JP4742513B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell that can effectively use surplus water in a cell.

A polymer electrolyte fuel cell (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell)”) can be operated in a low temperature region among various fuel cells, and has a high value of 50 to 60%. It shows energy conversion efficiency, has a short start-up time, and has a small and light system, and has attracted attention as an optimal power source for electric vehicles. This PEFC electrolyte uses a cation exchange resin membrane as a cation conductive membrane. This conductive film has a proton (hydrogen ion (H ⁺ )) exchange group in the molecule, and when it is saturated with water, it exhibits a specific resistance of 20 Ω · cm or less at room temperature. It functions as a functional electrolyte. And the saturation water content of this electrolyte membrane changes reversibly with temperature. That is, during operation of the PEFC, humidified water added in the form of water vapor in the fuel gas and oxidizing gas to prevent transpiration from the electrolyte membrane, and water generated by an electrochemical reaction on the cathode side By means of this, saturation is always maintained.

  However, if the water produced on the cathode side increases or the fuel gas and the oxidizing gas are consumed and the water vapor in the residual gas becomes supersaturated and the water condenses, the water supply becomes excessive. The membrane becomes soaked and enters a so-called “flooding” state. When this flooding state occurs, the gas contact area in the cell decreases, and further, the supply of oxygen gas to the cathode is hindered, and the generated voltage of PEFC decreases. Since this voltage drop leads to a decrease in the efficiency of PEFC, it is important to suppress the flooding phenomenon in order to maintain the high energy conversion efficiency of PEFC.

Several techniques have been proposed so far to suppress the flooding phenomenon and to increase the efficiency of PEFC. For example, in Patent Document 1, a separator partially including a porous portion is used, and by providing the porous portion below the gravity direction and in the vicinity of the outlet of the oxidizing gas flow path, moisture, oxygen, and A technique for uniformly supplying hydrogen to a reaction region of a fuel cell is disclosed.
JP 2003-109620 A

  However, according to the technique disclosed in Patent Document 1, moisture staying downward due to gravity is discharged out of the cell of the fuel cell before being added to the dry air side through the porous portion. There was a problem.

  Therefore, the present invention provides a fuel cell capable of effectively humidifying oxidizing gas with excess water in the cell and capable of suppressing flooding by improving drainage in the cell. This is the issue.

In order to solve the above problems, the present invention takes the following means. That is,
According to the first aspect of the present invention, a cell is configured by arranging a pair of separators on both sides of an MEA including an electrolyte, and a cathode and an anode arranged on both sides of the electrolyte, and arranged on the cathode side. and has a non-porous portion provided with a site other than the porous portion and said porous portion formed of a porous material to the separator, the porous part porous portion in the cathode surface opposed to the non-porous portion A first gas flow path communicating with the second gas flow path is provided in the porous portion on the other surface , and a downstream portion of the second gas flow path and an upstream portion of the first gas flow path communicate with each other. In the fuel cell, the moisture contained in the gas in the first gas passage that has passed through the porous portion is collected in the plane where the first gas passage is formed, and the collected moisture the supply to the porous portion, have a collecting means, in use of the fuel cell, the porous portion The gas passage A is disposed below the cell in the gravity direction, and the collecting means is provided in the first gas passage of the separator, and the gas passage A should flow upward from the porous portion in the gravity direction. The fuel cell is a gas flow path .
According to a second aspect of the present invention, in the fuel cell according to the first aspect , the first gas flow path further includes a gas flow path B that should flow from the upper side in the direction of gravity to the porous portion. To do.
According to a third aspect of the present invention, in the fuel cell according to the first or second aspect, the gas flow path A is provided with a flow rate lowering means for reducing the flow rate of the gas .
According to a fourth aspect of the present invention, in the fuel cell according to the third aspect , the flow velocity reducing means is a gas flow path A having a flow path wider than the flow path of the gas flow path B. .

According to the first aspect of the present invention, the moisture supplied to the porous portion humidifies the oxidizing gas in the second gas flow path through the porous portion, and the humidified oxidizing gas causes the first The oxidizing gas in one gas flow path can be humidified. Therefore, according to the present invention, it is possible to provide a fuel cell capable of effectively humidifying the oxidizing gas with the excess water in the cell. According to the first aspect of the present invention, moisture contained in the oxidizing gas in the first gas flow path that has passed through the porous portion is likely to accumulate in the porous portion located below the gravity direction due to gravity. . Therefore, it is possible to provide a fuel cell that can effectively humidify the oxidizing gas with excess water and that can suppress flooding by improving drainage in the cell.

According to the invention described in claim 2, the moisture generated by the electrochemical reaction in the cell is effectively applied to the porous portion disposed below the gravity direction by the gas flow and gravity in the gas flow path B. Therefore, it is possible to provide a fuel cell with further improved drainage in the cell .

According to the third aspect of the present invention, it is possible to reduce the amount of water taken out of the cell, so that it is possible to provide a fuel cell with improved utilization efficiency of excess water in the cell.

According to the invention described in claim 4, it is possible to provide a fuel cell having improved efficiency of use of water in the cell easily.

  The fuel cell of the present invention has a cell by arranging a pair of separators on both sides of an MEA including an electrolyte and a cathode and an anode arranged on both sides of the electrolyte, and is arranged on the cathode side. A porous portion formed of a porous material is provided in a part of the separator, the first gas flow path is provided on the surface of the porous portion facing the cathode, and the second gas flow path is provided on the other surface. The downstream part of the two gas flow paths communicates with the upstream part of the first gas flow path. In the present invention, moisture contained in the oxidizing gas is retained in the porous portion, and from the porous portion to the upstream portion of the first gas passage through the second gas passage to which the dried oxidizing gas is supplied. By moving the moisture, the oxidizing gas supplied to the first gas channel is humidified. With this configuration, the oxidizing gas of the fuel cell is described as a cell (hereinafter referred to as a “cell” including a portion where an electrochemical reaction occurs in the fuel cell, and the cell is defined as “cell”. In some cases, the fuel cell can be effectively humidified by the excess water in the cell and can improve drainage in the cell. .

FIG. 1 schematically shows a cross-sectional view of the fuel cell of the present invention. The fuel cell 100 of the present invention includes an MEA 5 including an electrolyte membrane 1, a cathode 2 and an anode 3 disposed on both sides of the membrane 1, and a pair of separators 10 and 20 disposed on both sides of the MEA 5. is doing. Part of the separator 10 disposed on the cathode 2 side is formed by the porous portion 30. A first gas flow path 15 is formed on the surface 11 of the separator 10 facing the cathode 2, and the second gas flow paths 16, 16 are formed on the surface 12 on the back side of the surface 11 in the porous portion 30. However, in portions other than the porous portion 30 (hereinafter referred to as “non-porous portion 31”), cooling water flow paths 17, 17, and 17 are formed. The downstream portions of the second gas passages 16 and 16 communicate with the upstream portion of the first gas passage 15. The first gas flow path 15 in the non-porous portion 31 is formed in a direction parallel to the gravity direction, while the flow path 15 in the porous portion 30 is a gas flow path that flows in the gravity direction, as will be described later. The flow of B is converted into the flow direction of the gas flow path A flowing in the antigravity direction.
In FIG. 1, the left-right direction of the paper surface is the normal direction of the MEA surface, and the direction from the top to the bottom of the paper surface is the direction of gravity.
When the fuel cell is used, the fuel cell 100 having such a configuration is arranged so that the porous portion 30 is below the direction of gravity, so that moisture contained in the oxidizing gas flowing in the first gas flow path 15 is reduced by gravity. It becomes easy to collect to the porous part 30 arrange | positioned below the direction. In the fuel cell 100, the moisture collected in the porous portion 30 moves to the second gas flow path 16, 16 formed on the surface 12 side, and the oxidizing gas flowing in the flow path 16, 16 The humidified oxidizing gas moves to the upstream portion of the flow path 15 so that the oxidizing gas in the flow path 15 can be humidified.

In FIG. 2, the front view which looked at the separator 10 in the fuel cell 100 of this invention from the surface 11 side is shown roughly. In FIG. 2, the direction perpendicular to the paper surface is the normal direction of the MEA surface, and the direction from the top to the bottom of the paper surface is the direction of gravity.
On the surface 11 of the separator 10, there are a gas flow path B that should flow from the upper side to the lower side in the gravity direction, and a gas flow path A that flows in the antigravity direction in the porous portion 30. A flow path 14 for converting to the flow direction and a flow path A for the gas that should flow from the lower side to the upper side in the direction of gravity are formed. The gas flow path B, the flow path 14, and the gas flow path A allow U A first gas channel 15 having a letter-shaped channel shape is formed. Here, the gas flowing through the first gas flow path 15 is introduced into the flow path 15 from the oxidizing gas flow path inlet 18, and after passing through the flow path B, the flow path 14, and the flow path A, the gas is oxidized gas. It is led out of the cell from the channel outlet 19. In addition, the arrow in the 1st gas flow path 15 in FIG. 2 represents the flow direction of the gas in the said flow path 15. FIG.
The fuel cell 100 of the present invention can effectively utilize the surplus water generated in the cell, as described later, by adopting the first gas flow path 15 in this form.

In order to facilitate the description of the first gas flow path 15 in the fuel cell of the present invention, a general flow path formed in a conventional fuel cell separator is schematically shown in FIG.
In a conventional fuel cell, a so-called serpentine type flow path shown in FIG. 3 is generally used. However, when a channel having a plurality of curved portions is formed in the separator as described above, a stagnation point of oxidizing gas occurs in the curved portion of the channel. For this reason, the water generated at the site in the reaction in the cell is difficult to be taken away by the oxidizing gas, and particularly when the oxidizing gas has a low flow rate, the drainage is reduced. For this reason, there is a problem that water pools 50, 50, 50, 50, 50 are generated in the curved portion, and the performance of the fuel cell is deteriorated.
In addition, in the conventional fuel cell, the surplus water generated in the cell cannot be effectively used for humidifying the oxidizing gas, and the humidifying device is used to oxidize the oxidizing gas in order to wet the electrolyte membrane in the cell. Needed to be humidified.

Therefore, in the fuel cell according to the present invention, as shown in FIG. With this configuration, it is possible to reduce the occurrence of the stagnation point. In the present invention, the portion where the curved portion is located is constituted by the porous portion 30. By setting it as this form, a water pool can be forcedly generated in the porous part 30 in which a stagnation point is located. Furthermore, in the present invention, by arranging the porous portion 30 below the gravitational direction, the directions of the flow paths A and B can be made parallel to the gravitational direction. Moisture contained in the gas can be easily collected in the porous portion 30, and the drainage in the flow channel 15 can be improved even when the gas in the flow channel 15 has a low flow rate.
If water is collected in the porous portion 30 in this way, excess water on the surface 11 side can be moved to the back side of the surface 11 via the porous portion 30. And since the 2nd gas flow path formed in the back side of the said surface 11 has communicated with the upstream part of the 1st gas flow path in the downstream part, the moisture moved to the 2nd gas flow path concerned The oxidizing gas in the flow path is humidified, and the humidified oxidizing gas humidifies the oxidizing gas supplied to the flow path 15 in the upstream portion of the first gas flow path 15. Therefore, by forming the first gas flow path 15 in the fuel cell of the present invention as shown in FIG. 2, it is possible to effectively utilize the excess water generated in the cell and humidify the oxidizing gas. Thus, the advantage that the humidifier required in the conventional fuel cell can be reduced in size or made unnecessary can be obtained.

In the fuel cell 100 of the present invention, the gas flow path A of the first gas flow path 15 is preferably provided with a gas flow rate lowering means. By providing such means, it becomes possible to suppress the oxidizing gas in the first gas flow path from taking away the excess water in the cell to the outside of the cell, so that the utilization efficiency of the excess water in the cell is improved. be able to. In the fuel cell 100 of the present invention, if the utilization efficiency of surplus water is improved, it becomes possible to humidify the oxidizing gas introduced into the first gas flow path more efficiently, and consequently the power generation efficiency of the fuel cell. It becomes possible to improve.
Furthermore, it is preferable to reduce the gas flow rate in the gas channel A by making the channel width of the gas channel A wider than the channel width of the gas channel B in the first gas channel 15. By configuring the fuel cell 100 of the present invention in such a form, it is possible to provide the gas flow rate lowering means by a simple method. In addition, although the flow path width of the said gas flow path A may be fixed to the specific flow path width, it is set as the gas flow path A provided with the flow path wall which can change a flow path width. More preferred. By adopting such a configuration for the gas flow path A, the flow path width of the flow path A can be appropriately changed according to the gas flow rate in the flow path A, and surplus water due to the oxidizing gas in the flow path A It is possible to humidify the oxidizing gas more effectively by suppressing the removal of the gas more effectively.

  In the fuel cell 100 of the present invention, the porous portion 30 provided in at least a part of the first gas channel 15 and the second gas channel 16 can pass water from the channel 15 to the channel 16. If so, the material is not particularly limited, but it is preferably a member that can move water to the flow channel 16 side earlier than the gas in the flow channel 15. For example, by using a porous member composed of pores having a pore diameter of about 1 μm to 2 μm as the member, a porous portion capable of moving water from the flow channel 15 to the flow channel 16 side by capillary action is used. Can do. With this configuration, when the pores of the porous portion 30 are blocked with water, it becomes difficult for the gas in the flow path 15 to move to the flow path 16 side, The porous member 30 can be moved to the flow path 16 side earlier than the gas.

It is a figure which shows the fuel cell of this invention roughly. It is a figure which shows roughly the separator in the fuel cell of this invention. It is a figure which shows schematically the separator in the conventional fuel cell.

Explanation of symbols

1 Electrolyte membrane 2 Cathode 3 Anode 5 MEA
DESCRIPTION OF SYMBOLS 10, 20 Separator 11 The surface facing a cathode 12 The back surface of the surface facing a cathode 15 1st gas flow path 16 2nd gas flow path 30 Porous part 100 Cell (fuel cell)

Claims (4)

A cell is configured by arranging a pair of separators on both sides of an MEA including an electrolyte, and a cathode and an anode arranged on both sides of the electrolyte,
Nonporous portion and a provided surface porous portion is the cathode and the counter, which is a portion between the cathode-side porous portion formed of a porous material to the separator is disposed in addition to the porous portion Provided with a first gas flow path communicating with the porous portion and the non-porous portion, and provided with a second gas flow path in the porous portion on the other surface,
A fuel cell in which a downstream portion of the second gas flow channel and an upstream portion of the first gas flow channel communicate with each other;
Moisture contained in the gas in the first gas flow path that has passed through the porous portion is collected in the plane where the first gas flow path is formed, and the collected water is supplied to the porous portion, it has a collecting means,
When the fuel cell is used, the porous portion is disposed below the cell in the gravitational direction,
The collecting means is a gas flow path A provided in the first gas flow path of the separator;
The fuel cell according to claim 1, wherein the gas channel A is a gas channel that should flow upward from the porous portion in the direction of gravity . 2. The fuel cell according to claim 1, wherein the first gas flow path further includes a gas flow path B that should flow from above in the direction of gravity to the porous portion . Wherein the gas flow path A, is characterized in that is provided with the flow velocity reducing means for reducing the flow rate of the gas, the fuel cell according to claim 1 or 2. 4. The fuel cell according to claim 3 , wherein the flow velocity lowering means is the gas flow path A having a flow path wider than the flow path of the gas flow path B. 5 .

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