Exhaust purification device

Abstract

The invention provides an exhaust gas purification device capable of improving stirring performance of urea water and properly cooling an injection device. An exhaust gas purification device (1) for purifying nitrogen oxides in exhaust gas is provided with: an exhaust pipe (10) through which exhaust gas discharged from an engine (100) flows; a catalyst reactor (11) (catalyst) that is provided in the exhaust pipe (10) and that reduces nitrogen oxides in the exhaust gas; a through pipe (12) provided so as to pass through the exhaust pipe (10); and an injection device (13) that is provided inside the through pipe (12) and injects a reducing agent that reduces the exhaust gas into the exhaust pipe (10).

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification device for purifying nitrogen oxides in exhaust gas. Background Art

[0002] Conventionally, an exhaust gas purification device reduces nitrogen oxides contained in exhaust gas discharged from an engine to purify the exhaust gas, and is configured by a so-called SCR system. The exhaust gas purification device is configured to provide a catalyst in an exhaust passage of the exhaust gas and supply urea to the exhaust gas, thereby reducing nitrogen oxides accumulated in the catalyst.

[0003] In addition, for example, in the exhaust gas purification device disclosed in Patent Document 1, a urea water injection nozzle is provided in a portion of an exhaust pipe on the downstream side of an exhaust switching valve. The double tube of the urea water injection nozzle is arranged such that the downstream side is inside the exhaust pipe and the upstream side is outside the exhaust pipe, and an air nozzle of the urea water injection nozzle is arranged on the downstream side of a liquid nozzle in such a manner that the upstream side end abuts against the downstream side end of the double tube. That is, in the exhaust gas purification device, a urea water injection nozzle protruding from a wall portion of the exhaust pipe toward the central portion is provided.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-234793

[0005] In the exhaust gas purification device, in order to suppress thermal damage to urea water caused by injection devices such as an injection valve and an injection nozzle for injecting urea water being exposed to exhaust gas, it is necessary to cool the injection devices. In the urea water injection nozzle disclosed in Patent Document 1, a cooling method using air for injecting urea water is applied to cool the nozzle. However, depending on the structure of the exhaust gas purification device, it may not be possible to appropriately cool the injection devices. For example, in an exhaust gas purification device using a non-air injection device (airless method) for injecting urea water, it is not possible to cool the injection devices with air, so it is necessary to have another cooling mechanism. In addition, due to the arrangement of the injection devices and the cooling mechanism in the exhaust pipe, the agitation of the exhaust gas and urea water may decrease. Summary of the Invention

[0006] An object of the present invention is to provide an exhaust gas purification device capable of enhancing the agitation of urea water and appropriately cooling injection devices.

[0007] To solve the above problems, an exhaust gas purification device of the present invention is an exhaust gas purification device for purifying nitrogen oxides in exhaust gas, characterized by including: an exhaust pipe through which the exhaust gas discharged from the engine flows; a catalyst provided in the exhaust pipe for reducing the nitrogen oxides in the exhaust gas; a through pipe provided to penetrate the exhaust pipe; and an injection device provided inside the through pipe for injecting a reducing agent for reducing the exhaust gas into the inside of the exhaust pipe.

[0008] According to the present invention, an exhaust gas purification device capable of improving the agitation of urea water and appropriately cooling an injection device can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic view showing an exhaust gas purification device according to an embodiment of the present invention and an engine to which the exhaust gas purification device is applied.

[0010] Figure 2 It is a perspective view showing an exhaust pipe and a through pipe in the exhaust gas purification device according to an embodiment of the present invention.

[0011] Figure 3 It is a front view showing an exhaust pipe and a through pipe in the exhaust gas purification device according to an embodiment of the present invention.

[0012] Figure 4 It is a front view showing an exhaust pipe and a through pipe in the exhaust gas purification device according to another example of an embodiment of the present invention.

[0013] Figure 5 It is a front view showing an exhaust pipe and a through pipe in the exhaust gas purification device according to another example of an embodiment of the present invention.

[0014] Figure 6 It is a front view showing an exhaust pipe and a through pipe in the exhaust gas purification device according to another embodiment of the present invention.

[0015] DESCRIPTION OF REFERENCE NUMERALS

[0016] 1... Exhaust gas purification device; 10... Exhaust pipe; 10a... Straight pipe portion; 11... Catalyst reactor (catalyst); 12... Through pipe; 13... Injection device; 14... Reducing agent supply device; 15... Cooling medium supply device; 16... Reducing agent supply pipe; 17... Reducing agent tank; 18... Cooling medium supply pipe; 19... Air supply portion; 20... Side wall portion; 20a... Straight portion; 20b... Bent portion; 20c... Protrusion; 21... Upstream side portion; 22... Downstream side portion; 100... Engine; 101... Exhaust port. DETAILED DESCRIPTION OF THE INVENTION

[0017] An exhaust gas purification device 1 according to an embodiment of the present invention will be described with reference to the drawings. As Figure 1 shown, the exhaust gas purification device 1 is applied to an engine 100 and purifies the exhaust gas discharged from the engine 100. Figure 1 It is an example showing that the exhaust gas purification device 1 is applied to an engine 100 that discharges exhaust gas in the vertical direction.

[0018] The engine 100 is configured to have a plurality of cylinders composed of a cylinder head and a cylinder block. The engine 100 has an intake port (not shown) for sucking fuel gas and an exhaust port 101 for discharging exhaust gas in a specified exhaust direction (e.g., upward). An exhaust pipe 10 of the exhaust purification device 1 is connected to the exhaust port 101, and the engine 100 discharges exhaust gas to the exhaust pipe 10 of the exhaust purification device 1 via the exhaust port 101.

[0019] The exhaust purification device 1 is composed of a so-called SCR (selective catalytic reduction) system that purifies exhaust gas by reducing nitrogen oxides (NOx) in the exhaust gas. For example, as Figure 3 shown, the exhaust purification device 1 includes an exhaust pipe 10, a catalyst reactor 11 (catalyst), a through pipe 12, an injection device 13, a reductant supply device 14, and a cooling medium supply device 15.

[0020] The main part of the exhaust purification device 1 (exhaust pipe 10, catalyst reactor 11, through pipe 12, injection device 13) is provided at the exhaust port 101 of the engine 100, for example, disposed above the exhaust port 101. The reductant supply device 14 and the cooling medium supply device 15 can be provided separately from the main part of the exhaust purification device 1. As Figure 1 shown, the reductant supply device 14 and the cooling medium supply device 15 can be integrally formed as a unit, or can be formed relatively independently.

[0021] The exhaust pipe 10 allows the exhaust gas discharged from the engine 100 to flow in a specified exhaust direction (e.g., upward). The exhaust pipe 10 is connected to the upper side of the exhaust port 101 of the engine 100. The exhaust pipe 10 includes a straight pipe portion 10a formed in a straight line.

[0022] The catalyst reactor 11 causes the exhaust gas mixed with a reductant such as aqueous urea to contact the catalyst, promotes the reduction reaction of selectively reducing the nitrogen oxides contained in the exhaust gas to nitrogen and water, and purifies the exhaust gas. The catalyst reactor 11 includes a catalyst such as a NOx reduction catalyst and is connected to the exhaust pipe 10 on the downstream side in the exhaust direction. The catalyst reactor 11 introduces the exhaust gas that is mixed with the reductant injected from the injection device 13 and flows in the exhaust pipe 10, and causes it to contact the catalyst.

[0023] The through pipe 12 is disposed in the exhaust pipe 10 at a position upstream of the catalyst reactor 11 (catalyst) in the exhaust direction, and is disposed to pass through the radial center of the exhaust pipe 10 and penetrate in the radial direction (direction orthogonal to the exhaust direction) of the exhaust pipe 10. The through pipe 12 is preferably disposed in a straight pipe portion 10a formed in a straight line in the exhaust pipe 10. The through pipe 12 is a cylindrical member with both ends open, and both ends of the through pipe 12 are connected to the openings provided on two opposed side surfaces of the exhaust pipe 10 by welding or the like, so that the through pipe 12 is disposed inside the exhaust pipe 10. The exhaust gas flowing inside the exhaust pipe 10 flows on the outer peripheral surface side of the through pipe 12.

[0024] The through pipe 12 has a substantially elliptical cross-sectional shape that is long in the exhaust direction, and is formed such that the cross-sectional shape is axisymmetric with respect to its major axis and has this cross-sectional shape uniformly in the through direction. The through pipe 12 is formed to have side surfaces with a streamline shape without corners.

[0025] The through pipe 12 has a pair of side wall portions 20 extending in the exhaust direction, an upstream side portion 21 disposed on the upstream side in the exhaust direction and straddling the pair of side wall portions 20, and a downstream side portion 22 disposed on the downstream side in the exhaust direction and straddling the pair of side wall portions 20, forming a substantially elliptical cross-sectional shape. The through pipe 12 is configured such that in the width direction orthogonal to the through direction and the major axis of the cross-sectional shape, the two ends of the downstream side portion 22 are located inside the upstream side portion 21.

[0026] The upstream side portion 21 of the through pipe 12 is formed, for example, to have a semicircular or semi-elliptical arc-shaped cross section that bulges toward the upstream side in the exhaust direction, so that the exhaust gas flowing from the upstream side flows to the outer peripheral surface side of the pair of side wall portions 20.

[0027] The pair of side wall portions 20 of the through pipe 12 are formed to bend in a streamline shape in such a way that the width of the cross-sectional shape decreases toward the downstream side in the exhaust direction. The pair of side wall portions 20 are formed, for example, to bend with a smaller curvature than the upstream side portion 21. For example, the side wall portion 20 is formed to have a straight portion 20a that is continuous from the end of the upstream side portion 21 and extends in the exhaust direction, and a bent portion 20b that is continuous from the downstream end of the straight portion 20a and bends toward the center side in the width direction of the cross-sectional shape. The side wall portion 20 causes the exhaust gas flowing from the upstream side to flow along the outer peripheral surface, forming a flow toward the downstream side and toward the center side in the width direction of the cross-sectional shape.

[0028] The downstream side portion 22 of the through pipe 12 has a flat portion 22a orthogonal to the exhaust direction and is formed to be continuous from the downstream ends of the pair of side wall portions 20.

[0029] The through pipe 12 is formed, for example, by joining components of the same shape by welding or the like. Welding positions are provided at the upstream side portion 21 and the downstream side portion 22, so that a streamline-shaped side surface without corners can be formed without providing a build-up portion of welding on the side surface.

[0030] With the structure of the through pipe 12 described above, the exhaust gas flowing on the outer peripheral surface side of the through pipe 12 branches to both sides in the width direction from the upstream side portion 21, and then flows continuously toward the center in the width direction along a pair of side wall portions 20 having a streamline shape toward the center in the width direction, and merges on the downstream side of the downstream side portion 22 without forming a dead water area such as a vortex-shaped stagnant area. In other words, the through pipe 12 is formed with a pair of side wall portions 20 having a streamline shape so that a dead water area is not formed on the downstream side of the downstream side portion 22.

[0031] The injection device 13 is disposed inside the through pipe 12 in such a manner that only the front end having the ejection holes is exposed inside the exhaust pipe 10. For example, the injection device 13 is composed of an injection nozzle, an injection valve, and the like. The injection device 13 is connected to the reducing agent supply device 14 and injects a reducing agent such as urea water of the reduced exhaust gas supplied from the reducing agent supply device 14 into the exhaust pipe 10. In addition, the injection device 13 is preferably arranged to inject the reducing agent at a position where the exhaust gas merges on the downstream side of the downstream side portion 22 of the through pipe 12.

[0032] The reducing agent supply device 14 is connected to a control device (not shown) and injects the reducing agent through the injection device 13 according to an instruction signal from the control device. The injection device 13 is cooled by a cooling medium such as air flowing inside the through pipe 12.

[0033] The injection device 13 is disposed inside the through pipe 12 on the downstream side in the exhaust direction between a pair of side wall portions 20, for example, disposed at the downstream side portion 22 of the through pipe 12, specifically, disposed at the flat portion 22a of the downstream side portion 22. The injection device 13 is arranged to face the downstream side in the exhaust direction, for example, to inject a reducing agent toward the catalyst reactor 11 (catalyst) disposed on the downstream side. For example, one injection device 13 may be provided at the center in the through direction of the through pipe 12, or a plurality of injection devices 13 may be provided at intervals in the through direction of the through pipe 12. Further, in the present embodiment, since the injection device 13 is disposed in the straight pipe portion 10a of the exhaust pipe 10 and the catalyst reactor 11 is disposed at the downstream end of the straight pipe portion 10a, the injection device 13 is configured to inject a reducing agent toward the catalyst reactor 11, but the present invention is not limited to this embodiment. Or, in other examples, the catalyst reactor 11 may be disposed in the bent pipe of the exhaust pipe 10 instead of the straight pipe portion 10a. Specifically, it may be configured such that a bent pipe is connected to the downstream end of the straight pipe portion 10a and the catalyst reactor 11 is connected to the downstream end of the bent pipe. In this case, the injection device 13 may be disposed in the straight pipe portion 10a or may be disposed in the bent pipe. That is, the reducing agent may be injected toward the downstream side in the exhaust direction in the exhaust pipe 10.

[0034] The reducing agent supply device 14 is connected to the injection device 13 via the reducing agent supply pipe 16, sucks the reducing agent stored in the reducing agent tank 17 by a pump or the like, and supplies it to the injection device 13 via the reducing agent supply pipe 16.

[0035] The cooling medium supply device 15 is connected to the injection device 13 via the cooling medium supply pipe 18, and supplies a cooling medium such as air supplied from the air supply unit 19 to the injection device 13 via the cooling medium supply pipe 18. For example, the cooling medium supply device 15 may introduce air cooled by an intercooler (not shown) and supply it as the cooling medium. Or, the cooling medium supply device 15 may supply cooling water as the cooling medium instead of air.

[0036] As described above, according to the present invention, the exhaust gas purification device 1 for purifying nitrogen oxides in exhaust gas includes: an exhaust pipe 10 through which exhaust gas discharged from the engine 100 flows in a predetermined exhaust direction; a catalyst reactor 11 (catalyst) provided in the exhaust pipe 10 to reduce nitrogen oxides in the exhaust gas; a through pipe 12 disposed at a position upstream of the catalyst reactor 11 in the exhaust direction and provided to penetrate the exhaust pipe 10 in a direction orthogonal to the exhaust direction; and an injection device 13 disposed inside the through pipe 12 to inject a reducing agent for reducing exhaust gas into the exhaust pipe 10.

[0037] Accordingly, in the exhaust gas purification device 1 of the present invention, by using the through pipe 12, the injection device 13 for injecting the reducing agent can be easily arranged and maintained at the central position of the exhaust pipe 10. In addition, by using the through pipe 12, the reducing agent can be injected at the central position of the exhaust pipe 10 without inserting most of the injection device 13 into the interior of the exhaust pipe 10. Moreover, by using the through pipe 12 with both ends penetrating, the air permeability inside the through pipe 12 can be improved, the influence of radiant heat from the wall surface of the through pipe 12 can be suppressed, heat accumulation inside the through pipe 12 can be inhibited, the cooling performance at the position of the injection device 13 can be improved, and thermal damage to the injection device 13 can be suppressed.

[0038] In addition, in the exhaust gas purification device 1 of the present invention, the injection device 13 is arranged to inject the reducing agent toward the catalyst reactor 11 on the downstream side in the exhaust gas direction inside the through pipe 12.

[0039] Accordingly, the reducing agent can be injected into the exhaust gas flowing toward the catalyst reactor 11, so that the agitation efficiency of the reducing agent can be improved, and the generation of deposits can be suppressed.

[0040] In addition, in the exhaust gas purification device 1 of the present invention, the through pipe 12 has a planar portion 22a orthogonal to the exhaust gas direction on the downstream side in the exhaust gas direction, and the injection device 13 is arranged on the planar portion 22a of the through pipe 12.

[0041] Accordingly, the accuracy of the injection direction of the injection device 13 can be improved, the agitation efficiency of the reducing agent can be increased, and the generation of deposits can be suppressed.

[0042] In addition, in the exhaust gas purification device 1 of the present invention, the through pipe 12 is arranged in a straight pipe portion 10a formed in a straight line in the exhaust pipe 10.

[0043] Accordingly, the reducing agent can be injected into the exhaust gas advancing toward the catalyst reactor 11, so that the attachment of the reducing agent to the exhaust pipe 10 and the through pipe 12 can be suppressed.

[0044] In addition, in the exhaust gas purification device 1 of the present invention, the through pipe 12 has a pair of side wall portions 20 extending in the exhaust gas direction, has a substantially elliptical cross-sectional shape that is long in the exhaust gas direction, and the pair of side wall portions 20 are formed to be curved in a streamline shape so as to reduce the width of the cross-sectional shape toward the downstream side in the exhaust gas direction.

[0045] Thus, it is possible to suppress the exhaust gas flowing on the outer peripheral surface side of the pair of side wall portions 20 from peeling off from the pair of side wall portions 20, and it is possible to make the exhaust gas flow continuously along the pair of side wall portions 20 toward the center side in the width direction, and it is possible to make the exhaust gas merge so that no dead water areas such as vortex-shaped stagnant regions are formed on the downstream side. Therefore, regardless of the penetration power of the injection device 13, the reducing agent injected from the injection device 13 can be efficiently mixed with the exhaust gas and supplied to the catalyst reactor 11.

[0046] In addition, in the exhaust gas purification device 1 of the present invention, the through pipe 12 has an upstream side portion 21 with an arc-shaped cross section at a position upstream of the pair of side wall portions 20 in the exhaust gas direction, and the pair of side wall portions 20 are formed to bend with a curvature smaller than that of the upstream side portion 21.

[0047] Thus, the performance of making the exhaust gas flow continuously along the pair of side wall portions 20 toward the center side in the width direction can be improved.

[0048] In addition, in the exhaust gas purification device 1 of the present invention, the through pipe 12 is formed such that its cross-sectional shape is axisymmetric with respect to the central axis extending in the exhaust gas direction.

[0049] Thus, inside the exhaust pipe 10, the flow of the exhaust gas on the outer peripheral surface side of the through pipe 12 can be made symmetric, and the flow of the injected reducing agent toward the inner wall surface side of the exhaust pipe 10 can be suppressed.

[0050] In addition, in the above-described embodiment, an example in which the pair of side wall portions 20 constituting the streamline shape of the side surface of the through pipe 12 has a straight portion 20a that is continuous from the end of the upstream side portion 21 and extends in the exhaust gas direction has been described, but the present invention is not limited to this example. In another example, as Figure 4 shown, the pair of side wall portions 20 may also be formed such that the bent portion 20b constituting the streamline shape is continuous from the end of the upstream side portion 21 and does not have the straight portion 20a.

[0051] In addition, in the above-described embodiment, an example in which the through pipe 12 has a downstream side portion 22 including a flat surface portion 22a orthogonal to the exhaust gas direction has been described, but the present invention is not limited to this example. In another example, as Figure 5 shown, the through pipe 12 may also be configured such that the pair of bent portions 20b are joined at the center in the width direction and do not have the downstream side portion 22. In this case, the injection device 13 is preferably provided at the joining portion of the pair of bent portions 20b.

[0052] And, in another embodiment, as Figure 6As shown, the through pipe 12 may also have a protrusion 20c that protrudes outward in the width direction on at least one of the pair of side wall portions 20. The protrusion 20c functions as a vortex generator on the outer side of the side wall portion 20. After the exhaust gas is separated from the side wall portion 20 due to the protrusion 20c, a swirling flow is generated toward the downstream side in the exhaust direction and toward the center in the width direction. The protrusion 20c is provided, for example, at a transition portion where the straight portion 20a transitions to the curved portion 20b in the side wall portion 20. In this case, the side wall portion 20 where the protrusion 20c is provided may not be in a streamline shape. One protrusion 20c may be provided at the center in the through direction, or a plurality of protrusions 20c may be provided at intervals in the through direction.

[0053] According to such another embodiment, by generating a vortex acting on the exhaust gas flowing on the outer peripheral surface side of the side wall portion 20, it is possible to suppress the peeling of the exhaust gas from the side wall portion 20, enable the exhaust gas to flow toward the center in the width direction on the downstream side of the through pipe 12, and enable the exhaust gas to merge on the downstream side without forming a swirling stagnant region or other dead water regions. Therefore, regardless of the penetration power of the injection device 13, the reducing agent injected from the injection device 13 can be efficiently mixed with the exhaust gas and supplied to the catalyst reactor 11.

[0054] In addition, the present invention can be appropriately modified within the scope not violating the gist or idea of the invention that can be read from the entire claims and the specification, and the exhaust gas purification device accompanied by such a modification is also included in the technical idea of the present invention.

[0055] 〔Notes on the Invention〕

[0056] Hereinafter, a summary of the invention extracted from the above embodiments will be noted. In addition, each structure and each processing function described in the following notes can be arbitrarily combined in an alternative manner.

[0057] <Note 1>

[0058] An exhaust gas purification device for purifying nitrogen oxides in exhaust gas, comprising:

[0059] An exhaust pipe through which the exhaust gas discharged from the engine flows;

[0060] A catalyst provided in the exhaust pipe to reduce the nitrogen oxides in the exhaust gas;

[0061] A through pipe provided to penetrate the exhaust pipe; and

[0062] An injection device provided inside the through pipe to inject a reducing agent for reducing the exhaust gas into the inside of the exhaust pipe.

[0063] <Note 2>

[0064] The exhaust gas purification device according to Note 1, wherein,

[0065] The injection device is arranged to inject the reducing agent downstream in the exhaust gas direction.

[0066] <Note 3>

[0067] The exhaust gas purification device according to Note 1 or 2, wherein,

[0068] The through pipe has a flat portion on the downstream side in the exhaust gas direction,

[0069] The injection device is arranged on the flat portion.

[0070] <Note 4>

[0071] The exhaust gas purification device according to any one of Notes 1 to 3, wherein,

[0072] The through pipe is arranged in a straight pipe portion formed linearly in the exhaust pipe.

[0073] <Note 5>

[0074] The exhaust gas purification device according to any one of Notes 1 to 4, wherein,

[0075] The through pipe has a pair of side wall portions extending in the exhaust gas direction and has a substantially elliptical cross-sectional shape that is longer in the exhaust gas direction,

[0076] The pair of side wall portions are formed to reduce the width of the cross-sectional shape toward the downstream side in the exhaust gas direction.

[0077] <Note 6>

[0078] The exhaust gas purification device according to Note 5, wherein,

[0079] The through pipe has an upstream side portion with an arc-shaped cross-section at a position upstream of the pair of side wall portions,

[0080] The pair of side wall portions are formed to bend with a smaller curvature than the upstream side portion.

[0081] <Note 7>

[0082] The exhaust gas purification device according to any one of Notes 1 to 6, wherein,

[0083] The through pipe is formed such that the cross-sectional shape is axisymmetric with respect to the central axis extending in the exhaust gas direction.

Claims

1. An exhaust gas purification device for purifying nitrogen oxides in exhaust gas, characterized in that: have: an exhaust pipe for circulating the exhaust gas discharged from the engine; A catalyst, disposed in the exhaust pipe, for reducing the nitrogen oxides in the exhaust gas; a through pipe, configured to penetrate the exhaust pipe; and The injection device is provided inside the through pipe and injects a reducing agent for reducing the exhaust gas into the exhaust pipe.

2. The exhaust gas purification device according to claim 1, characterized in that: The injection device is configured to inject the reducing agent toward the downstream side in the exhaust direction.

3. The exhaust gas purification device according to claim 1, characterized in that: The through pipe has a flat surface on the downstream side in the exhaust direction. The injection device is disposed on the planar portion.

4. The exhaust gas purification device according to claim 1, characterized in that: The through pipe is provided in a straight pipe portion formed in a linear shape in the exhaust pipe.

5. The exhaust gas purification device according to claim 1, characterized in that: The through pipe has a pair of side wall portions extending in the exhaust direction and has a substantially elliptical cross-sectional shape that is long in the exhaust direction. The pair of side wall portions are formed so as to reduce the width of the cross-sectional shape toward the downstream side in the exhaust direction.

6. The exhaust gas purification device according to claim 5, characterized in that: The through pipe has an upstream side portion having an arc-shaped cross section at a position closer to the upstream side than the pair of side wall portions. The pair of side wall portions are formed to be curved with a smaller curvature than the upstream side portion.

7. The exhaust gas purification device according to claim 1, characterized in that: The through pipe is formed so that the cross-sectional shape is axisymmetric with respect to the central axis extending in the exhaust direction.

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