JP2023004041A - fuel cell stack - Google Patents

Abstract

To provide a fuel cell stack capable of buying time for liquid water to flow in a gas manifold.SOLUTION: In a fuel cell stack 11, a plurality of power generation cells 12 are stacked in a vertical direction Z, each power generation cell being configured to generate power by using fuel gas. Each power generation cell 12 includes a support frame 18 that supports a membrane electrode assembly 17, and a pair of separators 19 that holds the support frame 18 between the separators. In the support frame 18 and the pair of separators 19, there are formed fuel gas supply holes 22 forming a fuel gas supply passage 28 which extends in the vertical direction Z and through which the fuel gas flows. On the peripheral edges of the fuel gas supply holes 22 in the pair of separators 19, there are provided a first protrusion 42 and a second protrusion 44, respectively. The first protrusion 42 and the second protrusion 44 in the pair of separators 19 are offset in the circumferential direction of the fuel gas supply hole 22 while the positions of the first and second protrusions partially overlap each other in the vertical direction Z.SELECTED DRAWING: Figure 1

Description

The present invention relates to fuel cell stacks.

2. Description of the Related Art Conventionally, as a fuel cell stack, for example, the one disclosed in Patent Document 1 is known. Such a fuel cell stack is formed by horizontally stacking a plurality of rectangular plate-shaped unit cells. A single cell includes a MEGA plate, and an anode-side separator and a cathode-side separator that sandwich the MEGA plate. The MEGA plate has a MEGA (membrane electrode gas diffusion layer assembly) and a frame member joined around the MEGA.

The MEGA has a structure in which a cathode electrode and an anode electrode are arranged on both sides of an electrolyte membrane, respectively, and one gas diffusion layer is arranged on each of the outer surfaces of the cathode electrode and the anode electrode. Manifold holes constituting gas manifolds of the fuel cell stack are formed through the respective ends of the frame member and the separators.

JP 2019-192444 A

By the way, the fuel cell stack as described above has the following problems when used with the gas manifold extending in the vertical direction. That is, when the fuel cell stack is operated at a high temperature and then stopped and the temperature drops to a low temperature, liquid water adheres to the inner wall of the gas manifold due to condensation of water vapor contained in the gas in the gas manifold. Liquid water adhering to the inner wall of the gas manifold flows down inside the gas manifold due to gravity.

Therefore, in cold regions, the liquid water flowing down the gas manifold may flow into the pipes connected to the gas manifold from below and freeze, causing malfunction of the valves installed in the pipes. . Therefore, there is still room for improvement in keeping liquid water generated by condensation of water vapor in the gas manifold for a long time.

Means for solving the above problems and their effects will be described below.
A fuel cell stack that solves the above problems is a fuel cell stack in which a plurality of power generation cells that generate power using gas are stacked in a vertical direction, and each power generation cell includes a support frame that supports a membrane electrode assembly. and a pair of separators sandwiching the support frame, wherein through holes are formed in the support frame and the pair of separators to form a gas manifold extending in a vertical direction and through which the gas flows, and the separator in the pair of separators A convex portion is provided on each of the peripheral edges of the through hole, and the convex portions of the pair of separators are partially overlapped with each other in the vertical direction and are displaced in the circumferential direction of the through hole. is the gist.

According to this configuration, liquid water such as condensed water and residual water that has condensed and adhered to the inner wall of the gas manifold flows down through the through-holes of the power generation cells that constitute the gas manifold. At this time, in the through holes of the pair of separators of each power generation cell, projections are formed so that the positions of the separators partially overlap each other in the vertical direction and are displaced in the circumferential direction. Therefore, the liquid water flowing downward through the through-holes (gas manifolds) of the power generating cells collides with the projections of the through-holes of the separators of the power generating cells one by one, and flows while changing the flow direction. Therefore, compared to the case where the liquid water flows down straight through the gas manifold, the liquid water can flow for a longer period of time inside the gas manifold. That is, it is possible to gain time for the liquid water to flow through the gas manifold.

1 is an end view of an embodiment fuel cell stack; FIG. FIG. 2 is an exploded perspective view of a power generation cell; FIG. 4 is an enlarged plan view of the first fuel gas supply hole of the first separator; FIG. 4 is an enlarged plan view of a second fuel gas supply hole of the second separator; FIG. 4 is a schematic diagram showing a part of the inner wall of the fuel gas supply passage; FIG. 11 is an enlarged plan view of the first fuel gas supply hole of the first separator of the modified example; FIG. 11 is an enlarged plan view of a second fuel gas supply hole of a second separator of a modified example; FIG. 11 is an enlarged plan view of the first fuel gas supply hole of the first separator of another modified example; FIG. 11 is an enlarged plan view of a second fuel gas supply hole of a second separator of another modified example;

An embodiment of a fuel cell stack will be described below with reference to the drawings.
As shown in FIG. 1, a fuel cell stack 11 includes a plurality of rectangular plate-shaped power generation cells 12 that generate power using a fuel gas containing hydrogen and an oxidant gas containing oxygen. It has a cell laminate 13 laminated in the following manner. End plates 16 are arranged at both upper and lower ends of the cell laminate 13 via terminal plates 14 for current collection and insulating plates 15 for insulation.

As shown in FIGS. 1 and 2, each power generation cell 12 is made of synthetic resin and has a frame-like shape and supports a rectangular sheet-like membrane electrode assembly 17 (MEA: Membrane Electrode Assembly) in the central opening. and a pair of metal separators 19 . A pair of separators 19 sandwich the membrane electrode assembly 17 and the support frame 18 in the vertical direction Z. As shown in FIG. Of the pair of separators 19 , the upper one is a first separator 20 and the lower one is a second separator 21 .

Each power generation cell 12 is supplied with a fuel gas to a portion on one side (anode side) of the membrane electrode assembly 17 in the vertical direction Z and an oxidizing gas is supplied to a portion on the other side (cathode side) of the membrane electrode assembly 17. Electricity is generated based on the electrochemical reaction of the gas and the oxidant gas in the membrane electrode assembly 17 . A plurality of (six in this example) holes penetrate through both ends of each power generation cell 12 in the long side direction, that is, both ends of the support frame 18, the first separator 20, and the second separator 21 in the long side direction. It is formed by

These six holes are a fuel gas supply hole 22, a fuel gas discharge hole 23, an oxidant gas supply hole 24, an oxidant gas discharge hole 25, a coolant supply hole 26, and a coolant discharge hole 27 as examples of through holes. It is said that Each fuel gas supply hole 22 extends in the vertical direction Z to form a fuel gas supply passage 28 as an example of a gas manifold through which fuel gas as an example of gas flows. As an example, each fuel gas supply hole 22 in this embodiment has a rectangular shape.

Each fuel gas discharge hole 23 extends in the vertical direction Z to form a fuel gas discharge passage 29 through which the fuel gas is discharged. Each oxidant gas supply hole 24 extends in the vertical direction Z to form an oxidant gas supply passage (not shown) through which the oxidant gas is supplied. Each oxidizing gas discharge hole 25 extends in the vertical direction Z to form an oxidizing gas discharge passage (not shown) through which the oxidizing gas is discharged. Each cooling medium supply hole 26 extends in the vertical direction Z to form a cooling medium supply passage (not shown) to which a cooling medium such as cooling water is supplied. Each cooling medium discharge hole 27 extends in the vertical direction Z to form a cooling medium discharge passage (not shown) through which the cooling medium is discharged.

As shown in FIG. 1, in the fuel cell stack 11, gaskets 30 seal between the terminal plate 14 and the separator 19, between the support frame 18 and the separator 19, and between the separators 19. FIG. A fuel gas supply port 31 and a fuel gas discharge port 32 are formed through the terminal plate 14, the insulating plate 15, and the end plate 16 positioned at the lower end of the fuel cell stack 11, respectively. The fuel gas supply port 31 and the fuel gas discharge port 32 communicate with the fuel gas supply passage 28 and the fuel gas discharge passage 29, respectively.

A gas supply pipe 34 extending from a gas tank 33 containing fuel gas is connected to the fuel gas supply port 31 . A pressure regulating valve 35 for adjusting the pressure of the fuel gas supplied from the gas tank 33 through the gas supply pipe 34 to the fuel gas supply port 31 is provided at an intermediate position of the gas supply pipe 34 .

An upper end side of a discharge pipe 36 extending in the vertical direction Z is connected to the fuel gas discharge port 32 . Unreacted fuel gas containing moisture is discharged from the fuel gas discharge port 32 to the discharge pipe 36 . A gas-liquid separator 37 for separating moisture from the unreacted fuel gas discharged from the fuel gas discharge port 32 and an on-off valve 38 are provided in the middle of the discharge pipe 36 .

The on-off valve 38 is arranged below the gas-liquid separator 37 in the discharge pipe 36 . The on-off valve 38 is normally closed, and is opened when the water separated from the unreacted fuel gas by the gas-liquid separator 37 is discharged. A side portion of the gas-liquid separator 37 and a position between the pressure regulating valve 35 and the fuel gas supply port 31 in the gas supply pipe 34 are connected by a connecting pipe 39 extending in the horizontal direction. A pump 40 is provided in the middle of the connecting pipe 39 to send the unreacted fuel gas from which water has been separated by the gas-liquid separator 37 toward the gas supply pipe 34 .

The terminal plate 14, the insulating plate 15, and the end plate 16 positioned at the lower end of the fuel cell stack 11 are provided with an oxidant gas supply port (not shown) and an oxidant gas discharge port (not shown) penetrating them. are formed respectively. The oxidant gas supply port and the oxidant gas discharge port communicate with the oxidant gas supply passage (not shown) and the oxidant gas discharge passage (not shown), respectively. Pipes (not shown) are connected to the oxidant gas supply port and the oxidant gas outlet, respectively.

A terminal plate 14, an insulating plate 15, and an end plate 16 positioned at the lower end of the fuel cell stack 11 are provided with a cooling medium supply port (not shown) and a cooling medium outlet (not shown), respectively. formed. The cooling medium supply port and the cooling medium discharge port communicate with the cooling medium supply passage (not shown) and the cooling medium discharge passage (not shown), respectively. Pipes (not shown) are connected to the cooling medium supply port and the cooling medium discharge port, respectively.

Next, the configuration of each fuel gas supply hole 22 of the first separator 20 and the second separator 21 will be described in detail.
As shown in FIGS. 2 and 3 , the fuel gas supply holes 22 of the first separator 20 are used as first fuel gas supply holes 41 . First protrusions 42 as an example of a plurality of protrusions are provided along the periphery of the first fuel gas supply hole 41 at intervals in the circumferential direction of the first fuel gas supply hole 41 . Three first protrusions 42 are arranged on each side of the first separator 20 in the long side direction at the periphery of the first fuel gas supply hole 41 . Two first protrusions 42 are arranged on both sides of the first separator 20 in the short side direction at the periphery of the first fuel gas supply hole 41 .

The first protrusions 42 on both sides in the long side direction of the first separator 20 at the periphery of the first fuel gas supply hole 41 are arranged in the short side direction of the first separator 20 at the periphery of the first fuel gas supply hole 41 . The width in the circumferential direction is smaller than that of each of the first projections 42 on both sides of the . Each first protrusion 42 protrudes inward and has a substantially semicircular shape when viewed in the vertical direction Z. As shown in FIG.

As shown in FIGS. 2 and 4 , the fuel gas supply holes 22 of the second separator 21 are used as second fuel gas supply holes 43 . Second protrusions 44 , which are an example of a plurality of protrusions, are provided along the periphery of the second fuel gas supply hole 43 at intervals in the circumferential direction of the second fuel gas supply hole 43 . Two second protrusions 44 are arranged on both sides of the second separator 21 in the long side direction at the periphery of the second fuel gas supply hole 43 . One second convex portion 44 is arranged on each side portion of the second separator 21 in the short side direction at the periphery of the second fuel gas supply hole 43 . One second protrusion 44 is arranged at each of the four corners on the periphery of the second fuel gas supply hole 43 .

Each of the second projections 44 on both sides of the second separator 21 in the long side direction at the periphery of the second fuel gas supply hole 43 extends in the short side direction of the second separator 21 at the periphery of the second fuel gas supply hole 43 . The length in the circumferential direction is shorter than each of the second protrusions 44 on both sides of the . Each second protrusion 44 protrudes inward and has a substantially semicircular shape when viewed in the vertical direction Z. As shown in FIG.

As shown in FIGS. 2 to 4, the second protrusions 44 on both sides in the long side direction of the second separator 21 at the peripheral edges of the second fuel gas supply holes 43 are located at the peripheral edges of the first fuel gas supply holes 41. As shown in FIGS. The shape and size are the same as those of the first protrusions 42 on both sides of the first separator 20 in the long side direction of . The second protrusions 44 on both side portions in the short side direction of the second separator 21 at the periphery of the second fuel gas supply hole 43 are arranged in the short side direction of the first separator 20 at the periphery of the first fuel gas supply hole 41 . It has the same shape and size as the first projections 42 on both sides.

As shown in FIGS. 3 to 5, the position of the second protrusion 44 is shifted in the circumferential direction of the second fuel gas supply hole 43 with respect to the position of the first protrusion 42 . Each of the second protrusions 44 is configured such that both ends of the second fuel gas supply hole 43 in the circumferential direction are aligned with one end of each of the two first protrusions 42 adjacent to each other in the circumferential direction of the first fuel gas supply hole 41 . They are arranged so as to overlap in the vertical direction Z.

That is, the second convex portion 44 is arranged so as to straddle two adjacent first convex portions 42 in the circumferential direction of the first fuel gas supply hole 41 when viewed from the vertical direction Z. As shown in FIG. That is, the first convex portion 42 and the second convex portion 44 of the pair of separators 19 are partially overlapped with each other in the vertical direction Z so as to form the first fuel gas supply hole 41 and the second fuel gas supply hole. 43 are offset in the circumferential direction. In other words, the first protrusions 42 and the second protrusions 44 are arranged in a staggered manner on the inner wall of the fuel gas supply passage 28 .

Next, the action of the fuel cell stack 11 will be described.
As shown in FIG. 1 , when generating power in the fuel cell stack 11 , the fuel gas in the gas tank 33 is supplied to the fuel gas supply passage 28 through the gas supply pipe 34 and the fuel gas supply port 31 . In this case, the pressure of the fuel gas supplied to the fuel gas supply passage 28 is regulated by the pressure regulating valve 35 . The fuel gas supplied to the fuel gas supply passage 28 is supplied to the anode-side surface of the membrane electrode assembly 17 of each power generation cell 12 .

On the other hand, an oxidant gas is supplied from an oxidant gas supply port (not shown) through an oxidant gas supply passage (not shown) to the cathode side surface of the membrane electrode assembly 17 of each power generation cell 12 . A film formed by the oxidant gas supplied to the cathode-side surface of the membrane electrode assembly 17 of each power generation cell 12 and the fuel gas supplied to the anode-side surface of the membrane electrode assembly 17 of each power generation cell 12 Electricity is generated based on the electrochemical reaction at the electrode assembly 17 .

The unreacted fuel gas in the membrane electrode assembly 17 contains water and is discharged to the discharge pipe 36 through the fuel gas discharge passage 29 and the fuel gas discharge port 32 . After water is separated from the unreacted fuel gas discharged to the discharge pipe 36 by the gas-liquid separator 37 , the fuel gas is sent to the gas supply pipe 34 via the connecting pipe 39 by the pump 40 . The unreacted fuel gas delivered to the gas supply pipe 34 is supplied again to the fuel gas supply passage 28 together with the fuel gas from the gas tank 33 . The unreacted oxidant gas in the membrane electrode assembly 17 is discharged from an oxidant gas supply port (not shown) through an oxidant gas discharge passage (not shown).

Further, since the temperature of the fuel cell stack 11 is high during the operation of the fuel cell stack 11, water in the fuel cell stack 11 becomes water vapor. In particular, since the fuel gas supplied to the fuel gas supply passage 28 contains moisture, water vapor exists in the fuel gas supply passage 28 . When the operation of the fuel cell stack 11 is stopped, the temperature of the fuel cell stack 11 drops, so the water vapor in the fuel gas supply passage 28 condenses into liquid water and adheres to the inner wall of the fuel gas supply passage 28 .

The liquid water adhering to the inner wall of the fuel gas supply passage 28 normally flows downward due to gravity. Liquid water flowing downward along the inner wall of the fuel gas supply passage 28 flows from the fuel gas supply passage 28 into the gas supply pipe 34 via the fuel gas supply port 31 . Therefore, when the fuel cell stack 11 is used in cold regions where the air temperature is below freezing, the liquid water flowing into the gas supply pipe 34 freezes, clogging the inside of the gas supply pipe 34 and causing the pressure regulating valve 35 to malfunction. It will freeze. As a result, it becomes difficult to supply the fuel gas from the gas tank 33 to the fuel gas supply passage 28, so that there is a problem that the starting of the fuel cell stack 11 becomes difficult.

In this regard, in the fuel cell stack 11 of the present embodiment, the first protrusions 42 and the second protrusions 44 are provided in a staggered manner on the inner wall of the fuel gas supply passage 28 . Therefore, as shown in FIG. 5, the liquid water flowing down the inner wall of the fuel gas supply passage 28 collides with the first projection 42 and the second projection 44 one by one and flows slowly while changing the flow direction. .

Therefore, compared to the case where the liquid water flows straight down the inner wall of the fuel gas supply passage 28, the liquid water flows over the inner wall of the fuel gas supply passage 28 for a longer time. That is, it is possible to gain time for the liquid water to flow along the inner wall of the fuel gas supply passage 28 . That is, the liquid water can be kept in the fuel gas supply passage 28 for a long time. Therefore, when the fuel cell stack 11 is used in cold regions where the air temperature is below freezing, the liquid water flowing on the inner wall of the fuel gas supply passage 28 freezes before reaching the gas supply pipe 34 .

As a result, even when the fuel cell stack 11 is used in a place where the air temperature is below freezing, such as in cold regions, freezing of liquid water in the gas supply pipe 34 is suppressed. That is, clogging of the inside of the gas supply pipe 34 and freezing of the pressure regulating valve 35 due to freezing of the liquid water are suppressed. Therefore, the startability of the fuel cell stack 11 is improved in places where the temperature is below freezing, such as in cold regions.

According to the embodiment detailed above, the following effects are exhibited.
(1) In the fuel cell stack 11, a plurality of power generation cells 12 that generate power using fuel gas are stacked in the vertical direction Z. As shown in FIG. Each power generation cell 12 includes a support frame 18 supporting a membrane electrode assembly 17 and a pair of separators 19 sandwiching the support frame 18 . The support frame 18 and the pair of separators 19 are formed with a fuel gas supply hole 22 extending in the vertical direction Z to form a fuel gas supply passage 28 through which the fuel gas flows. A first protrusion 42 and a second protrusion 44 are provided on the periphery of the fuel gas supply hole 22 in the pair of separators 19, respectively. The first convex portion 42 and the second convex portion 44 of the pair of separators 19 overlap each other in the vertical direction Z and are shifted in the circumferential direction of the fuel gas supply hole 22 .

According to this configuration, liquid water such as condensed water and residual water condensed and adhered to the inner wall of the fuel gas supply passage 28 flows through the fuel gas supply holes 22 of the power generation cells 12 constituting the fuel gas supply passage 28. flows downwards. At this time, in the fuel gas supply holes 22 of the pair of separators 19 of each power generation cell 12, the first protrusion 42 and the second protrusion 42 are displaced in the circumferential direction while partially overlapping each other in the vertical direction Z. Two convex portions 44 are formed respectively. Therefore, the liquid water flowing downward through the fuel gas supply hole 22 (fuel gas supply passage 28) of each power generation cell 12 flows into the first protrusion 42 and the second protrusion 42 of the fuel gas supply hole 22 of the separator 19 of each power generation cell 12. It collides with the projections 44 one by one and flows while changing the flow direction. Therefore, compared to the case where the liquid water flows straight down the fuel gas supply passage 28, the liquid water can flow through the fuel gas supply passage 28 for a longer time. That is, it is possible to gain time for the liquid water to flow through the fuel gas supply passage 28 .

(Change example)
The above embodiment can be implemented with the following modifications. Moreover, the above embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

- As shown in FIGS. 6 and 7, the first convex portion 42 provided around the periphery of the first fuel gas supply hole 41 of the first separator 20 and the second protrusion 42 provided around the periphery of the second fuel gas supply hole 43 of the second separator 21 The two projections 44 may both have a triangular shape when viewed from the vertical direction Z.

As shown in FIGS. 8 and 9, the first convex portion 42 provided on the periphery of the first fuel gas supply hole 41 of the first separator 20 and the second protrusion 42 provided on the periphery of the second fuel gas supply hole 43 of the second separator 21 The shape of the two convex portions 44 may both be trapezoidal (rectangular) when viewed from the vertical direction Z.

- One first protrusion 42 and one second protrusion 44 are provided on the periphery of the first fuel gas supply hole 41 of the first separator 20 and the periphery of the second fuel gas supply hole 43 of the second separator 21. can be

the number, size, The shape and the like may be changed as appropriate.

・The fuel gas discharge holes 23 (through holes) forming the fuel gas discharge passages 29 (gas manifolds) in the pair of separators 19 of each power generation cell 12 are provided with the first convex portion 42 and the second convex portion 44, respectively. good too.

・The first convex portion 42 and the second convex portion 44 are provided in the oxidant gas supply holes 24 (through holes) that form the oxidant gas supply passages (gas manifolds) in the pair of separators 19 of each power generation cell 12. may

The first protrusion 42 and the second protrusion 44 are provided in the oxidant gas discharge holes 25 (through holes) that form the oxidant gas discharge passages (gas manifolds) in the pair of separators 19 of each power generation cell 12. may

- The fuel cell stack 11 may be used in a fuel cell system mounted on an electric vehicle, a hybrid vehicle, or the like, or may be used in a stationary fuel cell system installed outdoors.

DESCRIPTION OF SYMBOLS 11... Fuel cell stack 12... Power generation cell 13... Cell laminate 14... Terminal plate 15... Insulating plate 16... End plate 17... Membrane electrode assembly 18... Support frame 19... Separator 20... First separator 21... Second separator 22 ... Fuel gas supply hole as an example of a through hole 23 ... Fuel gas discharge hole 24 ... Oxidant gas supply hole 25 ... Oxidant gas discharge hole 26 ... Coolant supply hole 27 ... Coolant discharge hole 28 ... As an example of a gas manifold Fuel gas supply passage 29 Fuel gas discharge passage 30 Gasket 31 Fuel gas supply port 32 Fuel gas discharge port 33 Gas tank 34 Gas supply pipe 35 Pressure control valve 36 Discharge pipe 37 Gas-liquid separator 38 ... On-off valve 39 ... Connection pipe 40 ... Pump 41 ... First fuel gas supply hole 42 ... First projection as an example of a projection 43 ... Second fuel gas supply hole 44 ... Second projection as an example of a projection Z...vertical direction

Claims (2)

A fuel cell stack in which a plurality of power generation cells that generate power using gas are vertically stacked,
Each power generation cell includes a support frame that supports a membrane electrode assembly, and a pair of separators sandwiching the support frame,
The support frame and the pair of separators are formed with through-holes extending in the vertical direction to form a gas manifold through which the gas flows,
A convex portion is provided on each peripheral edge of the through hole in the pair of separators,
The fuel cell stack, wherein the convex portions of the pair of separators are partially overlapped with each other in the vertical direction and are displaced in the circumferential direction of the through hole. 2. The apparatus according to claim 1, wherein a plurality of said protrusions are provided at intervals in the circumferential direction of said through-holes on the periphery of said through-holes in said pair of said separators of said power generation cells. fuel cell stack.

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