A three-dimensional flow field structure of a bionic scale-type fuel cell

Abstract

The present invention discloses a bionic flaked fuel cell three-dimensional flow field structure. It includes a bipolar plate body and a reaction gas diffusion layer, the reaction gas diffusion layer is closely attached to the bottom of the bipolar plate body, and multiple columns of flaked flow field unit groups are arranged on the top surface of the bipolar plate body, each column of flaked flow field unit groups is composed of multiple flaked flow field units arranged at equal intervals, and two adjacent columns of flaked flow field unit groups are arranged in a staggered manner, along the direction of the reaction gas flow, the volume of multiple columns of flaked flow field units gradually increases in sequence, and multiple microchannels are distributed on the inner wall of the flaked flow field unit. The present invention promotes the diffusion and convection of the reaction gas and improves the uniformity of the reaction gas distribution by changing the size and arrangement of the flaked flow field unit; the capillary action of the microchannel on the inner wall of the flaked flow field unit promotes the discharge of residual droplets of water in the channel, enhances the drainage performance of the fuel cell cathode, and improves the power generation performance and durability of the fuel cell.

Description

Technical Field

[0001] The invention relates to a three-dimensional flow field structure in the field of fuel cells, and in particular to a three-dimensional flow field structure of a bionic scale-type fuel cell. Background Art

[0002] With the continuous consumption of fossil energy and the increasing environmental pollution, the development of clean and efficient new energy has become an important issue facing the world. Proton exchange membrane fuel cells (PEMFC) have the advantages of zero emissions, zero pollution, and high power density, and have become the research focus in the energy field.

[0003] The bipolar plate is one of the important components of the proton exchange membrane fuel cell (PEMFC). Its main functions include providing mechanical support for the membrane electrode, transporting the reaction gas, conducting current, and discharging the liquid water generated inside the fuel cell. The flow field design of the bipolar plate is a key factor affecting the uniformity of the reaction gas distribution and the electrochemical reaction rate. An unreasonable flow field structure design can easily lead to problems such as low mass transfer efficiency, uneven distribution of reaction gas, and flooding, which in turn affects the battery life and output performance.

[0004] Common bipolar plate flow field structures are mainly divided into serpentine flow fields, parallel flow fields, and finger-shaped flow fields. Among them, the gas flow rate in the serpentine flow field flow channel is high, which makes it easier to blow away the liquid water generated by the reaction, avoiding the accumulation and blockage of liquid water. However, its channel is too long and there are many turns, which will increase the flow field pressure drop, generate additional power loss, and easily lead to insufficient gas concentration at the end of the flow channel, resulting in too low current density. The parallel flow field flow channel is shorter, so the pressure drop inside the flow channel is smaller, but it has a low gas flow rate and is prone to problems such as liquid water or impurities gathering and being unable to be discharged, blocking the flow channel. The characteristic of the finger-shaped flow field is that there is a dead end in the flow field, which can enhance the forced convection of the reaction gas, but it will also cause a large pressure drop, thereby generating unnecessary parasitic power losses.

[0005] Based on the limitations of the above-mentioned common flow fields, it has become an urgent problem to develop a new flow field structure that has the advantages of good mass transfer and drainage effects, excellent power generation performance and moderate flow field pressure drop. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention provides a three-dimensional flow field structure of a bionic flake fuel cell, which enhances the flow field mass transfer performance, promotes the diffusion and convection of the reaction gas, and promotes the discharge of residual liquid droplets on the bipolar plate by changing the arrangement of the flow field units and the micro-texture morphology thereon, thereby improving the efficiency and current density of the fuel cell.

[0007] The technical solution adopted by the present invention is:

[0008] The present invention comprises a bipolar plate body and a gas diffusion layer, wherein the gas diffusion layer is closely attached to the bottom of the bipolar plate body, and a plurality of parallel scale-type flow field unit groups are arranged on the top surface of the bipolar plate body;

[0009] Each column of the scale-type flow field unit group is composed of a plurality of identical scale-type flow field units arranged in sequence at equal intervals, and the scale-type flow field units in two adjacent columns of scale-type flow field unit groups are arranged in an alternating manner, and the multiple columns of scale-type flow field unit groups arranged on the top surface of the bipolar plate body are sequentially two columns of first scale-type flow field unit groups, multiple columns of second scale-type flow field unit groups, one column of third scale-type flow field unit groups, one column of fourth scale-type flow field unit groups and one column of fifth scale-type flow field unit groups along the flow direction of the reaction gas; and the volumes of the scale-type flow field units of the first scale-type flow field unit group, the scale-type flow field units of the second scale-type flow field unit group, the scale-type flow field units of the third scale-type flow field unit group, the scale-type flow field units of the fourth scale-type flow field unit group and the scale-type flow field units of the fifth scale-type flow field unit group gradually increase in sequence to form a bionic scale-like three-dimensional flow field structure;

[0010] The area where the two rows of first scale-type flow field unit groups are located on the bipolar plate body forms an inlet distribution area, the area where the multiple rows of second scale-type flow field unit groups are located forms an intermediate reaction area, and the area where the one row of third scale-type flow field unit groups, one row of fourth scale-type flow field unit groups and one row of fifth scale-type flow field unit groups are located forms an outlet area; so that the reaction gas flows into the intermediate reaction area through the inlet distribution area and then flows out from the outlet area.

[0011] The flaked flow field units of the first flaked flow field unit group, the flaked flow field units of the second flaked flow field unit group, the flaked flow field units of the third flaked flow field unit group, the flaked flow field units of the fourth flaked flow field unit group and the flaked flow field units of the fifth flaked flow field unit group all have the same structure and the same vertical height;

[0012] Each scale-type flow field unit on the top surface of the bipolar plate body is a trapezoidal platform structure with a hollow interior and open two ends, and the two side surfaces of each scale-type flow field unit are fan-shaped scale-type flow field unit side surfaces, and the top surface of each scale-type flow field unit is a trapezoidal scale-type flow field unit top surface parallel to the bipolar plate body; the cross-sectional area of ​​each scale-type flow field unit decreases successively along the flow direction of the reaction gas, and the inner side surfaces of the fan-shaped scale-type flow field unit side surfaces and the trapezoidal scale-type flow field unit top surfaces are provided with a plurality of parallel and spaced microchannels along the flow direction of the reaction gas, and the microchannels are microchannels with semicircular cross-sections or dovetail cross-sections. The end surface of the scale-type flow field unit through which the reaction gas flows in is the inlet end, and the end surface of the scale-type flow field unit through which the reaction gas flows out is the outlet end, and the end surface area of ​​the inlet end of each scale-type flow field unit is larger than the end surface area of ​​its own outlet end.

[0013] The wall thickness of the scale-type flow field unit is 30 μm to 60 μm, and the length of the scale-type flow field unit along the flow direction of the reaction gas is 0.3 mm to 0.8 mm.

[0014] The spacing between two adjacent semicircular cross-section microchannels or two adjacent dovetail cross-section microchannels is 50 μm to 100 μm.

[0015] The mid-sectional area of ​​the flake flow field units of the second scaled flow field unit group is 1.2 to 1.6 times the mid-sectional area of ​​the flake flow field units of the first scaled flow field unit group, the mid-sectional area of ​​the flake flow field units of the third scaled flow field unit group is 1.2 to 1.6 times the mid-sectional area of ​​the flake flow field units of the second scaled flow field unit group, the mid-sectional area of ​​the flake flow field units of the fourth scaled flow field unit group is 1.2 to 1.6 times the mid-sectional area of ​​the flake flow field units of the third scaled flow field unit group, and the mid-sectional area of ​​the flake flow field units of the fifth scaled flow field unit group is 1.2 to 1.6 times the mid-sectional area of ​​the flake flow field units of the fourth scaled flow field unit group.

[0016] The spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group in the same column is 1.2mm~1.6mm, the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group in the same column is 1.1~1.5 times the spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group, the spacing between two adjacent scale-type flow field units in the third scale-type flow field unit group in the same column is the same as the spacing between two adjacent scale-type flow field units in the fourth scale-type flow field unit group and the spacing between two adjacent scale-type flow field units in the fifth scale-type flow field unit group, and both are 1.1~1.5 times the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group, and the spacing between two adjacent flow field units in the two columns along the flow direction of the reaction gas is equal.

[0017] The channel depth of the microchannel with semicircular cross section and the channel depth of the microchannel with dovetail cross section are both 20μm to 40μm, and the cross-sectional diameter of the microchannel with semicircular cross section and the cross-sectional diameter of the microchannel with dovetail cross section are the same, and are both 40μm to 70μm.

[0018] The bipolar plate body is made of titanium alloy thin plate or stainless steel thin plate.

[0019] The microchannel with a semicircular cross section and the microchannel with a dovetail cross section are manufactured by a milling process using electron beams, lasers, heat rays or high-frequency currents. The beneficial effects of the present invention are:

[0020] The present invention is based on the scale-type bionic bipolar plate flow field structure, which is evenly arranged and staggered. The scale-type flow field unit group can enhance the convective mass transfer effect of the reaction gas, promote the reaction gas to flow to the gas diffusion layer, and make the electrochemical reaction inside the fuel cell more uniform and sufficient; the scale-type flow field unit at the gas inlet of the bipolar plate is small in size and large in number, and can achieve uniform distribution of gas at the inlet; the scale-type flow field units in the middle reaction zone are of the same size and evenly arranged, which can enhance the uniformity of current density distribution; increasing the volume of the scale-type flow field unit at the gas outlet can reduce the pressure of the gas at the outlet, promote the diffusion and convection of the reaction gas at the flow field outlet, avoid the problem of insufficient gas diffusion and concentration in the terminal section in the traditional two-dimensional flow channel, and reduce unnecessary pumping power loss. The capillary force of the microchannel on the inner wall of the scale-type flow field unit on the droplet water forms a directional driving effect on the droplet water, which can promote the movement of residual droplet water along the microchannel, accelerate the separation of residual droplet water on the bipolar plate, and have a good drainage effect.

[0021] The present invention promotes the diffusion and convection of the reaction gas by changing the size and arrangement of the scale-type flow field units, thereby improving the uniformity of the reaction gas distribution without significantly changing the pressure drop; at the same time, the capillary action of the microchannels on the inner wall of the scale-type flow field units can promote the discharge of residual liquid droplets in the channel, enhance the emission performance of the battery cathode channel, and improve the power generation performance and durability of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a three-dimensional flow field structure of a bionic flake fuel cell provided by the present invention;

[0023] Figure 2 A partial schematic diagram of the scale-type flow field structure provided by the present invention;

[0024] Figure 3 The internal streamline diagram of the reaction gas in the flow field of the bipolar plate of the scale-type bionic fuel cell provided by the present invention;

[0025] Figure 4 An isometric view of a scale-type flow field unit with a semicircular cross-section microchannel provided by the present invention;

[0026] Figure 5 A schematic diagram of a semicircular cross-section microchannel inside a scale-type flow field unit provided by the present invention;

[0027] Figure 6 An isometric view of a scale-type flow field unit with a dovetail-shaped cross-section microchannel provided by the present invention;

[0028] Figure 7 Schematic diagram of the dovetail-shaped cross-section microchannel inside the scale-type flow field unit provided by the present invention.

[0029] As shown in the figure: 1-bipolar plate body, 2-first scale-type flow field unit group, 3-second scale-type flow field unit group, 4-third scale-type flow field unit group, 5-fourth scale-type flow field unit group, 6-fifth scale-type flow field unit group, 7-gas diffusion layer, 8-side of scale-type flow field unit, 9-outlet end, 10-semicircular cross-section microchannel, 11-trapezoidal scale-type flow field unit top surface, 12-inlet end, 13-dovetail cross-section microchannel. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, the present invention comprises a bipolar plate body 1 and a gas diffusion layer 7, wherein the gas diffusion layer 7 is closely attached to the bottom of the bipolar plate body 1, and a plurality of parallel rows of scale-type flow field unit groups are arranged on the top surface of the bipolar plate body 1;

[0032] Each column of the flaked flow field unit group is composed of a plurality of identical flaked flow field units arranged in sequence at equal intervals, and the flaked flow field units in two adjacent columns of the flaked flow field unit group are arranged in an alternating manner, and the multiple columns of the flaked flow field unit groups arranged on the top surface of the bipolar plate body 1 are arranged in sequence along the flow direction of the reaction gas, namely, two columns of the first flaked flow field unit group 2, multiple columns of the second flaked flow field unit group 3, a column of the third flaked flow field unit group 4, a column of the fourth flaked flow field unit group 5 and a column of the fifth flaked flow field unit group 6; and the flaked flow field units of the first flaked flow field unit group 2, the flaked flow field units of the second flaked flow field unit group 3, the flaked flow field units of the third flaked flow field unit group 4, the flaked flow field units of the fourth flaked flow field unit group 6 are arranged in an alternating manner. The volumes of the flake flow field units of the flake flow field unit group 5 and the flake flow field units of the fifth flake flow field unit group 6 gradually increase in sequence to form a bionic flake-like three-dimensional flow field structure; specifically, the flake flow field units of the fifth flake flow field unit group 6 are larger than the flake flow field units of the fourth flake flow field unit group 5, the flake flow field units of the fourth flake flow field unit group 5 are larger than the flake flow field units of the third flake flow field unit group 4, the flake flow field units of the third flake flow field unit group 4 are larger than the flake flow field units of the second flake flow field unit group 3, and the flake flow field units of the second flake flow field unit group 3 are larger than the flake flow field units of the first flake flow field unit group 2.

[0033] The area where two rows of first flaked flow field unit groups 2 are located on the bipolar plate body 1 forms an inlet distribution area, the area where multiple rows of second flaked flow field unit groups 3 are located forms an intermediate reaction area, and the area where one row of third flaked flow field unit groups 4, one row of fourth flaked flow field unit groups 5 and one row of fifth flaked flow field unit groups 6 are located forms an outlet area; so that the reaction gas flows into the intermediate reaction area through the inlet distribution area and then flows out from the outlet area.

[0034] When the reaction gas enters the middle reaction zone of the bipolar plate body 1, the reaction gas flowing through the second scale-type flow field unit group 3 is divided into two parts, one part of the reaction gas flows into the inside of the second scale-type flow field unit group 3, and the other part of the reaction gas flows to the outside of the second scale-type flow field unit group 3 and is transmitted to the adjacent scale-type flow field unit group. The secondary distribution of the reaction gas by the scale-type flow field unit enhances the uniformity of the reaction gas flow in the flow field, strengthens the mass transfer effect inside the flow field, ensures the uniformity of the electrochemical reaction in the catalyst layer, and avoids the phenomenon of local hot spots or local cold spots.

[0035] The flaked flow field units of the first flaked flow field unit group 2, the flaked flow field units of the second flaked flow field unit group 3, the flaked flow field units of the third flaked flow field unit group 4, the flaked flow field units of the fourth flaked flow field unit group 5 and the flaked flow field units of the fifth flaked flow field unit group 6 all have the same structure and the same vertical height;

[0036] like Figure 4 As shown, each flaked flow field unit on the top surface of the bipolar plate body 1 is a trapezoidal structure with a hollow interior and open ends, and the two sides of each flaked flow field unit are fan-shaped flaked flow field unit sides 8, and the top surface of each flaked flow field unit is a trapezoidal flaked flow field unit top surface 11 parallel to the bipolar plate body 1; the cross-sectional area of ​​each flaked flow field unit decreases successively along the flow direction of the reaction gas, so that the flaked flow field unit changes in a conical shape, and the fan-shaped flaked The side surface 8 of the flow field unit and the inner surface of the top surface 11 of the trapezoidal scale-type flow field unit are provided with a plurality of parallel and spaced microchannels along the flow direction of the reaction gas. The microchannels are microchannels 10 with a semicircular cross section or microchannels 13 with a dovetail cross section. The end surface of the scale-type flow field unit through which the reaction gas flows in is the inlet end 12, and the end surface of the scale-type flow field unit through which the reaction gas flows out is the outlet end 9, and the end surface area of ​​the inlet end 12 of each scale-type flow field unit is larger than the end surface area of ​​its own outlet end 9. The reaction gas enters the scale-type flow field unit from the inlet end 12 and flows out from the outlet end 9. The gradually decreasing cross-sectional area can increase the flow rate of the reaction gas at the outlet end 9, thereby enhancing the driving effect of the reaction gas inside the scale-type flow field unit on the droplet water and promoting the discharge of liquid water; at the same time, it will also promote the flow of the reaction gas to the diffusion layer 7 and enhance the sub-ridge convection of the reaction gas. When the reaction gas flow rate is high or the volume of the water droplets is large, the microchannel structure can cause the water droplets to tear apart and break away from the baffle adsorption, so that the water droplets are discharged from the microchannel.

[0037] The wall thickness of the scale-type flow field unit is 30 μm to 60 μm, and the length of the scale-type flow field unit along the flow direction of the reaction gas is 0.3 mm to 0.8 mm.

[0038] The spacing between two adjacent semicircular cross-section microchannels 10 or two adjacent dovetail cross-section microchannels 13 is 50 μm to 100 μm, which produces a capillary effect on the droplets gathered on the inner wall of the scale-type flow field unit, thereby enhancing the drainage effect of the flow field.

[0039] The middle cross-sectional area of ​​the flake flow field units of the second scaled flow field unit group 3 is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the first scaled flow field unit group 2, the middle cross-sectional area of ​​the flake flow field units of the third scaled flow field unit group 4 is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the second scaled flow field unit group 3, the middle cross-sectional area of ​​the flake flow field units of the fourth scaled flow field unit group 5 is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the third scaled flow field unit group 4, and the middle cross-sectional area of ​​the flake flow field units of the fifth scaled flow field unit group 6 is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the fourth scaled flow field unit group 5.

[0040] The spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group 2 in the same column is 1.2mm~1.6mm, the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group 3 in the same column is 1.1~1.5 times the spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group 2, the spacing between two adjacent scale-type flow field units in the third scale-type flow field unit group 4 in the same column is the same as the spacing between two adjacent scale-type flow field units in the fourth scale-type flow field unit group 5 and the spacing between two adjacent scale-type flow field units in the fifth scale-type flow field unit group 6, and are all 1.1~1.5 times the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group 3, the spacing between two adjacent flow field units respectively located in two columns along the flow direction of the reaction gas is equal, and the spacing h between the cross sections of each of the two adjacent flow field units is 0.7mm~1.8mm.

[0041] like Figure 5 , Figure 6 and Figure 7 As shown, the channel depth of the microchannel 10 with a semicircular cross-section and the channel depth of the microchannel 13 with a dovetail cross-section are both 20μm to 40μm, and the cross-sectional diameter of the microchannel 10 with a semicircular cross-section and the cross-sectional diameter of the microchannel 13 with a dovetail cross-section are the same, and are both 40μm to 70μm. The cross-sectional shape of the microchannel can be selected according to different application scenarios of the fuel cell.

[0042] Preferably, the bipolar plate body 1 is made of titanium alloy thin plate or stainless steel thin plate through stamping and cutting processes.

[0043] Preferably, the microchannel 10 with a semicircular cross section and the microchannel 13 with a dovetail cross section are manufactured by a milling process using electron beams, lasers, heat rays or high-frequency current.

[0044] like Figure 5 As shown, the interior of the semicircular cross-section microchannel 10 is smooth and regularly shaped, the reaction gas flows smoothly therein, the flow velocity is relatively large, and the turbulence effect is relatively strong, so it is easier to blow away the liquid water attached to the inner wall of the flake flow field unit at the outlet end 9; in addition, when the droplets of water generated by the electrochemical reaction are attached to the inner wall of the flake flow field unit, the capillary action of the microflow field on the droplets is used to directionally transport the liquid water accumulated on the inner wall of the channel to the end of the microchannel, which can accelerate the desorption of liquid water in the microchannel, thereby improving the drainage effect of the flow field.

[0045] like Figure 7 As shown, the dovetail-shaped cross-section microchannel 13 not only has certain drainage performance due to capillary action, but also can effectively reduce the contact resistance between the reaction gas and the inner wall of the microchannel due to the large cross-sectional area of ​​the dovetail shape, thereby improving the power generation efficiency of the fuel cell. The cross-sectional shape with gradually increasing width can make the reaction gas pressure drop in the scale-type flow field unit smaller, thereby reducing the energy loss of the battery.

[0046] The specific embodiments are as follows:

[0047] The present invention is mainly applied to the cathode of a proton exchange membrane fuel cell PEMFC, but is also applicable to the anode.

[0048] Inspired by bionics, several scale-type flow field units of different sizes are designed according to the different sizes of scales. The smallest flow field unit forms the inlet distribution area to solve the problem of uneven distribution of reaction gas in the flow field; the flow field unit of moderate size forms the intermediate reaction area to ensure the progress of electrochemical reaction; the larger flow field unit forms the reaction outlet area to reduce the gas pressure at the end of the flow channel, promote the flow of reaction gas to the end of the flow channel, and solve the problem of uneven current density caused by insufficient gas concentration at the end of the flow field.

[0049] The reaction gas flows in from the inlet distribution area, and after passing through the first scale-type flow field unit group 2, which is small in size, large in number, and uniformly dense, the airflow can be more evenly distributed, thereby improving the uniformity of the electrochemical reaction in the intermediate reaction zone. The scale-type flow field units of the same size and staggered in the intermediate reaction zone redistribute the reaction gas, promote the utilization of the reactants, and greatly enhance the convective mass transfer effect of the reaction gas. Compared with traditional flow channels, the contact area between the scale-type flow field unit and the gas diffusion layer is smaller, and the convection effect is stronger, which increases the mass transfer interface, can greatly reduce the concentration loss inside the fuel cell, and obtain a more uniform current density.

Claims

1. A bionic scale-type fuel cell three-dimensional flow field structure, characterized in that: It comprises a bipolar plate body (1) and a gas diffusion layer (7), wherein the gas diffusion layer (7) is closely attached to the bottom of the bipolar plate body (1), and a plurality of rows of mutually parallel scale-type flow field unit groups are arranged on the top surface of the bipolar plate body (1); Each row of the scale-type flow field unit groups is composed of a plurality of identical scale-type flow field units arranged in sequence at equal intervals, and the scale-type flow field units in two adjacent rows of scale-type flow field unit groups are arranged in a staggered manner, and the plurality of rows of scale-type flow field unit groups arranged on the top surface of the bipolar plate body (1) are respectively two rows of first scale-type flow field unit groups (2), a plurality of rows of second scale-type flow field unit groups (3), a row of third scale-type flow field unit groups (4), and a row of fourth scale-type flow field unit groups (5). unit group (5) and a row of fifth scale-type flow field unit groups (6); and the volumes of the scale-type flow field units of the first scale-type flow field unit group (2), the scale-type flow field units of the second scale-type flow field unit group (3), the scale-type flow field units of the third scale-type flow field unit group (4), the scale-type flow field units of the fourth scale-type flow field unit group (5) and the scale-type flow field units of the fifth scale-type flow field unit group (6) gradually increase in sequence, forming a bionic scale-like three-dimensional flow field structure; The area where the two rows of first flaked flow field unit groups (2) are located on the bipolar plate body (1) forms an inlet distribution area, the area where the multiple rows of second flaked flow field unit groups (3) are located forms an intermediate reaction area, and the area where the row of third flaked flow field unit groups (4), the row of fourth flaked flow field unit groups (5) and the row of fifth flaked flow field unit groups (6) are located forms an outlet area; so that the reaction gas flows into the intermediate reaction area through the inlet distribution area and then flows out from the outlet area; The flaked flow field units of the first flaked flow field unit group (2), the flaked flow field units of the second flaked flow field unit group (3), the flaked flow field units of the third flaked flow field unit group (4), the flaked flow field units of the fourth flaked flow field unit group (5) and the flaked flow field units of the fifth flaked flow field unit group (6) all have the same structure and the same vertical height; Each flaked flow field unit on the top surface of the bipolar plate body (1) is in the form of a trapezoidal platform structure with a hollow interior and open ends, and both sides of each flaked flow field unit are fan-shaped flaked flow field unit sides (8), and the top surface of each flaked flow field unit is a trapezoidal flaked flow field unit top surface (11) parallel to the bipolar plate body (1); the cross-sectional area of ​​each flaked flow field unit decreases in sequence along the flow direction of the reaction gas, and the fan-shaped flaked flow field unit sides (8) and the trapezoidal The inner side surface of the top surface (11) of the scale-type flow field unit is provided with a plurality of parallel and spaced microchannels along the flow direction of the reaction gas, the microchannels being microchannels (10) with a semicircular cross section or microchannels (13) with a dovetail cross section, the end surface of the scale-type flow field unit through which the reaction gas flows in is the inlet end (12), the end surface of the scale-type flow field unit through which the reaction gas flows out is the outlet end (9), and the end surface area of ​​the inlet end (12) of each scale-type flow field unit is larger than the end surface area of ​​its own outlet end (9).

2. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The wall thickness of the scale-type flow field unit is 30 μm to 60 μm, and the length of the scale-type flow field unit along the flow direction of the reaction gas is 0.3 mm to 0.8 mm.

3. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The spacing between two adjacent semicircular cross-section microchannels (10) or two adjacent dovetail cross-section microchannels (13) is 50 μm to 100 μm.

4. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The middle cross-sectional area of ​​the flake flow field units of the second flake flow field unit group (3) is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the first flake flow field unit group (2), the middle cross-sectional area of ​​the flake flow field units of the third flake flow field unit group (4) is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the second flake flow field unit group (3), the middle cross-sectional area of ​​the flake flow field units of the fourth flake flow field unit group (5) is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the third flake flow field unit group (4), and the middle cross-sectional area of ​​the flake flow field units of the fifth flake flow field unit group (6) is 1.2 to 1.6 times the middle cross-sectional area of ​​the flake flow field units of the fourth flake flow field unit group (5).

5. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group (2) in the same row is 1.2 mm to 1.6 mm, the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group (3) in the same row is 1.1 to 1.5 times the spacing L between two adjacent scale-type flow field units in the first scale-type flow field unit group (2), the spacing between two adjacent scale-type flow field units in the third scale-type flow field unit group (4) in the same row is the same as the spacing between two adjacent scale-type flow field units in the fourth scale-type flow field unit group (5) and the spacing between two adjacent scale-type flow field units in the fifth scale-type flow field unit group (6), and both are 1.1 to 1.5 times the spacing between two adjacent scale-type flow field units in the second scale-type flow field unit group (3), and the spacing between two adjacent flow field units in the two rows along the reaction gas flow direction is equal.

6. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The channel depth of the microfluidic channel (10) with a semicircular cross-section and the channel depth of the microfluidic channel (13) with a dovetail cross-section are both 20 μm to 40 μm, and the cross-sectional diameter of the microfluidic channel (10) with a semicircular cross-section and the cross-sectional diameter of the microfluidic channel (13) with a dovetail cross-section are the same, and are both 40 μm to 70 μm.

7. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The bipolar plate body (1) is made of a titanium alloy thin plate or a stainless steel thin plate.

8. The bionic scale-type fuel cell three-dimensional flow field structure according to claim 1, characterized in that: The microchannel (10) with a semicircular cross section and the microchannel (13) with a dovetail cross section are manufactured by a milling process using electron beams, lasers, heat rays or high-frequency current.

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