A combination fuel cell bipolar plate flow field and bipolar plate and fuel cell

Abstract

The present application relates to a kind of combination fuel cell bipolar plate flow field and bipolar plate and fuel cell, bipolar plate flow field includes flow field air inlet, parallel flow field, serpentine flow field and flow field air outlet;Parallel flow field is equipped with multiple parallel flow channels, multiple parallel flow channels are connected with the beginning of parallel flow field respectively, multiple parallel flow channels converge and narrow to the end of parallel flow field;Serpentine flow field is equipped with serpentine flow channel, the beginning of serpentine flow channel is connected to the end of parallel flow field, the end of serpentine flow channel is connected to flow field air outlet;Serpentine flow channel includes multiple mutually parallel and sequentially head-to-tail connected branch flow channels;In every two adjacent branch flow channels, reaction gas flow direction is opposite, upstream serpentine flow channel half is surrounded outside downstream serpentine flow channel.This application improves the reaction gas distribution uniformity of parallel flow field in the combined flow field of parallel flow field and serpentine flow field, while overcome the low concentration of reaction gas in the latter section of serpentine flow field, effectively reduce the risk of waterlogging.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a bipolar plate flow field and a bipolar plate of a combined fuel cell, as well as a fuel cell. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs), a key form of hydrogen energy utilization, are clean energy cells based on hydrogen oxidation reactions. They boast high power generation efficiency, a simple and compact structure, low noise levels, and environmental friendliness, leading to their widespread application in fuel cell vehicles and power generation equipment. The flow field on the bipolar plates of a PEMFC serves as a channel for the transport of reactants and products, responsible for the supply of reactant gases and the removal of water from the cell. Therefore, the design of the flow field influences the efficiency of reactant gas transport to the gas diffusion layer, the uniformity of reactant gas distribution, and water and thermal management. It can be said that the flow field structure largely determines the performance of the cell. A suitable flow field structure can effectively improve the cell's output power and water and thermal management.

[0003] In proton exchange membrane fuel cells, common flow fields include parallel flow fields, serpentine flow fields, and interdigital flow fields. Interdigital flow fields cause large pressure drops due to the discontinuity of the flow channels, and are prone to impacting and damaging the gas diffusion layer, so they are less commonly used. Parallel flow fields have the advantages of simple structure and low pressure drop, but they have the disadvantages of uneven distribution of reaction gases and poor drainage. Serpentine flow fields are widely used in proton exchange membrane fuel cells due to their advantages such as good drainage. However, serpentine flow fields have long flow channels, large pressure drops, and high power consumption. In addition, the reaction gases mostly undergo chemical reactions in the front section of the flow channel, resulting in insufficient reaction gases in the back section of the flow channel, affecting the performance of the fuel cell.

[0004] In the prior art, combining the parallel flow field and the serpentine flow field can combine the advantages of the two flow fields and improve the shortcomings of a single flow field. The combined flow field of the parallel flow field and the serpentine flow field has improved the drainage of the single parallel flow field and reduced the pressure drop of the single serpentine flow field to a certain extent. However, there is still the disadvantage of uneven distribution of the reaction gas in the parallel flow field part, and the drainage needs to be further improved. In the two combined fuel cell flow fields with publication numbers: CN206697552U and CN213878159U, a certain point-like transition zone is set upstream of the parallel flow field to ensure the distribution of the reaction gas in the parallel flow field part of the combined flow field.

[0005] However, it has the following technical problems:

[0006] The unreasonable point block design in the point-shaped transition zone is likely to produce dead zones and hot spots in the fluid flow channel. At the same time, the point block setting reduces the gas flow rate, and the drainage in the parallel flow field part is difficult to ensure. Summary of the Invention

[0007] In response to the problems existing in the prior art, one of the objectives of the present invention is to provide a bipolar plate flow field for a combined fuel cell, which can improve the uniformity of the reaction gas distribution in the parallel flow field, increase the concentration of the reaction gas in the rear section of the serpentine flow field, and effectively reduce the risk of flooding.

[0008] A second object of the present invention is to provide a bipolar plate for a combined fuel cell.

[0009] A third object of the present invention is to provide a combined fuel cell.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A bipolar plate flow field of a combined fuel cell comprises a flow field air inlet, a parallel flow field, a serpentine flow field and a flow field air outlet sequentially connected along the flow direction of the reaction gas;

[0012] The starting end of the parallel flow field is connected to the flow field air inlet;

[0013] The parallel flow field is provided with a plurality of parallel flow channels, the plurality of parallel flow channels are respectively connected to the starting ends of the parallel flow field, and the plurality of parallel flow channels are narrowed at the end of the parallel flow field after merging;

[0014] The serpentine flow field is provided with a serpentine flow channel, the starting end of the serpentine flow channel is connected to the end of the parallel flow field, and the end of the serpentine flow channel is connected to the air outlet of the flow field;

[0015] The serpentine flow channel includes a plurality of branch flow channels which are parallel to each other and connected end to end in sequence; in every two adjacent branch flow channels, the reaction gas flows in opposite directions, and the upstream serpentine flow channel half surrounds the downstream serpentine flow channel.

[0016] Furthermore, the transverse cross-section of the parallel flow channel is rectangular, U-shaped, triangular, trapezoidal or inverted trapezoidal.

[0017] Furthermore, a plurality of parallel flow fields are provided, and the plurality of parallel flow fields are sequentially connected, and along the flow direction of the reaction gas, the areas of the plurality of parallel flow fields gradually decrease.

[0018] Furthermore, in every two adjacent parallel flow fields, the extending directions of the parallel flow channels are perpendicular to each other.

[0019] Furthermore, three parallel flow fields are provided, and the three parallel flow fields are respectively located outside the serpentine flow field, forming a semi-enclosed structure for the serpentine flow field.

[0020] Furthermore, within the semi-enclosed structure formed by the three parallel flow fields, multiple branch channels of the serpentine flow field shrink inward step by step.

[0021] Furthermore, the serpentine flow channel is a single flow channel, a double flow channel or a multi-flow channel.

[0022] A bipolar plate for a combined fuel cell includes a bipolar plate flow field for the combined fuel cell.

[0023] A combined fuel cell includes a bipolar plate of the combined fuel cell.

[0024] In general, the present invention has the following advantages:

[0025] The reactant gas enters the parallel flow field from the flow field inlet, passes through multiple parallel flow channels arranged in the parallel flow field, and then converges and narrows at the end of the parallel flow field, slowing the decrease in reactant gas concentration and improving distribution uniformity. After the reactant gas enters the serpentine flow field from the parallel flow field, because the serpentine flow field comprises multiple parallel branch channels connected end to end, the reactant gas flows in opposite directions in each two adjacent branch channels, with the upstream branch channel semi-enclosing the downstream branch channel. This increases the concentration difference and pressure of the gas between adjacent branch channels, facilitating gas permeation from the side with higher concentration and pressure to the side with lower concentration and pressure. The reactant gas concentration and pressure are highest at the inlet of the serpentine flow channel, gradually decreasing along the flow direction, and reaching the lowest concentration and pressure at the outlet. The pressure is higher on the outside of the serpentine flow channel and lower on the inside. Under the action of the pressure difference, the reactant gas permeates from the outside to the inside, thereby enhancing the gas's sub-ridge convection, making the distribution of the reactant gas more uniform throughout the serpentine flow field, and reducing the risk of reactant gas short-circuiting in the serpentine flow channel. Without the need to design a point transition zone, the present invention improves the uniformity of reaction gas distribution in the parallel flow field in the combined flow field of the parallel flow field and the serpentine flow field, while overcoming the disadvantage of low reaction gas concentration in the rear section of the serpentine flow field, which is beneficial to the uniform distribution of reaction gas, current density and temperature in the bipolar plate flow field, and promotes the discharge of liquid water in the porous medium. The liquid water saturation of the parallel flow field is low, and water accumulation will not occur, effectively reducing the risk of flooding. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of Example 1 of the present invention.

[0027] Figure 2 Schematic diagram of the reaction gas flow in Example 1 of the present invention.

[0028] Figure 3 Schematic diagram of the combined flow field of ordinary parallel flow field and serpentine flow field.

[0029] Figure 4 This is a comparison chart of the fuel cell performance of Example 1 of the present invention and the combined flow field of the ordinary parallel flow field and the serpentine flow field.

[0030] Figure 5 This is a structural diagram of Example 2 of the present invention.

[0031] Description of reference numerals:

[0032] 101 - flow field air inlet; 102 - flow field air outlet; 103 - parallel flow channel; 104 - ridge; 105 - first parallel flow field; 106 - second parallel flow field; 107 - third parallel flow field; 108 - serpentine flow field. DETAILED DESCRIPTION

[0033] The present invention will be described in further detail below.

[0034] Example 1

[0035] like Figure 1 、 Figure 2 As shown, a bipolar plate flow field of a combined fuel cell includes a flow field inlet 101, a parallel flow field, a serpentine flow field 108 and a flow field outlet 102 connected in sequence along the flow direction of the reaction gas;

[0036] The starting end of the parallel flow field is connected to the flow field air inlet 101;

[0037] The parallel flow field is provided with a plurality of parallel flow channels 103, and the plurality of parallel flow channels 103 are respectively connected to the starting ends of the parallel flow field, and the plurality of parallel flow channels 103 are narrowed at the end of the parallel flow field after merging;

[0038] The serpentine flow field 108 is provided with a serpentine flow channel, the starting end of the serpentine flow channel is connected to the end of the parallel flow field, and the end of the serpentine flow channel is connected to the flow field air outlet 102;

[0039] The serpentine flow channel includes a plurality of branch flow channels which are parallel to each other and connected end to end in sequence; in every two adjacent branch flow channels, the reaction gas flows in opposite directions, and the upstream serpentine flow channel half surrounds the downstream serpentine flow channel.

[0040] Specifically, the bipolar plate flow field has a flow field inlet 101 at the beginning and a flow field outlet 102 at the end. Three parallel flow fields and a serpentine flow field 108 are sequentially arranged between the flow field inlet 101 and the flow field outlet 102. The three parallel flow fields are a first parallel flow field 105, a second parallel flow field 106, and a third parallel flow field 107, which are connected in sequence.

[0041] Each parallel flow field is provided with a plurality of parallel flow channels 103, the cross-section of which is preferably rectangular, and ridges 104 are provided on both sides of the parallel flow channels 103. The planar flow channel areas of the first parallel flow field 105, the second parallel flow field 106, and the third parallel flow field 107 gradually decrease. Preferably, the planar flow channel areas of the three parallel flow fields are in a ratio of approximately 3:2:1, and the sum of the planar flow channel areas of the three parallel flow fields is approximately equal to the planar flow channel area of ​​the serpentine flow field 108.

[0042] The first parallel flow field 105, the second parallel flow field 106, and the third parallel flow field 107 are respectively located on the three sides of the serpentine flow field 108, forming a semi-enclosed structure for the serpentine flow field 108. During operation, the gas outside the bipolar plate enters from the flow field inlet 101, passes through the first parallel flow field 105, the second parallel flow field 106, and the third parallel flow field 107 in sequence, and then flows to the serpentine flow field 108. After each reaction gas enters a parallel flow field, it passes through the multiple parallel flow channels 103 of the parallel flow field, and then merges and narrows at the end of the parallel flow field.

[0043] The serpentine flow channel of the serpentine flow field 108 includes multiple parallel branch channels that are sequentially connected end to end. The multiple branch channels are arranged in a serpentine shape along the inner side of the semi-enclosed structure formed by the first parallel flow field 105, the second parallel flow field 106, and the third parallel flow field 107. After the reaction gas enters the serpentine flow field 108, it flows in sequence along the multiple branch channels, first flowing from the side of the third parallel flow field 107 in the direction of the third parallel flow field 107-the second parallel flow field 106-the first parallel flow field 105. After reaching the side of the first parallel flow field 105, it flows in the opposite direction and flows along the direction of the first parallel flow field 105-the second parallel flow field 106-the third parallel flow field 107. In this way, it continuously contracts from the outside to the inside step by step, and finally flows out from the flow field outlet 102.

[0044] By setting up three parallel flow fields with decreasing flow channel areas, the reaction gas can be redistributed by converging and narrowing after passing through each parallel flow field, which slows down the decrease in reaction gas concentration and improves the uniformity of reaction gas distribution.

[0045] After the reactant gas enters the serpentine flow field 108 from the parallel flow field, the serpentine flow channel of the serpentine flow field 108 includes multiple parallel branch channels connected end to end. In each two adjacent branch channels, the reactant gas flows in opposite directions, and the upstream branch channel semi-encloses the downstream branch channel. The concentration difference and pressure of the gas between adjacent branch channels increase, enhancing forced convection, which is conducive to the infiltration and replenishment of gas from the side with high concentration and pressure to the side with low concentration and pressure. The concentration and pressure of the reactant gas are the highest at the inlet of the serpentine flow channel, gradually decreasing along the flow direction, and the concentration and pressure are the lowest at the outlet. The pressure outside the serpentine flow channel is higher, and the pressure inside is lower. Under the action of the pressure difference, the reactant gas permeates from the outside to the inside, thereby enhancing the convection of the gas under the ridge 104, making the distribution of the reactant gas more uniform throughout the serpentine flow field 108, and reducing the risk of reactant gas short-circuiting in the serpentine flow channel.

[0046] Without requiring a point-like transition zone, the present invention improves the uniformity of reactant gas distribution in the parallel flow field within the combined flow field of the parallel and serpentine flow fields 108. This also overcomes the disadvantage of low reactant gas concentration in the rear section of the serpentine flow field 108, facilitating a uniform distribution of reactant gas, current density, and temperature within the bipolar plate flow field, effectively reducing the risk of flooding. Furthermore, because the first, second, and third parallel flow fields 105, 106, and 107 semi-enclose the serpentine flow field 108, liquid water in the parallel flow channels 103 flows toward the downstream channels under the influence of a pressure differential. The pressure differential between adjacent branch channels within the serpentine flow field 108 facilitates the drainage of liquid water from beneath the ridges 104, thereby enhancing the flow field's drainage capacity.

[0047] A bipolar plate for a combined fuel cell includes the bipolar plate flow field of the combined fuel cell.

[0048] A combined fuel cell comprises the bipolar plate of the combined fuel cell mentioned above.

[0049] like Figure 3 , which is a schematic diagram of a combined flow field of a common parallel flow field and a serpentine flow field 108 .

[0050] like Figure 4 , which is a fuel cell performance comparison diagram of Example 1 of the present invention and the combined flow field of the ordinary parallel flow field and the serpentine flow field 108 .

[0051] Numerical simulations were performed under the same conditions. When the current density was greater than 1.0 A / cm 2 The battery performance of Example 1 is significantly higher than that of the battery with the conventional combined flow field. This shows that compared with the conventional combined flow field, the bipolar plate flow field of the combined fuel cell of the present invention can effectively improve the battery performance.

[0052] Example 2

[0053] Figure 5 Schematic diagram of the structure of Example 2 of the present invention. Compared with Example 1, the main difference is that the serpentine flow channel of Example 2 is a double flow channel.

[0054] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A bipolar plate flow field of a combined fuel cell, characterized in that: It includes a flow field inlet, a parallel flow field, a serpentine flow field and a flow field outlet that are sequentially connected along the flow direction of the reaction gas; The starting end of the parallel flow field is connected to the flow field air inlet; The parallel flow field is provided with a plurality of parallel flow channels, the plurality of parallel flow channels are respectively connected to the starting ends of the parallel flow field, and the plurality of parallel flow channels converge and narrow at the end of the parallel flow field; The serpentine flow field is provided with a serpentine flow channel, the starting end of the serpentine flow channel is connected to the end of the parallel flow field, and the end of the serpentine flow channel is connected to the air outlet of the flow field; The serpentine flow channel includes a plurality of parallel branch channels connected end to end in sequence; in every two adjacent branch channels, the reaction gas flows in opposite directions, and the upstream branch channel half surrounds the downstream branch channel; There are three parallel flow fields, which are connected in sequence. Along the flow direction of the reaction gas, the area of ​​the three parallel flow fields gradually decreases. The three parallel flow fields are respectively located on the three sides of the serpentine flow field, forming a semi-enclosed structure for the serpentine flow field. Within the semi-enclosed structure formed by the three parallel flow fields, multiple branch channels of the serpentine flow field shrink inward step by step.

2. The bipolar plate flow field of a combined fuel cell according to claim 1, characterized in that: The transverse cross section of the parallel flow channel is rectangular, U-shaped, triangular, trapezoidal or inverted trapezoidal.

3. The bipolar plate flow field of a combined fuel cell according to claim 1, characterized in that: In every two adjacent parallel flow fields, the extending directions of the parallel flow channels are perpendicular to each other.

4. The bipolar plate flow field of a combined fuel cell according to claim 1, characterized in that: The serpentine flow channel is a single flow channel, a double flow channel or a multi-flow channel.

5. A bipolar plate for a combined fuel cell, characterized in that: A bipolar plate flow field comprising a combined fuel cell according to any one of claims 1 to 4.

6. A combined fuel cell, characterized in that: A bipolar plate for a combined fuel cell comprising the method of claim 5.

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