JP2019127879A - Exhaust emission control system - Google Patents

Abstract

To provide an exhaust emission control system capable of increasing purification efficiency of exhaust gas while restricting increasing in pressure loss.SOLUTION: One preferred embodiment of this disclosure relates to an exhaust gas purification device. This exhaust gas purification device comprises a reductant feed section; an exhaust gas pipe passage; and a swirl flow generating section. The swirl flow generating section has a first shield part and a second shield part arranged at a downstream side of the first shield part. The second shield part has an annular part for shielding a flow in a center axial direction at a radial outer side of the opening; and a side wall extending from the annular part to the first shielding part and also partially enclosing the opening of the annular part in a peripheral direction. As seen from the central axis direction, the first shielding part has a central part overlapping on the opening of the annular part; a peripheral edge part extending from the central part up to an inner peripheral surface of the exhaust gas pipe passage; and several open holes arranged at the peripheral part. The peripheral edge part, as seen from the central axis direction, is arranged to overlap on an area outside a radial direction at a released part not enclosed by the side wall part of the outer edge at the opening. The reductant supply part injects reductant toward the side wall part.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an exhaust gas purification device.

  An exhaust gas purification device is installed in an exhaust gas passage of the internal combustion engine for the purpose of complying with the regulation on the exhaust gas component of the internal combustion engine. If it is a diesel engine, exhaust gas purification members, such as a diesel oxidation catalyst (DOC), a diesel particulate collection filter (DPF), and a catalyst for selective catalyst reduction (SCR), are used in combination with the exhaust gas purification device.

  Of these exhaust gas purification members, the SCR catalyst (hereinafter also referred to as “reduction catalyst”) is generally installed downstream of other catalysts or filters. 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 to make the reduction catalyst function efficiently and improve the purification rate of the exhaust gas, the reducing agent is mixed and uniformly dispersed in the exhaust gas, and the exhaust gas containing the reducing agent is evenly distributed. It is necessary to contact the reduction catalyst.

  As a method of dispersing the reducing agent in the exhaust gas, there is a method of disposing a diffusion plate in the exhaust gas flow path. However, disposing the diffusion plate in the flow path causes a disadvantage that the pressure loss increases and the flow of exhaust gas is uneven.

  Therefore, an exhaust gas purification device has been proposed in which a guide wall is provided in the exhaust gas flow path, and the reducing agent is diffused by the swirling flow generated by the guide wall (see Patent Document 1). In this exhaust gas purification device, in order to guide the flow path to the guide wall, the upper portion of the guide wall is closed with a plate, and an introduction hole is provided in this plate.

JP 2017-145717 A

  According to the exhaust gas purification device of Patent Document 1, the reducing agent can be diffused by the swirling flow. However, in order to promote mixing, it is necessary to make the introduction hole smaller. Therefore, the area of the gas flow path is reduced, and as a result, the pressure loss of the apparatus is increased.

  One aspect of the present disclosure aims to provide an exhaust gas purification device capable of improving exhaust gas purification efficiency while suppressing an increase in pressure loss.

  One aspect of the present disclosure is an exhaust gas purification device for an internal combustion engine. The exhaust gas purification device includes an exhaust gas purification unit, a reduction unit, a reducing agent supply unit, an exhaust gas pipe, and a swirl flow generation unit. The exhaust gas purification unit is configured to reform or collect environmental pollutants in the exhaust gas. The reduction unit is provided downstream of the exhaust gas purification unit in the flow direction of the exhaust gas, and configured to reduce the exhaust gas in the presence of a reducing agent. The reducing agent supply unit is configured to supply the reducing agent to the exhaust gas upstream of the reducing unit in the flow direction of the exhaust gas. The exhaust gas conduit communicates the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit. The swirl flow generation unit is installed in the exhaust gas pipe.

  In addition, the swirl flow generating portion includes a first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas pipe, and a second shielding portion disposed on the downstream side of the first shielding portion. And having. The second shielding part has an opening formed at the radial center of the exhaust gas channel, and an annular part configured to shield the flow in the central axis direction on the radial outside of the opening, and the first shielding part from the annular part And a side wall part that partially surrounds the opening of the annular part in the circumferential direction. The first shielding portion overlaps with the opening of the annular portion when viewed from the central axis direction, and has a central portion that is separated from the inner surface of the exhaust gas conduit and a peripheral portion that extends from the central portion to the inner peripheral surface of the exhaust gas conduit. And a plurality of through holes provided in the peripheral portion. The peripheral edge portion is disposed so as to at least overlap with the radially outer region of the open portion not surrounded by the side wall portion of the outer edge of the opening of the annular portion when viewed from the central axis direction. The reducing agent supply unit jets the reducing agent toward the side wall.

  According to such a configuration, first, the flow of exhaust gas in the central axis direction of the exhaust gas pipe (hereinafter also referred to as “first direction”) is caused to flow outside the side wall portion of the second shielding portion by the first shielding portion. Be guided to. The flow induced to the side wall portion is divided into two flows by the side wall portion and flows toward the opening of the annular portion. As a result, the flow path of the exhaust gas extends, and two swirling flows in opposite directions having a swirling axis parallel to the first direction are generated. Therefore, the reducing agent injected toward the side wall portion is efficiently diffused. As a result, evaporation of the reducing agent is promoted and the dispersibility is improved. Furthermore, a part of the exhaust gas flow passes through the plurality of through holes of the first shielding portion and merges with the two swirling flows. As a result, the reductant and the exhaust gas are effectively stirred.

  In the above-described configuration, it is not necessary to provide an introduction hole in the plate that closes the flow path, and the flow path diameter can be adjusted to an arbitrary size by the first shielding portion. Therefore, an increase in pressure loss can be suppressed while improving the exhaust gas purification efficiency.

  In one aspect of the present disclosure, the area of the region where the first shielding portion is not disposed in the exhaust gas pipe line may be larger than the total area of the plurality of through holes as viewed from the central axis direction. According to such a configuration, the above-described two swirl flows can be more reliably generated. As a result, the exhaust gas purification efficiency can be increased.

  In one aspect of the present disclosure, the length in the circumferential direction of the contact portion between the peripheral edge portion and the inner peripheral surface of the exhaust gas conduit may be ½ or less of the inner peripheral length of the exhaust gas conduit. . According to such a configuration, an increase in pressure loss can be more reliably suppressed while enhancing the purification efficiency of the exhaust gas.

  In one aspect of the present disclosure, the circumferential first end of the side wall overlaps with the circumferential first end of the peripheral edge as viewed from the central axis direction, and the circumferential second end of the side wall Further, it may overlap with the second end portion in the circumferential direction of the peripheral edge portion as viewed from the central axis direction. According to such a configuration, the exhaust gas flowing from the upstream side reliably collides with the side wall portion. As a result, stirring performance can be secured while reducing pressure loss.

1A is a schematic partial perspective view of the exhaust gas purification device of the embodiment, and FIG. 1B is a schematic central sectional view of the exhaust gas purification device of FIG. 1A. FIG. 2A is a schematic perspective view of a swirl flow generation unit in the exhaust gas purification apparatus of FIG. 1A, and FIG. 2B is a schematic plan view of the swirl flow generation unit of FIG. 2A. FIG. 3 is a schematic perspective view of a second shielding part in the swirl flow generating part of FIG. 2A. FIG. 4 is a schematic partial cross-sectional perspective view for explaining the flow of exhaust gas in the swirl flow generating portion of FIG. 2A.

Hereinafter, embodiments to which the present disclosure is applied will be described using the drawings.
[1. First embodiment]
[1-1. Constitution]
An exhaust gas purification apparatus (hereinafter, also simply referred to as “purification apparatus”) 1 shown in FIGS. 1A and 1B is provided in an exhaust gas flow path of an internal combustion engine to reduce environmental pollutants in the exhaust gas. The purification device 1 includes an exhaust gas purification unit 2, a reduction unit 3, a reducing agent supply unit 4, an exhaust gas pipe 5, and a swirling flow generation unit 6.

  The internal combustion engine provided with the purification device 1 is not particularly limited, but the purification device 1 can be used particularly suitably as an exhaust gas purification device of a diesel engine. Examples of diesel engines include those used for driving or power generation in transportation equipment such as automobiles, railways, ships, construction machinery, and power generation facilities.

<Exhaust gas purification unit>
The exhaust gas purification unit 2 reforms or collects environmental pollutants in the exhaust gas. Here, "environmental pollutants" mean carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), sulfur oxides (SOx), hydrocarbons (HC) and the like.

  As shown in FIG. 1B, the exhaust gas purification unit 2 has a purification member 21 for purifying the exhaust gas, and a cylindrical casing 22 accommodating the purification member 21. The exhaust gas flows along the central axial direction of the casing 22 while being in contact with the purification member 21 inside the casing 22.

  Examples of the purification member 21 include a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a NOx adsorbent. DOC is a catalyst that oxidizes soluble organic components (SOF), CO, and HC in PM contained in exhaust gas. The DPF is a filter that collects PM contained in the exhaust gas. The NOx adsorbent is a substance that adsorbs and removes NOx.

  As the purification member 21, a cylindrical body having a honeycomb structure is generally used. When the exhaust gas passes through the inside of the honeycomb structure, environmental pollutants in the exhaust gas are reformed by the catalytic metal contained in the purification member 21 or captured by the purification member 21.

  In FIGS. 1A and 1B, the exhaust gas purification unit 2 is disposed such that the flow direction of the exhaust gas in the inside is the vertical direction, that is, the central axis of the cylindrical casing 22 is the vertical direction. Further, the exhaust gas outlet 2A of the exhaust gas purification unit 2 is formed such that the exhaust gas is discharged in the vertical direction. However, the flow direction of the exhaust gas in the exhaust gas purification unit 2 is not limited to the vertical direction, and may be a horizontal direction or a direction inclined with respect to the horizontal direction.

<Reduction part>
The reducing unit 3 reduces the exhaust gas in the presence of a reducing agent. Specifically, the reducing unit 3 reduces NOx in the exhaust gas by ammonia and a reduction catalyst and reforms it into harmless nitrogen. Ammonia, which is a reducing agent, is generally generated by injecting urea water into exhaust gas and hydrolyzing urea in the urea water.

  The reduction unit 3 includes a reduction catalyst 31 and a cylindrical casing 32 that houses the reduction catalyst 31. The reduction catalyst 31 is composed of a base material such as ceramic and a metal catalyst supported on the base material. The exhaust gas flows along the central axis direction of the casing 32 while contacting the reduction catalyst 31 inside the casing 32.

  The reduction unit 3 is connected to the downstream side of the exhaust gas purification unit 2 in the flow direction of the exhaust gas via the exhaust gas line 5. The reduction unit 3 is arranged so that the flow direction of the exhaust gas inside is the same direction as the exhaust gas purification unit 2. That is, the central axis of the casing 32 of the reduction unit 3 is disposed in the same direction as the central axis of the casing 22 of the exhaust gas purification unit 2.

<Reducing agent supply unit>
The reducing agent supply unit 4 supplies the reducing agent to the exhaust gas upstream of the reducing unit 3 in the exhaust gas flow direction. In the present embodiment, as shown in FIGS. 1A and 1B, the reducing agent supply unit 4 is configured to inject a reducing agent into the exhaust gas pipe 5.

  Specifically, the reducing agent supply unit 4 includes an injector that injects the reducing agent toward a side wall 8B of the second shielding unit 8 described later. The injector injects urea water, which is a reducing agent, toward the central axis of the exhaust gas pipe 5 from the circumferential surface of the exhaust gas pipe 5.

  In addition, a well-known thing can be used for the injector of the reducing agent supply part 4. FIG. In FIGS. 1A and 1B, only the connecting pipe to the exhaust gas pipe 5 is shown as the reducing agent supply unit 4, and members such as an injector are not shown.

<Exhaust gas pipeline>
The exhaust gas conduit 5 is a pipe body that communicates the exhaust port 2A of the exhaust gas purification unit 2 and the introduction port 3A of the reduction unit 3. That is, the exhaust gas discharged from the exhaust gas purification unit 2 is introduced into the reduction unit 3 through the exhaust gas pipe 5. A swirling flow generating unit 6 is disposed inside the exhaust gas pipeline 5. Further, the reducing agent supply unit 4 is connected to the circumferential surface of the exhaust gas pipe line 5.

  The central axial direction of the exhaust gas pipe line 5 coincides with the central axial direction of the casing 22 of the exhaust gas purification unit 2 and the casing 32 of the reduction unit 3. That is, the exhaust gas pipe 5 forms a straight, straight exhaust gas flow path between the exhaust gas purification unit 2 and the reduction unit 3.

  In the present embodiment, the exhaust gas pipe 5 is a straight pipe, and the exhaust port 2A of the exhaust gas purification unit 2 and the introduction port 3A of the reduction unit 3 have the same diameter. However, the outlet 2A of the exhaust gas purification unit 2 and the inlet 3A of the reduction unit 3 may not necessarily have the same diameter.

<Swirling flow generation part>
The swirl flow generator 6 is installed in the exhaust gas pipe 5 and generates a plurality of swirl flows in the exhaust gas. As shown in FIGS. 2A and 2B, the swirling flow generating unit 6 includes a first shielding unit 7 and a second shielding unit 8.

(First shielding part)
The first shielding unit 7 shields a part of the flow in the first direction D <b> 1 that is the central axis direction of the exhaust gas pipeline 5 from the exhaust gas flowing in the exhaust gas pipeline 5.

  As shown in FIG. 2A, the first shielding portion 7 has a central portion 7A, a peripheral portion 7B, and a plurality of through holes 7C. The first shielding portion 7 shields part of the flow of the exhaust gas in the first direction D1 by the central portion 7A and the peripheral portion 7B.

  The central portion 7A is a plate-like portion disposed in a direction in which the thickness direction coincides with the first direction D1. As shown in FIG. 2B, the central portion 7A is disposed at a position overlapping with an opening 8C of an annular portion 8A described later as viewed from the central axis direction. Specifically, the central portion 7A covers a portion of the opening 8C of the annular portion 8A not overlapping the side wall 8B (that is, a portion visible from the upstream side) from the upstream side. The central portion 7 </ b> A is connected to the side wall portion 8 </ b> B, and is disposed apart from the inner surface of the exhaust gas conduit 5. Of the space located above the side wall 8B, the portion that is not covered (that is, not overlapped) by the central portion 7A constitutes the opening 7G.

  The peripheral portion 7 </ b> B is a portion extending in the radial direction from the outer edge of the central portion 7 </ b> A to the inner peripheral surface of the exhaust gas conduit 5. The peripheral edge portion 7B is disposed so as to at least overlap with the radially outer region of the open portion 8D not surrounded by the side wall portion 8B among the outer edges of the opening 8C of the annular portion 8A as viewed from the central axis direction. In the present embodiment, the peripheral portion 7B is disposed so as to partially overlap with the side wall portion 8B as viewed from the central axis direction. The upstream surface of the peripheral edge portion 7B is flush with the upstream surface of the central portion 7A.

  The first end portion 7D and the second end portion 7E in the circumferential direction of the exhaust gas conduit 5 at the peripheral edge portion 7B extend in the radial direction of the exhaust gas conduit 5, respectively. Further, the contact portion 7F of the peripheral edge portion 7B with the inner peripheral surface of the exhaust gas pipe line 5 extends to the downstream side (that is, the second shielding portion 8 side) along the first direction D1.

  The circumferential length L of the abutting portion 7F of the peripheral edge portion 7B (that is, the length of the outer edge of the peripheral edge portion 7B) L is preferably ½ or less of the inner peripheral length of the exhaust gas conduit 5. If the length L of the abutting portion is more than ½ of the inner peripheral length of the exhaust gas pipe 5, the opening 7G (see FIG. 1B) of the first shielding part 7 is reduced, and the pressure loss may be increased. There is. Since the length L of the contact portion is not more than 1/2 of the inner circumferential length of the exhaust gas pipe 5, the area of the side wall 8B where the exhaust gas flowing from the upstream collides becomes wider, so the stirring performance is improved. The pressure loss can be reduced while securing the above.

  The plurality of through holes 7C are provided in the peripheral portion 7B. The plurality of through holes 7C penetrate the peripheral edge portion 7B along the first direction D1. The plurality of through-holes 7C are arranged on the outer side in the radial direction from the opening 8C when viewed from the central axis direction.

  In the present embodiment, the plurality of through holes 7 </ b> C are arranged at equal intervals on two arcs having different distances from the center of the exhaust gas conduit 5. The plurality of through holes 7C can be formed by punching, for example. Further, the shape of the plurality of through holes 7C is not limited to a circle.

  When viewed from the central axis direction, the area of the region in the exhaust gas pipe 5 where the first shielding portion 7 is not disposed (that is, the opening 7G of the first shielding portion 7) is the total area of the plurality of through holes 7C. Bigger than.

(Second shielding part)
As shown in FIG. 3, the second shielding part 8 has an annular part 8A and a side wall part 8B.
The annular portion 8A is a portion where an opening 8C is formed at the radial center of the exhaust gas conduit 5 and shields the flow in the first direction D1 on the radially outer side of the opening 8C. The outer diameter of the annular portion 8 </ b> A matches the inner diameter of the exhaust gas pipe 5. Further, the contact portion 8H of the annular portion 8A with the inner peripheral surface of the exhaust gas pipe 5 extends downstream along the first direction D1.

  The side wall portion 8B is a portion extending from the annular portion 8A to the central portion 7A of the first shielding portion 7 in the first direction D1. The side wall portion 8B partially surrounds the opening 8C of the annular portion 8A in the circumferential direction. That is, the side wall 8B protrudes from the part of the periphery of the opening 8C in the first direction D1.

  The side wall portion 8B is disposed at a position overlapping the opening of the first shielding portion 7 as shown in FIG. 2A. In other words, the open portion 8D of the opening 8C of the annular portion 8A is disposed at a position facing the opening 7G of the first shielding portion 7 with respect to the central axis of the exhaust gas conduit 5.

  When viewed from the central axis direction, the circumferential center position of the open portion 8D faces the reducing agent injection position of the reducing agent supply unit 4 in the side wall portion 8B (that is, sandwiching the central axis of the exhaust gas pipe 5) It should be on the other side.

  The first end portion 8E in the circumferential direction of the side wall portion 8B overlaps the first end portion 7D in the circumferential direction of the peripheral edge portion 7B in the first shielding portion 7 when viewed from the central axis direction. Further, the second end portion 8F in the circumferential direction of the side wall portion 8B overlaps with the second end portion 7E in the circumferential direction of the peripheral edge portion 7B in the first shielding portion 7 when viewed from the central axis direction. That is, a part of the side wall part 8B exists at a position overlapping the first shielding part 7 when viewed from the central axis direction.

  As described above, the first end 8E and the second end 8F of the side wall 8B overlap the first end 7D and the second end 7E of the peripheral portion 7B, respectively, so that the exhaust flowing from the upstream side The gas reliably collides with the side wall portion 8B. As a result, stirring performance can be secured while reducing pressure loss.

  The side wall portion 8B has a connection portion 8G. As shown in FIG. 3, the connection portion 8G is a portion provided at the upstream end of the side wall portion 8B. The connecting portion 8G has a shape in which the band plate is annular in a direction in which the thickness direction coincides with the radial direction. As shown in FIG. 2A, the upstream end surface of the connecting portion 8 </ b> G is connected to the downstream surface of the central portion 7 </ b> A of the first shielding portion 7.

[1-2. function]
Next, the generation mechanism of the swirling flow in the purification device 1 will be described.
In the purification device 1, the exhaust gas discharged from the exhaust gas purification unit 2 enters the exhaust gas pipe 5 as it is without changing the flow direction.

  In the exhaust gas conduit 5, as shown in FIG. 4, the exhaust gas is first partially shielded by the central portion 7 </ b> A of the first shielding portion 7. That is, the flow path of the exhaust gas is restricted to the opening 7G that is not blocked by the central portion 7A and the peripheral portion 7B, and the plurality of through holes 7C.

  The exhaust gas that has passed through the opening 7G in the first direction D1 collides with the annular portion 8A of the second shielding portion 8. As a result, two swirl flows (only one swirl flow is shown in FIG. 4) that bypass the side wall 8B and go to the opening 8C are formed. Further, the flow of the exhaust gas that has passed through the plurality of through holes 7C collides with the two swirling flows.

  As a result, the reducing agent that collides with the side wall portion 8B and is atomized is caught in the flow of the exhaust gas, and is diffused and dispersed. As a result, the reducing agent and the exhaust gas that have passed through the exhaust gas conduit 5 come into homogeneous contact with the reduction catalyst 31.

[1-3. effect]
According to the embodiment described above, the following effects can be obtained.
(1a) The flow of exhaust gas in the first direction D1 is guided to the outside of the side wall portion 8B of the second shielding portion 8 by the first shielding portion 7. The flow guided to the side wall portion 8B flows toward the opening 8C of the annular portion 8A while being divided into two flows by the side wall portion 8B. As a result, the flow path of the exhaust gas extends, and two swirling flows in opposite directions having a swirling axis parallel to the first direction D1 are generated. Therefore, the reducing agent injected toward the side wall portion 8B is diffused efficiently. As a result, evaporation of the reducing agent is promoted and the dispersibility is improved. Further, part of the flow of the exhaust gas passes through the plurality of through holes 7 </ b> C of the first shielding part 7 and joins the two swirl flows. As a result, the reductant and the exhaust gas are effectively stirred.

  (1b) It is not necessary to provide an introduction hole in the plate that closes the flow passage, and the flow passage diameter can be adjusted to an arbitrary size by the first shielding portion 7. Therefore, an increase in pressure loss can be suppressed while improving the exhaust gas purification efficiency.

  (1c) When viewed from the central axis direction, the area of the exhaust gas conduit 5 where the first shielding part 7 is not disposed (that is, the opening part 7G of the first shielding part 7) has a plurality of through holes 7C. Therefore, the two swirling flows described above can be generated more reliably. As a result, the exhaust gas purification efficiency can be increased.

[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 exhaust gas purification apparatus 1 of the above embodiment, a region in which the first shielding portion 7 is not disposed in the exhaust gas pipeline 5 when viewed from the central axis direction (that is, the opening of the first shielding portion 7) The area of 7G) is not necessarily larger than the total area of the plurality of through holes 7C.

  (2b) In the exhaust gas purification apparatus 1 of the above embodiment, the first end 8E and the second end 8F in the circumferential direction of the side wall 8B do not necessarily have to have the first end 8E and the second end 8F in the circumferential direction of the peripheral edge 7B. The first end 7D and the second end 7E may not overlap.

  (2c) In the exhaust gas purification apparatus 1 of the above embodiment, the plurality of through holes 7C do not have to be arranged in a circular arc at equal intervals. For example, the plurality of through holes 7C may be arranged in a lattice shape or randomly.

  (2d) In the exhaust gas purification apparatus 1 of the above-described embodiment, the swirl flow generation unit 6 is integrated by assembling parts separately formed as the first shielding unit 7 and the second shielding unit 8. It may be made of one member integrally formed.

  (2e) In the exhaust gas purification apparatus 1 of the above embodiment, the inner diameter of the exhaust gas purification unit 2 and / or the reduction unit 3 and the inner diameter of the exhaust gas pipe line 5 may not be the same. For example, the inner diameter of the exhaust gas purification unit 2 may be smaller than the inner diameter of the exhaust gas pipe 5. In this case, the exhaust gas pipe line 5 has a tapered portion whose diameter decreases from the downstream side toward the upstream side.

  Further, a connecting pipe may be further disposed between the exhaust gas purification unit 2 and the exhaust gas pipe 5. This connecting pipe may be curved. By using the curved connecting pipe, the degree of freedom of arrangement of the exhaust gas purification unit 2 can be increased.

  (2f) 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.

[3. Example]
Next, a comparison between Example 1 and Comparative Example 1 performed to confirm the effect of the present disclosure will be described.

Example 1
The pressure loss in the swirling flow generation unit 6 when the gas was supplied to the exhaust gas purification device 1 of FIG. 1 and the uniformity of ammonia as a reducing agent were obtained by analysis.

Here, the uniformity γ of ammonia is a value calculated by the following equations (1), (2), and (3). In the following formula, n is the number of measurement points, Wi is the mass distribution of ammonia at each measurement point, and Wm is the average value of Wi.
Ii = {(Wi−Wm) ² } ^1/2 / Wm (1)
= = Φ i / n (2)
γ = 1−Φ / 2 (3)

(Comparative example 1)
In the conventional exhaust gas purification apparatus in which the introduction hole is provided in the plate for closing the flow path disclosed in Patent Document 1, the pressure loss in the swirling flow generation portion and the uniformity of ammonia are obtained under the same conditions as the first embodiment. Obtained by analysis.

(result)
The uniformity of the ammonia of Example 1 was almost equivalent to that of Comparative Example 1. Moreover, in Example 1, compared with Comparative Example 1, the pressure loss was reduced by about 80%. That is, in Example 1, it is estimated that the gas flow can be made uniform while reducing the pressure loss in the swirl flow generating portion.

DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification apparatus, 2 ... Exhaust gas purification part, 2A ... Discharge port, 3 ... Reduction part,
3A ... inlet, 4 ... reducing agent supply unit, 5 ... exhaust gas conduit, 6 ... swirl flow generating unit,
7 ... 1st shielding part, 7A ... Center part, 7B ... Peripheral part, 7C ... Through-hole, 7D ... 1st edge part,
7E ... second end, 7F ... contact portion, 7G ... opening, 8 ... second shielding portion, 8A ... annular portion,
8B ... side wall, 8C ... opening, 8D ... open part, 8E ... first end, 8F ... second end,
8G ... Connection part, 21 ... Purifying member, 22 ... Casing, 31 ... Reduction catalyst,
32. Casing.

Claims (4)

An exhaust gas purification device for an internal combustion engine
An exhaust gas purification unit configured to reform or collect environmental pollutants in the exhaust gas;
A reduction unit provided downstream of the exhaust gas purification unit in the flow direction of the exhaust gas and configured to reduce the exhaust gas in the presence of a reducing agent;
A reducing agent supply unit configured to supply a reducing agent to the exhaust gas upstream of the reducing unit in the flow direction of the exhaust gas;
An exhaust gas conduit communicating the exhaust port of the exhaust gas purification unit and the introduction port of the reduction unit;
A swirl flow generation unit installed in the exhaust gas pipeline;
With
The swirling flow generating unit is
A first shielding portion configured to shield a part of the flow in the central axis direction of the exhaust gas conduit;
A second shielding portion disposed downstream of the first shielding portion;
Have
The second shielding unit is
An annular portion formed so that an opening is formed at a radial center of the exhaust gas conduit, and the flow in the central axis direction on the radially outer side of the opening is shielded;
A side wall portion extending from the annular portion to the first shielding portion and partially surrounding the opening of the annular portion in the circumferential direction;
Have
The first shielding unit is
A central portion that overlaps with the opening of the annular portion as viewed from the central axis direction and is spaced apart from the inner surface of the exhaust gas conduit;
A peripheral portion extending from the central portion to the inner circumferential surface of the exhaust gas pipe;
A plurality of through holes provided in the peripheral portion;
Have
The peripheral edge portion is disposed so as to at least overlap a radially outer region of an open portion not surrounded by the side wall portion of the outer edge of the opening of the annular portion as viewed from the central axis direction.
The said reducing agent supply part is an exhaust gas purification apparatus which injects the said reducing agent toward the said side wall part. The exhaust gas purification device according to claim 1,
The exhaust gas purification apparatus, as viewed from the central axis direction, the area of the region in the exhaust gas pipe where the first shielding portion is not disposed is larger than the total area of the plurality of through holes. The exhaust gas purification apparatus according to claim 1 or 2, wherein
The exhaust gas purification apparatus, wherein the length in the circumferential direction of the contact portion between the peripheral edge portion and the inner circumferential surface of the exhaust gas passage is not more than half the inner circumferential length of the exhaust gas passage. It is an exhaust-gas purification apparatus of any one of Claims 1-3, Comprising:
The circumferential first end of the side wall overlaps with the circumferential first end of the peripheral edge as viewed from the central axis direction, and the circumferential second end of the side wall is, An exhaust gas purifier that overlaps the second end portion of the peripheral portion in the circumferential direction when viewed from the central axis direction.