JP5694093B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to an internal structure of a fuel cell.

  A fuel cell has a structure in which an electrolyte membrane is sandwiched between both electrodes of a cathode and an anode. A cathode gas (oxidizing gas) containing oxygen such as air is in contact with the cathode while an anode gas containing hydrogen ( When the fuel gas is in contact with the anode, an electrochemical reaction occurs between the electrodes, and as a result, a voltage is generated between the electrodes.

  Various structures of such fuel cells have been proposed. For example, Patent Document 1 discloses a serpentine type anode gas channel and cathode gas formed so that the gas flow directions are opposite to each other. A fuel cell having a flow path is described. This fuel cell is provided with a drainage channel in the middle of the gas flow path to prevent cathode flooding, and in order to prevent drying near the cathode gas inlet, The width on the downstream side of the width is narrowed, and the gas flow rate is increased toward the downstream side.

JP 2002-198069 A

  By the way, in a fuel cell, in general, an anode inlet (a portion where the anode gas flows in) is disposed on the cathode outlet (portion where the cathode gas flows out) side, and a cathode is disposed on the anode outlet (a portion where anode gas flows out) side. By placing the inlet (portion into which the cathode gas flows) and transporting water generated on the cathode side from the cathode outlet (anode inlet) to the anode outlet (cathode inlet), the electrolyte membrane is in a wet state, that is, in a fuel cell. A method of maintaining the water balance is widely adopted, and the same applies to the fuel cell described in Patent Document 1.

  However, in the conventional fuel cell described in Patent Document 1, the serpentine channel is defined by a rib-shaped partition wall, and adjacent gas channels sandwiching the partition wall are configured in opposite directions. Therefore, the gas flow may cause a path cut (short circuit) between the adjacent gas flow paths. In particular, when a path cut occurs in the anode gas flow, it becomes difficult to sufficiently transport moisture near the cathode outlet (anode inlet) to the anode outlet (cathode inlet).

  Also, since the gas flow rate is relatively slow on the inlet side and relatively fast on the outlet side, the amount of water vapor in the anode gas tends to reach saturation near the anode inlet, and it becomes difficult to remove moisture at the cathode outlet by the anode gas. There is also a risk of inducing cathode flooding. Furthermore, since the gas flow rate is relatively slow on the inlet side, it is assumed that the anode gas that has received moisture dries before reaching the downstream of the flow path, and sufficient moisture cannot be supplied near the anode outlet (cathode inlet). Can be done. These concerns may be particularly noticeable during high temperature operation such as high temperature non-humidification operation.

  Therefore, the present invention has been made in view of such circumstances, the moisture generated on the cathode outlet side can be efficiently transported and supplied to the cathode inlet side through the anode gas flow path and circulated. Accordingly, an object of the present invention is to provide a fuel cell that can maintain a wet state of an electrolyte membrane well and suppress a decrease in output even during high-temperature operation.

  In order to solve the above problems, a fuel cell according to the present invention comprises a membrane electrode assembly in which a cathode and an anode are disposed on both surfaces of an electrolyte membrane, and a separator provided opposite to the membrane electrode assembly, A cathode gas channel and an anode gas channel configured so as to be substantially orthogonal, the anode inlet is disposed in the vicinity of the cathode outlet, and the anode outlet is disposed in the vicinity of the cathode inlet; The anode gas flow path is defined so as to roll in a U shape (U-turn) by a rib, and the pressure loss on the outer peripheral side (outer side) of the U-shaped flow path is the same on the inner peripheral side (inner side). It is comprised so that it may become smaller than the pressure loss of.

  In the fuel cell according to the present invention configured as described above, the cathode gas channel and the anode gas channel are provided so as to be orthogonal or substantially orthogonal to each other. Since the U-shaped flow path is defined, the outer peripheral side portion of the U-shaped flow path is the cathode outlet end side (most downstream) that is most easily flooded and the cathode inlet end side (most upstream) that is most dry. It extends so as to go through a site that faces each other. The anode inlet and the anode outlet are arranged in the vicinity of the cathode outlet and in the vicinity of the cathode inlet, respectively, and most of the anode gas flowing through the anode gas channel flows through the outer peripheral side of the U-shaped channel with a relatively small pressure loss. As a result, more water can be taken away from the cathode outlet side by the anode gas, and much water thus taken can be supplied to the cathode inlet side.

  In addition, most of the anode gas flowing in the anode gas flow path in this way flows through the outer peripheral side of the U-shaped flow path having a relatively small pressure loss, which is a concern in the conventional fuel cell (Patent Document 1). The path cut of the anode gas can be suppressed.

  Further, in the anode gas flow path, by providing a partition like a rib that separates the outer peripheral side and the inner peripheral side of the U-shaped flow path, the pressure loss difference between the outer peripheral side and the inner peripheral side is further increased. And anode gas flowing on the outer peripheral side can be effectively prevented from diffusing to the inner peripheral side. As a result, the above-described path cut of the anode gas can be further prevented.

  From the above, according to the fuel cell of the present invention, the water generated on the cathode outlet side can be efficiently transported and supplied to the cathode inlet side via the anode gas flow path and circulated (counter flow). As a result, not only during normal operation but also during high temperature operation, the wet state of the electrolyte membrane can be maintained much better than in the past, effectively reducing output degradation. It becomes.

1 is an exploded perspective view schematically showing a part of the configuration of a preferred embodiment of a fuel cell according to the present invention. FIG. 2 is a plan view schematically showing a configuration of an anode separator of the fuel cell stack shown in FIG. 1. It is a top view which shows typically the structure of the anode separator which has a single flow path as an anode gas flow path.

  Hereinafter, embodiments of the present invention will be described in detail. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. Furthermore, the following embodiment is an illustration for explaining the present invention, and is not intended to limit the present invention only to the embodiment. Furthermore, the present invention can be variously modified without departing from the gist thereof.

  FIG. 1 is an exploded perspective view schematically showing a part of the configuration of a preferred embodiment of a fuel cell according to the present invention. The fuel cell stack 1 (fuel cell) is a polymer electrolyte fuel cell (PEMFC) provided with a solid electrolyte membrane, and is mainly mounted on a fuel cell vehicle or the like. The fuel cell stack 1 has a stack structure in which a plurality of unit cells are stacked (only one unit is shown in the figure). The unit cell is an MEA 30 (membrane electrode assembly) in which an anode and a cathode are disposed between a cathode separator 10 made of a conductive metal material such as stainless steel and titanium and an anode separator 20 with an electrolyte membrane interposed therebetween. : Membrane Electrode Assembly). Further, gas diffusion layers 40 and 40 are integrally provided by a seal gasket (not shown) or the like so as to face both surfaces of the MEA 30 and the cathode separator 10 and the anode separator 20.

  On the other hand, a plurality of cathode inlets 11 are formed along the long side of the lower end portion of the cathode separator 10 in the figure, and a plurality of the cathode inlets 10 are formed along the long side of the upper end portion of the cathode separator 10. A plurality of cathode outlets 12 are drilled at positions facing the cathode inlets 11. Thereby, between the cathode separator 10 and the gas diffusion layer 40, the cathode gas flows substantially linearly from the cathode inlet 11 toward the cathode outlet 12 (see the arrow Yc in the drawing), and the cathode gas flow path 13 is defined. Is done. The cathode gas flow channel 13 is a porous material flow channel, and the pressure loss of the cathode gas flowing therethrough can be averaged and maintained substantially constant.

  On the other hand, an anode inlet 21 is drilled in the upper stage of the left end of the anode separator 20 in the figure, and an anode outlet 22 is drilled in the lower stage of the left end of the anode separator 20. Further, the rib 25 extends linearly along the long side of the anode separator 20 and starting from the vicinity of the portion between the anode inlet 21 and the anode outlet 22. Thus, between the anode separator 20 and the gas diffusion layer 40, the anode gas circulates in a U-shape (U-turn) from the anode inlet 21 toward the anode outlet 22 (see arrows Ya1 and Ya2 in the drawing). ) Anode gas passages 23 and 24 are defined.

  Thus, the anode gas flow paths 23 and 24 are U-shaped flow paths, both of which are porous flow paths, and are anode gas flow paths as outer peripheral (outer) flow paths of the U-shaped flow paths. 23 is made smaller than the pressure loss of the anode gas flow path 24 as the inner peripheral side (inner side) flow path. Specifically, for example, the porosity of the portion corresponding to the anode gas flow path 23 in the anode separator 20 is configured to be larger than the porosity of the portion corresponding to the anode gas flow path 24 in the anode separator 20. Yes. As a result, the flow rate of the anode gas (see the arrow Ya1 in the figure) flowing through the anode gas flow path 23 is faster than the flow rate of the anode gas (see the arrow Ya2 in the figure) flowing through the anode gas flow path 24, and the anode gas flow path 23 The flow rate of the anode gas flowing through the anode gas flow passage is larger than the flow rate of the anode gas flowing through the anode gas flow path 24.

  According to the fuel cell stack 1 configured as described above, the cathode gas passage 13 and the anode gas passages 23 and 24 are provided so as to be orthogonal or substantially orthogonal to each other, and the anode inlet 21 and the anode outlet 22 are provided. Are arranged in the vicinity of the cathode outlet 12 and in the vicinity of the cathode inlet 11, respectively. Therefore, as the anode gas in a dry state near the anode inlet 21 (one end of the upper stage of the anode gas flow path 23) flows through the anode gas flow paths 23 and 24, the moisture of the cathode gas is deprived via the MEA 30; The humidity is substantially saturated before reaching the other upper end (the tip side of the rib 25) of the anode gas flow paths 23, 24 in the figure. The anode gas having become high humidity in this way supplies moisture to the cathode gas via the MEA 30 in the lower stage of the anode gas passages 23 and 24.

  And since the anode gas flow paths 23 and 24 roll in the U shape and the U-shaped flow path is defined, the anode gas flow path 23 which is the outer peripheral side part of the U-shaped flow path is the most. It extends so as to pass through portions facing the cathode exit 12 end side (the most downstream side of the cathode channel 13) that is easily flooded and the cathode inlet 11 end side (the most upstream side of the cathode channel 13) that is most dry. .

  Therefore, more water can be taken away from the cathode outlet 12 side by the anode gas, and more water can be efficiently supplied to the cathode inlet 11 side, so that flooding caused by variation in humidity distribution is caused. And excessive drying can be effectively prevented. In other words, water (reaction product water) generated on the cathode outlet 12 side can be efficiently transported and supplied to the cathode inlet 11 side via the anode gas flow paths 23 and 24 and circulated (counter flow). As a result, not only during normal operation but also during high-temperature operation, the wet state of the electrolyte membrane can be maintained much better than in the past, and the output reduction of the fuel cell stack 1 can be effectively suppressed. It becomes possible to do.

  Furthermore, since most of the anode gas flowing through the anode gas passages 23 and 24 circulates in the anode gas passage 23 having a relatively small pressure loss, the path cut of the anode gas may be a concern in the conventional fuel cell. As a result, the counter flow effect described above can be further promoted.

  Here, FIGS. 2 and 3 are plan views schematically showing the configuration of the anode separator 20 of the fuel cell stack 1 and the anode separator 200 having a single flow path as the anode gas flow path, respectively. The anode separator 200 includes an anode inlet 221, an anode outlet 222, and a rib 225 provided in the same manner as the anode inlet 21, the anode outlet 22, and the rib 25 of the anode separator 20. Unlike the anode separator 20, the anode separator 200 includes an anode gas flow path 226 as a porous body flow path in which the pressure loss of the anode gas is averaged as a whole.

The porosity of the portion corresponding to the anode gas flow path 23 of the anode separator 20 thus configured is 83%, the porosity of the portion corresponding to the anode gas flow path 24 of the anode separator 20 is 78%, and The pressure loss at the time of 3 A / cm ² power generation was evaluated by setting the porosity of the portion corresponding to the anode gas flow path 226 of the anode separator 200 to 78%. As a result, the pressure loss in the anode gas channel 23 was 30 kPa, and the pressure loss in the anode gas channels 24 and 226 was 44 kPa.

  When the fuel cell stack including the anode separators 20 and 200 was operated, the flow rate of the anode gas flowing through the anode gas flow path 23 (outer flow path) of the anode separator 20 was improved by 10%. When the overall average hydrogen stoichiometry is 1.25, anode gas equivalent to hydrogen stoichiometry 1.5 flows in the anode gas flow path 23, and the amount of moisture supplied to the vicinity of the cathode inlet 11 is sufficiently increased to cause drying. It was confirmed that it was suppressed. Further, when the hydrogen stoichiometry increases from 1.25 to 1.5 in this way, the humidity near the anode outlet 22 (cathode inlet 11) increases by 1.8 to 4.1%, and thereby the voltage of the unit cell. It was estimated that (cell voltage) would increase by 40 mV.

  In addition, as above-mentioned, this invention is not limited to the said embodiment, A various deformation | transformation is possible in the limit which does not change the summary. For example, the anode separator 20 of the fuel cell stack 1 may be additionally provided with a partition such as a rib that separates the anode gas flow paths 23 and 24 that are U-shaped flow paths. By doing so, the pressure loss difference between the anode gas passages 23 and 24 can be further increased, and the anode gas flowing through the anode gas passage 23 is effectively prevented from diffusing into the anode gas passage 24. can do. Thereby, the path cut of the anode gas from the anode gas channel 23 to the anode gas channel 24 can be further prevented.

  As described above, the present invention can effectively maintain the wet state of the electrolyte membrane in the fuel cell and effectively prevent a decrease in the output of the fuel cell. Therefore, the fuel cell in general, devices and systems equipped with the fuel cell, It can be used widely and effectively for facilities and the production thereof.

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack (fuel cell), 10 ... Cathode separator, 11 ... Cathode inlet, 12 ... Cathode outlet, 13 ... Cathode gas flow path, 20 ... Anode separator, 21 ... Anode inlet, 22 ... Anode outlet, 23, 24 Anode gas flow path, 25 ... rib, 30 ... MEA, 40 ... gas diffusion layer, 200 ... anode separator, 221 ... anode inlet, 222 ... anode outlet, 225 ... rib, 226 ... anode gas flow path.

Claims (2)

A membrane electrode assembly in which a cathode and an anode are disposed on both sides of the electrolyte membrane;
A separator provided to face the membrane electrode assembly;
A cathode gas channel and an anode gas channel configured to be orthogonal or substantially orthogonal to each other, the anode inlet being disposed in the vicinity of the cathode outlet, and the anode outlet being disposed in the vicinity of the cathode inlet; With
The anode gas flow path is defined so as to turn in a U shape by a rib extending from the vicinity of a portion between the anode inlet and the anode outlet , and the U-shaped flow The pressure loss on the outer peripheral side of the path is made smaller than the pressure loss on the inner peripheral side of the U-shaped flow path.
Fuel cell. The fuel cell according to claim 1, further comprising a partition that separates an outer peripheral side and an inner peripheral side of the U-shaped channel.

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