Fuel cell bipolar plate runner design method and fuel cell bipolar plate

Abstract

The invention relates to a design method of a fuel cell bipolar plate runner and a fuel cell bipolar plate. The method comprises the following steps: acquiring design parameters of a fuel cell; determining fuel cell bipolar plate flow field active region parameters based on the design parameters; preset flow channel parameters are generated based on the flow field active area parameters; determining flow channel fluid pressure drop and flow resistance and flow channel substance concentration based on preset flow channel parameters; based on the flow channel fluid pressure drop and flow resistance and the flow channel substance concentration, preset flow channel parameters are adjusted, and the flow channel parameters are obtained; a flow channel with flow channel parameters is arranged in the flow field active area. According to the design method of the fuel cell bipolar plate flow channel and the fuel cell bipolar plate, the flow channel is designed from the uniformity of the fluid and the substance on the basis of the section shape of the flow channel and the substance concentration distribution during electrochemical reaction, so that the requirement of good mass transfer is met by designing the reasonable flow channel; and the current density distribution consistency of the whole plate of the fuel cell is improved.

Description

Technical Field

[0001] The present application relates to the technical field of proton exchange membrane fuel cells, and in particular to a fuel cell bipolar plate flow channel design method and a fuel cell bipolar plate. Background Art

[0002] As a highly efficient, clean, zero-emission power source, fuel cells have become one of the technical routes for reducing automobile emissions. The core of fuel cell stack research is mostly focused on the design of the flow channel of the bipolar plate, which has become one of the core structural components of the stack.

[0003] The performance of fuel cells is highly correlated with the design of the bipolar plate flow channel. It is necessary to consider the material distribution of the entire plate (hydrogen, air and coolant), the consistent current distribution, the reasonable fluid pressure drop loss, and the ohmic polarization loss caused by the electrochemical reaction. All these characteristics need to be achieved through the bipolar plate flow channel design. The structure of the fuel cell flow channel includes flow channels and ridges, which respectively support and transfer water vapor and export electrons.

[0004] In traditional technology, most flow channel design considerations are flow resistance, flow distribution uniformity, and processing capabilities, and there is a lack of methods to improve the consistency of current density distribution across the entire fuel cell plate. Summary of the invention

[0005] Based on this, it is necessary to provide a fuel cell bipolar plate flow channel design method and a fuel cell bipolar plate that can improve the current density distribution consistency of the entire fuel cell plate in response to the above technical problems.

[0006] In a first aspect, the present application provides a method for designing a flow channel of a fuel cell bipolar plate, the method comprising: obtaining fuel cell design parameters; determining flow field active area parameters of the fuel cell bipolar plate based on the design parameters; generating preset flow channel parameters based on the flow field active area parameters; determining flow channel fluid pressure drop, flow resistance and flow channel material concentration based on the preset flow channel parameters; adjusting the preset flow channel parameters based on the flow channel fluid pressure drop, flow resistance and flow channel material concentration to obtain the flow channel parameters; and setting a flow channel with the flow channel parameters in the flow field active area.

[0007] In one embodiment, the preset flow channel parameters include a preset flow channel number, a preset flow channel cross-sectional parameters and a preset flow channel length, and the flow channel fluid pressure drop resistance is determined based on the preset flow channel parameters, including: determining the fuel cell flow rate based on the current density, flow field active area, stoichiometric coefficient, gas constant, temperature, Faraday constant, oxygen content, inlet pressure, inlet relative humidity and inlet protection pressure under rated operating conditions; determining the flow channel flow rate based on the fuel cell flow rate and the preset flow channel number; determining the flow channel fluid pressure drop resistance based on the flow channel flow rate, friction coefficient, fluid density, preset flow channel cross-sectional parameters and preset flow channel length.

[0008] In one embodiment, the flow resistance of the fluid pressure drop in the flow channel is determined along the length of the flow channel.

[0009] In one embodiment, determining the flow channel substance concentration based on preset flow channel parameters includes: determining the flow channel substance concentration based on the flow channel initial substance concentration, a metering coefficient, a flow channel length increment, and a preset flow channel length.

[0010] In one of the embodiments, the concentration of the substance in the flow channel is determined along the direction of the substance flowing in the flow channel.

[0011] In the second aspect, the present application also provides a fuel cell bipolar plate, comprising: a cathode plate and an anode plate, each of the cathode plate and the anode plate comprising: an inlet and outlet area for the reaction material and the coolant to enter and exit; a distribution area, comprising an entry distribution area and an outlet distribution area; a flow field active area, comprising a flow channel, the flow channel comprising a reaction material flow channel and a cooling flow channel; wherein the flow channel is designed using the method of any embodiment of the first aspect.

[0012] In one embodiment, the flow channel is a meandering flow channel, and the included angle of the meandering flow channel is greater than 120 degrees and less than 150 degrees.

[0013] In one of the embodiments, the flow channels are repeatedly arranged along a second direction in the flow field active region; the second direction is a direction perpendicular to the flow of the fluid in the flow field active region.

[0014] In one embodiment, the flow channel includes a flow channel portion and a ridge portion, the flow channel portion is used for the flow of reactants, and the ridge portion is used to separate the reactants; the flow channel widths of the cathode plate and the anode plate are the same, the width of the flow channel portion of the cathode plate is the same as the width of the ridge portion of the anode plate, and the width of the ridge portion of the cathode plate is the same as the width of the flow channel portion of the anode plate.

[0015] In one embodiment, the flow channel portion and the ridge portion include a fillet portion at the bottom of the flow channel, a fillet portion at the top of the flow channel and a connecting portion, the radii of the fillet portion at the bottom of the flow channel and the fillet portion at the top of the flow channel are the same, and the angle between the connecting portion and the normal line of the cathode plate or anode plate plane is greater than 15 degrees and less than 25 degrees.

[0016] The above-mentioned fuel cell bipolar plate flow channel design method and fuel cell bipolar plate are designed based on the cross-sectional shape of the flow channel and the material concentration distribution during the electrochemical reaction, and the flow channel is designed from the uniformity of both fluid and material aspects. By designing a reasonable flow channel, the requirements for good mass transfer are met and the current density distribution consistency of the entire fuel cell plate is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] FIG1 is a schematic flow chart of a method for designing a flow channel of a bipolar plate of a fuel cell in one embodiment;

[0019] FIG2 is a schematic flow chart of a method for designing a flow channel of a bipolar plate of a fuel cell in another embodiment;

[0020] FIG3 is a schematic diagram of the change of oxygen concentration in a flow channel along the flow direction of the flow channel in one embodiment;

[0021] FIG4 is a schematic diagram of the structure of one of the bipolar plates of a fuel cell in one embodiment;

[0022] FIG5 is a schematic diagram of a flow channel structure of a bipolar plate of a fuel cell in one embodiment;

[0023] Figure 6 A schematic diagram of the cross-sectional shape and size of a flow channel of a bipolar plate of a fuel cell in one embodiment;

[0024] Figure 7 Schematic diagram of the flow channel structure of a bipolar plate of a fuel cell in yet another embodiment. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0027] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0028] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0031] In order to obtain high-quality fuel cell performance, the flow channels of the fuel cell bipolar plates need to be designed. However, in traditional technologies, most flow channel designs consider flow resistance, flow distribution uniformity, and processing capabilities. In the process of flow channel design, the cross-sectional shape of the flow channel is usually ignored, and the flow channel form used is a straight flow channel or a serpentine flow channel. There is little consideration of the geometry and performance of the flow channel itself, so there is a lack of methods to improve the consistency of current density distribution of the entire fuel cell plate.

[0032] In order to improve the current density distribution consistency of the entire fuel cell plate, the present application provides a design method for a fuel cell bipolar plate flow channel.

[0033] In an exemplary embodiment, as shown in FIG1 , a method for designing a flow channel of a bipolar plate of a fuel cell is provided. This embodiment is illustrated by applying the method to a terminal. It is understandable that the method can also be applied to a server, and can also be applied to a system including a terminal and a server, and is implemented through the interaction between the terminal and the server. In this embodiment, the method includes steps 102 to 112. Among them:

[0034] Step 102, obtaining fuel cell design parameters.

[0035] Specifically, determine the fuel cell characteristic parameter targets, power, operating conditions, rated / peak operating conditions, number of cells and other parameters to facilitate starting the design calculations.

[0036] More specifically, the power W of the fuel cell stack is determined stack ; Rated working condition I e A / cm²@V, where I e is the current density under rated conditions, V e is the rated operating voltage; peak operating voltage I peak A / cm²@V peak , I peak is the peak operating current density, V peak is the peak operating voltage; the target number of batteries is N cell . Operating conditions under operating conditions, pressure drop ΔP; inlet pressure P in ; Outlet pressure P out ; Inlet temperature T in ; Relative humidity RH at the inlet; Saturation pressure P at a given inlet temperature sat .

[0037] Step 104 , determining the flow field active area parameters of the fuel cell bipolar plate based on the design parameters.

[0038] Step 106: Generate preset flow channel parameters based on the flow field active area parameters.

[0039] Exemplarily, the form of the flow channel in the fuel cell bipolar plate and the basic structural parameters and designed operating parameters of the bipolar plate are clarified; the cross-sectional shape of the flow channel of the fuel cell bipolar plate is designed to clarify the width, depth, and specific shape of the flow channel. Exemplarily, the specific shape of the flow channel includes but is not limited to a trapezoid, a triangle, or a semicircle.

[0040] Specifically, after determining the main parameters of the bipolar plate based on the design parameters, the flow field active area parameters are clarified, including the area A of the flow channel active area. ac, the length of the active area of ​​the flow field L ac , the width W of the flow field active area ac ; The number of flow channels is estimated based on the area of ​​the flow field active area and the length and width of the flow field active area. At this time, it is necessary to preset the flow channel parameters, including preset flow channel cross-sectional parameters, including preset flow channel flow channel width W ch , preset flow channel ridge width W rib The sum of the width of the channel and the ridge is the period of the channel. The active area of ​​the flow field is usually the periodic repetition of a single channel.

[0041] Step 108 : determining the flow channel fluid pressure drop resistance and flow channel substance concentration based on preset flow channel parameters.

[0042] Step 110, adjusting the preset flow channel parameters based on the flow channel fluid pressure drop flow resistance and the flow channel material concentration to obtain the flow channel parameters.

[0043] Step 112, setting a flow channel with flow channel parameters in the flow field active area.

[0044] The above-mentioned fuel cell bipolar plate flow channel design method is based on the cross-sectional shape of the flow channel and the material concentration distribution during the electrochemical reaction, and designs the flow channel from the uniformity of both fluid and material aspects. Therefore, by designing a reasonable flow channel, the requirements for good mass transfer are met and the current density distribution consistency of the entire fuel cell plate is improved.

[0045] In an exemplary embodiment, the preset flow channel parameters include a preset flow channel number, a preset flow channel cross-sectional parameters and a preset flow channel length, and the flow channel fluid pressure drop resistance is determined based on the preset flow channel parameters, including: determining the fuel cell flow rate based on the current density, flow field active area area, stoichiometric coefficient, gas constant, temperature, Faraday constant, oxygen content, inlet pressure, inlet relative humidity and inlet protection pressure under rated operating conditions; determining the flow channel flow rate based on the fuel cell flow rate and the preset flow channel number; determining the flow channel fluid pressure drop resistance based on the flow channel flow rate, friction coefficient, fluid density, preset flow channel cross-sectional parameters and preset flow channel length.

[0046] In an exemplary embodiment, the flow channel fluid pressure drop resistance is determined along the length direction of the flow channel.

[0047] Specifically, when designing the flow channel, flow resistance is the first factor to be considered. Usually, the pressure drop flow resistance target is preset when designing the fuel cell. Based on the fuel cell design parameters and the bipolar plate flow field active area parameters, the relevant parameters required for the flow channel design can be preliminarily calculated.

[0048] Q stack = (I e ×A ac ×S×R×T in ×N cell ) / (4F×Ro2 ×P in -RH×P sat ) (1)

[0049] Q cell = Q stack / N cell (2)

[0050] The flow rate of the battery stack Q stack It can be calculated by formula (1), where I e is the current density under rated conditions, A ac is the area of ​​the flow field active region, T in is the inlet temperature, P in is the inlet pressure, RH is the inlet relative humidity, S is the metering coefficient, N cell is the number of cells in the battery stack, F is the Faraday constant, R is the gas constant, and R o2 is the oxygen content in the air, P sat is the saturation pressure at a given inlet temperature. At the same time, the flow rate of a single battery Q cell It can be obtained by formula (2).

[0051] Furthermore, the single channel flow rate Q is obtained by formula (3): ch .

[0052] Q ch = Q cell / N ch (3)

[0053] Among them, N ch is the number of flow channels in the active area of ​​the bipolar plate flow field.

[0054] According to the fluid flow calculation, the flow rate Q can be obtained ch The relationship between the fluid velocity and the flow channel cross-sectional area is as follows:

[0055] Q ch = V ch ×A ch_sec (4)

[0056] Among them A ch_sec is the cross-sectional area of ​​the flow channel, which is obtained when designing the flow channel. The fluid velocity V at the flow channel inlet can be obtained by calculation ch .

[0057] The flow resistance of the flow channel fluid pressure drop can be calculated by formula (5):

[0058] ΔP = f × L ch / D ch ×ρ×V ch 2 / 2+ KL ×ρ×V ch 2 / 2 (5)

[0059] Where f is the friction coefficient, L ch is the flow channel length, D ch is the hydraulic diameter of the flow channel, V ch is the flow velocity of the fluid in the flow channel, ρ is the fluid density, K L is the local loss drag coefficient.

[0060] Through equations (4) and (5), the design of the flow channel cross-sectional shape is linked to the flow channel fluid pressure drop resistance, and the flow channel fluid pressure drop resistance can be effectively determined when designing the flow channel.

[0061] Exemplarily, the pressure drop flow resistance characteristics of the calculated fluid are considered in the length direction of the flow channel, and based on the calculation method of the flow channel fluid pressure drop flow resistance in the above embodiment, the anode flow channel fluid pressure drop flow resistance, the cathode flow channel fluid pressure drop flow resistance and the cooling flow channel fluid pressure drop flow resistance are obtained.

[0062] In this embodiment, the pressure drop flow resistance characteristics of the fluid are calculated by considering the length direction of the flow channel. By combining the design of the flow channel cross-sectional shape with the pressure drop flow resistance of the flow channel fluid, the pressure drop flow resistance of the flow channel fluid can be effectively determined when designing the flow channel.

[0063] In an exemplary embodiment, the preset flow channel parameters include a preset flow channel length, and determining the flow channel substance concentration based on the preset flow channel parameters includes: determining the flow channel substance concentration based on the initial flow channel substance concentration, the metering coefficient, the flow channel length increment and the preset flow channel length.

[0064] In an exemplary embodiment, the concentration of the flow channel substance is determined along the flow direction of the substance in the flow channel.

[0065] Since the fluid flow in the flow channel participates in the electrochemical reaction from the inlet to the outlet, the flow channel design considering performance needs to clarify the changes in the fluid in the flow channel during the reaction, mainly the concentration changes of the reactants. Since the anode is pure hydrogen, the concentration change can be ignored; the cathode is air, and the concentration change of the cathode participating in the reaction has a greater impact on the performance.

[0066] Specifically, oxygen in the flow channel is a substance that participates in the reaction, and its concentration gradient changes with the change of the flow channel length in the flow field. This relationship can be expressed as the relationship between channel length and concentration, as shown in formula (6):

[0067] C(l)=C0(1-1 / S) l / L ch (6)

[0068] Where C(l) is the concentration of the substance at a specific local position in the flow channel; C0 is the initial concentration of the flow channel substance, S is the stoichiometric coefficient, l is the specific position of the flow channel length along the flow direction of the flow channel or the increment of the flow channel length from the inlet, that is, the flow channel length increment, L ch is the flow channel length.

[0069] According to the hydrogen-oxygen reaction equation and Faraday's law, the consumption of fuel hydrogen and oxidant oxygen participating in the electrochemical reaction along the flow direction of the flow channel can be calculated, and the oxygen concentration at different positions in the cathode side flow channel can be calculated.

[0070] In this embodiment, the consumption measurement of the reactant when the fuel cell reacts is considered according to the flow direction of the flow channel, as well as the changing gradient of the material concentration in the fluid flow direction caused by the consumption, the material consumption is discretized, and the concentration of the reactant at different positions of the flow channel is obtained based on the flow channel length increment to ensure the uniformity of the reactant in the flow channel, thereby obtaining a flow channel with uniform current distribution.

[0071] In an exemplary embodiment, as shown in FIG. 2 , a method for designing a flow channel of a bipolar plate of a fuel cell is provided. The method includes steps 202 to 212 .

[0072] Step 202, obtaining fuel cell design parameters.

[0073] Step 204 , determining the flow field active area parameters of the fuel cell bipolar plate based on the design parameters.

[0074] Step 206 , generating preset flow channel parameters based on the flow field active area parameters, wherein the preset flow channel parameters include a preset flow channel quantity, preset flow channel cross-sectional parameters, and a preset flow channel length.

[0075] Step 208 , determining the fuel cell flow rate based on the current density, flow field active area, stoichiometric coefficient, gas constant, temperature, Faraday constant, oxygen content, inlet pressure, inlet relative humidity and inlet protection pressure under rated operating conditions.

[0076] Step 210 , determining the flow rate of the flow channel based on the fuel cell flow rate and the preset number of flow channels.

[0077] Step 212 , determining the flow channel fluid pressure drop resistance along the length direction of the flow channel based on the flow channel flow rate, friction coefficient, fluid density, preset flow channel cross-sectional parameters and preset flow channel length.

[0078] Step 214 , determining the flow channel substance concentration along the material flow direction in the flow channel based on the flow channel initial substance concentration, the metering coefficient, the flow channel length increment and the preset flow channel length.

[0079] Step 216, adjusting the preset flow channel parameters based on the flow channel fluid pressure drop flow resistance and the flow channel material concentration to obtain the flow channel parameters.

[0080] Step 218, setting a flow channel with flow channel parameters in the flow field active area.

[0081] Since the uniformity requirement when designing the flow channel requires the flow channel to have a small pressure drop resistance and a uniform current distribution, that is, a uniform concentration distribution, this embodiment designs the flow channel based on the relationship between the cross-sectional shape of the flow channel and the pressure drop resistance of the flow channel fluid and the substance concentration distribution during the electrochemical reaction, from the uniformity of both the fluid and the substance, thereby obtaining a fuel cell with a small pressure drop resistance and a uniform current distribution.

[0082] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0083] For example, the pressure drop of the cathode flow field of a 100 cm² battery pack is used as an example. The fuel cell battery pack operates at an inlet pressure P in = 125kPa, temperature 60℃ and air saturation, the operating parameters are: stoichiometric ratio, that is, stoichiometric coefficient S is 2, working voltage 0.7V, current density 1A / cm²; the cathode flow field has 10 flow channels, the flow channel width W ch =1mm; channel depth h=1mm, channel spacing is the ridge W rib =1mm, the flow channel is a parallel serpentine flow channel.

[0084] Calculation of fluid pressure drop in a single flow channel: ΔP = f × L ch / D ch ×ρ×V ch 2 / 2.

[0085] Calculation of hydraulic diameter of flow channel: D ch =2×W ch ×h / (W ch +h)=2×1×1 / 2=1mm.

[0086] Flow channel length Lch = A cell / (W ch +W rib ) / 10=100 / 0.2 / 10=50cm.

[0087] Calculate the cross-sectional area of ​​the flow channel: 1mm².

[0088] Calculation of air flow required for flow field reaction:

[0089] Q air = Q stack =(I e ×A ac ×S×R×T in ×N cell ) / (4F×R o2 ×P in -RH×P sat ) = 65.1ml / s.

[0090] Flow velocity at the flow channel entrance: V ch = Q air / A ch_sec = 65.1 / 10 / 0.1 / 0.1=651cm / s.

[0091] Calculation of inlet Reynolds coefficient: Re = ρ × V ch ×D ch / μ = 400; where μ is the corresponding fluid viscosity of the fluid.

[0092] Calculation of friction loss resistance coefficient: Re×f≈55+41.5exp(-3.4 / W ch / h)f≈0.1399.

[0093] Finally, the single channel fluid pressure drop is calculated to be: ΔP=3743Pa.

[0094] And, the oxygen concentration at the outlet of the flow channel is obtained, as shown in Figure 3. Figure 3 is a schematic diagram of the change of oxygen concentration in the flow channel along the flow channel direction, wherein the horizontal axis represents the discreteness of the flow channel distance to the inlet, and the vertical axis represents the oxygen concentration.

[0095] Based on this flow channel design method, the bipolar plate structure can be further designed. The active area of ​​the bipolar plate is a repetition of a single flow channel structure. At the same time, the inlet and outlet of the fuel (hydrogen) and oxidant (air (oxygen)) and cooling are designed to complete the design of the bipolar plate.

[0096] In an exemplary embodiment, the present application provides a fuel cell bipolar plate, the fuel cell bipolar plate comprising: a cathode plate and an anode plate, each of the cathode plate and the anode plate comprising:

[0097] The inlet and outlet areas are used for the entry and exit of reactants and coolants; the distribution area includes an entry distribution area and an exit distribution area; the flow field active area includes flow channels, which include reactant flow channels and cooling flow channels; wherein the flow channels are designed using the design method for fuel cell bipolar plate flow channels as described in the previous embodiments.

[0098] Exemplarily, the present application designs flow channels based on the design method of fuel cell bipolar plate flow channels, and then designs the bipolar plates of fuel cells. The bipolar plate includes a cathode plate and an anode plate, and the cathode plate and the anode plate together form a bipolar plate. The structure on the anode and cathode plates includes three main areas, the inlet and outlet areas of the reaction gas and the coolant; the distribution area for the fluid to enter and the distribution area for the fluid to flow out; the flow field active area where the reaction occurs, and the flow field active area is mainly composed of gas flow channels, the cathode plate is an air flow channel, and the anode plate is a hydrogen flow channel. On the back of the air and hydrogen side flow channels are cooling channels.

[0099] Please refer to FIG. 4, which is a schematic diagram of the structure of one of the bipolar plates of a fuel cell in one embodiment. Exemplarily, the bipolar plate of the fuel cell includes: a cathode plate and an anode plate, each of which includes: an inlet and outlet area for reactants and coolants to enter and exit. A distribution area includes an inlet distribution area 42 and an outlet distribution area 42; a flow field active area 6 includes a flow channel, and the flow channel includes a reactant flow channel and a cooling flow channel.

[0100] Specifically, the inlet area for the reaction substances and coolant to enter includes an air inlet 11, a coolant inlet 21, a hydrogen inlet 31, and an upstream entry distribution area 41 before the fluid enters the reaction active area, which can be divided into a cathode plate entry distribution area and an anode plate entry distribution area. The flow field active area 6, also known as the reaction active area, can be divided into a cathode reaction active area and an anode reaction active area. Downstream of the reaction active area is the outflow distribution area 42, which distinguishes between the positive and negative plates, that is, it is divided into a cathode plate flow field distribution area and an anode plate flow field distribution area. There is a flow channel structure 5 in the distribution area for achieving uniform distribution of the fluid.

[0101] In an exemplary embodiment, the flow channel is a serpentine flow channel, and an angle of the serpentine flow channel is greater than 120 degrees and less than 150 degrees.

[0102] For example, please refer to FIG. 5 , which is a schematic diagram of the flow channel structure of a fuel cell bipolar plate in one embodiment. The flow channel is a meandering flow channel. The angle α of the meandering flow channel is 120° to 150°, and optionally, the angle α of the meandering flow channel is 120° to 125°.

[0103] In an exemplary embodiment, the flow channels are repeatedly arranged along a second direction in the flow field active region; the second direction is a direction perpendicular to the flow of the fluid in the flow field active region.

[0104] In an exemplary embodiment, the flow channel includes a flow channel portion and a ridge portion, the flow channel portion is used for the flow of reactants, and the ridge portion is used to separate the reactants; the flow channel widths of the cathode plate and the anode plate are the same, the width of the flow channel portion of the cathode plate is the same as the width of the ridge portion of the anode plate, and the width of the ridge portion of the cathode plate is the same as the width of the flow channel portion of the anode plate.

[0105] The flow field active area 6, i.e., the reaction active area, mainly includes the cathode plate flow channel and the anode plate flow channel. The design of the flow channel mainly includes the flow channel portion 7 for the flow of the reaction material and the ridge 8 for separating the reaction material. The anode side in the flow channel is the reaction fuel. For example, the reaction fuel is a substance that undergoes a reduction reaction, such as hydrogen, methanol, etc., and the cathode side is an oxidant for an oxidation reaction. For example, the oxidant is a substance that undergoes an oxidation reaction, such as oxygen, air, etc. The flow channel portion and the ridge separating the reaction material form a complete flow channel cycle. The flow direction along the fluid flow in the flow field active area 6 is the first direction, and the second direction is perpendicular to the first direction in the active area plane. The flow channel is arranged in an array according to the size of the active area and the width of the active area in the second direction. For example, the first direction in Figure 4 is the x-axis direction, and the second direction is the y-axis direction. The flow channel can be a straight flow channel, a serpentine flow channel, a winding flow channel, and a wavy shape, which is not limited in this application. Downstream of the outflow distribution area 42 is the outlet of the fluid, including an air outlet 12, a coolant outlet 22, and a hydrogen outlet 32. The flow direction of the battery reaction materials can be cocurrent, as shown in Figure 4. It can also be countercurrent, the flow direction of hydrogen and air is convection, and the inlet and outlet will change.

[0106] In an exemplary embodiment, the flow channel portion and the ridge portion include a bottom fillet portion, a top fillet portion and a connecting portion, the radii of the bottom fillet portion and the top fillet portion of the flow channel are the same, and the angle between the connecting portion and the normal to the cathode plate or anode plate plane is greater than 15 degrees and less than 25 degrees.

[0107] For example, please refer to FIG. 4 and FIG. 5 again, and also refer to Figure 6 and Figure 7 ,in Figure 6 A schematic diagram of the cross-sectional shape and size of a flow channel of a bipolar plate of a fuel cell in one embodiment; Figure 7 Schematic diagram of the flow channel structure of a bipolar plate of a fuel cell in yet another embodiment.

[0108] In one embodiment, the target power of the fuel cell stack is designed to be 240kW, the number of cells in the stack ranges from 500 to 550; the battery operating rating is 0.62V@2A / cm²; the active area of ​​a single cell is set at 350cm 2 ~400cm², considering the number of battery cells, the active area is set to 380cm².

[0109] Select the operating conditions of the stack, the temperature range is 65℃~90℃, and the optional temperature range is 70℃~85℃; the working pressure of the cathode and anode is 2 bar ~2.5bar absolute pressure. The cathode metering coefficient range is 1.5~3, and the optional cathode metering coefficient is 1.8. The anode metering coefficient range is 1.2~2, and the optional anode metering coefficient range is 1.5. The pressure drop target is set to less than 40kPa.

[0110] There are many commonly used flow channel forms, usually parallel flow channels, and also include multi-serpentine parallel flow channels, straight parallel flow channels and winding (wavy) parallel flow channels. This embodiment is illustrated by taking a winding flow channel as an example. The period of the flow channel (flow channel portion + ridge portion) ranges from 1.2mm to 1.6mm, and optionally, the flow channel period is 1.4mm. The angle α of the winding flow channel ranges from 120° to 150°, and optionally, the angle α of the winding flow channel ranges from 120° to 125°. The length of the flow field active area ranges from 280 mm to 300mm, and the optional length of the flow field active area is 285mm. The width of the flow field active area ranges from 123mm to 140mm.

[0111] Furthermore, Figure 6 Schematic diagram of the cross-sectional shape and size of the flow channel of a fuel cell bipolar plate in one embodiment; wherein W rib Indicates the ridge width; W ch Indicates the width of the flow channel; W indicates the flow channel period; h indicates the flow channel depth. The anode flow channel depth ranges from 0.3 mm to 0.35 mm, and the optional anode flow channel depth is 0.3 mm. The cathode flow channel depth ranges from 0.3 mm to 0.4 mm, and the optional cathode flow channel depth is 0.38 mm. R c Indicates the radius of the bottom corner of the flow channel, for example, R c =0.1mm; R l Describe the radius of the top corner of the flow channel, for example, R l =0.1mm; θ represents the draft angle, which is the angle between the side of the metal bipolar plate flow channel and the normal line of the plate plane. The draft angle range is 15°~25°. Optionally, the draft angle is 20°. Calculate the cross-sectional area of ​​the flow channel, the cathode flow channel width W ch The anode flow channel width is 0.66mm, and the anode cross-sectional area is 0.09mm². Furthermore, the cathode inlet velocity used to calculate the flow velocity in the flow channel is 16m / s, and the anode inlet velocity is 8m / s.

[0112] In an exemplary embodiment, the flow channel period is 1.4 mm, the cathode flow channel width is 0.74 mm, and the ridge width is 0.66 mm; the depth range is 0.3 mm~0.4 mm, and optionally 0.38 mm; the anode flow channel width is 0.66 mm, the ridge width is 0.74 mm, and the depth range is 0.3 mm~0.35 mm, and optionally 0.3 mm.

[0113] Specifically, the flow resistance of the cathode and the anode is calculated according to the pressure drop flow resistance formula. Since the flow channel is a winding flow channel, for the convenience of calculation, the winding flow channel is equivalent to a straight flow channel, and the flow channel length is calculated based on the winding angle of 125° being equivalent to a straight flow channel.

[0114] Based on formula (5), the pressure drop of a single channel is calculated to be 3743 Pa. Furthermore, based on the pressure drop of a single channel and the pressure drop of the distribution area, the pressure drop of the cathode channel is 36 kPa, and the pressure drop of the anode channel is 9 kPa.

[0115] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for designing a flow channel of a bipolar plate of a fuel cell, characterized in that: The method comprises: Obtain fuel cell design parameters; Determining the flow field active area parameters of the fuel cell bipolar plate based on the design parameters; generating preset flow channel parameters based on the flow field active area parameters; Determine the flow channel fluid pressure drop resistance and flow channel substance concentration based on the preset flow channel parameters; Based on the pressure drop resistance of the flow channel fluid and the concentration of the flow channel substance, adjusting the preset flow channel parameters to obtain the flow channel parameters; A flow channel having the flow channel parameters is arranged in the flow field active area.

2. The method according to claim 1, characterized in that: The preset flow channel parameters include the preset flow channel quantity, preset flow channel cross-sectional parameters and preset flow channel length. Determining the flow channel fluid pressure drop flow resistance based on the preset flow channel parameters includes: Determine the fuel cell flow rate based on the current density, flow field active area, stoichiometric coefficient, gas constant, temperature, Faraday constant, oxygen content, inlet pressure, inlet relative humidity and inlet protection pressure at rated operating conditions; Determining a flow channel flow rate based on the fuel cell flow rate and a preset number of flow channels; The flow channel fluid pressure drop flow resistance is determined based on the flow channel flow rate, friction coefficient, fluid density, preset flow channel cross-sectional parameters and preset flow channel length.

3. The method according to claim 2, characterized in that The flow channel fluid pressure drop resistance is determined along the length direction of the flow channel.

4. The method according to claim 2, characterized in that: Determining the concentration of the flow channel substance based on the preset flow channel parameters includes: The flow channel substance concentration is determined based on the flow channel initial substance concentration, the metering coefficient, the flow channel length increment and the preset flow channel length.

5. The method according to claim 4, characterized in that Determine the material concentration in the flow channel along the material flow direction in the flow channel.

6. A fuel cell bipolar plate, characterized in that: include: A cathode plate and an anode plate, each of the cathode plate and the anode plate comprising: Inlet and outlet areas for reactants and coolant to enter and exit; distribution areas, including entry into distribution areas and outflow from distribution areas; The flow field active area includes flow channels, wherein the flow channels include reaction material flow channels and cooling flow channels; wherein the flow channels are designed using the method described in any one of claims 1-5.

7. The bipolar plate according to claim 6, characterized in that: The flow channel is a meandering flow channel, and the included angle of the meandering flow channel is greater than 120 degrees and less than 150 degrees.

8. The bipolar plate according to claim 6, characterized in that: The flow channels are repeatedly arranged along a second direction in the flow field active region; the second direction is a direction perpendicular to the flow of the fluid in the flow field active region.

9. The bipolar plate according to claim 6, characterized in that: The flow channel includes a flow channel portion and a ridge portion, the flow channel portion is used for the flow of reactants, and the ridge portion is used to separate reactants; the flow channel widths of the cathode plate and the anode plate are the same, the width of the flow channel portion of the cathode plate is the same as the width of the ridge portion of the anode plate, and the width of the ridge portion of the cathode plate is the same as the width of the flow channel portion of the anode plate.

10. The bipolar plate according to claim 9, characterized in that: The flow channel portion and the ridge portion include a fillet portion at the bottom of the flow channel, a fillet portion at the top of the flow channel and a connecting portion, the radii of the fillet portion at the bottom of the flow channel and the fillet portion at the top of the flow channel are the same, and the angle between the connecting portion and the normal line of the cathode plate or anode plate plane is greater than 15 degrees and less than 25 degrees.

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