Fuel Cell Stack

Abstract

To provide a fuel cell stack capable of reducing the amount of liquid water generated by condensation of water vapor 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 19 that supports a membrane electrode assembly 18, and a pair of separators 20 that holds the support frame 19 between the separators. In each power generation cell 12, there are formed: a fuel gas supply hole 21 forming a fuel gas supply passage 28 which extends in the vertical direction Z and through which the fuel gas flows; and a passage formation hole 22 forming a passage 29 which is adjacent to the fuel gas supply passage 28 and extends in the vertical direction Z. The fuel gas supply passage 28 and the passage 29 are connected to each other at upper ends of the fuel gas supply passage and the passage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fuel cell stack. [Background technology]

[0002] Conventionally, a fuel cell stack is known, for example, as shown in Patent Document 1. Such a fuel cell stack is formed by horizontally stacking a plurality of rectangular plate-shaped power generation cells. Each power generation cell includes a resin-framed membrane electrode assembly, and a first metal separator and a second metal separator that sandwich the resin-framed membrane electrode assembly. The membrane electrode assembly includes a solid polymer electrolyte membrane, and an anode electrode and a cathode electrode that sandwich the solid polymer electrolyte membrane.

[0003] The fuel cell stack is formed with a gas manifold extending horizontally and a drain (passage) extending horizontally below the gas manifold, penetrating each power generating cell. The gas manifold and the drain communicate with each other at one end in the horizontal direction. The drain discharges water generated during operation of the fuel cell stack. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-121562 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the fuel cell stack described above, the gas manifold and the drain extend horizontally and communicate with each other at one end, and the gas manifold is located above the drain. Therefore, even when the fuel cell stack is operated and the temperature becomes high, almost no water vapor contained in the gas in the gas manifold flows into the drain.

[0006] On the other hand, when the operation of the fuel cell stack is stopped and the temperature drops, water vapor condenses in the gas manifold, generating a large amount of liquid water in the gas manifold. If a large amount of liquid water is generated in the gas manifold, in cold regions, the liquid water may flow into pipes connected to the gas manifold and freeze, causing valves in the pipes to malfunction. Therefore, there is still room for improvement in reducing the amount of liquid water generated by condensation of water vapor in the gas manifold. [Means for solving the problem]

[0007] The means for solving the above problems and their effects will be described below. The fuel cell stack that solves the above problem is a fuel cell stack in which a plurality of power generation cells that generate electricity using gas are stacked in the vertical direction, and each of the power generation cells includes a support frame that supports a membrane electrode assembly and a pair of separators that sandwich the support frame, and each of the power generation cells is formed with a first hole that forms a gas manifold extending in the vertical direction through which the gas flows, and a second hole that is adjacent to the gas manifold and forms a passage extending in the vertical direction, and the gas manifold and the passage are connected to each other at their upper ends.

[0008] With this configuration, when the temperature of the fuel cell stack is high, some of the water vapor in the gas manifold flows into the passage, thereby reducing the amount of liquid water generated by condensation of water vapor in the gas manifold when the temperature of the fuel cell stack drops. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an end view of an embodiment of a fuel cell stack. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 2 is an enlarged view of the main part of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a fuel cell stack will be described with reference to the drawings. 1, the fuel cell stack 11 includes a cell stack 14 in which a plurality of rectangular plate-shaped power generating cells 12 that generate power using a fuel gas containing hydrogen and an oxidant gas containing oxygen, and one rectangular plate-shaped dummy cell 13 that does not generate power, are stacked in the thickness direction. The plurality of power generating cells 12 and the one dummy cell 13 are stacked in the vertical direction Z.

[0011] The dummy cell 13 is stacked on the power generating cell 12 located at the upper end of the multiple stacked power generating cells 12. In other words, the dummy cell 13 is located at the upper end of the cell stack 14. End plates 17 are respectively arranged on the upper and lower ends of the cell stack 14, with terminal plates 15 for current collection and insulating plates 16 for insulation therebetween.

[0012] 1 and 2, each power generating cell 12 has a synthetic resin support frame 19 that is formed in a frame shape and supports a rectangular sheet-shaped membrane electrode assembly (MEA) 18 at a central opening, and a pair of metal separators 20. The pair of separators 20 sandwich the membrane electrode assembly 18 and the support frame 19 in the vertical direction Z.

[0013] When fuel gas is supplied to one side (anode side) of the membrane electrode assembly 18 in the vertical direction Z and oxidant gas is supplied to the other side (cathode side), each power generating cell 12 generates power based on an electrochemical reaction between the fuel gas and the oxidant gas in the membrane electrode assembly 18. A plurality of holes (seven in this example) are formed penetrating both ends of each power generating cell 12 in the longitudinal direction, i.e., both ends of each support frame 19 and each separator 20 in the longitudinal direction.

[0014] These seven holes are a fuel gas supply hole 21 as an example of a first hole, a passage forming hole 22 as an example of a second hole, 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. Each fuel gas supply hole 21 extends in the vertical direction Z and forms a fuel gas supply passage 28 as an example of a gas manifold to which a fuel gas as an example of a gas is supplied.

[0015] Each passage forming hole 22 is disposed adjacent to the fuel gas supply hole 21 on the opposite side to the membrane electrode assembly 18 side, and is adjacent to the fuel gas supply passage 28 on the opposite side to the membrane electrode assembly 18 side to form a passage 29 extending in the vertical direction Z. The fuel gas supply passage 28 and the passage 29 communicate with each other at their upper ends. Each fuel gas supply hole 21 in this embodiment has a rectangular shape, for example. Each passage forming hole 22 in this embodiment has a circular shape, for example. The fuel gas supply hole 21 has a larger area than the passage forming hole 22.

[0016] Each fuel gas discharge hole 23 extends in the vertical direction Z to form a fuel gas discharge passage 30 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 oxidant gas discharge hole 25 extends in the vertical direction Z to form an oxidant gas discharge passage (not shown) through which the oxidant gas is discharged. Each cooling medium supply hole 26 extends in the vertical direction Z to form a cooling medium supply passage (not shown) through 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.

[0017] 1 and 3, the dummy cell 13 is obtained by changing the membrane electrode assembly 18 in the power generating cell 12 to a rectangular sheet-shaped conductor 31 and changing the upper separator 20 to a dummy separator 20a. The dummy cell 13 shares the lower separator 20 with the power generating cell 12. That is, the dummy cell 13 has a support frame 19 supporting the conductor 31 at a central opening, a dummy separator 20a, and a separator 20. The support frame 19 supporting the conductor 31 in the dummy cell 13 is sandwiched between the dummy separator 20a and the separator 20 in the vertical direction Z.

[0018] The dummy separator 20a is obtained by omitting the fuel gas supply hole 21 and the passage forming hole 22 from the separator 20 of the power generation cell 12 and by providing a protrusion 34 on a lower surface 33, which is an example of a wall surface, but otherwise has the same configuration as the separator 20. The dummy cell 13 does not have a membrane electrode assembly 18, and therefore does not generate electricity even when fuel gas and oxidant gas are supplied thereto.

[0019] The lower surface 33 of the dummy separator 20a is located above the communication portion between the fuel gas supply passage 28 and the passage 29. The protrusion 34 is located at a position on the lower surface 33 of the dummy separator 20a corresponding to the communication portion between the fuel gas supply passage 28 and the passage 29. The protrusion 34 is triangular in cross section, and has an inclined surface 35 that decreases in height from the fuel gas supply passage 28 side toward the passage 29 side. The lowest part of the inclined surface 35 corresponds to the passage 29. The highest part of the inclined surface 35 corresponds to the fuel gas supply passage 28.

[0020] As shown in FIG. 1, in the fuel cell stack 11, the spaces between the terminal plate 15 and the separator 20, between the terminal plate 15 and the dummy separator 20a, between the support frame 19 and the separator 20, between the support frame 19 and the dummy separator 20a, and between the separators 20 themselves are sealed by gaskets 36.

[0021] A fuel gas supply port 37, a fuel gas discharge port 38, and a liquid water discharge port 39 are formed through the terminal plate 15, the insulating plate 16, and the end plate 17 located at the lower end of the fuel cell stack 11. The fuel gas supply port 37, the fuel gas discharge port 38, and the liquid water discharge port 39 are connected to the fuel gas supply passage 28, the fuel gas discharge passage 30, and the passage 29, respectively.

[0022] A gas supply pipe 41 extending from a gas tank 40 containing fuel gas is connected to the fuel gas supply port 37. A pressure regulating valve 42 for regulating the pressure of the fuel gas supplied from the gas tank 40 to the fuel gas supply port 37 via the gas supply pipe 41 is provided midway along the gas supply pipe 41.

[0023] An upper end side of a first discharge pipe 43 extending in the vertical direction Z is connected to the fuel gas discharge port 38. Unreacted fuel gas containing moisture is discharged from the fuel gas discharge port 38 to the first discharge pipe 43. A gas-liquid separator 44 that separates moisture from the unreacted fuel gas discharged from the fuel gas discharge port 38 and a first opening / closing valve 45 are provided in the middle of the first discharge pipe 43.

[0024] The first on-off valve 45 is disposed at a position in the first discharge piping 43 below the gas-liquid separator 44. The first on-off valve 45 is normally closed, and is opened when discharging water separated from the unreacted fuel gas in the gas-liquid separator 44. A side portion of the gas-liquid separator 44 and a position in the gas supply piping 41 between the pressure regulating valve 42 and the fuel gas supply port 37 are connected by a connecting pipe 46 extending horizontally.

[0025] A pump 47 is provided at a midpoint of the connecting pipe 46, which sends out unreacted fuel gas after water has been separated in the gas-liquid separator 44, toward the gas supply pipe 41. The upper end of a second discharge pipe 48 extending in the vertical direction Z is connected to the liquid water discharge port 39. A second on-off valve 49 is provided at a midpoint of the second discharge pipe 48. The second on-off valve 49 is normally closed, and is opened when liquid water accumulated in the passage 29 is discharged.

[0026] An oxidant gas supply port (not shown) and an oxidant gas discharge port (not shown) are formed through the terminal plate 15, insulating plate 16, and end plate 17 located at the lower end of the fuel cell stack 11. The oxidant gas supply port and the oxidant gas discharge port are respectively connected to the oxidant gas supply passage (not shown) and the oxidant gas discharge passage (not shown). The oxidant gas supply port and the oxidant gas discharge port are each connected to a pipe (not shown).

[0027] A cooling medium supply port (not shown) and a cooling medium discharge port (not shown) are formed through the terminal plate 15, the insulating plate 16, and the end plate 17 located at the lower end of the fuel cell stack 11. The cooling medium supply port and the cooling medium discharge port are respectively connected to the cooling medium supply passage (not shown) and the cooling medium discharge passage (not shown). The cooling medium supply port and the cooling medium discharge port are respectively connected to pipes (not shown).

[0028] Next, the operation of the fuel cell stack 11 will be described. 1 and 4, when generating electricity in the fuel cell stack 11, fuel gas from a gas tank 40 is supplied to a fuel gas supply passage 28 via a gas supply pipe 41 and a fuel gas supply port 37. In this case, the pressure of the fuel gas supplied to the fuel gas supply passage 28 is adjusted by a pressure regulating valve 42. The fuel gas supplied to the fuel gas supply passage 28 is supplied to the anode side surface of the membrane electrode assembly 18 of each power generating cell 12 located below the dummy cell 13.

[0029] Meanwhile, 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 18 of each power generation cell 12. Then, power is generated based on an electrochemical reaction in the membrane electrode assembly 18 between the oxidant gas supplied to the cathode side surface of the membrane electrode assembly 18 of each power generation cell 12 and a fuel gas supplied to the anode side surface of the membrane electrode assembly 18 of each power generation cell 12.

[0030] The unreacted fuel gas in the membrane electrode assembly 18 contains moisture and is discharged to the first discharge pipe 43 via the fuel gas discharge passage 30 and the fuel gas discharge port 38. The unreacted fuel gas discharged to the first discharge pipe 43 has moisture separated therefrom in a gas-liquid separator 44, and is then sent to the gas supply pipe 41 via a connecting pipe 46 by a pump 47. The unreacted fuel gas sent to the gas supply pipe 41 is supplied again to the fuel gas supply passage 28 together with the fuel gas from the gas tank 40. The unreacted oxidant gas in the membrane electrode assembly 18 is discharged from an oxidant gas supply port (not shown) via an oxidant gas discharge passage (not shown).

[0031] Furthermore, since the temperature of fuel cell stack 11 is high during operation of fuel cell stack 11, the moisture in fuel cell stack 11 turns into water vapor. In particular, since the fuel gas supplied to fuel gas supply passage 28 contains moisture, water vapor is present in fuel gas supply passage 28. In this case, since fuel gas supply passage 28 and passage 29 communicate with each other at their upper ends, some of the water vapor in fuel gas supply passage 28 flows into passage 29.

[0032] When the operation of the fuel cell stack 11 is stopped, the temperature of the fuel cell stack 11 drops, causing the water vapor in the fuel gas supply passage 28 to condense into liquid water W. However, because some of the water vapor in the fuel gas supply passage 28 flows into passage 29 while the fuel cell stack 11 is in operation, the amount of liquid water W generated by the condensation of the water vapor in the fuel gas supply passage 28 is reduced.

[0033] In addition, some of the water vapor in the fuel gas supply passage 28 adheres to the lower surface 33 and the inclined surface 35 of the dummy separator 20a above the fuel gas supply passage 28 and condenses to become liquid water W. Then, this liquid water W flows due to gravity down the inclined surface 35 toward the passage 29 and drips into the passage 29. As a result, the amount of liquid water W dripping from the lower surface 33 of the dummy separator 20a into the fuel gas supply passage 28 is reduced.

[0034] Incidentally, if the passage 29 were not present in the fuel cell stack 11, a large amount of liquid water W would be generated due to condensation of water vapor in the fuel gas supply passage 28. Then, this liquid water W would flow by gravity from the fuel gas supply passage 28 through the fuel gas supply port 37 into the gas supply pipe 41.

[0035] For this reason, when the fuel cell stack 11 is used in a cold region or other place where the temperature falls below freezing, the liquid water W that has flowed into the gas supply pipe 41 freezes, causing the gas supply pipe 41 to become clogged or the pressure regulating valve 42 to freeze. As a result, it becomes difficult for fuel gas to be supplied from the gas tank 40 to the fuel gas supply passage 28, which causes a problem that it becomes difficult to start the fuel cell stack 11.

[0036] In this regard, the fuel cell stack 11 of this embodiment includes a passage 29 that communicates with the fuel gas supply passage 28 at its upper end, and an inclined surface 35 provided above the communication portion between the fuel gas supply passage 28 and the passage 29. Therefore, in the fuel cell stack 11 of this embodiment, some of the water vapor in the fuel gas supply passage 28 can be caused to flow into the passage 29, and some of the liquid water W generated in the fuel gas supply passage 28 by condensation of the water vapor can be led to the passage 29.

[0037] Therefore, when the temperature drops due to the shutdown of the fuel cell stack 11, the amount of liquid water W present in the fuel gas supply passage 28 is reduced, and the amount of liquid water W flowing by gravity from the fuel gas supply passage 28 into the gas supply piping 41 via the fuel gas supply port 37 is also reduced. As a result, even when the fuel cell stack 11 is used in a cold region or other place where the temperature drops below freezing, clogging of the gas supply piping 41 and freezing of the pressure regulating valve 42 due to freezing of the liquid water W are suppressed. This improves the startability of the fuel cell stack 11 in a cold region or other place where the temperature drops below freezing.

[0038] Furthermore, the liquid water W accumulated in the passage 29 can be smoothly discharged to the outside through the second discharge pipe 48 by opening the second on-off valve 49 when the temperature at the location where the fuel cell stack 11 is used is at a temperature at which the liquid water W will not freeze.

[0039] According to the embodiment described above in detail, the following effects are achieved. (1) The fuel cell stack 11 includes a plurality of power generating cells 12 that generate power using fuel gas stacked in the vertical direction Z. Each power generating cell 12 includes a support frame 19 that supports a membrane electrode assembly 18, and a pair of separators 20 that sandwich the support frame 19. Each power generating cell 12 is formed with a fuel gas supply hole 21 that forms a fuel gas supply passage 28 that extends in the vertical direction Z and through which fuel gas flows, and a passage forming hole 22 that forms a passage 29 that is adjacent to the fuel gas supply passage 28 and extends in the vertical direction Z. The fuel gas supply passage 28 and the passage 29 communicate with each other at their upper ends.

[0040] According to this configuration, when the temperature of the fuel cell stack 11 is high, part of the water vapor in the fuel gas supply passage 28 flows into the passage 29, so that it is possible to reduce the amount of liquid water W generated in the fuel gas supply passage 28 by condensation of the water vapor when the temperature of the fuel cell stack 11 drops. Therefore, it is possible to reduce the amount of liquid water W that flows down due to gravity from the fuel gas supply passage 28 into the gas supply piping 41. As a result, it is possible to suppress clogging of the gas supply piping 41 and malfunction of the pressure regulating valve 42 caused by freezing of the liquid water W in the gas supply piping 41 when the temperature of the fuel cell stack 11 drops below freezing.

[0041] (2) In the fuel cell stack 11, the lower surface 33 of the dummy separator 20a located above the communication portion between the fuel gas supply passage 28 and the passage 29 is formed with an inclined surface 35 whose height decreases from the fuel gas supply passage 28 side toward the passage 29 side.

[0042] According to this configuration, when the water vapor in the fuel gas supply passage 28 adheres to the inclined surface 35 and condenses to become liquid water W, the liquid water W flows by gravity along the inclined surface 35 to the passage 29. Therefore, the liquid water W formed by the condensation of the water vapor in the fuel gas supply passage 28 can be suitably guided to the passage 29.

[0043] (Example of change) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other as long as they are not technically inconsistent.

[0044] The inclined surface 35 on the lower surface 33 of the dummy separator 20a may be made more hydrophilic than the other parts of the lower surface 33 other than the inclined surface 35. In this case, the hydrophilicity of the material constituting the protrusion 34 having the inclined surface 35 may be made higher than the hydrophilicity of the material constituting the dummy separator 20a. Alternatively, the inclined surface 35 may be coated with a coating material having a higher hydrophilicity than the material constituting the dummy separator 20a. In this way, when water vapor adheres to the other parts of the lower surface 33 of the dummy separator 20a other than the inclined surface 35 and condenses to become liquid water W, the liquid water W can be made to flow easily to the inclined surface 35.

[0045] The protrusion 34 may be omitted. The protrusion 34 may be formed integrally with the lower surface 33 of the dummy separator 20a, or may be formed separately from the dummy separator 20a and attached to the lower surface 33 of the dummy separator 20a.

[0046] The protrusion 34 may be formed in a cone or pyramid shape. In the power generating cell 12, the fuel gas supply holes 21 and the passage forming holes 22 may be modified to any shape.

[0047] In the power generating cell 12 , the fuel gas supply hole 21 may have the same area as the passage forming hole 22 , or may have an area smaller than that of the passage forming hole 22 . In the power generating cell 12, the fuel gas supply hole 21 and the passage forming hole 22 may have the same shape.

[0048] In the fuel cell stack 11, the gas is an oxidant gas, the first holes are oxidant gas supply holes 24, and the gas manifold is an oxidant gas supply passage (not shown) that extends in the vertical direction Z and through which the oxidant gas is supplied. A passage 29 may be formed so that the upper end of the oxidant gas supply passage and the upper end of the gas manifold communicate with each other.

[0049] In the fuel cell stack 11, the dummy cell 13 may be omitted, and the lower surface of the upper terminal plate 15 may be used as a wall surface located above the communication portion between the fuel gas supply passage 28 and the passage 29, instead of the lower surface 33 of the dummy separator 20a. In this case, the protrusion 34 is provided on the lower surface of the upper terminal plate 15.

[0050] The fuel cell stack 11 may be used in a fuel cell system installed in an electric vehicle or a hybrid vehicle, or may be used in a stationary fuel cell system installed outdoors. [Explanation of symbols]

[0051] 11...Fuel cell stack 12…Power generation cell 13…Dummy cell 14...Cell stack 15…Terminal plate 16…Insulating plate 17…End plate 18...Membrane electrode assembly 19…Support frame 20…Separator 20a…Dummy separator 21...Fuel gas supply hole as an example of a first hole 22... Passage forming hole as an example of a second hole 23...Fuel gas exhaust hole 24...Oxidant gas supply hole 25...Oxidant gas exhaust hole 26…Cooling medium supply hole 27…Cooling medium discharge hole 28...Fuel gas supply passage as an example of a gas manifold 29...Aisle 30...Fuel gas exhaust passage 31...Conductor 33...The bottom surface as an example of a wall surface 34…Convex part 35…Slope surface 36…Gasket 37…Fuel gas supply port 38…Fuel gas exhaust port 39…Liquid water outlet 40…Gas tank 41...Gas supply pipe 42...Pressure regulating valve 43...1st discharge piping 44…Gas-liquid separator 45…First opening and closing valve 46…Connecting pipe 47…Pump 48…Second discharge piping 49…Second on-off valve W…liquid water Z: Vertical direction

Claims

1. A fuel cell stack in which a plurality of power generation cells that generate electricity using gas are stacked vertically, Each of the power generation cells includes a support frame that supports a membrane electrode assembly, and a pair of separators that sandwich the support frame, Each of the power generation cells is formed with a first hole that extends in a vertical direction and forms a gas supply passage through which the gas is supplied, and a second hole that forms a passage adjacent to the gas supply passage and extends in the vertical direction, a gas supply passage and a passage, the gas supply passage and the passage being connected to each other at upper ends thereof;

2. A fuel cell stack in which a plurality of power generation cells that generate electricity using gas are stacked vertically, Each of the power generation cells includes a support frame that supports a membrane electrode assembly, and a pair of separators that sandwich the support frame, Each of the power generation cells is formed with a first hole that extends in a vertical direction and forms a gas manifold through which the gas flows, and a second hole that is adjacent to the gas manifold and forms a passage that extends in the vertical direction, the gas manifold and the passage communicate with each other at their upper ends; a wall surface located above the communication portion between the gas manifold and the passage has an inclined surface whose height decreases from the gas manifold side toward the passage side.

3. 3. The fuel cell stack according to claim 2, wherein the inclined surface of the wall surface is more hydrophilic than a portion of the wall surface other than the inclined surface.

4. A fuel cell stack in which a plurality of power generation cells that generate electricity using gas are stacked vertically, Each of the power generation cells includes a support frame that supports a membrane electrode assembly, and a pair of separators that sandwich the support frame, Each of the power generation cells is formed with a first hole that extends in a vertical direction and forms a gas manifold through which the gas flows, and a second hole that forms a passage that extends in the vertical direction and is adjacent to the gas manifold on an opposite side to the membrane electrode assembly side, A fuel cell stack, wherein the gas manifold and the passage communicate with each other at upper ends thereof.

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