A bionic peregrine falcon flow channel structure of a proton exchange membrane fuel cell and its application

Abstract

The present invention belongs to the technical field of fuel cells, and discloses a bionic peregrine falcon flow channel structure of a proton exchange membrane fuel cell, the upper surface of which is a periodic structure composed of a plurality of asymmetric waveform units with streamlined shapes of the abdomen of a bionic peregrine falcon, and the lower surface is horizontal. The three-dimensional structure flow channel of the present invention is applied to the bipolar plate of a proton exchange membrane fuel cell, which can not only force the reaction gas to impact the membrane electrode, making it easier to enter the interior of the battery, easier to diffuse evenly, forcing more oxygen to enter the catalyst layer, increasing the oxygen concentration of the battery catalyst layer, and increasing the maximum power density of the battery, but also can generate a horizontal fast airflow, which has a purging effect on the generated liquid water, and has excellent water removal ability, and can also use its drag-reducing streamlined structure to greatly reduce the pressure drop difference of the flow channel, reduce the parasitic power of the system, and improve the comprehensive performance of the fuel cell.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a bionic peregrine falcon flow channel structure of a proton exchange membrane fuel cell and an application thereof. Background Art

[0002] Proton exchange membrane fuel cells are composed of membrane electrodes (proton exchange membrane, catalyst layer, gas diffusion layer), bipolar plates, current collectors, etc., among which the membrane electrodes and bipolar plates determine the performance of the fuel cell. As the core component of the fuel cell, the bipolar plate plays many important roles in the fuel cell, such as supporting the membrane electrode structure, separating hydrogen and oxygen, collecting electrons, conducting heat, providing hydrogen and oxygen channels, discharging water generated by the reaction, and providing coolant channels. Among them, the flow channel structure determines the hydrothermal management, mass transport and current density distribution of PEMFC, which seriously affects the comprehensive performance of the fuel cell. The reaction gas in the flow channel enters the diffusion layer and the catalyst layer in turn by diffusion. The speed of diffusion and whether the diffusion is uniform, that is, the mass transfer capacity of the flow channel, directly affects the power generation performance. When the proton exchange membrane fuel cell is working, water will be generated at the cathode. Under high current density, if the generated water cannot be discharged in time, it will block the reaction gas transmission channel. This will cause the "flooding" phenomenon, affect the performance, and greatly reduce the service life of the fuel cell.

[0003] Conventional flow fields include straight channel, serpentine, spiral, interdigitated and grid shapes, and related researchers are also constantly developing new flow fields. At present, the back section of the ordinary three-dimensional flow channel structure of the proton exchange membrane fuel cell, under high current density, with the large consumption of reaction gas, especially oxygen, and due to the high pressure drop, often has insufficient gas supply to the cell catalyst layer and uneven distribution of reaction gas, resulting in a significant drop in current density, increasing the parasitic power of the system and reducing the net power of the battery. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a bionic peregrine falcon flow channel structure of a proton exchange membrane fuel cell and applications thereof.

[0005] In order to achieve the above purpose, the technical solution of the present invention is:

[0006] A bionic peregrine falcon flow channel structure for a proton exchange membrane fuel cell, wherein the upper surface is a periodic structure composed of a plurality of asymmetric waveform units with streamlined shapes similar to those of the abdomen of a bionic peregrine falcon, and the lower surface is horizontal; the asymmetric waveform unit is a streamlined asymmetric waveform curve formed by connecting a first arc and a second arc at the lowest point, the first arc and the second arc are arranged along a gas transmission direction and the highest points are located on the same horizontal line, L1 is the horizontal length of the first arc, L2 is the horizontal length of the second arc, h is the height difference between the highest point and the lowest point, and h:L1:L2=1:2.5-3.5:4.5-5.5.

[0007] Optionally, h:L1:L2=1:3:5.

[0008] Optionally, the height difference h between the highest point and the lowest point is 35%-85% of the height difference between the highest point and the lower surface.

[0009] Optionally, the horizontal distance s between adjacent asymmetric waveform units is 0-10 mm.

[0010] Optionally, adjacent asymmetric waveform units are connected at the highest point or through a horizontal line segment at the highest point.

[0011] Optionally, the bionic peregrine falcon flow channel structure is formed between the bipolar plate and the diffusion layer; wherein the asymmetric waveform unit is formed on the surface of the bipolar plate, or the asymmetric waveform unit is additionally provided on the surface of the bipolar plate.

[0012] A proton exchange membrane fuel cell comprises a proton exchange membrane and an anode flow channel and a cathode flow channel located on both sides of the proton exchange membrane; the anode flow channel and / or the cathode flow channel adopts the above-mentioned bionic peregrine falcon flow channel structure.

[0013] Optionally, an anode catalyst layer and an anode diffusion layer are sequentially provided between the proton exchange membrane and the anode flow channel; and a cathode catalyst layer and a cathode diffusion layer are sequentially provided between the proton exchange membrane and the cathode flow channel.

[0014] Optionally, an anode current collecting plate is further provided on the outer side of the anode flow channel, and a cathode current collecting plate is further provided on the outer side of the cathode flow channel.

[0015] The beneficial effects of the present invention are:

[0016] The bionic peregrine falcon streamlined asymmetric wave flow channel structure of the present invention firstly forms a certain angle between the flow direction and the diffusion direction through the ups and downs bionic wave flow channel, forcing more reaction gas to rush to the membrane electrode and enter the diffusion layer and the catalyst layer, thereby increasing the reaction gas concentration in the catalyst layer, and further increasing the current density and power density. Secondly, the bionic three-dimensional structure can quickly increase the gas flow rate, have a good purging effect on the liquid water generated by the reaction, effectively prevent the occurrence of "flooding", and also improve the situation of insufficient air supply in the second half of the flow channel. Finally, the peregrine falcon streamlined wave flow channel structure with excellent drag reduction effect is used to reduce the pressure drop difference of the flow channel, reduce the parasitic power of the system, and thus improve the comprehensive performance of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional schematic diagram of the bionic peregrine falcon flow channel structure of Example 1;

[0018] Figure 2 (a) is a photo of the bionic object Peregrine Falcon: Figure 2 (b) is a schematic diagram of the structure of the asymmetric waveform unit of the bionic peregrine falcon abdomen;

[0019] Figure 3 is a front view of the structure diagram of the proton exchange membrane fuel cell of Example 2;

[0020] Figure 4 is a side view of the structure of a proton exchange membrane fuel cell of Example 2;

[0021] Figure 5 is a three-dimensional structural diagram of the bionic peregrine flow channel proton exchange membrane fuel cell of Example 2;

[0022] Figure 6 is a three-dimensional structural diagram of a sinusoidal wave flow channel proton exchange membrane fuel cell of comparative example 1;

[0023] Figure 7 is a three-dimensional structural diagram of a conventional direct-flow proton exchange membrane fuel cell of comparative example 2;

[0024] Figure 8 1 is the polarization curve of the proton exchange membrane fuel cell of Example 2 and Comparative Examples 1 and 2;

[0025] Fig. 9 is a comparison diagram of the cathode flow channel pressure drop difference between Example 2 and Comparative Example 1;

[0026] Fig.10 It is a comparison chart of the average values ​​of the molar concentration of oxygen in the cathode catalyst layer of Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0027] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The various drawings of the present invention are only for illustration to make it easier to understand the present invention, and the specific proportions thereof can be adjusted according to design requirements. The upper and lower relationships of the relative elements in the figures described herein and the definition of high / low should be understood by those skilled in the art to refer to the relative positions of the components, and therefore they can all be flipped to present the same components, which should all fall within the scope disclosed in this specification.

[0028] Example 1

[0029] refer to Figure 1 The bionic peregrine falcon flow channel structure of Example 1 has an upper surface 100a which is a periodic structure composed of a plurality of asymmetric waveform units 110 with streamlined shapes of the bionic peregrine falcon abdomen, and a lower surface 100b which is horizontal. Figure 2The structural curve of the asymmetric waveform unit is fitted from the curve structure of the abdomen of the peregrine falcon. Specifically, it is a streamlined asymmetric waveform curve formed by the first arc 111 and the second arc 112 connected at the lowest point. The first arc 111 and the second arc 112 are arranged along the gas transmission direction (as shown by the arrow) and the highest points are located on the same horizontal line. L1 is the horizontal length of the first arc 111, L2 is the horizontal length of the second arc 112, h is the height difference between the highest point and the lowest point, and the ratio of h to L1 is 1:3, and the ratio of h to L2 is 1:5. The height difference h is 35%-85% of the height difference between the highest point and the lower surface (defined as the flow channel height). The horizontal distance s between adjacent asymmetric waveform units 110 is 0-10mm, that is, adjacent asymmetric waveform units are connected at the highest point or connected through the horizontal line segment of the highest point.

[0030] The first arc 111 and the second arc 112 are connected at the lowest point and smoothly transitioned to form an asymmetric inverted parabola-like curve. The smooth transition mentioned here means that the two arcs are tangent at the connecting point.

[0031] The design of the position, quantity and distribution of the bionic peregrine falcon streamlined asymmetric waveform unit is applicable to bipolar plates made of various materials, including but not limited to metal bipolar plates, graphite bipolar plates, composite bipolar plates, and bipolar plates made of various processing methods, including but not limited to stamping, molding, machining, blow molding, hydraulic pressure, etc. The present invention is further applicable to flow fields specially designed for bionic peregrine falcon streamlined asymmetric waveform units, and is also applicable to the initial design without bionic peregrine falcon streamlined asymmetric waveform units, and the subsequent addition of bionic peregrine falcon streamlined asymmetric waveform units to the flow field area. The spacing between the unit bodies can be, but not limited to, 0%-50% of the flow channel length; the forming method of the unit body structure can be, but not limited to: machining, molding, injection molding, stamping, second process bonding, welding, and dispensing.

[0032] Peregrine falcon is the fastest creature in the world, with a maximum speed of 389km / h. Almost all parts of the peregrine falcon's body are adapted to high-speed flight, especially with a special streamlined structure that can greatly reduce resistance, just like a high-speed aircraft. The simulation results show that the streamlined three-dimensional structure extracted from the abdomen of the peregrine falcon can simultaneously meet the three characteristics of a good bipolar plate structure. First, the nozzle effect of its three-dimensional structure can quickly increase the gas flow rate and enhance the gas mass transfer capacity. Secondly, it will generate a horizontal fast airflow, which has a sweeping effect on the generated liquid water and has high water removal performance. Finally, the drag reduction ability of its streamlined structure can greatly reduce the pressure drop difference of the flow channel, thereby reducing parasitic power.

[0033] Example 2

[0034] refer to Figure 3The proton exchange membrane fuel cell of the embodiment has a structure from top to bottom of a cathode bipolar plate 1, a cathode flow channel 2, a cathode diffusion layer 3, a cathode catalyst layer 4, a proton exchange membrane 5, an anode catalyst layer 6, an anode diffusion layer 7, an anode flow channel 8 and an anode bipolar plate 9. The cathode flow channel 2 adopts the bionic peregrine flow channel structure of embodiment 1. The cathode flow channel 2 is a channel between the cathode diffusion layer 3 and the cathode bipolar plate 1 (also serving as a current collector).

[0035] Combination Figures 3 to 5 In this embodiment, the ups and downs of the bionic corrugated flow channel make the flow direction and the diffusion direction form a certain angle, forcing more reaction gas to rush to the membrane electrode and enter the diffusion layer and the catalyst layer, thereby increasing the concentration of the reaction gas in the catalyst layer, and then increasing the current density and power density. Secondly, the bionic three-dimensional structure can quickly increase the gas flow rate, which has a good purge effect on the liquid water generated by the reaction, effectively preventing the occurrence of "flooding", and also improving the insufficient gas supply in the second half of the flow channel. Finally, the streamlined corrugated flow channel structure imitating the peregrine falcon with excellent drag reduction effect is used to reduce the pressure drop difference of the flow channel and reduce the parasitic power of the system, thereby improving the overall performance of the fuel cell.

[0036] The bionic peregrine falcon flow channel structure is applied to the cathode of the proton exchange membrane fuel cell, and its size characteristics are as follows: the overall length of the flow channel is 96mm, the width a2 is 1mm, and the height b2 (the flow channel height defined in Example 1) is 1mm; the h of the asymmetric waveform unit is 60% of the flow channel height, that is, 0.6mm, according to the ratio L1 is 1.8mm, and L2 is 3mm; in order to facilitate modeling and calculation, the distance s between the asymmetric waveform units is 0mm. The anode adopts a simple and easy-to-process rectangular direct current channel, which is 96mm long, 1mm wide, and 1mm high. The dimensions of the cathode and anode current collectors are 96mm long, 2mm wide, and 2mm high; the dimensions of the cathode and anode diffusion layers are 96mm long, 2mm wide, and 0.2mm high; the dimensions of the cathode and anode catalyst layers are 96mm long, 2mm wide, and 0.01mm high; the proton exchange membrane size parameters are set to 96mm long, 2mm wide, and 0.05mm high.

[0037] When the proton exchange membrane fuel cell is working, the humidified hydrogen and air enter the flow channel from the entrance of the anode and cathode respectively, and then pass through the diffusion layer to the catalyst layer to react. During the reaction, the hydrogen in the anode catalyst layer undergoes an oxidation reaction and loses an electron and generates hydrogen ions. The generated hydrogen ions directly pass through the proton exchange membrane to reach the cathode catalyst layer, while the generated electrons can only reach the cathode catalyst layer through the external circuit, thus forming a connected circuit, and the hydrogen ions and electrons reaching the cathode catalyst layer undergo a reduction reaction with the oxygen in the cathode to generate water. Through the ups and downs of the bionic waveform flow channel, the flow direction and the diffusion direction form a certain angle, forcing more reaction gas to rush to the membrane electrode, enter the diffusion layer and the catalyst layer, thereby increasing the concentration of the reaction gas in the catalyst layer, and then increasing the current density and power density. Secondly, the bionic three-dimensional structure can quickly increase the gas flow rate, have a good purge effect on the liquid water generated by the reaction, effectively prevent the occurrence of "flooding", and also improve the situation of insufficient gas supply in the second half of the flow channel. Finally, the streamlined corrugated flow channel structure imitating the peregrine falcon with excellent drag reduction effect is used to reduce the flow channel pressure drop difference, reduce the parasitic power of the system, and thus improve the overall performance of the fuel cell.

[0038] The bionic flow channel of this embodiment can achieve uniform distribution of reaction gas inside the battery and improve the performance of the battery.

[0039] Comparative Example 1

[0040] refer to Figure 6 In order to verify the drag reduction effect of the peregrine falcon structure, a proton exchange membrane fuel cell with a cathode as a sinusoidal wave flow channel is set as comparative example 1. The size characteristics are as follows: the cathode flow channel is 96 mm long, 1 mm wide, and 1 mm high. The cathode flow channel curve structure is driven by the equation: y=a*sin(b*x), where a is the amplitude, which is 0.6, the same height as the embodiment, and b is the angular frequency, which is π / 2; the anode adopts a simple and easy-to-process rectangular direct current channel, which is 96 mm long, 1 mm wide, and 1 mm high; the size parameters and materials used in the other components are the same as those of the bionic peregrine falcon flow channel proton exchange membrane fuel cell in Example 2.

[0041] Comparative Example 2

[0042] refer to Figure 7 A conventional direct current proton exchange membrane fuel cell is set as comparative example 2, in which both the anode and cathode flow channels adopt conventional direct current channels with dimensions of 96 mm in length, 1 mm in width and 1 mm in height; the size parameters of the remaining components and the materials used are the same as those of the bionic peregrine flow channel proton exchange membrane fuel cell in Example 2.

[0043] The cells of Example 2, Comparative Example 1 and Comparative Example 2 were all operated in constant voltage mode at a temperature of 333 K. The anode was fed with humidified hydrogen with a relative humidity of 60% and a mass flow rate of 2.273×10 -7kg / s; the cathode is fed with humidified air, the relative humidity is 60%, and the intake air mass flow rate is 2.8242×10 -6 kg / s, the pressure at the cathode and anode outlets is the same as standard atmospheric pressure, and the results are obtained through CFD simulation.

[0044] The comparison of polarization curves of three batteries is shown in Figure 8 As shown. Figure 8 It can be seen that compared with the single cell of the conventional direct current channel, the performance of the fuel cell with the bionic peregrine flow channel and the sine wave flow channel fuel cell has been greatly improved, especially in the case of low output voltage and high current density, the improvement is more obvious. The main reason is that the bionic peregrine structure and the sine wave structure can guide the reaction gas to impact the membrane electrode in the flow channel, which will have a better mass transfer effect than the free diffusion of the direct current channel, and improve the battery performance of the fuel cell on the basis of increasing a little pressure drop. Compared with the sine wave flow channel fuel cell, the peak current density and power density of the bionic peregrine flow channel fuel cell have been improved. The main reason is that the bionic peregrine structure flow channel is in the back section of the flow channel. When the reaction gas, especially oxygen, is consumed in large quantities, by reducing the resistance, the reaction gas in the flow channel is easier to enter the catalyst layer, the reaction intensity of the back section of the battery is increased, the power density of the battery is increased, the pressure drop is reduced, and the system parasitic power is reduced, thereby increasing the net output power, especially in the case of low output voltage and high current density. The improvement is more obvious.

[0045] The cathode flow channel pressure drop difference between Example 2 and Comparative Example 1 is as follows: Fig. 9 As shown, from Fig. 9 It can be seen that:

[0046] As the current density increases, the pressure drop at the cathode of the proton exchange membrane fuel cell also increases. At the same current density, compared with comparative example 1, the cathode flow channel pressure drop difference of the bionic peregrine flow channel is smaller, with a maximum reduction of 25.65%. The reason is: as the reaction proceeds further, more oxygen is consumed and water is generated while the current density increases, resulting in a further increase in the cathode flow channel pressure drop. The peregrine falcon-like structure has a better drag reduction effect on the basis of the same wave structure as the sine wave because of its special streamlined shape imitated from the abdomen of the peregrine falcon. It can reduce parasitic power and increase the net power density of the fuel cell without reducing the peak power density, which also verifies the excellent drag reduction effect of the peregrine falcon-like structure mentioned above.

[0047] The average values ​​of the molar concentration of oxygen in the cathode catalyst layer of Example 2 and Comparative Example 2 are as follows: Fig.10 As shown, from Fig. 9 It can be seen that:

[0048] At the same voltage, compared with Comparative Example 2, the average oxygen concentration of the battery catalyst layer of the bionic peregrine flow channel is significantly improved. The reason is that along the flow direction of the battery reaction gas, its structure forces the reaction gas to impact the membrane electrode, making it easier for the gas to enter the battery, and then the oxygen concentration of the catalyst layer is increased accordingly. Especially at low output voltage and high current density, the increase is greater, which also verifies the excellent mass transfer ability of the peregrine structure mentioned above.

[0049] The above embodiments are only used to further illustrate a proton exchange membrane fuel cell bionic peregrine flow channel structure and its application of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A bionic peregrine falcon flow channel structure for a proton exchange membrane fuel cell, characterized in that: The upper surface is a periodic structure composed of several streamlined asymmetric waveform units of the abdomen of a bionic peregrine falcon, and the lower surface is horizontal; the asymmetric waveform unit is a streamlined asymmetric waveform curve formed by the first arc and the second arc connecting at the lowest point and smoothly transitioning, the first arc and the second arc are arranged along the gas transmission direction and the highest points are located on the same horizontal line, L1 is the horizontal length of the first arc, L2 is the horizontal length of the second arc, h is the height difference between the highest point and the lowest point, h:L1:L2=1:3:5; adjacent asymmetric waveform units are connected at the highest point, and the horizontal distance s is 0; the bionic peregrine falcon flow channel structure is formed between the bipolar plate and the diffusion layer; wherein the asymmetric waveform unit is formed on the surface of the bipolar plate.

2. The bionic peregrine falcon flow channel structure of a proton exchange membrane fuel cell according to claim 1, characterized in that: The height difference h between the highest point and the lowest point is 35%-85% of the height difference between the highest point and the lower surface.

3. A proton exchange membrane fuel cell, characterized in that: It comprises a proton exchange membrane and an anode flow channel and a cathode flow channel located on both sides of the proton exchange membrane; the anode flow channel and / or cathode flow channel adopts the bionic peregrine falcon flow channel structure as described in any one of claims 1 to 2.

4. The proton exchange membrane fuel cell according to claim 3, characterized in that: An anode catalyst layer and an anode diffusion layer are sequentially arranged between the proton exchange membrane and the anode flow channel; and a cathode catalyst layer and a cathode diffusion layer are sequentially arranged between the proton exchange membrane and the cathode flow channel.

5. The proton exchange membrane fuel cell according to claim 4, characterized in that: An anode current collecting plate is also provided on the outer side of the anode flow channel, and a cathode current collecting plate is also provided on the outer side of the cathode flow channel.

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