Marine internal combustion engine with SCR device

Abstract

This invention discloses a marine internal combustion engine with an SCR device. The engine (1) includes a main engine (10) that propels the ship in a predetermined propulsion direction and an SCR device (90) for denitrifying the exhaust gas from the main engine (10). The SCR device (90) has: a mixer (92) housing a nozzle (92b) for injecting a reducing agent into the exhaust gas, and a reactor (94) arranged downstream of the mixer (92) and contacting the exhaust gas and the reducing agent with a catalyst (94b). The mixer (92) is arranged along the front surface (10a) of the main engine (10) and is configured to extend from the upper side to the lower side in the height direction of the main engine (10). In the marine internal combustion engine with the SCR device, the exhaust gas and the reducing agent are uniformly mixed.

Description

Technical Field

[0001] This disclosure relates to a marine internal combustion engine with an SCR device. Background Technology

[0002] For example, Patent Document 1 discloses an internal combustion engine with an exhaust aftertreatment system. This exhaust aftertreatment system is a so-called Selective Catalytic Reduction (SCR) exhaust aftertreatment system, which includes, from the upstream side, an inlet device, an inlet section, and a reaction chamber. The inlet device introduces a reducing agent into the exhaust gas, the inlet section is used to mix the reducing agent introduced from the inlet device with the exhaust gas, and the reaction chamber is equipped with an SCR catalytic converter.

[0003] In this case, the inlet section described in Patent Document 1 is arranged above the internal combustion engine, and the inlet section is formed to extend in the front-rear direction coaxially with the exhaust manifold of the internal combustion engine. Furthermore, the inlet device described in that document is configured to inject a reducing agent rearward in the front-rear direction.

[0004] Furthermore, Patent Document 2 discloses an internal combustion engine including an SCR device (SCR catalyst system) as another example of an internal combustion engine. The SCR device includes a mixing pipeline and an SCR reactor sequentially from the upstream side, wherein the mixing pipeline mixes urea into the exhaust gas and vaporizes the urea, and the SCR reactor reduces the exhaust gas mixed with the urea.

[0005] Here, similar to the introduction section involved in Patent Document 1 above, the mixing pipeline involved in Patent Document 2 above is arranged above the internal combustion engine and is formed to extend along the front-rear direction of the internal combustion engine.

[0006] Patent Document 1: Japanese Patent Publication No. 6803790

[0007] Patent Document 2: Japanese Patent Publication No. 6713745 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, as in Patent Documents 1 and 2 mentioned above, when the pipeline (inlet section, mixing pipeline) for mixing reducing agents such as urea is extended in the front-to-back direction, the reducing agent supplied to the pipeline will fall due to gravity.

[0010] Therefore, compared to the upper side in the direction of gravity, the reducing agent supplied to the pipeline is distributed more towards the lower side, which may lead to uneven mixing of the exhaust gas and the reducing agent. Uneven mixing of the exhaust gas and the reducing agent is undesirable for the SCR unit to function properly.

[0011] The technology disclosed herein was developed to solve the aforementioned technical problems, with the aim of enabling a uniform mixing of exhaust gas and reducing agent in a marine internal combustion engine equipped with an SCR device.

[0012] Technical solutions for solving technical problems

[0013] The first aspect of this disclosure relates to a marine internal combustion engine with an SCR device. The marine internal combustion engine with an SCR device includes a main engine and an SCR device, the main engine propelling the ship in a predetermined propulsion direction, the SCR device denitrifying exhaust gas from the main engine, the SCR device having a mixer and a reactor, a nozzle for injecting a reducing agent into the exhaust gas being housed in the mixer, and the reactor being arranged downstream of the mixer and contacting the exhaust gas and the reducing agent with a catalyst.

[0014] Furthermore, according to the first aspect described above, the mixer is arranged along the outer surface of the main engine facing the propulsion direction, and is configured to extend from the upper side toward the lower side in the height direction of the main engine.

[0015] According to the first aspect mentioned above, the direction of gravity acting on the reducing agent ejected from the nozzle is consistent with the direction of extension of the mixer. In other words, the direction of gravity acting on the reducing agent is orthogonal to the cross-section of the mixer. This prevents unevenness caused by gravity, thus enabling uniform mixing of the exhaust gas and the reducing agent.

[0016] Furthermore, compared to a structure that extends the mixer upwards, extending the mixer downwards, as described in the first aspect above, contributes to the overall compactness of the main engine and SCR unit. This allows the SCR unit to be installed on various ship types, thereby facilitating the optimization of the SCR unit for each ship type.

[0017] According to a second aspect of this disclosure, the nozzle may also spray the reducing agent downwards in the height direction from a central position observed in a cross-section perpendicular to the height direction of the mixer.

[0018] The direction of gravity acting on the reducing agent becomes orthogonal to the cross-section. This situation complements the situation where the reducing agent is sprayed from the central position as described in the second aspect above, and does not lead to unevenness caused by gravity, thereby enabling the exhaust gas and reducing agent to mix uniformly.

[0019] According to a third aspect of this disclosure, the mixer may also have a mixing tube for receiving the nozzle, the mixing tube being formed as a cylinder having a central axis extending along the height direction, and the nozzle orifice being arranged to coincide with the central axis in the cross-section.

[0020] According to the third aspect mentioned above, by arranging the nozzle so that its injection port coincides with the central axis of the mixing pipe, the reducing agent can be injected more isotropically. This is effective in ensuring uniform mixing of exhaust gas and reducing agent.

[0021] According to a fourth aspect of this disclosure, the main engine may also have a plurality of cylinders and an exhaust manifold, the plurality of cylinders being arranged along the propulsion direction, the exhaust manifold being connected to the plurality of cylinders and extending along the propulsion direction, and the mixer being arranged to face the propulsion direction and be aligned with the exhaust manifold.

[0022] According to the fourth aspect mentioned above, compared to arranging the mixer and exhaust manifold separately along the width of the ship, arranging the mixer and exhaust manifold side by side along the propulsion direction allows for a simpler shape in the pipe connecting the mixer and exhaust manifold. This facilitates the compactness of the SCR unit.

[0023] According to a fifth aspect of this disclosure, the upper end of the mixer may also be arranged in the height direction at a position lower than that of the exhaust manifold.

[0024] According to the fifth aspect above, a pipe connecting the mixer and the exhaust manifold can be constructed without bending upwards in the vertical direction. Since an upward bend is not required, the portion of the pipe extending along the mixing direction (downwards) can be shortened. This facilitates the compactness of the SCR device.

[0025] According to a sixth aspect of this disclosure, the reactor is arranged adjacent to the mixer along the outer surface and configured to extend from the lower side toward the upper side in the height direction.

[0026] According to the sixth aspect mentioned above, the reactor and mixer are arranged adjacent to each other along the outer surface. This allows for efficient use of the space near the outer surface of the main engine, thereby contributing to the compactness of the SCR unit.

[0027] According to the seventh aspect of this disclosure, the marine internal combustion engine with SCR device may also include a turbocharger disposed above the main engine and supplying gas purified by the reactor, the upper end of the reactor being disposed below the turbocharger in the height direction.

[0028] According to the seventh aspect above, a pipe connecting the reactor and the booster can be constructed without bending downwards in the vertical direction. Since a downward bend is not required, the portion of the pipe extending along the reactor's extension direction (above) can be shortened. This facilitates the compactness of the SCR unit.

[0029] Furthermore, as described in the seventh aspect above, by arranging the reactor below the booster, the soot accumulated on the catalyst inside the reactor is less likely to reach the booster under gravity. This is effective in maintaining the performance of the reactor and thus the SCR unit.

[0030] The effects of the invention

[0031] As explained above, according to this disclosure, in a marine internal combustion engine equipped with an SCR device, exhaust gas and reducing agent can be mixed uniformly. Attached Figure Description

[0032] Figure 1 This is a system diagram that exemplarily illustrates a simplified structure of a marine internal combustion engine;

[0033] Figure 2 This is a front view showing a specific example of a marine internal combustion engine;

[0034] Figure 3 This is a left-side view showing a specific example of a marine internal combustion engine;

[0035] Figure 4 This is a top view showing a specific example of a marine internal combustion engine;

[0036] Figure 5 This is a perspective view illustrating the layout of an SCR device;

[0037] Figure 6 This is an exemplary longitudinal sectional view showing the structure of the mixer;

[0038] Figure 7 This is a cross-sectional view illustrating the structure of the mixer;

[0039] Figure 8 This is a perspective view showing a specific example of a hybrid mechanism;

[0040] Figure 9 This is an exemplary longitudinal sectional view showing the structure of the reactor;

[0041] Figure 10 This shows a modified example of an SCR device. Figure 5 Corresponding diagram;

[0042] Figure 11A This is a first variant example of a mixer shown. Figure 6 Corresponding diagram;

[0043] Figure 11B This is a second variation of the mixer shown. Figure 6 Corresponding diagram;

[0044] Figure 11C This is a third variation of the mixer shown. Figure 6 The corresponding diagram.

[0045] Symbol explanation:

[0046] 1-Engine (Marine Internal Combustion Engine); 5-Turbocharger; 10-Main Engine; 10a-Front Surface (Outer Surface); 15-Cylinder; 30-Intake Passage; 40-Exhaust Passage; 42-Exhaust Manifold; 90-SCR Device; 92-Mixer; 92a-Mixing Pipe; 92b-Nozzle; 921-Inlet; 94-Reactor; 94b-Catalyst; Pc-Central Shaft. Detailed Implementation

[0047] The embodiments of this disclosure will now be described with reference to the accompanying drawings. It should be noted that the following description is illustrative. Figure 1 This is a system diagram illustrating, by way of example, a simplified structure of a marine internal combustion engine (hereinafter referred to as "engine") 1. Figure 2 , Figure 3 as well as Figure 4 These are the front view, left side view, and top view of a specific example of engine 1.

[0048] It should be noted that in the following description, the terms forward, aft, left, right, up, and down, with the ship as the reference point, will be simply referred to as forward, aft, left, right, up, and down, respectively. Here, in terms of the forward / backward direction, the direction of propulsion of the ship is called forward, and the opposite direction is called aft. The forward / backward direction is also the length direction of the output shaft of engine 1 (crankshaft 16, described later). In terms of the left / right direction, the left side when viewing the ship from the front is called left, and the right side is called right. The left / right direction is also the width direction of the ship. The up / down direction is also the up / down direction of the ship, engine 1, and the main engine 10, described later, and is also referred to as the "height direction."

[0049] Engine 1 is an inline multi-cylinder marine diesel engine comprising multiple cylinders 15. Engine 1 is configured as a direct-flow scavenging two-stroke cycle engine and is installed on large vessels such as tankers, container ships, and car carriers. The output shaft of engine 1, i.e., crankshaft 16, is connected to the ship's propeller (not shown) via a drive shaft (not shown). When engine 1 operates, its output is transmitted to the propeller, thereby propelling the ship.

[0050] In particular, in order to achieve a long stroke in the engine 1 disclosed herein, the engine 1 disclosed herein is configured as a so-called crosshead internal combustion engine. The engine 1 includes a piston rod supporting the piston from below and a connecting rod connected to the crankshaft, the piston rod and the connecting rod being connected together by a crosshead, detailed illustrations omitted.

[0051] Engine 1 is also configured as a so-called turbocharged engine. That is, as... Figure 1 As shown, engine 1 is configured to include an exhaust turbocharger (hereinafter referred to as "turbocharger") that operates using exhaust gas flowing in exhaust passage 40.

[0052] Engine 1 is also configured as a so-called marine internal combustion engine with an SCR device. That is, as... Figure 1 As shown, the engine 1 involved in this embodiment is configured to include an SCR device 90 in addition to a main engine 10. The main engine 10 propels the ship in a predetermined propulsion direction (forward), and the SCR device 90 denitrates the exhaust gas from the main engine 10.

[0053] (1) Overall structure

[0054] The main components of engine 1 will now be described. In the following description, when outlining the general structure of engine 1, please refer to... Figure 1 When describing the specific layout of engine 1, refer to Figures 2-4 .

[0055] The main engine 10 has multiple (in) Figure 1 In the example shown, there are six cylinders 15. Pistons (not shown) are inserted into each cylinder 15 in a reciprocating manner. These cylinders 15 are arranged along the propulsion direction of the ship. That is, the cylinder bank direction in the main engine 10 is consistent with the aforementioned fore-and-aft direction.

[0056] Specifically, such as Figures 2-4 As shown, the main engine 10 involved in this embodiment includes a base 11, a frame 12, a cylinder jacket 13, and a cylinder head 14. The base 11 is installed on the floor of the ship's cabin, the frame 12 is arranged on the base 11, the cylinder jacket 13 is arranged on the frame 12, and the cylinder head 14 is fixed to the upper part of the cylinder jacket 13. The base 11, the frame 12, and the cylinder jacket 13 are fastened together by a plurality of tie bolts and nuts extending along the height direction.

[0057] Here, the engine block 11 is part of the crankcase that constitutes the engine 1, and the engine block 11 supports the crankshaft 16 to rotate freely. The frame 12 houses the connecting rod and crosshead. The cylinder water jacket 13 supports the cylinder liner, which serves as the inner cylinder. The cylinder head 14, together with the cylinder liner inserted into the cylinder water jacket 13, constitutes the cylinder 15.

[0058] like Figure 1 As shown, an intake passage 30 and an exhaust passage 40 are connected to the main engine 10. The intake passage 30 is used to deliver air into each cylinder 15, and the exhaust passage 40 is used to allow exhaust gas from each cylinder 15 to circulate.

[0059] In detail, in the intake passage 30, starting from the upstream side of the air flow direction, the following are arranged in sequence: compressor 5a, air cooler (not shown), scavenging box 31, and intake pipe 32 connecting scavenging box 31 to cylinder 15. Compressor 5a pressurizes the air by operating integrally with turbine 5b, and sends the pressurized air into cylinder 15 through scavenging box 31 and intake pipe 32.

[0060] On the other hand, in the exhaust passage 40, starting from the upstream side, the following are sequentially arranged: a first exhaust pipe 41, an exhaust manifold 42, an SCR device 90, a turbine 5b driven by and connected to the compressor 5a, a second exhaust pipe 43, and a boiler 44 for incinerating the exhaust gas (regarding the first exhaust pipe 41, see...). Figure 2 and Figure 4 ).

[0061] like Figure 4 As shown, a first exhaust pipe 41 is disposed on each cylinder 15 and connected to an exhaust manifold 42. The exhaust manifold 42 is configured to collect exhaust gases from each cylinder 15, as shown below. Figure 1 and Figure 4 As shown, the exhaust manifold 42 extends in the front-to-back direction. A first bypass pipe 45 is connected to one side of the exhaust manifold 42 (the left side in the illustration).

[0062] like Figure 1As shown, the SCR device 90, from the upstream side, sequentially comprises: a third exhaust pipe 91, a mixer 92, a fourth exhaust pipe 93, a reactor 94, and a fifth exhaust pipe 95. The third exhaust pipe 91 is connected to an exhaust manifold 42. The mixer 92 houses a nozzle 92b for injecting a reducing agent into the exhaust gas. The fourth exhaust pipe 93 is connected to the mixer 92. The reactor 94 is located downstream of the mixer 92, allowing the exhaust gas and reducing agent to contact the catalyst 94b. The fifth exhaust pipe 95 is connected to the reactor 94. The SCR device 90 also includes a metering supply unit 96 and a pump unit 97. The metering supply unit 96 supplies the reducing agent and compressed air to the mixer 92, and the pump unit 97 supplies the reducing agent to the metering supply unit 96. Furthermore, a first sealing valve 64 is provided on the third exhaust pipe 91 to open and close it. Similarly, a second sealing valve 65 is provided on the fifth exhaust pipe 95 to open and close it.

[0063] It should be noted that the following description focuses on structures using urea (more specifically, urea solution) as a reducing agent, but ammonia precursors other than urea can also be used. Details regarding the SCR unit 90 will be described later.

[0064] The turbine 5b and the compressor 5a disposed in the intake passage 30 together constitute the supercharger 5 of this embodiment. In this supercharger 5, the compressor 5a and the turbine 5b are connected and rotate synchronously with each other. When the compressor 5a is driven to rotate by the exhaust gas passing through the turbine 5b, the air can be pressurized by the compressor 5a.

[0065] A second exhaust pipe 43 is connected to the downstream end (exhaust gas outlet) of turbine 5b. This second exhaust pipe 43 connects turbine 5b and boiler 44, thereby guiding the exhaust gas flowing from turbine 5b to boiler 44. It should be noted that turbine 5b can also be connected to components other than boiler 44, such as an exhaust gas economizer, to replace it. Figure 1 The turbine 5b and boiler 44 are directly connected as shown.

[0066] Furthermore, a first bypass pipe 45, a second bypass pipe 46, and a pressure reducing pipe 47 are provided on the exhaust passage 40. The first bypass pipe 45 bypasses the SCR device 90 and directly connects the exhaust manifold 42 and the turbine 5b. The second bypass pipe 46 and the pressure reducing pipe 47 allow exhaust gas to bypass the turbine 5b. An SCR bypass valve 61 is provided on the first bypass pipe 45 to open and close it. A turbine bypass valve 62 is provided on the second bypass pipe 46 to open and close it. A pressure reducing control valve 63 is provided on the pressure reducing pipe 47 to open and close it.

[0067] like Figure 1As shown, the first bypass pipe 45 merges with the fifth exhaust pipe 95 at its midpoint. The second bypass pipe 46 branches off downstream from the junction of the first bypass pipe 45 and the fifth exhaust pipe 95, bypasses the turbine 5b, and connects to the second exhaust pipe 43. The pressure reducing pipe 47 connects to the fifth exhaust pipe 95 upstream of the second sealing valve 65, and bypasses the turbine 5b to connect to the second exhaust pipe 43.

[0068] (2) Detailed information about the SCR device

[0069] Figure 5 This is a perspective view illustrating the layout of the SCR device 90. Figure 6 and Figure 7 These are, respectively, longitudinal and transverse sectional views illustrating the structure of mixer 92. It should be noted that... Figure 7 Equivalent to along Figure 6 The cross-section cut along line AA. Figure 8 This is a perspective view showing a specific example of the mixing mechanism 92c. Figure 9 This is an exemplary longitudinal sectional view showing the structure of reactor 94. Below, refer to... Figures 1-9 The specific layout and structure of the SCR device 90 are described in detail.

[0070] -Third exhaust pipe 91-

[0071] The third exhaust pipe 91 is configured as a conduit connecting the exhaust manifold 42 and the mixer 92. Specifically, as... Figure 2 As shown, the third exhaust pipe 91 in this embodiment has an upstream side portion 91a and a downstream side portion 91b, wherein the upstream side portion 91a extends forward from the front surface of the exhaust manifold 42, and the downstream side portion 91b is connected to the upstream side portion 91a and extends downward.

[0072] The upstream portion 91a of the third exhaust pipe 91 extends coaxially with the exhaust manifold 42 in the front-rear direction and then bends downward in an arc with a central angle of 90° when viewed from the side. The first sealing valve 64 is disposed in this upstream portion 91a.

[0073] On the other hand, the downstream portion 91b of the third exhaust pipe 91 extends downward from the lower end of the upstream portion 91a. This downstream portion 91b is configured to connect to the upper end of the mixer 92.

[0074] The exhaust gas delivered from the exhaust manifold 42 to the third exhaust pipe 91 flows forward in the fore-and-aft direction (the direction of propulsion of the ship), and then changes direction downwards to flow into the mixer 92.

[0075] -Mixer 92-

[0076] The mixer 92 is configured as an exhaust pipe that injects urea into the exhaust gas, mixes the exhaust gas with the urea, and vaporizes the reducing agent in the exhaust gas. Specifically, as... Figure 2 and Figure 5 As shown, the mixer 92 of this embodiment is arranged along the outer surface 10a of the main engine 10 in the propulsion direction (forward) facing the ship. The mixer 92 is also configured to extend from the upper side to the lower side in the height direction of the main engine 10. Hereinafter, the outer surface 10a will also be referred to as the "forward surface".

[0077] like Figure 4 As shown, the mixer 92 is located on the front side of the front surface 10a and is arranged at a distance from the front surface 10a in the front-rear direction. The mixer 92 may also be connected to the front surface 10a.

[0078] like Figure 2 As shown, the upper end of the mixer 92 is positioned lower than the exhaust manifold 42 and the turbocharger 5 in the height direction. Specifically, the upper end of the mixer 92 in this embodiment is located at approximately the same height as the upper end of the cylinder water jacket 13 (specifically, the boundary between the cylinder water jacket 13 and the cylinder head 14). On the other hand, the lower end of the mixer 92 is located at approximately the same height as the lower half of the frame 12.

[0079] In the left-right direction, the mixer 92 is arranged slightly off-center relative to the center of the main engine 10. For example, in this embodiment, the mixer 92 is located between the crankshaft 16 and the reactor 94 in the left-right direction (see reference). Figure 2 ).

[0080] In this left-right direction, the mixer 92 is positioned in the same location as the exhaust manifold 42 and the third exhaust pipe 91. That is, as Figure 4 As shown, the exhaust manifold 42, the third exhaust pipe 91, and the mixer 92 are arranged side by side along the front-rear direction and sequentially facing forward, which is the direction of propulsion. This arrangement direction is consistent with the axial direction of the exhaust manifold 42, that is, the cylinder bank direction of the main engine 10.

[0081] More specifically, such as Figure 6 As shown, the mixer 92 according to this embodiment includes a mixing pipe 92a, a nozzle 92b, and a mixing mechanism 92c. The mixing pipe 92a allows waste gas to flow through, the nozzle 92b is arranged inside the mixer 92 and sprays urea water as a reducing agent into the waste gas, and the mixing mechanism 92c is used to mix the reducing agent into the waste gas (see also the mixing pipe 92a). Figure 2 ).

[0082] The mixing pipe 92a is a cylindrical pipe. Specifically, the mixing pipe 92a is formed as a cylinder with a central axis Pc extending along the height direction, and houses a nozzle 92b. The mixing pipe 92a allows exhaust gas (refer to...) to flow in from the upper end of the cylinder... Figure 6 Arrow f1) flows out from the lower end while mixed with the reducing agent sprayed from nozzle 92b. The mixing tube 92a is sized so that urea is discharged from the mixing tube 92a in a fully vaporized state.

[0083] The nozzle 92b is arranged with its spray port facing downward and is configured to spray the reducing agent supplied from the metering supply unit 96 together with the compressed air supplied from the metering supply unit 96 downward.

[0084] like Figure 7 As shown, the nozzle 92b in this embodiment is arranged such that it sprays the reducing agent downwards in the height direction from the central position of the mixer 92 as viewed in a cross-section perpendicular to the height direction. Specifically, the nozzle orifice 921 of the nozzle 92b is arranged to coincide with the central axis Pc of the mixing tube 92a in a cross-section perpendicular to the height direction. With this arrangement, the reducing agent sprayed from the nozzle 92b is uniformly distributed radially (refer to arrow f2).

[0085] like Figure 6 As shown, the nozzle 92b is positioned closer to the upper side than the center of the mixing tube 92a in the height direction. This arrangement ensures a longer distance from the nozzle 92b to the lower end of the mixing tube 92a.

[0086] The mixing mechanism 92c is arranged in the height direction upstream of the nozzle 92b (in other words, it is arranged in the height direction between the upstream end of the mixing pipe 92a and the nozzle 92b). The mixing mechanism 92c is composed of a plurality of plate-shaped components 100 arranged in a direction orthogonal to the height direction, and is capable of adjusting the flow of exhaust gas to make the exhaust gas and reducing agent mix uniformly.

[0087] In detail, such as Figure 8 As shown, the plurality of plate-shaped components 100 involved in this embodiment are respectively formed as rectangular plates with the height direction as the short side direction, one direction orthogonal to the height direction (left and right direction in the example) as the long side direction, and another direction orthogonal to the height direction (front and back direction in the example) as the thickness direction.

[0088] Furthermore, each plate-shaped component 100 has a first inclined plate portion 101 and a second inclined plate portion 102. Here, the first inclined plate portion 101 and the second inclined plate portion 102 extend in a direction inclined relative to the height direction (i.e. the direction of exhaust gas flow).

[0089] Specifically, the first inclined plate portion 101 extends approximately downward from the periphery of the long side of each plate-shaped member 100, and as it approaches the lower side along the height direction, it extends obliquely in the front-back direction away from the plate-shaped member 100 (front side in the illustration).

[0090] On the other hand, the second inclined plate portion 102 is composed of a tongue-shaped portion, which is formed by cutting a portion of each plate-shaped component 100 into a tongue shape and bending the cut portion. For example... Figure 8 As shown, multiple (three in the example) tongue portions can also be provided along the long side of each plate-shaped member 100. Each tongue portion extends from the corresponding plate-shaped member 100 toward the generally upward side, and as it approaches the upper side along the height direction, it extends obliquely in the front-back direction away from the plate-shaped member 100 (the front side in the example).

[0091] In this way, the hybrid mechanism 92c can be composed of one or more components that are tilted relative to the height direction, but the tilting direction of each component can also be multiple directions, rather than as shown. Figure 8 The first inclined plate portion 101 and the second inclined plate portion 102 are shown in a specific direction as exemplarily.

[0092] The exhaust gas sent from the third exhaust pipe 91 into the mixer 92 is mixed with urea, and the urea is discharged from the mixing pipe 92a in the state of vaporization, reaching the fourth exhaust pipe 93.

[0093] -Fourth exhaust pipe 93-

[0094] The fourth exhaust pipe 93 is configured as a conduit connecting the mixer 92 and the reactor 94. Specifically, as... Figure 2 As shown, the fourth exhaust pipe 93 in this embodiment is formed in a generally J-shape in the front view, which can change the direction of the exhaust gas flowing downward from the lower end of the mixer 92 and make it flow upward.

[0095] The exhaust gas sent from mixer 92 to fourth exhaust pipe 93 is redirected in fourth exhaust pipe 93 and reaches reactor 94.

[0096] -Reactor 94-

[0097] Reactor 94 is configured as an exhaust pipe capable of purifying exhaust gas by contacting exhaust gas and reducing agent with catalyst 94b. In particular, as... Figures 2-5 As shown, the reactor 94 in this embodiment is arranged adjacent to the mixer 92 along the front surface 10a of the main engine 10 and is configured to extend from the lower side toward the upper side in the height direction.

[0098] like Figure 4As shown, reactor 94 is located on the front side of front surface 10a and is arranged at a distance from front surface 10a in the front-rear direction. Reactor 94 may also be connected to front surface 10a.

[0099] The upper end of the reactor 94 is positioned below the exhaust manifold 42 and the turbocharger 5 in the height direction. Specifically, the upper end of the reactor 94 in this embodiment is located at approximately the same height as the upper end of the cylinder water jacket 13 (specifically, the boundary between the cylinder water jacket 13 and the cylinder head 14). On the other hand, the lower end of the reactor 94 is located at approximately the same height as the center of the engine base 11 in the height direction.

[0100] In the left-right direction, the reactor 94 is arranged off to one side relative to the center of the main engine 10 in the left-right direction. For example, in this embodiment, the mixer 92 is located to the left of the reactor 94 in the left-right direction (see reference). Figure 2 The mixer 92 and the reactor 94 are arranged adjacent to each other in the left-right direction.

[0101] In this left-right direction, reactor 94 is arranged in the same position as booster 5 and fifth exhaust pipe 95. That is, as Figure 4 As shown, the turbocharger 5, the fifth exhaust pipe 95, and the reactor 94 are arranged side by side along the front-rear direction and sequentially facing forward, which is the direction of propulsion. This arrangement direction is consistent with the extension direction of the fifth exhaust pipe 95, that is, the cylinder bank direction of the main engine 10.

[0102] More specifically, such as Figure 9 As shown, the reactor 94 involved in this embodiment has a reaction tube 94a, multiple (three in the example) catalysts 94b, a soot blower 94c, an inspection hole 94d, and an insulation component 94e. The reaction tube 94a allows waste gas to circulate, the catalysts 94b promote the reaction of the waste gas, the soot blower 94c sprays compressed air onto each catalyst 94b, the inspection hole 94d is used for inspection, and the insulation component 94e covers the entire reactor 94 (see also the section on reaction tube 94a). Figure 2 ).

[0103] The reaction tube 94a is a generally cylindrical pipe, arranged such that its central axis extends along the height direction. The reaction tube 94a allows waste gas (refer to...) to flow in from its lower end... Figure 9 Arrow f3) flows out from the top after being purified by catalyst 94b. The size of reaction tube 94a is set according to the storage space of catalyst 94b, etc.

[0104] Multiple catalysts 94b are composed, for example, of SCR catalysts and ammonia slip catalysts. The SCR catalyst, upon activation, allows ammonia to react (reduce) with NOx in the exhaust gas, thus purifying it. The ammonia slip catalyst oxidizes unreacted ammonia emitted from the SCR catalyst, thus purifying it as well.

[0105] Soot blower 94c branches in a manner corresponding to catalyst 94b, using compressed air supplied from the outside ( Figure 9 Arrow f4) is sprayed onto each catalyst 94b, thereby blowing away the soot accumulated on the catalyst 94b.

[0106] Inspection port 94d is provided for each catalyst 94b. The inspection port 94d is configured to be opened and closed as needed when checking the condition of each catalyst 94b or maintaining each catalyst 94b.

[0107] The exhaust gas fed into reactor 94 from the fourth exhaust pipe 93, after being purified by catalyst 94b, is discharged from reaction pipe 94a and reaches the fifth exhaust pipe 95. At this time, if... Figure 5 As shown, the flow direction A2 of the exhaust gas in reactor 94 is opposite to the flow direction A1 of the exhaust gas in mixer 92.

[0108] -Fifth exhaust pipe 95-

[0109] The fifth exhaust pipe 95 is configured as a conduit connecting the reactor 94 and the booster 5. Specifically, as follows... Figure 3 As shown, the fifth exhaust pipe 95 in this embodiment has an upstream side portion 95a and a downstream side portion 95b, wherein the upstream side portion 95a extends upward from the upper surface of the reactor 94, and the downstream side portion 95b is connected to the upstream side portion 95a and extends rearward.

[0110] Among them, the upstream side portion 95a of the fifth exhaust pipe 95 extends coaxially with the reaction pipe 94a along the height direction and then bends backward in an arc that traces a central angle of 90° when viewed from the side.

[0111] On the other hand, the downstream portion 95b of the fifth exhaust pipe 95 extends rearward in a generally straight line from the rear end of the aforementioned upstream portion 95a. This downstream portion 95b is configured to connect to the turbine 5b of the supercharger 5. For example... Figure 3 and Figure 4 As shown, a first bypass pipe 45 is connected at the midpoint of the downstream portion 95b.

[0112] The exhaust gas sent from reactor 94 into the fifth exhaust pipe 95 flows upward along the height direction, and then changes direction to flow backward into the booster 5.

[0113] (3) Control System

[0114] The engine 1 also includes a control unit 100 for controlling the operation of the engine 1. The control unit 100 includes a central processing unit (CPU), a memory, and an input / output bus, and is electrically connected to various parts of the engine 1.

[0115] For example, when the SCR device 90 is not operating, the control unit 100 outputs control signals to each valve to open the SCR bypass valve 61 and close the first sealing valve 64 and the second sealing valve 65. In this case, the exhaust gas flowing from each cylinder 15 into the exhaust passage 40 bypasses the SCR device 90. The exhaust gas bypassing the SCR device 90 passes through or bypasses the turbocharger 5 according to the opening of the turbine bypass valve 62, and then passes through the second exhaust pipe 43 and the boiler 44 in sequence, where it is burned.

[0116] In contrast, when the SCR unit 90 is operating, the control unit 100 outputs control signals to each valve to close the SCR bypass valve 61 and open / close the first sealing valve 64 and the second sealing valve 65. In this case, exhaust gas flowing from each cylinder 15 into the exhaust passage 40 passes through the SCR unit 90. The exhaust gas passing through the SCR unit 90 is mixed with a reducing agent in the mixer 92 and, after the reducing agent is vaporized, is purified by contacting the catalyst 94b in the reactor 94. The exhaust gas purified by the SCR unit 90 passes through or bypasses the turbocharger 5 depending on the opening of the turbine bypass valve 62, and then sequentially passes through the second exhaust pipe 43 and the boiler 44.

[0117] (4) Regarding the performance of the SCR device

[0118] As explained above, according to the above implementation method, such as Figure 6 As shown, the direction of gravity acting on the urea ejected from nozzle 92b is consistent with the direction of extension of mixer 92. In other words, the direction of gravity acting on the reducing agent is consistent with... Figure 7 The cross-section shown is orthogonal to the direction. This situation complements the situation where the reducing agent is injected from the central position inside the mixing pipe 92a, and does not cause unevenness caused by gravity, thus enabling the exhaust gas and reducing agent to be mixed uniformly.

[0119] Moreover, such as Figure 5 As shown, compared to a structure that extends the mixer 92 upwards, extending the mixer 92 downwards contributes to the overall compactness of the main engine 10 and the SCR unit 90 (especially in the height direction). This allows the SCR unit 90 to be installed on various ship types, thereby facilitating the optimization of the SCR unit 90 for each ship type.

[0120] like Figure 7 As shown, by arranging the nozzle 92b so that its orifice 921 coincides with the central axis Pc of the mixing pipe 92a, the reducing agent can be sprayed more isotropically. This is effective in ensuring uniform mixing of exhaust gas and reducing agent.

[0121] like Figure 4 As shown, compared to an arrangement where the mixer 92 and exhaust manifold 42 are staggered along the width of the ship (left-right direction), by arranging the mixer 92 and exhaust manifold 42 side-by-side facing the propulsion direction (forward), the third exhaust pipe 91 can be formed into a simpler shape. This facilitates the compactness of the SCR device 90.

[0122] like Figure 1 and Figure 4 As shown, the third exhaust pipe 91, which connects the exhaust manifold 42 and the mixer 92, can be configured such that it does not bend upwards in the height direction when viewed from the flow direction. Since it does not need to bend upwards, the portion of the third exhaust pipe 91 that extends along the extending direction (downwards) of the mixer 92 can be made shorter. This facilitates the compactness of the SCR device 90.

[0123] like Figure 5 As shown, the reactor 94 and mixer 92 of this embodiment are arranged adjacent to each other along the front surface 10a of the main engine 10. In this way, the space near the front surface 10a of the main engine 10 can be effectively utilized, thereby contributing to the compactness of the SCR device 90.

[0124] like Figure 3 and Figure 4 As shown, the fifth exhaust pipe 95, which connects the reactor 94 and the booster 5, can be constructed without bending downwards in the height direction when viewed from the flow direction. Since it does not need to bend downwards, the portion of the fifth exhaust pipe 95 extending along the extending direction (upper) of the reactor 94 can be made shorter. This facilitates the compactness of the SCR device 90.

[0125] Furthermore, by arranging the reactor 94 closer to the bottom than the booster 5, the soot accumulated on the catalyst 94b inside the reactor 94 is less likely to reach the booster 5 under gravity. This is effective in maintaining the performance of the reactor 94 and thus the SCR unit 90.

[0126] The aforementioned drive shaft extends rearward from the rear surface of the main engine 10. Therefore, arranging the mixer 92 and reactor 94 along the front surface 10a of the main engine 10 is also effective in avoiding interference between the drive shaft and the SCR device 90.

[0127] In the existing SCR unit 90, the mixer 92 and reactor 94 are arranged in various ways depending on the ship type. In this case, in order to keep the pressure loss of the exhaust gas generated in the exhaust pipe within the allowable range, the design of the third exhaust pipe 91, fourth exhaust pipe 93, fifth exhaust pipe 95, etc., needs to be changed from time to time according to the ship type. In addition, the work required to design the support structure of each exhaust pipe is also required, and the existing structure requires a lot of labor.

[0128] In contrast, as described in the above embodiment, by configuring the main engine 10 and the SCR device 90 as a single unit, the shape and size of the third exhaust pipe 91, the fourth exhaust pipe 93, the fifth exhaust pipe 95, etc., can be fixed. In this way, regardless of the ship type, the pressure loss that may occur in each exhaust pipe can be fixed, which is advantageous in reducing the labor required for design and achieving optimization and compactness of the entire engine 1.

[0129] (5) Other implementation methods

[0130] Figure 10 This shows a modified example of an SCR device. Figure 5 The corresponding diagram. Figure 11A This shows a first modified example of the mixer 92. Figure 6 The corresponding diagram, Figure 11B This is a second variant of the mixer 92 shown. Figure 6 The corresponding diagram, Figure 11C This is a third variation of the mixer 92. Figure 6 The corresponding diagram.

[0131] In the above embodiments, the mixer 92 and the reactor 94 are constructed independently, but this disclosure is not limited to this structure. Alternatively, as... Figure 10 As exemplarily shown in the SCR device 90', the mixer 92' and the reactor 94' are configured as a single unit.

[0132] In the case of the SCR device 90', a baffle is provided inside its housing, with the portion on the right side of the baffle corresponding to the mixer 92' and the portion on the left side of the baffle corresponding to the reactor 94'. Even in this modified example, as in the embodiment described above, the flow direction of the exhaust gas in the mixer 92' is opposite to the flow direction in the reactor 94'.

[0133] The mixer 92 involved in the above embodiments includes Figure 6 The example is a hybrid mechanism 92c, but the structure of the hybrid mechanism 92c is not limited to this. Figure 6 The structure is shown as an example.

[0134] For example, as in the mixer 92' of the first modification, the mixing mechanism 92c' can be constituted by a plate extending vertically relative to the height direction, or as in the mixer 92” of the second modification, the mixing mechanism 92c can be constituted by a venturi tube arranged below the nozzle 92b (see reference). Figure 11A and Figure 11B Alternatively, it can be like this: Figure 11C Like the mixer 923 involved in the third variation shown, the mixing mechanism 92c3 is composed of a conical component whose diameter tapers as it approaches the bottom.

[0135] The nozzle 92b described in the above embodiment is configured such that the nozzle 921 coincides with the central axis Pc in a cross section perpendicular to the height direction, but this disclosure is not limited to such a structure.

[0136] For example, the nozzle 921 can be positioned at the center of the mixer 92, but this center position does not need to be strictly aligned with the central axis Pc; instead, the nozzle 921 can be positioned so that it does not coincide with the central axis Pc. In this case, it is preferable to position the nozzle 921 near the central axis Pc. That is, the "center position of the mixer 92" in this disclosure includes not only the intersection point of the central axis Pc and the aforementioned cross-section, but also any position within the region converging near the central axis Pc. The original structure of positioning the nozzle 921 at the center of the mixer 92 is not mandatory.

[0137] It should be noted that the "region near the central axis Pc" mentioned here refers to a region that is closer to the central axis Pc than the inner wall of the mixer 92 (more specifically, the inner wall of the mixing tube 92a) when the cross-section is divided into two regions in a radial direction extending radially from the central axis Pc.

[0138] The term "central axis Pc of mixer 92" can also be defined broadly. That is, the "center" here is not limited to the center point observed in a circular cross-section, but also includes the center of symmetry of a semi-circular cross-section (the so-called "center of rotational symmetry"), the geometric center of that cross-section (the so-called "center of mass"), the geometric center of various cross-sectional shapes, such as rectangles, etc. In other words, the mixing pipe 92a involved in this disclosure is not limited to a cylindrical pipe, but can also be a semi-cylindrical pipe or a rectangular pipe. The surface shape of the mixing pipe 92a can be arbitrary.

Claims

1. A marine internal combustion engine with SCR device, characterized in that: The marine internal combustion engine with the SCR device includes a main engine and an SCR device, The main engine propels a ship in a prescribed propelling direction, The SCR device denitrates exhaust gas from the main engine, The SCR device has a mixer and a reactor, A nozzle that injects a reducing agent into the exhaust gas is housed in the mixer, The reactor is arranged on a downstream side of the mixer and contacts the exhaust gas and the reducing agent with a catalyst, The mixer is arranged along an outer surface of the main engine that faces the propelling direction and is configured to extend from an upper side in a height direction of the main engine toward a lower side, The mixer is independently configured from the reactor, and the mixer has a mixing pipe that extends in the height direction and houses the nozzle and a mixing mechanism for mixing the reducing agent into the exhaust gas, The nozzle is arranged at a position closer to the upper side than a central portion in the height direction of the mixing pipe, and the nozzle is arranged on a downstream side of the mixing mechanism.

2. The marine internal combustion engine with the SCR device according to claim 1, wherein: The nozzle injects the reducing agent from a central position of the mixer, as viewed in a cross section perpendicular to the height direction, toward a lower side in the height direction.

3. The marine internal combustion engine with the SCR device according to claim 2, wherein: The mixer has a mixing pipe that houses the nozzle, The mixing pipe is formed in a cylindrical shape having a central axis that extends in the height direction, A nozzle opening of the nozzle is arranged to coincide with the central axis in the cross section.

4. The marine internal combustion engine with the SCR device according to any one of claims 1 to 3, wherein: The main engine has a plurality of cylinders and an exhaust manifold, The plurality of cylinders are arranged in the propelling direction, The exhaust manifold is connected to the plurality of cylinders and extends in the propelling direction, The mixer is arranged to be aligned with the exhaust manifold in the propelling direction.

5. The marine internal combustion engine with the SCR device according to claim 4, wherein: An upper end portion of the mixer is arranged in the height direction at a position lower than the exhaust manifold.

6. The marine internal combustion engine with the SCR device according to any one of claims 1 to 3, wherein: The reactor is arranged adjacent to the mixer along the outer surface and is configured to extend from a lower side in the height direction toward an upper side.

7. The marine internal combustion engine with the SCR device according to claim 6, wherein: The marine internal combustion engine with the SCR device includes a supercharger arranged on an upper side of the main engine and through which the gas purified by the reactor flows, An upper end portion of the reactor is arranged in the height direction at a position lower than the supercharger.

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