Fuel cell system

Abstract

To suppress a backflow of a gas downstream of an injector to the injector.SOLUTION: A fuel cell system includes: a fuel cell stack; a supply path that connects a supply source that supplies hydrogen to the fuel cell stack and the fuel cell stack and through which hydrogen supplied from the supply source flows; an injector provided in the supply path; a downstream pressure sensor that detects downstream pressure that is pressure downstream of the injector in the supply path; and a control device that controls the injector. The control device maintains a state in which downstream pressure is lower than upstream pressure, which is pressure upstream of the injector in the supply path, by closing the injector when predetermined conditions are satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] The fuel cell system disclosed in Patent Document 1 includes a fuel cell stack, a supply source, a supply path, an injector, a first pressure sensor, a second pressure sensor, and a control device. The supply source supplies hydrogen to the fuel cell stack. The supply path connects the supply source to the fuel cell stack. The injector is provided in the supply path. The injector injects hydrogen, thereby supplying hydrogen from the supply source to the fuel cell stack via the supply path. The first pressure sensor detects the pressure upstream of the injector. The second pressure sensor detects the pressure downstream of the injector. The control device controls the injector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-45620 Summary of the Invention [Problem to be solved by the invention]

[0004] If the pressure downstream of the injector becomes higher than the pressure upstream of the injector, the gas downstream of the injector will flow back into the injector. Because the gas downstream of the injector contains moisture, rust will form on the injector, causing it to fail. [Means for solving the problem]

[0005] A fuel cell system that solves the above problem includes a fuel cell stack, a supply channel that connects the fuel cell stack to a supply source that supplies anode gas to the fuel cell stack and through which the anode gas supplied from the supply source flows, an injector provided in the supply channel, a downstream pressure sensor that detects the downstream pressure in the supply channel downstream of the injector, and a control device that controls the injector, wherein the control device closes the injector when a predetermined condition is met, thereby maintaining a state in which the downstream pressure is lower than the upstream pressure in the supply channel upstream of the injector.

[0006] When the injector is closed, the downstream pressure decreases. This allows the downstream pressure to be kept lower than the upstream pressure, preventing gas downstream from flowing back into the injector.

[0007] In the fuel cell system, the condition may be that the control device receives a command to stop power generation of the fuel cell stack. In the above fuel cell system, when the control device closes the injector when the condition is met, the control device may maintain the closed state until the downstream pressure becomes equal to or lower than a first threshold, and when the downstream pressure becomes equal to or lower than the first threshold, maintain the injector in an open state until the downstream pressure becomes equal to or higher than a second threshold that is higher than the first threshold and lower than the upstream pressure.

[0008] In the fuel cell system, the control device may maintain the injector in an open state when a power generation command for the fuel cell stack is received. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent gas downstream of the injector from flowing back into the injector. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic diagram of a fuel cell system. [Figure 2] FIG. 2 is a timing chart showing the relationship between the command from the higher-level control device, the upstream pressure, the downstream pressure, and the open / closed state of the injector. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a fuel cell system will now be described. As shown in FIG. 1, the drive system 10 includes a host system 200 and a fuel cell system 20.

[0012] The host system 200 includes a load 201, a supply source 202, and a host control device 203. The load 201 is driven by power supplied from the fuel cell system 20. The supply source 202 supplies anode gas to the fuel cell system 20. The supply source 202 includes, for example, a storage unit that stores the anode gas, and a valve that adjusts the pressure of the anode gas supplied from the storage unit. The host control device 203 issues commands to the fuel cell system 20. The drive system 10 is a system that drives the load 201 by power supplied from the fuel cell system 20.

[0013] <Fuel cell system> The fuel cell system 20 includes a fuel cell stack 21 , a cathode system 40 , an anode system 60 , a diluter 71 , a power converter 91 , and a controller 110 .

[0014] The fuel cell stack 21 includes a plurality of fuel cell units 22. The fuel cell units 22 are polymer membrane fuel cell units. The fuel cell units 22 generate electricity through a chemical reaction between an anode gas and a cathode gas. The anode gas is hydrogen. The cathode gas is oxygen in the air.

[0015] The fuel cell stack 21 includes a cathode flow path 30 and an anode flow path 33. Air flows through the cathode flow path 30. Hydrogen flows through the anode flow path 33. The cathode flow path 30 includes an inlet 31 and an outlet 32. Air flows into the cathode flow path 30 through the inlet 31 and flows out through the outlet 32. The anode flow path 33 includes an inlet 34 and an outlet 35. Hydrogen flows into the anode flow path 33 through the inlet 34 and flows out through the outlet 35.

[0016] The cathode system 40 includes an intake port 41 , an electric compressor 42 , an inverter 44 , an intercooler 45 , a cathode supply channel 46 , a cathode discharge channel 49 , a first valve 51 , and a second valve 52 .

[0017] The intake port 41 draws air into the fuel cell system 20. The intake port 41 may be open to the atmosphere or may be connected to a gas cylinder. The electric compressor 42 includes an electric motor 43. The electric compressor 42 is driven by the electric motor 43. The electric compressor 42 supplies air to the fuel cell stack 21. Specifically, the electric compressor 42 compresses the air supplied from the intake port 41 and supplies the compressed air to the fuel cell stack 21. The air supplied from the electric compressor 42 to the fuel cell stack 21 flows through the cathode flow path 30.

[0018] The inverter 44 is connected to the electric motor 43. The inverter 44 converts DC power into AC power and supplies it to the electric motor 43. In this way, the electric motor 43 is driven.

[0019] The intercooler 45 is supplied with air discharged from the electric compressor 42. The intercooler 45 cools the air supplied from the electric compressor 42. The air supplied to the fuel cell stack 21 is the air that has been cooled by the intercooler 45.

[0020] The cathode supply path 46 connects the electric compressor 42 and the cathode flow path 30. More specifically, the cathode supply path 46 connects the electric compressor 42 and the inlet 31 of the cathode flow path 30. The cathode supply path 46 includes a first supply path 47 and a second supply path 48. The first supply path 47 connects the electric compressor 42 and the intercooler 45. The second supply path 48 connects the intercooler 45 and the cathode flow path 30.

[0021] The cathode discharge channel 49 connects the cathode flow path 30 and the diluter 71. More specifically, the cathode discharge channel 49 connects the outlet 32 ​​of the cathode flow path 30 and the diluter 71. The cathode discharge channel 49 is a passage through which the cathode exhaust gas flows. The cathode exhaust gas is air discharged from the fuel cell stack 21 and contains produced water. The produced water is water produced by power generation in the fuel cell stack 21.

[0022] The first valve 51 is provided in the cathode supply passage 46. In the present embodiment, the first valve 51 is provided in the second supply passage 48, i.e., between the intercooler 45 and the cathode flow passage 30. The first valve 51 may also be provided in the first supply passage 47, i.e., between the intercooler 45 and the electric compressor 42.

[0023] The second valve 52 is provided in the cathode discharge passage 49. The second valve 52 is a valve whose opening degree is adjustable. The anode system 60 includes a supply path 61, a circulation path 65, a gas-liquid separator 66, a circulation pump 67, an inverter 69, an exhaust / drain valve 70, an upstream pressure sensor 81, and a downstream pressure sensor 82.

[0024] The supply path 61 connects the supply source 202 and the inlet 34 of the anode flow path 33. The supply path 61 includes an upstream path 62 that connects the injector 64 and the supply source 202, and a downstream path 63 that connects the injector 64 and the inlet 34 of the anode flow path 33.

[0025] The injector 64 is provided in the supply path 61. The injector 64 injects hydrogen supplied from the supply source 202 toward the fuel cell stack 21. The circulation path 65 connects the outlet 35 of the anode flow path 33 and the downstream flow path 63. The anode exhaust gas flows through the circulation path 65. The anode exhaust gas contains unreacted hydrogen and generated water. The circulation path 65 is a passage for returning the unreacted hydrogen contained in the anode exhaust gas to the downstream flow path 63.

[0026] The gas-liquid separator 66 is provided in the circulation path 65. The gas-liquid separator 66 separates the anode exhaust gas into hydrogen and produced water. The produced water separated from the anode exhaust gas is stored in the gas-liquid separator 66.

[0027] The circulation pump 67 is provided in the circulation path 65. The circulation pump 67 includes an electric motor 68. The circulation pump 67 is driven by the electric motor 68. The circulation pump 67 supplies the hydrogen separated from the anode exhaust gas by the gas-liquid separator 66 to the downstream path 63. This circulates the hydrogen. The gas flowing in the downstream path 63 contains hydrogen and nitrogen. This gas is humidified.

[0028] The inverter 69 is connected to the electric motor 68. The inverter 69 converts DC power into AC power and supplies it to the electric motor 68. In this way, the electric motor 68 is driven.

[0029] The exhaust / drain valve 70 is connected to the gas-liquid separator 66. The exhaust / drain valve 70 can be switched between an open state and a closed state. When the exhaust / drain valve 70 is in the open state, the produced water is discharged from the gas-liquid separator 66. In addition, exhaust is performed from the circulation path 65. When the exhaust / drain valve 70 is in the closed state, the produced water cannot be discharged from the gas-liquid separator 66. In other words, when the exhaust / drain valve 70 is in the closed state, the produced water accumulates in the gas-liquid separator 66. The exhaust / drain valve 70 is switched from the closed state to the open state at predetermined valve opening intervals.

[0030] The gas-liquid separator 66 is connected to a diluter 71. When the exhaust / drain valve 70 is opened, the produced water stored in the gas-liquid separator 66 and the anode exhaust gas are supplied to the diluter 71. The diluter 71 dilutes the anode exhaust gas with the cathode exhaust gas and discharges it into the atmosphere.

[0031] The upstream pressure sensor 81 detects the pressure in the upstream flow path 62. The pressure in the upstream flow path 62 is an upstream pressure, which is the pressure in the supply path 61 upstream of the injector 64. Note that the upstream of the injector 64 is upstream in the direction in which hydrogen flows through the supply path 61.

[0032] The downstream pressure sensor 82 detects the pressure in the downstream flow path 63. The pressure in the downstream flow path 63 is a downstream pressure, which is the pressure in the supply path 61 downstream of the injector 64. Note that the downstream side of the injector 64 is downstream in the direction in which hydrogen flows through the supply path 61.

[0033] The power conversion device 91 is connected to the fuel cell stack 21. The power conversion device 91 is, for example, a DC / DC converter that transforms the output power of the fuel cell stack 21 and outputs the transformed power. The power conversion device 91 transforms the output power of the fuel cell stack 21 to 48 V and outputs the transformed power. The power output from the power conversion device 91 is supplied to the load 201, thereby driving the load 201.

[0034] The control device 110 includes a processor 111 and a memory unit 112. The memory unit 112 includes a random access memory (RAM) and a read-only memory (ROM). The memory unit 112 stores program code or instructions configured to cause the processor 111 to execute processes. The memory unit 112, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control device 110 may be configured with a hardware circuit such as an ASIC or FPGA. The control device 110, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as an ASIC or FPGA, or a combination thereof.

[0035] The control device 110 controls the fuel cell system 20. The control device 110 is configured to be able to communicate with the host control device 203. The control device 110 controls the amount of power generated by the fuel cell stack 21 in response to commands from the host control device 203. In this embodiment, the pressure of the hydrogen supplied from the supply source 202 is maintained at or below a predetermined value. The predetermined value is, for example, 0.1 [MPa.G]. The control device 110 supplies hydrogen to the fuel cell stack 21 by controlling the injector 64. The control of the injector 64 performed by the control device 110 will be described. The control device 110 can obtain the upstream pressure from the upstream pressure sensor 81. The control device 110 can obtain the downstream pressure from the downstream pressure sensor 82.

[0036] <Control performed by the control device> Fig. 2(a) shows the command output by the upper control device 203. Fig. 2(b) shows the fluctuations in downstream pressure and upstream pressure. Fig. 2(c) shows the open / closed state of the injector 64.

[0037] 2(a) to 2(c), the upper control device 203 outputs a power generation command and a power generation stop command. The power generation command is a command that requests the control device 110 to generate power in the fuel cell stack 21. The power generation stop command is a command that requests the control device 110 to stop power generation in the fuel cell stack 21.

[0038] When the controller 110 receives a command to generate electricity, it maintains the injector 64 in an open state. While the injector 64 is maintained in an open state, the downstream pressure is maintained constant. As described above, in this embodiment, the injector 64 is maintained in an open state while the fuel cell stack 21 is generating electricity. The flow rate of hydrogen to the fuel cell stack 21 depends on the difference between the upstream pressure and the downstream pressure. When the upstream pressure is low, it is difficult to create a difference between the upstream pressure and the downstream pressure, and therefore, when the injector 64 is operated intermittently, the flow rate of hydrogen to the fuel cell stack 21 decreases. For this reason, depending on the pressure of hydrogen supplied from the supply source 202, it may be necessary to maintain the injector 64 in an open state when the fuel cell stack 21 is generating electricity. In this embodiment, by maintaining the injector 64 in an open state when the fuel cell stack 21 is generating electricity, a decrease in the flow rate of hydrogen to the fuel cell stack 21 is prevented.

[0039] The control device 110 closes the injector 64 when a predetermined condition is met. The condition is set to be met when a situation in which the downstream pressure is higher than the upstream pressure can occur. In this embodiment, the condition is that the control device 110 receives a power generation stop command. When power generation by the fuel cell stack 21 stops, hydrogen is no longer consumed, and the downstream pressure increases. As a result, when the injector 64 is open, a situation in which the downstream pressure is higher than the upstream pressure can occur.

[0040] When the control device 110 receives the power generation stop command at time T1, it closes the injector 64, thereby stopping power generation in the fuel cell stack 21. When power generation in the fuel cell stack 21 stops, the downstream pressure decreases over time. This is because cross leakage occurs, in which hydrogen on the anode side moves to the cathode side.

[0041] The control device 110 maintains the injector 64 in a closed state until the downstream pressure becomes equal to or less than the first threshold at time T2. When the downstream pressure becomes equal to or less than the first threshold, the control device 110 opens the injector 64. The control device 110 maintains the injector 64 in an open state until the downstream pressure becomes equal to or greater than the second threshold. By keeping the injector 64 in an open state, the downstream pressure increases over time. When the downstream pressure becomes equal to or greater than the second threshold, the control device 110 closes the injector 64. As a result, the downstream pressure decreases over time. While power generation by the fuel cell stack 21 is stopped, the control device 110 switches the injector 64 between an open state and a closed state in accordance with fluctuations in the downstream pressure, as described above. That is, the injector 64 is operated intermittently so that the downstream pressure fluctuates between the first threshold and the second threshold.

[0042] The first threshold value is a value lower than the upstream pressure. The second threshold value is a value higher than the first threshold value and lower than the upstream pressure. The first threshold value and the second threshold value are determined in advance. The first threshold value and the second threshold value are set to values ​​higher than atmospheric pressure. The difference between the first threshold value and the second threshold value is determined, for example, by the driving durability number of the injector 64. The number of times the injector 64 can be driven without failure, guaranteed by the manufacturer, is set as the driving durability number. The difference between the first threshold value and the second threshold value may be set so that the driving number of the injector 64 does not exceed the driving durability number within the expected period of operation of the fuel cell system 20.

[0043] When the control device 110 receives a power generation command at time T3, the control device 110 resumes power generation by maintaining the injector 64 in an open state. The injector 64 is maintained in an open state until the control device 110 receives a power generation stop command.

[0044] [Operation of this embodiment] The upper control device 203 controls the fuel cell system 20 by outputting commands to the control device 110. For example, the upper control device 203 switches between generating power and stopping power generation of the fuel cell stack 21 by outputting a power generation command and a power generation stop command according to the state of the load 201.

[0045] When power generation by the fuel cell stack 21 is stopped, hydrogen is no longer consumed by the fuel cell stack 21. If the injector 64 is kept open at this time, the downstream pressure will increase. In response to this, the control device 110 of this embodiment closes the injector 64 upon receiving a power generation stop command. When the injector 64 is closed, hydrogen is not supplied downstream of the injector 64. This makes it possible to suppress the increase in downstream pressure.

[0046] [Effects of this embodiment] (1) When the conditions are met, the control device 110 closes the injector 64. When the injector 64 closes, the downstream pressure decreases. This makes it possible to maintain a state in which the downstream pressure is lower than the upstream pressure. This makes it possible to prevent gas downstream of the injector 64, i.e., gas in the downstream flow path 63, from flowing back into the injector 64. The gas in the downstream flow path 63 contains moisture. By preventing this gas from flowing back into the injector 64, it is possible to prevent failure of the injector 64 due to rust on the injector 64.

[0047] Condition (2) is that the control device 110 has received a command to stop power generation of the fuel cell stack 21. When power generation of the fuel cell stack 21 is stopped, hydrogen is not consumed, so the downstream pressure is likely to rise. In this case, by maintaining a state in which the downstream pressure is lower than the upstream pressure, it is possible to maintain a state in which the downstream pressure is lower than the upstream pressure in a situation in which the downstream pressure is likely to rise.

[0048] (3) When the control device 110 closes the injector 64, it maintains the closed state until the downstream pressure becomes equal to or less than the first threshold. When the downstream pressure becomes equal to or less than the first threshold, the control device 110 opens the injector 64 until the downstream pressure becomes equal to or greater than a second threshold that is higher than the first threshold and lower than the upstream pressure. This makes it possible to maintain the downstream pressure at a value equal to or greater than the first threshold and equal to or less than the second threshold while power generation by the fuel cell stack 21 is stopped. If the downstream pressure is set below the first threshold, the potential of the fuel cell stack 21 will drop excessively, which may prevent the output power from being increased quickly when power generation by the fuel cell stack 21 is resumed. By maintaining the downstream pressure equal to or greater than the first threshold, it is possible to increase the output power quickly when power generation by the fuel cell stack 21 is resumed.

[0049] Furthermore, if the downstream pressure becomes lower than atmospheric pressure, when the exhaust / drain valve 70 is opened, there is a risk that air may flow from the outside into the circulation path 65. By maintaining the downstream pressure at or above the first threshold value, it is possible to prevent air from flowing into the circulation path 65 even when the exhaust / drain valve 70 is opened.

[0050] (4) When the control device 110 receives a power generation command for the fuel cell stack 21, it keeps the injector 64 open. As described above, when the upstream pressure is low, it is necessary to keep the injector 64 open. On the other hand, if the injector 64 is kept open even while the fuel cell stack 21 is not generating power, there is a risk that the downstream pressure will become higher than the upstream pressure as the downstream pressure increases. By operating the injector 64 intermittently while the fuel cell stack 21 is not generating power, it is possible to keep the downstream pressure lower than the upstream pressure.

[0051] (5) By controlling the injector 64, it is possible to prevent gas downstream of the injector 64 from flowing back into the injector 64. This eliminates the need to provide a check valve to prevent backflow. Compared to providing a check valve, this can prevent the fuel cell stack 21 from becoming larger and more costly.

[0052] [Example of change] The embodiment can be modified as follows: The embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0053] The condition may be that the drive rate of the circulation pump 67 exceeds a threshold. The greater the drive rate of the circulation pump 67, the higher the downstream pressure. Therefore, if the drive rate of the circulation pump 67 increases, the downstream pressure may become higher than the upstream pressure. Therefore, when the drive rate of the circulation pump 67 exceeds a threshold, the injector 64 may be closed. In this case, the control device 110 may operate the injector 64 intermittently. Whether the drive rate of the circulation pump 67 has exceeded the threshold may be determined, for example, by setting a threshold for the rotation speed of the electric motor 68 that drives the circulation pump 67 and determining whether the rotation speed of the electric motor 68 has exceeded the threshold. In this way, the control device 110 may maintain a state in which the downstream pressure is lower than the upstream pressure by closing the injector 64 during power generation by the fuel cell stack 21.

[0054] The condition may be that the difference between the downstream pressure and the upstream pressure is a predetermined pressure threshold. The condition may be a combination of the above-mentioned conditions. In this case, the control device 110 may close the injector 64 when all of the combined conditions are met.

[0055] When the potential of the fuel cell stack 21 is to be reduced to 0 [V] when power generation by the fuel cell stack 21 is stopped, upon receiving a command to stop power generation by the fuel cell stack 21, the control device 110 may maintain the injector 64 in a closed state without performing intermittent operation. When the potential of the fuel cell stack 21 is to be reduced to 0 [V] when power generation by the fuel cell stack 21 is stopped, the control device 110 closes the first valve 51 and the second valve 52.

[0056] The fuel cell system 20 does not need to include the upstream pressure sensor 81. Fluctuations occur in the pressure of the hydrogen supplied from the supply source 202. The lower limit due to the fluctuations can be determined in advance, and the control device 110 can perform control by regarding this lower limit as the upstream pressure. [Explanation of symbols]

[0057] 20... fuel cell system, 21... fuel cell stack, 61... supply path, 64... injector, 82... downstream pressure sensor, 110... control device.

Claims

1. a fuel cell stack; a supply path connecting a supply source for supplying an anode gas to the fuel cell stack and the fuel cell stack, through which the anode gas supplied from the supply source flows; an injector provided in the supply path; a downstream pressure sensor for detecting a downstream pressure in the supply passage downstream of the injector; a control device for controlling the injector, The control device A fuel cell system that maintains a state in which the downstream pressure is lower than the upstream pressure, which is the pressure in the supply path upstream of the injector, by closing the injector when a predetermined condition is met.

2. 2. The fuel cell system according to claim 1, wherein the condition is that the control device receives a command to stop power generation by the fuel cell stack.

3. When the control device closes the injector due to the satisfaction of the condition, the control device maintains the closed state until the downstream pressure becomes equal to or less than a first threshold value, 3. The fuel cell system of claim 2, wherein when the downstream pressure becomes equal to or less than the first threshold, the injector is maintained in an open state until the downstream pressure becomes equal to or greater than a second threshold that is higher than the first threshold and lower than the upstream pressure.

4. 4. The fuel cell system according to claim 2, wherein the control device maintains the injector in an open state when a power generation command for the fuel cell stack is received.

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