JP2019075339A - Fuel battery cell - Google Patents

Abstract

To provide a fuel battery cell 100 capable of avoiding generation of degradation in drainage or shortage of an oxygen amount on the upstream side of an oxygen electrode under a high load requiring much oxygen amount.SOLUTION: A fuel battery cell 100 includes: at least a power generation surface 21 which is an oxygen electrode, an in-plane gas passage in which oxidant gas fed from an air manifold inlet 14 runs along the power generation surface 21; and a bypass passage C for feeding a part of oxidant gas to be fed to a middle area of the in-plane gas passage. The bypass passage C includes a turbulent flow generation area 63 having both or either one of a bent part or a part whose cross section rapidly changes in a middle area of the passage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell.

  A fuel cell is usually configured as a stack structure in which a plurality of fuel cells called single cells are stacked. Fuel cells mainly have a configuration in which separators are disposed on both sides of a membrane electrode assembly (MEA) via gas diffusion layers. The membrane electrode assembly has an electrolyte membrane, an electrode as a fuel electrode and an electrode as an oxygen electrode formed on both sides thereof, hydrogen as a fuel gas on the fuel electrode side, and an oxidant on the oxygen electrode side. Air as a gas is supplied respectively.

  The supplied hydrogen and oxygen in the air cause an electrochemical reaction in the membrane electrode assembly, and power generation proceeds. In a fuel cell, both surfaces of a membrane electrode assembly are commonly referred to as a power generation surface, and an in-plane gas flow path through which an oxidant gas (air) flows is formed along one surface of the power generation surface, In the surface of the fuel cell, an in-plane gas flow path through which fuel gas (hydrogen) flows is formed along the power generation surface.

  FIG. 4 is a plan view showing an example of a fuel cell. In this example, fuel manifolds 12, 12 are formed at left and right end portions of a separator 11 constituting the fuel cell 10, and hydrogen as a fuel gas is formed. Is supplied. Also, air manifolds are formed at the upper and lower end portions of the separator 11, and the air manifolds are shown as an air manifold inlet 14 and an air manifold outlet 16. Air as an oxidant gas is supplied from the lower air manifold inlet 14 in the figure, passes through the in-plane gas flow path along the power generation surface, and is discharged from the upper air manifold outlet 16. Further, in this example, cooling water manifolds 18 are also formed at the left and right end portions of the separator 11, and cooling water is supplied. In the figure, reference numeral 20 denotes a membrane electrode assembly, and on both sides of the membrane electrode assembly 20, a gas diffusion layer is usually disposed.

  FIG. 5 schematically shows the flow of air as an oxidant gas in the fuel cell 10. The air flowing in from the air manifold inlet 14 passes through the air flow path A, from the air inlet 22 located on the upstream side of the power generation surface 21 that is the oxygen electrode of the membrane electrode assembly 20 to the upstream side of the power generation surface 21 To flow. A part of the air (oxygen) that has flowed in is taken into the membrane electrode assembly 20 from the power generation surface 21, where an electrochemical reaction is performed with hydrogen supplied from the fuel manifolds 12. The air whose oxygen is consumed by the reaction flows down the power generation surface 21 and is discharged from the air manifold outlet 16.

  In the fuel cell unit 10 of this embodiment, the side of the air inlet 22 has a relatively large amount of gas because oxygen is not consumed yet, and the generated water is carried away a lot, and the power generation surface in that region tends to dry. Therefore, the power generation performance is lowered on the side of the air inlet 22 at high temperature or the like, and the power generation distribution may become uneven in the power generation surface 21.

  Patent Document 1 describes an example of a fuel cell that can solve the problem. The fuel cell includes a gas diffusion layer, a separator, and an oxidant gas flow path made of expanded metal disposed between the gas diffusion layer and the separator. As shown in FIG. 6, the expanded metal 30 is an upstream first expanded metal 31 having no opening through which the oxidant gas flowing on the gas diffusion layer side and the oxidant gas flowing on the separator side communicate with each other. And a downstream second expanded metal 33 provided with the opening 32.

Unexamined-Japanese-Patent No. 2012-226981

  In the fuel cell described in Patent Document 1, as shown in FIG. 7, the first expanded metal 31 is positioned in the region near the air manifold inlet 14 in the membrane electrode assembly 20, and the second region is positioned in the remaining region. The second expanded metal 33 is positioned. The fuel cell is expressed like the fuel cell 10a shown in FIG. 8 when it is expressed corresponding to the schematic view shown in FIG.

  That is, among the oxidant gas flowing down the first expanded metal 31, the oxidant gas flowing on the gas diffusion layer side flows into the power generation surface 21 from the air inlet 22, but the oxidant gas flowing on the separator side is downstream When it reaches the second expanded metal 33, it flows into the power generation surface 21. Therefore, the gas flow passage opened to the separator side in the first expanded metal 31 can be referred to as a bypass flow passage B bypassing the air inlet 22, and the bypass flow passage B branches from the air manifold inlet 14, In the downstream of the inlet 22, for example, a portion about 1/3 from the upstream side of the power generation surface 21 is opened to the power generation surface 21.

  As a result, at the upstream side of the open position of the bypass flow passage B, the amount of the oxidant gas flowing down to the power generation surface 21 can be reduced by an amount corresponding to the flow rate flowing through the bypass flow passage B. Film drying is suppressed. However, as shown in FIG. 6, two gas flow paths formed in the first expanded metal 31, that is, a gas flow path 34 of an oxidant gas flowing on the separator side (corresponding to the bypass flow path B); The gas flow channel 35 of the oxidant gas flowing on the gas diffusion layer side is both a straight flow channel having substantially no change in the flow channel cross section, and the gas flow flowing there is basically rectified. Therefore, regardless of whether the load is low or high, that is, regardless of the flow rate of the oxidant gas, the flow rate ratio of the oxidant gas (air) flowing through the two flow paths is uniform, and as a result, much oxygen At the time of high load which requires a quantity, the phenomenon that drainage nature falls and the amount of oxygen runs short may occur in the upper stream side of an oxygen electrode.

  An object of the present invention is to provide a fuel cell that can eliminate the above-mentioned disadvantages.

  A fuel cell according to the present invention comprises a power generation surface, an in-plane gas flow passage through which an oxidant gas fed from an oxidant gas manifold flows along the power generation surface, and an oxidation fed from the oxidant gas manifold A fuel cell including at least a bypass channel for feeding a part of the agent gas to an intermediate zone of the in-plane gas channel, wherein the bypass channel is bent in the intermediate zone of the channel It is characterized in that it comprises a part or a part where the cross-sectional area changes rapidly or both.

  In the fuel cell according to the present invention, the presence of the bypass channel makes it possible to reduce the amount of produced water carried away at low load in the upstream of the power generation surface, and also to reduce the power generation surface at high temperature. Drying can be suppressed. In addition, the bypass flow path is provided with a bending portion and / or a portion where the cross-sectional area changes rapidly, so that when the gas flow rate flowing through the bypass flow path is increased, the flow path is swirled. As a result, the relationship between the flow rate and the pressure loss non-linearly increases due to the turbulent flow. Therefore, when the load is high, the flow rate flowing through the bypass flow path can be relatively reduced, and the amount of gas (oxygen amount) flowing to the upstream side of the power generation surface can be increased accordingly. As a result, it is possible to simultaneously eliminate the decrease in drainage and the occurrence of oxygen deficiency at high load.

FIG. 1 is a schematic plan view of a fuel cell according to the present invention. The schematic diagram which shows the other example of a bypass flow path. The graph for demonstrating the relationship of the pressure loss and flow volume in the gas flow in this invention, and the gas flow in a prior art. FIG. 2 is a schematic plan view showing an example of a fuel cell. The figure which shows typically the state to which the air as oxidant gas flows in a fuel cell. The figure explaining the expanded metal used by prior art. The top view which shows the fuel cell in a prior art. The figure which shows typically the state to which the air as oxidant gas flows in the fuel cell in a prior art.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view schematically showing a fuel cell 100 according to the present embodiment. The basic configuration of the fuel cell unit 100 shown in FIG. 1 is the same as that of the fuel cell unit 10 described based on FIG. 5, and the same members will be denoted by the same reference numerals and detailed description thereof will be omitted.

  The fuel cell 100 adds the air from the air manifold inlet 14 to the main air flow path A for guiding the air to the air inlet 22, and a part of the air is along the power generation surface 21 which is an oxygen electrode of the membrane electrode assembly 20. A bypass channel C is provided which can be guided to a midway region of the in-plane gas channel. The bypass flow passage C has a uniform flow passage cross section, and has at least a midway region of the flow passage a turbulent flow region 63 in which a large diameter portion 61 and a small diameter portion 62 are alternately arranged in series. There is.

  The gas flow flowing in the bypass flow path C increases in flow velocity when flowing into the small diameter portion 62 from the large diameter portion 61, and decreases in flow velocity when flowing into the large diameter portion 61 from the small diameter portion 62. As a result, vortices and separation occur in the flow of gas flowing into the turbulent flow region 63 in a substantially straightened state, resulting in turbulent flow. As the flow rate increases, the state of turbulence increases accordingly.

  The relationship between the flow rate in the flow path and the pressure loss changes substantially linearly and linearly when flowing straight down without turbulence in the flow, whereas the bypass flow path in the present embodiment In C, as described above, the occurrence of turbulent flow causes the change to be non-linear, and at the same pressure loss value, the flow rate flowing through the bypass channel C is reduced as compared with the case of rectification. Do. The gas flow rate flowing through the main air flow passage A is increased by the reduction rate. The amount of increase increases with the air flow rate from the air manifold inlet 14.

  FIG. 3 graphically illustrates the relationship. As shown in the graph, at the low load flow rate, there is no large difference between the gas flow rate flowing in the bypass flow path B shown in FIG. 8 and the gas flow rate flowing in the bypass flow path C in the present embodiment. When the load flow rate is reached, the flow rate difference between the two becomes significantly large. Therefore, in the fuel cell 100 according to the present embodiment, the air flow rate from the air inlet 22 located on the upstream side of the power generation surface 21 which is an oxygen electrode is increased in the state of high load flow rate. It becomes possible to make the fuel cell 10a larger than the conventional one, that is, the fuel cell 10a of the form described based on FIG. 8, and the drainability and the decrease in the oxygen amount at high load can be reliably avoided.

  In fuel cell 100 in the present embodiment, the form of turbulent flow generation region 63 in bypass flow passage C is not limited to that shown in FIG. 1. FIG. 2 shows another form of the turbulent flow generation region 63 in the bypass flow passage C. In FIG. 2A, a place where the area of the cross section is rapidly expanded is provided at one place of the flow passage of the turbulent flow generation region 63. Also in this embodiment, the ejection velocity is high at the central portion of the enlarged diameter portion of the flow passage and is low at the peripheral portion, so that the flow becomes turbulent in the enlarged diameter portion. In FIG. 2 (b), a place where the area of the cross section sharply reduces is provided at one place of the flow passage of the turbulent flow generation region 63. In this form as well, since the flow velocity changes in the central portion and the peripheral portion when flowing into the small diameter portion, the rectification also becomes turbulent.

  In FIG. 2C, turbulent flow is not generated by changing the area of the cross section, but by providing appropriate number (four in the drawing) of bending portions (bending portions) in the flow path of the turbulent flow generation region 63. I am trying to make it happen. In the bent portion, the commutation is also turbulent because the distance required for bending is different between a portion near the inner corner and a portion far from the inner corner. By repeating the bending several times, the degree of turbulence also increases. In FIG. 2 (d), the turbulent flow generation area 63 has a shape in which the bifurcation and the aggregation are repeated. Even in this shape, the rectification is turbulent. In the shape of FIG. 2 (d), the bifurcation includes a bifurcation extending in the direction of 360 degrees, ie, a bifurcated bifurcation in addition to the bifurcation in the vertical direction as shown.

  Furthermore, although not shown, the fuel cell of the form described in Patent Document 1, that is, the gas diffusion layer, the separator, the gas diffusion layer, and the separator described above with reference to FIGS. 6 and 7. And an oxidant gas flow path made of expanded metal 30, and the expanded metal 30 flows through the gas diffusion layer side as shown in FIGS. 6 and 7, and the separator side With respect to a fuel cell having a form in which the upstream first expanded metal 31 having no opening through which the oxidant gas flowing in the gas communicates with each other and the downstream second expanded metal 33 provided with the opening 32 It is also possible to apply the technology of the bypass channel C according to the present invention.

  Specifically, the gas flow path 34 (corresponding to the bypass flow path C) opened to the separator side in the first expanded metal 31 and the flow path 35 opened to the gas diffusion layer shown in FIG. The fuel cell according to the present embodiment is provided with a bending portion and / or a portion where the cross-sectional area rapidly changes in the flow path while maintaining a state in which no opening is formed. It is possible to make a fuel cell that can exhibit the same function and effect as 100.

100 ... fuel cell,
14 ... Air manifold inlet,
20: Membrane electrode assembly,
21: Power generation surface which is an oxygen electrode,
22 ... air inlet,
61 ... large diameter part,
62 ... small diameter portion,
63 ... turbulent flow generation area,
A: Main air flow path,
C: bypass flow path.

Claims (1)

A power generation surface, an in-plane gas flow path through which an oxidant gas supplied from an oxidant gas manifold flows along the power generation surface, and a part of an oxidant gas supplied from the oxidant gas manifold A fuel cell comprising at least a bypass passage for feeding to a midway region of the inner gas passage,
The fuel cell according to claim 1, wherein the bypass flow path includes a bent portion or a portion where the cross-sectional area rapidly changes in the middle of the flow path.

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