Fuel cell system
The fuel cell system addresses ejector blockages in hydrogen supply by using impedance monitoring to detect and differentiate blockage causes, reducing sensor needs and costs, and preventing hydrogen shortages through defreezing.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-18
AI Technical Summary
Fuel cell systems using ejectors for hydrogen supply are prone to blockages due to narrow flow paths, which can be clogged by foreign substances, necessitating additional sensors for detection, increasing complexity and cost.
A fuel cell system that detects ejector blockage by monitoring impedance, cooling water temperature, and atmospheric pressure without additional sensors, differentiating between blockages caused by foreign matter and freezing, and performing defreezing processes if necessary.
Enables blockage detection without additional sensors, reducing installation complexity and cost, and preventing hydrogen shortages by distinguishing between blockage types and performing appropriate defreezing treatments.
Smart Images
Figure 2026099523000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a fuel cell system.
Background Art
[0002] Patent Document 1 describes a system for determining an ejector blockage from the ejector suction pressure. Patent Document 2 describes performing an ejector purge when the outside air temperature is below freezing. Patent Document 3 describes a technique for determining an ejector abnormality (blockage abnormality in the circulation flow path between the ejector and the pressure detection unit) when the detection result of a pressure detector that detects the pressure of circulating hydrogen does not fall below a predetermined threshold value.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Patent Document 3
Summary of the Invention
Problems to be Solved by the Invention
[0004] In a fuel cell system using an ejector as a hydrogen supply device, although the ejector has the advantage of miniaturizing the system, the flow path is narrow and thus tends to be clogged with foreign substances or the like. And in order to detect the blockage, it is necessary to install various sensors such as a flow rate sensor and a pressure sensor, which poses problems from the viewpoints of mounting property and cost.
[0005] The present disclosure provides a fuel cell system that detects blockage without installing various additional sensors for blockage detection.
Means for Solving the Problems
[0006] The present invention discloses a fuel cell system having an ejector in a path for introducing hydrogen into a fuel cell stack, and comprising a control device, wherein the control device acquires impedance when the current value of the fuel cell stack, the cooling water temperature at the outlet of the fuel cell stack, and the atmospheric pressure are all within predetermined ranges, and determines that the ejector is blocked if the impedance is greater than a predetermined threshold.
[0007] When the control device determines that the ejector is blocked, if the cooling water temperature or ambient temperature at the start of the fuel cell system is 0°C or lower, it may be determined that the ejector is frozen. If the cooling water temperature or ambient temperature at the start of the fuel cell system is higher than 0°C, it may be determined that the ejector is blocked by foreign matter. When it is determined that the ejector is frozen, the device may be configured to perform an unfreezing process until the impedance falls below a predetermined threshold.
[0008] The defreezing process may also involve transferring heat from the hydrogen pressure pulsation or the rise in fuel cell stack water temperature due to low-efficiency power generation. [Effects of the Invention]
[0009] According to the fuel cell system of this disclosure, there is no need to install additional sensors for blockage detection, thus enabling blockage detection while improving ease of installation and reducing costs. [Brief explanation of the drawing]
[0010] [Figure 1] Figure 1 is a conceptual diagram showing the configuration of the fuel cell system 10. [Figure 2] Figure 2 is a diagram illustrating the flow of foreign object detection control (Form 1). [Figure 3] Figure 3 is a diagram illustrating the flow of foreign object detection control (Form 2). [Figure 4] Figure 4 illustrates an example of the defreezing process. [Modes for carrying out the invention]
[0011] 1. Configuration of the fuel cell system Figure 1 schematically shows the configuration of one embodiment of the fuel cell system 10. As can be seen from Figure 1, this embodiment of the fuel cell system 10 includes a fuel cell 11, an oxygen supply path 20, a hydrogen supply path 30, a cooling water supply path 40, a boost converter 50, and a control device 60. Then, power is obtained by using the electricity generated by the fuel cell 11 to rotate the motor, etc.
[0012] 1.1.Fuel cell As is well known, the fuel cell 11 is, for example, a stack of multiple fuel cell cells arranged in a laminate housed in a stack case. A fuel cell cell is composed of a membrane electrode assembly (MEA) sandwiched between two separators. The MEA is a laminate of a solid polymer membrane, a negative electrode catalyst layer, a positive electrode catalyst layer, a negative electrode gas diffusion layer, a positive electrode gas diffusion layer, etc. The fuel cell 11 generates electricity by receiving oxygen gas and fuel gas (hydrogen gas in this embodiment). The supply of oxygen gas and fuel gas to the fuel cell 11, as well as the emission from the fuel cell 11, are carried out by an oxygen supply path 20 and a hydrogen supply path 30.
[0013] Here, oxygen gas and fuel gas are reaction gases used to generate electricity in the fuel cell. As described above, oxygen gas and fuel gas are supplied to the fuel cell to generate electricity, while gases not used for power generation are discharged from the fuel cell, becoming oxygen off-gas and fuel off-gas. Furthermore, the following explanation will use air as the oxygen gas and hydrogen gas as the fuel gas. Accordingly, oxygen off-gas may also be referred to as air off-gas, and fuel off-gas as hydrogen off-gas.
[0014] 1.2. Oxygen gas supply path 20 The oxygen gas supply path 20 includes a compressor 21, a supply flow path 22, and an exhaust flow path 23. Each component provided in the oxygen gas supply path 20 can be a known component. That is, the air in the atmosphere taken in by the compressor 21 flows through the supply flow path 22 and is supplied to the fuel cell 11. The air off-gas discharged from the fuel cell 11 flows through the exhaust flow path 23 and is discharged to the outside. Valves are provided in the supply flow path 22 and the exhaust flow path 23 as necessary.
[0015] 1.3. Fuel gas supply path 30 The fuel gas supply path 30 includes a supply system 31 and a circulation system 35.
[0016] 1.3a. Supply system The supply system 31 is a path for supplying hydrogen gas to the fuel cell 11. In this embodiment, the supply system 31 has an ejector 32 and a supply flow path 33.
[0017] The ejector 32 injects the hydrogen gas supplied from a hydrogen source such as a hydrogen tank and supplies the hydrogen gas to the fuel cell 11. In addition to this, the ejector 32 sucks the hydrogen off-gas from the circulation system 35 and supplies it to the fuel cell 11 together with the hydrogen gas from the hydrogen source.
[0018] The specific embodiment of the ejector 32 is not particularly limited and a known one can be applied. That is, the ejector generates a low-pressure space in the housing by injecting a gas at high speed through a nozzle and sucks in an external fluid. The gas injected at high speed from the nozzle and the sucked-in fluid are mixed and flow out of the ejector while reducing the speed in a diffuser. In terms of this embodiment, the ejector 32 injects the hydrogen gas from the hydrogen source from the nozzle toward the diffuser. The hydrogen off-gas from the circulation system 35 is sucked into the low-pressure space generated in the housing by the injection of the hydrogen gas from the nozzle, enters the diffuser from the suction port, mixes with the hydrogen gas injected from the nozzle, and flows out of the ejector 32.
[0019] The supply channel 33 is a channel for supplying hydrogen gas to the fuel cell 11, and has piping to allow hydrogen gas to flow from the ejector 32.
[0020] 1.3b.Circulatory system The circulation system 35 returns the hydrogen off-gas contained in the fluid discharged from the gas outlet of the fuel cell 11 to the supply system 31. Therefore, in this configuration, the circulation system 35 has a gas-liquid separator 36, a drain valve 37, and a circulation channel 38. The gas-liquid separator 36 separates the fluid discharged from the gas outlet of the fuel cell 11 into liquid and gas. The liquid is water produced by the reaction in the fuel cell 11, and after separation in the gas-liquid separator 36, it is discharged to the outside by opening the drain valve 37. The gas is hydrogen off-gas, and after separation in the gas-liquid separator 36, it is drawn into the low-pressure space of the ejector 34 as described above and mixed with the hydrogen gas in the supply system 31.
[0021] The circulation channel 38 is a channel through which the fluid discharged from the fuel cell 11 flows, and it has piping that connects each of the above-mentioned components so that the fluid can flow between them. Specifically, the circulation channel 38 includes piping that connects the fuel cell 11 to the gas-liquid separator 36, the gas-liquid separator 36 to the ejector 32, and the gas-liquid separator 36 to the drain valve 37.
[0022] 1.4. Cooling water supply path 40 The cooling water supply path 40 includes a pump 41, a radiator 42, and a circulation path 43. Known components can be used for each component of the cooling water supply path 40. Specifically, the cooling water pushed out by the pump 41 flows through the circulation path 43 and is supplied to the fuel cell 11. The supplied cooling water cools the fuel cell 11, causing its temperature to rise and then being discharged from the fuel cell 11. The discharged cooling water flows through the circulation path 43 and enters the radiator 43, where it undergoes heat exchange with the outside air and is cooled. The cooling water that exits the radiator 43 flows through the circulation path 43 and is supplied back to the pump 41.
[0023] 1.5. Boost Converter The boost converter 50 is a unit whose main body is mounted on the fuel cell 11. It boosts the voltage from the fuel cell, which converts hydrogen into electricity, and supplies power to devices that utilize the electricity generated by the fuel cell, such as motors. The boost converter consists of a main body and an electronic control unit that controls it. The main body and the control unit are electrically connected, either wired or wirelessly.
[0024] 1.6. Control Device The control device 60 is an electronic circuit-based control device, and is composed of a so-called computer. Therefore, the control device 60 includes a central operator (CPU), RAM, storage means, receiving means, and transmitting means. The central operator performs calculations according to a program stored in the memory and transmits signals containing the calculation results to each device that should follow them. The memory system stores the programs to be processed by the central operator and the results obtained from the calculations. RAM is used as a workspace for various tasks related to arithmetic processing. The receiving means is a so-called input port, etc., which is the part that takes in data to be obtained from the outside to the control device 60. In this embodiment, the receiving means is configured so that a temperature sensor, ammeter, voltmeter, and pressure gauge, which are necessary data for performing the foreign object detection control described later, can communicate with each other and take in the data as signals to the control device 60. The transmission means is a so-called output port, which outputs commands and other information to each device from the control device 60 based on the calculation results. In this configuration, it is communicated to the boost converter 50.
[0025] The specific foreign object detection control by the control device 60 will be explained later, but the control device 60 determines whether the ejector 32 is blocked based on information from a sensor that was originally installed in the fuel cell system for a different purpose.
[0026] 2. Operation of the fuel cell system The following describes power generation by the fuel cell system 10. 2.1. Basic Power Generation Process First, we will explain the basic power generation process using the fuel cell system 10. Air is supplied to the fuel cell 11 through the oxygen gas supply path 20. Specifically, air from the atmosphere taken in by the compressor 21 flows through the supply path 22, is pressurized, and supplied to the fuel cell 11. The oxygen off-gas (air off-gas) discharged from the fuel cell 11 flows through the exhaust path 23 and is discharged to the outside.
[0027] Meanwhile, hydrogen gas is supplied to the fuel cell 11 through the fuel gas supply path 30. Specifically, hydrogen gas from the hydrogen source enters the nozzle of the ejector 32 and is injected from the nozzle into the diffuser. The hydrogen gas that flows out of the diffuser is supplied to the fuel cell 11. Furthermore, water generated by the reaction and hydrogen off-gas not used for power generation are discharged from the fuel cell 11 and enter the gas-liquid separator 36. In the gas-liquid separator 36, the water and hydrogen off-gas are separated. The separated water is drained through the drain valve 37. The separated hydrogen off-gas heads towards the ejector 32. In the ejector 32, the hydrogen off-gas is drawn into the low-pressure space created inside the housing by the injection of hydrogen gas from the nozzle, enters the diffuser through the intake port, mixes with the hydrogen gas injected from the nozzle, flows out of the ejector 32, and is supplied back to the fuel cell 11.
[0028] Furthermore, cooling water is supplied to the fuel cell 11 from the cooling water path 40, and the temperature is controlled.
[0029] As described above, air and hydrogen gas are supplied to the fuel cell 11 to generate electricity, which drives, for example, a motor electrically connected to the fuel cell 11. This motor can be used as a power source for, for example, driving a car or flying an airplane.
[0030] 2.2. Foreign object detection control (Form 1) In this embodiment, foreign object detection control can be performed, for example, by the control device 60 described above. 2.2a. Control Flow In addition to the basic power generation described above, this fuel cell system 10 performs control to determine whether the ejector 32 is blocked. Figure 2 shows the flow of the foreign object detection control S10 for the first configuration. Each process is described below.
[0031] [Process S11] In process S11, it is determined whether the current state is a standard state. Here, a standard state means that the current value of the fuel cell stack, the temperature of the cooling water at the outlet of the fuel cell stack, and the atmospheric pressure are all within a predetermined range. The current value of the fuel cell stack can be obtained from the existing ammeter, the temperature of the cooling water at the outlet of the fuel cell stack can be obtained from the existing thermometer, and the atmospheric pressure can be obtained from the existing atmospheric pressure meter; none of these are installed specifically for foreign matter control S10. If it is determined that the state is standard, the answer is Yes and the process proceeds to S12. On the other hand, if it is determined that the state is not standard, the answer is No and the determination in S11 is performed again.
[0032] [Process S12] In process S12, the current impedance of the fuel cell stack is obtained. Since the fuel cell impedance is obtained during normal operation, that value can be used.
[0033] [Process S13] In process S13, it is determined whether the impedance obtained in process S12 is greater than the threshold impedance. If the ejector is blocked by foreign matter, the impedance will rise. The threshold impedance can be determined from the relationship between ejector blockage and impedance, which has been obtained in advance through experiments or other means. If the impedance obtained in process S12 is greater than the threshold impedance, the response is "Yes" and the process proceeds to process S14. If the impedance obtained in process S12 is less than or equal to the threshold impedance, the process returns to process S12 and the impedance is obtained again.
[0034] [Process S14, Process S15] In process S14, based on the results of process S13, it is determined that the ejector is blocked in at least part. Then, in process S15, the output is limited, and this fact is notified by means of a screen, sound, light, etc.
[0035] 2.2b. Effects, etc. This control system eliminates the need to prepare and install a new sensor for ejector blockage detection, thereby improving ease of installation and cost. Furthermore, it eliminates the need to worry about sensor failure or freezing. In other words, by utilizing the impedance measurement function, blockage can be detected using existing impedance measurement capabilities without the need to install various sensors.
[0036] 2.3. Foreign object detection control (Form 2) In this configuration as well, foreign object detection control can be performed, for example, by the control device 60 described above. 2.3a. Control Flow In addition to the basic power generation described above, this fuel cell system 10 performs control to determine whether the ejector 32 is blocked. Figure 3 shows the flow of the foreign object detection control S20 for the second embodiment. Each process is described below.
[0037] In this embodiment, it is assumed that the processes S11 to S14 described above have been performed and that the state at the time of process S14 is reached.
[0038] [Process S21] In process S21, it is determined whether the conditions for determining whether the blockage is due to freezing are met. Specifically, it is determined whether the temperature of the cooling water at the outlet of the fuel cell stack at the start of the fuel cell system is 0°C or lower, or whether the current ambient temperature is 0°C or lower. Each temperature can be obtained using an existing temperature sensor. If it is determined that the condition is met in process S21, the response is "Yes" and the process proceeds to process S22. On the other hand, if it is determined that the condition is not met in process S21, the response is "No" and the process returns to process S15 as described above and the control ends.
[0039] [Process S22] Process S22, based on the result of process S21, determines that the ejector blockage is caused by freezing.
[0040] [Process S23] In process S23, a defreezing process is performed based on the determination in process S22. The specific method of defreezing is not particularly limited, but as shown in Figure 4, the freeze can be undone by heat transfer, such as by pulsating the hydrogen pressure or by raising the stack water temperature through low-efficiency power generation.
[0041] [Process S24] In process S24, it is determined whether the impedance obtained in process S12 is greater than the threshold impedance. The relationship between impedance and occlusion is as described above. If the impedance obtained in process S12 is greater than the threshold impedance, the response is "Yes," and the process returns to S23 to continue unfreezing. If the impedance obtained in process S12 is less than or equal to the threshold impedance, the blockage is released and control is terminated.
[0042] [others] Furthermore, if processes S23 and S24 are repeated a predetermined number of times, it may be determined that the blockage is not due to freezing, and the system may be controlled to proceed to process S15.
[0043] 2.3b.Effect etc. This control system eliminates the need to prepare and install a new sensor for ejector blockage detection, thereby improving ease of installation and cost. Furthermore, it eliminates the need to worry about sensor failure or freezing. In other words, by utilizing the impedance measurement function, blockage can be detected using existing impedance measurement capabilities without the need to install various sensors. Furthermore, it is possible to differentiate between blockages caused by foreign objects and blockages caused by freezing, and then perform defreezing treatment. This can prevent hydrogen shortages due to freezing blockages and thus prevent deterioration of the fuel cell. [Explanation of Symbols]
[0044] 10…Fuel cell system, 11…Fuel cell, 20…Oxygen supply path, 30…Fuel supply circuit, 40…Cooling water supply path, 50…Boost converter, 60…Control device
Claims
1. A fuel cell system having an ejector in the path for introducing hydrogen into the fuel cell stack, It is equipped with a control device, The control device acquires impedance when the current value of the fuel cell stack, the cooling water temperature at the outlet of the fuel cell stack, and the atmospheric pressure are all within a predetermined range. If the impedance is greater than a predetermined threshold, it is determined that the ejector is blocked. Fuel cell system.
2. When the control device determines that the ejector is blocked, if the cooling water temperature or ambient temperature at the start of the fuel cell system is 0°C or lower, it determines that the ejector is frozen; if the cooling water temperature or ambient temperature at the start of the fuel cell system is higher than 0°C, it determines that the ejector is blocked by foreign matter. When it is determined that the ejector is frozen, an unfreezing process is performed until the impedance becomes smaller than the predetermined threshold. The fuel cell system according to claim 1.
3. The fuel cell system according to claim 2, wherein the defreezing process is a process that transfers heat from the rise in stack water temperature due to hydrogen pressure pulsation or low-efficiency power generation.