A method for water balance analysis and design of a fuel cell

Abstract

The application discloses a water balance analysis and design method of a fuel cell, which is based on the water transmission mechanism inside the fuel cell, fully considers the influence of material structure characteristics and operation conditions on water transmission and distribution, and establishes the direct correlation between the water distribution state and the fuel cell outlet humidity and proton exchange membrane resistance, so that the dry and wet states inside the fuel cell can be analyzed, and through comparison with the quantitative design index, the material selection, operation condition optimization and performance prediction of the water management design optimization of the fuel cell can be efficiently guided.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a water balance analysis and design method for fuel cells. Background Technology

[0002] Fuel cell water balance design refers to improving performance by optimizing the multi-component, multi-phase transport process within the fuel cell, based on the fundamental heat and mass transfer mechanisms, while ensuring membrane humidification (reducing resistance) and accelerating the transport of reactant gases and the discharge of liquid water (increasing the electrochemical reaction rate).

[0003] The contradiction in fuel cell water balance design lies in the fact that the membrane needs to retain sufficient water wettability at the electrode to reduce proton conduction resistance, while the transport of reactant gases requires unobstructed channels to support electrode reactions under high current density. The conflict between these two water requirements is the difficulty in designing and optimizing water management for fuel cells.

[0004] With the development of next-generation high-power-density fuel cell stacks and systems, both industrialization and fundamental theoretical research have placed new demands on fuel cell water management. On the one hand, high power density requires high system integration, while traditional water management designs rely on air humidification. However, air humidifier solutions are complex and costly, becoming a major bottleneck for system miniaturization and cost reduction. On the other hand, the continuous increase in current density has significantly increased the non-uniformity of the distribution of reaction gases, temperature, and liquid water, especially along the flow channel. This may lead to insufficient electrolyte wetting in the cathode inlet area and flooding of the electrodes or flow channels in the outlet area, resulting in localized insufficient gas supply and affecting battery performance and lifespan. Therefore, without external humidification technology, it is necessary to simultaneously address the regional wetting and drainage issues of the membrane electrode assembly.

[0005] In existing technologies, the development of fuel cell water balance typically relies on feedback from experimental results to achieve a balance between wetting and mass transfer by optimizing material structure and operating conditions.

[0006] For example, the invention application with publication number CN118610525A discloses a fuel cell water balance control method, device and fuel cell system. The method includes: obtaining the actual operating power of the fuel cell in the fuel cell system; determining the environmental state of the environment in which the fuel cell is located based on the actual operating power; and adjusting the target physical quantity corresponding to the target subsystem in response to the abnormal state of the environment in which the fuel cell is located, so as to make the environment in which the fuel cell is located reach water balance.

[0007] Because the heat, mass, and electrical conduction processes in the multi-scale structure of fuel cells are intertwined, water management research is extremely complex, making it difficult to decouple engineering design and optimization. This can lead to erroneous judgments by researchers in material selection, structural design, and operating condition optimization. Furthermore, hydrothermal sensitivity and performance evaluation experiments are very costly in terms of time, manpower, and financial resources, and the experimental results have significant limitations, making it difficult to comprehensively and accurately assess and optimize the water balance state of fuel cells.

[0008] Therefore, how to establish a direct correlation between operating conditions, material properties, water state distribution and performance, and to develop fuel cell water balance more efficiently and in a more targeted manner, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] To address the shortcomings of existing fuel cell water management optimization technologies, this invention proposes a fuel cell water balance analysis and design method. Based on theoretical analysis, it proposes key design points and quantitative indicators for water balance. Based on the developed water balance simulation tool, it establishes a direct correlation between operating conditions, material properties, water state distribution, and performance. This method can efficiently achieve material selection, operating condition optimization, and performance prediction, and has high universality and accuracy.

[0010] A water balance analysis and design method for fuel cells includes the following steps: Step 1: Obtain the key parameters of the fuel cell, including the operating condition parameters and physicochemical characteristic parameters of the fuel cell; Step 2: Input the key parameters into the theoretical analysis model. The theoretical analysis model responds and performs theoretical calculations to obtain the theoretical dry boundary of the fuel cell anode and cathode. Step 3: Input the key parameters into the simulation analysis model, and the simulation analysis model responds and performs simulation calculations to obtain the water distribution state of the fuel cell; Step 4: Compare the water distribution state obtained in Step 3 with the theoretical dry boundary obtained in Step 2 and the preset water balance design requirements. If it is within the theoretical dry boundary range and meets the preset water balance design requirements, then the water distribution state is determined to be the suitable water balance state for the fuel cell.

[0011] Preferably, in step 1, the operating condition parameters of the fuel cell include: cooling chamber inlet and outlet temperatures, anode inlet and outlet pressures, cathode inlet and outlet pressures, anode and cathode metering ratio, anode and cathode inlet relative humidity, operating current density, output voltage, and net water transmembrane transport ratio. α ; The physicochemical properties of fuel cells include: reaction zone area, anode and cathode flow field properties, anode and cathode gas diffusion layer properties, anode and cathode microporous layer properties, anode and cathode catalyst layer properties, and proton exchange membrane properties.

[0012] Preferably, the physical properties of the anode and cathode flow fields include the thickness and thermal conductivity of the anode and cathode flow fields; The physical properties of the anode and cathode gas diffusion layers include their thickness, thermal conductivity, and porosity. The physical properties of the anode and cathode microporous layers include their thickness, thermal conductivity, and porosity. The physical properties of the anode and cathode catalyst layers include their thickness, thermal conductivity, and porosity. The physical properties of proton exchange membranes include the thickness of the proton exchange membrane, dry equivalent mass, dry density, water content, water diffusion coefficient, water electroosmotic drag coefficient, and proton conductivity.

[0013] Preferably, in step 2, the theoretical dry-out boundary of the anode refers to the critical point at which all the water humidified at the anode inlet is transported to the cathode side through the proton exchange membrane, and the theoretical dry-out boundary of the cathode refers to the critical point at which all the total amount of water generated by the humidification at the cathode inlet and the reaction of the cathode catalytic layer is transported to the anode side through the proton exchange membrane.

[0014] Preferably, in step 3, inputting the key parameters into the simulation analysis model means obtaining the output water distribution state through simulation calculation based on the water transport mechanism and mass conservation equation in each layer under the pre-set input parameters.

[0015] Preferably, in step 3, the simulation analysis model includes: the structure of a single fuel cell includes: a proton exchange membrane, an anode catalyst layer, an anode microporous layer, an anode gas diffusion layer and an anode flow field arranged from the inside to the outside on the anode side of the proton exchange membrane, and a cathode catalyst layer, a cathode microporous layer, a cathode gas diffusion layer and a cathode flow field arranged from the inside to the outside on the cathode side of the proton exchange membrane; the anode and cathode gases are supplied and flow in opposite directions, and the cooling chamber medium and the cathode air flow direction are consistent.

[0016] More preferably, the positions of the anode inlet, anode outlet, anode flow field / gas diffusion layer interface, anode flow field / gas diffusion layer interface, anode microporous layer / catalytic layer interface, anode catalytic layer / proton exchange membrane interface, cathode inlet, and cathode outlet are set. Based on the principle of heat flow conservation, the relevant parameters of heat generation and thermal conductivity at each location are calculated, including the thermal resistance of each layer, the total thermal resistance of the anode, the total thermal resistance of the cathode, the total thermal resistance of the fuel cell, the total heat generation of the fuel cell, and the temperature at each location. Based on the principle of flow conservation and water transport mechanism, other key characteristic parameters at each location are calculated, including pressure, flow rate, relative humidity and mole fraction of each gas component at each layer. By combining the principle of flow conservation with the water transport mechanism in the proton exchange membrane, the water content, water transport properties and proton resistance at each location are calculated. Finally, the relative humidity at the anode outlet, the relative humidity at the cathode outlet, and the total proton resistance of the proton exchange membrane were calculated.

[0017] Preferably, in step 4, the pre-defined water balance design requirements include: The relative humidity requirements at the anode and cathode outlets are determined based on the fuel cell's drainage capacity. And, based on the performance requirements of fuel cells, determine the proton resistance requirements of the proton exchange membrane.

[0018] This invention provides a water balance analysis and design method for fuel cells. Starting from the water transport mechanism inside the fuel cell, this method fully considers the influence of material structure characteristics and operating conditions on water transport and distribution, and establishes a direct correlation between water distribution state and fuel cell outlet humidity and proton exchange membrane resistance. It can be used to analyze the dry and wet state inside the battery. By comparing with the proposed quantitative design indicators, it can efficiently guide the material selection, operating condition optimization, and performance prediction when optimizing the water management design of fuel cells. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a water balance analysis and design method for a fuel cell disclosed in an embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the water balance simulation analysis model disclosed in an embodiment of this application.

[0021] Figure 3 The ratio of relative humidity at the anode and cathode outlets of the fuel cell disclosed in this application as a function of net water transmembrane transport. α The changing simulation curve.

[0022] Figure 4 Different net water transmembrane transport ratios in fuel cells disclosed in the embodiments of this application α Simulation curves showing the change in water content along the thickness direction of the lower membrane.

[0023] Figure 5 Different net water transmembrane transport ratios in fuel cells disclosed in the embodiments of this application α Simulation curves showing the change in proton resistance along the thickness direction of the lower film.

[0024] Figure 6 The ratio of proton resistance of fuel cell membrane to net transmembrane transport in water disclosed in the embodiments of this application α The changing simulation curve. Detailed Implementation

[0025] This application discloses a water balance analysis and design method for fuel cells, the flowchart of which is shown below. Figure 1 As shown, the method mainly includes the following steps: Step S101: Obtain the key parameters of the fuel cell, including: current operating condition parameters and physicochemical characteristic parameters.

[0026] The current operating parameters include: cooling chamber inlet temperature. T in Cooling chamber outlet temperature T out Anode inlet pressure P in,an Anode outlet pressure P out,an Cathode inlet pressure P in,ca Cathode outlet pressure P out,ca Anode metering ratio Stock an Cathode metering ratio Stock ca Anode inlet relative humidity RH an Cathode inlet relative humidity RH ca Operating current density I Output voltage V Water transmembrane transport ratio α Among them, the stoichiometric ratio in the anode stoichiometric ratio and the cathode stoichiometric ratio refers to the stoichiometric ratio, which is the ratio of the actual gas supply to the theoretical gas supply required to maintain the electrochemical reaction.

[0027] Physicochemical properties, including: reaction zone area A act (Refers to the area of ​​the active region where electrochemical reactions can occur), anodic and cathode flow field properties (thickness) d aFF and d cFF Thermal conductivity k aFF and k cFF ), physical properties of the anode and cathode gas diffusion layers (thickness) d aGDL and d cGDL Thermal conductivity k aGDL and k cGDL Porosity e aGDL and e cGDL), physical properties of the microporous layers of the anode and cathode (thickness) d aMPL and d cMPL Thermal conductivity k aMPL and k cMPL Porosity e aMPL and e cMPL ), physical properties of the anode and cathode catalyst layers (thickness) d aCL and d cCL Thermal conductivity k aCL and k cCL Porosity e aCL and e cCL ), Proton exchange membrane properties (thickness) d PEM Thermal conductivity k PEM Dry equivalent quality E.W. PEM Dry density r PEM Water content l Water diffusion coefficient D PEM Hydroelectric drag coefficient x PEM Proton conductivity s PEM ).

[0028] Step S102: Input the key parameters of the fuel cell into the pre-built theoretical analysis model. The model responds and performs theoretical calculations to obtain the theoretical dry boundary of the fuel cell anode and cathode.

[0029] It should be noted that the theoretical dry-out boundary mentioned in this application refers to the critical state when the amount of water lost by the electrode equals the amount of water gained. The source of water gained by the anode is the amount of humidifying water at the anode inlet, and the source of water gained by the cathode is the amount of humidifying water at the cathode inlet and the amount of water generated by the reaction of the cathode catalyst layer. When the amount of water lost by the anode and the cathode is greater than the amount of water gained, their respective theoretical dry-out boundaries are reached. At this point, the performance of the fuel cell continues to decline and it cannot operate stably.

[0030] In this embodiment, the positive direction is defined as the flow of water from the anode to the cathode. At this point, the theoretical dry boundary of the anode is... Cathode theory dry boundary .in, and (mol / m 2 The / s refers to the amount of water humidified at the anode and cathode inlets, respectively, and is related to the current operating current density and operating conditions. I (A / m) 2 () represents the operating current density. F (96485 C / mol) is the Faraday constant.

[0031] Step S103: Input the key parameters of the fuel cell into the pre-built simulation analysis model, the model responds and performs simulation calculations to obtain the water distribution state of the fuel cell.

[0032] Figure 2 This is a schematic diagram of the simulation analysis model built in this embodiment. The fuel cell consists of an anode flow field, an anode gas diffusion layer, an anode microporous layer, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, a cathode microporous layer, a cathode gas diffusion layer, and a cathode flow field. The anode and cathode gases are supplied and flow in opposite directions, and the cooling chamber medium and the cathode air flow direction are consistent.

[0033] Positions 1 to 8 represent the anode inlet (aIN), anode outlet (aOUT), anode flow field / gas diffusion layer interface (aFF / aGDL), anode flow field / gas diffusion layer interface (aGDL / aMPL), anode microporous layer / catalytic layer interface (aMPL / aCL), anode catalytic layer / proton exchange membrane interface (aCL / PEM), cathode inlet (cIN), and cathode outlet (cOUT), respectively. It is worth noting that this embodiment uses the anode side as the calculation origin and focuses on the influence of water distribution on the membrane proton resistance and the relative humidity at the anode and cathode outlets. Therefore, the physical model and water transport calculations in this embodiment do not reflect the cathode catalytic layer, microporous layer, and gas diffusion layer.

[0034] Based on the principle of heat flow conservation, the relevant parameters for heat generation and thermal conductivity at various locations are calculated as follows: Thermal resistance of each layer: , , , , , , , , , Total thermal resistance of the anode: , Total thermal resistance of cathode: , Total thermal resistance of fuel cell: , Total heat output of fuel cells: .

[0035] Temperature calculations for each location are as follows: Location 1: , Position 2: , Position 3: , Position 4: , Position 5: , Position 6: , Position 7: , Position 8: .

[0036] in, R aFF This represents the thermal resistance of the anode flow field. R cFF This represents the thermal resistance of the cathode flow field. R aGDL This indicates the thermal resistance of the anode gas diffusion layer. R cGDL This indicates the thermal resistance of the cathode gas diffusion layer. R aMPL Indicates the thermal resistance of the anode microporous layer. R cMPL This indicates the thermal resistance of the cathode microporous layer. R aCL Indicates the thermal resistance of the anode catalyst layer. R cCL Indicates the thermal resistance of the cathode catalyst layer. R PEM Indicates the thermal resistance of the proton exchange membrane; i aFF and i cFF The trench proportions for the anode and cathode flow fields are shown in Table 1. y The coordinates are the flow field coordinates along the flow direction. The model can be calculated based on coordinates at any location; in this embodiment, the coordinates are taken at the middle position of the flow field. y =0.5 analysis.

[0037] Based on the principle of flow conservation and water transport mechanism, other key characteristic parameters at each location are calculated as follows: Location 1: , , , , .

[0038] Position 2: , , , , .

[0039] Position 3: , , .

[0040] Position 4: , , , .

[0041] Position 5: , , , .

[0042] Position 6: , , , , .

[0043] Position 7: , , , , .

[0044] Position 8: , , , , .

[0045] in, P 1- P 8 represents the pressure at positions 1 through 8 respectively; f 1 wv - f 8 wv (WV is an abbreviation for water vapor) represents the mole fraction of water vapor at positions 1 through 8 respectively; - These represent the mole fractions of hydrogen gas at positions 1 through 6, respectively. , These represent the mole fractions of oxygen at positions 7 and 8, respectively. RH in,an , RH in,ca These represent the relative humidity at the anode inlet and the cathode inlet, respectively. P sat Indicates saturated vapor pressure; N 1. N 2. N 7. N 8 represents the gas flow rates at positions 1, 2, 7, and 8, respectively; RH 1. RH 1. RH 7. RH The numbers 8 represent the relative humidity at positions 1, 2, 7, and 8, respectively. R This represents the ideal gas constant (8.314 J / K / mol). , , Let these represent the binary gas diffusion coefficients (hydrogen and water vapor, Pa∙m) at the interfaces of positions 3 and 4, 4 and 5, and 5 and 6, respectively. 2 / s); , These represent the molar masses (g / mol) of hydrogen gas and water vapor, respectively. , These represent the molecular volumes (cm³) of hydrogen gas and water vapor, respectively. 3 / mol); a 6 indicates the water activity at the anode catalyst layer / proton exchange membrane interface (aCL / PEM).

[0046] Considering the difference in moisture content between the anode and cathode, this embodiment divides the proton exchange membrane into 10 grid layers along its thickness direction (grids 1 to 10 represent the anode to cathode). Therefore, the model can simulate the gradient changes in water content and proton resistance from the anode to the cathode. Combining the principle of flow conservation with the main transport mechanisms of water in the proton exchange membrane (concentration diffusion and electroosmotic drag), the water content, water transport properties (water diffusion coefficient and electroosmotic drag coefficient), and proton resistance at each location are calculated as follows: Anode catalyst layer / proton exchange membrane interface (aCL / PEM): , , .

[0047] Grid 1: , , , .

[0048] Grid 2-Grid 10: , , , .

[0049] in, i Represents grid coordinates, with values ​​ranging from 2 to 10 (natural numbers). Water content is expressed in letters l Indicate, then l aCL / PEM This indicates the water content at the anode catalyst layer / proton exchange membrane interface. l 1 indicates the water content at grid 1. l i Represents a grid i Water content at the location, l max This represents the theoretical maximum water content of the proton exchange membrane (here, we take 22). diffusion coefficient Dexpress, D wv The water vapor diffusion coefficient is represented by . This represents the water diffusion coefficient at the anode catalyst layer / proton exchange membrane interface; MIN (·) represents the minimum value. Electroosmotic drag coefficient x express, x wv This represents the electroosmotic drag coefficient of water vapor. The electroosmotic drag coefficient of water vapor at the anode catalyst layer / proton exchange membrane interface; R Represents proton resistance. Indicates the proton resistance at grid 1 , indicating grid i The proton resistance at that location; (Unit: g / mol) (Unit: kg / m³) 3 ), (Unit: m) represent the dry molar mass, density, and thickness of the proton exchange membrane, respectively.

[0050] Cathode catalyst layer / proton exchange membrane interface (cCL / PEM): , , .

[0051] in, l cCL / PEM This indicates the water content at the cathode catalyst layer / proton exchange membrane interface; The diffusion coefficient of water vapor at the cathode catalyst layer / proton exchange membrane interface; This represents the electroosmotic drag coefficient of water vapor at the cathode catalyst layer / proton exchange membrane interface.

[0052] Total proton resistance of proton exchange membrane .

[0053] Thus, three main parameters characterizing the water balance state of a fuel cell have been calculated: anode outlet relative humidity. RH 2. Relative humidity at the cathode outlet RH 8. Total proton resistance of proton exchange membrane .

[0054] Step S104: Determine the appropriate water balance state for the fuel cell, which mainly includes two steps: setting a water balance target and comparing the current state with the target.

[0055] Setting water balance targets includes determining the relative humidity requirements at the anode and cathode outlets based on the fuel cell's drainage capacity. and The proton resistance requirement of the proton exchange membrane is determined based on the performance requirements of the fuel cell. .

[0056] The comparison between the current state and the target includes: comparing the relative humidity at the anode and cathode outlets and the total resistance of the proton exchange membrane at the current state with their respective target values; if both conditions are met... , , If the current state is satisfactory, then the current state is a suitable water balance state. If any one of the parameters does not meet the target value, it means that the current state is either flooded or dried out of the electrodes, which is not a suitable water balance state. It is necessary to adjust the fuel cell materials, structural design parameters, or operating conditions until the simulation value meets all three limit conditions at the same time. At this time, the design system meets the suitable water balance state.

[0057] Based on the above embodiments of the present invention, a method for water balance analysis and design of a fuel cell is disclosed, such as... Figure 3 As shown, this invention discloses the ratio of relative humidity at the anode and cathode outlets of a fuel cell as a function of transmembrane water transport. α The changing simulation curve.

[0058] Specifically, the transmembrane water transport ratio, a key parameter input into the fuel cell water balance simulation model, will be... α As an independent variable, by changing α With other key parameters remaining constant, the simulation model is used to predict the change in anode and cathode outlet humidity as dependent variables. α The changing relationship.

[0059] like Figure 3 As shown, with the proportion of transmembrane water transport α As the concentration of water decreases, the humidity at the cathode outlet gradually decreases, while the humidity at the anode outlet increases rapidly. This indicates that when a higher proportion of water is transferred from the cathode to the anode, the anode is prone to flooding. Conversely, when a certain proportion of water is transferred from the anode to the cathode, the anode is prone to drying out.

[0060] like Figure 4 As shown, this invention discloses different transmembrane water transport ratios in fuel cells. α Simulation curves showing the change in water content along the thickness direction of the lower membrane.

[0061] Specifically, the transmembrane water transport ratio, a key parameter input into the fuel cell water balance simulation model, will be... α With other key parameters remaining constant as independent variables, the simulation model is used to predict the change in water content along the thickness direction of the proton exchange membrane, which is the dependent variable.

[0062] like Figure 4 As shown, with the proportion of transmembrane water transport α With the increase of [something], the membrane water content on the cathode side remained unchanged, while the membrane water content on the anode side decreased rapidly, indicating that the degree of anode drying increased rapidly, [and / etc.]. Figure 3 The changes in export humidity are consistent.

[0063] like Figure 5 As shown, this invention discloses different transmembrane water transport ratios in fuel cells. α Simulation curves showing the change in proton resistance along the thickness direction of the lower film.

[0064] Specifically, the transmembrane water transport ratio, a key parameter input into the fuel cell water balance simulation model, will be... α With other key parameters unchanged, the simulation model is used to predict the proportion of transmembrane water transport. α Below, the change in membrane proton resistance along the thickness direction is considered as the dependent variable.

[0065] like Figure 5 As shown, with the proportion of transmembrane water transport α As the concentration of water increases, the water content on the anode side of the membrane decreases rapidly, thus causing the membrane proton resistance on the anode side to rise rapidly.

[0066] like Figure 6 As shown, this is the ratio of proton resistance of the fuel cell membrane to transmembrane water transport disclosed in an embodiment of the present invention. α The changing simulation curve.

[0067] Specifically, the transmembrane water transport ratio, a key parameter input into the fuel cell water balance simulation model, will be... α With other key parameters remaining constant as the independent variable, the simulation model is used to predict the membrane proton resistance as the dependent variable. α The changing relationship.

[0068] like Figure 6 As shown, with α As the transmembrane water transport ratio increases, the membrane proton resistance exhibits a pattern of first remaining stable, then rising slowly, and finally rising rapidly. This indicates that as the transmembrane water transport ratio increases... α When the value is increased to a certain level, the anode dries out rapidly, leading to a rapid increase in membrane impedance and a rapid decrease in performance.

[0069] like Figure 4 to Figure 6 As shown, when the transmembrane water transport ratio α Reaching the theoretical drying point of the cathode When the cathode outlet humidity drops to 0, it indicates that all the humidifying water at the cathode inlet and the water generated by the reaction have diffused to the anode, and the cathode is at a critical point of being slightly dry. Further reduction in humidity... α The cell will not function stably. When the transmembrane water transport ratio...α When the humidity is below -0.04, the anode outlet humidity is greater than 100%, indicating that liquid water begins to appear at the anode. Further reduction in humidity is necessary. α When the transmembrane water transport ratio is insufficient, significant water flooding of the anode can occur, leading to performance and durability issues. α When the value is above -0.05, the anode is in a relatively dry state, and the membrane proton resistance is... α The changes are quite sensitive. α Even a slight increase can lead to rapid battery drying and a rapid decline in performance. When the transmembrane water transport ratio α reaches the theoretical anodic drying point... At this point, the humidity at the anode outlet drops to 0, indicating that all the humidifying water at the anode inlet is being drawn to the cathode, leaving the anode in an extremely dry state. Based on the above analysis, the ideal water balance in this embodiment should be achieved through optimization of materials, structure, and operating conditions to maximize the transmembrane water transport ratio. α In ( b The interval is -0.05. b The selection is related to the battery's actual liquid water drainage capacity.

[0070] The specific values ​​of fuel cell materials, structural characteristics, and operating conditions used in the simulation calculations of this embodiment are shown in Tables 1 and 2.

[0071] Table 1:

[0072] Table 2:

[0073] It should be noted that the fuel cell materials, structural characteristics, and operating conditions in Tables 1 and 2 are only parameters used in the embodiments of this invention. When the fuel cell uses different material systems or operates under different conditions, the corresponding parameters can be adjusted, and the method proposed in this invention can be used to analyze and optimize the water balance state, thereby achieving a suitable water balance design.

Claims

1. A water balance analysis and design method for fuel cells, characterized in that, Includes the following steps: Step 1: Obtain the key parameters of the fuel cell, including the operating condition parameters and physicochemical characteristic parameters of the fuel cell; Step 2: Input the key parameters into the theoretical analysis model. The theoretical analysis model responds and performs theoretical calculations to obtain the theoretical dry boundary of the fuel cell anode and cathode. Step 3: Input the key parameters into the simulation analysis model, and the simulation analysis model responds and performs simulation calculations to obtain the water distribution state of the fuel cell; Step 4: Compare the water distribution state obtained in Step 3 with the theoretical dry boundary obtained in Step 2 and the preset water balance design requirements. If it is within the theoretical dry boundary range and meets the preset water balance design requirements, then the water distribution state is determined to be the suitable water balance state for the fuel cell.

2. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, In step 1, the operating parameters of the fuel cell include: cooling chamber inlet and outlet temperatures, anode inlet and outlet pressures, cathode inlet and outlet pressures, anode and cathode metering ratio, anode and cathode inlet relative humidity, operating current density, output voltage, and net water transmembrane transport ratio. α ; The physicochemical properties of fuel cells include: reaction zone area, anode and cathode flow field properties, anode and cathode gas diffusion layer properties, anode and cathode microporous layer properties, anode and cathode catalyst layer properties, and proton exchange membrane properties.

3. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, The physical properties of the anodic and cathode flow fields include the thickness and thermal conductivity of the anodic and cathode flow fields; The physical properties of the anode and cathode gas diffusion layers include their thickness, thermal conductivity, and porosity. The physical properties of the anode and cathode microporous layers include their thickness, thermal conductivity, and porosity. The physical properties of the anode and cathode catalyst layers include their thickness, thermal conductivity, and porosity. The physical properties of proton exchange membranes include the thickness of the proton exchange membrane, dry equivalent mass, dry density, water content, water diffusion coefficient, water electroosmotic drag coefficient, and proton conductivity.

4. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, In step 2, the theoretical dry-out boundary of the anode refers to the critical point at which all the water humidified at the anode inlet is transported to the cathode side through the proton exchange membrane, and the theoretical dry-out boundary of the cathode refers to the critical point at which all the total amount of water generated by the humidification at the cathode inlet and the reaction of the cathode catalyst layer is transported to the anode side through the proton exchange membrane.

5. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, In step 3, inputting the key parameters into the simulation analysis model means that, under the pre-set input parameters, the output water distribution state is obtained through simulation calculation based on the water transport mechanism and mass conservation equation in each layer.

6. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, In step 3, the simulation analysis model includes: the structure of a single fuel cell includes: a proton exchange membrane, an anode catalyst layer, an anode microporous layer, an anode gas diffusion layer and an anode flow field arranged from the inside to the outside on the anode side of the proton exchange membrane, and a cathode catalyst layer, a cathode microporous layer, a cathode gas diffusion layer and a cathode flow field arranged from the inside to the outside on the cathode side of the proton exchange membrane; the anode and cathode gases are supplied and flow in opposite directions, and the cooling chamber medium and the cathode air flow direction are consistent.

7. The water balance analysis and design method for fuel cells according to claim 6, characterized in that, The locations of the anode inlet, anode outlet, anode flow field / gas diffusion layer interface, anode microporous layer / catalytic layer interface, anode catalytic layer / proton exchange membrane interface, cathode inlet, and cathode outlet are defined. Based on the principle of heat flow conservation, the relevant parameters of heat generation and thermal conductivity at each location are calculated, including the thermal resistance of each layer, the total thermal resistance of the anode, the total thermal resistance of the cathode, the total thermal resistance of the fuel cell, the total heat generation of the fuel cell, and the temperature at each location. Based on the principle of flow conservation and water transport mechanism, other key characteristic parameters at each location are calculated, including pressure, flow rate, relative humidity and mole fraction of each gas component at each layer. By combining the principle of flow conservation with the water transport mechanism in the proton exchange membrane, the water content, water transport properties and proton resistance at each location are calculated. Finally, the relative humidity at the anode outlet, the relative humidity at the cathode outlet, and the total proton resistance of the proton exchange membrane were calculated.

8. The water balance analysis and design method for fuel cells according to claim 1, characterized in that, In step 4, the pre-defined water balance design requirements include: The relative humidity requirements at the anode and cathode outlets are determined based on the fuel cell's drainage capacity. And, based on the performance requirements of fuel cells, determine the proton resistance requirements of the proton exchange membrane.

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