JP7394605B2 - EGR system - Google Patents

Description

The present invention relates to an exhaust gas recirculation system, ie, an EGR system, provided in a marine diesel engine.

Conventionally, in the field of marine diesel engines installed on ships, an EGR system has been proposed as a method for reducing nitrogen oxides (NOx) in exhaust gas emitted from marine diesel engines (for example, Patent Document 1 , 2). Generally, an EGR system includes a scrubber unit that uses water to clean a portion of the exhaust gas (hereinafter referred to as EGR gas) emitted from a marine diesel engine, and a demister unit that removes moisture from the EGR gas after cleaning. It is equipped with

The scrubber unit injects water to the EGR gas, thereby removing foreign substances such as sulfur oxides (SOx) and particulates (PM) such as soot and dust from the EGR gas, thereby cleaning the EGR gas. The water used to clean the EGR gas in the scrubber unit (hereinafter referred to as scrubber water) is injected into the pipe of the scrubber unit to clean the EGR gas, and then remains in a mist form together with the cleaned EGR gas in the scrubber unit. flows into the demister unit. On the other hand, the demister unit includes a demister box in which a flow path is formed for separating EGR gas after cleaning from moisture such as scrubber water. In the demister unit, EGR gas and scrubber water after cleaning by the scrubber unit flow into the demister box and flow along the flow path within the demister box. Thereby, moisture such as scrubber water is separated and removed from the EGR gas after cleaning.

The EGR system causes the EGR gas after cleaning to flow out of the demister box, mixes it with air (fresh air) from the outside, and recirculates it as combustion gas to the marine diesel engine. As a result, the EGR system reduces the oxygen concentration during combustion in the combustion chamber of a marine diesel engine, suppressing the generation of NOx due to fuel combustion, and reducing the NOx content in the exhaust gas (i.e., NOx emissions). do.

Japanese Patent Application Publication No. 2017-144431 Japanese Patent Application Publication No. 2002-332919

By the way, an element (for example, the demister body described in Patent Document 2) is provided in the flow path in the demister box to remove moisture from the EGR gas by passing the EGR gas. Further, the pipe of the scrubber unit is joined to the side wall of the demister box via an elbow pipe. The EGR gas and scrubber water that flowed into the demister box through this elbow collide with the plate facing the side wall of the demister box, thereby removing some of the scrubber water before the EGR gas passes through the element. ing.

However, when the cleaned EGR gas and scrubber water are allowed to flow into the demister box from the pipe of the scrubber unit through the elbow pipe, the scrubber water accumulates in the elbow pipe. There is a risk of corrosion.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an EGR system that can prevent corrosion of piping.

In order to solve the above-mentioned problems and achieve the objects, the EGR system according to the present invention supplies EGR gas, which is a part of the exhaust gas discharged from the engine body of a marine diesel engine, to the engine body as combustion gas. The recirculating EGR system includes a scrubber pipe that receives the EGR gas from above and guides it downward, and the EGR gas that has flowed into the scrubber pipe is washed with scrubber water, and the EGR gas after washing is mixed with the scrubber water. a scrubber unit that causes a gas-liquid mixed fluid with water to flow down from the scrubber pipe; and a demister unit that separates the gas-liquid mixed fluid that has flowed in through the scrubber pipe into the EGR gas after cleaning and the scrubber water. The demister unit includes a moisture removal section that removes moisture contained in the EGR gas after cleaning, a demister inlet that communicates with the scrubber pipe, and a demister outlet that allows the EGR gas after cleaning to flow out. a demister box provided on the ceiling and containing the moisture removing section, the outlet of the scrubber pipe being joined to the demister inlet so as to face the bottom of the demister box. shall be.

Further, in the above invention, the ceiling portion of the demister box of the EGR system according to the present invention is lower than the first ceiling portion where the demister outlet portion is provided, and the first ceiling portion; and a second ceiling section in which the demister inlet section is provided.

Further, in the above invention, the ceiling part of the demister box of the EGR system according to the present invention has a rectangular shape when viewed from above, and the demister inlet part and the demister outlet part are arranged in a diagonal direction of the ceiling part. It is characterized by being located.

Further, in the above invention, the EGR system according to the present invention is such that the exhaust gas outlet pipe is branched from the exhaust gas outlet pipe provided in the engine body so as to communicate with the flue of the ship, and the scrubber pipe is connected to the scrubber pipe without going through the flue. It is characterized by comprising an EGR inlet pipe communicating with the inlet.

Further, in the above invention, in the EGR inlet pipe of the EGR system according to the present invention, the central axis of the EGR inlet pipe is located closer to the pipe wall side of the exhaust gas outlet pipe than the central axis of the exhaust gas outlet pipe. The exhaust gas outlet pipe is connected to the exhaust gas outlet pipe.

According to the present invention, it is possible to provide an EGR system that can prevent corrosion of pipes.

FIG. 1 is a schematic diagram showing a configuration example of a marine diesel engine to which an EGR system according to Embodiment 1 of the present invention is applied. FIG. 2 is a perspective view schematically showing a configuration example of an EGR system according to Embodiment 1 of the present invention. FIG. 3 is a side view schematically showing a configuration example of an EGR system according to Embodiment 1 of the present invention. FIG. 4 is a top view showing an example of the arrangement of the demister inlet and outlet of the demister box in Embodiment 1 of the present invention. FIG. 5 is a diagram illustrating a comparison in scale between the EGR system according to Embodiment 1 of the present invention and a conventional EGR system. FIG. 6 is a sectional view showing an example of a joined state of the EGR inlet pipe and the exhaust gas outlet pipe of the engine body in the first embodiment of the present invention. FIG. 7 is a perspective view schematically showing a configuration example of an EGR system according to Embodiment 2 of the present invention.

EMBODIMENT OF THE INVENTION Below, with reference to an accompanying drawing, the preferred embodiment of the EGR system based on this invention is described in detail. Note that the present invention is not limited to this embodiment. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from the actual one. Drawings may also include portions that differ in dimensional relationships and ratios. Further, in each drawing, the same components are given the same reference numerals.

(Embodiment 1)
A marine diesel engine according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic diagram showing a configuration example of a marine diesel engine to which an EGR system according to Embodiment 1 of the present invention is applied. As shown in FIG. 1, this marine diesel engine 11 includes an engine body 1, a supercharger 7 for supercharging combustion gas to the engine body 1, and cooling the combustion gas after compression by the supercharger 7. The engine includes a cooler 10 for recirculating exhaust gas to the engine body 1, and an EGR system 15 for recirculating exhaust gas to the engine body 1. The marine diesel engine 11 also includes an intake section 8 for taking in air from the outside as combustion gas, and a deformed pipe 9 as an exhaust gas outlet pipe for discharging exhaust gas from the engine body 1 to the flue 12 of the ship. . The EGR system 15 is an example of the EGR system according to the first embodiment of the present invention, and includes a scrubber unit 16, a demister unit 17, an EGR blower 18, an EGR inlet pipe 19, and an EGR outlet pipe 20.

Although not shown, the engine main body 1 is a propulsion engine (main engine) that drives and rotates a propulsion propeller of a ship via a propeller shaft. The engine main body 1 is a two-stroke diesel engine such as a uniflow scavenging and exhaust type crosshead type diesel engine. Specifically, as shown in FIG. 1, the engine body 1 includes a base plate 2 located below the engine body 1 in the height direction D1, a frame 3 provided on the base plate 2, and a frame 3 provided on the frame 3. A cylinder jacket 4 provided in the cylinder jacket 4 is provided. These bed plate 2, frame 3, and cylinder jacket 4 are fastened and fixed together by connecting members such as a plurality of tie bolts (not shown) and nuts (not shown) extending in the height direction D1. has been done.

The base plate 2 constitutes a crankcase. Although not shown, the base plate 2 is provided with a propeller shaft, a crankshaft, etc. that drive and rotate a propulsion propeller. The crankshaft is rotatably supported by bearings. A lower end portion of a connecting rod (not shown) is rotatably connected to the crankshaft via a crank.

The frame 3 is provided with the above-described connecting rod, a piston rod (not shown), and a crosshead (not shown) that rotatably connects the piston rod and the connecting rod. In particular, the lower end of the piston rod and the upper end of the connecting rod are connected to the crosshead. The crosshead is disposed between a pair of guide plates (not shown) fixed to the frame 3, and is supported slidably along the pair of guide plates.

Although not shown, the cylinder jacket 4 is provided with a cylinder liner extending upward from the inside of the cylinder jacket 4, and a cylinder cover is provided at the upper end of the cylinder liner. The cylinder of the engine body 1 is formed by these cylinder liners, cylinder covers, and the like. In the first embodiment, the engine body 1 is formed with a plurality of cylinders. Each of the plurality of cylinders is supplied with fuel from a fuel injection pump (not shown). On the other hand, a piston (not shown) is provided in the inner space of the cylinder so as to be able to reciprocate along the inner wall of the cylinder. The above-mentioned upper end of the piston rod is attached to the lower end of this piston.

The engine body 1 also includes a scavenging trunk 5 and an exhaust manifold 6. As shown in FIG. 1, the scavenging trunk 5 is provided in the cylinder jacket 4 and communicates with the combustion chamber in each cylinder via a scavenging port (not shown) of the engine body 1. The scavenging trunk 5 receives combustion gas through piping, etc., and sends the received combustion gas to the combustion chamber in each cylinder. As shown in FIG. 1, the exhaust manifold 6 is provided above the cylinder jacket 4 and communicates with the combustion chamber in each cylinder via an exhaust port (not shown) of the engine body 1. The exhaust manifold 6 receives exhaust gas generated by combustion of fuel from the combustion chamber in each cylinder and temporarily stores it, thereby converting the dynamic pressure of the exhaust gas into static pressure.

The engine main body 1 having the above-described configuration causes the piston to reciprocate by burning fuel together with the combustion gas sent from the scavenging trunk 5 in the combustion chamber in each cylinder. The engine main body 1 converts this reciprocating motion into rotational motion of an output shaft such as a propeller shaft or a crankshaft, thereby outputting the propulsive force of the ship from this output shaft. At this time, the engine main body 1 allows the intake and exhaust air in each cylinder to flow in one direction from below to above, thereby eliminating residual exhaust gas. Specifically, combustion gas is supplied from the scavenging trunk 5 to the combustion chamber in each cylinder, and exhaust gas after combustion is discharged from the combustion chamber in each cylinder to the exhaust manifold 6.

In addition, in this Embodiment 1, the height direction D1 of the engine main body 1 is an up-down direction, and is parallel to the direction of reciprocation of a piston, for example. The axial direction D2 of the engine body 1 is parallel to the output shaft direction C1 shown in FIG. The output shaft direction C1 is the longitudinal direction of the output shaft of the engine body 1. The width direction D3 of the engine body 1 is a direction perpendicular to the height direction D1 and the axial direction D2. That is, these height direction D1, axial direction D2, and width direction D3 are mutually perpendicular directions. Note that the height direction D1, axial direction D2, and width direction D3 are the same not only for the engine body 1 but also for each component constituting the engine body 1, the supercharger 7, and the EGR system 15 provided in the engine body 1. It is. Furthermore, simply "exhaust gas" means exhaust gas discharged from the engine body 1.

The supercharger 7 uses exhaust gas from the engine body 1 to pressurize and compress combustion gas supplied to the engine body 1. As shown in FIG. 1, the supercharger 7 includes a turbine section 7a, a compressor section 7b, and an exhaust gas section 7c, and is provided in the upper part of the engine main body 1. The turbine portion 7a includes a turbine (impeller) and a casing that rotatably accommodates the turbine, and is configured to rotate the turbine using exhaust gas from the engine body 1. Specifically, the gas inlet of the casing of the turbine section 7a communicates with the exhaust manifold 6 via piping. The compressor section 7b includes an impeller and a casing that rotatably accommodates the impeller. Although not shown, the turbine of the turbine section 7a and the impeller of the compressor section 7b are connected to each other by a rotating shaft, and are configured to rotate together with this rotating shaft as a central axis. The exhaust gas section 7c is provided at a gas outlet section of the casing of the turbine section 7a. A gas outlet portion of the exhaust gas section 7c communicates with a deformed pipe 9 communicating with the flue 12. The exhaust gas section 7c causes the exhaust gas flowing out from the turbine section 7a to flow into the irregularly shaped pipe 9.

Further, as shown in FIG. 1, an intake section 8 for sucking gas such as fresh air (also referred to as fresh air) from the outside is provided at the gas inlet section of the casing of the compressor section 7b. The intake section 8 is composed of a silencer, a filter, and the like. An EGR outlet pipe 20 is connected to this intake section 8 . Thereby, the compressor section 7b is configured so that air from the outside and EGR gas from the EGR outlet pipe 20 can be supplied via the intake section 8. The compressor section 7b rotates with the rotation of the turbine of the turbine section 7a described above, and pressurizes and compresses the combustion gas. Note that this combustion gas is a mixed gas of fresh air and EGR gas when the EGR system 15 is in operation, and is only fresh air when the EGR system 15 is stopped. The combustion gas after being pressurized and compressed by the compressor section 7b is supplied to the cooler 10 through piping or the like.

The irregularly shaped pipe 9 is an example of an exhaust gas outlet pipe provided in the engine body 1 so as to communicate with the flue 12 of the ship. As shown in FIG. 1, the irregularly shaped pipe 9 communicates the flue 12 with the exhaust gas part 7c whose opening shape is different from each other, and directs the exhaust gas discharged from the engine body 1 through the exhaust gas part 7c to the flue 12. Send it in. The flue 12 is a pipe (i.e., pipe on the ship side) that is provided to communicate with a ship's chimney during shipbuilding, and is connected to the irregularly shaped pipe 9 of the marine diesel engine 11 mounted on the ship. Further, as shown in FIG. 1, an EGR inlet pipe 19 is connected to a midway portion of the irregularly shaped pipe 9. As a result, part of the exhaust gas flowing into the flue 12 through the irregularly shaped pipe 9 flows from the irregularly shaped pipe 9 into the EGR inlet pipe 19 during operation of the EGR system 15.

The cooler 10 is for cooling the combustion gas after being pressurized and compressed by the supercharger 7. As shown in FIG. 1, the cooler 10 communicates with the compressor section 7b via piping and the like. The cooler 10 also communicates with the scavenging trunk 5 via piping and the like. The cooler 10 receives pressurized and compressed combustion gas from the compressor section 7b through a pipe or the like, and cools the received combustion gas by, for example, heat exchange with cooling water. The combustion gas cooled by the cooler 10 is supplied to the scavenging trunk 5 of the engine body 1 via piping or the like.

The EGR system 15 is a system that recirculates EGR gas, which is part of the exhaust gas discharged from the engine body 1 of the marine diesel engine 11, to the engine body 1 as combustion gas. As shown in FIG. 1, the EGR system 15 includes a scrubber unit 16, a demister unit 17, an EGR blower 18, an EGR inlet pipe 19, and an EGR outlet pipe 20, and is provided in the engine body 1. Furthermore, the EGR inlet pipe 19 is provided with an EGR inlet valve 19a, and the EGR outlet pipe 20 is provided with an EGR outlet valve 20a.

FIG. 2 is a perspective view schematically showing a configuration example of an EGR system according to Embodiment 1 of the present invention. FIG. 3 is a side view schematically showing a configuration example of an EGR system according to Embodiment 1 of the present invention. Note that FIG. 3 shows, as a side view of the EGR system 15, a view of the EGR system 15 viewed from the axial direction D2. The EGR system 15 will be described in detail below with reference to FIGS. 1 to 3.

The scrubber unit 16 cleans EGR gas so that it can be used as combustion gas. Specifically, as shown in FIGS. 2 and 3, the scrubber unit 16 includes a Venturi pipe 116 as an example of a scrubber pipe that receives EGR gas from above and guides it downward. The Venturi tube 116 is configured to extend in the height direction D1, and has an inlet 16a at the upper end and an outlet 16b at the lower end, as shown in FIG. 3, for example. The inlet 16a of the Venturi pipe 116 is joined to the outlet of the EGR inlet pipe 19. The outlet 16b of the Venturi tube 116 is joined to the inlet of the demister unit 17 (demister inlet to be described later). Further, although not shown, the scrubber unit 16 includes a water injection part at the upper part 116a of the Venturi pipe 116. This water injection unit injects scrubber water to the EGR gas in order to clean the EGR gas inside the venturi pipe 116 .

The scrubber unit 16 having such a configuration cleans the EGR gas flowing from the EGR inlet pipe 19 into the Venturi pipe 116 through the inlet 16a with scrubber water, and also removes the gas-liquid mixture of the cleaned EGR gas and the scrubber water. The mixed fluid flows down from the venturi tube 116. The scrubber unit 16 repeats the above-described cleaning of the EGR gas by jetting the scrubber water each time the EGR gas flows into the venturi pipe 116 from the EGR inlet pipe 19.

The demister unit 17 separates the gas-liquid mixed fluid that has flowed in through the scrubber pipe into EGR gas and scrubber water after being cleaned by the scrubber unit 16. Specifically, as shown in FIGS. 2 and 3, the demister unit 17 includes an element 17a and a demister box 17b for separating and removing scrubber water from the EGR gas after cleaning.

The element 17a is an example of a moisture removal section that removes moisture contained in the EGR gas after cleaning. Specifically, the element 17a is constituted by a plate-shaped body having a flow path bent a plurality of times through which the EGR gas can pass. The element 17a separates and removes moisture (mist) from the EGR gas while allowing the EGR gas to pass through its own flow path from one surface side, and releases the EGR gas after moisture removal from the other surface side. .

The demister box 17b is a hollow structure for separating and removing scrubber water from the EGR gas after cleaning by the scrubber unit 16. Specifically, as shown in FIGS. 2 and 3, the demister box 17b includes a ceiling, a bottom 117c, and a plurality of side walls connecting the ceiling and the bottom 117c. In the first embodiment, the ceiling portion of the demister box 17b is constituted by a first ceiling portion 117a and a second ceiling portion 117b having a step (height difference) in the height direction D1. The first ceiling portion 117a is a ceiling portion provided with a demister outlet portion 117e for allowing EGR gas to flow out after cleaning. The second ceiling portion 117b is lower than the first ceiling portion 117a, and is provided with a demister inlet portion 117d that communicates with the scrubber pipe. That is, as shown in FIG. 3, the demister box 17b has an L-shape when viewed from the side in the axial direction D2.

Further, as shown in FIG. 3, the demister box 17b includes an element 17a. At this time, the element 17a is supported by a support section provided inside the demister box 17b so as to be inclined at a predetermined angle with respect to the height direction D1. The demister box 17b forms therein a flow path 17c that extends from the demister inlet section 117d, passes through the element 17a, and reaches the demister outlet section 117e.

Further, as shown in FIGS. 2 and 3, an EGR blower 18 is provided on the first ceiling portion 117a of the demister box 17b. At this time, the inlet part of the EGR blower 18 is joined to the demister outlet part 117e of the first ceiling part 117a, so that the demister box 17b and the EGR blower 18 communicate with each other via the demister outlet part 117e. On the other hand, the venturi pipe 116 of the scrubber unit 16 is installed upright on the second ceiling portion 117b of the demister box 17b. At this time, the outlet 16b of the Venturi tube 116 is joined to the demister inlet 117d so as to face the bottom 117c of the demister box 17b, as shown in FIG. Thereby, the Venturi tube 116 communicates with the demister box 17b in a direction (for example, height direction D1) in which the outlet 16b and the bottom 117c of the demister box 17b face each other.

As shown in FIG. 3, the flow path 17c in the demister box 17b having the above-described configuration advances from the demister inlet 117d toward the bottom 117c of the demister box 17b, and then passes through the bottom 117c and the side wall of the demister box 17b. After passing through the element 17a, it reaches the demister outlet section 117e. That is, in the demister box 17b forming this flow path 17c, the bottom 117c causes the gas-liquid mixed fluid that has flowed into the demister box 17b from the outlet 16b of the venturi pipe 116 through the demister inlet 117d to collide with each other. It functions as a baffle plate that separates most of the scrubber water from the gas-liquid mixed fluid and reduces the flow rate of EGR gas (EGR gas after cleaning) in the gas-liquid mixed fluid.

Further, the heights H1 and H2 (see FIG. 3) of the first ceiling part 117a and the second ceiling part 117b with respect to the bottom part 117c of the demister box 17b are, for example, the size of the element 17a arranged in the demister box 17b. It can be set by the height, position and inclination, and the flow path 17c in the demister box 17b.

Specifically, the moisture removal ability of the element 17a arranged inside the demister box 17b decreases when the flow rate of the EGR gas to be passed therethrough is excessively high. That is, in order to efficiently remove water from the EGR gas by the element 17a, the flow velocity of the EGR gas flowing along the flow path 17c in the demister box 17b must be appropriately reduced when passing through the element 17a. preferable. From the viewpoint of reducing the flow rate of EGR gas in this way, the flow path area of the flow path 17c in the demister box 17b gradually (continuously or stepwise) increases from the demister inlet portion 117d side to the demister outlet portion 117e side. It is preferable to increase the size (target). In addition, the said flow path area is the passage area of the fluid which flows through the flow path 17c in the demister box 17b. Further, in order for the bottom portion 117c of the demister box 17b to efficiently function as the baffle plate described above, the demister inlet portion 117d is preferably closer to the bottom portion 117c of the demister box 17b. Considering these circumstances, it is preferable that the height H2 of the second ceiling part 117b is less than half the height H1 of the first ceiling part 117a, and the height H3 of the lower end of the element 17a (see FIG. (see) or more is preferable.

Further, as shown in FIG. 3, a drain port 117f is provided at the bottom 117c of the demister box 17b. Inside the demister box 17b, the scrubber water flowing from the demister inlet 117d together with the cleaned EGR gas collides with the bottom 117c of the demister box 17b and is separated from the EGR gas by the element 17a. It accumulates at the bottom 117c. The scrubber water accumulated in the bottom 117c is discharged to the outside of the demister box 17b from the drain port 117f, and is collected in equipment such as a tank (not shown) that communicates with the drain port 117f via piping or the like.

Further, as shown in FIG. 3, a vibration isolator 21 is provided between the demister box 17b and the Venturi tube 116. One end portion of the vibration isolating portion 21 is connected to a portion of the side wall portion (outer wall portion) of the demister box 17b that faces in the width direction D3 the Venturi tube 116 erected on the second ceiling portion 117b. The other end of the vibration isolator 21 is connected to a portion of the outer wall of the venturi tube 116 that faces the side wall of the demister box 17b in the width direction D3. The vibration isolator 21 connects the side wall of the demister box 17b and the venturi tube 116, thereby suppressing vibrations of the venturi tube 116 that are out of phase relative to the demister box 17b.

The EGR blower 18 generates a flow of EGR gas for recirculation to the engine body 1 . In the first embodiment, the EGR blower 18 is provided on the first ceiling part 117a of the demister box 17b so as to communicate with the demister box 17b via the demister outlet part 117e, as shown in FIGS. 2 and 3. . Further, as shown in FIG. 2, an EGR outlet pipe 20 is connected to the outlet portion of the EGR blower 18. The EGR blower 18 sucks EGR gas from inside the demister box 17b and sends the sucked EGR gas to the EGR outlet pipe 20.

The EGR inlet pipe 19 is a pipe for guiding a part of the exhaust gas discharged from the engine body 1 to the scrubber unit 16 as EGR gas. As shown in FIG. 2, the inlet end of the EGR inlet pipe 19 is joined to a midway portion of the irregularly shaped pipe 9. The outlet end of the EGR inlet pipe 19 is joined to the inlet 16a (see FIG. 3) of the Venturi pipe 116 of the scrubber unit 16. As described above, the irregularly shaped pipe 9 is provided in the engine body 1 so as to communicate with the flue 12 (see FIG. 1) of the ship. The EGR inlet pipe 19 branches from the irregularly shaped pipe 9 and is piped so as to communicate with the inlet 16a of the Venturi pipe 116 without going through the flue 12. From the viewpoint of downsizing the marine diesel engine 11, the EGR inlet pipe 19 is preferably arranged below the upper end of the exhaust manifold 6 in the height direction D1, as shown in FIG.

Further, the EGR inlet pipe 19 is provided with an EGR inlet valve 19a, as shown in FIGS. 1 and 2. The EGR inlet valve 19a is constituted by a drive valve that opens and closes according to the operation of a drive section. The EGR inlet valve 19a is controlled to be open when the EGR system 15 is operating. In this case, the EGR inlet pipe 19 causes part of the exhaust gas from inside the irregularly shaped pipe 9 to flow as EGR gas to the Venturi pipe 116 by the suction action of the EGR blower 18 . On the other hand, the EGR inlet valve 19a is controlled to be closed when the EGR system 15 is stopped. In this case, the flow of EGR gas from the EGR inlet pipe 19 to the Venturi pipe 116 is stopped. Note that the opening/closing drive of the EGR inlet valve 19a is controlled, for example, by a control section (not shown) of the engine body 1 according to the load of the engine body 1 (engine load), etc. Further, of the exhaust gas in the irregularly shaped pipe 9, the remaining exhaust gas that is not extracted to the scrubber unit 16 via the EGR inlet pipe 19 is discharged out of the ship from the chimney through the flue 12 and the like.

The EGR outlet pipe 20 is a pipe for guiding the cleaned EGR gas to the engine main body 1 side as combustion gas. An inlet end of the EGR outlet pipe 20 is joined to an outlet portion of the EGR blower 18. The outlet end of the EGR outlet pipe 20 is joined to the intake section 8, as shown in FIGS. 1 and 2. The EGR outlet pipe 20 is arranged so that the EGR blower 18 and the intake section 8 communicate with each other.

Further, the EGR outlet pipe 20 is provided with an EGR outlet valve 20a, as shown in FIG. The EGR outlet valve 20a is constituted by a drive valve that opens and closes by the operation of a drive section. The EGR outlet valve 20a is controlled to be open when the EGR system 15 is operating. In this case, the EGR outlet pipe 20 allows the cleaned EGR gas to flow from the demister box 17b side to the intake section 8 by the pressure feeding action of the EGR blower 18. The EGR gas that has flowed into the intake section 8 is used as combustion gas for the engine body 1 together with the air that has been drawn into the intake section 8 from the outside. On the other hand, the EGR outlet valve 20a is controlled to be closed when the EGR system 15 is stopped. In this case, the flow of EGR gas from the EGR outlet pipe 20 to the intake section 8 is stopped. Note that the opening/closing drive of the EGR outlet valve 20a is controlled according to the engine load and the like, similarly to the EGR inlet valve 19a described above.

Next, the arrangement of the demister inlet section 117d and the demister outlet section 117e provided in the demister box 17b will be described in detail. FIG. 4 is a top view showing an example of the arrangement of the demister inlet and outlet of the demister box in Embodiment 1 of the present invention. FIG. 4 shows, as a top view of the demister box 17b, a view of the demister box 17b viewed from above in the height direction D1.

In the first embodiment, the ceiling portion of the demister box 17b includes a first ceiling portion 117a provided with a demister outlet portion 117e, and a second ceiling portion 117a, as shown in FIGS. 2 and 3 described above. and a second ceiling part 117b, which is lower than the second ceiling part 117b and has a demister inlet part 117d. The ceiling portion of the demister box 17b has a rectangular shape when viewed from above, as shown in FIG. 4, for example. In such a demister box 17b, the demister inlet part 117d and the demister outlet part 117e are arranged in the diagonal direction D4 of the ceiling part of the demister box 17b, as shown in FIG.

Specifically, as shown in FIG. 4, the demister inlet portion 117d and the demister outlet portion 117e are arranged alternately in the axial direction D2 and the width direction D3 of the demister box 17b. More specifically, the demister inlet portion 117d has the above-described irregular shape among the side wall portions 117g and 117h facing each other in the axial direction D2 of the demister box 17b, with the center position CP of the demister box 17b in the axial direction D2 as a border. It is arranged to be biased toward the side wall portion 117g that is closer to the tube 9 (see FIGS. 1 and 2). On the other hand, the demister outlet portion 117e is arranged to be biased toward the side wall portion 117h that is far from the irregularly shaped tube 9 among the side wall portions 117g and 117h of the demister box 17b, with the center position CP as a boundary. .

As described above, arranging the demister inlet part 117d and the demister outlet part 117e in the diagonal direction D4 of the ceiling of the demister box 17b means that the demister box extends from the demister inlet part 117d through the element 17a to the demister outlet part 117e. The flow path 17c within 17b is made longer. As a result, the flow rate of the EGR gas when passing through the element 17a can be easily lowered, and moisture can be efficiently removed from the EGR gas by the element 17a, so the arrangement of the demister inlet section 117d and the demister outlet section 117e is preferable. Further, by arranging the demister inlet portion 117d closer to the irregularly shaped tube 9, the Venturi tube 116, which is erected above the demister inlet portion 117d, is brought closer to the irregularly shaped tube 9. As a result, the length of the EGR inlet pipe 19 that communicates the irregularly shaped pipe 9 and the Venturi pipe 116 can be made shorter and the pressure loss of the EGR inlet pipe 19 can be reduced, so the arrangement of the demister inlet section 117d is preferable. Further, by arranging the demister outlet portion 117e off-centered away from the irregularly shaped pipe 9, the distance between the EGR blower 18 provided above the demister outlet portion 117e and the above-mentioned intake portion 8 becomes longer. As a result, it is possible to easily secure a necessary area for providing necessary equipment such as the EGR outlet valve 20a in the middle of the EGR outlet pipe 20 that communicates the intake section 8 and the EGR blower 18, so that the demister outlet section 117e can be easily secured. The arrangement of is preferable.

Note that the rectangular shape of the ceiling of the demister box 17b when viewed from above includes not only a quadrilateral (square or rectangle) as shown in FIG. Shapes resembling quadrilaterals include oval shapes formed in an arc shape, polygonal shapes with chamfered corners, and the like.

Next, the scale of the EGR system 15 according to the first embodiment of the present invention will be explained. FIG. 5 is a diagram illustrating a comparison in scale between the EGR system according to Embodiment 1 of the present invention and a conventional EGR system. In FIG. 5, a conventional EGR system 200 is illustrated by a chain double-dashed line, and includes a scrubber unit 201, a demister unit 202, an EGR blower 203, and an elbow pipe 204. The scrubber unit 201 is the same venturi type as the scrubber unit 16 in the first embodiment. The demister unit 202 includes a cubic or rectangular parallelepiped demister box. The EGR blower 203 is the same as the EGR blower 18 in the first embodiment. Although not shown in FIG. 5, the conventional EGR system 200 includes an EGR inlet pipe that communicates the inlet of the venturi pipe of the scrubber unit 201 with the ship's flue 12 (see FIG. 1), and an EGR blower 203. It includes an EGR outlet pipe that communicates with the intake section 8 (see FIGS. 1 and 2).

As shown in FIG. 5, in the conventional EGR system 200, the outlet of the venturi pipe of the scrubber unit 201 is joined to the side wall of the demister box of the demister unit 202 via an elbow pipe 204. The size in the height direction D1 of the conventional EGR system 200 having such a structure is the height Hb from the bottom of the demister box of the demister unit 202 to the upper end of the Venturi pipe of the scrubber unit 201. Further, the size of the conventional EGR system 200 in the width direction D3 is the length Lb from the positive side wall of the demister box of the demister unit 202 in the width direction D3 to the outer wall of the venturi pipe of the scrubber unit 201. becomes.

On the other hand, in the EGR system 15 according to the first embodiment, as shown in FIG. It is erected on the demister inlet portion 117d of the low second ceiling portion 117b. Therefore, the size of the EGR system 15 in the height direction D1 is based on the same standard as the conventional EGR system 200, and as shown in FIG. becomes. Furthermore, the size of the EGR system 15 in the width direction D3 is based on the same standard as the conventional EGR system 200, and has a shorter length La (<Lb) than the conventional EGR system 200, as shown in FIG. . As described above, the scale of the EGR system 15 according to the first embodiment is smaller than that of the conventional EGR system 200 in both the height direction D1 and the width direction D3.

Next, the joining state between the EGR inlet pipe 19 and the irregularly shaped pipe 9, which is an example of the exhaust gas outlet pipe in the engine body 1, in the first embodiment of the present invention will be described. FIG. 6 is a sectional view showing an example of a joined state of the EGR inlet pipe and the exhaust gas outlet pipe of the engine body in the first embodiment of the present invention. FIG. 6 shows a cross-sectional view of the irregularly shaped pipe 9, which is an example of this exhaust gas outlet pipe, and a part of the EGR inlet pipe 19 connected to the midway part of this irregularly shaped pipe 9, viewed from above in the height direction D1. It is shown.

As shown in FIG. 6, the EGR inlet pipe 19 is arranged such that the central axis C11 of the EGR inlet pipe 19 is located closer to the pipe wall portion 9a of the irregularly shaped pipe 9 than the central axis C12 of the irregularly shaped pipe 9. It is joined with 9. At this time, the central axis C11 of the EGR inlet pipe 19 is located in the pipe inner region 9b between the central axis C12 of the irregularly shaped pipe 9 and the pipe wall portion 9a, as shown in FIG. Here, the pressure of the exhaust gas flowing into the flue 12 (see FIG. 1) through the irregularly shaped pipe 9 is higher as it is closer to the central axis C12 of the irregularly shaped pipe 9, and from the central axis C12 of the irregularly shaped pipe 9 to the pipe wall 9a. The pressure becomes lower as it approaches. Therefore, from the viewpoint of making it easier to bleed exhaust gas from the irregularly shaped pipe 9, it is preferable that the EGR inlet pipe 19 is closer to the pipe wall portion 9a from the central axis C12 of the irregularly shaped pipe 9. In particular, in the connection structure between the EGR inlet pipe 19 and the irregularly shaped pipe 9, the distance from the inner wall surface of the EGR inlet pipe 19 to the central axis C11 (that is, the radius of the EGR inlet pipe 19) is It is preferable that the distance be the same as the distance between the inner wall surface and the central axis C11 of the EGR inlet pipe 19. For example, it is preferable that the inner wall surface of the EGR inlet pipe 19 is continuously connected to the inner wall surface of the pipe wall portion 9a in the tangential direction of the irregularly shaped pipe 9.

As described above, in the EGR system 15 according to the first embodiment of the present invention, the outlet 16b of the venturi pipe 116 receives the EGR gas, which is a part of the exhaust gas from the engine body 1, from above and guides it downward. It is joined to the demister inlet 117d provided on the ceiling of the demister box 17b so as to face the bottom 117c of the demister box 17b containing the element 17a, and the EGR gas flowing into the Venturi pipe 116 is cleaned with scrubber water. At the same time, a gas-liquid mixed fluid of EGR gas and scrubber water after cleaning is made to flow down from the Venturi pipe 116.

With the above configuration, the venturi pipe 116 and the demister box 17b can be communicated without using an elbow pipe, and when the gas-liquid mixed fluid is caused to flow from the venturi pipe 116 to the demister box 17b through the demister inlet portion 117d, It is possible to suppress the scrubber water (scrubber water after being used for cleaning the EGR gas) in the gas-liquid mixed fluid from accumulating on the inner wall surface of the Venturi pipe 116. Therefore, corrosion of the Venturi pipe 116 (that is, corrosion of the piping of the EGR system 15) due to scrubber water can be prevented. As a result, it is possible to prevent EGR gas and scrubber water from leaking from the corroded and deteriorated elbow pipe to the outside of the EGR system and, furthermore, to the interior of a ship equipped with a marine diesel engine.

Further, in the EGR system 15 according to the first embodiment of the present invention, the ceiling of the demister box 17b is formed by the first ceiling 117a and the second ceiling 117b which is lower than the first ceiling 117a. A demister outlet section (specifically, a demister outlet section 117e that communicates with the EGR blower 18) is provided in the first ceiling section 117a for draining the cleaned EGR gas, and a demister inlet section 117d that communicates with the Venturi pipe 116 is provided. is provided on the second ceiling portion 117b.

With the above configuration, the flow path 17c in the demister box 17b for separating the gas-liquid mixed fluid flowing into the demister box 17b from the venturi pipe 116 through the demister inlet 117d into the cleaned EGR gas and scrubber water is established. , is secured in the internal area of the demister box 17b from the demister inlet 117d through the element 17a to the demister outlet 117e, and the Venturi pipe 116 can be installed upright on the second ceiling 117b, making it suitable for conventional EGR systems. The scale can be made smaller in comparison.

In addition, the outlet 16b of the venturi tube 116 can be brought closer to the bottom 117c of the demister box 17b. As a result, the gas-liquid mixed fluid flowing into the demister box 17b from the venturi pipe 116 collides with the bottom 117c of the demister box 17b, and most of the scrubber water is transferred from the gas-liquid mixed fluid to the upstream side of the element 17a in the channel 17c. At the same time, the flow rate of this gas-liquid mixed fluid (the flow rate of the EGR gas after cleaning) can be lowered. As a result, it is possible to suppress a decrease in the water removal ability of the element 17a due to an excessive flow rate of the EGR gas, so that this gas-liquid mixed fluid is efficiently separated into the EGR gas after cleaning and the scrubber water, and the EGR after cleaning is Scrubber water can be efficiently removed from gas.

Furthermore, since the venturi tube 116 erected on the second ceiling portion 117b and the box portion of the demister box 17b that accommodates the element 17a can be installed together, this box portion and the venturi tube 116 can be prevented. They can be easily connected by the swinging part 21. As a result, vibration-proofing measures for suppressing relative vibrations of the venturi tube 116 with respect to the demister box 17b can be easily configured, and as a result, damage to the venturi tube 116 due to vibration can be prevented, etc. The reliability against vibrations can be improved compared to conventional EGR systems.

Furthermore, in the EGR system 15 according to the first embodiment of the present invention, in the ceiling section of the demister box 17b, which has a rectangular shape when viewed from above, the demister inlet section 117d and the demister outlet section 117e are arranged in the diagonal direction D4 of the ceiling section. are doing. Therefore, the flow path 17c in the demister box 17b from the demister inlet 117d through the element 17a to the demister outlet 117e can be made longer, and as a result, the flow rate of EGR gas when passing through the element 17a can be increased. This makes it easier to lower the temperature, and the element 17a can efficiently remove moisture from the EGR gas.

Furthermore, the demister inlet portion 117d can be arranged closer to the exhaust gas outlet pipe (for example, the irregularly shaped pipe 9) of the engine body 1, and the demister outlet portion 117e can be arranged farther away from the exhaust gas outlet pipe. . Therefore, without increasing the size of the demister box 17b in the axial direction D2, the distance between the EGR blower 18 provided above the demister outlet section 117e and the intake section 8 that takes in fresh air can be made longer. Therefore, it is possible to easily secure an area in the EGR outlet pipe 20 that connects the EGR blower 18 and the intake part 8 to provide equipment necessary for piping of the EGR system 15, such as the EGR outlet valve 20a. Furthermore, the length of the pipe (EGR inlet pipe 19 in the first embodiment) that communicates the venturi pipe 116 erected above the demister inlet portion 117d and the exhaust gas outlet pipe is made shorter, and the length of the pipe is shortened. Pressure loss of exhaust gas can be reduced.

In addition, in the EGR system 15 according to the first embodiment of the present invention, an exhaust gas outlet pipe (unshaped pipe 9 in the first embodiment) and an EGR inlet pipe are provided in the engine body 1 so as to communicate with the flue 12 of the ship. 19, and an EGR inlet pipe 19 branches from this exhaust gas outlet pipe and is piped so as to communicate with the inlet 16a of the Venturi pipe 116 without going through the flue 12.

With the above configuration, EGR gas is transferred between the engine body 1 and the EGR system 15 by the piping assembled at the time of manufacturing the marine diesel engine 11, that is, the piping on the engine side, without passing through the piping on the ship side such as the flue 12. Piping can be configured for recirculation. Therefore, physical quantities such as the pressure drop of the EGR gas flowing through the piping of the EGR system 15 (for example, the EGR inlet pipe 19 and the EGR outlet pipe 20) can be specified without being influenced by the piping on the ship side. This reduces the EGR blower performance margin (excessive performance) that was previously set by taking into account the piping on the ship side, making it possible to efficiently set the performance of the EGR blower 18 necessary for recirculating EGR gas. can. As a result, it is possible to reduce the effort and cost required for designing and manufacturing the EGR system 15, and there is no need to take the performance of the EGR blower 18 into consideration in the piping on the ship, improving the flexibility of piping on the ship. .

Further, in the EGR system 15 according to the first embodiment of the present invention, the central axis C11 of the EGR inlet pipe 19 is biased toward the tube wall portion 9a of the irregularly shaped pipe 9 than the central axis C12 of the irregularly shaped pipe 9 serving as the exhaust gas outlet pipe. The EGR inlet pipe 19 is joined to the irregularly shaped pipe 9 so as to be located in the same position. Therefore, part of the exhaust gas can be extracted from the tube wall portion 9a side where the pressure of the exhaust gas is lower than that near the center axis C12 of the irregularly shaped tube 9. As a result, EGR gas, which is a part of the exhaust gas, can easily flow into the EGR inlet pipe 19 from the irregularly shaped pipe 9, and the performance of the EGR blower 18 required for the inflow of this EGR gas can be lowered. The cost of the blower 18 can be reduced.

(Embodiment 2)
Next, an EGR system according to a second embodiment of the present invention will be described. FIG. 7 is a perspective view schematically showing a configuration example of an EGR system according to Embodiment 2 of the present invention. As shown in FIG. 7, the EGR system 25 according to the second embodiment includes a demister unit 27 in place of the demister unit 17 of the EGR system 15 according to the first embodiment described above. In addition, a marine diesel engine (not shown) to which the EGR system 25 according to the second embodiment is applied has the structure shown in FIG. It is provided with a deformed tube 29 as shown. The other configurations are the same as those of the first embodiment, and the same components are given the same reference numerals.

As in the first embodiment described above, the demister unit 27 separates the gas-liquid mixed fluid that has flowed in through the scrubber pipe into EGR gas and scrubber water after being cleaned by the scrubber unit 16. Specifically, as shown in FIG. 7, the demister unit 27 includes a demister box 27b for separating and removing scrubber water from the EGR gas after cleaning. Although not shown in FIG. 7, the demister unit 27 includes the same element 17a as in the first embodiment inside the demister box 27b.

The demister box 27b is a hollow structure for separating and removing scrubber water from the EGR gas after cleaning by the scrubber unit 16. Specifically, as shown in FIG. 7, the demister box 27b includes a ceiling 127a, a bottom 127c, and a plurality of side walls connecting the ceiling 127a and the bottom 127c. In the second embodiment, the ceiling portion 127a of the demister box 27b is a square portion that faces the bottom portion 127c in the height direction D1. For example, as shown in FIG. 7, the ceiling portion 127a is provided with a demister inlet portion 117d and a demister outlet portion 117e in a diagonal direction of the ceiling portion 127a. As shown in FIG. 7, such a demister box 27b has a rectangular shape when viewed from the side in the axial direction D2.

Further, as shown in FIG. 7, a scrubber unit 16 and an EGR blower 18 are provided on the ceiling portion 127a of the demister box 27b. The joint structure between the venturi pipe 116 of the scrubber unit 16 and the demister inlet portion 117d on the ceiling portion 127a is the same as in the first embodiment. The Venturi tube 116 is erected on the ceiling 127a and communicates with the demister box 27b so that its outlet and the bottom 127c of the demister box 27b face each other. Further, the joint structure between the EGR blower 18 and the demister outlet portion 117e on the ceiling portion 127a is the same as that in the first embodiment. The demister box 27b communicates with the EGR blower 18 via the demister outlet 117e.

Note that, although not shown in FIG. 7, inside the demister box 27b, the flow advances from the demister inlet 117d toward the bottom 127c of the demister box 27b, and then proceeds along the bottom 127c and side wall of the demister box 27b. After passing through the element 17a, a flow path is formed that reaches the demister outlet section 117e. Further, the bottom 127c of the demister box 27b is provided with a drain port 117f similar to that in the first embodiment.

The irregularly shaped pipe 29 is an example of an exhaust gas outlet pipe provided in the engine body 1 (see FIG. 1) so as to communicate with the flue 12 (see FIG. 1) of the ship. As shown in FIG. 7, the irregularly shaped pipe 29 is configured to extend in the height direction D1 corresponding to the height of the EGR inlet pipe 19 communicating with the Venturi pipe 116. As shown in FIG. 7, the inlet end of the EGR inlet pipe 19 is joined to the middle part of this irregularly shaped pipe 29. As shown in FIG. The configuration of the irregularly shaped tube 29 is the same as that of the irregularly shaped tube 9 in Embodiment 1, except for the length of the tube in the height direction D1. Further, the connection structure between the irregularly shaped pipe 29 and the EGR inlet pipe 19 is the same as in the first embodiment.

As described above, in the EGR system 25 according to the second embodiment of the present invention, the demister box 27b is a hollow structure having a rectangular shape in side view and having one ceiling part 127a facing the bottom part 127c. , a demister inlet part 117d and a demister outlet part 117e are provided on the ceiling part 127a of the demister box 27b, and the other configuration is the same as in the first embodiment. Therefore, even if the demister box 27b is a hollow structure that is rectangular in side view, unlike the demister box 17b in Embodiment 1, which is L-shaped in side view, the same effects as in Embodiment 1 can be obtained. It is possible to realize an EGR system 25 that does the following.

Note that in the first and second embodiments described above, an EGR system including the scrubber unit 16 (that is, a Venturi-type scrubber unit) having the Venturi pipe 116 is illustrated, but the present invention is not limited thereto. In the present invention, the scrubber unit may be of a type other than a venturi type, that is, the scrubber pipe is not limited to the venturi pipe 116.

Further, in the first and second embodiments described above, the case where a single element 17a is arranged inside the demister box is illustrated, but the present invention is not limited to this. In the present invention, a single moisture removal section or a plurality of moisture removal sections may be arranged inside the demister box.

Furthermore, in the first and second embodiments described above, the exhaust gas outlet pipe (for example, irregularly shaped pipes 9, 29) of the marine diesel engine and the scrubber pipe of the scrubber unit were communicated through the EGR inlet pipe without going through the flue. However, the present invention is not limited thereto. In the present invention, the EGR inlet pipe may communicate between the middle part of the flue and the scrubber pipe.

Further, in the first and second embodiments described above, the demister inlet and the demister outlet are arranged diagonally on the ceiling of the demister box, but the present invention is not limited to this. For example, the demister inlet part and the demister outlet part may be arranged side by side in the vertical direction (axial direction D2) or the horizontal direction (width direction D3) in the ceiling part of the demister box, which has a rectangular shape when viewed from above.

Further, the present invention is not limited to the first and second embodiments described above, and the present invention also includes structures constructed by appropriately combining each of the above-mentioned components. In addition, all other embodiments, examples, operational techniques, etc. made by those skilled in the art based on the first and second embodiments described above are included in the scope of the present invention.

1 Engine body 2 Base plate 3 Frame 4 Cylinder jacket 5 Scavenging trunk 6 Exhaust manifold 7 Supercharger 7a Turbine section 7b Compressor section 7c Exhaust gas section 8 Intake section 9, 29 Deformed pipe 9a Pipe wall section 9b Pipe internal region 10 Cooler 11 Marine diesel engine 12 Flue 15, 25 EGR system 16 Scrubber unit 16a Inlet 16b Outlet 17, 27 Demister unit 17a Element 17b, 27b Demister box 17c Flow path 18 EGR blower 19 EGR inlet pipe 19a EGR inlet valve 20 EGR outlet pipe 20a EGR outlet valve 21 Vibration isolation part 116 Venturi pipe 116a Pipe upper part 117a First ceiling part 117b Second ceiling part 117c, 127c Bottom part 127a Ceiling part 117d Demister inlet part 117e Demister outlet part 117f Drain port 117g, 117h Side wall part 200 Conventional EGR system 201 Scrubber unit 202 Demister unit 203 EGR blower 204 Elbow pipe C1 Output shaft direction C11, C12 Center axis CP Center position D1 Height direction D2 Axial direction D3 Width direction D4 Diagonal direction

Claims (6)

In an EGR system that recirculates EGR gas, which is a part of exhaust gas discharged from the engine body of a marine diesel engine, to the engine body as combustion gas,
It has a scrubber pipe that receives the EGR gas from above and guides it downward, the EGR gas that has flowed into the scrubber pipe is washed with scrubber water, and a gas-liquid mixed fluid of the EGR gas and the scrubber water after washing is provided. a scrubber unit that causes the water to flow down from the scrubber pipe;
a demister unit that separates the gas-liquid mixed fluid that has flowed in through the scrubber pipe into the EGR gas after cleaning and the scrubber water;
Equipped with
The demister unit is
a moisture removal unit that removes moisture contained in the EGR gas after cleaning;
a demister box that includes a demister inlet part communicating with the scrubber pipe and a demister outlet part for discharging the EGR gas after cleaning, and which includes the moisture removing part;
Equipped with
The outlet of the scrubber pipe is joined to the demister inlet so as to face the bottom of the demister box ,
The ceiling part of the demister box has a rectangular shape when viewed from above,
The demister inlet part and the demister outlet part are arranged diagonally of the ceiling part,
The EGR system is characterized by: In an EGR system that recirculates EGR gas, which is a part of exhaust gas discharged from the engine body of a marine diesel engine, to the engine body as combustion gas,
It has a scrubber pipe that receives the EGR gas from above and guides it downward, the EGR gas that has flowed into the scrubber pipe is washed with scrubber water, and a gas-liquid mixed fluid of the EGR gas and the scrubber water after washing is provided. a scrubber unit that causes the water to flow down from the scrubber pipe;
a demister unit that separates the gas-liquid mixed fluid that has flowed in through the scrubber pipe into the EGR gas after cleaning and the scrubber water;
an EGR inlet pipe that branches from an exhaust gas outlet pipe provided in the engine body so as to communicate with a flue of a ship and communicates with an inlet of the scrubber pipe without going through the flue;
Equipped with
The EGR inlet pipe is joined to the exhaust gas outlet pipe such that the central axis of the EGR inlet pipe is located closer to the wall of the exhaust gas outlet pipe than the central axis of the exhaust gas outlet pipe,
The demister unit is
a moisture removal unit that removes moisture contained in the EGR gas after cleaning;
a demister box that includes a demister inlet part communicating with the scrubber pipe and a demister outlet part for discharging the EGR gas after cleaning, and which includes the moisture removing part;
Equipped with
The outlet of the scrubber pipe is joined to the demister inlet so as to face the bottom of the demister box.
The EGR system is characterized by: The ceiling portion of the demister box is
a first ceiling portion in which the demister outlet portion is provided;
a second ceiling section that is lower than the first ceiling section and is provided with the demister inlet section;
The EGR system according to claim 1 or 2 , characterized in that the EGR system is configured by: The ceiling part of the demister box has a rectangular shape when viewed from above,
The demister inlet part and the demister outlet part are arranged diagonally of the ceiling part,
The EGR system according to claim 2 or 3 , characterized in that: The engine is characterized by comprising an EGR inlet pipe that branches from an exhaust gas outlet pipe provided on the engine body so as to communicate with a flue of a ship and communicates with an inlet of the scrubber pipe without going through the flue. The EGR system according to claim 1 or 3 . The EGR inlet pipe is joined to the exhaust gas outlet pipe such that the central axis of the EGR inlet pipe is located closer to the wall of the exhaust gas outlet pipe than the central axis of the exhaust gas outlet pipe.
The EGR system according to claim 5 , characterized in that:

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