BIPOLAR PLATE WITH MEDIA REGULATION AND FUEL CELL STACK

Abstract

A bipolar plate for a fuel cell is provided having an active region and a marginal region surrounding the active region, and having a first media guide having a first passage and a second media guide having a second passage, and having a media duct extending through the active region and fluidically connecting the first passage to the second passage, wherein the first passage and/or the second passage is associated with a diaphragm, which is adjustable by an actuator to establish or to regulate the flow cross section of the first passage and/or of the second passage. A fuel cell stack having a fuel cell with such a bipolar plate is also provided.

Claims

1. A bipolar plate for a fuel cell, the bipolar plate having an active region and a marginal region surrounding the active region, and the bipolar plate comprising: a first media guide having a first passage; and a second media guide having a second passage; and a media duct extending through the active region and fluidically connecting the first passage to the second passage, wherein the first passage and/or the second passage is associated with a diaphragm, which is adjustable by an actuator to establish or to regulate the flow cross section of the first passage and/or of the second passage.

2. The bipolar plate according to claim 1, wherein the diaphragm is elliptical.

3. The bipolar plate according to claim 1, wherein the cross sectional shape of the diaphragm is a polygon.

4. The bipolar plate according to claim 1, wherein the diaphragm is mounted rotatably at or in the first passage and/or that the diaphragm is mounted rotatably at or in the second passage.

5. The bipolar plate according to claim 1, wherein the diaphragm is mounted movably on or in the first passage and/or that the diaphragm is mounted movably on or in the second passage.

6. The bipolar plate according to claim 1, wherein the first media guide has a plurality of first passages and the second media guide has a plurality of second passages, the first passages are fluidically joined together with the second passages by media ducts running through the active region, and at least two of the first passages and/or at least two of the second passages are each associated with a diaphragm, adjustable by the actuator, for adapting the flow cross section of the passages.

7. The bipolar plate according to claim 6, wherein the diaphragms are individually adjustable by the actuator.

8. The bipolar plate according to claim 6, wherein the plurality of the diaphragms form a comb with comb teeth and recesses arranged between the comb teeth.

9. The bipolar plate according to claim 6, wherein the plurality of the diaphragms form a lattice structure with lattice walls and lattice recesses arranged between the lattice walls.

10. A fuel cell stack formed from a plurality of fuel cells stacked one on another in a stacking direction, each fuel cell comprising: at least one bipolar plate according to claim 1; and a membrane electrode assembly.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0019] Further benefits, features, and details will emerge from the claims, the following description of embodiments, and the drawings.

[0020] FIG. 1 shows a schematic representation of the bipolar plate.

[0021] FIG. 2 shows a schematic sectional view of the bipolar plate.

[0022] FIG. 3 shows a schematic representation of the fuel cell stack.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a bipolar plate 1 for a fuel cell having an active region 3 and a marginal region 4 surrounding the active region 3. The marginal region 4 has three first media guides 10 formed as first media ports, namely, a media port 10a for supplying the first reactant, a media port 10b for supplying the second reactant and a media port 10c for supplying the coolant to the active region 3 of the bipolar plate 1. Furthermore, three second media guides 7 are present, formed as second media ports, namely a media port 7a for removal of the first reactant, a media port 7b for removal of the second reactant, and a media port 7c for removal of the coolant. Between the first media guide 10 and the second media guide 7 there are media ducts 8 extending over the active region 3, forming a respective flow field for the particular operating medium.

[0024] The first media guides 10 have a plurality of first passages 5. The second media guides 7 have multiple second passages 6. Furthermore, a plurality of media ducts 8 are formed and run through the active region 3 of the bipolar plate 1. The media ducts 8 fluidically connect the first passages 5 of the first media guides 10 to the second passages 6 of the respective second media guides 7. The media ducts 8 are shown simplified in FIG. 1. Thus, the media ducts 8 may be formed as a media duct network, which may run meandering through the active region 3 of the bipolar plate 1. In particular, the media ducts 8 run open on one side, in order to supply the media to the active regions of the layers adjacent to the bipolar plate 1. The first passages 5 and the second passages 6 are formed inside a bipolar plate body 15, so that the passages 5, 6 tunnel under the bipolar plate 1.

[0025] FIG. 2 shows that the first passages 5 are associated with a diaphragm 9, which can be moved, in particular pushed, using an actuator, not shown, to establish or regulate the flow cross section of the first passage 5. This makes it possible to dynamically control the media guide or the media mass flow through the bipolar plate 1. For ease of drawing, not every one of the first passages 5 is associated with a diaphragm 9. In some embodiments, however, each of the first passages 5 and each of the second passages 6 is associated with a diaphragm 9. The diaphragms 9 may have an elliptical, circular, or polygonal cross sectional shape.

[0026] The diaphragm 9 may be mounted movably at or in the passage 5, 6, so that a pushing of the diaphragm 9 by the actuator results in a changing of the flow cross section of the passage 5, 6. The diaphragm 9 can be arranged in front of the passage 5, 6 or in the passage 5, 6. Furthermore, the diaphragm 9 can also be configured to be pushed through or installed in the passage 5, 6. The passages 5, 6 can be formed as simple passage openings or as a passage duct.

[0027] Alternatively, the flow cross section of the passages 5, 6 can also be changed by a rotatable mounting of the diaphragm 9 on or in the passages 5, 6.

[0028] The bipolar plate 1 described in FIGS. 1 and 2 can be integrated in a fuel cell stack 14 having many fuel cells 2 stacked one on another in a stacking direction stack. This is shown as an example in FIG. 3. For this, between every two such bipolar plates 1 there is placed a membrane electrode assembly, in order to supply them with the reactant through the flow fields of the bipolar plates 1. This stacking produces a media space extending substantially parallel to the stacking direction. Through these media guides, the reactant and the coolant are taken to the fuel cells 2. In the present instance, the diaphragms 9 of the bipolar plate are formed as a comb 11 having comb teeth 12 and recesses 13 arranged between the comb teeth 12. This plurality of diaphragms 9, formed as a comb 11, can be moved using the actuator. In order to reduce the flow cross section of the passages 5, 6, the comb teeth 12 can at least partly close the passages 5,6. On the other hand, if the recesses 13 are situated in front of the passages 5, 6, the passages are not closed and the media mass flow can move unhindered into or through the passages 5, 6 into the media ducts 8, and hence into the particular flow field. This enables a dynamic control of the media in the bipolar plate 1 and thus in the fuel cell stack 14. It will be noticed that the fuel cell stack 14 shown can be supplemented with external headers, so that the diaphragm 9 is introduced into the axially extending media space created by them.

[0029] Aspects of the various embodiments described above can be combined to provide further embodiments. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.