JP7808482B2 - Marine internal combustion engine with SCR device - Google Patents

Description

This disclosure relates to a marine internal combustion engine equipped with an SCR device.

For example, Patent Document 1 discloses an internal combustion engine with an exhaust gas aftertreatment system. This exhaust gas aftertreatment system is a so-called selective catalytic reduction (SCR) exhaust gas aftertreatment system, and includes, from upstream to downstream, an introduction device that introduces a reducing agent into the exhaust gas, an introduction section for mixing the reducing agent introduced from this introduction device with the exhaust gas, and a reaction chamber in which an SCR catalytic converter is located.

The introduction section described in Patent Document 1 is located above the internal combustion engine and is formed to extend in the longitudinal direction so as to be coaxial with the exhaust gas manifold of the internal combustion engine. The introduction device described in this document is configured to inject reducing agent rearward in the longitudinal direction.

Patent Document 2 also discloses, as another example of an internal combustion engine, an internal combustion engine equipped with an SCR device (SCR catalyst system). This SCR device includes, from the upstream side, a mixing pipe that mixes urea into the exhaust gas and vaporizes it, and an SCR reactor that reduces the exhaust gas mixed with the urea.

Here, the mixing pipe according to Patent Document 2 is located above the internal combustion engine and, like the introduction section according to Patent Document 1, is formed to extend along the longitudinal direction of the internal combustion engine.

Patent No. 6803790 Patent No. 6713745

However, if the conduit (mixing section, mixing conduit) for mixing a reducing agent such as urea is extended in the front-to-rear direction, as in Patent Documents 1 and 2, the reducing agent supplied into the conduit will fall due to gravity.

As a result, the reducing agent supplied to the piping may be distributed more to the lower side than the upper side in the direction of gravity, which may lead to uneven mixing of the exhaust gas and reducing agent. For the SCR device to function properly, it is necessary to mix the exhaust gas and reducing agent evenly.

The technology disclosed here was developed in light of these issues, and its purpose is to uniformly mix exhaust gas and reducing agent in a marine internal combustion engine equipped with an SCR device.

A first aspect of the present disclosure relates to a marine internal combustion engine with an SCR device. This marine internal combustion engine with an SCR device includes a main engine that propels the ship forward in a predetermined propulsion direction, and an SCR device that denitrifies exhaust gas from the main engine. The SCR device has a mixer that houses an injection nozzle that injects a reducing agent into the exhaust gas, and a reactor that is positioned downstream of the mixer and brings the exhaust gas and reducing agent into contact with a catalyst.

According to the first aspect, the mixer is arranged along the outer surface of the main engine facing the propulsion direction and is configured to extend vertically from the top to the bottom of the main engine.

In the first aspect, the direction of gravity acting on the reducing agent injected from the injection nozzle coincides with the extension direction of the mixer. In other words, gravity acting on the reducing agent is perpendicular to the cross section of the mixer. This allows the exhaust gas and reducing agent to be mixed uniformly without causing unevenness due to gravity.

Furthermore, extending the mixer downward as in the first embodiment contributes to making the main engine and the entire SCR system more compact than a configuration in which it is extended upward. This makes it possible to install the SCR system on a variety of ship types, which is advantageous in optimizing the SCR system for each ship type.

Furthermore, according to a second aspect of the present disclosure, the injection nozzle may inject the reducing agent downward in the height direction from a central position of the mixer as viewed in a cross section perpendicular to the height direction.

Gravity acts on the reducing agent in a direction perpendicular to the cross-section. This, combined with the fact that the reducing agent is injected from the central position as in the second embodiment, allows the exhaust gas and reducing agent to mix uniformly without causing unevenness due to gravity.

Furthermore, according to a third aspect of the present disclosure, the mixer may have a mixing tube that houses the injection nozzle, the mixing tube being formed in a cylindrical shape having a central axis extending along the height direction, and the nozzle of the injection nozzle may be positioned so as to overlap the central axis on the cross section.

According to the third aspect, by aligning the injection nozzle's injection port with the central axis of the mixing tube, the reducing agent can be injected more isotropically. This is effective in uniformly mixing the exhaust gas and reducing agent.

Furthermore, according to a fourth aspect of the present disclosure, the main engine may have a plurality of cylinders aligned in the propulsion direction and an exhaust manifold connected to the plurality of cylinders and extending in the propulsion direction, and the mixer may be arranged to be aligned with the exhaust manifold in the propulsion direction.

According to the fourth aspect, by arranging the mixer and exhaust manifold side by side in the propulsion direction, the piping connecting the mixer and exhaust manifold can be made simpler in shape than if they were arranged offset in the ship's width direction, etc. This is advantageous in making the SCR device more compact.

Furthermore, according to a fifth aspect of the present disclosure, the upper end of the mixer may be positioned lower than the exhaust manifold in the height direction.

According to the fifth aspect, the piping connecting the mixer and exhaust manifold can be configured without bending it upward in the height direction. Because there is no need to bend it upward, the shape of the piping can be configured to be shorter along the extension direction (downward) of the mixer. This is advantageous for making the SCR device more compact.

Furthermore, according to a sixth aspect of the present disclosure, the reactor may be arranged adjacent to the mixer along the outer surface and configured to extend from the lower side to the upper side in the height direction.

According to the sixth aspect, the reactor and mixer are arranged adjacent to each other along the outer surface. This allows for effective use of the space near the outer surface of the main engine, which in turn contributes to making the SCR device more compact.

Furthermore, according to a seventh aspect of the present disclosure, the marine internal combustion engine with an SCR device may include a turbocharger disposed on the upper surface of the main engine and into which gas purified by the reactor flows, and the upper end of the reactor may be disposed below the turbocharger in the height direction.

According to the seventh aspect, the piping connecting the reactor and turbocharger can be realized without bending it downward in the height direction. Because there is no need to bend it downward, the shape of the piping can be configured to be shorter along the extension direction (upward) of the reactor. This is advantageous for making the SCR device more compact.

Furthermore, by placing the reactor below the turbocharger, as in the seventh aspect, soot that has accumulated on the catalyst in the reactor is less likely to reach the turbocharger due to the action of gravity. This is effective in maintaining the performance of the reactor and, ultimately, the SCR device.

As described above, according to the present disclosure, exhaust gas and reducing agent can be mixed evenly in a marine internal combustion engine equipped with an SCR device.

FIG. 1 is a system diagram illustrating the schematic configuration of a marine internal combustion engine. FIG. 2 is a front view showing a specific example of a marine internal combustion engine. FIG. 3 is a left side view showing a specific example of a marine internal combustion engine. FIG. 4 is a plan view showing a specific example of a marine internal combustion engine. FIG. 5 is a perspective view illustrating the layout of an SCR device. FIG. 6 is a vertical cross-sectional view illustrating the configuration of the mixer. FIG. 7 is a cross-sectional view illustrating the configuration of the mixer. FIG. 8 is a perspective view showing a specific example of the mixing mechanism. FIG. 9 is a vertical cross-sectional view illustrating the configuration of the reactor. FIG. 10 is a diagram corresponding to FIG. 5, showing a modified example of the SCR device. FIG. 11A is a view corresponding to FIG. 7, showing a first modified example of the mixer. FIG. 11B is a view corresponding to FIG. 7, showing a second modified example of the mixer. FIG. 11C is a view corresponding to FIG. 7 and showing a third modified example of the mixer.

Embodiments of the present disclosure will now be described with reference to the drawings. Note that the following description is for illustrative purposes only. Figure 1 is a system diagram illustrating the general configuration of a marine internal combustion engine (hereinafter simply referred to as "engine") 1. Figures 2, 3, and 4 are a front view, a left side view, and a plan view, respectively, showing a specific example of engine 1.

In the following explanation, the front, rear, left, right, top, and bottom of the vessel will be referred to simply as front, rear, left, right, top, and bottom, respectively. Here, the forward/backward direction refers to the propulsion direction of the vessel, and the opposite direction refers to the rear. The front/back direction is also the length direction of the engine 1 output shaft (crankshaft 16, described below). The left side when viewing the vessel from the front is referred to as the left, and the right side is referred to as the right. The left/right direction is also the width direction of the vessel. The up/down direction is also the up/down direction of the vessel, engine 1, and main engine 10, described below, and is also referred to as the "height direction."

Engine 1 is an in-line multi-cylinder marine diesel engine equipped with multiple cylinders 15. Engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine and is installed on large ships such as tankers, container ships, and car carriers. The crankshaft 16, which is the output shaft of engine 1, is connected to the ship's propeller (not shown) via a propeller shaft (not shown) or the like. When engine 1 is operating, its output is transmitted to the propeller, propelling the ship.

In particular, the engine 1 disclosed herein is configured as a so-called crosshead-type internal combustion engine to achieve a long stroke. While detailed illustrations are omitted, the engine 1 is equipped with a piston rod that supports the piston from below and a connecting rod that is connected to the crankshaft, and the piston rod and connecting rod are connected by a crosshead.

Engine 1 is also configured as a so-called supercharged engine. That is, as shown in FIG. 1, engine 1 is configured with an exhaust turbocharger (hereinafter simply referred to as "supercharger") that is powered by exhaust gas flowing through exhaust passage 40.

The engine 1 is also configured as a marine internal combustion engine with an SCR device. That is, as shown in Figure 1, the engine 1 according to this embodiment is configured to include a main engine 10 that propels the ship forward in a predetermined propulsion direction, as well as an SCR device 90 that denitrifies exhaust gas from the main engine 10.

(1) Overall Configuration The following describes the main parts of the engine 1. In the following description, reference will be made to FIG. 1 when describing the outline of the engine 1, and to FIGS. 2 to 4 when describing the specific layout of the engine 1.

The main engine 10 has multiple cylinders 15 (six in the example shown in Figure 1). A piston (not shown) is inserted into each cylinder 15 so that it can reciprocate. These cylinders 15 are aligned in the propulsion direction of the ship. In other words, the direction in which the cylinders are lined up in this main engine 10 coincides with the fore-and-aft direction mentioned above.

Specifically, as shown in Figures 2 to 4, the main engine 10 according to this embodiment comprises a bedplate 11 installed on the cabin floor or the like, a frame 12 arranged on the bedplate 11, a cylinder jacket 13 arranged on the frame 12, and a cylinder cover 14 fixed to the top of the cylinder jacket 13. The bedplate 11, frame 12, and cylinder jacket 13 are fastened together by a plurality of tie bolts and nuts extending in the vertical direction.

Here, the base plate 11 constitutes the crankcase of the engine 1 and rotatably supports the crankshaft 16. The frame 12 houses the connecting rod and crosshead. The cylinder jacket 13 supports the cylinder liner as the inner cylinder. The cylinder cover 14, together with the cylinder liner inserted into the cylinder jacket 13, constitutes the cylinder 15.

As shown in Figure 1, the main engine 10 is connected to an intake passage 30 for supplying air to each cylinder 15 and an exhaust passage 40 for circulating exhaust gas from each cylinder 15.

More specifically, the intake passage 30 is provided with, in order from upstream in the air flow direction, a compressor 5a, an air cooler (not shown), a scavenging trunk 31, and an intake pipe 32 connecting the scavenging trunk 31 and the cylinder 15. The compressor 5a supercharges the air by driving it together with the turbine 5b, and sends the supercharged air to the cylinder 15 via the scavenging trunk 31 and the intake pipe 32.

On the other hand, the exhaust passage 40 is provided with, in order from the upstream side, a first exhaust pipe 41, an exhaust manifold 42, an SCR device 90, a turbine 5b drivingly connected to the compressor 5a, a second exhaust pipe 43, and a boiler 44 that incinerates exhaust gas (see Figures 2 and 4 for the first exhaust pipe 41).

As shown in Figure 4, a first exhaust pipe 41 is provided for each cylinder 15 and is connected to an exhaust manifold 42. The exhaust manifold 42 is configured to collect exhaust gas from each cylinder 15 and extends in the front-to-rear direction as shown in Figures 1 and 4. A first bypass pipe 45 is connected to one side of the exhaust manifold 42 (the left side in the illustrated example).

As shown in FIG. 1 , the SCR device 90 includes, from upstream to downstream, a third exhaust pipe 91 connected to the exhaust manifold 42; a mixer 92 housing an injection nozzle 92b that injects a reducing agent into the exhaust gas; a fourth exhaust pipe 93 connected to the mixer 92; a reactor 94 located downstream of the mixer 92 and bringing the exhaust gas and reducing agent into contact with a catalyst 94b; and a fifth exhaust pipe 95 connected to the reactor 94. The SCR device 90 also includes a dosing unit 96 that supplies reducing agent and compressed air to the mixer 92, and a pump unit 97 that supplies reducing agent to the dosing unit 96. The third exhaust pipe 91 is provided with a first seal valve 64 that opens and closes the third exhaust pipe 91. Similarly, the fifth exhaust pipe 95 is provided with a second seal valve 65 that opens and closes the fifth exhaust pipe 95.

Note that the following description will focus on a configuration using urea (more specifically, urea water) as the reducing agent, but ammonia precursors other than urea may also be used. Details of the SCR device 90 will be described later.

The turbine 5b, together with the compressor 5a provided in the intake passage 30, constitutes the turbocharger 5 in this embodiment. In this turbocharger 5, the compressor 5a and turbine 5b are connected and rotate synchronously with each other. When the compressor 5a is driven to rotate by exhaust gas passing through the turbine 5b, the compressor 5a can supercharge the air.

A second exhaust pipe 43 is connected to the downstream end (exhaust gas outlet) of the turbine 5b. This second exhaust pipe 43 connects the turbine 5b to the boiler 44, and can guide the exhaust gas flowing out of the turbine 5b to the boiler 44. Note that instead of directly connecting the turbine 5b to the boiler 44 as shown in Figure 1, the turbine 44 may be connected to a component other than the boiler 44, such as an exhaust gas economizer.

In addition, the exhaust passage 40 is provided with a first bypass pipe 45 that directly connects the exhaust manifold 42 and turbine 5b, bypassing the SCR device 90; a second bypass pipe 46 that causes exhaust gas to bypass the turbine 5b; and a relief pipe 47. The first bypass pipe 45 is provided with an SCR bypass valve 61 that opens and closes the first bypass pipe 45. The second bypass pipe 46 is provided with a turbine bypass valve 62 that opens and closes the second bypass pipe 46. The relief pipe 47 is provided with a relief control valve 63 that opens and closes the relief pipe 47.

As shown in FIG. 1, the first bypass pipe 45 merges with the fifth exhaust pipe 95 midway. The second bypass pipe 46 branches off downstream of the junction of the first bypass pipe 45 and the fifth exhaust pipe 95, bypassing the turbine 5b and connecting to the second exhaust pipe 43. The relief pipe 47 is connected to the fifth exhaust pipe 95 upstream of the second seal valve 65, and bypasses the turbine 5b and connecting to the second exhaust pipe 43.

(2) Details of the SCR Device FIG. 5 is a perspective view illustrating the layout of the SCR device 90. Also, FIGS. 6 and 7 are a longitudinal cross-sectional view and a transverse cross-sectional view, respectively, illustrating the configuration of the mixer 92. Note that FIG. 7 corresponds to the A-A cross-section in FIG. 6. Also, FIG. 8 is a perspective view showing a specific example of the mixing mechanism 92c, and FIG. 9 is a longitudinal cross-sectional view illustrating the configuration of the reactor 94. The specific layout and configuration of the SCR device 90 will be described in detail below with reference to FIGS. 1 to 9.

-Third exhaust pipe 91-
The third exhaust pipe 91 is configured as a pipe that connects the exhaust manifold 42 and the mixer 92. Specifically, as shown in Fig. 2, the third exhaust pipe 91 according to this embodiment has an upstream portion 91a that extends forward from the front surface of the exhaust manifold 42, and a downstream portion 91b that is continuous with the upstream portion 91a and extends downward.

Of these, the upstream section 91a of the third exhaust pipe 91 extends coaxially with the exhaust manifold 42 in the longitudinal direction, and then bends downward in a circular arc with a central angle of 90° in side view. The SCR bypass valve 61 is located in this upstream section 91a.

On the other hand, the downstream section 91b of the third exhaust pipe 91 extends downward from the lower end of the upstream section 91a. This downstream section 91b is connected to the upper end of the mixer 92.

Exhaust gas sent from the exhaust manifold 42 to the third exhaust pipe 91 flows forward (in the direction of propulsion of the vessel) along the longitudinal direction, then changes direction downward and reaches the mixer 92.

-Mixer 92-
The mixer 92 is configured as an exhaust pipe that injects urea into the exhaust gas to mix them and vaporizes the reducing agent in the exhaust gas. In particular, the mixer 92 according to this embodiment is arranged along the outer surface 10a of the main engine 10 that faces in the propulsion direction (forward) of the ship, as shown in Figures 2 and 5. This 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, this outer surface 10a will also be referred to as the "front surface."

As shown in FIG. 4, the mixer 92 is located in front of the front surface 10a and is spaced apart from the front surface 10a in the front-to-rear direction. The mixer 92 may be connected to the front surface 10a.

As shown in FIG. 2, the upper end of the mixer 92 is positioned lower in the height direction than the exhaust manifold 42 and the turbocharger 5. Specifically, in this embodiment, the upper end of the mixer 92 is located at approximately the same height in the height direction as the upper end of the cylinder jacket 13 (specifically, the boundary between the cylinder jacket 13 and the cylinder cover 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.

Furthermore, in the left-right direction, the mixer 92 is positioned slightly offset from the left-right 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 Figure 2).

In the left-right direction, the mixer 92 is positioned at the same position as the exhaust manifold 42 and the third exhaust pipe 91. That is, as shown in FIG. 4, the exhaust manifold 42, the third exhaust pipe 91, and the mixer 92 are aligned along the fore-and-aft direction, and are lined up in order toward the forward direction, which is the propulsion direction. This alignment direction coincides with the axial direction of the exhaust manifold 42, i.e., the direction in which the cylinders of the main engine 10 are lined up.

More specifically, as shown in Figure 6, the mixer 92 according to this embodiment has a mixing tube 92a through which exhaust gas flows, an injection nozzle 92b disposed inside the mixer 92 for injecting urea water as a reducing agent into the exhaust gas, and a mixing mechanism 92c for mixing the reducing agent with the exhaust gas (see also Figure 2 for the mixing tube 92a).

Of these, the mixing tube 92a is a cylindrical pipe. More specifically, this mixing tube 92a is formed in a cylindrical shape with a central axis Pc extending along the height direction, and houses an injection nozzle 92b. The mixing tube 92a receives exhaust gas (see arrow f1 in Figure 6) that flows in from the upper end of the cylinder, mixes it with the reducing agent injected from the injection nozzle 92b, and discharges it from the lower end. The dimensions of the mixing tube 92a are set so that the urea is discharged from the mixing tube 92a in a fully vaporized state.

The injection nozzle 92b is positioned with its injection port facing downward, and is configured to inject the reducing agent supplied from the dosing unit 96 downward together with the compressed air supplied from the same unit 96.

As shown in FIG. 7, the injection nozzle 92b according to this embodiment is positioned so as to inject reducing agent downward in the height direction from the center position of the mixer 92 as viewed in a cross section perpendicular to the height direction. Specifically, the nozzle 921 of this injection nozzle 92b is positioned so as to overlap the central axis Pc of the mixing tube 92a in a cross section perpendicular to the height direction. By positioning it in this way, the reducing agent injected from the injection nozzle 92b is distributed uniformly in the radial direction (see arrow f2).

Furthermore, as shown in Figure 6, the injection nozzle 92b is positioned above the center of the mixing tube 92a in the height direction. By positioning it in this way, it is possible to ensure a longer section length from the injection nozzle 92b to the lower end of the mixing tube 92a.

The mixing mechanism 92c is positioned vertically upstream of the injection nozzle 92b (in other words, vertically between the upstream end of the mixing tube 92a and the injection nozzle 92b). The mixing mechanism 92c is composed of multiple plate-shaped members 100 arranged in a direction perpendicular to the vertical direction, and can adjust the flow of exhaust gas so that it is mixed uniformly with the reducing agent.

More specifically, as shown in FIG. 8, the multiple plate-like members 100 according to this embodiment are each formed into a rectangular plate shape with the height direction as the short side, one direction perpendicular to the height direction (the left-right direction in the illustrated example) as the long side, and another direction perpendicular to the height direction (the front-to-back direction in the illustrated example) as the thickness direction.

Each plate-like member 100 has a first inclined plate portion 101 and a second inclined plate portion 102. Here, the first and second inclined plate portions 101, 102 each extend in a direction inclined with respect to the height direction (i.e., the flow direction of the exhaust gas).

Specifically, the first inclined plate portion 101 extends substantially downward from the longitudinal peripheral edge of each plate-shaped member 100, and extends obliquely in a direction away from the plate-shaped member 100 in the front-to-rear direction (toward the front in the illustrated example) as it moves from top to bottom along the height direction.

On the other hand, the second inclined plate portion 102 is formed by cutting out a portion of each plate-shaped member 100 in the shape of a tongue and bending the cut-out portion. As illustrated in Figure 8, multiple tongue portions (three in the illustrated example) may be provided along the longitudinal direction of each plate-shaped member 100. Each tongue portion extends generally upward from the corresponding plate-shaped member 100, and extends obliquely in the front-to-rear direction away from the plate-shaped member 100 (toward the front in the illustrated example) as it moves from the bottom to the top along the height direction.

In this way, the mixing mechanism 92c can be composed of one or more components inclined in the height direction, but the inclination direction of each component may be multidirectional rather than being limited to a specific direction, as in the case of the first and second inclined plate sections 101, 102 illustrated in Figure 8.

Exhaust gas sent from the third exhaust pipe 91 to the mixer 92 is mixed with urea, and the urea is vaporized and discharged from the mixer pipe 92a, reaching the fourth exhaust pipe 93.

-Fourth exhaust pipe 93-
The fourth exhaust pipe 93 is configured as a pipe that connects the mixer 92 and the reactor 94. Specifically, the fourth exhaust pipe 93 according to this embodiment is formed in a substantially J-shape when viewed from the front, as shown in Fig. 2, and can change the direction of the exhaust gas that flows downward from the lower end of the mixer 92 so that it flows upward.

The exhaust gas sent from the mixer 92 to the fourth exhaust pipe 93 changes direction in the fourth exhaust pipe 93 and reaches the reactor 94.

-Reactor 94-
The reactor 94 is configured as an exhaust pipe capable of purifying the exhaust gas by bringing the exhaust gas and a reducing agent into contact with a catalyst 94b. In particular, the reactor 94 according to 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 to the upper side in the height direction, as shown in Figures 2 to 5 .

As shown in FIG. 4, the reactor 94 is located in front of the front surface 10a and is spaced apart from the front surface 10a in the longitudinal direction. The reactor 94 may be coupled to the front surface 10a.

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

Furthermore, in the left-right direction, the reactor 94 is positioned offset from the left-right center of the main engine 10. For example, in this embodiment, the mixer 92 is located to the left of the reactor 94 in the left-right direction (see Figure 2). The mixer 92 and reactor 94 are positioned adjacent to each other in the left-right direction.

In the left-right direction, the reactor 94 is positioned at the same position as the turbocharger 5 and the fifth exhaust pipe 95. That is, as shown in FIG. 4, the turbocharger 5, the fifth exhaust pipe 95, and the reactor 94 are aligned along the fore-and-aft direction, and are lined up in order toward the forward direction, which is the propulsion direction. This alignment direction coincides with the extension direction of the fifth exhaust pipe 95, i.e., the direction of the cylinder row of the main engine 10.

More specifically, as shown in Figure 9, the reactor 94 according to this embodiment has a reaction tube 94a through which exhaust gas flows, multiple catalysts 94b (three in the illustrated example) that promote the reaction of the exhaust gas, a soot blower 94c that blows compressed air onto each catalyst 94b, an inspection manhole 94d, and insulation 94e that covers the entire reactor 94 (see also Figure 2 for the reaction tube 94a).

Of these, the reaction tube 94a is a substantially cylindrical pipe arranged with its central axis aligned along the height direction. The exhaust gas (see arrow f3 in Figure 9) that flows into the reaction tube 94a from its lower end is purified by the catalyst 94b and flows out from its upper end. The dimensions of the reaction tube 94a are set according to the accommodation space for the catalyst 94b, etc.

The multiple catalysts 94b consist of, for example, an SCR catalyst, a slip catalyst, etc. When activated, the SCR catalyst can purify the exhaust gas by reacting (reducing) ammonia with NOx in the exhaust gas. The slip catalyst can oxidize and purify the unreacted ammonia emitted from the SCR catalyst.

The soot blower 94c branches off for each catalyst 94b, and by blowing compressed air supplied from outside (arrow f4 in Figure 9) onto each catalyst 94b, it is possible to blow away the soot that has accumulated on them.

A manhole 94d is provided for each catalyst 94b, and can be opened and closed as needed to check the condition of each catalyst 94b or perform maintenance on each catalyst 94b.

Exhaust gas sent from the fourth exhaust pipe 93 to the reactor 94 is purified by the catalyst 94b and discharged from the reaction pipe 94a to reach the fifth exhaust pipe 95. As shown in Figure 5, the flow direction A2 of the exhaust gas in the reactor 94 and the flow direction A1 of the exhaust gas in the mixer 92 are opposite to each other.

- 5th exhaust pipe 95 -
The fifth exhaust pipe 95 is configured as a pipe that connects the reactor 94 and the turbocharger 5. Specifically, as shown in Fig. 2 , the fifth exhaust pipe 95 according to this embodiment has an upstream portion 95a that extends upward from the upper surface of the reactor 94, and a downstream portion 95b that is continuous with the upstream portion 95a and extends rearward.

Of these, the upstream portion 95a of the fifth exhaust pipe 95 extends coaxially with the reaction tube 94a along the height direction, and then bends rearward to form an arc with a central angle of 90° in side view.

On the other hand, the downstream section 95b of the fifth exhaust pipe 95 extends rearward in a generally straight line from the rear end of the upstream section 95a. This downstream section 95b is connected to the turbine 5b of the turbocharger 5. Furthermore, as shown in Figures 3 and 4, the first bypass pipe 45 is connected to a midpoint of the downstream section 95b.

The exhaust gas sent from the reactor 94 into the fifth exhaust pipe 95 flows upward in the vertical direction, then changes direction and heads rearward, reaching the turbocharger 5.

(3) Control System The engine 1 also includes a control unit 100 that controls 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 each part of the engine 1.

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 seal valve 64 and second seal valve 65. In this case, exhaust gas that flows into the exhaust passage 40 from each cylinder 15 bypasses the SCR device 90. The exhaust gas that bypasses the SCR device 90 passes through or bypasses the turbocharger 5 depending on the opening of the turbine bypass valve 62, and then passes through the second exhaust pipe 43 and boiler 44 in that order, before being incinerated in the boiler 44.

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

(4) Performance of the SCR Device As described above, according to the embodiment, the direction of gravity acting on the urea injected from the injection nozzle 92b coincides with the extension direction of the mixer 92 as shown in Fig. 6. In other words, gravity acting on the reducing agent is in a direction perpendicular to the cross section shown in Fig. 7. This, combined with the fact that the reducing agent is injected from the center position within the mixing tube 92a, makes it possible to uniformly mix the exhaust gas and the reducing agent without causing unevenness due to gravity.

Furthermore, extending the mixer 92 downward as shown in Figure 5 contributes to making the main engine 10 and the SCR device 90 as a whole more compact (particularly in terms of height) compared to a configuration in which the mixer is extended upward. This makes it possible to mount the SCR device 90 on a variety of ship types, which is advantageous in optimizing the SCR device 90 for each ship type.

Furthermore, as shown in Figure 7, by arranging the injection port 921 of the injection nozzle 92b so that it overlaps with the central axis Pc of the mixing tube 92a, it becomes possible to inject the reducing agent more isotropically. This is effective in uniformly mixing the exhaust gas and reducing agent.

Furthermore, as shown in Figure 4, by arranging the mixer 92 and exhaust manifold 42 side by side facing in the propulsion direction (forward), the third exhaust pipe 91 can have a simpler shape than if they were arranged offset in the ship's width direction (left and right direction). This is advantageous in making the SCR device 90 more compact.

Furthermore, as shown in Figures 1 and 4, the third exhaust pipe 91 connecting the exhaust manifold 42 and the mixer 92 can be configured without bending it upward in the height direction when viewed from the flow direction. Since there is no need to bend it upward, the shape of the third exhaust pipe 91 can be configured to be shorter along the extension direction (downward) of the mixer 92. This is advantageous for making the SCR device 90 more compact.

Furthermore, as shown in FIG. 5, the reactor 94 and mixer 92 according to this embodiment are arranged adjacent to each other along the front surface 10a of the main engine 10. This allows for effective use of the space near the front surface 10a of the main engine 10, which in turn contributes to making the SCR device 90 more compact.

Furthermore, as shown in Figures 3 and 4, the fifth exhaust pipe 95 connecting the reactor 94 and the turbocharger 5 can be realized without bending it downward in the height direction when viewed from the flow direction. Since there is no need to bend it downward, the shape of the fifth exhaust pipe 95 can be configured to be shorter along the extension direction (upward) of the reactor 94. This is advantageous for making the SCR device 90 more compact.

Furthermore, by placing the reactor 94 below the turbocharger 5, soot that has accumulated on the catalyst 94b inside the reactor 94 is less likely to reach the turbocharger 5 due to the action of gravity. This is effective in maintaining the performance of the reactor 94 and, ultimately, the SCR device 90.

In addition, the aforementioned propeller shaft extends rearward from the rear face of the main engine 10. Therefore, arranging the mixer 92 and reactor 94 along the front face 10a of the main engine 10 is also effective in avoiding interference between the propeller shaft and the SCR device 90.

Furthermore, in the case of conventional SCR devices 90, the mixer 92 and reactor 94 have been positioned in various ways depending on the ship's type. In this case, it was necessary to change the design of the third exhaust pipe 91, fourth exhaust pipe 93, fifth exhaust pipe 95, etc. each time depending on the ship's type so that the exhaust gas pressure loss occurring in the exhaust pipe would be within an acceptable range. Combined with the time required to design the support structure for each exhaust pipe, conventional configurations required a great deal of effort.

In contrast, by configuring the main engine 10 and SCR device 90 as a single set, as in the above embodiment, the shapes and dimensions of the third exhaust pipe 91, fourth exhaust pipe 93, fifth exhaust pipe 95, etc. can be fixed. This makes it possible to fix the pressure loss that can occur in each exhaust pipe regardless of the hull form, reducing the effort required for design and being advantageous for optimizing and compacting the entire engine 1.

(5) Other Embodiments Fig. 10 is a diagram corresponding to Fig. 5 and shows a modified SCR device. Also, Fig. 11A is a diagram corresponding to Fig. 7 and shows a first modified example of the mixer 92, Fig. 11B is a diagram corresponding to Fig. 7 and shows a second modified example of the mixer 92, and Fig. 11C is a diagram corresponding to Fig. 7 and shows a third modified example of the mixer 92.

In the above embodiment, the mixer 92 and reactor 94 are configured as separate units, but the present disclosure is not limited to such a configuration. The mixer 92' and reactor 94' may also be configured as an integrated unit, as in the SCR device 90' illustrated in Figure 10.

In the case of this SCR device 90', a partition is provided inside the housing, with the area to the right of the partition corresponding to the mixer 92' and the area to the left corresponding to the reactor 94'. Even when this modified example is adopted, the flow direction of the exhaust gas in the mixer 92' and the flow direction in the reactor 94' will be opposite to each other, as in the previous embodiment.

Furthermore, the mixer 92 according to the above embodiment is equipped with the mixing mechanism 92c illustrated in FIG. 6, but the configuration of the mixing mechanism 92c is not limited to that illustrated in FIG. 6.

For example, as in the evaporator 92' according to the first modified example, the mixing mechanism 92c' may be formed by a single plate extending perpendicular to the height direction, or as in the evaporator 92'' according to the second modified example, the mixing mechanism 92c'' may be formed by a Venturi tube disposed below the injection nozzle 92b (see FIGS. 11A and 11B). Alternatively, as in the evaporator 923 according to the third modified example shown in FIG. ^11C , the mixing mechanism ^92c3 may be formed by a conical member whose diameter tapers downward.

Furthermore, the injection nozzle 92b in the above embodiment is configured so that the injection port 921 and the central axis Pc overlap on a cross section perpendicular to the height direction, but the present disclosure is not limited to such a configuration.

For example, the nozzle 921 may be positioned at the center of the mixer 92, but the center position may not be precisely aligned with the central axis Pc, and the nozzle 921 and the central axis Pc may not overlap. In this case, it is preferable to position the nozzle 921 near the central axis Pc. In other words, the "center position of the mixer 92" in this disclosure includes not only the intersection of the central axis Pc and the cross section, but also any position that falls within the area near the central axis Pc. Furthermore, it is not necessary to position the nozzle 921 at the center of the mixer 92.

Note that the "region near the central axis Pc" referred to here refers to one of the regions closer to the central axis Pc than the inner wall portion of the mixer 92 (more specifically, the inner wall portion of the mixing tube 92a) when the cross section is divided into two regions in the radial direction extending radially from the central axis Pc.

The term "central axis Pc of the mixer 92" can also be defined in a broad sense. In other words, the "center" here is not limited to the central point as viewed in a circular cross section, but includes the center of symmetry in a semicircular cross section (so-called "center of rotational symmetry"), the geometric center in the same cross section (so-called "center of gravity"), and the geometric center of various cross-sectional shapes, including rectangular. In other words, the mixing tube 92a according to the present disclosure is not limited to cylindrical piping, but may also be semi-cylindrical piping or rectangular piping. The cross-sectional shape of the mixing tube 92a includes any shape.

1. Engine (marine internal combustion engine)
5 Turbocharger 10 Main engine 10a Front (outer surface)
15 Cylinder 30 Intake passage 40 Exhaust passage 42 Exhaust manifold 90 SCR device 92 Mixer 92a Mixing tube 92b Injection nozzle 921 Injection port 94 Reactor 94b Catalyst Pc Central axis

Claims (7)

a main engine for propelling the vessel in a predetermined propulsion direction;
an SCR device that denitrifies exhaust gas from the main engine,
The SCR device is
a mixer accommodating an injection nozzle for injecting a reducing agent into the exhaust gas;
a reactor disposed downstream of the mixer and bringing the exhaust gas and the reducing agent into contact with a catalyst;
the mixer is arranged along an outer surface of the main engine facing the propulsion direction, and is configured to extend from an upper side to a lower side in a height direction of the main engine ,
The mixer is separate from the reactor, and
a mixing tube extending along the height direction and accommodating the injection nozzle;
a mixing mechanism for mixing the reducing agent with the exhaust gas,
The injection nozzle is disposed above the center of the mixing tube in the height direction and downstream of the mixing mechanism.
A marine internal combustion engine equipped with an SCR device. 2. The marine internal combustion engine with an SCR device according to claim 1,
the injection nozzle injects the reducing agent downward in the height direction from a central position of the mixer as seen in a cross section perpendicular to the height direction. 3. The marine internal combustion engine with an SCR device according to claim 2,
the mixer has a mixing tube that houses the injection nozzle;
The mixing tube is formed in a cylindrical shape having a central axis extending along the height direction,
10. A marine internal combustion engine with an SCR device, wherein the injection nozzle has an injection port disposed so as to overlap with the central axis on the cross section. 4. The marine internal combustion engine with an SCR device according to claim 1,
The main engine comprises:
A plurality of cylinders aligned in the propulsion direction;
an exhaust manifold connected to the plurality of cylinders and extending in the propulsion direction;
The mixer is disposed in line with the exhaust manifold in the propulsion direction. 5. The marine internal combustion engine with an SCR device according to claim 4,
An SCR device-equipped marine internal combustion engine, characterized in that an upper end of the mixer is disposed lower than the exhaust manifold in the height direction. 6. The marine internal combustion engine with an SCR device according to claim 1,
The reactor is disposed adjacent to the mixer along the outer surface and is configured to extend from the lower side to the upper side in the height direction. 7. The marine internal combustion engine with an SCR device according to claim 6,
a turbocharger disposed on an upper surface of the main engine and into which the gas purified in the reactor flows,
An SCR device-equipped marine internal combustion engine, characterized in that an upper end of the reactor is disposed lower than the turbocharger in the height direction.