JP2011023279A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing liquid water discharged to the outside of a cell stack from flowing backward to an anode gas passage inside the cell stack, even when reducing the pressure in the anode gas passage inside the cell stack. <P>SOLUTION: In a fuel cell system that supplies fuel gas to an anode by repeating a process of opening a supply valve (14) to increase the pressure in an anode gas passage (36) inside a cell stack (2) and a process of closing the supply valve (14) to reduce the pressure inside the anode gas passage (36) inside the cell stack (2), a fuel cell supply pipe (12) located on the downstream side of the supply valve (14) is provided with a fuel cell supply means (15), that supplies the fuel gas from the fuel gas supply pipe (12) side to the anode gas passage (36) inside the cell stack (2) when the valve (14) is closed to reduce the pressure in the anode gas passage (36) inside the cell stack (2). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  A fuel reservoir is formed in the discharge pipe for discharging impurities (product water, nitrogen, etc.) together with the fuel gas from the anode to the outside of the cell stack, and a drain valve is provided downstream thereof, while the fuel gas to the cell stack A supply valve is provided in the supply pipe, and power generation is performed with the supply valve and the drain valve closed, and the supply valve is opened after the anode gas flow path and the water reservoir inside the cell stack are decompressed by this power generation. The fuel gas is injected and supplied to the anode gas flow path and the water reservoir inside the cell stack in a depressurized state, and the liquid water on the anode gas flow path inside the cell stack is supplied to the water reservoir by the injected fuel gas. There is what is discharged (see Patent Document 1).

JP 11-270390 A

  However, in the technique of Patent Document 1, when power generation is performed with the supply valve and the drain valve closed, the fuel gas in the anode gas passage inside the cell stack is consumed and the anode gas passage inside the cell stack is consumed. Is depressurized. Then, the fuel gas existing downstream of the cell stack flows toward the anode gas flow path inside the cell stack, and the liquid water discharged from the cell stack by the flow of the fuel gas at this time (particularly the liquid in the water reservoir). Water) may flow back into the anode gas flow path inside the cell stack.

  In view of this, the present invention enables liquid power (especially a water reservoir) discharged to the outside of the cell stack even in the case where power generation is performed with the supply valve and the drain valve closed, and the anode gas flow path inside the cell stack is decompressed. It is an object of the present invention to provide a fuel cell system capable of suppressing the back flow of the liquid water in the part to the anode gas flow path inside the cell stack.

  The present invention includes a cell stack in which a plurality of unit fuel cells configured by sandwiching an electrolyte membrane between an anode and a cathode, and a supply valve that opens and closes a fuel gas supply pipe to the cell stack, and opens the supply valve. A fuel cell that operates to supply fuel gas to the anode by repeating the process of increasing the pressure of the anode gas flow path inside the cell stack and the process of reducing the pressure of the anode gas flow path inside the cell stack by closing the supply valve The system is assumed. In this case, when the supply valve is closed and the anode gas flow path inside the cell stack is decompressed, the fuel gas that supplies the fuel gas from the fuel gas supply pipe side toward the anode gas flow path inside the cell stack Supply means is provided in the fuel gas supply pipe downstream of the supply valve.

  According to the present invention, when the fuel gas discharged to the outside of the cell stack flows back to the anode gas flow path inside the cell stack, the fuel gas is supplied from the fuel gas supply pipe side toward the anode gas flow path inside the cell stack. Since the fuel gas is supplied, the flow of the fuel gas is forward in the upstream portion of the anode gas flow path inside the cell stack. As a result, the backflow of the fuel gas flowing backward from the downstream to the anode gas flow path inside the cell stack during decompression is weakened, and the backflow of liquid water from the downstream to the anode gas flow path inside the cell stack can be suppressed.

1 is a schematic configuration diagram of a fuel cell system according to a first embodiment of the present invention. It is a schematic block diagram of a cell stack. It is each top view of MEA and the anode side separator facing this MEA. It is an image figure of the anode gas flow at the time of pressure reduction in the anode dead end operation of the conventional apparatus. It is a timing chart of the anode gas channel pressure at the time of anode dead end operation. It is a characteristic diagram for demonstrating the behavior of the droplet on the anode gas flow path inside the cell stack at the time of pressure reduction in the anode dead end operation. It is an image figure of the anode gas flow at the time of pressure reduction in the anode dead end operation of this embodiment. 6 is a timing chart showing changes in forward fuel mass flow and reverse fuel mass flow when the first buffer volume and the second buffer volume are made equal in a state where power is generated at a constant current by anode dead-end operation. . It is a schematic block diagram of the 2nd buffer which has a volume variable mechanism of 2nd Embodiment. It is a schematic block diagram of the 2nd buffer which has a volume variable mechanism of 3rd Embodiment. It is a schematic block diagram of the 2nd buffer which has a volume variable mechanism of 4th Embodiment. It is a schematic block diagram of the fuel cell system of 5th Embodiment. It is a schematic block diagram of the 2nd buffer in case the volume variable mechanism is a piston type volume variable mechanism in 5th Embodiment. It is a schematic block diagram of the 2nd buffer in case the volume variable mechanism is a partition plate type volume variable mechanism in 5th Embodiment. It is a top view of the 2nd buffer of FIG. It is a schematic block diagram of the fuel cell system of 6th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a fuel cell system 1 according to an embodiment of the present invention. The fuel cell system 1 of the present embodiment uses a solid polymer fuel cell that is relatively small and excellent in power generation efficiency, and is mounted on a vehicle.

  The cell stack 2 is supplied with a reaction gas (fuel gas and oxidant gas) used for an electrochemical reaction and a cooling medium for cooling the cell stack 2. Air is supplied from the compressor 3 through the supply pipe 4 to the cathode of the cell stack 2. Instead of the compressor, air supply means such as a blower can be used. The air discharged from the cathode of the cell stack 2 is released into the atmosphere through the discharge pipe 5. A pressure regulating valve 6 is disposed in the discharge pipe 5 to adjust the back pressure (the pressure in the cathode gas flow path).

  Hydrogen (fuel gas) is supplied to the anode of the cell stack 2 through a fuel gas supply pipe 12 from a hydrogen tank 11 storing high-pressure hydrogen. Instead of the hydrogen tank 11, hydrogen may be generated by a reforming reaction using alcohol, hydrocarbon, or the like as a raw material. The fuel gas supply pipe 12 includes a pressure regulating valve (regulator) 13 that controls the upper limit pressure of the fuel gas, and a valve that opens and closes the fuel gas supply pipe 4 to cut off the supply of the fuel gas (this valve). The valves are hereinafter referred to as “supply valves”) 14.

  The cell stack 2 is connected to one end (front end) of an anode gas exhaust manifold 44, which discharges impurities (product water, nitrogen, etc.) together with fuel gas from the anode to the outside of the cell stack 2. The discharge pipe 16 is provided with a buffer 17 (second volume portion) having a predetermined volume. Water vapor generated by electrochemical reaction (power generation) is discharged to the buffer 17, and water condensed in the buffer 17 is stored in the lower part of the buffer 17. A pipe 18 for discharging the accumulated water is provided below the buffer 17, and a normally closed drain valve 19 is provided in the pipe 18.

  Cooling water is further supplied to the cell stack 2 from the radiator 21 via the pipe 23. Instead of the cooling water, an antifreeze such as ethylene glycol or a cooling medium such as air can be used. Since the circulation path of the cooling water may have a known configuration, it is not shown.

  FIG. 2 is a schematic configuration diagram of the cell stack 2. The cell stack 2 is configured by stacking a plurality of unit fuel battery cells (single cells) 31. The single cell 31 has a membrane electrode assembly (hereinafter referred to as “MEA”) in the center of the laminated structure. The MEA 32 has a structure in which an electrode catalyst layer and a gas diffusion layer are sequentially laminated on both surfaces of an electrolyte membrane. One side of the electrolyte membrane is used as a cathode, and the other side is used as an anode. A cathode side separator 33 and an anode side separator 34 made of carbon or metal, which are conductive members, are arranged on both surfaces of the MEA 32. An air (oxidant gas) flow path 35 is formed on the surface of the cathode separator 33 facing the MEA 32, and a cooling water flow path 37 is provided on the opposite surface. A flow path 36 for hydrogen (fuel gas) is formed on the surface of the anode separator 34 facing the MEA 32, and a cooling water flow path 37 is provided on the opposite surface.

  A plurality of single cells 31 formed in this way are stacked, and a manifold for distributing air, hydrogen, and cooling water to each single cell 31 is provided at both ends. That is, as shown in FIG. 1, a supply manifold 41 and an exhaust manifold 42 for supplying air, a supply manifold 43 and an exhaust manifold 44 for supplying fuel gas, a supply manifold 45 and an exhaust manifold 46 for supplying cooling water are provided. Yes. Air, fuel gas, and cooling water supplied from the outside of the cell stack 2 are distributed to each single cell 31 by these manifolds 41 to 46. Further, in order to efficiently perform water circulation inside the cell stack 2, the air flow path 35 and the hydrogen flow path 36 are opposed to each other.

  Hereinafter, the air supplied to the cathode is also referred to as “cathode gas”, and the hydrogen supplied to the anode is also referred to as “anode gas”. The air channel 45 is also referred to as a “cathode gas channel”, and the hydrogen channel 46 is also referred to as an “anode gas channel”.

  FIG. 3 shows the MEA 32 and the anode separator 34 facing the MEA 32 taken out from the cell stack 2 of FIG. 2, and a plan view of the MEA 32 and a plan view of the anode separator 34 facing the MEA 32 are shown side by side. It is. 3A is a plan view of the MEA 32, and FIG. 3B is a plan view of the anode separator 34. As shown in FIG.

  As shown in FIG. 3A, as a reaction gas humidifying means, an anode reaction surface (active area) 41 is provided at the center of the MEA 32, and the electrolyte does not have a catalyst layer on the outer side in the left-right direction of the anode reaction surface 41. A portion consisting only of the layer is provided as the humidification area 42, and the reaction gas is humidified by moving the water at one gas flow path outlet to the other gas flow path inlet through the electrolyte layer. However, in the low load operation, the relative humidity on the outlet side of the cathode gas is extremely reduced, so even if the humidification area 42 is provided outside the anode reaction surface 41 in this way, the downstream side of the anode gas cannot be humidified.

  Therefore, in the present embodiment, the process of opening the supply valve 14 and increasing the pressure of the anode gas flow path 36 inside the cell stack 2 and the process of closing the supply valve 14 and reducing the pressure of the anode gas flow path 36 inside the cell stack 2 are repeated. Thus, an anode dead end operation is performed in which the fuel gas supplied to the anode is not discharged outside the cell stack 2 and the buffer 17.

  This anode dead end operation will be described next. In FIG. 1, the supply valve 14 is opened after the upper limit pressure is determined by the pressure regulating valve 13, the fuel gas is supplied to the anode inside the cell stack 2, the compressor 3 is started, and air is pumped to the cathode inside the cell stack 2. (Supply) and start power generation at the MEA 32. When the MEA 32 starts power generation, water is generated at the cathode along with power generation. The generated water moves from the cathode toward the anode and reaches the anode. The water (brackish water and liquid water) that has passed through the anode reaction surface 41 passes through the gas diffusion layer in the anode and emerges on the anode gas flow path 36. If the power generation is continued as it is, the pressure of the anode gas flow path 36 remains stuck to the upper limit pressure determined by the pressure regulating valve 13, and the fuel gas supplied from the supply valve 14 is a mass consumed by the power generation. Only flow rate.

  When the cell stack 2 is operated by flowing the mass flow rate, a dynamic pressure sufficient to drain the water on the anode gas flow path 36 to the buffer 17 cannot be obtained. It has been found from the experiments of the inventors that the MEA 32 becomes unable to generate power before long because it causes a voltage drop due to insufficient supply of fuel gas by inhibiting gas diffusion.

If the supply valve 14 is temporarily closed during power generation to avoid this problem, the fuel gas is not supplied from the tank 11 to the cell stack 2 and the anode gas flowing from the supply valve 14 to the drain valve 19 is not supplied. Power generation is continued using the fuel gas remaining in the flow path.
In this case, the buffer 17 provided in the discharge pipe 16 has the largest volume, and the fuel gas mainly flows from the buffer 17 toward the anode gas flow path 36 inside the cell stack 2. Then, the pressure in the anode gas flow path 36 and the buffer 17 inside the cell stack 2 decreases in order to consume the volume of the anode gas flow path 36 and the fuel gas remaining in the buffer 17 by power generation.

  When the pressure drops, the supply valve 14 is opened again. Then, the fuel gas from the tank 11 flows toward the anode flow path 36 inside the cell stack 2, and the anode gas flow path 36 inside the cell stack 2 is pressurized. The water on the anode gas flow path 36 inside the cell stack 2 moves to the downstream side of the anode gas flow path 36 and the buffer 17 by the dynamic pressure generated at that time, so that power generation can be continued to some extent. That is, the process of increasing and decreasing the pressure of the anode gas flow path 36 inside the cell stack 2 is repeated at a constant period. Thus, by repeating the process of increasing and decreasing the pressure of the anode gas flow path 36 in the cell stack 2, the operation of supplying the fuel gas to the anode, and accordingly the fuel gas supplied to the anode is supplied to the cell stack 2 and An operation that does not discharge to the outside of the second buffer 17 is called an anode dead end operation.

  In the anode dead end operation, the flow direction of the fuel gas is switched. Therefore, when the anode gas flow path 36 in the cell stack 2 is pressurized, the flow direction from the supply valve 14 toward the anode is defined as the forward direction, and the gas flow flowing in the forward direction. Is defined as “forward flow”. Further, the flow direction from the second buffer 17 toward the anode gas flow path 36 in the cell stack 2 when the anode gas flow path 36 in the cell stack 2 is depressurized is the reverse direction, and the gas flow flowing in the reverse direction is “back flow”. Define in.

  The controller 51 is configured as a logic circuit centered on a microcomputer, and more specifically, a CPU (not shown) that executes predetermined calculations in accordance with a preset control program, and various arithmetic processes are executed by the CPU. A ROM (not shown) in which control programs, control data, and the like necessary for storage are stored in advance, and a RAM (not shown) in which various data necessary for various arithmetic processes performed by the CPU are temporarily read and written. And an input / output port (not shown) for inputting and outputting various signals. The controller 51 drives the compressor 3 to control the pressure regulating valve 6, the pressure regulating valve 13, and the supply valve 14 to generate power with the MEA 32 inside the cell stack 2 and to supply fuel to the anode inside the cell stack 2. An anode dead end operation in which the gas is not discharged to the outside of the cell stack 2 and the buffer 17 is performed. The anode dead end operation itself is known (see Japanese Patent Application Laid-Open No. 2007-149630).

  Now, what becomes a problem is the behavior of water on the anode gas passage 36 when the supply valve 14 is closed and the anode gas passage 36 in the cell stack 2 is decompressed. As in the conventional apparatus (Japanese Patent Laid-Open No. 2007-149630), a buffer 17 having a volume equivalent to the volume of the anode gas flow path 36 inside the cell stack 2 is installed only in the discharge pipe 16 outside the cell stack 2, and a supply valve When power generation is performed with the valve 14 and the drain valve 19 closed, the fuel gas stored in the buffer 17 flows backward toward the anode gas flow path 36 inside the cell stack 2 as shown in FIG. FIG. 4 shows an image of what happens to the anode gas flow at the time of depressurization in the anode dead end operation, and shows how the fuel gas flows back through the anode gas flow path 36 inside the cell stack 2 at the time of depressurization in the anode dead end operation. ing.

  When the anode gas flow path pressure is changed from increased pressure to reduced pressure as shown in FIG. 5 for anode dead end operation, liquid water on the anode gas flow path 36 (this liquid water is hereinafter referred to as “liquid water”). FIG. 6 shows the experimental results showing how the behavior of) becomes. At the timing t1 when the pressure increase starts in FIG. 5, when the droplet (liquid water) on the anode gas flow path 36 at the position A in FIG. 6 reaches the timing t2 when the pressure increase ends in FIG. It moves to the position B in FIG. 6 by the pressure. However, at the timing t3 when the decompression ends in FIG. 5, the droplet returns to the position C in FIG. 6 due to the backflow of the fuel gas being decompressed. In this way, the liquid water that has moved to the downstream side of the anode flow path 36 at the time of pressure increase in the anode dead end operation returns to the anode gas flow path 36 again by the backflow of the fuel gas at the time of pressure reduction in the next anode dead end operation. It was clear from the experiment of the inventor how it came.

  Therefore, in the present embodiment, as shown in FIG. 1, the buffer 15 (fuel gas supply means, first volume portion) is provided in the fuel gas supply pipe 12 between the supply valve 14 and the supply manifold 43 for supplying fuel gas. Is installed. The buffer 15 installed in the fuel gas supply pipe 12 also has a predetermined volume, like the buffer 17 installed in the discharge pipe 16. At the time of pressure increase in the anode dead operation, the fuel gas from the tank 11 is stored in a predetermined volume in the buffer 15. When the pressure in the next anode dead operation is reduced, that is, when power generation is continued with the supply valve 14 fully closed, if the fuel gas is consumed and the pressure of the anode gas flow path 36 inside the cell stack decreases, The stored fuel gas flows toward the anode gas passage 36 having a lower pressure, that is, the cell stack 2.

  In the present embodiment, since the two buffers 15 and 17 are installed outside the cell stack 2, in order to distinguish between them, hereinafter, the buffer 15 installed in the fuel gas supply pipe 12 is referred to as a “first buffer”, a discharge pipe. The buffer 17 installed in 16 is distinguished as a “second buffer”.

  Thus, in this embodiment, since the first buffer 15 is provided in the fuel gas supply pipe 12 downstream of the supply valve 14, the anode gas flow path 36 in the cell stack 2 from the first buffer 15 during decompression in the anode dead end operation. The fuel gas can be supplied in the forward direction. For this reason, if the load is the same, the anode gas flow path from the second buffer 17 is increased by the amount of the forward fuel mass flow rate (fuel amount per unit time) compared to the case where the first buffer 15 is not installed. The fuel mass flow rate in the reverse direction toward 36 can be reduced. As a result, the upstream dynamic pressure generated by the backflow of the fuel gas in the second buffer 17 can be reduced, and the amount of liquid water that is about to return from the second buffer 17 to the anode gas flow path 36 in the cell stack 2 accordingly. Can be reduced. As a result, drainage performance from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 is improved.

  FIG. 7 shows a state of gas flow to the anode gas flow path 36 when the ratio of the volume V1 of the first buffer 15 and the volume V2 of the second buffer 17 is changed during decompression in the anode dead end operation. As shown in FIG. 7, as V1 / V2, which is a ratio obtained by dividing the first buffer volume V1 by the second buffer volume V2, is increased, the gas in the anode gas flow path 36 during decompression in the anode dead end operation is increased. It can be seen that the flow approaches the forward flow.

  FIG. 8 shows that the first buffer volume V1 and the second buffer volume V2 are made equal (that is, V1 / V2 = 1.0 from V1 = V2) in a state where power is generated at a constant current by the anode dead end operation. In some cases, the fuel mass flow rate in the forward flow and the fuel mass flow rate in the reverse flow are shown. As shown in FIG. 8, according to the present invention, the forward flow fuel mass flow rate is increased at the time of depressurization in the anode dead end operation, so that the reverse flow fuel mass flow rate is reduced to half that of the conventional apparatus.

  7 and 8, the higher the ratio of V1 / V2, the smaller the backflow fuel mass flow rate during decompression in the anode dead end operation, and when the ratio of V1 / V2 becomes 1 or more (first buffer volume V1 ≧ Since the second buffer volume V2) and the reverse fuel mass flow rate reach the downstream side from the intermediate portion of the anode gas flow path 36, the liquid water in the second buffer 17 and the liquid water on the discharge pipe 16 are in the cell stack. 2 even if it flows backward, it stops in the downstream region of the anode gas flow path 36 inside the cell stack 2, so that the distance that must be moved to the second buffer 17 at the time of pressure increase in the anode dead-end operation immediately after that is shortened. The liquid water on the anode gas flow path 3 inside the cell stack 2 can be drained outside the cell stack 2 at the time of pressure increase in the anode dead end operation immediately after that. It made.

  Among the anode gas flow paths that flow from the supply valve 14 to the drain valve 19, the ones having the largest volume are the first buffer 15 and the second buffer 17, but strictly speaking, from the supply valve 14 to the drain valve 19. All the volumes of the fuel gas flow path up to this affect the behavior of the liquid water in the anode gas flow path 36 during decompression in the anode dead end operation. Therefore, inside the cell stack 2, as shown in FIG. 3B, a plurality of anode gas flow paths 36 provided in the left-right direction are connected to the portion where the anode reaction surface 41 of the MEA 32 is in contact with the anode gas flow path 36. The anode gas flow path 36B and the anode reaction flow path 41 of the MEA 32 are not in contact with the anode gas flow path 36 in the portion where the anode gas flow path 36A and the anode reaction flow path 41 of the MEA 32 are not in contact with the anode gas flow path 36. The portion is divided into three parts, the anode gas flow path 36C on the downstream side.

  All of the anode gas flow paths that flow from the supply valve 14 to the upstream anode gas flow path 36B are defined as “upstream outside the anode”. Therefore, “upstream outside the anode” includes a supply manifold 43 for supplying fuel gas, a fuel gas supply pipe 12 from the inlet of the supply manifold 43 to the supply valve 14, and the first buffer 15.

  Further, all of the anode gas passages flowing from the downstream anode gas passage 36 </ b> C to the drain valve 19 are defined as “downstream outside the anode”. Therefore, “downstream outside the anode” includes the exhaust manifold 44, the exhaust pipe 16 from the outlet of the exhaust manifold 44 to the drain valve 19, the second buffer 17, and the pipe 18 from the second buffer 17 to the drain valve 19.

  When “anode external upstream” and “anode external downstream” are defined in this way, the “anode external upstream” volume is replaced with the first buffer volume V1, and the “anode external downstream” is replaced with the second buffer volume V2. Volume can be used. That is, when the pressure in the anode dead-end operation is reduced, the volume upstream of the anode is made larger than the volume downstream of the anode, so that the liquid water on the discharge pipe 16 and the liquid water in the second buffer 17 are transferred to the anode inside the cell stack 2. Returning to the gas flow path 36 (reverse flow) can be suppressed.

  As will be described later, the entire volume of the anode gas flow path 36A where the anode reaction surface 41 is in contact with the anode gas flow path 36 is defined as “anode volume”.

  The second buffer 17 has a variable volume mechanism. That is, when power generation is continued without opening the drain valve 19 in the anode dead end operation in FIG. 1, the anode gas passage 36 in the cell stack 2 is drained to the exhaust pipe 44 through the exhaust manifold 44 and is discharged into the second buffer 17. As the liquid water stored in the second buffer 17 increases, the volume of the gas phase portion in the second buffer 17 decreases. The ratio of the first buffer volume V1 / second buffer volume V2 increases as the volume of the gas phase portion in the second buffer 17 decreases during the pressure reduction in the anode dead end operation, and the anode gas flow inside the cell stack 2 increases. The drainage performance from the passage 36 to the discharge pipe 16 and the second buffer 17 can be improved.

  As described above, the second buffer 17 of the present embodiment has a variable volume mechanism that makes the volume of the gas phase portion in the second buffer 17 variable according to the amount of liquid water stored therein.

  Moreover, according to this embodiment, since the drain valve 19 which discharges the liquid water collected in the 2nd buffer 17 (anode exterior downstream) is provided, it is stored in the 2nd buffer 17 by opening and closing the drain valve 19. The amount of liquid water (the amount of liquid water downstream of the anode) can be arbitrarily adjusted, and the volume of the gas phase portion in the second buffer 17 (downstream of the anode downstream) can be adjusted by the amount of liquid water stored in the second buffer 17. Gas phase volume) can be adjusted. Thereby, drainage from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 can be improved without changing the shape downstream of the anode.

  9, 10, and 11 are schematic configuration diagrams of the second buffer 17 ′ having a variable volume mechanism that can arbitrarily adjust the volume of the second, third, and fourth embodiments. In relation to FIG. 1, the second buffer 17 ′ having the variable volume mechanism shown in FIGS. 9, 10, and 11 is replaced with the second buffer 17 of FIG. 1.

  Even though the second buffer 17 of the first embodiment has a variable volume mechanism, the amount of liquid water stored in the second buffer 17 only increases according to the operation time, so that it is arbitrarily (for example, It is not possible to increase the amount of liquid water stored in the second buffer 17 (during depressurization in the anode dead end operation only).

  Therefore, the second, third, and fourth embodiments include the second buffer 17 ′ having a variable volume mechanism that can arbitrarily adjust the internal volume (particularly, the volume of the gas phase portion), and in the anode dead end operation. When the pressure is increased, the volume of the second buffer 17 ′ is relatively enlarged, and when the anode dead end operation is reduced, the volume of the second buffer 17 ′ is relatively reduced to reduce the anode gas inside the cell stack 2. The drainage from the flow path 36 to the discharge pipe 16 is improved.

  In the second embodiment, as shown in FIG. 9, a piston-type variable volume mechanism 61 comprising a cylinder 62, a piston 63 that can slide the cylinder 62 in the vertical direction, and an actuator 64 that drives the piston 63 is provided. A second buffer 17 '. According to the second buffer 17 ′ having the piston type variable volume mechanism 61, the actuator 64 is driven to move the position of the piston 63 downward, so that the inner wall of the cylinder 62 and the outer wall of the piston 63 are partitioned. The volume of the space 65 is expanded. On the other hand, by driving the actuator 64 and moving the position of the piston 63 upward, the volume of the space 65 defined by the inner wall of the cylinder 62 and the outer wall of the piston 63 is reduced.

  In this case, the discharge pipe 16 opens into the space 65, and the pipe 18 also opens into the space 65.

  Therefore, in the second embodiment, the position of the piston 63 is moved downward by the actuator 64 at the time of pressure increase in the anode dead operation, and the volume of the space 65 partitioned by the inner wall of the cylinder 62 and the outer wall of the piston 63 is relatively set. When the pressure is reduced during anode dead-end operation, the position of the piston 63 is moved upward by the actuator 64 to relatively reduce the volume of the space 65 defined by the inner wall of the cylinder 62 and the outer wall of the piston 63. By reducing the size, the ratio of the first buffer volume V1 / second buffer volume V2 is increased, and the drainage performance from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 ′ is improved. Can do.

  In the third embodiment, as shown in FIG. 10, the cylindrical tank 72 with a bottomed lid having an elliptical cross section and the cylindrical tank 72 are moved to the left and right chambers while sliding on the inner wall of the cylindrical tank 72. A second buffer 17 ′ having a partition plate type variable volume mechanism 71 including a partition plate 73 partitioning into 75 and 76 and an actuator 74 that rotationally drives the partition plate 73 is provided. According to the second buffer 17 ′ having the partition plate type variable volume mechanism 71, the partition wall 73 is partitioned by the inner wall of the cylindrical tank 72 by driving the actuator 74 to rotate the partition plate 73. The volume of the left and right chambers 75 and 76 can be arbitrarily adjusted.

  In this case, when the partition plate 73 rotates clockwise as shown in the drawing, for example, if the volume of the left chamber 75 is reduced and the volume of the right chamber 76 is increased, the discharge pipe 16 is opened to the left chamber 75. The pipe 18 is also opened in the left chamber 75.

  Therefore, in the third embodiment, the actuator 74 is driven at the time of pressure increase in the anode dead operation, and the partition plate 73 is rotated counterclockwise to enlarge the volume of the left chamber 75, and the pressure reduction in the anode dead end operation is performed. When the hour comes, the actuator 74 is driven to rotate the partition plate 73 in the clockwise direction to reduce the volume of the left chamber 75, so that the ratio of the first buffer volume V1 / second buffer volume V2 increases, and the cell The drainage performance from the anode gas flow path 36 inside the stack 2 to the discharge pipe 16 and the second buffer 17 'can be improved.

  In the fourth embodiment, as shown in FIG. 11, the discharge pipe 16 is branched into two, and tanks 82 and 83 having the same volume are connected to the branch pipes 16a and 16b, respectively. A second buffer 17 ′ having a variable volume mechanism 81 is constituted by the normally open on-off valves 84 and 85 provided on the upstream side. According to the second buffer 17 ′ having the variable volume mechanism 81, the volume can be arbitrarily adjusted by opening and closing the two open / close valves 84 and 85. In this case, the pipe 18 is opened to one of the tanks 82 and 83, for example, the tank 83.

  Therefore, in the fourth embodiment, the two on-off valves 84 and 85 are opened at the time of pressure increase in the anode dead operation so that the total volume of the two tanks 82 and 83 becomes the second buffer volume V2, that is, the second buffer. The volume V2 is enlarged, and at the time of pressure reduction in the anode dead end operation, the first buffer volume is reduced by closing at least one of the opening / closing valves 84, 85, for example, the opening / closing valve 84 and reducing the second buffer volume V2. The ratio of V1 / second buffer volume V2 is increased, and the drainage performance from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 ′ can be improved. Here, the number of tanks is not limited to two.

  In the second to fourth embodiments, it can be known from the signal supplied to the supply valve 14 whether the pressure is increased during the anode dead operation or when the pressure is decreased during the anode dead end operation. That is, in the controller 51 of the second to fourth embodiments, if the open signal is given to the supply valve 14 after the anode dead operation is started, if the pressure is increased in the anode dead operation, the close signal is also given. In the second embodiment, the actuator 64 and 74 are driven in FIG. 9 according to the second embodiment and FIG. 10 according to the third embodiment according to the determination result. In FIG. 11, the open / close valves 84 and 85 are opened and closed.

  Note that the method for determining whether the pressure is increased during anode dead operation or during pressure reduction during anode dead end operation is not limited to this. For example, a pressure sensor is provided in the anode gas flow path (for example, the fuel gas supply pipe 12) flowing from the supply valve 14 to the drain valve 19, and based on the anode gas flow path pressure detected by the pressure sensor, It is possible to determine whether the pressure is increased during anode dead operation or when pressure is decreased during anode dead end operation.

  Thus, according to the second to fourth embodiments, the second buffer 17 ′ having the variable volume mechanisms 61, 71, 81 that can arbitrarily adjust the internal volume (particularly the volume of the gas phase portion) is provided. The volume of the second buffer 17 ′ (the volume downstream of the anode downstream) is relatively enlarged at the time of pressure increase in the anode dead end operation. Since the external downstream volume) is relatively reduced, the timing of reducing the anode external downstream volume can be surely adjusted at the time of pressure reduction in the anode dead end operation. As a result, the cell stack is more than in the case of including the second buffer 17 having the volume variable mechanism 17 in which the volume of the gas phase portion in the second buffer 17 is variable according to the amount of water stored therein. 2 It is possible to improve drainage performance from the anode gas flow path 36 inside to the discharge pipe 16 and the second buffer 17 ′.

  FIG. 12 is a schematic configuration diagram of the fuel cell system 1 of the fifth embodiment. The same parts as those in FIG. 1 of the first embodiment are denoted by the same reference numerals. However, the second buffer of the fifth embodiment includes the second buffer 17 ′ of the second to fourth embodiments instead of the second buffer 17 of the first embodiment.

  Therefore, also in the fifth embodiment, the volume of the second buffer 17 ′ (volume outside the anode downstream) is relatively enlarged during the pressure increase in the anode dead end operation, and when the pressure is reduced during the anode dead end operation, By reducing the volume 17 ′ (the volume downstream of the anode downstream) relatively, as in the second to fourth embodiments, the timing for reducing the volume downstream of the anode is reliably reduced in the anode dead end operation. As a matter of time, drainage is improved.

  In the first to fourth embodiments, the discharge pipe from the anode gas flow path 36 inside the cell stack 2 is made larger by increasing the volume outside the anode relative to the volume outside the anode at the time of pressure reduction in the anode dead end operation. 16 and the second buffer 17 ′ have improved drainage performance, but the fifth embodiment increases the volume outside the anode downstream with respect to the volume upstream outside the anode at the time of pressure increase in the anode dead end operation. By doing so, the drainage property from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 'is improved.

  This principle will be described. With the upper limit pressure set by the pressure regulating valve 13, the supply valve 14 is opened from the reduced pressure state, and the fuel gas is allowed to flow in the forward direction to increase the anode gas flow path 36 in the cell stack 2 to the upper limit pressure. Considering two cases, the volume of the anode gas flow path flowing from the valve 14 to the drain valve 19 is relatively large and relatively small, the fuel mass flow rate flowing forward from the supply valve 14 in both cases Are equal. At this time, the volume of the anode gas flow path flowing from the supply valve 14 to the drain valve 19 is relatively larger when the volume of the anode gas flow path flowing from the supply valve 14 to the drain valve 19 is relatively large. The time is longer until the pressure in the anode gas flow path 36 inside the cell stack 2 reaches the upper limit pressure than when the pressure is smaller. For this reason, when the volume of the anode gas flow path flowing from the supply valve 14 to the drain valve 19 is relatively large, it is downstream for a longer time than the liquid water on the anode gas flow path 36 inside the cell stack 2. The dynamic pressure toward the can be applied. As a result, when the volume of the anode gas flow path that flows from the supply valve 14 to the drain valve 19 is relatively large, the discharge pipe 16 and the second buffer 17 ′ from the anode gas flow path 36 inside the cell stack 2. This will improve drainage performance.

  Therefore, in the fifth embodiment, a pressure reducing means that can reduce the pressure downstream of the anode is provided, and this pressure reducing means is used to increase the pressure in the anode dead end operation (open the supply valve and increase the anode gas flow path inside the cell stack). The pressure downstream of the anode is made lower than the pressure of the anode gas flow path 36 inside the cell stack 2 (anode pressure). Specifically, the decompression means includes a pipe 91 that communicates the gas phase portion (downstream outside the anode) in the second buffer 17 ′ having the variable volume mechanism to the atmosphere, and a state in which the pressure is reduced by opening and closing the pipe 91. A pressure reducing valve 92 that switches between a state in which pressure is not reduced and a state in which pressure is reduced by opening the pressure reducing valve 92 at the time of pressure increase in anode dead end operation. Further, a pressure sensor 93 is provided in the discharge pipe 16.

  Based on the pressure of the discharge pipe 16 detected by the pressure sensor 93, the controller 51 determines whether the pressure is increased during anode dead end operation or during decompression during anode dead end operation. When it is determined that it is time, the pressure reducing valve 92 is fully closed, and when it is determined that the pressure is increased during anode dead end operation, the pressure reducing valve 92 is opened and the gas phase portion in the second buffer 17 ′ is opened to the atmosphere. Communicate with. This virtually increases the volume downstream of the anode. That is, when the pressure reducing valve 92 is opened, the volume of the anode gas flow path that flows from the supply valve 14 to the drain valve 19 is expanded more than when the pressure reducing valve 92 is closed.

  As described above, according to the fifth embodiment, the pressure reducing means (91, 92) capable of reducing the pressure downstream of the anode is provided, and the pressure reducing means (91, 92) is used to increase the pressure in the anode dead end operation. (When the supply valve is opened and the anode gas flow path inside the cell stack is increased), the decompression valve 92 is opened, and the gas phase portion (downstream outside the anode) in the second buffer 17 ′ is communicated with the atmosphere. Since the pressure in the gas phase portion (downstream downstream of the anode) in the second buffer 17 ′ is made smaller than the pressure in the anode gas flow path 36 (anode pressure) inside the cell stack 2, The gas can flow for a longer time than when the pressure reducing valve 92 is closed in the forward direction. As a result, it is possible to apply a dynamic pressure toward the downstream for a long time to the liquid water on the anode gas flow path 36 inside the cell stack 2, and the discharge pipe 16 and the second pipe 16 from the anode gas flow path 36 inside the cell stack 2. The drainage to the second buffer 17 ′ can be improved.

  Further, in the fifth embodiment, assuming that the lower limit pressure is set at the time of depressurization in the anode dead end operation, the time during which the upper limit pressure is reduced to the lower limit pressure (decompression speed) is constant if the load current is constant. When the pressure reducing valve 92 is opened, the time when the pressure reducing valve 92 is opened is shorter (larger), so the time for the fuel gas to flow backward from the second buffer 17 ′ toward the anode gas flow path 36 inside the cell stack 2 is reduced. The amount of return of liquid water to the inside of the cell stack 2 (reverse flow rate) can be reduced accordingly, and drainage from the anode gas flow path 36 inside the cell stack 2 to the discharge pipe 16 and the second buffer 17 ′ can be performed. improves.

  However, the pressure reducing valve 92 needs to have a valve diameter that can ensure a pressure reducing speed larger than the pressure reducing speed of the anode gas flow path 36 inside the cell stack 2 at the time of pressure reducing in the anode dead end operation.

  Next, in the fifth embodiment, a case where the second buffer 17 ′ has a piston type variable volume mechanism 61 will be described with reference to FIG. 13. FIG. 13 is a schematic configuration diagram when the second buffer 17 ′ of FIG. 12 is a second buffer 17 ′ having a piston type variable volume mechanism 61. In FIG. 13, the same parts as those in FIG. 9 of the second embodiment are denoted by the same reference numerals.

  In FIG. 13, in the second buffer 17 ′ having the piston type variable volume mechanism 61, the inner wall of the cylinder 62 is used by using the piston type variable volume mechanism 61 while the pressure reducing valve 92 is closed at the time of pressure reduction in the anode dead end operation. When trying to reduce the volume of the space 65 defined by the outer wall of the piston 63, the gas in the space 65 is adiabatically compressed, and the pressure in the space 65 increases. Therefore, in order to reduce the amount of water that returns to the cell stack 2 during decompression during anode dead end operation, even if the volume of the space 65 is to be reduced, adiabatic compression is performed on the space 65 to reduce the volume. Therefore, the fuel mass flow rate that flows backward from the second buffer 17 ′ to the anode gas flow path 36 inside the cell stack 2 increases, and there is a possibility that the reverse effect may be obtained.

  Therefore, in the fifth embodiment, when the second buffer 17 ′ has the piston type variable volume mechanism 61, the volume of the space 65 defined by the inner wall of the cylinder 62 and the outer wall of the piston 63 at the time of pressure reduction in the anode dead end operation. When the pressure is to be reduced, the pressure reducing valve 92 is opened. As a result, when the volume of the space 65 is to be reduced during decompression in the anode dead end operation, the gas in the space 65 is released to the atmosphere via the decompression valve 92, so the gas in the space 65 is compressed. In addition, the volume of the space 65 can be reduced.

  Next, in the fifth embodiment, a case where the second buffer 17 ′ has a partition plate type variable volume mechanism 71 will be described with reference to FIG. 14. FIG. 14 is a schematic configuration diagram in the case where the second buffer 17 ′ of FIG. 12 is a second buffer 17 ′ having a partition plate type variable volume mechanism 71. In FIG. 14, the same parts as those in FIG. 10 of the third embodiment are denoted by the same reference numerals.

  In FIG. 14, in the second buffer 17 ′ having the partition plate type volume variable mechanism 71, the volume of the left chamber 75 and the volume of the right chamber 76 become equal when the partition plate 73 rotates, so that the anode dead end operation is performed. The gas in the left chamber 75 is not adiabatically compressed when attempting to reduce the volume of the left chamber 75 during pressure reduction at the time of pressure reduction, but the pressure reduction valve 92 is closed during pressure reduction during anode dead end operation. When the volume is reduced, the gas in the right chamber 76 that is not connected to the discharge pipe 16 has no place to go anywhere, so the pressure of the gas in the right chamber 76 does not drop.

  This will be described in further detail. For example, when a plan view of the second buffer 17 ′ is shown in FIG. 15, the partition plate 73 is located at the position during pressure increase in the anode dead end operation (see the solid line), and the partition located at the position during pressure increase in the anode dead end operation. It is assumed that there is an opening end 16a of the discharge pipe 16 and an opening end 91a of the pipe 91 on the right side of the plate 73. In this case, in order to reduce the volume of the left chamber 75 during decompression in the anode dead end operation, the partition plate 73 is rotated clockwise in the drawing and moved to the position during decompression (see the broken line). Assume that the volume is reduced. In this state, since the right chamber 76 is not connected to the open end 16a of the discharge pipe 16, there is no place for the gas in the right chamber 76 to go out anywhere, so the pressure of the gas in the right chamber 76 does not drop.

  At the time of pressure increase in the next anode dead end operation, the partition plate 73 in FIG. 15 is rotated in the counterclockwise direction opposite to that at the time of pressure reduction in anode dead end operation to the position during pressure increase in anode dead end operation (see solid line). Assume that the volume of the return left chamber 75 is enlarged. At this time, the right chamber 76 in which the pressure has not decreased communicates with the discharge pipe 16 that has been decompressed at the time of decompression in the immediately preceding anode dead end operation via the open end 16a. As a result, the gas remaining in the right chamber 76 in a state where the pressure is not reduced flows backward from the open end 16a of the discharge pipe 16 toward the anode gas flow path 36 inside the cell stack 2.

  Therefore, in the fifth embodiment, when the second buffer 17 ′ has the partition plate type variable volume mechanism 71, also in this case, when trying to reduce the volume of the left chamber 75 during pressure reduction in the anode dead end operation. Then, the pressure reducing valve 92 is opened. As a result, when the volume of the left chamber 75 is to be reduced during decompression in the anode dead end operation, the gas in the right chamber 76 is released from the opening end 91a to the atmosphere via the decompression valve 92. The pressure of the gas in 76 is lower than when the pressure reducing valve 92 is closed. For this reason, even if the right chamber 76 and the discharge pipe 16 communicate with each other through the open end 16a when attempting to increase the volume of the left chamber 75 at the time of pressure increase in the anode dead end operation immediately after that, As the pressure is reduced, the gas in the right chamber 76 can be prevented from flowing back toward the anode gas flow path 36 inside the cell stack 2, and the discharge pipe 16 is discharged from the anode gas flow path 36 inside the cell stack 2. Further, drainage to the second buffer 17 ′ is improved.

  FIG. 16 is a schematic configuration diagram of the fuel cell system 1 according to the sixth embodiment. The same parts as those in FIG. 12 of the fifth embodiment are denoted by the same reference numerals.

  According to the conventional apparatus (Japanese Patent Laid-Open No. 2007-242265) and the experiment results of the inventor, the anode gas flow path (the first embodiment of the first embodiment) that flows from the supply valve 14 to the drain valve when the operation of the fuel cell system 1 is stopped. 1 buffer 15 and the second buffer 17 ′ having the variable volume mechanism of the second to fifth embodiments) are filled with inert gas or air, the supply valve 14 is opened at the next power generation start. When fuel gas is supplied from the tank 11 to the cell stack 2, inert gas or air is pushed out to the discharge pipe 16 or the second buffer 17 ′ in a tocorotene manner, and the anode reaction surface 41 may be filled with high-concentration fuel gas. all right. Therefore, it is desirable that the volume of the second buffer 17 'is larger before the start of power generation.

  Therefore, in the sixth embodiment, a water level sensor 101 for detecting the level of liquid water in the second buffer 17 ′ is further added to the fifth embodiment, and a second level detected by the water level sensor 101 by the controller 51 is added. The opening and closing of the drain valve 19 is controlled based on the liquid water level in the buffer 17 '. Specifically, the volume of the gas phase portion in the second buffer 17 ′ is equal to the volume of the first buffer 15 and the anode gas flow path 36 (the fuel gas supply manifold 43 and the exhaust manifold 44) in the cell stack 2. And the lower limit water level detected by the water level sensor 101 until the gas volume downstream of the anode becomes the sum of the volume upstream of the anode and the anode volume, Until this happens, the drain valve 19 is opened to discharge the liquid water in the second buffer 17 'out of the system, and the volume of the gas phase portion in the second buffer 17' is secured.

  Thus, in the sixth embodiment, the drain valve 19 is opened when the operation of the fuel cell system 1 is stopped based on the liquid water level detected by the water level sensor 101, and the gas volume downstream of the anode is the volume upstream of the anode. Since the liquid water is discharged until it becomes equal to the sum of the anode volume or the water level at the lower limit detected by the water level sensor 101, the startability at the start of operation can be improved.

  Here, the “anode volume” refers to the entire volume of the anode gas flow path 36 </ b> A where the anode reaction surface 41 is in contact with the anode gas flow path 36.

  In the sixth embodiment, the case where the water level sensor is provided has been described. However, a water amount sensor that detects the amount of liquid water in the second buffer 17 ′ may be provided.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Cell stack 12 Fuel gas supply pipe 14 Supply valve 15 1st buffer (fuel gas supply means, 1st volume part)
16 Discharge pipe 17 Second buffer (second volume part)
17 ′ Second buffer having a variable volume mechanism 18 Pipe 19 Drain valve 36 Anode gas flow path 51 Controller 61 Volume variable mechanism 71 Volume variable mechanism 81 Volume variable mechanism 91 Pipe 92 Pressure reducing valve 101 Water level sensor

Claims (9)

A cell stack in which a plurality of unit fuel cells configured by sandwiching an electrolyte membrane between an anode and a cathode, and
A supply valve for opening and closing the fuel gas supply pipe to the cell stack,
The fuel gas is supplied to the anode by repeating the process of opening the supply valve and increasing the pressure of the anode gas flow path inside the cell stack and the process of closing the supply valve and reducing the pressure of the anode gas flow path inside the cell stack. In a fuel cell system that operates,
A fuel gas supply means for supplying fuel gas from the fuel gas supply pipe side toward the anode gas flow path inside the cell stack when the supply valve is closed and the anode gas flow path inside the cell stack is depressurized; A fuel cell system comprising a fuel gas supply pipe downstream of a supply valve. A discharge pipe for discharging impurities together with the fuel gas from the anode to the outside of the cell stack;
A drain valve for discharging the liquid water accumulated in the discharge pipe,
A first volume part is provided in the fuel gas supply pipe downstream of the supply valve, a second volume part is provided in the discharge pipe upstream of the drain valve, and the volume of the first volume part is made larger than the volume of the second volume part. The fuel cell system according to claim 1. An anode gas flow path inside the cell stack,
A portion of the anode gas passage where the anode reaction surface is in contact with the anode gas passage;
Of the part where the anode reaction surface does not contact the anode gas channel, the upstream anode gas channel,
The portion where the anode reaction surface does not contact the anode gas flow path is divided into the anode gas flow path on the downstream side, and
All of the anode gas flow paths that flow from the supply valve to the upstream anode gas flow path are upstream of the anode, and all of the anode gas flow paths that flow from the downstream anode gas flow path to the drain valve 2. The fuel cell system according to claim 1, wherein a volume upstream of the anode is larger than a volume downstream of the anode when the anode is downstream of the anode. A variable volume mechanism capable of arbitrarily adjusting the volume downstream of the anode downstream of the anode outside,
Using this variable volume mechanism, when the supply valve is closed and the anode gas flow path inside the cell stack is decompressed, the volume outside the anode is opened and the supply valve is opened to boost the anode gas flow path inside the cell stack. The fuel cell system according to claim 3, wherein the fuel cell system is reduced more than the time. A second buffer having a variable volume mechanism capable of arbitrarily adjusting the internal volume downstream of the anode;
Using the second buffer having the variable volume mechanism, when the supply valve is opened and the anode gas flow path inside the cell stack is increased, the volume downstream of the anode is relatively enlarged, the supply valve is closed and the cell is closed. 4. The fuel cell system according to claim 3, wherein when the anode gas flow path inside the stack is decompressed, the volume downstream of the anode is relatively reduced. Pressure reducing means capable of lowering the pressure downstream of the anode,
Using this decompression means, when the supply valve is opened and the anode gas flow path inside the cell stack is increased, the pressure downstream of the anode is made smaller than the pressure of the anode or the pressure reduction rate of the pressure downstream of the anode is increased. The fuel cell system according to any one of claims 3 to 5, wherein the fuel cell system is made larger than a pressure reduction rate of the anode pressure. The pressure reducing means comprises a pipe communicating with the outside of the anode downstream to the atmosphere, and a pressure reducing valve for switching between a state where pressure is reduced and a state where pressure is not reduced by opening and closing the pipe,
The fuel cell system according to claim 6, wherein when the supply valve is opened and the anode gas flow path inside the cell stack is pressurized, the pressure reducing valve is opened to reduce the pressure.   The fuel cell system according to any one of claims 3 to 7, further comprising a drain valve that discharges liquid water accumulated downstream of the anode. A drainage valve for discharging liquid water collected downstream of the anode;
A water amount / water level sensor for detecting the amount or level of liquid water collected downstream of the anode;
Based on the amount or level of liquid water detected by the water amount / water level sensor when the operation is stopped when the anode volume is the entire volume of the anode gas passage where the anode reaction surface is in contact with the anode gas passage Open the drain valve until the gas volume downstream of the anode is equal to the sum of the volume upstream of the anode and the anode volume, or until the lower limit water amount or water level detected by the water amount / water level sensor is reached. The fuel cell system according to any one of claims 3 to 7, wherein water is discharged.

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