CN114320541A

CN114320541A - SCR aftertreatment device

Info

Publication number: CN114320541A
Application number: CN202111426107.9A
Authority: CN
Inventors: 王启琛; 李鹏远; 赵梦媛; 冯坦; 何胜勇; 李兴章; 魏明; 许法亮; 侯甲成; 赵文冉; 赵紫薇
Original assignee: Dongfeng Trucks Co ltd
Current assignee: Dongfeng Trucks Co ltd
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2022-04-12
Anticipated expiration: 2041-11-25
Also published as: CN114320541B

Abstract

The invention discloses an SCR (selective catalytic reduction) aftertreatment device, which comprises a vehicle particle trap and a vehicle catalytic reduction system, wherein the vehicle particle trap is connected with the vehicle catalytic reduction system through a pipeline, a backflow type aftertreatment mixer device is arranged in the pipeline, the backflow type aftertreatment mixer device comprises an air inlet chamber, a contraction chamber and a diffusion chamber, the air inlet chamber is arranged at the upstream of the contraction chamber, the contraction chamber is arranged at the upstream of the diffusion chamber, the volume of the air inlet chamber is larger than that of the contraction chamber, the volume of the diffusion chamber is larger than that of the contraction chamber, an exhaust port structure for forming vortex is arranged on the inner wall of one side of the diffusion chamber, which is close to the air inlet chamber, the direction of mixed gas entering the air inlet chamber from an air inlet is opposite to the direction of the mixed gas flowing out of the diffusion chamber from the exhaust port structure, the mixed gas flowing out of the diffusion chamber from the gas outlet structure flows around the peripheral wall of the diffusion chamber and then flows downstream. According to the invention, through the change of the cavity shape, the design of contraction, expansion, reverse rotational flow and flow winding of air flow in the mixer is realized, and the purposes of uniform mixing of urea and exhaust gas and prevention of rapid crystallization of urea are realized.

Description

SCR aftertreatment device

Technical Field

The invention discloses a mixer device, belongs to the technical field of mixers, and particularly discloses an SCR (selective catalytic reduction) aftertreatment device.

Background

With the development of society, the national emission requirements on diesel engines are higher and higher, and the post-treatment device of the national VI/Euro VI diesel engine generally adopts a technical route of CH injection plus DOC plus DPF plus SCR. The SCR technology is a main post-treatment technology for eliminating nitrogen oxides in diesel engine exhaust and is used for reducing main harmful components of nitrogen oxides in the diesel engine exhaust into nitrogen and water. SCR technology is one of the major aftertreatment technologies for the elimination of nitrogen oxides in diesel exhaust. The device is mainly divided into a control unit, a urea dosage unit and a catalytic reaction unit according to functions; the control unit of the SCR system is integrated with a control unit (ECU) of an engine, and is mainly used for executing an SCR control strategy, controlling a urea dosage unit according to ambient temperature, exhaust temperature, urea liquid level, urea temperature and urea pressure sensor signals, and injecting urea solution into exhaust airflow regularly and quantitatively according to requirements; the urea dosage unit mainly comprises a urea box, a urea supply unit, a urea injection unit, a heating assembly, a connecting pipeline and a circuit, and ensures the sufficient atomization and decomposition of urea solution; the catalytic reaction unit mainly comprises an SCR catalyst, a carrier and a package thereof, and is used for reducing main harmful components of nitrogen oxide in the exhaust gas of the diesel engine into nitrogen and water. A series of complex chemical reactions occur during the hydrolysis of the aqueous urea solution ejected from the nozzle to produce ammonia. Various intermediate products such as biuret and cyanuric acid are generated in the chemical reaction process. And urea crystals attached to an air inlet mixing pipeline of the SCR catalytic muffler, especially a urea injection drop point, can be condensed into biuret and cyanuric acid at high temperature, and even can generate melamine and the like to form calculus. Decomposition also occurs at higher temperatures, but if the rate of decomposition of the intermediate product is less than the rate of formation, stones will accumulate, thus greatly increasing the probability of the urea aqueous solution colliding with the walls and accelerating the formation of crystals.

When the SCR device works, exhaust flows out of a turbocharger turbine and then enters an exhaust pipe, a urea injection unit arranged on the exhaust pipe injects a quantitative urea water solution into the exhaust pipe in a mist form, and urea liquid drops are subjected to hydrolysis and pyrolysis reactions under the action of high-temperature exhaust gas. In order to improve the uniformity of mixing, a mixing device for mixing the exhaust gas and the urea aqueous solution needs to be provided inside the SCR device. At present, the air flow speed at the bottom of a mixing cavity of a mixing device is reduced, urea crystals are easy to form, post-treatment crystallization faults of a diesel engine are easy to occur, and the content of urea solution in mixed air is inconsistent with a set value. Therefore, how to avoid the reduction of the bottom air velocity of the mixing cavity of the mixing device, avoid the formation of urea crystals at the bottom of the mixing cavity, reduce the failure rate caused by the post-treatment crystallization of the diesel engine, and ensure the content of the urea solution in the mixed gas becomes a technical problem to be solved urgently by the technical personnel in the field.

To above-mentioned technical problem, chinese utility model patent CN205370704U discloses in the specification an SCR air intake mixer, it includes columniform body, the body includes the outer pipe that admits air, the inlayer pipe and the transition connecting plate admit air, the outer pipe that admits air is connected the inlayer pipe that admits air through the transition connecting plate, the diameter of the inlayer pipe that admits air is less than 70mm, the transition connecting plate extends to the inside enclosed construction that constitutes of the inlayer pipe that admits air, the transition connecting plate is the irregular shape that prevents urea condensation with the inlayer pipe that admits air, its theory of operation is as follows: the SCR air inlet mixer mainly comprises an air inlet outer layer pipe, an air inlet inner layer pipe and a transition connecting plate. The air inlet inner layer pipe is an irregular pipeline which is formed by processing a regular pipe body. The position (namely the air inlet end) on the pipe body is determined according to one side far away from the urea nozzle, and the determination principle is to ensure that the urea water solution sprayed by the urea nozzle completely enters the air inlet inner-layer pipe. Meanwhile, through holes are formed from top to bottom in the range of 200 degrees in the diameter direction of the gas inlet inner-layer pipe, so that mixed gas flows out. And a pipeline with the diameter direction within 150 degrees is cut downwards by taking the air inlet end determined by the pipe body as a starting point at one side close to the urea nozzle, and the cutting height is used for ensuring that the urea solution sprayed out of the urea nozzle cannot touch the air inlet inner-layer pipe. The bottom of the air inlet inner layer pipe is provided with four square grooves to prevent the bottom of the air inlet inner layer pipe from forming a flowing dead zone. Secondly, the transition connecting plate is designed according to the determined height of the air inlet inner pipe, the air inlet inner pipe and the air inlet outer pipe are fully and reliably connected according to the principle of the design of the transition connecting plate, and the final and only flow direction of gas is ensured to be through holes formed in the air inlet inner pipe, so that the mixing uniformity of tail gas is improved, and the catalytic conversion efficiency of the SCR catalytic muffler is improved. Although the technical scheme can increase the conversion efficiency of the SCR box and improve the mixing uniformity of the discharged tail gas and the urea solution, the technical scheme has the following technical defects: the drum aftertreaters are all arranged horizontally, and when the drum aftertreaters are arranged numerically, when the urea spray and the mixer hit the wall to form a wall film, the wall film will fall and gather under the action of weight to form urea crystals, so the drum aftertreaters cannot be adapted to the vertically arranged drum aftertreaters.

Further, the specification of chinese patent application CN107530655B discloses a mixer for a vehicle exhaust system, comprising a mixer body defining a mixer central axis and having an inlet configured for receiving engine exhaust gases and an outlet. The mixer further comprises: an upstream baffle positioned within the mixer body; and a downstream baffle positioned within the mixer body spaced from the upstream baffle in a direction along the mixer central axis. A doser defines a doser axis and is positioned to spray a reducing agent into an area between the upstream baffle and the downstream baffle such that a mixture of reducing agent and exhaust gas exits the outlet. The mixture moves through a rotational flow path of at least 360 degrees before exiting the outlet. The disclosed compact mixer allows flow rotation of 300 degrees up to 480 degrees or more to increase mixing performance and DEF conversion. In addition, this improved performance is provided without increasing the axial length of the mixer and otherwise adversely affecting the back pressure. This significant amount of rotation is provided, for example, within a mixer having an overall length of between 7 and 10 inches. However, it has the following technical disadvantages: the drum aftertreaters are all arranged horizontally, and when the drum aftertreaters are arranged numerically, when the urea spray and the mixer hit the wall to form a wall film, the wall film will fall and gather under the action of weight to form urea crystals, so the drum aftertreaters cannot be adapted to the vertically arranged drum aftertreaters.

Further, the specification of chinese patent CN110578581A also discloses an intake mixing device, which comprises a housing, wherein an intake rectifying plate is arranged in the housing, an intake baffle is arranged on one side of the intake rectifying plate close to the intake end, and an intake swirling plate is arranged on one side of the intake rectifying plate close to the exhaust end; a mixing cavity is formed between the air inlet baffle and the air inlet rectifying plate, a flow guide cavity is formed between the air inlet rectifying plate and the air inlet swirling plate, and an air guide channel is arranged between the mixing cavity and the flow guide cavity; the upper space of the mixing chamber is larger than the lower space of the mixing chamber. The air inlet mixing device can avoid the reduction of the air flow speed at the bottom of the mixing cavity of the mixing device, prevent the formation of urea crystals at the bottom of the mixing cavity, reduce the failure rate caused by post-treatment crystallization of a diesel engine and ensure the content of urea solution in the mixed gas. However, it has the following technical disadvantages: the drum aftertreaters are all arranged horizontally, and when the drum aftertreaters are arranged numerically, when the urea spray and the mixer hit the wall to form a wall film, the wall film will fall and gather under the action of weight to form urea crystals, so the drum aftertreaters cannot be adapted to the vertically arranged drum aftertreaters.

Further, the specification of the chinese invention patent CN105464764B also discloses a mixer and an SCR system for an exhaust facility. The mixer for an exhaust facility includes: a gas swirler and a liquid disperser; the gas swirler is in a shape of a shell and comprises a gas inlet, and a first hole and a second hole which are opposite to each other are formed in the gas swirler in a direction perpendicular to the gas inlet direction; one end of the liquid disperser penetrates through the second hole and is vertically connected with the gas cyclone; the first hole of the gas swirler is used for introducing the reducing agent sprayed by the nozzle; the liquid disperser is provided with at least one blade influencing the flow direction of the gas, and the blade is positioned in the gas swirler; the liquid disperser is provided with a plurality of through holes, and the through holes are positioned outside the gas swirler and used for dispersing the reducing agent introduced by the gas swirler. The invention makes the reducing agent distribute evenly, avoids crystallization and improves the efficiency of the selective catalytic reduction reaction. However, it has the following technical disadvantages: the drum aftertreaters are all arranged horizontally, and when the drum aftertreaters are arranged numerically, when the urea spray and the mixer hit the wall to form a wall film, the wall film will fall and gather under the action of weight to form urea crystals, so the drum aftertreaters cannot be adapted to the vertically arranged drum aftertreaters.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention provides an SCR post-treatment device which realizes the design of contraction, expansion, reverse rotational flow and flow winding of airflow in a mixer through the change of a cavity shape, and realizes the purposes of uniform mixing of urea and exhaust gas and prevention of rapid crystallization of the urea.

The invention discloses an SCR (selective catalytic reduction) aftertreatment device, which comprises a vehicle particle trap and a vehicle catalytic reduction system, wherein the vehicle particle trap is connected with the vehicle catalytic reduction system through a pipeline, a backflow type aftertreatment mixer device is arranged in the pipeline, the backflow type aftertreatment mixer device comprises an air inlet chamber, a contraction chamber and a diffusion chamber, the air inlet chamber is arranged at the upstream of the contraction chamber, the contraction chamber is arranged at the upstream of the diffusion chamber, the volume of the air inlet chamber is larger than that of the contraction chamber, the volume of the diffusion chamber is larger than that of the contraction chamber, an exhaust port structure for forming vortex is arranged on the inner wall of one side of the diffusion chamber, which is close to the air inlet chamber, the direction of mixed gas entering the air inlet chamber from an air inlet is opposite to the direction of the mixed gas flowing out of the diffusion chamber from the exhaust port structure, the mixed gas flowing out of the diffusion chamber from the gas outlet structure flows around the peripheral wall of the diffusion chamber and then flows downstream.

In a preferred embodiment of the present invention, the exhaust port structure includes four sets of rotationally symmetric array exhaust structures, each set of array exhaust structure includes a plurality of exhaust square holes, the plurality of exhaust square holes are arranged in an equilateral right-angled triangle array, and each exhaust square hole is provided with a rotational flow plate forming a certain inclination angle with the exhaust square hole.

In a preferred embodiment of the invention, the array exhaust structures in the first quadrant and the array exhaust structures in the third quadrant are arranged in mirror image with respect to the rotational symmetry center of the exhaust port structures, the array exhaust structures in the second quadrant and the array exhaust structures in the fourth quadrant are arranged in mirror image with respect to the rotational symmetry center of the exhaust port structures, and the array exhaust structures in the first quadrant are rotated 90 ° around the rotational symmetry center of the exhaust port structures to coincide with the array exhaust structures in the second quadrant.

In a preferred embodiment of the present invention, the rotational symmetry axes of the array exhaust structures in the first quadrant and the array exhaust structures in the second quadrant are parallel to the central axis of the diffusion chamber, and the rotational symmetry axes of the array exhaust structures in the second quadrant and the array exhaust structures in the third quadrant are perpendicular to the central axis of the diffusion chamber.

In a preferred embodiment of the present invention, the angle of the swirl plate with respect to the angle of inclination of the discharge square hole is 3 ° to 30 °.

In a preferred embodiment of the invention, the intake chamber comprises a plug-in housing section for connecting a pipeline and a flow guiding housing section for guiding the gas mixture into the contraction chamber.

In a preferred embodiment of the invention, the plug housing section is connected to the pipeline in a sealed manner.

In a preferred embodiment of the invention, the flow-guiding shell section is in the shape of a circular arch, the center of which is located on the same side as the central axis of the contraction chamber.

In a preferred embodiment of the invention, the contraction chamber comprises a cylindrical shell section having a central axis perpendicular to or intersecting a central axis of the intake chamber, the central axis of the cylindrical shell section being collinear with a central axis of the diffusion chamber.

In a preferred embodiment of the invention, the cross-sectional shape of the diffusion chamber is a sector, the radius of the sector corresponding to the radius of the duct.

In a preferred embodiment of the present invention, the mixed gas is urea and air.

The invention has the beneficial effects that: the invention has the advantages of simple structure, easy processing and forming, low cost, short mixing distance and light weight, and adopts the following technical scheme that the device comprises an air inlet chamber, a contraction chamber and a diffusion chamber, wherein the air inlet chamber is arranged at the upstream of the contraction chamber, the contraction chamber is arranged at the upstream of the diffusion chamber, the volume of the air inlet chamber is larger than that of the contraction chamber, the volume of the diffusion chamber is larger than that of the contraction chamber, an air outlet structure for forming vortex is arranged on the inner wall of one side of the diffusion chamber close to the air inlet chamber, the direction of mixed gas entering the air inlet chamber from an air inlet is opposite to the direction of the mixed gas flowing out of the diffusion chamber from the air outlet structure, and the mixed gas flowing out of the diffusion chamber from the air outlet structure flows to the downstream after flowing around the peripheral wall of the diffusion chamber; therefore, the contraction, expansion, reverse rotational flow and streaming of the mixed gas are realized, the uniform mixing of the urea and the exhaust gas in the mixed gas is effectively promoted, and the aim of uniform mixing is fulfilled; the air flow reversely flows and bypasses the two sides of the mixer, so that the exhaust improves the temperature of the fan-shaped plate of the mixer, and the urea crystallization caused by low internal temperature of the mixer is avoided;

furthermore, the air inlet chamber, the contraction chamber and the diffusion chamber are arranged, so that the flow speed of exhaust is effectively improved, the improvement of the exhaust speed is beneficial to the crushing of urea, and small urea particles are formed, so that the urea crystallization is effectively prevented;

furthermore, the exhaust port structure adopts the following technical scheme: the device comprises four groups of rotationally symmetrical array exhaust structures, each group of array exhaust structure comprises a plurality of exhaust square holes, the exhaust square holes are arranged in an equilateral right triangle array, each exhaust square hole is provided with a rotational flow plate which forms a certain inclination angle with the exhaust square hole, the array exhaust structure in a first quadrant and the array exhaust structure in a third quadrant are arranged in a mirror image mode relative to the rotationally symmetrical center of an exhaust port structure, the array exhaust structure in a second quadrant and the array exhaust structure in a fourth quadrant are arranged in a mirror image mode relative to the rotationally symmetrical center of the exhaust port structure, the array exhaust structure in the first quadrant rotates for 90 degrees around the rotationally symmetrical center of the exhaust port structure and is superposed with the array exhaust structure in the second quadrant, the rotationally symmetrical axes of the array exhaust structure in the first quadrant and the array exhaust structure in the second quadrant are parallel to the central axis of a diffusion chamber, the rotational symmetry axes of the array exhaust structure in the second quadrant and the array exhaust structure in the third quadrant are vertical to the central axis of the diffusion chamber; according to the technical scheme, mixed components of mixed gas (urea and air) can flow through two sides of the diffusion shell after coming out of the cyclone plate to form a large vortex, so that the mixing uniformity is promoted, and exhaust gas flows around two sides of the diffusion cavity shell after coming out of the cyclone plate, so that the temperature of the diffusion cavity shell is improved, and urea is prevented from being attached to the interior of the mixer to form crystals;

furthermore, the inclination angle of the swirl plate relative to the exhaust square hole can be reasonably selected according to the requirement, so that the flow velocity of the large vortex is effectively controlled, and the universality of the cyclone plate is improved;

further, the air inlet chamber of the invention adopts the following design: the gas-liquid separation device comprises an inserting shell section and a flow guide shell section, wherein the inserting shell section is used for connecting a pipeline, the flow guide shell section is used for guiding mixed gas into a contraction cavity, the inserting shell section is hermetically connected with the pipeline, the flow guide shell section is in a circular arch shape, and the center of the circular arch and the central axis of the contraction cavity are positioned on the same side; the technical scheme can effectively prevent the mixed gas at the upstream of the pipeline from flowing to the downstream of the pipeline, and can increase the time for the mixed gas to flow into the contraction cavity from the pipeline, so that the mixed gas (urea and air) is more fully contacted and mixed;

furthermore, the flow guide shell section is in a circular arch shape, the center of the circular arch and the central axis of the contraction cavity are positioned on the same side, the contraction cavity comprises a cylindrical shell section, the central axis of the cylindrical shell section is perpendicular to or intersected with the central axis of the air inlet cavity, and the central axis of the cylindrical shell section is collinear with the central axis of the diffusion cavity, so that the contraction of air flow can be promoted, the air flow can completely pass through the middle throat position of the mixer, the exhaust flow speed is effectively increased, the increase of the exhaust speed is favorable for the crushing of urea, and smaller urea particles are formed;

furthermore, the cross section of the diffusion chamber is in a fan shape, the radius of the fan shape corresponds to that of the pipeline, and the fan-shaped diffusion shell is favorable for mixing exhaust gas and urea in the chamber.

Drawings

FIG. 1 is a schematic view of an SCR aftertreatment device of the present invention;

FIG. 2 is a schematic illustration of a recirculation aftertreatment mixer arrangement of an SCR aftertreatment apparatus of the present invention;

FIG. 3 is a front view of a recirculation aftertreatment mixer arrangement of an SCR aftertreatment apparatus of the present invention;

FIG. 4 is a cross-sectional view of a recirculation aftertreatment mixer arrangement of an SCR aftertreatment arrangement of the present invention;

FIG. 5 is a schematic illustration of an array exhaust configuration of a recirculation aftertreatment mixer arrangement of an SCR aftertreatment apparatus of the present invention;

FIG. 6 is an isometric view of an array exhaust structure of a recirculation aftertreatment mixer arrangement of an SCR aftertreatment device of the present invention;

in the figure: 1-an air inlet chamber; 2-contracting the chamber; 3-a diffusion chamber; 4-a vent port configuration; 11-an insertion housing section; 12-a flow guiding shell section; 21-a cylindrical shell section; 41-array exhaust structure; 42-exhaust square holes; 43-a swirl plate; a-a pipeline; and B-urea nozzle.

Detailed Description

The invention will now be described in further detail, including the preferred embodiments, with reference to the accompanying drawings and by way of illustration of some alternative embodiments of the invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

Further, in the present application, relational terms such as "first" and "second", and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The invention discloses a vehicle catalytic reduction system and a vehicle particulate trap, wherein the vehicle particulate trap DPF is connected with the vehicle catalytic reduction system SCR through a pipeline A, a backflow type aftertreatment mixer device is arranged in the pipeline, a urea nozzle B is arranged on the pipeline A and is positioned at the upstream of the backflow type aftertreatment mixer device, the backflow type aftertreatment mixer device comprises an air inlet chamber 1, a contraction chamber 2 and a diffusion chamber 3, the air inlet chamber 1, the contraction chamber 2 and the diffusion chamber 3 are arranged in sequence from top to bottom in space, the air inlet chamber 1 is communicated with the upstream of the pipeline, mixed gas (urea + exhaust) flows in from the air inlet chamber 1, the diffusion chamber 3 is communicated with the downstream of the pipeline, the mixed gas (urea + exhaust) flows into a downstream pipeline from the diffusion chamber 3, the contraction chamber 2 is communicated with the air inlet chamber 1 and the diffusion chamber 3, so that the mixed gas (urea + exhaust) flows downwards from the air inlet chamber 1 into the contraction chamber 2 and then flows into the exhaust chamber, Then flows downwards into a diffusion chamber 3, an air inlet chamber 1 is arranged at the upstream of a contraction chamber 2, the contraction chamber 2 is arranged at the upstream of the diffusion chamber 3, the volume of the air inlet chamber 1 is larger than that of the contraction chamber 2, the volume of the diffusion chamber 3 is larger than that of the contraction chamber 2, no limitation is imposed between the volume of the air inlet chamber 1 and that of the contraction chamber 2, the reasonable design is carried out as required, an air outlet structure 4 for forming vortex is arranged on the inner wall of one side of the diffusion chamber 3 close to the air inlet chamber 1, namely the air outlet structure 4 is positioned on the inner wall of the upstream side, the direction of the mixed gas (urea + exhaust) entering the air inlet chamber 1 from an air inlet is opposite to the direction of the mixed gas (urea + exhaust) flowing out of the diffusion chamber 3 from the air outlet structure 4, and the mixed gas (urea + exhaust) flowing out of the diffusion chamber 3 from the air outlet structure 4 flows around the outer peripheral wall of the diffusion chamber 3 and then flows to the downstream, by using the device according to the invention, the flow direction of the mixed gas (urea + exhaust) can be summarized as follows: when the mixed gas (urea + exhaust gas) passes through the mixer, the mixed gas (urea + exhaust gas) vertically flows downwards into the contraction cavity 2, so that the gas flow completely passes through the middle throat of the mixer; after passing through the contraction chamber 2, the mixed gas (urea + exhaust gas) flows vertically downwards to the fan-shaped diffusion chamber 3, and the mixed gas (urea + exhaust gas) is diffused in a fan shape in the diffusion chamber 3; after the mixed gas (urea + exhaust) flows out of the diffusion chamber 3 through the rotational flow plate with the angle on the diffusion chamber 3, the mixed gas (urea + exhaust) flows to the downstream of the pipeline around the outer walls of the two sides of the diffusion chamber 3.

In a preferred embodiment of the invention, the reflux type aftertreatment mixer device adopts one-time injection molding or drawing molding of a plate, and can realize the design of contraction, expansion, reverse rotational flow and flow winding of mixed gas (urea and air) in a cavity through the change of the shape of the cavity, thereby realizing the purposes of uniform mixing of the urea and exhaust gas and preventing the rapid crystallization of the urea.

In a preferred embodiment of the present invention, the exhaust port structure 4 comprises four sets of rotational symmetric array exhaust structures 41, the four sets of rotational symmetric array exhaust structures 41 form a square array structure, each set of array exhaust structures 41 comprises a plurality of exhaust square holes 42, the plurality of exhaust square holes 42 are arranged in an equilateral right triangle array, as shown in the figure, the square array structure comprises 5 rows and 4 columns, the first row comprises 1 exhaust square hole 42, the second row comprises 2 exhaust square holes 42, the third row comprises 3 exhaust square holes 42, the fourth row comprises 4 exhaust square holes 42, the fifth row comprises 5 exhaust square holes 42, the row spacing and the column spacing between the exhaust square holes 42 correspond to each other, each exhaust square hole 42 is provided with a swirl plate 43 having a certain inclination angle with the exhaust square holes 42, the presence of the swirl plate 43 enables the diffusion chamber 3 to form a rotational airflow when flowing out, the mixed gas (urea and exhaust) is enabled to bypass to the two sides of the sector plate to form colliding gas flow, urea mixing is promoted, urea mixing uniformity is promoted, and the aim of mixing uniformity is achieved.

In a preferred embodiment of the present invention, four sets of array exhaust structures 41 arranged in a rotational symmetry correspond to four quadrants, respectively, the array exhaust structures 41 in the first quadrant and the array exhaust structures 41 in the third quadrant are arranged in a mirror image with respect to the rotational symmetry center of the exhaust port structure 4, the array exhaust structures 41 in the second quadrant and the array exhaust structures 41 in the fourth quadrant are arranged in a mirror image with respect to the rotational symmetry center of the exhaust port structure 4, the array exhaust structures 41 in the first quadrant are rotated 90 ° around the rotational symmetry center of the exhaust port structure 4 to coincide with the array exhaust structures 41 in the second quadrant, the array exhaust structures 41 in the second quadrant are rotated 90 ° around the rotational symmetry center of the exhaust port structure 4 to coincide with the array exhaust structures 41 in the third quadrant, the array exhaust structures 41 in the third quadrant are rotated 90 ° around the rotational symmetry center of the exhaust port structure 4 to coincide with the array exhaust structures 41 in the fourth quadrant, the array exhaust structure 41 in the fourth quadrant is rotated 90 around the rotational symmetry centre of the exhaust port structure 4 to coincide with the array exhaust structure 41 in the first quadrant.

In a preferred embodiment of the present invention, the rotational symmetry axes of the array exhaust structure 41 in the first quadrant and the array exhaust structure 41 in the second quadrant are parallel to the central axis of the diffusion chamber 3, and the rotational symmetry axes of the array exhaust structure 41 in the second quadrant and the array exhaust structure 41 in the third quadrant are perpendicular to the central axis of the diffusion chamber 3.

In a preferred embodiment of the invention, the gas mixture (urea + exhaust gas) is rotated counterclockwise by the swirl plate 43, seen from the inside to the outside of the diffusion chamber 3.

In a preferred embodiment of the present invention, the angle of inclination of the swirl plate 43 with respect to the discharge square hole 42 is 3 ° to 30 °, which can be selected as desired.

In a preferred embodiment of the invention, the vent structure 4 may be manufactured separately, i.e. as a disc-shaped standardized structure which can be welded or glued to the diffusion chamber 3, in order to facilitate the shaping according to the invention.

In a preferred embodiment of the invention, the intake chamber 1 comprises a plug-in housing section 11 for connecting to a pipeline and a flow guiding housing section 12 for guiding the mixture into the contraction chamber 2, the shape of the plug-in housing section 11 corresponding to the shape of the pipeline, in order to facilitate the flow of the mixture (urea + exhaust gas) in the pipeline into the flow guiding housing section 12, the plug-in housing section 11 can be designed in an arc shape, i.e. the plug-in housing section 11 and the diffusion chamber 3 form a trigger similar to a pistol.

In a preferred embodiment of the invention, the plug housing section 11 is connected to the pipeline in a sealed manner, i.e. the plug housing section 11 can divide the pipeline into two parts: the device comprises an upstream pipeline and a downstream pipeline, wherein the upstream pipeline and the downstream pipeline are communicated only through an air inlet chamber 1, a contraction chamber 2 and a diffusion chamber 3, namely, mixed gas (urea + exhaust gas) cannot flow into the downstream pipeline from the upstream pipeline without passing through the device; the downstream pipeline is communicated with the diffusion chamber 3 only through the exhaust square hole 42, that is, the mixed gas (urea + exhaust gas) in the diffusion chamber 3 cannot be directly communicated with the downstream pipeline without passing through the exhaust square hole 42.

In a preferred embodiment of the invention, the flow guiding housing section 12 is in the shape of a circular arch, the center of which is located on the same side as the central axis of the contraction chamber 2, and the mixed gas (urea + exhaust gas) can flow more smoothly into the contraction chamber 2 under the action of the circular arch shaped flow guiding housing section 12.

In a preferred embodiment of the invention, the contraction chamber 2 comprises a cylindrical shell section 21, the horizontal area of the cylindrical shell section 21 is smaller than the horizontal projection of the flow guiding shell section 12, the central axis of the cylindrical shell section 21 is perpendicular to or intersects the central axis of the air inlet chamber 1, and the central axis of the cylindrical shell section 21 is collinear with the central axis of the diffusion chamber 3.

In a preferred embodiment of the present invention, the cross-sectional shape of the diffusion chamber 3 is a sector, that is, the projection of the diffusion chamber 3 on the vertical plane is a sector, and the radius of the sector corresponds to the radius of the pipeline, so that the sealing between the diffusion chamber 3 and the pipeline can be ensured, and the mixed gas (urea + exhaust gas) in the diffusion chamber 3 is prevented from directly diffusing to the downstream pipeline without passing through the exhaust square hole 42, and thus the bypass flow of the mixed gas (urea + exhaust gas) cannot be realized.

The invention promotes the uniform mixing of urea and exhaust gas through the design of shrinkage, expansion, reverse rotational flow and streaming, thereby achieving the aim of uniform mixing; through making the air current reverse flow, the air current walks around the blender both sides, and the exhaust has promoted the temperature of blender sector plate, avoids the inside low urea crystallization that causes of temperature of blender to produce. It has the following advantages:

1. uniformly mixing: the flow speed of the exhaust gas is improved through shrinkage, and the improvement of the exhaust speed is beneficial to the crushing of the urea to form smaller urea particles; the fan-shaped diffusion shell is beneficial to mixing of exhaust gas and urea in the cavity; the rotational flow plate forms rotational flow to promote the mixing of the urea and the exhaust gas; after the mixed components of urea and exhaust gas come out from the cyclone plate, the mixed components flow through the two sides of the diffusion shell to form a large vortex, so that the mixing uniformity is promoted.

2. Preventing urea from crystallizing: the exhaust flow speed is improved through shrinkage, the urea is crushed by the improvement of the exhaust speed, smaller urea particles are formed, and urea crystallization can be prevented; after the exhaust comes out from the rotational flow plate, the exhaust flows to the two sides of the diffusion cavity shell in a winding manner, so that the temperature of the diffusion cavity shell is improved, and the urea is prevented from being attached to the inside of the mixer to form crystals

3. According to the invention, a technical scheme of closing in and fan-shaped diffusion is adopted, through the technical scheme, the exhaust speed can be increased at the closing in position, the exhaust speed is reduced in a fan-shaped area, and the exhaust gas and urea are promoted to be uniformly mixed by using a jet drainage mode;

4. according to the invention, by adopting the technical scheme that the airflow passes through the fan-shaped cyclone plate and a mode of reverse main airflow flow, the airflow mixing distance is increased, and the mixing uniformity is promoted;

5. the invention adopts the technical scheme that the airflow bypasses the two sides of the sector plate, thereby achieving the purposes of promoting the uniform mixing of the urea and the exhaust gas and heating the sector plate, and the heating of the sector plate is helpful for solving the problem of urea crystallization.

The invention can be applied to various types of vehicles, a mixer is arranged in a connecting cavity between the DPF and the SCR of the vehicle, and the uniform mixing of the urea and the exhaust gas is promoted through the design of contraction, expansion, reverse rotational flow and flow winding, so that the aim of uniform mixing is fulfilled; through making the air current reverse flow, the air current detours the blender both sides, and the exhaust has promoted the temperature of blender sector plate, avoids the inside low urea crystallization that causes of temperature of blender to produce to the working property of vehicle has been improved effectively.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and any modification, combination, replacement, or improvement made within the spirit and principle of the present invention is included in the scope of the present invention.

Claims

1. An SCR aftertreatment device comprising a vehicle particulate trap and a vehicle catalytic reduction system connected by a conduit, the SCR aftertreatment device comprising: the pipeline is internally provided with a reflux type aftertreatment mixer device, the reflux type aftertreatment mixer device comprises an air inlet cavity (1), a contraction cavity (2) and a diffusion cavity (3), the air inlet cavity (1) is arranged at the upstream of the contraction cavity (2), the contraction cavity (2) is arranged at the upstream of the diffusion cavity (3), the volume of the air inlet cavity (1) is larger than that of the contraction cavity (2), the volume of the diffusion cavity (3) is larger than that of the contraction cavity (2), an air outlet structure (4) for forming vortex is arranged on the inner wall of one side of the diffusion cavity (3) close to the air inlet cavity (1), the direction of mixed gas in the pipeline entering the air inlet cavity (1) from an air inlet is opposite to the direction of the mixed gas flowing out of the diffusion cavity (3) from the air outlet structure (4), the mixed gas flowing out of the diffusion chamber (3) from the gas outlet structure (4) flows around the peripheral wall of the diffusion chamber (3) and then flows downstream.

2. The SCR aftertreatment device of claim 1, wherein: the exhaust port structure (4) comprises four groups of array exhaust structures (41) which are arranged in a rotational symmetry mode, each group of array exhaust structures (41) comprises a plurality of exhaust square holes (42), the exhaust square holes (42) are arranged in an equilateral right-angled triangle array mode, and each exhaust square hole (42) is provided with a cyclone plate (43) which forms a certain inclination angle with the exhaust square hole (42).

3. The SCR aftertreatment device of claim 2, wherein: the array exhaust structure (41) in the first quadrant and the array exhaust structure (41) in the third quadrant are arranged in a mirror image mode relative to the rotational symmetry center of the exhaust port structure (4), the array exhaust structure (41) in the second quadrant and the array exhaust structure (41) in the fourth quadrant are arranged in a mirror image mode relative to the rotational symmetry center of the exhaust port structure (4), and the array exhaust structure (41) in the first quadrant is rotated by 90 degrees around the rotational symmetry center of the exhaust port structure (4) and is overlapped with the array exhaust structure (41) in the second quadrant.

4. The SCR aftertreatment device of claim 2, wherein: the rotational symmetry axes of the array exhaust structures (41) in the first quadrant and the array exhaust structures (41) in the second quadrant are parallel to the central axis of the diffusion chamber (3), and the rotational symmetry axes of the array exhaust structures (41) in the second quadrant and the array exhaust structures (41) in the third quadrant are perpendicular to the central axis of the diffusion chamber (3).

5. The SCR aftertreatment device of claim 2, wherein: the angle of the swirl plate (43) relative to the inclination angle of the exhaust square hole (42) is 3-30 degrees.

6. The SCR aftertreatment device of claim 1, wherein: the gas inlet chamber (1) comprises a plug-in housing section (11) for connecting a pipeline and a flow guiding housing section (12) for guiding mixed gas into the contraction chamber (2).

7. The SCR aftertreatment device of claim 6, wherein: the inserting shell section (11) is connected with the pipeline in a sealing mode.

8. The SCR aftertreatment device of claim 6, wherein: the diversion shell section (12) is in a circular arch shape, and the center of the circular arch and the central axis of the contraction cavity (2) are positioned on the same side.

9. The SCR aftertreatment device of claim 1, wherein: the contraction chamber (2) comprises a cylindrical shell section (21), the central axis of the cylindrical shell section (21) is perpendicular to or intersects the central axis of the intake chamber (1), and the central axis of the cylindrical shell section (21) is collinear with the central axis of the diffusion chamber (3).

10. The SCR aftertreatment device of claim 1, wherein: the cross section of the diffusion chamber (3) is in the shape of a sector, and the radius of the sector corresponds to that of the pipeline.