CN210033574U

CN210033574U - Integrated type tail gas post-treatment box

Info

Publication number: CN210033574U
Application number: CN201920877391.3U
Authority: CN
Inventors: 丁宁宁; C·德林
Original assignee: Robert Bosch GmbH
Current assignee: Bosch Automotive System Wuxi Co Ltd
Priority date: 2019-06-12
Filing date: 2019-06-12
Publication date: 2020-02-07
Anticipated expiration: 2029-06-12

Abstract

An integrated exhaust aftertreatment case comprising: a box body (1); an oxidation catalyst (2), a reducing agent mixer (3) and a selective catalytic reduction device (4, 5) carried by the tank and arranged alongside one another in succession through which the exhaust gases flow; a reductant injector (9) arranged facing the reductant mixer; a diffuser plate (36) disposed between the outlet of the reductant mixer and the inlet of the selective catalytic reducer, the diffuser plate having a plurality of through holes therethrough between two plate surfaces thereof. The uniformity of the mixed flow of the tail gas and the reducing agent flowing into the selective catalytic reducer can be improved.

Description

Integrated type tail gas post-treatment box

Technical Field

The application relates to an integrated type tail gas post-treatment box which is used for treating tail gas discharged by an engine, in particular a diesel engine.

Background

Engine exhaust gases contain harmful components. In order to reduce the emission of harmful components in the exhaust gas, various post-treatment techniques have been developed. A typical integrated exhaust aftertreatment tank for a diesel engine includes a diesel oxidation catalyst, a selective catalytic reduction, and a diesel particulate trap.

In order to meet higher levels of exhaust emission requirements, such as the euro-six standard and the real road emissions (RDE) test requirements, on the one hand, it is necessary to increase the exhaust gas treatment elements, in particular the selective catalytic reducer, and on the other hand, it is necessary for the mixed gas stream of exhaust gas and reductant to flow uniformly into the selective catalytic reducer so that more nitrogen oxides are converted into nitrogen.

Existing exhaust aftertreatment boxes still leave room for improvement in the uniformity of flow of the mixture of exhaust gas and reductant into the selective catalytic reducer.

SUMMERY OF THE UTILITY MODEL

It is an object of the present application to provide an integrated exhaust aftertreatment tank for engine exhaust gas that enables a mixed flow of exhaust gas and reductant to flow into a selective catalytic reducer with high uniformity.

To this end, the present application provides in one of its aspects an exhaust gas aftertreatment tank comprising: a box body; an oxidation catalyst, a reductant mixer and a selective catalytic reducer carried by the tank and arranged alongside one another in sequence to be flowed through by the exhaust gases; and a reductant injector disposed facing the reductant mixer; the integrated type exhaust gas post-treatment tank also comprises a flow dispersion plate arranged between the outlet of the reducing agent mixer and the inlet of the selective catalytic reducer, and the flow dispersion plate is provided with a plurality of through holes which are communicated between two plate surfaces of the flow dispersion plate.

Alternatively, the diffuser plate is formed in a grid shape by connecting metal strips crossing each other, the strips defining through holes therebetween.

Optionally, the diffuser plate is made of a metal plate in which a plurality of through holes are punched.

Optionally, the outlet of the reductant mixer and the inlet of the selective catalytic reducer are covered by a common cover in which the diffuser plate is arranged.

Optionally, the diffuser plate is arranged such that a central axis of the selective catalytic reducer is substantially parallel to the diffuser plate.

Optionally, the diffuser plate is inclined with respect to a perpendicular between a centerline of the reductant mixer and a centerline of the selective catalytic reducer.

Optionally, the selective catalytic reducer is at least two selective catalytic reducers arranged side by side, and an inlet of each selective catalytic reducer is located on the same side as an outlet of the reducing agent mixer.

Alternatively, the reductant mixer closest to the selective catalytic reducer is defined as a first reductant mixer, and the diffuser plate is disposed obliquely with respect to a perpendicular line between a centerline of the first reductant mixer and a centerline of the selective catalytic reducer.

Optionally, the angle between the diffuser plate and the vertical is between 30 degrees and 80 degrees.

Optionally, the integrated exhaust aftertreatment tank further comprises a swirl flow guiding element arranged in the reductant mixer, the swirl flow guiding element having a plurality of fins causing the mixture of reductant and exhaust gas to form a swirl flow, each fin being inclined with respect to a plane perpendicular to a central axis of the swirl flow guiding element.

According to the application, the flow dispersing plate is arranged between the outlet of the reducing agent mixer and the inlet of the selective catalytic reducer, so that the mixed gas of the tail gas discharged by the reducing agent mixer and the reducing agent is dispersed through the flow dispersing plate and uniformly flows into the selective catalytic reducer, the conversion rate of nitrogen oxides is improved, and the requirement of higher-level tail gas emission is met more easily.

For the tail gas after-treatment box comprising two or more selective catalytic reducers, the flow dispersing plate can enable the mixed gas flow of the tail gas discharged by the reducing agent mixer and the reducing agent to flow into each selective catalytic reducer in a mode of matching with the treatment capacity of each selective catalytic reducer, so that each selective catalytic reducer can convert nitrogen oxides with high efficiency, and the requirements of higher-level tail gas emission can be met.

Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description, taken with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are perspective views from the front and rear of an exhaust aftertreatment tank, respectively, according to one possible embodiment of the present application;

FIG. 3 is a perspective view of the exhaust gas aftertreatment tank taken from the front side thereof after the peripheral wall of the tank body has been removed;

FIG. 4 is a perspective view of the exhaust aftertreatment tank taken from the rear side thereof, with the third enclosure separated from the tank to show the flow of exhaust gases within the third enclosure;

FIG. 5 is a rear view of the exhaust aftertreatment tank with the third housing removed to show the mounting location of the diffuser plate;

FIG. 6 is a schematic cross-sectional view through an oxidation catalyst (integrated with a particulate trap) and a reductant mixer of an exhaust aftertreatment tank;

FIG. 7 is a schematic cross-sectional view of a selective catalytic reducer through an exhaust aftertreatment box;

FIG. 8 is a perspective view of one possible configuration of swirl guide elements in a reductant mixer;

FIGS. 9 and 10 are perspective and front views of a diffuser plate according to one possible embodiment of the present application;

fig. 11 is a front view of a diffuser plate according to another possible embodiment of the present application.

Detailed Description

The present application relates generally to an integrated exhaust aftertreatment tank for treating engine exhaust, in particular exhaust of a diesel engine; however, the exhaust aftertreatment tank may also be suitable for engines consuming other types of fuel (some components in the exhaust aftertreatment tank may need to be modified accordingly).

An integrated exhaust gas aftertreatment tank according to a possible embodiment of the present application will be described with reference to the accompanying drawings. It is to be noted that the terms "upstream" and "downstream" used in the following description to indicate relative positions are defined with respect to the flow direction of the exhaust gas.

The integrated exhaust gas aftertreatment tank shown in figures 1 to 7 comprises a tank 1 and various exhaust gas treatment elements carried by the tank 1. These exhaust gas treatment components mainly comprise: an oxidation catalyst 2 with an attached particulate trapping function, a reducing agent mixer 3, a pair of selective

catalytic reduction devices

4, 5 disposed in parallel with each other, which are arranged side by side or substantially in parallel with each other, and whose main portions are located in a case 1 with both axial ends supported by the case 1.

The tank 1 includes a first end wall 11 and a second end wall 12 opposed to each other, and a peripheral wall 13 extending along the outer peripheries of the two end walls, the two end walls and the peripheral wall 13 defining a tank interior space.

The oxidation catalyst 2 has a generally cylindrical housing defining an inlet 21 and an outlet 22 of the oxidation catalyst 2, the inlet 21 passing through the first end wall 11 and being supported by the first end wall 11, the outlet 22 passing through the second end wall 12 and being supported by the second end wall 12. The inlet 21 is provided with or integrally formed with an exhaust gas inlet 23 located on the front side (the side of the first end wall 11) of the casing 1.

The exhaust gas inlet 23 receives exhaust gas emitted from the engine. Arranged in the housing of the oxidation catalytic converter 2 are an oxidation catalytic section 25 and a particle trap section 26, which particle trap section 26 is located downstream of the oxidation catalytic section 25. The exhaust gas entering the oxidation catalyst 2 flows through the oxidation catalyst section 25 and the particulate trap section 26 in this order, so that hydrocarbons and carbon monoxide in the exhaust gas undergo oxidation catalytic reaction to produce water and carbon dioxide, and particulate matter in the exhaust gas is trapped.

The reducing agent mixer 3 is arranged beside the oxidation catalyst 2, for example above it as shown in the figure, and defines a mixing chamber for the reducing agent with the exhaust gases. In the example illustrated, the reductant mixer 3 comprises two axially joined sections, an upstream conical section (e.g. conical section) 31 and a downstream cylindrical section (e.g. cylindrical section) 32. The tapered section 31 has a cross-sectional dimension that gradually decreases in a direction from upstream to downstream. The upstream port of the conical section 31 constitutes the inlet of the reducing agent mixer 3, the downstream port of the conical section 31 is joined to the upstream port of the cylindrical section 32, and the downstream port of the cylindrical section 32 constitutes the outlet of the reducing agent mixer 3. The upstream port of the conical section 31 is supported by the second end wall 12 and the downstream port of the cylindrical section 32 is supported by the first end wall 11. The swirl guide element 35 is arranged in the cylindrical section 32, preferably close to the upstream port of the cylindrical section 32.

Selective

catalytic reducers

4, 5 are arranged beside the reducing agent mixer 3 and the oxidation catalyst 2, wherein the selective catalytic reducer 4 is arranged side by side with the reducing agent mixer 3 and the selective catalytic reducer 5 is arranged side by side with the oxidation catalyst 2. The selective

catalytic reducers

4, 5 have

inlets

41, 51 and outlets 42, 52, respectively, the

inlets

41, 51 being supported by the first end wall 11, and the outlets 42, 52 being supported by the second end wall 12.

The selective

catalytic reducers

4, 5 each have a substantially cylindrical housing, and since the reducing agent mixer 3 occupies a smaller radial space than the oxidation catalyst 2, the diameter of the selective catalytic reducer 4 can be larger than that of the selective catalytic reducer 5. Of course, the selective

catalytic reducers

4, 5 may also have the same diameter.

On the rear side (the second end wall 12 side) of the case 1, the outlet 22 of the oxidation catalyst 2 and the inlet of the reducing agent mixer 3 communicate with the sealed first cover 6.

Meanwhile, at the rear side of the case 1, the outlets 42, 52 of the selective

catalytic reducers

4, 5 are covered by the second cover 7 and communicate with the inner space of the second cover 7.

On the front side of the case 1, the outlet of the reducing agent mixer 3 and the

inlets

41, 51 of the selective

catalytic reducers

4, 5 are closed by the third cover 8, and communicate with the internal space of the third cover 8. The third cover 8 comprises a first portion 81 facing said outlet, a second portion 82 facing said inlet 41 and a third portion 83 facing said inlet 51, respectively.

A reducing agent injector 9 is mounted on the first housing part 6 for injecting a reducing agent, for example an aqueous solution of urea, typically AdBlue, into the reducing agent mixer 3 in a metered manner. The reducing agent injector 9 is mounted in a recess on the first cover 6 with its injection port facing the inlet of the reducing agent mixer 3. Preferably, the central axis of the injection port of the reducing agent injector 9 is substantially collinear (coaxial) with the central axis of the reducing agent mixer 3.

In addition, the exhaust gas aftertreatment tank comprises an exhaust gas outlet 14 for discharging treated exhaust gas.

The exhaust gas outlet 14 may be arranged at any suitable location for discharging the treated exhaust gas, for example at the peripheral wall 13 of the tank 1, as shown in fig. 1 and 2. The portion of the second end wall 12 covered by the second cover 7 is provided with through holes to communicate the outlets 42, 52 of the selective

catalytic reducers

4, 5 with the exhaust gas outlet 14. Alternatively, the exhaust gas outlet 14 may be provided in the second cover 7.

The exhaust gas aftertreatment tank according to various embodiments of the present application forms an exhaust gas flow path, and the exhaust gas enters from the exhaust gas inlet 23, flows through the oxidation catalyst 2, the reducing agent mixer 3, the selective

catalytic reduction devices

4 and 5 in sequence, and is finally discharged from the exhaust gas outlet 14. While flowing through the reducing agent mixer 3, the reducing agent is injected into the exhaust gas by the reducing agent injector 9, so that the reducing agent is mixed with the exhaust gas to form a mixed gas flow.

In order to increase the mixing degree of the reducing agent in the exhaust gas, the swirl flow guide element 35 is configured to generate a swirl flow in the reducing agent mixer 3.

The swirl guide element 35 may be designed with any suitable structure for swirling the gas flow passing through it, i.e. the swirl guide element 35 constitutes a swirl guide. According to one possible embodiment, as shown in fig. 8, the swirl guide element 35 comprises a cylindrical wall 351 and a plurality of evenly distributed

fins

352 and 353 extending radially inwards from the axial front and rear edges of the cylindrical wall 351, respectively. The cylindrical wall 351 is sized to fit within the cylindrical section 32. The surface of each of the

fins

352 and 353 is inclined with respect to a plane perpendicular to the central axis of the cylindrical wall 351 (i.e., the central axis of the swirl guide element 35), and the angle at which each of the fins is inclined with respect to this plane may be the same. Further, the tip (distal end) of each airfoil may also be twisted relative to its root (the point where the airfoil joins the cylinder wall). Thus, the mixed flow of the reducing agent and the exhaust gas that impinges on each of the

vanes

352 and 353 is deflected by the vanes in the circumferential direction. Under the deflection of all the

fins

352 and 353, the air flow will flow through the swirl guide element 35 in the form of a swirl.

The mixed gas flow discharged from the outlet of the reducing agent mixer 3 enters the third cover 8 and flows toward the

inlets

41, 51 of the selective

catalytic reducers

4, 5. In order to make the ratio of the amount of the mixture gas flow flowing into the selective

catalytic reduction devices

4, 5 substantially equal to the processing capacity of both, and to flow relatively uniformly in each selective

catalytic reduction device

4, 5, a diffuser plate 36 is installed on the first end wall 11 downstream of the outlet of the reducing agent mixer 3, as shown in fig. 4, 5. The diffuser plate 36 is located in the third casing 8, and the plate body of the diffuser plate 36 is substantially perpendicular to the first end wall 11, i.e., the central axis of the selective

catalytic reduction devices

4 and 5 is substantially parallel to the plate body of the diffuser plate 36. Due to the structure of the third cover 8, the diffuser plate 36 is arranged between the outlet of the reducing agent mixer 3 and the inlet 41 of the selective catalytic reducer 4. The diffuser plate 36 has a plurality of through holes that penetrate between both plate surfaces thereof, whereby the mixture flow discharged from the outlet of the reducing agent mixer 3 can be dispersed so that the mixture flow can flow into the selective

catalytic reduction devices

4 and 5 relatively uniformly.

Further, in FIG. 5, the vertical line between the centerline of the reductant mixer 3 and the centerline of the selective catalytic reducer 4 is indicated by "L", the diffuser plate 36 is disposed obliquely with respect to the vertical line L, and the plate surface thereof is inclined in such a manner as to direct the air flow more toward the selective catalytic reducer 5. the angle α between the plate surface of the diffuser plate 36 facing the inlet 41 of the selective catalytic reducer 4 and the vertical line L is between 30 degrees and 80 degrees, preferably between 30 degrees and 60 degrees. therefore, the diffuser plate 36 helps direct the mixed air flow toward the selective catalytic reducer 5 so that the mixed air flow is more reasonably distributed between the selective

catalytic reducers

4, 5. specifically, the angle α at which the diffuser plate 36 is inclined with respect to the vertical line L is set so that the mixed air flow is distributed as closely as possible to the handling capacity of the selective

catalytic reducers

4, 5, which can be achieved through experiments or simulations.

The diffuser plate 36 can have any suitable shape and configuration. According to one possible embodiment, as shown in fig. 9 and 10, the diffuser 36 is formed in a grid shape by a set of first strips 361 of metal oriented in a first direction and a set of second strips 362 of metal oriented in a second direction, the width direction of each strip being perpendicular to the two plate surfaces of the diffuser 36. A square, rectangular, or diamond-shaped through-hole is defined between the first strip 361 and the second strip 362. The diffuser plate 36 thus constructed has not only a good airflow dispersing function but also an airflow guiding function (mainly realized by the width of the strip).

According to another possible embodiment, as shown in fig. 11, the diffuser plate 36 is made of a metal plate 363, and a plurality of through holes 364 are punched in the metal plate 363. Further, a flange 365 is formed along one or both long sides of the metal plate 363, which flange 365 may be secured to the second end wall 12, for example by welding, riveting, screwing, etc. The diffuser plate 36 thus constructed has a larger airflow blocking area and thus a better airflow dispersing function than the examples shown in fig. 9 and 10. In order to provide the airflow guide function to the diffuser plate 36 shown in fig. 11, after the through holes 364 are punched, a flanging process may be performed along the edge of each through hole 364 to form a flange (not shown) extending from the edge of each through hole 364 substantially perpendicular to the metal plate 363.

Other forms of distribution plates 36 are also contemplated.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above in accordance with the basic principles of the application.

For example, in the illustrated example, two selective catalytic reducers are provided, however, a single selective catalytic reducer may be provided, or more than two selective catalytic reducers may be provided in parallel with each other, according to the actual needs. For the scheme of arranging a plurality of selective catalytic reducers, the shape and size (especially, the radial size) of each of them can be optimally designed according to the condition of the internal space of the box body.

In the case of a single selective catalytic reducer, the diffuser plate may help the mixed flow of the exhaust gas and the reducing agent to uniformly flow into the selective catalytic reducer. In the case of two or more selective catalytic reducers, the diffuser plate may help to distribute the mixed gas flow more reasonably between the selective catalytic reducers in a manner that matches the processing capacity of the selective catalytic reducers, and to help to flow the mixed gas flow uniformly into each selective catalytic reducer.

In addition, the individual exhaust gas treatment elements, in particular the oxidation catalytic converters and the selective catalytic reduction converters, can be designed as modules, in particular modules having different specifications, so that exhaust gas aftertreatment boxes having various exhaust gas treatment capacities are easily realized by the combination of the various modules.

Modifications to other aspects of the exhaust aftertreatment tank of the present application are also contemplated.

According to the exhaust gas post-treatment box, the flow dispersing plate arranged at the downstream of the reducing agent mixer is used for enabling the mixed gas flow of the exhaust gas and the reducing agent to uniformly flow into the selective catalytic reduction device, so that the conversion rate of nitrogen oxides is improved, and the exhaust gas easily meets the requirement of higher exhaust gas emission standard.

Although the present application has been described herein with reference to particular embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims

1. An integrated exhaust aftertreatment case comprising:

a box body (1);

an oxidation catalyst (2), a reducing agent mixer (3) and a selective catalytic reduction device (4, 5) carried by the tank and arranged alongside one another in succession through which the exhaust gases flow; and

a reductant injector (9) arranged facing the reductant mixer;

characterized in that the integrated exhaust gas aftertreatment tank further comprises a diffuser plate (36) arranged between the outlet of the reductant mixer and the inlet of the selective catalytic reducer, the diffuser plate having a plurality of through holes passing between its two plate surfaces.

2. The integrated exhaust aftertreatment tank of claim 1, wherein the diffuser plate is formed in a grid shape by connecting metal strips crossing each other, the strips defining through-holes therebetween.

3. The integrated exhaust aftertreatment tank of claim 1, wherein the diffuser plate is formed from a metal plate having a plurality of through holes punched therein.

4. Integrated exhaust gas aftertreatment tank according to claim 1, characterized in that the outlet of the reductant mixer and the inlet of the selective catalytic reducer are covered by a common cover (8) in which the diffuser plate is arranged.

5. The integrated exhaust aftertreatment tank of claim 1, wherein the diffuser plate is arranged such that a central axis of the selective catalytic reducer is substantially parallel to the diffuser plate.

6. The integrated exhaust aftertreatment tank of any one of claims 1 to 5, wherein the diffuser plate is inclined relative to a perpendicular between a centerline of the reductant mixer and a centerline of the selective catalytic reducer.

7. The integrated exhaust aftertreatment tank of any one of claims 1 to 5, wherein the selective catalytic reducer is at least two selective catalytic reducers arranged side by side, an inlet of each selective catalytic reducer being located on the same side as an outlet of the reductant mixer.

8. The integrated exhaust aftertreatment tank of claim 7, wherein the reductant mixer closest to the selective catalytic reducer is defined as a first reductant mixer, and the diffuser plate is disposed at an inclination with respect to a perpendicular between a centerline of the first reductant mixer and a centerline of the selective catalytic reducer.

9. The integrated exhaust aftertreatment tank of claim 8, wherein the diffuser plate is angled between 30 degrees and 80 degrees from the vertical.

10. The integrated exhaust aftertreatment tank of any one of claims 1 to 5, further comprising a swirl flow guide element (35) arranged in the reductant mixer, the swirl flow guide element having a plurality of fins causing the mixture of reductant and exhaust gas to form a swirl flow, each fin being inclined with respect to a plane perpendicular to a swirl flow guide element central axis.