Fuel cell

Abstract

To provide a structure capable of reducing water remaining in a valley of a gas passage, in a fuel cell in which a separator has a wavy gas passage.SOLUTION: A fuel cell disclosed in the present specification includes a membrane electrode assembly, a separator adjacent to the membrane electrode assembly, and a gas flow path through which fuel gas, oxygen gas, or air passes. The gas flow path is provided on a surface of the separator facing the membrane electrode assembly. The gas flow path has a wavy shape extending in the lateral direction while meandering in the vertical direction. In the gas flow path, an upwardly convexly curved portion that is curved convexly upward and a downwardly convexly curved portion that is curved convexly downward are alternately connected, and the downwardly convexly curved portion is shorter than the upwardly convexly curved portion. By making the downwardly convexly curved portion shorter than the upwardly convexly curved portion, the water remaining in the downwardly convexly curved portion is easily blown off to the gas downstream side by the force of the gas. That is, the amount of water remaining in the gas flow path can be reduced.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell in which a separator is provided with a gas flow path. [Background technology]

[0002] A fuel cell includes a membrane electrode assembly (MEA), which is a pair of electrodes sandwiching an electrolyte membrane, and a separator adjacent to the membrane electrode assembly. The membrane electrode assembly is sometimes abbreviated as MEA (Membrane Electrode Assembly).

[0003] Gas channels are provided on the separator's surface facing the membrane electrode assembly. Hydrogen gas flows through the gas channel facing the cathode, and oxygen gas or air flows through the gas channel facing the anode. In the fuel cells disclosed in Patent Documents 1 and 2, the gas channels meander vertically and extend horizontally in a wavy pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-186052 [Patent Document 2] Japanese Patent Application Publication No. 2019-175834 Summary of the Invention [Problem to be solved by the invention]

[0005] The gas (hydrogen gas, oxygen gas, or air) flowing through the gas flow passage contains water vapor. Some of the water vapor in the gas is liquefied within the gas flow passage. Most of the water in the gas flow passage is expelled from the outlet by the force of the gas, but some water remains in the valleys of the waves in the gas flow passage. This specification provides a structure that can reduce the amount of water remaining in the valleys of the gas flow passage in a fuel cell whose separator has wavy gas flow passages. [Means for solving the problem]

[0006] The fuel cell disclosed in this specification includes a membrane electrode assembly, a separator adjacent to the membrane electrode assembly, and a gas flow channel through which fuel gas, oxygen gas, or air flows. The gas flow channel is provided on the surface of the separator facing the membrane electrode assembly. The gas flow channel has a corrugated shape that meanders vertically and extends horizontally. The gas flow channel alternates between upper convex curved portions that are curved convexly upward and lower convex curved portions that are curved convexly downward, and the lower convex curved portions are shorter than the upper convex curved portions. By making the lower convex curved portions shorter than the upper convex curved portions, water remaining in the lower convex curved portions is more easily blown away downstream by the force of the gas. In other words, the amount of water remaining in the gas flow channel can be reduced.

[0007] An example of a specific shape of the gas flow path is as follows: The upward convex curved portion of the gas flow path follows a curve of a sine wave with a pitch A and an amplitude B, from an angle of 0 to an angle of 180 degrees. The downward convex curved portion of the gas flow path follows a curve of a sine wave with a pitch C and an amplitude D, from an angle of 180 to an angle of 360 degrees. Here, A>C and B>D.

[0008] The downstream end of the wavy gas flow path (the downstream end in the gas flow direction) preferably ends in an upward convex curve, so that no water remains at the downstream end of the gas flow path.

[0009] The separator may have multiple gas flow paths. For example, the gas flow path includes a first gas flow path and a second gas flow path adjacent to and vertically below the first gas flow path. In this case, the separator may have the following structural features: Each of the first gas flow path and the second gas flow path has a linear extension portion extending horizontally from the downstream end (downstream end in the gas flow direction) of the wavy portion of the gas flow path. The first and second gas flow paths are connected by a connecting flow path extending obliquely downward along the gas flow from the linear extension portion of the first gas flow path to the linear extension portion of the second gas flow path. By adopting such a structure, water discharged from the first gas flow path reliably flows downstream.

[0010] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is an exploded perspective view of the fuel cell according to the embodiment. [Figure 2] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] A fuel cell 10 according to an embodiment will be described with reference to the drawings. FIG. 1 shows an exploded perspective view of the fuel cell 10. The fuel cell 10 includes a membrane electrode assembly 20 (MEA 20) and a separator 30. As mentioned above, "MEA" stands for Membrane Electrode Assembly. The MEA 20 has a structure in which an electrolyte membrane 22 is sandwiched between a pair of electrodes (anode layer 21p and cathode layer 21n). The electrodes include catalyst layers that promote reactions.

[0013] A separator 30 is adjacent to each side of the MEA 20. The fuel cell 10 includes a plurality of MEAs 20 and a plurality of separators 30. The plurality of MEAs 20 and the plurality of separators 30 are stacked alternately one by one. In FIG. 1, only a pair of separators 30 and one MEA 20 sandwiched between them are shown.

[0014] The fuel cell 10 includes various components in addition to the MEA 20 and the separators 30, but these are not shown or described. A stack of multiple MEAs 20 and multiple separators 30 is sometimes called a fuel cell stack in the narrow sense.

[0015] The separator 30 is electrically conductive, corrosion-resistant, and gas-impermeable, and is typically made of a carbon-based material and a metal-based material.

[0016] The separator 30 has a wavy gas flow channel 31 on the surface facing the MEA 20. As mentioned above, since the MEAs 20 are arranged on both sides of the separator 30, the separator 30 has a gas flow channel 31 on each of its two surfaces. The gas flow channels 31 are grooves formed in the separator 30, and when the separator 30 is coupled to the MEA 20, the upper openings of the grooves are closed, allowing gas to flow in one direction. Oxygen gas (or air) flows through the gas flow channel 31 facing the anode layer 21p of the MEA 20, and hydrogen gas flows through the gas flow channel 31 facing the cathode layer 21n. Gas is supplied from a gas inlet 38, a portion of which is used for reaction, and the remainder is discharged from a gas outlet 39. The gas flowing through the gas flow channel 31 diffuses to the catalyst layer (electrode) of the MEA 20 and reacts there. Note that gas flows in opposite directions in the gas flow channels 31 formed on one surface of the separator 30 and the gas flow channels 31 formed on the other surface. A gas inlet 38 (gas inlet 38 of the gas flow path 31 provided on one side of the separator 30) and a gas outlet 39 (gas outlet 39 of the gas flow path 31 provided on the other side of the separator 30) are provided on one side of the separator 30.

[0017] As will be described later, the gas flow path 31 includes an upwardly convexly curved portion 32 and a downwardly convexly curved portion 33, but the reference numerals (31, 32) are omitted in Fig. 1. The upwardly convexly curved portion 32 and the downwardly convexly curved portion 33 are shown in Fig. 2.

[0018] In the coordinate system of FIG. 1, the +Z direction corresponds to the vertically upward direction. The XY plane corresponds to the horizontal plane. The +X direction corresponds to the direction in which gas flow path 31 extends. The meaning of each axis of the coordinate system is the same in FIG. 2.

[0019] FIG. 2 shows a plan view of separator 30. FIG. 2 also shows separator 30 as viewed from the normal direction of its wide surface. Separator 30 in FIG. 2 has four gas flow paths 31. For ease of explanation, gas flow paths may be referred to as 31a, 31b, 31c, and 31d from vertically above to below. When referring to each of the four gas flow paths without distinction, they will be referred to as gas flow path 31.

[0020] Each gas flow path 31 includes a wavy portion (wave portion) when viewed horizontally, an introduction path 37 connecting the gas inlet 38 to the wave portion, a straight extension portion 34 connecting the gas outlet 39 to the wave portion, and connecting paths 35, 36.

[0021] The wavy portion extends laterally (horizontally) while meandering up and down when viewed horizontally. For ease of explanation, the wavy portion of the gas flow path 31 is divided into an upper convex curved portion 32 that is curved convexly upward (vertically upward) and a lower convex curved portion 33 that is curved convexly downward (vertically downward) when viewed horizontally. The wavy portion of the gas flow path 31 is made up of multiple upper convex curved portions 32 and multiple lower convex curved portions 33 that are alternately connected one by one. In Figure 2, only the gas flow path 31a is labeled with the reference numeral 32 (upper convex curved portion) and the reference numeral 33 (lower convex curved portion), and the reference numerals 32 and 33 are not shown for the remaining gas flow paths 31b-31d.

[0022] The curves of the upward convex curved portion 32 and the downward convex curved portion 33 both follow a sine wave. However, the length of the downward convex curved portion 33 is shorter than the length of the upward convex curved portion 32. As shown in FIG. 2, the upward convex curved portion 32 follows the curved portion S1a of the sine wave S1 with a pitch A and an amplitude B, which extends from an angle of 0 to 180 degrees. The downward convex curved portion 33 follows the curved portion S2a of the sine wave S2 with a pitch C and an amplitude D, which extends from an angle of 180 to 360 degrees. Here, the vertical axis of the sine wave coordinate system coincides with the vertical direction. The pitch A is greater than the pitch C, and the amplitude B is greater than the amplitude D. These relationships ensure that the length of the downward convex curved portion 33 is shorter than the length of the upward convex curved portion 32. Note that in FIG. 2, the horizontal axis of the sine wave is in degrees, but the symbols A and C represent the numerical values ​​when the pitch of the sine wave is expressed as a length. The symbols B and D, which represent the amplitude, also have a length dimension.

[0023] When the upward convex curved portion 32 and the downward convex curved portion 33 satisfy the relationships of pitch A > pitch C and amplitude B > amplitude D, the following advantages are obtained. The gas (hydrogen gas, oxygen gas, or air) flowing through the gas flow path 31 contains water vapor. Some of the water vapor liquefies in the gas flow path 31. In the gas flow path 31, water accumulates in the valleys of the wavy gas flow path 31 (i.e., the downward convex curved portion 33). Most of the water in the gas flow path 31 is discharged from the outlet by the momentum of the gas, but some water remains in the valleys of the waves in the gas flow path 31. When the relationships of pitch A > pitch C and amplitude B > amplitude D are satisfied, the water remaining in the downward convex curved portion 33 is more likely to flow over the upward convex curved portion 32 downstream due to the momentum of the gas. A gas flow path 31 in which the relationships of pitch A > pitch C and amplitude B > amplitude D are satisfied can reduce the amount of water remaining in the gas flow path 31.

[0024] 2, the downstream end (downstream end in the gas flow direction) of the wavy portion of the gas flow channel 31 ends in an upward convex curved portion 32. By employing such a structure, no water remains at the downstream end of the wavy portion.

[0025] As shown in FIG. 2 , gas flow path 31b is adjacent to and vertically below gas flow path 31a. Each of gas flow paths 31a, 31b has a linear extension 34 extending horizontally from the downstream end of the corrugated portion. Gas flow paths 31a, 31b are connected by a connecting path 35 that extends obliquely downward along the gas flow from the linear extension 34 of the upper gas flow path 31a to the linear extension 34 of the lower gas flow path 31b. Similarly, gas flow paths 31c, 31d are adjacent to each other vertically. Gas flow path 31c is located above gas flow path 31d. Each of gas flow paths 31c, 31d has a linear extension 34 extending horizontally from the downstream end. Gas flow paths 31c, 31d are connected by a connecting path 35 that extends obliquely downward along the gas flow from the linear extension 34 of the upper gas flow path 31c to the linear extension 34 of the lower gas flow path 31d. Furthermore, the linear extension 34 of gas flow path 31b and the linear extension 34 of gas flow path 31d are connected by a connecting flow path 36 that extends obliquely downward along the gas flow from the linear extension 34 of the upper gas flow path 31b to the linear extension 34 of the lower gas flow path 31d. A gas outlet 39 is located at the tip of the linear extension 34 of the lowest gas flow path 31d.

[0026] The upstream ends of the plurality of gas flow passages 31a-31d are connected to a gas inlet 38 via an introduction passage 37. The gas inlet 38 is located above the wavy portion of the uppermost gas flow passage 31.

[0027] Of the two vertically adjacent gas flow paths 31a and 31b, the upper gas flow path 31a may be referred to as the first gas flow path and the lower gas flow path 31b may be referred to as the second gas flow path. In this case, the connection structure of the two adjacent gas flow paths can be expressed as follows: The first gas flow path 31a and the second gas flow path 31b are connected by a connection path 35 that extends obliquely downward along the gas flow from the linear extension 34 of the first gas flow path 31a to the linear extension 34 of the second gas flow path 31b. The same applies to the gas flow paths 31c and 31d. That is, the first gas flow path 31c and the second gas flow path 31d are connected by a connection path 35 that extends obliquely downward along the gas flow from the linear extension 34 of the first gas flow path 31c to the linear extension 34 of the second gas flow path 31d.

[0028] The features of the fuel cell 10 of the embodiment are summarized as follows: The separator 30 has a wavy gas flow path 31. The gas flow path 31 is a groove provided in the separator 30. The gas flow path 31 has a wavy shape that meanders vertically and extends laterally (horizontally). In the wavy portion of the gas flow path 31, upper convex curved portions 32 that are curved convexly upward and lower convex curved portions 33 that are curved convexly downward are alternately connected. The lower convex curved portions 33 are shorter than the upper convex curved portions 32.

[0029] When viewed along the normal to separator 30 (the normal to the surface on which gas flow path 31 is formed), upward convex curved portion 32 follows a curve of a sine wave with pitch A and amplitude B, which extends from angle 0 to angle 180 degrees, and downward convex curved portion 33 follows a curve of a sine wave with pitch C and amplitude D, which extends from angle 180 to angle 360 ​​degrees, where A>C and B>D. In other words, pitch A is longer than pitch C, and amplitude B is greater than amplitude D. Therefore, downward convex curved portion 33 is shorter than upward convex curved portion 32. In other words, upward convex curved portion 32 is curved convexly upward in the vertical direction, and downward convex curved portion 33 is curved convexly downward in the vertical direction.

[0030] The following points should be noted regarding the technology described in the embodiment: The separator 30 may have five or more flow channels extending in parallel.

[0031] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0032] 10: fuel cell 20: membrane electrode assembly 21n: cathode layer 21p: anode layer 22: electrolyte membrane 30: separator 31, 31a-31d: gas flow path 32: upward convex curved portion 33: downward convex curved portion 34: straight extension portion 35, 36: connecting flow path 37: introduction path 38: gas inlet 39: gas outlet

Claims

1. a membrane electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes; a separator adjacent to the membrane electrode assembly; a gas flow channel provided on a surface of the separator facing the membrane electrode assembly; It is equipped with The gas flow path has a wave-like shape that meanders vertically and extends horizontally, and upper convex curved portions that are curved convexly upward and lower convex curved portions that are curved convexly downward are alternately connected, and the lower convex curved portions are shorter than the upper convex curved portions.

2. 2. The fuel cell of claim 1, wherein the upward convex curved portion follows a curve of a sine wave with a pitch A and an amplitude B, the curve extending from an angle of 0 degrees to an angle of 180 degrees, and the downward convex curved portion follows a curve of a sine wave with a pitch C and an amplitude D, the curve extending from an angle of 180 degrees to an angle of 360 degrees, and wherein A>C and B>D.

3. 3. The fuel cell according to claim 1, wherein a downstream end of the wavy portion of the gas flow path terminates in the upwardly convex curved portion.

4. the gas flow path includes a first gas flow path and a second gas flow path adjacent to and vertically below the first gas flow path, each of the first gas flow passage and the second gas flow passage has a linear extension portion extending horizontally from the downstream end; 4. The fuel cell according to claim 3, wherein the first and second gas flow paths are connected by a connecting flow path that extends obliquely downward along the gas flow from the linear extension portion of the first gas flow path to the linear extension portion of the second gas flow path.

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