Sealing element for sealing a fuel cell stack against leakage of operating media

Abstract

The presented invention relates to a sealing element (100) for sealing a fuel cell stack (200) against leakage of operating media. The sealing element (100) comprises: - a base body (101), wherein a number of recesses (103) for the flow of operating media are formed in the base body (101), wherein the base body (101) forms a structured surface (107) on the edge (105) of at least one recess (103) of the number of recesses (103), wherein the structured surface comprises a plurality of structural elements (111) raised relative to a base (109) of the edge.

Description

The present invention relates to a sealing element for sealing a fuel cell stack against leaks of operating media, to a fuel cell stack and to a fuel cell system according to the appended claims.Prior ArtIn fuel cell systems, liquid water may form during operation, which accumulates particularly in the region between respective last fuel cells and respective end plates of a fuel cell stack.A collection of liquid water may damage a fuel cell stack.Disclosure of the InventionIn the context of the present invention, a sealing element, a fuel cell stack and a fuel cell system are provided. Further features and details of the invention are evident from the respective dependent claims, the description and the drawings. Features and details which are described in connection with the sealing element according to the invention naturally also apply in connection with the fuel cell stack according to the invention or the fuel cell system according to the invention and vice versa, so that with regard to the disclosure reference is or can always be made to the individual aspects of the invention in a mutually alternating manner.The present invention serves in particular to provide a possibility for a robust fuel cell system.According to a first aspect of the present invention, a sealing element for sealing a fuel cell stack against leaks of operating media is thus provided.The seal element presented comprises a base body, wherein a number of recesses for flowing operating media are formed in the base body, wherein the base body forms a structured surface on the edge of at least one recess of the number of recesses, and wherein the structured surface comprises a plurality of structural elements raised in the direction of the recess with respect to a base of the edge.In the context of the present invention, a base of an edge is understood to mean a region of the base body of the present sealing element that runs uniformly or flat and is unprocessed or in which no structural elements form. The structural elements rise out of the base or on the base. Accordingly, the base of the edge is completely closed or forms a closed surface, while the structured surface is open in regions or forms an only partially closed surface.The present invention is based on a sealing element that is arranged on respective last or uppermost / lowermost fuel cells of a fuel cell stack and that comprises recesses that have an edge or circumference, the surface of which is structured, in particular frayed or has gaps.The structural elements extend from a base at the edge of a respective recess in the direction of the recess, in particular a center of the recess. Therefore, the structural elements are in particular planar or flat with the remaining base body.Liquid water produced during operation of the fuel cell stack is drawn into the structured surface on the surface of the sealing element due to capillary forces, so that accumulation of liquid water on the fuel cells is minimized.The main body of the seal element presented can consist, for example, of polyethylene naphthalate (PEN) and can therefore be at least moderately hydrophilic.A base body made of PEN is particularly stable and durable.It is provided in particular that the structured surface is assigned to the outlet side, for example an anode outlet channel.It can be provided that the structural elements are angular or wave-shaped.In particular angular structural elements have proven to be particularly suitable for providing a capillary force.Furthermore, angular structural elements require a particularly large surface area, on which a correspondingly large amount of liquid water can collect and evaporate.Wavy structural elements have proven to be particularly suitable for slowing down a flow through the recess, so that the residence time of liquid water on the structured surface is extended and this evaporates through a wall heat transition from the fuel cell stack to the liquid water.It can be provided that the structural elements are triangular.Triangular structural members have been found to be particularly suitable for providing capillary force and a large surface area for collecting liquid water.In particular, triangular structural elements bring about a discharge of water drops impinging on the structural elements in narrow points formed between respective triangles, where high capillary forces prevail.Furthermore, constrictions formed between two triangles form pockets in which liquid water for the fuel cell stack can collect harmlessly and, if appropriate, evaporate later.It can furthermore be provided that the structural elements comprise equilateral triangles.Equilateral triangles form symmetrical pockets in which a particularly high capillary force prevails.It can furthermore be provided that the structural elements are between 0.1 mm and 0.7 mm high.In particular, triangles having a height of between 0.3 mm and 0.5 mm have proven to be particularly suitable for use in the sealing element presented.According to a second aspect, the present invention relates to a fuel cell stack for a fuel cell system.The fuel cell stack presented comprises a plurality of fuel cells stacked one on top of the other, end plates arranged at opposite ends of the fuel cell stack and a number of intermediate seals which are arranged between respective fuel cells of the plurality of fuel cells, wherein a possible configuration of the presented sealing element is arranged between a respective last fuel cell and a respective end plate of the fuel cell stack.Due to the proposed sealing element, an accumulation of liquid water between respective last fuel cells or edge fuel cells and respective end plates of the proposed fuel cell stack is minimized. Accordingly, the fuel cell stack presented is particularly robust, fault-resistant and durable.It can be provided that a respective recess of a respective sealing element overlaps a respective channel for the flow of operating medium in a respective last fuel cell, wherein a cross section of the respective recess of the sealing element is smaller than a cross section of the overlapped channel.By superimposing respective channels of a fuel cell by the sealing element, in particular structural elements of the sealing element project into a mass flow flowing through the respective channels, so that liquid water located in the mass flow impinges on the structural elements and accumulates there.In particular, the structural elements can swirl the mass flow due to their shape, so that the entire mass flow or a major part of the mass flow comes into contact with the flow element and at least a major part of liquid water located in the mass flow accumulates in the structural elements and evaporates.It can be provided that the structured surface of the edge of the respective recess overlaps the respective channel in a range between 0.1 mm and 0.7 mm.In particular, structural elements having a height of between 0.3 mm and 0.5 mm have proven to be particularly suitable for use in the seal element presented.It can furthermore be provided that the base body overlaps the respective channel in addition to the structured surface in a range between 0.2 mm and 0.9 mm.By means of a region in which the base body itself overlaps a channel, the channel is greatly reduced in size, so that the structural elements project far into the channel and a particularly large amount of mass flow flowing through the channel comes into contact with the structural elements.In particular, it can be provided that the base body itself or the base projects approximately 0.7 mm far into a channel and that structural elements are connected thereto which project 0.5 mm far into the channel. In this case, the structural elements can be triangular, for example isosceles.Alternatively or additionally, it can be provided that the base body itself or the base projects approximately 0.5 mm far into a channel and that structural elements are connected thereto which project 0.3 mm far into the channel. In this case, the structural elements can be in particular wave-shaped.According to a third aspect, the present invention relates to a fuel cell system for converting energy, the fuel cell system including a possible configuration of the present fuel cell stack.Advantages described in detail with respect to the sealing member for sealing a fuel cell stack according to the first aspect of the invention apply equally to the fuel cell stack for a fuel cell system according to the second aspect of the invention and the fuel cell system for converting power according to the third aspect of the invention.Further advantages, features and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination.The following are shown: FIG. 1 shows a schematic illustration of a possible configuration of the sealing element presented, FIG. 2 shows a schematic illustration of a possible configuration of the fuel cell stack presented, FIG. 3 shows a schematic illustration of a possible configuration of the fuel cell system presented.FIG. 1 shows a sealing element 100 for sealing a fuel cell stack against a leakage of operating media.The sealing element 100 comprises a base body 101.A number of recesses 103 for the flow of operating media are formed in the base body 101.A structured surface 107 is formed on the edge 105 of a respective recess 103, which comprises a plurality of structural elements 111 raised with respect to a base 109 of the edge 105.The structural elements 111 are shown triangularly in the present case by way of example and have the effect that these liquid water accumulate there on account of capillary force applied between the structural elements 111 or building up and evaporate efficiently on account of a surface area which is particularly large by the structural elements 111.Referring to FIG. 2, a fuel cell stack 200 for a fuel cell system is shown.The fuel cell stack 200 comprises a plurality of fuel cells 201 stacked on top of each other, end plates 203 arranged at opposite ends of the fuel cell stack 200, a number of intermediate seals 205 arranged between respective fuel cells 201 of the plurality of fuel cells 201, and a number of possible configurations of the sealing element 100 according to FIG. 1.In this case, a sealing element 100 is arranged in each case between a respective last fuel cell 201 and a respective end plate 203 of the fuel cell stack 200. Accordingly, the fuel cell stack 200 comprises two different sealing types, namely, on the one hand, the intermediate seals 205 and, on the other hand, the sealing elements 100.FIG. 3 illustrates a fuel cell system 300 for converting energy.The fuel cell system comprises the fuel cell stack 200 according to FIG. 2 and a number of ancillary units 301 for supplying the fuel cell stack 200 with operating media.

Claims

Sealing element (100) for sealing a fuel cell stack (200) against a leak of operating media, wherein the sealing element (100) comprises: - a base body (101), wherein a number of recesses (103) for flowing operating media are formed in the base body (101), wherein the base body (101) forms a structured surface (107) at the edge (105) of at least one recess (103) of the number of recesses (103), wherein the structured surface comprises a plurality of structural elements (111) raised in the direction of the recess with respect to a base (109) of the edge.Sealing element (100) according to Claim 1, characterized in that the structural elements (111) are angular or wave-shaped.Sealing element (100) according to claim 1 or 2, characterised in that the structural elements (111) are triangular.Sealing element (100) according to one of the preceding claims, characterized in that the structural elements (111) comprise equilateral triangles.Sealing element (100) according to one of the preceding claims, characterized in that the structural elements (111) are between 0.1 mm and 0.7 mm high.Fuel cell stack (200) for a fuel cell system (300), the fuel cell stack (200) comprising: - a plurality of fuel cells (201) stacked one on top of the other, - end plates (203) arranged at opposite ends of the fuel cell stack (200), - a number of intermediate seals (205) arranged between respective fuel cells (201) of the plurality of fuel cells (201), wherein a sealing element (100) according to one of claims 1 to 5 is arranged between a respective last fuel cell (201) and a respective end plate (203) of the fuel cell stack (200).Fuel cell stack (200) according to Claim 6, characterized in that a respective recess (103) of a respective sealing element (100) overlaps a respective channel for the flow of operating medium in a respective last fuel cell (201), wherein a cross section of the respective recess (103) of the sealing element (100) is smaller than a cross section of the overlapped channel.Fuel cell stack (200) according to claim 6 or 7, characterised in that the structured surface (107) of the edge of the respective recess (103) overlaps the respective channel in a range between 0.1 mm and 0.7 mm.Fuel cell stack (200) according to one of the preceding claims 6 to 8, characterized in that the base body (101) overlaps the respective channel in addition to the structured surface (107) in a range between 0.2 mm and 0.9 mm.A fuel cell system (300) for converting energy, the fuel cell system (300) comprising a fuel cell stack (200) according to any one of claims 6 to 9.

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