Additive mixing device and exhaust emission control device

Abstract

A fuel mixing device 80 is provided in a flow passage of exhaust gas discharged from a diesel engine 100, and is provided downstream of a fuel injection device 30 injecting unburned fuel to the flow passage. The fuel mixing device 80 includes: a tubular body part 81 having a circular, elliptical, or oblong cross section; and at least one opening 82 provided on a side surface 86 of the body part 81.

Description

Additive mixing device and exhaust purification device

[0001] The present invention relates to an additive mixing device and an exhaust purification device.

[0002] BACKGROUND ART There is known a device that purifies exhaust gas generated in an internal combustion engine by passing the exhaust gas through an oxidation catalyst (DOC: Diesel Oxidation Catalyst), a catalyst-loaded filter (DPF: Diesel Particulate Filter), and a selective catalytic reduction catalyst (SCR) in that order (see, for example, Patent Document 1).

[0003] During normal operation, particulate matter that has not been completely burned accumulates in the DPF. The particulate matter that accumulates in the DPF increases the pressure loss of the DPF. Therefore, "forced regeneration" is required to forcibly burn the particulate matter that has accumulated in the DPF. Forced regeneration refers to the following series of reactions. First, unburned fuel is added to the exhaust gas flowing through the exhaust gas flow path (hereinafter referred to as the "flow path") from upstream of the position where the oxidation catalyst is located. The unburned fuel is oxidized by contacting the oxidation catalyst. This causes the temperature of the exhaust gas to rise rapidly to a high temperature. The heated exhaust gas then flows into the DPF, burning the particulate matter that has accumulated in the DPF.

[0004] To perform the forced regeneration, a fuel injector that adds unburned fuel to the exhaust gas is located upstream of the oxidation catalyst in the flow path. The distance between the fuel injector and the oxidation catalyst in the flow path is long to ensure uniform mixing of the exhaust gas and unburned fuel.

[0005] As exhaust gas regulations become stricter, there is a demand for devices with higher exhaust gas purification capabilities than before. For example, devices that further include a selective reduction catalyst or storage catalyst upstream of the oxidation catalyst in the flow path to suppress the emission of NOx (nitrogen oxides).

[0006] However, selective reduction catalysts and storage catalysts deteriorate when they come into contact with unburned fuel. Therefore, fuel injection devices are installed downstream of these catalysts in the flow path. This can shorten the distance between the fuel injection device and the oxidation catalyst in the flow path. In this case, it is thought that exhaust gas and unburned fuel may come into contact with the oxidation catalyst without being uniformly mixed.

[0007] Patent Publication No. 2023-147843

[0008] If the exhaust gas is not uniformly mixed with the unburned fuel, the liquid unburned fuel may adhere to a portion of the oxidation catalyst. The liquid unburned fuel adhering to the oxidation catalyst does not cause an oxidation reaction. Furthermore, when the liquid unburned fuel vaporizes, it lowers the temperature of the exhaust gas, preventing the exhaust gas from burning the particulate matter deposited in the DPF. Furthermore, in areas of the oxidation catalyst where the liquid unburned fuel does not adhere, the unburned fuel causes an oxidation reaction, which can cause some of the exhaust gas to become very hot. However, because the high-temperature exhaust gas only flows into a portion of the DPF, the high-temperature exhaust gas can only burn a portion of the particulate matter deposited in the DPF.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide an apparatus for uniformly mixing exhaust gas emitted from an internal combustion engine with unburned fuel.

[0010] In one aspect, the present invention provides an additive mixing device that is provided in a flow path of exhaust gas emitted from an internal combustion engine and is provided downstream of an additive injection section that injects an additive into the flow path, the additive mixing device comprising a tubular main body having a circular, elliptical or oblong cross section, and at least one opening provided on a side surface of the main body.

[0011] According to the present invention, it is possible to provide an apparatus for uniformly mixing exhaust gas emitted from an internal combustion engine with unburned fuel.

[0012] 4 is a schematic diagram showing the flow of exhaust gas in the first embodiment. A perspective view of the exhaust purification device 1. A view showing the first connecting pipe 20 and the fuel mixing device 80 as viewed in the X-axis direction. A view showing the first connecting pipe 20 and the fuel mixing device 80 as viewed in the Y-axis direction. A cross-sectional view taken along A-A in FIG. 3. A cross-sectional view taken along B-B in FIG. 4. A perspective view of the fuel mixing device 80. A front view of the fuel mixing device 80. A view of the fuel mixing device 80 as viewed from one end 84. A schematic diagram showing how exhaust gas flows into the space inside the main body 81. A schematic diagram showing the flow of exhaust gas in a second embodiment. A view showing the exhaust purification device 101 as viewed in the Y-axis direction. A view showing a modified example of the exhaust purification device 101.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, although the embodiments described below are subject to various limitations that are technically preferable for implementing the present invention, the scope of the present invention is not limited to the following embodiments and illustrated examples.

[0014] <<First Embodiment>> <Exhaust Gas Purification Device> Fig. 1 is a schematic diagram showing the flow of exhaust gas, and Fig. 2 is a perspective view of an exhaust gas purification device 1. The exhaust gas purification device 1 is a device that removes nitrogen oxides, particulates, etc. from exhaust gas. The exhaust gas purification device 1 includes a first SCR unit 10, a first connecting pipe 20, a fuel injection device 30, a DOC unit 40, a DPF unit 50, a second connecting pipe 60, and a second SCR unit 70.

[0015] The exhaust gas purification device 1 is mounted on a vehicle equipped with a diesel engine 100 (an example of an internal combustion engine) and removes nitrogen oxides, particulates, etc. from exhaust gas from the diesel engine 100. In the following description, the positional relationship of the components of the exhaust gas purification device 1 will be explained using an XYZ Cartesian coordinate system defined by mutually orthogonal X-, Y-, and Z-axes as shown in Fig. 2. The X-axis is parallel to the extension direction of the first SCR unit 10.

[0016] The exhaust gas purification device 1 is provided as part of the flow path of exhaust gas from a diesel engine 100. As shown in Fig. 1, the exhaust gas purification device 1 is configured such that a first SCR unit 10, a first connecting pipe 20, a DOC unit 40, a DPF unit 50, a second connecting pipe 60, and a second SCR unit 70 are connected in this order to form a flow path.

[0017] When exhaust gas is discharged from the diesel engine 100, it flows through piping to the exhaust gas purification device 1. The exhaust gas flows through the exhaust gas purification device 1, which is part of the flow path, in the following order: first SCR unit 10, first connecting pipe 20, DOC unit 40, DPF unit 50, second connecting pipe 60, and second SCR unit 70. The exhaust gas that has passed through the exhaust gas purification device 1 is released into the atmosphere through the piping. In the exhaust gas purification device 1, the exhaust gas flows from the first SCR unit 10 toward the second SCR unit 70. Therefore, the first SCR unit 10 side is upstream and the second SCR unit 70 side is downstream in the exhaust gas flow path.

[0018] 2, in the exhaust gas purification device 1 according to this embodiment, the first SCR unit 10, the DOC unit 40, the DPF unit 50, and the second SCR unit 70 are arranged at the vertices of a triangle when viewed in the X-axis direction. In this way, the elements constituting the exhaust gas purification device 1 are arranged close to each other, making the exhaust gas purification device 1 compact. As a result, the exhaust gas purification device 1 can be arranged even in a small space.

[0019] (First SCR Unit) The first SCR unit 10 has a substantially cylindrical case 11 and a substantially columnar SCR catalyst 12 (SCR: Selective Catalytic Reduction) housed in the case 11 .

[0020] [Case] ​​The case 11 accommodates the SCR catalyst 12. The case 11 is a cylindrical member. Both ends of the case 11 are open.

[0021] [SCR Catalyst] The SCR catalyst 12 is a catalyst that reduces nitrogen oxides contained in exhaust gas using a reducing agent. In this embodiment, a first reducing agent injection device (not shown) that injects a reducing agent into the exhaust gas is provided upstream of the first SCR unit 10 in the flow path.

[0022] (First Connecting Pipe) The first connecting pipe 20 is a member that connects the first SCR unit 10 and the DOC unit 40. The first connecting pipe 20 has a first connecting portion 21 and a second connecting portion 22 (see FIGS. 3 and 4).

[0023] [First Connection Portion] The first connection portion 21 is a portion that is connected to the first SCR unit 10. The first connection portion 21 is a cylindrical member. One end of the first connection portion 21 is connected to the first SCR unit 10 via the case 11. The other end of the first connection portion 21 is closed. The first connection portion 21 has a portion that protrudes from the side surface. An opening 21a with an elliptical cross section is provided in the portion of the first connection portion 21 that protrudes from the side surface.

[0024] [Second Connection Portion] The second connection portion 22 is a portion that is connected to the DOC unit 40. The second connection portion 22 is a cylindrical member. One end of the second connection portion 22 is connected to the DOC unit 40 via a case 41, which will be described later. The other end of the second connection portion 22 is closed. The second connection portion 22 has a portion that protrudes from the side surface. An opening 22a with an elliptical cross section is provided in the portion of the second connection portion 22 that protrudes from the side surface.

[0025] In this embodiment, the first connecting pipe 20 is provided such that the opening 22a of the second connecting portion 22 and the opening 21a of the first connecting portion 21 are opposed to each other while being spaced apart from each other. The opening 22a is connected to the opening 21a via the fuel mixing device 80.

[0026] (Fuel Mixing Device) Next, a fuel mixing device 80 (an example of an additive mixing device) will be described using FIGS. 3 to 9 . The fuel mixing device 80 mixes exhaust gas with unburned fuel (an example of an additive). The fuel mixing device 80 connects the first connecting portion 21 and the second connecting portion 22. As shown in FIG. 6 , the fuel mixing device 80 is disposed across the internal space of the first connecting portion 21 and the internal space of the second connecting portion 22. The fuel mixing device 80 connects the internal space of the first connecting portion 21 and the internal space of the second connecting portion 22. The fuel mixing device 80 has a main body 81, an opening 82, and a protrusion 83. For the sake of explanation, FIGS. 7 to 9 only show the fuel mixing device 80.

[0027] [Main Body] As shown in Fig. 7, the main body 81 is a tubular member having a circular, elliptical, or oblong cross section. The main body 81 is open at both ends. In this embodiment, the main body 81 has an elliptical cross section. As shown in Fig. 6, one end 84 of the main body 81 is disposed in the internal space of the first connecting portion 21. The other end 85 of the main body 81 is disposed in the internal space of the second connecting portion 22. The main body 81 is fixed to the openings 21a and 22a without any gaps.

[0028] [Opening] As shown in Fig. 7 , the opening 82 is provided on a side surface 86 of the main body portion 81. The opening 82 connects the internal space of the main body portion 81 with the external space of the main body portion 81. At least one opening 82 is provided on the side surface 86. For example, the opening 82 is provided at one end 84. The length of the opening 82 in the direction in which the main body portion 81 extends is shorter than the length from one end 84 to the other end 85 of the main body portion 81. Note that the position at which the opening 82 is provided is not limited to the one end 84, and may be any position on the side surface 86. Furthermore, the number of openings 82 may be any number equal to or greater than one.

[0029] As shown in Fig. 7 , in this embodiment, three openings 82 are provided. As shown in Fig. 9 , one of the openings 82 is provided on a side surface 86 at a position intersecting the minor axis of the ellipse that forms the cross-sectional shape of the main body 81 in the cross section of the main body 81 (hereinafter, this opening 82 is referred to as the minor axis opening 82a). In the cross section of the main body 81, the center line of the major axis of the minor axis opening 82a overlaps with the minor axis of the ellipse that forms the cross-sectional shape of the main body 81. The remaining two openings 82 are provided on the side surfaces 86 at positions intersecting the major axes of the ellipse that forms the cross-sectional shape of the main body 81 in the cross section of the main body 81 (hereinafter, these openings 82 are referred to as the major axis openings 82b).

[0030] 7, the protrusion 83 is provided on the inner circumferential surface of the main body 81. The protrusion 83 is a portion that protrudes from the inner circumferential surface of the main body 81. The apex of the protrusion 83 may be positioned opposite the center line of the opening 82 in the longitudinal direction in the cross section of the main body 81. The protrusion 83 may be a member separate from the main body 81, or may be molded integrally with the main body 81.

[0031] In this embodiment, the convex portion 83 is formed in a mountain shape with a curved apex. As shown in FIG. 5 , the convex portion 83 and the main body portion 81 form an ω-shape in a cross section of the main body portion 81 on which the convex portion 83 is provided. The convex portion 83 is disposed on the inner circumferential surface of the main body portion 81, biased toward the side surface 86 facing the fuel injection device 30. Specifically, as shown in FIG. 9 , the apex of the convex portion 83 is located at a position facing the minor axis opening 82a in the cross section of the main body portion 81. The apex of the convex portion 83 is located offset from a position facing the center line of the minor axis opening 82a in the major axis direction in the cross section of the main body portion 81 (the position of the minor axis in the cross section of the main body portion 81). The convex portion 83 is offset from a position facing the center line of the minor axis opening 82a in the major axis direction inside the main body portion 81 so as to be closer to the portion of the side surface 86 from which unburned fuel is injected from the fuel injection device 30 (see FIGS. 5 and 6 ).

[0032] (Fuel Injection Device) The fuel injection device 30 (an example of an additive injection unit) is a device that injects unburned fuel. The fuel injection device 30 is provided in the first connection part 21 (see FIG. 3 ). The fuel injection device 30 injects unburned fuel into the space inside the first connection part 21.

[0033] Here, the positional relationship between the fuel injection device 30 and the fuel mixing device 80 will be described. As shown in Fig. 5, the fuel injection device 30 is provided at a position opposite the side surface 86 on which the longitudinal axis opening 82b is provided. As shown in Fig. 6, the fuel injection device 30 is provided at a position opposite the side surface 86 on which the longitudinal axis opening 82b is provided, but not opposite the longitudinal axis opening 82b. As shown by the dashed line in Fig. 6, the fuel injection device 30 injects unburned fuel toward the opposite side surface 86.

[0034] (DOC Unit) As shown in FIG. 2 , the DOC unit 40 has a substantially cylindrical case 41 and a substantially columnar oxidation catalyst (DOC: Diesel Oxidation Catalyst) 42 housed in the case 41 .

[0035] [Case] ​​The case 41 accommodates the oxidation catalyst 42. The case 41 is a cylindrical member. Both ends of the case 41 are open. One end of the case 41 is connected to one end of the second connection part 22.

[0036] [Oxidation Catalyst] The oxidation catalyst 42 oxidizes unburned fuel (hydrocarbons) and carbon monoxide contained in the exhaust gas. The oxidation catalyst 42 generates heat due to an oxidation reaction that occurs when the unburned fuel comes into contact with the oxidation catalyst 42, thereby increasing the temperature of the exhaust gas.

[0037] (DPF Unit) As shown in FIG. 2 , the DPF unit 50 has a substantially cylindrical case 51 and a substantially columnar DPF (Diesel Particulate Filter) 52 housed in the case 51 .

[0038] [Case] ​​The case 51 houses the DPF 52. The case 51 is a cylindrical member. Both ends of the case 51 are open. One end of the case 51 is connected to the other end of the case 41.

[0039] [DPF] The DPF 52 is a filter for collecting and removing particulate matter from exhaust gases. The DPF 52 is, for example, a ceramic filter having a large number of air holes formed therein.

[0040] (Second Connecting Pipe) The second connecting pipe 60 is a member that connects the DPF unit 50 and the second SCR unit 70. The second connecting pipe 60 has a first connecting portion 61, a second connecting portion 62, a coupling portion 63, and a second reducing agent injection device (not shown).

[0041] [First Connection Portion] The first connection portion 61 is a portion that is connected to the DPF unit 50. The first connection portion 61 is a member that has a substantially cylindrical shape. One end of the first connection portion 61 is connected to the other end of the case 51.

[0042] [Second Connection Portion] The second connection portion 62 is a portion that is connected to the second SCR unit 70. The second connection portion 62 is a substantially cylindrical member. One end of the second connection portion 62 is connected to a case 71 of the second SCR unit 70, which will be described later.

[0043] [Connecting portion] The connecting portion 63 connects the first connecting portion 61 and the second connecting portion 62. The connecting portion 63 is a tubular member. One end of the connecting portion 63 covers the other end of the first connecting portion 61. The other end of the connecting portion 63 covers the other end of the second connecting portion 62.

[0044] The second reducing agent injection device is provided in the connecting portion 63. The second reducing agent injection device injects the reducing agent into the space inside the connecting portion 63.

[0045] (Second SCR Unit) The second SCR unit 70 has a substantially cylindrical case 71 and a substantially columnar SCR catalyst 72 housed in the case 71 .

[0046] [Case] ​​The case 71 houses the SCR catalyst 72. The case 71 is a cylindrical member. Both ends of the case 71 are open. One end of the case 71 is connected to one end of the second connection part 62. The other end of the case 71 is connected to a pipe (not shown).

[0047] [SCR Catalyst] The SCR catalyst 72 is a catalyst that reduces nitrogen oxides contained in exhaust gas using a reducing agent.

[0048] <Purification of Exhaust Gas> A description will be given of the purification of exhaust gas by the exhaust purification device 1. The exhaust gas emitted from the diesel engine 100 contains a reducing agent injected from a first reducing agent injection device (not shown). The exhaust gas flows into the exhaust purification device 1 in a state containing the reducing agent.

[0049] 1 and 2, exhaust gas first flows into the first SCR unit 10. Then, the exhaust gas comes into contact with the SCR catalyst 12. At this time, nitrogen oxides in the exhaust gas are reduced by a reduction reaction between the SCR catalyst 12 and a reducing agent. Then, the exhaust gas flows into the first connecting pipe 20.

[0050] The exhaust gas that flows into the first connecting pipe 20 passes through the inside of the first connecting portion 21 and reaches the vicinity of the fuel mixing device 80. Then, the exhaust gas is divided into two and flows along the outside of the side surface 86 (see FIG. 5).

[0051] After the exhaust gas flow is split into two, one portion enters the interior space of the main body 81 through the major axis opening 82b. The remaining exhaust gas enters the interior space of the main body 81 through the minor axis opening 82a. In this way, the exhaust gas enters the interior space of the main body 81 not only through the minor axis opening 82a but also through the two major axis openings 82b, thereby reducing pressure loss. Here, as shown in FIG. 10 , the exhaust gas flowing along the outside of the side surface 86 facing the fuel injection device 30 is referred to as one exhaust gas, and the exhaust gas flowing along the outside of the side surface 86 not facing the fuel injection device 30 is referred to as the other exhaust gas.

[0052] As one exhaust gas flows along the outside of the side surface 86 facing the fuel injection device 30, unburned fuel is injected from the fuel injection device 30 (see FIG. 10). Therefore, one exhaust gas contains unburned fuel.

[0053] Of the two exhaust gases, the exhaust gas that does not enter the internal space of the main body 81 through the major axis opening 82b enters the internal space of the main body 81 through the minor axis opening 82a. The exhaust gas then flows along the inner circumferential surface of the main body 81, creating a swirling flow (hereinafter referred to as a swirling flow). In this embodiment, the exhaust gas creates two swirling flows in the internal space of the main body 81. The exhaust gas flows through the internal space of the main body 81 toward the other end 85 while maintaining the swirling flow.

[0054] A portion of the first exhaust gas that enters the space inside the main body 81 through the minor axis opening 82a collides with the convex portion 83. The first exhaust gas that collides with the convex portion 83 splits into two at the apex of the convex portion 83, following the mountain-shaped shape of the convex portion 83. One of the two exhaust gas flows forms a swirling flow together with the other exhaust gas that did not collide with the convex portion 83. The other of the two exhaust gas flows forms a swirling flow together with the other exhaust gas. Here, one exhaust gas contains unburned fuel. Therefore, by forming a swirling flow together with the other exhaust gas, the exhaust gas tends to contain unburned fuel uniformly.

[0055] A portion of the other exhaust gas that enters the space inside the main body 81 from the short-axis opening 82a collides with the convex portion 83. The other exhaust gas that collides with the convex portion 83 splits into two and flows from the apex of the convex portion 83 along the mountain-shaped shape of the convex portion 83. One of the two other exhaust gas flows forms a swirling flow together with the other exhaust gas that did not collide with the convex portion 83. The other of the two other exhaust gas flows forms a swirling flow together with the one exhaust gas.

[0056] Here, the position of the convex portion 83 is provided at a position facing the minor axis opening 82a in the cross section of the main body portion 81, so that the exhaust gas that enters the internal space of the main body portion 81 from the minor axis opening 82a easily collides with the convex portion 83. Therefore, the convex portion 83 easily divides the flow of exhaust gas into two.

[0057] As shown in FIG. 5, a portion of the exhaust gas that enters the space inside the main body 81 through the longitudinal opening 82 b is caught up in the swirling flow created in the space inside the main body 81 .

[0058] The exhaust gas that enters the internal space of the main body 81 from the minor axis opening 82a or the major axis opening 82b flows from one end 84 to the other end 85 while maintaining a swirling flow. At this time, the exhaust gas and unburned fuel mix by flowing in a swirling flow. As a result, the gas flowing from the other end 85 to the second connecting portion 22 becomes a mixed gas in which the exhaust gas is uniformly mixed with the unburned fuel. The mixed gas flows from the second connecting portion 22 to the DOC unit 40.

[0059] The mixed gas that flows into the DOC unit 40 comes into contact with the oxidation catalyst 42. At this time, the catalytic action of the oxidation catalyst 42 promotes the oxidation reaction of the unburned fuel in the mixed gas. As a result, the unburned fuel in the mixed gas is oxidized. Furthermore, the mixed gas becomes high-temperature exhaust gas due to the heat generated by the oxidation reaction of the unburned fuel. Here, the mixed gas, which is a gas in which the exhaust gas is uniformly mixed with the unburned fuel, comes into contact with the oxidation catalyst 42, so the unburned fuel in the mixed gas tends to come into uniform contact with the oxidation catalyst 42. Therefore, the exhaust gas that has passed through the oxidation catalyst 42 becomes uniformly hot. The exhaust gas flows into the DPF unit 50.

[0060] The exhaust gas that flows into the DPF unit 50 comes into contact with the DPF 52. At this time, the DPF 52 captures particulate components in the exhaust gas. As the high-temperature exhaust gas flows into the DPF 52, the exhaust gas burns the particulate components captured by the DPF 52. As a result, the particulate capturing ability of the DPF 52 is restored. Furthermore, as the particulate capturing ability of the DPF 52 is restored, the exhaust gas passes through the DPF 52 smoothly. The exhaust gas then flows into the second connecting pipe 60.

[0061] The exhaust gas that flows into the second connecting pipe 60 flows through the first connecting part 61, the coupling part 63, and the second connecting part 62, in that order. As the exhaust gas passes through the coupling part 63, a reducing agent is injected into the exhaust gas from a second reducing agent injection device (not shown). Therefore, the exhaust gas contains the reducing agent again. The exhaust gas that reaches the second connecting part 62 flows into the second SCR unit 70.

[0062] The exhaust gas that has flowed into the second SCR unit 70 comes into contact with the SCR catalyst 72. At this time, the exhaust gas undergoes a reduction reaction with the SCR catalyst 72 and a reducing agent, thereby reducing nitrogen oxides in the exhaust gas.

[0063] <Effects> In this embodiment, the fuel mixing device 80 is provided in the flow path of exhaust gas discharged from the diesel engine 100, and is provided downstream of the fuel injection device 30 that injects unburned fuel into the flow path. The fuel mixing device 80 is tubular and includes a main body 81 having a circular, elliptical, or oblong cross section, and at least one opening 82 provided in a side surface 86 of the main body 81.

[0064] According to the above configuration, exhaust gas and unburned fuel flow from the opening 82 into the internal space of the main body 81, which has a circular, elliptical, or oblong cross section. The exhaust gas and unburned fuel then create a swirling flow along the inner circumferential surface of the main body 81. The exhaust gas and unburned fuel then mix as they form a swirling flow through the internal space of the main body 81. As a result, it is possible to provide a device that uniformly mixes exhaust gas and unburned fuel emitted from an internal combustion engine.

[0065] The opening 82 is provided at one end 84 of the main body 81 on the upstream side in the direction in which exhaust gas flows inside the main body 81 .

[0066] According to the above configuration, the opening 82 is provided at one end 84 of the main body 81, so that it is possible to ensure a long distance from the opening 82 to the other end 85 of the main body 81. In other words, since the length of the swirling flow can be ensured to be long, the exhaust gas and unburned fuel are mixed more efficiently.

[0067] The length of the opening 82 is shorter than the length from one end 84 to the other end 85 of the main body 81 .

[0068] According to the above configuration, a tubular portion where no opening 82 is formed remains in main body 81. Therefore, the exhaust gas and unburned fuel that flow into the internal space of main body 81 from opening 82 do not flow out of main body 81 from the internal space of main body 81, but instead flow out from other end 85 while maintaining a swirling flow. In other words, the swirling flow created by the exhaust gas and unburned fuel in the internal space of main body 81 is less likely to be broken, so the exhaust gas and unburned fuel are mixed more efficiently.

[0069] The fuel mixing device 80 further has a protrusion 83 provided on the inside of the main body 81 at a position opposite the opening 82 .

[0070] According to the above configuration, some of the exhaust gas and unburned fuel flowing from the opening 82 into the space inside the main body 81 collide with the protrusion 83. As a result, the exhaust gas and unburned fuel that collide with the protrusion 83 are separated into two flows, which makes it easier for the exhaust gas and unburned fuel to create two swirling flows inside the main body 81. Therefore, the exhaust gas and unburned fuel are more likely to mix.

[0071] In the fuel mixing device 80, the cross section of the main body 81 at the location where the protrusion 83 is provided is ω-shaped.

[0072] According to the above configuration, the exhaust gas and unburned fuel that collide with the convex portion 83 are separated into two flows along the ω shape. As a result, the exhaust gas and unburned fuel tend to create two swirling flows inside the main body portion 81. Therefore, the exhaust gas and unburned fuel tend to mix together.

[0073] The exhaust purification device 1 includes a fuel mixing device 80, a fuel injection device 30, and an oxidation catalyst 42 arranged downstream of the fuel mixing device 80 in the flow path.

[0074] According to the above configuration, since the fuel mixing device 80 is disposed downstream of the fuel injection device 30, the fuel injected by the fuel injection device 30 is uniformly mixed with the exhaust gas. Therefore, the oxidation catalyst 42 disposed downstream of the fuel mixing device 80 comes into contact with the mixed gas in which the exhaust gas is uniformly mixed with the fuel. As a result, the oxidation catalyst 42 efficiently causes an oxidation reaction.

[0075] In conventional vehicles, if there is a sufficient distance between the fuel injector and the oxidation catalyst, the fuel injected into the exhaust gas flow path by the fuel injector is uniformly mixed with the exhaust gas before reaching the oxidation catalyst. However, the flow path distance required for uniform mixing of fuel with exhaust gas varies depending on factors such as the exhaust gas flow rate, flow velocity, flow path shape, amount of injected fuel, droplet size of the injected fuel, and the position of the fuel injector. Therefore, depending on the vehicle requirements, it may not be possible to ensure the flow path distance required for uniform mixing of fuel with exhaust gas. Even in such cases, by employing the exhaust purification device 1 equipped with the fuel mixing device 80, exhaust gas and fuel can be mixed efficiently.

[0076] The exhaust purification device 1 comprises a fuel mixing device 80, a fuel injection device 30, and an oxidation catalyst 42 arranged downstream of the fuel mixing device 80 in the flow path, and the fuel injection device 30 injects fuel toward a portion of the side surface 86 of the main body portion 81 where the opening 82 is not provided, and the convex portion 83 is arranged biased inside the main body portion 81 so as to be closer to the portion of the main body portion 81 where the fuel is injected.

[0077] According to the above configuration, fuel is injected into a position on the side surface 86 of the main body 81 that is offset from the opening 82. Therefore, the fuel flowing in from the opening 82 flows into the space inside the main body 81 in an uneven state. Here, the convex portion 83 is unevenly positioned so as to be closer to the location where the fuel is injected, so that the exhaust gas containing a large amount of fuel collides with the convex portion 83. As a result, the exhaust gas containing a large amount of fuel is divided into two by the convex portion 83 and flows, so that the fuel is efficiently mixed with the exhaust gas in the space inside the main body 81.

[0078] <<Second Embodiment>> <Exhaust Gas Purification Device> Next, an exhaust gas purification device 101 according to a second embodiment will be described. Here, components in the second embodiment that are similar to those in the first embodiment are denoted by the same reference numerals as in the first embodiment, and detailed description thereof will be omitted. Fig. 11 is a schematic diagram showing the flow of exhaust gas, and Fig. 12 is a diagram showing the exhaust gas purification device 101 as viewed in the Y-axis direction. The exhaust gas purification device 101 includes a first unit 110, a first connecting pipe 20, a urea water injection device 130, and a second unit 140.

[0079] The exhaust purification device 101 is mounted on a vehicle equipped with a diesel engine 100, and removes nitrogen oxides, particulates, etc. from the exhaust gas of the diesel engine 100. In the following description, the X axis is parallel to the direction in which the first unit 110 and the second unit 140 extend.

[0080] The exhaust gas purification device 101 is provided as part of the flow path of exhaust gas from the diesel engine 100. As shown in Fig. 11 , the exhaust gas purification device 101 is connected in this order to the first unit 110, the first connecting pipe 20, and the second unit 140 to form a flow path.

[0081] When exhaust gas is discharged from the diesel engine 100, it flows through a pipe to the exhaust purification device 101. The exhaust gas flows through the exhaust purification device 101, which is part of the flow path, in the order of first unit 110, first connecting pipe 20, and second unit 140. The exhaust gas that has passed through the exhaust purification device 101 is released into the atmosphere through the pipe. In the exhaust purification device 101, the exhaust gas flows from the first unit 110 toward the second unit 140. Therefore, the flow path of the exhaust gas is such that the first unit 110 side is upstream and the second unit 140 side is downstream.

[0082] (First Unit) The first unit 110 has a substantially cylindrical case 111 , and the oxidation catalyst 42 and the DPF 52 housed in the case 111 .

[0083] [Case] ​​The case 111 accommodates the oxidation catalyst 42 and the DPF 52. The case 111 is a cylindrical member. Both ends of the case 111 are open.

[0084] The oxidation catalyst 42 and the DPF 52 are housed in the case 111 in the order of the oxidation catalyst 42 and the DPF 52 from the upstream side of the exhaust gas flow path. Note that a fuel injection device (not shown) that injects unburned fuel into the exhaust gas may be provided upstream of the oxidation catalyst 42 in the exhaust gas flow path.

[0085] (First Connecting Pipe) In the second embodiment, the first connecting pipe 20 connects the first unit 110 and the second unit 140. Specifically, one end of a first connecting portion 21 of the first connecting pipe 20 is connected to the first unit 110 at a case 111. Furthermore, one end of a second connecting portion 22 of the first connecting pipe 20 is connected to the second unit 140 at a case 141 (described later). A urea water injection device 130 is provided in the first connecting portion 21 instead of the fuel injection device 30. Note that, similar to the first embodiment, the first connecting portion 21 and the second connecting portion 22 are connected via a fuel mixing device 80.

[0086] (Urea water injection device) The urea water injection device 130 (an example of an additive injection unit) is a device that injects urea water (an example of an additive). The urea water injection device 130 is provided in the first connection part 21 (see FIG. 12 ). The urea water injection device 130 injects urea water into the space inside the first connection part 21.

[0087] (Second Unit) The second unit 140 has a substantially cylindrical case 141 , and a first SCR catalyst 142 , a second SCR catalyst 143 , and an ammonia slip catalyst 144 housed in the case 141 .

[0088] [Case] ​​The case 141 houses the first SCR catalyst 142, the second SCR catalyst 143, and the ammonia slip catalyst 144. The case 141 is a cylindrical member. Both ends of the case 141 are open. One end of the case 141 is connected to one end of the second connection part 22. The other end of the case 141 is connected to a pipe (not shown).

[0089] The case 141 accommodates a first SCR catalyst 142, a second SCR catalyst 143, and an ammonia slip catalyst 144 in this order from the upstream side of the exhaust gas flow path.

[0090] [First SCR Catalyst] The first SCR catalyst 142 is a catalyst that reduces nitrogen oxides contained in exhaust gas using a reducing agent. In this embodiment, the reducing agent is ammonia produced by decomposing urea.

[0091] [Second SCR Catalyst] The second SCR catalyst 143 is a catalyst that reduces nitrogen oxides contained in exhaust gas using a reducing agent, similar to the first SCR catalyst 142. The second SCR catalyst 143 reduces nitrogen oxides contained in exhaust gas that were not reduced by the first SCR catalyst 142. The second SCR catalyst 143 may be the same as the first SCR catalyst 142, or may have a different shape and performance from the first SCR catalyst 142.

[0092] Since the second unit 140 accommodates not only the first SCR catalyst 142 but also the second SCR catalyst 143, the second unit 140 has a high ability to reduce nitrogen oxides contained in exhaust gas.

[0093] [Ammonia Slip Catalyst] The ammonia slip catalyst (ASC) 144 is a catalyst that oxidizes ammonia. The ammonia slip catalyst 144 oxidizes ammonia that has not been used to reduce nitrogen oxides in the first SCR catalyst 142 and the second SCR catalyst 143, converting it into nitrogen, nitrogen monoxide, water, etc., thereby preventing ammonia from being released into the atmosphere along with exhaust gas.

[0094] <Purification of Exhaust Gas> A description will be given of the purification of exhaust gas by the exhaust purification device 101. Exhaust gas emitted from the diesel engine 100 flows to the exhaust purification device 101 through a pipe.

[0095] 11 and 12, the exhaust gas first flows into the first unit 110. Then, the exhaust gas comes into contact with the oxidation catalyst 42. If unburned fuel is mixed in the exhaust gas, the unburned fuel is oxidized, and the exhaust gas becomes hot.

[0096] Next, the exhaust gas flows into the DPF 52 and comes into contact with the DPF 52. The DPF 52 traps particulate components in the exhaust gas. When the exhaust gas is at a high temperature, the exhaust gas burns the particulate components trapped by the DPF 52. As a result, the particulate trapping capacity of the DPF 52 is restored. The exhaust gas then flows into the first connecting pipe 20.

[0097] The exhaust gas that flows into the first connecting pipe 20 passes through the inside of the first connecting portion 21 and reaches the vicinity of the fuel mixing device 80. Here, urea water is injected into the exhaust gas from the urea water injection device 130. The urea water injected into the exhaust gas is hydrolyzed to generate ammonia gas. Therefore, the exhaust gas contains ammonia gas.

[0098] The exhaust gas containing ammonia gas passes through the fuel mixing device 80 and flows to the second connecting part 22. Here, when the exhaust gas containing ammonia gas passes through the fuel mixing device 80, it creates a swirling flow in the space inside the main body part 81. Therefore, the exhaust gas containing ammonia gas flows in a swirling flow and is mixed, becoming a mixed gas in which the ammonia gas and the exhaust gas are uniformly mixed. The mixed gas flows from the second connecting part 22 to the second unit 140.

[0099] The mixed gas that flows into the second unit 140 comes into contact with the first SCR catalyst 142. At this time, some of the nitrogen oxides and ammonia gas in the mixed gas undergo a reduction reaction and are converted into nitrogen and water. Here, the mixed gas, in which exhaust gas and ammonia gas are uniformly mixed, comes into contact with the first SCR catalyst 142, so the ammonia gas in the mixed gas tends to come into uniform contact with the first SCR catalyst 142. Therefore, the reduction of nitrogen oxides by the first SCR catalyst 142 is efficiently performed.

[0100] Next, the mixed gas comes into contact with the second SCR catalyst 143. At this time, some of the nitrogen oxides and ammonia gas in the mixed gas that were not reduced by the first SCR catalyst 142 undergo a reduction reaction and are converted into nitrogen and water.

[0101] Next, the mixed gas comes into contact with the ammonia slip catalyst 144. At this time, the ammonia gas in the mixed gas undergoes an oxidation reaction and is converted into nitrogen, nitrogen monoxide, water, and the like.

[0102] <Effects> In this embodiment, the fuel mixing device 80 is provided in the flow path of exhaust gas emitted from the diesel engine 100, and is provided downstream of the urea water injection device 130 that injects urea water into the flow path. The fuel mixing device 80 is tubular and includes a main body 81 having a circular, elliptical, or oval cross section, and at least one opening 82 provided in a side surface 86 of the main body 81.

[0103] According to the above configuration, exhaust gas and ammonia gas generated by hydrolysis of urea water flow from the opening 82 into the internal space of the main body 81, which has a circular, elliptical, or oblong cross section. The exhaust gas and ammonia gas then form a swirling flow along the inner circumferential surface of the main body 81. The exhaust gas and ammonia gas then mix by flowing in the swirling flow through the internal space of the main body 81. As a result, it is possible to provide a device that uniformly mixes exhaust gas and ammonia gas emitted from an internal combustion engine.

[0104] The exhaust purification device 101 includes a fuel mixing device 80, a urea water injection device 130, and a first SCR catalyst 142 arranged downstream of the fuel mixing device 80 in the flow passage.

[0105] According to the above configuration, since the fuel mixing device 80 is disposed downstream of the urea-water injection device 130, the urea-water injected by the urea-water injection device 130 is hydrolyzed to generate ammonia gas, and the generated ammonia gas is uniformly mixed with the exhaust gas. Therefore, the first SCR catalyst 142 disposed downstream of the fuel mixing device 80 comes into contact with the mixed gas in which the exhaust gas is uniformly mixed with ammonia gas. As a result, the first SCR catalyst 142 efficiently causes a reduction reaction.

[0106] <Modifications> The modifications described below may be applied in combination.

[0107] (1) Modification 1 The first SCR unit 10, the DOC unit 40, the DPF unit 50, and the second SCR unit 70 constituting the exhaust gas purification device 1 may be disposed in any positions with their internal spaces connected. For example, the exhaust gas purification device 1 may be configured such that the first SCR unit 10, the DOC unit 40, the DPF unit 50, and the second SCR unit 70, which are cylindrical when viewed in the X-axis direction, are disposed in parallel when viewed in the X-axis direction. Alternatively, the first SCR unit 10, the DOC unit 40, the DPF unit 50, and the second SCR unit 70 may be disposed alternately along the X-axis direction.

[0108] (2) Modification 2 In the first SCR unit 10 and the second SCR unit 70, the SCR catalyst 12 and the SCR catalyst 72 may be replaced with a storage catalyst.

[0109] (3) Modification 3 The position at which the fuel injection device 30 is provided is not limited to the position facing the side surface 86 of the first connecting pipe 20 where the major axis opening 82b is provided. For example, the fuel injection device 30 may be provided so as to face the opening on the one end 84 side of the main body 81 (so as to face the elliptical cross section of the main body 81). The fuel injection device 30 may also be provided so as to face the minor axis opening 82a.

[0110] Furthermore, the position where the fuel injection device 30 is provided is not limited to the first connecting pipe 20. The fuel injection device 30 may be provided at any position upstream of the fuel mixing device 80, which is provided upstream of the DOC unit 40 in the flow path.

[0111] Similarly, the position at which the urea water injection device 130 is provided is not limited to the position at the first connecting pipe 20 opposite the side surface 86 at which the longitudinal axis opening 82b is provided.

[0112] (4) Modification 4 The fuel mixing device 80 has the protrusion 83 at a position facing the minor axis opening 82 a on the inner circumferential surface of the main body 81. The protrusion 83 may also be provided on the inner circumferential surface of the main body 81 between the minor axis opening 82 a and the other end 85.

[0113] (5) Modification 5 In the second embodiment, the first connecting pipe 20 is attached to the case 111 so as to form a right angle with the DPF 52 when viewed in the Y-axis direction. As shown in FIG. 13 , the first connecting pipe 20 may be attached to the case 111 so as to form an angle θ with the DPF 52 other than a right angle when viewed in the Y-axis direction.

[0114] DESCRIPTION OF SYMBOLS 1...Exhaust gas purification device 30...Fuel injection device (additive injection section) 42...Oxidation catalyst (catalyst) 80...Fuel mixing device (additive mixing device) 81...Main body 82...Opening 83...Convex section 84...One end 85...Other end 86...Side 100...Diesel engine (internal combustion engine) 101...Exhaust gas purification device 130...Urea water injection device (additive injection section) 142...First SCR catalyst (catalyst)

Claims

1. An additive mixing device that is provided in a flow path of exhaust gas emitted from an internal combustion engine and is provided downstream of an additive injection unit that injects an additive into the flow path, the additive mixing device comprising: a tubular main body having a circular, elliptical or oblong cross section; and at least one opening provided in a side surface of the main body.

2. The additive mixing device according to claim 1, wherein the opening is provided at an upstream end of the main body in the direction in which the exhaust gas flows through the main body.

3. The additive mixing device according to claim 1, wherein the length of the opening is shorter than the length from one end to the other end of the main body.

4. The additive mixing device according to claim 1, further comprising a protrusion provided on the inside of said main body at a position opposite said opening.

5. The additive mixing device according to claim 4, wherein the cross section of the main body at the location where the protrusion is provided is ω-shaped.

6. An exhaust purification device comprising: the additive mixing device according to any one of claims 1 to 5; the additive injection unit; and a catalyst arranged downstream of the additive mixing device in the flow path.

7. An exhaust purification device comprising: the additive mixing device according to claim 4 or 5; the additive injection unit; and a catalyst arranged downstream of the additive mixing device in the flow path, wherein the additive injection unit injects the additive toward a portion of the side surface of the main body where the opening is not provided, and the convex portion is biasedly arranged inside the main body so as to be closer to the portion of the main body where the additive is injected.

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