JP2011014462A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power generation efficiency by promoting water drain from a supply gas passage in a fuel cell.SOLUTION: The fuel cell is equipped with a membrane-electrode assembly; a pair of gas diffusion layers pinching the membrane-electrode assembly; and a pair of separators 56 pinching the pair of gas diffusion layers 52, and has in a face at least on one gas diffusion layer side of the pair of separators, a groove state first gas passage 62, in which the upstream end is connected to a supply manifold and the downstream end is closed; and a groove state second gas passage 72; in which the upstream end is closed and the downstream end is connected to the exhaust manifold. The pressure difference between a first region 80 that is the downstream end of the first gas passage and a second region 82 that is a region nearest the first region between the second gas passage is larger than the pressure difference between a third region 84, that is the upstream end of the second gas passage and a fourth region 86 that is a region nearest the third region out of the first gas passage.

Description

  The present invention relates to a fuel cell.

  A fuel cell is a device for obtaining electrical energy using hydrogen and oxygen as fuel. Since fuel cells have high conversion efficiency into energy and are excellent in terms of environment, they are widely developed as future energy supply systems.

  A general fuel cell includes a membrane-electrode assembly having an electrolyte membrane and a catalyst layer, a gas diffusion layer provided adjacent to the membrane-electrode assembly, and a separator in which a gas flow path is formed. ing. Conventionally, there has been known a comb-shaped gas flow path in which a supply flow path for supplying gas to a gas diffusion layer and a discharge flow path for recovering gas from the gas diffusion layer are alternately formed at predetermined intervals. Yes. If water accumulates at the tip of the supply gas flow path, gas diffusion from the supply gas flow path to the gas diffusion layer is hindered, resulting in a problem that power generation efficiency is reduced. Therefore, in such a comb-shaped gas flow path, a gas flow path is known in which a drainage path is provided at the tip of the supply-side gas flow path to suppress the retention of water droplets in the region (for example, Patent Documents). 1).

JP 2005-166545 A

  However, in the technique described in Patent Document 1, it is necessary to newly provide a drainage channel penetrating the separator, which may complicate the separator production process.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell capable of improving power generation efficiency by promoting drainage from a supply gas flow path by a relatively simple method. And

  The present invention comprises a membrane-electrode assembly, a pair of gas diffusion layers that sandwich the membrane-electrode assembly, and a pair of separators that sandwich the pair of gas diffusion layers, and at least one of the pair of separators On one gas diffusion layer side surface, the upstream end is connected to the supply manifold, the downstream end is closed, and the upstream end is closed, and the downstream end is connected to the discharge manifold. A groove-shaped second gas channel, and a first region that is the downstream end of the first gas channel, and a second region that is the closest to the first region of the second gas channel. The differential pressure between the second region and the second region is based on the differential pressure between the third region that is the upstream end of the second gas flow channel and the fourth region that is the region closest to the third region in the first gas flow channel. It is a large fuel cell. According to this configuration, drainage from the first region can be promoted by increasing the differential pressure between the first region and the second region as compared with other regions. As a result, the penetration of gas from the first region into the gas diffusion layer is promoted, and the power generation efficiency can be improved. Moreover, according to this structure, since it is not necessary to newly provide a drainage channel, the complexity of the manufacturing process of a separator can be suppressed.

  The said structure WHEREIN: The flow-path cross-sectional area of the said 2nd area | region in the said 2nd gas flow path can be set as the structure smaller than the flow-path cross-sectional area other than the said 2nd area | region in the said 2nd gas flow path. According to this configuration, by reducing the channel cross-sectional area of the second region, the differential pressure between the first region and the second region can be increased compared to other regions.

  The said structure WHEREIN: The flow path cross-sectional area of the said 2nd gas flow path can be set as the structure smaller than the flow path cross-sectional area of the said 1st gas flow path. According to this configuration, the differential pressure between the first region and the second region can be increased compared to other regions.

  The present invention comprises a membrane-electrode assembly, a pair of gas diffusion layers that sandwich the membrane-electrode assembly, and a pair of separators that sandwich the pair of gas diffusion layers, and at least one of the pair of separators On one gas diffusion layer side surface, the upstream end is connected to the supply manifold, the downstream end is closed, and the upstream end is closed, and the downstream end is connected to the discharge manifold. A groove-shaped second gas flow path, a first area that is a downstream end of the first gas flow path, and a second area that is the area closest to the first area of the second gas flow path. The differential pressure is larger than the differential pressure between the third region that is the upstream end of the second gas flow channel and the fourth region that is the region closest to the third region in the first gas flow channel. And a differential pressure control means for controlling the fuel cell. According to this configuration, drainage from the first region can be promoted by increasing the differential pressure between the first region and the second region as compared with other regions by the differential pressure control means. As a result, the penetration of gas from the first region into the gas diffusion layer is promoted, and the power generation efficiency can be improved. Moreover, according to this structure, since it is not necessary to newly provide a drainage channel, the complexity of the manufacturing process of a separator can be suppressed.

  The said structure WHEREIN: The said differential pressure control means can be set as the structure which is a negative pressure application means which applies a negative pressure with respect to the said 2nd area | region. According to this configuration, by applying a negative pressure to the second region, the differential pressure between the first region and the second region can be increased compared to the other regions.

  In the above configuration, the differential pressure control unit is a channel cross-sectional area reducing unit that is provided in at least the second region of the second gas channel and reduces the channel cross-sectional area as the humidity increases. can do. According to this configuration, since the flow path cross-sectional area can be adjusted according to humidity, the amount of drainage from the first region can be adjusted according to humidity.

  The said structure WHEREIN: The flow-path surface area of the said 2nd area | region in the said 2nd gas flow path can be set as the structure larger than flow-path surface areas other than the said 2nd area | region in the said 2nd gas flow path. According to this configuration, the drainage can be further promoted by increasing the channel surface area of the second region.

  According to the present invention, power generation efficiency can be improved by promoting drainage from the supply gas flow path by a relatively simple method.

FIG. 1 is a diagram illustrating the configuration of the fuel cell system according to the first embodiment. 2A to 2C are diagrams illustrating a detailed configuration of the fuel cell according to the first embodiment. FIGS. 3A to 3B are diagrams illustrating a detailed configuration of a gas flow path of the fuel cell according to the first embodiment. FIG. 4 is a diagram illustrating a detailed configuration of the negative pressure applying unit of the fuel cell system according to the first embodiment. FIG. 5 is a diagram illustrating the operation of the fuel cell system according to the first embodiment. FIG. 6A is a diagram illustrating a detailed configuration of the gas flow path of the fuel cell according to the second embodiment, and FIG. 6B is a modification thereof. FIG. 7A is a diagram showing a detailed configuration of the gas flow path of the fuel cell according to Example 3, and FIG. 7B is a graph showing the gas distribution in the supply gas flow path. . FIG. 7C shows a modification of the third embodiment. FIGS. 8A to 8B are diagrams illustrating the detailed configuration of the gas flow path of the fuel cell according to the fourth embodiment. FIGS. 9A to 9B are diagrams illustrating the detailed configuration of the gas flow path of the fuel cell according to the fifth embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a fuel cell system 100 according to the first embodiment. The fuel cell system 100 includes a polymer electrolyte fuel cell 10 configured by stacking a plurality of single cells. An anode gas supply means 12 for supplying anode gas to each single cell and a cathode gas supply means 14 for supplying cathode gas to each single cell are connected to the fuel cell 10. In addition, an ammeter 16 and a voltmeter 18 for measuring output and a hygrometer 20 for measuring the humidity in the cell are connected to the fuel cell 10. Further, the fuel cell 10 is connected to a cooling water supply means 22 for supplying cooling water into the cell. A thermometer 26 for detecting the temperature in the cell is installed in the cooling water passage 24 for collecting the cooling water from the fuel cell 10.

  The fuel cell system 100 also includes a negative pressure applying unit 30 for applying a negative pressure to a predetermined area in the fuel cell 10 and a control unit 28 for controlling the negative pressure applying unit 30. Signals from the ammeter 16, the voltmeter 18, the hygrometer 20, and the thermometer 26 are input to the control means 28, and the negative pressure applying means is based on the internal state of the fuel cell 10 grasped by these signals. 30 controls are performed. The control means 28 is comprised by CPU (Central Processing Unit), ECU (Engine Control Unit), etc., for example.

  FIG. 2A is a schematic cross-sectional view of the fuel cell 10 (a single cell is illustrated as the fuel cell 10). The fuel cell 10 has a membrane-electrode assembly 40 at the center. The membrane-electrode assembly 40 is sandwiched between a pair of gas diffusion layers (the anode gas diffusion layer 50 and the cathode gas diffusion layer 52). The pair of gas diffusion layers 50 and 52 are further sandwiched between a pair of separators (an anode separator 54 and a cathode separator 56).

  The membrane-electrode assembly 40 includes an electrolyte membrane 42, an anode catalyst layer 44, and a cathode catalyst layer 46. As the electrolyte membrane 42, for example, a solid polymer electrolyte membrane (eg, perfluorosulfonic acid membrane) having proton conductivity can be used.

  The anode catalyst layer 44 and the cathode catalyst layer 46 are disposed so as to sandwich the electrolyte membrane 42. The catalyst contained in the anode catalyst layer 44 promotes protonation of hydrogen, and the catalyst contained in the cathode catalyst layer 46 promotes the reaction between protons and oxygen. As a catalyst for the anode catalyst layer 44 and the cathode catalyst layer 46, for example, platinum can be used. In this case, the anode catalyst layer 44 and the cathode catalyst layer 46 include, for example, platinum-supporting carbon.

  The anode gas diffusion layer 50 and the cathode gas diffusion layer 52 have conductivity and gas diffusion properties. The anode gas diffusion layer 50 has a function of diffusing an anode gas containing hydrogen and supplying the anode gas to the anode catalyst layer 44. The cathode gas diffusion layer 52 has a function of diffusing a cathode gas containing oxygen and supplying it to the cathode catalyst layer 46. As the anode gas diffusion layer 50 and the cathode gas diffusion layer 52, for example, carbon fibers such as carbon paper and carbon cloth can be used.

The anode separator 54 and the cathode separator 56 are disposed in contact with the anode gas diffusion layer 50 and the cathode gas diffusion layer 52, respectively. Each separator has a gas flow path for supplying gas to the gas diffusion layer.

  FIG. 2B is a view of the cathode separator 56 viewed from the membrane-electrode assembly 40 side. The arrows in the figure indicate the gas flow. FIG. 2C is a cross-sectional view of the cathode separator 56 as viewed from the direction of the A-A ′ line in FIG. 1B (components other than the cathode separator 56 are omitted). As shown in FIG. 2C, a groove-like recess is formed on the surface of the cathode separator 56 on the cathode gas diffusion layer 52 side. A region defined by the recess and the cathode gas diffusion layer 52 functions as a gas flow path for the cathode gas to flow.

  As shown in FIG. 2B, the gas flow path of the fuel cell 10 is formed so that two opposing comb gas flow paths are alternately meshed. The gas flow path includes a plurality of supply gas flow paths 62 (first gas flow paths) branched from the supply manifold 60 and a plurality of exhaust gas flow paths 72 (second gas flow paths) branched from the discharge manifold 70. . The upstream end of the supply manifold 60 is connected to a gas supply port 64, and the downstream end of the discharge manifold 70 is connected to a gas discharge port 74. The gas flow path (60, 62) on the supply side and the gas flow path (70, 72) on the discharge side are not connected as a groove-shaped recess.

  The supply gas channel 62 is a channel for supplying gas to the cathode gas diffusion layer 52, and its upstream end is connected to the supply manifold 60 and its downstream end is closed. The exhaust gas flow path 72 is a flow path for collecting and discharging the gas from the cathode gas diffusion layer 52, the upstream end thereof is closed, and the downstream end is connected to the discharge manifold 70. The supply gas passage 62 and the exhaust gas passage 72 are alternately formed with a predetermined interval.

  Fig.3 (a) is the figure which expanded a part of gas flow path in FIG.2 (b). In the following description, a region corresponding to the downstream end of the supply gas passage 62 is referred to as a first region 80, and a region of the exhaust gas passage 72 that is closest to the first region 80 is referred to as a second region 82. Similarly, a region corresponding to the upstream end of the exhaust gas passage 72 is referred to as a third region 84, and a region closest to the third region 84 in the supply gas passage 62 is referred to as a fourth region 86.

  FIG. 3B is a schematic cross-sectional view taken along the line A-A ′ of FIG. The arrows in the figure indicate the gas flow. As shown in the figure, gases such as cathode gas and water vapor permeate into the cathode gas diffusion layer 52 from the supply gas channel 62 and move to the exhaust gas channel through the cathode gas diffusion layer 52. During the low temperature operation, water droplets may be generated in the supply gas flow path 62 and the cathode gas diffusion layer 52. In this case, the water droplet movement path is along the arrow as in the case of the gas.

  As shown in FIG. 3 (b), the downstream end of the supply gas flow path 62 is closed, so that the gas that has reached the tip (the first region 80) is hidden in the cathode gas diffusion layer 52. For this reason, the amount of cathode gas permeating from the supply gas channel 62 to the cathode gas diffusion layer 52 is increased, and the reaction of the gas is increased as compared with the conventional gas channel in which the tip of the supply gas channel is connected to the discharge side. The power generation efficiency is improved by being promoted. On the other hand, particularly during low-temperature operation, there is a problem in that water accumulates at the front end (first region 80) of the supply gas flow path 62, thereby inhibiting gas permeation in the region. The fuel cell system 100 according to the present embodiment aims to solve such problems.

  FIG. 4 is a diagram showing a detailed configuration of the negative pressure applying means 30 in FIG. The negative pressure applying means 30 includes a negative pressure pump 32, a negative pressure tank 34, and a negative pressure switching valve 36. The negative pressure pump 32 stores negative pressure in the negative pressure tank 34. The negative pressure switching valve 36 is installed in the exhaust system 58 of the cathode separator 56, and its opening / closing is controlled by the control means 28. As described above, the negative pressure applying means 30 is configured to apply the negative pressure stored in the negative pressure tank 34 to the downstream region (second region 82) of the exhaust gas passage 72. ing.

  FIG. 5 is a flowchart showing the operation of the fuel cell system 100 according to the present embodiment. First, the control means 28 detects the operating state of the fuel cell 10 based on signals from the ammeter 16, the voltmeter 18, the hygrometer 20, and the thermometer 26 (step S10). Next, the control means 28 determines whether or not to operate the negative pressure applying means 30 based on the detected operating state (step S12). If YES in step S12, the negative pressure applying means 30 under the control of the control means 28 applies a negative pressure to the second region 82 of the exhaust gas flow path 72 (step S14).

  For example, when a state in which the output of the fuel cell 10 is low, the temperature is low, the humidity is high, or the like is detected, it is estimated that water is collected at the tip of the supply gas flow path 62. Therefore, in step S10, when all or a part of these parameters cause the retention of water at the tip of the supply gas flow path 62 to be estimated, the control means 28 may be configured to activate the negative pressure application means 30. it can. Note that these measuring devices are examples of devices for grasping the operating state of the fuel cell 10, and some of them may be omitted.

  By applying a negative pressure to the downstream region (second region 82) of the exhaust gas passage 72, the pressure difference from the downstream end (first region 80) of the supply gas passage 62 is expanded (in detail, (The differential pressure between the first region 80 and the second region 82 is greater than the differential pressure between the third region 84 and the fourth region 86). Thereby, in the second region 82, the force for sucking gas and water droplets from the first region 80 through the cathode gas diffusion layer 52 is increased, and drainage from the first region 80 is promoted. As a result, gas permeation from the first region 80 to the cathode gas diffusion layer 52 can be promoted, and the power generation efficiency of the fuel cell 10 can be improved.

  As described above, the differential pressure between the first region 80 that is the downstream end of the supply gas passage 62 and the second region 82 that is the region closest to the first region 80 in the exhaust gas passage 72 is the exhaust gas. The supply gas is set to be larger than the differential pressure between the third region 84 that is the upstream end of the flow channel 72 and the fourth region 86 that is the region closest to the third region 84 in the supply gas flow channel 62. It is possible to promote drainage from the downstream end of the flow path 62 and improve power generation efficiency.

  In the first embodiment, the fuel cell system 100 is configured to include the control unit 28. However, such a control unit may not be provided when the drainage is always performed.

  Example 2 is an example in which the differential pressure with respect to the supply gas channel is increased by reducing the partial cross-sectional area of the exhaust gas channel. The overall configuration of the fuel cell system 100 and the basic configuration of the fuel cell 10 are the same as those of the first embodiment (FIGS. 1 to 2), but the control means 28 and the negative pressure applying means 30 are not essential in this embodiment.

  FIG. 6A is an enlarged view of a part of the gas flow path of the fuel cell 10 according to the second embodiment, and corresponds to FIG. 3A of the first embodiment. As shown in the drawing, the channel width in the downstream region (second region 82) of the exhaust gas channel 72 is narrower than the gas channel of the first embodiment. That is, the channel cross-sectional area of the second region 82 in the exhaust gas channel 72 is smaller than the channel cross-sectional area of other regions of the exhaust gas channel 72. As a result, the gas flow rate increases in the second region 82, and the differential pressure between the second region 82 and the first region 80 increases.

  FIG. 6B is a view showing a modification of the second embodiment, and shows a cross section in the second region 82 of the exhaust gas passage 72. A top view of the exhaust gas passage 72 is the same as FIG. 3A of the first embodiment. As shown in FIG. 6B, the height (solid line portion) of the exhaust gas flow path 72 in the second region 82 is smaller than the other regions (dotted line portion). Thereby, the channel cross-sectional area in the second region 82 can be reduced as in FIG.

  As shown in FIGS. 6A and 6B, the cross-sectional area of the second region 82 of the exhaust gas passage 72 is made smaller than the cross-sectional area of the other regions of the exhaust gas passage 72. Thus, the gas flow rate in the second region 82 can be increased. Thereby, as in the first embodiment, the differential pressure between the first region 80 and the second region 82 can be made larger than the differential pressure between the third region 84 and the fourth region 86. As a result, drainage from the first region 80 of the supply gas passage 62 can be promoted, and the power generation efficiency of the fuel cell 10 can be improved.

  Note that both the channel width and the channel height may be reduced in order to reduce the channel cross-sectional area. Further, the cross-sectional shape of the flow path is not limited to a rectangular shape, and may be an arbitrary shape.

  Example 3 is an example in which the flow path cross-sectional area of the entire exhaust gas flow path is reduced. The configuration other than the gas flow path is the same as that of the second embodiment.

  FIG. 7A is an enlarged view of a part of the gas flow path of the fuel cell 10 according to the third embodiment, and corresponds to FIG. 6A of the second embodiment. As shown in the figure, the channel width of the exhaust gas channel 72 is narrower than that of the supply gas channel 62. That is, the cross-sectional area of the exhaust gas flow path 72 is smaller than the cross-sectional area of the supply gas flow path 62. Thereby, compared with the case where both channel cross-sectional areas are the same, the flow velocity of the gas in the exhaust gas flow path 72 whole region containing the 2nd area | region 82 increases.

  FIG. 7B is a graph showing the gas distribution in the supply gas passage 62. The horizontal axis of the graph indicates the position of the supply gas passage 62 in the groove direction, and the origin side is upstream. The vertical axis of the graph indicates the amount of gas that permeates from the supply gas channel 62 into the cathode gas diffusion layer 52. The graph of A shows the gas distribution when the channel cross-sectional areas of the supply gas channel 62 and the exhaust gas channel 72 are equal (comparative example). The graph of B shows the gas distribution when the cross-sectional areas of the supply gas passage 62 and the exhaust gas passage 72 are both smaller than the case of A (comparative example). The graph of C shows the gas distribution when the flow passage cross-sectional area of the exhaust gas flow passage 72 is smaller than the flow passage cross-sectional area of the supply gas flow passage 62 as in this embodiment. The distribution of the gas submerged in the diffusion layer is determined by the pressure loss in the flow path portion and the pressure loss in the diffusion layer. The higher the pressure loss in the diffusion layer, the closer the distribution is from A to B.

  In the graph of A, the gas permeation amount is large on the downstream side (first region 80) of the supply gas flow path 62, and the drainage performance is high. However, the supply of gas to the cathode gas diffusion layer 52 is insufficient in the central portion of the supply gas flow path 62, and this region becomes a power generation failure. In the graph of B, the gas permeation amount is small on the downstream side (first region 80) of the supply gas flow path 62, and the drainage property in the region is not good.

  On the other hand, when the flow path cross-sectional area of the exhaust gas flow path 72 is smaller than the flow path cross-sectional area of the supply gas flow path 62 as in the graph of C, the total pressure loss on the supply gas flow path 62 side is the exhaust gas flow path 72. Smaller than the overall pressure loss on the side. As a result, the amount of gas permeation on the upstream side (fourth region 86) and downstream side (first region 80) of the supply gas flow path 62 is larger than B. Further, the amount of gas permeation in the central portion of the supply gas flow path 62 is larger than that of A, and sufficient gas is supplied to the cathode gas diffusion layer 52. Further, due to the pressure loss difference, the differential pressure between the first region 80 and the second region 82 is larger than the differential pressure between the third region 84 and the fourth region 86. Thereby, compared with the upstream side (4th area | region 86) of the supply gas flow path 62, the permeation amount of the gas in the downstream (1st area | region 80) becomes large. As a result, drainage from the first region 80 of the supply gas channel 62 is promoted. As described above, according to the flow path configuration of the present embodiment, drainage can be improved while supplying a sufficient amount of gas to the cathode gas diffusion layer 52.

  FIG. 7C is a view showing a modification of the third embodiment, and shows a cross section in the second region 82 of the exhaust gas passage 72. A top view of the exhaust gas passage 72 is the same as FIG. 3A of the first embodiment. As shown in FIG. 7C, the height of the exhaust gas passage 72 is lower than that of the supply gas passage 62. Thereby, the channel cross-sectional area of the exhaust gas channel 72 can be reduced as in FIG.

  As shown in FIGS. 7A and 7C, the cross-sectional area of the entire exhaust gas flow path 72 is made smaller than the cross-sectional area of the supply gas flow path 62, which is sufficient for the cathode gas diffusion layer 52. It is possible to improve drainage in the supply gas channel 62 while supplying a sufficient amount of gas.

  As in the second embodiment, both the channel width and the channel height may be reduced in order to reduce the channel cross-sectional area. Further, the cross-sectional shape of the flow path is not limited to a rectangular shape, and may be an arbitrary shape.

  Example 4 is an example in which a member that changes the cross-sectional area of the flow path according to the surrounding environment is used. The overall configuration of the fuel cell system 100 and the basic configuration of the fuel cell 10 are the same as in the first embodiment, but the control means 28 and the negative pressure applying means 30 are not essential as in the second to third embodiments.

  FIGS. 8A and 8B are enlarged views of a part of the gas flow path of the fuel cell 10 according to the fourth embodiment, and correspond to FIG. 3A of the first embodiment. As shown in the drawing, a water absorbent resin 90 is provided on the wall surface of the exhaust gas passage 72. The water absorbent resin 90 expands due to water absorption, and changes the cross-sectional area of the exhaust gas flow path 72. FIG. 8A shows a case where the water absorbent resin 90 is in a dry state, and the flow path cross-sectional area is increased due to the reduction of the water absorbent resin 90. FIG. 8B shows a case where the water absorbent resin 90 is in a wet state, and the flow path cross-sectional area is reduced due to the expansion of the water absorbent resin 90.

  In the state of FIG. 8B, the differential pressure between the first region 80 and the second region 82 is greater than the differential pressure between the third region 84 and the fourth region 86. Thereby, in the second region 82, the force for sucking gas and water droplets from the first region 80 through the cathode gas diffusion layer 52 is increased, and drainage from the first region 80 is promoted. As a result, power generation efficiency can be improved.

  Further, when the necessity for drainage is low (low humidity), the water absorbent resin 90 is reduced, so that the cross-sectional area of the flow path and the gas flow rate are increased. In this way, by using the channel cross-sectional area reducing member (water absorbent resin 90) that reduces the channel cross-sectional area as the humidity increases, the channel cross-sectional area of the exhaust gas channel can be adjusted according to the environment. Can do. In this embodiment, the water absorbent resin 90 is provided in the entire area of the exhaust gas flow path 72, but the water absorbent resin 90 may be provided at least in the second region 82 of the exhaust gas flow path 72. When the water absorbent resin 90 is provided only in the second region 82, the same effects as those of the second embodiment can be obtained when the water absorbent resin 90 expands.

  Example 5 is an example in which drainage is promoted by increasing the channel surface area of the exhaust gas channel. The overall configuration of the fuel cell system 100 and the basic configuration of the fuel cell 10 are the same as in the first embodiment, but the control means 28 and the negative pressure applying means 30 are not essential as in the second to fourth embodiments.

  FIGS. 9A and 9B are enlarged views of a part of the gas flow path of the fuel cell 10 according to the fifth embodiment, and correspond to FIGS. 3A and 3B of the first embodiment. As shown in the figure, a protrusion 92 as a channel surface area increasing means is formed on the wall surface of the second region 82 in the exhaust gas channel 72. Thereby, the channel surface area of the second region 82 is larger than the channel surface area of other regions of the exhaust gas channel 72. Further, due to the protrusion 92, the flow passage cross-sectional area of the second region 82 is smaller than the other regions in the exhaust gas flow passage 72. As a result, as in the second embodiment, the differential pressure between the first region 80 and the second region 82 is larger than the differential pressure between the third region 84 and the fourth region 86, so that the drainage from the first region 80 is performed. Is promoted.

  In addition, most of the water droplets in the exhaust gas flow path 72 condense on the flow path wall surface or the like when the water vapor is cooled, and move in the discharge direction by the shearing force caused by the gas flow. Therefore, if the gas flow rate and flow velocity are the same, the greater the surface area (flow channel surface area) to which water droplets can adhere, the greater the amount of water discharged. In the present embodiment, the channel surface area of the second region 82 where the protrusions 92 are formed is larger than the channel surface area of other portions. Thereby, discharge of water in the second region 82 can be further promoted.

  As described above, according to the fuel cells and fuel cell systems of Examples 1 to 5, the discharge of water at the tip end portion (first region 80) of the supply gas passage 62 is promoted, and the power generation efficiency is improved. Can do. Moreover, since it is not necessary to newly form a drainage channel in the separator, the manufacturing process can be prevented from becoming complicated. The plurality of embodiments can be implemented in combination with each other except for the combination of the second embodiment and the third embodiment.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Fuel cell 28 Control part 30 Negative pressure application means 60 Supply manifold 62 Supply gas flow path 70 Discharge manifold 72 Exhaust gas flow path 90 Water absorbing resin 92 Protrusion 100 Fuel cell system

Claims (7)

A membrane-electrode assembly;
A pair of gas diffusion layers sandwiching the membrane-electrode assembly;
A pair of separators sandwiching the pair of gas diffusion layers,
At least one of the pair of separators on the gas diffusion layer side surface, the upstream end is connected to the supply manifold and the downstream end is closed, and the upstream end is closed and the downstream end is closed. A groove-shaped second gas flow path connected to the discharge manifold,
The differential pressure between the first region which is the downstream end of the first gas channel and the second region which is the region closest to the first region of the second gas channel is the second gas channel. Greater than the differential pressure between the third region which is the upstream end and the fourth region which is the region closest to the third region in the first gas flow path,
The fuel cell characterized by the above-mentioned.   2. The fuel cell according to claim 1, wherein a cross-sectional area of the second region in the second gas flow path is smaller than a cross-sectional area of the second gas flow path other than the second region.   3. The fuel cell according to claim 1, wherein a flow path cross-sectional area of the second gas flow path is smaller than a flow path cross-sectional area of the first gas flow path. A membrane-electrode assembly;
A pair of gas diffusion layers sandwiching the membrane-electrode assembly;
A pair of separators sandwiching the pair of gas diffusion layers,
At least one surface of the pair of separators on the gas diffusion layer side, the upstream end is connected to the supply manifold and the downstream end is closed, and the upstream end is closed and the downstream end is closed. A groove-shaped second gas flow path connected to the discharge manifold;
The differential pressure between the first region which is the downstream end of the first gas channel and the second region which is the region closest to the first region of the second gas channel is the second gas channel. Differential pressure control means for controlling to be greater than the differential pressure between the third region which is the upstream end and the fourth region which is the region closest to the third region in the first gas flow path;
A fuel cell comprising:   5. The fuel cell according to claim 4, wherein the differential pressure control means is a negative pressure applying means for applying a negative pressure to the second region.   The differential pressure control means is provided in at least the second region of the second gas flow path, and is a flow path cross-sectional area reduction means for reducing the flow path cross-sectional area as the humidity increases. Item 6. The fuel cell according to Item 4 or 5.   The flow channel surface area of the second region in the second gas flow channel is larger than the flow channel surface area of the second gas flow channel other than the second region. Fuel cell.

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