JP2010225536A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct fuel cell for coping with both reduction of an amount of water flowing out from an air electrode and prevention of condensation in an air supply passage. <P>SOLUTION: The fuel cell includes a membrane-electrode assembly having an electrolyte membrane, a fuel electrode, and the air electrode; a fuel electrode passage for supplying a fuel to the fuel electrode; an air electrode passage for supplying an air to the air electrode; a first air introduction port for introducing the air to the air electrode passage; a gas exhaust port for discharging an exhaust gas from the air electrode; and a second air introduction port communicated with the gas exhaust port and merged with the exhaust gas without passing through the air electrode and introducing the air discharged outside the fuel cell. When the whole water generated in power generation on the air electrode is converted into water vapor, vapor pressure of the water vapor to an amount of first air supply introduced from the first air introduction port exceeds saturated vapor pressure, and vapor pressure of the water vapor to the sum total of an amount of the first air supply and an amount of second air supply supplied from the second air introduction port is controlled to be the saturated vapor pressure or below. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell suitable for a direct fuel cell.

  Direct fuel cells that generate power by supplying liquid fuel such as alcohol directly to the power generation unit do not require auxiliary equipment such as vaporizers and reformers, and are expected to be used for small power sources for portable devices. Yes. As such a direct type fuel cell, an alcohol aqueous solution is directly supplied to the power generation unit to extract protons, and discharges such as water discharged from the power generation unit are placed in a mixing tank or the like disposed on the upstream side of the power generation unit. Circulating fuel cell systems that are circulated and reused are known.

In a direct methanol supply type fuel cell (hereinafter referred to as DMFC), a membrane electrode assembly (hereinafter referred to as MEA) generally comprising a fuel electrode (anode), an air electrode (cathode) and an electrolyte membrane, and a fuel electrode flow path, A cell stack in which power generation cells including an air electrode channel are stacked functions as a power generation unit, and power generation is performed. A mixed solution of water and methanol is sent to the fuel electrode channel via a liquid feed pump or the like, and the reaction shown in the following formula (1) occurs in the fuel electrode to generate carbon dioxide. On the other hand, air is sent to the air electrode channel by an air supply pump or the like, and the reaction shown in the following formula (2) occurs in the air electrode to generate water.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O (2)

  A mixed solution containing carbon dioxide generated at the fuel electrode, water, and unreacted methanol is generally discharged from the fuel electrode channel as a gas-liquid two-phase flow. The gas-liquid two-phase flow discharged from the fuel electrode channel is separated into a gas and a liquid by a gas-liquid separator provided on the outlet side of the fuel electrode channel. The separated liquid is circulated to a mixing tank or the like through a recovery channel, and the separated gas is released to the atmosphere.

  On the other hand, in the reaction at the air electrode, water generated by the power generation reaction (2), water that permeates the membrane, and water that reacts with methanol and air that permeate the membrane are generated, but this water is not used for the reaction at the air electrode Exhausted together with air. Here, if the air supply amount supplied to the air electrode is large, water is accompanied by air more than necessary and discharged. For this reason, the amount of water flowing out from the air electrode increases, and a mechanism for collecting the water is required, which makes it difficult to reduce the size of the DMFC. On the other hand, if the amount of air supplied to the air electrode is small, the amount of water flowing out from the air electrode is small, so that the above-described problems are unlikely to occur. However, since the amount of air supplied is small, water vapor generated by the water is saturated, and condensation may occur in the air electrode channel. As a result, the air supply path becomes narrow due to condensation, pressure loss occurs in that part, air supply is not performed sufficiently, power generation is not possible in part of the cell, power generation characteristics of the whole cell and also the stack May cause problems. In order to solve such a problem, a pressure loss such as a throttle is provided at the inlet of the air electrode channel using an air pump with a large protruding pressure, and even if the air electrode channel is blocked by condensation, the condensed liquid A configuration is required to discharge water by air pressure. In fact, in a semi-passive type fuel cell, in order to solve the same problem, a technique for blowing away condensation in an air supply path has been studied (Patent Document 1). However, an air pump with a large protruding pressure consumes a large amount of power and has a high noise level, which is an obstacle to downsizing the DMFC.

US Patent Application 2007 / 009061A1 Specification

  The present invention provides a direct fuel cell that achieves both a reduction in the amount of water flowing out from an air electrode and prevention of condensation in an air supply path.

The fuel cell according to the first embodiment of the present invention comprises:
A membrane electrode assembly comprising an electrolyte membrane, and a fuel electrode and an air electrode that sandwich the electrolyte membrane;
A fuel electrode flow path for supplying fuel to the fuel electrode;
An air electrode passage for supplying air to the air electrode;
A first air inlet for introducing air from the outside into the air electrode channel;
A gas discharge port for discharging exhaust gas after power generation reaction at the air electrode from the air electrode channel;
A second air introduction port that communicates with the gas discharge port, joins the exhaust gas without passing through the air electrode, and introduces air discharged outside the fuel cell;
When all the water generated at the air electrode during the power generation at the air electrode is water vapor, the vapor pressure of the water vapor with respect to the first air supply amount introduced from the first air inlet exceeds the saturated vapor pressure. And the vapor pressure of the water vapor is controlled to be equal to or lower than the saturated vapor pressure with respect to the sum of the first air supply amount and the second air supply amount supplied from the second air introduction port. It is characterized by.

The fuel cell according to the second embodiment of the present invention comprises:
A membrane electrode assembly comprising an electrolyte membrane, and a fuel electrode and an air electrode that sandwich the electrolyte membrane;
A fuel electrode flow path for supplying fuel to the fuel electrode;
An air electrode flow path for supplying first air to the air electrode;
A first manifold in communication with the air electrode channel via a first air inlet at one end of the air electrode channel;
A second manifold communicating with the air electrode channel through a gas outlet at the other end of the air electrode channel;
An air inlet of a second manifold for supplying the second manifold with a second air different from the air supplied to the air electrode;
When the water generated at the air electrode during power generation is all steam, the supply amount of the first air introduced from the first air inlet is controlled so that the steam pressure of the steam exceeds the saturated steam pressure. And a control unit for controlling the supply amount of the second air so that the vapor pressure of the water vapor is equal to or lower than the saturated vapor pressure with respect to the sum of the supply amounts of the first air and the second air,
It is characterized by comprising.

  According to the present invention, in the direct fuel cell, it is possible to reduce both the amount of water flowing out from the air electrode and the prevention of water condensation in the air supply path. As a result, the pressure loss in the air supply path can be reduced while maintaining good power generation efficiency, and the fuel cell can be reduced in size.

1 is a conceptual cross-sectional view of a fuel cell that is one embodiment of the present invention. The conceptual diagram for demonstrating the prevention of dew condensation in the air electrode vicinity area | region in this invention. 1 is a conceptual cross-sectional view of a fuel cell that is one embodiment of the present invention. The conceptual diagram which shows the structure of the control apparatus in this invention. 1 is a conceptual cross-sectional view of a fuel cell having a cell stack structure according to an embodiment of the present invention. 1 is a conceptual cross-sectional view of a fuel cell having a cell stack structure according to an embodiment of the present invention. 1 is a conceptual cross-sectional view of a fuel cell having a cell stack structure according to an embodiment of the present invention. The perspective view for demonstrating the fuel cell which has the cell stack structure which is one embodiment of this invention. 1 is a conceptual cross-sectional view of a fuel cell in Example 1 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  A conceptual cross-sectional view of a fuel cell according to an embodiment of the present invention is as shown in FIG. A single cell is shown in FIG.

  The membrane electrode assembly MEA that is the center of the power generation reaction includes a fuel electrode 102 and an air electrode 103 formed on both sides of the electrolyte membrane 101. In general, the fuel electrode 102 includes a fuel electrode catalyst layer and a fuel electrode gas diffusion layer, and the air electrode 103 includes an air electrode catalyst layer and an air diffusion layer. In FIG. 1, the structure of a single cell is shown, but the number of cells included in the battery is not particularly limited, and it is sufficient that there is at least one cell. However, in general, a plurality of cells are stacked from the viewpoint of required electromotive force and power generation stability.

  The cell used in one embodiment of the present invention may be of any generally known structure. Further, the material used is not particularly limited.

  Fuel, for example, a mixed solution of methanol and water, is supplied to the fuel electrode 102 from the fuel electrode channel 104 in contact therewith. In FIG. 1, the fuel electrode channel 104 is covered with a housing 104A. When cells are stacked, the fuel electrode channel 104 and the fuel electrode 102 are separated from the air electrode channel 110, which will be described later, by the housing 104A. Isolated. In the embodiment shown in FIG. 1, fuel flows in the fuel electrode channel 104 in a direction perpendicular to the cross section.

  On the other hand, air (oxygen) is supplied to the air electrode 103 from the air electrode channel 110 in contact therewith. The air electrode channel 110 is a path from the first air inlet 106 to the gas outlet 108. In the embodiment shown in FIG. 1, the air introduced from the first air inlet 106 to the air electrode channel 110 is subjected to the above-described reaction to generate power. Water generated by reaction or the like is discharged from the air electrode together with unreacted air, and is discharged from the gas outlet 108 to the outside of the cell. Here, the flow of air is controlled by a fan or a pump (not shown) installed upstream of the first air inlet or downstream of the gas outlet. The flow of air and exhaust gas is as shown by solid arrows in FIG.

  Here, the fuel cell according to an embodiment of the present invention further includes a second air inlet 107. The second air inlet 107 communicates with the gas outlet 108. That is, the air supplied from the air inlet 107 to the fuel cell does not supply air that contributes to the power generation reaction itself. The air introduced from the second air inlet 107 merges with the exhaust gas containing water after the power generation reaction exhausted from the air electrode passage 110, and as indicated by the broken line arrow in FIG. The flow is merged with the exhaust gas after the reaction, which is indicated by a solid line in the middle, and discharged outside the battery.

  In the present invention, the amount of air introduced from the first air inlet can be reduced by introducing air from the second air inlet. And by reducing the amount of air introduced from the first air inlet, the relative humidity of the air introduced from the first air inlet is increased, and the amount of water that permeates the membrane is reduced. Thus, it is possible to reduce the amount of water entrained in the air introduced from the first air introduction port, and to suppress dew condensation on the air electrode channel and downstream of the air electrode channel. This is thought to be due to the following reasons.

  FIG. 2 shows the flow of air in the region formed by the air electrode 103, the air electrode channel 110, and the wall surface 201 of the air electrode channel 110 opposite to the air electrode 103, and water vapor or water generated by the power generation reaction. It is a schematic diagram which shows the relationship.

First, the air supply amount f ₁ from the first air introduction port is all water generated by power generation, water generated by crossover and oxidation of methanol, and water by permeation, that is, water generated at the air electrode during power generation. Even when all of the above evaporate, it is considered that it is excessive so as not to exceed the saturated water vapor pressure (FIG. 2A). In this case, since the supply amount of air is abundant, the water generated at the air electrode 103 becomes water vapor and is discharged from the region together with the air. However, since the supply amount of air is abundant at this time, the water vapor pressure in that region decreases, and the generated water evaporates more than necessary, so that the amount of water flowing out accompanying the air increases.

On the other hand, if the water supply amount f ₁ from the first air introduction port evaporates all the water generated by power generation, the water generated by crossover and oxidation of methanol, and the water by permeation, the saturated water vapor pressure is exceeded. When the amount is small, the vapor pressure in this region increases, so the amount of water evaporated from the air electrode decreases, and the amount of water accompanying the air in the air electrode channel decreases. However, when the water vapor pressure is equal to or higher than the saturated water vapor pressure, condensation occurs in this region (FIG. 2B). If dew condensation occurs in the air electrode channel, the supply of air is hindered. And, as will be described later, when the cells are stacked and have a stack structure having a parallel flow path configuration, the pressure loss of the flow path where condensation occurs increases, and it becomes difficult for air to flow through the flow path. Air flows only through the flow path. When the air flow rate is lowered, condensation is more likely to occur and the flow path is blocked. As a result, the power generation characteristics deteriorate because there are cells that do not operate effectively.

On the other hand, in the embodiment of the present invention, the air flow introduced from the second air inlet joins the air flow exiting from the air electrode channel 110 (FIG. 2 (c)). At this time, even if the air supply amount f ₁ from the first air introduction port is small enough that the water vapor pressure exceeds the saturated water vapor pressure in the air electrode channel 110, the air supply amount f ₁ is supplied from the second air introduction port. The air supply amount f ₂ is set so that the sum of f ₁ and f ₂ is equal to or less than saturated water vapor with respect to the amount of water generated at the time of power generation at the air electrode, thereby preventing condensation in this region. It can be discharged out of the battery.
At this time, the air supply amount f ₂ supplied from the second air introduction port, decreases the water vapor concentration in the gas outlet 108. As a result, dew condensation occurs in the vicinity of the gas exhaust port 108 only with the air supply amount f _1, but the direction of the water vapor gas exhaust port 108 in the air electrode channel 110 is caused by the air supplied from the second air introduction port. The diffusion to the fuel cell is promoted, the saturation vapor pressure is avoided, and the stacked fuel cells can be stably generated without causing condensation in the air supply path.

Here, an air supply amount introduced from the first air introduction port is f ₁ , and an air supply amount introduced from the second air introduction port is f ₂ . Further, the flow rate of oxygen consumed by the cathode f _O2, the flow rate of the water vapor generating the air electrode and f _{H2 O.} The flow rate of oxygen consumed at the air electrode is a flow rate determined by the amount of oxygen consumed by power generation and the amount of oxygen used for oxidation of the crossover fuel. The flow rate of water vapor generated at the air electrode is determined by the amount of water generated by power generation, the amount of water generated when the crossed fuel is oxidized, and the amount of water moving through the membrane. . The pressure in the air electrode channel is P, and the saturated water vapor pressure in the air electrode channel is P _H2O . If the water vapor partial pressure Ps does not exceed the saturated water vapor pressure at the air electrode outlet, condensation does not occur in the air electrode channel. Further, even when the air supply amount f ₁ introduced from the first air introduction port is small and condensation occurs in the air electrode passage, condensation is caused by the air introduced from the second air introduction port downstream of the air electrode. The vaporized water is vaporized again, and the air electrode channel is less likely to be blocked by droplets. Further, dew condensation is less likely to occur between the second air inlet and the gas outlet 108, and air can be circulated smoothly.

となる。また、空気極流路において結露を生じさせない第二の空気導入口からの空気供給量ｆ_２は、

である。 The air supply amount f ₁ from the first air inlet where condensation occurs in the air electrode channel is:

It becomes. In addition, the air supply amount f ₂ from the second air inlet that does not cause dew condensation in the air electrode channel is:

It is.

In the present invention, the air supply amounts f ₁ and f ₂ from the first and second air inlets are not particularly limited because they are appropriately adjusted depending on the size of the battery, the members used, and the like. However, it is preferable that the ratio of f ₁ and f ₂ is 4: 1 to 1: 3 because the effect of the present invention is remarkably exhibited. Such adjustment of the ratio of the air supply amount from the first and second air inlets is controlled by a fan or a pump that introduces air into the respective inlets, or the first and second air inlets are adjusted. This can be done by adjusting the opening area ratio.

  One embodiment according to the present invention including such a control device is shown in FIG. In the example shown in this figure, a fan 302 for adjusting the amount of air introduced from the first air inlet 106 and a fan 303 for adjusting the amount of air introduced from the second air inlet are provided. The control device 301 is connected to the fans 302 and 303 via the circuits 304 and 305 and at the same time is connected to the cells via the circuit 306. Then, the control device 301 can control the amount of air introduced by the fans 302 and 303 in accordance with the power generation amount of the cell, and can control so that water condensation does not occur in the air electrode channel.

  A conceptual diagram of the control device is as shown in FIG. The control device receives the power generation amount of the cell by the signal input unit 402, and according to this, based on the information recorded in the database unit 403 and the data storage unit 405 that store past operation data and the like, arithmetic processing Unit 404 calculates the operating conditions of fans 302 and 303, and transmits the conditions to each fan from signal output unit 401. Here, the signal input unit 402 can receive the environmental temperature, humidity, fuel cell temperature, and the like, and the arithmetic processing unit can calculate the operating condition of the fan reflecting the same. In such a case, a temperature sensor, a humidity sensor, or the like may be provided.

  In addition, although the example which installs a fan in the 1st air introduction port and the 2nd air introduction port was shown here, an exhaust fan is provided in the downstream of a gas exhaust port, and it can also control it with a control apparatus. it can. Also, even if one of the exhaust fans and the fans provided at the two air inlets is excluded, the air flow rate can be controlled by the other two, so there are only two fans. Also good. Furthermore, in addition to a fan, another air amount control device such as a pump can be used.

  As described above, the fuel cell according to one embodiment of the present invention introduces air that does not directly contribute to the power generation reaction to the downstream side of the air electrode, and discharges it outside the fuel cell together with the gas discharged from the air electrode. This lowers the vapor pressure in the air electrode channel to prevent condensation. Therefore, the gas introduced from the second air inlet does not have to be the same as the air introduced from the first air inlet. That is, it is not necessary to contain oxygen, and may be nitrogen, for example. Furthermore, in order to lower the vapor pressure at the air electrode more effectively and increase the effect of preventing condensation, it is preferable to use a dry gas.

  The fuel cell according to the embodiment of the present invention is characterized by having the above-described structure, but can be combined with various generally well-known structures or members.

For example, the fuel cell according to the present invention may have a stack structure in which the power generation unit of the fuel cell is stacked with a plurality of cells. A conceptual diagram of such a fuel cell according to the present invention is as shown in FIG. When the fuel cell has such a structure, the air electrode channel is a plurality of channels that supply air to the air electrode, so-called parallel channels. Thus, when there are a plurality of air electrode channels, there are a plurality of first air inlets accordingly. Here, when supplying air to the plurality of air electrode channels, a first manifold 501 is generally provided. That is, the air introduced from the first manifold inlet 502 is distributed by the manifold 501 to the air electrode channels. At this time, it is cumbersome to control the amount of air introduced for each air electrode channel, and it is difficult to reduce the size of the fuel cell as a whole. Therefore, the total amount of air introduced into each air electrode channel f ₁ ^total That is, it is preferable to control the amount of air introduced from the inlet 502 of the manifold.

On the other hand, when there are a plurality of air electrode channels, there are a plurality of gas discharge ports and a plurality of second air introduction ports accordingly. Also at this time, the second manifold 503 can be provided on the gas outlet side. The second manifold 503 takes in air from the inlet 504 of the second manifold, merges it with a gas containing a reaction product such as water, which is discharged from a plurality of air electrode channels, and The battery is discharged from the discharge port 505 to the outside of the battery. Again, controlling the amount of air introduced for each air electrode channel is cumbersome and it is difficult to reduce the size of the entire fuel cell, so the total amount of air introduced into each air electrode channel f ₂ ^total That is, it is preferable to control the amount of air introduced from the manifold inlet 504.
When there is a first manifold for supplying air to the parallel flow path as described above, it is preferable that the flow path cross-sectional area of the manifold 501 becomes smaller toward the downstream side as shown in FIG. By adopting such a structure, air can be uniformly supplied to the parallel flow path, and the power generation characteristics of the fuel cell are also stabilized.

  Alternatively, a fluid resistance 701 may be provided in the parallel flow path so that air can be uniformly supplied to the parallel flow path (FIG. 7). In the example shown in FIG. 7, the amount of air introduced into each air electrode channel is made uniform by changing the size of the fluid resistance 701 according to the distance from the inlet 502 of the first manifold. It is what. A diaphragm, a porous body, etc. can be used as fluid resistance. The purpose of the present invention is to prevent condensation in the parallel flow path. However, if condensation occurs, the fluid resistance portion may be blocked. For this reason, by providing fluid resistance upstream of the parallel flow path or upstream of the portion where the parallel flow path becomes saturated steam, condensation is unlikely to occur in the fluid resistance section, and air is uniformly supplied to the parallel flow path. can do.

  FIG. 8 is a perspective view of a fuel cell according to another embodiment of the present invention. In this example, the orientation of the cells in the cell stack is different from that shown in FIG. FIG. 8A shows a stack of cells. Only one cell is shown in the figure, and the other cells are omitted. The fuel electrode channel 104 penetrates the cell stack in the horizontal direction. For example, fuel is introduced from the right side of the drawing, and carbon dioxide gas generated by reaction with the remaining fuel is discharged from the left side.

  On the other hand, the air electrode channel 105 is formed by a housing 105A stacked on the air electrode 103, and penetrates in the direction perpendicular to the cell stack plane. Housings 801 and 802 are further laminated on the upper and lower surfaces of the cell stack, and a groove provided in the housing constitutes a manifold that connects a plurality of air electrode channels (FIG. 8B). Here, FIG. 8C shows only the route through which air flows. The vertical flow paths in FIG. 8C are the air electrode flow paths, and the upper and lower horizontal flow paths are the first and second manifolds.

  In addition, various improvements can be combined to prevent damage to the air supply due to condensation. For example, at least a part of the air supply channel, particularly the surface of the surface of the air electrode channel facing the air electrode can be hydrophilized. By treating in this way, even if the vapor pressure of the air electrode channel becomes equal to or higher than the saturated vapor pressure and condensation occurs, water spreads on the surface of the air electrode channel and liquid water reaches the gas discharge port. Can be prevented from moving and vaporizing, and the air electrode channel can be prevented from being blocked by droplets.

  Conversely, at least a part of the air electrode channel can be water repellent. Such a process is effective when the width of the air electrode channel is wide enough to allow water droplets generated by condensation on the wall surface of the air electrode channel to fall. When the vapor pressure in the air electrode channel exceeds the saturated vapor pressure and condensation occurs, the droplets adhere to the wall surface of the air electrode channel, but when it reaches a certain size, it tends to drop due to its own weight, or It becomes easy to move by the air flow. Then, when the droplet moves to the gas discharge port by dropping or moving, the droplet is vaporized again because the vapor pressure is lowered by the second air supply in that portion. This can prevent the air electrode channel from being blocked by liquid droplets.

  In addition, a wick can be formed on at least a part of the surface of the air electrode channel. This wick is a groove structure formed in a direction parallel to the gas flow direction in the air electrode channel. The wick is preferably formed as a groove structure that extends from the air electrode channel to the gas outlet. With this wick, the vapor pressure in the air electrode channel becomes equal to or higher than saturated vapor, and even if dew condensation occurs, the liquid adhering to the wall moves to the gas discharge port with a low vapor pressure and is vaporized there. Therefore, this air wick prevents the air electrode channel from being blocked by droplets. In such a case, the wick is preferably hydrophilic.

These structures, or other structures known in the field of fuel cells, can be used in any combination as long as the objects do not conflict.
The present invention will be described below with reference to examples.

  A perspective sectional view of a fuel cell according to an embodiment of the present invention is as shown in FIG.

In the example shown in the figure, cells 901 are stacked to form a stack, and an air electrode channel is formed between single cells. Air is sucked by the fan 303, and the flow rates of f ₁ and f ₂ are adjusted by the fluid resistance 701. The stack temperature is generally controlled at 60-65 ° C. and the current density can be operated at 150-200 mA / cm ² . The flow rates of f ₁ and f ₂ are generally maintained at about 1.5 to 2 stoichio (ratio to the supply amount necessary for power generation reaction). In the example of FIG. 9, the manifold at the top of the cell has an inlet portion with a height of 3 mm and an end portion with a height of 1 mm, so that air is uniformly supplied to each air electrode channel.

When the stack temperature is 60 ° C. and the air flow rate is stoichio 2, an amount of water that reaches the saturated vapor pressure is generated in the air electrode in the air electrode channel. In Stoichio 2.5, the inside of the air electrode channel is below saturated water vapor. Therefore, by flowing air under the conditions of stoichio 2 as f ₁ and stoichio 2 as f ₂ , dew condensation does not occur at the lower manifold outlet. From stoichiometric 0.5 no condensation as f _2, reduces further the concentration of water vapor in the lower manifold, it is possible to set the flow rate in a range of stoichiometric about 3 that does not significantly increase the pressure loss.

If f ₂ is zero, condensation part of the air electrode channel is observed, the output of the fuel cell is lowered. The height of the manifold at the bottom of the cell was 3 mm, and power could be stably generated by flowing air so that f ₂ was about stoichiometric 2.

The air flow distributed from the first manifold to each air electrode channel may be unbalanced, and even if air is supplied from the second air inlet, the air flow from the first manifold is reduced. Condensation may occur in the air electrode channel. Even in such a case, the surface of the air electrode flow path plate is less likely to cause dew condensation by applying a SiO ₂ hydrophilic agent. In addition, when a Teflon (registered trademark) water-repellent material is applied to the surface of the air electrode channel, if the air electrode channel width is narrow, the droplet moves even if a spherical droplet is generated. However, when the channel width was increased to 1 mm or more, the droplets generated by condensation dropped and good power generation characteristics were obtained. In addition, by forming a wick with a width of 0.2 mm and a depth of 0.2 mm in the same direction as the air flow direction on the surface of the air electrode channel, liquid water in the case of condensation moves to the downstream of the air electrode channel As a result, good power generation performance was obtained.

When the stack temperature is about 60 to 65 ° C., even if the relative humidity at room temperature of the introduced air is 100%, the relative humidity is heated when heated to 60 to 65 ° C. which is the stack temperature in the fuel cell. Becomes lower than saturated water vapor. Therefore, even when the ambient temperature of the fuel cell is 35 ° C. and the relative humidity is 100%, if f ₁ is stoichio 2 and f ₂ is stoichio 1, condensation in the air electrode channel can be prevented.

DESCRIPTION OF SYMBOLS 101 Electrolyte membrane 102 Fuel electrode 103 Air electrode 104 Fuel supply path 106 1st air introduction port 107 2nd air introduction port 108 Gas exhaust port 110 Air electrode flow path 301 Control apparatus 501 1st manifold 503 2nd manifold 701 Fluid resistance 901 cell

Claims (9)

A membrane electrode assembly comprising an electrolyte membrane, and a fuel electrode and an air electrode that sandwich the electrolyte membrane;
A fuel electrode flow path for supplying fuel to the fuel electrode;
An air electrode passage for supplying air to the air electrode;
A first air inlet for introducing air from the outside into the air electrode channel;
A gas discharge port for discharging exhaust gas after power generation reaction at the air electrode from the air electrode channel;
A second air introduction port that communicates with the gas discharge port, joins the exhaust gas without passing through the air electrode, and introduces air discharged outside the fuel cell;
When all the water generated at the air electrode during the power generation at the air electrode is water vapor, the vapor pressure of the water vapor with respect to the first air supply amount introduced from the first air inlet exceeds the saturated vapor pressure. And the vapor pressure of the water vapor is controlled to be equal to or lower than the saturated vapor pressure with respect to the sum of the first air supply amount and the second air supply amount supplied from the second air introduction port. A fuel cell.   The fuel cell has a stack structure in which a plurality of the fuel cells are stacked, and the air electrode flow path supplies air to the plurality of air electrodes, and the air introduced from the first air introduction port is the parallel flow. The fuel cell according to claim 1, further comprising a first manifold that supplies the flow path.   The fuel cell according to claim 2, wherein a flow path cross-sectional area of the first manifold is smaller toward a downstream side of the manifold.   The fluid resistance is provided in any one of Claims 1-3 provided in the upstream of the said parallel flow path, or the upstream from the part which the water produced | generated by an electric power generation reaction saturates as water vapor | steam in the middle of a parallel flow path. Fuel cell.   The fuel cell according to any one of claims 1 to 4, wherein at least a part of a surface of the air supply path is hydrophilized.   The fuel cell according to any one of claims 1 to 4, wherein at least a part of a surface of the air electrode channel is water repellent.   The fuel according to any one of claims 1 to 6, wherein a groove formed in a direction parallel to a gas flow direction in the air electrode channel is formed on at least a part of a surface of the air electrode channel. battery.   The fuel cell according to any one of claims 1 to 7, wherein a ratio between the first air supply amount and the second air supply amount is 4: 1 to 1: 3. A membrane electrode assembly comprising an electrolyte membrane, and a fuel electrode and an air electrode that sandwich the electrolyte membrane;
A fuel electrode flow path for supplying fuel to the fuel electrode;
An air electrode flow path for supplying first air to the air electrode;
A first manifold in communication with the air electrode channel via a first air inlet at one end of the air electrode channel;
A second manifold communicating with the air electrode channel through a gas outlet at the other end of the air electrode channel;
An air inlet of a second manifold for supplying the second manifold with a second air different from the air supplied to the air electrode;
When the water generated at the air electrode during power generation is all steam, the supply amount of the first air introduced from the first air inlet is controlled so that the steam pressure of the steam exceeds the saturated steam pressure. And a control unit for controlling the supply amount of the second air so that the vapor pressure of the water vapor is equal to or lower than the saturated vapor pressure with respect to the sum of the supply amounts of the first air and the second air,
A fuel cell comprising:

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