A method and system for predicting cathode gas flow distribution of a fuel cell stack

Abstract

The present invention discloses a method and system for predicting cathode gas flow distribution in a fuel cell stack. The method comprises calculating the total inlet mass flow rate of the cathode gas, cathode gas physical properties, and generated water physical properties based on the operating conditions of the fuel cell stack; calculating the local pressure drop and friction pressure drop during stack cathode gas flow, and performing a two-phase flow correction on the flow pressure drop in the battery cathode flow field and outlet manifold by calculating a two-phase flow loss multiplier; establishing a two-phase flow network model for the cathode gas in the fuel cell stack by analyzing the flow resistance relationships in each flow branch of the stack cathode flow field, with the manifold and unit cells connected by mass conservation and energy conservation; and establishing a numerical solution algorithm for distributing gas flow to each unit cell in the stack. The inlet gas flow rate of each unit cell is iteratively solved by updating the pressure drop of each part until convergence and outputting the gas flow distribution result. This method can quickly and accurately predict cathode gas flow distribution.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell operation, and in particular relates to a method and system for predicting cathode gas flow distribution of a fuel cell stack. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) are highly efficient electrochemical energy conversion devices that utilize hydrogen. They can generate electricity stably with zero carbon emissions and have broad application prospects. Currently, commercially available fuel cells have an output voltage of approximately 0.65V. To meet practical application requirements, hundreds of cells are typically assembled in series into a stack to generate power on demand. During stack operation, cathode gas enters the stack through a common inlet manifold shared by all cells and is distributed to each cell. It then flows out of the cell cathode flow field and converges at a common outlet manifold shared by all cells before exiting the stack. The distribution of cathode gas to each cell in the manifold is affected by local and longitudinal flow resistance. The varying flow resistance between cells results in uneven cathode gas flow distribution across the stack, further causing uneven electrochemical reactions between cells and ultimately deteriorating the fuel cell stack's service life and output performance. Therefore, predicting cathode gas flow distribution within the stack is crucial for fuel cell stack design and can significantly improve R&D efficiency.

[0003] Among the existing stack flow distribution prediction technologies, CFD simulation and flow network models have become the main means to explore the dependence between the flow distribution uniformity in the stack and the stack structure. Since the generation of the computational domain of the CFD model of a large-scale stack is time-consuming and computationally expensive, it is not convenient to use in preliminary design and structural optimization. Although the flow network model can quickly calculate the flow and pressure in the stack, the existing model ignores the effect of liquid water generated after the cathode gas reaction on the flow distribution, which leads to a significant overestimation of the cathode gas flow distribution uniformity in the stack. At present, no numerical prediction method for the cathode gas flow distribution of a fuel cell stack has been found that takes into account the influence of the cathode flow field and the two-phase flow in the outlet manifold. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for predicting the cathode gas flow distribution of a fuel cell stack. The method aims to provide a numerical prediction method for the cathode gas flow distribution of a fuel cell stack, which can take into account the influence of water generated in the stack on the flow distribution and improve the accuracy of the prediction results of the cathode gas flow distribution of the stack.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a method for predicting cathode gas flow distribution of a fuel cell stack, comprising the following steps:

[0006] Calculating the total inlet mass flow rate of the cathode gas, the dynamic viscosity of the cathode humidifying air, and the dynamic viscosity of water according to the operating conditions of the fuel cell stack;

[0007] The local pressure drop and friction pressure drop during the flow of the cathode gas in the fuel cell stack are calculated based on the structural parameters of the fuel cell stack, the total inlet mass flow rate, the dynamic viscosity of the cathode humidification air, and the dynamic viscosity of water;

[0008] Combined with the calculation of the two-phase flow loss multiplier, the flow pressure drop in the battery cathode flow field and the outlet manifold is corrected for the two-phase flow;

[0009] A gas two-phase flow network model of the fuel cell stack cathode flow field is established based on the calculated local pressure drop and friction pressure drop during the stack cathode gas flow. The stack cathode flow field includes a gas inlet manifold, a gas outlet manifold, and each unit cell. The manifold segment and the unit cell are connected by mass conservation and energy conservation.

[0010] Based on the established gas two-phase flow network model, a numerical solution algorithm for distributing gas flow to each unit cell in the fuel cell stack is established. The inlet gas flow of each unit cell is iteratively solved by updating the pressure drop of each part until the calculation result converges, and the cathode gas flow distribution result is obtained.

[0011] Furthermore, the dynamic viscosity μ of the cathode humidified air gas and the dynamic viscosity of water μ water Calculated according to the empirical formula.

[0012] Furthermore, the specific steps of calculating the local pressure drop and friction pressure drop during the flow of the cathode of the stack include:

[0013] Establish the friction loss of gas in the manifold △P fm With the gas flow rate U and friction resistance coefficient R fm Relationship:

[0014]

[0015] Establish the local loss △P of gas diversion in the manifold st With the gas flow rate U and the local resistance coefficient R st Relationship:

[0016]

[0017] Establish the local loss of gas deflection in the manifold △P c With the gas flow rate U and the local resistance coefficient R c relationship,

[0018]

[0019] A geometric model of the cathode flow field of a unit cell was established. The pressure drop at the inlet and outlet of the flow field at different flow rates was obtained through fluid dynamics calculation. The pressure drop at the inlet and outlet of the flow field at different flow rates was fitted into a quadratic relationship with the gas flow rate. The local pressure loss coefficient A and the friction pressure loss coefficient B in the cathode flow channel were obtained. The relationship between the flow field pressure drop and the flow rate when there is only cathode gas was obtained by calculating the following formula:

[0020] ΔP ch_total =AU 2 +BU.

[0021] Furthermore, the total mass flow rate of cathode gas at the inlet of the stack manifold is m ca Combined stack oxygen consumption mass flow m O2 , gas molar mass M, relative humidity RH, water vapor saturation vapor pressure P sat and the manifold inlet pressure P c Calculated by the following formula:

[0022]

[0023] in, They represent the molecular molar masses of oxygen, nitrogen, and water vapor, respectively.

[0024] Furthermore, the specific steps of calculating the two-phase flow loss multiplier include:

[0025] Assume that the water generated by the electrochemical reaction is stably injected into the cathode flow channel in liquid form;

[0026] The flow rate U of the generated water is obtained based on the water flow generated by the chemical reaction water , two-phase flow friction loss multiplier and the two-phase flow local loss multiplier The calculation formula is,

[0027]

[0028] Among them, μ gas and μ water The dynamic viscosity of the cathode gas and the dynamic viscosity of water are respectively calculated according to the empirical formula. The dynamic viscosity of the cathode humidified air μ gas and the dynamic viscosity of water μ water ;U gas and U water are the flow rates of cathode gas and generated water, respectively, M 2 is the Mortazavi parameter.

[0029] When performing two-phase flow correction on the flow pressure drop in the battery cathode flow field and outlet manifold by combining the calculation of the two-phase flow loss multiplier:

[0030] The friction pressure drop △P in the flow channel after considering the influence of air-product water two-phase flow ch_fm Calculate according to the following formula:

[0031]

[0032] Considering the influence of air-product water two-phase flow, the local pressure drop △P in the flow channel ch_local Calculate according to the following formula:

[0033]

[0034] Furthermore, each manifold segment and the unit cell are connected by mass conservation and energy conservation, that is, the cathode gas two-phase flow network model satisfies the following mass conservation and energy conservation conditions:

[0035] The inlet gas mass flow rate of all unit cells m cell The sum is equal to the manifold inlet gas mass flow rate m ca , and the gas mass flow rate in the inlet / outlet manifold section of the i-th unit cell is m mani ; The algebraic sum of the pressure drops of the flow circuit composed of any two adjacent unit cells is 0.

[0036] Furthermore, the inlet gas flow rate of each unit cell is iteratively solved by updating the pressure drop of each part until the calculation result converges, and the cathode gas flow distribution result is obtained, including:

[0037] At the initial iteration step, the manifold inlet flow is evenly distributed to each unit cell;

[0038] Based on the flow rate of the current iteration step, the total pressure drop on the left side of the following equation and the first two pressure drops on the right side are calculated. According to the law of conservation of energy, the last pressure drop on the right side is calculated, and the corrected gas mass flow rate m in the i-th battery is deduced. cell_corr ;

[0039] ΔP st_in [i-1]+ΔP fm_in [i-1]+ΔP c_in [i-1]+ΔP ch_in [i-1]+ΔP c_out [i-1]+ΔP fm_out [i-1]+ΔP st_out [i-1]=ΔP c_in [i]+ΔP c_out [i]+ΔP ch_total [i]

[0040] The new gas flow rate in the i-th battery at the j+1th iteration step:

[0041] [m cell [i]] j+1 =[m cell [i]] j +(m cell_corr [i]-[m cell [i]] j )·F r

[0042] The gas flow rate of all cells in the stack is iteratively corrected. The residual value of the algorithm is the sum of the difference between the new flow rate of each cell in the stack and the previous flow rate. The convergence standard is that the residual is less than 10 -12 .

[0043] The present invention also provides a fuel cell stack cathode gas flow distribution prediction system based on a two-phase flow network model, comprising a calculation module, a correction module, a model building module and a solution module;

[0044] The calculation module is used to calculate the total inlet mass flow rate of the cathode gas, the dynamic viscosity of the cathode humidified air, and the dynamic viscosity of water according to the operating conditions of the fuel cell stack; and at the same time, calculate the local pressure drop and friction pressure drop when the cathode gas flows in the fuel cell stack according to the structural parameters of the fuel cell stack and the total inlet mass flow rate, the dynamic viscosity of the cathode humidified air, and the dynamic viscosity of water;

[0045] The correction module is used to perform two-phase flow correction on the flow pressure drop in the battery cathode flow field and the outlet manifold by combining the calculation of the two-phase flow loss multiplier;

[0046] The model building module is used to establish a gas two-phase flow network model of the fuel cell stack cathode flow field based on the calculated local pressure drop and friction pressure drop during the stack cathode gas flow. The stack cathode flow field includes a gas inlet manifold, a gas outlet manifold, and each unit cell. The manifold segment and the unit cell are connected by mass conservation and energy conservation.

[0047] The solution module is used to establish a numerical solution algorithm for distributing gas flow to each unit cell in the fuel cell stack based on the established gas two-phase flow network model. The inlet gas flow of each unit cell is iteratively solved by updating the pressure drop of each part until the calculation result converges to obtain the cathode gas flow distribution result.

[0048] The present invention also provides a computer device, including a processor and a memory, the memory is used to store a computer executable program, the processor reads the computer executable program from the memory and executes it, and when the processor executes the computer executable program, it can implement the fuel cell stack cathode gas flow distribution prediction method described in the present invention.

[0049] A computer-readable storage medium is also provided. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the method for predicting the cathode gas flow distribution of a fuel cell stack according to the present invention can be implemented.

[0050] The present invention provides a method for predicting cathode gas flow distribution of a fuel cell stack. The method first calculates the total flow rate and gas properties of the cathode gas of the fuel cell stack, determines the local pressure drop and friction pressure drop of the gas flow in the cathode inlet and outlet manifolds and the cathode flow field of the fuel cell stack, and performs two-phase flow correction on the above two types of pressure drops to consider the influence of the air-water two-phase flow in the cathode flow field and the outlet manifold on the flow distribution; then, based on the conservation of mass and energy, a cathode gas flow network model of the fuel cell stack is established and iterative solution is performed to obtain the flow distribution result of the unit cell. Compared with the prior art, the present invention has at least the following beneficial effects: the flow network model established by the present invention takes into account the electrochemical reaction in the flow channel and the manifold to generate water, is closer to the actual operation of the fuel cell stack, and can quickly and accurately realize the prediction of cathode gas flow distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] To more intuitively and clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for the embodiments. Obviously, the following drawings are only partial embodiments of the invention, and those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0052] Figure 1 Schematic diagram of cathode flow field of proton exchange membrane fuel cell stack in the present invention, in which 1-cathode gas inlet manifold; 2-manifold dead end; 3-unit cell cathode flow field; 4-cathode gas outlet manifold;

[0053] Figure 2 Schematic diagram of the two-phase flow network model in the present invention;

[0054] Figure 3 It is a flowchart of iterative solution of two-phase flow network in the present invention;

[0055] Figure 4 This is the predicted result of the cathode gas flow distribution of each unit cell in the 32-cell stack of the present invention. DETAILED DESCRIPTION

[0056] To make the technical solutions and advantages of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention:

[0057] Figure 1A schematic diagram of the cathode flow field of a fuel cell stack in a method for predicting cathode gas flow distribution of a fuel cell stack provided in an embodiment of the present invention. The cathode flow field of the fuel cell stack includes a cathode gas inlet manifold, a cathode gas outlet manifold and the cathode flow field of each unit cell.

[0058] The cathode flow distribution process is as follows: cathode gas flows from the inlet manifold, then flows to each unit cell from the inlet manifold, and finally converges at the outlet manifold to flow out of the stack. The cathode flow distribution process is dominated by flow resistance, so the stack cathode flow field is simplified to a flow network consisting of flow branches and flow pressure drops, see Figure 2 The electrochemical reaction in the cathode gas outlet manifold and the cathode flow field of each unit cell generates water, and the fluid flow in the above area is in a gas-liquid two-phase flow state.

[0059] The cathode flow fields of two adjacent unit cells and the inlet and outlet manifold sections together constitute a gas flow distribution network, and each flow section produces a corresponding pressure drop. Specifically, the flow pressure drop in the flow network includes the friction pressure drop ΔP in the inlet manifold fm_in , the local pressure drop △P caused by the fluid diversion in the inlet manifold st_in , Local pressure drop △P caused by flow deflection in the inlet manifold c_in , Friction pressure drop △P in the outlet manifold fm_out , the local pressure drop △P caused by the fluid diversion in the outlet manifold st_out , local pressure drop △P caused by flow deflection in the outlet manifold c_out and the voltage drop △P in the cathode flow field of the unit cell ch_total .

[0060] Figure 3 The solution process of the method of the present invention is demonstrated. First, the total flow rate and gas properties of the fuel cell stack cathode are calculated. The local pressure drop and friction pressure drop of the gas flow in the cathode inlet and outlet manifolds and cathode flow field of the fuel cell stack are determined. Two-phase flow corrections are performed on the above two types of pressure drops to consider the influence of the air-water two-phase flow in the cathode flow field and outlet manifold on the flow distribution. Then, based on the conservation of mass and energy, a fuel cell stack cathode gas flow network model is established and iterative solution is performed to obtain the unit cell flow distribution result. The specific implementation of the method of the present invention includes the following steps:

[0061] S1, calculating the total inlet mass flow rate of the cathode gas, the dynamic viscosity of the cathode humidifying air, and the dynamic viscosity of water according to the operating conditions of the fuel cell stack;

[0062] S2, calculating the local pressure drop and friction pressure drop when the cathode gas flows in the fuel cell stack according to the structural parameters of the fuel cell stack;

[0063] S3, two-phase flow correction for local pressure drop and friction pressure drop in the battery cathode flow field and outlet manifold;

[0064] S4, establishing a fuel cell stack cathode gas two-phase flow network model based on the calculated pressure drop results of each part, the stack cathode flow field includes a gas inlet manifold, a gas outlet manifold, and each unit cell, simplifying the stack cathode flow field into a flow network consisting of flow branches and flow pressure drops, and establishing the fuel cell stack cathode gas two-phase flow network model by analyzing the fluid flow resistance relationship in the flow network, and connecting each manifold segment and the unit cell through mass conservation and energy conservation;

[0065] S5. Based on the established flow network model, a numerical solution algorithm for distributing the gas flow to each unit cell in the fuel cell stack is established. The inlet gas flow of each unit cell is iteratively solved by updating the pressure drop of each part until the cathode gas flow distribution result is output after convergence.

[0066] The specific implementation of S1 is as follows:

[0067] Total mass flow rate of cathode gas in the inlet manifold m ca Combined stack oxygen consumption mass flow m O2 , gas molar mass M, relative humidity RH, water vapor saturation vapor pressure P sat and the manifold inlet pressure P c Formula (1) is used to calculate:

[0068]

[0069] Dynamic viscosity of cathode humidified air μ gas and the dynamic viscosity of water μ water Calculated according to the empirical formula.

[0070] The specific implementation of S2 is as follows:

[0071] S21: Establish the friction loss of gas in the manifold △P fm With the gas flow rate U and friction resistance coefficient R fm Relationship:

[0072]

[0073] S22: Establish the local loss of gas diversion in the manifold △P st With the gas flow rate U and the local resistance coefficient R st Relationship:

[0074]

[0075] S23: Establish the local loss of gas deflection in the manifold △P c With the gas flow rate U and the local resistance coefficient R c Relationship:

[0076]

[0077] The friction coefficient R in the above formula (2) is fm According to the Darcy-Weisbach equation, the two local resistance coefficients R in formula (3) and formula (4) are obtained: fm and R st Calculated according to the empirical formula in the hydraulic resistance manual.

[0078] S24: Establish a geometric model of the cathode flow field of the unit cell, obtain the pressure drop at the inlet and outlet of the flow field at different flow rates through fluid dynamics calculation, and further fit it into a quadratic relationship with the gas flow rate to obtain the local pressure loss coefficient A and friction pressure loss coefficient B in the cathode flow channel. The relationship between the flow field pressure drop and flow rate when there is only cathode gas can be calculated according to formula (5):

[0079] ΔP ch_total =AU 2 +BU (5)

[0080] The specific implementation of S3 is as follows:

[0081] S31: The water generated by the electrochemical reaction is stably injected into the cathode flow channel in liquid form. The flow rate of liquid water in the cathode flow field of the unit cell is m water Combining the Faraday constant F, current density j, and the effective active area A of the unit cell, we can calculate it using formula (6):

[0082]

[0083] S32: Obtaining the flow rate U of the generated water based on the calculated water flow rate water , the Lockhart-Martinelli method, an empirical correlation method, is used to perform two-phase flow correction for the friction losses in the cathode flow field and the outlet manifold section. Two-phase flow friction loss multiplier According to formula (7),

[0084]

[0085] The friction pressure drop △P in the flow channel after considering the influence of air-product water two-phase flow ch_fm According to formula (8),

[0086]

[0087] S33: By introducing the Mortazavi parameter χ into the Lockhart-Martinelli method M 2 To calculate the two-phase flow local loss multiplier

[0088]

[0089] Considering the influence of air-product water two-phase flow, the local pressure drop △P in the flow channel ch_local According to formula (10),

[0090]

[0091] The specific implementation of S4 is as follows:

[0092] S41: Based on mass conservation, the inlet gas mass flow rate m of all unit cells cell The sum is equal to the manifold inlet gas mass flow rate m ca , and the gas mass flow rate in the inlet / outlet manifold section of the i-th unit cell is

[0093]

[0094] m mani [i] = m mani [i-1]+m cell [i] (12)

[0095] S42: Based on the conservation of energy, the algebraic sum of the pressure drops of the flow circuit composed of any two adjacent unit cells is 0, satisfying the following relationship:

[0096]

[0097] The specific implementation of S5 is as follows:

[0098] S51: At the initial iteration step, the manifold inlet flow is evenly distributed to each unit cell;

[0099] S52: Based on the total pressure drop on the left side of the flow calculation formula (13) of the current iteration step and the first two pressure drops on the right side, the last pressure drop on the right side is calculated by energy conservation, and the corrected gas mass flow rate m in the i-th battery is deduced. cell_corr , the new gas flow in the i-th battery at the j+1th iteration step:

[0100] [m cell [i]] j+1 =[m cell [i]] j +(m cell_corr [i]-[m cell [i]] j )·F r (14)

[0101] S53: Perform iterative correction on the gas flow of all cells in the stack. The residual value of the algorithm is the sum of the difference between the new flow rate of each cell in the stack and the previous flow rate. The convergence standard is that the residual is less than 10 -12 .

[0102] The calculation results of the flow distribution of 32-cell battery stack using the method of the present invention and the flow network method without considering the influence of two-phase flow are shown in Figure 4 The uneven distribution of cathode gas flow in the fuel cell stack calculated without considering the two-phase flow in the cathode flow field is significantly overestimated. The cathode flow distribution result predicted by the method of the present invention is closer to the actual result. This method can serve as an effective reference for the design of fuel cell stacks.

[0103] In summary, the present invention provides a method for predicting the cathode gas flow distribution of a fuel cell stack. The method first calculates the total flow rate and gas properties of the cathode gas of the fuel cell stack, determines the local pressure drop and friction pressure drop of the gas flow in the cathode inlet and outlet manifolds and the cathode flow field of the fuel cell stack, and performs two-phase flow correction on the above two types of pressure drops to consider the influence of the air-water two-phase flow in the cathode flow field and the outlet manifold on the flow distribution; then, based on the conservation of mass and energy, a cathode gas flow network model of the fuel cell stack is established and iterative solution is performed to obtain the flow distribution results of the unit cell. Compared with the existing technology, the flow network model established by this method takes into account the electrochemical reaction in the flow channel and the manifold to generate water, is closer to the actual operation of the fuel cell stack, and can quickly and accurately realize the prediction of cathode gas flow distribution.

[0104] The present invention can also provide a computer device, including a processor and a memory, the memory is used to store a computer executable program, the processor reads the computer executable program from the memory and executes it, and when the processor executes the computer executable program, it can implement the fuel cell stack cathode gas flow distribution prediction method described in the present invention.

[0105] A computer-readable storage medium is also provided. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the method for predicting the cathode gas flow distribution of a fuel cell stack according to the present invention can be implemented.

[0106] The computer device may be a laptop computer, a desktop computer or a workstation.

[0107] The processor of the present invention may be a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC) or a readily available field programmable gate array (FPGA).

[0108] The memory of the present invention may be an internal storage unit of a laptop computer, desktop computer or workstation, such as a memory or a hard disk; or an external storage unit, such as a mobile hard disk or a flash memory card.

[0109] Computer-readable storage media may include computer storage media and communication media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented by any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer-readable storage media may include: read-only memory (ROM), random access memory (RAM), solid-state drives (SSD) or optical disks, etc. Among them, random access memory may include resistance random access memory (ReRAM) and dynamic random access memory (DRAM).

[0110] The above description is only a preferred embodiment of the present invention, which is used to illustrate the technical solutions and advantages of the present invention. However, the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A method for predicting cathode gas flow distribution of a fuel cell stack, characterized in that: The following steps are involved: Calculating the total inlet mass flow rate of the cathode gas, the dynamic viscosity of the cathode humidification air, and the dynamic viscosity of water according to the operating conditions of the fuel cell stack; The local pressure drop and friction pressure drop during the flow of the cathode gas in the fuel cell stack are calculated based on the structural parameters of the fuel cell stack, the total inlet mass flow rate, the dynamic viscosity of the cathode humidification air, and the dynamic viscosity of water; Combined with the calculation of the two-phase flow loss multiplier, the flow pressure drop in the battery cathode flow field and the outlet manifold is corrected for the two-phase flow; A gas two-phase flow network model of the fuel cell stack cathode flow field is established based on the calculated local pressure drop and friction pressure drop during stack cathode gas flow. The stack cathode flow field includes a gas inlet manifold, a gas outlet manifold, and each unit cell. The manifold segment and the unit cell are connected by mass conservation and energy conservation. That is, the cathode gas two-phase flow network model satisfies the following mass conservation and energy conservation conditions: Inlet gas mass flow rate of all unit cells m cell The sum is equal to the manifold inlet gas mass flow rate m ca , and the first i Gas mass flow rate in the inlet / outlet manifold section of each unit cell m mani satisfy , the algebraic sum of the pressure drops of the flow circuit composed of any two adjacent unit cells is 0, For the i- Gas mass flow rate in one unit cell inlet / outlet manifold segment m mani , is the inlet gas mass flow rate of the i-th unit cell; Based on the established gas two-phase flow network model, a numerical solution algorithm for distributing gas flow to each unit cell in the fuel cell stack is established. The inlet gas flow of each unit cell is iteratively solved by updating the pressure drop of each part until the calculation results converge, and the cathode gas flow distribution result is obtained. Specifically, it includes: At the initial iteration step, the manifold inlet flow is evenly distributed to each unit cell; Based on the flow rate of the current iteration step, calculate the total pressure drop on the left side of the following equation and the first two pressure drops on the right side. Calculate the last pressure drop on the right side according to the law of energy conservation, and inversely deduce the first pressure drop. i Corrected gas mass flow rate in the cell m cell_corr ; No. j +1 iteration step i New flow of gas in the cell: The gas flow rate of all cells in the stack is iteratively corrected. The residual value of the algorithm is the sum of the difference between the new flow rate of each cell in the stack and the previous flow rate. The convergence standard is that the residual is less than 10 -12 .

2. The method for predicting cathode gas flow distribution of a fuel cell stack according to claim 1, characterized in that: Dynamic viscosity of cathode humidified air μ gas and the dynamic viscosity of water μ water Calculated according to the empirical formula.

3. The method for predicting cathode gas flow distribution of a fuel cell stack according to claim 1, wherein: The specific steps of calculating the local pressure drop and friction pressure drop during the cathode flow of the stack include: Establish the friction loss of gas in the manifold △ P fm With gas flow rate U and friction coefficient R fm Relationship: Establish gas diversion in the manifold local loss △ P st With gas flow rate U and the local drag coefficient R st Relationship: Establish the local loss of gas deflection in the manifold △ P c With gas flow rate U and the local drag coefficient R c relationship, The geometric model of the cathode flow field of the unit cell was established. The pressure drop at the inlet and outlet of the flow field at different flow rates was obtained through fluid dynamics calculation. The pressure drop at the inlet and outlet of the flow field at different flow rates was fitted into a quadratic relationship with the gas flow rate to obtain the local pressure loss coefficient in the cathode flow field flow channel. A and friction pressure loss coefficient B , the relationship between the flow field pressure drop and flow velocity when there is only cathode gas is calculated according to the following formula: 。 4. The method for predicting cathode gas flow distribution of a fuel cell stack according to claim 1, wherein: Total mass flow rate of cathode gas at the stack manifold inlet m ca Combined with the stack oxygen consumption mass flow m O2 , gas molar mass M , relative humidity RH , water vapor saturation vapor pressure P sat and manifold inlet pressure P c Calculated by the following formula: in, 、 、 They represent the molecular molar masses of oxygen, nitrogen, and water vapor, respectively.

5. The method for predicting cathode gas flow distribution of a fuel cell stack according to claim 1, wherein: The specific steps of calculating the two-phase flow loss multiplier include: Assume that the water generated by the electrochemical reaction is stably injected into the cathode flow channel in liquid form; Obtain the flow rate of generated water based on the water flow generated by the chemical reaction U water , two-phase flow friction loss multiplier φ s 2 and the two-phase flow local loss multiplier φ b 2 The calculation formula is, （5） （6） in, μ gas and μ water The dynamic viscosity of the cathode gas and the dynamic viscosity of water are respectively calculated according to the empirical formula. μ gas and the dynamic viscosity of water μ water ; U gas and U water are the flow rates of cathode gas and produced water, respectively, χ M 2 is the Mortazavi parameter; When performing two-phase flow correction on the flow pressure drop in the battery cathode flow field and outlet manifold by combining the calculation of the two-phase flow loss multiplier: The friction pressure drop in the flow channel after considering the influence of air-product water two-phase flow P ch_fm Calculated according to the following formula: Considering the influence of air-product water two-phase flow, the local pressure drop in the flow channel △ P ch_local Calculated according to the following formula: 。 6. A fuel cell stack cathode gas flow distribution prediction system based on a two-phase flow network model, characterized in that: It includes calculation module, correction module, model building module and solution module; The calculation module is used to calculate the total inlet mass flow rate of the cathode gas, the dynamic viscosity of the cathode humidified air, and the dynamic viscosity of water according to the operating conditions of the fuel cell stack; and at the same time, calculate the local pressure drop and friction pressure drop when the cathode gas flows in the fuel cell stack according to the structural parameters of the fuel cell stack and the total inlet mass flow rate, the dynamic viscosity of the cathode humidified air, and the dynamic viscosity of water; The correction module is used to perform two-phase flow correction on the flow pressure drop in the battery cathode flow field and the outlet manifold by combining the calculation of the two-phase flow loss multiplier; The model building module is used to establish a gas two-phase flow network model of the fuel cell stack cathode flow field based on the calculated local pressure drop and friction pressure drop during the stack cathode gas flow. The stack cathode flow field includes a gas inlet manifold, a gas outlet manifold, and each unit cell. The manifold segment and the unit cell are connected by mass conservation and energy conservation. That is, the cathode gas two-phase flow network model satisfies the following mass conservation and energy conservation conditions: Inlet gas mass flow rate of all unit cells m cell The sum is equal to the manifold inlet gas mass flow rate m ca , and the first i Gas mass flow rate in the inlet / outlet manifold section of each unit cell m mani satisfy ,; the algebraic sum of the pressure drops of the flow circuit composed of any two adjacent unit cells is 0, For the i- Gas mass flow rate in one unit cell inlet / outlet manifold segment m mani , is the inlet gas mass flow rate of the i-th unit cell; The solution module is used to establish a numerical solution algorithm for distributing gas flow to each unit cell in the fuel cell stack based on the established gas two-phase flow network model. The inlet gas flow of each unit cell is iteratively solved by updating the pressure drop of each part until the calculation results converge to obtain the cathode gas flow distribution result. Specifically, it includes: At the initial iteration step, the manifold inlet flow is evenly distributed to each unit cell; Based on the flow rate of the current iteration step, calculate the total pressure drop on the left side of the following equation and the first two pressure drops on the right side. Calculate the last pressure drop on the right side according to the law of energy conservation, and inversely deduce the first pressure drop. i Corrected gas mass flow rate in the cell m cell_corr ; No. j +1 iteration step i New flow of gas in the cell: The gas flow rate of all cells in the stack is iteratively corrected. The residual value of the algorithm is the sum of the difference between the new flow rate of each cell in the stack and the previous flow rate. The convergence standard is that the residual is less than 10 -12 .

7. A computer device, characterized in that: It includes a processor and a memory, the memory is used to store a computer executable program, the processor reads the computer executable program from the memory and executes it, and when the processor executes the computer executable program, it can implement the fuel cell stack cathode gas flow distribution prediction method described in any one of claims 1-5.

8. A computer-readable storage medium, characterized in that A computer program is stored in the computer-readable storage medium. When the computer program is executed by a processor, the method for predicting cathode gas flow distribution of a fuel cell stack as claimed in any one of claims 1 to 5 can be implemented.

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