A fuel cell bipolar plate flow field structure for improved mass transfer performance

Abstract

The application discloses a fuel cell bipolar plate flow field structure with improved mass transfer performance, which comprises a flow field area formed by a base plate, a first baffle and a second baffle, and comprises an upstream area, a cross area and a downstream area; gas enters the flow field area from the upstream area, flows through the cross area and the downstream area in sequence, and then flows out of the flow field area; a first secondary structure is fixedly arranged in the upstream area; the cross area is used for prolonging the residence time of the gas in the flow field area; and a second secondary structure is fixedly arranged in the downstream area. The cross area, the first secondary structure and the second secondary structure are designed in the flow field, the reaction products are promoted to enter the diffusion layer for reaction, the concentration polarization is reduced, the internal material transmission of the PEMFC is enhanced, the performance of the PEMFC is improved, and the problem that the forced convection means is limited to the single vertical direction is solved. Meanwhile, the contact area of the gas in the flow field is increased, and the diffusion efficiency of the reactants is improved.

Description

Technical Field

[0001] This invention relates to the field of flow field design technology, and in particular to a flow field structure for a fuel cell bipolar plate that improves mass transfer performance. Background Technology

[0002] Bipolar plates are one of the key components of proton exchange membrane fuel cells (PEMFCs). The flow field structure significantly affects several important parameters of the fuel cell, such as power, current density distribution, and voltage consistency, thus determining its performance indicators and lifespan, and is an important aspect of fuel cell structural design. Improving the geometry of the flow field is one of the most direct methods to enhance the reactant utilization efficiency of PEMFCs.

[0003] In the current research phase, baffles or blockages are added to the flow channel to improve the utilization efficiency of the reactant gas. Current research on baffles mainly focuses on the effects of their height, number, and arrangement. However, these factors only affect the vertical direction of gas flow and cannot create a more complex flow field within the channel. Furthermore, the relatively low proportion of the flow channel surface area in contact with the bipolar plate and diffuser layer relative to the total reaction surface area of ​​the battery is another problem in PEMFC flow field design. Conventional serpentine flow fields only have an effect on gas flow within a single channel and cannot induce forced convection over a wider area in the global flow field. Summary of the Invention

[0004] This invention provides a bipolar plate flow field structure for fuel cells to improve mass transfer performance, thereby overcoming the aforementioned technical problems.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A bipolar plate flow field structure for improving mass transfer performance in a fuel cell includes a substrate, a first baffle, a second baffle, a plurality of first second-order structures, and a plurality of second second-order structures. The base plate, the first baffle, and the second baffle together form a flow field region that supports the flow field structure of the bipolar plate of the fuel cell. The flow field region includes an upstream region, an intersecting region, and a downstream region arranged sequentially along the centerline of the substrate; gas enters the flow field region from the upstream region, flows through the intersecting region and the downstream region in sequence, and then flows out of the flow field region; The first and second-order structures are fixedly disposed in the upstream region, and are used to cause forced convection of gas when gas enters the flow field region through the upstream region; The intersection area is used to increase the gas flow path and prolong the gas residence time in the flow field area; The second-order structure is fixedly disposed in the downstream region to reduce the cross-sectional area through which the gas passes and increase the local gas concentration.

[0006] Furthermore, the first baffle is fixedly disposed on one side of the top of the base plate; the second baffle is fixedly disposed on the other side of the top of the base plate, and the first baffle and the second baffle are arranged parallel to each other.

[0007] Furthermore, the upstream region includes 2n-1 upstream baffles; the upstream baffles are fixedly disposed on the top of the base plate; 2n-1 upstream baffles are sequentially and evenly disposed between the first baffle and the second baffle, and the upstream baffles are parallel to the first baffle; The first baffle, 2n-1 sequentially arranged upstream baffles, and the second baffle sequentially form the first upstream flow channel, the second upstream flow channel, ..., the 2nth upstream flow channel on the top of the base plate; where n is a positive integer greater than 1; The first and second-order structures are disposed inside the first upstream channel, the second upstream channel, ..., the 2nth upstream channel.

[0008] Furthermore, the first second-order structure includes a first triangular cone and a second triangular pyramid that are symmetrically fixed. The vertices of the base triangle of the first triangular pyramid are the first vertex, the second vertex, and the third vertex, all of which are located on the top of the base plate. The cone vertex of the first triangular pyramid is the fourth vertex. The third vertex is located on the side of the second vertex away from the flow field inlet, and the first vertex is located between the second vertex and the flow field inlet. The vertices of the base triangle of the second triangular pyramid are the fifth vertex, the third vertex, and the second vertex, and the cone vertex is the fourth vertex; and the fifth vertex and the first vertex are symmetrical with respect to the line connecting the third vertex and the second vertex, and the plane formed by the fourth vertex, the third vertex, and the second vertex is perpendicular to the base plate; The fifth vertex, the second vertex, and the first vertex form a narrowing angle with the second vertex as the vertex, the line connecting the fifth vertex and the second vertex as one side, and the line connecting the second vertex and the first vertex as the other side. The fourth vertex, the second vertex, and the third vertex form an angle of inclination with the second vertex as the vertex, the line connecting the fourth vertex and the second vertex as one side, and the line connecting the second vertex and the third vertex as the other side. The second second-order structure is identical to the first second-order structure.

[0009] Furthermore, the narrowing angle is obtained as follows:

[0010] in, The narrowing angle is represented by W, which is the width of the flow channels, i.e., the width of the 1st upstream channel, the 2nd upstream channel, ..., the 2nth upstream channel. X It is the length of the line connecting the second vertex to the fifth vertex and the first vertex.

[0011] Furthermore, the tilt angle is obtained as follows:

[0012] In the formula: y is the tilt angle; h is the distance between the fourth vertex and the base surface; Y is the distance between the projection of the fourth vertex onto the base surface and the second vertex.

[0013] Furthermore, in the first second-order structure, l =1 / 3L, where, l L represents the length of the projection of the first and second order structures onto the base plate; L is the length of the first upstream channel. h = H, where H is the height of the base plate.

[0014] Furthermore, the downstream region includes 2n-1 downstream baffles; the downstream baffles are fixedly disposed on the top of the base plate; The downstream baffles described in 2n-1 are sequentially and evenly arranged between the first baffle and the second baffle, and the downstream baffles are parallel to the first baffle; The first baffle, 2n-1 downstream baffles arranged in sequence, and the second baffle sequentially form the first downstream flow channel, the second downstream flow channel, ... the 2nth downstream flow channel on the top of the base plate; The second second-order structure is disposed inside the first downstream channel / the second downstream channel / ... / the 2nth downstream channel.

[0015] Furthermore, the intersection area includes 2n-2 intersection stops, several stops, a first intersection baffle, a second intersection baffle, a first triangular stop, and a second triangular stop; The cross baffle includes a first connecting baffle and a second connecting baffle; the first connecting baffle and the second connecting baffle are arranged collinearly. The first upstream baffle is connected to the first connecting baffle of the first cross baffle, and the (n+1)th downstream baffle is connected to the second connecting baffle of the first cross baffle; The second upstream baffle is connected to the first connecting baffle of the second cross baffle, and the (n+2)th downstream baffle is connected to the second connecting baffle of the second cross baffle;

[0016] The (n-1)th upstream baffle is connected to the first connecting baffle of the (n-1)th cross baffle, and the (2n-1)th downstream baffle is connected to the second connecting baffle of the (n-1)th cross baffle; The (n+1)th upstream baffle is connected to the first connecting baffle of the (n+1)th cross baffle, and the first downstream baffle is connected to the second connecting baffle of the nth cross baffle; The (n+2)th upstream baffle is connected to the first connecting baffle of the (n+2)th cross baffle, and the second downstream baffle is connected to the second connecting baffle of the (n+1)th cross baffle;

[0017] The (2n-1)th upstream baffle is connected to the first connecting baffle of the (2n-2)th cross baffle, and the (n-1)th downstream baffle is connected to the second connecting baffle of the (2n-2)th cross baffle; the baffle block is disposed between the first connecting baffle and the second connecting baffle of the cross baffle; The first cross baffle is disposed between the first upstream baffle and the first downstream baffle, fixed to the top of the base plate and collinear with the first upstream baffle and the first downstream baffle; The second cross baffle is disposed between the 2n-1th upstream baffle and the 2n-1th downstream baffle, fixed to the top of the base plate and collinear with the 2n-1th upstream baffle and the 2n-1th downstream baffle; The first triangular baffle is disposed in the flow field formed by the first cross baffle, the first cross baffle and the nth cross baffle to form a first flow channel; The second triangular baffle is disposed in the flow field formed by the second cross baffle, the (n-1)th cross baffle and the (2n-2)th cross baffle to form a second flow channel.

[0018] Beneficial effects: This invention relates to a bipolar plate flow field structure for fuel cells that improves mass transfer performance. By designing a cross region in the flow field and setting a first second-order structure and a second second-order structure in the upstream and downstream regions respectively, it can promote the reaction products to enter the diffusion layer for reaction, reduce concentration polarization, enhance the internal mass transport of PEMFC, improve its performance, solve the problem that forced convection means are limited to acting in a single vertical direction, and increase the contact area of ​​gas in the flow field, thereby improving the diffusion efficiency of reactants. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the flow field structure of the fuel cell bipolar plate of the present invention; Figure 2 This is a schematic diagram of the first second-order structure in an embodiment of the present invention; Figure 3 This is a polarization curve diagram from an embodiment of the present invention; Figure 4 This is a diagram illustrating the effect of narrowing the angle in an embodiment of the present invention; Figure 5 This is a diagram illustrating the effect of the tilt angle in an embodiment of the present invention; Figure 6 This is a current density cloud diagram from an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This embodiment provides a flow field structure for a fuel cell bipolar plate that improves mass transfer performance, such as... Figure 1 As shown, it includes a base plate 1, a first baffle 21, a second baffle 22; and several first second-order structures 8 and second second-order structures 9; The base plate 1, the first baffle 21 and the second baffle 22 together form a flow field region that supports the flow field structure of the bipolar plate of the fuel cell. The flow field region includes an upstream region, an intersection region, and a downstream region arranged sequentially along the centerline e of the base plate 1; The first second-order structure 8 is fixedly disposed in the upstream region, and is used to cause forced convection of the gas and enhance gas disturbance when the gas enters the flow field region through the upstream region. The intersection area is used to increase the gas flow path and prolong the gas residence time in the flow field area, so that the gas can fully react in the entire flow field area; The second second-order structure 9 is fixedly disposed in the downstream region to reduce the cross-sectional area through which the gas passes, increase the local gas concentration, and promote the gas to enter the diffusion layer to participate in the reaction after leaving the flow field region through the downstream region. Preferably, the first baffle 21 is fixedly disposed on one side of the top of the base plate 1; the second baffle 22 is fixedly disposed on the other side of the top of the base plate 1, and the first baffle 21 and the second baffle 22 are arranged parallel to each other; for example Figure 1 As shown; Preferably, the upstream region includes 2n-1 upstream baffles 3; the upstream baffles 3 are fixedly disposed on the top of the base plate 1; 2n-1 upstream baffles 3 are evenly arranged between the first baffle 21 and the second baffle 22, and the upstream baffles 3 are parallel to the first baffle 21; The first baffle 21, 2n-1 upstream baffles 3 arranged in sequence, and the second baffle 22 sequentially form the first upstream flow channel 301, the second upstream flow channel 302, ... the 2nth upstream flow channel 302n on the top of the base plate 1; The first second-order structure 8 is disposed inside the first upstream channel / the second upstream channel / ... / the 2nth upstream channel.

[0023] Preferably, the first second-order structure 8 includes a first triangular cone and a second triangular pyramid that are symmetrically and fixedly arranged; for example... Figure 2 As shown.

[0024] The vertices of the base triangle of the first triangular pyramid are the first vertex B, the second vertex D, and the third vertex C, all of which are located on the top of the base plate 1. The cone vertex of the first triangular pyramid is the fourth vertex E. The third vertex C is located on the side of the second vertex D away from the flow field inlet a, and the first vertex B is located between the second vertex D and the flow field inlet a. The vertices of the base triangle of the second triangular pyramid are the fifth vertex A, the third vertex C, and the second vertex D, and the cone vertex is the fourth vertex E; and the fifth vertex A and the first vertex B are symmetrical with respect to the line connecting the third vertex C and the second vertex D, and the plane formed by the fourth vertex E, the third vertex C, and the second vertex D is perpendicular to the base plate 1. The fifth vertex A, the second vertex D, and the first vertex B form a narrowing angle with the second vertex D as the vertex, the line connecting the fifth vertex A and the second vertex D as one side, and the line connecting the second vertex D and the first vertex B as the other side. The fourth vertex E, the second vertex D, and the third vertex C form an angle of inclination with the second vertex D as the vertex, the line connecting the fourth vertex E and the second vertex D as one side, and the line connecting the second vertex D and the third vertex C as the other side. The second second-order structure is identical to the first second-order structure.

[0025] Preferably, the narrowing angle is obtained as follows:

[0026] in, The narrowing angle is represented by W, which is the width of the flow channel, i.e., the width of the 1st upstream channel, the 2nd upstream channel, ..., the 2nth upstream channel; X is the length of the line AB connecting the second vertex D to the fifth vertex A and the first vertex B. Specifically, since the first second-order structure is a symmetrical structure, the line CD connecting the second vertex D and the third vertex C is set on the center line of the flow channel. The fifth vertex A and the first vertex B are symmetrical with respect to the line CD, so the line CD should be perpendicular to the line AB. Therefore, X is also equal to the length between the third vertex C and the line AB minus the length of the line CD.

[0027] Preferably, the tilt angle is obtained as follows:

[0028] In the formula: y is the tilt angle; h is the distance between the fourth vertex E and the base surface; Y is the distance between the projection of the fourth vertex E onto the base surface and the second vertex D. Preferably, in the first second-order structure, l =1 / 3L, where, l L represents the length of the projection of the first and second order structures onto the substrate; L is the length of the first upstream channel; that is, the length of the second upstream channel, ..., the 2nth upstream channel; h = H, where H is the height of the base plate.

[0029] Specifically, in this embodiment, the narrowing angle and the tilt angle are key dimensions of the first second-order structure; the magnitudes of the narrowing angle and the tilt angle are related to the X and Y distances in the figure, respectively. Because the length of the second-order structure is fixed, the positions of its three vertices A, B, and C on its top view projection are fixed. Points 1 and 2 are defined as movable points; the length of X is the perpendicular distance from point 1 to the line connecting the fifth vertex A and the first vertex B; the length of Y is the distance from point 1 to point 2. When the length of X is longer, the angle of the narrowing angle 7 is smaller, which reduces the cross-sectional area through which gas can pass, increasing the local concentration. When the length of Y is smaller, the angle of the tilt angle is larger, which is more conducive to generating a velocity component perpendicular to the flow direction.

[0030] Preferably, the downstream region includes 2n-1 downstream baffles 4; the downstream baffles 4 are fixedly disposed on the top of the base plate 1; 2n-1 downstream baffles 4 are sequentially and evenly arranged between the first baffle 21 and the second baffle 22, and the downstream baffles 4 are parallel to the first baffle 21; The first baffle 21, 2n-1 downstream baffles 4 arranged in sequence, and the second baffle 22 sequentially form the first downstream flow channel 401, the second downstream flow channel 402, ... the 2nth downstream flow channel 402n on the top of the base plate 1; The second second-order structure is disposed inside the first downstream channel / the second downstream channel / ... / the 2nth downstream channel.

[0031] Specifically, the area on the base plate 1 where the upstream baffle 3 is provided forms the upstream area, the area where the downstream baffle 4 is provided forms the downstream area, and the area where the cross baffle is provided forms the cross area. Preferably, the intersection area includes 2n-2 intersection blocks 5, a plurality of blocks 53, a first intersection block 54, a second intersection block 55, a first triangular block 56, and a second triangular block 57; The cross baffle 5 includes a first connecting baffle 51 and a second connecting baffle 52; the first connecting baffle 51 and the second connecting baffle 52 are arranged colinearly. The first upstream baffle is connected to the first connecting baffle 51 of the first cross baffle 501, and the (n+1)th downstream baffle is connected to the second connecting baffle 52 of the first cross baffle 501; The second upstream baffle 3 is connected to the first connecting baffle 51 of the second cross baffle 502, and the (n+2)th downstream baffle 4 is connected to the second connecting baffle 52 of the second cross baffle 502;

[0032] The (n-1)th upstream baffle 3 is connected to the first connecting baffle 51 of the (n-1)th cross baffle, and the (2n-1)th downstream baffle 4 is connected to the second connecting baffle 52 of the (n-1)th cross baffle; The (n+1)th upstream baffle 3 is connected to the first connecting baffle 51 of the (n+1)th cross baffle 50n, and the first downstream baffle 4 is connected to the second connecting baffle 52 of the nth cross baffle 50n; The (n+2)th upstream baffle 3 is connected to the first connecting baffle 51 of the (n+2)th cross baffle, and the second downstream baffle 4 is connected to the second connecting baffle 52 of the (n+1)th cross baffle.

[0033] The (2n-1)th upstream baffle 3 is connected to the first connecting baffle 51 of the (2n-2)th cross baffle, and the (n-1)th downstream baffle 4 is connected to the second connecting baffle 52 of the (2n-2)th cross baffle; the baffle block 53 is disposed between the first connecting baffle 51 and the second connecting baffle 52 of the cross baffle; The first cross baffle 54 is disposed between the first upstream baffle 3 and the first downstream baffle 4, fixed to the top of the base plate and collinear with the first upstream baffle 3 and the first downstream baffle 4; The second cross baffle 55 is disposed between the (2n-1)th upstream baffle 3 and the (2n-1)th downstream baffle 4, fixed to the top of the base plate and collinear with the (2n-1)th upstream baffle 3 and the (2n-1)th downstream baffle 4; The first triangular baffle 56 is disposed in the flow field formed by the first cross baffle 54, the first cross baffle 501 and the nth cross baffle to form the first flow channel 58; The second triangular baffle 57 is disposed in the flow field formed by the second cross baffle 55, the (n-1)th cross baffle and the (2n-2)th cross baffle 502n-2 to form the second flow channel 59.

[0034] The intersection region enables the first upstream flow channel to be linearly connected to the (n+1)th downstream flow channel; enables the second upstream flow channel to be linearly connected to the (n+2)th downstream flow channel; enables the nth upstream flow channel to be linearly connected to the 2nth downstream flow channel; enables the (n+1)th upstream flow channel to be linearly connected to the first downstream flow channel; enables the 2nth upstream flow channel to be linearly connected to the (n+1)th downstream flow channel. Specifically, this embodiment introduces a first- and second-order structure and intersecting flow channels formed in the intersection region, which together induce forced convection throughout the entire space, promoting the transfer of reactants in the flow field and improving utilization efficiency. In this embodiment, the lengths of the upstream region, intersection region, and downstream region are all 10 mm.

[0035] In this embodiment, the cross region set in the middle of the flow field forms a cross flow channel, which increases the gas diffusion area. The blocks in the cross baffle form a cross node, which obstructs the gas flow and can increase the residence time of the gas in the flow field.

[0036] A second-order structure was also placed downstream of the flow field. Because most of the gas has already reacted upstream in the downstream part of the flow field, the gas concentration is lower downstream, and the second-order structure facilitates the gas to enter the diffusion layer.

[0037] This embodiment utilizes both a "second-order" structure and intersecting channels to improve mass transfer performance. The "second-order" structure, located upstream of the flow field, generates forced convection, promoting gas entry into the diffusion layer for reaction. The narrowing angle also converges the flowing gas, enhancing the disturbance effect. Downstream, the concentration decreases due to gas consumption during the reaction. The nodes formed by the intersecting channels extend the gas residence time. The combination of the "second-order" structure and intersecting channels allows for sufficient gas reaction throughout the global flow field, improving the uniformity of current density. Figure 3 The polarization curves show that, under low voltage conditions, the novel flow field can achieve a higher current density because it promotes gas mass transfer and reduces the influence of concentration polarization. Figure 4 The velocity vector diagram shows that the narrowing angle alters the horizontal motion of the gas, causing the gas that would normally flow directly from the inlet to the outlet to accumulate. From... Figure 5 As can be seen, the tilt angle can generate a velocity component of the gas perpendicular to the flow direction, which is beneficial for the gas to enter the reaction zone and improve the utilization rate. Figure 6 The current density contour plot shows the extent to which nodes in the cross region can increase the current density.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bipolar plate flow field structure for improving mass transfer performance in a fuel cell, characterized in that, Includes a base plate (1), a first baffle (21), a second baffle (22); several first second-order structures (8), and several second second-order structures (9); The base plate (1), the first baffle (21), and the second baffle (22) together form a flow field region that supports the bipolar plate flow field structure of the fuel cell; The flow field region includes an upstream region, an intersecting region, and a downstream region arranged sequentially along the centerline of the base plate (1); the gas enters the flow field region from the upstream region, flows through the intersecting region and the downstream region in sequence, and then flows out of the flow field region; The first second-order structure (8) is fixedly disposed in the upstream region, and is used to cause forced convection of gas when gas enters the flow field region through the upstream region; The intersection area is used to increase the gas flow path and prolong the gas residence time in the flow field area; The second second-order structure (9) is fixedly disposed in the downstream region to reduce the cross-sectional area through which the gas passes and increase the local gas concentration.

2. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 1, characterized in that, The first baffle (21) is fixedly disposed on one side of the top of the base plate (1); the second baffle (22) is fixedly disposed on the other side of the top of the base plate (1), and the first baffle (21) and the second baffle (22) are arranged in parallel.

3. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 2, characterized in that, The upstream region includes 2n-1 upstream baffles (3); the upstream baffles (3) are fixedly disposed on the top of the base plate (1); 2n-1 upstream baffles (3) are evenly arranged between the first baffle (21) and the second baffle (22), and the upstream baffles (3) are parallel to the first baffle (21). The first baffle (21), 2n-1 upstream baffles (3) arranged in sequence, and the second baffle (22) sequentially form the first upstream flow channel (301), the second upstream flow channel (302), ... the 2nth upstream flow channel (302n) on the top of the base plate (1); where n is a positive integer greater than 1; The first second-order structure (8) is disposed inside the first upstream channel / the second upstream channel / ... / the 2nth upstream channel.

4. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 1, characterized in that, The first second-order structure (8) includes a first triangular cone and a second triangular pyramid that are symmetrically fixed. The vertices of the triangle on the base of the first triangular pyramid are the first vertex (B), the second vertex (D), and the third vertex (C), and all are located on the top of the base plate (1). The cone vertex of the first triangular pyramid is the fourth vertex (E). The third vertex (C) is located on the side of the second vertex (D) away from the flow field inlet, and the first vertex (B) is located between the second vertex (D) and the flow field inlet. The vertices of the base triangle of the second triangular pyramid are the fifth vertex (A), the third vertex (C), and the second vertex (D), and the cone vertex is the fourth vertex (E); and the fifth vertex (A) and the first vertex (B) are symmetrical with respect to the line connecting the third vertex (C) and the second vertex (D), and the plane formed by the fourth vertex (E), the third vertex (C), and the second vertex (D) is perpendicular to the base plate (1). The fifth vertex (A), the second vertex (D), and the first vertex (B) form a narrowing angle with the second vertex (D) as the vertex, the line connecting the fifth vertex (A) and the second vertex (D) as one side, and the line connecting the second vertex (D) and the first vertex (B) as the other side. The fourth vertex (E), the second vertex (D), and the third vertex (C) form an angle of inclination with the second vertex (D) as the vertex, the line connecting the fourth vertex (E) and the second vertex (D) as one side, and the line connecting the second vertex (D) and the third vertex (C) as the other side. The second second-order structure is identical to the first second-order structure.

5. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 4, characterized in that, The narrowing angle is obtained as follows: in, The narrowing angle is represented by W, which is the width of the flow channels, i.e., the width of the 1st upstream channel, the 2nd upstream channel, ..., the 2nth upstream channel. X It is the length of the line connecting the second vertex to the fifth vertex and the first vertex.

6. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 4, characterized in that, The tilt angle is obtained as follows: In the formula: y is the tilt angle; h is the distance between the fourth vertex and the base surface; Y is the distance between the projection of the fourth vertex onto the base surface and the second vertex.

7. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 1, characterized in that, In the first and second order structures, l =1 / 3L, where, l L represents the length of the projection of the first and second order structures onto the base plate; L is the length of the first upstream flow channel. h = H, where H is the height of the base plate.

8. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 1, characterized in that, The downstream region includes 2n-1 downstream baffles (4); the downstream baffles (4) are fixedly disposed on the top of the base plate (1); The downstream baffle (4) of 2n-1 is uniformly arranged between the first baffle (21) and the second baffle (22) in sequence, and the downstream baffle (4) is parallel to the first baffle (21). The first baffle (21), the 2n-1 downstream baffles (4) arranged in sequence, and the second baffle (22) sequentially form the first downstream flow channel (401), the second downstream flow channel (402), ... the 2n downstream flow channel (402n) on the top of the base plate (1). The second second-order structure (9) is disposed inside the first downstream channel / the second downstream channel / ... / the 2nth downstream channel.

9. The fuel cell bipolar plate flow field structure for improving mass transfer performance according to claim 1, characterized in that, The intersection area includes 2n-2 intersection blocks (5), several blocks (53), a first intersection baffle (54), a second intersection baffle (55), a first triangular block (56), and a second triangular block (57); The cross baffle (5) includes a first connecting baffle (51) and a second connecting baffle (52); the first connecting baffle (51) and the second connecting baffle (52) are arranged colinearly. The first upstream baffle is connected to the first connecting baffle (51) of the first cross baffle (501), and the (n+1)th downstream baffle is connected to the second connecting baffle (52) of the first cross baffle (501); The second upstream baffle (3) is connected to the first connecting baffle (51) of the second cross baffle (502), and the (n+2)th downstream baffle (4) is connected to the second connecting baffle (52) of the second cross baffle (502); The (n-1)th upstream baffle (3) is connected to the first connecting baffle (51) of the (n-1)th cross baffle, and the (2n-1)th downstream baffle (4) is connected to the second connecting baffle (52) of the (n-1)th cross baffle; The (n+1)th upstream baffle (3) is connected to the first connecting baffle (51) of the (n+1)th cross baffle, and the first downstream baffle (4) is connected to the second connecting baffle (52) of the nth cross baffle; The (n+2)th upstream baffle (3) is connected to the first connecting baffle (51) of the (n+2)th cross baffle, and the second downstream baffle (4) is connected to the second connecting baffle (52) of the (n+1)th cross baffle; The (2n-1)th upstream baffle (3) is connected to the first connecting baffle (51) of the (2n-2)th cross baffle, and the (n-1)th downstream baffle (4) is connected to the second connecting baffle (52) of the (2n-2)th cross baffle (502n-2); the baffle (53) is disposed between the first connecting baffle (51) and the second connecting baffle (52) of the cross baffle; The first cross baffle (54) is disposed between the first upstream baffle (3) and the first downstream baffle (4), fixed to the top of the base plate and collinear with the first upstream baffle (3) and the first downstream baffle (4); The second cross baffle (55) is disposed between the 2n-1th upstream baffle (3) and the 2n-1th downstream baffle (4), fixed to the top of the base plate and collinear with the 2n-1th upstream baffle (3) and the 2n-1th downstream baffle (4); The first triangular baffle (56) is disposed in the flow field formed by the first cross baffle (54), the first cross baffle (501) and the nth cross baffle to form a first flow channel (58). The second triangular baffle (57) is disposed in the flow field formed by the second cross baffle (55), the (n-1)th cross baffle and the (2n-2)th cross baffle (502n-2) to form a second flow channel (59).

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