Exhaust gas after-treatment mixing device

The present application discloses an exhaust gas after-treatment mixing device including a casing, a mixing pipe and a partition plate fixed on a periphery of the mixing pipe. The partition plate includes a first plate on one side of the mixing pipe, a second plate on the other side of the mixing pipe and a third plate connecting the first plate and the second plate. The mixing pipe includes a first pipe portion and a second pipe portion. The first pipe portion is provided with at least two first openings located on two sides thereof, respectively. The exhaust gas after-treatment mixing device includes a first shielding plate and a second shielding plate shielding front ends of the first openings, respectively, so that most of exhaust gas needs to flow bypass the first shielding plate and the second shielding plate before entering the first openings.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a 35 U.S.C. § 371 National Phase conversion of International (PCT) Patent Application No. PCT/CN2018/092996, filed on Jun. 27, 2018, which claims priority to a Chinese Patent Application No. 201710851869.0, filed on Sep. 19, 2017 with an invention title of “Exhaust Gas After-Treatment Mixing Device”, the entire content of which is incorporated herein by reference. The PCT International Patent Application was filed and published in Chinese.

TECHNICAL FIELD

This application relates to an exhaust gas after-treatment mixing device which belongs to a technical field of engine exhaust gas after-treatment.

BACKGROUND

Studies have shown that the uniformity of ammonia distribution in the exhaust gas after-treatment system (such as Selective Catalytic Reduction system, SCR system) has a significant impact on the overall performance and durability of the system. If the ammonia distribution is not uniform, it will cause too much ammonia in the local area and easily cause ammonia leakage, while in other ammonia-thin areas, the conversion efficiency of nitrogen oxides (NOx) will be too low. The uneven distribution of ammonia over a long period of time will lead to uneven aging of the catalyst, which will affect the overall performance of the catalyst. In addition, the uneven distribution of urea droplets will cause the temperature of the local pipe wall or the mixed structure to be too low, forming crystals, and in severe cases, the exhaust pipe will be blocked, resulting in a decrease in engine power performance.

SUMMARY

An object of the present application is to provide an exhaust gas after-treatment mixing device with better mixing effect.

In order to achieve the above object, the present application adopts the following technical solution: an exhaust gas after-treatment mixing device includes a casing, a mixing pipe located in the casing and a partition plate fixed on a periphery of the mixing pipe. The casing is separated by the partition plate to form a first space communicating with a first after-treatment carrier assembly and a second space communicating with a second after-treatment carrier assembly. The partition plate includes a first plate on one side of the mixing pipe, a second plate on the other side of the mixing pipe and a third plate connecting the first plate and the second plate. The third plate is provided with a through hole through which the mixing pipe extends. The mixing pipe comprises a first pipe portion located in the first space and a second pipe portion located in the second space, wherein the first pipe portion is provided with at least two first openings located on two sides thereof, respectively. The exhaust gas after-treatment mixing device further includes a first shielding plate and a second shielding plate shielding front ends of the first openings, respectively, so that most of exhaust gas needs to flow bypass the first shielding plate and the second shielding plate before entering the first openings.

As a further improved technical solution of the present application, the second pipe portion is provided with at least two second openings located on two sides thereof, respectively, and the second openings communicate with the second space.

As a further improved technical solution of the present application, the casing is provided with a first axis, the mixing pipe is provided with a second axis, and the first axis is perpendicular to the second axis.

As a further improved technical solution of the present application, the mixing pipe is arranged vertically, the first plate and the second plate both extend vertically but along opposite directions, and the third plate extends horizontally.

As a further improved technical solution of the present application, the partition plate is substantially Z-shaped, the first plate is located at a lower left of the mixing pipe, and the second plate is located at an upper right of the mixing pipe.

As a further improved technical solution of the present application, the first plate is provided with a first arc-shaped surface abutting on the second pipe portion, and the second plate is provided with a second arc-shaped surface abutting on the first pipe portion.

As a further improved technical solution of the present application, the exhaust gas after-treatment mixing device further includes a rectifying plate fixed to the mixing pipe, and the first shielding plate and the second shielding plate are located on two sides of the rectifying plate, respectively.

As a further improved technical solution of the present application, the rectifying plate comprises a third curved surface abutting on the first pipe portion, and the first shielding plate and the second shielding plate extend sidewardly from the third curved surface along opposite directions.

As a further improved technical solution of the present application, the first shielding plate is provided with a first arc edge abutting on an inside of the casing, and the second shielding plate is provided with a second arc edge abutting on an inside of the casing.

As a further improved technical solution of the present application, the exhaust gas after-treatment mixing device further includes a plate located at a bottom of the mixing pipe, and the plate is provided with an arc-shaped protrusion protruding into the second pipe portion.

Compared with the prior art, the present application improves the uniformity of airflow distribution and the mixing effect by providing the first shielding plate and the second shielding plate for the airflow adjustment.

DETAILED DESCRIPTION

Please refer toFIG. 1toFIG. 9, the present application discloses an exhaust gas after-treatment mixing device3for purifying exhaust gas of an engine. The exhaust gas after-treatment mixing device3includes a casing31, a mixing pipe32located in the casing31, a partition plate33fixed on a periphery of the mixing pipe32, a plate34located at a bottom of the mixing pipe32, and a rectifying plate38for partially shielding the mixing pipe32.

The casing31is separated by the partition plate33to form a first space301for communicating with a first after-treatment carrier assembly and a second space302for communicating with a second after-treatment carrier assembly. In one embodiment of the present application, the first after-treatment carrier assembly may include a Diesel Oxidation Catalyst (DOC) and a Diesel Particulate Filter (DPF) located downstream of the DOC. The second after-treatment carrier assembly includes a Selective Catalytic Reduction (SCR).

The mixing pipe32includes a first pipe portion321located in the first space301and a second pipe portion322located in the second space302. The first pipe portion321is provided with at least two first openings3211on two sides of the first pipe portion321, respectively. The second pipe portion322is provided with at least two second openings3221on two sides of the second pipe portion322, respectively. The second openings3221communicate with the second space302. The first openings3211are used for airflow to flow in, and the second openings3221are used for airflow to flow out, so that a double swirl mixing effect is formed.

The rectifying plate38includes a first shielding plate381and a second shielding plate382shielding front ends of the first openings3211, respectively. As a result, most of the exhaust gas needs to flow bypass the first shielding plate381and the second shielding plate382before entering the first openings3211. This arrangement prevents the exhaust gas from directly rushing into the mixing pipe32and reflecting on the pipe wall, which affects the uniformity and stability of the airflow mixing. In the illustrated embodiment of the present application, the rectifying plate38includes a third curved surface383abutting on the first pipe portion321. The first shielding plate381and the second shielding plate382are respectively extended oppositely from two sides of the third curved surface383. Preferably, the third curved surface383is welded to the first pipe portion321. The first shielding plate381is provided with a first arc edge3811abutting on an inside of the casing31, and the second shielding plate382is provided with a second arc edge3821abutting on an inside of the casing31, thereby forming an obstruction to the airflow in order to achieve the rectification effect.

In the illustrated embodiment of the present application, the casing31is of a cylindrical shape and is provided with a first axis311. The mixing pipe32is of a cylindrical shape and is provided with a second axis323. The first axis311intersects the second axis323. Preferably, the first axis311is perpendicular to the second axis323. Of course, in other embodiments, the casing31and the mixing pipe32may have other shapes, such as an oval shape.

The partition plate33includes a first plate331on one side of the mixing pipe32, a second plate332on the other side of the mixing pipe32, and a third plate333connecting the first plate331and the second plate332. The third plate333is provided with a through hole334through which the mixing pipe32extends. In the illustrated embodiment of the present application, the mixing pipe32is arranged vertically. The first plate331and the second plate332both extend vertically but along opposite directions. The third plate333extends horizontally. Please refer toFIG. 5toFIG. 7, the partition plate33is substantially Z-shaped. The first plate331is located at a lower left of the mixing pipe32, and the second plate332is located at an upper right of the mixing pipe32. The first plate331is provided with a first curved surface335abutting on the second pipe portion322, and the second plate332is provided with a second curved surface336abutting on the first pipe portion321.

The plate34is located at the bottom of the second pipe portion322. The plate34is provided with an arc-shaped protrusion341protruding toward the second pipe portion322in order to guide the airflow to flow backwardly. The plate34can prevent the urea solution from being sprayed directly onto the exhaust pipe, thereby reducing the risk of urea deposit.

The exhaust gas after-treatment mixing device3is provided with an injector mounting seat (not shown) located on the casing31and used to install a urea injector for spraying atomized urea solution into the mixing pipe32.

In the illustrated embodiment of the present application, when the exhaust gas of the engine passes through the first after-treatment carrier assembly into the first space301, the exhaust gas bypasses the first shielding plate381and the second shielding plate382and then enters the mixing pipe32through the first openings3211. When the injection conditions are satisfied, the urea injector sprays urea droplets into the mixing pipe32, and the atomized urea droplets is mixed with the exhaust gas of the engine and move downstream, and then enter the second space302through the second openings3221to reach the second after-treatment carrier assembly. Under the action of the plate34, the airflow is better reversed (for example, flow upstream) to form a double swirl flow. In this way, the distance and time of urea evaporation are increased by the swirl flow, the uniformity of airflow mixing is improved and the risk of urea deposit is reduced.

The above embodiments are only used to illustrate the present application and not to limit the technical solutions described in the present application. The understanding of this specification should be based on those skilled in the art, although the present application has been carried out with reference to the above-mentioned embodiments in the detailed description, however, those of ordinary skill in the art should understand that those skilled in the art can still modify or equivalently replace the present application, and all technical solutions and improvements without departing from the spirit and scope of the present application should be within the scope of the claims of the present application.