Fuel supply system for hydrogen aircraft and method for adjusting internal pressure of tank

Abstract

This fuel supply system (1) for a hydrogen aircraft comprises: a fuel tank (2) that stores liquefied hydrogen; a pump (5) that discharges liquefied hydrogen from the fuel tank (2) and supplies the same to a propulsion device (102); a pressure-increase mechanism (3) that increases tank internal pressure, which is the pressure inside the fuel tank (2); a flow rate controller (71) that controls the flow rate of liquefied hydrogen supplied to the propulsion device (102) from the fuel tank (2); and a pressure controller (73) that controls the pressure-increase mechanism (3) to adjust the tank internal pressure, on the basis of information relating to the flow rate of the liquefied hydrogen input from the flow rate controller (71).

Description

Technical Field

[0001] The present disclosure relates to a fuel supply system and a method for adjusting the internal pressure of a tank, which are applied to a hydrogen aircraft that uses hydrogen as an energy source (fuel) for propulsion.

Background Art

[0002] The hydrogen aircraft of Patent Document 1 below is known. This hydrogen aircraft includes a propulsion device using a hydrogen gas turbine engine or a fuel cell system, and a fuel tank that stores hydrogen as fuel to be supplied to the propulsion device.

[0003] When liquefied hydrogen is stored in the fuel tank, a pump for discharging liquefied hydrogen from the fuel tank toward the propulsion device is provided. The pressure of the liquefied hydrogen introduced into this pump, that is, the inlet pressure of the pump, is affected by the internal pressure of the fuel tank, which is the tank internal pressure. Therefore, if the tank internal pressure fluctuates inadvertently, the inlet pressure of the pump will fluctuate, and the discharge flow rate of the liquefied hydrogen may become unstable. In addition, if fluctuations in the tank internal pressure occur repeatedly, in the worst case, the tank may undergo fatigue failure. Therefore, when tank internal pressure fluctuations are considered, it is conceivable that the tank weight will increase in order to set the fatigue strength of the tank in anticipation of its effects.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a fuel supply system and a method for adjusting the internal pressure of a tank for a hydrogen aircraft that can stabilize the inlet pressure of a pump for discharging liquefied hydrogen from a fuel tank.

[0006] As a solution to the above problems, a system according to an aspect of the present disclosure is a fuel supply system applied to a hydrogen aircraft including a propulsion device that uses hydrogen as an energy source, the system including a fuel tank that stores liquefied hydrogen, a pump that discharges liquefied hydrogen from the fuel tank and supplies the liquefied hydrogen to the propulsion device, a pressure boosting mechanism that increases the internal pressure of the fuel tank, i.e., the tank internal pressure, a flow rate controller that controls the flow rate of the liquefied hydrogen supplied from the fuel tank to the propulsion device, and a pressure controller that controls the pressure boosting mechanism to adjust the tank internal pressure based on information regarding the flow rate of the liquefied hydrogen input from the flow rate controller.

[0007] Further, a method according to another aspect of the present disclosure is a method for adjusting the internal pressure of a tank applied to a hydrogen aircraft, where the hydrogen aircraft includes a propulsion device that uses hydrogen as an energy source, a fuel tank that stores liquefied hydrogen, a pump that discharges liquefied hydrogen from the fuel tank and supplies the liquefied hydrogen to the propulsion device, a pressure boosting mechanism that increases the internal pressure of the fuel tank, i.e., the tank internal pressure, and a control device to which an operation for the hydrogen aircraft is input. The method includes controlling the pressure boosting mechanism to adjust the tank internal pressure based on any one of information regarding the output of the propulsion device, information regarding the flow rate of the liquefied hydrogen discharged from the fuel tank toward the propulsion device, and information regarding the operation performed on the control device.

[0008] According to the present disclosure, the inlet pressure of the pump that discharges liquefied hydrogen from the fuel tank can be stabilized.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0010] [First Embodiment] 1. Fuel Supply System FIG. 1 is a front view showing a schematic configuration of a hydrogen aircraft to which a fuel supply system 1 (FIG. 2) according to a first embodiment of the present disclosure is applied. The hydrogen aircraft shown in this figure is an aircraft that uses hydrogen as an energy source (fuel) for propulsion, and includes an airframe 101 and a plurality of engines 102 (propulsion devices) attached to the airframe 101. The airframe 101 includes a fuselage portion 101a and a pair of wings 101b attached to the left and right of the fuselage portion 101a. The engines 102 are respectively attached to the pair of wings 101b. The engine 102 is a hydrogen turbine engine including a gas turbine that is rotationally driven by the combustion energy of hydrogen.

[0011] FIG. 2 is a system diagram showing a schematic configuration of the fuel supply system 1. The fuel supply system 1 shown in this figure is a system that supplies hydrogen as fuel to the engine 102 and is installed inside the airframe 101. The fuel supply system 1 includes a fuel tank 2, a boosting mechanism 3, a fuel supply pipe 4, a pump 5, a pressure limiting mechanism 6, and a controller 7.

[0012] The fuel tank 2 is a container for storing liquefied hydrogen LH, which is extremely low-temperature liquefied hydrogen. The fuel tank 2 has both heat insulation and pressure resistance, and stores liquefied hydrogen LH inside while keeping it cold and under pressure. The fuel tank 2 is made of a metal such as aluminum, or a composite material such as CFRP or GFRP. The fuel tank 2 shown in FIG. 2 has both end portions formed in a hemispherical shape and an intermediate portion formed in a cylindrical shape. However, it is not limited to this as long as it can maintain high pressure.

[0013] Above the liquefied hydrogen LH inside the fuel tank 2, a gas phase portion 2a is formed. The gas phase portion 2a is a space occupied by hydrogen gas containing boil-off gas (BOG) generated when the liquefied hydrogen LH evaporates due to heat input. A pressure sensor SN1 for detecting the tank internal pressure, which is the pressure of the gas phase portion 2a, is attached to the fuel tank 2.

[0014] The pressure boosting mechanism 3 is a mechanism for increasing the tank internal pressure. In the present embodiment, the pressure boosting mechanism 3 includes a plurality of heaters 31 disposed inside the fuel tank 2. The plurality of heaters 31 are disposed near the bottom of the fuel tank 2 at intervals from each other. The heaters 31 in such a position are likely to be immersed in the liquefied hydrogen LH in the fuel tank 2.

[0015] The heater 31 heats the liquefied hydrogen LH, for example, by receiving power supply from an external power source and raising its temperature. When the liquefied hydrogen LH is heated by the heater 31, the evaporation (vaporization) of the liquefied hydrogen LH is promoted, and the tank internal pressure rises. That is, by promoting the evaporation of the liquefied hydrogen LH by heating with the heater 31, the amount of gas (hydrogen gas) present in the gas phase portion 2a of the fuel tank 2 increases, and the pressure of the gas phase portion 2a, that is, the tank internal pressure, rises. In this way, the pressure boosting mechanism 3 is configured to increase the tank internal pressure by heating and promoting the evaporation of the liquefied hydrogen LH.

[0016] Each of the plurality of heaters 31 is attached with a temperature sensor SN2. The temperature sensor SN2 is a sensor that detects the temperature of the heater 31, and is provided to determine the presence or absence of abnormal heating in which the temperature of the heater 31 rises abnormally.

[0017] The fuel supply pipe 4 is a pipe that connects the fuel tank 2 and the engine 102. The liquefied hydrogen LH in the fuel tank 2 is supplied to the engine 102 through the fuel supply pipe 4. The fuel supply pipe 4 has one end portion disposed inside the fuel tank 2 and the other end portion connected to the engine 102. One end portion of the fuel supply pipe 4 extends to the vicinity of the bottom of the fuel tank 2.

[0018] The pump 5 is an electric pump that sends out the liquefied hydrogen LH in the fuel tank 2 to the engine 102 through the fuel supply pipe 4. The pump 5 is provided in the middle of the fuel supply pipe 4 located outside the fuel tank 2. The pump 5 sucks out the liquefied hydrogen LH in the fuel tank 2 to the outside and discharges the sucked liquefied hydrogen toward the downstream engine 102. Note that the pump 5 is not limited to an electric type, and may be, for example, a mechanical pump using the shaft power of the engine 102.

[0019] A flow rate adjustment valve 9 is provided at a position downstream of the pump 5 in the fuel supply pipe 4. The flow rate adjustment valve 9 is an electric valve that adjusts the flow rate of the liquefied hydrogen LH supplied to the engine 102 through the fuel supply pipe 4.

[0020] The pressure limiting mechanism 6 is a mechanism that limits the pressure so that the tank internal pressure does not rise excessively. The pressure limiting mechanism 6 includes a vent pipe 61, an internal pressure control valve 62, a flame arrester 63, a check valve 64, a vent heater 65, a branch pipe 66, and an emergency relief valve 67.

[0021] The vent pipe 61 is a pipe connected to the upper part of the fuel tank 2, and communicates the gas phase part 2a of the fuel tank 2 and the outside air with each other.

[0022] The internal pressure control valve 62 is a valve that opens when the tank internal pressure, which is the pressure in the gas phase part 2a, exceeds a predetermined upper limit value, and is provided in the middle of the vent pipe 61. The internal pressure control valve 62 may be either mechanical or electric. In response to the opening of the internal pressure control valve 62, hydrogen gas is discharged from the gas phase part 2a of the fuel tank 2 to the outside air through the vent pipe 61. Thereby, the tank internal pressure is limited to below the upper limit value.

[0023] The flame arrester 63 is a device that prevents the advancement (backfire) of a flame upstream, and is arranged at a position downstream of the internal pressure control valve 62 in the vent pipe 61. The flame arrester 63 is provided as a countermeasure against a fire or the like occurring outside the fuel tank 2.

[0024] The check valve 64 is a valve that regulates the flow of gas flowing through the vent pipe 61 in one direction, and is arranged at a position downstream of the flame arrester 63 in the vent pipe 61. Specifically, the check valve 64 allows hydrogen gas to flow out from the inside (gas phase part 2a) of the fuel tank 2 to the outside air through the vent pipe 61, while prohibiting gas from flowing into the inside of the fuel tank 2 from the outside air through the vent pipe 61.

[0025] The vent heater 65 is a heater that heats the hydrogen gas discharged through the vent pipe 61, and is arranged at the downstream end of the vent pipe 61. The vent heater 65 is provided to prevent the hydrogen gas from being released to the outside air at an extremely low temperature.

[0026] The branch pipe 66 is a pipe that connects the middle of the vent pipe 61 and the fuel tank 2. Specifically, the branch pipe 66 connects the part between the internal pressure control valve 62 and the flame arrester 63 in the vent pipe 61 and the upper part of the fuel tank 2 to each other. Note that it is not essential for the branch pipe 66 to connect the middle of the vent pipe 61 and the fuel tank 2. For example, a pipe corresponding to the branch pipe 66 extending from the fuel tank 2 may be connected to a flame arrester different from the flame arrester 63 and communicate to the outside of the machine.

[0027] The emergency relief valve 67 is a valve that opens when the internal pressure of the tank exceeds a predetermined abnormal value, and is provided in the middle of the branch pipe 66. The emergency relief valve 67 may be either mechanical or electric. The pressure (abnormal value) at which the emergency relief valve 67 opens is greater than the pressure (upper limit value) at which the above-described internal pressure control valve 62 opens. Such an emergency relief valve 67 functions as a backup when the internal pressure control valve 62 does not operate normally.

[0028] The controller 7 is a control device that comprehensively controls each part of the fuel supply system 1. The controller 7 includes a FADEC 71, an airframe controller 72, and an in-tank pressure controller 73. The FADEC 71 is a control module mainly responsible for controlling the engine 102. The airframe controller 72 is a control module mainly responsible for controlling the airframe 101. The in-tank pressure controller 73 is a control module responsible for controlling the in-tank pressure, which is the pressure inside the fuel tank 2 (vapor phase part 2a). The FADEC 71, the airframe controller 72, and the in-tank pressure controller 73 each include a processor and a memory. All or part of the FADEC 71, the airframe controller 72, and the in-tank pressure controller 73 may be configured to use a common processor or memory. Note that the FADEC 71 corresponds to the "flow controller" in the present disclosure, and the in-tank pressure controller 73 corresponds to the "pressure controller" in the present disclosure.

[0029] The FADEC 71 is signal-connected to the engine 102 and the flow rate adjustment valve 9. The FADEC 71 controls each control element in the engine 102 so that the output of the engine 102 becomes an appropriate value according to the operating conditions, and controls the opening degree of the flow rate adjustment valve 9 so that the flow rate of the liquefied hydrogen LH supplied to the engine 102 becomes an appropriate flow rate according to the operating conditions.

[0030] Further, the FADEC 71 is signal-connected to a control device 103 provided in the cockpit of the aircraft 101. The control device 103 includes, for example, a control stick for operating the attitude of the aircraft 101 and a power lever for operating the output of the engine 102. Signals including the operation amounts of these control sticks and power levers are sequentially input to the FADEC 71 as control signals.

[0031] The tank internal pressure controller 73 is electrically connected to each heater 31 in the fuel tank 2. The tank internal pressure controller 73 controls the energization of each heater 31 so that the tank internal pressure stays within a certain range.

[0032] Also, the tank internal pressure controller 73 is electrically connected to the pressure sensor SN1 and the temperature sensor SN2. Information on the tank internal pressure detected by the pressure sensor SN1 and information on the temperature of the heater 31 detected by the temperature sensor SN2 are sequentially input to the tank internal pressure controller 73.

[0033] 2. Control of Tank Internal Pressure Next, the details of the control by the tank internal pressure controller 73 will be described. In this embodiment, two types of control (first and second control) are prepared as the control of the tank internal pressure by the tank internal pressure controller 73. The first control is control for operating the heater 31 based on the input information from the FADEC 71, and the second control is control for operating the heater 31 based on the input information from the pressure sensor SN1. The first control is the main control that is always performed during the operation of the engine 102, and the second control is the backup control for when the first control cannot be performed normally.

[0034] Figure 3 is a time chart for explaining the contents of the above-described first and second controls. The upper chart in Figure 3 shows the time change of the pressure inside the tank, and the lower chart shows the time change of the heater output. First, the first control will be explained using the chart in Figure 3. In this first control, as shown by the solid line waveform in the lower chart, the heater 31 is turned on at time t1, and the power supply to the heater 31 is started. Then, at time t4 after that, the heater 31 is turned off, and the power supply to the heater 31 is stopped. Time t1 is the time when the flow rate increase information indicating that the flow rate of the liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 increases is input from the FADEC 71 to the tank internal pressure controller 73. Time t4 is the time when the flow rate decrease information indicating that the flow rate of the liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 decreases is input from the FADEC 71 to the tank internal pressure controller 73.

[0035] The flow rate increase information and the flow rate decrease information are information issued from the FADEC 71 based on the prediction of the output change of the engine 102. For example, when at least one of the operation of raising the aircraft 101 and the operation of increasing the output (rotation speed) of the engine 102 is performed on the control device 103, the FADEC 71 predicts that the discharge flow rate of the liquefied hydrogen LH from the fuel tank 2 will increase, and transmits the flow rate increase information to the tank internal pressure controller 73. Conversely, when at least one of the operation of canceling the ascent of the aircraft 101 and the operation of reducing the output of the engine is performed on the control device 103, the FADEC 71 predicts that the discharge flow rate of the liquefied hydrogen LH from the fuel tank 2 will decrease, and transmits the flow rate decrease information to the tank internal pressure controller 73. Note that the flow rate increase information and the flow rate decrease information do not have to be information based on the operation status of such a control device 103, and may be, for example, information based on a control signal transmitted from the FADEC 71 to the flow rate adjustment valve 9.

[0036] When flow rate increase information is input at time point t1 in FIG. 3, the tank internal pressure controller 73 switches the heater 31 from OFF to ON. As a result, the temperature of the heater 31 rises, and the evaporation (vaporization) of liquefied hydrogen LH in the fuel tank 2 is promoted. However, since it takes time for evaporation to actually be promoted, for some time after time point t1, the effect of the decrease in the internal pressure of the tank due to the increase in the discharge amount of liquefied hydrogen LH from the fuel tank 2 is greater than the effect of the increase in the internal pressure of the tank due to the evaporation of liquefied hydrogen LH. This is why the internal pressure of the tank continues to decrease from time point t1 to time point t3 in the upper chart of FIG. 3. On the other hand, after time point t3, the effect of the evaporation of liquefied hydrogen LH becomes apparent, and the internal pressure of the tank starts to rise.

[0037] When flow rate decrease information is input at time point t4, which is delayed from time point t3, the tank internal pressure controller 73 switches the heater 31 from ON to OFF. As a result, the temperature of the heater 31 drops, making it difficult for liquefied hydrogen LH to evaporate. This, combined with the decrease in the flow rate of liquefied hydrogen LH, has the effect of suppressing the increase in the internal pressure of the tank. However, for some time after time point t4, the internal pressure of the tank rises due to the residual heat of the heater 31. This is why the internal pressure of the tank continues to rise from time point t4 to time point t6 in the upper chart of FIG. 3. On the other hand, after time point t6, the effect of the decrease in the internal pressure of the tank due to the discharge of liquid hydrogen LH from the fuel tank 2 becomes greater than the effect of the increase in the internal pressure of the tank due to the residual heat, and the internal pressure of the tank starts to drop.

[0038] As described above, in the first control, the tank internal pressure controller 73 controls the heater 31 based on the input information from the FADEC 71. However, for example, the signal from the FADEC 71 may be interrupted for some reason. The second control assumes such a case and is a control for turning the heater 31 ON / OFF based on the input information from the pressure sensor SN1 instead of the input information from the FADEC 71.

[0039] In the second control, as shown by the broken line waveform in the lower chart of FIG. 3, the heater 31 is turned on at time t2, and then turned off at time t5. As shown by the broken line waveform in the upper chart of FIG. 3, time t2 is the time when the detected value of the internal pressure of the tank input from the pressure sensor SN1 falls below a predetermined first threshold value X1, and time t5 is the time when the detected value of the internal pressure of the tank exceeds a predetermined second threshold value X2.

[0040] The first threshold value X1 is set to a value larger than the lower limit value of the internal pressure of the tank. The lower limit value of the internal pressure of the tank is the lower limit value for ensuring the normal discharge operation of the pump 5. When the internal pressure of the tank falls below the lower limit value, the pressure of the liquefied hydrogen LH introduced from the fuel tank 2 to the pump 5, that is, the inlet pressure of the pump 5 becomes too low, and the discharge operation of the liquefied hydrogen LH by the pump 5 may become unstable. Therefore, the first threshold value X1 is set to a level higher than the lower limit value so that the heater 31 is turned on before the internal pressure of the tank drops to such a lower limit value.

[0041] The second threshold value X2 is set to a value larger than the first threshold value X1 and smaller than the upper limit value of the internal pressure of the tank. The upper limit value of the internal pressure of the tank is the pressure at which the internal pressure control valve 62 of the pressure limiting mechanism 6 described above opens, that is, the pressure at which forced venting of hydrogen gas from the fuel tank 2 is performed. The second threshold value X2 is set to a level lower than the upper limit value so that the heater 31 is turned off before the internal pressure of the tank rises to such an upper limit value.

[0042] As shown in FIG. 3, at time t2 when the detected value of the internal pressure of the tank falls below the first threshold value X1, the tank internal pressure controller 73 switches the heater 31 from OFF to ON. When the heater 31 is turned on, the temperature of the heater 31 rises and the evaporation of the liquefied hydrogen LH is promoted. As a result, the internal pressure of the tank turns to rise after some delay time.

[0043] At time t5 after the tank internal pressure starts to rise, the detected value of the tank internal pressure exceeds the second threshold value X2. In response to this, the tank internal pressure controller 73 switches the heater 31 from ON to OFF. When the heater 31 is turned OFF, the temperature of the heater 31 decreases, suppressing the evaporation of the liquefied hydrogen LH. As a result, the tank internal pressure starts to decrease after a certain delay time.

[0044] As described above, in the second control, the tank internal pressure controller 73 controls the heater 31 based on the detected value of the tank internal pressure input from the pressure sensor SN1. Therefore, the control timing of the heater 31 in the second control is later than that of the first control in which the heater 31 is controlled based on the input information from the FADEC 71. That is, the time point t2, which is the timing to turn ON the heater 31 in the second control, is later than the time point t1, which is the timing to turn ON the heater 31 in the first control, and the time point t5, which is the timing to turn OFF the heater 31 in the second control, is later than the time point t4, which is the timing to turn OFF the heater 31 in the first control. From time point t1 to time point t3 in the upper chart of FIG. 3, the broken line waveform is lower than the solid line waveform, and the difference between the solid line waveform and the broken line waveform widens. This indicates that the pressure decrease rate in the second control is greater than that in the first control because the heating of the heater 31 in the second control is slower than that in the first control. Also, after time point t3 in the upper chart of FIG. 3, the time point corresponding to the valley of the broken line waveform is later than the time point (time point t3) corresponding to the valley of the solid line waveform. This indicates that the pressure increase time point in the second control is later than that in the first control because the heating of the heater 31 in the second control is slower than that in the first control.

[0045] Here, depending on the attitude of the aircraft 101, at least a part of the plurality of heaters 31 may emerge from the liquid level of the liquefied hydrogen LH in the fuel tank 2. For example, when the aircraft 101 is greatly tilted, the angular difference between the bottom surface of the fuel tank 2 and the liquid level of the liquefied hydrogen LH increases, and some of the heaters 31 may emerge from the liquid level. The heater 31 that has emerged from the liquid level is much more likely to experience a significant temperature rise compared to the other heaters 31 immersed in the liquefied hydrogen LH. That is, the fact that the heater 31 has emerged from the liquid level can be regarded as a heating abnormality in which the temperature of the heater 31 abnormally rises. Below, the control when such a heating abnormality occurs will be described.

[0046] During the operation of the engine 102, the tank internal pressure controller 73 determines the presence or absence of a heating abnormality in which the temperature abnormally rises for each heater 31 based on the input information from each temperature sensor SN2 provided in the plurality of heaters 31. And when it is confirmed that such a heating abnormality has occurred in any of the heaters 31, the tank internal pressure controller 73 stops the power supply to the heater 31 with the heating abnormality and turns off the heater 31. That is, the temperature of the heater 31 is decreased by stopping the power supply, and the heating abnormality of the heater 31 is eliminated.

[0047] Also, when a heating abnormality of the heater 31 is confirmed, the tank internal pressure controller 73 executes control to increase the output (power supply amount) of the other heaters 31 where no heating abnormality has occurred, in addition to the above-described control of turning off the heater 31 with the heating abnormality. This control raises the temperature of the other heaters 31 immersed in the liquefied hydrogen LH and promotes the evaporation of the liquefied hydrogen LH. This compensates for the decrease in the heating amount due to some of the heaters 31 emerging from the liquid level of the liquefied hydrogen LH and plays a role in maintaining the pressure increasing effect of the tank internal pressure due to the evaporation of the liquefied hydrogen LH.

[0048] 3. Operational Effects As described above, in this embodiment, during the operation of the engine 102 in which the liquefied hydrogen LH in the fuel tank 2 is discharged by the pump 5, the heater 31 (pressure boosting mechanism 3) in the fuel tank 2 is controlled based on the flow rate of the liquefied hydrogen LH, whereby the internal pressure of the fuel tank 2, i.e., the tank internal pressure, is adjusted. For example, when flow rate increase information indicating an increase in the flow rate of the liquefied hydrogen LH is input from the FADEC 71, the tank internal pressure controller 73 raises the temperature of the heater 31 to increase the tank internal pressure. According to such a configuration, the inlet pressure of the pump 5 can be stabilized, and the required amount of liquefied hydrogen LH can be accurately supplied to the engine 102.

[0049] That is, in this embodiment, when the flow rate of the liquefied hydrogen LH increases, that is, in a situation where the acceleration rate of the volume of the gas phase portion 2a in the fuel tank 2 becomes faster, the evaporation of the liquefied hydrogen LH is promoted by the heating of the heater 31. Therefore, the decrease in the tank internal pressure caused by the increase in the volume of the gas phase portion 2a can be compensated by the pressure boosting effect brought about by the evaporated hydrogen (hydrogen gas). As a result, it becomes possible to keep the tank internal pressure within a certain range regardless of the change in the flow rate of the liquefied hydrogen LH, and the inlet pressure of the pump 5 can be stabilized. When the inlet pressure of the pump 5 is stabilized, it becomes easier to make the discharge amount of the liquefied hydrogen LH by the pump 5 coincide with the target amount. Therefore, the required amount of liquefied hydrogen LH according to the operating conditions of the engine 102 can be accurately supplied to the engine 102.

[0050] On the other hand, when flow rate decrease information indicating a decrease in the flow rate of the liquefied hydrogen LH is input from the FADEC 71, the tank internal pressure controller 73 lowers the temperature of the heater 31 to suppress the increase in the tank internal pressure. According to such a configuration, it is possible to avoid the continuous heating by the heater 31 in a situation where the acceleration rate of the volume of the gas phase portion 2a becomes slow, and it is possible to prevent the tank internal pressure from rising excessively.

[0051] In this embodiment, a pressure sensor SN1 for detecting the internal pressure of the tank is attached to the fuel tank 2. When the detected pressure by the pressure sensor SN1 falls below the first threshold value X1, control is executed to increase the temperature of the heater 31 to increase the internal pressure of the tank. Conversely, when the detected pressure by the pressure sensor SN1 exceeds the second threshold value X2 that is greater than the first threshold value X1, control is executed to lower the temperature of the heater 31 to suppress the increase in the internal pressure of the tank. According to such a configuration, even when the signal from the FADEC 71 is interrupted for some reason, that is, when the information regarding the flow rate of the liquefied hydrogen LH becomes unavailable, the inlet pressure of the pump 5 can be stabilized by the control of the heater 31 based on the actual internal pressure of the tank.

[0052] Also, in this embodiment, during the operation of the engine 102 in which the internal pressure of the tank is adjusted using the heater 31 as described above, it is checked for each of the plurality of heaters 31 whether a heating abnormality in which the temperature rises abnormally has occurred. When it is confirmed that a heating abnormality has occurred in any one of the heaters 31, control is executed to stop the heater 31 with the heating abnormality and increase the output of the other heaters 31. According to such a configuration, for example, when a part of the heater 31 comes out of the liquid level of the liquefied hydrogen LH due to a change in the attitude of the aircraft 101, the heating abnormality of the heater 31 can be eliminated. In addition, since the output of the other heaters 31 in which no heating abnormality has occurred is increased, it is possible to compensate for the decrease in the heating amount due to a part of the heater 31 coming out of the liquid level of the liquefied hydrogen LH, and it is possible to maintain the pressure increasing effect of the internal pressure of the tank due to the evaporation of the liquefied hydrogen LH.

[0053] 4. Modification In the first embodiment, an engine 102 composed of a hydrogen turbine engine was used as a propulsion device for imparting propulsion force to the airframe 101. However, the propulsion device may be any device that generates propulsion force using hydrogen as an energy source, and is not limited to an engine. For example, it is also possible to use a fuel cell system as the propulsion device. The fuel cell system may include, for example, a power generation unit that generates power by chemically reacting hydrogen and oxygen, a power storage unit that stores the power generated by the power generation unit, and a motor that rotationally drives a turbine or a propeller by the power supplied from the power storage unit. The fuel supply system of the present disclosure can also be used as a system that supplies liquefied hydrogen to the power generation unit of such a fuel cell system.

[0054] In the first embodiment, as a mechanism for increasing the tank internal pressure, which is the pressure inside the fuel tank 2 (vapor phase portion 2a), a pressure boosting mechanism 3 including a plurality of heaters 31 disposed in the fuel tank 2 was provided. However, the pressure boosting mechanism only needs to include at least one heater. That is, the number of heaters disposed in the fuel tank may be one or two or more. Also, the shape of the heater 31 is not particularly limited. The heater 31 may be in the form of a sheet or may have an elongated shape with a longitudinal direction.

[0055] Also, the heater does not necessarily have to be disposed inside the fuel tank and may be disposed outside the fuel tank. For example, it is conceivable to provide a reflux line for leading out liquefied hydrogen from the fuel tank and then returning it to the fuel tank, and provide a heater in this reflux line.

[0056] Furthermore, it is also possible to use elements other than the heater as the pressure boosting mechanism. For example, separately from the fuel tank, an accumulator for storing high-pressure hydrogen gas is provided, and in a situation where the discharge flow rate of liquefied hydrogen from the fuel tank increases (a situation where the tank internal pressure decreases), hydrogen gas may be supplied from the accumulator to the fuel tank. Even in such a case, the tank internal pressure can be kept within a certain range and the inlet pressure of the pump can be stabilized.

[0057] Based on any one of the information on the output of the engine 102, the information on the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102, and the information on the operations performed on the control device 103, the pressure boosting mechanism may be controlled to adjust the internal pressure of the tank. The information on the output of the engine 102 can be obtained from the control signal of the engine 102 output from the controller 7. The information on the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 can be obtained from the control signal transmitted to the flow rate adjustment valve 9 or the value of a flow rate sensor (not shown) provided in the fuel supply pipe 4. The information on the operations performed on the control device 103 can be obtained from the value of a sensor attached to the control device 103 or the value of a sensor built into the control device 103.

[0058] In the first embodiment, as the pressure limiting mechanism 6, a mechanism for discharging the hydrogen gas in the gas phase portion 2a of the fuel tank 2 to the outside air is provided, but the pressure limiting mechanism may be one that recovers the pressure discharged from the gas phase portion 2a by a recovery device.

[0059] [Second Embodiment] Hereinafter, a second embodiment of the present disclosure will be described. FIG. 4 is a diagram showing a fuel supply system of a hydrogen aircraft according to the second embodiment of the present disclosure.

[0060] 1. Control System

[0061] (1) The controller monitors the internal pressure of the tank detected by the pressure sensor, and controls the opening degree of the electronic internal pressure control valve and the heating time by the tank pressurization heater or the pressurization time by the accumulator, thereby controlling the inside of the tank to a constant pressure. By controlling to a constant pressure, the pump inlet pressure is made constant, and a stable pump discharge pressure is obtained.

[0062] (2) Even when the pump transfer amount changes according to the engine operating state, the inside of the tank is controlled to a constant pressure.

[0063] (3) The tank internal pressure controller receives data on the states of the engine and pump and the fuel quantity from the engine control unit, and performs tank internal pressure control and fault diagnosis.

[0064] (4) The tank internal pressure controller monitors the fuel quantity in the tank. Also, even when the liquid level changes due to the aircraft attitude signal, it corrects the level and displays the correct capacity.

[0065] 2. Components

[0066] (1) There is one or more tank pressurizing heaters. If there are multiple tank pressurizing heaters, redundancy can be ensured.

[0067] (2) The pump may be installed either inside or outside the tank. Considering maintainability, when installed outside, the impeller part is installed inside the tank and the motor part is installed outside the tank. That is, only the motor part, which is prone to failure without draining liquid hydrogen from the tank, can be replaced.

[0068] (3) The internal pressure control valve and the emergency relief valve operate both on the ground and at high altitudes, and the operating pressure can be either absolute pressure or gauge pressure. Also, each valve can be either mechanical or electric.

[0069] 3. Arrangement

[0070] (1) The tank pressurizing heater is installed at a position away from the fuel gauge and the pump so as not to be affected by the hydrogen vaporization when the tank pressurizing heater operates.

[0071] 4. Energy reduction

[0072] (1) In addition to the tank pressurizing heater, the power of the tank pressurizing heater is reduced by vaporizing (boil-off) liquid hydrogen by the heat generated by the pump or other equipment and pressurizing the inside of the tank.

[0073] (2) By returning a part of the pressurized liquid hydrogen downstream of the pump to the tank, the internal pressure of the tank is increased and the power of the tank pressurizing heater is reduced.

[0074] As shown in FIG. 1, in accordance with the pressure reducing action by supplying fuel to the engine, the tank pressurizing heater and the internal pressure control valve are controlled by the tank internal pressure controller, and the internal pressure of the tank is adjusted to increase or decrease the pressure inside the tank, thereby maintaining the tank internal pressure at a desired target value. In addition, an emergency relief valve is provided in parallel so that the tank is not pressurized above a predetermined value during an emergency / grounding.

[0075] [Third Embodiment] Hereinafter, a third embodiment of the present disclosure will be described. FIG. 5 is a diagram showing a fuel supply system of a hydrogen aircraft according to the third embodiment of the present disclosure. In this specification, "connected signal-wise" means being connected by wire or wirelessly so as to be able to transmit or receive an electrical signal for information transmission between a plurality of devices.

[0076] 1. Components

[0077] (1) Fuel Tank The fuel tank is for storing liquid hydrogen inside. The fuel tank is composed of metal (such as aluminum) or composite materials (such as CFRP and GFRP). The fuel tank shown in FIG. 2 has hemispherical shapes at both ends and a cylindrical shape in the middle part. However, it is not limited to this as long as it can maintain high pressure.

[0078] (2) Tank Internal Pressure Controller The tank internal pressure controller is for controlling the internal pressure of the fuel tank to a desired value or a desired range by exchanging signals with a plurality of components of the fuel supply system. The tank internal pressure controller includes a processor and a memory. Programs for obtaining desired control results and various data (various threshold values, etc.) used in the programs are stored in the memory of the tank internal pressure controller. The program stored in the memory is executed by the processor.

[0079] (3) Fuel supply pipe The fuel supply pipe is for supplying the liquid hydrogen stored in the fuel tank to an engine (not shown). One end of the fuel supply pipe is provided inside the fuel tank, and the other end is connected to the engine. The fuel supply pipe may be provided with a return pipe for returning a part of the pressurized liquid hydrogen existing downstream of the pump to the tank. A flow control valve for controlling the return amount of the liquid hydrogen may be provided in the return pipe, and the flow control valve may be signal-connected to the tank internal pressure controller.

[0080] (4) Pump (not shown) The pump is for flowing liquid hydrogen through the fuel supply pipe and is connected to the fuel supply pipe. Also, the pump is signal-connected to the tank internal pressure controller. The pump may be provided inside the fuel tank or outside the fuel tank. Also, a part of the pump may be provided inside the fuel tank and another part of the pump may be provided outside the fuel tank. When the pump is provided inside the fuel tank, the heat generated during pump operation can be utilized for heating the liquid hydrogen fuel for fuel tank pressurization as described later. Providing the pump outside the fuel tank facilitates maintenance of the pump. When using a pump having an impeller and a motor, the impeller may be provided inside the fuel tank while the motor, which requires frequent maintenance, is provided outside the fuel tank. By doing so, it becomes possible to replace the motor without draining the liquid hydrogen from the fuel tank. In this case, the pump penetrates the wall of the fuel tank, and the space between the pump and the wall of the fuel tank is sealed to prevent leakage of the liquid hydrogen.

[0081] (5) Tank pressurization heater The tank pressurizing heater (heater) is for increasing the internal pressure of the fuel tank and is provided inside the fuel tank. Also, the tank pressurizing heater is signal-connected to the tank internal pressure controller. When the tank pressurizing heater is operated, a part of the liquid hydrogen in the fuel tank is heated and vaporized, increasing the volume. As a result, the internal pressure of the fuel tank rises. The tank pressurizing heater may be provided at a position where liquid hydrogen exists inside the fuel tank or at a position where liquid hydrogen does not exist. The tank pressurizing heater may be provided at the bottom of the fuel tank. In the case of a fuel tank with a cylindrical middle part as shown in Figure 2, the tank pressurizing heater may be provided at the cylindrical bottom part. By arranging the tank pressurizing heater at as low a position as possible, liquid hydrogen can be heated regardless of the storage amount of liquid hydrogen in the fuel tank. A plurality of tank pressurizing heaters may be provided to ensure redundancy. To avoid being affected by hydrogen vaporization during operation of the tank pressurizing heater, the tank pressurizing heater is provided at a position far from the fuel level gauge and the pump (when the pump is arranged inside the fuel tank). For example, the fuel level gauge and the pump may be arranged so that there is no fuel level gauge or pump above the tank pressurizing heater, or the fuel level gauge and the pump may be arranged outside the range where the hydrogen vaporized by the tank pressurizing heater moves upward in the liquid hydrogen (the range where vaporized hydrogen exists).

[0082] (6) Internal pressure control valve The internal pressure control valve receives a signal from the tank internal pressure controller and opens and closes the valve. By opening the valve of the internal pressure control valve, the internal pressure of the fuel tank approaches atmospheric pressure (usually the internal pressure of the fuel tank decreases). An internal pressure control valve that operates both on the ground and at high altitudes is selected. The internal pressure control valve may operate in either absolute pressure or gauge pressure, and may operate in either a mechanical or an electrical manner.

[0083] (7) Emergency relief valve The emergency relief valve is for maintaining the internal pressure of the fuel tank within a safe range. When the internal pressure of the fuel tank exceeds a predetermined threshold value, the emergency relief valve opens and the pressure inside the fuel tank is reduced.

[0084] (8) Pressure sensor The pressure sensor is for detecting the internal pressure of the fuel tank and is signal-connected to the tank internal pressure controller. The pressure sensor is provided in a region (gas phase part) within the fuel tank where liquid hydrogen does not exist. The pressure sensor may be provided above the upper limit position where liquid hydrogen exists within the fuel tank. When the fuel tank has a mechanism for preventing the amount of liquid hydrogen within the fuel tank from becoming equal to or greater than the upper limit value, the pressure sensor may be provided above the upper limit position where the amount of liquid hydrogen of the said upper limit value can exist, at least in the steady state (parked state or horizontal flight state) of the aircraft. Note that the position of the pressure sensor is not limited to the above positions, and for example, it may be arranged in the middle of a pipe extending from the fuel tank and connected to the emergency relief valve.

[0085] (9) Fuel quantity gauge The fuel quantity gauge is for detecting the storage amount of liquid hydrogen stored within the fuel tank.

[0086] (10) Accumulator (not shown) The accumulator is for increasing the internal pressure within the fuel tank and is connected to the fuel tank so that fluid can flow into the fuel tank. Also, the accumulator is signal-connected to the tank internal pressure controller.

[0087] (11) Engine control unit (not shown) The engine control unit (FADEC) is for controlling the engine and is signal-connected to the tank internal pressure controller.

[0088] 2. Control <Purpose of control> By controlling the internal pressure of the tank within a certain value or within a certain range, the pump inlet pressure is made within a certain value or within a certain range to obtain a stable pump discharge pressure.

[0089] <Method of control> The control method will be described below. All of the following methods may be included in the above program, or only a part of the following methods may be included in the above program.

[0090] (1) When the internal pressure control valve is electric, the tank internal pressure controller reads the detection value of the pressure sensor. When the detection value is greater than a predetermined value, the tank internal pressure controller sends a signal to the internal pressure control valve to open the valve.

[0091] (2) When the tank internal pressure controller reads the detection value of the pressure sensor and the detection value is less than a predetermined value, the tank internal pressure controller sends a signal to the tank pressurizing heater to heat the liquid hydrogen. The tank internal pressure controller controls the heating time of the tank pressurizing heater. When the tank pressurizing heater has a heating temperature adjustment function, the tank internal pressure controller may control the heating temperature of the tank pressurizing heater.

[0092] (3) When the tank internal pressure controller reads the detection value of the pressure sensor and the detection value is less than a predetermined value, the tank internal pressure controller sends a signal to the accumulator to pressurize the liquid hydrogen. The tank internal pressure controller controls the pressurizing time of the accumulator.

[0093] (4) The tank internal pressure controller may receive a signal regarding the operating state (such as the degree of output) of an engine (not shown) from the engine and control the internal pressure control valve, the tank pressurizing heater, and the accumulator based on the signal. By doing so, even when the pump transfer amount changes according to the operating state of the engine, the internal pressure of the fuel tank can be controlled with higher precision. That is, when the pump transfer amount changes according to the operating state of the engine, the reduction rate of the liquid hydrogen in the fuel tank also changes, and fluctuations in the internal pressure of the fuel tank due to the reduction of the liquid hydrogen occur, which has an adverse effect on control. However, this adverse effect can be avoided. The signal regarding the operating state may be obtained from an engine control unit or from the detection values of various sensors provided in the aircraft.

[0094] (5) The tank internal pressure controller receives data on the states of the engine and pump and the fuel quantity from the engine control unit, and performs internal pressure control of the fuel tank and fault diagnosis.

[0095] (6) The tank internal pressure controller may read the detected value of the fuel quantity gauge and control the internal pressure control valve, the tank pressurization heater, and the accumulator based on the detected value. Since the liquid hydrogen level in the fuel tank changes depending on the aircraft attitude, the tank internal pressure controller may correct the detected value of the fuel quantity gauge based on the aircraft attitude information. The aircraft attitude information can be obtained from the detected values of various sensors installed in the aircraft.

Claims

1. A fuel supply system applied to a hydrogen aircraft including a propulsion device that uses hydrogen as an energy source, comprising: a fuel tank for storing liquefied hydrogen; a pump for discharging liquefied hydrogen from the fuel tank and supplying it to the propulsion device; a heater for increasing the internal pressure of the fuel tank, which is the tank internal pressure; a control device to which an operation on the hydrogen aircraft is input; a flow controller for controlling the flow rate of liquefied hydrogen supplied from the fuel tank to the propulsion device, predicting whether the discharge flow rate of the liquefied hydrogen from the fuel tank increases or decreases based on information regarding an operation performed on the control device, transmitting information indicating that the flow rate of the liquefied hydrogen increases when it is predicted that the discharge flow rate of the liquefied hydrogen from the fuel tank increases, and transmitting information indicating that the flow rate of the liquefied hydrogen decreases when it is predicted that the discharge flow rate of the liquefied hydrogen from the fuel tank decreases; and a pressure controller that controls the heater to increase the tank internal pressure when receiving information indicating that the flow rate of the liquefied hydrogen increases, and controls the heater to suppress the increase in the tank internal pressure when receiving information indicating that the flow rate of the liquefied hydrogen decreases, for the fuel supply system of a hydrogen aircraft.

2. In the fuel supply system of a hydrogen aircraft according to Claim 1, the heater is disposed inside the fuel tank, for the fuel supply system of a hydrogen aircraft.

3. In the fuel supply system of a hydrogen aircraft according to Claim 1, the heater includes a plurality of heaters dispersed and disposed inside the fuel tank, for the fuel supply system of a hydrogen aircraft.

4. A fuel supply system applied to a hydrogen aircraft including a propulsion device that uses hydrogen as an energy source, comprising: a fuel tank for storing liquefied hydrogen; a pump for discharging liquefied hydrogen from the fuel tank and supplying it to the propulsion device; a heater disposed inside the fuel tank, the heater being a plurality of heaters for increasing the internal pressure of the fuel tank, which is the tank internal pressure; a plurality of temperature sensors for detecting the temperatures of the heaters respectively; a flow controller for controlling the flow rate of liquefied hydrogen supplied from the fuel tank to the propulsion device; and a pressure controller for adjusting the tank internal pressure by controlling the heater based on information regarding the flow rate of the liquefied hydrogen input from the flow controller. The pressure controller determines the presence or absence of abnormal heating in which the temperature of the heater rises abnormally based on the input information from the temperature sensor, and when it is confirmed that the abnormal heating has occurred in any of the heaters, the heater with the abnormal heating is stopped and the output of the other heaters is increased. A fuel supply system for a hydrogen aircraft.

5. In the fuel supply system for a hydrogen aircraft according to claim 1, When information indicating an increase in the flow rate of the liquefied hydrogen is input from the flow rate controller, the pressure controller raises the temperature of the heater to increase the internal pressure of the tank. A fuel supply system for a hydrogen aircraft.

6. In the fuel supply system for a hydrogen aircraft according to claim 5, When information indicating a decrease in the flow rate of the liquefied hydrogen is input from the flow rate controller, the pressure controller lowers the temperature of the heater to suppress an increase in the internal pressure of the tank. A fuel supply system for a hydrogen aircraft.

7. In the fuel supply system for a hydrogen aircraft according to claim 1, Further comprising a pressure sensor for detecting the internal pressure of the tank, When the internal pressure of the tank detected by the pressure sensor falls below a predetermined first threshold value, the pressure controller raises the temperature of the heater to increase the internal pressure of the tank. A fuel supply system for a hydrogen aircraft.

8. In the fuel supply system for a hydrogen aircraft according to claim 7, When the internal pressure of the tank detected by the pressure sensor exceeds a second threshold value greater than the first threshold value, the pressure controller lowers the temperature of the heater to suppress an increase in the internal pressure of the tank. A fuel supply system for a hydrogen aircraft.

9. A method for adjusting the internal pressure of a tank applied to a hydrogen aircraft, The hydrogen aircraft includes A propulsion device that uses hydrogen as an energy source, A fuel tank for storing liquefied hydrogen, A pump that discharges liquefied hydrogen from the fuel tank and supplies it to the propulsion device, A heater that increases the internal pressure of the fuel tank, which is the internal pressure of the fuel tank, A control device to which an operation on the hydrogen aircraft is input, and The method includes Predicting whether the discharge flow rate of the liquefied hydrogen from the fuel tank increases or decreases based on information regarding the operation performed on the control device, When it is predicted that the discharge flow rate of the liquefied hydrogen from the fuel tank increases, the heater is controlled to increase the internal pressure of the tank, A method for adjusting the internal pressure of a tank in a hydrogen aircraft, including controlling the heater to suppress the internal pressure of the tank when it is predicted that the discharge flow rate of the liquid hydrogen from the fuel tank will decrease.

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