Separator plate for an electrochemical system

Abstract

Separator plate (2) for an electrochemical system (1), comprising: - at least one through-opening (11a-c) for passing a fluid through the separator plate (2), - at least one distribution area (20) having a plurality of first channels (22) and first webs (24) formed between each two first channels (22), - at least one flow field (17) which is in fluid communication with the through-opening (11a-c) via the distribution region (20) and which has a plurality of second channels (26) and second webs (28) formed between each two second channels (26), wherein first ends (32) of the first webs (24) are opposite ends (29) of the second webs (28) and / or merge into ends (29) of at least selected ones of the second webs (28), wherein first distances (A) between the respective first ends (32) of mutually adjacent first webs (24) are inhomogeneous.

Description

The invention relates to a separator plate for an electrochemical system, in particular a fuel cell system.Known electrochemical systems usually comprise a multiplicity of separator plates, which can be designed in particular as bipolar plates, each of which is composed of two individual plates. The separator plates are typically arranged in a stack, so that two adjacent separator plates each enclose an electrochemical cell. The separator plates can serve, for example, for the electrical contacting of the electrodes of the individual electrochemical cells (for example fuel cells) and / or for the electrical connection of adjacent cells (series connection of the cells). The separator plates may also serve to dissipate heat generated in the cells between the separator plates. Such waste heat can arise, for example, during the conversion of electrical or chemical energy in a fuel cell.The separator plates usually each have at least one through-opening. In the separator plate stack of the electrochemical system, the passage openings of the stacked separator plates, which are arranged so as to be aligned or at least partially overlapping, form media channels for the media supply or for the media discharge.The separator plates may also have channel structures for supplying an active region of the separator plate with one or more of the media and / or for transporting away media.The separator plate typically comprises a so-called flow field, which forms the active region of the separator plate, and at least one distribution region, which connects a passage opening to the flow field in a fluid-conducting manner. Depending on the direction of flow out of the flow field or into the flow field, the distribution region can also be referred to as a collection region or have a fluid-collecting function. In the following, the term distribution region includes both a possible fluid-collecting function and a possible function distributing the fluid to the flow field.By means of the distribution region, the fluid which exits from the passage opening typically along a comparatively small edge region can be introduced into the flow field (or vice versa). The latter typically has an inlet region for the fluid which is significantly larger compared to the edge region of the through-opening. This inlet region can extend, for example, along more than half of a width dimension of the separator plate. In order for the fluidic connection of the aforementioned regions or sections of passage opening and flow field to be successful, wherein these regions or sections are generally also not aligned centrally with respect to one another, the fluid-conducting structures and in particular channels of the distribution region have to be aligned suitably. Up to now, this typically results in different channel lengths within the distribution region.It is generally desirable to further improve the efficiency of operation of electrochemical systems. The present application is accordingly directed to this object.According to the invention, it has been recognized that in the case of previous separator plates there is an efficiency improvement potential, in particular in connection with the passage of the fluid through the at least one distribution region. More precisely, it has been recognized that the channel lengths of the distribution region that have typically been different up to now are associated with different and more precisely channel-specific mass flows when flowing through the distribution region. Thus, in the flow field, flows through the channels present there are also generated with a correspondingly different mass flow, depending on the channel of the distribution region to which the channels of the flow field are connected in a fluid-conducting manner.These previously clearly different mass flows arise in particular because the number of channels of the flow field which are connected to a respective channel of the distribution region in a fluid-conducting manner and in particular lie opposite the latter is substantially constant. In other words, in previous solutions, a predominant number of the channels of the distribution region supplies fluid from the through-opening (or vice versa) in each case independently of their respective length. The present invention is, on the other hand, based in particular on the finding that this ratio of channels connected to one another in a fluid-conducting manner can be used as a degree of freedom in order to reduce the difference between the mass flows of the channels when flowing through the distribution region and / or the flow field. In particular, it can be provided that channels of the distribution region having a comparatively short length and thus a higher mass flow are connected to a higher number of channels of the flow field in a fluid-conducting manner than channels of the distribution region having a comparatively long length and thus correspondingly low mass flows. This can be achieved structurally by the inhomogeneous distances disclosed here between webs of the distribution region.In particular, the invention proposes a separator plate for an electrochemical system, having:at least one through opening for passing a fluid through the separator plate,at least one distribution region having a multiplicity of first channels and first webs formed between in each case two first channels,at least one flow field which is in fluid communication with the through opening via the distribution region and which has a multiplicity of second channels and second webs formed between in each case two second channels,wherein first ends of the first webs are opposite ends of the second webs and / or merge into ends of at least selected ones of the second webs, wherein first distances between the respective first ends of mutually adjacent first webs are inhomogeneous.As is generally customary, it can be provided that distances between the ends of the second webs, which face the distribution region and / or merge at least partially into webs located there, are homogeneous. At least these distances can vary less than in comparison with the first distances of the first ends of the distribution region webs. As explained below, the distances under consideration can be considered in each case in the width direction of the separator plate and / or orthogonally to a flow direction (see the following main flow direction) through the flow field.As a result of the inhomogeneous first spacings, the channel width can be varied in the region of the first ends. Additionally or alternatively, the number of those channels of the flow field which are supplied at least predominantly or exclusively with fluid by a respective channel of the distribution region or into which they introduce predominantly or exclusively fluid can be varied. This can be used to vary this number according to the expected mass flows of the distribution area channels. The larger the mass flows, the more channels of the flow field are preferably connected to a channel of the distribution region in a fluid-conducting manner and / or are situated opposite the latter.According to the above, in particular only the first distances between such first webs can be considered, which are adjacent to a channel on both sides or which are arranged between two channels.In other words, according to a further embodiment, the first ends of the first webs can be distributed along a width axis of the separator plate and the distribution region can have a first outermost first web and a second outermost first web, as viewed along the width axis, wherein inner first webs are arranged between these two outermost first webs, and wherein first distances between the respective first ends of mutually adjacent first webs are inhomogeneous for the inner first webs. The respective distances of the outermost webs from an outermost contour delimiting the distribution region cannot be considered intentionally in the present case. This takes into account the fact that in the prior art the distances of the inner first webs are usually homogeneous, although it has been recognized according to the invention that a high potential for efficiency improvements exists, in particular in connection with these inner first webs.The separator plate may be characterized by a longer dimension along a longitudinal axis and a shorter dimension along a width axis that is orthogonal to the longitudinal axis. For example, the separator plate may have a rectangular-like shape or, in other words, a rectangular plan view, each with a correspondingly shorter and a longer dimension. The width axis or width dimension can extend orthogonally to a main flow direction through the flow field. This main flow direction can generally be predefined by the alignment of the channels and / or webs of the flow field. For example, the main flow direction can run parallel to longitudinal axes of the channels and / or webs or coincide with such a longitudinal axis. In the case of corrugated flow fields, the main flow direction corresponds to the macroscopic flow direction, neglecting amplitudes on both sides. Additionally or alternatively, the width axis or an axis parallel thereto may be oriented such that it is opposite, extends along, and / or intersects the first ends of the first webs and / or the ends of the second webs.The expression "opposing" of webs and / or channels can generally be understood to mean that, at the latest in the case of virtual extensions of the webs and / or channels and / or viewed along a respective longitudinal axis, these structures merge into one another or are aligned with one another. Additionally or alternatively, a fluid guided in a channel can be guided into an opposite channel along a flow path, for example a rectilinear or curved flow path, and / or along a flow path which corresponds to an extension of the respective channel longitudinal axes.According to a further embodiment, the separator plate further comprises a transition region in which the first ends of the first webs are opposite the ends of the second webs and / or in which the first ends of the first webs are transition into the ends of the at least selected second webs, wherein the transition region is lowered with respect to the flow field and / or the distribution region with respect to a height axis running perpendicular to a plane surface plane of the separator plate. In particular, the maximum height of the transition region can be considered in comparison with mean maximum heights of the webs of the distribution region and the flow field, wherein this maximum height can be lowered with respect to these mean maximum heights. A transition region lowered in this way provides a free space for receiving further components, such as the overlap region of a reinforcing edge of a membrane electrode unit (MEA).In a manner known per se, the plane of the planar surface can be defined, for example, by an edge of a separator plate and / or by those plane regions which are not deformed as a result of an embossing or deep-drawing process, for example, for forming web-channel structures or beads described herein.According to a further embodiment, the fluid flows in the flow field along a main flow direction, to which all of the explanations above can apply, and:the first webs and / or first channels each run at an angle to this main flow direction, i.e. at an angle different from 0°, and / ora virtual connecting line of the first ends of the first channels runs substantially orthogonally to the main flow direction or at least at an angle of more than 75° and less than 105°, and / orthe distribution region extends along an entire width of the flow field, wherein the width is measured orthogonally to the main flow direction and / or along a width axis of the separator plate explained above, and / orthe first distances are measured orthogonally to the main flow direction. Alternatively, the first distances can be measured orthogonally to the channel longitudinal axis of a second channel enclosed by the two adjacent webs in each case.In principle, the inhomogeneous web spacings and the inhomogeneous channel widths resulting therefrom can occur along the entire width of the flow field.If a wavy connecting line is produced between the first ends of the first channels, the virtual connecting line can be, for example, the connecting line of the wave peaks pointing away from the flow field at the maximum.According to a further embodiment, the distances between the respective ends of mutually adjacent second channels are homogeneous or at least less inhomogeneous than the first distances. Alternatively or additionally, the number of first channels is less than the number of second channels, wherein in particular the number of first channels is not more than half as large or not more than one third as large as the number of second channels. It has been shown that the sought improvement in efficiency can be achieved particularly reliably with these measures.According to a further embodiment, the first ends of the first webs are distributed along a width axis of the separator plate and the distribution region has a first outermost first web and a second outermost first web as viewed along the width axis. These may enclose and / or surround further inner first webs between them.The first outermost first web and in particular its first end can be positioned closer to the through-opening than the second outermost first web and in particular as its first end. In this case, the distances can be measured along or parallel to a plane surface plane and / or surface of the separator plate. For example, the shortest straight lines can be considered, which connect the corresponding first webs and in particular their first ends to the through opening and in particular to a fluid outlet region and / or a geometric center thereof.Viewed along the width axis and from the first outermost first web in the direction of the second outermost first web, the first distances may decrease and / or may not increase at least in sections. Additionally or alternatively, within the first half of a route from the first outermost first land to the second outermost first land, the first distances may be at least on average higher than within the second half of that route. By providing correspondingly distributed distance inhomogeneities, mass flow differences that otherwise occur can be compensated for at least proportionally and the operating efficiency of the electrochemical system can be improved.Additionally or alternatively, the channel lengths in the distribution region can increase at least in sections and / or not decrease and / or be higher within a first half at least on average than within the second half, as viewed along the section from the first outermost first web to the second outermost first web. The distance inhomogeneities described above can represent efficiency-increasing compensations of this channel length distribution.A further development provides that a maximum first distance is present at least between the first outermost first web and a further first web directly adjacent thereto, which may be a correspondingly inner web, and / or that a minimum first distance is present at least between the second outermost first web and a further first web directly adjacent thereto, which may be a correspondingly inner web.Within the scope of this disclosure, outermost structures delimiting the distribution region, which are not enclosed on both sides by channels and / or adjoin channels on both sides, cannot be considered as first webs of the distribution region. This relates, for example, to plateau surfaces and / or sealing beads delimiting the distribution region, which in each case typically only adjoin a single outermost channel of the distribution region.According to a further embodiment, each first channel is configured to supply fluid to or receive fluid from at least one associated second channel, wherein the number of second channels associated with a respective first channel is inhomogeneous. In particular, the number of second channels which are assigned to a respective one of the first inner channels arranged between two inner first webs can be inhomogeneous.According to a further embodiment, a respective width of the first webs is constant or varies by not more than 20% along a respective length of a first web; and / or the respective widths of the first webs are identical and / or deviate from one another by not more than 20%. The mean and / or maximum and / or minimum widths of the first channels, however, can be different from one another-in particular due to the inhomogeneous spacings of the first webs disclosed here. Additionally or alternatively, the widths of at least selected first channels may vary along their respective length, in particular by at least 10% and / or at least 20%.The above measures have proven to be advantageous for achieving efficient fluid guidance in the distribution region. For example, comparatively narrow webs can be formed as a result and the available installation space can be used for a corresponding cross-sectional widening of the channels.According to a further embodiment, the first webs and / or the first channels are substantially kink-free and / or substantially curvature-free over at least two thirds of their length. This can be understood, for example, to mean that any angles in the course of the first webs and / or first channels are not more than 20°. In particular, the first webs and / or first channels can run in a straight line over at least two thirds of their length. Additionally or alternatively, the first webs can run nonparallel to one another along at least half of their length. In this way, too, the spacing non-homogeneity of the first ends disclosed here can be implemented in a structurally compact manner and the available installation space can be used for forming correspondingly wide flow cross sections of the channels.According to a further embodiment, the first webs are not more than five times, preferably not more than four times and in particular not more than three times as wide as the second webs. Additionally or alternatively, the first channels can be not more than eight times, preferably not more than six times and in particular not more than five times as wide as the second channels at least in the middle third of their longitudinal extent.To determine the widths of webs and channels, the total height is first determined, which webs and channels together span perpendicular to the plane of the plane of the separator plate. Within the scope of this disclosure, a web width can then be determined generally as the maximum width of the region which extends above half the height. A channel width, on the other hand, can be determined as the width of the region that extends below half the height. This can enable meaningful determination of the widths, for example, independently of possible manufacturing radii.According to a variant, a width of at least some of the first channels decreases in the direction of the flow field. Alternatively or additionally, the width of at least some of the first channels may increase in the direction of the flow field. In particular, a combination can also be provided, according to which the width of some first channels increases in the direction of the flow field and the width of some other of the first channels decreases in the direction of the flow field. It is also possible that, in particular in the context of such a combination, at least selected first channels with constant width are provided. The above variants open up additional degrees of freedom in order to ensure efficient flow through the distribution region.According to a further embodiment, within the distribution region and / or within a region of the separator plate which comprises the distribution region and at least one sealing bead adjoining the latter, a distance between regions of maximum height is not more than 5 mm and in particular not more than 3 mm. These regions of maximum height can form an abutment surface for adjacent components of the electrochemical system. By limiting distances between these regions, a size of regions of the separator plate in which no corresponding abutting surfaces are present can be reduced. The adjacent sealing bead can be, in particular, a sealing bead which surrounds the passage opening at least in sections and / or seals off this. In a manner known per se, such a sealing bead can be locally broken through in order to provide a fluid connection between the through-opening and the distribution region.Preferably, the above distance limits apply in particular in connection with first outermost first or first outermost first channels adjacent lands, i.e. in areas with comparatively short first channels. There are typically wide channels present there, which, however, should not exceed the aforementioned distance limits, in order that sufficient structural support can nevertheless be ensured.According to a further embodiment, second ends of the first webs can face the through-opening and be connected to one another by a virtual connecting line. This connecting line can be straight, but can also have a non-straight shape, for example a shape which is folded several times or once and / or curved. The through-opening can be configured along a first edge section for a fluid-conducting connection to the distribution region, for example by providing corresponding fluid channels and / or perforations in an optionally encircling sealing bead. In this case, the extension along the edge section does not assume a constant distance from this edge section, which can be optionally provided, however. In general, the extension along the edge section can comprise that this extension locally deviates from a direction of extension of the edge section by not more than 90° and preferably not more than 45°.The first edge section can extend along at least one third and in particular along at least half of the virtual connecting line. In pictorial terms, this means that a fluid exchange with the through opening and thus with the media channel connected thereto is made possible over a correspondingly large area of the through opening. This also allows for distribution of the second ends of the first lands along a correspondingly large range, providing additional degrees of freedom for forming the extents of and distances between the first lands disclosed herein.Additionally or alternatively, second ends of the first webs face the through-opening and are connected to one another by a virtual connecting line, wherein the virtual connecting line and an edge section of the through-opening, which can comprise an edge delimiting the through-opening, run at a constant distance from one another at least over the necks, preferably over at least 70% of their course. In this case, only a portion of the edge portion that is opposite the second ends can be considered, i.e. the constant distance can be present along at least half or at least 70% of the course of this portion. Alternatively, only a portion of the edge of the through-opening, to which the second ends of the first webs are opposite, can be considered as an edge portion.According to a development, the first channels and / or the first webs are at least five times and in particular at least ten times as long as wide. This preferably applies to at least 80% of the first channels and / or to at least 80% of the first webs.In general, it can be provided within the scope of this disclosure that the webs are locally interrupted along their extension from the through opening in the direction of the flow field (or vice versa), in particular by local depressions. Such interruptions can, for example, enable targeted transverse flows between adjacent channels. Such depressions can subdivide the webs into different part sections. An overall length of the webs can also relate in such a case to the entire course of the webs between their respective first and second ends and can in particular comprise all possible partial sections of a web.Furthermore, it can be advantageous if for the second ends of the first webs, i.e. for the ends which are opposite the through-opening, at least some of the distances between the respective second ends of mutually adjacent first webs are homogeneous. The second ends can therefore have the same distances and thus have a comparable flow cross section, although the distances of the first ends are inhomogeneous.If the second ends of the first webs are distributed along a width axis of the separator plate and the distribution region has a first outermost first web and a second outermost first web, as viewed along the width axis, and if first inner webs are arranged between these two outermost first webs, it is advantageous if first distances between the respective second ends of mutually adjacent first webs are homogeneous for the inner first webs. The homogeneity of the second ends should therefore apply in particular to first inner webs; any deviation of the outermost webs can optionally remain disregarded in this consideration.The invention also relates to a separator plate for an electrochemical system, comprising:at least one through opening for passing a fluid through the separator plate,at least one distribution region having a multiplicity of first channels and first webs formed between in each case two first channels,at least one flow field which is in fluid communication with the through opening via the distribution region,wherein second ends of the first webs are opposite the through-opening, wherein distances between the respective second ends of mutually adjacent second webs are inhomogeneous. These distances correspond to the second distances disclosed herein.In particular, in this connection, the second ends of the first webs can be distributed along a width axis of the separator plate and the distribution region can have a first outermost first web and a second outermost first web, as viewed along the width axis, wherein inner webs are arranged between these two outermost first webs, and wherein distances between the respective second ends of mutually adjacent first webs are inhomogeneous for the inner first webs.According to the invention, it has consequently also been recognized that the fluid exchange with the passage opening offers an improvement potential with regard to the flow behavior of the distribution region, for which purpose the distances between adjacent webs and / or associated channel widths can in turn be suitably adapted. For example, channels along whose course correspondingly mass flows that are reduced without further measures can have larger channel widths in the region of their second ends than channels in which larger mass flows are established in comparison therewith. The width configuration of the channel ends can be oriented in particular to results of simulation calculations.Any embodiments described herein concerning distances of the first ends of the first webs may be combined with any embodiments described herein concerning distances of the second ends of the first webs.Embodiments of the invention are explained below with reference to the attached schematic figures. The same reference numerals can be used for the same features across the figures. Within a respective figure, not all instances of a feature can be provided with the reference sign assigned to this feature. FIG. 1 shows a perspective view of an electrochemical system, which can in principle comprise separator plates according to an embodiment of the invention. FIG. 2 shows perspective individual views of separator plates according to the prior art (SdT), which can likewise be used in principle in the electrochemical system from FIG. 1. FIGS. 3A and 3B are schematically simplified partial views of a separator plate according to prior art examples. FIG. 4 is a schematically simplified partial view of a separator plate according to an embodiment of the invention. FIG. 5 is a schematically simplified partial view of a separator plate according to another embodiment of the invention. FIG. 6 is a schematically simplified partial view of a separator plate according to another embodiment of the invention. FIG. 7 is a schematically simplified partial view of a separator plate according to another embodiment of the invention. FIG. 8 is a schematically simplified partial view of a separator plate according to another embodiment of the invention. FIG. 9 is a schematically simplified partial view of a separator plate according to another embodiment of the invention. FIG. 10 is a diagram for illustrating effects according to the invention with regard to an improved mass flow homogeneity in the distribution region.FIG. 1 shows an electrochemical system 1 having a plurality of identically constructed metallic separator plates 2 which are arranged in a stack 6 and stacked along a z-direction 7. The separator plates 2 of the stack 6 are usually clamped between two end plates 3, 4. The z-direction 7 is also called the stacking direction. In the present example, the system 1 is a fuel cell stack. Each two adjacent separator plates 2 of the stack 6 thus delimit an electrochemical cell which serves, for example, for the conversion of chemical energy into electrical energy.To form the electrochemical cells of the system 1, a membrane electrode unit (MEA) 10 is arranged in each case between adjacent separator plates 2 of the stack 6 (see, for example, FIG. 2 ). The MEA 10 typically includes at least one membrane, e.g., an electrolyte membrane, respectively. Further, a gas diffusion layer (GDL) may be disposed on one or both surfaces of the MEA 10. The MEA 10 also often includes a frame-shaped reinforcement layer that frames and reinforces the electrolyte membrane. The reinforcing layer is generally designed to be electrically insulating and prevents a short circuit from occurring during operation of the electrochemical system 1.In alternative embodiments, the system 1 can likewise be designed as an electrolyser, electrochemical compressor or as a redox flow battery. In these electrochemical systems, separator plates 2 can also be used. The structure of these separator plates can then correspond to the structure of the separator plates 2 explained in more detail here, even if the media guided on or through the separator plates in an electrolyser, in an electrochemical compressor or in a redox flow battery can in each case differ from the media used for a fuel cell system.The z-axis 7 together with an x-axis 8 and a y-axis 9 span a right-handed Cartesian coordinate system. The separator plates 2 each define a plate plane, wherein the plate planes can be planar surface planes of individual plates 2 a, 2 b(see FIG. 2 ), from which a respective separator plate 2 is composed, or wherein the plate planes can run at least parallel to such planar surface planes. The plate planes or plane surface planes are oriented parallel to the x-y plane and thus perpendicular to the stacking direction or to the z-axis 7. The end plate 4 generally has a plurality of media connections 5, via which media can be supplied to the system 1 and via which media can be discharged from the system 1, wherein the media connections 5 are sometimes referred to as ports. These media that can be supplied to the system 1 and discharged from the system 1 can comprise, for example, fuels such as molecular hydrogen or methanol, reaction gases such as air or oxygen, reaction products such as water vapor or depleted fuels or coolants such as water and / or glycol.In an electrochemical system 1, as shown in FIG. 1, both known separator plates 2 according to the prior art and separator plates 2 according to the invention can be used.FIG. 2 shows in perspective two adjacent separator plates 2 according to examples of the prior art, which can be used in an electrochemical system of the type of system 1 from FIG. 1. With the exception of the design of the distribution region disclosed herein and its fluid exchange with a flow field, the following explanations regarding this separator plate 2 can also apply to separator plates 2 according to the invention of this disclosure.FIG. 2 also shows a membrane electrode unit (MEA) 10 arranged between the adjacent separator plates 2 and known from the prior art, wherein the MEA 10 in FIG. 2 is covered for the most part by the separator plate 2 facing the observer. The separator plate 2 is formed from two individual plates 2 a, 2 b,joined together in a materially bonded manner, of which only the first individual plate 2 a,which faces the observer and covers the second individual plate 2 b,is visible in FIG. 2. The individual plates 2 a, 2 bmay each be manufactured from a metal sheet, e.g. from a stainless steel sheet. The individual plates 2 a, 2 bmay be welded to one another, for example, along their outer edge, for example by means of laser welded connections.The individual plates 2 a, 2 bhave typically mutually aligned through-openings which form through-openings 11 a- cof the separator plate 2. When stacking a plurality of separator plates 2, the through-openings 11 a- cform lines or else media channels which extend through the stack 6 in the stacking direction 7 (see FIG. 1 ). Typically, each of the conduits formed by the through openings 11a-c is each in fluid communication with one of the ports 5 in the endplate 4 of the system 1.By way of lines formed by one of the through-openings 11 aof the separator plates 2, for example, coolant can be introduced into the stack 6, while the coolant is discharged from the stack 6 by way of a through-opening 11 a, which is situated opposite one another in each case. The lines formed by the through openings 11 b, 11 cmay, on the other hand, be configured to supply the electrochemical cells of the fuel cell stack 6 of the system 1 with fuel and with reaction gas and to discharge the reaction products from the stack 6. The medium-carrying through-openings 11 a- care formed substantially parallel to a respective plate plane.In order to seal the through-openings 11 a- cto the interior of the stack 6 and to the environment, the first individual plates 2 aeach have sealing beads 12 a- c, which are arranged in each case around the through-openings 11 a- cand which in each case completely surround the through-openings 11 a- c. The second individual plates 2 bhave corresponding sealing beads (not shown) on the rear side of the separator plates 2 facing away from the observer of FIG. 2 for sealing the through-openings 11 a- c.In an electrochemically active region 18, the first individual plates 2 acomprise, on their front side facing the observer of FIG. 2, a flow field 17 with structures 14 for guiding a reaction medium along the outer side (or else front side) of the individual plate 2 a. These structures 14 are provided in FIG. 2 by a multiplicity of webs and channels running between the webs and bounded by the webs. On the front side of the separator plate 2 facing the observer of FIG. 2, the first individual plates 2 aalso each have a distribution and / or collection region 20, which is referred to here simply as distribution region 20. Between the distribution regions 20 and the flow field 17 of the electrochemically active region, a transition region 21 with lowered webs can extend.The distribution region 20 comprises structures which are configured to distribute a medium introduced into the adjoining distribution region 20 starting from a first of the two passage openings 11 cvia the flow field 17 and to collect or bundle a medium flowing from the flow field 17 towards the second of the passage openings 11 cvia the collection region 20. The distribution structures of the distribution and / or collection region 20 are likewise provided in FIG. 2 by webs and channels running between the webs and bounded by the webs.The sealing beads 12 a- 12 care crossed by feedthroughs 13 a- 13 c, which are each formed into all individual plates 2 a, 2 band which allow fluid communication with a respectively associated through-opening 11 a- 11 c.In the following FIGS. 3A / B to 9, partial views of separator plates 2 are shown, which, with the exception of the already mentioned differences, can be embodied as largely analogous to the example from FIG. 2. The views correspond here to a plan view of one of the outer sides of a respective separator plate 2. Also, not all through-openings 11 a- c, which are analogous to FIG. 2, are shown, but which can nevertheless be present in a respective separator plate 2.In FIGS. 3A-B, first of all, further examples of separator plates 2 according to the prior art are shown. These separator plates 2 have a substantially rectangular contour, not shown separately. They are characterized by a longitudinal axis L 17 which runs along the larger dimension of the rectangular shape, not shown separately, and by a width axis B 17, which runs along the smaller dimension of the rectangular shape, not shown separately. The partial views shown in each case show two through-openings 11 b, which are connected in a fluid-conducting manner via two distribution regions 20 and a flow field 17 arranged between the distribution regions 20. The number of through-openings 11 bshown is not restrictive and, as mentioned, further through-openings 11 b, 11 cmay also be provided, for example according to FIG. 2.The distribution regions 20 comprise, as fluid-conducting structures, a plurality of elongate first channels 22 and elongate first webs 24 each extending between two first channels 22.As fluid-conducting structures, the flow field 17 likewise comprises a plurality of elongate channels, which are referred to as second channels 26, and a plurality of elongate webs, which are referred to as second webs 28. These correspond to the structures 14 from FIG. 2 ; a main flow direction, not shown separately, through the flow field 17 runs parallel to the longitudinal axis L 17.In all FIGS. 3A / B to 9, only selected ones of the channels 22, 26 and webs 24, 28 are provided with a corresponding reference sign. Furthermore, in the description of all FIGS. 3A / B to 9, reference can be made primarily to only one of the distribution regions 20 and in particular to its interaction with the flow field 17 and / or the adjacent passage opening 11 b, wherein, however, an analogous statement can apply to the other distribution region 20.In the examples of FIGS. 3A-B, the through-openings 11 bare again surrounded by a sealing bead 12 b. This is provided in an edge section 30, which faces a respective adjacent distribution region 20, with schematically indicated feedthroughs 13 b.The first webs 24 and first channels 22 of the distribution regions 20 run completely or at least over a large part of their lengths parallel to one another, but have different lengths. This results in particular from the non-central arrangement of the passage openings 11 brelative to the flow field 17, for example as viewed along the width axis B. In order to be connected in a fluid-conducting manner also to a region of the flow field 17 remote from the view of the through-openings 11 b, viewed along the width axis B 17 the first channels 22 and first webs 24 leading to this remote region must be formed with a correspondingly increased length. This applies in FIG. 3A, for example, to the upper first channels 22 and webs 24 of the left distribution region 20 and to the lower first channels 22 and webs 24 of the right distribution region 20.The first webs 24 and first channels 22 of the distribution regions 20 each have first ends, of which those of the first webs 24 are denoted by the reference numeral 32, and these first ends are opposite ends 29 of the second webs 28 and ends 27 of the second channels 26 of the flow field 17. Furthermore, the first webs 24 and first channels 22 each have second ends 34 which are opposite the passage opening 11 band at least in most cases the described feedthroughs 13 b.From the first channels 22 directly adjacent to the first ends 32 of the first webs 24, fluid passes from one of the distribution regions 20 into the flow field 17 or from the flow field 17 into one of the distribution regions 20. A lowered transition region 36 is flowed through in this case.In the example from FIG. 3A, the first webs 24 of the distribution regions 20 do not pass over into the second webs 28 of the flow field 17, but instead remain at a distance therefrom. In the example from FIG. 3B, the first webs 24 of the distribution regions 20 each pass into a second web 28 of the flow field 17, starting from a first web height in the distribution region 20, the webs in the transition region 36 decrease in order to rise again towards the flow field 17, but only to a lesser extent. The number of second webs 28 and second channels 26 of the flow field 17 is higher than the corresponding number within the distribution regions 20.Both in the case of FIG. 3A and in the case of FIG. 3B, the distances A of the first ends 32 of the first webs 24 of the distribution regions 20 to a respectively directly adjacent first end 32 of a further first web 24 are homogeneous. An example distance A is shown in FIG. 3A. These distances A can be measured along the width axis B 17 and thus orthogonally to the longitudinal axis L 17 and / or a main flow direction through the flow field 17. Alternatively, these distances A can be measured orthogonally to the longitudinal axis of that first channel 22 which is bounded by the correspondingly spaced first webs 24.The second webs 28 of the flow field 17 are likewise constantly spaced apart from one another, as viewed along the longitudinal axis L 17. The constant distances A of the first and second webs 24, 28 result in correspondingly constant widths of the first and second channels 22, 26 formed between these webs 24, 28.In addition, the distances B between second ends 34 of the first webs 24 of the distribution regions 20 are also homogeneous.Furthermore, at least the plurality of respective first channels 22 of one of the distribution regions 20 are opposite by the same number of, for example, four second channels 26 of the flow field 17. This is illustrated in particular from a view along a schematically entered flow path S, which illustrates a division of the fluid from a respective first channel 22 into a plurality of first channels 26 of the flow field 17 (and vice versa).The foregoing relates in particular to the inner first channels 22 and the inner first webs 24 delimiting them, which are arranged between outermost first channels 22' and outermost first webs 24'. This intermediate arrangement is present, in particular, viewed along the width axis B in 17 fashion. A group I of the inner first channels 22 and inner first webs 24 is emphasized by way of example for the right-hand distribution region 20 from FIG. 3A, but is likewise present in the other distribution regions 20 from FIGS. 3A-B.Because the first channels 22 of the distribution regions 20 have different lengths, inhomogeneous mass flows occur at least after flowing through the distribution regions 20, that is to say at the end 32 of the first webs of the left-hand distribution region 20 in FIG. 3B. These also have an effect on the flowing through the second channels 26 of the flow field 17, with the result that the flowing through the flow field 17 can also have corresponding inhomogeneities. This has been found to negatively affect the efficiency of operation of the electrochemical system 1.In the following FIGS. 4-9, example embodiments are described in views analogous to FIGS. 3A-B to limit such efficiency losses. Reference will be made to the explanations relating to FIGS. 3A-B and to FIG. 2 and these apply analogously in the context of FIGS. 4-9, with the exception of the specific features described. Modifications with respect to FIGS. 3A-B and 2 result in particular with respect to the distribution regions 20, whereas the flow field 17 and the passage openings 11 bare formed analogously to FIGS. 3A-B.FIG. 4 shows a first embodiment in which not all of the first webs 24 of the distribution regions 20 run parallel to one another. Consequently, not all of the first channels 22 formed between the first webs 24 and bounded thereby are equally wide either. In particular, for at least some of the first channels 22, the channel widths increase in the direction of the flow field 17. This relates in FIG. 4 to at least the first five inner lower first channels 22 in the left distribution region 20 and viewed along the width axis B 17 However, constant channel widths or else decreasing channel widths can optionally also be provided as they extend in the direction of the flow field 17, as shown for some of the upper first channels 22 of the left distribution region 20 from FIG. 4.As a result, the distances of the first ends 32 of the first webs 24 and in particular of the inner first webs 24 are inhomogeneous and decrease at least on average from vertically bottom to vertically top in FIG. 4 and with reference to the left-hand distribution region 20. By way of example, a virtual connecting line V of these first ends 32 is shown. It can be seen in FIG. 4 that in a lower half H 2 of the connecting line V, at least on average, there are significantly greater distances between respectively directly adjacent first ends 32 than in the upper half H 1. Exemplary distances A 1, A 2 within the respective halves H 1, H 2 are entered. In the first half H 1, in particular a minimum distance may be present and in the second half H 2 a maximum distance may be present. At the same time, the first channels 22, which are bounded by those webs 24 to which the first ends 32 within the lower half H 2 belong, are significantly shorter than the first channels 22 assigned to the upper half H 1.In FIG. 4, a first outermost first web 24' and a second outermost first web 24' are marked. In the view of Fig. 4, the first outermost first land 24' is positioned below the second outermost first land 24'. The first end 32 of the first or lower outermost first web 24' is positioned closer to the through opening 11b immediately adjacent to the distribution region 20 than the first end 32 of the second or upper outermost first web 24'. The first or lower outermost first web 24' has a greater and in particular a maximum distance from a directly adjacent inner web 24 than the second or uppermost outermost first web 24' from its directly adjacent inner web 24. The minimum and maximum distance relate in each case to the totality of the distances A between the adjacent ends 32 of the first webs 24.A result of the described structure of the distribution region 20 is that the inner first channels 22 assigned to the lower half H 2 are situated opposite a larger number, and in particular a maximum number, of second channels 26 of the flow field 17 at least on average than the first channels 22 assigned to the upper half H 1. This means that the shorter, lower first inner channels 22, after the flow of which results in a higher mass flow, are connected directly or predominantly in a fluid-conducting manner to a larger number of second channels 26 of the flow field 17 than the first channels 22 which are longer in comparison. This improves the flow behavior of the distribution region 20 and thus increases the efficiency during operation of an electrochemical system 1 comprising the separator plate 2.It should be noted that all of the first lands 24 and first channels 22 are elongated and are significantly longer than wide. In the example of FIG. 4, they also each run in a straight line and without any curvature. In addition, they each extend at an angle to the longitudinal axis L 17, along which a main flow direction also extends through the flow field 17. The first webs 24 are also of similar width and at least not significantly wider than the second webs 28, for example not more than three times as wide. Both the first and the second webs 24, 28 have a constant width in the example shown.Furthermore, the fluid is 17 or discharged from the through openings 11 bin a substantially identical direction relative to the longitudinal axis L through the first channels 22 and also. The main flow direction is guided to the flow field 17 (or vice versa). In the case of the left-hand lower distribution region 20 in FIG. 4, this relates to a diagonally extending direction which is inclined toward the flow field 17. Furthermore, it is clear from FIG. 4 that the distribution region 20 extends over an entire width of the flow field 17 and in particular the first ends 32 are distributed over almost the entire width.Finally, FIG. 4 shows that the distances B between mutually adjacent second ends 34 of the first webs 24 are likewise inhomogeneous in this example shown. Exemplary different distances B 1, B 2 are entered. The second ends 34 are distributed along a virtual connecting line V'. This runs almost along the entire edge section 30 of the through-opening 11 bin which the feedthroughs 13 bare formed.If the ratios of the widths A 1, A 2 of the first channels 22 adjacent to the first ends 32 of the first webs 24 to the widths B 1, B 2 of the same first channels 22 adjacent to the second ends 34 of the first webs 24 are considered, A 1 / B 1<A 2 / B 2 is here. In addition, A 1<B 1 is in the first considered first channel 22, while A 2>B 2 is in the second considered first channel 22. There are a small number of first channels 22 which become narrower in their course from the edge section 30 to the transition region 36 and a larger number of first channels 22 which become wider on the same route, most increases in width being significantly more pronounced than the decreases.FIG. 5 shows a further embodiment which differs from the example from FIG. 4 above all in that the first webs 24 each merge into a second web 28 of the flow field 17. Due to the higher number of channels and webs of the flow field 17 compared to the distribution regions 20, webs 28 of the flow field 17 also remain, however, which do not merge into any of the first webs 24. The first webs 24 each run linearly over a major part of their length and are curved near their first ends 32 in the direction of the flow field 17 or of its webs 28.Again, the distances A between the first ends 32 of respectively adjacent first webs 24 vary analogously to the example from FIG. 4, see the different distances A 1, A 2. The first ends 32 can lie in particular where the first webs 24 enter the transition region 36 or also in a middle of this transition region 36. What is not entered but nevertheless optionally provided is also an non-homogeneity of the distances B between the second ends 34 of the first webs 24 explained with reference to FIG. 4.FIG. 6 shows an embodiment comparable to FIG. 4, in which the first webs 24 do not merge directly into second webs 28 of the flow field 17. Again, these first webs 24 are straight and extend at an angle to the longitudinal axis L 17. Inhomogeneous distances A1, A2 are also present between the first ends 32 and between the second ends 34 of the first webs 22 (not shown). In contrast to the variant of FIG. 4, however, the webs 24 are locally interrupted, see the depressions 40. Furthermore, in this case the distances between directly adjacent webs 24 and thus the channel widths decrease in the case of a course from one of the passage openings 11 bin the direction of the flow field 17. Furthermore, this embodiment differs from that of FIG. 4 in that all channel widths decrease from the edge region 30 to the transition region 36, A<B applies to the ratio A 1 / B 1 just as to A 2 / B 2.FIG. 7 shows an embodiment comparable to FIG. 5, in which the first webs 24 each merge into one of the second webs 28 of the flow field 17. Again, these webs 24 are straight and extend at an angle to the longitudinal axis L 17. Inhomogeneous distances A1, A2 are also present between the first ends 32. Between the second ends 34, the respective distances B 1, B 2 are homogeneous. In the example shown, the distances between at least some adjacent first webs 24 and thus the channel widths resulting therefrom decrease starting from the second ends 34 and in the direction of the flow field 17 at least in sections as far as the first ends 32. Again, B1>A1 and B2>A2 apply at least to the two first channels 22 under more detailed consideration. Only in the transition region does the width change in the opposite direction in order to increase again in the direction of the flow field 17.FIGS. 4-7 illustrate, but without being exhaustive examples, the design freedom for achieving the spacing non-homogeneity according to the invention.FIG. 8 shows a further embodiment in which the distribution regions 20 are configured differently from one another. The left-hand distribution region 20 in FIG. 8 is formed substantially analogously to the example from FIG. 4, but optionally with local depressions 40 in the first webs 24. The two distribution regions 20 thus differ in particular with regard to the number, length and orientation of the first webs 24, the entire length of which extends in the region of the height extent of the respectively adjoining through-opening 11 b. One of the distribution regions 20 could also be formed according to an example of the prior art, i.e. not both distribution regions 20 need to have the spacing non-homogeneity according to the invention. The latter may, however, be advantageous in order to increase the overall efficiency.FIG. 9 shows a still further embodiment in which the left-hand distribution region 20 is formed in a manner comparable to the variant of FIG. 5, but has a higher number of webs and channels. The right-hand distribution region 10 has the same number of webs and channels as the left-hand distribution region 20, but differs therefrom in that none of the webs 24 of the right-hand distribution region 20 directly merges into a web of the flow field 17. Such different designs may be due, for example, to the coolant guidance in the interior of the separator plate 2. Furthermore, a fluid-conducting connection to another through-opening 11 cis shown in comparison to the preceding FIGS. 3A / B-8. This through-opening 11 cmay be, analogously to the example from FIG. 2, a through-opening 11 cto supply or discharge fuel, reaction gas and / or discharge the reaction products, wherein the guided media may differ from those of the through-opening 11 b. Not only the distribution regions 20 are not point-symmetrically formed here, but also the through openings 11 c, which have different approximately triangular shapes. It should be noted again that all the through openings 11 a- cof the separator plates 2 are not shown in the schematic partial views of FIGS. 3A / B- 9, but may be present there analogously to the example from FIG. 2.FIG. 10 shows a diagram for illustrating an improved homogeneity of the mass flow at half the length of the flow field 17 when flowing through a surface of a separator plate according to any of the embodiments of the invention disclosed herein. Deviations from an averaged mass flow are plotted along the vertical diagram axis. The curves shown are only shown as smoothed curves. From left to right, the channels of the flow field 17 of a point-symmetric separator plate 2 are shown, i.e. the horizontal direction corresponds, for example, to a view along the width axis B 17 in FIG. 4, and positions in the horizontal direction correspond to positions of these channels along the width axis B 17.The dashed line indicates values obtained with an embodiment according to the invention. The dotted line indicates values obtained with a separator plate according to the prior art. It can be seen that with the embodiment according to the invention the fluctuations of the mass flow are reduced compared to the prior art. Thus, the dashed line runs over long distances at a smaller distance from the horizontal diagram axis 0.0% than the dotted line. As mentioned, the improved homogeneity of the mass flow according to the invention is associated with an overall improved and therefore efficiency-increasing flow behavior of the distribution regions 20 and also of the flow field 17.

Claims

Separator plate (2) for an electrochemical system (1), having: - at least one passage opening (11a-c) for passing a fluid through the separator plate (2), - at least one distribution region (20) having a multiplicity of first channels (22) and first webs (24) formed between in each case two first channels (22), - at least one flow field (17) which is in fluid communication with the passage opening (11a-c) via the distribution region (20) and which has a multiplicity of second channels (26) and second webs (28) formed between in each case two second channels (26), wherein first ends (32) of the first webs (24) are opposite ends (29) of the second webs (28) and / or merge into ends (29) of at least selected ones of the second webs (28), wherein first distances (A) between the respective first ends (32) of mutually adjacent first webs (24) are inhomogeneous.Separator plate (2) according to the preceding claim, wherein the first ends (32) of the first webs (24) are distributed along a width axis (B 17) of the separator plate (2) and the distribution region (20), as viewed along the width axis (B 17) has a first outermost first web (24') and a second outermost first web (24'), wherein inner first webs (24) are arranged between these two outermost first webs (24'), and wherein first distances (A) between the respective first ends (32) of mutually adjacent first webs (24) are inhomogeneous for the inner first webs (24).Separator plate (2) according to one of the preceding claims, further comprising a transition region (36) in which the first ends (32) of the first webs (24) are opposite the ends (29) of the second webs (28) and / or in which the first ends (32) of the first webs (24) are transition into the ends (29) of the at least selected second webs (28), wherein the transition region (36) is lowered with respect to the flow field (17) and / or the distribution region (20) with respect to a height axis running perpendicular to a plane surface plane of the separator plate (2).Separator plate (2) according to one of the preceding claims, wherein the fluid flows in the flow field (17) along a main flow direction and: - the first webs (24) and / or first channels (22) each extend at an angle to this main flow direction, and / or - a virtual connecting line (V) of the first ends (32) of the first channels extends substantially orthogonally to the main flow direction and / or - the distribution region (20) extends along an entire width of the flow field (17), wherein the width is measured orthogonally to the main flow direction, and / or - the first distances (A) are measured orthogonally to the main flow direction.Separator plate (2) according to one of the preceding claims, wherein the distances (A) between the respective ends (27) of mutually adjacent second channels (26) are homogeneous or at least less inhomogeneous than the first distances (A); and / or wherein the number of first channels (22) is less than the number of second channels (26), in particular wherein the number of first channels (22) is not more than half as large or not more than one third as large as the number of second channels (26).Separator plate (2) according to one of the preceding claims, wherein the first ends (32) of the first webs (24) are distributed along a width axis (B 17) of the separator plate (2) and the distribution region (20), as viewed along the width axis (B 17) has a first outermost first web (24') and a second outermost first web (24'), wherein the first outermost first web (24') and in particular its first end (32) is positioned closer to the through opening (11a-c) than the second outermost first web (24') and in particular as its first end (32), wherein, viewed along the width axis (B 17) and from the first outermost first web (24') in the direction of the second outermost first web (24'), the first distances (A) decrease and / or do not increase at least in sections.Separator plate (2) according to claim 6, wherein a maximum first distance (A) is present at least between the first outermost first web (24') and a further first web (24') directly adjacent thereto, and / or wherein a minimum first distance (A) is present at least between the second outermost first web (24') and a further first web (24) directly adjacent thereto.Separator plate (2) according to one of the preceding claims, wherein each first channel (22) is configured to supply fluid to or to receive fluid from at least one associated second channel (26), wherein the number of second channels (26) associated with a respective first channel (22) is inhomogeneous, in particular the number of second channels (26) associated with a respective one of the respective first inner channels (24') arranged between inner first webs (24) is inhomogeneous.Separator plate (2) according to any of the preceding claims, wherein a respective width of the first webs (24) is constant or varies by not more than 20% along a respective length of a first web (24); and / or wherein the respective widths of the first webs (24) are identical and / or differ by not more than 20%.Separator plate (2) according to one of the preceding claims, wherein the first webs (24) are substantially kink-free and / or substantially curvature-free over at least two thirds of their length.Separator plate (2) according to one of the preceding claims, wherein the first webs (24) run non-parallel to one another along at least half of their length.Separator plate (2) according to one of the preceding claims, wherein the first webs (24) are not more than five times, preferably not more than four times, in particular not more than three times as wide as the second webs (24).Separator plate according to one of the preceding claims, wherein second ends (34) of the first webs (24) face the through-opening (11a-c) and are connected to one another by a virtual connecting line (V'), wherein the through-opening (11a-c) is configured along a first edge section (30) for a fluid-conducting connection to the distribution region (20), wherein the first edge section (30) extends along at least one third and in particular along at least half of the virtual connecting line (V').Separator plate (2) according to one of the preceding claims, wherein second ends (34) of the first webs (24) face the through-opening (11a-c) and are connected to one another by a virtual connecting line (V'), wherein the virtual connecting line (V') and an edge section (30) of the through-opening (11a-c) run at a constant distance from one another at least over the necks, preferably over at least 70% of their course.Separator plate (2) according to one of the preceding claims, wherein second ends (34) of the first webs (24) are opposite the through-opening (11a-c), wherein at least a part of the distances (B) between the respective second ends (34) of mutually adjacent first webs (24) are homogeneous.Separator plate (2) according to the preceding claim, wherein the second ends (34) of the first webs (24) are distributed along a width axis (B 17) of the separator plate (2) and the distribution region (20), as viewed along the width axis (B 17) has a first outermost first web (24') and a second outermost first web (24'), wherein inner first webs (24) are arranged between these two outermost first webs (24'), and wherein for the inner first webs (24), first distances (A, B) between the respective second ends (34) of mutually adjacent first webs (24) are homogeneous.Separator plate (2) according to one of the preceding claims, wherein for at least 80% of the first channels (22) and / or of the first webs (24), the first channels (22) and / or the first webs (24) are at least five times and in particular at least ten times as long as wide.Separator plate (2) for an electrochemical system (1), having: - at least one passage opening (11a-c) for passing a fluid through the separator plate (2), - at least one distribution region (20) having a multiplicity of first channels (22) and first webs (24) formed between in each case two first channels (22), - at least one flow field (17) which is in fluid communication with the passage opening (11a-c) via the distribution region (20), wherein second ends (34) of the first webs (24) are opposite the passage opening (11a-c), wherein at least some of the spacings (B) between the respective second ends (34) of mutually adjacent first webs (24) are inhomogeneous.Separator plate (2) according to the preceding claim, wherein the second ends (34) of the first webs (24) are distributed along a width axis (B 17) of the separator plate (2) and the distribution region (20), as viewed along the width axis (B 17) has a first outermost first web (24') and a second outermost first web (24'), wherein first inner webs (24) are arranged between these two outermost first webs (24'), and wherein for the inner first webs (24), distances (B) between the respective second ends (34) of mutually adjacent first webs (24) are inhomogeneous.

Images