Fuel cell system

Abstract

To provide a fuel cell system in which a control unit can determine whether an air flow rate detected by a flow meter corresponds to an actual air flow rate or to a lower air flow rate than the actual air flow rate.SOLUTION: The present invention provides a fuel cell system A that includes: a housing container (9) having an internal space (9s) for accommodating a cell stack (6) and a combustion unit (8); an air supply passage (13) connecting an air blower (7) and the housing container (9), the air supply passage being provided with a flow meter (22) disposed between the air blower and the housing container; and a control unit (10). The control unit (10) acquires an air flow rate passing through the air supply passage (13) and controls the duty ratio of power supplied to the air blower (7) to regulate the air flow rate. When the period during which the duty ratio required to maintain a predetermined flow rate exceeds a predetermined duty ratio by a predetermined margin or more continues for a predetermined time or longer, and when the duty ratio required to maintain a low-output flow rate exceeds a low-output duty ratio by a predetermined margin or more, the control unit (10) determines that the flow meter (22) is detecting an air flow rate smaller than the actual air flow rate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] The fuel cell system generates electricity by subjecting a plurality of cells provided in a cell stack to a power generation reaction between a hydrogen-containing gas supplied from a reformer and air supplied from an air blower. In the combustion section, combustible components in the anode exhaust gas discharged through the gas discharge edge of each cell are combusted with oxygen in the cathode exhaust gas also discharged through the gas discharge edge of each cell, and the resulting combustion heat heats the reformer and evaporator. The reformer, which reforms the raw fuel into a hydrogen-containing gas, the evaporator, which evaporates supplied reforming water to produce steam for the reforming process, the combustion section, which heats the reformer and evaporator, and the cell stack are all housed in the internal space of a storage container.

[0003] The hydrogen-containing gas produced in the reformer is supplied to a manifold through a hydrogen-containing gas passage, and is then distributed from the manifold to the fuel electrodes of the multiple cells in the cell stack. Meanwhile, air is supplied by an air blower through an air supply passage into the internal space of the storage container, and the air supplied to the internal space of the storage container is then supplied to the oxygen electrodes of each cell via the air inlet of each of the multiple cells in the cell stack (see, for example, Patent Document 1). The fuel cell system has a control unit, which controls the operation of the fuel cell system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-191710 Summary of the Invention [Problem to be solved by the invention]

[0005] The outside air supplied to the interior space of the container by the air blower through the air supply passage contains fine particulate matter such as dust, PM2.5, and yellow sand. Therefore, the air supply system including the air blower and the air supply passage includes an air filter that purifies the air sent out by the air blower. The air filter is located upstream of the air blower.

[0006] As the fuel cell system continues to operate, particulate matter may adhere to the air supply system, such as the air filter and air blower, causing clogging. If clogging occurs, the pressure loss in the air supply system increases over the course of the fuel cell system's operation, causing the air flow condition in the air supply system to deteriorate. The air flow condition is determined by the control unit by constantly detecting the air flow rate using a flow meter installed in the air supply path.

[0007] When the control unit determines that the air flow condition of the air supply system is deteriorating due to an increase in pressure loss, it increases the duty ratio of the voltage applied to the air blower to increase the flow rate of air supplied to the internal space of the storage container. However, depending on the state of adhesion of particulate matter, the flow meter may detect a flow rate lower than the actual flow rate of air, which has decreased due to an increase in pressure loss. In this case, the control unit increases the air flow rate based on the lower flow rate than the actual flow rate, thereby increasing the duty ratio of the voltage applied to the air blower more than necessary. This has led to the problem of the amount of air supplied to the storage container being greater than necessary.

[0008] The present invention has been made in consideration of the above-mentioned situation, and its purpose is to provide a fuel cell system in which a control unit can determine whether the air flow rate detected by a flow meter is the actual air flow rate or a flow rate lower than the actual air flow rate. [Means for solving the problem]

[0009] In order to achieve the above object, the fuel cell system according to the present invention has an evaporator that evaporates reforming water supplied by a reforming water pump, a reformer that generates hydrogen-containing gas by causing a reforming reaction between raw fuel supplied by a raw fuel pump and steam supplied from the evaporator, an air blower that takes in air from the outside and sends it out, an air filter that purifies the air taken in by the air blower, a fuel electrode, and an oxygen electrode, and the hydrogen-containing gas is supplied from the reformer to the fuel electrode and the air sent out by the air blower is supplied to the oxygen electrode, and the fuel cell system generates electricity by using a plurality of cells. a combustion unit that burns combustible components in the anode exhaust gas discharged from the anode with oxygen in the cathode exhaust gas discharged from the cathode, and heats the reformer and the evaporator with the combustion heat; a storage container that houses the evaporator, the reformer, the cell stack, and the combustion unit in its internal space; an air supply path that connects the air blower to the storage container and supplies the air sent out from the air blower to the internal space of the storage container; and a detector that is disposed in the air supply path and detects the flow rate of the air sent out by the air blower. The air filter and the air blower are provided with a flow meter and a control unit for controlling operation, and the control unit acquires the flow rate of the air sent from the air blower and detected by the flow meter, and controls the flow rate by controlling the duty ratio to control the supply of electricity to the air blower, and is configured to determine that the flow meter is detecting a flow rate that is smaller than the actual flow rate when: a predetermined duty ratio, which is the duty ratio for passing a predetermined flow rate when a predetermined power is output, which is a predetermined output power when an air supply system including the air filter, the air blower, and the air supply path is not clogged, is greater than the predetermined duty ratio by at least a predetermined percentage for a predetermined period of time; and a low-power duty ratio, which is the duty ratio for passing a low-power flow rate, which is the flow rate when a power lower than the predetermined power is output when the air supply system is not clogged, is greater than the low-power duty ratio by at least the predetermined percentage.

[0010] According to the above characteristic configuration, the fuel cell system is operated at a predetermined output power, and the control unit continuously acquires the air flow rate and duty ratio. Then, the system is operated at a low power, and the control unit acquires the air flow rate and duty ratio. By comparing the duty ratio and air flow rate when the air supply path is not clogged with particulate matter with the duty ratio and air flow rate when the air supply path is clogged with particulate matter, it is possible to determine that the flow meter is detecting a flow rate that is lower than the actual flow rate and to identify signs of a malfunction.

[0011] A further characteristic feature of the fuel cell system according to the present invention is that the control unit is configured to, when it determines that the flow meter is detecting a flow rate that is smaller than the actual flow rate, execute an air flow improvement operation in which the control unit activates the reforming water pump and stops the raw fuel pump and the air blower.

[0012] According to the above characteristic configuration, by performing the air flow improvement operation, high-temperature water vapor can be caused to flow back from the storage container to the air supply passage, thereby eliminating blockage of particulate matter in the air supply passage.

[0013] A further characteristic feature of the fuel cell system according to the present invention is that the predetermined ratio is 20%.

[0014] According to the above characteristic configuration, it is possible to reliably determine that the flow meter is detecting a flow rate that is smaller than the actual flow rate.

[0015] A further characteristic feature of the fuel cell system according to the present invention is that the predetermined period is one month.

[0016] According to the above characteristic configuration, it is possible to reliably determine that the flow meter is detecting a flow rate that is smaller than the actual flow rate.

[0017] A further characteristic feature of the fuel cell system according to the present invention is that when the increase in the duty ratio for passing the low-power flow rate relative to the low-power duty ratio is less than the predetermined percentage relative to the low-power duty ratio, the control unit determines that a blockage has occurred in the air supply path including the flow meter, or that the air blower has failed.

[0018] According to the above characteristic configuration, it is possible to know the occurrence of a fault other than a symptom of a fault such as the flow meter detecting a flow rate that is lower than the actual flow rate. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a block diagram showing the flow state of fluids during normal operation of the fuel cell system according to the first embodiment. [Figure 2] FIG. 10 is a flowchart showing a control operation. [Figure 3] FIG. 2 is a block diagram showing the fluid flow state during air flow improvement operation of the fuel cell system according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] [First embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a fuel cell system A according to an embodiment of the present invention is configured to include an evaporator 2, a raw fuel pump 3, a reformer 4, a cell stack 6, an air blower 7, a combustion unit 8, a storage container 9, and a control unit 10. The evaporator 2 evaporates reforming water supplied by a reforming water pump 1. The reformer 4 generates a hydrogen-containing gas by a reforming reaction between the raw fuel gas (e.g., natural gas-based city gas such as 13A) supplied by the raw fuel pump 3 and the steam supplied from the evaporator 2. The cell stack 6 is configured by stacking a plurality of cells 5, each of which generates electricity by supplying the hydrogen-containing gas from the reformer 4 to the fuel electrode 5a and air from the air blower 7 to the oxygen electrode 5c. The combustion unit 8 combusts combustible components in the fuel electrode exhaust gas discharged from the fuel electrode 5a with oxygen in the oxygen electrode exhaust gas discharged from the oxygen electrode 5c, and heats the reformer 4 and the evaporator 2 with the resulting combustion heat. The storage container 9 accommodates the evaporator 2, the reformer 4, the cell stack 6, and the combustion section 8 in an internal space 9s. The control section 10 controls the operation of the fuel cell system A.

[0021] The cell stack 6 is provided with a manifold 12 that can distribute and supply the hydrogen-containing gas supplied from the reformer 4 through a hydrogen-containing gas passage 11 to the fuel electrodes 5a of each cell 5. In addition, an air supply passage 13 that can supply air from an air blower 7 to the internal space 9s of the storage container 9 is connected to the storage container 9. Furthermore, in the internal space 9s of the storage container 9, the multiple cells 5 of the cell stack 6 are configured so that they can discharge the fuel electrode exhaust gas from the fuel electrode 5a of each cell 5 and the oxygen electrode exhaust gas from the oxygen electrode 5c of each cell 5 to the surrounding space through a gas discharge edge portion 5e that is part of the periphery of each cell 5, and can introduce air from the surrounding space to the oxygen electrode 5c of each cell 5 through an air inlet portion 5i that is separated from the gas discharge edge portion 5e of each cell 5.

[0022] Next, each component of the fuel cell system A will be described. The cells 5 and the cell stack 6 are well known, and therefore will be briefly described without detailed explanation or illustration. The cells 5 are configured as solid oxide cells with a solid electrolyte layer (not shown) between the fuel electrode 5a and the oxygen electrode 5c. The solid electrolyte layer is made of, for example, zirconium oxide. Each cell 5 of the cell stack 6 is configured as a roughly rectangular plate, allowing a hydrogen-containing gas to flow along the surface of the fuel electrode 5a and air to flow along the surface of the oxygen electrode 5c. One of a pair of opposing edge portions of each cell 5 is configured as a gas discharge edge portion 5e through which fuel electrode exhaust gas from the fuel electrode 5a and oxygen electrode exhaust gas from the oxygen electrode 5c are discharged, and the vicinity of the other edge portion is configured as an air inlet portion 5i through which air can be introduced into the oxygen electrode 5c. Although not shown, the edge portion of each cell 5 near which the air inlet portion 5i is configured is provided with a hydrogen-containing gas inlet through which a hydrogen-containing gas can be introduced into the fuel electrode 5a.

[0023] Then, a cell stack 6 is formed by assembling multiple cells 5 in a stacked state while electrically connected in series, with each cell 5 having its gas discharge edge 5e facing in the same direction and each edge having a hydrogen-containing gas inlet facing in the same direction.

[0024] The manifold 12 is disposed on the side surface of the cell stack 6 where the edge portion where the hydrogen-containing gas inlet of each cell 5 is provided is located, in a state where the hydrogen-containing gas inlet of each cell 5 is in communication with the manifold 12. In this way, in the cell stack 6 equipped with the manifold 12, the air inlet 5i of each cell 5 is exposed to the surrounding space and is configured so that the air inlet 5i of each cell 5 can receive air from the surrounding space.

[0025] The cell stack 6 configured in this manner is disposed in the storage container 9 in an orientation in which the manifold 12 is located below, the gas discharge edge 5e of each cell 5 faces upward, and the stacking direction of the multiple cells 5 is horizontal. In the internal space 9s of the storage container 9, an evaporator 2 and a reformer 4 are disposed side by side above the cell stack 6 at a distance from the cell stack 6.

[0026] A combustion space 14 between the cell stack 6 and the evaporator 2 and reformer 4 in the internal space 9s of the storage container 9 is configured so that the anode exhaust gas and oxygen electrode exhaust gas are discharged from the gas discharge edge 5e of each cell 5 and combustible components in the anode exhaust gas can be combusted with oxygen in the oxygen electrode exhaust gas, and this combustion space 14 is used as a combustion unit 8. The combustion unit 8 is provided with an ignition heater 15 that ignites the combustible components in the anode exhaust gas. The combustion unit 8 formed in the combustion space 14 is configured so that the combustible components in the anode exhaust gas can be combusted with oxygen in the oxygen electrode exhaust gas and the combustion heat generated by this combustion can heat the evaporator 2, reformer 4, and cell stack 6 disposed in the internal space 9s of the storage container 9.

[0027] A reforming water supply path 16, through which reforming water is pumped by a reforming water pump 1, is drawn from the outside of the storage container 9 and connected to the evaporator 2, and a raw fuel gas supply path 17, through which raw fuel gas is pumped by a raw fuel pump 3, is also drawn from the outside of the storage container 9 and connected to the evaporator 2. A raw fuel adjustment valve 18 is provided in the raw fuel gas supply path 17 to adjust the flow rate of the raw fuel gas.

[0028] The evaporator 2 is configured to heat and evaporate the reforming water supplied through the reforming water supply passage 16 using the combustion heat transmitted from the combustion section 8, and to mix the water vapor generated by the evaporation of the reforming water with the raw fuel gas supplied through the raw fuel gas supply passage 17.

[0029] The reformer 4 is filled with a reforming catalyst (not shown). The evaporator 2 and the reformer 4 are connected by a relay path 19 so that the raw fuel gas mixed with steam in the evaporator 2 is introduced into the reformer 4. The reformer 4 is configured to reform the raw fuel gas mixed with steam supplied from the evaporator 2 with steam using combustion heat transferred from the combustion section 8, thereby reforming the raw fuel gas into a reformed gas containing hydrogen, i.e., a hydrogen-containing gas.

[0030] The reformer 4 and the manifold 12 are connected by a hydrogen-containing gas passage 11 so as to supply the hydrogen-containing gas produced in the reformer 4 to the manifold 12. The hydrogen-containing gas supplied to the manifold 12 is distributed from the hydrogen-containing gas inlet of each of the plurality of cells 5 of the cell stack 6 to the fuel electrodes 5a of each cell 5, flows upward through the fuel electrodes 5a of each cell 5, and is used for the power generation reaction. After that, the gas is discharged from the gas discharge edge 5e of each cell 5 as fuel electrode exhaust gas into the combustion space 14 used as the combustion section 8.

[0031] An air inlet 20 is provided at the bottom of the storage container 9, and an air supply path 13 through which air is sent out by an air blower 7 is connected to the air inlet 20. An air filter 21 that purifies the air sent out by the air blower 7 is provided in a portion of the air supply path 13 upstream of the air blower 7. In addition, an air flow meter 22 (an example of a flow meter) that detects the flow rate of air supplied through the air supply path 13 is provided in a portion of the air supply path 13 downstream of the air blower 7. In other words, the air supply path 13, the air blower 7, the air filter 21, and the air flow meter 22 constitute an air supply system 23 that supplies air to the oxygen electrodes 5c of each of the multiple cells 5 in the cell stack 6.

[0032] Then, air is purified by the air blower 7 through the air filter 21 and then supplied to the internal space 9s of the storage container 9 through the air supply path 13. The air supplied to the internal space 9s of the storage container 9 in this manner is supplied to the oxygen electrodes 5c of each of the multiple cells 5 of the cell stack 6 from the air inlet portions 5i of each of the cells 5, flows upward through the oxygen electrodes 5c of each cell 5, and is used for the power generation reaction. After that, the air is discharged as oxygen electrode exhaust gas from the gas discharge edge portions 5e of each cell 5 into the combustion space 14 used as the combustion section 8. Then, in the combustion section 8, combustible components in the anode exhaust gas are combusted with the oxygen in the oxygen electrode exhaust gas.

[0033] Furthermore, the storage container 9 is formed with a combustion exhaust gas outlet 24 at the bottom or the like, which discharges the combustion exhaust gas generated in the combustion section 8 to the outside, and a carbon monoxide removal section 25 is provided near the opening of the combustion exhaust gas outlet 24 on the inner surface of the storage container 9, which contains a combustion catalyst (e.g., a platinum-based catalyst) that removes carbon monoxide gas from the combustion exhaust gas discharged to the outside from the combustion exhaust gas outlet 24.

[0034] Next, a description will be given of the control operation of the control unit 10. An operation unit 26 is provided to transmit various information, such as operation commands for the fuel cell system A, to the control unit 10, and the operation unit 26 is provided with a display 27 that displays and outputs various information. Incidentally, the display 27 is configured as an LCD (liquid crystal display).

[0035] The control unit 10 includes a communication unit 30 and a judgment and instruction unit 31. The communication unit 30 communicates with a host computer 29 in a management center (not shown) via a communication network 28 such as the Internet. The management center is installed at a city gas supply company or the like, and the host computer 29 is configured to be able to communicate with the communication units 30 of multiple fuel cell systems A. The communication unit 30 is configured to communicate operating information of the fuel cell system A, such as the consumption amount of raw fuel gas, the output power value, the flow rate of air flowing through the air supply path 13, the voltage applied to the air blower 7, and abnormality information, to the host computer 29 via the communication network 28. The fuel cell system A can also be operated from the host computer 29 via the communication network 28.

[0036] The judgment instruction unit 31 is configured to control the operation of the reforming water pump 1, the raw fuel pump 3, the raw fuel regulating valve 18, the air blower 7, the ignition heater 15, etc., based on commands from the operation unit 26, including commands for the output power value output from the fuel cell system A, and detection information from the air flow meter 22, etc.

[0037] An explanation will now be given of the control of the voltage applied to the air blower 7 to adjust the flow rate of air flowing through the air supply path 13. The judgment instruction unit 31 controls the voltage value applied to the air blower 7 by changing the duty ratio using PWM (Pulse Width Modulation) control, which controls the voltage applied to the air blower 7 through duty control.

[0038] Normal operation will now be described. During normal operation, the judgment and instruction unit 31 operates the raw fuel pump 3, the reforming water pump 1, and the air blower 7 based on the predetermined power setting, which is the predetermined output power of the fuel cell system A set by the operation unit 26. The predetermined power is, for example, rated power. At this time, the judgment and instruction unit 31 operates the raw fuel regulating valve 18 so that the flow rate of the raw fuel gas corresponds to the predetermined power output from the cell stack 6. The judgment and instruction unit 31 also controls the output of the reforming water pump 1 so that the flow rate of the reforming water corresponds to the flow rate of the raw fuel gas. The fuel cell system A has a memory unit (not shown) that stores a data table relating to the flow rates of the raw fuel gas and the reforming water corresponding to the predetermined power. The judgment and instruction unit 31 reads data relating to the flow rates of the raw fuel gas and the reforming water corresponding to the set predetermined power from the memory unit, and controls the aperture of the raw fuel regulating valve 18 and the output of the reforming water pump 1. In addition, the judgment instruction unit 31 controls the duty ratio of the voltage applied to the air blower 7 (hereinafter simply referred to as the duty ratio of the air blower 7) so that the flow rate of air flowing through the air supply path 13 detected by the air flow meter 22 corresponds to the flow rate of the raw fuel gas.

[0039] In normal operation of the fuel cell system A when outputting a predetermined power in a state where the air supply system 23 is not clogged with particulate matter, a predetermined duty ratio is applied to the air blower 7, and a predetermined flow rate, which is the flow rate of air flowing through the air supply path 13, is detected by the air flow meter 22. The judgment instruction unit 31 continuously acquires the predetermined flow rate and the duty ratio. A data table showing the relationship between the predetermined flow rate and the predetermined duty ratio is pre-stored in the memory unit. In addition, a data table showing the relationship between the low output duty ratio and the low output flow rate at low power where the output of the fuel cell system A is lower than the predetermined power by a predetermined percentage (for example, 70%) or more is also pre-stored in the memory unit. The low output duty ratio is the duty ratio in a state where the air supply system 23 is not clogged with particulate matter when outputting low power, and the low output flow rate is the flow rate of air in this state.

[0040] In this embodiment, during normal operation, the judgment and instruction unit 31 acquires the air flow rate detected by the air flow meter 22 and controls the duty ratio of the air blower 7. However, as the operation time of the fuel cell system A passes, particulate matter such as dust, PM2.5, and yellow sand contained in the outside air may adhere to the air supply system 23, causing clogging. When clogging occurs, the pressure loss in the air supply system 23 increases, deteriorating the air flow condition of the air supply system 23. Specifically, the air flow rate detected by the air flow meter 22 decreases. When the air flow condition deteriorates, the judgment and instruction unit 31 increases the duty ratio of the air blower 7 to maintain a predetermined power, thereby controlling the air flow rate corresponding to the predetermined power. In other words, when the air supply system 23 is clogged, a higher duty ratio is applied to the air blower 7 than when the air supply system 23 is not clogged, in order to ensure the same air flow rate.

[0041] In the fuel cell system A, depending on the state of adhesion of particulate matter to the air supply system 23, the air flow meter 22 may detect a flow rate lower than the actual flow rate of air that has decreased due to an increase in pressure loss. In this case, the control unit 10 increases the air flow rate based on the flow rate lower than the actual air flow rate, resulting in an unnecessarily large duty ratio for the air blower 7. As a result, a problem occurs in that more air than is required to output a predetermined amount of power is supplied to the oxygen electrodes 5c of the multiple cells 5 of the cell stack 6 disposed in the internal space 9s of the storage container 9.

[0042] Therefore, in the fuel cell system A, the judgment instruction unit 31 judges whether the air flow rate detected by the air flow meter 22 is the same as the actual air flow rate (hereinafter simply referred to as a "normal reading") or is lower than the actual air flow rate (hereinafter simply referred to as a "low reading") based on the duty ratio of the air blower 7 and the air flow rate detected by the air flow meter 22 when the air flows through the air supply path 13 at that duty ratio. In this embodiment, the occurrence of a "low reading" is regarded as a sign of a malfunction in the fuel cell system A. This judgment procedure will be explained below using FIG. 2.

[0043] During normal operation of the fuel cell system A when outputting a predetermined power when the air supply system 23 is not clogged with particulate matter, a predetermined duty ratio is applied to the air blower 7, and a predetermined flow rate, which is the flow rate of air flowing through the air supply path 13, is detected by the air flow meter 22. The judgment instruction unit 31 continuously acquires this predetermined flow rate and duty ratio (step S1). Thereafter, if normal operation continues and the air supply system 23 becomes clogged with particulate matter, the duty ratio that needs to be applied to the air blower 7 to ensure the predetermined flow rate increases. The judgment instruction unit 31 applies a voltage with a high duty ratio to the air blower 7.

[0044] Then, when the duty ratio of the voltage applied to the air blower 7 becomes greater than the predetermined duty ratio by a predetermined percentage (for example, 20%) or more (Yes in step S2) and this period continues for a predetermined period (for example, one month) or more (Yes in step S3), the judgment instruction unit 31 judges to switch to low power. Specifically, the judgment instruction unit 31 controls the aperture of the raw fuel regulating valve 18, the output of the reforming water pump 1, and the duty ratio of the air blower 7 to reduce the flow rate of air flowing through the air supply path 13, and switch the output of the fuel cell system A to low power (step S4).

[0045] The judgment command unit 31 acquires the air flow rate and duty ratio even during low power output. When the air flow rate during low power output is the low-power flow rate, if the duty ratio applied to the air blower 7 is greater than the low-power duty ratio by a predetermined percentage (e.g., 20%) or more (Yes in step S5), the judgment command unit 31 determines that the air flow rate detected by the air flow meter 22 is less than the actual flow rate, that is, that the air flow meter 22 is reading low (step S6).

[0046] When the air flow rate is the low-power flow rate during low-power output, if the duty ratio applied to the air blower 7 is less than a predetermined percentage of the low-power duty ratio (No in step S5), the judgment commander 31 determines that the air flow rate detected by the air flow meter 22 is the same as the actual flow rate, that is, the air flow meter 22 is reading normally (not low), and the air supply system 23 is clogged with particulate matter, or the air blower 7 is broken (step S7). If the air flow meter 22 is reading normally, this is because when the air is at a low-power flow rate, pressure loss decreases and the duty ratio applied to the air blower 7 approaches the low-power duty ratio.

[0047] As described above, a low reading from the air flow meter 22 is a sign of a malfunction in the fuel cell system A, and therefore, after step S6, measures are taken to reduce the pressure loss as necessary. For example, when the judgment instruction unit 31 determines that the air flow meter 22 has read a low reading, it terminates normal operation in which the reforming water pump 1, the raw fuel pump 3, and the air blower 7 are activated, and executes air flow improvement operation in which the reforming water pump 1 is activated and the raw fuel pump 3 and the air blower 7 are stopped.

[0048] In the air flow improved operation, as shown in Fig. 3, the raw fuel pump 3 and the air blower 7 are stopped, and the reforming water pump 1 is operated to supply reforming water to the evaporator 2 through the reforming water supply passage 16. Then, in the evaporator 2, the reforming water is evaporated by the residual heat of the evaporator 2 itself, the residual heat of the combustion section 8, and the residual heat in the storage container 9. The high-temperature steam generated by the evaporation of the reforming water is supplied to the reformer 4 through the relay passage 19, heated by the residual heat of the reformer 4, and further supplied to the manifold 12 through the hydrogen-containing gas passage 11. The high-temperature steam supplied to the manifold 12 is distributed and supplied to the fuel electrodes 5a of the multiple cells 5 of the cell stack 6, flows upward through the fuel electrodes 5a of each cell 5, and is discharged from the gas discharge edge 5e of each cell 5 into the combustion space 14 formed in the combustion section 8.

[0049] The high-temperature water vapor discharged into the combustion space 14 fills the internal space 9s of the storage container 9, and most of the high-temperature water vapor that has filled the internal space 9s flows from the air inlet 20 into the air supply path 13, passes through the air flow meter 22 and the air filter 21, flows back through the air supply path 13, and is discharged to the outside of the storage container 9, and the remainder is discharged to the outside of the storage container 9 from the combustion exhaust gas discharge port 24. Incidentally, the water vapor discharged to the outside of the storage container 9 from the combustion exhaust gas discharge port 24 passes through the carbon monoxide removal section 25, and therefore the pressure loss of the water vapor passing through the combustion exhaust gas discharge port 24 is considerably greater than the pressure loss of the water vapor flowing back through the air supply path 13. Therefore, the water vapor that has filled the internal space 9s is preferentially discharged back through the air supply path 13.

[0050] Then, the high-temperature water vapor flows backward through the air supply passage 13 while passing through the air flow meter 22 and the air filter 21, and thereby deposits (for example, deposits containing ammonium sulfate) attached to the air filter 21, the air flow meter 22, etc. are dissolved and removed by the water vapor, improving the air flow condition of the air supply system 23. Therefore, the air flow condition of the air supply system 23 can be improved in a timely and automatic manner.

[0051] In this way, the fuel cell system A is operated at a predetermined power, and the judgment and instruction unit 31 continuously acquires the air flow rate and duty ratio. If the period during which the duty ratio when air is flowing at the predetermined flow rate is greater than the predetermined duty ratio by a predetermined percentage or more continues for a predetermined period or more, the fuel cell system A is operated at low power, and the judgment and instruction unit 31 acquires the air flow rate and duty ratio and judges whether or not the reading is low. In this way, it can be determined whether or not the air flow meter 22 is reading low by the simple method of comparing the duty ratio and air flow rate when the air supply system 23 is not clogged with particulate matter with the duty ratio and air flow rate when the air supply system 23 is clogged with particulate matter.

[0052] Other Embodiments (1) In the first embodiment, the predetermined percentage at which the duty ratio of the applied voltage increases at a predetermined power level is the same as the predetermined percentage at which the duty ratio of the applied voltage increases at a low power level, but these percentages may be different. Also, the predetermined percentage may be other than 20%.

[0053] (2) In the first embodiment, the predetermined period during which the duty ratio continuously increases by a predetermined rate or more is set to one month, but it may be set to a period other than one month.

[0054] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0055] The present invention can be used in a fuel cell system. [Explanation of symbols]

[0056] 1: Reformed water pump 2: Evaporator 3: Raw fuel pump 4: Reformer 5: Cell 5a: Fuel electrode 5c: Oxygen electrode 6: Cell stack 7: Air blower 8: Combustion section 9: Storage container 9s :Internal space 10: Control section 13: Air supply channel 22: Air flow meter (flow meter) A: Fuel cell system

Claims

1. an evaporator that evaporates reforming water supplied by a reforming water pump; a reformer that generates a hydrogen-containing gas by causing a reforming reaction between the raw fuel supplied by the raw fuel pump and the steam supplied from the evaporator; An air blower that takes in air from the outside and sends it out; an air filter for cleaning the air taken into the air blower; a cell stack including a plurality of stacked cells each having a fuel electrode and an oxygen electrode, the hydrogen-containing gas being supplied from the reformer to the fuel electrode and the air delivered by the air blower being supplied to the oxygen electrode to generate electricity; a combustion unit that burns combustible components in the anode exhaust gas discharged from the anode with oxygen in the cathode exhaust gas discharged from the cathode, and heats the reformer and the evaporator with the resulting combustion heat; a storage container that houses the evaporator, the reformer, the cell stack, and the combustion unit in its internal space; an air supply path connecting the air blower and the storage container and supplying the air blown out from the air blower to the internal space of the storage container; a flow meter disposed in the air supply path and configured to detect the flow rate of the air blown by the air blower; a control unit that controls the operation, The control unit The flow rate of the air sent from the air blower and detected by the flow meter is acquired, and the flow rate is controlled by controlling a duty ratio to control energization of the air blower; a predetermined duty ratio for passing a predetermined flow rate, which is the flow rate when a predetermined power is output, which is a predetermined output power when an air supply system including the air filter, the air blower, and the air supply path is not clogged, and the duty ratio for passing the predetermined flow rate is greater than the predetermined duty ratio by at least a predetermined percentage for a predetermined period of time or more, and the duty ratio for passing the low-power flow rate is greater than the low-power duty ratio by at least the predetermined percentage for a low-power duty ratio for passing a low-power flow rate, which is the flow rate when a power lower than the predetermined power is output when the air supply system is not clogged.

2. 2. The fuel cell system according to claim 1, wherein the control unit, when determining that the flow meter detects a flow rate that is smaller than the actual flow rate, executes an air flow improvement operation in which the control unit operates the reforming water pump and stops the raw fuel pump and the air blower.

3. 3. The fuel cell system according to claim 1, wherein the predetermined percentage is 20%.

4. 3. The fuel cell system according to claim 1, wherein the predetermined period is one month.

5. 3. The fuel cell system according to claim 1, wherein the control unit determines that a blockage has occurred in the air supply path including the flow meter or that the air blower has failed when an increase in the duty ratio for flowing the low-power flow rate relative to the low-power duty ratio is less than the predetermined percentage relative to the low-power duty ratio.

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