Method for predicting optimal flow channel width of proton exchange membrane fuel cell

Abstract

The invention discloses a method for predicting the optimal flow channel width of a proton exchange membrane fuel cell, and the method comprises the following steps: carrying out the discrete processing of the proton exchange membrane fuel cell in the channel direction, solving the mass transfer of oxygen and water vapor in a segmented manner, associating all segments through boundary conditions, building a flow and mass transfer coupling model, and carrying out the prediction of the optimal flow channel width of the proton exchange membrane fuel cell. The mass transfer condition of oxygen and water vapor at each position of the fuel cell is obtained, the limiting current density of the fuel cell is calculated according to the mass transfer of the oxygen, and finally, the limiting current density is used as an evaluation standard and combined with an optimization method to realize rapid prediction of the optimal flow channel width of the proton exchange membrane fuel cell. According to the prediction method, the optimal flow channel width of the proton exchange membrane fuel cell can be quickly obtained, and the method has the advantages of short optimization time, good optimization effect, simplicity in implementation and the like.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a method for predicting an optimal flow channel width of a proton exchange membrane fuel cell. Background Art

[0002] Fuel cells have shown great development potential due to their green and pollution-free nature, high specific energy density, low noise, and wide fuel range. Among them, proton exchange membrane fuel cells (PEMFCs) are considered the most competitive next-generation power source due to their low operating temperature and fast start-stop response. The flow field of the PEMFC bipolar plate affects the transport of reactants within the cell, the conduction of electrons, the diffusion of heat, and other factors, which determine the output performance and service life of the PEMFC. Designing a suitable PEMFC flow field structure is one of the important ways to improve PEMFC performance. Parallel channels are simple to process and have low pumping power losses, making them widely used in commercial PEMFCs. Parallel channels are composed of multiple single channels, and many scholars have studied single-channel structures in order to obtain the best PEMFC output performance.

[0003] PEMFC research primarily involves two methods: experiments and numerical simulations. Experiments can directly and accurately determine fuel cell performance. However, traditional experiments often rely on a trial-and-error approach, requiring multiple sets of experiments. This is time-consuming and labor-intensive, resulting in high R&D costs and a long development cycle. Numerical simulations can effectively replicate the complex physical and chemical phenomena within PEMFCs, but they require significant computer resources and computational time. When studying the optimal width for a single-channel PEMFC, it is often necessary to repeatedly vary the PEMFC channel width and perform performance evaluations, which consumes significant computational resources and time. Therefore, it is imperative to develop an efficient, accurate, and comprehensive method for predicting the optimal channel width for proton exchange membrane fuel cells.

[0004] Pan et al. (Pan WT, Chen XL, Wang FC, Dai G. Mass transfer enhancement of PEM fuel cells with optimized flow channel dimensions [J]. International Journal of Hydrogen Energy, 2020, 46 (57): 29541-29555.) proposed a series resistance model, analyzed the rate control steps under various voltages of PEMFC, theoretically derived the relationship between the optimal flow channel width and flow rate of single-channel PEMFC, and verified the reliability of the method using computational fluid dynamics. The results show that the more the channel width deviates from the optimal value, the worse the performance of the battery. However, this method ignores the diffusion mass transfer in the flow channel and ignores the influence of parameters such as rib width and flow channel length on the optimal flow channel width. At present, there is still a lack of an efficient, accurate and comprehensive method for predicting the optimal flow channel width of proton exchange membrane fuel cells. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for predicting the optimal flow channel width of a proton exchange membrane fuel cell with a simple process, a short optimization period and high reliability, which can quickly determine the optimal flow channel width.

[0006] The present invention is achieved through at least one of the following technical solutions.

[0007] A method for predicting an optimal flow channel width of a proton exchange membrane fuel cell comprises the following steps:

[0008] S01. Obtaining initial structural parameters and operating parameters of a proton exchange membrane fuel cell;

[0009] S02. Divide the proton exchange membrane fuel cell into N parts along the channel direction, consider the battery in the limiting current working state, and calculate the theoretical maximum oxygen mass transfer flux of the first part based on the oxygen molar concentration at the flow channel inlet;

[0010] S03, calculating the molar concentration of water in the flow channel at the outlet of the first part and the catalyst layer and the molar concentration of oxygen in the flow channel at the outlet of the first part;

[0011] S04. Using the gas composition and flow rate at the outlet of the first flow channel as the initial conditions at the inlet of the next flow channel, and performing the calculation in this way, the theoretical maximum oxygen mass transfer flux of each part is determined;

[0012] S05. Calculate the theoretical limiting current density of the battery for the current flow channel width based on the theoretical maximum oxygen mass transfer rate of each part;

[0013] S06. Based on the theoretical limiting current density, adjust the flow channel width using an optimization method, return to step S02, and repeat steps S02 to S05 until the limiting current density no longer increases. At this time, the flow channel width corresponding to the maximum limiting current density is the optimal flow channel width for the proton exchange membrane fuel cell.

[0014] Furthermore, in step S01, the initial structural parameters of the battery include flow channel width, rib width, flow channel height, bipolar plate thickness, gas diffusion layer thickness, catalyst layer thickness and proton exchange membrane thickness, gas diffusion layer porosity and catalyst layer porosity; the operating parameters include operating temperature, operating pressure, anode and cathode inlet gas humidity and anode and cathode inlet gas flow rate.

[0015] Furthermore, in step S02 , the battery is divided into N parts along the channel direction, where N can be any integer greater than 0, and the lengths of each part can be the same or different.

[0016] Furthermore, in step S02, when calculating the theoretical maximum oxygen mass transfer flux, Taylor dispersion is used to describe the convective mass transfer and diffusion mass transfer of oxygen in the flow channel; Fick's law is used to describe the diffusion mass transfer of oxygen in the gas diffusion layer. The theoretical maximum oxygen mass transfer flux is calculated using the following formula:

[0017]

[0018] Among them, R c is the mass transfer flux of oxygen; h is the flow channel height; K is the oxygen diffusion degree; δ GDL is the thickness of the gas diffusion layer; is the molar concentration of oxygen in the cathode flow channel; is the effective diffusion coefficient of oxygen; A is the mass transfer area;

[0019] The general formula for solving the oxygen diffusion K is:

[0020]

[0021] Among them, D c is the oxygen diffusion coefficient; Pe is the Peclet number, which is used to measure the relative importance of gas diffusion and convection in the flow channel; v is the oxygen flow rate in the flow channel;

[0022] The effective diffusion coefficient of oxygen is calculated by the following formula:

[0023]

[0024] Where ε is the porosity of the diffusion layer; P0 and T0 are the reference pressure and reference temperature, respectively; P and T are the operating pressure and operating temperature of the battery, respectively.

[0025] Furthermore, in step S03, when calculating the water vapor concentration in the catalyst layer and the flow channel at the outlet of the first part, a conservation equation is established based on the mass conservation of water vapor to establish the relationship between the water membrane transport flux, the water vapor diffusion flux, and the water generation flux:

[0026] N g +N d -N diff -N c =0;

[0027] N g -N c -N a =0;

[0028]

[0029] Among them, N g is the water generation flux; N d is the electrochemical drag mass transfer flux of water; N diff is the back diffusion flux of water; N c is the diffusion flux of water vapor in the cathode gas diffusion layer; N a is the diffusion flux of water vapor in the anode gas diffusion layer; is the molar concentration of water vapor at the anode flow channel; is the molar concentration of water vapor at the cathode flow channel; q a is the total gas flow in the anode channel; q c is the total gas flow in the cathode flow channel; i+1 refers to the inlet of the i+1th part, which is also the outlet of the i-th part;

[0030] Considering the two modes of water diffusion in the membrane, electrochemical drag and back diffusion, the electrochemical drag mass transfer flux of water N d and the water back diffusion flux N diff Calculate by the following formula respectively:

[0031]

[0032] Among them, n d is the electric drag coefficient; F is the Faraday constant; I is the transfer current density; ρ m is the dry film density; M m is the equivalent mass of the membrane; D l is the water diffusion coefficient in the membrane; λ is the membrane water content; is the gradient operator;

[0033] The transfer current density I is obtained by the following formula:

[0034] I=4FR c ;

[0035] Fick's law is used to describe the diffusion mass transfer of water vapor in the gas diffusion layer:

[0036]

[0037] in, is the molar concentration of water vapor at the cathode flow channel and the anode flow channel; is the molar concentration of water vapor at the cathode catalyst layer and cathode flow channel; δ GDL is the thickness of the gas diffusion layer; is the effective diffusion coefficient of water vapor in the gas diffusion layer;

[0038] The water vapor generation flux is based on the chemical reaction conservation equation and is obtained by the following formula:

[0039] N g =2R c ;

[0040] Among them, R c is the mass transfer flux of oxygen;

[0041] The gas flow rate at the inlet of the i+1 part can be calculated by the following formula:

[0042]

[0043] Among them, N c (i) is the diffusion flux of water vapor in the cathode gas diffusion layer of the i-th part; N a (i) is the diffusion flux of water vapor in the anode gas diffusion layer of the i-th part; R c (i) is the mass transfer flux of oxygen in the i-th part; P and T are the operating pressure and operating temperature of the cell respectively; R a (i) is the hydrogen consumption in the anode flow channel of the i-th part, which is obtained by the following formula:

[0044] R a (i) = 2R c (i).

[0045] Furthermore, in step S03, the oxygen molar concentration in the flow channel at the outlet of the first part is calculated using the following formula:

[0046]

[0047] in, and represents the oxygen concentration at the cathode flow channel entrance of the i+1th part and the ith part respectively; q c (i+1) and q c (i) represents the total gas flow rate at the cathode flow channel inlet of the i+1th part and the ith part, respectively.

[0048] Furthermore, in step S04, the initial conditions at the inlet of the next part of the flow channel include the flow rates of the cathode side and anode side flow channels, the molar fractions of water vapor in the cathode side and anode side flow channels, and the molar fraction of oxygen in the cathode side flow channel.

[0049] Furthermore, in step S04, considering two adjacent battery parts, the gas composition and flow rate at the outlet of the flow channel of the i-th part are used as the initial conditions at the inlet of the flow channel of the i+1-th part. Based on this initial condition, the theoretical maximum oxygen mass transfer flux of the latter part and the molar concentrations of water and oxygen at the flow channel outlet can be calculated. In this way, the theoretical maximum oxygen mass transfer flux of each part can be obtained by progressive solution for N parts.

[0050] Furthermore, in step S05, the theoretical limiting current density I m The relationship between the theoretical maximum oxygen transfer mass of each part is shown in the following formula:

[0051]

[0052] Among them A act is the active area of ​​the battery, R t It is the sum of the theoretical maximum oxygen mass transfer flux of each part, and the formula is:

[0053]

[0054] where R c (i) is the mass transfer flux of oxygen in the i-th part.

[0055] Furthermore, in step S06, the optimization method is a single-parameter optimization method, including but not limited to the ergodic method, the quadratic interpolation method, and the Newton iteration method.

[0056] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0057] 1. Short optimization time. Compared with conventional numerical methods, the method proposed in this paper considers the operating state of limiting current density, effectively reducing the number of equations to be calculated. At the same time, the proposed method solves algebraic equations, significantly reducing the complexity of the calculation and shortening the calculation time.

[0058] 2. Excellent optimization results. The mass transfer model employed in this invention couples one-dimensional flow and one-dimensional mass transfer, improving the accuracy of limiting current density prediction while maintaining computational efficiency. This allows for relatively accurate evaluation of the performance of PEMFCs of varying structures during the optimization process. By combining the mass transfer model with the optimization method, this invention achieves superior optimization results.

[0059] 3. Simple implementation. The prediction method provided by the present invention includes two key technical steps during implementation: first, calculating the limiting current density using a mass transfer model; and second, optimizing the target variable using a single parameter optimization method to obtain the optimal target variable. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a schematic diagram of the division of a single-channel PEMFC in an embodiment of the present invention.

[0061] Figure 2 1 is a curve showing the change of current density with flow channel width in Example 1 of the present invention.

[0062] Figure 3 1 is a curve showing the change of current density with flow channel width in Example 2 of the present invention.

[0063] Figure 4 3 is a curve showing the change of current density with flow channel width in Example 3 of the present invention. DETAILED DESCRIPTION

[0064] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0065] A method for predicting the optimal flow channel width of a proton exchange membrane fuel cell in this embodiment uses the flow channel width as an optimization variable and the limiting current density as an indicator to characterize the performance of a single-channel PEMFC. The ergodic method is used to determine the optimal flow channel width. The detailed operation includes the following steps:

[0066] Step S01: Determine the initial structural parameters and operating parameters of the PEMFC. The initial structural parameters include flow channel width, rib width, flow channel height, bipolar plate thickness, gas diffusion layer thickness, catalyst layer thickness, proton exchange membrane thickness, gas diffusion layer porosity, and catalyst layer porosity. Operating parameters include operating temperature, operating pressure, anode and cathode inlet gas humidity, and anode and cathode inlet gas flow rates.

[0067] The single-channel PEMFC structure considered in this implementation case is as follows Figure 1 As shown, PEMFC consists of an anode bipolar plate a, an anode gas diffusion layer b, an anode catalyst layer c, a proton exchange membrane d, a cathode catalyst layer e, a cathode gas diffusion layer f and a cathode bipolar plate g. The structural parameters of PEMFC are shown in Table 1.

[0068] Table 1 PEMFC geometric parameters

[0069]

[0070] In order to solve the model, it is also necessary to specify boundary conditions and operating parameters. The key operations and design parameters for the calculation of the method of the present invention are shown in Table 2.

[0071] Table 2 Key operations and operating parameters of the simulation

[0072]

[0073]

[0074] Step S02: Segment the PEMFC and calculate the theoretical maximum oxygen mass transfer flux of the first section. The present invention segments the PEMFC into N sections along the channel direction. Considering the cell operating in a limiting current state, the theoretical maximum oxygen mass transfer flux of the first section is calculated based on the oxygen molar concentration at the channel inlet. N can be any integer greater than 0, and each section can be the same or different in length.

[0075] As an example, Figure 1 As shown, the single-channel PEMFC is divided into 9 parts at equal distances along the channel direction, and the length of each part is 5 mm.

[0076] When calculating the theoretical maximum oxygen mass transfer flux, Taylor dispersion is used to describe the convective and diffusive mass transfer of oxygen in the flow channel; Fick's law is used to describe the diffusive mass transfer of oxygen in the gas diffusion layer. The theoretical maximum oxygen mass transfer flux calculation formula is as follows:

[0077]

[0078] Among them, R c is the mass transfer flux of oxygen; h is the flow channel height; K is the oxygen diffusion degree; δ GDL is the thickness of the gas diffusion layer; is the molar concentration of oxygen in the cathode flow channel; is the effective diffusion coefficient of oxygen; A is the mass transfer area.

[0079] The general formula for solving the oxygen diffusion K is:

[0080]

[0081] Among them, D c is the oxygen diffusion coefficient; Pe is the Peclet number, which is used to measure the relative importance of gas diffusion and convection in the flow channel; v is the oxygen flow rate in the flow channel.

[0082] The effective diffusion coefficient of oxygen is calculated by the following formula:

[0083]

[0084] Where ε is the porosity of the diffusion layer; P0 and T0 are the reference pressure and reference temperature, respectively; P and T are the operating pressure and operating temperature of the battery, respectively.

[0085] Step S03: Calculate the molar concentration of water in the flow channel at the outlet of the first part and the catalyst layer and the molar concentration of oxygen in the flow channel at the outlet of the first part.

[0086] Based on the conservation of mass of water vapor, a conservation equation is established between the water membrane transport flux, the water vapor diffusion flux and the water generation flux. Solving the conservation equation can obtain the molar concentration of water in the cathode flow channel, cathode catalyst layer, anode flow channel and anode catalyst layer at the outlet of the first part.

[0087] N g +N d -N diff -N c =0;

[0088] N g -N c -N a =0;

[0089]

[0090] Among them, N g is the water generation flux; N d is the electrochemical drag mass transfer flux of water; N diff is the back diffusion flux of water; N c is the diffusion flux of water vapor in the cathode gas diffusion layer; N a is the diffusion flux of water vapor in the anode gas diffusion layer; is the molar concentration of water vapor at the anode flow channel; is the molar concentration of water vapor at the cathode flow channel; q a is the total gas flow in the anode channel; q c is the total gas flow in the cathode flow channel; i+1 refers to the inlet of the i+1th part, which is also the outlet of the i-th part.

[0091] Considering the two modes of water diffusion in the membrane, electrochemical drag and back diffusion, the electrochemical drag mass transfer flux of water N d and the water back diffusion flux N diff Calculate by the following formula respectively:

[0092]

[0093] Among them, n d is the electric drag coefficient; F is the Faraday constant; I is the transfer current density; ρ m is the dry film density; M m is the equivalent mass of the membrane; D l is the water diffusion coefficient in the membrane; λ is the membrane water content; is the gradient operator.

[0094] The transfer current density I is obtained by the following formula:

[0095] I=4FR c ;

[0096] Fick's law is used to describe the diffusion mass transfer of water vapor in the gas diffusion layer:

[0097]

[0098] in, is the molar concentration of water vapor at the cathode flow channel and the anode flow channel; is the molar concentration of water vapor at the cathode catalyst layer and cathode flow channel; δ GDL is the thickness of the gas diffusion layer; is the effective diffusion coefficient of water vapor in the gas diffusion layer.

[0099] The water vapor generation flux is based on the chemical reaction conservation equation and is obtained by the following formula:

[0100] N g =2R c ;

[0101] Among them, R c is the mass transfer flux of oxygen.

[0102] The gas flow rate at the inlet of the i+1 part can be calculated by the following formula:

[0103]

[0104] Among them, N c (i) is the diffusion flux of water vapor in the cathode gas diffusion layer of the i-th part; N a (i) is the diffusion flux of water vapor in the anode gas diffusion layer of the i-th part; R c (i) is the mass transfer flux of oxygen in the i-th part; P and T are the operating pressure and operating temperature of the cell respectively; R a (i) is the hydrogen consumption in the anode flow channel of the i-th part, which is obtained by the following formula:

[0105] R a (i) = 2R c (i);

[0106] Calculate the molar concentration of oxygen in the flow channel at the outlet of the first part. According to the law of conservation of mass, the molar concentration of oxygen in the flow channel at the outlet of the first part is:

[0107]

[0108] in, and represents the oxygen concentration at the cathode flow channel entrance of the i+1th part and the ith part respectively; qc (i+1) and q c (i) represents the total gas flow rate at the cathode flow channel inlet of the i+1th part and the ith part, respectively.

[0109] Step S04: progressively calculate and determine the theoretical maximum oxygen mass transfer flux of each part.

[0110] The gas composition and flow rate at the outlet of the i-th part of the flow channel are used as the initial conditions of the i+1-th part. The initial conditions include the flow rates of the cathode and anode side channels, the mole fractions of water vapor in the cathode and anode side channels, and the mole fraction of oxygen in the cathode side channel.

[0111] According to the initial conditions, the theoretical maximum oxygen mass transfer flux of the i+1th part and the molar concentrations of water and oxygen at the outlet of the flow channel can be calculated. By solving the problem in this way, the theoretical maximum oxygen mass transfer flux of each part can be obtained.

[0112] Step S05: Calculate the theoretical limiting current density of the battery at the flow channel width based on the theoretical maximum oxygen mass transfer rate of each part.

[0113] Theoretical limiting current density I m The relationship between the theoretical maximum oxygen transfer mass of each part is shown in the following formula:

[0114]

[0115] Among them, R t is the sum of the theoretical maximum oxygen mass transfer flux of each part; A act is the active area of ​​the battery.

[0116]

[0117] Step S06: Based on the theoretical limiting current density, the flow channel width is adjusted using an optimization method. The process returns to step S02 and repeats steps S02 through S05 until the limiting current density no longer increases. At this point, the flow channel width corresponding to the maximum limiting current density is the optimal flow channel width for the proton exchange membrane fuel cell. In one embodiment, the optimization method is a single-parameter optimization method, including but not limited to ergodic methods, quadratic interpolation methods, and Newton iteration methods.

[0118] This embodiment adopts the traversal method, the channel width traverses [0.1mm, 3mm], and the equation is solved using matlab2023a. The entire optimization cycle is 6.5 seconds. Figure 2 Figure (a) shows the curve of limiting current density versus channel width calculated using the inventive method. As shown, as the channel width increases, the limiting current density first increases and then decreases. At a channel width of 1.3 mm, the limiting current density reaches its maximum, and PEMFC performance is optimal, confirming that a channel width of 1.3 mm is the optimal channel width.

[0119] In order to verify the accuracy of the invented method, a three-dimensional PEMFC model was used to calculate the output current density of PEMFC with different flow channel widths. Figure 2 (b) is the curve of the PEMFC output current density changing with the channel width when the voltage is 0.3V. As shown in the figure, the output current density increases first and then decreases with the increase of the channel width. When the channel width is 1.3mm, the current density reaches the maximum, which is 2.65A / cm 2 The further the channel width deviates from 1.3mm, the lower the PEMFC current density and the worse the battery output performance. Under this PEMFC structure and flow rate, the single-channel PEMFC performance is best when the channel width is 1.3mm. This result proves the reliability of the invented method.

[0120] As another embodiment, the fixed rib width of this embodiment is 1 mm, and the rest is the same as that of embodiment 1. Figure 3 Figure (a) shows the curve of limiting current density versus channel width calculated using the inventive method. As shown, as the channel width increases, the limiting current density first increases and then decreases. At a channel width of 1.1 mm, the limiting current density reaches its maximum, and PEMFC performance is optimal, confirming that a channel width of 1.1 mm is the optimal channel width. Figure 3 (b) is the curve of the output current density of a single-channel PEMFC as the channel width changes when the end voltage is 0.3 V. As shown in the figure, the output current density increases first and then decreases with the increase of the channel width. When the channel width is 1.1 mm, the current density reaches the maximum, which is 3.26 A / cm 2 The further the channel width deviates from 1.1 mm, the lower the PEMFC current density and the worse the battery output performance. Under this PEMFC structure and flow rate, the single-channel PEMFC performance is best when the channel width is 1.1 mm. This result proves the reliability of the invented method.

[0121] As another embodiment, the fixed flow channel length of this embodiment is 70 mm, and the rest is the same as that of embodiment 1. Figure 4 Figure (a) shows the curve of limiting current density versus channel width calculated using the inventive method. As shown, as the channel width increases, the limiting current density first increases and then decreases. At a channel width of 1.1 mm, the limiting current density reaches its maximum, and PEMFC performance is optimal, confirming that a channel width of 1.1 mm is the optimal channel width. Figure 4 (b) is the curve of the output current density of a single-channel PEMFC as the channel width changes when the end voltage is 0.3 V. As shown in the figure, the output current density increases first and then decreases with the increase of the channel width. When the channel width is 1.1 mm, the current density reaches the maximum of 2.15 A / cm 2The further the channel width deviates from 1.1 mm, the lower the PEMFC current density and the worse the battery output performance. Under this PEMFC structure and flow rate, the single-channel PEMFC performance is best when the channel width is 1.1 mm. This result proves the reliability of the invented method.

[0122] The above description is only a representative embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the scope disclosed by the present invention, which fall within the scope of protection of the present invention.

Claims

1. A method for predicting the optimal flow channel width of a proton exchange membrane fuel cell, characterized in that: The following steps are involved: S01. Obtaining initial structural parameters and operating parameters of a proton exchange membrane fuel cell; S02. Divide the proton exchange membrane fuel cell into N parts along the channel direction, consider the battery in the limiting current working state, and calculate the theoretical maximum oxygen mass transfer flux of the first part based on the oxygen molar concentration at the flow channel inlet; S03, calculating the molar concentration of water in the flow channel at the outlet of the first part and the catalyst layer and the molar concentration of oxygen in the flow channel at the outlet of the first part; S04. Using the gas composition and flow rate at the outlet of the first flow channel as the initial conditions at the inlet of the next flow channel, and performing the calculation in this way, the theoretical maximum oxygen mass transfer flux of each part is determined; S05. Calculate the theoretical limiting current density of the battery for the current flow channel width based on the theoretical maximum oxygen mass transfer rate of each part; S06. Based on the theoretical limiting current density, adjust the flow channel width using an optimization method, return to step S02, and repeat steps S02 to S05 until the limiting current density no longer increases. At this time, the flow channel width corresponding to the maximum limiting current density is the optimal flow channel width for the proton exchange membrane fuel cell.

2. A method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S01, the initial structural parameters of the battery include flow channel width, rib width, flow channel height, bipolar plate thickness, gas diffusion layer thickness, catalyst layer thickness and proton exchange membrane thickness, gas diffusion layer porosity and catalyst layer porosity; the operating parameters include operating temperature, operating pressure, anode and cathode inlet gas humidity and anode and cathode inlet gas flow rate.

3. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, wherein: In step S02 , the battery is divided into N parts along the channel direction, where N can be any integer greater than 0, and the lengths of each part can be the same or different.

4. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S02, when calculating the theoretical maximum oxygen mass transfer flux, Taylor dispersion is used to describe the convective mass transfer and diffusion mass transfer of oxygen in the flow channel; Fick's law is used to describe the diffusion mass transfer of oxygen in the gas diffusion layer. The theoretical maximum oxygen mass transfer flux is calculated as follows: Among them, R c is the mass transfer flux of oxygen; h is the flow channel height; K is the oxygen diffusion degree; δ GDL is the thickness of the gas diffusion layer; is the molar concentration of oxygen in the cathode flow channel; is the effective diffusion coefficient of oxygen; A is the mass transfer area; The general formula for solving the oxygen diffusion K is: Among them, D c is the oxygen diffusion coefficient; Pe is the Peclet number, which is used to measure the relative importance of gas diffusion and convection in the flow channel; v is the oxygen flow rate in the flow channel; The effective diffusion coefficient of oxygen is calculated by the following formula: Where ε is the porosity of the diffusion layer; P0 and T0 are the reference pressure and reference temperature, respectively; P and T are the operating pressure and operating temperature of the battery, respectively.

5. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, wherein: In step S03, when calculating the water vapor concentration in the catalyst layer and the flow channel at the outlet of the first part, a conservation equation is established based on the mass conservation of water vapor to establish the relationship between the water membrane transport flux, the water vapor diffusion flux and the water generation flux: Among them, N g is the water generation flux; N d is the electrochemical drag mass transfer flux of water; N diff is the back diffusion flux of water; N c is the diffusion flux of water vapor in the cathode gas diffusion layer; N a is the diffusion flux of water vapor in the anode gas diffusion layer; is the molar concentration of water vapor at the anode flow channel; is the molar concentration of water vapor at the cathode flow channel; q a is the total gas flow in the anode channel; q c is the total gas flow in the cathode flow channel; i+1 refers to the inlet of the i+1th part, which is also the outlet of the i-th part; Considering the two modes of water diffusion in the membrane, electrochemical drag and back diffusion, the electrochemical drag mass transfer flux of water N d and the water back diffusion flux N diff Calculate by the following formula respectively: Among them, n d is the electric drag coefficient; F is the Faraday constant; I is the transfer current density; ρ m is the dry film density; M m is the equivalent mass of the membrane; D l is the water diffusion coefficient in the membrane; λ is the membrane water content; is the gradient operator; The transfer current density I is obtained by the following formula: I=4FR c ; Fick's law is used to describe the diffusion mass transfer of water vapor in the gas diffusion layer: in, is the molar concentration of water vapor at the cathode flow channel and the anode flow channel; is the molar concentration of water vapor at the cathode catalyst layer and cathode flow channel; δ GDL is the thickness of the gas diffusion layer; is the effective diffusion coefficient of water vapor in the gas diffusion layer; The water vapor generation flux is based on the chemical reaction conservation equation and is obtained by the following formula: N g =2R c ; Among them, R c is the mass transfer flux of oxygen; The gas flow rate at the inlet of the i+1 part can be calculated by the following formula: Among them, N c (i) is the diffusion flux of water vapor in the cathode gas diffusion layer of the i-th part; N a (i) is the diffusion flux of water vapor in the anode gas diffusion layer of the i-th part; R c (i) is the mass transfer flux of oxygen in the i-th part; P and T are the operating pressure and operating temperature of the cell respectively; R a (i) is the hydrogen consumption in the anode flow channel of the i-th part, which is obtained by the following formula: R a (i)=2R c (i)。 6. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S03, the oxygen molar concentration in the flow channel at the outlet of the first part is calculated using the following formula: : in, and represents the oxygen concentration at the cathode flow channel entrance of the i+1th part and the ith part respectively; q c (i+1) and q c (i) represents the total gas flow rate at the cathode flow channel inlet of the i+1th part and the ith part, respectively.

7. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S04, the initial conditions at the inlet of the next part of the flow channel include the flow rates of the cathode side and anode side flow channels, the molar fractions of water vapor in the cathode side and anode side flow channels, and the molar fraction of oxygen in the cathode side flow channel.

8. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S04, considering two adjacent battery sections, the gas composition and flow rate at the outlet of the flow channel of section i are used as the initial conditions at the inlet of the flow channel of section i+1. Based on this initial condition, the theoretical maximum oxygen mass transfer flux of the latter section and the molar concentrations of water and oxygen at the flow channel outlet can be calculated. By solving the problem in this way, the theoretical maximum oxygen mass transfer flux of each section can be obtained.

9. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S05, the theoretical limiting current density I m The relationship between the theoretical maximum oxygen transfer mass of each part is shown in the following formula: Among them A act is the active area of ​​the battery, R t It is the sum of the theoretical maximum oxygen mass transfer flux of each part, and the formula is: where R c (i) is the mass transfer flux of oxygen in the i-th part.

10. The method for predicting the optimal flow channel width of a proton exchange membrane fuel cell according to claim 1, characterized in that: In step S06, the optimization method is a single-parameter optimization method, including but not limited to the ergodic method, the quadratic interpolation method, and the Newton iteration method.

Images