Engine System

Abstract

To provide a compact inert gas supply system in an engine system equipped with a double pipe through which hydrogen gas and inert gas flow. [Solution] The engine system S comprises a hydrogen engine 1 mounted on a ship 1000, a hydrogen flow passage 41 through which hydrogen gas supplied to the hydrogen engine 1 circulates, a generator 51 mounted on the ship 1000 and generating an inert gas, a nitrogen flow passage 72 including outer pipes 72c, 72d surrounding the inner pipes 41a, 41b so as to form a double pipe 8 with at least a portion of the hydrogen flow passage 41 as the inner pipes 41a, 41b, and discharging nitrogen gas supplied from the generator 51 overboard via the outer pipes 72c, 72d, and a flow rate adjustment unit 73 positioned closer to the hydrogen engine 1 than the generator 51 on the flow path formed by the nitrogen flow passage 72 and adjusting the flow rate of nitrogen gas in the nitrogen flow passage 72.

Description

[Technical Field]

[0001] The present disclosure relates to an engine system including a hydrogen engine. [Background technology]

[0002] Patent Document 1 discloses a gas supply system for a gas engine or dual-fuel engine that can be installed on a ship. The gas supply system includes a double-walled gas line extending from a gas control station to the engine cylinder. The double-walled gas line has an inner pipe through which gaseous fuel flows and an outer pipe that at least partially surrounds the inner pipe and through which inert gas flows.

[0003] According to the patent document 1, the outer pipe at least partially surrounds the inner pipe and is able to evacuate potential gas leaks with the aid of an inert gas.

[0004] Patent Document 2 also discloses a hydrogen leak monitoring system equipped with a double pipe as another example of the double-walled gas line. This double pipe has an inner pipe through which a mixed gas of hydrogen and nitrogen flows from a hydrogen production plant to a hydrogen station, and an outer pipe in the space between the inner pipes through which nitrogen flows from the hydrogen station to the hydrogen production plant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-1762 [Patent Document 2] Patent No. 6265166 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the double pipes as disclosed in Patent Documents 1 and 2 require an inert gas supply source such as a nitrogen tank. However, in the case of hydrogen engines for ships, the space on board or inside the ship is limited, so it is necessary to devise a way to make the inert gas supply system more compact.

[0007] The present disclosure has been made in consideration of these points, and its purpose is to construct a compact inert gas supply system in an engine system equipped with a double pipe through which hydrogen gas and an inert gas flow. [Means for solving the problem]

[0008] A first aspect of the present disclosure relates to an engine system including: a hydrogen engine mounted on a ship that burns hydrogen gas in a combustion chamber; a first flow passage connected to the hydrogen engine and through which the hydrogen gas supplied to the hydrogen engine flows; a generator mounted on the ship that generates inert gas; a second flow passage including an outer pipe surrounding the inner pipe to form a double pipe with at least a portion of the first flow passage as the inner pipe, through which the inert gas supplied from the generator is discharged overboard via the hydrogen engine; and a flow rate regulator that regulates the flow rate of the inert gas in the second flow passage.

[0009] Generally, tanks for storing inert gases such as nitrogen are inconvenient to install on ships, considering the space available on or inside the ship.

[0010] In contrast, according to the first aspect, an inert gas generator is installed on the ship instead of a tank storing the inert gas. The configuration for generating the inert gas as needed contributes to making the inert gas supply system more compact.

[0011] Furthermore, even if a generator such as that of the first embodiment is used, depending on the amount of inert gas generated, the generator itself may become large. In order to realize a compact inert gas system, it is desirable to be able to set the flow rate of the inert gas to a desired value without increasing the size of the generator.

[0012] In contrast, according to the first aspect, by using the flow rate adjustment unit, it is possible to appropriately set the flow rate of the inert gas so as to achieve smooth discharge of leaked hydrogen gas and reliable containment of leaked hydrogen gas without changing the dimensions of the generator itself.

[0013] According to the second aspect of the present disclosure, the flow rate adjusting unit may adjust the flow rate of the inert gas so that the flow rate is equal to or greater than a predetermined value.

[0014] According to the second aspect, it is possible to maintain the flow rate of the inert gas near the hydrogen engine at a predetermined level or higher while suppressing the amount of inert gas supplied from the generator to the second flow passage, which contributes to both a compact inert gas supply system and measures against hydrogen gas leakage.

[0015] Furthermore, according to a third aspect of the present disclosure, the flow rate adjusting unit may be arranged in a midway portion of the second flow passage and may have a pressure adjusting unit that generates a pressure difference in the inert gas between the primary side and the secondary side of the midway portion.

[0016] According to the third aspect, the use of a pressure adjusting unit such as a pressure reducing valve is advantageous in ensuring the flow rate of the inert gas near the hydrogen engine.

[0017] According to a fourth aspect of the present disclosure, the flow rate adjuster may be disposed on a flow path formed by the second flow passage, closer to the hydrogen engine than the generator.

[0018] According to the fourth aspect, the flow rate regulator is disposed in the second flow passage closer to the hydrogen engine than the generator. This configuration can more reliably regulate the flow rate of the inert gas near the hydrogen engine to a desired value than, for example, a configuration in which the flow rate regulator is disposed near the generator. This makes it possible to more appropriately respond to hydrogen gas leaks.

[0019] According to a fifth aspect of the present disclosure, the flow rate adjusting unit may be arranged at least one of an inlet portion of the second flow passage leading into the hydrogen engine and an outlet portion of the second flow passage leading from the hydrogen engine.

[0020] According to the fifth aspect, arranging the flow rate adjustment unit as in this aspect is advantageous in ensuring the flow rate of the inert gas near the hydrogen engine compared to a configuration in which, for example, the pressure adjustment unit is arranged near the generator.

[0021] According to a sixth aspect of the present disclosure, the flow rate adjusting section may be arranged at a downstream end of the second flow passage and may have a restricting section that restricts a cross-sectional area of ​​the flow passage at the downstream end.

[0022] According to the sixth aspect, the throttle portion can be used to increase the flow rate of the inert gas discharged from the second flow passage, which is advantageous for adjusting the flow rate of the inert gas and makes it possible to more appropriately deal with hydrogen gas leakage.

[0023] According to a seventh aspect of the present disclosure, the flow rate adjusting section may be arranged at an outlet located at a downstream end of the second flow passage, and may have a blocking section that blocks the outlet.

[0024] According to the seventh aspect, instead of maintaining the flow rate of the inert gas at a predetermined level or higher, the flow rate is set to zero, which makes it possible to confine hydrogen gas leaking from the first flow passage serving as the inner pipe, thereby making it possible to more appropriately deal with hydrogen gas leakage.

[0025] For example, if the generator malfunctions, the outlet is blocked by a blocking section to prevent the inert gas and hydrogen gas leaked into the inert gas from being discharged. This makes it possible to both deal with the leakage of hydrogen gas and continue operation of the hydrogen engine using hydrogen gas, even if the supply of inert gas from the generator is cut off.

[0026] According to an eighth aspect of the present disclosure, the inert gas is nitrogen gas, and the engine system further comprises a gas property sensor disposed at a downstream end of the second flow passage and configured to detect at least one of an oxygen concentration and a nitrogen concentration at the downstream end, and a controller configured to determine whether or not the hydrogen engine can be operated using the hydrogen gas based on a detection signal from the gas property sensor, wherein the limit oxygen concentration is a lower limit of the oxygen concentration that is predetermined in a hydrogen-oxygen-nitrogen ternary system and at which the hydrogen gas is explosive, and the limit nitrogen concentration is an upper limit of the nitrogen concentration that is predetermined in the hydrogen-oxygen-nitrogen ternary system and at which the hydrogen gas is explosive, and the controller allows the hydrogen engine to be operated using the hydrogen gas when a first condition is met when the detected value of the oxygen concentration is equal to or less than the limit oxygen concentration, or a second condition is met when the detected value of the nitrogen concentration is equal to or greater than the limit nitrogen concentration, and the controller determines whether or not at least one of the first and second conditions is met while adjusting the flow rate of the nitrogen gas using the flow rate adjuster so as to increase the flow velocity of the nitrogen gas.

[0027] According to the eighth aspect, the controller determines whether operation of the hydrogen engine is permitted based on a limit oxygen concentration or a limit nitrogen concentration defined based on the explosiveness of a three-component hydrogen-oxygen-nitrogen system. This determination is made by referring to the oxygen concentration or the nitrogen concentration, and does not require detection of the hydrogen concentration.

[0028] In this way, by using the limit oxygen concentration or limit nitrogen concentration, it is possible to determine that an explosion due to leaked hydrogen gas will not occur even if the nitrogen concentration in the second flow passage does not reach 100% and a small amount of oxygen is contained therein. The amount of nitrogen gas generated in the generator can be set just right, making it possible to compact the generator and, ultimately, the nitrogen gas supply system.

[0029] Furthermore, according to the eighth aspect, by increasing the flow rate of the nitrogen gas using the flow rate adjuster, it is possible to perform a determination based on the limit oxygen concentration or limit nitrogen concentration while suppressing the amount of nitrogen gas supplied from the generator to the second flow passage, thereby reducing the amount (pressure) of nitrogen gas supplied to the second flow passage and reducing nitrogen gas leakage in the event of damage to the outer tube.

[0030] In particular, by providing a flow rate adjusting section such as the throttle section, the flow rate of nitrogen gas can be increased when the gas is discharged overboard. This increases the diffusibility around the overboard discharge port even in the event of a hydrogen gas leak. The increased diffusibility provided by the flow rate adjusting section reduces the nitrogen flow rate.

[0031] In addition, the hydrogen concentration is more likely to be diluted after it is released overboard, which reduces the risk of hydrogen ignition and combustion even if the leaked hydrogen mixes with the atmosphere or air (oxygen concentration: 21%).

[0032] According to a ninth aspect of the present disclosure, the engine system may further include a booster that stores the nitrogen gas at a pressurized state higher than that of the generator, and a leakage sensor that detects gas leakage from the first flow passage, and the controller may supply the nitrogen gas into the first flow passage via the booster before starting operation of the hydrogen engine using the hydrogen gas, and determine whether a third condition indicating that gas leakage from the first flow passage does not occur is met based on a detection signal from the leakage sensor, and if the third condition is met, supply the nitrogen gas into the second flow passage via the generator instead of the booster, and after the supply of the nitrogen gas via the generator has started, adjust the flow rate of the nitrogen gas via the flow rate adjuster and determine whether the first condition or the second condition is met, and start operation of the hydrogen engine if the first condition or the second condition is met.

[0033] According to the ninth aspect, before starting operation by burning hydrogen gas, the controller supplies relatively high-pressure nitrogen gas into the first flow passage, determines whether or not there is a hydrogen gas leak based on the leak sensor, and then supplies relatively low-pressure nitrogen gas into the second flow passage, and determines whether or not the hydrogen engine can be operated based on the limit oxygen concentration or limit nitrogen concentration.

[0034] Furthermore, by configuring as in the ninth aspect, the nitrogen concentration in the first flow passage can be increased quickly by using relatively high-pressure nitrogen gas. Rapidly increasing the nitrogen concentration in the first flow passage allows for a rapid determination based on the leak sensor. Rapid determination based on the leak sensor allows for a rapid start of subsequent processing. This allows for a rapid transition from supplying nitrogen gas to the first flow passage using the booster to supplying nitrogen gas to the second flow passage using the generator. This is advantageous for quickly starting a determination as to whether or not the hydrogen engine can be operated based on the first or second condition. Using the booster and the generator separately for different purposes is advantageous for quickly determining whether or not the hydrogen engine can be operated using hydrogen gas.

[0035] According to a tenth aspect of the present disclosure, the engine system may further include a leakage sensor that detects gas leakage from the first flow passage, and the controller, during operation of the hydrogen engine using the hydrogen gas, may continuously adjust the flow rate of the nitrogen gas via the flow rate regulator, determine whether the first condition or the second condition is met, and determine whether a third condition indicating that there is no gas leakage from the first flow passage is met based on a detection signal from the leakage sensor, and may reduce the amount of hydrogen gas supplied to the combustion chamber if any of the first condition, the second condition, or the third condition is not met.

[0036] According to the tenth aspect, while the hydrogen engine is operating using hydrogen gas, the controller continuously determines the explosiveness of the hydrogen gas based on the limiting oxygen concentration or limiting nitrogen concentration (determination to confirm that sufficient nitrogen gas is being supplied into the second flow passage) and monitors for hydrogen gas leaks.

[0037] The configuration of the tenth aspect reduces the amount of nitrogen gas supplied to the second flow passage, as described above, making it possible to achieve both a compact nitrogen gas supply system and high accuracy in detecting the oxygen concentration or hydrogen concentration contained in the second flow passage, and therefore high accuracy in determining whether the hydrogen engine is operable.

[0038] According to an eleventh aspect of the present disclosure, the hydrogen engine may be configured to combust a different fuel than the hydrogen gas together with the hydrogen gas in the combustion chamber, and the controller may increase the ratio of the heat generation amount of the different fuel to the heat generation amount of the hydrogen gas in the combustion chamber when any one of the first condition, the second condition, and the third condition is not satisfied.

[0039] According to the eleventh aspect, even if any one of the first condition, the second condition, and the third condition is not satisfied, the operation of the hydrogen engine can be continued using the different fuel.

[0040] It has been known that when hydrogen gas leaks, the supply of hydrogen gas to the hydrogen engine is cut off, causing the hydrogen engine to stop operating.

[0041] In practice, when a hydrogen engine for a vehicle is shut down, it is sufficient to park it on the side of the road or elsewhere. However, if a hydrogen engine for a ship stops completely, it may enter a so-called "dead ship" state. This is inconvenient because it can lead to various problems, such as the ship drifting.

[0042] In contrast, by continuing to operate the hydrogen engine using a different fuel as in the eleventh aspect, it is possible to respond appropriately to a hydrogen gas leak and prevent the ship from becoming a dead ship even if a hydrogen gas leak does occur. [Effects of the Invention]

[0043] As described above, according to the present disclosure, in an engine system equipped with a double pipe through which hydrogen gas and an inert gas flow, it is possible to configure a compact inert gas supply system. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 is a diagram illustrating a ship equipped with an engine system. [Figure 2] FIG. 2 is a side view illustrating a partial configuration of a hydrogen engine. [Figure 3] FIG. 3 is a cross-sectional view that schematically illustrates an example of the upper structure of a hydrogen engine. [Figure 4] FIG. 4 is a diagram illustrating a flow path structure of the engine system. [Figure 5] 5A and 5B are cross-sectional views taken along the lines AA and BB in FIG. [Figure 6] FIG. 6 is a block diagram illustrating the configuration of the controller. [Figure 7]FIG. 7 is a flowchart illustrating a process that is performed before the engine using hydrogen gas starts to operate. [Figure 8] FIG. 8 is a flowchart illustrating a process performed during operation of an engine using hydrogen gas. [Figure 9] FIG. 9 is a diagram for explaining whether the first condition and the second condition are met. DETAILED DESCRIPTION OF THE INVENTION

[0045] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is for illustrative purposes only.

[0046] <Overall structure> FIG. 1 is a diagram illustrating a ship 1000 equipped with an engine system S. FIG. 2 is a side view illustrating a partial configuration of a hydrogen engine (hereinafter referred to as "engine") 1. FIG. 3 is a cross-sectional view illustrating a schematic example of the upper structure of the engine 1. FIG. 4 is a diagram illustrating the flow path structure of the engine system S. In FIG. 4, arrows shown with solid lines indicate the flow of hydrogen gas. In the same figure, arrows shown with dashed lines indicate the flow of nitrogen gas as an inert gas. The terms "upstream" and "downstream" below are defined based on the flow direction of the corresponding gas.

[0047] As shown in Figure 1, the engine system S includes a marine engine 1, a hydrogen tank 2, a GVT (Gas Valve Train) 3 interposed between the hydrogen tank 2 and the engine 1, a hydrogen gas system 4 connecting the GVT 3 to the engine 1, an inert gas source 5, an outlet 6 that opens outside the engine room 1003 and outside the ship and discharges inert gas, an inert gas system 7 that connects the inert gas source 5 and the outlet 6 to the engine 1, and a controller 100 that controls the engine system S.

[0048] A hydrogen gas supply system is configured by the hydrogen tank 2, the GVT 3, and the hydrogen gas system 4. An inert gas supply system is configured by the inert gas source 5 and the inert gas system .

[0049] The engine 1, hydrogen tank 2, GVT 3, hydrogen gas system 4, inert gas source 5, inert gas system 7, and controller 100 are all mounted on the same ship 1000. The ship 1000 is a large ship such as a tanker, a container ship, or a car carrier.

[0050] Note that regarding the engine 1 and the controller 100 as separate elements is merely a classification for convenience. The controller 100 may be considered as one element of the engine 1. The same applies to other elements such as the hydrogen tank 2, GVT 3, hydrogen gas system 4, inert gas source 5, and inert gas system 7. Furthermore, some of the elements may be considered as one element of the engine 1.

[0051] The engine 1 includes a plurality of cylinders 11 connected via a common output shaft (crankshaft 10c). As shown in Fig. 3, each cylinder 11 defines a combustion chamber 12 for burning hydrogen gas. A propeller shaft 1001 and a propeller 1002 for propelling the vessel 1000 are connected to the crankshaft 10c.

[0052] The engine 1 is a hydrogen engine that burns hydrogen gas in the combustion chamber 12 of each cylinder 11. In other words, the engine 1 is a gas engine that uses hydrogen gas as gas fuel. Note that it is not essential that there be multiple cylinders 11.

[0053] The engine 1 may be one that burns hydrogen gas alone, or one that burns (mixes) a different fuel other than hydrogen gas together with hydrogen gas in the combustion chamber 12. The different fuel may be, in particular, an oil fuel, or, more particularly, heavy oil. In this embodiment, heavy oil is used as the different fuel.

[0054] As an example, the engine 1 according to this embodiment is an engine that can be switched between a first mode in which hydrogen gas is burned alone, a second mode in which hydrogen gas and a different fuel are burned together (for example, a mode in which hydrogen gas and heavy oil are mixed and burned), and a third mode in which a different fuel is burned alone. The engine 1 according to this embodiment is configured to execute processing to set the engine to any of the first mode, second mode, and third mode based on a control signal from the controller 100.

[0055] Specifically, the engine 1 according to this embodiment is configured as a uniflow scavenging two-stroke one-cycle engine, and is used as a main engine for propelling the ship 1000 by receiving and controlling a control signal from the controller 100. The engine 1 is disposed in an engine room 1003 partitioned inside the ship 1000.

[0056] The hydrogen tank 2 stores hydrogen gas. The hydrogen tank 2 is located outside the engine room 1003, for example, on the ship 1000, for example, on an open deck. The hydrogen tank 2 stores liquefied hydrogen replenished from outside the ship when the ship calls at a port, etc., in a liquefied state under low pressure. In other words, the hydrogen tank 2 is configured to store liquefied hydrogen (LH2).

[0057] The GVT 3 connects the hydrogen tank 2 to the engine 1 via a hydrogen gas system 4. The GVT 3 is located inside or outside the engine room 1003. As shown in FIG. 1 , the GVT 3 according to this embodiment is located in a room of the ship 1000 formed outside the engine room 1003. The GVT 3 is composed of pipes for circulating hydrogen gas and a plurality of control valves for opening and closing the pipes. The GVT 3 is electrically connected to the controller 100. The GVT 3 opens and closes each control valve based on a control signal received from the controller 100.

[0058] The hydrogen gas system 4 is connected to the engine 1. The hydrogen gas system 4 distributes hydrogen gas to be supplied to the engine 1. The hydrogen gas system 4 has a first hydrogen gas system 4A connecting the hydrogen tank 2 and the GVT 3, a second hydrogen gas system 4B connecting the GVT 3 to each cylinder 11 of the engine 1, and a hydrogen pump 42 shown in FIGS. 4 and 6.

[0059] As will be described later, the hydrogen gas system 4 has pipes for circulating hydrogen gas, such as a hydrogen flow passage 41 serving as a "first flow passage." As shown in FIG. 4 , the pipes constituting the hydrogen gas system 4 include pipes that pass through the engine 1, such as pipes connecting the cylinders 11. The hydrogen gas system 4 is arranged both inside and outside the engine compartment 1003.

[0060] The inert gas source 5 has a generator 51 that generates an inert gas. In this embodiment, the inert gas includes a gas that does not contain oxygen, and more specifically, includes nitrogen gas. In this embodiment, nitrogen gas is used as the inert gas. The inert gas source 5 is disposed inside the vessel 1000, for example, in the engine room 1003.

[0061] The exhaust port 6 exhausts the inert gas. The exhaust port 6 exhausts the inert gas (hereinafter referred to as "nitrogen gas" or "nitrogen") supplied from the inert gas source 5 overboard. As described above, the exhaust port 6 is arranged outside the engine room 1003, and connects the space outside the engine room 1003 to the space outside the ship. The exhaust port 6 according to this embodiment opens from the outside of the engine room 1003 toward the outside of the ship, as illustrated in FIG. 1, for example.

[0062] The inert gas system 7 is connected to both the inert gas source 5 and the exhaust port 6. The inert gas system 7 has a first nitrogen gas system 7A that connects the inert gas source 5 and the engine 1, and a second nitrogen gas system 7B that connects the engine 1 and the exhaust port 6.

[0063] As will be described later, the inert gas system 7 has pipes for circulating nitrogen gas, such as a nitrogen flow passage 72 serving as a "second flow passage." As shown in the first connecting pipe 72c in FIG. 4, each pipe constituting the inert gas system 7 includes a pipe that passes through the engine 1, such as a pipe connecting between the cylinders 11. The inert gas system 7 is arranged inside and outside the engine compartment 1003.

[0064] <Engine 1> As described above, the engine 1 according to this embodiment has a plurality of (six in this embodiment) cylinders 11. The plurality of cylinders 11 are aligned in the propulsion direction of the boat 1000.

[0065] Hereinafter, the direction in which the cylinders 11 are arranged will be referred to as the front-rear direction, and the direction perpendicular to both the front-rear direction and the central axis Op (the central axis of the piston 13 inserted in each cylinder 11) illustrated in FIG. 3 will be referred to as the left-right direction.

[0066] The terms "forward" and "rear" used here correspond to the forward and rearward directions of the boat 1000, respectively. The fore-and-aft direction can be rephrased as "first direction." The left-right direction can be rephrased as "second direction."

[0067] Hereinafter, the six cylinders 11 may be referred to and distinguished from one another as the "first cylinder 11A," "second cylinder 11B," "third cylinder 11C," "fourth cylinder 11D," "fifth cylinder 11E," and "sixth cylinder 11F," in order from the rear of Figure 2.

[0068] The engine 1 according to this embodiment is a two-stroke diesel engine. To achieve a long stroke, the engine 1 is configured as a so-called crosshead internal combustion engine.

[0069] Specifically, the engine 1 includes a cylinder liner 10a and a cylinder cover 10b. Each cylinder 11 is formed by the cylinder liner 10a and the cylinder cover 10b. The engine 1 also includes a piston 13 that is disposed in the cylinder 11 and reciprocates within the cylinder 11.

[0070] The cylinder liner 10a constitutes an inner cylinder that reciprocates the piston 13. The piston 13 is disposed inside the cylinder liner 10a. The cylinder liner 10a is supported by a cylinder jacket that houses a piston rod, crosshead, connecting rod, etc. that are connected to the piston 13.

[0071] The cylinder cover 10b is fixed to the upper end of the cylinder liner 10a. The cylinder cover 10b closes the upper end of the cylinder liner 10a, thereby serving as a lid for the cylinder 11.

[0072] As shown in Figure 3, the engine 1 is equipped with an exhaust valve 14. The exhaust valve 14 is supported by the cylinder cover 10b. The exhaust valve 14, together with the inner wall surface of the cylinder 11 and the top surface of the piston 13, defines a combustion chamber 12. The exhaust valve 14 opens and closes an exhaust port that leads from the inside of the combustion chamber 12 to the outside. The exhaust port discharges exhaust gases produced by combustion.

[0073] The engine 1 is equipped with one or more (one in the illustrated example) gas fuel injection valves 15. The one or more gas fuel injection valves 15 are valves for supplying hydrogen gas into the combustion chamber 12. The one or more gas fuel injection valves 15 operate in accordance with the hydraulic pressure of the hydraulic oil to inject hydrogen gas into the cylinder 11. The hydraulic pressure of the hydraulic oil is adjusted by opening and closing a solenoid valve. The opening and closing of the solenoid valve is controlled in accordance with a control signal from a controller 100 electrically connected to the solenoid valve.

[0074] In this embodiment, two gas fuel injection valves 15 are provided for each cylinder 11, and each is provided in a position facing the interior of the combustion chamber 12. Each gas fuel injection valve 15 injects hydrogen gas from an injection port located at its tip.

[0075] As shown in FIG. 3, the gas fuel injection valve 15 is connected to the hydrogen gas system 4, and hydrogen gas is supplied from the hydrogen gas system 4. In detail, as shown in FIG. 4, the second hydrogen gas system 4B branches into multiple hydrogen gas inlet channels 16 for each cylinder 11. The hydrogen gas system 4 supplies hydrogen gas to the gas fuel injection valve 15 of each cylinder 11 via these hydrogen gas inlet channels 16. The hydrogen gas inlet channel 16 is further branched into channels equal to the number of gas fuel injection valves 15 in each cylinder 11.

[0076] In the illustrated example, the hydrogen gas inlet passage 16 is configured inside the cylinder cover 10b, but such a configuration is not essential. The hydrogen gas inlet passage 16 may also be configured using piping separate from the cylinder liner 10a and the cylinder cover 10b.

[0077] The engine 1 also includes one or more oil fuel injection valves 19, as shown only in FIG. 6 described later. The oil fuel injection valve 19 is a valve for supplying heavy oil into the combustion chamber 12. The one or more oil fuel injection valves 19 inject heavy oil into the cylinder 11 by operating according to the hydraulic pressure of the hydraulic oil. More specifically, oil fuel is pressure-fed to each oil fuel injection valve 19 by operating a fuel pump for oil fuel using the hydraulic pressure of the hydraulic oil. The hydraulic pressure of the hydraulic oil is adjusted by controlling an electromagnetic valve connected to the fuel pump. The electromagnetic valve is controlled according to a control signal from a controller 100 electrically connected to the electromagnetic valve. Note that the oil fuel injection valve 19 is not essential.

[0078] The engine 1 includes a gas accumulator chamber 17 and a GGV (Gas Gate Valve: GGV) 18. The gas accumulator chamber 17 and the GGV 18 are disposed on the flow path formed by the hydrogen gas inlet channel 16.

[0079] Specifically, the gas accumulator chamber 17 and the GGV 18 are disposed midway along the hydrogen gas inlet passage 16. Even more specifically, the gas accumulator chamber 17 and the GGV 18 are disposed from the upstream side along the flow direction of the hydrogen gas in the order of the gas accumulator chamber 17 and the GGV 18. These elements are disposed for each cylinder 11, similar to the hydrogen gas inlet passage 16.

[0080] Specifically, the gas accumulator 17 is connected to the GVT 3 via the hydrogen gas system 4 and the hydrogen gas inlet passage 16. The gas accumulator 17 accumulates the hydrogen gas supplied to each gas fuel injection valve 15 under pressure.

[0081] In the illustrated example, the gas accumulator chamber 17 is formed inside the cylinder cover 10b, but such a configuration is not essential. The gas accumulator chamber 17 may be formed by a tank-like member separate from the cylinder liner 10a and the cylinder cover 10b.

[0082] The GGV 18 opens and closes in response to the hydraulic oil pressure, thereby interrupting the fluid connection between the gas accumulator chamber 17 and the gas fuel injection valve 15. For example, when the GGV 18 is fully closed, the supply of hydrogen gas to the gas fuel injection valve 15 is stopped. The hydraulic oil pressure is adjusted by opening and closing a solenoid valve. The opening and closing of the solenoid valve is controlled in accordance with a control signal from a controller 100 electrically connected to the solenoid valve.

[0083] In the illustrated example, the GGV 18 is inserted into the cylinder cover 10b, but this configuration is not essential. The GGV 18 may be formed by a member inserted into a separate member for the cylinder liner 10a and the cylinder cover 10b.

[0084] As shown in FIG. 3, each of the gas fuel injection valve 15 and the GGV 18 has a double seal structure with two seal rings.

[0085] The gas fuel injection valve 15 is sealed by a first seal ring 151 and a second seal ring 152 arranged in the axial direction of the gas fuel injection valve 15. The first and second seal rings 151, 152 seal between the outer peripheral surface of the gas fuel injection valve 15 and the inner peripheral surface of an insertion hole in the cylinder cover 10b, into which the gas fuel injection valve 15 is inserted.

[0086] The GGV 18 is sealed by a third seal ring 181 and a fourth seal ring 182 that are aligned in the axial direction of the GGV 18. The third and fourth seal rings 181, 182 seal between the outer peripheral surface of the GGV 18 and the inner peripheral surface of the insertion hole in the cylinder cover 10b into which the GGV 18 is inserted.

[0087] <Hydrogen gas system 4> The hydrogen gas system 4 will be described below mainly with reference to Figure 4. Note that Figure 4 corresponds to a diagram in which the third cylinder 11C, the fourth cylinder 11D, and the fifth cylinder 11E of the six cylinders 11 are omitted.

[0088] As described above, the hydrogen gas system 4 includes the first hydrogen gas system 4A, the vaporizer 42, the hydrogen pump 43, and the second hydrogen gas system 4B. The first hydrogen gas system 4A includes one or more flow paths. The one or more flow paths connect the hydrogen tank 2 and the GVT 3 and allow hydrogen gas to flow from the hydrogen tank 2 to the GVT 3.

[0089] The vaporizer 42 vaporizes the liquefied hydrogen stored in the hydrogen tank 2. The vaporizer 42 is disposed midway from the hydrogen tank 2 to the GVT 3 via the first hydrogen gas system 4A. The vaporizer 42 is, for example, a heat exchanger that exchanges heat between the heat medium supplied to the vaporizer 42 and the liquefied hydrogen. It is not essential that the vaporizer 42 be a heat exchanger. The vaporizer 42 may be, for example, an electric heater.

[0090] Hydrogen pump 43 increases the pressure of the vaporized liquefied hydrogen so that it reaches an injection pressure (for example, 15 to 30 MPa absolute pressure) for engine 1. Hydrogen pump 43 can also be called a booster pump. Hydrogen pump 43 as a booster pump is located midway from hydrogen tank 2 to vaporizer 42.

[0091] The hydrogen pump 43 has an actuator for changing its discharge flow rate. The actuator is, for example, a hydraulic motor that drives a piston that pushes out liquefied hydrogen. The controller 100 is electrically connected to a control valve (not shown in FIG. 6) for controlling the flow rate of hydraulic oil supplied to the hydraulic motor. The controller 100 operates the hydrogen pump 43 via the control valve and controls its discharge flow rate.

[0092] The second hydrogen gas system 4B includes a hydrogen flow passage 41 formed of one or more flow paths. The hydrogen flow passage 41 connects the GVT 3 and the engine 1 and is configured to allow the hydrogen gas supplied from the GVT to the engine 1 to flow therethrough. The hydrogen flow passage 41 is an example of the "first flow passage" in this embodiment.

[0093] Specifically, the hydrogen flow passage 41 according to this embodiment includes, in order from the upstream side in the direction of hydrogen gas flow, a first hydrogen flow pipe 41a and a second hydrogen flow pipe 41b. All or part of the hydrogen flow passage 41 may be flexible or rigid.

[0094] The first hydrogen flow pipe 41a is a tubular member that connects the GVT 3 to one of the multiple cylinders 11 that is closer to the GVT 3 than the other cylinders 11 in the direction of hydrogen gas flow. In Figure 4, the first hydrogen flow pipe 41a is connected to the sixth cylinder 11F. In other words, the cylinder 11 to which the first hydrogen flow pipe 41a is connected is the cylinder 11 that is farther from the outlet 6 than the other cylinders 11 when viewed along the hydrogen gas flow path.

[0095] The second hydrogen flow pipe 41b is a tubular member that connects two adjacent cylinders 11 in the direction of hydrogen gas flow among the multiple cylinders 11. In Fig. 4, two second hydrogen flow pipes are shown, in order from the upstream side in the direction of hydrogen gas flow: a second hydrogen flow pipe 41b that connects the third cylinder 11C and the second cylinder 11B, and a second hydrogen flow pipe 41b that connects the second cylinder 11B and the first cylinder 11A. Although omitted in Fig. 4, the third cylinder 11C is connected upstream of the second cylinder 11B in the direction of hydrogen gas flow, as shown in Fig. 2.

[0096] The third hydrogen flow pipe 41c is a tubular member connected to one of the plurality of cylinders 11 that is farther away from the GVT 3 than the other cylinders 11 in the flow direction of hydrogen gas.

[0097] In the illustrated example, hydrogen gas supplied from the hydrogen tank 2 via the GVT 3 reaches the sixth cylinder 11F via the first hydrogen flow pipe 41a. The hydrogen flow passage 41 branches inside or outside the sixth cylinder 11F.

[0098] One branched portion of the first hydrogen flow pipe 41a extends from the branched portion to the accumulator chamber 17 of the sixth cylinder 11F as the hydrogen gas inlet passage 16. The hydrogen gas that reaches the accumulator chamber 17 via the hydrogen gas inlet passage 16 is guided to the gas fuel injection valve 15 of the sixth cylinder 11F via the GGV 18, as described above.

[0099] The other branched portion of the first hydrogen flow pipe 41a extends from the branched portion as a second hydrogen flow pipe 41b, which connects the sixth cylinder 11F to the fifth cylinder 11E. Of the hydrogen gas supplied to the sixth cylinder 11F, the remaining gas, excluding the hydrogen gas that reaches the pressure accumulator chamber 17 of the sixth cylinder 11F, is guided to the fifth cylinder 11E via the second hydrogen flow pipe 41b.

[0100] In the illustrated example, the second hydrogen flow pipe 41b, which connects the third cylinder 11C and the second cylinder 11B and guides hydrogen gas from the third cylinder 11C to the second cylinder 11B, branches off inside or outside the second cylinder 11B, similar to the first hydrogen flow pipe 41a.

[0101] One branch of the second hydrogen flow pipe 41b extends from the branched portion as the hydrogen gas inlet passage 16, which reaches the pressure accumulator chamber 17 of the second cylinder 11B. The hydrogen gas that reaches the pressure accumulator chamber 17 via the hydrogen gas inlet passage 16 is guided to the gas fuel injection valve 15 of the second cylinder 11B via the GGV 18, as described above.

[0102] The other branched end of second hydrogen flow pipe 41b extends from the branched portion as third hydrogen flow pipe 41c, which is connected to the outside of engine 1. Of the hydrogen gas supplied to second cylinder 11B, the remaining gas, excluding the hydrogen gas that reaches accumulator chamber 17 of cylinder 11B, is guided to first cylinder 11A via second hydrogen flow pipe 41b, which connects second cylinder 11B and first cylinder 11A.

[0103] Therefore, the hydrogen gas supplied from GVT3 flows through each cylinder 11 in the following order from the front in the fore-and-aft direction: sixth cylinder 11F, fifth cylinder 11E, fourth cylinder 11D, third cylinder 11C, second cylinder 11B, and first cylinder 11A.

[0104] <Inert gas source 5> As shown in FIG. 4, the inert gas source 5 has, in addition to the generator 51 described above, a booster 52, a flow path control valve 53, and a second flow path control valve .

[0105] The generator 51 generates nitrogen gas and temporarily stores the generated nitrogen gas in a state in which it is pressurized to a predetermined first pressure. The first pressure is, for example, a positive pressure that exceeds atmospheric pressure. Specifically, the first pressure may be 0.05 MPa or more and 0.8 MPa or less, and more specifically, 0.05 MPa or more and 0.3 MPa or less. Note that the first pressure here is a gauge pressure measured with atmospheric pressure as a reference. Setting the first pressure within the latter range can suppress leakage of nitrogen gas into the engine compartment 1003 due to damage to the outer pipe and reduce the amount of nitrogen gas consumed.

[0106] The generator 51 is connected to a generator-side flow passage 71 of the inert gas system 7. As will be described later, the generator-side flow passage 71 is connected to the engine 1. The nitrogen gas generated by the generator 51 flows through the generator-side flow passage 71 and into the engine 1.

[0107] The booster 52 stores the nitrogen gas generated by the generator 51 at a pressure higher than that of the generator 51. The booster 52 supplies, for example, nitrogen gas pressurized to a predetermined second pressure. The second pressure is, for example, a positive pressure higher than the first pressure. The second pressure may be, in particular, 10 MPa or more and 50 MPa or less, and more particularly, 20 MPa or more and 40 MPa or less. The second pressure is a gauge pressure, like the first pressure.

[0108] The booster 52 is electrically connected to, for example, the controller 100 and operates upon receiving a control signal from the controller 100 .

[0109] The booster 52 is connected to the hydrogen flow passage 41, which serves as a first flow passage, via a nitrogen branch passage 74. A flow path control valve 53 is disposed midway along the nitrogen branch passage 74.

[0110] The flow path control valve 53 is electrically connected to, for example, the controller 100, and operates in response to a control signal from the controller 100. By opening and closing the flow path control valve 53, nitrogen gas can be supplied from the generator 51 to the hydrogen flow path 41.

[0111] The second flow path control valve 54 is electrically connected to, for example, the controller 100, and operates in response to a control signal from the controller 100. By opening and closing the second flow path control valve 54, nitrogen gas can be supplied from the generator 51 to the booster 52. The second flow path control valve 54 is, for example, a three-way valve.

[0112] <Inert gas system 7> Figure 5 is a cross-sectional view taken along line AA or BB in Figure 4. As described above, the inert gas system 7 has the first nitrogen gas system 7A and the second nitrogen gas system 7B. The first nitrogen gas system 7A has the generator-side flow passage 71 and the nitrogen branch passage 74 described above.

[0113] The second nitrogen gas system 7B has a nitrogen flow passage 72 and one or more flow rate adjusters 73. The nitrogen flow passage 72 is continuous with the generator-side flow passage 71 and is connected to the outlet 6.

[0114] In this embodiment, the nitrogen gas in each flow path is set to a positive pressure equal to or higher than atmospheric pressure, as described above. The nitrogen gas in each flow path may also be set to a negative pressure equal to or lower than atmospheric pressure. In this case, the engine system S is provided with an exhaust fan located near the exhaust port 6. In this case, the exhaust fan is activated by receiving a control signal from the controller 100, and operates to suck the nitrogen gas from the nitrogen flow passage 72 toward the exhaust port 6.

[0115] -Nitrogen flow passage 72- The nitrogen flow passage 72 passes the nitrogen gas supplied from the generator-side flow passage 71 through the engine 1 and then discharges it overboard. The nitrogen flow passage 72 is an example of a "second flow passage" in this embodiment. As will be described later, the nitrogen flow passage 72 as the second flow passage includes a first connecting pipe 72c and a second connecting pipe 72d that constitute the outer pipe of the double pipe 8.

[0116] The nitrogen flow passage 72 is configured to pass through components of the engine 1. More specifically, the nitrogen flow passage 72 is configured to pass through each cylinder 11 of the engine 1. More specifically, the nitrogen flow passage 72 according to this embodiment is configured to pass through each cylinder cover 10b of the engine 1.

[0117] In order to realize the above-described configuration, the nitrogen flow passage 72 is configured to include, in addition to the first connecting pipe 72c and the second connecting pipe 72d that constitute the outer pipe of the double pipe 8, a flow path that passes through the inside of the engine 1, such as the branch passage 72b described below.

[0118] As described above, the nitrogen flow passage 72 according to this embodiment is configured to include an outer pipe (e.g., the first connecting pipe 72c and the second connecting pipe 72d) that surrounds the inner pipe to form a double pipe 8, and a flow path (e.g., the branch path 72b) that passes through components of the engine 1, such as the cylinder cover 10b.

[0119] Specifically, the nitrogen flow passage 72 according to this embodiment includes a shared passage 72a shared among the plurality of cylinders 11, a plurality of branch passages 72b branching from the shared passage 72a and provided for each cylinder 11, a plurality of first connecting pipes 72c connecting the cylinders 11, and a second connecting pipe 72d connecting one cylinder 11 to the discharge port 6. The term "one cylinder 11" as used herein refers to the cylinder 11 that is located furthest downstream in the flow direction of nitrogen gas among the plurality of cylinders 11.

[0120] The shared passage 72a is configured by a pipe disposed outside the cylinder 11. The shared passage 72a has an upstream end connected to the generator 51 via the first nitrogen gas system 7A.

[0121] Each of the multiple branch paths 72b is configured by at least one of a pipe disposed outside the cylinder 11 and a flow path formed inside the cylinder 11. Each branch path 72b has an upstream end connected to the shared path 72a and a downstream end connected to the corresponding first connecting pipe 72c.

[0122] 3 and 4, each branch passage 72b extends to pass through or connect to at least one (both in this embodiment) of the gas fuel injector 15 and the GGV 18 of each cylinder 11. For example, the branch passage 72b in this embodiment is configured to pass through the gas fuel injector 15 of each cylinder 11 and to be connected to the GGV 18 of the same cylinder 11.

[0123] Each of the multiple first connecting pipes 72c includes a pipe that is arranged outside the cylinder 11, for example, in the internal space of the engine compartment 1003. Each of the first connecting pipes 72c includes a tubular member that connects two cylinders 11 that are adjacent in the flow direction of the nitrogen gas. Figure 4 shows an example of the first connecting pipe 72c that connects the first cylinder 11A and the second cylinder 11B.

[0124] Each first connecting pipe 72c has an upstream end connected to the branch passage 72b of the cylinder 11 located upstream in the flow direction of nitrogen gas, of the two cylinders 11 connected by the first connecting pipe 72c, and a downstream end connected to the branch passage 72b of the cylinder 11 located downstream in the flow direction of nitrogen gas.

[0125] In the illustrated example, the upstream end of the former is connected to the downstream end of the branch passage 72b of the first cylinder 11A, for example, and the downstream end of the latter is connected to the downstream end of the branch passage 72b of the second cylinder 11B, for example.

[0126] Furthermore, the second connecting pipe 72d is configured by a pipe arranged outside the cylinder 11, for example, in the internal space of the engine compartment 1003. The second connecting pipe 72d is a tubular member that connects the discharge port 6 to a cylinder 11 among the multiple cylinders 11 that is closer to the discharge port 6 than the other cylinders 11 in the flow direction of the nitrogen gas. In FIG. 4, the second connecting pipe 72d is connected to the sixth cylinder 11F. In other words, the cylinder 11 to which the second connecting pipe 72d is connected is a cylinder 11 that is farther away from the generator 51 than the other cylinders 11 when viewed along the flow path of the nitrogen gas.

[0127] As illustrated in the upper part of Figure 5, the first connecting pipe 72c included in the nitrogen flow passage 72 as the second flow passage forms a double pipe 8 together with the second hydrogen flow pipe 41b included in the hydrogen flow passage 41 as the first flow passage.

[0128] Similarly, as illustrated in the lower part of Figure 5, the second connecting pipe 72d included in the nitrogen flow passage 72 as the second flow passage forms a double pipe 8 together with the first hydrogen flow pipe 41a included in the hydrogen flow passage 41 as the first flow passage.

[0129] For example, in this embodiment, first connecting pipe 72c is configured as an outer pipe surrounding second hydrogen flow pipe 41b. Second hydrogen flow pipe 41b constitutes an inner pipe for first connecting pipe 72c. When second hydrogen flow pipe 41b is normal, hydrogen gas flows through flow path Sf1 formed inside second hydrogen flow pipe 41b, while nitrogen gas flows through flow path Sf2 formed between second hydrogen flow pipe 41b and first connecting pipe 72c.

[0130] On the other hand, if a problem such as damage occurs in the second hydrogen flow pipe 41b, the leaked gas (hydrogen gas) leaking from the second hydrogen flow pipe 41b will be pushed into the first connecting pipe 72c or sucked into the first connecting pipe 72c.

[0131] Similarly, the second connecting pipe 72d is configured as an outer pipe surrounding the first hydrogen flow pipe 41a. The first hydrogen flow pipe 41a constitutes an inner pipe for the second connecting pipe 72d. When the first hydrogen flow pipe 41a is normal, hydrogen gas flows through the flow path Sf1 formed inside the first hydrogen flow pipe 41a, while nitrogen gas flows through the flow path Sf2 formed between the first hydrogen flow pipe 41a and the second connecting pipe 72d.

[0132] On the other hand, if a problem such as breakage occurs in the first hydrogen flow pipe 41a, the leaked gas (hydrogen gas) leaking from the first hydrogen flow pipe 41a will be pushed into the second connecting pipe 72d or sucked into the second connecting pipe 72d.

[0133] -Flow rate adjustment section 73- The flow rate adjusting unit 73 is disposed in the nitrogen flow passage 72, which serves as a second flow passage, closer to the engine 1 than the generator 51. The flow rate adjusting unit 73 is configured to adjust the flow rate of nitrogen gas in the nitrogen flow passage 72. Here, "close" includes being relatively close on the flow path when viewed along the generator-side flow passage 71 and the nitrogen flow passage 72.

[0134] The flow rate adjusting unit 73 according to this embodiment is configured to adjust the flow rate of the nitrogen gas so that the flow rate is equal to or greater than a predetermined value. The flow rate may be adjusted by adjusting the pressure using a pressure reducing valve or the like, or by adjusting the flow rate using a throttle or the like.

[0135] For example, the flow rate adjustment unit 73 includes a pressure adjustment unit 731 disposed in the middle portion P1 of the nitrogen flow passage 72. The pressure adjustment unit 731 generates a pressure difference in the nitrogen gas between the primary side and the secondary side of the middle portion P1. This pressure difference promotes the flow of the nitrogen gas. Note that the term "primary side" here refers to the upstream side of the middle portion P1. Similarly, the term "secondary side" refers to the "downstream side" of the same middle portion P1.

[0136] 4, the midway portion P1 here may be set upstream of the branch point P2 between the shared path 72a and the branch path 72b in the nitrogen flow passage 72, and, as described above, at a position on the flow path that is relatively closer to the engine 1 than the generator 51. A position on the flow path that is relatively closer to the engine 1 than the generator 51 may be a position where the flow path length between the midway portion P1 and the engine 1 is shorter than the flow path length between the same midway portion P1 and the generator 51. The flow path length between the midway portion P1 and the engine 1 may be, for example, the flow path length between the midway portion P1 and the branch point P2, or may be the flow path length between the midway portion P1 and the first cylinder 11A that is located most upstream in the flow direction of the nitrogen gas.

[0137] A pressure reducing valve, for example, can be used as the pressure adjusting unit 731. In this case, it is more preferable to arrange the pressure adjusting unit 731 at an inlet portion of the nitrogen flow passage 72 into the engine 1 (a portion that can be considered as an inlet for nitrogen gas), like the midway portion P1. The midway portion P1 is an example of the "inlet portion" in this embodiment.

[0138] Including the case where a pressure reducing valve is used, the pressure adjusting unit 731 is electrically connected to the controller 100. The pressure adjusting unit 731 operates upon receiving an electrical signal from the controller 100, thereby adjusting the pressure of the nitrogen gas.

[0139] The use of a pressure reducing valve in the pressure adjusting unit 731 is particularly suitable when the nitrogen gas is to be put under positive pressure. Alternatively, the nitrogen gas may be put under negative pressure as described above. In this case, instead of using a pressure reducing valve in the pressure adjusting unit 731, a flow generator that operates to suck the nitrogen gas from the nitrogen flow passage 72 may be used in the pressure adjusting unit 731. It is more suitable to arrange the flow generator at the outlet of the nitrogen gas from the engine 1 (a location that can be considered as an outlet for the nitrogen gas), such as, for example, a location midway through the second connecting pipe 72d. Even in such an arrangement, the flow rate adjusting unit 73 is arranged closer to the engine 1 than the generator 51.

[0140] In this way, it is not essential to use a pressure reducing valve in pressure adjusting unit 731. It is also not essential to place pressure adjusting unit 731 at the inflow portion into engine 1. Furthermore, it is not essential to configure flow rate adjusting unit 73 solely by pressure adjusting unit 731.

[0141] 4, the flow rate adjusting unit 73 is arranged downstream of the engine 1 in the nitrogen flow passage 72 serving as the second flow passage, and further includes a throttle unit 732 that throttles the flow path cross-sectional area of ​​the nitrogen flow passage 72. By narrowing the flow path cross-sectional area with the throttle unit 73, it is possible to increase the flow rate of the nitrogen gas passing through the throttle unit 732. Note that the throttle unit 732 is not essential.

[0142] Specifically, the throttle portion 732 in the illustration is disposed in the second connecting pipe 72d located downstream of the engine 1. More specifically, the throttle portion 732 according to this embodiment is disposed at the downstream end of the nitrogen flow passage 72, i.e., near the connection portion between the second connecting pipe 72d and the exhaust port 6.

[0143] The flow rate of nitrogen gas adjusted by the flow rate adjuster 73 includes a state where the flow rate is zero. In other words, the flow rate adjuster 73 may be configured to confine leaking gas within the nitrogen flow passage 72 serving as the second flow passage by closing the outlet 6.

[0144] For example, as shown in Fig. 4, the flow rate adjustment unit 73 is disposed at the outlet 6 and further includes a blocking unit 733 that blocks the outlet 6. The blocking unit 733 is configured, for example, by a solenoid valve electrically connected to the controller 100. The blocking unit 733 closes the outlet 6 by operating in response to an electrical signal from the controller 100. Note that by using a movable throttle unit 732, the throttle unit 732 may also function as the blocking unit 733. Note that the blocking unit 733 is not essential.

[0145] In the illustrated example, nitrogen gas supplied from the inert gas source 5 flows into the engine 1 through a nitrogen flow passage 72. The flow rate of the nitrogen gas flowing into the engine 1 is maintained at a predetermined level or higher by a pressure adjustment unit 731 serving as a flow rate adjustment unit 73. The nitrogen gas that has flowed into the engine 1 flows from the shared passage 72a through a branch passage 72b into the cylinder 11.

[0146] The nitrogen gas that has flowed into the nitrogen flow passage 72 flows inside and outside the engine 1 according to the arrows shown by dashed lines in Fig. 4. Meanwhile, as described above, the gas fuel injection valve 15 and the GGV 18 each have a double seal structure with two seal rings.

[0147] In this case, even if the first seal ring 151, which is close to the combustion chamber 12, of the first and second seal rings 151, 152, is damaged, or even if the third seal ring 181, which is close to the gas accumulator chamber 17, of the third and fourth seal rings 181, 182, is damaged, the second or fourth seal ring 152, 182 can prevent hydrogen gas from leaking outside the engine 1.

[0148] However, since the first or third seal ring 151, 181 is damaged, a mechanism is required to discharge the hydrogen gas that has entered the gap between the gas fuel injection valve 15 or GGV 18 and the cylinder cover 10b as quickly as possible.

[0149] 3, the leaked gas flows into the branch path 72b. The leaked gas flows through the branch path 72b, the first connecting pipe 72c, and the second connecting pipe 72d in this order, and is discharged from the outlet 6.

[0150] Furthermore, in the hydrogen flow passage 41, leaked gas generated in the first and second hydrogen flow pipes 41a, 41b, which constitute the inner pipe of the double pipe 8, also flows through the first connecting pipe 72c and the second connecting pipe 72d, which serve as outer pipes, and is also discharged from the outlet 6.

[0151] <Controller 100> 6 is a block diagram illustrating the configuration of the controller 100. The controller 100 has a processor, a volatile memory, a non-volatile memory, and an input / output device. The controller 100 is connected to various sensors and a telegraph 101. In addition, as described above, the hydrogen pump 43, booster 52, flow path control valve 53, flow rate regulator 73, etc. are electrically connected to the controller 100.

[0152] The controller 100 is also connected to the gas fuel injection valve 15, the oil fuel injection valve 19, and the GGV 18 of each cylinder 11. Although only one gas fuel injection valve 15, one oil fuel injection valve 19, and one GGV 18 are shown in Fig. 6, in this embodiment, one or more gas fuel injection valves 15, one or more oil fuel injection valves 19, and one GGV 18 are provided for each cylinder 11.

[0153] The controller 100 generates a control signal based on signals input from sensors, for example, when the telegraph 101 is operated. The controller 100 inputs the generated control signals to a plurality of solenoid valves, and controls the GVT 3, the gas fuel injection valve 15, the GGV 18, etc. via the solenoid valves.

[0154] For example, the controller 100 is connected to the gas fuel injector 15 via a first injection control valve 153. The first injection control valve 153 is an electromagnetic valve that controls the supply of hydraulic oil to the gas fuel injector 15.

[0155] The controller 100 is also connected to the oil fuel injection valve 19 via a second injection control valve 193. The second injection control valve 193 is an electromagnetic valve that controls the supply of hydraulic oil to the oil fuel injection valve 19.

[0156] The controller 100 is also connected to the GGV 18 via a gate control valve 183. The gate control valve 183 is an electromagnetic valve that controls the supply of hydraulic oil to the GGV 18.

[0157] For example, the controller 100 controls the GVT 3 and opens the GGV 18, so that hydrogen gas is supplied from the GVT 3 to each gas fuel injector 15. This supply can be controlled individually for each cylinder 11.

[0158] Then, the controller 100 opens the gas fuel injection valves 15, whereby hydrogen gas is injected into the combustion chamber 12 from the injection port of each gas fuel injection valve 15. This injection can also be controlled individually for each cylinder 11.

[0159] In this way, the controller 100 can inject hydrogen gas into each cylinder 11, thereby burning the hydrogen gas in the corresponding combustion chamber 12. The engine 1 is operated by burning the hydrogen gas in the combustion chamber 12. The controller 100 can control the amount of hydrogen supplied to the combustion chamber 12 via the GVT 3 and the GGV 18.

[0160] The sensors connected to the controller 100 also include a gas property sensor 91. The gas property sensor 91 is disposed at the downstream end of the nitrogen flow passage 72, which serves as the second flow passage, and detects at least one of the oxygen concentration and the nitrogen concentration at the downstream end. For example, the gas property sensor 91 according to this embodiment is disposed downstream of the throttle section 732.

[0161] The gas property sensor 91 according to this embodiment is configured with both an oxygen concentration sensor that detects the oxygen concentration at the downstream end of the nitrogen flow passage 72, and a nitrogen concentration sensor that detects the nitrogen concentration at the downstream end of the nitrogen flow passage 72. The gas property sensor 91 may be configured with only an oxygen concentration sensor or only a nitrogen concentration sensor.

[0162] The sensors connected to the controller 100 include a leakage sensor 92. The leakage sensor 92 detects gas leakage from the hydrogen flow passage 41, which serves as the first flow passage. The leakage sensor 92 is disposed, for example, in the nitrogen flow passage 72, and detects at least one of the hydrogen concentration, oxygen concentration, nitrogen concentration, and internal pipe pressure at the downstream end thereof.

[0163] The controller 100 according to this embodiment is configured to determine whether or not the engine 1 can be operated using hydrogen gas, based on the detection signal of the gas property sensor 91.

[0164] As is well known, in a hydrogen-oxygen-nitrogen ternary system, there exists a lower limit for the oxygen gas concentration (oxygen concentration) at which hydrogen gas remains explosive, and an upper limit for the nitrogen gas concentration (nitrogen concentration) at which hydrogen gas remains explosive. Hereinafter, the former lower limit will be referred to as the limit oxygen concentration, and the latter upper limit will be referred to as the limit nitrogen concentration.

[0165] The controller 100 according to this embodiment allows the engine 1 to operate using hydrogen gas when a first condition is met, which is met when the detected value of the oxygen concentration is equal to or lower than the limit oxygen concentration, or a second condition is met, which is met when the detected value of the nitrogen concentration is equal to or higher than the limit nitrogen concentration. It is sufficient to detect the oxygen concentration or the nitrogen concentration without detecting the hydrogen concentration.

[0166] Specific values ​​of the limit oxygen concentration and limit nitrogen concentration are predetermined for the aforementioned hydrogen-oxygen-nitrogen ternary system, as exemplified in literature such as "On the Physical Properties and Safe Handling of Hydrogen" by Atsushi Shigemori, Cryogenic Engineering, Vol. 55, No. 1, 2020. The controller 100 stores the predetermined values ​​in advance. The controller 100 is configured to read out the stored predetermined values ​​when determining whether the first or second condition is satisfied.

[0167] Specifically, as shown in the above document and in Figure 9, an explosion range R1, which represents the gas composition within which hydrogen gas can explode, has been defined by those skilled in the art. Generally, if the gas composition falls within the explosion range R1, hydrogen gas can explode with oxygen gas as the supporting gas. As shown in Figure 9, a first composition Pa, which represents the composition of general air, is positioned outside the explosion range R1, as is well known.

[0168] As an example, consider the case where hydrogen gas is mixed into air. In this case, as the hydrogen concentration in the air increases, the composition of the hydrogen-oxygen-nitrogen ternary mixed gas changes, along the dashed arrow in Figure 9, from the first composition Pa toward the second composition Pb, which indicates a state in which hydrogen gas is 100%. In this case, the dashed arrow crosses the explosion range R1. As the hydrogen concentration increases, there is a risk of hydrogen gas explosion. Note that the first composition Pa corresponds to a state in which the oxygen concentration is approximately 21% and the nitrogen concentration is just over 78%. In this state, neither the first nor second condition described below is met. In the case of ordinary air, the proportion of oxygen and nitrogen in the air reaches 99% or more.

[0169] On the other hand, consider the case where nitrogen gas is supplied to air. In this case, as the nitrogen concentration in the air increases, the composition of the hydrogen-oxygen-nitrogen ternary mixed gas changes, along the solid arrows in Figure 9, from the first composition Pa toward a third composition Pc, which indicates a state in which nitrogen gas accounts for 100%. During this change, the oxygen concentration decreases from the oxygen concentration in air toward 0%, and the nitrogen concentration increases from the nitrogen concentration in air toward 100%.

[0170] Here, the composition of the mixed gas when the oxygen concentration is below the limit oxygen concentration and the nitrogen concentration exceeds the limit nitrogen concentration is referred to as the fourth composition Pd. When the composition of the mixed gas reaches the fourth composition Pd, the explosiveness of the hydrogen gas disappears even without further supply of nitrogen gas. Note that the fourth composition Pd satisfies both the first and second conditions described below.

[0171] For example, consider the case where hydrogen gas is mixed into a mixed gas after the composition of the mixed gas reaches a fourth composition Pd. In this case, as the hydrogen concentration in the mixed gas increases, the composition of the hydrogen-oxygen-nitrogen ternary mixed gas changes from the fourth composition Pd toward the second composition Pb, as indicated by the solid arrow in Figure 9. In this case, unlike the dashed arrow in the same figure, the solid arrow no longer crosses the explosion range R1. Once the fourth composition Pd is reached, there is no risk of a hydrogen gas explosion even if the hydrogen concentration increases from that state.

[0172] As described above, for example, when the oxygen concentration is less than the limit oxygen concentration, or when the nitrogen concentration exceeds the limit nitrogen concentration, the explosiveness of hydrogen gas disappears. In this case, even if hydrogen is mixed into the nitrogen flow passage 72, an explosion is prevented. According to the above-mentioned literature, the limit oxygen concentration is preferably set within a range of 0% to 5.0%, more preferably 0% to 5.3%. Similarly, the limit nitrogen concentration is preferably set within a range of 95% to 100%, more preferably 94.7% to 100%.

[0173] Furthermore, the proportion of oxygen and nitrogen in the air, such as the first composition Pa, reaches 99% or more. An oxygen concentration below the critical oxygen concentration is essentially equivalent to a nitrogen concentration exceeding the critical nitrogen concentration. Therefore, it is not essential in the present disclosure to determine whether both the first and second conditions are met.

[0174] The controller 100 performs such a determination at least one of (in this embodiment, both) the timing before the engine 1 starts to operate using hydrogen gas and the timing while the engine 1 is operating using hydrogen gas.

[0175] Furthermore, the controller 100 executes the determination of at least one of the first condition and the second condition while adjusting the flow rate of the nitrogen gas by the flow rate adjusting unit 73.

[0176] A specific example of the processing executed by the controller 100 will now be described.

[0177] <Specific example of processing by the controller 100> Fig. 7 is a flowchart illustrating a process performed before starting operation of the engine 1 using hydrogen gas. The process illustrated in Fig. 7 is performed by the controller 100 before starting operation of the engine 1 using hydrogen gas.

[0178] For example, in this embodiment, the controller 100 executes the process illustrated in FIG. 7 when starting the engine 1 in the first or second mode, or when switching from the third mode to the first or second mode.

[0179] First, in step S101, the controller 100 activates the booster 52. The controller 100 supplies nitrogen gas into the hydrogen flow passage 41 via the booster 52.

[0180] In the next step S102, the controller 100 reads the detection signal from the leak sensor 92 and determines whether the third condition is met based on the detection signal. The third condition is defined to be met when it is determined that no gas leak is occurring from the hydrogen flow passage 41, particularly the first or second hydrogen flow pipe 41a, 41b. For example, if the leak sensor 92 is a pressure sensor that detects the pressure inside the pipe, the presence or absence of a leak can be determined by monitoring the progress of the detected pressure. In this case, the determination may be based on the magnitude relationship between the detected pressure and a predetermined threshold, or on changes in the detected pressure over time.

[0181] If the determination in step S102 is NO, that is, if the third condition is not met, the controller 100 ends the processing in Fig. 7. In this case, the controller 100 does not permit operation of the engine 1 using hydrogen gas. The controller 100 operates the engine 1 in the third mode in which oil fuel is burned.

[0182] If the determination in step S102 is YES, that is, if the third condition is met, the controller 100 advances the control process to step S103. In step S103, the controller 100 supplies nitrogen gas into the nitrogen flow passage 72 via the generator 51.

[0183] In step S104, the controller 100 starts adjusting the flow rate of the nitrogen gas via the flow rate adjuster 73. In the following step S105, the controller 100 reads the detection signal of the gas property sensor 91, and determines whether the first condition or the second condition is met based on the detection signal.

[0184] The first condition is defined to be met when the detected oxygen concentration is equal to or lower than the limit oxygen concentration. The second condition is defined to be met when the detected nitrogen concentration is equal to or higher than the limit nitrogen concentration. Both the limit oxygen concentration and the limit oxygen concentration are stored in advance in the controller 100.

[0185] It is not essential to determine whether both the first and second conditions are met. If only an oxygen concentration sensor is used as the gas property sensor 91, only the first condition may be determined, and if only a nitrogen concentration sensor is used, only the second condition may be determined.

[0186] As shown in FIG. 7, the processes from step S104 to step S105 are performed after the supply of nitrogen gas via the generator 51 starts.

[0187] If the determination in step S105 is YES, that is, if the first condition or the second condition is met, the controller 100 proceeds to step S106. In this case, the controller 100 permits the engine 1 to operate using hydrogen gas (step S106) and starts operating the engine 1 in the first or second mode in which hydrogen gas is burned.

[0188] In addition, if the determination in step S105 is YES, the controller 100 reduces the flow rate of the nitrogen gas via the flow rate adjuster 73. This makes it possible to suppress the supply amount of nitrogen gas. In other words, the timing for adjusting the flow rate of the nitrogen gas by the flow rate adjuster 73 may be either before or after the determination of the first or second condition.

[0189] In other words, the controller 100 can adjust the flow rate of the nitrogen gas by the flow rate adjuster 73 so that the flow rate of the nitrogen gas increases before and after determining whether at least one of the first condition and the second condition is met.

[0190] If the determination in step S105 is NO, the controller 100 ends the processing in Fig. 7, similarly to the case where the determination in step S102 is NO. In this case, the controller 100 does not permit operation of the engine 1 using hydrogen gas. The controller 100 operates the engine 1 in the third mode in which oil fuel is burned.

[0191] Next, Fig. 8 is a flowchart illustrating a process performed during operation of the engine 1 using hydrogen gas. The process illustrated in Fig. 8 is performed by the controller 100 during operation of the engine 1 using hydrogen gas.

[0192] For example, in this embodiment, the controller 100 executes the process illustrated in FIG. 8 while the engine 1 is operating in the first or second mode.

[0193] Specifically, in step S201, the controller 100 starts or continues the supply of nitrogen gas into the nitrogen flow passage 72 via the generator 51. When the process illustrated in Fig. 8 is executed for the first time, the supply of nitrogen gas is started, and when the process is executed for the second time or later, the supply of nitrogen gas is continued.

[0194] In the following step S202, the controller 100 starts or continues adjusting the flow rate of the nitrogen gas via the flow rate adjuster 73. When the process illustrated in FIG. 8 is executed for the first time, the flow rate adjustment is started, and when the process is executed for the second time or later, the flow rate adjustment is continued.

[0195] In the following step S203, the controller 100 reads the detection signals of the gas property sensor 91 and the leakage sensor 92, and determines whether any of the first condition, the second condition, and the third condition is not satisfied based on these detection signals.

[0196] Here, the determination of each condition in step S203 is the same as the determination in step S102 and step S105 in Fig. 7. In other words, it is not essential to determine both the first condition and the second condition. Furthermore, it is not essential to determine the third condition either. The controller 100 only needs to determine one or more of the first condition, the second condition, and the third condition.

[0197] If the determination in step S203 is NO, the controller 100 returns the control process to step S201 and executes steps S201 to S203 again. In other words, while the engine 1 is operating using hydrogen gas, the controller 100 continuously adjusts the flow rate of nitrogen gas via the flow rate adjuster 73, determines whether the first condition or the second condition is met, and determines whether the third condition is met based on the detection signal of the leak sensor 92.

[0198] On the other hand, if the determination in step S203 is YES, the controller 100 advances the control process to step S204. In this case, the controller 100 does not permit the engine 1 to operate using hydrogen gas.

[0199] Therefore, when the process proceeds to step S204 (when any one of the first, second and third conditions is not satisfied), the amount of hydrogen gas supplied into the combustion chamber 12 is reduced.

[0200] If the engine is operating in the first mode, the amount of hydrogen gas injected may be reduced while continuing operation in the first mode, or the ratio of the heat generation rate of heavy oil to the heat generation rate of hydrogen gas in the combustion chamber 12 (mixed combustion ratio) may be increased from zero to a non-zero value by switching from the first mode to the second or third mode.

[0201] When the fuel cell is operated in the second mode, the fuel cell may continue to operate in the second mode while reducing the amount of hydrogen gas injected to increase the fuel-mix ratio, or the fuel-mix ratio may be increased from a value less than 100% to 100% by switching from the second mode to the third mode.

[0202] <Significance of flow rate adjusting unit 73> Generally, tanks for storing inert gases such as nitrogen are inconvenient to install on ships, considering the space available on or inside the ship.

[0203] In contrast to this, according to the embodiment, instead of a tank storing nitrogen gas, a nitrogen gas generator 51 is mounted on the ship 1000. Configuring the ship 1000 to generate nitrogen gas as needed contributes to making the nitrogen gas supply system, such as the inert gas source 5 and the inert gas system 7, more compact.

[0204] Furthermore, even if a generator 51 such as that of the first embodiment is used, depending on the amount of nitrogen gas generated, the generator 51 itself may become large. In order to realize a compact inert gas source 5, it is desirable to be able to set the flow rate of nitrogen gas to a desired value without increasing the size of the generator 51.

[0205] In contrast, by using the flow rate adjustment unit 73 illustrated in Figure 4, it is possible to appropriately set the flow rate of nitrogen gas so as to achieve smooth discharge of leaked hydrogen gas and reliable containment of leaked hydrogen gas without changing the dimensions of the generator 51 itself.

[0206] 4, by configuring the flow rate adjusting unit 73 with at least one of the throttle unit 732 and the pressure adjusting unit 731, it becomes possible to maintain the flow rate of nitrogen gas near the engine 1 at a predetermined level or higher while suppressing the amount of nitrogen gas supplied from the generator 51 to the nitrogen flow passage 72. This contributes to achieving both a compact inert gas source 5 and measures against hydrogen gas leakage.

[0207] As described with reference to FIG. 4, configuring the flow rate adjusting section 73 with a pressure adjusting section 731 such as a pressure reducing valve is advantageous in ensuring the flow rate of nitrogen gas near the engine 1.

[0208] 4, the flow rate adjuster 73 is disposed closer to the engine 1 than the generator 51 when viewed along the flow path formed by the nitrogen flow passage 72. This configuration can more reliably adjust the flow rate of nitrogen gas near the engine 1 to a desired value compared to, for example, a configuration in which the flow rate adjuster 73 is disposed near the generator 51. This makes it possible to more appropriately deal with hydrogen gas leakage.

[0209] Furthermore, by arranging the pressure adjustment unit 731 at the midpoint P1 in Figure 4, it is advantageous to ensure the flow rate of nitrogen gas near the engine 1 compared to a configuration in which the pressure adjustment unit 731 is arranged near the generator 51, for example.

[0210] 4, by configuring the flow rate adjusting unit 73 with the throttle unit 732, it is possible to increase the flow rate of the nitrogen gas discharged from the nitrogen flow passage 72. This is advantageous for adjusting the flow rate of the nitrogen gas, and makes it possible to more appropriately deal with leakage of hydrogen gas.

[0211] 4, instead of maintaining the flow rate of nitrogen gas at a predetermined level or higher, the flow rate is set to zero. This makes it possible to confine hydrogen gas leaking from the hydrogen flow passage 41 serving as the inner pipe, thereby enabling a more appropriate response to hydrogen gas leakage.

[0212] For example, if generator 51 malfunctions, outlet 6 is blocked by blocking section 733 to prevent nitrogen gas and hydrogen gas leaked into the nitrogen gas from being discharged. This makes it possible to both deal with hydrogen gas leakage and continue operation of engine 1 using hydrogen gas, even if the supply of nitrogen gas from generator 51 is cut off.

[0213] In addition, the controller 100 determines whether or not operation of the engine 1 is permitted based on the limit oxygen concentration or limit nitrogen concentration defined based on the explosiveness of a three-component hydrogen-oxygen-nitrogen system, as illustrated in Figures 7 and 8.

[0214] In this way, by using the limit oxygen concentration or limit nitrogen concentration, it can be determined that an explosion due to leaked hydrogen gas will not occur even if the nitrogen concentration in the nitrogen flow passage 72 does not reach 100% and a small amount of oxygen is contained therein. The amount of nitrogen gas generated in the generator 51 can be set to be neither too much nor too little, and it is possible to make the generator 51, and therefore the inert gas source 5, compact.

[0215] 7 and steps S201 to S203 in Fig. 8, by increasing the flow rate of the nitrogen gas by the flow rate adjuster 73, particularly the throttle unit 732, it is possible to perform a determination based on the limit oxygen concentration or the limit nitrogen concentration while suppressing the amount of nitrogen gas supplied from the generator 51 to the nitrogen flow passage 72. This makes it possible to reduce the amount (pressure) of nitrogen gas supplied to the nitrogen flow passage 72 and reduce nitrogen gas leakage when the outer tube is damaged.

[0216] In detail, the provision of the throttle portion 732 can increase the flow rate of nitrogen gas when it is discharged overboard. This can increase the diffusibility around the discharge port 6 even in the event of a hydrogen gas leak. The throttle portion 732 increases the diffusibility, thereby suppressing the flow rate of nitrogen.

[0217] In addition, the hydrogen concentration is more likely to be diluted after it is released overboard, which reduces the risk of hydrogen ignition and combustion even if the leaked hydrogen mixes with the atmosphere or air (oxygen concentration: 21%).

[0218] Furthermore, as illustrated in step S101 of FIG. 7 , the nitrogen concentration in the hydrogen flow passage 41 can be rapidly increased by using relatively high-pressure nitrogen gas (gas derived from the booster 52). Rapidly increasing the nitrogen concentration in the hydrogen flow passage 41 allows for a rapid determination based on the leak sensor 92. Rapid determination based on the leak sensor 92 allows subsequent processing to be initiated promptly. This allows for a rapid transition from supplying nitrogen gas to the hydrogen flow passage 71 using the booster 52 to supplying nitrogen gas to the nitrogen flow passage 72 using the generator 51. This is advantageous for quickly initiating a determination as to whether the hydrogen engine is operable based on the first or second condition. Using the booster 52 and the generator 51 separately for different purposes is advantageous for determining whether the engine 1 is operable using hydrogen gas as quickly as possible.

[0219] Furthermore, as illustrated in steps S201 to S203 of FIG. 8, while the engine 1 is operating on hydrogen gas, the controller 100 continuously determines the explosibility of the hydrogen gas based on the limit oxygen concentration or limit nitrogen concentration (determination to confirm that sufficient nitrogen gas is being supplied into the nitrogen flow passage 72) and monitors for hydrogen gas leakage.

[0220] This configuration reduces the amount of nitrogen gas supplied to the nitrogen flow passage 72. This makes it possible to achieve both a compact inert gas source and high accuracy in detecting the oxygen concentration or hydrogen concentration contained in the nitrogen flow passage 72, and therefore high accuracy in determining whether the engine 1 is operable.

[0221] Furthermore, as explained as a specific example of step S204 in Figure 8, even if any of the first condition, the second condition, and the third condition is not satisfied, the engine 1 can continue to operate using heavy oil.

[0222] It has been known that when hydrogen gas leaks, the supply of hydrogen gas to the engine 1 is cut off. When the supply of hydrogen gas is cut off, the engine 1 stops operating.

[0223] In practice, when stopping a vehicle engine 1, it is sufficient to park the vehicle on the side of the road or the like. However, if a marine engine 1 stops completely, it may enter a so-called "dead ship state." A dead ship state is inconvenient because it can lead to various troubles, such as the ship drifting.

[0224] In contrast, by continuing to operate the engine 1 using heavy oil as in the above embodiment, it is possible to respond appropriately to a hydrogen gas leak, and even if a hydrogen gas leak does occur, it is possible to prevent the ship from becoming a dead ship.

[0225] <Other embodiments> In the above embodiment, a configuration has been exemplified in which the nitrogen gas generator 51 is mounted on the ship 1000 instead of a tank storing nitrogen gas as an inert gas, but the present disclosure is not limited to such a configuration. The engine system S may include a tank for storing an inert gas such as nitrogen gas in addition to the generator 51. Using both the generator 51 and the tank contributes to making the tank more compact than in conventional configurations.

[0226] 4, in the above embodiment, the flow directions of the hydrogen gas and the nitrogen gas are opposite to each other, but the present disclosure is not limited to such a configuration. The flow directions of the hydrogen gas and the nitrogen gas may be the same.

[0227] 7 and 8 are shown as examples of processing performed by the controller 100 in the above embodiment, but these processes are not essential to the present disclosure. The controller 100 may execute either the process shown in Fig. 7 or the process shown in Fig. 8, or may omit both. [Explanation of symbols]

[0228] S Engine System 1 Engine (hydrogen engine) 11 cylinders 12 Combustion chamber 15 Gas fuel injection valve 19 Oil fuel injection valve 2 Hydrogen Tanks 3 GVT 4 Hydrogen gas system 41 Hydrogen flow passage (first flow passage) 41a First hydrogen flow pipe (inner pipe) 41b Second hydrogen flow pipe (inner pipe) 5. Inert gas source 51 Generator 52 Booster 6 Outlet 7 Inert gas system 72 Nitrogen flow passage (second flow passage) 72c 1st connection pipe (outer pipe) 72d 2nd connecting pipe (outer pipe) 73 Flow rate adjustment section 731 Pressure adjustment unit 732 Constriction section 733 Occlusion 8 double tube 91 Gas property sensor 92 Leak Sensor 100 Controllers 1000 ships P1 midway section (inlet)

Claims

1. a hydrogen engine that is installed on a ship and burns hydrogen gas in a combustion chamber; a first flow passage connected to the hydrogen engine and through which the hydrogen gas to be supplied to the hydrogen engine flows; a generator installed on the vessel for generating an inert gas; a second flow passage including an outer pipe surrounding the inner pipe so as to form a double pipe with at least a portion of the first flow passage as the inner pipe, and discharging the inert gas supplied from the generator to the outside of the ship via the hydrogen engine; a flow rate adjusting unit that adjusts the flow rate of the inert gas in the second flow passage, An engine system characterized by:

2. 2. The engine system according to claim 1, The flow rate adjusting unit adjusts the flow rate of the inert gas so that the flow rate is equal to or greater than a predetermined value. An engine system characterized by:

3. 3. The engine system according to claim 2, the flow rate adjusting unit is disposed in a middle portion of the second flow passage and has a pressure adjusting unit that generates a pressure difference in the inert gas between a primary side and a secondary side of the middle portion. An engine system characterized by:

4. 4. The engine system according to claim 3, the flow rate adjusting unit is disposed on a flow path formed by the second flow passage, closer to the hydrogen engine than the generator. An engine system characterized by:

5. 5. The engine system according to claim 4, the flow rate adjusting unit is disposed at at least one of an inlet portion of the second flow passage into the hydrogen engine and an outlet portion of the second flow passage from the hydrogen engine. An engine system characterized by:

6. 6. The engine system according to claim 2, the flow rate adjusting section is disposed at a downstream end of the second flow passage and has a throttle section that throttles a flow path cross-sectional area at the downstream end. An engine system characterized by:

7. 2. The engine system according to claim 1, the flow rate adjusting unit is disposed at a discharge port located at a downstream end of the second flow passage and has a blocking unit that blocks the discharge port. An engine system characterized by:

8. 3. The engine system according to claim 2, the inert gas is nitrogen gas, a gas property sensor disposed at a downstream end of the second flow passage and detecting at least one of an oxygen concentration and a nitrogen concentration at the downstream end; a controller that determines whether or not the hydrogen engine can be operated using the hydrogen gas based on a detection signal from the gas property sensor, If the lower limit of the oxygen concentration, which is predetermined in advance in a hydrogen-oxygen-nitrogen ternary system and ensures the explosiveness of the hydrogen gas, is defined as the limit oxygen concentration, and the upper limit of the nitrogen concentration, which is predetermined in advance in the hydrogen-oxygen-nitrogen ternary system and ensures the explosiveness of the hydrogen gas, is defined as the limit nitrogen concentration, the controller permits operation of the hydrogen engine using the hydrogen gas when a first condition is satisfied when the detected value of the oxygen concentration is equal to or less than the limit oxygen concentration, or a second condition is satisfied when the detected value of the nitrogen concentration is equal to or greater than the limit nitrogen concentration, the controller determines whether at least one of the first condition and the second condition is met while adjusting the flow rate of the nitrogen gas by the flow rate adjusting unit so as to increase the flow rate of the nitrogen gas. An engine system characterized by:

9. 9. The engine system according to claim 8, a booster that stores the nitrogen gas in a pressurized state higher than that of the generator; a leakage sensor that detects gas leakage from the first flow passage, The controller, before starting operation of the hydrogen engine using the hydrogen gas, supplying the nitrogen gas into the first flow passage through the booster; determining whether a third condition indicating that gas leakage from the first flow passage does not occur is met based on the detection signal of the leakage sensor; When the third condition is satisfied, the nitrogen gas is supplied into the second flow passage via the generator instead of the booster; At a timing after the start of supply of the nitrogen gas via the generator, adjusting the flow rate of the nitrogen gas via the flow rate adjusting unit and determining whether the first condition or the second condition is met, When the first condition or the second condition is satisfied, the operation of the hydrogen engine is started. An engine system characterized by:

10. 9. The engine system according to claim 8, a leakage sensor that detects gas leakage from the first flow passage; The controller, during operation of the hydrogen engine using the hydrogen gas, continuously performing the adjustment of the flow rate of the nitrogen gas via the flow rate adjustment unit, the determination of whether the first condition or the second condition is met, and the determination of whether a third condition indicating that there is no gas leakage from the first flow passage is met based on the detection signal of the leakage sensor; When any one of the first condition, the second condition, and the third condition is not satisfied, the amount of the hydrogen gas supplied into the combustion chamber is reduced. This engine system is characterized by:

11. 11. The engine system according to claim 10, The hydrogen engine burns a different fuel from the hydrogen gas in the combustion chamber together with the hydrogen gas, the controller increases a ratio of a heat generation amount of the different fuel to a heat generation amount of the hydrogen gas in the combustion chamber when any one of the first condition, the second condition, and the third condition is not satisfied. An engine system characterized by:

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