Z-shaped foam metal runner composite flow field bipolar plate for fuel cell

Abstract

The invention discloses a composite flow field bipolar plate with a Z-shaped foam metal flow channel for a fuel cell. The composite flow field bipolar plate comprises a flow channel main body, a ridge structure, a pressure balance cavity, a metal substrate and a foam metal layer, the metal substrate is spliced with the foam metal layer, and the foam metal layer is of a porous structure; the flow channel body comprises a plurality of Z-shaped flow channels, the ridge structure comprises a plurality of Z-shaped ridges, the flow channels and the ridges are distributed in a flow field in a crossed mode, liquid water in an area prone to water accumulation (such as the center of the flow field) is absorbed and conveyed to an area prone to water loss (such as an inlet of the flow field) through capillary force generated by the micropore structure in the foam metal layer, and dynamic balance of water management is achieved. And if the pressure balance cavity is blocked by liquid water, the gas pressure at the upstream of the pressure balance cavity is properly increased, so that the capability of purging accumulated water in the pipe is enhanced. However, the pressure of the upstream gas cannot suddenly rise based on the porous structure having the characteristic of slow pressure release, so that the operation stability of the system is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a composite metal bipolar plate structure for a fuel cell suitable for generating liquid water. Background Art

[0002] Low water content in the proton exchange membrane (PEM) significantly reduces the proton conductivity of the sulfonic acid groups, triggering ohmic polarization. High water content, however, causes liquid water to form a continuous film at the catalyst layer / gas diffusion layer (CL / GDL) interface, leading to concentration polarization and hindering gas diffusion. Large-scale fuel cell stacks are particularly susceptible to flooding due to insufficient gas purge at the interface between the GDL and the plate ridges. Conventional plates utilize a dense solid ridge structure, forming a close interface with the GDL. This prevents gas from being effectively purged from the microchannels beneath the ridges, leading to liquid water retention. Furthermore, the solid ridges and flow channels are difficult to retain water, which can easily lead to localized drying of the membrane electrode.

[0003] By changing the cross-sectional area of ​​the flow channel, the drainage of water accumulated under the ridge can be accelerated (patent CN216624345U), but this increases the flow channel resistance and the difficulty of flow channel processing. A TiN / TiC gradient coating (patent CN113921832A) is used to separate the hydrophilic and hydrophobic regions, but this increases material costs. Although introducing temperature-humidity-pressure closed-loop control into the fuel cell can balance the membrane electrode wettability (RH=40-60%) with drainage requirements in real time (patent CN116826120A), it increases the control cost of the fuel cell. Therefore, a low-cost, easy-to-manufacture bipolar plate that actively controls the membrane electrode water balance needs to be developed. Summary of the Invention

[0004] In order to overcome at least one of the deficiencies of the prior art, the present invention provides a bipolar plate with a Z-shaped foam metal flow channel and a composite flow field for a fuel cell.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a "Z"-shaped foam metal flow channel composite flow field bipolar plate for a fuel cell, comprising a flow channel body, a ridge structure, a pressure balance cavity, a metal substrate, and a foam metal layer;

[0006] The metal substrate is spliced ​​with the foam metal layer, and the foam metal layer has a porous structure;

[0007] The flow channel body includes several "Z"-shaped flow channels, and the ridge structure includes several "Z"-shaped ridges. The flow channels and ridges are cross-distributed in the flow field. The flow channels and ridges guide the gas to change the flow direction and use the fluid inertia to purge the liquid water in the ridges.

[0008] The pressure balance chamber dynamically compensates for the upstream and downstream pressure differences in the flow field through airflow redistribution optimization;

[0009] The flow channel body and the ridge structure form a three-dimensional flow guide structure, and the three-dimensional flow guide structure establishes a membrane electrode water content self-regulating mechanism through the synergistic effect of the water storage characteristics of the porous medium and the inertial effect of the flow channel.

[0010] Further, the ridge is arranged between adjacent flow channels, and the shape of the ridge on the flow field projection plane forms a repeatedly arranged "Z" shaped structure.

[0011] Further, the flow channel comprises a flow channel metal substrate and a flow channel foam metal layer, the ridge comprises a ridge metal substrate and a ridge foam metal layer, the flow channel metal substrate and the ridge metal substrate are partial structures of the metal substrate, the flow channel foam metal layer and the ridge foam metal layer are partial structures of the foam metal layer, the flow channel foam metal layer and the ridge foam metal layer are both arranged to face the membrane electrode, and the ridge foam metal layer directly contacts the gas diffusion layer of the membrane electrode.

[0012] Further, the flow channel is a convex structure, and the ridge is a concave structure.

[0013] Further, the flow channel body comprises a plurality of parallel flow channels arranged in parallel, the parallel flow channel comprises a plurality of flow channels arranged in parallel, a pressure balance cavity is arranged at the upstream and downstream of the flow channel body, and the end portions of two adjacent groups of parallel flow channels are communicated through the pressure balance cavity, so as to collect and redistribute the gas in the flow field.

[0014] Further, the flow field wall is further arranged, and the flow field wall is fixedly arranged on the metal substrate, the flow field region is formed in the flow field wall, and the flow field wall is used for restricting the flow path of the gas in the flow field.

[0015] Further, the flow field inlet structure and the flow field outlet structure are further arranged, and the flow field inlet structure and the flow field outlet structure are arranged on the metal substrate and located at the upper and lower sides of the flow field respectively, the flow field inlet structure is used for distributing the reaction gas to the flow field, the reaction gas enters the flow channel through the flow field inlet, is transmitted to the flow field outlet through the flow channel, and is output through the flow field outlet structure.

[0016] Further, the sealing structure is further arranged, and the sealing structure comprises a sealing gasket, the sealing gasket is fixedly arranged on the metal substrate, and the flow field wall, the flow field inlet structure and the flow field outlet structure are all located in the sealing region formed by the sealing gasket.

[0017] Further, the flow channel foam metal layer comprises a flow channel foam layer elbow and a flow channel foam layer straight line, the ridge foam metal layer comprises a ridge foam metal layer elbow and a ridge foam metal layer straight line, the flow channel foam layer elbow and the ridge foam metal layer elbow are "Z" shaped arc corner regions, which are gradual curvature transition structures, the ridge and the adjacent flow channel are seamlessly connected through geometric complementarity, and a continuous curved surface transition region is formed in the connection region.

[0018] In summary, the present application has the following advantages:

[0019] 1) The present application can realize the automatic dynamic adjustment function of the water content in the membrane electrode and the gas pressure distribution in the flow channel. When the membrane electrode is flooded, the ridge foam metal layer in direct contact with the membrane electrode can absorb and temporarily store excess water; the designed "Z" type flow channel structure can drive the gas to blow off the accumulated water in the ridge, and enhance the water discharge. When the flow channel is partially blocked due to water accumulation, the upstream gas will be diverted to the adjacent flow channel at the pressure balance chamber, thereby maintaining the continuity of the overall gas delivery. The liquid water in the water accumulation area will be absorbed by the porous structure of the ridge and the flow channel, thereby realizing the active dredging of the flow channel. When the membrane electrode is in a water loss state, the liquid water stored in the porous ridge will be transmitted to the membrane electrode in reverse through the diffusion mechanism, realizing the rewetting of the membrane electrode and maintaining the stability of its working state.

[0020] 2) The present application adopts a structure of multiple parallel flow channels and pressure balance chambers, and sets the pressure balance chamber 12 between two adjacent parallel flow channels. When a parallel flow channel is blocked due to water accumulation, the pressure balance chamber 12 can rebalance the gas pressure in the area, thereby avoiding a sudden rise in local gas pressure. The accumulated water can be absorbed by the porous material of the foam metal layer and guided to the remaining unobstructed flow channels through capillary action, avoiding local liquid water accumulation.

[0021] 3) The pressure balance chamber of the present application is arranged between the upstream and downstream of the flow channel, for realizing the collection and redistribution of gas in the flow field; compared with a single serpentine flow channel, the composite flow field structure effectively reduces the pressure difference between the gas inlet and outlet through the synergistic effect of the pressure balance chamber 12 and the parallel flow channel, reduces the power loss of the gas pump; compared with a single parallel flow field, the drainage capacity is significantly improved, the concentration polarization problem caused by local flooding is alleviated, and the overall performance and stability of the fuel cell are improved.

[0022] 4) The present application is aimed at the common problem of uneven distribution of dry and wet during the operation of the fuel cell, and uses the capillary force generated by the microporous structure in the foam metal layer to absorb and transport the liquid water in the easy water accumulation area (such as the center of the flow field) to the easy water loss area (such as the inlet of the flow field), realizing the dynamic balance of water management. If the pressure balance chamber is blocked by liquid water, the gas pressure upstream of the pressure balance chamber will increase moderately, thereby enhancing the blow-off capacity of the accumulated water in the pipe. However, based on the pressure relief characteristics of the porous structure, the upstream gas pressure will not rise suddenly, thereby ensuring the stability of the system operation.

[0023] 5) The sealing groove cooperates with the sealing gasket to form an airtight interface, thereby effectively sealing the gas inside the flow field. After being sealed by the sealing groove and the sealing gasket, the hydrogen, air and cooling liquid can be isolated from each other, thereby ensuring that the three kinds of gas are completely separated during the transmission process. The sealing gasket 7 located adjacent to the flow field wall 11 is used to separate the inlet and outlet areas of the gas, thereby preventing direct contact between different gases from a structural point of view. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the composite bipolar plate of the present application.

[0025] Figure 2 It is a schematic diagram of the cross-sectional structure of the flow channel and the ridge of the present application.

[0026] Figure 3 It is a schematic diagram of the air purging water in the ridge of the present application.

[0027] Figure 4 It is a schematic diagram of the water transfer in the gas diffusion layer to the ridge and the flow channel of the present application.

[0028] Figure 5 It is a schematic diagram of the back diffusion of water in the ridge and the flow channel to the gas diffusion layer of the present application. DETAILED DESCRIPTION

[0029] The embodiments of the present application will be described in detail below with specific reference to the drawings. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in the specification. The present application can also be implemented or applied in other different embodiments, and various modifications or changes can be made to the details in the specification without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict.

[0030] It should be noted that the diagrams provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components when actually implemented. The actual implementation of each component may be a random change in type, number and proportion, and the layout type of the components may also be more complex.

[0031] All directional indications (such as up, down, left, right, front, back, transverse, longitudinal, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain specific posture, and if the specific posture changes, the directional indications will also change accordingly.

[0032] Due to installation errors and other reasons, the parallel relationship referred to in the embodiments of the present invention may actually be an approximately parallel relationship, and the perpendicular relationship may actually be an approximately perpendicular relationship.

[0033] Example:

[0034] like Figures 1-5 As shown, a "Z"-shaped foam metal flow channel composite flow field bipolar plate for a fuel cell includes a flow channel body, a ridge structure, a pressure balance chamber 12, a metal substrate 10 and a foam metal layer. The metal substrate 10 is spliced ​​with the foam metal layer. A flow field is provided on the metal substrate 10. The flow channel body and the ridge structure constitute a three-dimensional flow guide structure. The flow channel body includes a plurality of "Z"-shaped flow channels 8, and the ridge structure includes a plurality of "Z"-shaped ridges 9. The flow channels 8 and the ridges 9 are cross-distributed in the flow field. The flow channels 8 and the ridges 9 guide the gas to change the flow direction and purge the porous ridges with the help of fluid inertia. The pressure balance chamber 12 is arranged upstream and downstream of the flow channel 8.

[0035] like Figure 1 As shown, the flow field includes an upstream 111 and a downstream 112 . The upstream 111 has a flow field inlet 113 , and the downstream 112 has a flow field outlet 114 .

[0036] The metal substrate 10 and the metal foam layer are joined together to form the bipolar plate. The bipolar plate, along with the flow channel body and ridge structure, fulfill core functions such as gas transmission, mechanical support, and current collection. The joining method is not limited to welding, cold pressing, plasma spraying, and other processing techniques. The metal substrate 10 and the metal foam layer are tightly bonded to avoid delamination or voids, ensuring structural integrity and excellent flow and electrical conductivity.

[0037] The metal substrate 10 and the metal foam plate can be made of the same or different materials, depending on the application environment and performance requirements. After being joined, they are processed into the desired structure through stamping and die-forming processes. The metal foam layer, due to its excellent ductility, effectively relieves localized stress during the stamping and die-forming process, reducing the risk of deformation or cracking of the metal substrate, thereby improving the yield rate of the finished bipolar plate.

[0038] Preferably, the metal substrate 10 is made of one or more alloy systems selected from 304L stainless steel, 316L stainless steel, AA6061 aluminum alloy or TU1 oxygen-free copper. Its coefficient of thermal expansion (CTE) must match the CTE of the foam metal layer and MEA, so that it has moderate hardness and ductility, facilitates the implementation of stamping and molding processes, and is beneficial to the thermal stability and long-term reliability of the composite structure; the thickness of the metal substrate 10 ranges from 0.1 to 0.3 mm, with a tolerance controlled within ±0.02 mm; the metal substrate 10 and the foam metal layer form a dense metallurgical bonding interface through welding or cold isostatic pressing.

[0039] The foam metal layer has a high specific surface area porous structure, which constitutes a porous medium channel, and a porosity of 10-75%.

[0040] The ridge 9 is arranged between the adjacent flow channels 8, and the shape of the ridge 9 on the projection plane of the flow field constitutes a repeated "Z" shaped structure.

[0041] The inertial force generated by the gas flow in the flow channel 8 sweeps the liquid water in the ridge 9 to the adjacent flow channel 8, and the three-dimensional flow guiding structure cooperates with the water storage characteristics of the porous medium and the inertial effect of the flow channel to establish a water content self-regulating mechanism of the membrane electrode.

[0042] As shown in Figure 2 , the flow channel 8 is an upwardly concave structure, and the ridge 9 is a downwardly convex structure. The flow channel 8 includes a flow channel metal substrate 81 and a flow channel foam metal layer 82, and the ridge 9 includes a ridge metal substrate 91 and a ridge foam metal layer 92. The flow channel metal substrate 81 and the ridge metal substrate 91 are partial structures of the metal substrate 10, and the flow channel foam metal layer 82 and the ridge foam metal layer 92 are partial structures of the foam metal layer. The flow channel foam metal layer 82 and the ridge foam metal layer 92 are porous medium layers, and both face the membrane electrode. The ridge foam metal layer 92 is in direct contact with the gas diffusion layer 13 of the membrane electrode.

[0043] When excess water accumulates inside the membrane electrode, the foam metal ridge in contact with the gas diffusion layer guides the liquid water in the membrane electrode into the foam metal layer of the ridge and the flow channel through capillary force. The "Z" shaped flow channel guides the gas to constantly change the flow direction. When the gas changes the flow direction each time, part of the gas enters the foam metal ridge due to the inertial effect, thereby carrying and removing the liquid water therein.

[0044] When the membrane electrode is in a dry state, the liquid water stored in the foam metal ridge and the foam metal flow channel will be reversely transmitted to the membrane electrode through the porous medium channel in contact with the membrane electrode, thereby re-wetting the membrane electrode.

[0045] As shown in Figure 3 , when a certain position of the flow channel 8 is blocked due to the accumulation of liquid water, the porous structure of the ridge foam metal layer 92 allows the gas in the adjacent flow channel 8 to diffuse to the blocked flow channel, so that the downstream area of the flow channel 8 can still continuously carry out the electrochemical reaction. The flow channel 8 adopts a "Z" shaped structure, and the gas in the flow channel 8 generates an inertial impact force when passing through the ridge 9 due to the change of the flow direction, thereby effectively sweeping the water accumulated in the ridge 9. The water accumulated in the ridge is driven and transferred to the adjacent flow channel 8 under the action, thereby relieving the local waterlogging problem.

[0046] As shown in Figure 3As shown, the reactant gas in the flow channel 9 can be smoothly delivered into the ridge foam metal layer 92, ensuring the gas diffusion into the gas diffusion layer 13 under the ridge. Since the gas diffusion layer 13 of the membrane electrode is adjacent to the ridge foam metal layer 92, sufficient air supply can be obtained thereunder, thereby achieving higher current density output and improving the overall performance of the fuel cell.

[0047] In the conventional solid structure, the liquid water in the area under the ridge is difficult to be effectively guided into the flow channel, which easily causes local water accumulation and gas transmission obstruction. In the present application, as shown, Figure 4 As shown, the liquid water in the gas diffusion layer 13 under the flow channel 8 can be easily transported to the surface to form liquid water droplets and be removed by the sweeping gas. The liquid water in the gas diffusion layer 13 under the ridge 9 migrates into the flow channel foam metal layer 82 in the direction of the arrow through the porous structure of the ridge foam metal layer 92. The liquid water in the flow channel foam metal layer 82 is precipitated on the surface to form water droplets and is finally carried away by the gas flow. Compared with the conventional flow field, the water droplets are only precipitated on the surface of the gas diffusion layer 13, which has a two-dimensional feature. In the present application, the water droplets are precipitated around the flow channel wall, which has a three-dimensional feature. The bipolar plate with the foam metal composite structure significantly enhances the gas transmission capacity in the gas diffusion layer 13 under the ridge, effectively alleviates the "water flooding" problem, improves the current density in the area under the ridge, and thus improves the overall power density of the fuel cell.

[0048] When the fuel cell is switched from a high-power density condition to a low-power density condition, the water production in the catalyst layer of the membrane electrode decreases due to the reduction of the electrochemical reaction rate, resulting in the decrease of the water content in the membrane electrode. Consequently, the water content in the gas diffusion layer 13 also decreases. As shown, Figure 5 The pre-accumulated liquid water in the ridge foam metal layer 92 can be diffused to the membrane electrode in the opposite direction along the concentration gradient, thereby maintaining the appropriate water content and high proton conductivity of the membrane electrode and ensuring the good power generation stability of the fuel cell under high-low load switching operation.

[0049] The water content in the downstream area 112 of the flow channel is usually higher than that in the upstream area 111, which causes the membrane electrode at the inlet 113 of the flow field to easily dry out, while the membrane electrode at the center of the flow field and the outlet 114 of the flow field is prone to water flooding. As shown, Figure 4 The liquid water in the gas diffusion layer 13 at the outlet 114 of the flow field can be absorbed by the ridge foam metal layer 92 connected thereto. The capillary force in the ridge foam metal layer 92 can drive the liquid water to be transported from the center of the flow field and the outlet 114 of the flow field to the inlet 113 of the flow field. At the inlet 113 of the flow field, as shown, Figure 5As shown, when the water content in the ridged metal foam layer 92 is higher than that in the gas diffusion layer 13, liquid water can be transferred from the ridged metal foam layer 92 to the gas diffusion layer 13, thereby increasing the water content in the membrane electrode at the flow field inlet 113. The balanced water content across the entire membrane electrode area helps improve the overall power density and operational stability of the fuel cell.

[0050] This invention addresses the common problem of uneven wet / dry distribution during fuel cell operation. By utilizing the capillary force generated by the microporous structure of the metal foam layer, it absorbs liquid water from areas prone to water accumulation (such as the center of the flow field) and transports it to areas prone to water loss (such as the flow field inlet 113), achieving dynamic water balance. If the pressure balancing chamber 12 is blocked by liquid water, the gas pressure upstream of the chamber will moderately increase, thereby enhancing the ability to purge accumulated water within the tube. However, due to the porous structure's ability to slowly release pressure, the upstream gas pressure will not increase suddenly, thus ensuring system operational stability.

[0051] like Figure 3 As shown, the flow channel 8 and the ridge 9 are both "Z"-shaped structures. Specifically, the flow channel foam metal layer 82 includes a flow channel foam layer bend 821 and a flow channel foam layer straight channel 822, and the ridge foam metal layer 92 includes a ridge foam metal layer bent arm 921 and a ridge foam metal layer straight arm 922. The flow channel foam layer bend 821 and the ridge foam metal layer bent arm 921 are "Z"-shaped arc-shaped corner areas, which are gradual curvature transition structures to facilitate the implementation of the stamping forming process; the ridge 9 and the adjacent flow channel 8 are seamlessly connected through geometric complementarity, and the connection area forms a continuous curved surface transition zone.

[0052] The cross section of the flow channel 8 is trapezoidal (base angle 30°±2°, upper base / lower base ratio 1:1.2-1:1.5) or rectangular (length-to-width ratio 1:1.8-1:2.2); the depth tolerance of the flow channel 8 is controlled within ±0.03mm (measuring range 0.3-0.5mm), and the width tolerance is ±0.05mm (measuring range 0.3-1.0mm).

[0053] The flow channel metal substrate 81 and the flow channel foam metal layer 82 of the flow channel 8 form a metallurgical bonding interface by welding or cold forging; the flow channel foam metal layer 82 is 304L stainless steel or 316L stainless steel foam metal (porosity 10-75%, preferably 40-75%).

[0054] The cross-section of ridge 9 is an isosceles trapezoid (base angle 35°±2°, upper base / lower base ratio 1:1.2-1:1.5) or a rectangle (length-to-width ratio 1:1.8-1:2.2). The ridge 9 and the adjacent flow channel are seamlessly connected through geometric complementarity, and the connection area forms a continuous curved transition zone; the width tolerance of ridge 9 is controlled within ±0.05mm (measuring range 0.3-1.0mm).

[0055] The ridge metal substrate 91 and the ridge foam metal layer 92 of the ridge 9 are formed into a metallurgical bonding interface by welding or cold forging; the ridge foam metal layer 92 is 304L stainless steel or 316L stainless steel foam metal (porosity 10-75%, preferably 40-75%);

[0056] The pressure balancing chamber 12 is arranged upstream and downstream of the flow channel body, and the pressure balancing chamber 12 realizes dynamic compensation of upstream and downstream pressure difference through airflow redistribution optimization.

[0057] The position of the pressure balance chamber 12 is specifically:

[0058] The flow channel body includes a number of parallel flow channels arranged in parallel, and the parallel flow channels include a number of parallel distributed and branched flow channels 8. The ends of two adjacent groups of parallel flow channels are connected through a pressure balancing chamber 12, that is, the pressure balancing chamber 12 connects the two adjacent upstream and downstream groups of parallel flow channels in series. For example, when the number of parallel flow channels is 5 groups, the ends of one side of group 1 and group 2 are respectively connected to the pressure balancing chamber 12, the other side of group 2 and the ends of group 3 on the same side are respectively connected to the pressure balancing chamber 12, the other side of group 3 and the ends of group 4 on the same side are respectively connected to the pressure balancing chamber 12, and the other side of group 4 and the ends of group 5 on the same side are respectively connected to the pressure balancing chamber 12; the pressure balancing chamber 12 collects the gas from the previous group of parallel flow channels and redistributes it to the next group of parallel flow channels, so as to achieve uniformity of the overall air pressure distribution by balancing the local high-pressure areas and low-pressure areas formed in the flow field.

[0059] like Figure 1 As shown, a group of parallel flow channels includes three branched flow channels 8 arranged in parallel. The gases in the three flow channels 8 are collected in a pressure balancing chamber 12 and redistributed to the three adjacent parallel flow channels. If one of the flow channels 8 is blocked by water, the gas will flow into the pressure balancing chamber 12 from the other two flow channels 8, and diffuse from the pressure balancing chamber 12 and return to the blocked flow channel, thereby ensuring that the gas pressure in the blocked flow channel will not rise suddenly. Any two adjacent groups of parallel flow channels have a pressure balancing chamber 12, so the pressure balancing chamber can control the pressure balance of the entire flow field.

[0060] This application utilizes a composite structure of multiple parallel flow channels and a pressure-balancing chamber 12, with the pressure-balancing chamber 12 positioned between two adjacent sets of parallel flow channels. When water accumulation in a parallel flow channel obstructs gas flow, the pressure-balancing chamber 12 rebalances the gas pressure in that area, thereby preventing localized pressure surges. Accumulated water is absorbed by the porous material of the metal foam layer and directed through capillary action to the remaining unobstructed flow channels, preventing localized accumulation of liquid or water.

[0061] The pressure balance cavity is arranged between the upstream and downstream of the flow channel, and is used for realizing the collection and redistribution of the gas in the flow field; compared with the single serpentine flow channel, the composite flow field structure effectively reduces the pressure difference between the gas inlet and outlet by the cooperation of the pressure balance cavity 12 and the parallel flow channel, and reduces the power loss of the gas pump; compared with the single parallel flow field, the drainage capacity is significantly improved, the concentration polarization problem caused by local flooding is relieved, and the overall performance and stability of the fuel cell are improved.

[0062] The pressure balance cavity 12 adopts a trapezoidal cross-section transition structure (upper base / lower base ratio 1:1.2-1:1.5) to realize pressure balance of the parallel flow channel, and the axial depth and the height difference of the flow channel bottom surface are ≤±0.02mm; the pressure balance cavity 12 is prepared by cold forging, the width range is 1-2mm, and the tolerance is controlled within ±0.05mm.

[0063] The "Z" type foam metal flow channel composite flow field bipolar plate for fuel cells also comprises a flow field wall 11 fixedly arranged on the metal substrate 10, and the flow field wall 11 is a continuous closed cavity structure, and the inside is a flow field area, that is, the flow field wall is an outer edge wall of the flow field, and is used for restricting the flow path of the gas in the flow field.

[0064] As shown in Figure 1 two adjacent parallel flow channels are arranged through the pressure balance cavity 12, specifically, one side of the outer flow channel 8 of the parallel flow channel is fixedly connected with the flow field wall 11, and the other side is connected with the adjacent parallel flow channel through the pressure balance cavity 12, and the path of the flow channel inlet, the flow channel to the flow channel outlet is sequentially connected in turn.

[0065] Preferably, the parallel flow channel comprises three branched flow channels 8, one side of the third flow channel 8 of the parallel flow channel A is fixedly connected with the flow field wall 11 located at the upstream, and a closed interval is formed at this position, the other side of the third flow channel 8 is connected with the adjacent parallel flow channel B through the pressure balance cavity 12 at the downstream area, one side of the third flow channel 8 of the parallel flow channel B is fixedly connected with the flow field wall 11 located at the downstream, and a closed interval is formed at this position, the other side of the third flow channel 8 is connected with the adjacent parallel flow channel C through the pressure balance cavity 12 at the upstream area, and the arrangement is sequentially and reciprocally arranged.

[0066] Preferably, the flow field wall 11 is formed into a continuous closed cavity structure by a cold forging process, and the forming pressure is 100-400MPa (pressure holding time ≥20min).

[0067] Preferably, the width of the flow field wall 11 is 0.6-1mm, and the tolerance is controlled within ±0.03mm; the axial height difference of the flow field wall 11 and the top surface height of the ridge 9 is ≤±0.02mm.

[0068] The "Z" type foam metal flow channel composite flow field bipolar plate for fuel cell further comprises a flow field inlet structure and a flow field outlet structure, which are arranged on the metal substrate 10 and located on the upper and lower sides of the flow field respectively, and the flow field inlet structure distributes the reaction gas to the flow field through the flow channel inlet 113, and the flow channel outlet 8, and then the flow field outlet 114, and then the flow field outlet structure outputs.

[0069] The flow field inlet structure comprises an air inlet manifold 1, a hydrogen inlet manifold 3, a cooling liquid inlet 21 and an inlet manifold 5, the air inlet manifold 1 and the hydrogen inlet manifold 3 are communicated with the inlet manifold 5 respectively, the inlet manifold 5 is connected with the flow channel inlet, the inlet manifold 5 is arranged between the air inlet manifold 1, the hydrogen inlet manifold 3 and the flow channel inlet, and the inlet manifold 5 is used for distributing the gas before entering the flow field; the flow field outlet structure comprises an air outlet manifold 2, a hydrogen outlet manifold 4, a cooling liquid outlet 22 and an outlet manifold 6, the air outlet manifold 2 and the hydrogen outlet manifold 4 are communicated with the outlet manifold 6 respectively, the outlet manifold 6 is connected with the flow channel outlet, the outlet manifold 6 is arranged between the air outlet manifold 2, the hydrogen outlet manifold 4 and the flow channel outlet, and the outlet manifold 6 is used for collecting the gas discharged from each flow channel; the air inlet manifold 1 and the hydrogen inlet manifold 3 distribute the reaction gas to the inlet manifold 5, and then the gas is transmitted to the outlet manifold 6 through the flow channel 8 and then flows into the air outlet manifold 2 and the hydrogen outlet manifold 4.

[0070] The air inlet manifold 1, the hydrogen inlet manifold 3, the air outlet manifold 2 and the hydrogen outlet manifold 4 all adopt a hollow flow guide structure, the cross section of which is in the shape of a rectangle (length-width ratio 1:1.5-2:1), an isosceles triangle (top angle 30°-60°) or an isosceles trapezoid (bottom angle 45°-75°), preferably, the hollow flow guide structure forms a gradually expanding inlet (converging angle ≤15°) and a gradually narrowing outlet (diffusion angle ≤20°) through a stamping forming process, so as to optimize the uniformity of gas flow distribution and reduce the flow resistance.

[0071] The orthogonal projection of the inlet manifold 5 and the outlet manifold 6 in the flow channel cross section plane is in the shape of an isosceles trapezoid (bottom angle 35°±2°, upper base / lower base ratio 1:1.2-1:1.5) or a rectangle (length-width ratio 1:1.8-1:2.2), so as to constitute a fluid distribution network; the number of parallel flow channels connected by the inlet manifold 5 and the outlet manifold 6 is 3-10, and the center distance tolerance of adjacent flow channels is controlled within ±0.08 mm, so as to ensure that the error of reaction gas distribution uniformity is not more than ±3% and reduce the flow separation effect.

[0072] The "Z" type foam metal runner composite flow field bipolar plate for fuel cell further comprises a sealing structure, the sealing structure comprises a sealing gasket 7 fixedly arranged on the metal substrate 10, the flow field wall 11, the flow field inlet structure and the flow field outlet structure are located in a sealing area formed by the sealing gasket 7, effective sealing of the gas in the flow field is realized, and the air inlet manifold 1, the hydrogen inlet manifold 3, the cooling liquid inlet 21, the air outlet manifold 2, the hydrogen outlet manifold 4 and the cooling liquid outlet 22 are arranged in isolation through the sealing gasket 7, so that effective isolation of hydrogen, air and cooling liquid is realized, and complete separation of the three gases in the transmission process is ensured.

[0073] The metal substrate 10 is provided with a sealing groove, the sealing gasket 7 is installed in the sealing groove, and the two cooperate to form an airtight interface, realize effective sealing of the gas in the flow field, and realize mutual isolation between hydrogen, air and cooling liquid after packaging through the sealing groove and the sealing gasket, so as to ensure complete separation of the three gases in the transmission process. The sealing gasket 7 located adjacent to the flow field wall 11 is used to separate the inlet and outlet areas of the gas, and to prevent direct contact between different gases from the structure.

[0074] In order to further improve the sealing performance, a sealing glue is arranged between the sealing gasket 7 and the flow field wall 11, which effectively fills the interface gap, thereby completely blocking the flow of gas between the inlet and the outlet, ensuring the independence of the gas flow path and the stability of the system operation.

[0075] The sealing gasket 7 is made of elastic sealing material, specifically fluororubber (FKM) or hydrogenated nitrile rubber (HNBR), and has a chemical corrosion resistance of 85℃ fuel cell working condition for 1000 hours, with a volume expansion rate of ≤3%.

[0076] The sealing groove is a groove structure formed by stamping process on the metal substrate; the cross section of the sealing groove is rectangular (length-width ratio 1:1.2-1:1.5) or semicircular (radius R=0.5-1.2mm); the depth tolerance of the sealing groove is controlled within ±0.05mm, the surface roughness Ra of the groove bottom is ≤0.8μm, and a continuous closed cavity is formed by cold forging process, and a chamfer structure (chamfer angle 45°±2°) is arranged at the inlet end of the sealing groove to reduce the assembly stress.

[0077] The flow field boundary is provided with a protruding structure, which forms a boundary wall of the flow field for limiting the gas leakage in the flow field. The boundary wall cooperates with the proton exchange membrane to seal and prevent gas leakage.

[0078] Preferably, the air inlet manifold 1 is connected with air, and the hydrogen inlet manifold 3 is connected with hydrogen.

[0079] The foam metal layer of the present application forms a composite flow field with the metal substrate, constituting a water management core. The flow field realizes dynamic wetting balance between the flow channel and the membrane electrode assembly (MEA) through a short-time water storage mechanism: when water accumulates under the ridge structure, the high specific surface area porous structure of the foam metal layer absorbs the liquid water inside the gas diffusion layer (GDL) through capillary driving force, and carries it away from the membrane electrode with the flow channel gas flow; when the water in the ridge area of the Z-shaped ridge structure exceeds the critical value, the inertial force (including Bernoulli effect pressure gradient and gas flow pulsation) of the high-speed gas in the adjacent flow channel drives the water to migrate across the flow channel and be discharged; when the water content of the membrane electrode is low, the water stored in the ridge foam metal layer is back permeated to the membrane electrode through capillary backflow or water vapor diffusion, compensating the water content of the proton exchange membrane to maintain the appropriate wetting state. Through the synergistic effect of capillary regulation-inertial purging-reverse compensation, the present application effectively suppresses the extreme working conditions of membrane electrode flooding and drying, significantly improves the output stability and power density of fuel cells under high current density.

[0080] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

Claims

1. "Z"-shaped foam metal flow channel composite flow field bipolar plate for fuel cells, characterized by: It includes a flow channel body, a ridge structure, a pressure balance cavity, a metal substrate and a foam metal layer; The metal substrate is spliced ​​with the foam metal layer, and the foam metal layer has a porous structure; The flow channel body includes several "Z"-shaped flow channels, and the ridge structure includes several "Z"-shaped ridges. The flow channels and ridges are cross-distributed in the flow field. The flow channels and ridges guide the gas to change the flow direction and use the fluid inertia to purge the liquid water in the ridges. The pressure balance chamber dynamically compensates for the upstream and downstream pressure differences in the flow field through airflow redistribution optimization; The flow channel body and the ridge structure constitute a three-dimensional guide structure. The three-dimensional guide structure establishes a self-regulating mechanism for the water content of the membrane electrode through the synergistic effect of the water storage characteristics of the porous medium and the inertia effect of the flow channel.

2. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: The ridges are arranged between adjacent flow channels, and their shapes on the flow field projection surface form a repeatedly arranged "Z"-shaped structure.

3. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: The flow channel includes a flow channel metal substrate and a flow channel foam metal layer, and the ridge includes a ridge metal substrate and a ridge foam metal layer. The flow channel metal substrate and the ridge metal substrate are local structures of the metal substrate, the flow channel foam metal layer and the ridge foam metal layer are local structures of the foam metal layer, the flow channel foam metal layer and the ridge foam metal layer both face the membrane electrode, and the ridge foam metal layer is in direct contact with the gas diffusion layer of the membrane electrode.

4. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: The flow channel is an upward concave structure, and the ridge is a downward convex structure.

5. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: The flow channel body includes several parallel flow channels arranged in parallel, and the parallel flow channels include several flow channels arranged in parallel. The pressure balance chamber is arranged upstream and downstream of the flow channel body. The ends of two adjacent groups of parallel flow channels are connected through the pressure balance chamber, which is used to collect and redistribute gas in the flow field.

6. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: It also includes a flow field wall, which is fixed on the metal substrate. A flow field area is formed inside the wall, and the wall is used to constrain the flow path of the gas inside the flow field.

7. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: It also includes a flow field inlet structure and a flow field outlet structure, which are respectively arranged on the metal substrate and located on the upper and lower sides of the flow field. The flow field inlet structure distributes the reaction gas to the flow field, enters the flow channel through the flow field inlet, is transmitted to the flow field outlet through the flow channel, and then output by the flow field outlet structure.

8. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 1, characterized in that: It also includes a sealing structure, which includes a sealing gasket. The sealing gasket is fixed on the metal substrate, and the flow field wall, the flow field inlet structure and the flow field outlet structure are all located in a sealing area formed by the sealing gasket.

9. The Z-shaped metal foam channel composite flow field bipolar plate for fuel cells according to claim 3, characterized in that: The flow channel foam metal layer includes a flow channel foam layer bend and a flow channel foam layer straight channel, and the ridge foam metal layer includes a ridge foam metal layer bent arm and a ridge foam metal layer straight arm. The flow channel foam layer bend and the ridge foam metal layer bent arm are "Z"-shaped arc-shaped corner areas, which are gradual curvature transition structures. The ridge and the adjacent flow channel are seamlessly connected through geometric complementarity, and the connection area forms a continuous curved surface transition zone.

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