CN203452874U - SCR catalyzing silencer and mixing tube device of SCR catalyzing silencer - Google Patents

Abstract

The utility model discloses an SCR catalyzing silencer and a mixing tube device of the SCR catalyzing silencer. The mixing tube device comprises an outer tube and an inner tube which is inserted in the outer tube, wherein one end of the inner tube is a gas inlet end, the gas inlet end is used for enabling exhaust gas in a gas inlet tube of the SCR catalyzing silencer to enter the inner tube, outer penetrating holes are formed in the tube wall of the outer tube, and inner penetrating holes are formed in the tube wall of the inner tube. Therefore, first atomization of a urea solution and the exhaust gas can be carried out at the tube wall of the inner tube, second atomization can be carried out under the effect of the outer penetrating holes of the outer tube, and then the atomized urea solution and the atomized exhaust gas enter an gas inlet cavity. According to the design, secondary crushing and mixing of urea liquid drops can be promoted, the atomization mixing effect of the urea solution and the exhaust gas is remarkably improved, and favorable conditions are created for a follow-up reduction reaction. In addition, the good atomization mixing effect contributes to prevention of adherence and aggregation of the urea liquid drops on the wall face of the mixing tube device or the wall face of an gas inlet cylinder and urea crystallization is prevented. In addition, the design of two layers of penetrating holes is adopted, so that the stroke of exhaust gas flow is lengthened, noise can be effectively reduced, and noise on different frequency bands is weakened.

Description

SCR catalytic muffler and its mixing tube device

technical field

The utility model relates to the technical field of exhaust aftertreatment, in particular to an SCR catalytic muffler and a mixing tube device thereof.

Background technique

SCR technology is one of the main aftertreatment technologies to eliminate nitrogen oxides in engine exhaust. According to the function, the SCR system mainly includes three parts: the control unit, the urea dosage unit and the catalytic reaction unit. The control unit of the SCR system is integrated with the engine control unit (ECU), which is mainly used to implement the SCR control strategy, and according to the ambient temperature, exhaust temperature, urea level, urea temperature, urea pressure, NOx concentration and other sensor signals The urea dosage unit is controlled, and the urea dosage unit injects the urea solution into the exhaust gas flow regularly and quantitatively according to the demand.

The urea solution is sprayed into the exhaust pipe through the urea nozzle or directly into the SCR catalytic muffler. Usually, a pyrolysis reaction occurs at a temperature above 200°C to produce ammonia (NH3). The nitrogen oxides (NOx) in the exhaust gas react to achieve the purpose of eliminating the nitrogen oxides (NOx) in the exhaust gas of the diesel engine.

Please refer to Figure 1, which is a schematic structural diagram of a typical SCR catalytic muffler.

The mixing tube device mainly includes a mixing tube 12, which is inserted into the air intake cavity of the intake cylinder 14 of the SCR catalytic muffler, and the wall of the mixing tube 12 is provided with a number of perforations 121 in its circumferential direction. One end of mixing pipe 12 is used to connect intake pipe 11, and as shown in Figure 1, intake pipe 11 comprises intake connecting pipe 111 and variable diameter eccentric pipe 112, and intake connecting pipe 111 connects the exhaust pipe of engine, and variable diameter eccentric pipe The two ends of 112 are respectively connected to the exhaust pipe of the engine and the mixing pipe 12. The nozzle 13 of the SCR catalytic muffler sprays urea solution into the mixing tube 12, and the urea solution is mixed with the discharged airflow in the mixing tube 12, and the perforation 121 of the mixing tube 12 strengthens the atomization effect of the two, so that the two are fully mixed and enter The inside of the outlet tube 15 participates in the reduction reaction, and is finally discharged from the outlet pipe 16 provided on the outlet tube 15 .

Yet there is following technical problem in above-mentioned technical scheme:

First, although the mixing tube 12 is provided with a perforation 121, the atomization effect is still not ideal, which affects the mixing effect of the urea solution and the exhaust gas, resulting in a poor follow-up reduction reaction, and the droplets of the urea solution are also easy to adhere to the mixing tube. Crystals are formed on the wall surfaces of the pipe 12 and the intake cylinder 14 .

Second, the air flow disturbance in the mixing tube 12 is small, and there is an air flow stagnation area, which also causes urea droplets to easily gather and adhere to the wall surface of the air inlet cylinder 14 and the mixing tube 12, so that the urea solution forms urea crystals under low temperature conditions, affecting Reliability and adaptability of SCR aftertreatment system.

In view of this, how to improve the mixing effect of exhaust gas and urea solution in the SCR catalytic muffler is a technical problem to be solved urgently by those skilled in the art.

Utility model content

In order to solve the above technical problems, the purpose of this utility model is to provide an SCR catalytic muffler and a mixing tube device thereof. The mixing tube device can improve the mixing effect of exhaust gas and urea solution.

The mixing tube device of the SCR catalytic muffler provided by the utility model includes an outer tube and an inner tube inserted in the outer tube, and one end of the inner tube is an air intake end for the exhaust gas in the intake pipe of the SCR catalytic muffler to enter , the tube wall of the outer tube is provided with an outer perforation, and the tube wall of the inner tube is provided with an inner perforation.

The pipe wall of the outer pipe is provided with an outer perforation, and the pipe wall of the inner pipe is provided with an inner perforation. With this design, the urea solution and exhaust gas can be atomized for the first time on the inner tube wall, and the atomized urea solution and exhaust gas mixture enters the outer tube, and is atomized for the second time under the action of the outer perforation of the outer tube , and then into the intake chamber. This design can promote the secondary crushing and mixing of urea droplets, so the two-time atomization can significantly improve the atomization and mixing effect of urea solution and exhaust gas, thereby improving the uniformity of urea spray distribution and creating benefits for the subsequent reduction reaction. Moreover, good atomization and mixing effect also helps to prevent urea droplets from adhering and accumulating on the wall of the mixing tube device or the inlet cylinder, thereby preventing urea from crystallizing. In addition, the two-layer perforated design lengthens the stroke of the exhaust airflow, which can effectively reduce noise and reduce noise in different frequency bands.

Preferably, a mixer for vortexing the gas is provided at the inlet end of the inner tube or inside the inner tube.

Preferably, the inner perforations are provided at the other end opposite to the intake end, and the inner perforations are arranged along the circumference of the inner tube.

Preferably, the inner perforations are arranged on the entire tube wall of the inner tube, and the inner perforations are arranged along the circumference of the inner tube.

Preferably, the inner perforation is provided close to the other end opposite to the inlet end, and the section of the pipe wall provided with the inner perforation is fan-shaped.

Preferably, the ratio of the total area of the inner perforations to the cross-sectional area of the intake pipe ranges from 1.5 to 2.5.

Preferably, the outer perforation is provided at an end of the outer pipe away from the intake pipe.

Preferably, the outer perforation is arranged in the middle of the outer tube.

Preferably, the diameter of the inner perforation is smaller than the diameter of the outer perforation.

Preferably, a bowl-shaped deflector arc plate is also provided, and the bowl-shaped deflector arc plate blocks an end of the outer pipe away from the intake pipe.

The utility model also provides an SCR catalytic muffler, which includes an inlet pipe, a mixing pipe device, an air inlet cylinder and an air outlet cylinder, the air inlet cylinder and the air outlet cylinder are connected, and the mixing pipe device is the mixing pipe described in any one of the above device, the outer tube and the inner tube of the mixing tube device are inserted into the air intake cavity of the air intake cylinder.

Since the above-mentioned mixing tube device has the above-mentioned technical effect, the SCR catalytic muffler having the mixing tube device also has the same technical effect.

Description of drawings

Fig. 1 is a structural schematic diagram of a typical SCR catalytic muffler;

Fig. 2 is the structural representation of the first embodiment of the mixing tube device provided by the utility model;

Fig. 3 is provided with the structural representation of the SCR catalytic muffler of mixing tube device in Fig. 2;

Fig. 4 is the structural representation of mixer among Fig. 2;

Fig. 5 is a schematic structural view of the second embodiment of the mixing tube device provided by the present invention;

Fig. 6 is a schematic structural view of the third embodiment of the mixing tube device provided by the present invention.

In Figure 1:

11 Inlet pipe, 111 Intake connecting pipe, 112 Reduced diameter eccentric pipe, 12 Mixing pipe, 13 Nozzle, 14 Intake cylinder, 15 Outlet cylinder, 16 Outlet pipe

In Figure 2-6:

21 intake pipe, 211 intake connection pipe, 212 variable diameter eccentric pipe, 22 outer pipe, 221 outer perforation, 23 nozzle, 24 inner pipe, 241 inner perforation, 25 intake cylinder, 251 spoiler, 251a through hole, 26 outlet , 27 bowl-shaped deflector arc plate, 28 outlet pipe, 29 mixer

Detailed ways

In order to make those skilled in the art better understand the technical solution of the utility model, the utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Fig. 2-4, Fig. 2 is the structural representation of the first embodiment of the mixing tube device provided by the utility model; Fig. 3 is the structural representation of the SCR catalytic muffler provided with the mixing tube device in Fig. 2; Fig. 4 is Fig. 2 Schematic diagram of the structure of the mixer.

The SCR catalytic muffler includes an intake pipe 21 , an air intake cylinder 25 and an air outlet cylinder 26 , and the mixing pipe device is located in the inner chamber of the air intake cylinder 25 , that is, the air intake chamber. The exhaust gas of the engine exhaust pipe enters the mixing pipe device through the intake pipe 21, and then enters the air intake chamber of the entire air intake cylinder 25, and then discharges to the inner cavity of the air outlet cylinder 26, that is, the air outlet chamber. The air outlet cylinder 26 may have an outlet pipe 28 passing through its end to communicate with its air outlet chamber, and the reduced gas is discharged through the outlet pipe 28 .

The mixing tube device specifically includes an outer pipe 22 and an inner pipe 24 connected with the intake pipe 21 of the SCR catalytic muffler, and the inner pipe 24 is inserted in the outer pipe 22. As shown in Figure 2, one end of the inner pipe 24 is an air intake The exhaust gas in the intake pipe 21 first enters the inner pipe 24 through the inlet end of the inner pipe 24 . Both the outer tube 22 and the inner tube 24 can be designed to be cylindrical.

In addition, the tube wall of the outer tube 22 is provided with an outer perforation 221 , and the tube wall of the inner tube 24 is provided with an inner perforation 241 . With such a design, the urea solution and exhaust gas can be atomized for the first time on the wall of the inner tube 24, and the atomized urea solution and exhaust gas mixture enter the outer tube 22, and under the action of the outer perforation 221 of the outer tube 22, the second atomization is carried out. Secondary atomization, and then into the air intake chamber. This design can promote the secondary crushing and mixing of urea droplets, so the two-time atomization can significantly improve the atomization and mixing effect of urea solution and exhaust gas, thereby improving the uniformity of urea spray distribution and creating benefits for the subsequent reduction reaction. Conditions; Moreover, good atomization mixing effect also helps to prevent urea droplets from adhering and gathering on the wall surface of the mixing tube device or the air inlet cylinder 25, thereby preventing urea from crystallizing. In addition, the two-layer perforated design lengthens the stroke of the exhaust airflow, which can effectively reduce noise and reduce noise in different frequency bands.

In addition, a mixer 29 can be provided at the inlet end of the inner pipe 24, and the mixer 29 can cause the gas to generate a vortex, which is helpful for the mixing of the exhaust gas and the urea solution, and prevents the urea droplets from directly touching the wall surface and crystallization, further avoiding the urea crystallization phenomenon. A specific structure of the mixer 29 can be understood with reference to FIG. 4 , which has rotating blades 291 that generate vortices to accelerate air flow disturbances.

Here, the mixer 29 is installed at the intake end of the inner pipe 24, and the mixer 29 is not limited to the intake end, as long as it is installed near the intake end. As shown in Fig. 2, the inlet end of the outer tube 22 is beyond the inlet end of the inner tube 24, and it is also feasible to place the mixer 29 inside the inlet end of the outer tube 22 (near the port of the inlet end of the inner tube 24). Of course, the exhaust gas finally enters through the inner tube 24 , so it is arranged at the inlet end of the inner tube 24 to better realize the mixing of the exhaust gas and the urea solution in the inner tube 24 . In fact, it is also feasible for the mixer 29 to be arranged inside the inner tube 24 , and the exhaust gas and urea solution entering the inner tube 24 are mixed under the disturbing action of the mixer 29 . It can be seen that the mixer 29 may be disposed after the intake pipe 21 .

In the above embodiment, the inner perforation 241 can be arranged on the entire pipe wall of the inner pipe 24, as shown in FIG. 2 , so that the urea solution and exhaust gas can be atomized for the first time along any position of the inner pipe 24 and enter the outer pipe. 22 Carry out the second atomization to improve the atomization efficiency. The inner perforations 241 should be opened on the tube wall as evenly as possible to improve the uniformity of mixing.

The inner perforation 241 can also be set in the following manner, as shown in FIG. 5 , which is a schematic structural diagram of the second embodiment of the mixing tube device provided by the present invention.

In this embodiment, the inner perforation 241 is not opened on the entire inner tube 24 wall, but is located at the bottom of the inner tube 24, and is arranged along its circumference, that is, 360-degree openings, and the bottom is the one shown in Figure 5. the right end of the display. In such a design, the inlet end of the inner pipe 24 has no opening, then along with the flow of exhaust, the urea solution and the air inlet end of the inner pipe 24 can be fully fused at a high speed for a period of time, and after fusion, at the tail end, by means of The inner perforation 241 realizes the first atomization, and then enters the outer tube 22 for the second atomization. Compared with the technical scheme in which holes are opened on the entire surrounding wall, the mixing effect can be improved.

Please refer to FIG. 6 , which is a schematic structural diagram of a third embodiment of the mixing tube device provided by the present invention.

In this embodiment, the tube wall of the inner tube 24 is also provided with an inner perforation 241. The inner perforation 241 is similar to the second embodiment and is also arranged near the tail end of the inner tube 24. In FIG. 6, the inner perforation 241 extends from the tail end. To the middle, the inner perforation 241 in this embodiment is not a 360-degree opening, but a fan-shaped opening, that is, the section of the pipe wall provided with the inner perforation 241 is fan-shaped.

With such a design, the urea solution and the exhaust gas can be fully mixed at the tail end of the inner pipe 24 (the left end in FIG. 6 ). The urea solution and exhaust gas can be atomized and mixed for the first time through the inner perforation 241 accompanied by strong turbulent mixing. The effect of this kind of mixed atomization method is better. The size of the sector angle formed by the provided inner perforations 241 can be adjusted in combination with actual working conditions.

At this time, the ratio of the total area of the inner perforations 241 to the cross-sectional area of the intake pipe 21 may range from 1.5 to 2.5, and the optimal solution is a ratio of 2. In this way, it is beneficial for the gas flow of the mixture of exhaust gas and urea solution to pass through the inner perforation 241 quickly, and the air flow is better.

When the fan-shaped opening is carried out at the tail end, the outer perforation 221 of the outer tube 22 can be arranged on the end of the outer tube 22 away from the intake pipe 21. its circumferential setting. Such design is compatible with the design of the inner perforation 241 of the inner tube 24, all near the right end. Because part of the tube wall of the inner tube 24 does not have the inner perforation 241, the outer perforation 221 is designed close to the inner perforation 241, which is convenient for secondary atomization and mixing. In view of the primary atomization, the outer tube 22 does not need to have outer perforations 221 on the entire tube wall, so that the processing cost can be reduced on the premise of satisfying the secondary atomization.

For the above-mentioned embodiments, the outer through hole 221 may be disposed in the middle of the outer tube 22 . As described in the third embodiment, the outer tube 22 does not need to be provided with the outer perforation 221 on the entire tube wall, and the set part can meet the secondary atomization requirement after the first atomization, thereby reducing the processing cost. The arrangement in the middle of the outer tube 22 is beneficial for the urea solution and the exhaust gas mixture filled in the outer tube 22 to perform secondary atomization more uniformly and smoothly. Of course, the location of the outer through hole 221 can be arranged in combination with the specific arrangement of the inner through hole 241 . As shown in FIG. 5 , the outer through hole 221 is arranged at the right end of the outer tube 22 and basically extends from the right end to the middle. In fact, in FIGS. 2 and 5 , the outer through hole 221 can also be arranged at the right end.

In the above embodiment, when the inner tube 24 is provided with the inner perforation 241 and the outer tube 22 is provided with the outer perforation 221 , the diameter of the inner perforation 241 can be made smaller than the diameter of the outer perforation 221 . Exhaust gas and urea solution mix and flow in the inner tube 24 at first, and the speed is faster, and the inner perforation 241 of the small aperture is opened in the inner tube 24, which can accelerate the mixing; after the inner tube 24, it flows to the outer tube 22, and a good process has been carried out. Mixing, and the speed is reduced, at this time, the aperture of the outer perforation 221 can be designed to be too large, which is compatible with the current state of mixed exhaust and urea solution, so that it can be further mixed. Moreover, the diameters of perforations provided in the inner and outer tube bodies are different, which can better reduce the noise of different frequencies.

For each of the above-mentioned embodiments, the mixing tube device can also include a bowl-shaped deflector arc plate 27. At this time, the inner pipe 24 and the outer pipe 21 can be welded and fixed on the intake pipe 21 and the bowl-shaped arc deflector plate 27, as shown in FIG. 2 , 5, 6, it can be seen that the tail end of the inner tube 24 provided with the inner perforation 241 is in contact with the bowl-shaped guide arc plate 27 . The bowl-shaped deflector arc plate 27 is used to block the end surface of the bottom end of the outer tube 22 . Generally, the mixture of urea solution and exhaust gas enters the inner pipe 24 , then flows out through the outer perforation 221 of the outer pipe 22 and enters the air intake chamber of the SCR catalytic muffler air intake cylinder 25 , and then enters the air outlet chamber of the air outlet cylinder 26 . The flow stagnation phenomenon at the bottom of the air intake chamber is relatively serious. The structure of the bowl-shaped deflector arc plate 27 can effectively enhance the disturbance of the exhaust gas flow at the bottom of the mixing tube device, further improve the flow stagnation phenomenon at the bottom of the air intake chamber, and promote the flow of urea solution droplets. The secondary crushing and mixing of the liquid droplets prevents the formation of urea crystals in the intake chamber.

In addition to the above-mentioned mixing tube device, the embodiment of the utility model also provides a SCR catalytic muffler, including an intake pipe 21, a mixing tube device, an air inlet cylinder 25 and an air outlet cylinder 26, the inlet cylinder 25 and the air outlet cylinder 26 are connected, and the mixing pipe device is any of the above-mentioned In the mixing tube device described in one embodiment, the outer tube 22 and the inner tube 24 of the mixing tube device are inserted into the air intake cavity of the air intake cylinder 25 . Since the above-mentioned mixing tube device has the above-mentioned technical effect, the SCR catalytic muffler having the above-mentioned mixing tube device also has the same technical effect.

Please continue to refer to Fig. 3, the mixing tube device is inserted from one end of the intake cylinder 25, and the outlet of the SCR catalytic muffler is located at the other end of the outlet cylinder 26, that is, the inlet and outlet of the exhaust gas are respectively located at the two ends of the SCR catalytic muffler, which is equivalent to adopting The exhaust "end-in and end-out" design is different from the exhaust "side-in and end-out" structure in Figure 1.

The design of side entry and end exit is adopted. If the vehicle chassis is low, the ground clearance of the vehicle will be reduced, which is not conducive to the layout of the whole vehicle. In this embodiment, the end-in-end-out structure is adopted, which can provide sufficient vehicle ground clearance, which is beneficial to the layout of the whole vehicle, and is especially adaptable to vehicles with a low chassis, such as trucks.

In this embodiment, a spoiler 251 may be disposed inside the air intake cylinder 25, the mixing tube device penetrates and is supported on the spoiler 251, and the spoiler 251 is provided with a through hole 251a. As shown in FIG. 3 , the annular peripheral wall of the spoiler 251 is positioned on the inner wall of the air intake cylinder 25 , and the bowl-shaped deflector arc plate 27 installed at the bottom of the outer tube 22 penetrates and supports the spoiler 251 . Then the spoiler 251 can play a better support and positioning effect on the mixing tube device. In addition, the spoiler 251 is provided with a through hole 251a, and the mixture of exhaust gas and urea solution can pass through the through hole 251a of the spoiler 251. It flows out and enters the air outlet cylinder 26, and the through hole 251a not only realizes circulation, but also has the function of disturbing the flow, thereby further preventing the crystallization of the urea solution on the wall surface of the air inlet cylinder 25.

For the above-mentioned embodiments, the intake pipe 21 includes an intake connection pipe 211 for connecting the exhaust pipe of the engine, and a diameter-reducing eccentric pipe 212, which is convenient for connecting the mixing pipe device. Wherein, the outer wall of the air intake connecting pipe 211 is provided with a fixed bracket, and the fixed bracket is installed with a cooling water pipe and a connecting wire harness. The intake connecting pipe 211 is directly connected to the exhaust pipe, and the surface of the exhaust pipe is high temperature. The cooling water pipe and the connecting wire harness are easy to contact the high-temperature exhaust pipe, resulting in high-temperature damage and failure. After the fixed bracket is set, the cooling water pipe and the connecting wire harness can be effectively positioned to prevent the two from contacting the high-temperature exhaust pipe and causing failure, and it is also helpful for the orderly arrangement of the pipeline and wire harness. The fixed bracket can be directly welded and fixed on the outer wall of the intake pipe 21 connecting pipe.

In addition, the SCR catalytic muffler has a nozzle 23, a temperature sensor and a nitrogen and oxygen sensor. The nozzle 23 is used to spray urea solution into the mixing tube device, the temperature sensor is used to detect the exhaust temperature, and the nitrogen and oxygen sensor is used to detect the reduction effect of the SCR catalytic muffler. . The nozzle 23, the temperature sensor and the nitrogen and oxygen sensor can all be integrated in the SCR catalytic muffler. Specifically, the temperature sensor seat where the temperature sensor seat and the nozzle 23 are installed, and the nozzle seat are all integrated into the variable diameter eccentric tube 212 , and the nitrogen and oxygen sensor seat where the nitrogen and oxygen sensor is installed is integrated into the outlet pipe 28 of the outlet tube 26 . Such a design can save the layout space of the whole vehicle, and at the same time allow the use of a shorter exhaust pipe, reduce the heat loss of the exhaust, increase the temperature of the airflow in front of the carrier, and create favorable conditions for the efficient elimination of NOX.

The SCR catalytic muffler may also include a clamp connecting the intake pipe 21 and the engine exhaust pipe. Usually, the exhaust pipe of the engine is connected to the intake flange of the intake pipe 21 of the SCR catalytic muffler through a flange. When the two flanges are connected by a clamp, the installation is very convenient and easy to operate.

In the above-mentioned embodiments, the shell of the air intake tube 25 may have a double wall structure, which can enhance the strength of the shell of the air intake tube 25 and also achieve the purpose of eliminating noise.

The SCR catalytic muffler and its mixing tube device provided by the utility model have been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present utility model, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present utility model. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the utility model, some improvements and modifications can also be made to the utility model, and these improvements and modifications also fall into the protection of the claims of the utility model. within range.

Claims (10)

1. a mixing tube device of an SCR catalytic muffler, characterized in that it comprises an outer tube (22) and an inner tube (24) inserted in the outer tube (22), one end of the inner tube (24) It is the intake end, for the exhaust gas in the SCR catalytic muffler intake pipe (21) to enter, the pipe wall of the outer pipe (22) is provided with an outer perforation (221), and the pipe wall of the inner pipe (24) is provided with Inner piercing (241). 2. The mixing tube device according to claim 1, characterized in that, the gas inlet end of the inner tube (24) or the inside of the inner tube (24) is provided with a mixer (29) that causes the gas to vortex . 3. The mixing tube device according to claim 1, wherein the inner perforation (241) is located at the other end opposite to the inlet end, and the inner perforation (241) is along the inner tube (24) circumferential arrangement. 4. The mixing tube device according to claim 1, characterized in that, the inner perforation (241) is arranged on the entire tube wall of the inner tube (24), and the inner perforation (241) is along the inner wall of the inner tube (24). Circumferential arrangement of tubes (24). 5. The mixing tube device according to claim 1, characterized in that, the inner perforation (241) is located at the other end opposite to the inlet end, and the pipe wall of the inner perforation (241) is provided The section is fan-shaped. 6. The mixing tube device according to claim 5, characterized in that, the outer perforation (221) is provided at an end of the outer tube (22) away from the inlet tube (21). 7. The mixing tube device according to any one of claims 1-5, characterized in that, the outer perforation (221) is arranged in the middle of the outer tube (22). 8. The mixing tube device according to any one of claims 1-6, characterized in that, the diameter of the inner perforation (241) is smaller than the diameter of the outer perforation (221). 9. The mixing tube device according to any one of claims 1-6, characterized in that, a bowl-shaped deflector arc (27) is also provided, and the bowl-shaped deflector arc (27) blocks the An end of the outer pipe (22) away from the air intake pipe (21). 10. A kind of SCR catalytic muffler, comprise intake pipe (21), mixing tube device, air intake cylinder (25) and air outlet cylinder (26), described air intake cylinder (25) and described air outlet cylinder (26) join, it is characterized in that , the mixing tube device is the mixing tube device described in any one of claims 1-9, the outer tube (22) and the inner tube (24) of the mixing tube device are inserted into the air inlet tube (25 ) of the intake cavity.

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