Marine engines

Abstract

This helps to mitigate the effects of alternative fuel contamination in the sealing oil. [Solution] A marine engine 1 that burns ammonia fuel in a cylinder 16 comprises a fuel injection valve 3 that injects ammonia fuel into the cylinder 16, having a cylindrical body 31 extending along a predetermined central axis Cf, and a valve stem 32 inserted into the cylindrical body 31 and moving reciprocally along the central axis Cf, and a housing 5 that circulates sealing oil between the fuel injection valve 3 and the gap 3b between the cylindrical body 31 and the valve stem 32 to seal the gap.

Description

Technical Field

[0001] The present disclosure relates to marine engines. Background Art

[0002] For example, Patent Document 1 discloses a dual fuel injection device for a cylinder of an internal combustion engine. This dual fuel injection device includes a first nozzle valve for introducing a first fuel, and a second nozzle valve for introducing a second fuel. Here, the first fuel is, for example, diesel fuel. The second fuel is an alternative fuel such as methanol, ethanol, or LPG.

[0003] Further, the second nozzle valve is configured to receive a supply of sealing and lubricating oil to prevent the second fuel from leaking to the surroundings via the needle guide of the second nozzle valve. Therefore, the second nozzle valve has a needle lubrication chamber that receives the sealing and lubricating oil.

[0004] Generally, the oil pressure of the sealing and lubricating oil is set to be higher than the fuel pressure. In contrast, the dual fuel injection device according to Patent Document 1 is configured such that the oil pressure of the sealing and lubricating oil is lower than the fuel pressure by elaborately designing the dimension of the needle lubrication chamber. Prior Art Documents Patent Documents

[0005] Patent Document 1 Japanese Patent Application Laid-Open No. 2019-70387 Summary of the Invention Problems to be Solved by the Invention

[0006] However, if a configuration such as that disclosed in Patent Document 1 is adopted, the second fuel may mix with the sealing oil due to the pressure difference between the sealing and lubricating oil (hereinafter referred to as sealing oil) and the second fuel. In this case, the second fuel may diffuse to various parts of the sealing oil supply system, such as the sealing oil supply pipe.

[0007] On the other hand, the inventors of the present application are considering using alternative fuels other than diesel fuel for marine engines, such as the second fuel described in Patent Document 1. Generally, depending on the composition of the alternative fuel, it may have adverse effects on equipment related to the supply system and on human health.

[0008] Therefore, as mentioned above, if the alternative fuel diffuses to various parts of the sealing oil supply system, the diffused alternative fuel may reach equipment related to the supply system or leak from unintended locations, potentially causing harm to equipment and human health.

[0009] Therefore, following the conventional method, one might consider setting the oil pressure of the sealing oil higher than the fuel pressure of the alternative fuel. However, since the pressure difference between the two is generally small, a small amount of alternative fuel may be mixed into the sealing oil. Furthermore, if a malfunction occurs in the sealing oil supply system, a drop in oil pressure could lead to a large amount of alternative fuel mixing. For this reason, even if the conventional method is followed, it is still problematic.

[0010] This disclosure has been made in view of the above, and its purpose is to suppress the effects of the mixing of alternative fuels into the sealing oil. [Means for solving the problem]

[0011] A first aspect of the present disclosure relates to a marine engine for burning a volatile alternative fuel in a cylinder. The marine engine comprises a fuel injector for injecting the alternative fuel into the cylinder, having a cylindrical body extending along a predetermined central axis and a valve stem inserted into the cylindrical body and reciprocating along the central axis, and a housing for circulating sealing oil between the fuel injector and the gap between the cylindrical body and the valve stem.

[0012] According to the first embodiment described above, even if a substitute fuel is mixed into the sealing oil and volatile components of the substitute fuel leak out, the leaked volatile components can be contained within the housing. This allows the substitute fuel that has leaked into the sealing oil to be isolated from the equipment and people. In this way, the effects of the substitute fuel contamination can be suppressed.

[0013] Furthermore, according to a second aspect of the present disclosure, the marine engine may include a motor body having a cylinder and moving a piston back and forth within the cylinder, and a support member fixed to the motor body, wherein the support member is spaced apart from the floor of the ship, and the housing is supported by the motor body via the support member.

[0014] According to the second embodiment, the housing is supported by a support member to the engine body. This allows the housing to be transported together with the engine body. Furthermore, the housing, supported by the support member to the engine body, is positioned at a distance from the ship's floor. This arrangement causes the housing to vibrate together with the engine body.

[0015] If the housing is placed on the floor, the engine body, as the source of vibration, will vibrate relatively more, while the floor and housing will not vibrate as much as the engine body. In this case, it is necessary to connect a member or mechanism to the piping connecting the housing and the engine body that can absorb the difference in vibration between the engine body and the floor. However, such a member or mechanism may lead to leakage of alternative fuel from the connection part to the piping.

[0016] In contrast, as in the second embodiment described above, by vibrating the housing and the engine body as a single unit, the aforementioned members or mechanisms become unnecessary. This reduces the risk of leakage from the connection point. Furthermore, by supporting the housing with the engine body, the seal oil supply system can be completed within the marine engine. Therefore, even if a leak of the alternative fuel occurs, the area over which the leaked alternative fuel diffuses can be kept to a minimum.

[0017] Furthermore, according to a third aspect of this disclosure, the engine body may comprise a base plate constituting the crankcase of the marine engine and a frame positioned above the base plate, wherein the housing is positioned laterally to the frame via the support members.

[0018] According to the third embodiment described above, the housing is positioned to the side of the frame, that is, above the crankcase. This arrangement allows the fuel injector and the housing to be brought closer together in the vertical direction. This makes the entire seal oil supply system more compact. The compactness of the entire seal oil supply system contributes to the reduction of the size of the tank for storing the seal oil and to the suppression of leakage of alternative fuel from the piping.

[0019] Furthermore, according to a fourth aspect of this disclosure, the marine engine may be provided with a seal oil tank for storing the seal oil, and the housing may house the seal oil tank.

[0020] According to the fourth embodiment, by housing the seal oil tank within the casing, when the seal oil becomes contaminated with the alternative fuel, both the volatile components of the alternative fuel leaking from the components related to the seal oil tank and the volatile components of the alternative fuel leaking from the connections between components (e.g., fluid couplings) can be contained within the casing. This is advantageous in suppressing the effects of the alternative fuel mixing with the seal oil.

[0021] Furthermore, according to a fifth aspect of the present disclosure, the marine engine may include a seal oil piping for circulating the seal oil between the seal oil tank and the fuel injector, an oil filter disposed on the seal oil piping for filtering the seal oil flowing through the seal oil piping toward the fuel injector, a first pump disposed on the seal oil piping for pressurizing the seal oil flowing through the seal oil piping toward the fuel injector, and a seal oil cooler disposed on the seal oil piping for cooling the seal oil flowing through the seal oil piping, wherein the housing may house one or more of the seal oil tank, the oil filter, the seal oil cooler, and the first pump, including the seal oil tank.

[0022] According to the fifth embodiment described above, by housing the first pump and various other components related to the flow of the sealing oil within the housing, when the alternative fuel is mixed into the sealing oil, both the volatile components of the alternative fuel leaking from these components and the volatile components of the alternative fuel leaking from the connections between the components (e.g., fluid couplings) can be contained within the housing. This is advantageous in suppressing the effects of the alternative fuel mixing into the sealing oil.

[0023] Furthermore, according to a sixth aspect of the present disclosure, the marine engine may be provided with a second pump located downstream of the first pump in the seal oil piping for further pressurizing the seal oil pressurized by the first pump, and the seal oil cooler may be located downstream of the first pump and upstream of the second pump on the seal oil piping.

[0024] According to the sixth embodiment described above, the viscosity of the seal oil can be ensured by cooling the seal oil with a seal oil cooler. In order to supply sufficiently cooled seal oil to the fuel injector, it is conceivable to place the seal oil cooler as close to the fuel injector as possible on the seal oil piping. However, if the seal oil cooler is placed downstream of the second pump, the seal oil, which has been pressurized by the second pump, will be supplied to the seal oil cooler, which may cause malfunction.

[0025] In contrast, by laying out the seal oil cooler as in the sixth aspect, both the viscosity of the seal oil and the suppression of abnormalities in the seal oil cooler can be achieved simultaneously.

[0026] Further, according to a seventh aspect of the present disclosure, the marine engine may include a seal oil replenishment system connected to the seal oil tank within the housing and configured to replenish the seal oil into the seal oil tank.

[0027] According to the seventh aspect, even if volatile components of alternative fuel leak from a connection between the seal oil replenishment system and the seal oil tank, such as a fluid coupling, the volatile components can be confined within the housing. This is advantageous in suppressing the influence of alternative fuel mixing into the seal oil.

[0028] Further, according to an eighth aspect of the present disclosure, the seal oil replenishment system includes a storage tank that stores the seal oil, and a seal oil replenishment pipe that circulates the seal oil from the storage tank to the seal oil tank, and at least one of the seal oil replenishment system and the seal oil tank may be configured to restrict backflow of the seal oil from the seal oil tank to the seal oil replenishment pipe.

[0029] According to the eighth aspect, even if alternative fuel mixes into the seal oil, backflow of the seal oil contaminated with alternative fuel into the storage tank is restricted. As a result, diffusion of the seal oil contaminated with alternative fuel can be prevented, which is advantageous in suppressing the influence of alternative fuel mixing.

[0030] Further, according to a ninth aspect of the present disclosure, the marine engine may include: a seal oil pipe that circulates the seal oil between the seal oil tank and the fuel injection valve; a ventilation mechanism that ventilates the interior of the housing; and a ventilation passage connected to at least one of the seal oil tank and the seal oil pipe, and configured to discharge the alternative fuel volatilized in at least one of the seal oil tank and the seal oil pipe.

[0031] According to the ninth embodiment described above, even if the alternative fuel enters and volatilizes into the seal oil flowing through at least one of the seal oil tank and the seal oil piping, the volatile components can be discharged through the ventilation passage. This allows the alternative fuel mixed into the seal oil to be isolated from the equipment and the human body. This is further advantageous in suppressing the effects of the contamination by the alternative fuel.

[0032] Furthermore, according to the ninth embodiment described above, even if volatile components of the alternative fuel leak out without being discharged through the ventilation passage, the leaked volatile components can be discharged by the ventilation mechanism. This allows the alternative fuel that has leaked and become mixed with the sealing oil to be isolated from the equipment and people. This is further advantageous in suppressing the effects of contamination by the alternative fuel.

[0033] In general, crew members perform routine inspections and other tasks on marine engines. By providing a ventilation mechanism, crew members working on marine engines are reliably isolated from ammonia fuel. That is, even if the housing is supported by the engine body, as in the configuration of the second embodiment described above, the crew can be isolated from alternative fuel by providing the ventilation mechanism of the ninth embodiment described above.

[0034] Furthermore, according to a tenth aspect of the present disclosure, the marine engine may be connected to at least one of the seal oil tank and the seal oil piping and provided with an introduction passage for introducing compressed air or scavenging gas into at least one of the seal oil tank and the seal oil piping.

[0035] According to the tenth embodiment described above, when volatile alternative fuel flows into at least one of the seal oil tank and the seal oil piping, the incoming alternative fuel can be pushed out by compressed air or exhaust gas introduced from the introduction passage and sent to the ventilation passage. This is further advantageous in suppressing the effects of contamination by alternative fuel.

[0036] Furthermore, according to an eleventh aspect of this disclosure, the marine engine may be provided with flow rate adjustment means arranged in the introduction passage for adjusting the flow rate of the compressed air or the scavenging gas in the introduction passage.

[0037] According to the 11th embodiment described above, by arranging a flow rate adjustment means in the introduction passage, it becomes possible to adjust the flow rate of compressed air or scavenging gas. This is further advantageous in suppressing the effects of mixing in alternative fuels.

[0038] Furthermore, according to a twelfth aspect of the present disclosure, the marine engine may include an oil pan housed in the housing and receiving the seal oil leaked from the contents of the housing, a seal oil discharge pipe connected to the oil pan and circulating the seal oil received in the oil pan, and a leak sensor for detecting the oil content in at least one of the oil pan and the seal oil discharge pipe.

[0039] According to the 12th embodiment described above, the seal oil leaking from the contents of the housing can be used to discharge the seal oil along with the substitute fuel mixed in with it. This is advantageous in suppressing the effect of the substitute fuel mixing with the seal oil.

[0040] Furthermore, according to a thirteenth aspect of this disclosure, the alternative fuel may be ammonia fuel.

[0041] Ammonia fuel poses a risk of adverse effects due to leakage and volatilization. This disclosure contributes to mitigating such adverse effects. [Effects of the Invention]

[0042] As explained above, this disclosure makes it possible to suppress the effects of mixing alternative fuels into the sealing oil. [Brief explanation of the drawing]

[0043] [Figure 1] Figure 1 is a schematic diagram illustrating a marine engine viewed from the front. [Figure 2] Figure 2 is a schematic diagram illustrating a marine engine viewed from the side. [Figure 3] Figure 3 is a schematic cross-sectional view illustrating the superstructure of a marine engine. [Figure 4] Figure 4 is an example diagram illustrating a seal oil supply system. [Figure 5] Figure 5 is a longitudinal cross-sectional view illustrating the configuration of a fuel injection valve. [Figure 6] Figure 6 is a block diagram illustrating the configuration of a controller for a marine engine. [Modes for carrying out the invention]

[0044] The embodiments of this disclosure will be described below with reference to the drawings. The following description is illustrative. Figure 1 is a schematic diagram illustrating a marine engine (hereinafter also simply referred to as "engine") 1 viewed from the front, and Figure 2 is a schematic diagram illustrating an engine 1 viewed from the side.

[0045] <Overall Structure> Engine 1 is a multi-cylinder in-line marine engine. This engine 1 is configured as a uniflow scavenging, two-stroke, one-cycle engine and is installed in large vessels such as tankers, container ships, and car carriers.

[0046] Engine 1 is configured to burn an alternative fuel in its cylinder 16. In this configuration, engine 1 may perform combustion of the alternative fuel alone, or it may perform mixed combustion of the alternative fuel and oil fuel (for example, mixed combustion of ammonia fuel and diesel fuel).

[0047] In this embodiment, a volatile fuel, such as ammonia fuel, is used as the alternative fuel. However, the alternative fuel is not limited to ammonia fuel. Other alternative fuels such as hydrogen gas, liquefied natural gas (LNG), liquefied petroleum gas (LPG), alcohol fuel, and biodiesel fuel may also be used. Here, alcohol fuel includes fuels containing alcohol in general, such as methanol and ethanol. Biodiesel fuel includes substances that can be used as biodiesel fuel in general, such as fatty acid methyl esters (FAME).

[0048] Engine 1, installed on a ship, is used as the main engine to propel the ship. The output shaft of engine 1 is connected to the ship's propeller via the propeller shaft. When engine 1 is operated, its output is transmitted to the propeller, causing the ship to move.

[0049] <Main configuration> As illustrated in Figure 1, the engine 1 comprises a motor body 10 having one or more (multiple in this embodiment) cylinders 16, a seal oil supply system 4, and a controller 100. Each cylinder 16 forms a combustion chamber 17 for burning ammonia fuel.

[0050] (1) Engine body 10 Figure 3 is a schematic cross-sectional view illustrating the superstructure of engine 1.

[0051] The engine body 10 is installed in the engine room of the ship. As mentioned above, the engine body 10 has multiple cylinders 16. Unless otherwise specified, the following description applies to each cylinder 16, even when there are multiple cylinders 16.

[0052] As shown in Figure 1, the engine 1 according to this embodiment is configured as a so-called crosshead type internal combustion engine in order to achieve a long stroke. Accordingly, the engine body 10 of the engine 1 is equipped with a piston rod 22 that supports the piston 21 from below for each cylinder 16, and a connecting rod 24 that is connected to the crankshaft 23. The piston rod 22 and the connecting rod 24 are connected by a crosshead 25.

[0053] Specifically, the engine body 10 comprises a base plate 11 located below, a frame 12 provided on the base plate 11, a cylinder jacket 13 provided on the frame 12, a cylinder liner 14, and a cylinder cover 15. Each cylinder 16 is located within the cylinder jacket 13. The engine body 10 also comprises a piston 21 positioned within the cylinder 16 and reciprocating within the cylinder 16, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating motion of the piston 21.

[0054] Here, the base plate 11 constitutes the crankcase of the engine 1. The base plate 11 houses the crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of the connecting rod 24 is connected to the crankshaft 23 via a crank 27.

[0055] The frame 12 houses a pair of guide plates 28, a connecting rod 24, and a crosshead 25. The pair of guide plates 28 are spaced apart in the width direction of the engine 1 (left-right direction in Figure 1). The connecting rod 24 is positioned between the pair of guide plates 28 with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via the crosshead 25.

[0056] The crosshead 25 is positioned between a pair of guide plates 28 and slides vertically along each guide plate 28. That is, the pair of guide plates 28 guide the sliding of the crosshead 25. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 so as to move vertically as a whole, while it is connected to the connecting rod 24 so as to allow the connecting rod 24 to rotate, with the upper end of the connecting rod 24 as the pivot point.

[0057] The cylinder jacket 13 supports the cylinder liner 14, which acts as the inner cylinder. The aforementioned piston 21 is located inside the cylinder liner 14. The cylinder liner 14 causes the piston 21 to reciprocate vertically along the inner wall of the cylinder liner 14. The upper end of the cylinder liner 14 is open.

[0058] The cylinder cover 15 is fixed to the upper end of the cylinder liner 14. The cylinder cover 15, together with the cylinder liner 14, constitutes the cylinder 16. The cylinder cover 15 acts as a lid for the cylinder 16 by closing off the upper end of the cylinder liner 14.

[0059] Furthermore, the cylinder cover 15 is provided with an exhaust valve 18, which is actuated by a valve train (not shown). The exhaust valve 18, together with the cylinder 16, which is composed of the cylinder liner 14 and the cylinder cover 15, and the top surface of the piston 21, forms a combustion chamber 17 (see Figure 1). The exhaust valve 18 opens and closes the connection between the combustion chamber 17 and the exhaust pipe 19. The exhaust pipe 19 has an exhaust port leading to the combustion chamber 17, and the exhaust valve 18 is configured to open and close this exhaust port.

[0060] Furthermore, the cylinder cover 15 partitions the ceiling surface of the combustion chamber 17. One or more fuel injectors 3 are provided on this ceiling surface. In this embodiment, each cylinder 16 is provided with two fuel injectors 3 (see Figure 1). Each fuel injector 3 injects ammonia fuel as an alternative fuel into the cylinder 16.

[0061] As illustrated in Figure 3, each fuel injector 3 has a cylindrical body 31, a valve stem 32, and a seal chamber 33. Each fuel injector 3 is also provided with an injection port 3a located within the combustion chamber 17.

[0062] The cylindrical body 31 has a cylindrical shape that extends along a predetermined central axis Cf. The cylindrical body 31 is connected to an ammonia fuel supply line (not shown) and a seal oil supply line (seal oil supply system 4 described later).

[0063] The valve stem 32 is inserted into the cylindrical body 31. The valve stem 32 has a needle shape that extends along the central axis Cf. The valve stem 32 reciprocates along the central axis Cf. This reciprocating motion is the relative motion of the valve stem 32 with respect to the cylindrical body 31. Ammonia fuel is supplied to the space formed between the valve stem 32 and the cylindrical body 31 (see fuel chamber 35 in Figure 5).

[0064] The seal chamber 33 is located in the gap 3b between the cylindrical body 31 and the valve stem 32 (see Figure 5, described later). This gap 3b is located where the outer surface of the valve stem 32 slides against the inner wall surface of the cylindrical body 31 during the reciprocating movement of the valve stem 32. Seal oil is supplied to the seal chamber 33.

[0065] In this embodiment, fuel oil that can be burned in the cylinder 16 is supplied to the seal chamber 33. The fuel injection valve 3 is configured to seal the gap 3b with the fuel oil supplied to the seal chamber 33.

[0066] In other words, the fuel injector 3 according to this embodiment, and the engine 1 equipped with the fuel injector 3, use fuel oil as the sealing oil instead of conventional oil known as a lubricant for oil seals.

[0067] The fuel oil used in sealing oil includes diesel fuel. Here, the term diesel fuel includes any fossil fuel-derived fuel applicable to low-speed diesel engines. The diesel fuel used as fuel oil may be heavy oil A, heavy oil B, or heavy oil C.

[0068] As an example, in this embodiment, MGO (Marine Gas Oil) is used as the diesel fuel. MGO is a low-sulfur diesel fraction and is an environmentally friendly fuel oil for ships.

[0069] Furthermore, the fuel oil used for sealing is not limited to diesel fuel. The fuel oil for sealing may also be an alternative fuel derived from non-fossil fuels. Specifically, the alternative fuel derived from non-fossil fuels may be alcohol fuel or biodiesel fuel. Here, alcohol fuel includes fuels containing alcohol in general, such as methanol and ethanol. Biodiesel fuel includes substances that can be used in biodiesel fuel in general, such as fatty acid methyl esters (FAME). The fuel oil for sealing is preferably any type of oil that does not leave any residue in the fuel injector 3, such as biodiesel fuel.

[0070] The injection port 3a opens into the cylindrical body 31. The injection port 3a opens and closes as the valve stem 32 moves back and forth. Each fuel injection valve 3 injects ammonia fuel supplied into the cylindrical body 31 through the open injection port 3a.

[0071] As will be described in more detail later, the valve stem 32 of each fuel injector 3 operates in accordance with the balance between the fuel pressure (ammonia fuel pressure) within the fuel injector 3 and the biasing force provided by the biasing member 34 that biases the valve stem 32 to close the injection port 3a. The ammonia fuel pressure within the fuel injector 3 is controlled by the operation of the piston shaft 36 through the supply of hydraulic fluid. The supply of hydraulic fluid is controlled by the operation of a solenoid valve (second switching valve 644) located in the seal oil supply system 4, which also serves as the hydraulic fluid supply line. This solenoid valve is electrically connected to the controller 100 and operates when a control signal is input from the controller 100. In other words, the opening and closing of each fuel injector 3, and consequently the injection of ammonia fuel from the injection port 3a of each fuel injector 3, are controlled by the controller 100.

[0072] In addition, the cylinder cover 15 may be provided with one or more oil injection valves for injecting "pilot oil" to ignite the ammonia fuel. The opening and closing of one or more oil injection valves can also be controlled by the controller 100, similar to the fuel injection valve 3.

[0073] Each fuel injector 3 supplies ammonia fuel to the combustion chamber 17, where it is burned. This combustion causes the piston 21 to reciprocate vertically. When the exhaust valve 18 is activated and the combustion chamber 17 is opened, the exhaust gas produced by the combustion is pushed out into the exhaust pipe 19, and gas is introduced into the combustion chamber 17 from a scavenging port (not shown).

[0074] Furthermore, as the piston 21 reciprocates due to combustion, the piston rod 22 reciprocates vertically along with the piston 21. This causes the crosshead 25, which is connected to the piston rod 22, to reciprocate vertically. The crosshead 25 is designed to allow the connecting rod 24 to rotate, and the connecting rod 24 rotates using the connection point with the crosshead 25 as a pivot point. Then, the crank 27 connected to the lower end of the connecting rod 24 performs a cranking motion, and the crankshaft 23 rotates in response to this cranking motion. In this way, the crankshaft 23 converts the reciprocating motion of the piston 21 into rotational motion, and together with the propeller shaft, rotates the propeller of the ship. This propels the ship forward.

[0075] Here, in order to inject ammonia fuel from each fuel injector 3, as described above, it is necessary to move the valve stem 32 along the central axis Cf of the cylindrical body 31. In doing so, the valve stem 32 slides along the inner wall of the cylindrical body 31. To ensure smooth sliding and to seal the gap between the valve stem 32 and the cylindrical body 31, sealing oil is supplied to the sealing chamber 33 of each fuel injector 3 as needed. The engine 1 supplies sealing oil to each fuel injector 3 via the sealing oil supply system 4.

[0076] The configuration of the seal oil supply system 4 and each fuel injection valve 3 connected to the seal oil supply system 4 will be described in detail below.

[0077] (2) Seal oil supply system 4 Figure 4 is an example of a seal oil supply system 4.

[0078] As shown in Figure 4, the seal oil supply system 4 comprises, as its main components, a housing 5, a seal oil circulation system 6, a seal oil replenishment system 7, and a seal oil discharge system 8.

[0079] (Cabinet 5) The housing 5 circulates the sealing oil between itself and the fuel injector 3. More specifically, the housing 5 circulates the sealing oil between itself and the fuel injector 3. More specifically, the housing 5 supplies the sealing oil to the fuel injector 3 and also receives the sealing oil discharged from the fuel injector 3 as drain oil. Hereinafter, the sealing oil discharged as drain oil will also be referred to as "drain oil".

[0080] Furthermore, the housing 5 is fluidically connected to the fuel injector 3 via a seal oil circulation system 6. The housing 5 circulates seal oil between itself and the fuel injector 3 via the fluid connection provided by the seal oil circulation system 6.

[0081] The housing 5 in this embodiment is an enclosure for housing various contents. The housing 5, as an enclosure, is configured as a separate unit from the engine body 10. The housing 5 is supported by the engine body 10.

[0082] More specifically, the engine 1 according to this embodiment includes a support member 91 for supporting the housing 5. The housing 5 is supported by the engine body 10 via this support member 91.

[0083] Specifically, the support member 91 according to this embodiment is fixed to the engine body 10 and is positioned to the side of the frame 12. The support member 91 is configured as a so-called frame and forms an installation surface 91a on which the housing 5 is installed. This installation surface 91a extends in a horizontal direction perpendicular to the height direction of the engine body 10, that is, the direction of movement of the piston 21.

[0084] Therefore, by installing the housing 5 on the mounting surface 91a, the housing 5 will be positioned laterally to the frame 12 via the support member 91.

[0085] Furthermore, the support members 91 are positioned at a distance from the ship's floor F. The support members 91 are integrally fixed to the engine body 10. As a result, the housing 5 vibrates integrally with the engine body 10. In addition, the supply system for the seal oil, such as the seal oil supply system 4, is completed within the engine 1 without being constructed outside the engine 1.

[0086] Furthermore, the contents that are airtightly housed in the enclosure 5 include components that may leak if the alternative fuel is mixed into the sealing oil. Here, the components that may leak the alternative fuel include components that are fluidically connected to each other via fluid couplings, and the fluid couplings themselves.

[0087] More specifically, the housing 5 houses one or more components, including the seal oil tank 51, from among the seal oil tank 51, oil filter 52, low-pressure pump 53, seal oil cooler 54, seal oil supply valve 55, and seal oil discharge valve 56. These components, like the housing 5, constitute the engine 1 according to this embodiment.

[0088] More specifically, the housing 5 according to this embodiment houses a seal oil tank 51, an oil filter 52, a low-pressure pump 53, a seal oil cooler 54, a seal oil supply valve 55, and a seal oil discharge valve 56.

[0089] The seal oil tank 51 stores seal oil. As shown in Figure 4, the seal oil tank 51 according to this embodiment has a box shape with a top surface 51a and a bottom surface 51b. As mentioned above, the seal oil tank 51 is housed in the housing 5.

[0090] A level sensor Sw1 for detecting the oil level of the seal oil is attached to the seal oil tank 51. The level sensor Sw1 is electrically connected to the controller 100 and outputs an oil level detection signal to the controller 100. The level sensor Sw1 is housed in the housing 5.

[0091] The seal oil tank 51 is equipped with an alternative fuel sensor Sw2 that detects the amount or concentration of ammonia fuel in the seal oil tank 51. The alternative fuel sensor Sw2 is electrically connected to the controller 100 and outputs a detection signal for the amount or concentration of ammonia fuel to the controller 100. The alternative fuel sensor Sw2 is housed in the housing 5. Note that the alternative fuel sensor Sw2 is not mandatory.

[0092] More specifically, the alternative fuel sensor Sw2 is composed of an ammonia sensor that detects the ammonia concentration in the air within the seal oil tank 51. As shown in Figure 4, the alternative fuel sensor Sw2 is positioned above the upper limit Ll of the allowable oil level in the seal oil tank 51. This positioning allows for more reliable detection of ammonia fuel volatilized from the seal oil in the seal oil tank 51. As an example, the alternative fuel sensor Sw2 according to this embodiment is positioned on the top surface 51a of the seal oil tank 51.

[0093] A seal oil supply pipe 61, which constitutes the seal oil circulation system 6, is connected to the seal oil tank 51. The seal oil supply pipe 61 is composed of piping that circulates seal oil from the seal oil tank 51 to the fuel injection valve 3, particularly to the seal chamber 33. The seal oil supply pipe 61 exemplifies the "seal oil piping" in this embodiment in that it can circulate seal oil between the seal oil tank 51 and the fuel injection valve 3.

[0094] More specifically, the seal oil supply pipe 61 fluidly connects the seal oil tank 51 and the seal chamber 33 of the fuel injection valve 3. The seal oil supply pipe 61 supplies fuel oil as seal oil to the seal chamber 33. More specifically, as indicated in Figure 4, the seal oil supply pipe 61 is connected to the bottom surface 51b of the seal oil tank 51 or near the bottom surface 51b. The portion of the seal oil supply pipe 61 near its upstream end (one end on the seal oil tank 51 side) is housed in the housing 5.

[0095] The oil filter 52 is located on the seal oil supply pipe 61. The oil filter 52 filters the seal oil flowing through the seal supply pipe 61 toward the fuel injection valve 3. As mentioned above, the oil filter 52 is housed in the housing 5.

[0096] More specifically, the oil filter 52 is located in the seal oil supply pipe 61, downstream of the seal oil tank 51 and upstream of the low-pressure pump 53. The oil filter 52 filters the seal oil that is discharged from the seal oil tank 51 and flows into the seal oil supply pipe 61.

[0097] The low-pressure pump 53 is located on the seal oil supply pipe 61. The low-pressure pump 53 pressurizes the seal oil flowing through the seal supply pipe 61 toward the fuel injection valve 3. As mentioned above, the low-pressure pump 53 is housed in the housing 5. The low-pressure pump 53 is an example of the "first pump" in this embodiment.

[0098] More specifically, the low-pressure pump 53 is located in the seal oil supply pipe 61, downstream of the oil filter 52 and upstream of the seal oil cooler 54. The low-pressure pump 53 is electrically connected to the controller 100 and operates in response to an electrical signal from the controller 100. Upon receiving the electrical signal, the low-pressure pump 53 pressurizes the seal oil filtered by the oil filter 52.

[0099] Although only one low-pressure pump 53 is shown in the diagram, multiple oil pumps may be connected in parallel to the seal oil supply pipe 61, and these multiple oil pumps may constitute the low-pressure pump 53. In that case, some of the multiple oil pumps may be operated while the remaining oil pumps are assigned as backups, or multiple oil pumps may be operated simultaneously.

[0100] The seal oil cooler 54 is located on the seal oil supply pipe 61. The seal oil cooler 54 cools the seal oil flowing through the seal oil supply pipe 61. As mentioned above, the seal oil cooler 54 is housed in the enclosure 5.

[0101] More specifically, the seal oil cooler 54 is located in the seal oil supply pipe 61, downstream of the oil filter 52 and the low-pressure pump 53, and upstream of the high-pressure pump 63. The seal oil cooler 54 is composed of a heat exchanger using a heat exchange medium supplied from, for example, inside or outside the engine room. The heat exchange medium is, for example, water. The seal oil cooler 54 cools the seal oil, which has been pressurized by the low-pressure pump 53, through the heat exchange medium flowing through the seal oil cooler 54.

[0102] The seal oil tank 51 is connected to a seal oil replenishment pipe 71, which constitutes the seal oil replenishment system 7. The seal oil replenishment pipe 71 is a pipe that circulates seal oil (fuel oil in this embodiment) from the seal oil supply source 72, which constitutes the seal oil replenishment system 7, to the seal oil tank 51. The seal oil replenishment pipe 71 fluidly connects the seal oil supply source 72 and the seal oil tank 51.

[0103] The seal oil supply valve 55 is located on the seal oil replenishment pipe 71. The seal oil supply valve 55 opens and closes the seal oil replenishment pipe 71. By opening and closing the seal oil supply valve 55, the supply of seal oil from the seal oil supply source 72 to the seal oil tank 51 can be started or stopped. As mentioned above, the seal oil supply valve 55 is housed in the housing 5.

[0104] More specifically, the seal oil supply valve 55 is located in the seal oil replenishment pipe 71, downstream of the seal oil supply source 72 and upstream of the seal oil tank 51. The seal oil supply valve 55 is electrically connected to the controller 100 and operates in response to electrical signals from the controller 100. Upon receiving the electrical signals, the seal oil supply valve 55 opens or closes accordingly. When the seal oil supply valve 55 is closed, the supply of seal oil from the seal oil supply source 72 to the seal oil tank 51 is cut off, and when the seal oil supply valve 55 is open, the supply of seal oil from the seal oil supply source 72 to the seal oil tank 51 is restored.

[0105] A first discharge pipe 81, which constitutes the seal oil discharge system 8, is connected to the seal oil tank 51. The first discharge pipe 81 is composed of piping that discharges seal oil (fuel oil in this embodiment) from the seal oil tank 51.

[0106] The seal oil discharge valve 56 is located on the first discharge pipe 81. The seal oil discharge valve 56 opens and closes the first discharge pipe 81. By opening and closing the seal oil discharge valve 56, it is possible to start or stop the discharge of seal oil from the seal oil tank 51. As mentioned above, the seal oil discharge valve 56 is housed in the housing 5.

[0107] More specifically, the seal oil discharge valve 56 is electrically connected to the controller 100 and operates in response to an electrical signal from the controller 100. Upon receiving the electrical signal, the seal oil discharge valve 56 closes or opens accordingly. When the seal oil discharge valve 56 is closed, the discharge of seal oil from the seal oil tank 51 is cut off, and when the seal oil discharge valve 56 is open, the seal oil is discharged from the seal oil tank 51.

[0108] In addition, engine 1 is further equipped with an oil pan 57 housed in the casing 5. The oil pan 57, like other components including the seal oil tank 51, is housed in the casing 5. The oil pan 57 receives seal oil that leaks from the contents of the casing 5.

[0109] Here, the contents of the housing 5 refer to one or more components, including the seal oil tank 51, from among the seal oil tank 51, oil filter 52, low-pressure pump 53, seal oil cooler 54, seal oil supply valve 55, and seal oil discharge valve 56, as described above.

[0110] The oil pan 57 receives seal oil leaked from the contents of the housing 5, or seal oil leaked from the connection between the contents and the seal oil supply pipe 61, seal oil replenishment pipe 71, or first discharge pipe 81 (for example, a fluid coupling).

[0111] A second discharge pipe 82, which constitutes the seal oil discharge system 8, is connected to the oil pan 57. The second discharge pipe 82 is composed of piping that circulates the seal oil (fuel oil in this embodiment) received in the oil pan 57. The second discharge pipe 82 is an example of a "seal oil discharge pipe" in this embodiment.

[0112] A first leak sensor Sw3 is connected to at least one of the oil pan 57 and the second discharge pipe 82. The first leak sensor Sw3 detects the amount of oil in at least one of the oil pan 57 and the second discharge pipe 82.

[0113] More specifically, the first leak sensor Sw3 in this embodiment is, for example, located on the second discharge pipe 82. This first leak sensor Sw3 detects the seal oil flowing through the second discharge pipe 82. The first leak sensor Sw3 is electrically connected to the controller 100 and outputs an oil detection signal to the controller 100. When the first leak sensor Sw3 is located on the second discharge pipe 82, a so-called float switch can be used for the first leak sensor Sw3. In this case, a storage tank for seal oil can be formed on the second discharge pipe 82, and the float switch can be laid out in the storage tank.

[0114] Furthermore, when the first leak sensor Sw3 is placed in the oil pan 57, a ribbon-shaped sensor (sensor ribbon), for example, can be used for the first leak sensor Sw3.

[0115] As mentioned above, there are concerns about leakage of sealing oil from the contents of the housing 5, or leakage of sealing fuel oil from the connection portion (the connection portion between the contents of the housing 5 and the sealing oil supply pipe 61, the sealing oil replenishment pipe 71, or the first discharge pipe 81). If ammonia fuel is mixed in with the sealing oil, various problems can be expected due to the volatilization of the ammonia fuel.

[0116] To address these inconveniences, the housing 5 according to this embodiment has a ventilation mechanism 58 for ventilating the inside of the housing 5. This ventilation mechanism 58 includes a ventilation fan 58a. The ventilation fan 58a is electrically connected to the controller 100 and operates by receiving an electrical signal from the controller 100.

[0117] For example, when the sealing oil is circulating between the housing 5 and the fuel injection valve 3, the ventilation mechanism 58 ventilates the housing 5 in parallel with the circulation of the sealing oil. In this way, even if ammonia fuel is mixed in with the sealing oil, the ammonia fuel that volatilizes from the sealing oil can be kept inside the housing 5. Furthermore, by operating the ventilation fan 58a, the ammonia fuel that volatilizes from the sealing oil can be quickly discharged.

[0118] It is not essential that the ventilation fan 58a be operated by an electrical signal from the controller 100. The ventilation fan 58a may be configured to operate by receiving an electrical signal output from a control board independent of the controller 100. In this case, the ventilation fan 58a can operate independently without being linked to the operating status of the engine 1.

[0119] When the ventilation fan 58a operates, the air sent out from inside the enclosure 5 flows into the ventilation passage 58b. This ventilation passage 58b is connected to the mist box 58c. The mist box 58c is connected to another exhaust passage 58d that communicates with the outside space, such as the atmosphere (see Figure 4).

[0120] Therefore, the air sent out from inside the enclosure 5 by the operation of the ventilation fan 58a passes through the ventilation passage 58b, is collected by the mist box 58c, and then, after the oil is removed from the air, is discharged through the exhaust passage 58d.

[0121] (Seal oil circulation system 6) The seal oil circulation system 6 fluidly connects the housing 5 and the fuel injector 3 to circulate seal oil between them. In other words, the housing 5 circulates seal oil between itself and the fuel injector 3 via the fluid connection provided by the seal oil circulation system 6.

[0122] Specifically, the seal oil circulation system 6 according to this embodiment includes, in addition to the seal oil supply pipe 61 described above, a high-pressure pump 63, a first pressure sensor Sw4, a control valve unit 64, and a seal oil return pipe 62.

[0123] The high-pressure pump 63 is located downstream of the low-pressure pump 53 in the seal oil supply pipe 61, which serves as the seal oil piping. The high-pressure pump 63 further pressurizes the seal oil that has been pressurized by the low-pressure pump 53. The high-pressure pump 63 is an example of the "second pump" in this embodiment.

[0124] More specifically, the high-pressure pump 63 is located in the seal oil supply pipe 61, downstream of the low-pressure pump 53 and the seal oil cooler 54, and upstream of the control valve unit 64. The high-pressure pump 63 is electrically connected to the controller 100 and operates in response to electrical signals from the controller 100. Upon receiving the electrical signal, the high-pressure pump 63 pressurizes the seal oil, which has been boosted by the low-pressure pump 53 and then cooled by the seal oil cooler 54.

[0125] In other words, the seal oil cooler 54 according to this embodiment is positioned downstream of the low-pressure pump 53 and upstream of the high-pressure pump 63 on the seal oil supply pipe 61.

[0126] Although only one high-pressure pump 63 is shown in the diagram, multiple oil pumps may be connected in parallel to the seal oil supply pipe 61, and these multiple oil pumps may constitute the high-pressure pump 63. In that case, some of the multiple oil pumps may be operated while the remaining oil pumps are assigned as backups, or the system may be configured to operate all of the oil pumps simultaneously.

[0127] Furthermore, as shown in Figure 2, the high-pressure pump 63 is configured as a separate unit from the housing 5, and may be fixed to the engine body 10 via a support member 91, similar to the housing 5.

[0128] Furthermore, as shown in Figure 2, the high-pressure pump 63 is housed in an enclosure 93 separate from the housing 5. This enclosure 93 is connected to the housing 5 via a duct 94. Ammonia that volatilizes within the enclosure 93 is sent to the housing 5 via the duct 94 and then ventilated by a ventilation mechanism 58.

[0129] Furthermore, the enclosure 93 for the high-pressure pump 63 houses an oil pan (not shown), similar to the housing 5 and the enclosure 95 for the control valve unit 64, which will be described later. This oil pan receives the sealing oil leaked from the high-pressure pump 63. The oil pan for the high-pressure pump 63 is connected to the junction pipe 84 between the second discharge pipe 82 and the third discharge pipe 83. Oil leakage can be detected by detecting the oil flowing through this connecting pipeline, for example, using a float sensor.

[0130] The first pressure sensor Sw4 is located downstream of the high-pressure pump 63 in the seal supply pipe 61. The first pressure sensor Sw4 detects the pressure of the seal oil immediately after it is pressurized by the high-pressure pump 63.

[0131] More specifically, the first pressure sensor Sw4 is located in the seal supply pipe 61, downstream of the high-pressure pump 63 and upstream of the control valve unit 64. The first pressure sensor Sw4 is electrically connected to the controller 100 and outputs a detection signal of the seal oil pressure to the controller 100. The first pressure sensor Sw4 is composed of, for example, a pressure transmitter (a so-called "PT") which integrates a pressure sensor and an amplifier.

[0132] The control valve unit 64 is located downstream of the first pressure sensor Sw4 and upstream of the fuel injector 3 in the seal oil supply pipe 61, which serves as the seal oil piping. The control valve unit 64 controls the supply of seal oil to the fuel injector 3.

[0133] More specifically, the control valve unit 64 includes, in order from the upstream side in the direction of seal oil flow, a first pressure reducing valve 641, a first switching valve 642, and a second pressure sensor Sw5. All of these elements are located on the seal oil supply pipe 61.

[0134] The first pressure reducing valve 641 regulates the pressure of the sealing oil that has been pressurized by the high-pressure pump 63. Specifically, the sealing oil pressurized by the high-pressure pump 63 flows into the primary side (upstream side) of the first pressure reducing valve 641, and the sealing oil that has been regulated by the first pressure reducing valve 641 flows out from the secondary side (downstream side) of the first pressure reducing valve 641.

[0135] The first switching valve 642 opens and closes the seal oil supply pipe 61. When the seal oil supply pipe 61 is opened by the first switching valve 642, the seal oil, whose pressure has been regulated by the first pressure reducing valve 641, passes through the first switching valve 642 to the fuel injection valve 3. When the seal oil supply pipe 61 is closed by the first switching valve 642, the seal oil, whose pressure has been regulated by the first pressure reducing valve 641, is shut off by the first switching valve 642.

[0136] More specifically, the first switching valve 642 is electrically connected to the controller 100 and operates in response to electrical signals from the controller 100. Upon receiving the electrical signals, the first switching valve 642 closes or opens in response to those signals. The first switching valve 642 is, for example, composed of a solenoid-type electromagnetic valve.

[0137] The second pressure sensor Sw5 is located downstream of the first switching valve 642 in the seal supply pipe 61. The second pressure sensor Sw5 detects the pressure of the seal oil immediately after it has passed through the first switching valve 642.

[0138] More specifically, the second pressure sensor Sw5 is located in the seal supply pipe 61, downstream of the first switching valve 642 and upstream of the fuel injection valve 3. The second pressure sensor Sw5 is electrically connected to the controller 100 and outputs a detection signal for the seal oil pressure to the controller 100. The second pressure sensor Sw5 is composed of, for example, a pressure transmitter (a so-called "PT") which integrates a pressure sensor and an amplifier.

[0139] Furthermore, in this embodiment, the fuel oil, which functions as a sealing oil, also serves as the hydraulic fluid.

[0140] For this purpose, the seal oil supply pipe 61 according to this embodiment is connected to a hydraulic fluid supply pipe 65, as shown in Figure 4. The hydraulic fluid supply pipe 65 connects the seal oil supply pipe 61 to the fuel injection valve 3. More specifically, as shown in Figure 4, the hydraulic fluid supply pipe 65 connects the space between the first pressure sensor Sw4 and the first pressure reducing valve 641 in the seal oil supply pipe 61 to the hydraulic fluid chamber 38 in the fuel injection valve 3.

[0141] As elements related to the supply of hydraulic fluid, the control valve unit 64 according to this embodiment further includes, in order from the upstream side in the flow direction of the sealing oil (hydraulic fluid), a second switching valve 644, a second pressure reducing valve 645, a third pressure sensor Sw7, and a hydraulic fluid pump 646. All of these elements are located on the hydraulic fluid supply pipe 65.

[0142] The second switching valve 644 opens and closes the hydraulic fluid supply pipe 65. When the hydraulic fluid supply pipe 65 is opened by the second switching valve 644, the seal oil pressurized by the high-pressure pump 63 passes through the second switching valve 644 to the second pressure reducing valve 645. When the hydraulic fluid supply pipe 65 is closed by the second switching valve 644, the seal oil pressurized by the high-pressure pump 63 is shut off by the second switching valve 644.

[0143] More specifically, the second switching valve 644 is electrically connected to the controller 100 and operates in response to electrical signals from the controller 100. Upon receiving these electrical signals, the second switching valve 644 closes or opens accordingly. The second switching valve 644 is, for example, composed of a solenoid-type electromagnetic valve.

[0144] The second pressure reducing valve 645 regulates the pressure of the sealing oil that has passed through the second switching valve 644. Specifically, the sealing oil that has passed through the second switching valve 644 flows into the primary side (upstream side) of the second pressure reducing valve 645, and the sealing oil that has been regulated by the second pressure reducing valve 645 flows out from the secondary side (downstream side) of the second pressure reducing valve 645.

[0145] The third pressure sensor Sw7 is located downstream of the second pressure reducing valve 645 in the hydraulic fluid supply pipe 65. The third pressure sensor Sw7 detects the pressure of the seal oil immediately after it has been regulated by the second pressure reducing valve 645.

[0146] More specifically, the third pressure sensor Sw7 is located in the hydraulic fluid supply pipe 65, downstream of the second pressure reducing valve 645 and upstream of the hydraulic fluid pump 646. The third pressure sensor Sw7 is electrically connected to the controller 100 and outputs a detection signal for the seal oil pressure to the controller 100. The third pressure sensor Sw7 is composed of, for example, a pressure transmitter (a so-called "PT") which integrates a pressure sensor and an amplifier.

[0147] The hydraulic oil pump 646 is located downstream of the third pressure sensor Sw7 in the hydraulic oil supply pipe 65. After the pressure is regulated by the second pressure reducing valve 645, the hydraulic oil pump 646 pumps the sealing oil, whose pressure is detected by the third pressure sensor Sw7, to the fuel injection valve 3.

[0148] More specifically, the hydraulic oil pump 646 is located in the hydraulic oil supply pipe 65, downstream of the second pressure reducing valve 645 and the third pressure sensor Sw7, and upstream of the fuel injection valve 3. The hydraulic oil pump 646 is electrically connected to the controller 100 and operates in response to an electrical signal from the controller 100. Upon receiving the electrical signal, the hydraulic oil pump 646 pressurizes the seal oil, which has been regulated by the second pressure reducing valve 645, and sends it to the fuel injection valve 3 as hydraulic oil.

[0149] In addition, the control valve unit 64 is housed in an enclosure 95 for the control valve unit 64. For example, as shown in Figure 2, this enclosure 95 is separate from both the housing 5 and the enclosure 93 for the high-pressure pump 63.

[0150] It is not essential to have a separate enclosure 95 for the control valve unit 64 for both the housing 5 and the enclosure 93 for the high-pressure pump 63. The enclosure 95 may be integrated with at least one of the housing 5 and the enclosure 93 for the high-pressure pump 63. Alternatively, the enclosure 95 may be composed of multiple housings, each housing different components.

[0151] As shown in Figure 4, the control valve unit 64 further comprises a second oil pan 643 housed in an enclosure 95 for the control valve unit 64. The second oil pan 643 receives sealing oil leaked from the components of the control valve unit 64. The components of the control valve unit 64 include a first pressure reducing valve 641, a first switching valve 642, a second pressure sensor Sw5, a second switching valve 644, a second pressure reducing valve 645, a third pressure sensor Sw7, and a hydraulic oil pump 646.

[0152] A third discharge pipe 83, which constitutes the seal oil discharge system 8, is connected to the second oil pan 643. The third discharge pipe 83 is composed of piping that circulates the seal oil (fuel oil in this embodiment) received in the second oil pan 643.

[0153] A second leak sensor Sw6 is connected to at least one of the second oil pan 643 and the third discharge pipe 83. The second leak sensor Sw6 detects oil in at least one of the second oil pan 643 and the third discharge pipe 83.

[0154] In detail, the second leak sensor Sw6 in this embodiment is, for example, located on the third discharge pipe 83. This second leak sensor Sw6 detects the seal oil flowing through the third discharge pipe 83. The second leak sensor Sw6 is electrically connected to the controller 100 and outputs an oil detection signal to the controller 100. When the second leak sensor Sw6 is located on the third discharge pipe 83, a so-called float switch can be used for the second leak sensor Sw6. In this case, a storage tank for seal oil can be formed on the third discharge pipe 83, and the float switch can be laid out in the storage tank.

[0155] Furthermore, when the second leak sensor Sw6 is placed in the second oil pan 643, a ribbon-shaped sensor (sensor ribbon), for example, can be used for the second leak sensor Sw6.

[0156] Returning to Figure 2, the control valve unit 64 is configured as a separate unit from the housing 5 and the high-pressure pump 63. In this embodiment, the control valve unit 64 is supported by the engine body 10 via a second support member 92.

[0157] The second support member 92 is composed of a so-called frame and is fixed to the cylinder jacket 13 or cylinder liner 14. The second support member 92 supports the control valve unit 64 in the height direction of the engine 1, at a position above the housing 5 and the high-pressure pump 63.

[0158] The seal oil return pipe 62 is a pipe that circulates seal oil from each part of the fuel injection valve 3 and the seal oil supply system 4 to the seal oil tank 51. The seal oil return pipe 62 includes a first return pipe 621, a second return pipe 622, a third return pipe 623, a fourth return pipe 624, a fifth return pipe 625, a first on-off valve 626, and a second on-off valve 627. The seal oil return pipe 62, together with the seal oil supply pipe 61, exemplifies the "seal oil piping" in this embodiment in that it can circulate seal oil between the seal oil tank 51 and the fuel injection valve 3.

[0159] The first return pipe 621 is a pipe that sends the drain oil discharged from the fuel injector 3 back from the fuel injector 3 to the seal oil tank 51. The first return pipe 621 fluidly connects each fuel injector 3 to the seal oil tank 51. The portion of the first return pipe 621 near the downstream end (one end on the seal oil tank 51 side) is housed in the housing 5.

[0160] The second return pipe 622 is a pipe that sends the seal oil leaking from the high-pressure pump 63 (hereinafter also referred to as "leak oil") back from the high-pressure pump 63 to the seal oil tank 51. The second return pipe 622 fluidly connects the high-pressure pump 63 and the seal oil tank 51. The portion of the second return pipe 622 near the downstream end (one end on the seal oil tank 51 side) is housed in the housing 5.

[0161] The third return pipe 623 controls the discharge pressure of the high-pressure pump 63. The third return pipe 623 fluidly connects the outlet of the high-pressure pump 63 to the seal oil tank 51. The portion of the third return pipe 623 near the downstream end (one end on the seal oil tank 51 side) is housed in the housing 5. As illustrated in Figure 4, a first on-off valve 626 is positioned in the middle of the third return pipe 623. The first on-off valve 626 changes its opening degree by receiving an electrical signal from the controller 100. The controller 100 adjusts the discharge pressure of the high-pressure pump 63 to the desired pressure by controlling the opening degree of the first on-off valve 626. A pressure regulating valve may be used instead of the first on-off valve 626 which is electrically connected to the controller 100.

[0162] The fourth return pipe 624 is a piping system that sends the leaked oil from the first switching valve 642 back from the first switching valve 642 to the seal oil tank 51. The fourth return pipe 624 is fluidly connected to the first switching valve 642 and to an intermediate point of the third return pipe 623. In other words, the fourth return pipe 624 merges with the third return pipe 623 before being connected to the seal oil tank 51.

[0163] The fifth return pipe 625 controls the discharge pressure of the low-pressure pump 53. The fifth return pipe 625 fluidly connects the outlet of the low-pressure pump 53 to the seal oil tank 51. The entire fifth return pipe 625, from its upstream end to its downstream end, is housed in the housing 5. As illustrated in Figure 4, a second on-off valve 627 is positioned in the middle of the fifth return pipe 625. The second on-off valve 627 changes its opening degree by receiving an electrical signal from the controller 100. The controller 100 adjusts the discharge pressure of the low-pressure pump 53 to the desired pressure by controlling the opening degree of the second on-off valve 627. A pressure regulating valve may be used instead of the second on-off valve 627 which is electrically connected to the controller 100.

[0164] Here, the connection point between the seal oil return pipe 62 and the seal oil tank 51 is located above the connection point between the seal oil supply pipe 61 and the seal oil tank 51.

[0165] More specifically, the connection point between the seal oil return pipe 62 and the seal oil tank 51 is located above the upper limit Ll of the allowable oil level in the seal oil tank 51. Further specifically, the seal oil return pipe 62 is connected to the top surface 51a of the seal oil tank 51 or near the top surface 51a.

[0166] (Seal oil replenishment system 7) The seal oil replenishment system 7 is connected to the housing 5. More specifically, the seal oil replenishment system 7 is connected to the seal oil tank 51 inside the housing 5. This seal oil replenishment system 7 replenishes the seal oil in the seal oil tank 51 inside the housing 5.

[0167] Specifically, the seal oil replenishment system 7 according to this embodiment includes, in addition to the seal oil replenishment pipe 71 described above, the seal oil supply source 72 described above, an oil cooler 73, and a filter 74.

[0168] The seal oil supply source 72 is an oil tank that stores fuel oil used as seal oil, such as MGO. The seal oil supply source 72 is fluidly connected to the seal oil tank 51 inside the housing 5 via the seal oil replenishment pipe 71. The seal oil supply source 72 is an example of a "storage tank" in this embodiment.

[0169] The oil cooler 73 is located on the seal oil replenishment pipe 71. The oil cooler 73 cools the seal oil flowing through the seal oil replenishment pipe 71. The oil cooler 73 is composed of a heat exchanger using a heat exchange medium supplied from, for example, inside or outside the engine room. The heat exchange medium is, for example, water.

[0170] The filter 74 is positioned on the seal oil replenishment pipe 71 and filters the seal oil flowing through the seal oil replenishment pipe 71.

[0171] Furthermore, at least one of the seal oil replenishment system 7 and the seal oil tank 51 is configured to restrict the backflow of seal oil from the seal oil tank 51 to the seal oil replenishment pipe 71.

[0172] For example, in this embodiment, as illustrated in Figure 4, the connection point between the seal oil replenishment pipe 71 and the seal oil tank 51 is located above the connection point between the seal oil supply pipe 61 and the seal oil tank 51.

[0173] More specifically, the connection point between the seal oil replenishment pipe 71 and the seal oil tank 51 is located above the upper limit Ll of the allowable oil level in the seal oil tank 51. Further specifically, the seal oil replenishment pipe 71 is connected to the top surface 51a of the seal oil tank 51 or near the top surface 51a.

[0174] In this way, by devising the connection position between the seal oil replenishment pipe 71 and the seal oil tank 51, backflow of seal oil from the seal oil tank 51 to the seal oil replenishment pipe 71 is suppressed. In addition to these configurations, or as an alternative to these configurations, a component capable of suppressing backflow of seal oil, such as a check valve, may be placed on the seal oil replenishment pipe 71, or the seal oil supply source 72 may be placed at a higher position than the seal oil replenishment pipe 71.

[0175] (Seal oil discharge system 8) The seal oil discharge system 8 discharges excess seal oil, such as leaked oil, that has leaked out from various parts of the seal oil supply system 4.

[0176] Specifically, the seal oil discharge system 8 according to this embodiment includes a confluence pipe 84 in addition to the first discharge pipe 81, second discharge pipe 82, first leak sensor Sw3, third discharge pipe 83, and second leak sensor Sw6 mentioned above.

[0177] The confluence pipe 84 is connected to the first discharge pipe 81, the second discharge pipe 82, and the third discharge pipe 83, respectively. The confluence pipe 84 discharges the seal oil that flows into the first discharge pipe 81, the second discharge pipe 82, and the third discharge pipe 83 to the outside of the engine room. Even if ammonia fuel is mixed in with the seal oil, that ammonia fuel will be discharged to the outside of the engine room along with the seal oil.

[0178] (3) Fuel injection valve 3 Figure 5 is a longitudinal cross-sectional view illustrating the configuration of the fuel injection valve 3.

[0179] As shown in Figure 5, the fuel injection valve 3 includes, in addition to the cylindrical body 31, valve stem 32, and seal chamber 33 described above, a fuel chamber 35, a piston stem 36, a pressure chamber 37, and a hydraulic fluid chamber 38.

[0180] Hereinafter, the direction extending along the central axis Cf of the cylindrical body 31 will be referred to as the central axis direction. One end of the cylindrical body 31 in the central axis direction (the lower side in the figure) will be called the tip, and the other end in the central axis direction will be called the base. For example, the injection port 3a of the fuel injection valve 3 opens at the tip of the cylindrical body 31, as shown in Figure 5.

[0181] The hydraulic fluid chamber 38 is formed inside the cylindrical body 31. The hydraulic fluid chamber 38 is fluidly connected to the hydraulic fluid supply pipe 65. Fuel oil, which serves as the hydraulic fluid, is pumped into the hydraulic fluid chamber 38 from the hydraulic fluid supply pipe 65. Any excess hydraulic fluid in the hydraulic fluid chamber 38 is discharged from the hydraulic fluid chamber 38 as drain oil.

[0182] The pressurized chamber 37 is formed inside the cylindrical body 31. The pressurized chamber 37 is located at the tip of the hydraulic fluid chamber 38 in the central axis direction. Ammonia fuel, as an alternative fuel, is supplied to the pressurized chamber 37 from the outside via a check valve 39. The pressurized chamber 37 is also fluidly connected to the fuel chamber 35 via a first path L1 formed inside the cylindrical body 31.

[0183] A through-hole 3c is formed inside the cylindrical body 31. The through-hole 3c extends along the central axis direction, connecting the hydraulic fluid chamber 38 and the pressure chamber 37. The piston shaft 36 is inserted into this through-hole 3c.

[0184] The piston shaft 36 reciprocates in a predetermined direction to pump ammonia fuel. The fuel injector 3 according to this embodiment is configured to reciprocate the piston shaft 36 using the hydraulic pressure of the fuel oil supplied to the piston shaft 36. In other words, the fuel oil functions as a hydraulic fluid that causes the piston shaft 36 to reciprocate.

[0185] More specifically, in this embodiment, the piston shaft 36 is located inside the cylindrical body 31 and reciprocates along the central axis Cf of the cylindrical body 31, as illustrated in Figure 5. It is not essential that the piston shaft 36 reciprocates along the central axis Cf, that is, that the central axis of the piston shaft 36 coincides with the central axis Cf of the cylindrical body 31. For example, the direction of movement of the piston shaft 36 may intersect the central axis Cf of the cylindrical body 31. In that case, the fuel injection valve 3 may include a separate cylindrical body, inclined with respect to the cylindrical body 31, that houses the piston shaft 36, in addition to the cylindrical body 31 that houses the valve stem 32.

[0186] More specifically, the piston shaft 36 extends from the hydraulic fluid chamber 38 through the through hole 3c to the fuel chamber 35, blocking communication between the hydraulic fluid chamber 38 and the pressure chamber 37. The ceiling surface of the pressure chamber 37 is formed by the lower surface (top surface at the tip) of the piston shaft 36.

[0187] The piston shaft 36 then slides along the through hole 3c in the axial direction according to the hydraulic pressure of the hydraulic fluid chamber 38. As the piston shaft 36 slides, the volume of the pressurized chamber 37 changes. As a result, the ammonia fuel supplied to the pressurized chamber 37 from the outside is pressurized and sent from the pressurized chamber 37 to the first path L1.

[0188] The fuel chamber 35 is formed inside the cylindrical body 31. The fuel chamber 35 is located in the central axis direction, further forward than the pressurizing chamber 37 and further back than the injection nozzle 3a. Ammonia fuel is pressurized into the fuel chamber 35 from the pressurizing chamber 37 via the first path L1. The fuel chamber 35 is also in communication with the injection nozzle 3a.

[0189] As described above, the valve stem 32 is located inside the cylindrical body 31. The valve stem 32 extends through the fuel chamber 35 and slides along the inner wall of the cylindrical body 31 in the direction of the central axis. The sliding of the valve stem 32 blocks or releases communication between the fuel chamber 35 and the injection port 3a. The valve stem 32 is biased by the biasing member 34 to maintain the blockage of communication between the fuel chamber 35 and the injection port 3a.

[0190] When the fuel pressure (ammonia fuel pressure) in the fuel chamber 35 increases, the valve stem 32 slides in a direction that resists the biasing force of the biasing member 34, thereby creating communication between the fuel chamber 35 and the injection nozzle 3a. With the fuel chamber 35 and the injection nozzle 3a in communication, ammonia fuel is supplied from the fuel chamber 35 to the injection nozzle 3a, and that ammonia fuel is injected from the injection nozzle 3a.

[0191] In this manner, the valve stem 32 slides along the inner wall of the cylindrical body 31. Therefore, in order to seal the gap 3b between the outer wall of the valve stem 32 and the inner wall of the cylindrical body 31, fuel oil is supplied as a sealing oil to the seal chamber 33 located in the gap 3b, as described above.

[0192] The sealing oil supplied to the sealing chamber 33 seals the gap 3b between the cylindrical body 31 and the valve stem 32. By supplying sealing oil to the sealing chamber 33, leakage of ammonia fuel through the gap 3b is suppressed, and the sliding motion of the valve stem 32 against the cylindrical body 31 is lubricated.

[0193] Returning to the description of the seal chamber 33, in this embodiment, the seal chamber 33 is located between the biasing member 34 and the fuel chamber 35. The seal chamber 33 is fluidly connected to the seal oil supply pipe 61. Fuel oil, which serves as the seal oil, is pumped into the seal chamber 33 from the seal oil supply pipe 61. Any excess hydraulic fluid in the seal chamber 33 is discharged from the seal chamber 33 as drain oil.

[0194] (4)Alternative fuel exhaust system9 In the various piping systems that make up the seal oil supply system 4, there is a concern about the contamination of these piping systems with ammonia fuel, and consequently, the volatilization of the contaminated ammonia fuel. Of the volatile ammonia fuel, the volatile components that leak into the housing 5 can be discharged to the outside by the ventilation mechanism 58 described above. However, it would be advantageous if such volatile components could be discharged in the first place.

[0195] Therefore, the engine 1 according to this embodiment further includes an alternative fuel discharge system 9 as illustrated in Figure 4. As shown in the figure, the alternative fuel discharge system 9 has a ventilation passage 96, an introduction passage 97, and a flow rate adjustment means 98.

[0196] The ventilation passage 96 is connected to at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62). The ventilation passage 96 discharges volatile ammonia fuel from at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62).

[0197] More specifically, the ventilation passage 96 according to this embodiment includes a downstream end connected to the mist box 58c and upstream ends that branch into two passages and are connected to the seal oil tank 51 and the seal oil return pipe 62, respectively. More specifically, the two upstream ends of the ventilation passage 96 are connected to the mist box 58c and the first return pipe 621.

[0198] Furthermore, the ventilation passage 96 according to this embodiment discharges the ammonia fuel that has evaporated in the seal oil tank 51 and the ammonia fuel that has evaporated in the seal oil return pipe 62, or in the illustrated example, the first return pipe 621, through the mist box 58c.

[0199] The introduction passage 97 is connected to at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62). The introduction passage 97 introduces compressed air or scavenging gas into at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62). Here, the term "scavenging gas" refers to the gas that scavenges the inside of the combustion chamber 17.

[0200] More specifically, the introduction passage 97 according to this embodiment is connected to the seal oil tank 51. This introduction passage 97 introduces compressed air or scavenging gas into the seal oil tank 51.

[0201] The flow rate adjustment means 98 is located in the introduction passage 97. The flow rate adjustment means 98 adjusts the flow rate of compressed air or scavenging gas in the introduction passage 97.

[0202] More specifically, the flow rate adjustment means 98 according to this embodiment is composed of, for example, an orifice or a flow rate adjustment valve. More specifically, in this embodiment, the flow rate adjustment means 98 is composed of a flow rate adjustment valve.

[0203] (5) Controller 100 Figure 6 is a block diagram illustrating the configuration of the controller 100 of engine 1. The controller 100 includes a processor, volatile memory, non-volatile memory, and an input / output bus. The controller 100 is connected to, for example, a level sensor Sw1, an alternative fuel sensor Sw2, a first leak sensor Sw3, a first pressure sensor Sw4, a second pressure sensor Sw5, a second leak sensor Sw6, and a third pressure sensor Sw7.

[0204] The controller 100 generates control signals based on signals received from these sensors and inputs these control signals to the low-pressure pump 53, seal oil supply valve 55, ventilation mechanism 58, high-pressure pump 63, first switching valve 642, second switching valve 644, hydraulic oil pump 646, first on-off valve 626, and second on-off valve 627, etc. Through these control signals, the controller 100 controls the circulation of fuel oil, which functions as both seal oil and hydraulic oil in the seal oil supply system 4, and ventilation inside the housing 5 by the ventilation mechanism 58.

[0205] (6) Effects etc. As described above, according to the embodiment described above, even if ammonia fuel is mixed into the sealing oil and the ammonia fuel volatilizes and leaks, the leaked volatile components can be contained within the housing 5 illustrated in Figure 4. This allows the ammonia fuel that has mixed into the sealing oil and leaked to be isolated from the equipment and the human body. In this way, the effects of ammonia fuel contamination can be suppressed.

[0206] Furthermore, as illustrated in Figures 1 and 2, the housing 5 is supported by the engine body 10 by the support members 91. This allows the housing 5 to be transported together with the engine body 10. In addition, the housing 5, supported by the support members 91, is positioned at a distance from the ship's floor F. This arrangement allows the housing 5 to vibrate together with the engine body 10.

[0207] If the housing 5 is placed on the floor F, the engine body 10, which acts as the excitation source, will vibrate relatively more, while the floor F and housing 5 will not vibrate as much as the engine body 10. In this case, it would be necessary to connect a member or mechanism to the piping connecting the housing 5 and the engine body 10 that can absorb the difference in vibration between the engine body 10 and the floor F. However, such a member or mechanism may lead to leakage of ammonia fuel from the connection point with the piping.

[0208] In contrast, by vibrating the housing 5 and the engine body 10 as a single unit, the aforementioned components or mechanisms become unnecessary. This reduces the risk of leakage from the connection point. Furthermore, as mentioned above, since the seal oil supply system 4 is contained within the engine 1, even if ammonia fuel leakage occurs, the area over which the leaked ammonia fuel diffuses can be kept to a minimum.

[0209] Furthermore, as illustrated in Figures 1 and 2, the housing 5 is positioned to the side of the frame 12, that is, above the crankcase. This arrangement allows the fuel injector 3 and the housing 5 to be brought closer together in the vertical direction. This makes the entire seal oil supply system more compact. The compactness of the entire seal oil supply system contributes to the miniaturization of the seal oil tank 51 for storing the seal oil and to the suppression of ammonia fuel leakage from the piping.

[0210] Furthermore, as illustrated in Figure 4, by housing various components, including the seal oil tank 51 and the low-pressure pump 53, within the housing 5, when ammonia fuel is mixed into the seal oil, both the volatile components of the ammonia fuel leaking from the various components related to the seal oil tank 51, and the volatile components of the ammonia fuel leaking from the connections between components (for example, fluid couplings) can be contained within the housing 5. This is advantageous in suppressing the effects of ammonia fuel mixing into the seal oil.

[0211] Furthermore, as illustrated in Figure 4, the viscosity of the seal oil can be ensured by cooling the seal oil with the seal oil cooler 54. Here, in order to supply sufficiently cooled seal oil to the fuel injector 3, it is conceivable to position the seal oil cooler 54 as close as possible to the fuel injector 3 on the seal oil supply pipe 61, which serves as the seal oil piping. However, if the seal oil cooler 54 is positioned downstream of the high-pressure pump 63, the seal oil, which has been pressurized by the high-pressure pump 63, will be supplied, potentially causing malfunctions in the seal oil cooler 54.

[0212] In contrast, as illustrated in Figure 4, by arranging the seal oil cooler 54 between the low-pressure pump 53 and the high-pressure pump 63, it is possible to achieve both the viscosity of the seal oil and the suppression of abnormalities in the seal oil cooler 54.

[0213] Furthermore, as illustrated in Figure 4, by connecting the seal oil replenishment system 7 and the seal oil tank 51 within the housing 5, even if volatile components of ammonia fuel leak from the connection point between the seal oil replenishment system 7 and the seal oil tank 51, such as a fluid coupling, these volatile components can be contained within the housing 5. This is advantageous in suppressing the effects of ammonia fuel contamination of the seal oil.

[0214] Furthermore, as illustrated in Figure 4, by configuring the system to restrict the backflow of seal oil from the seal oil tank 51 to the seal oil replenishment pipe 71, even if ammonia fuel is mixed into the seal oil, the backflow of the ammonia fuel-contaminated seal oil to the seal oil supply source 72 is restricted. As a result, the diffusion of the ammonia fuel-contaminated seal oil can be prevented, which is advantageous in suppressing the effects of ammonia fuel contamination.

[0215] Furthermore, even if ammonia fuel enters and volatilizes the seal oil flowing through at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62), the volatile components can be discharged through the ventilation passage 96 illustrated in Figure 4. This isolates the ammonia fuel mixed in the seal oil from the equipment and the human body. This further enhances the ability to suppress the effects of ammonia fuel contamination.

[0216] Furthermore, even if volatile components of the ammonia fuel leak out without being discharged through the ventilation passage 96, the leaked volatile components can be discharged by the ventilation mechanism 58 illustrated in Figure 4. This isolates the ammonia fuel that has leaked mixed with the sealing oil from the equipment and people. This is further advantageous in suppressing the effects of ammonia fuel contamination.

[0217] In general, the crew will perform routine inspections and other tasks on the engine 1. By providing the ventilation mechanism 58, the crew working on the engine 1 will be reliably isolated from the ammonia fuel. In other words, by providing the ventilation mechanism 58, the crew can be isolated from the ammonia fuel even if the housing 5 is supported by the engine body 10.

[0218] Furthermore, when volatile ammonia fuel flows into at least one of the seal oil tank 51 and the seal oil piping (seal oil supply pipe 61 and seal oil return pipe 62), the ammonia fuel can be pushed out by compressed air or exhaust gas introduced from the introduction passage 97 illustrated in Figure 4 and sent to the ventilation passage 96. This is even more advantageous in suppressing the effects of ammonia fuel contamination.

[0219] Furthermore, as illustrated in Figure 4, by arranging the flow rate adjustment means 98 in the introduction passage 97, it becomes possible to adjust the flow rate of compressed air or scavenging gas. This is even more advantageous in suppressing the effects of mixing in alternative fuels.

[0220] Furthermore, as illustrated in Figure 4, the sealing oil leaking from the contents of the housing 5 can be discharged along with the ammonia fuel mixed in the sealing oil using the sealing oil discharge system (sealing oil discharge system 8). This is advantageous in suppressing the effects of ammonia fuel contamination on the sealing oil.

[0221] Furthermore, fuel oil does not produce residue even at high temperatures. Therefore, as in the embodiment described above, by sealing the fuel injection valve 3 with fuel oil, even if the sealing oil were to mix with the ammonia fuel, various problems caused by residue would not occur. This makes it possible to suppress the impact of the sealing oil mixing with the ammonia fuel.

[0222] Furthermore, as in the embodiment described above, using diesel fuel as the sealing oil more reliably suppresses the generation of residues. This is advantageous in suppressing the impact of the sealing oil mixing with ammonia fuel. In addition, using an alternative fuel instead of diesel fuel as the sealing oil can promote carbon neutrality.

[0223] Furthermore, in order to supply sufficiently cooled seal oil to the fuel injector 3, it is conceivable to position the seal oil cooler 54 as close as possible to the fuel injector 3 on the seal oil supply pipe 61, which serves as the seal oil piping. However, if the seal oil cooler 54 is positioned downstream of the high-pressure pump 63, the seal oil, which has been pressurized by the high-pressure pump 63, may cause malfunction in the seal oil cooler 54.

[0224] In contrast, as illustrated in Figure 4, by arranging the seal oil cooler 54 between the low-pressure pump 53 and the high-pressure pump 63, it is possible to achieve both the viscosity of the seal oil and the suppression of abnormalities in the seal oil cooler 54.

[0225] Furthermore, as mentioned above, fuel oil does not produce residue even at high temperatures. Therefore, by using fuel oil as the hydraulic fluid to operate the fuel injection valve 3, as in the embodiment described above, even if the hydraulic fluid were to mix with the ammonia fuel, various problems caused by residue would not occur. This makes it possible to suppress the effects of hydraulic fluid mixing with ammonia fuel.

[0226] (7) Other embodiments In the above embodiment, fuel oil was used for both the sealing oil and the hydraulic fluid, but this disclosure is not limited to such a configuration. At least one of the sealing oil and the hydraulic fluid may be a lubricating oil for oil seals. If a lubricating oil is used for the sealing oil, one of the low-pressure pump 53 and the high-pressure pump 63 may be omitted accordingly. [Explanation of Symbols]

[0227] 1. Engine (marine engine) 10 Engine body 11 base plate 12 Frame 16 cylinders 3. Fuel Injector 31. Cylindrical body 32 Valve stem 33 Seal Chamber 36 Piston shaft 4. Seal oil supply system 5 cabinets 51 Seal oil tank 52 Oil Filter 53 Low-pressure pump (Pump No. 1) 54 Seal oil cooler 57 Oil pan 58 Ventilation mechanism 58a Ventilation fan 91 Support member 6. Seal oil circulation system 61. Seal oil supply pipe (seal oil piping) 62. Seal oil return pipe (seal oil piping) 63. High-pressure pump (Pump No. 2) 7. Seal oil replenishment system 71 Seal oil replenishment tube 72. Seal oil supply source (storage tank) 9 Alternative Fuel Exhaust System 96 Ventilation passage 97 Introduction passage 98 Flow rate adjustment means 8. Seal oil discharge system 82. Second discharge pipe (seal oil discharge pipe) SW3 No. 1 Leak Sensor Cf center axis F Ship floor

Claims

1. A marine engine that burns a volatile alternative fuel in a cylinder, A fuel injector comprising a cylindrical body extending along a predetermined central axis, and a valve stem inserted into the cylindrical body and reciprocating along the central axis, wherein the fuel injector injects the alternative fuel into the cylinder, The system comprises a housing through which sealing oil, which seals the gap between the cylindrical body and the valve stem, is circulated between the fuel injection valve and the housing, Marine engine.

2. In the marine engine described in claim 1, An engine body having the aforementioned cylinder and moving a piston back and forth within the cylinder, The engine body is equipped with a support member that is fixed to the engine body, The support members are arranged at intervals relative to the ship's floor, The housing is supported by the engine body via the support member. Marine engine.

3. In the marine engine described in claim 2, The aforementioned engine body is The base plate that constitutes the crankcase of the aforementioned marine engine, The structure comprises a frame positioned above the base plate, The housing is positioned to the side of the frame via the support member, Marine engine.

4. In the marine engine described in claim 1, The facility includes a seal oil tank for storing the aforementioned seal oil, The housing houses the seal oil tank, Marine engine.

5. In the marine engine described in claim 4, A sealing oil piping for circulating the sealing oil between the sealing oil tank and the fuel injection valve, An oil filter is placed on the seal oil piping and filters the seal oil flowing through the seal oil piping toward the fuel injector, A first pump is positioned on the seal oil piping and pressurizes the seal oil flowing through the seal oil piping toward the fuel injector, The system includes a seal oil cooler positioned on the seal oil piping and cooling the seal oil flowing through the seal oil piping, The housing contains one or more of the following: the seal oil tank, the oil filter, the seal oil cooler, and the first pump, including the seal oil tank. Marine engine.

6. In the marine engine described in claim 5, The seal oil piping includes a second pump located downstream of the first pump, which further increases the pressure of the seal oil that has been pressurized by the first pump, The seal oil cooler is positioned downstream of the first pump and upstream of the second pump on the seal oil piping. Marine engine.

7. In the marine engine described in claim 4, The housing is connected to the seal oil tank and includes a seal oil replenishment system for replenishing the seal oil in the seal oil tank. Marine engine.

8. In the marine engine described in claim 7, The aforementioned seal oil replenishment system is A storage tank for storing the aforementioned sealing oil, The system includes a seal oil replenishment pipe for circulating the seal oil from the storage tank to the seal oil tank, At least one of the seal oil replenishment system and the seal oil tank is configured to restrict the backflow of the seal oil from the seal oil tank to the seal oil replenishment pipe. Marine engine.

9. In the marine engine described in claim 4, A sealing oil piping for circulating the sealing oil between the sealing oil tank and the fuel injection valve, A ventilation mechanism for ventilating the inside of the enclosure, A ventilation passage connected to at least one of the seal oil tank and the seal oil piping, for discharging the alternative fuel that has evaporated from at least one of the seal oil tank and the seal oil piping, Marine engine.

10. In the marine engine described in claim 9, A connection is made to at least one of the seal oil tank and the seal oil piping, and includes an introduction passage for introducing compressed air or scavenging gas into at least one of the seal oil tank and the seal oil piping. Marine engine.

11. In the marine engine described in claim 10, The introduction passage is provided with a flow rate adjustment means for adjusting the flow rate of the compressed air or the scavenging gas in the introduction passage, Marine engine.

12. In the marine engine described in claim 4, An oil pan housed in the aforementioned housing, which receives the sealing oil leaking from the contents of the housing, A seal oil discharge pipe connected to the oil pan and for circulating the seal oil received in the oil pan, The system includes a leak sensor that detects oil in at least one of the oil pan and the seal oil discharge pipe. Marine engine.

13. In a marine engine according to any one of claims 1 to 12, The aforementioned alternative fuel is ammonia fuel. Marine engine.

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