A fuel cell metal bipolar plate with divided flow channels

Abstract

A fuel cell metal bipolar plate divided flow channel belongs to the technical field of fuel cells, and proposes a new structure of metal bipolar plate divided flow channels, each hydrogen flow channel includes a hydrogen flow channel air intake area, a hydrogen flow channel descending area, a hydrogen flow channel lowest area, and a hydrogen flow channel air outlet area, the air intake area includes at least two air intake steps, the descending area includes at least one step, and the lowest area and the air outlet area respectively include one step; each oxygen flow channel includes an oxygen flow channel air intake area, an oxygen flow channel highest area, an oxygen flow channel descending area, and an oxygen flow channel air outlet area; the ends of each adjacent step of the oxygen and hydrogen flow channels are connected by a slope surface; the depth of the hydrogen flow channel is gradually reduced as a whole, and then increases after reaching the lowest area; the depth of the oxygen flow channel is gradually increased as a whole, and then decreases after reaching the highest area; the present invention can solve the problems of slow gas flow rate and insufficient pressure in the metal bipolar plate flow channel, and can improve the sufficiency of electrochemical reaction, drainage and service life of the plate.

Description

Technical Field

[0001] The invention relates to a regional flow channel of a metal bipolar plate of a fuel cell, and belongs to the technical field of fuel cells. Background Art

[0002] Metal bipolar plate fuel cells are devices that convert chemical energy into electrical energy. The main reactants are hydrogen and oxygen, and the only product is water. They are environmentally friendly devices. Metal bipolar plates are an important component of fuel cells and the "skeleton" of the stack. Their weight accounts for more than 80% of the weight of the fuel cell stack. Fuel cells have high requirements for hydrogen purity, which needs to reach more than 99.99%. The impurity content of sulfur, carbon and ammonia has a serious impact on the service life of proton exchange membranes and catalysts. The existing metal bipolar plate direct current channel configuration is prone to cause slow reaction gas flow rate and insufficient pressure in the flow channel, resulting in inadequate local reaction. It may even cause reactant impurities and products to accumulate on the plate due to the slow flow rate, thereby corroding the plate and affecting the performance of the fuel cell. Therefore, it is necessary to invent a new metal bipolar plate flow channel configuration to improve the fuel cell reaction gas diffusion, drainage and plate corrosion resistance. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of insufficient electrochemical reaction caused by slow gas flow rate and insufficient pressure in the flow channel under the condition of determined intake pressure, and at the same time solve the problem of reduced service life caused by deposition of impurities in the reactants on the surface of the metal bipolar plate due to low reactant flow rate; in order to overcome the defects of the above-mentioned prior art, a new type of hydrogen flow channel and oxygen flow channel configuration with divided regions of the metal bipolar plate of a fuel cell is proposed.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A fuel cell metal bipolar plate with divided flow channels, the metal bipolar plate includes a cathode monopolar plate and an anode monopolar plate, the cathode monopolar plate is provided with an oxygen flow channel, the anode monopolar plate is provided with a hydrogen flow channel, the cathode monopolar plate and the anode monopolar plate are symmetrical in convex and concave, characterized in that: each hydrogen flow channel includes a hydrogen flow channel inlet area, a hydrogen flow channel descending area, a hydrogen flow channel lowest area and a hydrogen flow channel outlet area along the gas flow direction, the hydrogen flow channel inlet area includes at least two inlet steps, the hydrogen flow channel descending area includes at least one descending step, the hydrogen The lowest area of ​​the flow channel includes a lowest step, the outlet area of ​​the hydrogen flow channel includes an outlet step, and each of the hydrogen flow channels includes m steps; each of the oxygen flow channels includes an oxygen flow channel air inlet area, an oxygen flow channel highest area, an oxygen flow channel descending area and an oxygen flow channel air outlet area along the gas flow direction, the oxygen flow channel air inlet area includes an air inlet step, the oxygen flow channel highest area includes a highest step, the oxygen flow channel descending area includes at least one descending step, the oxygen flow channel air outlet area includes at least two air outlet steps, and each of the oxygen flow channels includes m steps;

[0006] The depth of the hydrogen flow channel step includes four categories: the step flow channel depth of the hydrogen flow channel inlet area, the step flow channel depth of the hydrogen flow channel descending area, the step flow channel depth of the hydrogen flow channel lowest area, and the step flow channel depth of the hydrogen flow channel outlet area. The step flow channel depth Y1 (X, Z) of the hydrogen flow channel inlet area is determined according to the following model:

[0007]

[0008] In formula (1), H1 is the depth of the hydrogen flow channel at the coordinate (X, Z) = (0, 0) at the inlet of the hydrogen flow channel; ΔH is the difference in the depth of the flow channel projected onto the Y-axis direction from the slope surface connecting the head and tail of the two adjacent steps of each hydrogen flow channel, ΔH∈[0.05, 0.15] mm; l is the projection length from the starting position to the tail of each step on the X-axis, and the projection length of each step is equal; N1 is an integer, which is the sequential numbering of the steps in the inlet area of ​​the hydrogen flow channel along the air flow direction, N1∈[1, b], b≥2, where 1 refers to the minimum value of the first step number at the inlet area entrance, b is an integer, which refers to the last step number at the outlet of the inlet area, and the independent variable X∈[0, bl]; a is the depth coefficient of each step, a∈[0, 0.02]; K is the slope of the slope surface of the two adjacent steps of each hydrogen flow channel, K>0.

[0009] Furthermore, the regional flow channel of the metal bipolar plate of a fuel cell is characterized in that the depth of the step flow channel in the descending area and the lowest area of ​​the hydrogen flow channel is determined according to the following model:

[0010] 1) The step flow channel depth Y2 (X, Z) of the hydrogen flow channel descending area is determined according to the following model:

[0011]

[0012] In formula (2), N2 is an integer, which is the sequential numbering of the steps in the hydrogen flow channel along the gas flow direction, N2∈[b+1,m-2], mb≥3, where b+1 refers to the minimum number of the first step at the entrance of the descending zone, m-2 refers to the maximum number of the last step at the exit of the descending zone, m is an integer, and the independent variable X∈[(b+1)l,(m-2)l];

[0013] 2) The step flow channel depth Y3 (X, Z) of the lowest area of ​​the hydrogen flow channel is determined according to the following model:

[0014]

[0015] In formula (3), N3 is an integer, which is the sequential numbering of the steps in the lowest area of ​​the hydrogen flow channel along the direction of the gas flow, N3 = m-1, and the independent variable X∈((m-2)l,(m-1)l].

[0016] Furthermore, the regional flow channel of the metal bipolar plate of a fuel cell is characterized in that the step flow channel depth Y4 (X, Z) of the hydrogen flow channel outlet area is determined according to the following model:

[0017]

[0018] In formula (4), N4 is an integer, which is the sequential numbering of the steps in the hydrogen flow channel outlet area along the gas flow direction, N4=m, and the independent variable X∈((m-1)l,ml]; the depth of the hydrogen flow channel gradually decreases from the hydrogen flow channel inlet area to the hydrogen flow channel descending area to the lowest area of ​​the hydrogen flow channel, and then increases in the hydrogen flow channel outlet area, wherein the flow channel depth is the lowest in the lowest area of ​​the hydrogen flow channel.

[0019] Furthermore, the regional flow channel of the metal bipolar plate of a fuel cell is characterized in that the step flow channel depth y1(x,z) of the oxygen flow channel inlet area is determined according to the following model:

[0020]

[0021] In formula (5), h1 is the depth of the oxygen channel at the coordinate (x, z) = (0, 0) at the inlet of the oxygen channel, and h1 and H1 are equal; the independent variable x∈[0, l], a is the depth coefficient of each step, a∈[0, 0.02].

[0022] Furthermore, the regional flow channel of the metal bipolar plate of a fuel cell is characterized in that the step flow channel depths of the highest area and the descending area of ​​the oxygen flow channel are determined according to the following model:

[0023] 1) The step flow channel depth y2(x,z) of the highest area of ​​the oxygen flow channel is determined according to the following model:

[0024]

[0025] In formula (6), Δh is the difference in channel depth between the inclined surfaces connecting the two adjacent steps of each oxygen flow channel and projected onto the y-axis direction, and Δh and ΔH are equal; n2 is an integer, which is the sequential numbering of the steps in the highest area of ​​the oxygen flow channel along the airflow direction, n2=2, the independent variable x∈(l,2l], k is the slope of the inclined surface of the two adjacent steps of each oxygen flow channel, and k and K are equal;

[0026] 2) The step flow channel depth y3(x,z) of the oxygen flow channel descending area is determined according to the following model:

[0027]

[0028] In formula (7), n3 is an integer, which is the sequential numbering of the steps in the oxygen flow channel descending zone along the airflow direction, n3∈[3,c], c≥3, 3 refers to the minimum value of the number of the first step at the entrance of the descending zone, c is an integer, which refers to the number of the last step at the exit of the descending zone, and the independent variable x∈[3l,cl].

[0029] Furthermore, the regional flow channel of the metal bipolar plate of a fuel cell is characterized in that the step flow channel depth y4(x,z) of the oxygen flow channel outlet area is determined according to the following model:

[0030]

[0031] In formula (8), n4 is an integer, which is the sequential numbering of the steps in the oxygen flow channel outlet area along the air flow direction, n4∈[c+1,m], mc≥2, c+1 refers to the minimum value of the number of the first step at the entrance of the oxygen flow channel outlet area, and the independent variable x∈[(c+1)l,ml]; the depth of the oxygen flow channel gradually increases from the oxygen flow channel inlet area to the oxygen flow channel highest area, and after reaching the oxygen flow channel highest area, it decreases in the oxygen flow channel descending area and the oxygen flow channel outlet area, wherein the flow channel depth in the oxygen flow channel highest area is the largest.

[0032] Furthermore, the regional flow channels of the metal bipolar plate of a fuel cell are characterized in that the ends of each two adjacent steps on the oxygen flow channel and the hydrogen flow channel are connected by a slope surface structure;

[0033] 1) The depth Y(X, Z) of the hydrogen flow channel on the slope surface is determined according to the following model:

[0034]

[0035]

[0036] In formulas (9) and (10), N is an integer, which is the serial number of all steps in the hydrogen flow channel along the gas flow direction, N∈[1,m], 1 refers to the minimum value of the number of the first step at the entrance of the hydrogen flow channel, m is an integer, which refers to the number of the last step at the exit of the hydrogen flow channel, when the step number N∈[1,m-1] is calculated using formula (9), when the step number N=m, it is calculated using formula (10);

[0037] 2) The oxygen flow channel depth y(x,z) of the slope surface is determined according to the following model:

[0038] y5(x,z)=h1+k(x-nl) (11)

[0039]

[0040]

[0041] In formulas (11, 12, and 13), n is an integer, which is the numbering of the steps in the oxygen flow channel in sequence along the airflow direction, n∈[1,m], 1 refers to the minimum number of the first step at the entrance of the oxygen flow channel, and m refers to the maximum number of the last step at the exit of the oxygen flow channel. When the step number n=1, formula (11) is used for calculation, when the step number n=2, formula (12) is used for calculation, and when the step number n∈[3,m], formula (13) is used for calculation.

[0042] When the amplitude coefficient a of each step is 0, the bottom surfaces of the hydrogen flow channel and the oxygen flow channel are planes; when the amplitude coefficient a of each step is ≠ 0, the bottom surfaces of the hydrogen flow channel and the oxygen flow channel are curved surfaces.

[0043] The beneficial effects of the present invention are:

[0044] The present invention proposes a metal bipolar plate with divided flow channels, which divides the depths of oxygen flow channels and hydrogen flow channels into four step areas along the gas flow direction. By setting a reasonable flow channel depth for each area and internal step, and adopting a slope surface connection structure between adjacent steps, the disturbance performance of the reaction gas is enhanced, so that it is more evenly distributed in the flow field, and the electrochemical reaction capacity inside the battery is promoted; at the same time, compared with the existing straight channel structure, the present invention can increase the reaction gas flow rate, which is beneficial to the timely discharge of water generated in the flow channel; at the same time, it can overcome the deposition of impurities such as sulfur, carbon and ammonia on the surface of the metal bipolar plate, and improve the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the local structure of the hydrogen flow channel region when the number of steps is 5, the amplitude coefficient a≠0, and the bottom surface of the anode monopolar plate is a curved surface;

[0046] Figure 2 This is a schematic diagram of the local structure of the hydrogen flow channel region when the number of steps is 5, the amplitude coefficient a=0, and the bottom surface of the anode monopolar plate is a plane;

[0047] Figure 3 This is a schematic diagram of the local structure of the oxygen flow channel region when the number of steps is 5, the amplitude coefficient a≠0, and the bottom surface of the cathode monopolar plate is a curved surface;

[0048] Figure 4 This is a schematic diagram of the local structure of the oxygen flow channel region when the number of steps is 5, the amplitude coefficient a=0, and the bottom surface of the cathode monopolar plate is a plane;

[0049] Figure 5 This is a schematic diagram of the flow channel steps when the number of steps is 5, the amplitude coefficient a≠0, and the bottom surface of the hydrogen flow channel is a curved surface;

[0050] Figure 6 This is a schematic diagram of the flow channel steps when the number of steps is 5, the amplitude coefficient a=0, and the bottom surface of the hydrogen flow channel is a plane;

[0051] Figure 7 This is a schematic diagram of the flow channel steps when the number of steps is 5, the amplitude coefficient a≠0, and the bottom surface of the oxygen flow channel is a curved surface;

[0052] Figure 8 This is a schematic diagram of the flow channel steps when the number of steps is 5, the amplitude coefficient a=0, and the bottom surface of the oxygen flow channel is a plane;

[0053] In the figure, 1-hydrogen flow channel, 2-oxygen flow channel, 3-anode monopolar plate, 4-cathode monopolar plate, 5-hydrogen flow channel groove bottom, 6-hydrogen flow channel wall, 7-slope surface, 8-oxygen flow channel groove bottom, 9-oxygen flow channel wall. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

[0055] Figure 1 to Figure 4As shown, a fuel cell metal bipolar plate has regional flow channels, including an oxygen flow channel 2 provided on a cathode monopolar plate 4 and a hydrogen flow channel 1 provided on an anode monopolar plate 3, wherein the cathode monopolar plate 4 is symmetrical with the anode monopolar plate 3 in convex and concave directions, wherein each hydrogen flow channel 1 includes a hydrogen flow channel inlet area, a hydrogen flow channel descending area, a hydrogen flow channel lowest area and a hydrogen flow channel outlet area along the gas flow direction, wherein the hydrogen flow channel inlet area includes at least two inlet steps, the hydrogen flow channel descending area includes at least one descending step, each hydrogen flow channel lowest area includes a lowest step, and the hydrogen flow channel outlet area includes The oxygen flow channel 2 includes an outlet step, and each hydrogen flow channel includes m steps; each oxygen flow channel 2 includes an oxygen flow channel air inlet area, an oxygen flow channel highest area, an oxygen flow channel descending area and an oxygen flow channel air outlet area along the gas flow direction, the oxygen flow channel air inlet area includes an air inlet step, the oxygen flow channel highest area includes a highest step, each oxygen flow channel descending area includes at least one descending step, the oxygen flow channel air outlet area includes at least two air outlet steps, and each oxygen flow channel includes m steps; each oxygen flow channel and each adjacent step on the hydrogen flow channel are connected in a slope surface form, such as Figures 5 to 8 shown.

[0056] The depth of the hydrogen flow channel step includes four categories: the step flow channel depth of the hydrogen flow channel inlet area, the step flow channel depth of the hydrogen flow channel descending area, the step flow channel depth of the hydrogen flow channel lowest area, and the step flow channel depth of the hydrogen flow channel outlet area. The step flow channel depth Y1 (X, Z) of the hydrogen flow channel inlet area is determined according to the following model:

[0057]

[0058] In formula (1), H1 is the depth of the hydrogen flow channel at the coordinate (X, Z) = (0, 0) at the inlet of the hydrogen flow channel; ΔH is the difference in the depth of the flow channel projected onto the Y-axis direction from the slope surface connecting the head and tail of the two adjacent steps of each hydrogen flow channel, ΔH∈[0.05, 0.15] mm; l is the projection length from the starting position to the tail of each step on the X-axis, and the projection length of each step is equal; N1 is an integer, which is the sequential numbering of the steps in the inlet area of ​​the hydrogen flow channel along the air flow direction, N1∈[1, b], b≥2, where 1 refers to the number of the first step at the inlet area, b is an integer, which refers to the number of the last step at the outlet of the inlet area, and the independent variable X∈[0, bl]; a is the depth coefficient of each step, a∈[0, 0.02]; K is the slope of the slope surface of the two adjacent steps of each hydrogen flow channel, K>0.

[0059] The depth of the step flow channel in the descending area and the lowest area of ​​the hydrogen flow channel is determined according to the following model:

[0060] 1) The step flow channel depth Y2 (X, Z) of the hydrogen flow channel descending area is determined according to the following model:

[0061]

[0062] In formula (2), N2 is an integer, which is the sequential numbering of the steps in the hydrogen flow channel along the gas flow direction, N2∈[b+1,m-2], mb≥3, where b+1 refers to the number of the first step at the entrance of the descending zone, m-2 refers to the number of the last step at the exit of the descending zone, m is an integer, and the independent variable X∈[(b+1)l,(m-2)l];

[0063] 2) The step flow channel depth Y3 (X, Z) of the lowest area of ​​the hydrogen flow channel is determined according to the following model:

[0064]

[0065] In formula (3), N3 is an integer, which is the sequential numbering of the steps in the lowest area of ​​the hydrogen flow channel along the direction of the gas flow, N3 = m-1, and the independent variable X∈((m-2)l,(m-1)l].

[0066] The step flow channel depth Y4 (X, Z) of the hydrogen flow channel outlet area is determined according to the following model:

[0067]

[0068] In formula (4), N4 is an integer, which is the serial number of the steps in the hydrogen flow channel outlet area along the gas flow direction, N4 = m, and the independent variable X∈((m-1)l,ml].

[0069] The step flow channel depth y1(x,z) of the oxygen flow channel inlet area is determined according to the following model:

[0070]

[0071] In formula (5), h1 is the depth of the oxygen channel at the coordinate (x, z) = (0, 0) at the inlet of the oxygen channel, and h1 and H1 are equal; the independent variable x∈[0, l], a is the depth coefficient of each step, a∈[0, 0.02].

[0072] The depth of the step flow channel in the highest area and the descending area of ​​the oxygen flow channel is determined according to the following model:

[0073] 1) The step flow channel depth y2(x,z) of the highest area of ​​the oxygen flow channel is determined according to the following model:

[0074]

[0075] In formula (6), Δh is the difference in channel depth between the slope surface connecting the two adjacent steps of each oxygen flow channel and projected onto the y-axis direction, and Δh and ΔH are equal; n2 is an integer, which is the sequential numbering of the steps in the highest area of ​​the oxygen flow channel along the airflow direction, n2=2, the independent variable x∈(l,2l], k is the slope of the slope surface of the two adjacent steps of each oxygen flow channel, and k and K are equal;

[0076] 2) The step flow channel depth y3(x,z) of the oxygen flow channel descending area is determined according to the following model:

[0077]

[0078] In formula (7), n3 is an integer, which is the sequential numbering of the steps in the oxygen flow channel descending zone along the airflow direction, n3∈[3,c], c≥3, 3 refers to the number of the first step at the entrance of the descending zone, c is an integer, which refers to the number of the last step at the exit of the descending zone, and the independent variable x∈[3l,cl].

[0079] The step flow channel depth y4(x,z) of the oxygen flow channel outlet area is determined according to the following model:

[0080]

[0081] In formula (8), n4 is an integer, which is the sequential numbering of the steps in the oxygen flow channel outlet area along the air flow direction, n4∈[c+1,m], mc≥2, c+1 refers to the number of the first step at the entrance of the oxygen flow channel outlet area, and the independent variable x∈[(c+1)l,ml].

[0082] The oxygen flow channel and the hydrogen flow channel each have two adjacent steps connected in a sloped surface structure at the beginning and the end;

[0083] 1) The depth Y (XZ) of the hydrogen flow channel on the slope surface is determined according to the following model:

[0084]

[0085]

[0086] In formulas (9 and 10), N is an integer, which is the serial number of all steps of the hydrogen flow channel along the gas flow direction, N∈[1,m], 1 refers to the number of the first step at the entrance of the hydrogen flow channel, and m is an integer, which refers to the number of the last step at the exit of the hydrogen flow channel. When the step number N∈[1,m-1] is calculated using formula (9), when the step number N=m, it is calculated using formula (10);

[0087] 2) The oxygen flow channel depth y(x,z) of the slope surface is determined according to the following model:

[0088] y5(x,z)=h1+k(x-nl) (11)

[0089]

[0090]

[0091] In formulas (11, 12, and 13), n is an integer, which is the numbering of the steps in the oxygen flow channel in sequence along the airflow direction, n∈[1,m], 1 refers to the number of the first step at the entrance of the oxygen flow channel, and m refers to the number of the last step at the exit of the oxygen flow channel. When the step number n=1, formula (11) is used for calculation, when the step number n=2, formula (12) is used for calculation, and when the step number n∈[3,m], formula (13) is used for calculation.

[0092] Figure 1-2 It is shown that each hydrogen flow channel has an inlet area including two inlet steps, a descending area of ​​the hydrogen flow channel including a descending step, a lowest area of ​​the hydrogen flow channel including a lowest step, and an outlet area of ​​the hydrogen flow channel including an outlet step, so each hydrogen flow channel includes 5 steps; when each oxygen flow channel is along the gas flow direction, the inlet area of ​​the oxygen flow channel includes an inlet step, the highest area of ​​the oxygen flow channel includes a highest step, the descending area of ​​the oxygen flow channel includes a descending step, the outlet area of ​​the oxygen flow channel includes two outlet steps, and each oxygen flow channel includes 5 steps, such as Figure 3-4 As shown; each adjacent step on each oxygen flow channel and hydrogen flow channel is connected in a slope surface structure, such as Figure 1 , 3 shown.

[0093] When the amplitude coefficient a of each step is ≠0, and both the hydrogen and oxygen flow channels include 5 steps, the bottom surfaces of the hydrogen flow channel 1 and the oxygen flow channel 2 are curved surfaces, such as Figure 5 , Figure 7 As shown; when the amplitude coefficient a of each step is 0, and the hydrogen and oxygen flow channels include 5 steps, the bottom surfaces of the hydrogen flow channel 1 and the oxygen flow channel 2 are both planes, such as Figure 6 , Figure 8 shown.

[0094] When hydrogen passes through Figure 1 , Figure 2 When the hydrogen flow channels in the anode monopolar plate are shown, Figure 5 , Figure 6Taking the single flow channel shown as an example, the gas change characteristics in each flow channel are the same. When hydrogen passes through the hydrogen flow channel inlet area, the flow channel depth of the hydrogen flow channel inlet area shows an overall decreasing characteristic, which reduces the pressure of the hydrogen passing through and increases the flow rate; when hydrogen passes through the hydrogen flow channel descending area and the lowest area of ​​the hydrogen flow channel in sequence, the depth of each step flow channel in the hydrogen flow channel descending area and the lowest area of ​​the hydrogen flow channel is smaller than the depth of each step flow channel in the hydrogen flow channel inlet area, which further reduces the hydrogen pressure and increases the hydrogen flow rate, which is beneficial to the diffusion of the humidification reaction gas in the flow channel; compared with the lowest area of ​​the hydrogen flow channel, when hydrogen passes through the hydrogen flow channel outlet area, the depth of each step flow channel in the hydrogen flow channel outlet area is greater than that in the lowest area of ​​the hydrogen flow channel, the hydrogen pressure increases, and the flow rate decreases, which can increase the hydrogen flow to this area. Figure 5 The diffusion capacity of the gas diffusion layer in the membrane electrode on the mid-coordinate plane XOZ increases the current density in this area and improves the uniformity of the current density in this flow channel.

[0095] Figure 5 The partial views of various zones of the hydrogen flow channel are shown: the depth of each step flow channel in the hydrogen flow channel inlet zone and the hydrogen flow channel outlet zone has a characteristic of increasing from small to small and then decreasing, so that the hydrogen pressure in each step increases from small to small and then decreases, and the hydrogen flow rate decreases from large to large; the depth of each step flow channel in the hydrogen flow channel descending zone and the lowest zone of the hydrogen flow channel has a characteristic of decreasing from large to large, so that the hydrogen pressure decreases from large to large and then increases, and the hydrogen flow rate increases from small to small. Figure 6 The partial sections of each area of ​​the hydrogen flow channel are shown: in the four areas of the hydrogen flow channel, the channel depth of each step is different, the bottom surface of each step is a plane, and the channel depth of each step body remains unchanged. The change in the local channel depth in the four areas of each channel increases the gas turbulence characteristics in the area, promotes the diffusion of hydrogen into the gas diffusion layer in the membrane electrode, and improves the hydrogen utilization rate.

[0096] When oxygen passes through Figure 3 , Figure 4 When the oxygen flow channels in the cathode monopolar plate are shown, Figure 7 , Figure 8 Taking a single channel as an example, the gas change characteristics in each channel are the same. When oxygen passes through the oxygen channel inlet area and the highest area of ​​the oxygen channel in sequence, the channel depth of the oxygen channel inlet area and the highest area of ​​the oxygen channel increases as a whole, which increases the pressure of the oxygen passing through and reduces the flow rate, thus improving the oxygen flow to the area. Figure 7The diffusion capacity of the gas diffusion layer in the membrane electrode on the middle coordinate plane xoz improves the oxygen utilization rate; when oxygen passes through the descending area of ​​the oxygen flow channel, the depth of each step in the descending area of ​​the oxygen flow channel is smaller than the step flow channel depth in the highest area of ​​the oxygen flow channel, the oxygen pressure is reduced, and the oxygen flow rate is increased; compared with the descending area, when oxygen passes through the oxygen flow channel outlet area, the depth of each step in the oxygen flow channel outlet area is smaller than the flow channel depth of the oxygen flow channel descending area, the oxygen pressure is further increased, and the flow rate is further reduced, which can improve the water vapor discharge capacity of this area and avoid cathode flooding.

[0097] Figure 7 The partial sections of each area of ​​the oxygen flow channel are shown: the depth of each step flow channel in the oxygen flow channel inlet area and the oxygen flow channel outlet area has the characteristic of decreasing from large to large and then increasing, so that the oxygen pressure in each step local area decreases from large to large and then increases, and the oxygen flow rate increases from small to small and then decreases; the depth of each step flow channel in the highest area of ​​the oxygen flow channel and the descending area of ​​the oxygen flow channel has the characteristic of increasing from small to small and then decreasing, so that the oxygen pressure increases from small to small and then decreases, and the oxygen flow rate decreases from large to large and then increases. Figure 8 The oxygen flow channel is shown in each area: in the four areas of the oxygen flow channel, the flow channel depth of each step is different, the bottom surface of each step is a plane, and the flow channel depth of each step body remains unchanged. The change in the local depth of each flow channel micro-area increases the gas turbulence characteristics in the area, promotes the diffusion of oxygen to the gas diffusion layer in the membrane electrode, and improves the oxygen utilization rate.

[0098] Compared with the existing direct current channel, the slope surface structure enhances the gas turbulence ability in each flow channel of the anode monopolar plate and the cathode monopolar plate, and keeps the gas flow resistance at the step connection within a reasonable range, so that impurities deposited on the bottom plate of the flow channel can be discharged in time, avoiding corrosion of the plate caused by impurities in the reaction gas adhering to the inner wall of the flow channel, thereby extending the service life of the plate.

Claims

1. A fuel cell metal bipolar plate with divided flow channels, including an oxygen flow channel provided on a cathode monopolar plate and a hydrogen flow channel provided on an anode monopolar plate, wherein the cathode monopolar plate and the anode monopolar plate are symmetrical in convex and concave directions, characterized in that: Each of the hydrogen flow channels includes a hydrogen flow channel inlet area, a hydrogen flow channel descending area, a hydrogen flow channel lowest area and a hydrogen flow channel outlet area along the gas flow direction, the hydrogen flow channel inlet area includes at least two inlet steps, the hydrogen flow channel descending area includes at least one descending step, the hydrogen flow channel lowest area includes a lowest step, the hydrogen flow channel outlet area includes an outlet step, and each of the hydrogen flow channels includes m steps; each of the oxygen flow channels includes an oxygen flow channel inlet area, an oxygen flow channel highest area, an oxygen flow channel descending area and an oxygen flow channel outlet area along the gas flow direction The oxygen flow channel inlet zone includes an inlet step, the oxygen flow channel highest zone includes a highest step, the oxygen flow channel descending zone includes at least one descending step, the oxygen flow channel outlet zone includes at least two outlet steps, and each of the oxygen flow channels includes m steps; the depth of the hydrogen flow channel step includes four categories: the step flow channel depth of the hydrogen flow channel inlet zone, the step flow channel depth of the hydrogen flow channel descending zone, the step flow channel depth of the hydrogen flow channel lowest zone, and the step flow channel depth of the hydrogen flow channel outlet zone. The step flow channel depth Y1(X,Z) of the hydrogen flow channel inlet zone is determined according to the following model: ， In formula (1), H1 is the depth of the hydrogen flow channel at the coordinate (X, Z) = (0, 0) at the inlet of the hydrogen flow channel; ΔH is the difference in the depth of the flow channel projected onto the Y-axis direction from the slope surface connecting the head and tail of the two adjacent steps of each hydrogen flow channel, ΔH∈[0.05, 0.15] mm; l is the projection length from the starting position to the tail of each step on the X-axis, and the projection length of each step is equal; N1 is an integer, which is the sequential numbering of the steps in the inlet area of ​​the hydrogen flow channel along the air flow direction, N1∈[1, b], b≥2, where 1 refers to the first step number at the inlet area entrance, b is an integer, which refers to the last step number at the outlet of the inlet area, and the independent variable X∈[0, bl]; a is the depth coefficient of each step, a∈[0, 0.02]; K is the slope of the slope surface of the two adjacent steps of each hydrogen flow channel, K>0; The depth of the step flow channel in the descending area of ​​the hydrogen flow channel and the lowest area of ​​the hydrogen flow channel is determined according to the following model: 1) The step flow channel depth Y2 (X, Z) of the hydrogen flow channel descending area is determined according to the following model: ， In formula (2), N2 is an integer, which is the sequential numbering of the steps in the hydrogen flow channel along the gas flow direction, N2∈[b+1,m-2], mb≥3, where b+1 refers to the number of the first step at the entrance of the descending zone, m-2 refers to the number of the last step at the exit of the descending zone, m is an integer, and the independent variable X∈[(b+1)l,(m-2)l]; 2) The step flow channel depth Y3 (X, Z) of the lowest area of ​​the hydrogen flow channel is determined according to the following model: ， In formula (3), N3 is an integer, which is the sequential numbering of the steps in the lowest area of ​​the hydrogen flow channel along the gas flow direction, N3 = m-1, independent variable X∈((m-2)l,(m-1)l]; The step flow channel depth Y4 (X, Z) of the hydrogen flow channel outlet area is determined according to the following model: ， In formula (4), N4 is an integer, which is the sequential numbering of the steps in the hydrogen flow channel outlet area along the gas flow direction, N4=m, and the independent variable X∈((m-1)l,ml]; the depth of the hydrogen flow channel gradually decreases from the hydrogen flow channel inlet area to the hydrogen flow channel descending area to the lowest area of ​​the hydrogen flow channel, and then increases in the hydrogen flow channel outlet area, wherein the flow channel depth is the lowest in the lowest area of ​​the hydrogen flow channel.

2. A fuel cell metal bipolar plate with divided flow channels according to claim 1, characterized in that: The step flow channel depth y1(x,z) of the oxygen flow channel inlet area is determined according to the following model: ， In formula (5), h1 is the depth of the oxygen channel at the coordinate (x, z) = (0, 0) at the inlet of the oxygen channel, and h1 and H1 are equal; the independent variable x∈[0, l], a is the depth coefficient of each step, a∈[0, 0.02].

3. The fuel cell metal bipolar plate regional flow channel according to claim 1, characterized in that: The step flow channel depths of the highest area of ​​the oxygen flow channel and the descending area of ​​the oxygen flow channel are determined according to the following model: 1) The step flow channel depth y2(x,z) of the highest area of ​​the oxygen flow channel is determined according to the following model: ， In formula (6), Δh is the difference in channel depth between the slope surface connecting the two adjacent steps of each oxygen flow channel and projected onto the y-axis direction, and Δh and ΔH are equal; n2 is an integer, which is the sequential numbering of the steps in the highest area of ​​the oxygen flow channel along the airflow direction, n2=2, the independent variable x∈(l,2l], k is the slope of the slope surface of the two adjacent steps of each oxygen flow channel, and k and K are equal; 2) The step flow channel depth y3(x,z) of the oxygen flow channel descending area is determined according to the following model: ， In formula (7), n3 is an integer, which is the sequential numbering of the steps in the oxygen flow channel descending zone along the airflow direction, n3∈[3,c], c≥3, 3 refers to the number of the first step at the entrance of the descending zone, c is an integer, which refers to the number of the last step at the exit of the descending zone, and the independent variable x∈[3l,cl].

4. The fuel cell metal bipolar plate regional flow channel according to claim 1, characterized in that: The step flow channel depth y4(x,z) of the oxygen flow channel outlet area is determined according to the following model: ， In formula (8), n4 is an integer, which is the sequential numbering of the steps in the oxygen flow channel outlet zone along the air flow direction, n4∈[c+1,m], mc≥2, c+1 refers to the number of the first step at the entrance of the oxygen flow channel outlet zone, and the independent variable x∈[(c+1)l,ml]; the depth of the oxygen flow channel gradually increases from the oxygen flow channel inlet zone to the oxygen flow channel highest zone, and after reaching the oxygen flow channel highest zone, it decreases in the oxygen flow channel descending zone and the oxygen flow channel outlet zone, wherein the flow channel depth in the oxygen flow channel highest zone is the largest.

5. The fuel cell metal bipolar plate regional flow channel according to claim 1, characterized in that: Each two adjacent steps on the oxygen flow channel and the hydrogen flow channel are connected at the ends by a slope surface structure; 1) The depth Y(X, Z) of the hydrogen flow channel on the slope surface is determined according to the following model: ， In formulas (9 and 10), N is an integer, which is the serial number of all steps of the hydrogen flow channel along the gas flow direction, N∈[1,m], 1 refers to the number of the first step at the entrance of the hydrogen flow channel, and m is an integer, which refers to the number of the last step at the exit of the hydrogen flow channel. When the step number N∈[1,m-1] is calculated using formula (9), when the step number N=m, it is calculated using formula (10); 2) The oxygen flow channel depth y(x,z) of the slope surface is determined according to the following model: ， In formulas (11, 12, and 13), n is an integer, which means that the oxygen flow channel sequentially numbers the steps along the airflow direction, n∈[1,m], 1 refers to the number of the first step at the entrance of the oxygen flow channel, and m refers to the number of the last step at the exit of the oxygen flow channel. When the step number n=1, formula (11) is used for calculation, when the step number n=2, formula (12) is used for calculation, and when the step number n∈[3,m], formula (13) is used for calculation.

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