JP2008059754A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformalize wettability condition on the fuel electrode side of each part of the fuel cell, prevent condensation of moisture in a fuel flow channel, restrain retention of moisture in the fuel flow channel, quickly exhaust remaining moisture, and surely prevent performance degradation of the fuel cell and deterioration of the fuel electrode, by partitioning the fuel flow channel of one fuel cell into a plurality of small flow channels arranged in parallel, and control an amount of fuel gas flowing in each small flow channel by a flow volume control valve corresponding to each flow channel. <P>SOLUTION: The fuel cell system includes a fuel cell assembly with a plurality of fuel cells each with an electrolyte layer pinched by a fuel electrode and an oxygen electrode, electrically connected through a separator with a fuel flow channel formed along the fuel electrode and an oxidant flow channel formed along the oxygen electrode, and a tube channel system for fuel connected to the fuel flow channel. The fuel flow channel is partitioned into a plurality of parallel small flow channels, and the tube channel system for fuel is equipped with a flow volume control valve controlling the amount of fuel gas flowing in each of the small flow channels in correspondence with each of the small flow channels. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put into practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as buses, trucks, passenger carts, and luggage carts. The fuel cell may be of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) using pure hydrogen as a fuel gas is actively used because it can reduce the system volume and weight per output.

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as fuel is supplied to the surface thereof, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  In the polymer electrolyte fuel cell, moisture generated by the electrochemical reaction moves as proton-entrained water from the fuel electrode side to the oxygen electrode side, and reverses from the oxygen electrode side to the fuel electrode side. Move as diffusion water. Thereby, both sides of the solid polymer electrolyte membrane are maintained in a wet state. However, when the amount of moisture increases, the hydrogen gas flow path is locally blocked by moisture on the fuel electrode side, and the performance of the fuel cell deteriorates or the fuel electrode deteriorates. It is known.

Therefore, a technique has been proposed in which the hydrogen gas flow path is divided into a plurality of blocks, and the directions of hydrogen gas flow in adjacent blocks are opposite to each other, thereby preventing moisture retention and making the current density uniform. (For example, refer to Patent Document 1).
JP 2003-323905 A

  However, in the conventional fuel cell system, since the flow of hydrogen gas is not controlled according to the temperature distribution in the cell, the water vapor is likely to condense due to the condensation of the water vapor at a high temperature in the cell. End up. If the amount of water accumulated in the hydrogen gas flow path increases, a part of the fuel electrode is covered with water, and the performance of the fuel cell deteriorates or the fuel electrode deteriorates. There was a case. In addition, the retained water is difficult to be discharged and remains, which hinders quick gas replacement particularly when the fuel cell is started and stopped.

  Usually, the produced | generated water | moisture content is discharge | released as water vapor | steam in hydrogen gas in a hydrogen gas flow path. And since saturated water vapor pressure becomes so high that temperature is high, the absolute amount of the water vapor | steam in hydrogen gas increases in the site | part with a high temperature in a cell. However, when hydrogen gas is consumed by an electrochemical reaction for power generation, the partial pressure of the hydrogen gas decreases, so that the water vapor in the hydrogen gas becomes supersaturated and condenses. In particular, since the absolute amount of water vapor in the hydrogen gas is large in a portion having a high temperature in the cell, the amount of moisture condensed is also large. For this reason, in the portion where the temperature is high in the cell, the amount of water condensed from the water vapor is large, so that the retention of water tends to occur.

  The present invention solves the problems of the conventional fuel cell system, divides the fuel flow path in one fuel cell into a plurality of parallel small flow paths, and each flow control valve corresponding to each small flow path By controlling the flow rate of the fuel gas flowing through the small flow path, the wet state on the fuel electrode side in each part of the fuel cell is made uniform, moisture condensation in the fuel flow path is prevented, and moisture in the fuel flow path is An object of the present invention is to provide a fuel cell system capable of suppressing stagnation and quickly discharging the stagnation water, and reliably preventing deterioration of the performance of the fuel cell and deterioration of the fuel electrode.

  Therefore, in the fuel cell system of the present invention, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode has a fuel flow path formed along the fuel electrode, and an oxidant flow path along the oxygen electrode. A fuel cell system comprising a plurality of fuel cell assemblies electrically connected via a separator formed with a fuel conduit system connected to the fuel flow path, wherein the fuel flow path includes: The fuel pipe system is divided into a plurality of parallel small flow paths, and includes a flow rate control valve for controlling the flow rate of the fuel gas flowing through each small flow path, corresponding to each small flow path.

  In another fuel cell system of the present invention, the fuel flow path is further divided in the direction of a temperature gradient in the fuel cell, and the fuel gas has a smaller flow path corresponding to a part having a higher temperature. The distribution ratio is controlled to be high.

  In still another fuel cell system of the present invention, the flow rate control valve is controlled according to the temperature of each part of the fuel cell.

  In still another fuel cell system of the present invention, the flow rate control valve is controlled according to the load of the fuel cell.

  In still another fuel cell system of the present invention, the fuel gas is further controlled to flow in a small flow path with a large amount of accumulated water.

  In still another fuel cell system of the present invention, the fuel cell assembly further includes a coolant flow path, and the fuel flow path is divided in the direction of the coolant flow in the coolant flow path.

  According to the present invention, in a fuel cell system, a fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode has a fuel flow path formed along the fuel electrode, and an oxidant flow path along the oxygen electrode. A fuel cell system comprising a plurality of fuel cell assemblies electrically connected via a separator formed with a fuel conduit system connected to the fuel flow path, wherein the fuel flow path includes: The fuel pipe system is divided into a plurality of parallel small flow paths, and includes a flow rate control valve for controlling the flow rate of the fuel gas flowing through each small flow path, corresponding to each small flow path.

  In this case, the flow rate of the fuel gas flowing through each small flow path can be controlled, the amount of water condensed in each part in the fuel flow path can be leveled, and the fuel electrode side wet in each part of the fuel cell The state can be made uniform. Therefore, it is possible to prevent condensation of moisture in the fuel flow path, to suppress the retention of moisture in the fuel flow path, and to reliably prevent the performance degradation of the fuel cell and the deterioration of the fuel electrode.

  In another fuel cell system, the fuel flow path is further divided in the direction of a temperature gradient in the fuel cell so that the fuel gas has a higher distribution ratio in a smaller flow path corresponding to a part having a higher temperature. Be controlled.

  In this case, since the fuel gas distribution ratio can be controlled to be higher as the temperature is higher, the amount of moisture to be condensed can be reliably leveled.

  In still another fuel cell system, the flow control valve is controlled in accordance with the temperature of each part of the fuel cell.

  In this case, the fuel gas distribution ratio can be accurately controlled.

  In still another fuel cell system, the flow control valve is controlled in accordance with the load of the fuel cell.

  In this case, since it is not necessary to detect the temperature of each part of the fuel cell, the configuration can be simplified.

  In still another fuel cell system, the fuel gas is further controlled to flow in a small flow path with a large amount of accumulated water.

  In this case, the water staying in the small flow path can be quickly and reliably discharged, so that the fuel electrode is not covered with water, and the performance of the fuel cell and the deterioration of the fuel electrode are ensured. Can be prevented.

  In still another fuel cell system, the fuel cell assembly further includes a cooling medium flow path, and the fuel flow path is divided in the direction of the cooling medium flow in the cooling medium flow path.

  In this case, the fuel gas distribution ratio can be controlled to be higher as the temperature is higher, the amount of water condensed in each part in the fuel flow path can be leveled, and the fuel in each part of the fuel cell can be leveled. The wet state on the pole side can be made uniform.

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

  FIG. 2 is a plan view showing the configuration of the fuel cell stack according to the first embodiment of the present invention. FIG. 3 is an air supply flow attached to the air inlet side of the fuel cell stack according to the first embodiment of the present invention. It is a figure which shows a path | route.

  In the figure, 20 is a fuel cell stack as a fuel cell assembly composed of a plurality of fuel cells (FC), and is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, luggage carts, etc. Is done. Here, the vehicle is equipped with a large number of auxiliary equipment that consumes electricity, such as lighting devices, radios, and power windows. Since the output range is extremely wide, it is desirable to use the fuel cell stack 20 as a power source in combination with a battery, a secondary battery such as a lithium ion battery, and a power storage means including a capacitor.

  The fuel cell may be of an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but is preferably a solid polymer type fuel cell.

  More preferably, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) type fuel cell using hydrogen gas as fuel and oxygen or air as oxidant. Here, the PEM type fuel cell is generally a stack in which a plurality of cells (Fuel Cell) in which a catalyst, an electrode and a separator are combined on both sides of a solid polymer electrolyte membrane that transmits ions such as protons are connected in series. (Stack).

  In this case, the solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and integrated to join. Then, when one of the gas diffusion electrodes is used as a fuel electrode and hydrogen gas as a fuel gas is supplied to the fuel electrode via a fuel flow path 14 to be described later in contact with the surface of the fuel electrode, hydrogen is converted into hydrogen ions (protons). It is decomposed into electrons and hydrogen ions permeate the solid polymer electrolyte membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode, and air as an oxidant is supplied to the oxygen electrode through an air channel 16 described later as an oxidant channel in contact with the surface of the oxygen electrode, Oxygen, the hydrogen ions and electrons combine to produce water. An electromotive force is generated by such an electrochemical reaction. In the present embodiment, the fuel cell stack 20 is a so-called normal pressure type fuel cell, and normal pressure air flows through the air flow path 16. Here, the normal pressure is a range from atmospheric pressure to a pressure higher by about 100 mmAq than the atmospheric pressure.

  For example, in the present embodiment, as an example, a PEM type fuel cell is used, for example, a stack in which 100 cells are connected in series is used. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, etc. with a reformer, can be directly supplied to the fuel cell, a sufficient amount of hydrogen can be stably supplied even during high-load operation of the vehicle. It is desirable to supply the hydrogen gas stored in the fuel storage means so that the fuel can be supplied.

  Here, the fuel storage means is preferably a container storing a hydrogen storage alloy, but a container storing a hydrogen storage liquid such as decalin, a container storing hydrogen gas such as a hydrogen gas cylinder, and the like. Also good. Thereby, hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell can follow the fluctuation of the load of the vehicle and supply a necessary current. In this case, the output impedance of the fuel cell is extremely low and can be approximated to zero.

  In the present embodiment, the fuel cell stack 20 includes a plurality of cell modules 21 as shown in FIG. In addition, the arrow in FIG. 2 has shown the flow of the hydrogen gas as fuel gas. The cell module 21 includes a unit cell (MEA) as a fuel cell, an electrical connection between the unit cells, and a fuel flow path 14 through which hydrogen gas introduced into the unit cell flows and an oxidant. The separator 15 described later for separating the air flow path 16 through which the air flows, and the unit cell and the separator 15 as one set are configured by overlapping a plurality of sets in the thickness direction. In the cell module 21, the unit cells and the separators 15 are stacked and stacked in multiple stages so that the unit cells are arranged with a predetermined gap.

  The unit cell is composed of an air electrode as an oxygen electrode provided on the solid polymer electrolyte membrane side as an electrolyte layer and a fuel electrode provided on the other side. The air electrode includes an electrode diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and a catalyst layer that is formed on the electrode diffusion layer and is supported in contact with the solid polymer electrolyte membrane. Also, an air electrode side collector as a current collector for collecting current by contacting the electrode diffusion layer on the air electrode side of the unit cell, and a current collector for collecting current by contacting the electrode diffusion layer on the fuel electrode side of the unit cell And a fuel electrode side collector.

  In the fuel cell stack 20 shown in FIG. 2, a plurality of cell modules 21 are stacked in the horizontal direction in the figure and are sandwiched by end plates as holding members from both the left and right ends. In the example shown in FIG. 2, 10 unit cells and separators 15 are stacked to form one cell module 21, and 10 cell modules 21 are stacked to form one fuel cell stack 20. Forming. Since the separators 15 are always provided on both sides of the unit cell, the number of separators 15 in one cell module 21 is eleven.

  In this case, the fuel cell stack 20 has a flattened rectangular parallelepiped shape as a whole, and the air flow inside is the direction of gravity as a direction perpendicular to the drawing in FIG. It is straight. Further, as indicated by arrows in FIG. 2, the flow of hydrogen gas is in a serpentine shape that is folded for each cell module 21 in a horizontal plane that is substantially orthogonal to the direction of gravity, that is, in a meandering shape. A fuel inlet line 33 as a fuel line system for supplying hydrogen gas to one end plate is connected, and a fuel outlet line 31 as a fuel line system for discharging hydrogen gas to the other end plate. Is connected.

  In the present embodiment, as shown in FIG. 3, the fuel cell system includes an air supply fan unit 45 as an oxidant supply source in order to supply normal pressure air as an oxidant to the fuel cell stack 20. Have. The air supply fan unit 45 is generally called a sirocco fan, and includes a centrifugal multi-blade fan (not shown) as an impeller driven by a fan drive motor 46. The rotation axis of the multiblade fan is arranged so as to extend in the vertical direction (the vertical direction in FIG. 3), that is, to rotate in a horizontal plane. In this case, the air supply fan unit 45 sucks air from above into the center of the rotating multi-blade fan, discharges air to the outer periphery of the multi-blade fan, and distributes the air around the multi-blade fan. Normal pressure air is discharged to the outside of the air supply fan unit 45 through an approximately spiral pressure boosting duct provided.

  An air filter 47 is disposed on the upper surface of the air supply fan unit 45 so as to remove dust, contaminants, harmful components, etc. in the air sucked into the air supply fan unit 45. It has become. Then, the air discharged from the air supply fan unit 45 passes through the air introduction duct 42 connected to the air outlet of the air supply fan unit 45, and is above the fuel cell stack 20, that is, at the oxidant inlet side. Is supplied into an air supply chamber 44 attached to the air inlet side. The air introduction duct 42 may be formed integrally with the pressure increasing duct of the air supply fan unit 45, or may be formed separately and connected. An air discharge chamber 43 as an oxidant discharge channel is connected to the lower side of the fuel cell stack 20, that is, the air outlet side as the oxidant outlet side.

  A plurality of water supply nozzles 51 for spraying water are disposed at the boundary between the air introduction duct 42 and the air supply chamber 44, that is, at the inlet of the air supply chamber 44. A water supply pipe (not shown) is connected to the water supply nozzle 51, and water stored in a water tank (not shown) is pumped by a water pump and supplied to the water supply nozzle 51 via the water supply pipe. Is done. Thereby, water can be supplied to the surface of the oxygen electrode via the air flow path 16 to maintain the solid polymer electrolyte membrane in a wet state. In addition, since the air flowing through the air flow path 16 includes water, the heat capacity increases, so that the function as a cooling medium for cooling the unit cell is increased.

  A condenser unit (not shown) is disposed in the air discharge chamber 43 or downstream thereof. The condenser unit condenses and separates moisture contained in the air discharged from the fuel cell stack 20, and cools the air discharged from the fuel cell stack 20 to condense the moisture. It is like that. Thereby, the air discharged from the fuel cell stack 20 into the air discharge chamber 43 is introduced into the condenser unit. The air is cooled while passing through the condenser unit, separates the condensed moisture, and is released into the atmosphere from the exhaust port of the condenser unit. The separated water is preferably collected in a water tank through a water distribution pipe (not shown).

  In the present embodiment, the fuel cell system has a control device (not shown). The control device includes a calculation means such as a CPU and MPU, a storage means such as a semiconductor memory, an input / output interface, etc., and a flow rate of hydrogen, oxygen, air, etc. supplied from the pressure sensor and other sensors to the fuel cell, The temperature, output voltage, etc. are detected, and the operation of the air supply fan unit 45, a hydrogen exhaust solenoid valve 37, a first flow control valve 35a, a second flow control valve 35b, a third flow control valve 35c, etc., which will be described later, is performed. Control. Further, the control device comprehensively controls the operation of the fuel cell system in cooperation with other control devices. In addition, the said control apparatus may be comprised integrally with another control apparatus.

  Next, the flow path of hydrogen gas in the fuel cell system will be described.

  FIG. 1 is a schematic diagram showing a hydrogen gas flow path of a fuel cell system according to a first embodiment of the present invention, and FIG. 4 is a diagram showing a configuration on the fuel electrode side of a separator according to the first embodiment of the present invention. FIG. 5 is a diagram showing a configuration of the separator on the air electrode side in the first embodiment of the present invention. In FIG. 4, (a) is a sectional view taken along the line DD of (b), and (b) is a plan view. Moreover, in FIG. 5, (a) is a top view, (b) is FF arrow sectional drawing of (a).

  As shown in FIG. 1, the hydrogen gas passes through a fuel supply line 22 and a fuel inlet line 33 connected to the fuel supply line 22 from a fuel storage means (not shown), and the fuel in the fuel cell stack 20. It is supplied to the flow path 14. Then, hydrogen gas discharged as an unreacted component from the fuel flow path 14 of the fuel cell stack 20 is discharged out of the fuel cell stack 20 through the fuel outlet pipe 31. A water recovery drain tank 34 as a recovery container is connected to the fuel outlet pipe 31.

  The water recovery drain tank 34 is connected to a fuel circulation line 30 for discharging hydrogen gas separated from water, and the fuel circulation line 30 is provided with a suction circulation pump 36 as a pump. . The end of the fuel circulation line 30 opposite to the water recovery drain tank 34 is connected to the fuel inlet line 33. Thereby, the hydrogen gas discharged out of the fuel cell stack 20 can be recovered, supplied to the fuel flow path 14 of the fuel cell stack 20, and reused.

  Further, a fuel discharge pipe 38 is connected to the water recovery drain tank 34, and a hydrogen exhaust electromagnetic valve 37 is disposed in the fuel discharge pipe 38, and the fuel cell stack 20 is activated when the fuel cell stack 20 is started. The hydrogen gas discharged from the can be discharged into the atmosphere. The outlet end of the fuel discharge line 38 is preferably connected to the air discharge chamber 43 so that the discharged hydrogen is diluted with air.

  In the present embodiment, the fuel flow path 14 in each unit cell is divided into a plurality of parallel small flow paths, for example, a first small flow path 14a to a third small flow path 14c. The number of divisions of the fuel flow path 14 can be arbitrarily determined. For example, the number of divisions may be divided into two or four or more. 2 to 5 is an appropriate number of divisions. Moreover, the division | segmentation form of the fuel flow path 14 is the direction of the temperature gradient in a unit cell. That is, the fuel flow path 14 is divided into a plurality along the direction in which the temperature changes.

  As indicated by an arrow E in FIG. 5, in the present embodiment, air containing water that functions as a cooling medium flows in the air flow path 16 in the direction of gravity, that is, the vertical direction in the drawing. For this reason, the unit cell is cooled most at the portion of the air flow path 16 on the air inlet side and has the lowest temperature, and the portion of the air flow path 16 on the air outlet side has the highest temperature. Therefore, in the unit cell, a temperature gradient is generated such that the temperature becomes higher at the lower side. Therefore, the fuel flow path 14 is divided into a first small flow path 14a, a second small flow path 14b, and a third small flow path 14c in order from the top in the direction of the temperature gradient. Since the temperature gradient occurs in the direction of the coolant flow, it can be said that the fuel flow path 14 is divided in the direction of the coolant flow.

  In this case, the fuel through hole 13 formed on the side of the separator 15 is also divided into a first fuel through hole 13a to a third fuel through hole 13c. Then, as indicated by an arrow C in FIG. 4, the hydrogen gas passes through the first fuel through hole 13 a and the second fuel through hole on one side of the separator 15 (left side in the example shown in FIG. 4). From the hole 13b and the third fuel through hole 13c, through the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c, the other of the separators 15 (right in the example shown in FIG. 4). The first fuel through-hole 13a, the second fuel through-hole 13b, and the third fuel through-hole 13c on the other side.

  Further, the downstream portion of the fuel inlet pipe 33 also branches into a first fuel inlet pipe 33a, a second fuel inlet pipe 33b, and a third fuel inlet pipe 33c. The second fuel through hole 13b and the third fuel through hole 13c are connected to each other. Further, the upstream portion of the fuel outlet pipe 31 also branches into a first fuel outlet pipe 31a, a second fuel outlet pipe 31b, and a third fuel outlet pipe 31c. The second fuel through hole 13b and the third fuel through hole 13c are connected to each other.

  The first fuel outlet pipe 31a, the second fuel outlet pipe 31b, and the third fuel outlet pipe 31c have a first flow rate control valve 35a, a second flow rate control valve 35b, and a third flow rate as flow rate control valves. Each control valve 35c is provided. The first flow rate control valve 35a, the second flow rate control valve 35b, and the third flow rate control valve 35c are operable independently of each other, and are controlled by the control device, so that the first small flow channel 14a and the second small flow channel are controlled. The flow rate of hydrogen gas flowing through 14b and the third small flow path 14c is independently controlled. The first flow control valve 35a, the second flow control valve 35b, and the third flow control valve 35c are disposed in the first fuel inlet pipe 33a, the second fuel inlet pipe 33b, and the third fuel inlet pipe 33c. In order to fill the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c with hydrogen gas, the first fuel outlet line 31a and the second fuel outlet line may be used. It is desirable to dispose 31b and the third fuel outlet pipe 31c. When the first flow control valve 35a, the second flow control valve 35b, and the third flow control valve 35c are described in an integrated manner, they will be described as the flow control valve 35.

  Next, an operation for controlling the distribution ratio of hydrogen gas to the first small flow path 14a to the third small flow path 14c in the fuel cell system having the above configuration will be described.

  FIG. 6 is a diagram showing an operation for controlling the hydrogen gas distribution ratio of the fuel cell system according to the first embodiment of the present invention, and FIG. 7 shows the temperature difference in the unit cell according to the first embodiment of the present invention. FIG. 8 is a graph showing the relationship between the temperature difference in the unit cell and the hydrogen gas distribution ratio in the first embodiment of the present invention.

  As shown in FIG. 6, the fuel cell stack 20 includes a first temperature detector 56a that detects temperatures of portions corresponding to the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c. A second temperature detector 56b and a third temperature detector 56c are provided. Note that it is not always necessary to detect the temperatures of the portions corresponding to all the fuel flow paths 14 in the fuel cell stack 20. For example, only the temperatures of the positions corresponding to the air inlet side and the outlet side of the air flow path 16 are detected. You may make it do. That is, only the temperature at the lowest temperature part and the highest temperature part in the fuel cell stack 20 may be detected. In FIG. 6, a thick arrow A indicates a flow of air containing water as a cooling medium, and a thin arrow B indicates a flow of hydrogen gas.

  Then, the control device determines the first flow rate control valve 35a, the first flow rate control valve 35a, the second temperature detector 56b, and the third temperature detector 56c based on the temperature of each part in the fuel cell stack 20 detected by the first temperature detector 56a, the second temperature detector 56b, and the third temperature detector 56c. The opening degree of the 2 flow rate control valve 35b and the third flow rate control valve 35c is controlled, thereby controlling the flow rate of hydrogen gas flowing through the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c. To do. That is, the distribution ratio of hydrogen gas to each of the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c is controlled.

  In this case, control is performed so that the higher the temperature of the part, the higher the hydrogen gas distribution ratio. As described in “Problems to be Solved by the Invention”, in a portion having a high temperature in the fuel flow path 14, when the hydrogen gas is consumed and the partial pressure of the hydrogen gas is reduced, the amount of moisture to be condensed is increased. . Therefore, by controlling the hydrogen gas distribution ratio to be higher at the higher temperature part, a large amount of hydrogen gas is supplied to the higher temperature part to prevent a decrease in the partial pressure of the hydrogen gas and condense moisture. The amount of can be reduced. Thereby, the amount of water condensed in each part in the fuel flow path 14 can be leveled, and the wet state on the fuel electrode side in each part of the unit cell can be made uniform. Therefore, the fuel electrode is not covered with moisture, and the performance of the unit cell can be prevented from being deteriorated and the fuel electrode can be prevented from deteriorating.

  Therefore, for example, as shown in FIG. 7, the control device controls the opening degree of the first flow rate control valve 35a, the second flow rate control valve 35b, and the third flow rate control valve 35c. Here, for convenience of explanation, the control device detects the temperature T1 of the portion corresponding to the first small flow path 14a detected by the first temperature detector 56a, that is, the lowest temperature portion, and the third temperature detector 56c. It is assumed that the opening degree of each flow control valve 35 is controlled based on the difference ΔT from the portion corresponding to the third small flow path 14c detected by the above, that is, the temperature T3 of the highest temperature portion.

  Here, ΔT = T3−T1. In addition, lines 35a, 35b, and 35c in FIG. 7 indicate the opening degrees of the first flow control valve 35a, the second flow control valve 35b, and the third flow control valve 35c, respectively. In addition, the vertical axis | shaft of FIG. 7 shows the opening degree [%] of the flow control valve 35, and the horizontal axis has shown (DELTA) T.

  In this case, the opening degree of the third flow rate control valve 35c corresponding to the highest temperature part is kept constant regardless of ΔT, that is, maintained at 100 [%], and the first flow rate control valve 35a increases as ΔT increases. And it turns out that the opening degree of the 2nd flow control valve 35b is controlled so that it may decrease sequentially.

  FIG. 8 shows the change in the hydrogen gas distribution ratio corresponding to FIG. Lines 14a, 14b, and 14c in FIG. 8 indicate distribution ratios of hydrogen gas flowing through the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c, respectively. The total distribution ratio is 100 [%]. In addition, the vertical axis in FIG. 8 indicates the hydrogen gas distribution ratio, and the horizontal axis indicates ΔT.

  Thereby, as shown in FIG. 7, by controlling the opening degree of the first flow rate control valve 35a, the second flow rate control valve 35b, and the third flow rate control valve 35c, the hydrogen gas distribution ratio becomes higher at the higher temperature part. It turns out that becomes high.

  Note that the control device replaces the temperature of the portion corresponding to the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c with the load of the fuel cell stack 20, that is, the generated current. Based on this, the opening degree of the first flow control valve 35a, the second flow control valve 35b, and the third flow control valve 35c can be controlled. This is because the consumption of hydrogen gas increases as the current generated by the fuel cell stack 20 increases, so that the amount of condensed water increases at a high temperature in the fuel flow path 14. In this case, the opening of the first flow control valve 35a, the second flow control valve 35b, and the third flow control valve 35c, and the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c are set. The distribution ratio of the flowing hydrogen gas can be expressed by replacing the horizontal axis in FIGS. 7 and 8 with current.

  Further, the control device replaces the opening of the first flow control valve 35a, the second flow control valve 35b and the third flow control valve 35c with the first flow control valve 35a, the second flow control valve 35b and the third flow control valve 35c. The length of the open time of the flow control valve 35c can also be controlled. That is, the distribution ratio of hydrogen gas may be controlled by changing the ratio of the open times of the respective flow control valves 35.

  Next, an operation for discharging the water remaining in the first small flow path 14a to the third small flow path 14c in the fuel cell system having the above-described configuration will be described.

  FIG. 9 is a diagram showing an operation of discharging the moisture remaining in the flow path of the fuel cell system according to the first embodiment of the present invention. In FIG. 9, (a) shows a state of normal operation, and (b) to (c) show states of discharging water from the first small channel to the third small channel. The white valve indicates that the valve is open, and the black valve indicates that the valve is closed.

  During steady operation in the fuel cell system of the present embodiment, the pressure of the hydrogen gas supplied from the fuel storage means to the fuel cell stack 20 is adjusted to a predetermined constant pressure and held. Further, the air supply fan unit 45 operates so that air set in advance according to the output current of the fuel cell stack 20 is supplied. In this case, the amount of air supplied is an amount sufficiently larger than the amount of air necessary for the output of the fuel cell stack 20 to be maximized. In FIG. 9, as in FIG. 6, the thick arrow A indicates the flow of air containing water as a cooling medium, and the thin arrow B indicates the flow of hydrogen gas.

  When the fuel cell stack 20 starts operation, reverse diffusion water is generated in each unit cell constituting the fuel cell stack 20, and the reverse diffusion water permeates the solid polymer electrolyte membrane and enters the fuel flow path 14. Until the fuel electrode side of the solid polymer electrolyte membrane is humidified. As a result, the fuel electrode side of the solid polymer electrolyte membrane becomes wet, and hydrogen ions generated from hydrogen by the electrochemical reaction can move smoothly in the solid polymer electrolyte membrane.

  Further, the hydrogen gas as an unreacted component supplied to the fuel flow path 14 and surplus is mixed with the back-diffused water that has permeated into the fuel flow path 14 and surplus, and a gas-liquid mixture Become. As shown in FIG. 9A, the hydrogen gas that has become the gas-liquid mixture is sucked by the suction circulation pump 36 and passes through the fuel outlet line 31 connected to the fuel cell stack 20. 20 is discharged to the outside. In this case, since all of the first flow rate control valve 35a, the second flow rate control valve 35b, and the third flow rate control valve 35c are opened, the hydrogen gas that has become the gas-liquid mixture flows into the first small flow path 14a, The second small flow path 14b and the third small flow path 14c are discharged to the outside of the fuel cell stack 20 through the first fuel outlet pipe 31a, the second fuel outlet pipe 31b, and the third fuel outlet pipe 31c. The

  The gas-liquid mixture passes through the fuel outlet pipe 31 and is introduced into the water recovery drain tank 34. Here, when the gas-liquid mixture stays in the water recovery drain tank 34 having a relatively wide space, moisture which is a heavy material falls downward due to gravity, and reverse diffusion water is separated from hydrogen gas. The hydrogen gas in a state where the reverse diffusion water is separated and dried is discharged out of the water recovery drain tank 34 and flows into the fuel circulation line 30. During steady operation, the hydrogen gas that has flowed into the fuel circulation line 30 is circulated by the suction circulation pump 36, introduced into the fuel inlet line 33, and again into the fuel flow path 14 of the fuel cell stack 20. Supplied and reused. Further, since the hydrogen exhaust electromagnetic valve 37 is closed, the hydrogen gas is not discharged from the fuel discharge line 38.

  In addition, the fuel cell system discharges the moisture remaining in the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c as needed.

  First, when the water staying in the first small flow path 14a is discharged, as shown in FIG. 9B, the first flow control valve 35a is opened, and the second flow control valve 35b and the third flow control valve are opened. 35c is closed. In this state, the hydrogen exhaust solenoid valve 37 is opened for a predetermined time (for example, 0.3 [second]). As a result, the hydrogen gas supplied to the fuel cell stack 20 through the fuel inlet pipe 33 flows only through the first small flow path 14a, so that the flow path cross-sectional area is smaller and the flow velocity is higher than in the normal operation state. Become. For this reason, it is possible to reliably discharge the water remaining in the first small flow path 14a. The water discharged from the first small flow path 14 a is separated from the hydrogen gas in the water recovery drain tank 34 and then discharged to the outside through the fuel discharge pipe 38.

  Further, when the water staying in the second small flow path 14b is discharged, as shown in FIG. 9C, the second flow rate control valve 35b is opened, and the first flow rate control valve 35a and the third flow rate control valve are opened. 35c is closed. In this state, the hydrogen exhaust electromagnetic valve 37 is opened for a predetermined time. As a result, the hydrogen gas supplied to the fuel cell stack 20 through the fuel inlet pipe 33 flows only through the second small flow path 14b, so that the flow path cross-sectional area is smaller and the flow velocity is higher than in the normal operation state. Become. For this reason, it is possible to reliably discharge the water remaining in the second small flow path 14b. The water discharged from the second small flow path 14b is separated from the hydrogen gas in the water recovery drain tank 34 and then discharged to the outside through the fuel discharge pipe 38.

  Furthermore, when the water staying in the third small flow path 14c is discharged, as shown in FIG. 9D, the third flow rate control valve 35c is opened, and the first flow rate control valve 35a and the second flow rate control valve are opened. 35b is closed. In this state, the hydrogen exhaust electromagnetic valve 37 is opened for a predetermined time. Thereby, the hydrogen gas supplied to the fuel cell stack 20 through the fuel inlet pipe 33 flows only through the third small flow path 14c, so that the flow path cross-sectional area is smaller than that in the normal operation state, and the flow velocity is high. Become. For this reason, it is possible to reliably discharge the moisture remaining in the third small flow path 14c. The water discharged from the third small flow path 14 c is separated from the hydrogen gas in the water recovery drain tank 34 and then discharged to the outside through the fuel discharge pipe 38.

  In this way, the operations of the first flow control valve 35a, the second flow control valve 35b, the third flow control valve 35c, and the hydrogen exhaust electromagnetic valve 37 are controlled, and the first small flow path 14a, the second small flow path 14b, By flowing hydrogen gas through only one of the third small flow paths 14c, the water remaining in the small flow paths is discharged. Therefore, the flow passage cross-sectional area of the hydrogen gas is reduced, and the flow rate of the hydrogen gas can be locally increased, so that the remaining water can be blown away. In a normal operation state, since the flow path cross-sectional area is large, hydrogen gas passes through a portion without moisture, so that it is difficult to blow off the remaining moisture.

  Here, the case where hydrogen gas is caused to flow through only one small flow path has been described, but when the number of divisions of the fuel flow path 14 is large, the hydrogen gas is caused to flow through only a plurality of, for example, two small flow paths. You can also That is, hydrogen gas is allowed to flow through only a few selected small channels among a plurality of small channels, and the flow rate of hydrogen gas is increased by making the channel cross-sectional area smaller than in the normal operation state. By doing so, the staying water can be surely discharged.

  Note that the operation of discharging water as shown in FIGS. 9B to 9D may be performed at a predetermined cycle, or the amount of water remaining in the fuel flow path 14 reaches a predetermined value. You may be made to do it. When the operation of discharging moisture is performed at a predetermined cycle, it is desirable that the frequency of the operation is higher as the temperature is higher. Further, the amount of water remaining in the fuel flow path 14 can be obtained from the value of the current generated by the fuel cell stack 20 and the temperature without directly measuring.

  Thus, in the present embodiment, the fuel flow path 14 is divided into a plurality of parallel small flow paths, that is, the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c, The flow rate of hydrogen gas flowing through each small flow path is controlled by the first flow rate control valve 35a, the second flow rate control valve 35b, and the third flow rate control valve 35c. Thereby, since the distribution ratio of hydrogen gas can be controlled to be higher as the temperature is higher, the amount of moisture condensed in each part in the fuel flow path 14 can be leveled, and each part of the unit cell The wet state on the fuel electrode side can be made uniform.

  In addition, hydrogen gas is allowed to flow only in the selected small flow path, and more hydrogen gas flows in the small flow path with a large amount of retained water. In addition, it can be surely discharged. Therefore, the fuel electrode is not covered with moisture, and the performance of the unit cell can be prevented from being deteriorated and the fuel electrode can be prevented from deteriorating.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 10 is a diagram showing the configuration of the separator on the fuel electrode side in the second embodiment of the present invention, FIG. 11 is a diagram showing the configuration of the separator on the cooling medium side in the second embodiment of the present invention, and FIG. These are figures which show the structure by the side of the air electrode of the separator in the 2nd Embodiment of this invention.

  In the first embodiment, the fuel cell system using the air flowing through the air flow path 16 as a cooling medium for cooling the fuel cell stack 20 has been described. In the present embodiment, an independent cooling system is used. A fuel cell system using a medium other than air, for example, a medium such as cooling water, as a cooling medium will be described.

  As shown in FIG. 10, in the present embodiment, the fuel flow path 14 in each unit cell is divided into a first small flow path 14a to a third small flow path 14c in parallel. In this case, in addition to the first fuel through hole 13a to the third fuel through hole 13c, a cooling medium through hole 18 and an air through hole 19 are formed in the side portion of the separator 15. As in the first embodiment, the hydrogen gas flows in a direction perpendicular to the direction of gravity, that is, in the horizontal direction, as indicated by an arrow C in FIG. Specifically, from the first fuel through hole 13a, the second fuel through hole 13b, and the third fuel through hole 13c on one side of the separator 15 (left side in the example shown in FIG. 10), A first fuel through hole on the other side (right side in the example shown in FIG. 10) of the separator 15 through the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c. 13a, the second fuel through hole 13b and the third fuel through hole 13c.

  Further, as indicated by an arrow G in FIG. 11, the cooling medium meanders in the gravity direction, that is, the vertical direction in the figure, and flows in the cooling medium flow path 17. Specifically, the cooling medium flow path 17 is formed by connecting in series a first cooling medium flow path 17a to a third cooling medium flow path 17c, each extending in the horizontal direction. Therefore, in the unit cell, the portion of the cooling medium flow path 17 on the inlet side of the cooling medium is cooled to the lowest temperature, and the temperature of the cooling medium flow path 17 on the outlet side of the cooling medium is highest. Therefore, in the unit cell, a temperature gradient is generated such that the temperature increases toward the upper side. Therefore, the fuel flow path 14 is divided in the direction of the temperature gradient, that is, in the direction of the flow of the cooling medium. In the present embodiment, unlike the first embodiment, the first small flow path 14a, the second small flow path 14b, and the third small flow path 14c correspond to portions where the temperature decreases in this order. To do.

  Further, as shown by an arrow E in FIG. 12, the air meanders in the direction of gravity, that is, the vertical direction in the figure, and flows in the air flow path 16. Specifically, the air flow path 16 is formed by connecting in series a first air flow path 16a to a third air flow path 16c each extending in the horizontal direction. In addition, the surface of the separator 15 is shown in FIG. 11 and 12 as mutually reversed so that the right and left may be reversed.

  Since the configuration and operation of other points are the same as those in the first embodiment, description thereof is omitted.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by providing the same code | symbol. Also, the description of the same operations and effects as those of the first and second embodiments is omitted.

  FIG. 13 is a diagram showing the configuration of the separator on the cooling medium side in the third embodiment of the present invention, and FIG. 14 is a diagram showing the configuration of the separator on the fuel electrode side in the third embodiment of the present invention.

  Also in the present embodiment, as in the second embodiment, an independent cooling system is used, and a medium other than air, for example, a medium such as cooling water, is used as the cooling medium. A fuel cell system will be described.

  As shown in FIG. 13, in the present embodiment, the cooling medium flows in the cooling medium flow path 17 in a direction orthogonal to the direction of gravity, that is, in the horizontal direction, as indicated by an arrow G. Air also flows in the air flow path 16 not shown in FIG. 13 in the horizontal direction as indicated by the dotted arrow E. In this case, a cooling medium through hole 18 and an air through hole 19 are formed on the side of the separator 15.

  Further, the hydrogen gas flows in the direction of gravity, that is, in the vertical direction in the figure, as indicated by an arrow C in FIG. The fuel flow path 14 in each unit cell is divided into a first small flow path 14a to a third small flow path 14c extending in parallel in the vertical direction. In this case, a first fuel through hole 13 a to a third fuel through hole 13 c are formed at the upper end and the lower end of the separator 15. Specifically, from the first fuel through hole 13a, the second fuel through hole 13b, and the third fuel through hole 13c at the upper end of the separator 15, the first small flow path 14a, the second small flow path 14b, It flows through the third small flow path 14c to the first fuel through hole 13a, the second fuel through hole 13b, and the third fuel through hole 13c at the lower end of the separator 15.

  As indicated by the dotted arrow G in FIG. 14, the cooling medium flows in the horizontal direction, so that the unit cell is cooled most at the inlet side of the cooling medium in the cooling medium flow path 17 and the temperature is lowered. The portion of the medium flow path 17 on the outlet side of the cooling medium has the highest temperature. Therefore, in the unit cell, a temperature gradient is generated such that the temperature increases toward the right side in the figure. Therefore, the fuel flow path 14 is arranged in the direction of the temperature gradient, that is, in the direction of the flow of the cooling medium, from left to right in the drawing, in order, the first small flow path 14a, the second small flow path 14b, and the third. The small flow path 14c is divided.

  Since the configuration and operation of other points are the same as those in the first embodiment, description thereof is omitted.

  The present invention is not limited to the above-described embodiment, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

  Furthermore, in this embodiment, the case where a fuel cell stack in which a plurality of fuel cells are stacked with a separator interposed therebetween is used as the fuel cell assembly. However, a fuel cell module in which a plurality of tubular fuel cells are bundled is described. It may be used.

It is a schematic diagram which shows the flow path of the hydrogen gas of the fuel cell system in the 1st Embodiment of this invention. It is a top view which shows the structure of the fuel cell stack in the 1st Embodiment of this invention. It is a figure which shows the air supply flow path attached to the air inlet side of the fuel cell stack in the 1st Embodiment of this invention. It is a figure which shows the structure by the side of the fuel electrode of the separator in the 1st Embodiment of this invention. It is a figure which shows the structure by the side of the air electrode of the separator in the 1st Embodiment of this invention. It is a figure which shows the operation | movement which controls the distribution ratio of the hydrogen gas of the fuel cell system in the 1st Embodiment of this invention. It is a graph which shows the relationship between the temperature difference in the unit cell in the 1st Embodiment of this invention, and the opening degree of a flow control valve. It is a graph which shows the relationship between the temperature difference in the unit cell in 1st Embodiment of this invention, and the distribution ratio of hydrogen gas. It is a figure which shows the operation | movement which discharges | emits the water | moisture content stagnated in the flow path of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the structure by the side of the fuel electrode of the separator in the 2nd Embodiment of this invention. It is a figure which shows the structure by the side of the cooling medium of the separator in the 2nd Embodiment of this invention. It is a figure which shows the structure by the side of the air electrode of the separator in the 2nd Embodiment of this invention. It is a figure which shows the structure by the side of the cooling medium of the separator in the 3rd Embodiment of this invention. It is a figure which shows the structure by the side of the fuel electrode of the separator in the 3rd Embodiment of this invention.

Explanation of symbols

14 Fuel channel 14a First small channel 14b Second small channel 14c Third small channel 15 Separator 16 Air channel 16a First air channel 16b Second air channel 16c Third air channel 17 Cooling medium flow Path 17a first cooling medium flow path 17b second cooling medium flow path 17c third cooling medium flow path 20 fuel cell stack 31 fuel outlet line 31a first fuel outlet line 31b second fuel outlet line 31c third fuel outlet Line 33 Fuel inlet line 33a First fuel inlet line 33b Second fuel inlet line 33c Third fuel inlet line 35a First flow rate control valve 35b Second flow rate control valve 35c Third flow rate control valve

Claims (6)

A fuel cell in which an electrolyte layer is sandwiched between a fuel electrode and an oxygen electrode is electrically connected via a separator in which a fuel channel is formed along the fuel electrode and an oxidant channel is formed along the oxygen electrode. A connected fuel cell assembly;
A fuel cell system having a fuel pipeline connected to the fuel flow path,
The fuel flow path is divided into a plurality of parallel small flow paths,
The fuel pipeline system includes a flow rate control valve that controls the flow rate of the fuel gas flowing through each small flow path, corresponding to each small flow path. The fuel flow path is divided in the direction of the temperature gradient in the fuel cell,
2. The fuel cell system according to claim 1, wherein the fuel gas is controlled so that a distribution ratio becomes higher in a small flow path corresponding to a part having a higher temperature.   The fuel cell system according to claim 2, wherein the flow rate control valve is controlled according to the temperature of each part of the fuel cell.   The fuel cell system according to claim 1, wherein the flow control valve is controlled according to a load of the fuel cell.   2. The fuel cell system according to claim 1, wherein the fuel gas is controlled to flow more in a small flow path with a large amount of accumulated water. The fuel cell assembly includes a cooling medium flow path,
The fuel cell system according to claim 1, wherein the fuel flow path is divided in a flow direction of the cooling medium in the cooling medium flow path.

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