JP7469215B2 - Exhaust purification equipment - Google Patents

Description

This disclosure relates to an exhaust purification device.

The SCR (Selective Catalytic Reduction) system, which reduces nitrogen oxides contained in exhaust gas using a catalyst and a reducing agent such as urea water, is known as a technology for purifying exhaust gas emitted from an internal combustion engine. In the SCR system, a reducing agent is injected into the exhaust gas flowing through the exhaust passage, and the mixture of exhaust gas and reducing agent is guided to the catalyst. To increase the purification rate of exhaust gas in the SCR system, it is preferable that the exhaust gas and reducing agent are mixed uniformly.

Cited Document 1 discloses an exhaust purification device that supplies a mixture of exhaust gas and a reducing agent injected into the exhaust flow path to a catalyst housed in a reactor located downstream of a curved exhaust pipe, and in which a shield plate is provided in the reactor to make the flow of exhaust gas turbulent in order to make the density of the exhaust gas uniform.

Japanese Patent Application Laid-Open No. 10-30431

However, when installing an SCR system in a vehicle or the like, due to placement restrictions imposed by compatibility with other peripheral devices, the exhaust pipe is often placed in a curved state, as in the exhaust purification device described above.

In the above-mentioned exhaust purification device, when exhaust gas passes through a curved exhaust pipe, centrifugal force causes the exhaust gas to flow more toward the outer periphery of the bent part of the exhaust pipe. As a result, the reducing agent is also biased toward the outer periphery of the bent part, and since the reducing agent is supplied to the reactor in a biased state, there is an issue that the reducing agent is difficult to diffuse sufficiently even if turbulence is generated in the reactor.

One aspect of the present disclosure provides a technology that makes it easier for the reducing agent to be discharged evenly from the downstream side of the bend.

One aspect of the present disclosure is an exhaust purification device that purifies exhaust gas from an internal combustion engine, and includes a flow path member, a supply unit, and an agitation unit. The flow path member has an upstream portion that forms an exhaust flow path on the upstream side, a bent portion that forms a curved exhaust flow path downstream of the upstream portion, and a downstream portion that forms an exhaust flow path downstream of the bent portion. The supply unit supplies a reducing agent to the exhaust flow path of the flow path member. The agitation unit is provided in the exhaust flow path downstream of the upstream portion so as to block a part of the flow path cross section of the exhaust flow path in a first plane perpendicular to the central axis of the flow path member, and generates a swirling flow in the exhaust gas. In addition, the agitation unit is arranged so that when the flow path cross section is divided into a first flow path cross section and a second flow path cross section in the normal direction of the second plane by a second plane passing through the curved central axis extending from the upstream side of the bent portion to the downstream side, the area covering the first flow path cross section and the area covering the second flow path cross section are different.

In this configuration, the stirring section generates a swirling flow that rotates around the central axis of the flow path member behind the stirring section along the inner surface of the flow path member. This makes it easier for the exhaust gas to flow through the exhaust flow path with less bias, and makes it easier for the reducing agent to be discharged evenly from the downstream side of the bend. In other words, even if the reducing agent is biased to the outer periphery of the bend because the exhaust gas flows more to the outer periphery of the bend due to centrifugal force, the reducing agent is also diffused to the inner periphery by the swirling flow, making it easier for the reducing agent to be diffused sufficiently. Therefore, exhaust gas with the reducing agent sufficiently diffused can be easily supplied to the catalyst.

In one aspect of the present disclosure, the stirring portion is disposed so that the area ratio of the region other than the projected region onto which the stirring portion is projected in the first flow path cross section and the second flow path cross section is different.
In one aspect of the present disclosure, the stirring portion may be provided on the first flow passage cross-section side or the second flow passage cross-section side such that the projected area occupies 25 to 50 percent of the total area of the flow passage cross-section. With this configuration, it is possible to generate a swirling flow that is sufficient to obtain a diffusing effect of the reducing agent, while suppressing an increase in pressure loss caused by blocking a portion of the flow passage cross-section of the exhaust flow passage by the stirring portion.

In one aspect of the present disclosure, the stirring section may be provided in the exhaust flow path of the bent section. In such a configuration, the stirring section is provided at the bent section where the flow of exhaust gas is most likely to be biased due to centrifugal force. This can further enhance the diffusion effect of the reducing agent due to the swirling flow generated by the stirring section.

In one aspect of the present disclosure, the agitation section is a plate-like member extending from the inner surface of the flow path member in the direction of the central axis of the flow path member, and the portion of the flow path member on the central axis side may have a larger area blocking the flow path cross section of the exhaust flow path in the first plane than the portion on the inner surface side of the flow path member. In such a configuration, a gap may be formed around the portion of the agitation section on the inner surface side of the flow path member, making it easier to suppress pressure loss that increases when the agitation section blocks too much of the flow path cross section of the exhaust flow path.

In one aspect of the present disclosure, the stirring section may extend from the inner surface of the flow path member in the direction of the central axis of the flow path member and toward the downstream side. In such a configuration, the stirring section has an inclination toward the downstream side with respect to the flow of the exhaust gas. Therefore, even when the stirring section has the same area of projected region on a first plane perpendicular to the central axis of the flow path member, the pressure loss can be reduced compared to, for example, a configuration in which the stirring section extends perpendicularly from the inner surface of the flow path member toward the central axis of the flow path member.

FIG. 2 is a perspective view of the exhaust purification device. FIG. 2 is a side view of the exhaust purification device. FIG. 2 is a bottom view of the exhaust purification device. FIG. 2 is a front view of the exhaust purification device. 3 is an enlarged cross-sectional view taken along the line VV in FIG. 2. FIG. 6 is an enlarged cross-sectional view taken along the line VI-VI in FIG. FIG. 2 is a side view of the exhaust purification device, showing a schematic flow of exhaust gas. FIG. 2 is a front view of the exhaust purification device, showing a schematic flow of exhaust gas. FIG. 9 is an enlarged cross-sectional view taken along the line IX-IX of FIG. 7, showing a schematic diagram of the flow of exhaust gas. FIG. 2 is a side view of an exhaust gas purification device having a configuration in which an agitation unit is disposed downstream. 11 is a cross-sectional view taken along the line XI-XI of FIG. FIG. 13 is a diagram showing a semicircular stirring part. FIG. 13 is a diagram showing a stirring section having an inclination toward the downstream side with respect to the flow of exhaust gas. FIG. 13 is a diagram showing a stirring section having an inclination toward the upstream side with respect to the flow of exhaust gas.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
1. Embodiment
[1-1. Configuration]
The exhaust purification device 100 shown in Figures 1 to 4 is a device for purifying exhaust gas G discharged from an internal combustion engine of an automobile. The exhaust purification device 100 includes a flow path member 1, a supply section 2, a mixing section 3, an agitation section 4, a catalyst case 5, and a catalyst 6. In the following description, the up-down direction, the left-right direction, and the front-rear direction are expressed based on Figure 1, but these are merely expressions for the convenience of description, and the direction in which the exhaust purification device 100 is provided is not particularly limited. Note that the catalyst 6 is omitted from Figures 2 to 4, and the mixing section 3 is omitted from Figure 4.

The flow path member 1 and the catalyst case 5 form part of the exhaust flow path for directing the exhaust gas G to the outside of the automobile. The flow path member 1 is a cylindrical member curved into an L-shape. The flow path member 1 may be a single member, or may be formed from multiple different members. The flow path member 1 has a circular flow path cross section in a direction perpendicular to the central axis A of the flow path member 1. The flow path member 1 has, from the upstream side in the flow direction of the exhaust gas G, an upstream portion 11, a bent portion 12, and a downstream portion 13.

The upstream section 11 forms an upstream exhaust flow passage. The upstream section 11 is a straight pipe section that extends in the front-rear direction about a central axis A.
The downstream section 13 forms an exhaust flow passage downstream of the upstream section 11. The downstream section 13 is a straight pipe section extending in the vertical direction about the central axis A. In this embodiment, the downstream section 13 extends upward such that an extension line of the central axis of the downstream section 13 is perpendicular to an extension line of the central axis of the upstream section 11.

The bent section 12 forms a curved exhaust flow passage downstream of the upstream section 11 and upstream of the downstream section 13. The bent section 12 is a curved tubular section with a nearly constant flow passage cross-sectional area that connects the upstream section 11 and the downstream section 13. The flow passage cross-sectional area is the cross section perpendicular to the flow direction of the exhaust gas G in the exhaust flow passage, i.e., the area of the flow passage cross section of the exhaust flow passage. In this embodiment, the diameter of the upstream section 11, the diameter of the bent section 12, and the diameter of the downstream section 13 are nearly equal. In other words, the flow passage cross-sectional areas of the upstream section 11, the bent section 12, and the downstream section 13 are nearly equal.

The catalyst case 5 is a cylindrical tube that forms an exhaust flow path downstream of the flow path member 1, in other words, downstream of the downstream portion 13. The catalyst case 5 has a flow path cross-sectional area larger than that of the flow path member 1. In other words, the catalyst case 5 has an inner diameter larger than the outer diameter of the flow path member 1. In this embodiment, the catalyst case 5 is disposed above the downstream portion 13 of the flow path member 1, and the downstream end of the downstream portion 13 is joined to the lower side surface of the upstream end side of the catalyst case 5 by welding or the like. In this way, the catalyst case 5 and the flow path member 1 are connected. As a result, the exhaust gas G flowing through the downstream portion 13 is supplied into the catalyst case 5 from the side of the catalyst case 5 and supplied to the catalyst 6.

The downstream portion refers to a member that forms an exhaust flow path downstream of the bent portion 12, and does not necessarily have to be a tubular member with the same diameter as the bent portion 12. For example, in a configuration in which the bent portion 12 and the catalyst case 5 are directly connected, the portion of the catalyst case 5 immediately downstream of the bent portion 12 corresponds to the downstream portion.

The catalyst 6 is an SCR (Selective Catalytic Reduction) type catalyst that has the function of reducing nitrogen oxides ( _NOx ), which are air pollutants contained in the exhaust gas G. The catalyst 6 is housed in the catalyst case 5 with a cushioning member such as a mat (not shown) provided on the outer circumferential surface of the catalyst 6.

The supply unit 2 functions as a supply device that injects liquid reducing agent raw material and supplies reducing agent upstream of the mixing unit 3 (described later) in the exhaust flow path of the upstream portion 11 of the flow path member 1. The urea water injected into the exhaust gas G is hydrolyzed by the heat of the exhaust gas G to produce ammonia (NH3), and the ammonia thus produced functions as a reducing agent. The ammonia produced by hydrolysis of the urea water is supplied to the catalyst 6 together with the exhaust gas G, and the nitrogen oxides in the exhaust gas G react with the ammonia in the catalyst 6 and are reduced and purified.

The mixing section 3 is provided in the exhaust flow path in the upstream section 11 downstream of the supply section 2. The mixing section 3 functions as a mixing device that vaporizes the liquid reducing agent supplied from the supply section 2 and mixes the vaporized reducing agent with the exhaust gas G. The mixing section 3 may be, for example, a metallic blade member or a metallic circular member with holes formed therein, but is not limited to these.

The agitation section 4 is provided in the exhaust flow passage downstream of the upstream section 11 and upstream of the catalyst 6, and functions as an agitation device that generates a swirling flow in the exhaust gas G to agitate the reducing agent and exhaust gas G in order to guide the exhaust gas G in a state in which the reducing agent has been sufficiently diffused to the catalyst 6.

In this embodiment, the stirring section 4 is provided in the exhaust flow path of the bent section 12, specifically, in the part of the bent section 12 where the curvature is the largest. More specifically, the stirring section 4 is provided in a part of the bent section 12 that is approximately half the length of the central axis A of the bent section 12, with the bent section 12 bent at approximately 90°. The stirring section 4 is a plate-shaped member extending from the inner surface of the bent section 12 in the direction of the central axis A, and is joined to the inner surface of the bent section 12 by welding or the like. The stirring section 4 blocks a part of the flow path cross section of the exhaust flow path in the first plane B1 shown in FIG. 5. The first plane B1 is a virtual plane perpendicular to the central axis A. In this embodiment, the stirring section 4 extends parallel to the first plane B1 as shown in FIG. 6. In other words, the stirring section 4 extends perpendicularly from the inner surface of the bent section 12 toward the central axis A. As shown in FIG. 5, the stirring section 4 has a shape in which the portion on the central axis A side of the end on the inner side of the bent section 12, specifically the end on the central axis A side, is wider in the inner diameter direction of the bent section 12 than the end on the inner side of the bent section 12. In other words, the stirring section 4 has a shape in which the end on the central axis A side is wider in the direction perpendicular to the direction in which the stirring section 4 extends from the inner side of the bent section 12 and perpendicular to the flow direction of the exhaust gas G than the end on the inner side of the bent section 12. Specifically, the stirring section 4 is formed in a substantially T-shape when viewed from a direction perpendicular to the central axis A.

In this embodiment, the area of the cross section of the exhaust flow path in the first plane B1 is larger in the portion of the stirring section 4 on the central axis A side than in the portion on the inner side of the bent section 12. Here, the portion of the stirring section 4 on the inner side of the bent section 12 is the portion from the end of the inner side of the bent section 12 to where the width of the stirring section 4 becomes wider, and the portion of the stirring section 4 on the central axis A side is the portion from the end on the central axis A side to where the width of the stirring section 4 becomes narrower. As described above, other examples of the area being larger in the portion on the central axis A side of the stirring section 4 include a shape in which the width gradually increases toward the central axis A side of the stirring section 4, and a shape in which a through hole through which exhaust gas passes is formed at the end position on the inner side of the bent section 12 of the stirring section 4.

5, the flow cross section of the exhaust flow path of the bent portion 12 is divided into a first flow cross section 121 and a second flow cross section 122 by, for example, the second plane B2. The second plane B2 is a virtual plane passing through the curved central axis A extending from the upstream side to the downstream side of the bent portion 12, i.e., the central axis A having two different directions, the front-rear direction on the upstream side of the bent portion 12 and the up-down direction on the downstream side. The second plane B2 is perpendicular to the first plane B1. Therefore, the flow cross section of the exhaust flow path of the bent portion 12 is divided into the first flow cross section 121 and the second flow cross section 122 in the left-right direction, i.e., in the normal direction of the second plane B2. In other words, the flow cross section of the exhaust flow path of the bent portion 12 is divided into the first flow cross section 121 on the left side and the second flow cross section 122 on the right side by a plane extending in the up-down direction that divides the bent portion 12 so as to have a symmetrical shape with respect to the central axis A. In other words, the second plane B2 is a plane that passes through the central axis A and divides the cross section of the exhaust flow path of the bent portion 12 into two, left and right.

In this embodiment, when the flow cross section of the exhaust flow passage of the bent portion 12 is divided into two regions as described above, the stirring portion 4 is provided on the first flow cross section 121 side so as to block a part of the first flow cross section 121. The stirring portion 4 may be provided on the second flow cross section 122 side so as to block a part of the second flow cross section 122. The stirring portion 4 is preferably arranged on the first flow cross section 121 side or the second flow cross section 122 side so that the projected area of the stirring portion 4 on the first flow cross section 121 or the second flow cross section 122 occupies 25 to 50 percent of the total area of the flow cross section. In this embodiment, the stirring portion 4 is arranged on the first flow cross section 121 side so that the projected area of the stirring portion 4 on the first flow cross section 121 occupies about 35 percent of the total area of the flow cross section.

[1-2. Flow of exhaust gas due to swirling flow generated by the stirring section]
7 to 9, the flow direction of the exhaust gas G caused by the swirling flow generated by the agitator 4 is simply indicated as an exhaust flow G1.

When exhaust gas G passes through the bent section 12, centrifugal force causes it to flow more toward the outer periphery of the bent section 12. As a result, the reducing agent also flows biased toward the outer periphery of the bent section 12. In this embodiment, the agitation section 4 is disposed on the first flow path cross section 121 side of the bent section 12, so the exhaust gas G passes through the second flow path cross section 122 side and flows into the rear side of the agitation section 4 due to negative pressure. As a result, a counterclockwise swirling flow is generated behind the agitation section 4, centered on the central axis A, along the inner surface of the bent section 12 when viewed from the upstream side of the bent section 12.

More specifically, in the first plane B1 of the bending section 12 where the stirring section 4 is provided, the exhaust gas G flows most easily to the area (first area C1 shown in FIG. 9) on the outer periphery of the bending section 12 that is not covered by the stirring section 4, and then to the area (second area C2 shown in FIG. 9) on the inner periphery of the bending section 12 that is not covered by the stirring section 4. And, since the area behind the part covered by the stirring section 4 (third area C3 shown in FIG. 9) tends to become negative pressure, a counterclockwise swirling flow is generated.

Therefore, as shown in Figures 7 to 9, exhaust gas G flows like exhaust flow G1 downstream of the stirring section 4. In this way, by providing the stirring section 4, even if the exhaust gas G flows more toward the outer periphery of the bending section 12 due to centrifugal force when passing through the bending section 12 of the flow path member 1 and the reducing agent is biased toward the outer periphery of the bending section 12, the reducing agent is also diffused to the inner periphery by the swirling flow as described above. Note that when the stirring section 4 is provided on the second flow path cross section 122 side, a clockwise swirling flow is generated behind the stirring section 4 along the inner surface of the bending section 12 with the central axis A as the center when viewed from the upstream side of the bending section 12. In this case, the reducing agent biased toward the outer periphery is diffused as in the present embodiment.

2. Effects
According to the embodiment described above in detail, the following effects can be obtained.
(2a) In this embodiment, the agitation section 4 is provided on the first flow path cross section 121 side in the exhaust flow path of the bent section 12. For this reason, a swirling flow that rotates around the central axis A along the inner surface of the bent section 12 is generated behind the agitation section 4. As a result, the agitation section 4 makes it easier for the exhaust gas to flow through the exhaust flow path with less bias, and the reducing agent discharged from the downstream side of the bent section 12 tends to be uniform.

In the case of an exhaust purification device 100 having a mixing section 3 and an agitation section 4 as in this embodiment, even if the exhaust gas G flows more toward the outer periphery of the bent section 12 due to centrifugal force, causing the reducing agent to be biased toward the outer periphery of the bent section 12, the reducing agent is also diffused to the inner periphery of the bent section 12 by the swirling flow, so the reducing agent is likely to be sufficiently diffused. Therefore, exhaust gas G in which the reducing agent has been sufficiently diffused can be easily supplied to the catalyst.

In addition, in this embodiment, the stirring section 4 is located at the portion of the bent section 12 with the greatest curvature. In this way, the stirring section 4 is located in a position within the exhaust flow passage downstream of the upstream section 11 where the exhaust gas G is biased toward the outer periphery of the exhaust flow passage and where the distance from the catalyst 6 is large. This makes it possible to further increase the diffusion effect of the reducing agent biased toward the outer periphery of the exhaust flow passage at the bent section 12 due to the swirling flow generated by the stirring section 4, and the dispersion effect of the reducing agent that is reduced by the smaller distance from the catalyst 6.

(2b) In this embodiment, the stirring section 4 is formed in a substantially T-shape when viewed from a direction perpendicular to the central axis A. As a result, a gap can be formed around the end of the stirring section 4 on the inner side of the bent section 12, reducing pressure loss compared to a configuration in which the inner side area of the bent section 12 is largely blocked. Therefore, it is easier to suppress pressure loss that increases when the stirring section 4 blocks too much of the flow path cross section of the exhaust flow path of the bent section 12.

(2c) In this embodiment, the projection area of the agitation section 4 on the first flow passage cross section 121 occupies approximately 35 percent of the total area of the flow passage cross section. This makes it possible to generate a swirling flow sufficient to achieve a diffusion effect of the reducing agent, while suppressing an increase in pressure loss caused by the agitation section 4 blocking a partial area of the flow passage cross section of the exhaust flow passage at the bent section 12.

3. Other embodiments
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(3a) In the above embodiment, the stirring section 4 is provided at the part of the bent section 12 with the largest curvature, but the position at which the stirring section 4 is provided within the exhaust flow path is not limited to this. For example, the stirring section 4 may be provided at any position of the bent section 12 and downstream section 13 that is downstream of the upstream section 11 and upstream of the catalyst 6.

For example, as shown in Figures 10 and 11, the stirring unit 4a may be provided in the downstream section 13. It is preferable that the stirring unit 4a is provided upstream of the downstream section 13 so that the distance between the stirring unit 4a and the catalyst 6 is large. This makes it possible to prevent the reduction in the dispersion effect of the reducing agent from decreasing due to the small distance between the catalyst 6.

(3b) In the above embodiment, the stirring unit 4 is provided on the first flow cross section 121 side, but the position of the stirring unit is not limited to this, as long as the stirring unit is arranged so that the area covering the first flow cross section 121 and the area covering the second flow cross section 122 are different. For example, the stirring unit may be provided on the second flow cross section 122 side. Also, for example, the stirring unit may be arranged to include both the first flow cross section 121 and the second flow cross section 122 as long as the area ratio of the area other than the projection area where the stirring unit is projected on the first flow cross section 121 and the second flow cross section 122 is different. In this case, the stirring unit is arranged so that the projection area of the first flow cross section 121 is larger than the projection area of the second flow cross section 122, or the projection area of the second flow cross section 122 is larger than the projection area of the first flow cross section 121.

(3c) In the above embodiment, the stirring portion 4 is formed in a substantially T-shape, but the shape of the stirring portion 4 is not limited to this. The stirring portion may have any shape as long as it blocks a part of the flow passage cross section of the exhaust flow passage of the flow passage member 1 so that the area ratio of the area other than the projection area where the stirring portion is projected in the first flow passage cross section 121 and the second flow passage cross section 122 is different. For example, as shown in FIG. 12, the stirring portion 4b may be formed in a semicircular shape. The stirring portion 4b may be arranged so as to block the entire area of either the first flow passage cross section 121 or the second flow passage cross section 122. In the example shown in FIG. 12, the stirring portion 4b is arranged in the first flow passage cross section 121, and the projection area where the stirring portion 4b is projected in the first flow passage cross section 121 occupies 50% of the total area of the flow passage cross section.

(3d) In the above embodiment, the stirring portion 4 is configured to extend parallel to the first plane B1, but the stirring portion may be configured to have an angle with respect to the first plane B1. For example, as shown in FIG. 13, the stirring portion 4c may extend from the inner surface of the flow path member 1 in the direction of the central axis A and in the downstream direction so that the stirring portion 4c has an inclination toward the downstream side with respect to the flow of the exhaust gas G, in other words, the first plane B1. This makes it possible to reduce pressure loss compared to a configuration in which the stirring portion 4c extends perpendicularly from the inner surface of the flow path member 1 toward the central axis A of the flow path member 1, even when the stirring portion 4c has the same area projected area on the first plane B1 perpendicular to the central axis A. Also, as shown in FIG. 14, the stirring portion 4d may extend from the inner surface of the flow path member 1 in the direction of the central axis A and in the upstream direction so that the stirring portion 4d has an inclination toward the upstream side with respect to the flow of the exhaust gas G, in other words, the first plane B1.

(3e) If the bent portion is bent in three dimensions, the present disclosure can be applied by regarding it as being two-dimensional, within the scope of the present disclosure.
(3f) The exhaust gas purification device may be configured without the mixing section 3.

(3g) In the above embodiment, the supply unit 2 is provided in the exhaust flow path of the upstream section 11, but the location where the supply unit is provided is not limited to this. For example, the supply unit may be provided in the exhaust flow path of either the bent section 12 or the downstream section 13. However, as in the above embodiment, it is preferable that the supply unit is provided in the upstream section 11.

(3h) The function of one component in the above embodiments may be distributed among multiple components, or the functions of multiple components may be integrated into one component. In addition, part of the configuration of the above embodiments may be omitted. In addition, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments. All aspects included in the technical idea identified from the wording of the claims are embodiments of the present disclosure.

1...flow path member, 2...supply section, 3...mixing section, 4, 4a-4d...agitation section, 5...catalyst case, 6...catalyst, 11...upstream section, 12...bent section, 13...downstream section, 100...exhaust gas purification device, 121...first flow path cross section, 122...second flow path cross section, A...central axis, B1...first plane, B2...second plane, G...exhaust gas.

Claims (5)

An exhaust gas purification device that purifies exhaust gas from an internal combustion engine,
a flow path member having an upstream portion that forms an exhaust flow path on an upstream side, a bent portion that forms a curved exhaust flow path downstream of the upstream portion, and a downstream portion that forms an exhaust flow path downstream of the bent portion;
A supply unit that supplies a reducing agent to the exhaust flow path of the flow path member;
a stirring section that is provided in the exhaust flow passage downstream of the upstream section so as to block a partial area of a flow passage cross section of the exhaust flow passage in a first plane perpendicular to a central axis of the flow passage member, and that generates a swirling flow in the exhaust gas;
Equipped with
The stirring unit includes:
when the flow path cross section is divided into a first flow path cross section and a second flow path cross section in a normal direction of a second plane passing through a curved central axis extending from the upstream side to the downstream side of the bent portion, an area covering the first flow path cross section and an area covering the second flow path cross section are arranged so as to be different from each other,
an exhaust gas purification device comprising: a plate-shaped member extending from an inner surface of the flow path member in a direction of a central axis of the flow path member, wherein a portion of the flow path member on the central axis side has a larger area blocking a flow path cross-sectional area of the exhaust flow path in the first plane than a portion on the inner surface side of the flow path member. The exhaust gas purification device according to claim 1 ,
an agitation portion disposed in the first flow passage cross section and in the second flow passage cross section such that an area ratio of a region other than a projected region on which the agitation portion is projected differs from an area ratio of a region on the first flow passage cross section and a projected region on which the agitation portion is projected. The exhaust gas purification device according to claim 2 ,
The stirring portion is provided on the first flow path cross section side or the second flow path cross section side such that the projected area occupies 25 to 50 percent of an entire area of the flow path cross section. The exhaust gas purification device according to any one of claims 1 to 3 ,
The agitation portion is provided in the exhaust flow path of the bent portion. The exhaust gas purification device according to any one of claims 1 to 4 ,
The agitation portion extends from an inner surface of the flow path member in a direction along a central axis of the flow path member and toward a downstream side.

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