Fuel supply system and vessel

Abstract

To provide a fuel supply system capable of returning liquefied hydrogen of excessive critical pressure or more or supercritical hydrogen to a tank in a liquefied hydrogen state after decompression without increasing boil-off gas generated in the tank.SOLUTION: A fuel supply system 1A according to one embodiment includes a tank 2 that stores liquefied hydrogen, and a fuel supply line 3 that discharges the liquefied hydrogen from the tank 2. The fuel supply line 3 is provided with a pump 5 that pressurizes the liquefied hydrogen to convert it to supercritical hydrogen. The fuel supply system 1A also includes a reflux line 8 that branches off from the fuel supply line 3 on the downstream side with respect to the pump 5 and is connected to the tank 2. The reflux line 8 is provided with a pressure reduction valve 81 and a gas-liquid separator 82. The hydrogen gas flowing out of the gas-liquid separator 82 is condensed by an agitation device 7 using liquefied hydrogen that is below a saturation temperature at a pressure of a gas layer in the tank 2. The liquefied hydrogen condensed by the agitation device 7 is returned to the tank 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fuel supply system for an internal combustion engine, and to a marine vessel including said fuel supply system. [Background technology]

[0002] Conventionally, there have been known fuel supply systems for internal combustion engines, such as reciprocating engines and gas turbine engines, mounted on ships, etc. For example, Patent Document 1 discloses a fuel supply system for diesel engines. This fuel supply system forcibly vaporizes liquefied gas and supplies the vaporized gas to the diesel engine as fuel.

[0003] Specifically, in the fuel supply system of Patent Document 1, liquefied gas is discharged from a tank through a fuel supply line. The fuel supply line is provided with a pump that pressurizes the liquefied gas so that the vaporized gas has a pressure higher than the pressure required by the diesel engine, and a carburetor is provided downstream of the pump. Furthermore, in the fuel supply system of Patent Document 1, a reflux line branches off from the fuel supply line between the pump and the carburetor and leads to the tank. A flow control valve is provided in the reflux line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-049881 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes that the liquefied gas may be liquefied hydrogen. When the liquefied gas is liquefied hydrogen, the liquefied hydrogen reaches or exceeds its critical pressure when the liquefied hydrogen is pressurized by a pump to a pressure higher than the pressure required by the diesel engine. Note that when fuel is supplied to an internal combustion engine other than a diesel engine, the liquefied hydrogen also reaches or exceeds its critical pressure when the liquefied hydrogen is pressurized by a pump to a pressure higher than the pressure required by the internal combustion engine.

[0006] The pump discharges either liquefied hydrogen (below its critical temperature) or supercritical hydrogen (above its critical temperature). In either case, the vaporizer acts as a heater. In particular, when the pump discharges liquefied hydrogen (below its critical temperature), the liquid hydrogen becomes supercritical hydrogen when heated by the vaporizer.

[0007] When the amount of supercritical hydrogen used per unit time in an internal combustion engine is less than the pump discharge flow rate, it is desirable to return the excess liquefied hydrogen or supercritical hydrogen above the critical pressure to the tank through the reflux line. In this case, the flow control valve installed in the reflux line functions as a pressure reducing valve.

[0008] When liquefied hydrogen or supercritical hydrogen above the critical pressure is decompressed to return it to the tank, a part or a large part of it becomes hydrogen gas. For this reason, it is desirable to condense the hydrogen gas produced by the decompression and return the condensed liquefied hydrogen to the tank. Furthermore, it is desirable not to increase the amount of boil-off gas generated in the tank when the condensed liquefied hydrogen is returned to the tank.

[0009] Therefore, an object of the present disclosure is to provide a fuel supply system that can return excess liquefied hydrogen or supercritical hydrogen at or above the critical pressure to a tank in the form of liquefied hydrogen after decompression without increasing the amount of boil-off gas generated in the tank. Another object of the present disclosure is to provide a ship including the fuel supply system. [Means for solving the problem]

[0010] From one aspect, the present disclosure provides a fuel supply system for supplying supercritical hydrogen as fuel to an internal combustion engine, the fuel supply system comprising: a tank for storing liquefied hydrogen; a fuel supply line for drawing out liquefied hydrogen from the tank; a first pump provided in the fuel supply line; a second pump provided in the fuel supply line downstream of the first pump for pressurizing the liquefied hydrogen to a pressure equal to or higher than its critical pressure; a reflux line provided with a pressure reducing valve that branches off from the fuel supply line downstream of the second pump and leads to the tank; a gas-liquid separator provided in the reflux line downstream of the pressure reducing valve; and an agitator that condenses the hydrogen gas by agitating liquefied hydrogen that is below a saturation temperature at the pressure of the gas layer in the tank and that is extracted from the fuel supply line between the first pump and the second pump, and hydrogen gas flowing out from the gas-liquid separator, and the liquefied hydrogen condensed by the agitator is returned to the tank.

[0011] From another aspect, the present disclosure provides a ship including the above-mentioned fuel supply system. Effect of the Invention

[0012] According to the present disclosure, there is provided a fuel supply system that can return excess liquefied hydrogen or supercritical hydrogen at or above its critical pressure to a tank in the form of liquefied hydrogen after decompression without increasing the amount of boil-off gas generated in the tank, and a ship including the fuel supply system. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a reliquefaction device according to an embodiment. [Diagram 2] FIG. 13 is a schematic diagram of a reliquefaction device according to a modified example. [Diagram 3] FIG. 13 is a schematic diagram of a reliquefaction device according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] FIG. 1 shows a fuel supply system 1A according to one embodiment. The fuel supply system 1A supplies supercritical hydrogen as fuel to an internal combustion engine. For example, the fuel supply system 1A may be mounted on a ship or incorporated in a land-based power generation facility. The internal combustion engine is, for example, a reciprocating engine or a gas turbine engine. The reciprocating engine may be any of an Otto cycle, a Diesel cycle, and a Sabate cycle.

[0015] Specifically, the fuel supply system 1A includes a tank 2 for storing liquefied hydrogen, and a fuel supply line 3 for leading out the liquefied hydrogen from the tank 2.

[0016] In this embodiment, the tank 2 is a double-shell tank including an inner tank 21 and an outer tank 22. A vacuum layer is formed between the inner tank 21 and the outer tank 22. However, the tank 2 may be a single-shell tank covered with a heat insulating material. Also, in this embodiment, the tank 2 is a horizontal cylindrical shape. However, the tank 2 may be a vertical cylindrical shape. Alternatively, the tank 2 may be a spherical shape or a substantially rectangular parallelepiped shape.

[0017] Boil-off gas (BOG) is generated by evaporation of the liquefied hydrogen in the tank 2. That is, in the tank 2, a liquid layer is formed by the liquefied hydrogen, and a gas layer is formed by the boil-off gas.

[0018] The liquefied hydrogen is sufficiently cooled when it is poured into tank 2. For this reason, for a while after the liquefied hydrogen is poured into tank 2 while the liquid level of the liquefied hydrogen is kept high, for example, for several weeks, a temperature layer is formed in the liquefied hydrogen in tank 2, and the liquid level of the upper layer of the liquefied hydrogen is kept at equilibrium at the saturation temperature at the pressure of the gas layer in tank 2 near the liquid level, but in the lower layer of the liquefied hydrogen, the temperature can be kept below the saturation temperature at the pressure of the gas layer in tank 2. For example, the pressure of the gas layer in tank 2 is equal to or higher than atmospheric pressure, and the temperature of the liquefied hydrogen in tank 2 is equal to or higher than 20K.

[0019] The fuel supply line 3 is provided with a first pump 4, a second pump 5, and a heater 6 in this order from the upstream side. In this embodiment, the first pump 4 is provided on the fuel supply line 3 downstream of the upstream end of the fuel supply line 3. In this embodiment, the first pump 4 and the second pump 5 are disposed outside the tank 2, and the first pump 4 is disposed in a vacuum insulation pod 11. The vacuum insulation pod 11 has a vacuum layer formed between an inner wall and an outer wall.

[0020] The inner tank 21 of the tank 2 and the first pump 4 are connected by an outlet path 31. The inside of the vacuum insulation pod 11 is filled with liquefied hydrogen or hydrogen gas. The portion of the outlet path 31 located within the outer tank 22 of the tank 2 is composed of a single pipe, the portion between the outer tank 22 and the inner or outer wall of the vacuum insulation pod 11 is composed of a vacuum insulation double pipe, and the portion located within the inner or outer wall of the vacuum insulation pod 11 is composed of a single pipe.

[0021] However, the inner tank 21 of the tank 2 and the vacuum insulation pod 11 may be connected by the outlet path 31, the inside of the vacuum insulation pod 11 may be filled with liquefied hydrogen discharged from the inner tank 21 of the tank 2 through the outlet path 31, and the first pump 4 may suck in the liquefied hydrogen in the vacuum insulation pod 11. In this case, the outlet path 31 and the inside of the vacuum insulation pod 11 form the upstream portion of the fuel supply line 3.

[0022] The first pump 4 draws in liquefied hydrogen in the tank 2 through an outlet passage 31. The first pump 4 and the second pump 5 are connected by a first discharge passage 32, and the second pump 5 and the heater 6 are connected by a second discharge passage 33, with a supply passage 34 extending from the heater 6. A shutoff valve is provided in the supply passage 34 to switch whether or not fuel is supplied to the internal combustion engine.

[0023] The portion of the first discharge passage 32 located inside the inner wall or outer wall of the vacuum insulation pod 11 is made up of a single pipe, and the portion located outside the inner wall or outer wall of the vacuum insulation pod 11 is made up of a vacuum insulation double pipe. The second discharge passage 33 may be made up of either a single pipe or a vacuum insulation double pipe. The supply passage 34 is made up of a single pipe. However, when the fuel supply system 1A is installed on a ship, the portion of the supply passage 34 located inside the engine room may be made up of a double pipe.

[0024] The first pump 4 pumps the liquefied hydrogen from the tank 2 to the second pump 5. For example, the pressure of the liquefied hydrogen at the outlet of the first pump 4 is not less than 0.3 MPaG and not more than 1.0 MPaG.

[0025] The second pump 5 boosts the pressure of the liquefied hydrogen to a pressure higher than the pressure required by the internal combustion engine, to above the critical pressure. If the outlet temperature of the second pump 5 is below the critical temperature, liquefied hydrogen at or above the critical pressure is discharged from the second pump 5, and if the outlet temperature of the second pump 5 is above the critical temperature, supercritical hydrogen is discharged from the second pump 5. For example, if the internal combustion engine is a diesel cycle reciprocating engine, the pressure of the liquefied hydrogen or supercritical hydrogen at or above the critical pressure at the outlet of the second pump 5 is 25 MPaG or more and 35 MPaG or less.

[0026] The heater 6 heats liquefied hydrogen or supercritical hydrogen at or above the critical pressure to a temperature higher than the temperature required by the internal combustion engine. For example, if the internal combustion engine is a diesel cycle reciprocating engine, the temperature of the supercritical hydrogen at the outlet of the heater 6 is 273 K or higher and 333 K or lower.

[0027] Furthermore, the fuel supply system 1A includes a reflux line 8 that branches off from the fuel supply line 3 downstream of the second pump 5 and upstream of the heater 6 to connect to the tank 2. The downstream portion of the reflux line 8 passes through the tank 2 from the outside to the inside. In the illustrated example, the downstream end of the reflux line 8 opens near the bottom of the inner tank 21 of the tank 2, but the downstream end of the reflux line 8 may be configured to be able to spray liquefied hydrogen in the gas layer within the tank 2. The portion of the reflux line 8 located outside the outer tank 22 of the tank 2 is made up of a vacuum insulated double pipe, and the portion located inside the outer tank 22 is made up of a single pipe.

[0028] The reflux line 8 is provided with, in order from the upstream side, a pressure reducing valve 81 and a gas-liquid separator 82. Liquefied hydrogen or supercritical hydrogen at or above the critical pressure is reduced in pressure reducing valve 81 to become 100% hydrogen gas or a gas-liquid two-phase fluid. When liquefied hydrogen or supercritical hydrogen at or above the critical pressure is reduced in pressure to become a gas-liquid two-phase fluid, hydrogen gas and liquefied hydrogen are separated in gas-liquid separator 82 and flow out from gas-liquid separator 82. The liquefied hydrogen separated in gas-liquid separator 82 is returned to tank 2 via reflux line 8.

[0029] Furthermore, the fuel supply system 1A includes an agitator 7 that condenses hydrogen gas flowing out from the gas-liquid separator 82. In this embodiment, the agitator 7 is disposed in the vacuum insulation pod 12. The vacuum insulation pod 12 has a vacuum layer formed between an inner wall and an outer wall. For example, the inside of the vacuum insulation pod 12 is filled with liquefied hydrogen or hydrogen gas. The inside of the vacuum insulation pod 12 may be kept in a vacuum, in which case the vacuum insulation pod 12 may not have an inner wall. Instead of disposing the agitator 7 in the vacuum insulation pod 12, the surface of the agitator 7 may be covered with a vacuum insulation structure.

[0030] The agitator 7 is connected to the gas-liquid separator 82 by an air supply line 71. The agitator 7 is also connected to the first discharge path 32 of the fuel supply line 3 by an extraction line 72, and is connected to the tank 2 by a return line 74. The downstream portion of the return line 74 passes through the tank 2 from the outside to the inside. In the illustrated example, the downstream end of the return line 74 opens near the bottom of the inner vessel 21 of the tank 2, but the downstream end of the return line 74 may be configured to be able to spray liquefied hydrogen in the gas layer within the tank 2.

[0031] The agitator 7 agitates the liquefied hydrogen extracted from the fuel supply line 3 via the extraction line 72 and the hydrogen gas flowing out from the gas-liquid separator 82 via the gas delivery line 71, thereby condensing the hydrogen gas.

[0032] The portion of the air supply line 71 located outside the inner or outer wall of the vacuum insulation pod 12 is made of a vacuum insulated double pipe, and the portion located inside the inner or outer wall of the vacuum insulation pod 12 is made of a single pipe. The portion of the extraction line 72 located outside the inner or outer wall of the vacuum insulation pod 12 is made of a vacuum insulated double pipe, and the portion located inside the inner or outer wall of the vacuum insulation pod 12 is made of a single pipe. The portion of the return line 74 located inside the inner or outer wall of the vacuum insulation pod 12 and inside the outer tank 22 is made of a single pipe, and the portion between the inner or outer wall of the vacuum insulation pod 12 and the outer tank 22 is made of a vacuum insulated double pipe.

[0033] The extraction line 72 is provided with a flow control valve 73. The flow control valve 73, as well as the above-mentioned first pump 4, second pump 5, and pressure reducing valve 81, are controlled by a control device 9. Note that in Fig. 1, some signal lines are omitted for simplification of the drawing.

[0034] With respect to the control device 9, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. In the case where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0035] The control device 9 is electrically connected to a pressure gauge 91 provided in the first discharge passage 32 of the fuel supply line 3 and a pressure gauge 92 provided in the second discharge passage 33. The pressure gauge 91 detects the pressure P1 of the liquefied hydrogen discharged from the first pump 4. The pressure gauge 92 detects the pressure P2 of the liquefied hydrogen or supercritical hydrogen at or above the critical pressure discharged from the second pump 5. However, the pressure gauge 92 may also be provided in the supply passage 34 of the fuel supply line 3 to detect the pressure of the supercritical hydrogen flowing out from the heater 6.

[0036] The control device 9 controls the rotation speed of the first pump 4 within a predetermined range so that the pressure P1 detected by the pressure gauge 91 is equal to or higher than a predetermined value. The control device 9 also controls the flow control valve 73 to a predetermined opening degree or higher so that the discharge flow rate of the first pump 4 does not become equal to or lower than the minimum flow rate. By setting the opening degree of the flow control valve 73 to a predetermined opening degree or higher, a part of the liquefied hydrogen that is less than the saturation temperature at the pressure of the gas layer in the tank 2 and that is drawn out from the tank 2 through the fuel supply line 3 is extracted from the fuel supply line 3 through the extraction line 72 and supplied to the agitator 7. The liquefied hydrogen supplied to the agitator 7 is returned to the tank 2 through the return line 74 after passing through the agitator 7. In other words, the extraction line 72, the agitator 7, the vacuum insulation pod 12, and the return line 74 are cooled by the liquefied hydrogen circulating through a part of the fuel supply line 3, the extraction line 72, the agitator 7, and the return line 74.

[0037] The control device 9 controls the rotation speed of the second pump 5 and the opening of the pressure reducing valve 81 based on the pressure P2 detected by the pressure gauge 92. More specifically, when the pressure P2 detected by the pressure gauge 92 is lower than the threshold value α, the control device 9 fully closes the pressure reducing valve 81. As a result, most of the liquefied hydrogen that is below the saturation temperature at the pressure of the gas layer in the tank 2 and is drawn out of the tank 2 through the fuel supply line 3 becomes supercritical hydrogen and is supplied to the internal combustion engine.

[0038] On the other hand, when the pressure P2 detected by the pressure gauge 92 is greater than the threshold value α, the control device 9 opens the pressure reducing valve 81 to an opening degree corresponding to the deviation ΔP between the pressure P2 and the threshold value α. As a result, the surplus of the liquefied hydrogen or supercritical hydrogen at or above the critical pressure discharged from the second pump 5 is depressurized by the pressure reducing valve 81 and then flows into the gas-liquid separator 82. In addition, the hydrogen gas flowing out from the gas-liquid separator 82 is supplied to the agitator 7, which agitates the hydrogen gas with the liquefied hydrogen extracted from the fuel supply line 3, thereby condensing the hydrogen gas. The liquefied hydrogen condensed by the agitator 7 is returned to the tank 2 through the return line 74.

[0039] As described above, in the fuel supply system 1A of the present embodiment, the hydrogen gas generated when excess liquefied hydrogen or supercritical hydrogen at or above the critical pressure is depressurized by the pressure reducing valve 81 is condensed by utilizing the cold heat of the liquefied hydrogen below the saturation temperature at the pressure of the gas layer in the tank 2, so that the condensed liquefied hydrogen is prevented from re-vaporizing after being returned to the tank 2. Therefore, the excess liquefied hydrogen or supercritical hydrogen at or above the critical pressure can be returned to the tank 2 in the form of liquefied hydrogen after being depressurized without increasing the boil-off gas in the tank 2.

[0040] In addition, in this embodiment, since the first pump 4, the second pump 5 and the agitator 7 are disposed outside the tank 2, maintenance of the first pump 4, the second pump 5 and the agitator 7 can be easily performed.

[0041] <Modification> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0042] For example, as in a modified fuel supply system 1B shown in Fig. 2, the agitator 7 may be disposed inside the tank 2, and the first pump 4 and the second pump 5 may be disposed outside the tank 2. This configuration allows the fuel supply system 1B to be made more compact. Note that when the agitator 7 is disposed inside the tank 2, the vacuum insulation pod 12 and the return line 74 can be omitted.

[0043] 3, the first pump 4 and the agitator 7 may be disposed inside the tank 2, and the second pump 5 may be disposed outside the tank 2. In this modification, the first pump 4 is provided in the fuel supply line 3 at the upstream end of the fuel supply line 3. This configuration allows the fuel supply system 1C to be significantly more compact. In this modification, the vacuum insulation pod 11 may also be omitted.

[0044] <Summary> As a first aspect, the present disclosure provides, from one aspect, a fuel supply system for supplying supercritical hydrogen as fuel to an internal combustion engine, the fuel supply system comprising: a tank for storing liquefied hydrogen; a fuel supply line for drawing out liquefied hydrogen from the tank; a first pump provided in the fuel supply line; a second pump provided in the fuel supply line downstream of the first pump for pressurizing the liquefied hydrogen to a pressure equal to or higher than its critical pressure; a reflux line provided with a pressure reducing valve that branches off from the fuel supply line downstream of the second pump and leads to the tank; a gas-liquid separator provided in the reflux line downstream of the pressure reducing valve; and an agitator that condenses the hydrogen gas by agitating liquefied hydrogen that is below a saturation temperature at the pressure of the gas layer in the tank and that is extracted from the fuel supply line between the first pump and the second pump, and hydrogen gas flowing out of the gas-liquid separator,

[0045] According to the above configuration, the hydrogen gas generated by depressurizing excess liquefied hydrogen or supercritical hydrogen above its critical pressure with the pressure reducing valve is condensed by utilizing the cold heat of the liquefied hydrogen below its saturation temperature at the pressure of the gas layer in the tank, so that the condensed liquefied hydrogen is prevented from re-vaporizing after being returned to the tank. Therefore, the excess liquefied hydrogen or supercritical hydrogen above its critical pressure can be returned to the tank in the form of liquefied hydrogen after being depressurized without increasing the boil-off gas in the tank.

[0046] As a second aspect, in the first aspect, the first pump, the second pump, and the stirring device may be disposed outside the tank. With this configuration, the first pump, the second pump, and the stirring device can be easily maintained.

[0047] As a third aspect, in the first aspect, the stirring device may be disposed inside the tank, and the first pump and the second pump may be disposed outside the tank. With this configuration, the fuel supply system can be made compact.

[0048] As a fourth aspect, in the first aspect, the stirring device and the first pump may be disposed inside the tank, and the second pump may be disposed outside the tank. With this configuration, the fuel supply system can be significantly made compact.

[0049] According to a fifth aspect, the present disclosure provides, from another aspect, a ship including the fuel supply system according to any one of the first to fourth aspects. [Explanation of symbols]

[0050] 1A, 1B, 1C Fuel supply system 2 Tank 3 Fuel supply line 4. First Pump 5. Second Pump 7 Mixing device 74 Return Line 8 Reflux Line 81 Pressure reducing valve 82 Gas-liquid separator

Claims

1. A fuel supply system that supplies supercritical hydrogen as fuel to an internal combustion engine, A tank for storing liquefied hydrogen; a fuel supply line for delivering liquefied hydrogen from the tank; a first pump provided in the fuel supply line; a second pump provided in the fuel supply line downstream of the first pump, for pressurizing the liquefied hydrogen to a critical pressure or higher; a return line provided with a pressure reducing valve, the return line branching off from the fuel supply line downstream of the second pump and leading to the tank; a gas-liquid separator provided in the reflux line downstream of the pressure reducing valve; a mixing device that mixes liquefied hydrogen that is below a saturation temperature at the pressure of the gas layer in the tank and that is extracted from the fuel supply line between the first pump and the second pump with hydrogen gas that flows out from the gas-liquid separator, thereby condensing the hydrogen gas; A fuel supply system wherein the liquefied hydrogen condensed in the agitator is returned to the tank.

2. 2. The fuel supply system of claim 1, wherein the first pump, the second pump and the agitator are located outside the tank.

3. 2. The fuel supply system of claim 1, wherein the agitator is disposed within the tank, and the first pump and the second pump are disposed outside the tank.

4. 2. The fuel supply system of claim 1, wherein the agitator and the first pump are disposed within the tank, and the second pump is disposed outside the tank.

5. A ship comprising a fuel supply system according to any one of claims 1 to 4.

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