Fuel supply system and vessel

Abstract

To provide a fuel supply system capable of re-liquefying hydrogen gas generated by pressure reduction of surplus liquefied hydrogen of critical pressure or higher so as to be sucked into a pump.SOLUTION: A 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. A first pump 4A, a stirring device 5, and a second pump 4B are provided in the fuel supply line 3. The second pump 4B increases a pressure of the liquefied hydrogen to a critical pressure or higher. The fuel supply system 1A includes a reflux line 7 which is branched off from the fuel supply line 3 in a downstream side of the second pump 4B, is connected to the stirring device 5, and is provided with a pressure reduction valve 71. The stirring device 5 stirs hydrogen gas generated by pressure reduction by the pressure reduction valve 71 together with the liquefied hydrogen flowing through the fuel supply line 3 so as to condense the hydrogen gas.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. [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 discharge flow rate of the pump, it is desirable to discharge liquefied hydrogen above the critical pressure from the pump and to reduce the pressure of the excess liquefied hydrogen above the critical pressure and to suck it back into the pump. However, since reducing the pressure of liquefied hydrogen above the critical pressure turns most of the liquefied hydrogen into hydrogen gas, it is desirable to condense the hydrogen gas produced by the reduction in pressure.

[0008] Therefore, an object of the present disclosure is to provide a fuel supply system that can re-liquefy hydrogen gas generated by reducing the pressure of liquefied hydrogen above its critical pressure and suck the hydrogen gas into a pump. [Means for solving the problem]

[0009] 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 discharging liquefied hydrogen from the tank; a first pump provided in the fuel supply line; a stirring device provided in the fuel supply line downstream of the first pump; a second pump provided in the fuel supply line downstream of the stirring device for pressurizing the liquefied hydrogen to a pressure equal to or higher than its critical pressure; and 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 stirring device, wherein the stirring device condenses the hydrogen gas by mixing hydrogen gas generated by pressure reduction by the pressure reducing valve with the liquefied hydrogen flowing through the fuel supply line.

[0010] From another aspect, the present disclosure provides a ship including the above-mentioned fuel supply system. Effect of the Invention

[0011] According to the present disclosure, there is provided a fuel supply system that can re-liquefy hydrogen gas generated by decompressing liquefied hydrogen above its critical pressure and suck the hydrogen gas into a pump. [Brief description of the drawings]

[0012] [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

[0013] 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.

[0014] Specifically, the fuel supply system 1A includes a tank 2 that stores liquefied hydrogen, and a fuel supply line 3 that leads out the liquefied hydrogen from the tank 2. In the tank 2, boil-off gas (BOG) is generated due to evaporation of the liquefied hydrogen.

[0015] 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.

[0016] The fuel supply line 3 is provided with a first pump 4A, an agitator 5, a second pump 4B, and a heater 6, in this order from the upstream side. In this embodiment, the first pump 4A 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 4A is disposed outside the tank 2 and in a vacuum insulation pod 11. The vacuum insulation pod 11 has a vacuum layer formed between an inner wall and an outer wall.

[0017] The inner tank 21 of the tank 2 and the first pump 4A 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.

[0018] Alternatively, the inner tank 21 of the tank 2 and the vacuum insulation pod 11 may be connected by an 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 4A 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.

[0019] The first pump 4A draws in liquefied hydrogen in the tank 2 through an outlet passage 31. The first pump 4A and the agitator 5 are connected by a first discharge passage 32, and the agitator 5 and the second pump 4B are connected by a suction passage 33. The second pump 4B and the heater 6 are connected by a second discharge passage 34, and a supply passage 35 extends from the heater 6. A shutoff valve is provided in the supply passage 35 to switch whether or not fuel is supplied to the internal combustion engine.

[0020] In this embodiment, the agitator 5 and the second pump 4B are disposed outside the tank 2, and the agitator 5 is disposed inside 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 5 inside the vacuum insulation pod 12, the surface of the agitator 5 may be covered with a vacuum insulation structure.

[0021] The portion of the first discharge passage 32 located within the inner or outer wall of the vacuum insulation pod 11 is made of a single pipe, the portion between the inner or outer wall of the vacuum insulation pod 11 and the inner or outer wall of the vacuum insulation pod 12 is made of a vacuum insulation double pipe, and the portion located within the inner or outer wall of the vacuum insulation pod 12 is made of a single pipe. The portion of the suction passage 33 located within the inner or outer wall of the vacuum insulation pod 12 is made of a single pipe, and the portion located outside the inner or outer wall of the vacuum insulation pod 12 is made of a vacuum insulation double pipe. The second discharge passage 34 may be made of either a single pipe or a vacuum insulation double pipe. The supply passage 35 is made of a single pipe. However, when the fuel supply system 1A is installed in a ship, the portion of the supply passage 35 located within the engine room may be made of a double pipe.

[0022] The first pump 4A pumps liquefied hydrogen from the tank 2 through the agitator 5 to the second pump 4B. The second pump 4B pressurizes the liquefied hydrogen to a pressure higher than the pressure required by the internal combustion engine, to a pressure equal to or higher than the critical pressure. In this embodiment, the outlet temperature of the second pump 4B is lower than the critical temperature, and liquefied hydrogen at a pressure equal to or higher than the critical pressure is discharged from the second pump 4B. For example, when the internal combustion engine is a diesel cycle reciprocating engine, the pressure of the liquefied hydrogen at the outlet of the second pump 4B is 25 MPaG or more and 35 MPaG or less, and the temperature of the liquefied hydrogen at the outlet of the second pump 4B is 20K or more.

[0023] The heater 6 heats the liquefied hydrogen to a temperature higher than the temperature required by the internal combustion engine. The liquefied hydrogen becomes supercritical hydrogen as a result of heating by the heater 6. 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.

[0024] Furthermore, the fuel supply system 1A includes a reflux line 7 that branches off from the fuel supply line 3 downstream of the second pump 4B and upstream of the heater 6 to connect to the agitator 5. The portion of the reflux line 7 located outside the inner or outer wall of the vacuum insulation pod 12 is made up of a vacuum insulation double pipe, and the portion located inside the inner or outer wall of the vacuum insulation pod 12 is made up of a single pipe.

[0025] The reflux line 7 is provided with, in this order from the upstream side, a pressure reducing valve 71 and a gas-liquid separator 72. Liquefied hydrogen at or above its critical pressure is reduced in pressure by the pressure reducing valve 71 to become 100% hydrogen gas or a gas-liquid two-phase fluid. When the liquefied hydrogen is reduced in pressure to become a gas-liquid two-phase fluid, hydrogen gas and liquefied hydrogen are separated in the gas-liquid separator 72 and flow out from the gas-liquid separator 72.

[0026] The gas-liquid separator 72 is connected to the tank 2 by a liquid delivery line 73. The liquefied hydrogen separated in the gas-liquid separator 72 is returned to the tank 2 through the liquid delivery line 73.

[0027] The downstream portion of the liquid supply line 73 penetrates the tank 2 from the outside to the inside. In the illustrated example, the downstream end of the liquid supply line 73 opens near the bottom of the inner tank 21 of the tank 2, but the downstream end of the liquid supply line 73 may be configured to be able to spray liquefied hydrogen above the liquid level in the tank 2. The portion of the liquid supply line 73 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 agitator 5 condenses the hydrogen gas by mixing the hydrogen gas flowing out of the gas-liquid separator 72 with the liquefied hydrogen flowing through the fuel supply line 3. Instead of disposing the agitator 5 inside the vacuum insulation pod 12, the surface of the agitator 5 may be covered with a vacuum insulation structure.

[0029] In this embodiment, a return line 8 branches off from the suction passage 33 of the fuel supply line 3, and the return line 8 is connected to the tank 2. The downstream portion of the return line 8 penetrates the tank 2 from the outside to the inside. In the illustrated example, the downstream end of the return line 8 opens near the bottom of the inner tank 21 of the tank 2, but the downstream end of the return line 8 may be configured to be able to spray liquefied hydrogen above the liquid level in the tank 2. The portion of the return 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.

[0030] The return line 8 is provided with a flow control valve 81. The flow control valve 81, the first pump 4A, the second pump 4B, and the pressure reducing valve 71 are controlled by a control device 9. Note that in Fig. 1, some signal lines are omitted for simplification of the drawing.

[0031] 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.

[0032] The control device 9 is electrically connected to a pressure gauge 91 provided in the suction passage 33 of the fuel supply line 3 and a pressure gauge 92 provided in the second discharge passage 34. The pressure gauge 91 detects the pressure P1 of the liquefied hydrogen sucked into the second pump 4B. The pressure gauge 92 detects the pressure P2 of the liquefied hydrogen discharged from the second pump 4B, which is equal to or higher than the critical pressure. However, the pressure gauge 92 may also be provided in the supply passage 35 of the fuel supply line 3 to detect the pressure of the supercritical hydrogen flowing out from the heater 6.

[0033] The control device 9 controls the rotation speed of the first pump 4A so that the pressure P1 detected by the pressure gauge 91 becomes equal to or greater than a predetermined value α, and controls the rotation speed of the second pump 4B so that the pressure P2 detected by the pressure gauge 92 becomes equal to or greater than a predetermined value β. The predetermined value α, which is the target value for the inlet pressure of the second pump 4B, is a pressure (saturation pressure or greater) at which the hydrogen gas sent from the reflux line 7 can be condensed.

[0034] The control device 9 also controls the flow control valve 81 so that the discharge flow rate of the first pump 4A does not fall below a predetermined minimum flow rate. It is preferable that the flow control valve 81 is fully closed. However, if the discharge flow rate of the first pump 4A falls below the predetermined minimum flow rate when the flow control valve 81 is fully closed, the flow control valve 81 is opened, thereby connecting the suction passage 33 to the tank 2 through the return line 8, thereby controlling the discharge flow rate of the first pump 4A to be equal to or higher than the predetermined minimum flow rate.

[0035] Furthermore, the control device 9 controls the aperture of the pressure reducing valve 71 based on the pressure P2 detected by the pressure gauge 92. More specifically, when the pressure P2 detected by the pressure gauge 92 is smaller than the threshold value γ, the control device 9 fully closes the pressure reducing valve 71. On the other hand, when the pressure P2 detected by the pressure gauge 92 is greater than the threshold value γ, the control device 9 opens the pressure reducing valve 71 to an aperture corresponding to the deviation ΔP between the pressure P2 and the threshold value γ. As a result, the excess liquefied hydrogen at or above the critical pressure is reduced in pressure by the pressure reducing valve 71, generating hydrogen gas, which is supplied to the agitator 5 and condensed.

[0036] In the fuel supply system 1A having the configuration described above, hydrogen gas generated by depressurizing excess liquefied hydrogen above its critical pressure by the pressure reducing valve 71 is condensed in the agitator 5 upstream of the second pump 4B. Therefore, the hydrogen gas generated by depressurizing excess liquefied hydrogen above its critical pressure can be re-liquefied and sucked into the second pump 4B.

[0037] In addition, in this embodiment, since the first pump 4A, the second pump 4B, and the agitator 5 are disposed outside the tank 2, maintenance of the first pump 4A, the second pump 4B, and the agitator 5 can be easily performed.

[0038] <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.

[0039] For example, the reflux line 7 may not be provided with the gas-liquid separator 72, and the liquid delivery line 73 may be omitted. However, with the configuration as in the above embodiment, the liquefied hydrogen separated in the gas-liquid separator 72 can be returned to the tank 2. Furthermore, regardless of whether the reflux line 7 is provided with the gas-liquid separator 72 or not, the return line 8 may be omitted.

[0040] 2, the agitator 5 may be disposed inside the tank 2, and the first pump 4A and the second pump 4B may be disposed outside the tank 2. With this configuration, the fuel supply system 1B can be made compact.

[0041] 3, the first pump 4A and the agitator 5 may be disposed inside the tank 2, and the second pump 4B may be disposed outside the tank 2. In this modification, the first pump 4A is provided in the fuel supply line 3 at the upstream end of the fuel supply line 3. With this configuration, the fuel supply system 1C can be significantly made compact.

[0042] In FIG. 3, the first discharge passage 32 of the fuel supply line 3 passes through the tank 2 from the inside to the outside and then from the outside to the inside. However, the entire first discharge passage 32 may be disposed within the tank 2.

[0043] <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 discharging liquefied hydrogen from the tank; a first pump provided in the fuel supply line; a stirring device provided in the fuel supply line downstream of the first pump; a second pump provided in the fuel supply line downstream of the stirring device for pressurizing the liquefied hydrogen to a pressure equal to or higher than its critical pressure; and 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 stirring device, wherein the stirring device condenses the hydrogen gas by mixing hydrogen gas generated by pressure reduction by the pressure reducing valve with the liquefied hydrogen flowing through the fuel supply line.

[0044] According to the above configuration, hydrogen gas generated by depressurizing liquefied hydrogen above its critical pressure by the pressure reducing valve is condensed by the agitator upstream of the second pump. Therefore, the hydrogen gas generated by depressurizing liquefied hydrogen above its critical pressure can be re-liquefied and drawn into the second pump.

[0045] As a second aspect, the fuel supply system according to the first aspect may further include a gas-liquid separator provided in the reflux line downstream of the pressure reducing valve, and a liquid supply line connecting the gas-liquid separator and the tank. With this configuration, the liquefied hydrogen separated by the gas-liquid separator can be returned to the tank.

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

[0047] As a fourth aspect, in the first or second 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 fifth aspect, in the first or second 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 sixth aspect, the present disclosure provides, from another aspect, a ship including the fuel supply system according to any one of the first to fifth aspects. [Explanation of symbols]

[0050] 1A, 1B, 1C Fuel supply system 2 Tank 3 Fuel supply line 4A First Pump 4B Second pump 5. Mixing device 7 Reflux Line 71 Pressure reducing valve 72 Gas-liquid separator 73 Liquid delivery line 8 Return Line 81 Flow control valve

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; an agitator provided in the fuel supply line downstream of the first pump; a second pump provided in the fuel supply line downstream of the stirring device, the second pump pressurizing the liquefied hydrogen to a critical pressure or higher; a reflux line provided with a pressure reducing valve, the reflux line branching off from the fuel supply line downstream of the second pump and leading to the agitator; The mixing device mixes the hydrogen gas generated by the pressure reduction using the pressure reducing valve with the liquefied hydrogen flowing through the fuel supply line, thereby condensing the hydrogen gas.

2. a gas-liquid separator provided in the reflux line downstream of the pressure reducing valve; a liquid transfer line connecting the gas-liquid separator and the tank; The fuel delivery system of claim 1 further comprising:

3. 3. The fuel supply system according to claim 1, wherein the first pump, the second pump and the agitator are disposed outside the tank.

4. 3. The fuel supply system according to claim 1, wherein the stirring device is disposed inside the tank, and the first pump and the second pump are disposed outside the tank.

5. 3. The fuel supply system according to claim 1, wherein the stirring device and the first pump are disposed inside the tank, and the second pump is disposed outside the tank.

6. A ship comprising the fuel supply system according to claim 1 or 2.

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