A bipolar plate flow channel structure for a proton exchange membrane fuel cell based on a bionic structure

Abstract

The present invention discloses a proton exchange membrane fuel cell bipolar plate flow channel structure based on a bionic structure, comprising a cathode flow field plate body and a plurality of gas flow channels arranged in the cathode flow field plate body, each of the gas flow channels being provided with an air inlet and an air outlet at both ends; a plurality of fin-type guide blocks are provided in each of the gas flow channels, and a flow channel side-contracted guide block is provided at the fin-type guide block; when the fin-type guide block and the side-contracted guide block are used in combination, the flow field in the flow channel can generate periodic forced convection not only in a direction perpendicular to the flow channel, but also in a direction parallel to the flow channel; while maintaining high gas permeability, the flow field is accelerated by changing the vertical cross-sectional area of ​​the flow channel, thereby actively enhancing the convection effect of the gas to the GDL layer.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a bipolar plate flow channel structure of a proton exchange membrane fuel cell based on a bionic structure. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is an electrochemical device that converts chemical energy into electrical energy. It has the advantages of high power density, zero emissions, fast response, cold start, and low operating temperature. It has a wide range of applications in future automotive, military, power plants and other fields.

[0003] Proton exchange membrane fuel cells include several key components:

[0004] 1) Catalyst layer: Usually made of platinum (Pt) or platinum alloy, it is used to accelerate the redox reaction of hydrogen and oxygen.

[0005] 2) Gas-diffusion layer (GDL): Usually made of carbon fiber paper or cloth, it is used to transport the reaction gases to the catalyst layer and help remove water and heat generated by the reaction.

[0006] 3) Proton-exchange membrane (PEM): A special polymer membrane that allows protons (H+) to pass through but does not allow electrons to pass through, thereby forming an electric potential difference on both sides of the membrane.

[0007] 4) Bipolar Plate: This separates the different battery cells, provides gas and coolant channels, and collects current. Heat and mass transfer in proton exchange membrane fuel cells still present numerous challenges. During operation, significant heat is generated. Excessive internal temperatures or uneven temperature distribution can affect membrane performance, leading to unstable proton transport and reduced fuel cell efficiency and durability.

[0008] The bipolar plate flow field is a major factor influencing heat and mass transfer in fuel cells. Optimizing the flow field structure is generally considered an effective method for improving fuel cell performance. Optimizing the flow field structure primarily involves two approaches: optimizing the flow channel geometry and adding guide blocks. Common flow channel shapes include parallel channels and serpentine channels, which are simple but offer poor heat transfer. Common guide blocks include hemispherical, semi-cylindrical, and hexahedral shapes, which have some effect on enhancing convection, but there is still considerable room for improvement. Summary of the Invention

[0009] In order to overcome the problems of low heat transfer efficiency, low reaction gas transfer efficiency, poor drainage effect and water management of proton exchange membrane fuel cells, the present invention proposes a proton exchange membrane fuel cell bipolar plate flow channel structure based on a bionic structure, which overcomes the above problems to a certain extent.

[0010] The technical solution adopted by the present invention to solve its technical problem is:

[0011] A proton exchange membrane fuel cell bipolar plate flow channel structure based on a bionic structure includes a cathode flow field plate body and multiple gas flow channels arranged in the cathode flow field plate body, each of the gas flow channels is provided with an air inlet and an air outlet at both ends; each of the gas flow channels is provided with multiple fin-shaped guide blocks, and flow channel side contraction guide blocks are provided at the fin-shaped guide blocks.

[0012] Furthermore, the plurality of gas flow channels are arranged in parallel, and the structure of each gas flow channel is the same.

[0013] Based on the circuit structure of the Tesla valve, an improved check valve structure with no moving parts was designed. This structure is arranged periodically to form a gas flow channel.

[0014] Furthermore, the gas flow channel includes a plurality of straight flow channels and a plurality of arc flow channels, the straight flow channels and the flow channel center line form an angle of 15° to 45°, and the center angle of the arc flow channel is 150° to 180°.

[0015] Furthermore, the direct current channel includes an upper direct current channel and a lower direct current channel, and the arc flow channel includes an upper curved flow channel and a lower curved flow channel; the upper direct current channel is connected to the left and right ends of the upper curved flow channel respectively to form an upper loop, and the lower direct current channel is connected to the left and right ends of the lower curved flow channel respectively to form a lower loop.

[0016] Furthermore, the upper curved flow channel includes a short upper straight flow channel and an upper circular arc flow channel, and the right end of the short upper straight flow channel is connected to the left end of the upper circular arc flow channel to form an upper curved flow channel; the lower curved flow channel includes a short lower straight flow channel and a lower circular arc flow channel, and the right end of the short lower straight flow channel is connected to the left end of the lower circular arc flow channel to form a lower curved flow channel.

[0017] Furthermore, the upper circuit and the lower circuit are arranged alternately, and the inlet of each circuit forms a diverging intersection in the forward flow direction of the gas, and the outlet forms a merging intersection in the forward flow direction of the gas, thereby realizing gas acceleration in the forward flow direction of the gas and deceleration in the reverse flow direction of the gas.

[0018] Furthermore, the fin-shaped guide block is based on the bionic structure of a shark fin design, having a head tip and a top tip, with a fin peak formed between the two tips; each fin-shaped guide block is composed of two tetrahedrons, of which the two surfaces facing the air inlet constitute the windward surface, and the two surfaces facing away from the air inlet constitute the leeward surface.

[0019] Furthermore, the side-reduced guide block is composed of two triangular pyramids, which are arranged on both sides of the fin-type guide block respectively; and the throat at the narrowest point of the side-reduced guide block and the bottom end point of the leeward side of the fin-type guide block are on the same plane. When the gas flows to the bottom end point of the leeward side, it is also located at the throat, which has a better acceleration effect compared with other relative positions. Subsequently, the gas flows to both sides and upward along the expansion section, which has a better convection effect compared with the vortex formed at other relative positions.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) When the gas flows through the parallel channels in the forward direction, it will be divided into two paths at the intersection of each loop, and then the two paths will converge at the next intersection and accelerate; each set of loops will be accelerated twice, and each parallel channel will be accelerated 8 times; when the gas flows through the parallel channels in the reverse direction, the gas will be divided into two paths at the intersection of the first loop, and then the two paths will converge at the second intersection. Since the two paths of gas flow in opposite directions, resistance is formed, which reduces the gas flow speed and prevents gas backflow;

[0022] 2) When fin-type guide blocks and side-reduction guide blocks are used in combination, the flow field in the flow channel can generate periodic forced convection not only in the direction perpendicular to the flow channel, but also in the direction parallel to the flow channel. While maintaining high gas permeability, the flow field is accelerated by changing the vertical cross-sectional area of ​​the flow channel, actively enhancing the convection effect of gas to the GDL layer.

[0023] 3) The flow channel is divided into two layers, upper and lower. When the reaction gas contacts the fin-shaped guide block, the upper layer of gas acquires a downward velocity component. In addition, due to the angle effect of the windward side, the airflow diffuses to both sides of the flow channel. After the airflow passes through the top tip of the fin-shaped guide block, the lower layer of reaction gas acquires an upward velocity component due to the low pressure on the leeward side and contracts toward the center of the flow channel. After passing through a complete fin-shaped guide block, the flow channel achieves a regular exchange of upper and lower layers of gas, and effectively circulates the gas layers on the flow channel wall and center. Placing a side-shrinking guide block on the side of the fin-shaped guide block can significantly enhance the regular forced convection in the vertical direction of the flow channel.

[0024] 4) Each set of loops is not symmetrical along the center line of the flow channel, forming an asymmetric design for each parallel flow channel, achieving a smaller spacing between parallel flow channels, increasing the contact area between the cathode plate and the gas diffusion layer, and significantly improving the mass transfer performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0026] Figure 1 A schematic diagram of the flow channel structure of a bipolar plate of a proton exchange membrane fuel cell based on a biomimetic structure provided by the present invention;

[0027] Figure 2 A schematic diagram of a parallel flow channel in a bipolar plate flow channel structure of a proton exchange membrane fuel cell based on a bionic structure;

[0028] Figure 3 Schematic diagram of the improved non-moving parts check valve structure in the bipolar plate flow channel structure of a proton exchange membrane fuel cell based on a biomimetic structure;

[0029] Figure 4 Schematic diagram of the two-dimensional structure of the fin-shaped guide block and the side-shrinkage guide block based on the shark fin bionic structure in the flow channel structure of the bipolar plate of the proton exchange membrane fuel cell based on the bionic structure;

[0030] Figure 5 Schematic diagram of the three-dimensional structure of the fin-shaped guide block and the side-shrinkage guide block based on the shark fin bionic structure;

[0031] Figure 6 The simulated forward streamline diagram of the positions of the fin-type guide blocks and the side-contracted guide blocks in the flow channel;

[0032] Figure 7 The simulated lateral streamline diagram of the positions of the fin-type guide block and the side-contracted guide block in the flow channel;

[0033] Figure 8 The simulated oblique streamline diagram of the position of the fin-type guide block and the side-contracted guide block in the flow channel;

[0034] Figure 9 The simulated velocity vector diagram of the position of the fin-type guide block and the side-contracted guide block in the flow channel;

[0035] In the figure: 1. cathode flow field plate body; 2. air inlet; 3. air outlet; 4. multiple gas flow channels; 5. fin-type guide block; 6. side-contracted guide block; 7. upper curved flow channel; 8. lower straight flow channel; 9. upper straight flow channel; 10. lower curved flow channel; 11. flow channel centerline; 12. short upper straight flow channel; 13. upper arc flow channel; 14. short lower straight flow channel; 15. lower arc flow channel; 16. head tip; 17. top tip; 18. fin peak; 19. windward side; 20. leeward side; 21. throat; 22. contraction section; 23. expansion section; 24. bottom endpoint of leeward side. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail with reference to the following specific embodiments. The present invention is provided with accompanying drawings, which form part of the disclosure of the present invention and are mainly used to illustrate the embodiments and to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. Reference is made to these contents. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] The present invention provides a bipolar plate flow channel structure of a proton exchange membrane fuel cell based on a bionic structure.

[0038] like Figure 1-Figure 5 As shown, it includes a cathode flow field plate body 1, an air inlet 2, an air outlet 3 and multiple gas flow channels 4; multiple fin-shaped guide blocks 5 are arranged in the flow channels, and flow channel side contraction guide blocks 6 are arranged at the fin-shaped guide blocks.

[0039] The multiple gas flow channels 4 adopt a multi-row parallel arrangement structure, with a total of 7 parallel flow channels, each of which is identical; based on the circuit structure of the Tesla valve, an improved check valve structure with no moving parts is designed. This structure is arranged periodically to form a gas flow channel, each flow channel consists of 4 groups of check valves with no moving parts, and each group of check valves with no moving parts consists of two upper and lower circuits; each parallel flow channel has 4 upper circuits and 4 lower circuits.

[0040] Each parallel flow channel comprises an upper curved flow channel 7, a lower straight flow channel 8, an upper straight flow channel 9 and a lower curved flow channel 10, and the straight flow channel and the flow channel center line 11 form an angle of 30 degrees.

[0041] The upper curved flow channel is composed of a short upper straight flow channel 12 and an upper arc flow channel 13 , and the right end of the straight flow channel is connected to the left end of the arc flow channel to form the upper curved flow channel 7 .

[0042] The lower curved flow channel is composed of a short lower straight flow channel 14 and a lower arc flow channel 15 , and the right end of the straight flow channel is connected to the left end of the arc flow channel to form the lower curved flow channel 10 .

[0043] The short upper spur channel 12 and the short lower spur channel 14 form an angle of 15° to 45° with the channel centerline 11; the central angle of the arc channel is 180°.

[0044] The short upper direct current channel 12 is tangent to the upper arc flow channel 13, and the short lower direct current channel 14 is tangent to the lower arc flow channel 15; the lower direct current channel 8 and the short lower direct current channel 14 are collinear, and the upper direct current channel 9 is collinear with the short upper direct current channel of the next group of loops.

[0045] The upper curved flow channel 7 and the lower straight flow channel 8 are connected at their left and right ends to form an upper loop; the upper straight flow channel 9 and the lower arc flow channel 15 are connected at their left and right ends to form a lower loop.

[0046] The right intersection of the upper circuit is connected to the left intersection of the lower circuit to form a group of circuits. The right intersection of each group of circuits is connected to the left intersection of the next group of circuits. Each group of circuits is identical and periodically distributed to form a parallel flow channel.

[0047] In each group of circuits, one fin-type guide block 5 is arranged in the short upper direct current channel 12, two are arranged in the lower direct current channel 8, two are arranged in the upper direct current channel 9, one is arranged in the short lower direct current channel 14, and none is arranged in the upper arc flow channel 13 and the lower arc flow channel 15; a total of three are arranged in the upper circuit, a total of three are arranged in the lower circuit, a total of six are arranged in each group of circuits, and an additional one is arranged near the air inlet and near the air outlet. A total of 26 fin-type guide blocks 5 are arranged in each flow channel.

[0048] The structure of the fin-type guide block 5 is a bionic structure based on the design of shark fins. Each fin-type guide block 5 is composed of two tetrahedrons. Among the four faces of one tetrahedron, one face coincides with a face of the other tetrahedron, and an adjacent face is coplanar with a face of the other tetrahedron. The coplanar face coincides with the top of the above-mentioned flow channel.

[0049] The fin-shaped guide block 5 has a head tip 16 and a top tip 17 , a fin peak 18 is formed between the two tips, the two surfaces facing the air inlet constitute the windward surface 19 , and the two surfaces facing away from the air inlet constitute the leeward surface 20 .

[0050] In the short upper direct current channel 12, the lower direct current channel 8, the upper direct current channel 9, and the short lower direct current channel 14, a side-reduced guide block 6 based on the Laval nozzle design is arranged in conjunction with the fin-type guide block 5. The side-reduced guide block consists of two triangular pyramids, which are arranged on both sides of the fin-type guide block 5.

[0051] The two triangular pyramids each have a surface that coincides with the wall of the gas flow channel and an edge facing the fin-shaped guide block 5 , forming the narrowest throat 21 , which is on the same plane as the leeward bottom endpoint 24 of the fin-shaped guide block 5 .

[0052] Working principle:

[0053] When gas flows forward through parallel channels, it is divided into two flow paths at the starting intersection of each loop. The gas in these two paths then reunite at the next intersection. At this time, because the angle between the flow directions of the gas in the two paths is less than 90 degrees, the gas flow rate is increased, achieving an acceleration effect. This acceleration process occurs twice in each loop, so the gas in each set of loops will experience two accelerations. Since there are eight loops in each parallel channel, the gas in each parallel channel will experience a total of eight acceleration processes.

[0054] When gas flows through parallel channels in the reverse direction, it is divided into two flow paths at the starting intersection of each loop. The gas from these two paths then reunite at the next intersection, which is the same as flowing through parallel channels in the forward direction. However, because the angle between the two gas flows is greater than 90° when they merge, an interaction force is generated between them, reducing the gas flow rate and affecting its flow efficiency, thus preventing gas backflow.

[0055] The tip 16 of the fin-type guide block head faces the direction of the air inlet. When the gas flows through the tip 16 of the head, it flows downward along the fin peak 18 and is guided downward to both sides of the flow channel by the windward surface 19 of the fin-type guide block; due to the formation of a low-pressure area on the leeward side 20, the airflow leaves the surface of the guide block after bypassing the fin peak and converges toward the center line of the top of the flow channel to form a vortex, so that the gas generates periodic forced convection perpendicular to the direction of the flow channel around each fin-type guide block 5; resulting in a more uniform flow field distribution, and without hindering the permeability of the gas in the flow channel, it enhances the circulation of the gas in the GDL layer, efficiently removes the water produced by the proton exchange membrane fuel cell discharged from the gas diffusion layer, and sends hydrogen into the gas diffusion layer, effectively improving the reaction efficiency.

[0056] When the gas enters the side-retracted guide block 6, it first passes through a contraction section 22. The cross-sectional area of ​​this part gradually decreases, and the fin peaks 18 of the fin-type guide block 5 will cause the gas to flow to both sides, forming a cooperation, forcing the fluid to accelerate, and generate forced convection in the direction parallel to the flow channel without affecting the flow field perpendicular to the flow channel direction; according to the continuity equation of fluid dynamics, when the cross-sectional area of ​​the fluid decreases, its speed will increase; after the contraction section 22 is the throat 21, which is the part with the smallest cross-sectional area of ​​the flow channel; after passing through the throat 21, the cross-sectional area of ​​the flow channel begins to increase, forming an expansion section 23, which strengthens the forced convection effect parallel to the flow channel direction, and cooperates with the tail of the fin-type guide block 5 to make the fluid continue to accelerate in the expansion section. This is because the expansion of the fluid causes the pressure to decrease, and the pressure energy of the fluid is converted into kinetic energy, thereby increasing the speed.

[0057] In a specific embodiment, the effectiveness of the flow channel structure of the bipolar plate of a proton exchange membrane fuel cell based on a biomimetic structure is verified, and the specific contents include:

[0058] The bipolar plate flow channel is three-dimensionally modeled, and combined with CFD simulation, the positions of the fin-type guide blocks and side-shrinkage guide blocks in the flow channel are simulated and calculated based on the finite volume method.

[0059] like Figure 6 As shown, when the fluid passes through the fin-type guide block and the side-retracted guide block, part of the fluid flows along the fin peak 18 of the fin-type guide block, passes through the top tip 17, and then flows downward along the leeward side 20; the other part of the fluid flows to both sides along the windward side 19 of the fin-type guide block, is blocked by the throat 21 of the side-retracted guide block, and then flows upward; the two parts of the fluid change their upper and lower positions to form convection.

[0060] like Figure 7 and Figure 8 As shown, a part of the fluid flows downward along the leeward side 20 and then flows to both sides; the other part of the fluid is blocked by the throat 21 and flows upward, and then flows from both sides to the middle; the two parts of the fluid move in the same direction along the circumference to form a vortex, which enhances the convection effect, as shown in FIG. Figure 9 shown.

[0061] The above embodiment is only a specific implementation method for realizing the technical solution of the present invention, and the protection scope of the present invention is not limited to this embodiment. Any modification, replacement and other implementation methods that can be conceived by those skilled in the art based on conventional technical means within the technical scope disclosed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A bipolar plate flow channel structure for a proton exchange membrane fuel cell based on a biomimetic structure, characterized in that: The invention comprises a cathode flow field plate body and a plurality of gas flow channels arranged in the cathode flow field plate body, wherein each gas flow channel is provided with an air inlet and an air outlet at both ends thereof; a plurality of fin-shaped guide blocks are provided in each gas flow channel, and a flow channel side-contracting guide block is provided at the fin-shaped guide block; the side-contracting guide block is composed of two triangular pyramids, which are respectively arranged on both sides of the fin-shaped guide block; and the throat of the narrowest part of the side-contracting guide block and the bottom end point of the leeward side of the fin-shaped guide block are on the same plane; The fin-shaped guide block has a head tip and a top tip, and a fin peak is formed between the two tips; each fin-shaped guide block is composed of two tetrahedrons, wherein the two surfaces facing the air inlet constitute the windward surface, and the two surfaces facing away from the air inlet constitute the leeward surface; The fin-type guide block structure is a bionic structure based on the shark fin design. Each fin-type guide block is composed of two tetrahedrons. Among the four faces of one tetrahedron, one face coincides with a face of the other tetrahedron, and an adjacent face is coplanar with a face of the other tetrahedron. The coplanar face coincides with the top of the above-mentioned flow channel.

2. The proton exchange membrane fuel cell bipolar plate flow channel structure based on a biomimetic structure according to claim 1, characterized in that: The multiple gas flow channels are arranged in parallel, and each gas flow channel has the same structure.

3. The proton exchange membrane fuel cell bipolar plate flow channel structure based on a biomimetic structure according to claim 1, characterized in that: The gas flow channel includes a plurality of straight flow channels and a plurality of arc flow channels. The straight flow channel and the center line of the flow channel form an angle of 15-45 degrees, and the center angle of the arc flow channel is 150-180 degrees.

4. The proton exchange membrane fuel cell bipolar plate flow channel structure based on a biomimetic structure according to claim 3, characterized in that: The direct current channel includes an upper direct current channel and a lower direct current channel, and the arc flow channel includes an upper curved flow channel and a lower curved flow channel; the upper direct current channel is connected to the left and right ends of the upper curved flow channel respectively to form an upper loop, and the lower direct current channel is connected to the left and right ends of the lower curved flow channel respectively to form a lower loop.

5. The proton exchange membrane fuel cell bipolar plate flow channel structure based on a biomimetic structure according to claim 4, characterized in that: The upper curved flow channel includes a short upper straight flow channel and an upper circular arc flow channel, and the right end of the short upper straight flow channel is connected to the left end of the upper circular arc flow channel to form an upper curved flow channel; the lower curved flow channel includes a short lower straight flow channel and a lower circular arc flow channel, and the right end of the short lower straight flow channel is connected to the left end of the lower circular arc flow channel to form a lower curved flow channel.

6. The proton exchange membrane fuel cell bipolar plate flow channel structure based on a biomimetic structure according to claim 4, characterized in that: The upper circuit and the lower circuit are arranged alternately, and the inlet of each circuit forms a diverging intersection in the forward flow direction of the gas, and the outlet forms a merging intersection in the forward flow direction of the gas, thereby realizing gas acceleration in the forward flow direction of the gas and deceleration in the reverse flow direction of the gas.

Images