Post-treatment drum mixer

Abstract

The invention relates to an after-treatment cylinder type mixer which comprises a double-layer shell assembly with a heat preservation structure and an inner core assembly. A urea nozzle seat is arranged on the shell assembly; the inner core assembly is located in the shell assembly and comprises a support, a fixing cylinder, a rotary taper pipe and a Venturi pipe. The support is installed in the mixing cavity of the shell assembly and divides the mixing cavity into a front cavity and a rear cavity. The fixed cylinder is vertically arranged on the base plate of the bracket in a penetrating manner; the rotary cone tube is arranged at the upper end of the fixed cylinder, the upper end of the rotary cone tube is matched and aligned with a bottom jet orifice of the urea nozzle seat, and the upper end of the venturi tube is connected with the rotary cone tube while the lower end extends out of the fixed cylinder. The mixer is compact in structure, urea and exhaust gas can be efficiently and evenly mixed, urea spray can be prevented from being attached to the wall face, and the mixer has the advantages of being simple in structure, high in crystallization resistance and even and efficient in mixing.

Description

Technical Field

[0001] The invention relates to a post-treatment drum mixer, which is suitable for exhaust post-treatment and has the specific function of accelerating the mixing of urea and exhaust gas flow and utilizing exhaust gas energy to decompose urea with maximum efficiency. Background Art

[0002] The drum mixer can be designed in series due to its short length, compact structure and small temperature loss, which is convenient for layout in the post-processor. Because of its compact structure, there is not enough time and space for thermal decomposition and hydrolysis of urea.

[0003] The current cylinder post-processor has an empty cylinder structure in the inner core assembly and a purging structure at the bottom; a steel wool structure is also set on the inner core assembly to increase the action time of urea and heat energy. The former design has the disadvantage of a large amount of urea accumulating at the bottom of the cylinder, and the latter has a failure mode of urea crystallization due to the unevenness of the steel wool and the high back pressure.

[0004] In view of the above, it is necessary to further optimize the design of the drum after-processor for various harsh road conditions with low speed and high emission, so as to solve the urea crystallization problem when the mixer runs for a long time under low temperature, low displacement and high emission conditions. Summary of the invention

[0005] Aiming at the problem of urea crystallization when the above-mentioned engine runs for a long time under low temperature, low displacement and high emission conditions, the present invention proposes a post-treatment drum mixer which can accelerate urea decomposition, shorten the urea decomposition time and space, make mixing more uniform, and improve NOx conversion efficiency.

[0006] The present invention is achieved through the following technical solutions: The above-mentioned post-treatment barrel mixer includes a shell assembly and an inner core assembly; the shell assembly is a double-layer insulation structure with a urea nozzle seat on it; the inner core assembly is located inside the shell assembly, including a bracket, a fixed barrel, a spiral cone tube, and a venturi tube; the bracket is installed in the mixing chamber of the shell assembly to divide the mixing chamber into two front and rear chambers; it includes a horizontally arranged base plate, the two ends of the base plate in the horizontal direction are respectively bent upward and downward and extended to be fixedly connected to the shell assembly; the fixed barrel is vertically penetrated through the base plate of the bracket; the spiral cone tube is arranged at the upper end of the fixed barrel, the upper end matches and aligns with the bottom injection port of the urea nozzle seat, and the lower end is fixed to the fixed barrel; the upper end of the venturi tube is connected to the spiral cone tube, and the lower end extends from the fixed barrel.

[0007] The post-processing barrel mixer, wherein: a support ring is provided at the upper end of the fixed barrel, and the support ring is respectively fixedly connected to the spiral cone tube and the venturi tube.

[0008] The post-processing drum mixer, wherein: the venturi tube includes a front section cone tube structure and a rear section bell mouth structure; the inlet end diameter of the front section cone tube structure is large, and the lower part diameter is small; the taper of the front section cone tube structure is smaller than the taper of the rear section bell mouth structure; the outlet end of the rear section bell mouth structure is R-shaped.

[0009] The post-processing drum mixer, wherein: the taper of the front-stage cone tube structure is 30° to 60°, and the taper of the rear-stage bell-mouth structure is 50° to 80°.

[0010] The post-processing barrel mixer, wherein: between the venturi tube and the fixed barrel, there are air flow channels with a gap of 1-3 mm at the upper and lower parts.

[0011] The post-processing drum mixer, wherein: the taper of the spiral cone tube is 10° to 50°, 9 to 15 blades are arranged circumferentially, and the blade opening angle is 20 to 60°.

[0012] The post-treatment drum mixer, wherein: the shell assembly includes an outer shell, an inner shell, and a heat-insulating layer; the outer shell is a barrel structure, and both ends have folded edges formed by equidistant inward bending; the inner shell is a straight barrel structure, and both ends are fixedly connected to the folded edges at both ends of the outer shell, an annular cavity is formed between the outer side and the outer shell, and the inner side constitutes a urea mixing cavity; the heat-insulating layer is arranged in the annular cavity between the outer shell and the inner shell; the shell assembly is connected to the outside through a front bell mouth and a rear bell mouth.

[0013] The post-treatment drum mixer, wherein: the fixed end of the urea nozzle seat is fixedly mounted on the outer wall of the inner shell, and the free end sequentially passes through the insulation layer and the outer shell and obliquely extends to the outside of the shell assembly, cooperates with the urea nozzle, and the urea injection angle is coaxial with the spiral cone tube and the venturi tube; the urea nozzle seat adopts a tubular structure with an oblique cut, and a flange edge is provided at the welding portion with the inner shell.

[0014] The post-processing drum mixer, wherein: the shell assembly is also provided with a sensor seat; the sensor seat is fixedly mounted on the inner wall of the inner shell.

[0015] The post-processing drum mixer, wherein: the mixer also includes a mixing plate; the mixing plate is provided with a mixer outlet, which is a structure with blades, 2-3 circles of blades are provided in the circumferential direction, the number of blades is 9-24, and the blade opening angle is 20 to 60 degrees. Beneficial Effects

[0016] The present invention pioneers the use of a venturi tube in a mixer. When the urea spray enters the venturi tube under the action of the exhaust gas flow, the airflow is accelerated in the front cone section and concentrated at the throat. The urea spray and the exhaust gas flow are mixed to the maximum extent at the throat, and the exhaust energy utilization rate is optimized, promoting the full thermal decomposition of the urea spray. The airflow is accelerated here, and the crystallization caused by urea wall attachment is also avoided. In the rear trumpet section of the venturi tube, the airflow expands rapidly, accelerating the decomposition of urea; The present invention adopts a conical spiral tube, which can stir and mix the airflow when it enters the inner core assembly. Compared with other practical design schemes, the generated rotation force is stronger, the droplets are broken into smaller pieces, the time and space for urea decomposition are shortened, it is more conducive to preventing urea from adhering to crystals, and the mixing is more uniform; The present invention adopts a mixing plate, in which 2-3 circles of blades are arranged in the circumferential direction, and the number of blades is 9-24. The blade opening angle is 20°~60°. With the inner core assembly and mixing plate of the present invention, the airflow uniformity at the SCR inlet is >0.98, and the ammonia distribution uniformity is >0.97. When tested on the engine, when the ammonia nitrogen ratio is 1.2 and the exhaust temperature is 300-400℃, the NOx conversion efficiency at different air speeds can reach above 0.99; The mixer of the present invention has a compact structure, can not only efficiently and evenly mix urea and exhaust gas, but also can prevent urea spray from adhering to the wall surface, and has the characteristics of simple structure, strong anti-crystallization ability, and uniform and efficient mixing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a front view of the post-processing drum mixer of the present invention; Figure 2 for Figure 1 Sectional view; Figure 3 It is a schematic diagram of the structure of the venturi tube of the post-processing drum mixer of the present invention; Figure 4 A schematic diagram of an annular airflow channel between the venturi tube and the fixed cylinder of the post-processing cylinder mixer of the present invention; Figure 5 It is a schematic diagram of the structure of the tubular nozzle seat of the post-processing drum mixer of the present invention.

[0018] Figure 6 It is a schematic diagram of the position and connection relationship between the support ring and the fixed cylinder, the Venturi tube, and the spiral cone tube. DETAILED DESCRIPTION

[0019] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0020] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "inside", "outside", "up", "down", "front", and "back" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific examples.

[0022] like Figure 1 As shown, the post-processing drum mixer of the present invention includes a shell assembly 1, an inner core assembly 2 and a mixing plate 3.

[0023] The shell assembly 1 is a double-layer heat-insulating structure, including an outer shell 11, an inner shell 12, and a heat-insulating layer 13; The outer shell 11 is a cylindrical structure, and has folded edges formed by bending inwards at equal distances at both ends; The inner shell 12 is a straight cylinder structure, and its two ends are fixedly connected to the folded edges at the two ends of the outer shell 11, and an annular cavity is formed between the outer side and the outer shell 11, and the inner side constitutes a urea mixing cavity; The heat-insulating layer 13 is arranged in the annular cavity between the outer shell 11 and the inner shell 12 to achieve heat insulation of the mixer; The housing assembly 1 is also provided with a urea nozzle seat 14 and a sensor seat 15; the fixed end of the urea nozzle seat 14 is installed on the outer wall of the inner housing 12 by a fixed connection method such as welding, and the free end sequentially passes through the insulation layer 13 and the outer housing 11 to extend to the outside of the housing assembly 1 to cooperate with the urea nozzle; the sensor seat 15 is fixedly installed on the inner wall of the inner housing 12 for installing the sensor; The shell assembly 1 is connected to the outside through the front bell mouth 16 and the rear bell mouth 17 ; the front bell mouth 16 and the rear bell mouth 17 are fixedly mounted on both ends of the outer shell 11 .

[0024] The inner core assembly 2 is located inside the shell assembly 1, and includes a bracket 21, a fixing tube 22, a support ring 23, a venturi tube 24, and a spiral cone tube 25; The bracket 21 is installed in the mixing chamber of the shell assembly 1, and includes a horizontally arranged base plate 211, an upper connecting plate 212 formed by bending upward and extending from one end of the base plate 211 in the horizontal direction, and a lower connecting plate 213 formed by bending downward and extending from the other end of the base plate 211 in the horizontal direction; a through hole is provided in the middle of the base plate 211, and the upper connecting plate 212 and the lower connecting plate 213 are fixedly connected to the upper and lower inner walls of the inner shell 12 respectively; The fixing tube 22 is vertically fixedly installed in the middle through hole of the base plate 211 of the bracket 21; The support ring 23 is fixedly mounted on the top of the fixed cylinder 22; the support ring 23 can be welded to the fixed cylinder 22 through protrusions on all sides, and there is an annular gap around the support ring 23 to form an annular airflow inlet channel.

[0025] The venturi tube 24 is located in the fixed tube 22, with the upper end fixedly connected to the lower end surface of the support ring 23, and the lower end freely extending to the outlet of the fixed tube 22; the venturi tube 24 includes a front cone tube structure 241 and a rear bell mouth structure 242, the front cone tube structure 241 has a large inlet diameter and a small lower diameter, and collects and concentrates the airflow; the rear bell mouth structure has a large outlet diameter; the taper of the front cone tube structure 241 is smaller than that of the rear bell mouth structure 242; the bell mouth outlet end is R-shaped, such as Figure 3 As shown, the front section of the venturi tube 24 accelerates and collects the urea spray and the exhaust gas flow, gathers them at the throat to maximize the use of exhaust energy, and the rear section expands and decomposes them; The conical tube 25 is arranged at the upper end of the fixed cylinder 22, the upper end matches the bottom injection port of the urea nozzle seat 14, and the lower end is welded to the support ring 23. The conical tube 25 has a taper of 10° to 50°, 9 to 15 blades are arranged circumferentially, and the blade opening angle is 20 to 60°. The selection of parameters can make full use of the exhaust gas to rotate and mix the urea spray according to the exhaust flow of different engines, but the urea spray cannot contact and adhere to the wall of the conical tube 25 and the venturi tube 24, and the back pressure of the entire post-processor assembly can be met; the nozzle diameter and cone height of the conical tube 25 can be adjusted according to different engine exhaust flows; the conical tube 25 is a plurality of blades cut on the cone tube, which plays the role of mixing airflow and urea spray.

[0026] The mixing plate 3 is arranged at the outlet of the mixer, located inside the rear end bell mouth 17 of the shell assembly 1, and adopts a bladed structure, wherein 2-3 circles of blades are arranged in the circumferential direction, the number of blades is 9-24, and the blade opening angle is 20-60°. The opening angle and number of blades are set to ensure that the uniformity of ammonia distribution at the inlet of the rear end SCR carrier reaches above 0.98.

[0027] Furthermore, if Figure 4 As shown, there are air flow channels with a gap of 1-3 mm between the venturi tube 24 and the fixed cylinder 22 ; the air flow flows out from the air flow channels at the lower end of the fixed cylinder 22 and the venturi tube 24 , which prevents urea from adhering to and crystallizing at the outlet of the venturi tube 24 .

[0028] Furthermore, the taper of the front cone tube structure 241 of the venturi tube 24 is 30° to 60°, and the taper of the rear bell mouth structure 242 is 50° to 80°. The front cone angle is designed to be small in order to make the exhaust smooth and reduce vortex, and to concentrate the spray and exhaust; the rear cone angle is large in order to reduce the adhesion of urea to the wall of the venturi tube.

[0029] Furthermore, if Figure 5 As shown, the urea nozzle seat 14 adopts a tubular structure with an oblique cut, preferably a tubular structure with a wall thickness of 2-4 mm, and a flange edge 141 is designed at the welding position with the inner shell 12, providing a better installation and welding process; the urea nozzle seat 14 is set at a certain angle and is used in conjunction with the urea nozzle. The urea injection angle is coaxial with the spiral cone tube 25 and the venturi tube 24.

[0030] The working process of the post-processing drum mixer of the present invention is as follows: The airflow flows in from the front end of the bracket 21 through the blades of the spiral cone tube 25. When passing through the venturi tube 24, the airflow is accelerated in the front cone section, concentrated at the throat, and expanded in the rear trumpet section. Then, the airflow enters the lower end of the inner core assembly 2 and flows out of the mixer through the mixing plate 3.

[0031] The post-processing drum mixer of the present invention has the following characteristics: 1. The first application of the Venturi tube in the mixer. Under the action of the exhaust airflow of the urea spray, when it enters the Venturi tube, the airflow is accelerated in the front cone section and concentrated at the throat. The urea spray and the exhaust airflow are mixed to the maximum extent at the throat, and the exhaust energy utilization rate is optimized, which promotes the full thermal decomposition of the urea spray. The acceleration process of the airflow also avoids the crystallization caused by the urea wall. In the rear trumpet section of the Venturi tube, the airflow expands rapidly, which accelerates the decomposition of urea. 2. The tapered spiral tube is used to stir and mix the airflow when it enters the inner core assembly. Compared with other straight tube designs, the spiral tube generates stronger rotational force, breaks the droplets into smaller pieces, shortens the time and space for urea decomposition, and is more conducive to preventing urea from adhering to crystals, and makes the mixing more uniform; 3. The mixing plate is used to further improve the uniformity of airflow and ammonia distribution. With the inner core assembly and mixing plate of the present invention, the airflow uniformity at the SCR inlet is >0.98, and the ammonia distribution uniformity is >0.97. When tested on the engine, when the ammonia nitrogen ratio is 1.2 and the exhaust temperature is 300-400°C, the NOx conversion efficiency at different air speeds can reach above 0.99.

Claims

1. A post-processing drum mixer, comprising a shell assembly and an inner core assembly; characterized in that: The housing assembly is a double-layer heat-insulating structure with a urea nozzle seat disposed thereon; The inner core assembly is located inside the shell assembly and includes a bracket, a fixing cylinder, a spiral cone tube, and a venturi tube; The bracket is installed in the mixing chamber of the shell assembly to divide the mixing chamber into two chambers, front and rear chambers; it includes a horizontally arranged base plate, and the two ends of the base plate are bent upward and downward respectively in the horizontal direction and extend to be fixedly connected to the shell assembly; The fixing tube is vertically arranged through the base plate of the bracket; The spiral cone tube is arranged at the upper end of the fixed cylinder, the upper end matches and aligns with the bottom injection port of the urea nozzle seat, and the lower end is fixed to the fixed cylinder; The upper end of the venturi tube is connected to the spiral cone tube, and the lower end thereof extends out from the fixed tube.

2. The post-processing drum mixer according to claim 1, characterized in that: A support ring is provided at the upper end of the fixed cylinder, and the support ring is fixedly connected to the spiral cone tube and the venturi tube respectively.

3. The post-processing drum mixer according to claim 1, characterized in that: The venturi tube comprises a front cone tube structure and a rear bell mouth structure; the inlet end diameter of the front cone tube structure is large and the lower diameter is small; the taper of the front cone tube structure is smaller than the taper of the rear bell mouth structure; the outlet end of the rear bell mouth structure is R-shaped.

4. The post-processing drum mixer according to claim 3, characterized in that: The taper of the front cone tube structure is 30° to 60°, and the taper of the rear bell mouth structure is 50° to 80°.

5. The post-processing drum mixer according to any one of claims 1 to 4, characterized in that: Between the venturi tube and the fixed cylinder, there is an air flow channel with a gap of 1-3 mm at the upper part and the lower part.

6. The post-processing drum mixer according to claim 1, characterized in that: The conicity of the spiral cone tube is 10° to 50°, 9 to 15 blades are arranged circumferentially, and the blade opening angle is 20° to 60°.

7. The post-processing drum mixer according to claim 1, characterized in that: The shell assembly includes an outer shell, an inner shell, and an insulation layer; The outer shell is of cylindrical structure, and both ends have folded edges formed by bending inwards at equal distances; The inner shell is in a straight cylindrical structure, and its two ends are fixedly connected to the folded edges at the two ends of the outer shell respectively, an annular cavity is formed between the outer side and the outer shell, and the inner side constitutes a urea mixing cavity; The heat-insulating layer is arranged in the annular cavity between the outer shell and the inner shell; The shell assembly is connected to the outside through a front bell mouth and a rear bell mouth.

8. The post-processing drum mixer according to claim 7, characterized in that: The fixed end of the urea nozzle seat is fixedly mounted on the outer wall of the inner shell, and the free end passes through the insulation layer and the outer shell in sequence and extends obliquely to the outside of the shell assembly to cooperate with the urea nozzle. The urea injection angle is coaxial with the spiral cone tube and the venturi tube. The urea nozzle seat adopts a tubular structure with an oblique cut, and a flange edge is provided at the welding position with the inner shell body.

9. The post-processing drum mixer according to claim 6, characterized in that: The housing assembly is also provided with a sensor seat; the sensor seat is fixedly mounted on the inner wall of the inner housing.

10. The post-processing drum mixer according to claim 1, characterized in that: The mixer also includes a mixing plate; the mixing plate is provided with a mixer outlet and is a structure with blades, 2-3 circles of blades are provided in the circumferential direction, the number of blades is 9-24, and the blade opening angle is 20-60 degrees.

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