JP7476559B2 - Fuel Cell Systems - Google Patents

Description

The present invention relates to a fuel cell system.

There is known a fuel cell system equipped with a pump that passes at least a portion of the anode off-gas discharged from the fuel cell stack to the fuel gas exhaust passage through the fuel gas circulation passage. The anode off-gas flowing through the fuel gas circulation passage is mixed with hydrogen gas flowing through the fuel gas supply passage from the injector toward the fuel cell stack, and is then supplied again to the fuel cell stack (see, for example, Patent Document 1).

JP 2014-192033 A

Conventional fuel cell systems are equipped with a pump that circulates the anode off-gas from the fuel cell stack. This pump consumes a considerable amount of power to circulate the anode off-gas. Such power consumption by the pump reduces the power generation efficiency of the fuel cell system. In addition, the pump requires a considerable amount of installation space. The installation space for such a pump prevents the fuel cell system from being made smaller.

The present invention aims to provide a fuel cell system that can reuse the anode off-gas from the fuel cell stack for power generation, improve power generation efficiency, and be compact.

In order to solve the above problems, the fuel cell system of the present invention comprises a fuel cell that generates electricity by reacting an oxidant gas with a fuel gas, a storage tank for storing the fuel gas, a first injection device that adjusts the pressure of the fuel gas stored in the storage tank and supplies it to the fuel cell, a second injection device that adjusts the pressure of the fuel gas discharged from the fuel cell, a confluence device that connects the downstream side of the second injection device to the downstream side of the first injection device and confluences the fuel gas discharged from the fuel cell with the fuel gas supplied to the fuel cell, and a control unit that controls the injection amount of the second injection device.

The present invention makes it possible to reuse the anode off-gas from the fuel cell stack for power generation, thereby providing a fuel cell system that can improve power generation efficiency and be made compact.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. 4 is a flowchart showing an example of an algorithm for anode off-gas circulation control executed by the fuel cell system according to an embodiment of the present invention.

An embodiment of a fuel cell system according to the present invention will be described with reference to Figures 1 and 2. Note that the same or corresponding components are designated by the same reference numerals in the drawings.

Figure 1 is a diagram showing the configuration of a fuel cell system according to an embodiment of the present invention.

As shown in FIG. 1, the fuel cell system 1 according to this embodiment includes a fuel cell 3 that generates electricity by reacting hydrogen gas as a fuel gas with oxygen gas (oxygen gas contained in air) as an oxidant gas, an air supply passage 5 that supplies air to the fuel cell 3, an air exhaust passage 6 that exhausts air used in the power generation reaction from the fuel cell 3, a storage tank 7 that stores hydrogen gas, a hydrogen supply passage 8 that supplies hydrogen gas from the storage tank 7 to the fuel cell 3, a hydrogen circulation passage 9 that sends hydrogen gas exhausted from the fuel cell 3 to the hydrogen supply passage 8 and supplies it again to the fuel cell 3, and a control unit 11 that controls the operation of the fuel cell system 1.

The fuel cell system 1 supplies the power generated by the fuel cell 3 to the load 101. For example, when the fuel cell system 1 is mounted on a vehicle, the load 101 includes a motor 102 that drives the drive wheels. The motor 102 is connected to the fuel cell 3 via an inverter 103. When the vehicle is equipped with a battery 105 connected in parallel to the fuel cell system 1, the power required by the load 101 is shared between the fuel cell system 1 and the battery 105. In such a vehicle, it is preferable that the control unit 11 is able to calculate the output distribution between the fuel cell system 1 and the battery 105. The battery 105 is a storage battery, for example a lithium-ion battery.

The fuel cell 3 comprises a large number of fuel cell units 15 stacked along the stacking direction L. The fuel cell 3 comprises tens to hundreds of stacked fuel cell units 15, with the fuel cell unit 15 being the smallest unit. The number of stacked fuel cell units 15 depends on the power generation capacity required of the fuel cell 3. A stack of multiple fuel cell units 15 is called a fuel cell stack.

Each fuel cell 15 includes a membrane electrode assembly 19 (MEA) that integrates an anode 16 (fuel electrode), a solid polymer membrane 17 (electrolyte), and a cathode 18 (air electrode), and a pair of separators 21, 22 that sandwich the membrane electrode assembly 19 from the front and back.

Each fuel cell 15 also has a hydrogen gas flow passage 28 that supplies hydrogen gas as a reactant gas to the anode 16, and an air flow passage 29 that supplies air containing oxygen gas as a reactant gas to the cathode 18. The hydrogen gas flow passage 28 is defined between the anode 16 and the separator 21 facing the anode 16. The air flow passage 29 is defined between the cathode 18 and the separator 22 facing the cathode 18.

Hydrogen gas is supplied to each fuel cell 15 through the hydrogen gas flow passage 28, and air is supplied to each fuel cell 15 through the air flow passage 29. The hydrogen gas and oxygen gas contained in the air react across the membrane electrode assembly 19, generating a voltage in each fuel cell 15. The sum of the voltages generated in each fuel cell 15 is the output voltage of the fuel cell 3.

The air supply passage 5 is connected upstream of the air flow passage 29 of the fuel cell 3. The air supply passage 5 includes a compressor 35 capable of supplying air to the fuel cell 3, an intercooler 36 that cools the air compressed by the compressor 35 to a high temperature, and a bypass circuit 37 that branches off from the air supply passage 5 upstream of the intercooler 36 and merges with the air supply passage 5 downstream of the intercooler 36.

The compressor 35 is disposed upstream of the intercooler 36. The compressor 35 compresses the air it draws in and sends it to the air supply passage 5. The compressor 35 is a turbo type.

The intercooler 36 cools the air compressed by the compressor 35 when the temperature of the air is too high to supply to the fuel cell 3.

The intercooler 36 is disposed downstream of the compressor 35. The bypass circuit 37 changes the distribution amount of air passing through the intercooler 36 and the distribution amount of air bypassing the intercooler 36, among the air discharged from the compressor 35 and heading toward the fuel cell 3. In this way, the bypass circuit 37 adjusts the temperature of the air supplied to the fuel cell 3 so that it falls within an appropriate temperature range in which the power generation reaction of the fuel cell 15 occurs efficiently. The bypass circuit 37 is equipped with a bypass amount adjustment valve 39 that changes the distribution amount of air that passes through the bypass circuit 37 and bypasses the intercooler 36, thereby changing the distribution amount of air that passes through the intercooler 36.

The air exhaust passage 6 is connected downstream of the air flow passage 29 of the fuel cell 3. The air exhaust passage 6 is equipped with a back pressure valve 45. The back pressure valve 45 can change the pressure loss downstream of the fuel cell 3 to change the flow rate of air flowing to the fuel cell 3.

The hydrogen supply passage 8 is connected upstream of the hydrogen gas flow passage 28 of the fuel cell 3. The hydrogen supply passage 8 is equipped with a first injector 51 (first injection device) that adjusts the pressure of the hydrogen gas stored in the storage tank 7 to a pressure suitable for use as fuel gas for the fuel cell 3. The hydrogen gas stored in the storage tank 7 is reduced in pressure by the first injector 51 and supplied to the fuel cell 3.

The first injector 51 intermittently injects hydrogen gas at a target pressure into the fuel cell 3 at a predetermined cycle under the control of the control unit 11. The control of the injection amount of the first injector 51 functions to maintain the differential pressure between the hydrogen gas pressure in the hydrogen gas flow passage 28 of the fuel cell 3 and the air pressure in the air flow passage 29 within a predetermined range.

The hydrogen circulation passage 9 is connected downstream of the hydrogen gas flow passage 28 of the fuel cell 3. The hydrogen circulation passage 9 allows exhaust gas (hereinafter referred to as "anode off-gas") containing unreacted hydrogen gas discharged from the fuel cell 3 to flow into the hydrogen supply passage 8. The hydrogen circulation passage 9 merges with the hydrogen supply passage 8 downstream of the first injector 51 of the hydrogen supply passage 8. The hydrogen circulation passage 9 is equipped with a second injector 52 (second injection device) that adjusts the pressure of the anode off-gas, an ejector 53 (merging device) that connects the downstream side of the second injector 52 to the downstream side of the first injector 51 and merges the anode off-gas with the hydrogen gas supplied to the fuel cell 3, and a check valve 55 that prevents backflow of hydrogen gas flowing from the second injector 52 to the ejector 53.

When a valve (not shown) in the second injector 52 opens, the anode off-gas is sent through the check valve 55 and the ejector 53 into the hydrogen supply passage 8, where it merges with the hydrogen gas flowing out of the first injector 51 and is supplied again to the fuel cell 3. Note that a valve such as a pressure regulating valve or an on-off valve may be provided instead of the second injector 52.

Similarly to the first injector 51, the second injector 52 also injects hydrogen gas at a target pressure intermittently into the ejector 53 at a predetermined cycle under the control of the control unit 11. The control of the injection amount of the second injector 52 changes the pressure difference between the pressure on the upstream side of the check valve 55 (the pressure in the flow path from the second injector 52 to the check valve 55) and the pressure on the downstream side (the pressure in the flow path from the check valve 55 to the ejector 53). If this pressure difference is greater than the cracking pressure of the check valve 55, the check valve 55 opens and the anode off-gas is sent from the hydrogen circulation passage 9 to the hydrogen supply passage 8, whereas if this pressure difference is equal to or less than the cracking pressure of the check valve 55, the check valve 55 closes and the supply of the anode off-gas from the hydrogen circulation passage 9 to the hydrogen supply passage 8 is prevented.

The ejector 53 is disposed at the junction of the hydrogen supply passage 8 and the hydrogen circulation passage 9. The ejector 53 is provided at the most downstream of the hydrogen circulation passage 9 and is provided in the flow path between the first injector 51 and the fuel cell 3. The ejector 53 mixes the anode off-gas that has flowed through the hydrogen circulation passage 9 with the hydrogen gas that flows through the hydrogen supply passage 8 from the first injector 51 toward the fuel cell 3. The ejector 53 ejects the hydrogen gas flowing from the first injector 51 from a nozzle (not shown) at high speed to generate negative pressure, and uses this negative pressure to suck in the anode off-gas in the hydrogen circulation passage 9 and mix it with the hydrogen gas flowing out from the first injector 51. The ejector 53 also has a diffuser (not shown) that reduces the speed of the mixed fluid to restore pressure.

The hydrogen circulation passage 9 also includes a water-air separator 57 that separates the moisture contained in the anode off-gas that flows from the fuel cell 3 to the second injector 52. The water-air separator 57 separates the moisture contained in the anode off-gas discharged from the fuel cell 3, and sends the dry anode off-gas from which the moisture has been separated to the second injector 52. The water-air separator 57 stores the moisture separated from the anode off-gas. The water-air separator 57 includes a drain valve 58 that has the function of appropriately draining the stored moisture.

The hydrogen circulation passage 9 further includes a purge valve 59 that releases the anode off-gas to the atmosphere. The purge valve 59 is provided at a point branching off from the flow path from the steam separator 57 to the second injector 52. The purge valve 59 releases the anode off-gas from the hydrogen circulation passage 9 to the atmosphere when, for example, the check valve 55 is closed to prevent the supply of the anode off-gas from the hydrogen circulation passage 9 to the hydrogen supply passage 8. The purge valve 59 is, for example, a solenoid valve that opens and closes under the control of the control unit 11.

The air supplied to the fuel cell 3 from the air supply passage 5 is distributed to the cathode-side air flow passages 29 of each of the stacked fuel cell cells 15. The distributed air flows along the cathode-side surface of each membrane electrode assembly 19, and then is discharged to the air discharge passage 6.

The hydrogen gas supplied to the fuel cell 3 from the hydrogen supply passage 8 is distributed to the hydrogen gas flow passages 28 on the anode side of each of the stacked fuel cell cells 15. The distributed hydrogen gas flows along the anode side surface of each membrane electrode assembly 19 and is then discharged to the hydrogen circulation passage 9.

The control unit 11 is connected to the fuel cell 3, the compressor 35, the bypass amount adjustment valve 39, the back pressure valve 45, the first injector 51, the second injector 52, the steam separator 57, and the purge valve 59 via a signal line 61. The control unit 11 controls or issues an operation command to the fuel cell 3, the compressor 35, the bypass amount adjustment valve 39, the back pressure valve 45, the first injector 51, the second injector 52, the steam separator 57, and the purge valve 59 based on the amount of power (required amount of power, required output) required by the load 101. The control unit 11 may also include an operation control of the load 101. The amount of power required by the load 101 is included in a signal sent from the control unit of a higher-level system including the fuel cell system 1 to the control unit 11 of the fuel cell system 1.

The control unit 11 includes, for example, a central processing unit (CPU, not shown), an auxiliary storage device (for example, read only memory, ROM, not shown) that stores various calculation programs and parameters executed (processed) by the central processing unit, and a main storage device (for example, random access memory, RAM, not shown) in which a working area for the programs is dynamically allocated.

The fuel cell system 1 is equipped with various sensors required for the intake and exhaust of air, the reception, supply, circulation, and exhaust of hydrogen gas, and the operation control of the fuel cell 3, compressor 35, bypass amount adjustment valve 39, back pressure valve 45, first injector 51, second injector 52, steam separator 57, and purge valve 59. The control unit 11 controls the operation of the fuel cell system 1 based on information obtained from these various sensors, and supplies power to the load 101.

These various sensors include, for example, a temperature sensor 62 that measures the temperature of the fuel cell 3.

These various sensors also include, for example, a check valve upstream pressure sensor 65 (first pressure sensor) that measures the pressure (first pressure Pa) of hydrogen gas flowing from the second injector 52 to the check valve 55, a check valve downstream pressure sensor 66 (second pressure sensor) that measures the pressure (second pressure Pb) of hydrogen gas flowing from the check valve 55 to the ejector 53, and a hydrogen gas supply side pressure sensor 67 (third pressure sensor) that measures the pressure (third pressure Pc) of hydrogen gas flowing from the ejector 53 to the fuel cell 3.

Furthermore, these various sensors include, for example, a discharge flow rate sensor 71 that measures the flow rate of air discharged by the compressor 35, a rotation speed sensor 72 that measures the rotation speed of the compressor 35, a suction side pressure sensor 73 that measures the pressure on the suction side of the compressor 35, and a discharge side pressure sensor 75 that measures the pressure on the discharge side of the compressor 35.

The control unit 11 also has an anode off-gas circulation control function 81 that, for example, stops the circulation of anode off-gas through the hydrogen circulation passage 9 during warm-up operation of the fuel cell 3, and circulates the anode off-gas to the fuel cell 3 through the hydrogen circulation passage 9 after the warm-up operation is completed.

The anode off-gas circulation control function 81 is a calculation program. The anode off-gas circulation control function 81 controls the injection amount of the second injector 52 based on the differential pressure (pressure Pa-pressure Pb) between the pressure Pa measured by the check valve upstream pressure sensor 65 and the pressure Pb measured by the check valve downstream pressure sensor 66.

Here, the cracking pressure of the check valve 55 is CP. When circulating the anode off-gas, the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 so that the pressure difference between the first pressure Pa and the second pressure Pb is greater than the cracking pressure CP. When cutting off the circulation of the anode off-gas, the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 so that the pressure difference between the first pressure Pa and the second pressure Pb (pressure Pa - pressure Pb) is equal to or less than the cracking pressure CP. In other words, when circulating the anode off-gas, the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 so that the relationship of [Equation 1] is satisfied. When cutting off the circulation of the anode off-gas, the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 so that the relationship of [Equation 2] is satisfied. Furthermore, the relationship in [Equation 2] can be easily satisfied by closing the valve in the second injector 52 and setting the injection volume of the second injector 52 to zero.

[Equation 1]
(Pressure Pa) - (Pressure Pb) > (Cracking pressure CP)

[Equation 2]
(Pressure Pa) - (Pressure Pb) ≦ (Cracking pressure CP)

The control of circulating the anode off-gas by controlling the injection amount of the second injector 52 so that the relationship in [Equation 1] is satisfied, and the control of cutting off the circulation of the anode off-gas by controlling the injection amount of the second injector 52 so that the relationship in [Equation 2] is satisfied are called anode off-gas circulation control.

In addition, when the relationship between the pressure Pc of hydrogen gas flowing from the ejector 53 to the fuel cell 3 and the pressure Pb of hydrogen gas flowing from the check valve 55 to the ejector 53 is determined based on the specifications or experimental values of the ejector 53, the anode off-gas circulation control function 81 can execute anode off-gas circulation control based on the pressure Pc of hydrogen gas flowing from the ejector 53 to the fuel cell 3 and the pressure Pa of hydrogen gas flowing from the second injector 52 to the check valve 55. In this case, the fuel cell system 1 does not need to be provided with a check valve downstream pressure sensor 66 that measures the pressure Pb of hydrogen gas flowing from the check valve 55 to the ejector 53. In this case, if the relationship between the pressure Pc of the hydrogen gas flowing from the ejector 53 to the fuel cell 3 and the pressure Pb of the hydrogen gas flowing from the check valve 55 to the ejector 53 is defined as ΔP (ΔP = pressure Pc - pressure Pb), the difference obtained by subtracting ΔP from pressure Pc (pressure Pc - ΔP) is substituted into [Equation 1] and [Equation 2] instead of pressure Pb.

Furthermore, the fuel cell system 1 does not need to include a check valve 55. In this case, the anode off-gas circulation control function 81 may include an ejector suction pressure sensor (fourth pressure sensor, not shown) that measures the pressure (fourth pressure) of the hydrogen gas flowing from the second injector 52 to the ejector 53, instead of the check valve upstream pressure sensor 65 and the check valve downstream pressure sensor 66. The anode off-gas circulation control function 81 controls the injection amount of the second injector 52 based on the pressure Pc measured by the hydrogen gas supply side pressure sensor 67 and the pressure measured by the ejector suction pressure sensor.

The suction flow rate of the ejector 53 (the flow rate of hydrogen gas flowing from the second injector 52 to the ejector 53) is determined by the supply pressure of the hydrogen gas supplied from the first injector 51 to the ejector 53. When this suction flow rate is within the guaranteed flow rate range, the ejector 53 can stably suck in the hydrogen gas on the second injector 52 side. In other words, when the suction flow rate of the hydrogen gas sucked from the second injector 52 to the ejector 53 is within the guaranteed flow rate range (guaranteed flow rate lower limit value ≦ suction flow rate ≦ guaranteed flow rate upper limit value), the ejector 53 reliably sucks in hydrogen gas from the second injector 52 side, but when this suction flow rate is outside a certain guaranteed flow rate range (guaranteed flow rate lower limit value > suction flow rate, suction flow rate > guaranteed flow rate upper limit value), it cannot stably suck in hydrogen gas from the second injector 52 side. Therefore, the correlation between the fourth pressure and the suction flow rate of the ejector 53 is obtained in advance by experiment or testing, and the guaranteed pressure range corresponding to the guaranteed flow rate range is clarified. Then, when the anode off-gas is circulated, the anode off-gas circulation control controls the opening degree of the second injector 52 so that the fourth pressure falls within the guaranteed pressure range (guaranteed pressure lower limit value≦fourth pressure≦guaranteed pressure upper limit value). Also, when the anode off-gas circulation control does not circulate the anode off-gas, the second injector 52 is fully closed.

The fuel cell system 1 can also perform anode off-gas circulation control by controlling the opening and closing of the purge valve 59.

Figure 2 is a flowchart showing an example of an algorithm for anode off-gas circulation control executed by a fuel cell system according to an embodiment of the present invention.

As shown in FIG. 2, the control unit 11 of the fuel cell system 1 according to this embodiment starts anode off-gas circulation control when the fuel cell 3 is started. The control unit 11 acquires the temperature of the fuel cell 3 from the temperature sensor 62 (step S1).

Then, the anode off-gas circulation control function 81 judges whether the temperature of the fuel cell 3 is equal to or lower than a preset temperature threshold (step S2). If the judgment in step S2 is positive, that is, if the temperature of the fuel cell 3 is equal to or lower than a preset temperature threshold (step S2 Yes), the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 by anode off-gas circulation control to stop the circulation of the anode off-gas (step S3), returns to step S1, and continues processing. In this case, the control unit 11 controls the injection amount of the second injector 52 so that the relationship of [Equation 2] is satisfied, and opens the purge valve 59 to exhaust the anode off-gas to the atmosphere.

When low-load operation is continued in a low-temperature environment, the temperature of the fuel cell 3 drops. In addition, the fuel cell 3 is not sufficiently warmed up immediately after startup in a low-temperature environment. If moist anode off-gas is circulated through the low-temperature fuel cell 3, flooding may occur in the hydrogen gas flow passage 28 in the fuel cell 3. This flooding increases the pressure loss in the hydrogen gas flow passage 28, impeding the flow of hydrogen gas and reducing the output of the fuel cell 3. Therefore, the temperature threshold is set to a temperature that does not cause flooding in the hydrogen gas flow passage 28 in the fuel cell 3 by circulating moist anode off-gas through the fuel cell 3, for example.

On the other hand, if the judgment in step S2 is negative, that is, if the temperature of the fuel cell 3 is higher than the preset temperature threshold (step S2 No), the anode off-gas circulation control function 81 controls the injection amount of the second injector 52 by anode off-gas circulation control to circulate the anode off-gas (step S4), and returns to step S2 to continue processing. In this case, the control unit 11 controls the injection amount of the second injector 52 so that the relationship of [Equation 1] is satisfied.

In addition, for example, if the drainage function of the water separator 57 is reduced or lost due to malfunction of the drain valve 58 of the water separator 57, liquid water (liquid water) may flow from the water separator 57 into the hydrogen circulation passage 9. If the anode off-gas is circulated in a state in which liquid water flows from the water separator 57 into the hydrogen circulation passage 9, flooding will occur in the hydrogen gas flow passage 28 in the fuel cell 3. Therefore, if the drainage function of the water separator 57 is reduced or lost, the anode off-gas circulation control function 81 controls the second injector 52 to stop the flow of hydrogen gas toward the ejector 53.

As described above, the fuel cell system 1 according to this embodiment includes the second injector 52 that adjusts the pressure of the hydrogen gas discharged from the fuel cell 3, and the ejector 53 that connects the downstream side of the second injector 52 to the downstream side of the first injector 51 to merge the hydrogen gas discharged from the fuel cell 3 with the hydrogen gas supplied to the fuel cell 3. Therefore, the fuel cell system 1 can circulate the anode off-gas to the fuel cell 3 without using a pump as in conventional fuel cell systems. In other words, the fuel cell system 1 can circulate the anode off-gas to the fuel cell 3 using a fuel injection device or valve that is generally more energy-efficient and compact than a pump. Therefore, the fuel cell system 1 can suppress the decrease in power generation efficiency as in conventional fuel cell systems and can be easily miniaturized.

The fuel cell system 1 according to this embodiment is also provided with a check valve 55 that prevents the backflow of hydrogen gas flowing from the second injector 52 to the ejector 53. Therefore, the fuel cell system 1 can prevent the backflow of hydrogen gas in the hydrogen circulation passage 9 without consuming electricity. Compared to conventional fuel cell systems equipped with a pump, the fuel cell system 1 can switch between circulating and stopping the circulation of anode off-gas to the fuel cell 3 with a simple configuration including the second injector 52 or a valve and a check valve 55, and can prevent the backflow of hydrogen gas in the hydrogen circulation passage 9. Furthermore, the fuel cell system 1 can improve the robustness of the backflow prevention function of hydrogen gas in the hydrogen circulation passage 9 with the second injector 52 or the valve and the check valve 55.

Furthermore, the fuel cell system 1 according to this embodiment controls the injection amount of the second injector 52 based on the pressure difference (pressure Pa-pressure Pb) between the pressure Pa measured by the check valve upstream pressure sensor 65 and the pressure Pb measured by the check valve downstream pressure sensor 66. Therefore, the fuel cell system 1 can very easily switch between circulating the anode off-gas to the fuel cell 3 and stopping the circulation. The fuel cell system 1 can also control the injection amount of the second injector 52 based on the pressure Pc of the hydrogen gas flowing from the ejector 53 to the fuel cell 3 and the pressure Pa of the hydrogen gas flowing from the second injector 52 to the check valve 55. The fuel cell system 1 can also control the injection amount of the second injector 52 based on the pressure Pc measured by the hydrogen gas supply side pressure sensor 67 and the pressure measured by the ejector suction pressure sensor.

In addition, the fuel cell system 1 according to this embodiment controls the second injector 52 or the valve to stop the flow of hydrogen gas toward the ejector 53 when the temperature of the fuel cell 3 is equal to or lower than the temperature threshold. Therefore, the fuel cell system 1 can easily prevent flooding caused by a drop in the temperature of the fuel cell 3 when the fuel cell 3 is started up or operated at a low load in a low-temperature environment.

Furthermore, in the fuel cell system 1 according to this embodiment, if the water-air separator 57 loses its drainage function, the second injector 52 or the valve is controlled to stop the flow of hydrogen gas toward the ejector 53. Therefore, the fuel cell system 1 can easily prevent flooding from occurring even if the water-air separator 57 loses its drainage function.

Therefore, the fuel cell system 1 according to the present invention makes it possible to reuse the anode off-gas of the fuel cell 3 for power generation, improving power generation efficiency and enabling miniaturization.

1... fuel cell system, 3... fuel cell, 5... air supply passage, 6... air exhaust passage, 7... storage tank, 8... hydrogen supply passage, 9... hydrogen circulation passage, 11... control unit, 15... fuel cell cell, 16... anode electrode, 17... solid polymer membrane, 18... cathode electrode, 19... membrane electrode assembly, 21, 22... separator, 28... hydrogen gas flow passage, 29... air flow passage, 35... compressor, 36... intercooler, 37... bypass circuit, 39... bypass amount adjustment valve, 45... back pressure valve, 51... first injector, 52... second injector Injector, 53...Ejector, 55...Check valve, 57...Water-steam separator, 58...Drain valve, 59...Purge valve, 61...Signal line, 62...Temperature sensor, 65...Pressure sensor upstream of check valve, 66...Pressure sensor downstream of check valve, 67...Hydrogen gas supply side pressure sensor, 71...Discharge flow rate sensor, 72...Rotation speed sensor, 73...Suction side pressure sensor, 75...Discharge side pressure sensor, 81...Anode off-gas circulation control function, 101...Load, 102...Motor, 103...Inverter, 105...Battery.

Claims (6)

a fuel cell that generates electricity by reacting an oxidant gas with a fuel gas;
A storage tank for storing the fuel gas;
a first injection device that adjusts the pressure of the fuel gas stored in the storage tank and supplies the fuel gas to the fuel cell;
a second injection device for adjusting the pressure of the fuel gas discharged from the fuel cell;
a confluence device that connects a downstream side of the second injection device to a downstream side of the first injection device and confluences the fuel gas discharged from the fuel cell with the fuel gas supplied to the fuel cell;
a control unit that controls the injection amount of the second injection device. The fuel cell system according to claim 1 , further comprising a check valve for preventing a backflow of the fuel gas flowing from the second injection device to the merging device. a first pressure gauge for measuring a first pressure of the fuel gas flowing from the second injection device to the check valve;
a second pressure gauge for measuring a second pressure of the fuel gas flowing from the check valve to the junction device,
The fuel cell system according to claim 2 , wherein the control unit controls the injection amount of the second injection device based on a pressure difference between the first pressure and the second pressure. a third pressure gauge for measuring a third pressure of the fuel gas flowing from the junction device to the fuel cell;
a fourth pressure gauge that measures a fourth pressure of the fuel gas flowing from the second injection device to the junction device,
3. The fuel cell system according to claim 1, wherein the control unit controls an injection amount of the second injection device based on a pressure difference between the third pressure and the fourth pressure. a thermometer for measuring a temperature of the fuel cell;
5. The fuel cell system according to claim 1, wherein the control unit controls the second injection device to stop the flow of the fuel gas toward the merging device when the temperature is equal to or lower than a threshold value. a water-steam separator that separates water contained in the fuel gas flowing from the fuel cell to the second injection device ,
6. The fuel cell system according to claim 1, wherein the control unit controls the second injection device to stop the flow of the fuel gas toward the junction device when the steam-water separator loses its drainage function.

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