Fuel cell polar plate flow field structure with hydrophilic and hydrophobic grooves and ridges distributed at intervals

Abstract

The invention relates to a fuel cell polar plate flow field structure with hydrophilic and hydrophobic grooves and ridges distributed at intervals. The fuel cell polar plate flow field structure comprises a bipolar plate and a gas diffusion layer, the bipolar plate is provided with a bipolar plate ridge part and a bipolar plate groove, the surface of the bipolar plate ridge part and the surface of the gas diffusion layer are hydrophobic, liquid water of the ridge part gas diffusion layer is promoted to be rapidly separated, the water accumulation phenomenon is restrained, and the contact position of the bipolar plate ridge part and the surface of the gas diffusion layer has the drainage characteristic; the bipolar plate grooves are low in hydrophobicity or hydrophilic, so that the development of gas-liquid two-phase flow in a flow field to an annular flow pattern with smooth mass transfer is facilitated; the surface of the gas diffusion layer and the bipolar plate groove form a flow field; when liquid water generates small liquid drops on the surface of the gas diffusion layer in contact with the ridge part of the bipolar plate or converges into a thin liquid film, the liquid water can be quickly blown away by airflow, so that local water blockage is avoided. Compared with the prior art, the flow field drainage efficiency is enhanced, the internal water management of the fuel cell is optimized, and the cell performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to fuel cells, and in particular to a fuel cell plate flow field structure with grooves and ridges having hydrophilic and hydrophobic interval distribution. Background Art

[0002] Hydrogen energy is an efficient, clean, renewable energy source that has been widely explored and studied in recent years. Proton exchange membrane fuel cells are one of the most promising ways to utilize hydrogen energy. The monomer structure mainly includes bipolar plates and membrane electrode assemblies (gas diffusion layers, catalyst layers, and proton exchange membranes, etc.) sandwiched between the bipolar plates. It can directly convert the chemical energy in hydrogen and oxygen into electrical energy, is not restricted by the Carnot cycle, and has high energy conversion efficiency. The only reaction emission is water, with zero carbon emissions and no pollution. There is no mechanical transmission device inside the battery, almost no noise, and it can run quickly in a low-temperature environment. Therefore, it has great potential in the fields of new energy vehicles, fixed and distributed power generation, etc.

[0003] Bipolar plates, also known as flow field plates, are important components of proton exchange membrane fuel cells. Their main functions include evenly distributing the reaction gas, achieving electron conduction between the positive and negative electrodes, and timely discharging the reaction product water and waste heat. The flow field is composed of grooves and gas diffusion layers on the bipolar plates, and its physical parameters determine the flow state of the reactants and product water in the flow field. Unreasonable plate flow field design will not only increase the flow resistance, inhibit the reaction gas from being transferred to the catalyst layer, and reduce the battery power density, but also cause the product water to be unable to be discharged from the flow field in time, resulting in water blockage of the plates and membrane electrodes, causing reverse polarization and then causing corrosion of the membrane electrode, reducing the service life of the battery.

[0004] The commonly used straight and serpentine structures of the flow field are prone to the problem that the product water between the bipolar plate ridge and the gas diffusion layer is blocked and difficult to be swept away by the airflow, increasing the gas diffusion resistance. The fuel cell bipolar plate flow field design disclosed in patent CN112736263A and patent CN111082089A performs hydrophobic treatment on the grooves, and liquid water easily accumulates on the surface of the gas diffusion layer to block the gas mass transfer channel. More importantly, the vast majority of existing fuel cell plate flow field structures basically do not comprehensively consider the drainage status of different positions in the flow field, and only optimize the structure from a single perspective of groove drainage. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a fuel cell plate flow field structure with hydrophilic and hydrophobic interval distribution of grooves and ridges, which has better drainage and gas transmission performance. By combining the hydrophilicity of the grooves and the strong hydrophobicity of the ridges, the liquid water distribution and two-phase flow pattern in the flow field are induced, thereby avoiding the "flooding" effect in the flow field and the gas diffusion layer, reducing the mass transfer resistance, improving the water management inside the fuel cell, and improving the overall performance of the fuel cell.

[0006] The present invention provides a fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution, comprising: a bipolar plate and a gas diffusion layer;

[0007] The bipolar plate is provided with a bipolar plate ridge and a bipolar plate groove. The bipolar plate ridge and the surface of the gas diffusion layer are hydrophobic, which promotes the rapid separation of liquid water in the ridge gas diffusion layer and inhibits the occurrence of water accumulation. The contact position between the bipolar plate ridge and the gas diffusion layer surface has a drainage feature. The bipolar plate groove has low hydrophobicity or is hydrophilic, which is conducive to the development of an annular flow pattern with smooth gas-liquid two-phase flow and mass transfer in the flow field; the gas diffusion layer surface and the bipolar plate groove form a flow field; when liquid water generates small droplets or gathers into a thin liquid film on the surface of the gas diffusion layer in contact with the bipolar plate ridge, it can be quickly blown away by the airflow to avoid local water blockage.

[0008] Make liquid water easily adhere to the surface of the flow field, leave enough space for the central airflow to pass through, induce the gas-liquid two-phase flow in the flow field to develop into an annular flow state, strengthen the driving effect of the airflow on the discharge of liquid water in the flow field, and avoid flooding in the flow field. The surface of the gas diffusion layer in the flow field is highly hydrophobic and the bipolar plate grooves are less hydrophobic or hydrophilic. Guide the liquid water in the gas diffusion layer corresponding to the groove to quickly leave the surface of the gas diffusion layer and enter the flow field, reducing the problem of liquid water blocking the gas mass transfer channel.

[0009] In the flow field, common gas-liquid two-phase flow patterns include: bubbly flow, slug flow and annular flow. When the gas content and flow velocity in the flow field are low, the flow state of the gas-liquid two-phase is bubbly flow; in this flow pattern, the liquid phase is the continuous phase, the gas phase is discontinuous, and the flow field will be flooded; as the gas flow rate gradually increases, the flow state of the gas-liquid two-phase in the flow field will change from bubbly flow to slug flow, and the gas content of the flow field is higher than that of the bubbly flow stage; when the gas flow rate is further increased, the flow state of the gas-liquid two-phase in the flow field will change to annular flow. In the annular flow state, the gas phase converges to form a gas core, which can flow smoothly in the center of the flow field, while the liquid phase will form a flowing liquid ring (film) along the wall of the flow field.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] (1) Through the hydrophobic flow field design of the bipolar plate ridge and the gas diffusion layer surface, liquid water at the contact position between the bipolar plate ridge and the gas diffusion layer surface can be discharged, the distribution of liquid water in the flow field can be optimized, and liquid water can be prevented from accumulating on the GDL surface and clogging the pores.

[0012] (2) Through the flow field design of the bipolar plate grooves with lower hydrophobicity or hydrophilicity, liquid water can be induced to form an annular flow in the flow field grooves, thereby preventing water blockage and reducing gas pressure drop.

[0013] (3) Through the above-mentioned hydrophobic flow field design of the gas diffusion layer surface and the hydrophilic flow field design of the electrode groove, the liquid water in the gas diffusion layer corresponding to the groove can be guided to quickly detach from the surface, thereby reducing the problem of liquid water blocking the gas mass transfer channel.

[0014] (4) The present invention is applicable to electrode plate structures of all materials and has strong operability. It can be used in combination with existing structural designs for enhanced drainage to further improve the drainage efficiency of the flow field, improve the water management of the fuel cell, and ultimately improve the performance and life of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the flow channel structure of the gas diffusion layer plate;

[0016] Figure 2 This is a schematic diagram of drainage simulation of the flow field of Example 1;

[0017] Figure 3 is a diagram of the liquid water volume fraction at the flow field ridge of the flow field of Example 1;

[0018] Figure 4 is a diagram of the liquid water coverage rate at the flow field ridge of the flow field of Example 1;

[0019] Figure 5 This is the flow field liquid water pressure drop diagram of the flow field in Example 1.

[0020] Figure numerals: 1. contact position between bipolar plate ridge and gas diffusion layer surface; 2. bipolar plate ridge; 3. gas diffusion layer surface; 4. bipolar plate groove. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms and other features not clearly described in this technical solution are all considered to be common technical features disclosed in the prior art.

[0022] Example 1

[0023] This embodiment provides a fuel cell plate flow field structure with hydrophilic and hydrophobic grooves and ridges distributed alternately, such as Figure 1 As shown, it includes: a bipolar plate and a gas diffusion layer;

[0024] The bipolar plate is provided with a bipolar plate ridge 2 and a bipolar plate groove 4. The bipolar plate ridge 2 and the gas diffusion layer surface 3 are hydrophobic, which promotes the rapid separation of liquid water in the ridge gas diffusion layer and inhibits the occurrence of water accumulation. The contact position 1 between the bipolar plate ridge and the gas diffusion layer surface has a drainage feature. The bipolar plate groove 4 has low hydrophobicity or is hydrophilic, which is conducive to the development of an annular flow pattern with smooth gas-liquid two-phase flow and mass transfer in the flow field; the gas diffusion layer surface 3 and the bipolar plate groove 4 form a flow field; when liquid water generates small droplets or gathers into a thin liquid film on the gas diffusion layer surface 3 in contact with the bipolar plate ridge 2, it can be quickly blown away by the airflow to avoid local water blockage.

[0025] It makes liquid water easy to adhere to the surface of the flow field, leaving enough space for the central airflow to pass through, inducing the gas-liquid two-phase flow in the flow field to develop into an annular flow state, strengthening the driving effect of the airflow on the discharge of liquid water in the flow field, and avoiding flooding in the flow field. The surface 3 of the gas diffusion layer of the flow field is highly hydrophobic and the bipolar plate groove 4 is less hydrophobic or hydrophilic. The liquid water in the gas diffusion layer corresponding to the guide groove quickly leaves the surface of the gas diffusion layer and enters the flow field, reducing the problem of liquid water blocking the gas mass transfer channel.

[0026] In the flow field, common gas-liquid two-phase flow patterns include: bubbly flow, slug flow and annular flow. When the gas content and flow velocity in the flow field are low, the flow state of the gas-liquid two-phase is bubbly flow; in this flow pattern, the liquid phase is the continuous phase, the gas phase is discontinuous, and the flow field will be flooded; as the gas flow rate gradually increases, the flow state of the gas-liquid two-phase in the flow field will change from bubbly flow to slug flow, and the gas content of the flow field is higher than that of the bubbly flow stage; when the gas flow rate is further increased, the flow state of the gas-liquid two-phase in the flow field will change to annular flow. In the annular flow state, the gas phase converges to form a gas core, which can flow smoothly in the center of the flow field, while the liquid phase will form a flowing liquid ring (film) along the wall of the flow field.

[0027] In a specific embodiment, the bipolar plate has an outer dimension of 60 mm×60 mm; the bipolar plate thickness is 0.8 mm, and after deducting the thickness of the thin plate, the flow field height is 0.7 mm; the bipolar plate groove 4 has a length of 47 mm, and after deducting the corner, the bipolar plate groove 4 has a length of 45 mm; the bipolar plate groove 4 has a width of 1 mm; the bipolar plate ridge 2 has a width of 1 mm; the bipolar plate sealant height is 0.2 mm, and the height difference between the sealant spraying position and the bipolar plate ridge 2 is 0.1 mm, so the height difference between the bipolar plate ridge and the gas diffusion layer surface h=0.2-0.1=0.1 mm; the contact angle of the bipolar plate groove 4 is 40 degrees, and the contact angle between the bipolar plate ridge 2 and the gas diffusion layer surface 3 is 140 degrees.

[0028] The Comsol simulation platform was used to simulate the liquid water movement behavior of the flow field of this embodiment. Figure 2 shown. Figure 3 is the volume fraction diagram of liquid water on the ridge of the bipolar plate with contact angles of 140 degrees (hydrophobic) and 40 degrees (hydrophilic) respectively. Figure 4 This is a diagram of the liquid water coverage rate of the flow field ridge when the contact angle of the bipolar plate ridge 2 is 140 degrees (hydrophobic) and 40 degrees (hydrophilic). It can be clearly seen from the figure that when the bipolar plate ridge 2 is hydrophobic, the liquid water content in the ridge flow field is low and the liquid water discharge efficiency is high. Figure 5 It is a flow field liquid water pressure drop diagram when the contact angle of the bipolar plate ridge 2 is 140 degrees (hydrophobic) and 40 degrees (hydrophilic). It can be seen from the figure that the flow field pressure drop is better when the bipolar plate ridge 2 is hydrophobic.

[0029] Therefore, this embodiment enhances the drainage efficiency of the flow field, optimizes the water management inside the fuel cell, and improves the battery performance.

[0030] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0031] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution, characterized in that: include: Bipolar plates and gas diffusion layers; The bipolar plate is provided with a bipolar plate ridge (2) and a bipolar plate groove (4); the bipolar plate ridge (2) and the gas diffusion layer surface (3) are hydrophobic; the contact position (1) between the bipolar plate ridge and the gas diffusion layer surface has drainage characteristics; the bipolar plate groove (4) has low hydrophobicity or is hydrophilic; the gas diffusion layer surface (3) and the bipolar plate groove (4) form a flow field; when liquid water generates small droplets or gathers into a thin liquid film on the gas diffusion layer surface (3) in contact with the bipolar plate ridge (2), it can be quickly blown away by the airflow to avoid local water blockage.

2. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: In the flow field, the gas-liquid two-phase flow patterns include: bubbly flow, slug flow and annular flow.

3. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The bipolar plate has an outer dimension of 60 mm×60 mm.

4. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The bipolar plate has a thickness of 0.8 mm, and after deducting the thickness of the thin plate, the flow field height is 0.7 mm.

5. The fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The bipolar plate groove (4) has a length of 47 mm. After deducting the corners, the length of the bipolar plate groove (4) is 45 mm.

6. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The bipolar plate groove (4) has a width of 1 mm.

7. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The width of the bipolar plate ridge (2) is 1 mm.

8. The fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The height of the bipolar plate sealant is 0.2 mm, and the height difference between the sealant spraying position and the bipolar plate ridge (2) is 0.1 mm.

9. A fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The contact angle of the bipolar plate groove (4) is 40 degrees.

10. The fuel cell plate flow field structure with hydrophilic and hydrophobic groove-ridge interval distribution according to claim 1, characterized in that: The contact angle between the bipolar plate ridge (2) and the gas diffusion layer surface (3) is 140 degrees.

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