Fuel battery

Abstract

To provide a fuel battery which can be suppressed in an increase of pressure loss.SOLUTION: A fuel battery is provided, including: a power generation body; and a pair of separators that nip the power generation body. Each separator includes a gas flow channel. The gas flow channel comprises at least one throttled portion of which the flow channel cross sectional area becomes small. The throttled portion comprises: an upstream side inclined portion that is positioned on an upstream side in a gas flow direction; and a downstream side inclined portion that is positioned on a downstream side in the gas flow direction. An inclination angle of the upstream side inclined portion is larger than that of the downstream inclined portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fuel cell.

Background Art

[0002] Regarding fuel cells such as those disclosed in Patent Document 1, various technologies have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a fuel cell including a pair of separators, in which the gas flow paths formed on the separators include a plurality of throttle portions (first portions with a small flow path cross-sectional area) along the gas flow direction. Further, it is disclosed that the density of the throttle portions (first portions) increases toward the downstream side in the gas flow direction. The throttle portions can increase the amount of gas penetrating into the power generation region by reducing the flow path cross-sectional area, but simply reducing it will also increase the pressure loss at the same time.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a fuel cell capable of suppressing an increase in pressure loss.

Means for Solving the Problems

[0006] That is, the present disclosure includes the following aspects. <1> A fuel cell, wherein the fuel cell has a power generation body and a pair of separators sandwiching the power generation body, the separator has a gas flow path, The gas flow path includes at least one throttle portion where the cross-sectional area of the flow path becomes smaller. The throttle portion includes an upstream inclined portion located on the upstream side in the gas flow direction and a downstream inclined portion located on the downstream side in the gas flow direction. The inclination angle of the upstream inclined portion is larger than the inclination angle of the downstream inclined portion, fuel cell.

Advantages of the Invention

[0007] The fuel cell of the present disclosure can suppress an increase in pressure loss.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for the implementation of the present disclosure (for example, general configurations and manufacturing processes of fuel cells that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. Also, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships. In the present disclosure, the gas supplied to the anode of the fuel cell is a fuel gas (anode gas), and the gas supplied to the cathode of the fuel cell is an oxidant gas (cathode gas). The fuel gas is a gas mainly containing hydrogen and may be hydrogen. The oxidant gas is a gas containing oxygen and may be oxygen, air (air), or the like. In the present disclosure, the fuel gas and the oxidant gas are collectively referred to as a reaction gas or a gas.

[0010] In the present disclosure, a fuel cell is provided, The fuel cell includes a power generation body and a pair of separators sandwiching the power generation body. The separator has a gas flow path. The gas flow path includes at least one throttle portion where the cross-sectional area of the flow path becomes smaller. The throttle portion includes an upstream inclined portion located on the upstream side in the gas flow direction and a downstream inclined portion located on the downstream side in the gas flow direction. A fuel cell is provided in which the inclination angle of the upstream inclined portion is larger than the inclination angle of the downstream inclined portion.

[0011] Although various attempts have been made to improve the power generation distribution by the arrangement of the throttle portions of the separator, little consideration has been given to the shape of the throttle portions and the arrangement of those with different shapes. Simply optimizing the arrangement of the throttle portions with a fixed throttle shape as in the prior art may not be able to exert the effect of each throttle portion. The power generation state within the cell surface of the fuel cell varies depending on the site. Specifically, the oxygen concentration is high on the oxidant gas inlet side, and as it approaches the outlet, the oxygen concentration becomes low because oxygen is consumed by power generation. In order to improve the performance of the fuel cell, it is important to reduce the concentration overvoltage of the cell. Particularly, since the supply of oxygen is rate-determining, conventionally, a flow path having a throttle portion that promotes the penetration of oxygen into the power generation body by providing a pressure loss body in the middle of the gas flow path of the separator has been utilized as a means to promote the supply of oxygen. In the present disclosure, a more effective shape and arrangement of the throttle portion are proposed compared to the prior art.

[0012] The fuel cell of the present disclosure may have only one single cell (cell, fuel cell) of the fuel cell, or may be a fuel cell stack (stack) in which a plurality of cells are stacked. In the present disclosure, both the fuel cell and the fuel cell stack may be referred to as fuel cells in some cases. The number of cells stacked in the fuel cell stack is not particularly limited, and may be, for example, 2 to several hundred. The fuel cell stack may have gaskets, resin sheets, etc. for sealing each gas between cells and the like.

[0013] The cell has a power generation body. The shape of the power generation body may be rectangular in plan view. The power generation body may be a membrane electrode assembly (MEA) including an electrolyte membrane and two electrodes. The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of the solid polymer electrolyte membrane include fluorine-based electrolyte membranes such as thin films of perfluorosulfonic acid containing moisture, and hydrocarbon-based electrolyte membranes. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont). One of the two electrodes is an anode (fuel electrode), and the other is a cathode (oxidant electrode). The electrode includes a catalyst layer and may optionally include a gas diffusion layer. The power generation body may be a membrane electrode gas diffusion layer assembly (MEGA). The catalyst layer includes a catalyst, and the catalyst may include a catalyst metal that promotes an electrochemical reaction, an electrolyte having proton conductivity, and a carrier having electron conductivity. As the catalyst metal, for example, platinum (Pt), and alloys composed of Pt and other metals (for example, Pt alloys mixed with cobalt, nickel, etc.) can be used. The catalyst metal used as the cathode catalyst and the catalyst metal used as the anode catalyst may be the same or different. The electrolyte may be a fluorine-based resin or the like. As the fluorine-based resin, for example, a Nafion solution or the like may be used. The above-mentioned catalyst metal is supported on a carrier, and in each catalyst layer, the carrier supporting the catalyst metal (catalyst-supporting carrier) and the electrolyte may be mixed. Examples of the carrier for supporting the catalyst metal include carbon materials such as commercially available carbon. The gas diffusion layer may be a conductive member having pores or the like. Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous members such as metal mesh and foamed metal. The cell may include an insulating resin frame disposed on the outer side (outer periphery) in the plane direction of the membrane electrode assembly between the anode separator and the cathode separator. The resin frame is formed into a plate-like and frame-like shape using a thermoplastic resin, and seals the space between the anode separator and the cathode separator while holding the membrane electrode assembly in its central region. As the resin frame, for example, resins such as PE, PP, PET, and PEN can be used. The resin frame may be a three-layer sheet composed of three layers with an adhesive layer disposed on the surface layer.

[0014] The cell has a pair of separators. The separator collects the current generated by power generation and functions as a partition. In a fuel cell, a pair of separators are disposed on both sides in the stacking direction of the power generation body so as to sandwich the power generation body. One of the pair of separators is an anode separator, and the other is a cathode separator. Examples of the separator include dense carbon obtained by compressing carbon to make it gas-impermeable, and press-molded metals (for example, iron, aluminum, stainless steel, etc.). The separator may have holes that constitute a manifold such as supply holes and discharge holes for allowing fluids such as reaction gas and refrigerant to flow in the stacking direction of the cell. Examples of the refrigerant include water and a mixed solvent of water and ethylene glycol.

[0015] The separator has a gas flow path. The anode separator may have a fuel gas flow path on the surface on the power generation element side, and may have a cooling flow path on the surface opposite to the surface on the power generation element side. The cathode separator may have an oxidant gas flow path on the surface on the power generation element side, and may have a cooling flow path on the surface opposite to the surface on the power generation element side. The gas flow path may include at least one throttle portion where the cross-sectional area of the flow path becomes smaller, and may include a plurality of throttle portions at predetermined intervals.

[0016] (1) Shape of the throttle portion Conventionally, the shape of the throttle portion has been a symmetric structure on the upstream side (inlet side) and the downstream side (outlet side) in the gas flow direction. FIG. 1 is a schematic diagram showing an example of the shape of a conventional throttle portion and an example of the shape of the throttle portion of the present disclosure. As shown in FIG. 1, the throttle portion of the present disclosure includes an upstream inclined portion located on the upstream side in the gas flow direction and a downstream inclined portion located on the downstream side in the gas flow direction. The inclination angle of the upstream inclined portion is larger than the inclination angle of the downstream inclined portion, and it has an asymmetric shape. In the conventional throttle portion, the inclination angle of the upstream inclined portion is the same as the inclination angle of the downstream inclined portion, and it has a symmetric shape. In the present disclosure, by making the shapes of the throttle portions on the upstream side and the downstream side asymmetric (sharply reducing the gas inlet side), a large pressure loss can be generated, and the amount of gas penetrating into the power generation element disposed below the throttle portion can be increased. Also, since the downstream side (outlet side) in the gas flow direction gradually expands, the pressure loss there is small and the effect of the throttle can be obtained effectively. Therefore, in the present disclosure, by making the inclination angle of the upstream inclined portion larger than that of the downstream inclined portion, the differential pressure of the throttle portion becomes larger, and a pressure loss body can be provided efficiently. In the entire gas flow path, while suppressing an increase in pressure loss, the amount of gas penetrating into the power generation element can be increased.

[0017] (2) Arrangement of throttle portions with different shapes Conventionally, throttle portions having the same shape have been arranged in the gas flow path at a certain interval. In the present disclosure, the throttling strength of the throttle portion may be changed according to the position of the gas flow path (oxygen concentration of the power generation unit). Specifically, on the gas inlet side where the oxygen concentration is high, even if the effect of the throttle is small, since the gas reaches the power generation element, the throttle strength may be small (the throttle is loose). On the other hand, on the gas outlet side where the oxygen concentration is low, the throttle strength may be large (the throttle is strong).

[0018] As a basic effect of the throttle portion, since the throttle portion becomes a high-pressure loss body, the gas tries to bypass its periphery. Thereby, the gas can be made to penetrate into the power generation portion. Figure 2 is a graph showing an example of the relationship between the number of throttle portions, the throttle strength, and the oxygen concentration in the cathode (Ca) catalyst layer. For the throttle portion with a medium throttle strength, the dimensions were set as follows: flow path width 0.989, flow path height 0.2245, throttle width 0.585, and throttle height 0.0950. For the throttle portion with a strong throttle strength, the dimensions were set as follows: flow path width 0.989, flow path height 0.2245, throttle width 0.531, and throttle height 0.0733. As shown in Figure 2, the greater the throttle strength of the throttle portion, the more oxygen can penetrate. From the gas inlet side to the outlet side, the oxygen concentration decreases due to the consumption of the gas by power generation. Therefore, in order to increase the oxygen concentration near the gas outlet side, it is effective to increase the throttle strength of the throttle portion toward the outlet side. Therefore, as the gas is consumed from the gas inlet to the outlet (the oxygen concentration decreases), by increasing the throttle strength (providing a large pressure loss body), oxygen can be effectively delivered to the power generation element, the power generation distribution can be made uniform, and the cell performance can be improved. Specifically, the cross-sectional area of the throttle portion arranged on the gas inlet side may be made larger than the cross-sectional area of the throttle portion arranged on the gas outlet side.

[0019] Figure 3 is a schematic diagram showing an example of the arrangement of the throttle portion in the gas flow path of the separator of the present disclosure. As shown in Figure 3, for example, the shapes of the throttle portions in the main flow path of the gas flow path may be the same, and in the branch flow path on the gas outlet side, a throttle portion with a large throttle strength (a small cross-sectional area) may be provided.

Claims

Claim 1 A fuel cell, wherein the fuel cell includes a power generation body and a pair of separators sandwiching the power generation body, wherein the separator has a gas flow path, wherein the gas flow path includes at least one throttle portion where the cross-sectional area of the flow path becomes smaller, wherein the throttle portion includes an upstream inclined portion located on the upstream side in the gas flow direction and a downstream inclined portion located on the downstream side in the gas flow direction, and wherein the inclination angle of the upstream inclined portion is larger than the inclination angle of the downstream inclined portion. A fuel cell.

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