JP2018096262A - EGR system and diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress damage of an impeller of a compressor of a supercharger in an EGR system and a diesel engine.SOLUTION: An EGR system includes: a supercharger having an expander and a compressor that are connected by a rotating shaft; a scrubber for cleaning recirculation gas that is part of exhaust gas discharged from the expander with liquid; a demister for removing liquid droplets included in recirculation gas cleaned by the scrubber; an EGR blower disposed downstream of a flow of the recirculation gas in the demister; and a silencer having one end in the rotating shaft direction connected to the compressor and the other end in the rotating shaft direction connected to the EGR blower. The EGR blower is disposed on the other end side of the silencer in the rotating shaft direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an EGR system and a diesel engine.

  Exhaust gas discharged from a diesel engine contains harmful substances such as NOx, SOx, and dust. In particular, marine diesel engines using low-quality fuel also increase the amount of harmful substances contained in the exhaust gas. For this reason, marine diesel engines require technologies and exhaust gas treatment devices for treating these harmful substances in order to comply with various exhaust gas regulations.

  As a method for reducing NOx in exhaust gas, there is exhaust gas recirculation (EGR). In this EGR, a part of exhaust gas (recirculation gas) discharged from a combustion chamber of a diesel engine is mixed with combustion air to become combustion gas and returned to the combustion chamber. Therefore, the combustion gas has a reduced oxygen concentration, and the combustion temperature is lowered by delaying the combustion speed, which is a reaction between the fuel and oxygen, and the amount of NOx generated can be reduced.

  As described above, the exhaust gas discharged from the diesel engine contains SOx and dust that are also harmful to the engine. Therefore, a part of the exhaust gas used as the recirculation gas passes through the EGR valve and is scrubbed. Hazardous substances such as SOx and dust are removed. Thereafter, the recirculated gas is mixed into the combustion air sucked from the atmosphere and returned to the diesel engine as the combustion gas. At this time, the scrubber removes harmful substances by injecting liquid to the recirculation gas that is part of the exhaust gas. Here, when the recirculation gas passes through the scrubber, the recirculation gas after passing through the scrubber contains droplets. In order to remove the droplets, a mist separator is mounted downstream of the scrubber in the flow direction of the recirculation gas (Patent Document 1).

  Here, the EGR system including the scrubber and the mist separator is mounted on the diesel engine body in order to secure a space in the engine room. In this case, the EGR system is mounted so that the efficiency of the diesel engine is increased. For example, in a diesel engine, a turbocharger is mounted to improve performance. However, as described in Patent Document 2 and Patent Document 3, if the temperature of combustion air sucked into the turbocharger is high, engine performance is increased. Therefore, the exhaust gas passage and the recirculation gas passage in the EGR system are conventionally separated from the combustion air suction port of the supercharger so as not to increase the atmospheric temperature of the combustion air suction port of the supercharger. The structure which has been arrange | positioned was employ | adopted (nonpatent literature 1).

JP, 2006-168574, A Japanese Utility Model Publication No. 55-176437 Japanese Patent No. 6008495 JP 2014-163345 A

PROJECT MEET NEWS April 2015 No. 7

  However, even when a mist separator is mounted as in Patent Document 1, there is a possibility that droplets are still included in the recirculation gas. In a diesel engine, a supercharger is installed to improve performance. However, when recirculated gas containing droplets passes through the compressor that constitutes the supercharger, the droplets cause the surface of the compressor impeller to be machined. Erosion that may be deformed or scraped may occur. Further, when the S (sulfur) component is contained in the recirculated gas droplets, there is a possibility that scientific corrosion (corrosion) may occur on the blade surface of the compressor due to the droplets containing the S component (Patent Literature). 4). Even when coating is performed on the blade surface of the compressor, erosion / corrosion may occur due to peeling of the coating if there are many droplets.

  Furthermore, as in Non-Patent Document 1, priority is given to engine performance to increase the distance from the mist separator (demister) and EGR blower to the turbocharger, so that the water saturated in the recirculation gas is condensed. It has been newly found that there is a high possibility of doing. In this case as well, erosion and corrosion occurred on the compressor impeller of the turbocharger, and the impeller could be damaged.

  This invention solves the subject mentioned above, and it aims at providing the EGR system and diesel engine which suppress damage to the impeller of the compressor of a supercharger.

  In the EGR system of the present invention for achieving the above object, a supercharger in which an expander and a compressor are connected by a rotating shaft, and a recirculation gas that is a part of exhaust gas discharged from the expander are provided. A scrubber cleaned with a liquid, a demister for removing droplets contained in the recirculated gas cleaned with the scrubber, an EGR blower disposed downstream of the recirculated gas flow of the demister, and a rotational axis direction A silencer having one end connected to the compressor and the other end in the rotation axis direction connected to the EGR blower, and the EGR blower is disposed on the other end side of the silencer in the rotation axis direction It is characterized by being.

  Accordingly, the recirculated gas from which droplets have been removed by the demister is sucked into the EGR blower and then sent out to the compressor via the silencer. Here, when the EGR blower is disposed on the other end side of the silencer, the passage length can be shortened while reducing the bent portion of the passage between the silencer and the EGR blower. Even after the droplets have been removed by the demister, the water in the recirculation gas is in saturation, so droplets can form if the recirculation gas path is long. On the other hand, in the EGR system, the EGR blower is disposed on the other end side of the silencer, thereby reducing the bending portion of the passage (pipe) between the silencer and the EGR blower as described above, while reducing the passage length. Therefore, condensation of moisture in the recirculated gas can be suppressed up to the compressor. Thereby, the EGR system can suppress the occurrence of erosion and corrosion. The EGR system can suppress the occurrence of erosion and corrosion, thereby suppressing damage to the impeller and extending the life of the impeller.

  The EGR system of the present invention is characterized in that the demister is disposed on the other end side of the silencer.

  Therefore, in the EGR system, since the demister is present at the other end of the silencer, not only the passage between the EGR blower and the silencer but also the bent portion of the passage between the demister and the silencer is reduced and the passage length is reduced. Can be shortened. Even after the droplets are removed by the demister, the water in the recirculation gas is saturated, so droplets can form if the recirculation gas path is long. However, the EGR system uses the silencer and the demister. Since the length of the passage can be shortened while reducing the bent portion of the passage (pipe) therebetween, it is possible to further suppress the condensation of moisture in the recirculated gas up to the compressor. Thereby, the EGR system can suppress the occurrence of erosion and corrosion. Thereby, the EGR system can prevent the impeller from being damaged and can extend the life of the impeller.

  The EGR system according to the present invention is characterized in that the scrubber is mounted on an upper portion of the demister and is disposed closer to the EGR blower than the other end of the silencer.

  Accordingly, since the scrubber is mounted on the upper part of the demister, the recirculation gas including the drainage and droplets generated from the scrubber is directly introduced from the scrubber to the demister. Here, since the effluent used in the scrubber contains a lot of S component, it is necessary to manage the equipment that constitutes the EGR system so that it does not corrode, but the EGR system is used between the scrubber and the demister. By setting the distance to the shortest distance, the number of devices to be managed can be minimized. Therefore, the EGR system can greatly reduce the maintenance burden.

  In the EGR system of the present invention, the silencer includes a combustion air suction port that opens in a radial direction with respect to the rotation axis direction, and a recirculation gas suction port that opens in the rotation axis direction. It is said.

  Accordingly, the recirculated gas from which the droplets have been removed by the demister is sucked into the EGR blower and then flows into the silencer from the direction of the rotation axis, while the combustion air flows into the silencer from the radial direction. In addition, the combustion air (air sucked from the silencer) and the recirculation gas merge on the upstream side of the compressor. This allows the EGR system to facilitate mixing of combustion air and recirculation gas before reaching the compressor impeller. Here, since the combustion air is the air around the silencer, the moisture contained in the gas is less than that of the recirculation gas. By mixing both gases, the mixture of the combustion air and the recirculation gas is used. It becomes difficult for moisture to condense from inside. Furthermore, since the recirculation gas flows in the axial direction, it is possible to suppress the occurrence of droplets by colliding with the wall surface forming the recirculation gas passage in the silencer. For this reason, the EGR system can further suppress the occurrence of droplets when passing through the impeller of the compressor, and thus can further suppress the occurrence of erosion and corrosion. Thereby, the EGR system can suppress the damage of the impeller and can extend the life of the impeller even when performing EGR.

  The EGR system of the present invention is characterized in that the recirculation gas discharge port of the EGR blower faces the recirculation gas suction port of the silencer.

  Therefore, in the EGR system, the recirculation gas can minimize the passage length because the recirculation gas discharge port of the EGR blower and the recirculation gas suction port of the silencer face each other. Further, the EGR system can minimize the bent portion of the pipe connecting the recirculation gas discharge port and the recirculation gas suction port. Therefore, it is possible to further suppress condensation of moisture in the recirculated gas up to the compressor. Therefore, since the EGR system can suppress the phenomenon that droplets are generated when passing through the impeller of the compressor, it is possible to further suppress the occurrence of erosion and corrosion. Thereby, the EGR system can suppress the damage of the impeller and can extend the life of the impeller even when performing EGR.

  The EGR system of the present invention is characterized in that the recirculation gas discharge port of the EGR blower is disposed below the recirculation gas suction port of the silencer in the height direction.

  Accordingly, the recirculation gas discharge port of the EGR blower is disposed below the recirculation gas suction port of the silencer in the height direction. For this reason, the EGR system makes it easy for the droplets to return to the EGR blower even if the moisture contained in the recirculation gas is condensed to produce droplets. For this reason, the EGR system can suppress droplets from flowing into the compressor impeller. Thereby, since the EGR system can suppress the phenomenon that droplets are generated when passing through the impeller of the compressor, it is possible to suppress the occurrence of erosion and corrosion. Thereby, the EGR system can suppress the damage of the impeller and can extend the life of the impeller even when performing EGR.

  In order to achieve the above object, a diesel engine according to the present invention includes a diesel engine main body, an expander into which exhaust gas from the diesel engine main body is introduced, and a compressor that rotates coaxially with the expander. A supercharger, a scrubber that cleans the recirculated gas that is part of the exhaust gas discharged from the expander with a liquid, and a demister that removes droplets contained in the recirculated gas cleaned with the scrubber The EGR blower disposed downstream of the recirculation gas flow of the demister and one end in the rotation axis direction are connected to the compressor, and the other end in the rotation axis direction is connected to the EGR blower. A silencer, and the EGR blower is disposed on the other end side of the silencer in the rotation axis direction.

  Accordingly, the recirculated gas from which droplets have been removed by the demister is sucked into the EGR blower and then sent out to the compressor via the silencer. Here, when the EGR blower is disposed on the other end side of the silencer, the passage length can be shortened while reducing the bent portion of the passage between the silencer and the EGR blower. Even after the droplets have been removed by the demister, the water in the recirculation gas is in saturation, so droplets can form if the recirculation gas path is long. On the other hand, in the diesel engine, the EGR blower is disposed on the other end portion side of the silencer, thereby reducing the bent portion of the passage (pipe) between the silencer and the EGR blower as described above. Since the length can be shortened, condensation of moisture in the recirculated gas can be suppressed up to the compressor. Thereby, the diesel engine can suppress the occurrence of erosion and corrosion. The diesel engine can suppress the occurrence of erosion and corrosion, thereby suppressing damage to the impeller and extending the life of the impeller.

  In addition, the diesel engine of the present invention includes an auxiliary blower that is provided separately from the compressor so as to send combustion air to the diesel engine body without passing through the compressor, and the auxiliary blower It is arranged on the expander side in the axial direction.

  Therefore, since the auxiliary blower is disposed on the expander side of the rotating shaft, it is not necessary to provide a space for installing the auxiliary blower between the compressor and the EGR blower. Thereby, the passage length between a compressor and an EGR blower can be shortened. Even after the droplets are removed by the demister, the water in the recirculation gas is saturated, so if the recirculation gas passage is long, droplets may form, but the passage between the silencer and the EGR blower Since the passage length can be shortened while reducing the bent portion of (piping), it is possible to suppress condensation of moisture in the recirculated gas up to the compressor. Thereby, the diesel engine can suppress the occurrence of erosion and corrosion. The diesel engine can suppress the occurrence of erosion and corrosion, thereby suppressing damage to the impeller and extending the life of the impeller.

  According to the EGR system and the diesel engine of the present invention, damage to the impeller of the compressor of the supercharger can be suppressed.

FIG. 1 is a system diagram showing a diesel engine equipped with the EGR system of the first embodiment. FIG. 2 is a schematic diagram showing a diesel engine equipped with the EGR system of the first embodiment. FIG. 3 is a front view showing the EGR system of the first embodiment. FIG. 4A is an enlarged front view of a part of the EGR system of the first embodiment. FIG. 4B is an enlarged top view of a part of the EGR system of the first embodiment. FIG. 5A is an enlarged front view of a part of the EGR system of the EGR system according to the first modification of the first embodiment. FIG. 5B is an enlarged top view of a part of the EGR system of the EGR system according to the first modification of the first embodiment. FIG. 6A is an enlarged front view of a part of the EGR system of the EGR system of the second modification of the first embodiment. FIG. 6B is an enlarged top view of a part of the EGR system of the EGR system according to the second modification of the first embodiment. FIG. 7 is a front view showing the EGR system of the second embodiment.

  Exemplary embodiments of an EGR system and a diesel engine according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment, and when there are two or more embodiments, what comprises combining each embodiment is also included.

[First Embodiment]
FIG. 1 is a system diagram showing a diesel engine equipped with an EGR system according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a diesel engine equipped with the EGR system of the first embodiment. FIG. 3 is a front view showing the EGR system of the first embodiment. FIG. 4A is an enlarged front view of a part of the EGR system of the first embodiment. FIG. 4B is an enlarged top view of a part of the EGR system of the first embodiment.

  As shown in FIG. 1, the diesel engine 1 according to the first embodiment of the present invention includes a diesel engine body 10 and an EGR system 100.

  As shown in FIG. 2, the diesel engine body 10 is a crosshead type diesel engine that is mainly used as a main engine for ship propulsion, and includes a base plate 11 positioned below and a frame 12 provided on the base plate 11. And a cylinder jacket 13 provided on the frame 12. The base plate 11, the frame 12, and the cylinder jacket 13 are integrally fastened and fixed by a plurality of tie bolts and nuts extending in the piston axial direction. The diesel engine body 10 is a uniflow scavenging exhaust type diesel engine and a two-stroke diesel engine, in which the flow of scavenging exhaust in the cylinder is unidirectional from the bottom to the top so as to eliminate residual exhaust. is there.

  The base plate 11 is provided with a propeller shaft (not shown), and a propeller for propulsion (not shown) is driven to rotate through the propeller shaft. A lower end of a connecting rod (not shown) is rotatably connected to the upper end of the propeller shaft.

  The frame 12 is provided with a cross head (not shown) that rotatably connects a piston rod (not shown) and a connecting rod. That is, the lower end of the piston rod and the upper end of the connecting rod are connected to the cross head. On both sides of the crosshead, a pair of sliding plates (not shown) extending in the piston axial direction are provided in a state of being fixed to the frame 12.

  The cylinder jacket 13 is provided with a cylinder liner (not shown), and a cylinder cover (not shown) is provided at the upper end of the cylinder liner. A piston (not shown) is provided in a space (cylinder) formed by the cylinder liner and the cylinder cover so as to reciprocate in the piston axial direction. Moreover, the upper end of a piston rod is attached to the lower end of a piston so that a reciprocation is possible in a piston axial direction. Here, the scavenging trunk 16 and the exhaust manifold 14 are communicated with the cylinder.

  As shown in FIG. 1, the scavenging trunk 16 communicates with the cylinder of the cylinder jacket 13 of the diesel engine body 10. The scavenging trunk 16 feeds combustion gas, in which combustion air or a mixture of combustion air and recirculation gas is compressed, into the diesel engine body 10. The scavenging trunk 16 is fed mainly with combustion gas from the supercharger 20 in which combustion air or a mixture of combustion air and recirculation gas is compressed. On the other hand, when the engine load of the diesel engine main body 10 is less than a certain value, combustion air is sent from the auxiliary blower 17 disposed close to the scavenging trunk 16. The combustion gas sent into the combustion chamber burns with the fuel, thereby reciprocating the piston in the cylinder.

  The auxiliary blower 17 is an air compressor driven by an electric motor. The auxiliary blower 17 uses the air in the engine room in which the diesel engine 1 is disposed as combustion air, and sends the combustion air to the scavenging trunk 16 without passing through the supercharger 20. The auxiliary blower 17 according to the first embodiment of the present invention is disposed on the expander side (the side opposite to the silencer) of the supercharger 20 described later.

  As shown in FIG. 1, the exhaust manifold 14 communicates with the cylinder of the cylinder jacket 13 of the diesel engine body 10. The exhaust manifold 14 is a tank that makes static pressure by temporarily storing exhaust gas generated by combustion in a cylinder. The exhaust manifold 14 sends exhaust gas having a static pressure to the supercharger 20.

  Next, the EGR system 100 in this embodiment will be described with reference to FIG. The EGR system 100 of this embodiment includes a supercharger 20, a scrubber 101, a demister 102, and an EGR blower 104. Here, the EGR system 100 is a system in which a part of the exhaust gas discharged from the diesel engine body 10 is recirculated to the diesel engine body 10 as a recirculation gas and used as a combustion gas. Moreover, the EGR system 100 in this embodiment is arrange | positioned on the diesel engine main body 10 as shown in FIG. As for the diesel engine main body 10, the scaffold is assembled in the outer peripheral surface so that personnel can access each apparatus of the EGR system 100. FIG.

  The supercharger 20 includes an expander (turbine) 21, a compressor (compressor) 22, and a silencer 23. The expander 21 includes a turbine disk (not shown) including turbine blades (not shown). The compressor 22 is provided with an impeller (not shown) including compressor blades (not shown). In the supercharger 20, the impeller of the compressor 22 and the turbine disk of the expander 21 are coupled so as to be rotatable about a rotor shaft (rotary shaft). The rotor of the supercharger 20 includes an expander (turbine) 21, a compressor (compressor) 22, and a rotor shaft (rotary shaft). The rotor shaft is pivotally supported by a bearing stand (not shown) disposed between the expander 21 and the compressor 22. In the supercharger 20, the expander 21 is rotated by exhaust gas discharged from the diesel engine body 10 through the exhaust manifold 14. In the supercharger 20, the rotation of the expander 21 is transmitted by the rotor and the compressor 22 rotates, and the compressor 22 compresses the combustion air and / or the recirculated gas. The combustion gas obtained by compression by the compressor 22 is supplied to the diesel engine body 10 through the scavenging trunk 16. On the other hand, as shown in FIG. 1, the exhaust gas whose energy has been recovered by passing through the expander 21 is discharged to the exhaust gas pipe 15.

  The silencer 23 is a hollow cylindrical device connected to the compressor 22, and one end portion (one end surface) 23 a in the axial direction is the compressor 22 so that the axial direction of the cylinder coincides with the rotor shaft (rotating shaft). Connected to. In the silencer 23, passages (combustion air passages) for sending air in the engine room in which the diesel engine 1 is disposed to the compressor 22 as combustion air are formed radially about the axial direction. The silencer 23 has a silencer element (not shown). The silencer element suppresses noise generated by driving the compressor 22 from being transmitted to the engine room through the combustion air passage. Furthermore, the silencer 23 in the present embodiment includes an opening (recirculation gas suction port) 23c at the other end (other end surface) 23b in the axial direction. In the description of the present invention, as shown in FIG. 3, the axial direction of the rotation axis of the rotor shaft is the rotation axis direction (also referred to as the axial direction) and the direction perpendicular to the surface on which the diesel engine body 10 is installed. Is defined as the width direction and the direction perpendicular to both the rotation axis direction and the height direction.

  The scrubber 101 is a venturi-type scrubber, and includes a hollow throat portion, a venturi portion into which exhaust gas is introduced, and an enlarged portion that gradually returns to the original flow velocity. The scrubber 101 includes a liquid injection unit that injects a liquid to the recirculation gas when a part of the exhaust gas discharged to the exhaust gas pipe 15 is recirculated to the diesel engine body 10 as a recirculation gas. The scrubber 101 removes (cleans) harmful substances such as fine particles (PM) such as SOx and dust by injecting liquid to the recirculated gas.

  Here, as shown in FIG. 3, the scrubber 101 is disposed on the other end 23 b side in the axial direction of the silencer 23. More specifically, the scrubber 101 is disposed apart from the other end portion 23b in the axial direction of the silencer 23 in the axial direction. The scrubber 101 of the present embodiment is a venturi type scrubber, but is not limited to this configuration.

  The demister 102 is a hollow rectangular housing and is connected to the outlet of the scrubber 101. The recirculated gas from which harmful substances have been removed and the drained liquid flow into the demister 102 by the liquid being ejected by the scrubber 101. The demister 102 separates the recirculated gas and the drained liquid and removes droplets contained in the recirculated gas. The separated recirculation gas is discharged from the recirculation gas discharge port of the demister 102 to the EGR blower 104. On the other hand, the separated drainage and the removed liquid droplets are discharged to a collecting tank 103 disposed under the demister 102. The drained liquid and droplets discharged to the collecting tank 103 are neutralized by a cleaning liquid system (not shown), and then returned to the liquid ejecting portion of the scrubber 101 for reuse.

  Here, as shown in FIG. 3, the demister 102 is arranged on the other end 23 b side in the axial direction of the silencer 23. More specifically, the demister 102 is spaced apart from the other end 23b in the axial direction of the silencer 23 in the axial direction. The demister 102 is preferably separated from the silencer 23 in the axial direction as in the present embodiment, but may be configured such that a part thereof overlaps the silencer 23 in the axial direction.

  The EGR blower 104 is disposed on the demister 102. The EGR blower 104 sucks the recirculation gas from which droplets have been removed by the demister 102 from the recirculation gas discharge port of the demister 102 and sends the recirculation gas from the recirculation gas discharge port 104a to the recirculation gas suction port 23c of the silencer 23. A recirculation gas discharge port 104 a of the EGR blower 104 is connected to a recirculation gas suction port 23 c of the silencer 23 via a pipe 105. Here, the pipe 105 functions as a recirculation gas passage.

  Here, as shown in FIG. 3, the EGR blower 104 is disposed on the other end 23 b side in the axial direction of the silencer 23. More specifically, the recirculation gas discharge port 104a of the EGR blower 104 is disposed at a position facing (facing) the recirculation gas suction port 23c of the other end 23b in the axial direction of the silencer 23 in the axial direction. In this case, as shown in FIGS. 4A and 4B, the EGR blower 104 and the silencer 23 are preferably arranged so that the pipe 105 is a straight pipe. That is, in the EGR blower 104 and the silencer 23, the recirculation gas suction port 23c of the other end 23b in the axial direction of the silencer 23 and the recirculation gas discharge port 104a of the EGR blower 104 are in the same position in the width direction and the height direction. It is preferable to arrange so as to be. Note that the recirculation gas discharge port 104a of the EGR blower 104 does not need to be separated from the recirculation gas suction port 23c of the silencer 23 in the axial direction, and may be in contact therewith. In this case, the piping 105 may not be provided, or the EGR blower 104 and the piping 105 may be integrated.

  As described above, the recirculation gas sent from the EGR system 100 to the recirculation gas suction port 23c of the silencer 23 is burned from the combustion air passage formed radially around the axial direction of the silencer 23 and the silencer. 23 is mixed to become an air-fuel mixture. The air-fuel mixture is compressed by the compressor 22 and supplied to the diesel engine body 10 through the scavenging trunk 16 as a combustion gas.

  In the EGR system 100 according to the first embodiment of the present invention, the EGR blower 104 is disposed on the other end (other end surface) 23b side of the silencer 23 in the rotation axis direction of the expander 21. Thereby, the length of the passage can be shortened while reducing the bent portion of the passage (pipe 105) between the silencer 23 and the EGR blower 104. Even after the droplets are removed by the demister 102, the water in the recirculation gas is in a saturated state. Therefore, if the recirculation gas passage is long, droplets may be generated, but the silencer 23 and the EGR blower 104 Since the length of the passage can be shortened while reducing the bent portion of the passage (pipe 105) between them, the condensation of moisture in the recirculated gas can be suppressed up to the compressor. Thereby, since the quantity of the droplet which passes the impeller of a compressor can be suppressed, generation | occurrence | production of erosion and corrosion can be suppressed. Thereby, damage to an impeller can be suppressed and lifetime improvement of an impeller can be achieved.

  In the EGR system 100 according to the first embodiment of the present invention, the demister 102 is disposed on the other end 23 b side of the silencer 23. Accordingly, since the demister 102 exists on the other end 23b side of the silencer 23, not only the passage between the EGR blower 104 and the silencer 23 but also the bent portion of the passage between the demister 102 and the silencer 23 is reduced. However, since the passage length can be shortened, the condensation of moisture in the recirculated gas can be further suppressed until reaching the compressor. Thereby, since the quantity of the droplet which passes the impeller of a compressor can further be suppressed, generation | occurrence | production of erosion and corrosion can further be suppressed. Thereby, even if it is a case where the damage of an impeller is further suppressed and EGR is performed, the lifetime of an impeller can be achieved.

  In the EGR system 100 according to the first embodiment of the present invention, the scrubber 101 is mounted on the upper part of the demister 102 and disposed on the other end 23 b side of the silencer 23. As a result, the recirculation gas including the drainage and droplets generated from the scrubber 101 is directly introduced from the scrubber 101 to the demister 102. Here, since the effluent used in the scrubber 101 contains a large amount of S component, it is necessary to manage the equipment constituting the EGR system 100 so as not to corrode, but between the scrubber 101 and the demister 102. By setting the distance to the shortest distance, the number of devices to be managed can be minimized. Therefore, the maintenance burden can be greatly reduced.

  In the EGR system 100 according to the first embodiment of the present invention, the silencer 23 includes a combustion air suction port that opens in the radial direction with respect to the rotation axis direction, and a recirculation gas suction port 23c that opens in the rotation axis direction. Prepare. As a result, the recirculated gas from which droplets have been removed by the demister 102 is sucked into the EGR blower 104 and then flows into the silencer 23 from the direction of the rotation axis, while the combustion air flows into the silencer 23 from the radial direction. . In addition, the combustion air (air sucked from the silencer 23) and the recirculation gas join together upstream of the compressor 22. Therefore, before reaching the impeller of the compressor 22, the mixing of the combustion air and the recirculation gas can be promoted. Here, since the combustion air is the air around the silencer 23, there is a high possibility that the moisture contained in the gas is less than the recirculation gas, and the combustion air and the recirculation are mixed by mixing both gases. It becomes difficult for moisture to condense from the gas mixture. Furthermore, since the recirculation gas flows in the axial direction, the silencer 23 can be prevented from colliding with the wall surface forming the recirculation gas passage and generating droplets. Thereby, since the quantity of the droplet which passes the impeller of the compressor 22 can further be suppressed, generation | occurrence | production of erosion and corrosion can further be suppressed. Thereby, even if it is a case where the damage of an impeller is further suppressed and EGR is performed, the lifetime of an impeller can be achieved.

  The EGR system 100 according to the first embodiment of the present invention is configured such that the recirculation gas discharge port 104 a of the EGR blower 104 faces the recirculation gas suction port 23 c of the silencer 23. Thereby, since the recirculation gas discharge port 104a of the EGR blower 104 and the recirculation gas suction port 23c of the silencer 23 face each other, the recirculation gas can minimize the passage length. Further, the bent portion of the pipe connecting the recirculation gas discharge port 104a and the recirculation gas suction port 23c can be minimized. Therefore, it is possible to further suppress condensation of moisture in the recirculated gas up to the compressor. Thereby, since the quantity of the droplet which passes the impeller of a compressor can further be suppressed, generation | occurrence | production of erosion and corrosion can further be suppressed. Thereby, even if it is a case where the damage of an impeller is further suppressed and EGR is performed, the lifetime of an impeller can be achieved.

  In the diesel engine 1 according to the first embodiment of the present invention, the EGR blower 104 is disposed on the other end (other end surface) 23b side of the silencer 23 in the rotation axis direction of the expander 21. As a result, the diesel engine 1 can reduce the length of the passage while reducing the bent portion of the passage (pipe 105) between the silencer 23 and the EGR blower 104. Therefore, the recirculated gas from which droplets have been removed by the demister 102 is sucked into the EGR blower 104 and then sent out to the compressor 22 via the silencer 23. Here, when the EGR blower 104 is disposed on the other end 23 b side of the silencer 23, the passage length can be shortened while reducing the bent portion of the passage between the silencer 23 and the EGR blower 104. Even after the droplets are removed by the demister 102, the water in the recirculation gas is in a saturated state. Therefore, if the recirculation gas passage is long, droplets may be generated. Since the length of the passage can be shortened while reducing the bent portion of the passage (pipe 105) between the EGR blower 104 and the compressor 22, the condensation of moisture in the recirculated gas can be suppressed. . Thereby, the diesel engine 1 can suppress the occurrence of erosion and corrosion. The diesel engine 1 can suppress the occurrence of erosion and corrosion, thereby suppressing damage to the impeller and extending the life of the impeller.

  The diesel engine 1 according to the first embodiment of the present invention includes an auxiliary blower 17 that is provided separately from the compressor 22 so as to send combustion air to the diesel engine main body 10 without passing through the compressor 22. The blower 17 is arrange | positioned at the expander 21 side in the rotating shaft. Accordingly, since the auxiliary blower 17 is disposed on the expander 21 side on the rotating shaft, it is not necessary to provide a space for installing the auxiliary blower 17 between the compressor 22 and the silencer 23 and the EGR blower 104. Thereby, the path length between the compressor 22 and the EGR blower 104 can be shortened. Even after the droplets are removed by the demister 102, the water in the recirculation gas is in a saturated state. Therefore, if the recirculation gas passage is long, droplets may be generated. Since the length of the passage can be shortened while reducing the bent portion of the passage (pipe 105) between the EGR blower 104 and the compressor 22, the condensation of moisture in the recirculated gas can be suppressed. . Thereby, the diesel engine 1 can suppress the occurrence of erosion and corrosion. The diesel engine 1 can suppress the occurrence of erosion and corrosion, thereby suppressing damage to the impeller and extending the life of the impeller.

[First Modification of First Embodiment]
FIG. 5A is an enlarged front view of a part of an EGR system according to a first modification of the first embodiment. FIG. 5B is an enlarged top view of a part of the EGR system according to the first modification of the first embodiment. Next, an EGR system 100 according to a first modification of the first embodiment of the present invention will be described with reference to FIGS. 5A and 5B. In addition, the same code | symbol is attached | subjected to the member which has the same function as 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

  As shown in FIGS. 5A and 5B, the EGR system 100a in the first modification of the first embodiment of the present invention differs from the first embodiment in that the recirculation gas discharge port 104a of the EGR blower 104 and the silencer 23 The recirculation gas suction port 23c is arranged at a different position in the width direction. More specifically, the pipe 105 ′ is configured to have a bent portion in the width direction. In the EGR system 100a of FIGS. 5A and 5B, the recirculation gas discharge port 104a of the EGR blower 104 and the recirculation gas suction port 23c of the silencer 23 are arranged at the same position in the height direction, but at different positions. May be arranged.

  As described above, in the EGR system 100a according to the first modification of the first embodiment of the present invention, the recirculation gas discharge port 104a of the EGR blower 104 and the recirculation gas suction port 23c of the silencer 23 are different in the width direction. Since it is arrange | positioned at the position, the silencer 23 can be arrange | positioned away from the area | region where the temperature of the air of engine room is high. For this reason, the EGR system 100a can reduce the temperature of the combustion air sucked into the silencer 23 while shortening the passage length of the recirculation gas. Therefore, the EGR system 100a can improve the engine performance while suppressing the inflow of droplets to the impeller.

[Second Modification of First Embodiment]
FIG. 6A is an enlarged front view of a part of an EGR system according to a second modification of the first embodiment. FIG. 6B is an enlarged top view of a part of the EGR system according to the second modification of the first embodiment. Next, an EGR system 100b according to a second modification of the first embodiment of the present invention will be described with reference to FIGS. 6A and 6B. In addition, the same code | symbol is attached | subjected to the member which has the same function as 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

  As shown in FIGS. 6A and 6B, the EGR system 100b in the second modification of the first embodiment of the present invention differs from the first embodiment in that the recirculation gas discharge port 104a of the EGR blower 104 and the silencer 23 The recirculation gas suction port 23c is arranged at a different position in the height direction. More specifically, the pipe 105 ″ is configured to have a bent portion in the height direction. 6A and 6B, the recirculation gas discharge port 104a of the EGR blower 104 and the recirculation gas suction port 23c of the silencer 23 are arranged at the same position in the width direction, but they may be arranged at different positions. Good.

  As described above, in the EGR system 100b, the recirculation gas discharge port 104a of the EGR blower 104 and the recirculation gas suction port 23c of the silencer 23 are arranged at different positions in the height direction. Even when a droplet is generated between the recirculation gas discharge port 104 a and the recirculation gas suction port 23 c of the silencer 23, the droplet easily returns in the direction of the EGR blower 104. For this reason, the EGR system 100b can suppress the inflow of droplets to the impeller.

[Second Embodiment]
FIG. 7 is a front view showing the EGR system of the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the same function as 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

  As shown in FIG. 7, the EGR system 110 according to the second embodiment of the present invention includes a scrubber 101, a demister 102, and an EGR blower 114. Note that the scrubber 101 and the demister 102 have the same configuration as that of the first embodiment, and thus the description thereof is omitted.

  The EGR blower 114 is disposed on the demister 102. The EGR blower 114 sucks the recirculation gas from which droplets have been removed by the demister 102 from the recirculation gas discharge port of the demister 102, and sends the recirculation gas from the recirculation gas discharge port 114a to the recirculation gas suction port 23c of the silencer 23. The recirculation gas discharge port 114 a of the EGR blower 114 is connected to the recirculation gas suction port 23 c of the silencer 23 via a pipe 115. Here, the pipe 115 functions as a recirculation gas passage.

  Here, the EGR blower 114 of the second embodiment of the present invention is provided such that the recirculation gas discharge port 114a opens in the height direction. The recirculation gas discharge port 114a of the EGR blower 114 is connected to the recirculation gas suction port 115a of the pipe 115 that opens in the height direction. The recirculation gas that has flowed into the pipe 115 is discharged from the recirculation gas suction port 23c of the silencer 23 connected to the recirculation gas discharge port 115b of the pipe 115 that opens in the rotation axis direction.

  The EGR blower 114 is disposed on the other end 23 b side in the axial direction of the silencer 23. More specifically, the EGR blower 114 is disposed such that the recirculation gas discharge port 114a is separated from the recirculation gas suction port 23c of the other end 23b in the axial direction of the silencer 23 in the axial direction. In this case, as shown in FIG. 6, in the piping 115, the recirculation gas suction port 115a opens in the height direction, and the recirculation gas discharge port 115b opens in the rotation axis direction. The EGR blower 114 and the pipe 115 may be integrated.

  As described above, the recirculation gas sent from the EGR system 110 to the recirculation gas suction port 23c of the silencer 23 is combusted from the combustion air passage formed radially around the axial direction of the silencer 23 and the silencer. 23 is mixed inside. After being mixed inside the silencer 23, the air-fuel mixture is compressed by the compressor 22 and supplied to the diesel engine body 10 through the scavenging trunk 16 as a combustion gas.

  As described above, in the EGR system 110 of the second embodiment, the recirculation gas discharge port 114a of the EGR blower 114 is disposed below the recirculation gas suction port 23c of the silencer 23 in the height direction. Therefore, even when a droplet is generated between the recirculation gas discharge port 114 a of the EGR blower 114 and the recirculation gas suction port 23 c of the silencer 23, the droplet easily returns in the direction of the EGR blower 114. For this reason, the EGR system 110 can suppress the inflow of droplets into the impeller.

  Moreover, in embodiment mentioned above, although demonstrated using the marine 2-stroke engine as a diesel engine, it is applicable also to the other diesel engine which mounts an EGR system.

DESCRIPTION OF SYMBOLS 1 Diesel engine 10 Diesel engine main body 11 Base plate 12 Frame 13 Cylinder jacket 14 Exhaust trunk 15 Exhaust gas piping 16 Exhaust manifold 17 Auxiliary blower 20 Supercharger 21 Expander (turbine)
22 Compressor
23 Silencer 100, 110 EGR system 101 Scrubber 102 Demister 103 Collecting tank 104, 114 EGR blower 105, 105 ′, 105 ″, 115 Piping

Claims (8)

A supercharger in which an expander and a compressor are connected by a rotating shaft;
A scrubber that cleans the recirculated gas that is part of the exhaust gas discharged from the expander with a liquid;
A demister that removes droplets contained in the recirculation gas cleaned by the scrubber;
An EGR blower disposed downstream of the recirculated gas stream of the demister;
A silencer in which one end in the rotation axis direction is connected to the compressor and the other end in the rotation axis direction is connected to the EGR blower.
The EGR blower is arranged on the other end side of the silencer in the rotation axis direction.   The EGR system according to claim 1, wherein the demister is disposed on the other end side of the silencer.   The EGR system according to claim 2, wherein the scrubber is mounted on an upper portion of the demister and is disposed on the other end side of the silencer. The silencer is
A combustion air inlet opening in a radial direction with respect to the rotational axis direction;
A recirculation gas inlet opening in the rotational axis direction;
The EGR system according to any one of claims 1 to 3, further comprising:   5. The EGR system according to claim 4, wherein the recirculation gas discharge port of the EGR blower faces the recirculation gas suction port of the silencer.   The EGR system according to claim 5, wherein the recirculation gas discharge port of the EGR blower is disposed below the recirculation gas suction port of the silencer in the height direction. A diesel engine body,
A turbocharger in which an expander into which exhaust gas from the diesel engine main body is introduced and a compressor that rotates coaxially with the expander are coupled by a rotation shaft;
A scrubber that cleans the recirculated gas that is part of the exhaust gas discharged from the expander with a liquid;
A demister that removes droplets contained in the recirculation gas cleaned by the scrubber;
An EGR blower disposed downstream of the recirculated gas stream of the demister;
A silencer in which one end portion in the rotation axis direction is connected to the compressor and the other end portion in the rotation axis direction is connected to the EGR blower;
The diesel engine according to claim 1, wherein the EGR blower is disposed on the other end side of the silencer in the rotation axis direction. Provided separately from the compressor, without passing through the compressor, comprising an auxiliary blower that sends combustion air to the diesel engine body,
The diesel engine according to claim 7, wherein the auxiliary blower is disposed on the expander side in the rotation axis direction.

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