Fuel supply system of hydrogen air vehicle

Abstract

To provide a fuel supply system of a hydrogen air vehicle which can stabilize an inlet pressure of a pump which discharges liquid hydrogen from a fuel tank, and to provide a tank internal pressure adjustment method.SOLUTION: A fuel supply system (1) of a hydrogen air vehicle includes: a fuel tank (2) for storing liquid hydrogen; a pump (5) which discharges the liquid hydrogen from the fuel tank (2) to supply the liquid hydrogen to a propulsion unit (102); a plurality of heaters (31) which increase a tank internal pressure which is a pressure in the fuel tank (2); a plurality of temperature sensors (SN2) which respectively detect temperatures of the heaters (31); and a pressure controller (73) which controls the heaters (31) to regulate the tank internal pressure. When the pressure controller (73) determines that an abnormality occurs in any of the heaters (31) based on input information from the temperature sensors (SN2), the pressure controller (73) stops the heater (31) with the abnormality.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A known hydrogen aircraft is disclosed in Patent Document 1. 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 is provided to discharge the liquefied hydrogen from the fuel tank toward the propulsion device. The pressure of the liquefied hydrogen introduced into this pump, i.e., the pump inlet pressure, is affected by the tank internal pressure, which is the pressure inside the fuel tank. Therefore, if the tank internal pressure fluctuates inadvertently, the pump inlet pressure will fluctuate, which could cause the discharge flow rate of the liquefied hydrogen to become unstable. Furthermore, repeated fluctuations in the tank internal pressure could, in the worst case scenario, cause the tank to fail due to fatigue. For this reason, if fluctuations in the tank internal pressure are expected, the tank's fatigue strength must be set in anticipation of this effect, which could result in an increase in tank weight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2022 / 0227497 Summary of the Invention

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a fuel supply system and tank internal pressure adjustment method for a hydrogen aircraft that can stabilize the inlet pressure of a pump that discharges liquefied hydrogen from a fuel tank.

[0006] In order to solve the above problem, a system according to one aspect of the present disclosure is a fuel supply system for a hydrogen aircraft including a propulsion device that uses hydrogen as an energy source, the system comprising: a fuel tank that stores liquefied hydrogen; a pump that discharges liquefied hydrogen from the fuel tank and supplies it to the propulsion device; heaters that are arranged in the fuel tank and increase the internal tank pressure, which is the pressure inside the fuel tank; a plurality of temperature sensors that detect the temperatures of the heaters; and a pressure controller that controls the heaters to adjust the internal tank pressure, wherein the pressure controller, when it determines based on input information from the temperature sensors that there is an abnormality in any of the heaters, stops the heater that has been determined to have the abnormality.

[0007] According to the present disclosure, it is possible to stabilize the inlet pressure of a pump that discharges liquefied hydrogen from a fuel tank. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing a schematic configuration of a hydrogen aircraft to which a fuel supply system according to a first embodiment of the present disclosure is applied. [Figure 2] FIG. 2 is a system diagram showing a schematic configuration of the fuel supply system. [Figure 3] FIG. 3 is a time chart showing the time variations of each parameter observed during control to adjust the internal pressure of the fuel tank. [Figure 4] FIG. 4 is a diagram showing a fuel supply system according to the second embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram showing a fuel supply system according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] 1. Fuel supply system FIG. 1 is a front view showing the 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 a propulsion energy source (fuel), and comprises an airframe 101 and multiple engines 102 (propulsion devices) attached to the airframe 101. The airframe 101 includes a fuselage 101a and a pair of wings 101b attached to the left and right sides of the fuselage 101a. The engines 102 are attached to each of the pair of wings 101b. The engines 102 are hydrogen turbine engines that include gas turbines that are rotationally driven by the combustion energy of hydrogen.

[0010] 2 is a system diagram showing the general 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 an engine 102, and is installed inside an aircraft body 101. The fuel supply system 1 includes a fuel tank 2, a pressure boosting mechanism 3, a fuel supply pipe 4, a pump 5, a pressure limiting mechanism 6, and a controller 7.

[0011] The fuel tank 2 is a container that stores liquefied hydrogen (LH), which is cryogenically liquefied hydrogen. The fuel tank 2 is both thermally insulating and pressure-resistant, and stores the liquefied hydrogen (LH) inside while keeping it cold and pressurized. 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 a middle portion formed in a cylindrical shape. However, the shape is not limited to this as long as it can maintain high pressure.

[0012] A gas phase 2a is formed above the liquefied hydrogen LH inside the fuel tank 2. The gas phase 2a is a space occupied by hydrogen gas including boil-off gas (BOG) generated when the liquefied hydrogen LH evaporates due to heat input. A pressure sensor SN1 is attached to the fuel tank 2 to detect the internal tank pressure, which is the pressure in the gas phase 2a.

[0013] The pressure-boosting mechanism 3 is a mechanism that increases the pressure inside the tank. In this embodiment, the pressure-boosting mechanism 3 includes a plurality of heaters 31 that are arranged inside the fuel tank 2. The plurality of heaters 31 are arranged near the bottom of the fuel tank 2 with spaces between them. The heaters 31 that are located in such positions are likely to be immersed in the liquefied hydrogen LH in the fuel tank 2.

[0014] The heater 31 heats the liquefied hydrogen LH by, for example, receiving a supply of electric power from an external power source to raise its temperature. When the liquefied hydrogen LH is heated by the heater 31, evaporation (vaporization) of the liquefied hydrogen LH is promoted, and the internal tank pressure increases. In other words, heating by the heater 31 promotes the evaporation of the liquefied hydrogen LH, thereby increasing the amount of gas (hydrogen gas) present in the gas phase portion 2a of the fuel tank 2 and increasing the pressure in the gas phase portion 2a, i.e., the internal tank pressure. In this way, the pressure-boosting mechanism 3 is configured to increase the internal tank pressure by heating the liquefied hydrogen LH and promoting its evaporation.

[0015] A temperature sensor SN2 is attached to each of the heaters 31. The temperature sensor SN2 is a sensor that detects the temperature of the heater 31 and is provided to determine whether or not there is a heating abnormality in which the temperature of the heater 31 rises abnormally.

[0016] 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 that is disposed inside the fuel tank 2 and the other end that is connected to the engine 102. One end of the fuel supply pipe 4 extends to the vicinity of the bottom of the fuel tank 2.

[0017] The pump 5 is an electric pump that sends the liquefied hydrogen LH in the fuel tank 2 to the engine 102 through the fuel supply pipe 4. The pump 5 is provided midway along the fuel supply pipe 4, located outside the fuel tank 2. The pump 5 sucks the liquefied hydrogen LH out of the fuel tank 2 and discharges the sucked liquefied hydrogen downstream toward the engine 102. The pump 5 is not limited to being electric, and may be, for example, a mechanical pump that uses the shaft power of the engine 102.

[0018] A flow rate adjustment valve 9 is provided in the fuel supply pipe 4 at a position downstream of the pump 5. The flow rate adjustment valve 9 is an electrically operated valve that adjusts the flow rate of liquefied hydrogen LH supplied to the engine 102 through the fuel supply pipe 4.

[0019] The pressure limiting mechanism 6 is a mechanism for limiting the pressure inside the tank so that it 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.

[0020] The vent pipe 61 is a pipe connected to the top of the fuel tank 2, and connects the gas phase section 2a of the fuel tank 2 to the outside air.

[0021] The internal pressure control valve 62 is a valve that opens when the tank internal pressure, which is the pressure in the gas phase section 2a, exceeds a predetermined upper limit, and is provided midway along the vent pipe 61. The internal pressure control valve 62 may be either mechanical or electrical. When the internal pressure control valve 62 opens, hydrogen gas is discharged from the gas phase section 2a of the fuel tank 2 to the outside air through the vent pipe 61. This limits the tank internal pressure to below the upper limit.

[0022] The flame arrestor 63 is a device that prevents the progression of flames upstream (backfire), and is disposed in the vent pipe 61 at a position downstream of the internal pressure control valve 62. The flame arrestor 63 is provided as a measure against fires that occur outside the fuel tank 2.

[0023] The check valve 64 is a valve that restricts the flow of gas through the vent pipe 61 to one direction, and is disposed in the vent pipe 61 at a position downstream of the flame arrestor 63. Specifically, the check valve 64 allows hydrogen gas to flow from the inside of the fuel tank 2 (gas phase portion 2a) to the outside air through the vent pipe 61, while prohibiting gas from flowing from the outside air into the inside of the fuel tank 2 through the vent pipe 61.

[0024] The vent heater 65 is a heater that heats the hydrogen gas discharged through the vent pipe 61, and is disposed at the downstream end of the vent pipe 61. The vent heater 65 is provided to prevent the hydrogen gas from being released into the outside air while still at an extremely low temperature.

[0025] The branch pipe 66 is a pipe that connects a portion of the vent pipe 61 to the fuel tank 2. Specifically, the branch pipe 66 connects a portion of the vent pipe 61 between the internal pressure control valve 62 and the flame arrestor 63 to the upper portion of the fuel tank 2. It is not essential that the branch pipe 66 connects a portion of the vent pipe 61 to the fuel tank 2. For example, a pipe that corresponds to the branch pipe 66 extending from the fuel tank 2 may be connected to a flame arrestor different from the flame arrestor 63 and communicated with the outside of the aircraft.

[0026] The emergency relief valve 67 is a valve that opens when the tank internal pressure exceeds a predetermined abnormal value, and is provided midway along the branch pipe 66. The emergency relief valve 67 may be either mechanical or electrical. The pressure (abnormal value) at which the emergency relief valve 67 opens is greater than the pressure (upper limit) at which the above-mentioned internal pressure control valve 62 opens. Such an emergency relief valve 67 functions as a backup in case the internal pressure control valve 62 does not operate normally.

[0027] 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 aircraft controller 72, and a tank internal pressure controller 73. The FADEC 71 is a control module that mainly controls the engine 102. The aircraft controller 72 is a control module that mainly controls the aircraft 101. The tank internal pressure controller 73 is a control module that controls the tank internal pressure, which is the pressure inside the fuel tank 2 (gas phase portion 2a). The FADEC 71, the aircraft controller 72, and the tank internal pressure controller 73 each include a processor and a memory. All or some of the FADEC 71, the aircraft controller 72, and the tank internal pressure controller 73 may be configured to use a common processor or memory. Note that the FADEC 71 corresponds to the "flow rate controller" in this disclosure, and the tank internal pressure controller 73 corresponds to the "pressure controller" in this disclosure.

[0028] The FADEC 71 is signal-connected to the engine 102 and the flow rate control valve 9. The FADEC 71 controls each control element within the engine 102 so that the output of the engine 102 becomes an appropriate value according to the operating conditions, and also controls the opening of the flow rate control 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.

[0029] The FADEC 71 is also connected in terms of signals to a control device 103 provided in the cockpit of the aircraft 101. The control device 103 includes, for example, a control stick for controlling the attitude of the aircraft 101 and a power lever for controlling the output of the engine 102. Signals including the amounts of operation of the control stick and power lever are sequentially input to the FADEC 71 as control signals.

[0030] 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 supply of electricity to each heater 31 so that the tank internal pressure falls within a certain range.

[0031] 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 is sequentially input to the tank internal pressure controller 73, and information on the temperature of the heater 31 detected by the temperature sensor SN2 is sequentially input to the tank internal pressure controller 73.

[0032] 2. Tank internal pressure control Next, details of the control by the tank internal pressure controller 73 will be described. In this embodiment, two types of control (first and second controls) are provided as the control of the tank internal pressure by the tank internal pressure controller 73. The first control is a control that activates the heater 31 based on input information from the FADEC 71, and the second control is a control that activates the heater 31 based on input information from the pressure sensor SN1. The first control is a primary control that is always performed while the engine 102 is operating, and the second control is a backup control for when the first control is not performed normally.

[0033] FIG. 3 is a time chart for explaining the first and second controls described above. The upper chart in FIG. 3 shows the change over time in the tank internal pressure, and the lower chart shows the change over time in the heater output. The first control will be explained first using the chart in FIG. 3. In this first control, as shown by the solid waveform in the lower chart, the heater 31 is turned ON at time t1 to start supplying electricity to the heater 31, and then, at time t4, the heater 31 is turned OFF to stop supplying electricity to the heater 31. Time t1 is the time when flow rate increase information indicating an increase in the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 is input from the FADEC 71 to the tank internal pressure controller 73. Time t4 is the time when flow rate decrease information indicating a decrease in the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 is input from the FADEC 71 to the tank internal pressure controller 73.

[0034] The flow rate increase information and the flow rate decrease information are information issued by the FADEC 71 based on a predicted change in the output of the engine 102. For example, when at least one of an operation to lift the aircraft 101 and an operation to increase the output (rotation speed) of the engine 102 is performed on the flight 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 flow rate increase information to the tank internal pressure controller 73. Conversely, when at least one of an operation to cancel the lift of the aircraft 101 and an operation to reduce the engine output is performed on the flight 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 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 such an operation status of the flight control device 103, and may be information based on a control signal transmitted from the FADEC 71 to the flow control valve 9, for example.

[0035] When flow rate increase information is input at time t1 in Figure 3, the tank internal pressure controller 73 switches the heater 31 from OFF to ON. This increases the temperature of the heater 31, promoting the evaporation (vaporization) of the liquefied hydrogen LH in the fuel tank 2. However, since it takes time for evaporation to actually be promoted, for a while after time t1, the effect of decreasing the tank internal pressure due to the increase in the amount of liquefied hydrogen LH discharged from the fuel tank 2 is greater than the effect of increasing the tank internal pressure due to the evaporation of the liquefied hydrogen LH. This is why, in the upper chart of Figure 3, the tank internal pressure continues to decrease from time t1 to time t3. On the other hand, after time t3, the effect of the evaporation of the liquefied hydrogen LH becomes apparent, and the tank internal pressure begins to rise.

[0036] When the flow rate reduction information is input at time t4, which is later than time t3, the tank internal pressure controller 73 switches the heater 31 from ON to OFF. This reduces the temperature of the heater 31, making it more difficult for the liquefied hydrogen LH to evaporate. This, combined with the reduction in the flow rate of the liquefied hydrogen LH, has the effect of suppressing the increase in the tank internal pressure. However, for a while after time t4, the tank internal pressure increases due to the residual heat of the heater 31. This is why, in the upper chart of FIG. 3, the tank internal pressure continues to increase from time t4 to time t6. On the other hand, after time t6, the increase in the tank internal pressure due to the residual heat is outweighed by the decrease in the tank internal pressure due to the liquid hydrogen LH being discharged from the fuel tank 2, and the tank internal pressure begins to decrease.

[0037] As described above, in the first control, the tank internal pressure controller 73 controls the heater 31 based on input information from the FADEC 71. However, for example, it is possible that the signal from the FADEC 71 may be interrupted for some reason. The second control is designed to handle such a case, and is a control that turns the heater 31 on / off based on input information from the pressure sensor SN1 rather than input information from the FADEC 71.

[0038] In the second control, the heater 31 is turned on at time t2 and then turned off at time t5, as shown by the dashed waveform in the lower chart of Fig. 3. As shown by the dashed waveform in the upper chart of Fig. 3, time t2 is the time when the detected value of the tank internal pressure 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 tank internal pressure exceeds a predetermined second threshold value X2.

[0039] The first threshold value X1 is set to a value greater than the lower limit of the tank internal pressure. The lower limit of the tank internal pressure is a limit value that ensures normal discharge operation of the pump 5. If the tank internal pressure falls below this lower limit value, the pressure of the liquefied hydrogen LH introduced from the fuel tank 2 to the pump 5, i.e., the inlet pressure of the pump 5, will become too low, which could cause the discharge operation of the liquefied hydrogen LH by the pump 5 to become unstable. Therefore, the first threshold value X1 is set to a level higher than this lower limit value so that the heater 31 is turned on before the tank internal pressure drops to this lower limit value.

[0040] The second threshold value X2 is set to a value greater than the first threshold value X1 and less than the upper limit of the tank internal pressure. The upper limit of the tank internal pressure is the pressure at which the internal pressure control valve 62 of the pressure limiting mechanism 6 described above opens, i.e., the pressure at which forced venting of hydrogen gas occurs from the fuel tank 2. The second threshold value X2 is set to a level lower than the upper limit so that the heater 31 is turned off before the tank internal pressure rises to this upper limit.

[0041] 3, at time t2 when the detected value of the tank internal pressure falls below the first threshold value X1, the tank internal pressure controller 73 switches the heater 31 from OFF to ON. By switching the heater 31 ON, the temperature of the heater 31 rises, promoting the evaporation of the liquefied hydrogen LH. As a result, the tank internal pressure begins to rise after a certain delay time.

[0042] 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. By turning the heater 31 OFF, the temperature of the heater 31 drops, and evaporation of the liquefied hydrogen LH is suppressed. As a result, the tank internal pressure starts to decrease after a certain delay time.

[0043] As described above, in the second control, the tank internal pressure controller 73 controls the heater 31 based on the detected tank pressure value input from the pressure sensor SN1. Therefore, the control timing of the heater 31 in the second control is slower than in the first control, which controls the heater 31 based on input information from the FADEC 71. That is, time t2, when the heater 31 is turned on in the second control, is later than time t1, when the heater 31 is turned on in the first control, and time t5, when the heater 31 is turned off in the second control, is later than time t4, when the heater 31 is turned off in the first control. From time t1 to time t3 in the upper chart of FIG. 3 , the dashed waveform is lower than the solid waveform, widening the difference between the solid and dashed waveforms. This indicates that the heater 31 heats up more slowly in the second control than in the first control, resulting in a greater pressure drop rate in the second control than in the first control. 3, the point in time corresponding to the valley of the dashed waveform is later than the point in time (time t3) corresponding to the valley of the solid waveform. This indicates that the point in time when the pressure rises is later under the second control than under the first control because the heating of the heater 31 is slower under the second control than under the first control.

[0044] Depending on the attitude of the aircraft 101, at least some of the heaters 31 may rise above the liquid surface of the liquefied hydrogen LH in the fuel tank 2. For example, if the aircraft 101 tilts significantly, the angle difference between the bottom of the fuel tank 2 and the liquid surface of the liquefied hydrogen LH increases, and some of the heaters 31 may rise above the liquid surface. The heaters 31 that rise above the liquid surface are more likely to rise in temperature than the other heaters 31 that are immersed in the liquefied hydrogen LH. In other words, the heaters 31 rising above the liquid surface can be considered to be a heating abnormality, in which the temperature of the heaters 31 rises abnormally. Control when such a heating abnormality occurs will be described below.

[0045] While the engine 102 is running, the tank pressure controller 73 determines whether or not there is a heating abnormality, in which the temperature is abnormally rising, for each heater 31, based on input information from each temperature sensor SN2 provided in the heaters 31. If it is determined that the heating abnormality has occurred in any of the heaters 31, the tank pressure controller 73 stops power to the heater 31 with the heating abnormality, turning the heater 31 OFF. In other words, by stopping power, the temperature of the heater 31 is lowered, and the heating abnormality of the heater 31 is resolved.

[0046] Furthermore, if a heating abnormality in a heater 31 is confirmed, the tank internal pressure controller 73 not only controls the heater 31 with the heating abnormality to be turned off as described above, but also controls the other heaters 31 that are not experiencing a heating abnormality to increase their output (amount of current flow). This control increases the temperature of the other heaters 31 immersed in the liquefied hydrogen LH, promoting the evaporation of the liquefied hydrogen LH. This compensates for the decrease in the amount of heat generated by some of the heaters 31 rising above the liquid surface of the liquefied hydrogen LH, and serves to maintain the effect of increasing the tank internal pressure due to the evaporation of the liquefied hydrogen LH.

[0047] 3. Effects As described above, in this embodiment, while the engine 102 is operating and the liquefied hydrogen LH in the fuel tank 2 is being 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, thereby adjusting the internal tank pressure, which is the pressure inside the fuel tank 2. 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 increases the temperature of the heater 31 to increase the internal tank pressure. With this 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.

[0048] That is, in this embodiment, when the flow rate of the liquefied hydrogen LH increases, that is, when the rate of increase in the volume of the gas phase 2a in the fuel tank 2 increases, the evaporation of the liquefied hydrogen LH is promoted by the heating of the heater 31, and the decrease in the tank internal pressure caused by the increase in the volume of the gas phase 2a can be compensated for by the pressurization effect of the evaporated hydrogen (hydrogen gas). This makes it possible to keep the tank internal pressure within a certain range regardless of changes in the flow rate of the liquefied hydrogen LH, and stabilize the inlet pressure of the pump 5. When the inlet pressure of the pump 5 is stabilized, it becomes easier to match the discharge rate of the liquefied hydrogen LH by the pump 5 to a target amount, and 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.

[0049] 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 suppresses an increase in the tank internal pressure by lowering the temperature of the heater 31. With this configuration, it is possible to avoid the heater 31 continuing to heat the tank when the rate of increase in the volume of the gas phase portion 2a is slowing down, and it is possible to prevent an excessive increase in the tank internal pressure.

[0050] Furthermore, in this embodiment, a pressure sensor SN1 that detects the tank internal pressure is attached to the fuel tank 2, and when the pressure detected by the pressure sensor SN1 falls below a first threshold value X1, control is executed to increase the temperature of the heater 31 to increase the tank internal pressure. Conversely, when the pressure detected by the pressure sensor SN1 exceeds a second threshold value X2 that is greater than the first threshold value X1, control is executed to decrease the temperature of the heater 31 to suppress an increase in the tank internal pressure. With this configuration, even if the signal from the FADEC 71 is interrupted for some reason, that is, even if information regarding the flow rate of the liquefied hydrogen LH becomes unavailable, the inlet pressure of the pump 5 can be stabilized by controlling the heater 31 based on the actual tank internal pressure.

[0051] Furthermore, in this embodiment, during operation of the engine 102 in which the tank internal pressure is adjusted using the heaters 31 as described above, each of the heaters 31 is checked to see if a heating abnormality, in which the temperature is abnormally increased, has occurred. If a heating abnormality is confirmed in any of the heaters 31, the heater 31 with the heating abnormality is stopped and control is executed to increase the output of the other heaters 31. With this configuration, for example, if some of the heaters 31 rise above the liquid surface of the liquefied hydrogen LH due to a change in the attitude of the aircraft 101, the heating abnormality of the heaters 31 caused by this can be resolved. Furthermore, because 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 amount of heat caused by some of the heaters 31 rising above the liquid surface of the liquefied hydrogen LH, and the effect of increasing the tank internal pressure due to the evaporation of the liquefied hydrogen LH can be maintained.

[0052] 4. Variations In the first embodiment, the engine 102, which is a hydrogen turbine engine, is used as the propulsion device that provides thrust to the aircraft 101. However, the propulsion device is not limited to an engine as long as it generates thrust using hydrogen as an energy source. For example, a fuel cell system can also be used as the propulsion device. The fuel cell system can include, for example, a power generation unit that generates electricity through a chemical reaction between hydrogen and oxygen, a power storage unit that stores the electricity generated by the power generation unit, and a motor that rotates and drives a turbine or a propeller using the electricity 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.

[0053] In the first embodiment, the pressure-increasing mechanism 3 including a plurality of heaters 31 arranged in the fuel tank 2 is provided as a mechanism for increasing the tank internal pressure, which is the pressure inside the fuel tank 2 (gas phase portion 2a). However, the pressure-increasing mechanism may include at least one heater. That is, the number of heaters arranged in the fuel tank may be one or two or more. The shape of the heater 31 is also not particularly limited. The heater 31 may be sheet-shaped or may be elongated in the longitudinal direction.

[0054] Furthermore, the heater does not necessarily have to be located inside the fuel tank, but may be located outside the fuel tank. For example, it is conceivable to provide a reflux line that draws liquefied hydrogen from the fuel tank and returns it to the fuel tank, and to provide a heater on this reflux line.

[0055] Furthermore, elements other than a heater can be used as the pressure-boosting mechanism. For example, an accumulator for storing high-pressure hydrogen gas can be provided separately from the fuel tank, and hydrogen gas can be supplied to the fuel tank from the accumulator when the discharge flow rate of liquefied hydrogen from the fuel tank increases (when the tank internal pressure decreases). Even in this case, the tank internal pressure can be kept within a certain range, thereby stabilizing the pump inlet pressure.

[0056] The pressure boosting mechanism may be controlled to adjust the tank internal pressure based on any of the following information: information regarding the output of the engine 102, information regarding the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102, and information regarding an operation performed on the control device 103. The information regarding the output of the engine 102 can be obtained from a control signal for the engine 102 output from the controller 7. The information regarding the flow rate of liquefied hydrogen LH discharged from the fuel tank 2 toward the engine 102 can be obtained from a control signal sent 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 regarding an operation 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.

[0057] In the first embodiment, the pressure limiting mechanism 6 is a mechanism for discharging hydrogen gas in the gas phase section 2a of the fuel tank 2 to the outside air, but the pressure limiting mechanism may also be a mechanism for recovering the pressure discharged from the gas phase section 2a in a recovery vessel.

[0058] [Second embodiment] A second embodiment of the present disclosure will be described below. Fig. 4 is a diagram showing a fuel supply system for a hydrogen aircraft according to the second embodiment of the present disclosure.

[0059] 1. Control System (1) The controller monitors the tank internal pressure detected by the pressure sensor and controls the opening of the electronic internal pressure control valve and the heating time by the tank pressurization heater or the pressurization time by the accumulator to maintain a constant pressure inside the tank. By controlling the pressure at a constant level, the pump inlet pressure is kept constant, resulting in a stable pump discharge pressure.

[0060] (2) The pressure inside the tank is maintained at a constant level even when the pump transfer rate changes depending on the engine operating conditions.

[0061] (3) The tank pressure controller receives data on the engine and pump status and fuel volume from the engine control unit, and controls the tank pressure and performs fault diagnosis.

[0062] (4) The tank pressure controller monitors the amount of fuel in the tank and, in response to aircraft attitude signals, corrects any changes in the liquid level and displays the correct volume.

[0063] 2.Components (1) There is one or more tank pressurization heaters. If there are multiple tank pressurization heaters, redundancy can be ensured.

[0064] (2) The pump may be installed either inside or outside the tank. If the pump is installed outside for ease of maintenance, the impeller part should be installed inside the tank and the motor part should be installed outside the tank. In other words, only the motor part, which is prone to failure, can be replaced without draining the liquid hydrogen from the tank.

[0065] (3) The internal pressure control valve and emergency relief valve shall operate both on the ground and at high altitudes, and their operating pressure may be either absolute or gauge pressure. Each valve may be either mechanical or electrical.

[0066] 3.Placement (1) The tank pressure heater should be installed away from the fuel capacity meter and pump to avoid the effect of hydrogen vaporization when the tank pressure heater is activated.

[0067] 4. Energy Reduction (1) In addition to the tank pressurization heater, the liquid hydrogen is vaporized (boiled off) by heat generated by pumps or other equipment, and the inside of the tank is pressurized, thereby reducing the power consumption of the tank pressurization heater.

[0068] (2) By returning a portion of the pressurized liquid hydrogen downstream of the pump to the tank, the internal pressure of the tank is increased and the power consumption of the tank pressurization heater is reduced.

[0069] As shown in Figure 1, the tank pressure controller controls the tank pressurization heater and internal pressure control valve in accordance with the pressure reduction effect caused by supplying fuel to the engine, and by increasing or decreasing the pressure inside the tank, the internal tank pressure is maintained at the desired target value.In addition, an emergency relief valve is also installed to prevent the tank from being pressurized above a predetermined value in the event of an emergency or when the aircraft is parked.

[0070] [Third embodiment] A third embodiment of the present disclosure will now be described. Figure 5 is a diagram showing a fuel supply system for a hydrogen aircraft according to the third embodiment of the present disclosure. In this specification, "signally connected" means that multiple devices are connected by wire or wirelessly so that electrical signals for information transmission can be sent or received between them.

[0071] 1.Components (1) Fuel tank The fuel tank is used to store liquid hydrogen inside. It is made of metal (aluminum, etc.) or composite material (CFRP, GFRP, etc.). The fuel tank shown in Figure 2 has hemispherical end sections and a cylindrical middle section. However, this is not a limitation as long as it can maintain high pressure.

[0072] (2) Tank internal pressure controller The tank pressure controller controls the internal pressure of the fuel tank to a desired value or within a desired range by exchanging signals with multiple components of the fuel supply system. The tank pressure controller is equipped with a processor and memory. The tank pressure controller's memory stores programs for achieving the desired control results and various data used by the programs (various threshold values, etc.). The programs stored in the memory are executed by the processor.

[0073] (3)Fuel supply piping The fuel supply pipe is for supplying 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 also include a return pipe that returns a portion of the pressurized liquid hydrogen located downstream of the pump to the tank. The return pipe may be provided with a flow control valve for controlling the amount of liquid hydrogen returned, and the flow control valve may be signal-connected to a tank internal pressure controller.

[0074] (4) Pump (not shown) The pump is connected to the fuel supply pipe to flow liquid hydrogen through the fuel supply pipe. The pump is also connected to a tank internal pressure controller via signals. The pump may be provided inside or outside the fuel tank. Alternatively, part of the pump may be provided inside the fuel tank and the other part outside the fuel tank. When the pump is provided inside the fuel tank, heat generated during pump operation can be used to heat the liquid hydrogen fuel for pressurizing the fuel tank, as described below. Providing the pump outside the fuel tank facilitates pump maintenance. When a pump having an impeller and a motor is used, the impeller may be provided inside the fuel tank, while the motor, which is more likely to be maintained, may be provided outside the fuel tank. This allows the motor to be replaced without draining the liquid hydrogen from the fuel tank. In this case, the pump penetrates the wall of the fuel tank, and the gap between the pump and the wall of the fuel tank is sealed to prevent leakage of liquid hydrogen.

[0075] (5) Tank pressure heater The tank pressurization heater (heater) is installed inside the fuel tank to increase the internal pressure of the fuel tank. The tank pressurization heater is also connected to the tank internal pressure controller via signals. When the tank pressurization heater is activated, a portion of the liquid hydrogen in the fuel tank is heated and vaporized, increasing its volume. This increases the internal pressure of the fuel tank. The tank pressurization heater may be installed in a position inside the fuel tank where liquid hydrogen is present or where no liquid hydrogen is present. The tank pressurization heater may be installed at the bottom of the fuel tank. For fuel tanks with a cylindrical middle section as shown in FIG. 2, the tank pressurization heater may be installed at the bottom of the cylindrical shape. By locating the tank pressurization heater as low as possible, liquid hydrogen can be heated regardless of the amount of liquid hydrogen stored in the fuel tank. Multiple tank pressurization heaters may be installed for redundancy. To avoid the influence of hydrogen vaporization when the tank pressurization heater is activated, the tank pressurization heater is installed away from the fuel volume gauge and the pump (if the pump is installed inside the fuel tank). For example, the fuel capacity meter and pump may be positioned so that they are not above the tank pressurization heater, or the fuel capacity meter and pump may be positioned outside the range where hydrogen vaporized by the tank pressurization heater moves upward through the liquid hydrogen (the range where vaporized hydrogen exists).

[0076] (6) Internal pressure control valve The internal pressure control valve opens and closes in response to a signal from the tank internal pressure controller. Opening the internal pressure control valve allows the internal pressure of the fuel tank to approach atmospheric pressure (normally the internal pressure of the fuel tank decreases). The internal pressure control valve is selected to operate both on the ground and at high altitudes. The internal pressure control valve may operate on either absolute pressure or gauge pressure, and may be mechanically or electrically operated.

[0077] (7) Emergency relief valve The emergency relief valve maintains the internal pressure of the fuel tank within a safe range. If the internal pressure of the fuel tank exceeds a predetermined threshold, the emergency relief valve opens to release the pressure inside the fuel tank.

[0078] (8) Pressure sensor The pressure sensor detects the internal pressure of the fuel tank and is connected to the tank internal pressure controller via signals. The pressure sensor is provided in an area (gas phase) within the fuel tank where liquid hydrogen is not present. The pressure sensor may be provided within the fuel tank above the upper limit where liquid hydrogen can be present. If the fuel tank has a mechanism that prevents the amount of liquid hydrogen in the fuel tank from exceeding an upper limit, the pressure sensor may be provided above the upper limit where liquid hydrogen of that amount can be present at least when the aircraft is in a steady state (parked or level flight). The location of the pressure sensor is not limited to the above location, and it may be located, for example, midway along a pipe extending from the fuel tank and connected to the emergency relief valve.

[0079] (9)Fuel capacity meter The fuel capacity meter is used to detect the amount of liquid hydrogen stored in the fuel tank.

[0080] (10) Accumulator (not shown) The accumulator serves to increase the internal pressure in the fuel tank, and is connected to the fuel tank so as to allow fluid to flow into the fuel tank, and is also signal-connected to the tank internal pressure controller.

[0081] (11) Engine control unit (not shown) The engine control unit (FADEC) controls the engine and is connected to the tank pressure controller via signals.

[0082] 2. Control <Purpose of control> By controlling the internal pressure of the tank to a constant value or within a certain range, the pump inlet pressure is kept at a constant value or within a certain range, thereby obtaining a stable pump discharge pressure.

[0083] <Control method> The control method will be described below. The entire method may be included in the program, or only some of the method may be included in the program.

[0084] (1) If the internal pressure control valve is electric, the tank internal pressure controller reads the detected value of the pressure sensor, and if the detected 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.

[0085] (2) The tank internal pressure controller reads the detected value of the pressure sensor, and if the detected value is smaller than a predetermined value, the tank internal pressure controller sends a signal to the tank pressurization heater to heat the liquid hydrogen. The tank internal pressure controller controls the heating time of the tank pressurization heater. If the tank pressurization heater has a heating temperature adjustment function, the tank internal pressure controller may also control the heating temperature of the tank pressurization heater.

[0086] (3) The tank internal pressure controller reads the pressure sensor's detection value, and if the detection value is smaller 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 accumulator's pressurization time.

[0087] (4) The tank internal pressure controller may receive a signal from the engine (not shown) regarding the operating status (such as the level of power output) of the engine and control the internal pressure control valve, tank pressurization heater, and accumulator based on that signal. This allows for more accurate control of the fuel tank internal pressure even when the pump transfer rate changes depending on the engine operating status. In other words, when the pump transfer rate changes depending on the engine operating status, the rate at which liquid hydrogen in the fuel tank is reduced also changes, causing fluctuations in the internal pressure of the fuel tank due to the reduction in liquid hydrogen, which adversely affects control. However, this adverse effect can be avoided. The operating status signal may be obtained from the engine control unit or from the detected values ​​of various sensors installed on the aircraft.

[0088] (5) The tank pressure controller receives data on the engine and pump status and fuel quantity from the engine control unit, and controls the fuel tank pressure and diagnoses faults.

[0089] (6) The tank internal pressure controller may read the detected value of the fuel capacity meter and control the internal pressure control valve, tank pressurization heater, and accumulator based on the detected value. Since the liquid hydrogen level in the fuel tank changes depending on the aircraft's attitude, the tank internal pressure controller may correct the detected value of the fuel capacity meter based on aircraft attitude information. Aircraft attitude information can be obtained from the detected values ​​of various sensors equipped on the aircraft.

Claims

1. A fuel supply system for a hydrogen aircraft including a propulsion device that uses hydrogen as an energy source, comprising: 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 plurality of heaters disposed in the fuel tank, the heaters increasing the internal tank pressure; a plurality of temperature sensors each detecting a temperature of the heater; a pressure controller that controls the heater to adjust the internal pressure of the tank, When the pressure controller determines that any of the heaters has an abnormality based on input information from the temperature sensor, the pressure controller stops the heater determined to have an abnormality.

2. 2. The fuel supply system of claim 1, When the pressure controller determines that any of the heaters has an abnormality based on input information from the temperature sensor, the pressure controller increases the output of the heaters other than the heater determined to have the abnormality.

3. 3. The fuel supply system according to claim 1 or 2, The abnormality is a heating abnormality in which the temperature of the heater rises abnormally.

4. 3. The fuel supply system according to claim 1 or 2, a flow rate controller for controlling the flow rate of liquefied hydrogen supplied from the fuel tank to the propulsion device; The pressure controller controls the heater based on information about the flow rate of the liquefied hydrogen input from the flow rate controller.

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