Fuel cell system and aircraft

Abstract

The present application provides a fuel cell system and an aircraft, which can improve the performance of a fuel cell even at a high altitude. The fuel cell system is used for an aircraft, and is characterized by comprising: a fuel cell; an oxidant gas system that supplies an oxidant gas to the fuel cell; an altitude sensor; and a control unit, wherein the oxidant gas system includes an air compressor and a bypass flow path that bypasses the fuel cell, the bypass flow path includes a bypass valve, and when an increase in altitude measured by the altitude sensor is detected, the control unit increases the rotation speed of the air compressor and increases the opening degree of the bypass valve.

Description

Technical Field

[0001] This disclosure relates to fuel cell systems and aircraft. Background Technology

[0002] A fuel cell (FC) consists of a single cell (hereinafter referred to simply as a cell) or a fuel cell stack (hereinafter referred to simply as a cell stack) composed of multiple stacked single cells. It is a power generation device that extracts electrical energy through the electrochemical reaction of fuel gas such as hydrogen and oxidant gas such as oxygen. In many cases, the fuel gas and oxidant gas actually supplied to the fuel cell are mixtures with gases that do not contribute to oxidation / reduction. Air, which includes oxygen, is particularly common as the oxidant gas.

[0003] In some cases, fuel gas and oxidant gas are not specifically distinguished and are simply referred to as "reaction gas" or "gas". Additionally, both single cells and fuel cell stacks composed of stacked single cells are sometimes referred to as fuel cells.

[0004] Various studies have been conducted on fuel cells.

[0005] For example, Patent Document 1 discloses an aircraft equipped with a fuel cell.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-081559

[0007] When fuel cells are mounted on aircraft, they generate electricity at higher altitudes and lower air pressures compared to when they are mounted on vehicles.

[0008] In an oxidant gas system, when a fuel cell generates electricity at extremely high altitudes, the oxygen partial pressure decreases as the altitude increases, thus reducing the power generation performance of the fuel cell.

[0009] In addition, when fuel cells generate electricity at ultra-high altitudes, the air pressure is lower than at ground level. Therefore, in order to make the oxygen supply the same as at ground level, the air compressor needs to rotate at a speed higher than the normal speed at ground level to increase the air flow. As a result, the air velocity (volume flow rate) increases. Since more water vapor is carried away from the fuel cell, the fuel cell becomes drier, the power generation performance decreases, and the durability of the fuel cell is also reduced due to power generation in a dry state.

[0010] In fuel gas systems, when fuel cells generate electricity at extremely high altitudes, the pressure difference between the inside and outside of the fuel cell (the pressure difference between the inlet and outlet of the exhaust / drain valve) increases. When the exhaust / drain valve is used (opened), hydrogen emissions increase while fuel efficiency decreases.

[0011] If the exhaust frequency is reduced to prevent a decrease in fuel efficiency, the nitrogen concentration inside the fuel cell will increase and the amount of wastewater discharged will decrease, resulting in a hydrogen shortage inside the fuel cell. This will reduce the durability of the fuel cell, making it necessary to limit the output and shut down the system. Summary of the Invention

[0012] This disclosure was made in view of the above-mentioned circumstances, and its main purpose is to provide a fuel cell system that can improve the performance of fuel cells even under high-altitude conditions.

[0013] The fuel cell system disclosed herein is used in aircraft.

[0014] The aforementioned fuel cell system is characterized by having:

[0015] Fuel cells;

[0016] An oxidant gas system supplies oxidant gas to the aforementioned fuel cell;

[0017] Altitude sensor; and

[0018] Control Department

[0019] The aforementioned oxidant gas system includes an air compressor and a bypass flow path that bypasses the aforementioned fuel cell.

[0020] The aforementioned bypass flow path has a bypass valve.

[0021] When the increase in height measured by the height sensor is detected, the control unit increases the speed of the air compressor and increases the opening of the bypass valve.

[0022] In the fuel cell system disclosed herein, the aforementioned fuel cell system has:

[0023] The fuel gas system supplies fuel gas to the aforementioned fuel cell; and

[0024] The output sensor measures the output of the aforementioned fuel cell.

[0025] The aforementioned fuel gas system includes: a fuel gas supply section; and an exhaust / drain valve, capable of discharging the fuel exhaust gas emitted from the aforementioned fuel cell to the outside.

[0026] When at least one of the following conditions is met—that is, when an increase in height is detected by the height sensor or when the output of the fuel cell is less than a predetermined output value—the control unit may increase the amount of fuel gas supplied from the fuel gas supply unit to the fuel cell and reduce the opening frequency of the exhaust and drain valve.

[0027] The aircraft disclosed herein is equipped with the aforementioned fuel cell system.

[0028] According to the fuel cell system disclosed herein, the performance of the fuel cell can be improved even at high altitudes. Attached Figure Description

[0029] Figure 1 This is a graph illustrating an example of the relationship between the airflow rate and the pressure ratio of an air compressor.

[0030] Figure 2 This is a simplified structural diagram illustrating an example of a fuel cell system according to the present disclosure.

[0031] Figure 3 This is a simplified structural diagram illustrating another example of the fuel cell system disclosed herein.

[0032] Figure 4 This is a flowchart illustrating an example of the control of a fuel cell system according to the present disclosure.

[0033] Figure 5 This is a flowchart illustrating another example of the control of the fuel cell system disclosed herein.

[0034] Explanation of reference numerals in the attached figures:

[0035] 10…Fuel cell; 20…Air compressor; 21…Oxidant gas supply path; 22…Oxidant exhaust gas discharge path; 23…Oxidant gas pressure regulating valve; 24…Oxidant gas bypass path; 25…Bypass valve; 30…Fuel gas supply section; 31…Fuel gas supply path; 32…Fuel exhaust gas discharge path; 33…Exhaust drain valve; 34…Anode gas-liquid separator; 35…Circulation path; 36…Ejector; 40…Branch section; 41…Merging section; 50…Control section; 60…Height sensor; 70…Output sensor; 100…Fuel cell system; 200…Fuel cell system. Detailed Implementation

[0036] 1. First Implementation Method

[0037] The fuel cell system disclosed herein is used in aircraft.

[0038] The aforementioned fuel cell system is characterized by having:

[0039] Fuel cells;

[0040] An oxidant gas system supplies oxidant gas to the aforementioned fuel cell;

[0041] Altitude sensor; and

[0042] Control Department

[0043] The aforementioned oxidant gas system includes an air compressor and a bypass flow path that bypasses the aforementioned fuel cell.

[0044] The aforementioned bypass flow path has a bypass valve.

[0045] When the increase in height measured by the height sensor is detected, the control unit increases the speed of the air compressor and increases the opening of the bypass valve.

[0046] In this disclosure, fuel gas and oxidant gas are collectively referred to as reactant gases. The reactant gas supplied to the anode is the fuel gas, and the reactant gas supplied to the cathode is the oxidant gas. The fuel gas is a gas mainly containing hydrogen, but it can also be hydrogen gas. The oxidant gas can be oxygen, air, dry air, etc.

[0047] The fuel cell system disclosed herein is used when mounted on an aircraft.

[0048] In addition, the fuel cell system disclosed herein can be mounted on aircraft that can also fly using electricity from secondary batteries.

[0049] The aircraft disclosed herein can be an aircraft. An aircraft can be an airplane, a vertical takeoff and landing (VTOL) aircraft, etc. A VTOL aircraft can be a helicopter, a drone, etc.

[0050] The aircraft may be equipped with the fuel cell system disclosed herein.

[0051] The fuel cell system disclosed herein includes a fuel cell.

[0052] A fuel cell can be a structure with only one single cell, or it can be a stack of multiple single cells, i.e., a fuel cell stack.

[0053] The number of layers in a single cell is not particularly limited; for example, it can be 2 to several hundred, or 2 to 600.

[0054] Fuel cell stacks can have end plates at both ends in the stacking direction of the individual cells.

[0055] Each cell of a fuel cell has at least a membrane electrode gas diffusion layer junction.

[0056] The membrane electrode gas diffusion layer assembly sequentially comprises an anode-side gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode-side gas diffusion layer.

[0057] The cathode (oxidant electrode) includes a cathode catalyst layer and a cathode-side gas diffusion layer.

[0058] The anode (fuel electrode) includes an anode catalyst layer and an anode-side gas diffusion layer.

[0059] The cathode catalyst layer and the anode catalyst layer are collectively referred to as the catalyst layer. Examples of anode and cathode catalysts include Pt (platinum) and Ru (ruthenium), while examples of substrate materials for supporting the catalyst and conductive materials include carbon materials such as carbon.

[0060] The gas diffusion layer on the cathode side and the gas diffusion layer on the anode side are collectively referred to as the gas diffusion layer.

[0061] The gas diffusion layer can be a breathable conductive component, etc.

[0062] Examples of conductive components include porous carbon materials such as carbon cloth and carbon paper, as well as porous metal materials such as metal mesh and foamed metal.

[0063] Electrolyte membranes can be solid polymer electrolyte membranes. Examples of solid polymer electrolyte membranes include fluorinated electrolyte membranes such as perfluorosulfonic acid membranes containing water, and hydrocarbon electrolyte membranes. Examples of electrolyte membranes include Nafion membranes (manufactured by DuPont).

[0064] A single cell may have two separators on both sides of the membrane electrode gas diffusion layer junction as needed. One of the two separators is the anode-side separator, and the other is the cathode-side separator. In this disclosure, the anode-side separator and the cathode-side separator are collectively referred to as separators.

[0065] The separator may have supply and discharge ports for allowing the reactant gases and refrigerant to flow along the stacking direction of the single cell. As a refrigerant, to prevent freezing at low temperatures, a mixture of ethylene glycol and water, for example, can be used.

[0066] Examples of supply ports include fuel gas supply ports, oxidizer gas supply ports, and refrigerant supply ports.

[0067] Examples of discharge ports include fuel gas discharge ports, oxidizer gas discharge ports, and refrigerant discharge ports.

[0068] The baffle may have one or more fuel gas supply holes, one or more oxidant gas supply holes, one or more refrigerant supply holes, one or more fuel gas discharge holes, one or more oxidant gas discharge holes, and one or more refrigerant discharge holes.

[0069] The separator may have a reactive gas flow path on the surface in contact with the gas diffusion layer. Additionally, the separator may have a refrigerant flow path on the surface opposite to the surface in contact with the gas diffusion layer to maintain a constant temperature in the fuel cell.

[0070] When the partition is an anode-side partition, it may have one or more fuel gas supply holes, one or more oxidant gas supply holes, one or more refrigerant supply holes, one or more fuel gas discharge holes, one or more oxidant gas discharge holes, and one or more refrigerant discharge holes. The anode-side partition may have a fuel gas flow path on the surface in contact with the anode-side gas diffusion layer for fuel gas to flow from the fuel gas supply hole to the fuel gas discharge hole, and may have a refrigerant flow path on the surface opposite to the surface in contact with the anode-side gas diffusion layer for refrigerant to flow from the refrigerant supply hole to the refrigerant discharge hole.

[0071] When the partition is a cathode-side partition, it may have one or more fuel gas supply holes, one or more oxidant gas supply holes, one or more refrigerant supply holes, one or more fuel gas discharge holes, one or more oxidant gas discharge holes, and one or more refrigerant discharge holes. The cathode-side partition may have an oxidant gas flow path on the surface in contact with the cathode-side gas diffusion layer for oxidant gas to flow from the oxidant gas supply hole to the oxidant gas discharge hole, and may have a refrigerant flow path on the surface opposite to the surface in contact with the cathode-side gas diffusion layer for refrigerant to flow from the refrigerant supply hole to the refrigerant discharge hole.

[0072] The partition can be an airtight conductive component. Examples of conductive components include compressed carbon forming an airtight, dense carbon, and stamped metal sheets (such as iron, aluminum, and stainless steel). Furthermore, the partition can have a current-collecting function.

[0073] A fuel cell may have manifolds such as inlet manifolds connected to each supply port and outlet manifolds connected to each discharge port.

[0074] Examples of inlet manifolds include anode inlet manifolds, cathode inlet manifolds, and refrigerant inlet manifolds.

[0075] Examples of outlet manifolds include anode outlet manifolds, cathode outlet manifolds, and refrigerant outlet manifolds.

[0076] The fuel cell system is equipped with an altitude sensor.

[0077] Altitude sensors determine the altitude of the aircraft.

[0078] The altitude sensor is electrically connected to the control unit, which detects the altitude of the aircraft as determined by the altitude sensor.

[0079] The height sensor can use previously known altimeters, etc.

[0080] Fuel cell systems can be equipped with output sensors.

[0081] The output sensor measures the output of the fuel cell. The output can be power, voltage, or current.

[0082] The output sensor is electrically connected to the control unit, which detects the output of the fuel cell as measured by the output sensor.

[0083] The output sensor can use previously known output meters, power meters, voltage meters, current meters, etc.

[0084] The fuel cell system has an oxidant gas system that supplies oxidant gas to the fuel cell.

[0085] The oxidant gas system has an air compressor and a bypass path that bypasses the fuel cell.

[0086] The oxidant gas system of a fuel cell may also include an oxidant gas supply path, an oxidant exhaust gas discharge path, and an oxidant gas flow sensor.

[0087] An air compressor supplies oxidant gas to the cathode of the fuel cell.

[0088] The air compressor is electrically connected to the control unit. The air compressor is driven according to control signals from the control unit. The air compressor can be controlled by the control unit to select at least one from a group consisting of the flow rate and pressure of the oxidant gas supplied from the air compressor to the cathode.

[0089] The oxidant gas supply path connects the air compressor to the oxidant gas inlet of the fuel cell. This path enables the supply of oxidant gas from the air compressor to the cathode of the fuel cell. The oxidant gas inlet can be an oxidant gas supply port, a cathode inlet manifold, etc.

[0090] The oxidant exhaust gas discharge path is connected to the oxidant gas outlet of the fuel cell. This path allows the oxidant gas, i.e., the oxidant exhaust gas, to be discharged from the cathode of the fuel cell to the outside. The oxidant gas outlet can be an oxidant gas discharge port, a cathode outlet manifold, etc.

[0091] An oxidant gas pressure regulating valve can be installed in the oxidant exhaust gas discharge path.

[0092] The oxidant gas pressure regulating valve is electrically connected to the control unit. By opening the valve through the control unit, the reacted oxidant gas, i.e., the oxidant waste gas, is discharged to the outside through the oxidant waste gas discharge path. Furthermore, the pressure of the oxidant gas supplied to the cathode (cathode pressure) can be adjusted by changing the opening degree of the oxidant gas pressure regulating valve.

[0093] The bypass flow path bypasses the fuel cell. Specifically, the bypass flow path branches off from the oxidant gas supply flow path, bypassing the fuel cell to connect the branch of the oxidant gas supply flow path with the confluence of the oxidant exhaust flow path.

[0094] The bypass flow path has a bypass valve.

[0095] The bypass valve is electrically connected to the control unit. By opening the bypass valve through the control unit, the oxidant gas can be bypassed from the fuel cell and discharged to the outside through the oxidant exhaust gas discharge path without the need for the supply of oxidant gas to the fuel cell.

[0096] An oxidant gas flow sensor is configured in the oxidant gas supply path.

[0097] An oxidant gas flow sensor detects the flow rate of oxidant gas within the oxidant gas system. The oxidant gas flow sensor is electrically connected to the control unit. The control unit can infer the air compressor speed based on the oxidant gas flow rate detected by the oxidant gas flow sensor. The oxidant gas flow sensor is positioned upstream of the air compressor in the oxidant gas supply path.

[0098] Oxidant gas flow sensors can utilize conventionally known flow meters, etc.

[0099] Fuel cell systems can include a fuel gas system.

[0100] The fuel gas system supplies fuel gas to the fuel cell.

[0101] The fuel gas system may include: a fuel gas supply section; and an exhaust / drain valve that can discharge fuel exhaust gas from the fuel cell to the outside.

[0102] The fuel gas system may also include a fuel gas supply path, an injector, a circulation path, a gas-liquid separator, and a fuel exhaust gas discharge path.

[0103] The fuel gas supply unit supplies fuel gas to the anode of the fuel cell.

[0104] As a fuel gas supply unit, examples include fuel tanks, and more specifically, liquid hydrogen tanks and compressed hydrogen tanks.

[0105] The fuel gas supply unit is electrically connected to the control unit. The supply of fuel gas to the fuel cell can be controlled by opening and closing the main check valve of the fuel gas supply unit according to control signals from the control unit.

[0106] The fuel gas supply path connects the fuel gas supply unit to the fuel gas inlet of the fuel cell. The fuel gas supply path enables the supply of fuel gas to the anode of the fuel cell. The fuel gas inlet can be a fuel gas supply port, an anode inlet manifold, etc.

[0107] An injector can be configured in the fuel gas supply path.

[0108] The injector can be configured, for example, at the confluence of the fuel gas supply path and the recirculation path. The injector supplies a mixture of fuel gas and recirculation gas to the anode of the fuel cell. Conventionally known injectors can be used as the injector.

[0109] A pressure regulating valve and a medium-pressure hydrogen sensor can be installed in the area between the fuel gas supply section and the injector in the fuel gas supply flow path.

[0110] The pressure regulating valve regulates the pressure of the fuel gas supplied from the fuel gas supply section to the injector.

[0111] The pressure regulating valve is electrically connected to the control unit. By controlling the opening and closing of the pressure regulating valve and its opening degree, the pressure of the fuel gas supplied to the injector can be adjusted.

[0112] The medium-pressure hydrogen sensor is electrically connected to the control unit. The control unit detects the pressure of the fuel gas measured by the medium-pressure hydrogen sensor and adjusts the pressure of the fuel gas supplied to the injector by controlling the opening and closing of the pressure regulating valve and the opening degree based on the detected pressure.

[0113] The fuel exhaust path connects the fuel gas outlet of the fuel cell to the external environment of the fuel cell system.

[0114] In the fuel exhaust flow path, a gas-liquid separator can be configured in the area between the fuel gas outlet and the outside of the fuel cell system.

[0115] The fuel exhaust gas discharge path can branch off from the circulation path via a gas-liquid separator.

[0116] The fuel exhaust path discharges the fuel exhaust gas from the fuel gas outlet of the fuel cell to the outside of the fuel cell system. The fuel gas outlet can be a fuel gas outlet port, an anode outlet manifold, etc.

[0117] The exhaust drain valve (fuel exhaust gas discharge valve) can be configured in the fuel exhaust gas discharge path. The exhaust drain valve is configured downstream of the gas-liquid separator in the fuel exhaust gas discharge path.

[0118] The exhaust drain valve can discharge fuel exhaust gases and moisture to the outside (outside the system). The outside can be the outside of the fuel cell system or the outside of the aircraft.

[0119] The exhaust drain valve is electrically connected to the control unit. By controlling the opening and closing of the exhaust drain valve, the flow rate of fuel exhaust gas discharged to the outside and the flow rate of water (liquid water) drained can be adjusted. In addition, the fuel gas pressure (anode pressure) supplied to the anode of the fuel cell can be adjusted by adjusting the opening degree of the exhaust drain valve.

[0120] Fuel exhaust gases may include unreacted fuel gases that pass directly through the anode, as well as water generated at the cathode that reaches the anode. There may also be corrosive substances generated in the catalyst layer and electrolyte membrane, and oxidant gases that can be supplied to the anode during scavenging.

[0121] The recirculation path can connect the fuel gas outlet of the fuel cell to the injector.

[0122] The recirculation path can branch off from the fuel exhaust path and merge with the fuel gas supply path by connecting to an injector configured in the fuel gas supply path.

[0123] The circulating flow path can branch off from the fuel exhaust flow path via a gas-liquid separator and merge with the fuel gas supply flow path by connecting to an injector configured in the fuel gas supply flow path.

[0124] The recirculation path can recover the fuel gas, i.e. fuel exhaust gas, discharged from the fuel gas outlet of the fuel cell and supply it to the fuel cell as recirculation gas.

[0125] A gas circulation pump can be configured in the circulation path. The gas circulation pump circulates the fuel exhaust gas as circulating gas. The gas circulation pump is electrically connected to the control unit, and the flow rate of the circulating gas can be adjusted by controlling the on / off state of the gas circulation pump drive and its speed, etc., by the control unit.

[0126] A gas-liquid separator (anode gas-liquid separator) can be configured in the circulating flow path.

[0127] The gas-liquid separator can be configured at the branch point of the fuel exhaust gas discharge path and the circulation path. Therefore, the flow path from the fuel gas outlet to the gas-liquid separator can be either the fuel exhaust gas discharge path or the circulation path.

[0128] The gas-liquid separator is positioned upstream of the exhaust drain valve in the fuel exhaust gas discharge path.

[0129] The gas-liquid separator separates the fuel gas, i.e., fuel exhaust gas, discharged from the fuel gas outlet from moisture (liquid water). This allows the fuel exhaust gas to be returned to the circulation path as recirculated gas, and the exhaust drain valve in the fuel exhaust path can be opened to discharge unwanted gases and moisture to the outside. Furthermore, because the gas-liquid separator can suppress excess moisture from flowing into the circulation path, it can prevent the formation of ice in the circulation pump and other components caused by this moisture.

[0130] A fuel cell system can have a cooling system for the fuel cell.

[0131] The cooling system can have a refrigerant supply section or a refrigerant circulation path.

[0132] The refrigerant circulation path is connected to the refrigerant supply port and refrigerant discharge port located in the fuel cell, enabling the refrigerant supplied from the refrigerant supply section to circulate inside and outside the fuel cell.

[0133] The refrigerant supply unit is electrically connected to the control unit. The refrigerant supply unit is driven by control signals from the control unit. The flow rate of refrigerant supplied from the refrigerant supply unit to the fuel cell is controlled by the control unit. This allows for the control of the fuel cell temperature.

[0134] Examples of refrigerant supply components include cooling water pumps.

[0135] A radiator can be installed in the refrigerant circulation path to dissipate heat from the cooling water.

[0136] A storage tank for storing refrigerant can be installed in the refrigerant circulation path.

[0137] Fuel cell systems can have secondary batteries.

[0138] A secondary battery (rechargeable battery) only needs to be able to charge and discharge; examples include conventionally known secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries. Furthermore, a secondary battery may include energy storage components such as double-layer capacitors. A secondary battery can be a structure consisting of multiple batteries connected in series. The secondary battery supplies power to motors and air compressors, for example. The secondary battery can be charged, for example, from an external power source of the aircraft. The secondary battery can be charged by the output of a fuel cell. The charging and discharging of the secondary battery can be controlled by a control unit.

[0139] Physically, the control unit includes, for example, a processing unit such as a CPU (Central Processing Unit), a storage device such as ROM (Read-Only Memory) storing the control program and control data processed by the CPU, and RAM (Random Access Memory) used primarily for control processing, as well as input / output interfaces. Alternatively, the control unit may be, for example, a control device such as an Electronic Control Unit (ECU).

[0140] The control unit can be electrically connected to a switch that can be mounted on an aircraft. The control unit can be configured to operate with the aid of an external power source even when the switch is turned off.

[0141] When the height sensor detects an increase in height, the control unit increases the speed of the air compressor and increases the opening of the bypass valve.

[0142] For the increased air compressor speed and bypass valve opening, a data set showing the relationship between height, air compressor speed and bypass valve opening can be prepared in advance. The height can be compared with the data set to appropriately set the increased air compressor speed and bypass valve opening.

[0143] Figure 1 This is a graph illustrating an example of the relationship between the airflow rate and the pressure ratio of an air compressor.

[0144] like Figure 1 As shown, on the ground, air can be compressed to the desired pressure within the operating range of an air compressor. However, at extremely high altitudes, due to the lower air concentration, there are situations where the air cannot be compressed to the desired pressure within the operating range of the air compressor. Therefore, at extremely high altitudes, in order to compress air to the desired pressure within the operating range of the air compressor, it is necessary to increase the air compressor speed to increase the airflow. On the other hand, since increasing the airflow would exceed the flow rate required for the fuel cell to generate electricity, the air not needed for power generation needs to be discharged by increasing the opening of the bypass valve to bypass the fuel cell.

[0145] Therefore, in this disclosure, in the oxidant gas system, when the altitude is high, the pressure is increased by controlling the ACP speed (increasing the air flow rate), thereby reducing insufficient oxygen partial pressure. Simultaneously, the opening of the bypass valve is changed as the altitude increases, reducing fuel cell dryness by supplying only the air flow rate required for fuel cell power generation to the fuel cell.

[0146] When at least one of the following conditions is met—that is, when an increase in height is detected by the height sensor or when the output of the fuel cell is less than a specified output value—the control unit may increase the amount of fuel gas supplied from the fuel gas supply unit to the fuel cell and reduce the opening frequency of the exhaust and drain valves.

[0147] The increased supply of fuel gas only needs to be greater than the supply at the time of judgment or the supply at the current moment. There is no special limitation. It can be appropriately set by considering the fuel utilization rate within the range that can maintain normal power generation.

[0148] The reduced opening frequency of the exhaust and drain valves is only required to be less than the supply amount at the time of judgment or the supply amount at the current moment. There are no special restrictions. The fuel utilization rate can be considered to set it appropriately within the range that can maintain normal power generation.

[0149] The specified output value of the fuel cell can be appropriately set based on the output requested by the aircraft.

[0150] First, at extremely high altitudes, due to the lower air pressure compared to ground level, more hydrogen is released through the exhaust drain valve. Therefore, to improve fuel efficiency, reducing the frequency of exhaust drain valve opening is advisable. However, reducing the frequency of exhaust drain valve opening increases the nitrogen concentration (nitrogen partial pressure). Therefore, the hydrogen partial pressure within the fuel gas system is maintained within the desired range by reducing the frequency of exhaust drain valve opening and increasing the amount of fuel gas supplied from the fuel gas supply unit to the fuel cell.

[0151] Therefore, in this disclosure, the exhaust frequency of fuel exhaust gas and the fuel gas supply from the fuel tank are controlled in the fuel gas system according to the altitude and the output of the fuel cell, so as to maintain normal power generation and ensure good fuel utilization.

[0152] Figure 2 This is a simplified structural diagram illustrating an example of a fuel cell system according to the present disclosure.

[0153] Figure 2 The fuel cell system 100 shown includes a fuel cell 10, an air compressor 20, an oxidant gas supply path 21, an oxidant exhaust gas discharge path 22, an oxidant gas pressure regulating valve 23, a bypass path 24, a bypass valve 25, a control unit 50, and a height sensor 60.

[0154] Among them, Figure 2 The diagram only shows the oxidizer gas system; other systems such as fuel gas and cooling systems are omitted.

[0155] The bypass flow path 24 connects the branch 40 of the oxidant gas supply flow path 21 with the confluence 41 of the oxidant exhaust gas discharge flow path 22.

[0156] Figure 3 This is a simplified structural diagram illustrating another example of the fuel cell system disclosed herein.

[0157] Figure 3 The fuel cell system 200 shown includes a fuel cell 10, a fuel gas supply unit 30, a fuel gas supply path 31, a fuel exhaust gas discharge path 32, an exhaust drain valve 33, an anode gas-liquid separator 34, a circulation path 35, an injector 36, a control unit 50, a height sensor 60, and an output sensor 70. Among these, in... Figure 3 The diagram only shows the fuel gas system; other systems such as the oxidizer gas system and cooling system are omitted.

[0158] Figure 4 This is a flowchart illustrating an example of the control of a fuel cell system according to the present disclosure.

[0159] First, the altitude sensor measures the aircraft's altitude.

[0160] Then, upon detecting an increase in height as measured by the height sensor, the control unit increases the air compressor speed and the bypass valve opening to a greater degree than at the current moment, and then terminates the control.

[0161] On the other hand, if no increase in altitude is detected as measured by the altitude sensor, the control unit can either terminate control or maintain the current speed of the air compressor and the current opening of the bypass valve. For example, the absence of detected altitude increase could be due to the aircraft flying horizontally at a predetermined altitude. In such a case, maintaining the current speed of the air compressor and the current opening of the bypass valve is sufficient.

[0162] In addition, when a decrease in height is detected by the height sensor, the control unit can reduce the speed of the air compressor to less than the current time and reduce the opening of the bypass valve to less than the current time.

[0163] Figure 5 This is a flowchart illustrating another example of the control of the fuel cell system disclosed herein.

[0164] First, the altitude sensor measures the aircraft's altitude, and the output sensor determines the fuel cell's output.

[0165] Then, when at least one of the following conditions is met—that is, when an increase in height is detected by the height sensor or when the output of the fuel cell is less than a specified output value—the control unit increases the amount of fuel gas supplied from the fuel gas supply unit to the fuel cell to be greater than at the current time and decreases the opening frequency of the exhaust and drain valves to be less than at the current time, and then terminates the control.

[0166] On the other hand, if either of the following conditions is not met: the height sensor detects an increase in height or the fuel cell output is less than a specified output value, the control unit may terminate the control or maintain the current supply of fuel gas from the fuel gas supply unit to the fuel cell and maintain the current opening frequency of the exhaust and drain valves.

[0167] 2. Second Implementation Method

[0168] The fuel cell system disclosed herein is used in aircraft.

[0169] The aforementioned fuel cell system is characterized by having:

[0170] Fuel cells;

[0171] A fuel gas system supplies fuel gas to the aforementioned fuel cell;

[0172] The output sensor measures the output of the aforementioned fuel cell;

[0173] Altitude sensor; and

[0174] Control Department

[0175] The aforementioned fuel gas system includes: a fuel gas supply section; and an exhaust / drain valve, capable of discharging the fuel exhaust gas emitted from the aforementioned fuel cell to the outside.

[0176] When at least one of the following conditions is met—that is, when an increase in height is detected by the height sensor or when the output of the fuel cell is less than a specified output value—the control unit increases the amount of fuel gas supplied from the fuel gas supply unit to the fuel cell and decreases the opening frequency of the exhaust and drain valve.

[0177] In the second embodiment of this disclosure, the exhaust frequency of fuel exhaust gas and the fuel gas supply from the fuel tank are controlled in the fuel gas system according to the altitude and the output of the fuel cell, so as to maintain normal power generation and good fuel utilization.

[0178] The fuel cell system disclosed herein may include an oxidant gas system for supplying oxidant gas to the aforementioned fuel cell.

[0179] The aforementioned oxidant gas system includes an air compressor and a bypass flow path that bypasses the aforementioned fuel cell.

[0180] The aforementioned bypass flow path has a bypass valve.

[0181] When the increase in height measured by the height sensor is detected, the control unit increases the speed of the air compressor and increases the opening of the bypass valve.

[0182] Therefore, in the oxidant gas system, at high altitudes, the pressure is increased by controlling the ACP speed (increasing air flow), thus reducing insufficient oxygen partial pressure. Simultaneously, the opening of the bypass valve is changed as altitude increases, reducing fuel cell dryness by supplying only the air flow required for fuel cell power generation.

[0183] The fuel cell, fuel gas system, oxidant gas system, output sensor, height sensor, control unit, etc. in the second embodiment can be the same components as those exemplified in the first embodiment.

Claims

1. A method of using a fuel cell system for an aircraft, the fuel cell system having: a fuel cell; an oxidant gas system that supplies oxidant gas to the fuel cell; an altitude sensor; a fuel gas system that supplies fuel gas to the fuel cell; an output sensor that measures the output of the fuel cell; and a control section, the oxidant gas system having an air compressor, a bypass flow path that bypasses the fuel cell, the bypass flow path having a bypass valve, the fuel gas system having a fuel gas supply section and an exhaust drain valve that can discharge fuel exhaust gas discharged from the fuel cell to the outside, the method of using the fuel cell system characterized by the method of using the fuel cell system including, when an increase in the altitude measured by the altitude sensor is detected, increasing the rotation speed of the air compressor and increasing the opening degree of the bypass valve by means of the control section, and reducing the dryness of the fuel cell by supplying only the air flow required for power generation of the fuel cell to the fuel cell. the method of using the fuel cell system further including, when a condition that is at least either of when an increase in the altitude measured by the altitude sensor is detected or when the output of the fuel cell is less than a prescribed output value is satisfied, maintaining normal power generation and making the fuel utilization good by means of the control section, increasing the supply amount of fuel gas from the fuel gas supply section to the fuel cell and reducing the valve opening frequency of the exhaust drain valve.

2. An aircraft characterized by using the method of using the fuel cell system according to claim 1.

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