distance between the first arc-shaped baffle and the second arc-shaped baffle is 20 mm-80 mm.

To achieve the other object, the utility model provides an SCR system, which comprises a catalyst and a mixing device positioned at the upstream of the catalyst, wherein the mixing device is the mixing device according to any one of the above technical schemes, and the mixing device is provided with a reducing agent injection port above a mixing cavity thereof.

The mixing device provided by the utility model is provided with the first arc baffle and the second arc baffle, the first arc baffle and the second arc baffle form a mixing cavity, air flow can enter the mixing cavity through the front opening and the rear opening, the air flow enters the mixing cavity through the double-cyclone arc baffles to form four completely symmetrical opposite-impact vortex flows, urea is sprayed into the mixing cavity through the urea nozzle in the vertical air flow direction, the vortex flows are wrapped with urea liquid drops for mixing, the four cyclone flows are equivalent in size, the problem that urea is blown off can be greatly weakened, the air flow is dispersed again through the flow equalizing plate after further evaporation and decomposition through the evaporator below, and the air flow is forced to rotate, so that the mixed gas is distributed more uniformly on the section of a pipeline, the mixing capability of the mixing device is improved, the occurrence of crystallization is reduced, the uniformity of ammonia distribution is greatly improved, and the pressure loss can be effectively reduced.

The SCR system provided by the utility model is provided with the mixing device, and the mixing device has the technical effects, so that the SCR system provided with the mixing device also has the corresponding technical effects.

Drawings

Fig. 1 is a schematic structural diagram of a mixing device according to an embodiment of the present utility model.

FIG. 2 is a side view of the mixing device of FIG. 1;

fig. 3 is a schematic structural view of the flow equalization plate shown in fig. 1.

In the figure:

1-1, a first arc baffle 1-2, a second arc baffle 2, a drainage plate 3, a guide plate 31, an arc part 32, a side wing part 4, an evaporator 5, a flow equalizing plate 51, an air outlet 511, a cyclone drainage edge 52, a vent 6, a front opening 7, a rear opening 8, a through hole 9 and a hollow baffle

Detailed Description

In order to better understand the aspects of the present utility model, the present utility model will be described in further detail with reference to the accompanying drawings and detailed description.

In the present specification, the terms "upper, lower, inner, outer" and the like are established based on the positional relationship shown in the drawings, and the corresponding positional relationship may be changed according to the drawings, so that the terms are not to be construed as absolute limitation of the protection scope; moreover, relational terms such as "first" and "second", and the like, may be used solely to distinguish one element from another element having the same name, without necessarily requiring or implying any actual such relationship or order between such elements.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a cyclone mixer according to an embodiment of the utility model.

As shown in the figure, in a specific embodiment, the mixing device provided by the utility model mainly comprises a first arc-shaped baffle plate 1-1, a second arc-shaped baffle plate 1-2, a drainage plate 2, a flow guide plate 3, a flow equalization plate 5 and the like.

Wherein the first arc baffle plate 1-1 and the second arc baffle plate 1-2 are symmetrically arranged left and right in a mode of opposite openings, a mixing cavity is formed between the two arc baffle plates 1, a front opening 6 which is communicated with the mixing cavity is formed between the front side edges of the first arc baffle plate 1-1 and the second arc baffle plate 1-2, and a rear opening 7 which is communicated with the mixing cavity is formed between the rear side edges of the first arc baffle plate 1-1 and the second arc baffle plate 1-2; the drainage plate 2 is arc-shaped and is positioned at the rear side of the rear opening 7, an annular cavity which leads to the rear opening 7 from the left and right is formed between the drainage plate 2 and the first arc-shaped baffle plate 1-1 and between the drainage plate 2 and the second arc-shaped baffle plate 1-2, and through holes 8 distributed in a lattice form are respectively arranged on the plate bodies at the two sides of the opening formed by the two arc-shaped baffle plates 1.

The distance between the first arc baffle plate 1-1 and the second arc baffle plate 1-2 can be set between 20mm and 80mm according to different types, exhaust amount and temperature. In this way, an effective four swirl pattern of urea and exhaust gas in the mixer is ensured.

The bottoms of the first arc baffle plate 1-1, the second arc baffle plate 1-2 and the drainage plate 2 are provided with a hollow partition plate 9, a guide plate 3 perpendicular to the airflow direction is arranged below the hollow partition plate 9, and an evaporator 4, such as steel wool, positioned at the rear side of the guide plate can be arranged below the hollow partition plate 9.

The baffle 3 has an arcuate portion 31 which arches in the direction of the incoming air flow and wing portions 32 which are located on either side of the arcuate portion.

The front side edge of the flow guiding plate 2 is in an everted shape, and corresponds to the flank part 32 of the flow guiding plate 3, and the projections of the first arc-shaped baffle plate 1-1, the second arc-shaped baffle plate 1-2, the flow guiding plate 2 and the flow guiding plate 3 in the axial direction are provided with round outer contours on the whole so as to be convenient to install in the cylinder part. Of course, other shapes may be designed depending on the external member.

The rear side of the drainage plate 2 is provided with a flow equalizing plate 5, and a plurality of air outlet holes 51 are formed in the flow equalizing plate 5.

Referring to fig. 3 together, fig. 3 is a schematic structural diagram of the flow equalization plate shown in fig. 1.

As shown in the figure, the flow equalization plate 5 is circular, the air outlets 51 are distributed in a circular array with the center of the flow equalization plate 5 as the center, each air outlet 51 is a strip-shaped hole extending along the radial direction of the flow equalization plate 5, and the shape of radiating outwards from the position close to the center is shown in the whole. Of course, in other embodiments, the air outlet holes 51 may be arc holes, and the air outlet holes 51 are distributed in a vortex shape around the center of the flow equalizing plate 5.

Each air outlet hole 51 is provided with a cyclone drainage edge 511 on the same side, the cyclone drainage edge 511 protrudes towards the back surface of the flow equalizing plate 5, and is inclined or bent from the hole wall on one side to the hole wall on the other side, and the cyclone drainage edge 511 and the flow equalizing plate 5 can be integrally formed by stamping. Thus, when the air flow passes through the air outlet 51, the direction of the air flow is changed under the guiding action of the cyclone guiding edge 511, so as to form a plurality of air flows with an angle smaller than 90 degrees, such as 45 degrees or 60 degrees, with the plate surface of the flow equalizing plate 5, and then the air flows out in a cyclone shape.

In order to maintain the balance of the comprehensive performances of pressure loss, crystallization, uniformity and the like of the system, the flow equalizing plate 5 is also provided with a plurality of circular vent holes 52 distributed in a lattice form in the central area.

When the airflow passes through the flow equalizing plate 5, a part of the airflow passes through the air outlet holes 51 to form cyclone airflows, and the other part of the airflow passes through the air holes 52 in a dispersed manner along the axial direction to form axial airflows, and the cyclone airflows further flow backwards after being mixed with the axial airflows.

As shown in fig. 2, when the air flows into the mixing device from the arrow direction, the air flows can rotate at high speed under the combined action of the flow guiding plate 2, the flow guiding plate 3, the first arc baffle plate 1-1 and the second arc baffle plate 1-2 to form four uniformly distributed rotational flows, under the action of the rotational flows, the reducing agent liquid drops have enough time and conditions in the mixing space to be fully mixed with the waste gas, after the air flows downwards pass through the evaporator 4, the mixed air of urea and waste gas is subjected to disturbance and evaporation again, the mixing degree of various gases is further increased, the efficiency of the gasification conversion of urea is improved, the mixing uniformity of the air flows is enhanced, the mixed air after being mixed by the evaporator 4 is introduced into the downstream arranged flow equalizing plate 5, the air flows can be redistributed at the air outlet holes 51 and the vent holes 52 which are arranged according to the factors of flow speed, temperature and the like, so that the flow uniformity of the front end face of the SCR carrier is improved, and the occurrence of crystallization can be effectively reduced due to the fact that the urea spray can not be concentrated by the bias blowing, and the uniformity of ammonia distribution is improved.

The above embodiments are merely preferred embodiments of the present utility model, and are not limited thereto, and on the basis of these, specific adjustments may be made according to actual needs, thereby obtaining different embodiments. For example, the arc-shaped part 31 and the flank part 32 of the deflector 3 are also provided with air holes, etc. This is not illustrated here, as there are many possible implementations.

The mixing device provided by the utility model is used for an engine aftertreatment system, tail gas discharged by an engine and ammonia generated by urea decomposition are fully mixed in the mixing device, catalytic conversion is carried out in an SCR box under the high temperature effect of the tail gas, the effect of purifying the tail gas is achieved, the double rotational flow first arc baffle plate 1-1 and the second arc baffle plate 1-2 are matched with the flow equalizing plate 5, the interaction effect of the two arc baffle plates is far greater than the effect of independent use of the two arc baffle plates, the effect of the two arc baffle plates is enabled to be optimal, the passing air flows can be fully rotated and mixed, the conversion efficiency is improved, the urea crystallization risk is reduced, and the uniformity of ammonia distribution is greatly improved. In addition, the device has the advantages of simple structure, convenient process and manufacture, lower cost and the like.

In addition to the above-mentioned mixing device, the present utility model also provides an SCR system (i.e., a selective catalytic reduction system) comprising a catalyst and a mixing device located upstream of the catalyst, wherein the mixing device is the mixing device described above, which is disposed at the front side of the inlet of the catalyst, and a reducing agent injection port is disposed above the mixing chamber, and the reducing agent used may be urea or the like.

For the rest of the SCR system, please refer to the prior art, and the description thereof is omitted.

The mixing device and the SCR system provided by the utility model are described in detail above. The principles and embodiments of the present utility model have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the core concepts of the utility model. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the utility model can be made without departing from the principles of the utility model and these modifications and adaptations are intended to be within the scope of the utility model as defined in the following claims.

Claims

1. The mixing device is characterized by comprising a first arc-shaped baffle (1-1), a second arc-shaped baffle (1-2), a drainage plate (2) and a flow equalizing plate;

the first arc-shaped baffle plate (1-1) and the second arc-shaped baffle plate (1-2) are symmetrically arranged in a left-right mode in an opening opposite mode, and a mixing cavity is formed between the first arc-shaped baffle plate (1-1) and the second arc-shaped baffle plate (1-2); a front opening (6) which is communicated with the mixing cavity is formed between the front side edges of the first arc-shaped baffle plate (1-1) and the second arc-shaped baffle plate (1-2), and a rear opening (7) which is communicated with the mixing cavity is formed between the rear side edges of the first arc-shaped baffle plate (1-1) and the second arc-shaped baffle plate (1-2);

the drainage plate (2) is arc-shaped and is positioned at the rear side of the rear opening (7), and a cavity which is communicated to the rear opening (7) from the left side to the right side is formed between the drainage plate (2) and the first arc-shaped baffle (1-1) and the second arc-shaped baffle (1-2);

the flow equalizing plate (5) is arranged at the rear side of the flow guiding plate (2), air outlet holes (51) for forming cyclone air flow are formed in the flow equalizing plate (5), and the air outlet holes (51) are distributed in an annular array with the circle center of the flow equalizing plate (5) as the center.

2. The mixing device according to claim 1, wherein the first arched baffle (1-1), the second arched baffle (1-2) and the flow guiding plate (2) are arranged to guide the air flow into the mixing chamber through the front opening (6) and the rear opening (7), and four evenly distributed rotational flows can be formed under the action of the first arched baffle (1-1) and the second arched baffle (1-2) when the air flow passes through the mixing chamber.

3. The mixing device according to claim 1, wherein each of the gas outlet holes (51) extends from a center region of the flow equalizing plate (5) to an edge region.

4. A mixing device according to claim 3, wherein the air outlet holes (51) are elongated holes extending in the radial direction of the flow equalizing plate (5), or the air outlet holes (51) are arc-shaped holes, and a plurality of the air outlet holes (51) are spirally distributed around the center of the flow equalizing plate (5).

5. Mixing device according to claim 4, wherein each of said outlet holes (51) is provided with a cyclone drainage edge (511) on the same side.

6. The mixing device according to claim 5, characterized in that the cyclone drainage edge (511) protrudes towards the back of the flow equalization plate (5) and is inclined or curved from the wall of the hole on the side where it is located towards the wall of the hole on the other side.

7. The mixing device according to claim 6, characterized in that the central area of the flow equalization plate (5) is provided with a number of ventilation holes (52) distributed in a lattice.

8. The mixing device according to claim 1, wherein the bottoms of the first arc-shaped baffle plate (1-1), the second arc-shaped baffle plate (1-2) and the flow guiding plate (2) are provided with hollow partition plates (9), flow guiding plates (3) perpendicular to the air flow direction are arranged below the hollow partition plates (9), and the flow guiding plates (3) are provided with arc-shaped parts (31) arched towards the air flow coming direction and flank parts (32) positioned on two sides of the arc-shaped parts (31).

9. The mixing device according to any one of claims 1 to 8, wherein the spacing between the first and second arcuate baffles (1-1, 1-2) is 20mm to 80mm.

10. An SCR system comprising a catalyst and a mixing device upstream of the catalyst, characterized in that the mixing device is a mixing device according to any one of the preceding claims 1 to 9, which is provided with a reducing agent injection opening above its mixing chamber.