JP2019127880A - Agitator - Google Patents

Abstract

To provide an agitator capable of restricting occurrence of deposit while increasing dispersibility of reductant.SOLUTION: One preferred embodiment of this invention relates to an agitator for agitating exhaust gas. This agitator comprises an upstream pipe, a downstream pipe, an outer shell member, an injection part and a cylindrical agitating part. The upstream pipe is constituted to cause exhaust gas to pass. The downstream pipe is installed at a downstream side of the upstream pipe. The outer shell member constitutes a connecting flow passage connecting between a downstream side end part of the upstream pipe and an upstream side end part of the downstream pipe. The injection part is constituted to inject reductant into the connected flow passage. The agitating part protrudes from the upstream side end part of the downstream pipe into the upstream side part and at the same time at least a part of the outer peripheral surface is oppositely faced against the downstream side end part of the upstream pipe. In addition, the agitating part has a collision part where the reductant injected by the injection part strikes against it, several open holes arranged around the collision part and an opening arranged around a central axis of the agitating part at an opposite side of the downstream side end part of the upstream pipe.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a stirring device.

  An exhaust gas purification member such as a selective catalytic reduction (SCR) catalyst is disposed in the exhaust gas flow path of the internal combustion engine for the purpose of complying with regulations regarding exhaust gas components of the internal combustion engine. SCR is a method of reducing NOx in exhaust gas to harmless nitrogen by a reducing agent and a reduction catalyst.

  In SCR, in order for the reduction catalyst to function efficiently and to improve the exhaust gas purification rate, it is necessary to mix the reducing agent and disperse it uniformly in the exhaust gas. In view of this, a stirring device has been proposed in which a stirring portion is provided in the exhaust gas flow path, and the fluid is stirred by generating a swirling flow of the exhaust gas in the stirring portion (see Patent Document 1).

International Publication No. 2017/126121

  In the stirring device of Patent Document 1, the reducing agent is jetted from the jetting unit toward the cylindrical stirring unit. The reducing agent collides with the stirring unit and is refined, but a part of the reduced reducing agent droplets stays inside the outer shell member storing the stirring unit. As a result, deposits, which are white precipitates derived from urea, are deposited on the inside of the shell member.

  An object of one aspect of the present disclosure is to provide a stirring device that can suppress the generation of deposits while improving the dispersibility of the reducing agent.

  One aspect of the present disclosure is a stirring device for stirring exhaust gas. The stirrer includes an upstream pipe, a downstream pipe, an outer shell member, an injection unit, and a cylindrical stirring unit. The upstream pipe is configured to pass the exhaust gas therethrough. The downstream pipe is disposed downstream of the upstream pipe in the flow direction of the exhaust gas. The outer shell member constitutes a connection flow path that connects between the downstream end of the upstream pipe and the upstream end of the downstream pipe. The injection unit is configured to inject the reducing agent into the connection channel. The stirring unit protrudes from the upstream end of the downstream pipe into the connection flow path, and at least a part of the outer peripheral surface thereof faces the downstream end of the upstream pipe. In addition, the stirring unit includes a collision part where the reducing agent injected by the injection unit collides on the outer peripheral surface, a plurality of through holes arranged around the collision part, and a downstream side of the upstream pipe across the central axis of the stirring part. And an opening provided opposite to the end.

  According to such a structure, the dispersibility in the exhaust gas of a reducing agent improves because a reducing agent is refined | miniaturized by a collision part. At the same time, the reducing agent refined by the plurality of through-holes is taken into the stirring portion, so that it is possible to suppress the occurrence of deposit due to the retention of the reducing agent on the inner surface of the outer shell member.

  In one aspect of the present disclosure, the collision part may be non-porous. According to such a configuration, the reducing agent can be miniaturized more reliably. As a result, the dispersibility of the reducing agent can be further enhanced.

  In one aspect of the present disclosure, the plurality of through holes may be arranged to surround the entire circumference of the collision portion. According to such a configuration, the finely divided reducing agent can be more reliably guided to the inside of the stirring section. As a result, the generation of deposits can be suppressed more reliably.

FIG. 1 is a schematic partially transparent perspective view of the stirring device of the embodiment. FIG. 2 is a schematic central cross-sectional view of the stirring device of FIG. FIG. 3 is a schematic cross-sectional view taken along line III-III of FIG. 4A is a schematic perspective view of a stirring unit in the stirring apparatus of FIG. 1, and FIG. 4B is a schematic perspective view showing a state in which a reducing agent is injected into the stirring unit of FIG. 4A. FIG. 5A is a schematic plan view of the stirring unit of FIG. 4A viewed from the flow direction of the exhaust gas in the upstream pipe, and FIG. 5B is a schematic plan view of the stirring unit of FIG. 4A viewed from the opening side. is there.

Hereinafter, embodiments to which the present disclosure is applied will be described using the drawings.
[1. First embodiment]
[1-1. Constitution]
A stirring device 1 shown in FIG. 1 is provided upstream of an SCR device in an exhaust gas flow path of an internal combustion engine.

  The stirring device 1 includes an upstream pipe 2, a downstream pipe 3, an outer shell member 4, an injection unit 5, and a stirring unit 6. The stirring device 1 is configured to stir the exhaust gas while supplying the reducing agent to the exhaust gas.

  The internal combustion engine provided with the stirring device 1 is not particularly limited, and examples thereof include an internal combustion engine that is used for driving or power generation in transportation equipment such as automobiles, railways, ships, and construction equipment, and power generation facilities.

<Upstream pipe>
The exhaust pipe passes through the upstream pipe 2. The exhaust gas that has passed through the upstream pipe 2 is discharged from the downstream end 2A of the upstream pipe 2 to a connection flow path 10 that is formed by an outer shell member 4 described later.

<Downstream pipe>
The downstream pipe 3 is disposed downstream of the upstream pipe 2 in the exhaust gas flow direction. The exhaust gas that has passed through the downstream pipe 3 is supplied to an SCR device (not shown).

<Outer shell member>
The outer shell member 4 constitutes a connection flow path 10 that connects between the downstream end 2A of the upstream pipe 2 and the upstream end 3A of the downstream pipe 3.

  In the present embodiment, the outer shell member 4 has a shape in which two cylindrical bodies are integrated so that their central axes intersect each other. Specifically, the outer shell member 4 has a first pipe 4A connected to the downstream end 2A of the upstream pipe 2 and a second pipe 4B connected to the upstream end 3A of the downstream pipe 3. .

  As shown in FIG. 2, the second pipe 4 </ b> B is closed at the end opposite to the upstream end 3 </ b> A of the downstream pipe 3. The second pipe 4B is provided with an opening in a portion of the outer peripheral surface facing the downstream end 2A of the upstream pipe 2, and this opening is connected to the downstream end 2A of the upstream pipe 2 of the first pipe 4A. The opposite end is connected.

  Therefore, the exhaust gas that has passed through the upstream pipe 2 passes through the first pipe 4A, enters the second pipe 4B, and is supplied from the second pipe 4B to the downstream pipe 3 through the agitating unit 6 described later. That is, the connection flow path 10 is comprised by the interior space of the 1st pipe 4A and the 2nd pipe 4B.

  In FIG. 1, the central axis of the upstream pipe 2 (that is, the exhaust gas flow direction) and the central axis of the downstream pipe 3 are orthogonal, but the central axis of the upstream pipe 2 and the central axis of the downstream pipe 3 are It may intersect at an angle other than 90 ° or may be parallel.

<Injection part>
The injection unit 5 injects urea water, which is a reducing agent, into the connection flow passage 10. Specifically, the injection unit 5 includes an injector that injects a reducing agent toward a collision unit 6A of the stirring unit 6 described later. As shown in FIG. 1, this injector is attached to a connecting pipe 5 </ b> A that penetrates the outer shell member 4.

  In addition, the injector of the injection part 5 can use a well-known thing. Moreover, in FIG. 1 etc., only the connecting pipe 5A is shown as the injection part 5, and members, such as an injector, are abbreviate | omitting illustration.

  In the present embodiment, as shown in FIG. 3, the injection unit 5 is upstream of the central axis P <b> 1 of the downstream pipe 3 in the exhaust gas flow direction D <b> 1 in the upstream pipe 2 as viewed from the central axis direction of the downstream pipe 3. It is provided at a position close to the downstream end 2A of the two.

<Stirring section>
As shown in FIG. 2, the stirring unit 6 is a cylindrical body that protrudes into the connection channel 10 from the upstream end 3 </ b> A of the downstream pipe 3. The stirring unit 6 is arranged so that at least a part of the outer peripheral surface faces the downstream end 2 </ b> A of the upstream pipe 2.

As shown in FIG. 4A, the stirring unit 6 includes a main body 61 and a connection unit 62.
The main body 61 is a cylindrical body whose central axis is arranged in parallel with the central axis of the downstream pipe 3 and whose one end is connected to the connecting portion 62. An end portion of the main body 61 opposite to the connection portion 62 is closed by a bottom wall 61A. As shown in FIG. 2, the bottom wall 61 </ b> A faces the end of the first pipe 4 </ b> A of the outer shell member 4.

As shown in FIG. 4A, the main body 61 is provided with a collision portion 6A, a plurality of through holes 6B, and an opening 6C.
As shown in FIG. 4B, the collision part 6 </ b> A is a part where the reducing agent R injected by the injection unit 5 collides with the outer peripheral surface of the main body 61. That is, the collision portion 6 </ b> A is provided at a position overlapping the injection region of the injector of the injection unit 5 on the outer peripheral surface of the main body 61.

  In the present embodiment, the collision portion 6A is non-porous. Further, as shown in FIG. 5A, the collision portion 6A is disposed at a position where the entirety can be seen as viewed from the central axis direction (that is, the exhaust gas flow direction D1) in the downstream end portion 2A of the upstream pipe 2. . That is, the collision part 6A is opposed to the downstream end 2A of the upstream pipe 2.

  The plurality of through holes 6B are disposed around the collision portion 6A, as shown in FIG. 4A. Specifically, the plurality of through holes 6B are arranged on the outer peripheral surface of the main body 61 at regular intervals so as to surround the entire periphery of the collision portion 6A.

  The plurality of through holes 6B are formed, for example, by punching. The plurality of through holes 6B need not necessarily be arranged at the same interval. Moreover, the diameters of the plurality of through holes 6B may be different from each other.

  In the present embodiment, of the outer peripheral surface of the main body 61, the portion between the collision portion 6A and the opening 6C (the lower portion of the collision portion 6A in FIG. 4A), the collision portion 6A, and the bottom wall 61A of the main body 61. A plurality of through-holes 6B are arranged in multiple rows in a portion between them (in FIG. 4A, the right portion of the collision portion 6A).

  Further, in the circumferential direction of the main body 61, of the two regions sandwiched between the portion closest to the downstream end 2A of the upstream pipe 2 (the uppermost portion of the main body 61 in FIG. 4A) and the opening 6C, the collision A through hole 6B is not provided in a region where the portion 6A is not formed (see FIGS. 5A and 5B).

  4A, the maximum width W1 in the axial direction D2 of the main body 61 in the region where the plurality of through holes 6B of the main body 61 are arranged is larger than the maximum width W2 in the axial direction D2 of the main body 61 of the opening 6C. Too big.

  Since the maximum width W2 is smaller than the maximum width W1, the urea water refined by passing through the through-hole 6B around the collision portion 6A is well mixed with the swirling flow flowing from the opening 6C. On the other hand, if the maximum width W2 is larger than the maximum width W1, the gas flow path to the reduction catalyst is shortened and the contact of the exhaust gas to the reduction catalyst becomes poor, and exhaust gas that is not sufficiently mixed with urea water is produced. It may be supplied to the reduction catalyst.

  As shown in FIG. 1, the opening 6 </ b> C is provided on the opposite side of the downstream end 2 </ b> A of the upstream pipe 2 with the central axis P <b> 0 of the stirring unit 6 interposed therebetween. The opening 6C is formed by cutting the side wall of the main body 61 with a constant width in the axial direction and the circumferential direction. In the present embodiment, the central axis P0 of the stirring unit 6 is coincident with the central axis P1 of the downstream pipe 3 of the downstream pipe 3, but these central axes are not necessarily coincident.

  The connection portion 62 is a conical cylinder. The connecting portion 62 has a small-diameter end connected to the main body 61 and a large-diameter end connected to the upstream end 3 </ b> A of the downstream pipe 3. The large diameter end closes the upstream end 3A.

  Therefore, the exhaust gas in the connection channel 10 flows into the stirring unit 6 from the opening 6 </ b> C of the stirring unit 6 and flows into the downstream pipe 3. A part of the exhaust gas flows into the stirring portion 6 through the plurality of through holes 6B.

[1-2. function]
Next, the mechanism of stirring in the stirring device 1 will be described.
In the stirring device 1, the exhaust gas discharged from the upstream pipe 2 to the connection flow path 10 collides with the outer peripheral surface of the stirring unit 6. The exhaust gas that has collided with the outer peripheral surface moves along the outer peripheral surface of the stirring unit 6 and is sucked into the opening 6C. Thereby, the exhaust gas generates a swirling flow inside the stirring unit 6. Further, a part of the exhaust gas passes through the plurality of through holes 6 </ b> B and collides with the swirl flow inside the stirring unit 6.

  On the other hand, the reducing agent injected from the injection unit 5 collides with the collision unit 6A of the stirring unit 6 and is refined. The finely divided reducing agent is entrained in the swirling flow of the exhaust gas and mixed with the exhaust gas. As a result, the dispersibility of ammonia is improved, and the reducing agent and exhaust gas supplied from the downstream pipe 3 to the SCR device come into homogeneous contact with the reduction catalyst.

  Further, a part of the refined reducing agent passes through the plurality of through holes 6 </ b> B and flows to the downstream pipe 3. Therefore, the generation of deposits due to the reduced reducing agent adhering to the inner surface of the outer shell member 4 is suppressed.

[1-3. effect]
According to the embodiment described above, the following effects can be obtained.
(1a) The dispersibility of the reducing agent in the exhaust gas is improved by making the reducing agent finer by the collision portion 6A. At the same time, since the reducing agent miniaturized by the plurality of through holes 6B is taken into the inside of the agitating portion 6, generation of deposits due to retention of the reducing agent on the inner surface of the shell member 4 can be suppressed.

  Further, the positions of the collision portion 6A and the plurality of through holes 6B in the stirring portion 6 can be easily changed in accordance with the injection position of the reducing agent by the injection portion 5. Therefore, design changes can be made relatively easily.

  (1b) Since the collision part 6A where the reducing agent injected by the injection unit 5 collides is non-porous, the reducing agent can be more reliably miniaturized. As a result, the dispersibility of the reducing agent can be further enhanced.

  (1c) Since the plurality of through holes 6B are arranged so as to surround the entire circumference of the collision part 6A, the refined reducing agent can be more reliably guided to the inside of the stirring part 6. As a result, the generation of deposits can be suppressed more reliably.

[2. Other embodiments]
As mentioned above, although embodiment of this indication was described, it can not be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

  (2a) In the stirring device 1 of the above-described embodiment, the collision unit 6A may be provided with one or a plurality of fine holes as long as the reducing agent can be refined by collision. The diameter of the fine holes is smaller than the diameter of the plurality of through holes 6B.

  (2b) In the stirring device 1 of the above embodiment, the plurality of through holes 6B do not necessarily have to be arranged so as to surround the entire circumference of the collision portion 6A. For example, the plurality of through holes 6B are formed between the collision portion 6A and the opening 6C (the lower portion of the collision portion 6A in FIG. 4A) and between the collision portion 6A and the bottom wall 61A of the main body 61. It may be arranged only with the part (part on the right side of the collision part 6A in FIG. 4A).

  (2c) In the stirring apparatus 1 of the said embodiment, the shape of the outer shell member 4 and the stirring part 6 is an example. The shell member 4 does not necessarily have to be constituted by a combination of pipes. In addition, the cross-sectional shapes of the connection flow path 10 and the stirring unit 6 configured by the outer shell member 4 may be polygonal, elliptical, or the like.

  (2d) In the stirring device 1 of the above-described embodiment, the collision portion 6A does not necessarily face the downstream end portion 2A of the upstream pipe 2. That is, the collision part 6 </ b> A may not be partly or entirely visible when viewed from the central axis direction at the downstream end 2 </ b> A of the upstream pipe 2.

  (2e) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified from the wording as described in a claim are an embodiment of this indication.

DESCRIPTION OF SYMBOLS 1 ... Stirrer, 2 ... Upstream pipe, 2A ... Downstream end part, 3 ... Downstream pipe, 3A ... Upstream end part,
4 ... outer shell member, 4A ... 1st pipe, 4B ... 2nd pipe, 5 ... injection part, 5A ... connection pipe,
6 ... Stirring section, 6A ... Collision section, 6B ... Through hole, 6C ... Opening, 10 ... Connection flow path,
61 ... main body, 61 A ... bottom wall, 62 ... connection portion.

Claims (3)

A stirring device for stirring exhaust gas,
An upstream pipe configured to pass exhaust gas therethrough;
A downstream pipe disposed downstream of the upstream pipe in the flow direction of the exhaust gas;
An outer shell member constituting a connection flow path connecting the downstream end of the upstream pipe and the upstream end of the downstream pipe;
An injection unit configured to inject a reducing agent into the connection channel;
A tubular stirring portion which protrudes into the connection flow channel from the upstream end of the downstream pipe, and at least a part of an outer peripheral surface of the downstream pipe faces the downstream end of the upstream pipe;
With
The stirring unit is
A collision part with which the reducing agent injected by the injection part collides on the outer peripheral surface;
A plurality of through holes disposed around the collision portion;
An opening provided on the side opposite to the downstream end of the upstream pipe across the central axis of the stirring unit;
Having a stirring device. The stirring device according to claim 1,
The said collision part is a non-porous stirring apparatus. The stirrer according to claim 1 or 2, wherein
The plurality of through holes are stirring devices arranged to surround the entire circumference of the collision portion.