Exhaust gas treatment device and mixing device

Abstract

An exhaust gas treatment device (10) is provided with: an outer tube (24) in which one end (20) is open and another end (22) is closed; an inner tube (26) which is inserted into the outer tube (24) forming a gap (46) with an inner peripheral surface (30A) of the outer tube (24) allowing flow along the circumferential direction of the inner peripheral surface (30A), and which has an end opening section (40) which opens inside the outer tube (24); a catalyst (14) held inside the inner tube (26); a closing section (54) that closes the gap (46) on the one end (20) side of the outer tube (24); a cylindrical introduction section (36) which is connected to a side surface of the outer tube (24) and introduces exhaust gas (G) into the gap (46) to cause the exhaust gas (G) to flow through an outer peripheral section of the inner tube (26) and the end opening section (40) of the inner tube (26) to the inner tube (26) holding the catalyst (14); and an injector (90) which is provided in the introduction section (36) and sprays a reducing agent (12) onto a side surface of the inner tube (26).

Description

Exhaust gas treatment device and mixing device

[0001] The present invention relates to an exhaust gas treatment device and a mixing device.

[0002] JP2017-180133A discloses an exhaust gas purification system equipped with a device for mixing atomized liquid and gas. The exhaust gas purification system promotes mixing of the liquid and gas by passing the gas atomized with the liquid through a vane-shaped mixer plate.

[0003] However, the exhaust purification system described in JP2017-180133A requires installation space for the mixer plate, which may result in a long flow path.

[0004] An object of the present invention is to enable the flow path to be miniaturized.

[0005] According to one aspect of the present invention, an exhaust gas treatment device that treats exhaust gas emitted from an engine includes: an outer pipe that has one open end and the other closed end; an inner pipe that is inserted into the outer pipe with a gap formed between it and the inner surface of the outer pipe that allows flow along the circumferential direction of the inner surface, the inner pipe having an end opening that opens into the interior of the outer pipe; a catalyst held inside the inner pipe; a blocking section that blocks the gap on the one end side of the outer pipe; a cylindrical introduction section connected to the side of the outer pipe that introduces exhaust gas into the gap and causes the exhaust gas to flow through the outer periphery of the inner pipe and the end opening of the inner pipe into the inner pipe holding the catalyst; and an injector provided in the introduction section that sprays a reducing agent onto the side of the inner pipe.

[0006] In the above-described embodiment, the reducing agent in liquid form is sprayed onto the side surface of the inner pipe by the injector provided in the introduction section. The reducing agent then collides with the side surface of the inner pipe and is atomized. This promotes mixing of the atomized reducing agent with the exhaust gas in gas form introduced from the introduction section without using a mixer plate or the like.

[0007] Furthermore, exhaust gas introduced into the outer pipe from the inlet passes through the gap formed between the outer pipe and the inner pipe to the end opening of the inner pipe, then turns around at the end opening and flows into the inner pipe. The exhaust gas then passes through the catalyst held in the inner pipe. This allows for a more compact exhaust gas flow path without shortening the exhaust gas flow path length, compared to when the exhaust gas flow path is formed in a straight line without turning back.

[0008] FIG. 1 is a cross-sectional view of an exhaust gas treatment device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a cross-sectional view showing a main portion of an exhaust gas treatment device according to a first modified example. FIG. 4 is a view showing an exhaust gas treatment device according to a second modified example, which corresponds to the cross-sectional view taken along line IV-IV of FIG. 1. FIG. 5 is a view showing an exhaust gas treatment device according to a third modified example, which corresponds to the cross-sectional view taken along line II-II of FIG. 1. FIG. 6 is a view showing an exhaust gas treatment device according to a fourth modified example, which corresponds to the cross-sectional view taken along line VI-VI of FIG. 2.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] (Embodiment) Hereinafter, an exhaust gas treatment device 10 according to an embodiment of the present invention will be described with reference to Figs.

[0011] Fig. 1 is a cross-sectional view of an exhaust gas treatment device 10. Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1.

[0012] The exhaust gas treatment device 10 is a device that is mounted on a vehicle and treats exhaust gas G emitted from an engine (not shown). The exhaust gas treatment device 10 functions as a mixer 10A that mixes a reducing agent 12 in the form of a liquid with exhaust gas G in the form of a gas. The exhaust gas treatment device 10 may be used not only in automobiles but also in construction machinery, agricultural machinery, etc., for example.

[0013] The exhaust gas treatment device 10 generates ammonia by hydrolyzing, for example, urea water as a reducing agent 12 using the heat of exhaust gas G emitted from the engine, and absorbs and retains the generated ammonia in a catalyst (SCR catalyst) 14. Then, the exhaust gas treatment device 10 chemically reacts the ammonia with nitrogen compounds (NOx) in the exhaust gas G in the catalyst 14, reducing them to nitrogen and water.

[0014] As shown in FIG. 1 , the exhaust gas treatment device 10 includes an outer pipe 24 having an open end 20 and a closed end 22 , and an inner pipe 26 inserted into the outer pipe 24 .

[0015] (Outer Tube) The outer tube 24 is formed in a bottomed cylindrical shape having a cylindrical portion 30 and a flat bottom portion 32 that closes the end of the cylindrical portion 30. An introduction portion 36 is connected to the side surface of the cylindrical portion 30 of the outer tube 24.

[0016] (Inner Tube) The inner tube 26 is formed in a cylindrical shape. One end of the inner tube 26 is inserted into the outer tube 24 through an opening of the outer tube 24. An end opening 40 on one end side of the inner tube 26 opens inside the outer tube 24.

[0017] One end of the inner pipe 26 is disposed inside the outer pipe 24 with a gap 46 formed between it and the inner circumferential surface 30A of the cylindrical portion 30 of the outer pipe 24. As a result, the aforementioned gap 46 is formed between the inner pipe 26 and the outer pipe 24, allowing flow along the circumferential direction of the inner circumferential surface 30A of the cylindrical portion 30 of the outer pipe 24.

[0018] An exhaust pipe 50 is connected to the other end of the inner pipe 26. The exhaust pipe 50 extends in a direction intersecting the longitudinal direction of the inner pipe 26. The exhaust pipe 50 changes the flow direction of the exhaust gas G from the inner pipe 26 and discharges the exhaust gas G.

[0019] (Closing portion) A ring-shaped closing portion 54 is provided between the inner pipe 26 and the outer pipe 24 on the one end 20 side of the outer pipe 24. The gap 46 formed between the inner pipe 26 and the outer pipe 24 is closed by the closing portion 54.

[0020] In this embodiment, in order to make the closure portion 54 easier to understand, an example has been described in which the closure portion 54 is configured as a separate member from the outer tube 24, but the closure portion 54 is not limited to this configuration. For example, the closure portion 54 may be configured as a reduced diameter portion in which the diameter of one end 20 of the outer tube 24 is reduced until it is connected to the inner tube 26.

[0021] Furthermore, the spacing of the gap 46 formed between the inner pipe 26 and the outer pipe 24 is maintained by the blocking portion 54. The gap 46, the spacing of which is maintained by the blocking portion 54, is continuous with a gap 58 formed between the end opening 40 of the inner pipe 26 and the bottom portion 32 of the outer pipe 24.

[0022] (Catalyst) The catalyst 14 described above is housed inside the inner pipe 26. A cylindrical tubular holding member 60 is provided on the outer peripheral surface of the catalyst 14, and the cylindrical holding member 60 is disposed between the outer peripheral surface of the catalyst 14 and the inner peripheral surface of the inner pipe 26. The catalyst 14 is held in the inner pipe 26 via the cylindrical holding member 60.

[0023] The catalyst 14 absorbs and retains ammonia, and the catalyst 14 chemically reacts the retained ammonia with nitrogen compounds (NOx) in the exhaust gas G passing through it, reducing the ammonia to nitrogen and water.

[0024] (Introduction Section) The introduction section 36 is configured as a tubular body. The introduction section 36 has a connecting section 70 connected to the outer pipe 24, a curved section 72 connected to the connecting section 70, and an extension section 74 connected to the curved section 72.

[0025] A connection flange 76 for connecting the introduction portion 36 to another pipe is formed at the end of the extension portion 74 in the introduction portion 36. The extension portion 74 is connected to an engine (not shown) via another pipe, and guides exhaust gas G from the engine to the introduction portion 36.

[0026] The exhaust gas G introduced into the inlet 36 via the extension 74 is introduced into the gap 46 inside the outer pipe 24 via the connecting portion 70. The exhaust gas G introduced into the gap 46 is introduced into the inner pipe 26, which holds the catalyst 14, via the end opening 40 of the inner pipe 26. The exhaust gas G introduced into the inner pipe 26 passes through the catalyst 14 held in the inner pipe 26. The exhaust gas G that has passed through the catalyst 14 is discharged via the exhaust pipe 50.

[0027] 2, the connection part 70 in the introduction part 36 is formed in a cylindrical shape that extends linearly. When a plane 82 passing through the central axis 80 of the inner pipe 26 is imagined, the linearly formed connection part 70 is disposed so that a center line 84 passing through the center of the connection part 70 is inclined with respect to the plane 82.

[0028] The plane 82 is a plane that includes the center line of the reducing agent 12 sprayed from the injector 90. The introduction portion 36 is connected to the cylindrical portion 30 of the outer pipe 24 with the connection portion 70 inclined with respect to the plane 82 that passes through the central axis 80 of the inner pipe 26.

[0029] The exhaust gas G introduced from the connecting portion 70 of the inlet portion 36 flows in the circumferential direction along the outer peripheral surface 26B of the inner pipe 26 (see the arrows in FIGS. 1 and 2 ). The exhaust gas G flowing in the circumferential direction along the outer peripheral surface 26B of the inner pipe 26 flows in a spiral pattern toward one end of the inner pipe 26 while circling through gaps 46 formed in the outer periphery of the inner pipe 26. The exhaust gas G flowing in a spiral pattern is introduced into the inner pipe 26 through an end opening 40 formed on one end of the inner pipe 26.

[0030] As a result, the flow path length of the exhaust gas G becomes longer than when the exhaust gas G flows linearly along the length of the inner pipe 26 .

[0031] (Injector) The introduction section 36 is provided with an injector 90 that sprays the reducing agent 12 onto the outer peripheral surface 26B, which is the side surface of the inner pipe 26. The reducing agent 12 is made of urea water.

[0032] Specifically, a bulging portion 94 that bulges out to the side is formed at the connection portion 70 of the introduction portion 36. The amount of lateral protrusion of the bulging portion 94 increases with increasing distance from the outer pipe 24. A stepped surface 96 is formed at the end of the bulging portion 94. The stepped surface 96 is formed so as to be perpendicular to an imaginary line (82) that extends radially from the central axis 80 of the inner pipe 26.

[0033] In FIG. 2, an imaginary line extending from the central axis 80 of the inner tube 26 is positioned on a plane 82 passing through the central axis 80 of the inner tube 26, and therefore the imaginary line is shown by a dashed line indicating the plane 82.

[0034] In this embodiment, the step surface 96 serving as the seating surface of the injector 90 is perpendicular to the imaginary line (82) so that the reducing agent 12 from the injector 90 is sprayed toward the central axis 80 of the inner pipe 26, but this embodiment is not limited to this configuration. The spray direction of the reducing agent 12 from the injector 90 does not necessarily have to be toward the central axis 80 of the inner pipe 26.

[0035] An injector 90 is provided on this step surface 96. The injector 90 atomizes the reducing agent 12 as a liquid sent from a tank (not shown) and sprays the atomized reducing agent 12 toward the inner pipe 26. The sprayed urea water, which is the reducing agent 12, is hydrolyzed by the heat of the exhaust gas G and becomes ammonia.

[0036] In this embodiment, the reducing agent 12 injected from the injector 90 is urea water that is hydrolyzed to ammonia by the heat of the exhaust gas G, but the reducing agent 12 is not limited to this. In other words, the reducing agent 12 may be ammonia or another liquid.

[0037] The injector 90 sprays the reducing agent 12 toward an exhaust gas spraying point 100, which is a portion of the inner pipe 26 onto which the exhaust gas G is sprayed from the introduction portion 36. The reducing agent 12 is sprayed toward the exhaust gas spraying point 100, which is heated by the exhaust gas G. This promotes hydrolysis of the urea water serving as the reducing agent 12.

[0038] Furthermore, the injector 90 sprays the reducing agent 12 onto a portion of the outer circumferential surface 26B of the inner pipe 26 at a position where the cylindrical holding member 60 is provided. The reducing agent 12 is sprayed onto a portion of the inner pipe 26 where heat dissipation is suppressed by the cylindrical holding member 60. This further accelerates hydrolysis of the urea water as the reducing agent 12 compared to when the reducing agent 12 is sprayed onto a portion of the inner pipe 26 where heat dissipation is more likely.

[0039] The injector 90 is disposed so that the center line ( 82 ) of the injection hole 90 A that injects the reducing agent 12 passes through the central axis 80 of the inner pipe 26 .

[0040] 2, the center line of the ejection hole 90A coincides with an imaginary line extending from the central axis 80 of the inner tube 26, and the center line of the ejection hole 90A is located on a plane 82 that passes through the central axis 80 of the inner tube 26. For this reason, in FIG. 2, the center line of the ejection hole 90A is also indicated by a dashed line that indicates the plane 82.

[0041] The injector 90 sprays the reducing agent 12 from the nozzle holes 90A toward the central axis 80 of the inner tube 26. As a result, the injector 90 causes the atomized reducing agent 12 to collide with the outer peripheral surface 26B of the inner tube 26 and atomize it.

[0042] Furthermore, the injector 90 is configured so that even if the ejected reducing agent 12 is carried away by the exhaust gas G introduced from the introduction portion 36, the ejected reducing agent 12 is sprayed toward the central axis 80 of the inner pipe 26. To be more specific, for example, the mounting angle of the injector 90 or the shape of the ejection hole 90A is set so that the ejection direction of the reducing agent 12 is inclined toward the upstream side of the flow of the exhaust gas G. This allows the injector 90 to eject the reducing agent 12 so that the reducing agent 12, influenced by the flow of the exhaust gas G from the introduction portion 36, is directed toward the central axis 80 of the inner pipe 26.

[0043] Here, the shape of the ejection hole 90A is set so that when the reducing agent 12 is caused to flow by the exhaust gas G emitted from the engine at a predetermined engine speed, the reducing agent 12 is sprayed toward the central axis 80 of the inner pipe 26.

[0044] In this embodiment, the central axis of the ejection hole 90A of the injector 90 is aligned with the imaginary line (82) extending from the central axis 80, but this embodiment is not limited to this configuration. For example, the central axis of the ejection hole 90A of the injector 90 does not necessarily have to be aligned with the imaginary line (82) extending from the central axis 80.

[0045] (Operations and Effects) According to this embodiment, the following operations and effects are achieved.

[0046] According to this embodiment, the exhaust gas treatment device 10 is a device that treats exhaust gas G emitted from an engine. The exhaust gas treatment device 10 includes an outer pipe 24 that has one end 20 open and the other end 22 closed. The exhaust gas treatment device 10 includes an inner pipe 26 that is inserted into the outer pipe 24 with a gap 46 formed between it and the inner circumferential surface 30A of the outer pipe 24, allowing flow along the circumferential direction of the inner circumferential surface 30A, and whose end opening 40 opens into the interior of the outer pipe 24. The exhaust gas treatment device 10 includes a catalyst 14 held inside the inner pipe 26. The exhaust gas treatment device 10 includes a blocking portion 54 that blocks the gap 46 on the one end 20 side of the outer pipe 24. The exhaust gas treatment device 10 includes a cylindrical introduction portion 36 that is connected to the side of the outer pipe 24 and introduces exhaust gas G into the gap 46, allowing the exhaust gas G to flow through the outer periphery of the inner pipe 26 and the end opening 40 of the inner pipe 26 into the inner pipe 26 that holds the catalyst 14. The exhaust gas treatment device 10 includes an injector 90 that is provided in the introduction section 36 and sprays the reducing agent 12 onto the side surface (26B) of the inner pipe 26.

[0047] The mixer 10A configured by the exhaust gas treatment device 10 of this embodiment is a device that mixes a liquid reducing agent 12 and a gaseous exhaust gas G. The mixer 10A includes an outer pipe 24 that is open at one end 20 and closed at the other end 22. The mixer 10A includes an inner pipe 26 that is inserted into the outer pipe 24 with a gap 46 formed between the inner circumferential surface 30A of the outer pipe 24 and the inner pipe 26, allowing flow along the circumferential direction of the inner circumferential surface 30A. The end opening 40 of the inner pipe 24 opens to the interior of the outer pipe 24. The mixer 10A includes a closing section 54 that closes the gap 46 on the one end 20 side of the outer pipe 24. The mixer 10A includes a cylindrical introduction section 36 that is connected to the side of the outer pipe 24 and introduces the gaseous exhaust gas G into the gap 46, allowing the gaseous exhaust gas G to flow into the inner pipe 26 via the outer circumferential portion of the inner pipe 26 and the end opening 40 of the inner pipe 26. The mixer 10A is provided in the introduction section 36 and includes an injector 90 that atomizes and sprays the reducing agent 12 in liquid form toward the side surface (26B) of the inner tube 26.

[0048] According to these configurations, the reducing agent 12 in the form of a liquid is sprayed onto the side surface (26B) of the inner pipe 26 by the injector 90 provided in the introduction section 36. The reducing agent 12 then collides with the side surface (26B) of the inner pipe 26 and is atomized. This promotes mixing of the atomized liquid reducing agent 12 with the exhaust gas G in the form of a gas introduced from the introduction section 36, without using a mixer plate or the like.

[0049] Furthermore, exhaust gas G as a gas introduced from the introduction portion 36 into the outer pipe 24 moves through the gap 46 formed between the outer pipe 24 and the inner pipe 26 toward the end opening 40 of the inner pipe 26, then turns around at the end opening 40 and flows inside the inner pipe 26. In the exhaust gas treatment device 10, the exhaust gas G passes through the catalyst 14 held in the inner pipe 26. Therefore, compared to when the flow path of the exhaust gas G as a gas is formed in a straight line without turning back, the flow path can be made smaller without shortening the flow path length of the exhaust gas G. This allows for the device to be made smaller, and the installation space can be reduced.

[0050] Furthermore, the inlet 36 is connected to the side surface of the outer pipe 24, and the exhaust gas G introduced from the inlet 36 is directed toward the side surface (26B) of the inner pipe 26. As a result, the exhaust gas G introduced from the inlet 36 flows along the outer peripheral surface 26B of the inner pipe 26 and circulates around the outer periphery of the inner pipe 26.

[0051] In this way, the exhaust gas treatment device 10 and the mixing device 10A configured by the exhaust gas treatment device 10 can cause the exhaust gas G as a gas containing the reducing agent 12 as a liquid to circulate along the outer peripheral surface 26B of the inner pipe 26. Therefore, the flow path length of the exhaust gas G as a gas can be increased without extending the flow path, making it possible to promote mixing of the reducing agent 12 as a liquid and the exhaust gas G as a gas.

[0052] Furthermore, according to this embodiment, the introduction portion 36 is connected to the outer pipe 24 in a state inclined with respect to the plane 82 passing through the central axis 80 of the inner pipe 26 .

[0053] Furthermore, according to the mixer 10A configured by the exhaust gas treatment device 10 of this embodiment, the introduction section 36 is connected to the outer pipe 24 in a state inclined with respect to the plane 82 passing through the central axis 80 of the inner pipe 26 .

[0054] These configurations promote the exhaust gas G introduced from the introduction portion 36 to flow in the circumferential direction along the outer peripheral surface 26B of the inner pipe 26. Then, the exhaust gas G flowing in the circumferential direction along the outer peripheral surface 26B of the inner pipe 26 flows in a spiral pattern toward one end of the inner pipe 26 while circling the outer periphery of the inner pipe 26, and is then introduced into the interior of the inner pipe 26 through the end opening 40 of the inner pipe 26.

[0055] Therefore, the flow path length of the exhaust gas G becomes longer depending on the number of times it goes around the outer periphery of the inner pipe 26, which makes it possible to further promote mixing of the reducing agent 12 as a liquid and the exhaust gas G as a gas.

[0056] Furthermore, in the exhaust gas treatment device 10, the exhaust gas G introduced from the inlet 36 is circulated along the outer peripheral surface 26B of the inner pipe 26, which makes it possible to maintain the catalyst 14 held in the inner pipe 26 at a high temperature, thereby promoting the reduction reaction by the catalyst 14.

[0057] Furthermore, according to this embodiment, the injector 90 sprays the reducing agent 12 toward the central axis 80 of the inner pipe 26 .

[0058] Furthermore, according to the mixing device 10A configured by the exhaust gas treatment device 10 of this embodiment, the injector 90 sprays the atomized liquid (12) toward the central axis 80 of the inner pipe 26.

[0059] According to these configurations, the exhaust gas treatment device 10 and the mixing device 10A formed by the exhaust gas treatment device 10 can cause the reducing agent 12 as a liquid ejected from the injector 90 to collide at an angle close to perpendicular with the outer peripheral surface 26B of the inner pipe 26. This promotes the breaking down of the reducing agent 12 as a liquid into fine particles, thereby further promoting the mixing of the reducing agent 12 as a liquid and the exhaust gas G as a gas.

[0060] Furthermore, according to this embodiment, the injector 90 injects the reducing agent 12 so that the reducing agent 12 is influenced by the flow of the exhaust gas G from the inlet portion 36 and directed toward the central axis 80 of the inner pipe 26 .

[0061] According to this configuration, even if the reducing agent 12 ejected from the injector 90 is carried away by the exhaust gas G introduced from the introduction portion 36 , it is sprayed toward the central axis 80 of the inner pipe 26 .

[0062] Therefore, even if the reducing agent 12 ejected from the injector 90 is carried away by the exhaust gas G, the exhaust gas treatment device 10 can atomize the reducing agent 12 by causing it to collide with the outer peripheral surface 26B of the inner pipe 26. This makes it possible for the exhaust gas treatment device 10 to promote mixing of the reducing agent 12 and the exhaust gas G.

[0063] Furthermore, according to this embodiment, the injector 90 sprays the reducing agent 12 from the introduction portion 36 toward the location (100) of the inner pipe 26 where the exhaust gas G is sprayed.

[0064] According to this configuration, the reducing agent 12 is sprayed onto the exhaust gas spraying point 100 of the inner pipe 26, which is heated by the exhaust gas G. This enables the exhaust gas treatment device 10 to promote hydrolysis of the urea water as the reducing agent 12 by the heat of the exhaust gas G and the heat of the exhaust gas spraying point 100 heated by the exhaust gas G.

[0065] Furthermore, according to this embodiment, the catalyst 14 is held in the inner pipe 26 via a cylindrical holding member 60, and the injector 90 sprays the reducing agent 12 onto the portion of the outer surface 26B of the inner pipe 26 at the position where the cylindrical holding member 60 is provided.

[0066] According to this configuration, the reducing agent 12 is sprayed onto a portion of the inner pipe 26 where heat dissipation is suppressed by the cylindrical holding member 60. Therefore, the exhaust gas treatment device 10 can further promote the hydrolysis of urea water compared to a case where urea water as the reducing agent 12 is sprayed onto a portion of the inner pipe 26 where heat dissipates easily.

[0067] In this embodiment, an example has been shown in which the end of the outer tube 24 is closed by the flat bottom portion 32, but the outer tube 24 is not limited to this configuration. The outer tube 24 may also be configured as in the first and second modified examples shown below.

[0068] (First Modification) FIG. 3 is a cross-sectional view showing a main part of an exhaust gas treatment device 200 according to a first modification.

[0069] The exhaust gas treatment device 200 according to the first modification has a function as a mixing device 200A. In the exhaust gas treatment device 200, a bottom protrusion 210 that protrudes in a spherical shape toward the inner pipe 26 is formed in the center of the bottom 32. The shape, position, or number of the bottom protrusion 210 can be determined arbitrarily.

[0070] In this first variant, the bottom protrusion 210 can disperse exhaust gas G, which concentrates on the outer periphery of the catalyst 14, to the center of the catalyst 14, thereby making it possible to increase the efficiency of the reduction reaction in the catalyst 14.

[0071] (Second Modification) FIG. 4 is a diagram showing an exhaust gas treatment device 220 according to a second modification, and corresponds to the cross-sectional view taken along line IV-IV in FIG.

[0072] The exhaust gas treatment device 220 according to the second modification functions as a mixing device 220A. The exhaust gas treatment device 220 has four beads 230 extending radially from the bottom 32 of the outer pipe 24 and protruding toward the inner pipe 26 (see FIG. 1). The beads 230 are arranged at equal intervals in the circumferential direction.

[0073] The shape, position, and number of the beads 230 can be determined arbitrarily. In a second modified example, the beads 230 formed on the bottom portion 32 may be configured as plates that stand up toward the inner pipe 26 (see FIG. 1). In a second modified example, the bottom portion 32 may be provided with both the beads 230 and plates.

[0074] Like the first variant, this second variant uses the beads 230 to disperse exhaust gas G, which tends to concentrate on the outer periphery of the catalyst 14, to the center of the catalyst 14, thereby increasing the efficiency of the reduction reaction in the catalyst 14.

[0075] In the above-described embodiment, the connecting portion 70 of the introduction portion 36 is formed in a cylindrical shape extending linearly, but the connecting portion 70 of the introduction portion 36 is not limited to this shape. The connecting portion 70 of the introduction portion 36 may be configured as in the third modified example shown below.

[0076] (Third Modification) FIG. 5 is a diagram showing an exhaust gas treatment device 240 according to a third modification, and corresponds to the cross-sectional view taken along line II-II in FIG.

[0077] The exhaust gas treatment device 240 according to the third modification functions as a mixing device 240A. A connection protrusion 250 that protrudes inward is formed at the connection portion 70 of the inlet portion 36 of the exhaust gas treatment device 240, thereby narrowing a portion of the flow path formed by the inlet portion 36. The shape, position, or number of the connection protrusion 250 can be determined arbitrarily.

[0078] In this third variant, the flow of exhaust gas G flowing into the inside of the outer pipe 24 can be controlled to be turbulent, making it possible to increase the mixing efficiency of the reducing agent 12 as a liquid and the exhaust gas G as a gas.

[0079] In the above-described embodiment, the catalyst 14 is disposed inside the end opening 40 of the inner pipe 26, but the inner pipe 26 is not limited to this configuration. The inner pipe 26 may also be configured as in the fourth modified example shown below.

[0080] (Fourth Modification) FIG. 6 is a diagram showing an exhaust gas treatment device 260 according to a fourth modification, and corresponds to the cross-sectional view taken along line VI-VI in FIG.

[0081] The exhaust gas treatment device 260 according to the fourth modification functions as a mixing device 260A. A punched plate 272 having a plurality of holes 270 formed therein is provided in the inner pipe 26 of the exhaust gas treatment device 260 between the end opening 40 and the catalyst 14 (see FIG. 1).

[0082] The shape, position, or number of holes 270 can be determined arbitrarily. The punched plate 272 provided in the inner tube 26 can be replaced with a slit plate having multiple slits. The number of punched plates 272 or slit plates provided in the inner tube 26 is not limited to one, and may be multiple.

[0083] In this fourth variant, the exhaust gas G that concentrates on the outer periphery of the catalyst 14 can be dispersed to the center of the catalyst 14 by each hole 270, thereby making it possible to increase the efficiency of the reduction reaction in the catalyst 14.

[0084] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0085] This application claims priority from Japanese Patent Application No. 2024-053652, filed with the Japan Patent Office on March 28, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An exhaust gas treatment device that treats exhaust gas emitted from an engine, comprising: an outer pipe having one open end and the other closed end; an inner pipe that is inserted into the outer pipe with a gap formed between it and the inner peripheral surface of the outer pipe to allow flow along the circumferential direction of the inner peripheral surface, the inner pipe having an end opening that opens into the interior of the outer pipe; a catalyst held inside the inner pipe; a closing section that closes the gap on the one end side of the outer pipe; a cylindrical introduction section that is connected to a side of the outer pipe and introduces exhaust gas into the gap, causing the exhaust gas to flow through the outer peripheral part of the inner pipe and the end opening of the inner pipe into the inner pipe holding the catalyst; and an injector that is provided in the introduction section and sprays a reducing agent onto the side surface of the inner pipe.

2. An exhaust gas treatment device according to claim 1, wherein the introduction section is connected to the outer pipe in a state inclined with respect to a plane passing through the central axis of the inner pipe.

3. An exhaust gas treatment device according to claim 1, wherein the injector sprays a reducing agent toward the central axis of the inner pipe.

4. An exhaust gas treatment device according to claim 3, wherein the injector injects the reducing agent so that the reducing agent, influenced by the flow of exhaust gas from the inlet, is directed toward the central axis of the inner pipe.

5. An exhaust gas treatment device according to claim 3 or 4, wherein the injector sprays a reducing agent toward a portion of the inner pipe onto which exhaust gas is sprayed from the introduction portion.

6. An exhaust gas treatment device according to claim 1, wherein the catalyst is held in the inner pipe via a cylindrical holding member, and the injector sprays a reducing agent onto a portion of the outer circumferential surface of the inner pipe at a position where the cylindrical holding member is provided.

7. A mixing device for mixing a liquid and a gas, comprising: an outer tube having one open end and the other closed end; an inner tube inserted into the outer tube with a gap formed between it and the inner peripheral surface of the outer tube that allows gas to flow circumferentially around the inner peripheral surface, the inner tube having an end opening that opens into the interior of the outer tube; a closing part that closes the gap on the one end side of the outer tube; a cylindrical introduction part connected to a side surface of the outer tube that introduces gas into the gap and causes the gas to flow into the inner tube via the outer peripheral surface of the inner tube and the end opening of the inner tube; and an injector provided in the introduction part that atomizes and sprays liquid toward the side surface of the inner tube.

8. A mixing device according to claim 7, wherein the introduction section is connected to the outer pipe in a state inclined with respect to a plane passing through the central axis of the inner pipe.

9. A mixing device according to claim 7 or 8, wherein the injector sprays atomized liquid toward the central axis of the inner tube.

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