JP5274908B2 - Fuel cell stack - Google Patents

Description

  The present invention has at least first and second electrolyte / electrode structures in which a pair of electrodes are disposed on both sides of an electrolyte, and is a single unit interposed between the first and second electrolyte / electrode structures. This metal separator relates to a fuel cell stack having a fuel gas flow path on the surface facing the first electrolyte / electrode structure, and an oxidant gas flow path on the surface facing the second electrolyte / electrode structure.

  For example, a solid polymer fuel cell employs a solid polymer electrolyte membrane made of a polymer ion exchange membrane. In this fuel cell, an electrolyte membrane / electrode structure (electrolyte / electrode structure) in which an anode catalyst electrode and a cathode electrode made of porous carbon are disposed on both sides of a solid polymer electrolyte membrane, respectively. A unit cell is configured by being sandwiched between separators (bipolar plates). Usually, a fuel cell stack in which a predetermined number of unit cells are stacked is used.

  In the above fuel cell, a fuel gas channel (reactive gas channel) for flowing a fuel gas opposite to the anode side electrode and an oxidant gas for flowing the cathode gas facing the cathode side electrode in the plane of the separator. The oxidant gas flow path (reaction gas flow path) is provided.

  In this case, the condensed water and the water produced by the reaction are likely to stay in the reaction gas flow path, and there is a possibility that the fuel gas and the oxidant gas may not be satisfactorily supplied to the anode side electrode and the cathode side electrode.

  Therefore, for example, a separator disclosed in Patent Document 1 is known. Specifically, as shown in FIG. 9, the separator 1 has a collective portion 3 connected to the gas inlet 2, and a plurality of branch paths 4 extend from the collective portion 3 in a comb shape. Each branch passage 4 communicates with the collecting portion 6 through the drainage groove 5, and the collecting portion 6 communicates with the gas outlet 7.

  The drainage groove 5 is set to have a smaller cross-sectional area than the branch channel 4, and the flow rate of the gas passing through the drainage groove 5 is increased, so that dew condensation water is fed into the collecting portion 6 and discharged from the gas outlet 7. , And.

JP 2006-4702 A

  However, in the above prior art, the drainage groove 5 having a small cross-sectional area communicates with the collecting portion 6, so that the flow rate of the gas supplied to the collecting portion 6 decreases. Thereby, there exists a problem that the dew condensation water sent to the gathering part 6 cannot be reliably discharged | emitted to the gas outlet 7. FIG.

  The present invention solves this type of problem, and is provided with a fuel gas channel and an oxidant gas channel on both sides of the metal separator, and in particular, drains efficiently and reliably from the fuel gas channel. An object of the present invention is to provide a fuel cell stack capable of satisfying the requirements.

  The present invention has at least first and second electrolyte / electrode structures in which a pair of electrodes are disposed on both sides of an electrolyte, and is a single unit interposed between the first and second electrolyte / electrode structures. This metal separator relates to a fuel cell stack having a fuel gas flow path on the surface facing the first electrolyte / electrode structure, and an oxidant gas flow path on the surface facing the second electrolyte / electrode structure. is there.

The fuel gas flow path, provided with a throttle portion which communicates with the outlet buffer to the end of the fuel gas outlet side, the outlet buffer has a plurality of embossments protruding fuel gas passage side, the narrowed portion The channel width dimension and the channel depth are reduced, and the channel depth is set to be the same as the depth of the outlet buffer portion which is the height of the emboss .

Also, the oxidant gas flow path is preferably provided with a flared portion for expanding the and the throttle portion of the back surface shape communicating with the outlet buffer acid agent gas outlet side.

  Furthermore, the fuel gas channel and the oxidant gas channel are preferably configured as meandering corrugated channels.

  In the present invention, since the throttle portion is provided at least on the fuel gas outlet side of the fuel gas flow path, the flow velocity increases, the pressure loss increases, and the drainage performance in the separator surface improves favorably.

  Moreover, the flow path depth of the throttle part is set to be the same as the depth of the outlet buffer part. Therefore, the reaction product water can be smoothly and efficiently discharged from the throttle portion to the outlet buffer portion.

  FIG. 1 is an exploded perspective view of a fuel cell stack 10 according to an embodiment of the present invention. 2 is a cross-sectional view of the fuel cell stack 10 taken along line II-II in FIG. 1, and FIG. 3 is a cross-sectional view of the fuel cell stack 10 taken along line III-III in FIG.

  The fuel cell stack 10 is configured by stacking a plurality of power generation units 12 in the direction of arrow A (horizontal direction) (see FIGS. 2 and 3). The power generation unit 12 includes a first metal separator 14, a first electrolyte membrane / electrode structure (MEA) 16 a, a second metal separator 18, a second electrolyte membrane / electrode structure (MEA) 16 b, and a third metal separator 20 in this order. Laminated.

  As shown in FIG. 1, the upper end edge of the power generation unit 12 in the long side direction (arrow C direction) communicates with each other in the direction of arrow A to oxidize for supplying an oxidant gas, for example, an oxygen-containing gas. An agent gas supply communication hole 22a and a fuel gas supply communication hole 24a for supplying a fuel gas, for example, a hydrogen-containing gas, are provided.

  The lower end edge of the long side direction of the power generation unit 12 communicates with each other in the direction of arrow A, the fuel gas discharge communication hole 24b for discharging the fuel gas, and the oxidant gas discharge for discharging the oxidant gas. A communication hole 22b is provided.

  At one edge of the power generation unit 12 in the short side direction (arrow B direction), there is provided a cooling medium supply communication hole 26a that communicates with each other in the direction of arrow A and supplies a cooling medium. A cooling medium discharge communication hole 26b for discharging the cooling medium is provided at the other end edge in the short side direction.

  The first and second electrolyte membrane / electrode structures 16a and 16b include, for example, a solid polymer electrolyte membrane 28 in which a perfluorosulfonic acid thin film is impregnated with water, and a cathode side sandwiching the solid polymer electrolyte membrane 28 An electrode 30 and an anode side electrode 32 are provided. The cathode side electrode 30 and the anode side electrode 32 are formed by uniformly applying a gas diffusion layer made of carbon paper or the like and porous carbon particles carrying a platinum alloy on the surface thereof to the surface of the gas diffusion layer. An electrode catalyst layer. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 28.

  As shown in FIGS. 1 and 5, an oxidant gas supply communication hole 22a and an oxidant gas discharge communication hole 22b communicate with the surface 14a of the first metal separator 14 facing the first electrolyte membrane / electrode structure 16a. A first oxidant gas flow path 34 is formed.

  The first oxidant gas flow path 34 has a plurality of wave-shaped first oxidant gas flow path grooves 34 a that meander and extend in the direction of arrow C (long-side direction). An inlet buffer part 36a and an outlet buffer part 36b are provided at the upper and lower ends of the first oxidant gas channel 34 in the direction of arrow C. The inlet buffer part 36a and the outlet buffer part 36b have a plurality of embossments (convex parts).

  Between the surface 14 b of the first metal separator 14 and the surface 20 b of the adjacent third metal separator 20, the cooling medium supply communication hole 26 a and the cooling medium correspond to the back surface shape of the first oxidant gas flow path 34. A first cooling medium flow path 40a communicating with the discharge communication hole 26b is formed.

  As shown in FIG. 6, the surface 18a of the second metal separator 18 facing the first electrolyte membrane / electrode structure 16a has a first fuel gas communicating with the fuel gas supply communication hole 24a and the fuel gas discharge communication hole 24b. A flow path 42 is formed.

  The first fuel gas channel 42 has a plurality of wave-shaped first fuel gas channel grooves 42a that meander and extend in the direction of arrow C (long side direction). An inlet buffer 44a and an outlet buffer 44b are provided at the upper and lower ends of the first fuel gas passage 42 in the direction of arrow C. The inlet buffer portion 44a and the outlet buffer portion 44b have a plurality of embossments (convex portions).

  An inlet throttle portion 42b that communicates with the inlet buffer portion 44a and an outlet throttle portion 42c that communicates with the outlet buffer portion 44b are provided on the inlet side and the outlet side of the first fuel gas flow channel groove portion 42a (at least on the outlet side). Provided.

  As shown in FIGS. 3 and 4, the outlet throttle portion 42c has a channel width dimension and a channel depth that decrease toward the outlet buffer portion 44b, and the channel depth is the same as that of the outlet buffer portion 44b. Set to the same depth. Similarly, the flow path width dimension and flow path depth of the inlet throttle part 42b decrease toward the inlet buffer part 44a, and the flow path depth is set to be the same as the depth of the inlet buffer part 44a.

  As shown in FIG. 7, on the surface 18b of the second metal separator 18 facing the second electrolyte membrane / electrode structure 16b, the oxidant gas supply communication hole 22a and the oxidant gas discharge communication hole 22b communicate with each other. An oxidant gas flow path 48 is formed. The second oxidant gas flow channel 48 has a plurality of wave-shaped second oxidant gas flow channel grooves 48a that meander and extend in the direction of arrow C (long side direction).

  An inlet buffer 50a and an outlet buffer 50b are provided at the upper and lower ends of the second oxidant gas channel 48 in the direction of arrow C. The inlet buffer part 50a and the outlet buffer part 50b are provided with a plurality of embossments (convex parts).

  On the inlet side and the outlet side of the second oxidant gas flow path groove portion 48a, an inlet expanding portion 48b communicating with the inlet buffer portion 50a and an outlet expanding portion 48c communicating with the outlet buffer portion 50b are provided. The inlet expanding portion 48b expands toward the inlet buffer portion 50a due to the back surface shape of the inlet throttle portion 42b, while the outlet expanding portion 48c expands toward the outlet buffer portion 50b due to the back surface shape of the outlet throttle portion 42c. Open (see FIGS. 3 and 4).

  As shown in FIG. 8, on the surface 20a of the third metal separator 20 facing the second electrolyte membrane / electrode structure 16b, the second fuel gas that communicates the fuel gas supply communication hole 24a and the fuel gas discharge communication hole 24b. A flow path 54 is formed.

  The second fuel gas channel 54 has a plurality of wave-shaped second fuel gas channel grooves 54a that meander and extend in the direction of arrow C (long side direction). An inlet buffer portion 56a and an outlet buffer portion 56b are provided at the upper and lower ends of the second fuel gas passage 54 in the direction of arrow C. The inlet buffer portion 56a and the outlet buffer portion 56b are provided with a plurality of embossments (convex portions).

  The first oxidant gas channel 34 may be configured in the same manner as the second oxidant gas channel 48 described above. Similarly, the second fuel gas channel 54 may be configured in the same manner as the first fuel gas channel 42 described above.

  Between the surface 20b of the 3rd metal separator 20 and the surface 14b of the adjacent 1st metal separator 14, the 2nd cooling medium flow path 40b which connects the cooling-medium supply communication hole 26a and the cooling-medium discharge | emission communication hole 26b. Is formed (see FIG. 1).

  A first seal member 60, a second seal member 62, and a third seal member 64 are integrally formed on the surfaces of the first metal separator 14, the second metal separator 18, and the third metal separator 20.

  The operation of the fuel cell stack 10 configured as described above will be described below.

  First, as shown in FIG. 1, in each power generation unit 12 constituting the fuel cell stack 10, an oxidant gas such as an oxygen-containing gas, for example, air is supplied to the oxidant gas supply communication hole 22a, and the fuel gas A fuel gas such as a hydrogen-containing gas, for example, pure hydrogen is supplied to the supply communication hole 24a. Further, a coolant such as pure water or ethylene glycol is supplied to the coolant supply passage 26a.

  The oxidant gas is introduced into the first oxidant gas flow path 34 of the first metal separator 14 and the second oxidant gas flow path 48 of the second metal separator 18 from the oxidant gas supply communication hole 22a. For this reason, the oxidant gas moves vertically downward along the cathode-side electrodes 30 of the first and second electrolyte membrane / electrode structures 16a and 16b.

  On the other hand, the fuel gas is introduced into the first fuel gas channel 42 of the second metal separator 18 and the second fuel gas channel 54 of the third metal separator 20 from the fuel gas supply communication hole 24a. Therefore, the fuel gas moves vertically downward along the anode side electrodes 32 of the first and second electrolyte membrane / electrode structures 16a and 16b.

  As described above, in the first and second electrolyte membrane / electrode structures 16a and 16b, the oxidizing gas supplied to each cathode-side electrode 30 and the fuel gas supplied to each anode-side electrode 32 are electrodes. It is consumed by an electrochemical reaction in the catalyst layer and power is generated.

  Next, the oxidant gas consumed by being supplied to the cathode side electrode 30 is discharged to the oxidant gas discharge communication hole 22b. Similarly, the fuel gas consumed by being supplied to the anode side electrode 32 is discharged to the fuel gas discharge communication hole 24b.

  The cooling medium is introduced into the first and second cooling medium flow paths 40 a and 40 b formed between the power generation units 12. The cooling medium flows along an arrow B direction (horizontal direction in FIG. 1), and the second electrolyte membrane / electrode structure 16b of one power generation unit 12 and the first electrolyte membrane / electrode structure of the other power generation unit 12 are arranged. The body 16a is cooled. That is, the cooling medium is not cooled between the first and second electrolyte membrane / electrode structures 16a and 16b in the power generation unit 12, so-called thinning cooling, and then discharged to the cooling medium discharge communication hole 26b.

  In this case, in this embodiment, as shown in FIGS. 3, 4, and 6, a plurality of first fuel gas passages constituting the first fuel gas passage 42 are formed on the surface 18 a of the second metal separator 18. A groove portion 42a is provided, and an outlet throttle portion 42c communicating with the outlet buffer portion 44b is provided on the outlet side of the first fuel gas flow channel groove portion 42a.

  For this reason, the flow rate of the fuel gas is increased at the outlet throttle portion 42c, and the discharge of the produced water can be improved satisfactorily, and the decrease in the electrode surface pressure can be suppressed.

Specifically, as shown in FIGS. 2 and 3, if the flow rates of the first fuel gas flow channel groove 42a and the outlet throttle portion 42c are constant, the flow break of the first fuel gas flow channel groove 42a will be described. The area A _N and the flow path cross-sectional area A _{S of the} outlet throttle portion 42c have a relationship of A _N > A _S.

Furthermore, the hydraulic diameter D _S of the hydraulic diameter D _N and the outlet constricted portion 42c of the first fuel gas flow passage groove part 42a, which has a relationship of D _N> D _S, the flow rate of the first fuel gas flow passage groove part 42a V _N and the flow velocity V _S of the outlet throttle portion 42c have a relationship of V _S > V _N.

Then, from the relationship between the pressure loss ΔP = λ × (L / D ) × (ρV 2/2), the pressure loss [Delta] P _S of the pressure loss [Delta] P _N and the outlet constricted portion 42c of the first fuel gas flow passage groove part 42a is ΔP _S > ΔP _N and high pressure loss is obtained.

  Moreover, as shown in FIGS. 3 and 4, the outlet restricting portion 42 c has a channel width dimension and a channel depth that decrease toward the outlet buffer portion 44 b, and the channel depth is equal to the outlet buffer portion. It is set to the same depth as 44b. Therefore, it is possible to obtain an effect that the reaction product water can be discharged smoothly and efficiently from the outlet throttle portion 42c to the outlet buffer portion 44b.

  In particular, when pure hydrogen is used as the fuel gas, the flow rate of the fuel gas on the outlet buffer portion 44b side of the first fuel gas flow channel groove portion 42a is small, and the reverse diffusion of water through the solid polymer electrolyte membrane 28 causes the first. The generated water on the side of the oxidant gas flow channel 48 flows. When the thickness of the solid polymer electrolyte membrane 28 is thin (for example, 50 μm), the amount of reverse diffusion water increases. For this reason, said effect becomes still more remarkable.

  Further, as shown in FIGS. 3 and 7, the surface 18b of the second metal separator 18 is provided with a plurality of second oxidant gas flow channel grooves 48a constituting the second oxidant gas flow channel 48, On the outlet side of the second oxidant gas channel groove portion 48a, an outlet expanding portion 48c communicating with the outlet buffer portion 50b is provided.

  As a result, the pressure loss is reduced on the outlet side of the second oxidant gas channel groove 48a, and in particular, the output of a pump (not shown) for supplying the oxidant gas can be reduced, which is economical. . At that time, an inlet expanding portion 48b communicating with the inlet buffer portion 50a is provided on the inlet side of the second oxidant gas flow channel groove portion 48a. For this reason, the flow rate of the oxidant gas supplied to the second oxidant gas flow path groove 48a is increased satisfactorily, and the drainage is easily improved. In particular, when air is used as the oxidant gas, nitrogen remains on the outlet side of the second oxidant gas flow path groove 48a. Therefore, the generated water can be discharged smoothly by increasing the flow rate of the oxidant gas.

  In the present embodiment, the first fuel gas flow channel 42 and the second oxidant gas flow channel 48 are configured as a plurality of meandering wave-shaped flow channels, but the present invention is not limited to this. For example, The plurality of linear flow paths may be configured.

1 is an exploded perspective view of a fuel cell stack according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the fuel cell stack taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view of the fuel cell stack taken along line III-III in FIG. 1. It is explanatory drawing of the narrowing part and the expansion part of the 2nd metal separator which comprise the said fuel cell stack. It is front explanatory drawing of the 1st metal separator which comprises the said fuel cell stack. It is explanatory drawing of one surface of the said 2nd metal separator. It is explanatory drawing of the other surface of the said 2nd metal separator. It is front explanatory drawing of the 3rd metal separator which comprises the said fuel cell stack. It is explanatory drawing of the separator of patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Electric power generation unit 14, 18, 20 ... Metal separator 16a, 16b ... Electrolyte membrane and electrode structure 22a ... Oxidant gas supply communication hole 22b ... Oxidant gas discharge communication hole 24a ... Fuel gas supply communication hole 24b ... Fuel gas discharge communication hole 26a ... Cooling medium supply communication hole 26b ... Cooling medium discharge communication hole 28 ... Solid polymer electrolyte membrane 30 ... Cathode side electrode 32 ... Anode side electrode 34, 48 ... Oxidant gas flow path 34a, 48a ... Oxidant gas flow path grooves 36a, 44a, 50a, 56a ... Inlet buffer parts 36b, 44b, 50b, 56b ... Outlet buffer parts 40a, 40b ... Cooling medium flow paths 42, 54 ... Fuel gas flow paths 42a, 54a ... Fuel Gas channel groove part 42b ... Inlet restricting part 42c ... Outlet restricting part 48b ... Inlet expanding part 48c ... Outlet expanding part

Claims (3)

A single metal separator having at least first and second electrolyte / electrode structures in which a pair of electrodes are disposed on both sides of the electrolyte, and interposed between the first and second electrolyte / electrode structures, A fuel cell stack having a fuel gas flow path on the surface facing the first electrolyte / electrode structure, and an oxidant gas flow path on the surface facing the second electrolyte / electrode structure,
The fuel gas passage, provided with a throttle portion which communicates with the outlet buffer to the end of the fuel gas outlet side,
The outlet buffer portion has a plurality of embosses protruding toward the fuel gas flow path side,
The fuel cell according to claim 1, wherein the throttle portion is set to have the same width as the depth of the outlet buffer portion in which the flow channel width dimension and the flow channel depth are reduced and the flow channel depth is the height of the emboss. stack. The fuel cell stack according to claim 1, characterized by providing an expanding portion for expanding the oxidant gas flow path, by and back surface shape of the narrowed portion communicated with the outlet buffer acid agent gas outlet side And fuel cell stack.   3. The fuel cell stack according to claim 1, wherein the fuel gas flow path and the oxidant gas flow path are configured as meandering wave-shaped flow paths.

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