PLATE, SYSTEM AND FUEL CELL STACK

Abstract

plate (12, 20) comprising: a bead (42) which has a bead side (106) and a bead corner (108); and a flange edge (104) defining an opening (44) through the plate (12, 20), wherein the flange edge (104) has a first edge section (110, 116) near the bead side (106) and a second edge section (112, 118) near the bead corner (108), wherein the bead side (106) and the first edge section (110, 116) define a first edge distance (D1) between them, wherein the bead corner (108) and the second edge section (112, 118) define a second edge distance (D2) between them, the second edge distance (D2) being greater than the first edge distance (D1), characterized in that the bead side (106) follows a serpentine path and wherein the first edge section (110, 116) follows the serpentine path, such that the first edge distance (D1) is essentially constant along the serpentine path.

Description

INTRODUCTIONThe disclosure relates to the field of fuel cells, and more particularly to systems and methods for evenly distributing contact pressure across seals.Fuel cell systems can be used as a power source in a wide variety of applications for providing electrical power. The generated electric power can be used immediately to drive a device such as an electric motor. Additionally or alternatively, the generated electrical energy may be stored for later use, for example, using batteries.In some applications, fuel cells are integrated into stationary assemblies to provide electrical power to buildings, homes, and the like. In some applications, fuel cells are incorporated into devices such as smart phones, video cameras, computers, and the like. In some applications, fuel cells are installed in vehicles to provide or supplement the driving force.Fuel cell systems generally include fuel cells disposed in a fuel cell stack. The fuel cell stack, which may include more than one hundred plates, is compressed to apply contact pressure to seals between adjacent components of the fuel cell stack to prevent leakage of fluids passing therethrough.For example, a coolant mixture of the reactants or reactants that mix away from the active areas of the fuel cells reduces the effectiveness of the fuel cell stack. Due to the number of components, even slight differences in contact pressure distribution along the seals across the stack are increased, which can prevent the formation of liquid tight seals.Accordingly, it would be advantageous to distribute the contact pressure uniformly over seals of the fuel cell stack.The document DE 10 2009 006 413 A1 discloses a plate according to the preamble of claim 1, a system according to the preamble of claim 6 and a fuel cell stack according to the preamble of claim 9. The document DE 11 2012 000 477 T5 discloses related plates, systems and stacks.A plate includes a bead and a flange edge. The bead includes a bead side and a bead corner. The flange edge defines an opening through the plate. The flange edge has a first edge portion near the bead side and a second edge portion near the bead corner. A first edge distance is defined between the bead side and the first edge portion. A second edge distance is defined between the bead corner and the second edge portion, the second edge distance being greater than the first edge distance.In some aspects, the bead has a sealing surface thereon. The sealing surface is configured to flex when subjected to a contact pressure.In some further aspects, a third edge distance is defined between a second bead corner and a third edge portion, the third edge portion is proximate the second bead corner, the bead corner defines a first radius, and the second bead corner defines a second radius, wherein the second radius is greater than the first radius and the second edge distance is greater than the third edge distance.The bead side follows a serpentine path and the first edge portion follows the serpentine path such that the first edge distance along the serpentine path is generally constant.In some further aspects, the first edge distance and the second edge distance are configured to provide a contact pressure with less than about 50% variance along the bead.In some further aspects, the first edge distance and the second edge distance are configured to provide a contact pressure with less than about 30% variance along the bead.In some further aspects, the bead generally defines a first polygon and the flange edge generally defines a second polygon, the second polygon including more corners than the first polygon.In some further aspects, the bead side is generally linear and the bead corner is generally rounded.In some further aspects, the first edge portion is generally rounded and the second edge portion is generally linear.A system includes a first plate, a second plate, and a compression element. The first plate includes a bead and a flange. The bead has a bead side and a bead corner. The flange rim defines a first opening through the first plate. The flange edge has a first edge portion near the bead side and a second edge portion near the bead corner. The bead side and the first rim portion define a first rim distance therebetween. The bead corner and the second rim portion define a second rim distance therebetween. The second edge distance is greater than the first edge distance. The second plate abuts the first plate. The second plate includes a second opening therethrough. The second opening is aligned with the first opening. The compression member is configured to apply a compressive force to the first plate and the second plate. The compressive force is configured to seal the first plate and the second plate along the bead.In some further aspects, the second plate further includes a second bead and a second flange edge. The second bead has a second bead side and a second bead corner. The second flange edge defines the second opening. The second flange edge has a third edge portion near the second bead side and a fourth edge portion near the second bead corner. The second bead side and the third rim portion define a third rim distance therebetween. The second bead corner and the fourth rim portion define a fourth rim distance therebetween. The fourth edge distance is greater than the third edge distance.In some further aspects, the first panel further includes a first working surface and a first back surface. The bead is disposed on the first working surface. The first rear surface faces the first working surface. The second panel further includes a second working surface and a second back surface. On the second working surface, the bead is arranged. The second rear surface faces the second working surface. The first rear surface is disposed adjacent to the second rear surface. The first plate is attached to the second plate. The bead creates a first contact pressure distribution with a portion of relatively higher contact pressure. The second bead creates a second contact pressure distribution with a relatively lower contact pressure portion. The bead and the second bead are cooperatively configured such that the relatively higher contact pressure portion is relatively adjacent to the relatively lower contact pressure portion.In some further aspects, the bead creates a first contact pressure distribution with a portion of relatively higher contact pressure, the second bead creates a second contact pressure distribution with a portion of relatively lower contact pressure, and a first sealing surface of the bead abuts a second sealing surface of the second bead such that the portion of relatively higher contact pressure abuts the portion of relatively lower contact pressure.In some further aspects, the first edge portion is generally rounded and the second edge portion is generally linear.The bead side follows a serpentine path and the first edge portion follows the serpentine path such that the first edge distance along the serpentine path is generally constant.In some further aspects, the first edge portion is generally rounded and the second edge portion is generally linear.A fuel cell stack includes a first plate, a second plate, a unified electrode assembly, and a compression member. The first panel includes a first working surface, a first rear surface, a bead, and a first flange edge. The first working surface defines a plurality of first reactant channels. The first rear surface faces the first working surface. The bead is disposed on the first working surface. The bead has a bead side and a bead corner. The first flange edge defines a first opening through the first plate. The first flange edge has a first edge portion near the bead side and a second edge portion near the bead corner. The first edge portion and the bead side define a first edge distance therebetween. The second edge portion and the bead corner define a second edge distance therebetween. The second edge distance is greater than the first edge distance. The second panel includes a second working surface, a second back surface, and a second flange edge. The second working surface defines a plurality of second reactant channels. The second rear surface faces the second working surface. The second flange edge defines a second opening through the second plate. The second opening is aligned with the first opening. The unified electrode assembly is disposed between the first plate and the second plate. The unified electrode assembly includes a first side contacting the plurality of first reactant channels and a second side contacting the plurality of second reactant channels. The compression member is configured to apply a compressive force to each of the first plate, the second plate, and the unified electrode assembly. The compressive force is configured to apply a contact pressure to the bead to provide a substantially fluid-tight seal between the bead and an adjacent component.In some further aspects, the substantially fluid-tight seal is provided between the bead and the second plate.In some further aspects, the bead side is generally linear and the bead corner is generally rounded.In some further aspects, the first edge distance and the second edge distance are configured to provide less than about 50% variance in contact pressure along the bead.The above features and advantages and other features and advantages of the present disclosure will be readily apparent from the present detailed description taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSThe accompanying drawings are for illustrative purposes. Exemplary aspects are discussed in the following detailed description and shown in the accompanying drawings, in which: FIG. 1 is an exploded schematic view of a fuel cell stack in accordance with aspects of the present disclosure; FIG. 2 is a schematic top view of a monopolar plate of the fuel cell stack of 1 in accordance with aspects of the present disclosure; FIG. 3 is a schematic cross-sectional view of the panel of FIG. 2 ; FIG. 4 is a schematic isometric view of a bipolar plate shown in partial cross-section; FIG. 5A is a top view of an example manifold section, in accordance with aspects of the present disclosure; FIG. 5B is a top view of another exemplary manifold section in accordance with aspects of the present disclosure; FIG. 5C is a top view of yet another example manifold section in accordance with aspects of the present disclosure; FIG. 5D is a top view of yet another example manifold section in accordance with aspects of the present disclosure; FIG. 6 is a top view of an exemplary manifold section in accordance with aspects of the present disclosure; FIG. 6A is an enlarged view of a portion of the manifold portion shown in FIG. 6 ; FIG. 6B is an enlarged view of a portion of the manifold portion shown in FIG. 6 ; FIG. 7A is a thermal map illustrating contact pressure along a bead; FIG. 7B is a thermal map illustrating contact pressure along a bead with varied edge spacings, in accordance with aspects of the present disclosure; FIG. 8 illustrates a method of constructing a flange in accordance with aspects of the present disclosure.DETAILED DESCRIPTIONFIG. 1 is an exploded view of a fuel cell stack 10. the fuel cell stack 10 includes a plurality of plates 12, at least one unified electrode assembly 14, and a compression element 16. the plurality of plates 12 may include any suitable combination of plates 12. For example, the plurality of plates 12 may include endplates 18, monopolar plates 20 (shown in more detail in FIG. 2 ), and / or bipolar plates 22 (shown in more detail in FIG. 4 ). According to some aspects of the present disclosure, some or all of the gaskets between the plurality of plates 12, the at least one unified electrode assembly 14, and the compression member 16 may be configured to evenly distribute the contact pressure across the gaskets by controlling the flange construction as described herein.The end plates 18 are disposed on the upper and lower sides of the fuel cell stack 10. The end plates 18 include fuel inlets 24a, fuel outlets 24c, oxidant inlets 26a, oxidant outlets 26c, coolant inlets 28a, and coolant outlets 28c disposed thereon. As used herein, "fluids" may refer to fuels, oxidizers, refrigerants, or any combination thereof, as the context dictates, and "reactants" may refer to fuels, oxidizers, or both, depending on the context. For example, "fluid inlets 24 a, 26 a, 28 a" may refer to any or all of fuel inlets 24 a, oxidant inlets 26 a, or coolant inlets 28 a, as the context dictates, and "reactant channels 24 b, 26 b" may refer to one or both of fuel channels 24 band oxidant channels 26 b, as the context dictates. It is contemplated that certain of the fluid inlets 24 a, 26 a, 28 aand fluid outlets 24 c, 26 c, 28 cmay be disposed on one end plate 18, with the remaining fluid inlets 24 a, 26 a, 28 aand fluid outlets 24 c, 26 c, 28 cbeing located on the opposing end plate 18.The unified electrode assembly 14 includes a fuel cell 30 disposed between diffusion media 32. The fuel cell 30 may be, for example, a membrane electrode assembly including a membrane disposed between a cathode and an anode. The membrane may be, for example, a proton exchange membrane. The cathode and anode may contain, for example, a finely divided catalyst supported on carbon particles and mixed with an ionomer. In some aspects, the catalyst is platinum.The diffusion media 32 are porous layers that facilitate the delivery of reactants to the fuel cell 30. The reactants may comprise any suitable combination of fuel and oxidant. For example, the fuel may be hydrogen and the oxidant may be oxygen. In a hydrogen fuel cell 30, hydrogen and oxygen react with heat and water as byproducts to generate electricity. For example, other fuels may be used, such as natural gas, methanol, gasoline, and coal-derived synthetic fuels. In some aspects, the diffusion medium 32 is attached to a surface of the fuel cell 30 using lamination, adhesion, or any other suitable method. In some aspects, the diffusion medium 32 abuts but does not adhere to the surface of the fuel cell. For example, the diffusion medium 32 may be disposed on the surface of the fuel cell 30 and held in place by a retaining member 34. The retaining element 34 can be a seal, for example.The compression member 16 applies a compressive force to the fuel cell stack 10 along the stacking direction. The compressive force secures the plates 12 and the fuel cells 30 in position by contact pressure between adjacent components. In some aspects, the compression member 16 includes a plurality of threaded rods that engage structures on the end plates 18. By tightening the threaded rods, a compressive force is increased to a desired level along the stacking direction, which results in a contact pressure being distributed along seals between adjacent components. In some aspects, the compression elements 16 engage less than the entire fuel cell stack 10. For example, compression members 16 may engage two adjacent plates 12 to apply a compressive force to the two plates 12 or may engage a number of adjacent plates 12 to apply a compressive force to the number of adjacent plates 12.FIG. 2 is a top view of an exemplary monopolar plate 20 of the fuel cell stack 10. the monopolar plate 20 is a generally planar panel having a working surface 36, a rear surface 38 opposite the working surface, manifold sections 40, and beads 42. The structures are formed by punching the metal sheet. It is contemplated that other materials, such as carbon fibers and other methods of formation, such as molding and additive manufacturing, may be used to form the monopolar plate 20.The reactant channels 24 b, 26 bare defined on the working surface 36 of the monopolar plate 20. The reactant channels 24b, 26b of a particular monopolar plate 20 are either fuel channels 24b or oxidant channels 26b. The reactant channels 24 b, 26 btribut the fluid flowing therethrough over the surface of an adjacent unified electrode assembly 14 or fuel cell 30. for example, the fuel channels 24 btribut hydrogen to the anode of the fuel cell 30, and the oxidant channels 26 btribut oxygen to the cathode of the fuel cell 30.The manifold portion 40 is disposed in a peripheral region of the monopolar plate 20 and defines a plurality of apertures 44 extending through the monopolar plate 20. The apertures 44 allow fluid to flow from one side of the monopolar plate 20 to the other side of the monopolar plate 20.The beads 42 extend from the working surface 36 of the monopolar plate 20. at least one bead 42 is disposed along a perimeter of the working surface 36 of the monopolar plate 20 to prevent leakage of fluid from, for example, the reactant channels 24 b, 26 bto the exterior of the monopolar plate 20 (e.g., exiting the environment or into the fuel cell stack 10). Additional beads 42 are disposed adjacent to and surround each opening 44. The beads 42 surrounding each opening prevent leakage of fluid from the opening to the fluid channels 24 b, 26 b, 28 bof the monopolar plate 20. It is contemplated that a bead 42 may surround more than one opening 44.Optionally, the coolant channels 28 bmay be defined on the back 38 of the monopolar plate 20. The coolant channels 28 btribut the coolant flowing therethrough over the rear surface 38 of the monopolar plate 20 to remove heat generated during the chemical reaction. Additionally, the coolant passages 28 bmay be used to provide heat to the fuel cells 30 to facilitate the chemical reaction in, for example, cold operating conditions. It is contemplated that the beads 42 and other features may extend from the rear surface 38 of the monopolar plate 20.FIG. 3 is a cross-sectional view of the bead 42 of the monopolar plate 20 taken along line 3- 3. The bead 42 defines a generally arcuate shape. The bead 42 defines a sealing surface 46 on the working surface 36. the sealing surface 46 is configured to contact a component that abuts the working surface 36 of the monopolar plate 20. The sealing surface 46 forms a fluid tight seal with the adjacent component when the contact pressure at all points on the bead 42 exceeds a certain threshold.The beads 42 form an elastic structure that deflects when pressure is applied. The deflection increases the portion of the sealing surface 46 in contact with the adjacent component. While the illustrated bead 42 is generally curved in cross-section, it is contemplated that other shapes may be used. In some non-limiting examples, the cross-sectional profile of the bead 42 is generally rectangular, generally trapezoidal, generally linear sidewalls with an arcuate portion spreading therebetween, combinations thereof, or the like. Further, the illustrated bead 42 is generally symmetric, it being contemplated that asymmetric beads 42 may be used.FIG. 4 is a partial cross-sectional isometric view of the bipolar plate 22. Bipolar plates 22 may be formed in a variety of ways. For example, the back surfaces 38 of two monopolar plates 20 may be placed together and the monopolar plates 20 may be joined to form the bipolar plate 22. The joint may be formed by welding or using an adhesive, for example.The bipolar plate 22 includes a first working surface 36 aopposing a second working surface 36 b. Each working surface 36 defines reactant channels 24b, 26b thereon. For example, the first working surface 36a defines the fuel channels 24b, while the second working surface 36b defines the oxidant channels 26b. The cooperative arrangement of the rear surfaces 38 of the two monopolar plates 20 results in the coolant passages 28b being defined by the space between the two monopolar plates 20, as shown in FIG. 4.Bipolar plates 22 may also be formed using a variety of methods, such as 3D printing. In some aspects, the bipolar plate 22 is formed by embossing the reactant channels 24 b, 26 bon opposite sides of a single panel without the presence of cooling channels 28 bin between.When the fuel cell stack 10 is assembled, the openings 44 in the manifold sections 40 of each plate 12 are substantially aligned with respective openings 44 of adjacent plates 12 or unified electrode assemblies 14 to form a plurality of inlet manifolds (not shown) and a plurality of outlet manifolds (not shown). The beads 42 of each component are compressed against the beads 42 of adjacent components so that fluid tight seals are formed to define a plurality of fluid flow paths 24, 26, 28. The fuel flowpath 24 is defined by the fuel inlet 24a, a fuel inlet manifold (not shown), fuel channels 24b of respective plates 12, a fuel outlet manifold (not shown), and fuel outlet 24c. Similarly, an oxidant flowpath 26 is defined through the oxidant inlet 26 a, an oxidant inlet manifold (not shown), the oxidant channels 26 band the oxidant outlet manifold (not shown), and the oxidant outlet 26 c. The coolant flow path 28 includes the coolant inlet 28 a, a coolant inlet manifold (not shown), the coolant channels 28 b, a coolant outlet manifold (not shown), and a coolant outlet 28 c.In operation, at least two fluids flow through the fuel cell stack 10 in separate fluid flow paths 24, 26, 28. In some example fuel cell stacks 10, the fluids enter the fluid inlets 24 a, 26 a, 28 a, flow through a respective manifold along a circumferential side of the fuel cell stack 10, and traverse the components in a lateral direction via the fluid channels 24 b, 26 b, 28 b, flow through a respective manifold on an opposite circumferential side of the fuel cell stack 10, and exit the fuel cell stack 10 via the fluid outlets 24 c, 26 c, 28 c. In some examples, at least two of the fluids flow in a counter-current configuration.A substantially fluid tight seal is formed between components of the fuel cell stack 10 to prevent undesired mixing of the fluids flowing through the fuel cell stack 10. These substantially fluid tight seals are formed by applying contact pressure to the sealing surfaces 46. It is believed that differences in contact pressure along the sealing surfaces 46 of the beads 42 contribute leaks. It is also believed that a uniform distribution of contact pressure along the sealing surfaces 46 of the beads 42 may beneficially affect the characteristics of the fuel cell stack 10. For example, systems, components, and methods according to the present disclosure may increase sealing effectiveness by evenly distributing contact pressure across the manifold sections 40 of the plates 12. Further, systems, components, and methods consistent with the present disclosure may also reduce the manufacturing cost of components by reducing the amount of compressive force required to maintain an appropriate contact pressure through the stack. Furthermore, systems, components, and methods consistent with the present disclosure may also positively affect the longevity of the fuel cell stack by reducing the maximum contact pressure applied to the components.The contact pressure applied to the sealing surfaces 46 results from the compressive force applied to the fuel cell stack 10 and should be maintained above a threshold level to maintain the substantially fluid tight seals. Because the fuel cell stack 10 may include a substantial number of components, even minor variations in the distribution of contact pressure along the beads 42 may be greatly enhanced when the components are assembled into the fuel cell stack 10.Advantageously, the contact pressure distribution along the sealing surface 46 of a bead 42 surrounding an opening 44 may be evenly distributed by varying an edge distance D around a flange 50 between the opening 44 and the bead 42.FIGS. 5A-5D show top views of exemplary manifold sections 40A-40D for evenly distributing contact pressure on a sealing surface 46 along the bead 42 in accordance with the present disclosure. FIG. 5A is a top view of an example manifold portion 40 ato evenly distribute the contact pressure along the bead 42. The manifold section 40a includes a working surface 36 of the plate 12 having a bead 42 thereon. a flange 102 is defined between the bead 42 and the opening 44 with a flange edge 104 defining the opening 44. As can be seen, the bead 42 is a first polygon that is generally hexagonal, while the opening 44 is generally circular.The bead 42 includes a plurality of bead sides 106 and a bead corner 108 at the intersection of adjacent bead sides 106. The flange edge 104 includes a first edge portion 110 proximate the bead side 106 and a second edge portion 112 proximate the bead corner 108. As seen in the figure, portions of the bead 42 corresponding to respective portions of the flange edge 104 are disposed in an area extending generally perpendicular to the flange edge 104.A rim distance D is defined by the space between the bead 42 and the flange rim 104. A first edge distance D 1 is defined by the space between the bead side 106 and the first edge portion 110, and a second edge distance D 2 is defined by the space between the bead corner 108 and the second edge portion 112. As can be seen in FIG. 5A, the second edge distance D 2 is greater than the first edge distance D 1. In some aspects, the second edge distance D 2 is 30% greater than the first edge distance D 1. In some aspects, the second edge distance D 2 is 60% greater than the first edge distance D 1. In some aspects, the second edge distance D 2 is 100% greater than the first edge distance D 1.FIG. 5B is a top view of another example manifold portion 40 bto evenly distribute the contact pressure along the bead 42. In the illustrated example, the bead 42 is a first polygon that is generally hexagonal and the flange edge 104 is a second polygon that is also generally hexagonal. The first polygon is rotated about 30° from the second polygon such that each corner of the first polygon is generally adjacent a respective center of each side of the second polygon. The relative rotation of the first polygon from the second polygon makes the second edge distance D2 larger than the first edge distance D1. While the illustrated polygon is generally hexagonal, it is contemplated that other polygonal shapes may be used. Further, while the illustrated first polygon is rotated to the second polygon by about 30°, other rotations may be used that result in the second edge distance D 2 being greater than the first edge distance D 1.FIG. 5C is a top view of yet another example manifold portion 40 cto evenly distribute the contact pressure along the bead 42. The bead 42 is a first polygon that is generally hexagonal and the flange edge 104 is a second polygon that includes more corners than the first polygon - e.g., the illustrated second polygon is generally dodecagon. The second polygon is irregular and oriented relative to the first polygon such that the bead corners 108 are located proximate a corresponding side of the second polygon. As can be seen in FIG. 5C, the edge distances D for each bead corner 108 may be different distances even if the bead 42 forms a generally symmetric shape. For example, structures outside of the bead 42 may affect the deflection of the plate 12 such that different edge distances D at apparently symmetric regions may improve contact pressure distribution along the sealing surface 46 despite apparent symmetry of the bead 42 or the orifice 44.FIG. 5D is a top view of yet another example manifold portion 40 dto evenly distribute the contact pressure along the bead 42. The bead 42 is a first polygon that is generally hexagonal and irregular. The flange edge 104 is a second polygon that is generally dodecagon and irregular. The second polygon is oriented relative to the first polygon such that the bead corners 108 are located proximate a corresponding side of the second polygon.FIG. 6 is a top view of an example manifold portion 40 eto evenly distribute the contact pressure along the bead 42. The manifold section 40e includes a plurality of bead sides 106 and bead corners 108.As better seen in FIGS. 6A and 6B, the bead sides 106 include reinforcing structures 114 or "snubbings" following a generally convoluted path. These reinforcing structures 114 are configured to prevent occurrence of weak spots along straight paths of the bead 42 by preventing excessive deformation of the bead 42 when the plate 12 is compressed in the fuel cell stack 10. The bead side 106 is generally linear through the serpentine path of the reinforcing structures, as illustrated by line 120. Notably, the "warps" share a certain radius along the serpentine path, with first portions being rounded inward and second portions disposed between the first portions being rounded outward. For example, the serpentine portion of FIG. 6A may have a central portion that is rounded to the opening and outer portions that are rounded away from the opening 44. The radius of the central portion and the outer portions are generally the same.The bead corners 108 are generally rounded toward the opening 44. Each bead corner 108 has a generally uniform radius along the bead corner 108. An angled corner, represented by line 122, is shown along the bead 42 of FIGS. 6A and 6B. The rounded bead corner 108 intersects a vertex with the corner of the line 122. The radii of the bead corners are typically greater than the radii of the serpentine portions. The bead corners 108 generally have an increased contact pressure near the apex and a lower contact pressure near the bead sides 106.While the bead 42 of FIGS. 6, 6A and 6B includes features that are generally more curved than the angular features shown in the beads 42 of FIGS. 5A-5D, one of ordinary skill in the art will readily understand the differences between the serpentine feature bead sides 106 and the bead corners 108 having a generally continuous radius of curvature.For example, the bead corners 108 may be identified by determining areas of increased contact pressure along the bead 42. In this example, the bead corners 108 have a contact pressure that is generally higher near the apex and is generally lower near the bead sides 106.As also shown in FIGS. 6A and 6B, the flange edge 104 defines a plurality of features. For example, the flange edge 104 may include a first edge portion 116 disposed proximate the bead side 106 and a second edge portion 118 disposed proximate the bead corner 108. The edge distance along the second edge portion 118 is generally greater than the edge distance along the first edge portion 116.In some aspects, as shown in FIG. 6A, the bead side 106 is generally linear, while the first edge portion 116 near the bead side 106 is generally rounded. In some aspects, the bead corner 108 is generally rounded with a first radius while the second rim portion 118 is generally rounded with a larger radius. In some aspects, as further seen in FIG. 6A, the bead corner 108 is generally rounded while the second rim portion 118 is generally linear.In some aspects, as shown in FIG. 6B, both the bead side 106 and the first edge portion 116 follow a serpentine path near the bead side such that the edge distance D between the bead side and the first edge portion is generally constant.Advantageously, forming a flange having an edge distance D that is greater near the bead corners 108 than the edge distance D near the bead sides evenly distributes the contact pressure along the bead 42. In some examples, the edge distances D around the opening 44 are configured to provide a contact pressure distribution with a variance of less than about 30% along the bead 42.The determination of the contact pressure resulting from a particular design may be measured or modeled. For example, a model of a plate 12, manifold section 40, or flange 50 may use finite element analysis to estimate the contact pressure distribution along the bead 42 of an exemplary structure.FIGS. 7A and 7B are thermal maps of contact pressure along a bead 42 determined using finite element analysis. FIG. 7A shows a manifold where the distances between the bead 42 and the respective portions of the flange edge 104 are generally constant. As can be seen, the contact pressure along the sealing surface 46 at the indicated bead corners 108 is higher than the contact pressure along the sealing surface 46 at the bead sides 106 near the bead corners 108. In particular, not all bead corners 108 contain areas of significantly increased contact pressure. For example, the bead corners 108 shown in the upper left corner of FIG. 7A include significantly higher contact pressures than the bead corners 108 shown in the lower right corner of FIG. 7A. Accordingly, the edge distances D of certain bead corners 108 need not be increased to obtain a uniformly distributed contact pressure.FIG. 7B is a thermal map of contact pressure along a bead 42 for a flange 50 having a variable edge distance D, in accordance with aspects of the present disclosure. Notably, FIG. 7B differs from FIG. 7A in that the edge distance D for the bead corners 108 having a relatively higher contact pressure (e.g., the bead corners 108 in the upper left direction) is generally greater and the edge distance D for the bead corners 108 having a relatively lower contact pressure (e.g., the bead corners 108 in the lower right direction) is generally similar. FIG. 7B further differs from FIG. 7A in that the edge distance D along the bead side 106 at the right FIGS. 7A and 7B along the serpentine portion of the bead 42 is generally constant.FIG. 8 illustrates a method 800 for constructing a flange 50 in accordance with aspects of the present disclosure. The method 800 includes selecting 802 an initial construction, measuring 804 a contact pressure across the bead 42, analyzing 806 the contact pressure distribution, and reducing 808 variance in the contact pressure distribution. The initial flange construction includes at least a portion of a plate 12 having a through opening 44 and a bead 42 surrounding the opening. measuring 804 the contact pressure across the bead 42 creates a contact pressure distribution along the bead 42. measuring 804 the contact pressure may be accomplished, for example, using a mathematical model of the flange 50, direct testing of flange prototypes, in situ measurements, combinations thereof, and the like. The measurement via a mathematical model may be performed using, for example, finite element analysis, other calculation methods, combinations thereof, and the like. Analyzing 806 the contact pressure distribution includes identifying areas of relatively increased contact pressure and areas of relatively decreased contact pressure. Decreasing 808 the variance of the contact pressure distribution includes increasing an edge distance near one or more of the relatively increased contact pressure regions and / or decreasing an edge distance near one or more of the relatively decreased contact pressure regions.Advantageously, adjacent components including the beads 42 thereon may be configured to cooperatively operate to uniformly distribute the contact pressure along the beads 42. For example, a flange 50 of the first plate 12 may have a first construction and a corresponding flange 50 of the second plate 12 may have a second construction. The first construction and the second construction may be cooperatively configured such that areas of relatively greater contact pressure along the bead 42 on the first plate 12 correspond to areas of relatively lower contact pressure along the bead 42 of the second plate such that the contact pressure is still evenly distributed along the sealing surface 46.While the above-described areas of increased contact pressure have been described with respect to bead corners, it is contemplated that any area of increased stress may be evenly distributed by increasing plate material adjacent to the area of increased contact pressure and / or decreasing plate material adjacent to the areas of lower contact pressure.

Claims

A panel (12, 20) comprising: a bead (42) having a bead side (106) and a bead corner (108); and a flange edge (104) defining an opening (44) through the panel (12, 20), the flange edge (104) having a first edge portion (110, 116) proximate the bead side (106) and a second edge portion (112, 118) proximate the bead corner (108), the bead side (106) and the first edge portion (110, 116) defining a first edge distance (D1) therebetween, the bead corner (108) and the second edge portion (112, 118) defining a second edge distance (D2) therebetween, the second edge distance (D2) being greater than the first edge distance (D1), characterized in that, wherein the bead side (106) follows a serpentine path and wherein the first edge portion (110, 116) follows the serpentine path such that the first edge distance (D1) is substantially constant along the serpentine path.The panel (12, 20) of claim 1, wherein the first edge distance (D1) and the second edge distance (D2) are configured to provide a contact pressure with less than about 30% variance along the bead (42).The panel (12, 20) of claim 1, wherein the bead (42) generally defines a first polygon and the flange edge (104) generally defines a second polygon, the second polygon comprising more corners than the first polygon.The panel (12, 20) of claim 1, wherein the bead side (106) is generally linear and the bead corner (108) is generally rounded.The panel of claim 1, wherein the first rim portion (110, 116) is generally rounded and the second rim portion (112, 118) is generally linear.A system comprising: a first panel (12, 20) having: a bead (42) having a bead side (106) and a bead corner (108); and a flange edge (104) defining a first opening (44) through the first panel (12, 20), the flange edge (104) having a first edge portion (110, 116) proximate the bead side (106) and a second edge portion (112, 118) proximate the bead corner (108), the bead side (106) and the first edge portion (110, 116) defining a first edge distance (D1) therebetween, the bead corner (108) and the second edge portion (112, 118) defining a second edge distance (D2) therebetween, the second edge distance (D2) being greater than the first edge distance (D1); a second plate (12, 20) abutting the first plate (12, 20), the second plate (12, 20) having a second opening (44) therethrough, the second opening (44) aligned with the first opening (44); and a compression element (16) configured to apply a compressive force to the first plate (12, 20) and the second plate (12, 20), the compressive force configured to seal the first plate (12, 20) and the second plate (12, 20) along the bead (42), characterized in that the bead side (106) follows a serpentine path and wherein the first edge portion (110, 116) follows the serpentine path such that the first edge distance (D1) is substantially constant along the serpentine path.The system of claim 6, wherein the second plate (12, 20) further comprises: a second bead (42) having a second bead side (106) and a second bead corner (108); and a second flange edge (104) defining the second opening (44), the second flange edge (104) having a third edge portion proximate the second bead side (106) and a fourth edge portion proximate the second bead corner (108), the second bead side (106) and the third edge portion defining a third edge distance therebetween, and the second bead corner (108) and the fourth edge portion defining a fourth edge distance therebetween, the fourth edge distance being greater than the third edge distance.The system of claim 7, wherein the first plate (12, 20) further comprises a first working surface (36a) on which the bead (42) is disposed and a first rear surface opposite the first working surface (36a); and the second plate (12, 20) further comprises a second working surface (36b) on which the second bead (42) is disposed and a second rear surface opposite the second working surface (36b), the first rear surface being disposed adjacent the second rear surface, the first plate (12, 20) being attached to the second plate (12, 20); wherein the bead (42) produces a first contact pressure distribution with a portion of relatively higher contact pressure; wherein the second bead (42) produces a second contact pressure distribution with a portion of relatively lower contact pressure; and wherein the bead (42) and the second bead (42) are cooperatively configured such that the relatively higher contact pressure portion is relatively adjacent to the relatively lower contact pressure portion.A fuel cell stack (10) comprising: a first plate (12, 20) having: a first working surface (36a) defining a plurality of first reactant channels (24b, 26b); a bead (42) disposed on the first working surface (36a), the bead (42) having a bead side (106) and a bead corner (108); and a first flange edge (104) defining a first opening (44) through the first plate (12, 20), the first flange edge (104) having a first edge portion (110, 116) proximate the bead side (106) and a second edge portion (112, 118) proximate the bead corner (108), the first edge portion (110, 116) and the bead side (106) defining a first edge distance (D1) therebetween, the second edge portion (112, 116), 118) and the bead corner (108) defining a second edge distance (D2) therebetween, the second edge distance (D2) being greater than the first edge distance (D1); a second plate (12, 20) having: a second working surface (36b) defining a plurality of second reactant channels (24b, 26b); and a second flange edge (104) defining a second opening (44) through the second plate (12, 20), the second opening (44) aligned with the first opening (44); a unified electrode assembly (14) disposed between the first plate (12, 20) and the second plate (12, 20), the unified electrode assembly (14) having a first side contacting the plurality of first reactant channels (24b, 26b) and a second side contacting the plurality of second reactant channels (24b, 26b); and a compression element (16) configured to apply a compressive force to the first plate (12, 20), the second plate (12, 20), and the unified electrode assembly (14), wherein the compressive force is configured to apply a contact pressure to the bead (42) to provide a substantially fluid-tight seal between the bead (42) and the second plate (12, 20) or the unified electrode assembly (14), characterized in that the bead side (106) follows a serpentine path and wherein the first edge portion (110, 116) follows the serpentine path such that the first edge distance (D1) is substantially constant along the serpentine path.

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