High-performance hydrogen fuel cell numerical simulation research method based on magnetic-flow-thermal multi-physics field coupling

Abstract

The invention discloses a numerical simulation research method for a high-performance hydrogen fuel cell based on magnetic-flow-thermal multi-physics field coupling. The method comprises the following steps: globally defining geometric dimensions and physical performance parameters of the fuel cell; constructing a high-performance hydrogen fuel cell three-dimensional model with permanent magnets arranged at the cathode and anode, and creating a geometric domain; defining a magnetic field coupling equation expression; adding material attributes and physical fields, selecting a solution domain for each physical field, and setting boundary conditions and parameters according to a control equation of the added physical field; grid division is carried out on the constructed three-dimensional model, a domain probe is added, and grid independence verification is carried out; research steps are determined, steady-state calculation is carried out on the coupled model, post-processing is carried out on result data, and a state curve or image is obtained. A numerical simulation method is utilized, a coupling model of the hydrogen fuel cell, multiphase flow, solid and fluid heat transfer and the magnetic field is constructed, the action and influence mechanism of the magnetic field on other physical fields is researched, and the performance of the fuel cell is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physical field coupling. Background Art

[0002] With the rapid development of my country's economy, the consumption of non-renewable energy has increased dramatically year by year, and the emissions it produces will cause air pollution, water pollution, climate change and other hazards, which have a great impact on human health and the living environment. Therefore, it is extremely necessary to explore a new energy source that is environmentally friendly and sustainable. Hydrogen fuel cells, as a highly potential clean energy conversion device, use renewable energy hydrogen as fuel and convert chemical energy into electrical energy through electrochemical reactions. It has significant advantages such as high energy conversion efficiency and zero emissions, and is regarded as a key component of the future energy system.

[0003] Hydrogen fuel cells involve complex physical and chemical processes, including multiphase flow, heat and mass transfer, electrochemical reactions and other mutually coupled phenomena. These processes occur simultaneously and influence each other at the micro and macro scales, which makes experimental research face many challenges, such as high experimental costs, long cycles, difficult measurements, and difficulty in fully obtaining changes in the internal behavior of the battery. Numerical simulation research provides a powerful means to deeply explore the internal mechanism of hydrogen fuel cells. By establishing accurate mathematical models, numerical simulation can comprehensively and systematically study the distribution and interaction of various physical fields inside hydrogen fuel cells, revealing important information such as the diffusion laws of gases in flow channels and porous media, the generation and transfer paths of heat, the kinetic characteristics of electrochemical reactions, and the collaborative working mechanism between different components. This not only helps to deepen the understanding of the working principles of hydrogen fuel cells, but also provides a theoretical basis for their optimized design.

[0004] Patent CN116467913A discloses a numerical simulation method for solid oxide fuel cells, which is characterized by coupling four physical field interfaces: hydrogen fuel cells, free and porous media flow, porous media heat transfer, and solid mechanics, to achieve the modeling and simulation process of multi-physical field coupling of solid oxide fuel cells. However, this method only performs coupled modeling and analysis from the physical field of the solid oxide fuel cell itself, and does not explore the impact of other external physical fields on the solid oxide fuel cell.

[0005] Patent CN111079337A discloses a multi-physical field coupling simulation method for a proton exchange membrane fuel cell, comprising the following steps: S1: performing coupled steady-state simulation calculations on the multi-physical fields in the isothermal proton exchange membrane fuel cell; S2: coupling the solid heat transfer physical field according to the steady-state simulation results obtained in step S1, and calculating the heat generation temperature distribution of the isothermal battery; S3: combining the cooling medium flow field and the heat generation temperature distribution results obtained in step S2, coupling and inversely calculating the working parameters of the cooling medium flow field under isothermal steady-state operation. This simulation method uses the temperature field and the fluid field to perform distributed coupling calculations to study the influence of the cooling medium flow field on the battery temperature under isothermal steady-state operation. However, the temperature of the proton exchange membrane fuel cell changes during actual operation, and the temperature change will also affect the electrochemical reaction of the battery. Therefore, the study of isothermal steady-state working conditions is limited. In addition, this patent still does not study the influence of the physical field outside the proton exchange membrane fuel cell coupling itself on its mass transfer, heat transfer, electrochemical reaction and many other aspects, and secondly, it does not consider the optimization design for improving the performance of the fuel cell.

[0006] At present, traditional hydrogen fuel cells face many challenges in terms of performance improvement and operation stability optimization. There are technical difficulties such as limited improvement of battery power density, uneven gas distribution in the flow channel, and difficulty in timely discharge of water generated at the membrane electrode. The hydrogen and oxygen fuels and the product water in the hydrogen fuel cell are magnetic substances. In the magnetic field environment, they will be affected by the Lorentz force and Kelvin force, which can increase the speed of the gas in the flow channel, intensify the convection and diffusion between molecules, promote the discharge of products, and leave more pore space in the porous electrode, thereby accelerating the redox reaction, reducing battery polarization, and improving the performance of the fuel cell; at the same time, the Maxwell stress effect can affect the electrochemical reaction, change the interaction between the electrode and the electrolyte, and improve the catalytic performance. In this regard, a magnetic field is introduced outside the hydrogen fuel cell, and a coupling model of hydrogen fuel cells, multiphase flow, solid and fluid heat transfer, and magnetic field is constructed using numerical simulation methods. The role and influence of the magnetic field on other physical fields and the mechanism of hydrogen fuel cell performance improvement are studied in depth from a microscopic perspective to make up for the shortcomings of experimental research.

[0007] Therefore, how to provide a numerical simulation research method that can couple the complex multi-physical fields of the hydrogen fuel cell itself and optimize the design of the battery by coupling the external magnetic field physical field with the hydrogen fuel cell to improve the working performance of the battery is an urgent problem that technicians in this field need to solve. Summary of the invention

[0008] In response to existing technical problems or improvement needs, the present invention provides a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physical field coupling, which aims to explore the role and influence of the magnetic field on other physical fields and the mechanism of improving the performance of hydrogen fuel cells from a microscopic perspective, make up for the shortcomings of experimental research, and provide a reliable numerical simulation research method for studying the performance improvement and optimal design of hydrogen fuel cells.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling, including:

[0011] Globally define the geometric dimensions and physical performance parameters of high-performance hydrogen fuel cells;

[0012] Construct a 3D simulation model of a high-performance hydrogen fuel cell with permanent magnets arranged at the cathode and anode according to the defined geometric size parameters, and create a specific geometric domain;

[0013] Define and add the magnetic field and hydrogen fuel cell coupling equation expressions;

[0014] Add the material properties and physical fields required for the 3D simulation model, select the corresponding solution domain for each physical field, and set its boundary conditions and parameters according to the control equations of the added physical field;

[0015] Mesh the constructed 3D simulation model, add domain probes, and perform mesh independence verification;

[0016] Determine the research steps, perform steady-state calculations on the coupled model, post-process the result data, and obtain state curves or images.

[0017] Preferably, the globally defined geometric dimensions include: the length, width, and height of the battery cathode and anode flow channels, the rib width, the thickness of the gas diffusion layer, the gas diffusion electrode, and the proton exchange membrane, the length and height of the permanent magnet, and the distance between the permanent magnet and the flow channel;

[0018] The globally defined physical property parameters include: inlet mole fraction, temperature and velocity of water, hydrogen, oxygen and nitrogen, stoichiometry, transfer coefficient, reference exchange current density and active specific surface area of ​​cathode and anode, conductivity, potential and volume fraction of electrolyte, porosity, permeability, conductivity and gas pore volume fraction of gas diffusion layer, thermal conductivity, density, constant pressure heat capacity and specific heat rate of proton exchange membrane and fluid in flow channel, reference pressure and reference temperature of cathode and anode gas flow channel, residual magnetic flux density and conductivity of magnet.

[0019] Preferably, the constructed high-performance hydrogen fuel cell three-dimensional simulation model with permanent magnets arranged at the cathode and anode includes: a cathode permanent magnet, a cathode flow channel, a cathode gas diffusion layer, a cathode gas diffusion electrode, a proton exchange membrane, an anode gas diffusion electrode, an anode gas diffusion layer, an anode flow channel, an anode permanent magnet and an air domain;

[0020] The specific geometric domain created includes: an anode inlet, a cathode inlet, an anode outlet, a cathode outlet, an anode chamber, a cathode chamber and a membrane electrode, so as to be used for setting the physical field.

[0021] Preferably, the functions of the air domain are: the air domain serves as a medium for magnetic field propagation and a boundary condition for other objects; and provides a real simulation environment to better simulate the distribution and interaction of magnetic fields.

[0022] Preferably, the definition and addition of the magnetic field coupling equation expression specifically includes:

[0023] The expression of concentration overpotential is:

[0024]

[0025] In formula (1), ε is the concentration overpotential, R is the gas constant, T is the thermodynamic temperature, β is the number of electrons transferred in the electrode reaction, F is the Faraday constant, I is the net current density, and I d The limiting diffusion current density, where the limiting diffusion current density I d for:

[0026]

[0027] In formula (2), n is the chemical valence of the ion, F is the Faraday constant, D is the diffusion coefficient, C is the concentration of the reaction ions, and δ is the thickness of the retention layer. The magnetohydrodynamic effect generated by the combined action of the working current and the magnetic field will form a forced flow, and the forced convection phenomenon will reduce the thickness of the retention layer δ, thereby making the limiting diffusion current I d Become bigger;

[0028] Kelvin force acts on magnetic materials, thus affecting their electrocatalytic activity, accelerating mass transfer, and increasing limiting current:

[0029]

[0030] In formula (3), F k is the Kelvin force, μ0 is the vacuum permeability (4π×10 -7 H / m), is the magnetic induction gradient, χ m and c are the molar magnetic susceptibility and the concentration of electroactive species in the bulk solution, respectively;

[0031] Maxwell stress is the force generated by the interaction between the magnetic field and magnetic media such as hydrogen and oxygen, and can be described by the magnetic stress tensor:

[0032]

[0033] In formula (4), T ij is the Maxwell stress tensor, ε0 is the dielectric constant, μ0 is the vacuum permeability, E i 、E j is the component of the electric field strength E in the i and j directions, B i , B j is the component of magnetic induction intensity B in the i and j directions, δ ij is the Kronecker function; the Maxwell stress effect affects the electrochemical double layer, changes the interaction between the electrode and the electrolyte, and improves the electrocatalytic reaction;

[0034] Electromagnetic force per unit volume F f and the Maxwell stress tensor T ij The relationship is:

[0035]

[0036] In formula (5), is the vector differential operator, S is the Poynting vector, which is used to describe the vector of electromagnetic energy flux density;

[0037] The force expression of electrons in non-uniform electromagnetic fields is:

[0038]

[0039] In formula (6), F e is the force on the electron, q is the charge of the electron, E is the electric field strength, v is the electron speed, B is the magnetic induction intensity, μ ⊥ is the magnetic moment, is the magnetic induction gradient;

[0040] The expressions of the components of the volume force F exerted on the magnetic fluid in the magnetic field environment in various directions are:

[0041]

[0042] In formula (7), F x 、F y 、F z is the volume force on the magnetic fluid in the x, y, and z directions, μ0 is the magnetic permeability in vacuum, H x , H y , H z are the magnetic field strengths in the x, y, and z directions, respectively, M x 、M y 、Mz They are the magnetization intensities in the x, y, and z axes respectively. The magnetization intensity of the magnetic material is M = B r / μ0, where B r is the residual flux density of the permanent magnet.

[0043] Preferably, the material properties required for adding the three-dimensional simulation model include: adding neodymium iron boron magnet material to the cathode permanent magnet and the anode permanent magnet, adding oxygen material to the cathode flow channel, the cathode gas diffusion layer and the cathode gas diffusion electrode, adding hydrogen material to the anode flow channel, the anode gas diffusion layer and the anode gas diffusion electrode, adding perfluorosulfonic acid ion exchange membrane material to the proton exchange membrane, and adding air material to the air domain;

[0044] The physical fields required for adding a three-dimensional simulation model include: the hydrogen fuel cell physics interface in electrochemistry, the free and porous media flow physics interface in cathode and anode fluid flow, the solid and fluid heat transfer physics interface in heat transfer, and the magnetic field physics interface in electromagnetics.

[0045] Preferably, the hydrogen fuel cell physical field in the electrochemistry is used to obtain the electrochemical reaction, current density distribution, proton conduction and gas diffusion inside the fuel cell;

[0046] The free and porous medium flow physical fields in the cathode and anode fluid flows use the Navier-Stokes equation to accurately describe the fluid flow in the free area and use the Brinkman equation or Darcy's law to describe the fluid flow in the porous medium, so as to achieve the coupling of fluid flows in different areas and ensure the continuity of physical quantities, and to obtain the pressure change, gas flow distribution, velocity field distribution and material transfer inside the fuel cell;

[0047] The solid and fluid heat transfer physical fields in the heat transfer are used to obtain the temperature field distribution inside the fuel cell. By simulating heat conduction, the influence of thermal conductivity between different solid materials on the overall thermal performance of the battery can be determined. Good heat transfer can reduce temperature gradients, reduce thermal stress, and improve the thermal stability of the battery.

[0048] The magnetic field physics field in the electromagnetics is coupled with the hydrogen fuel cell of the complex multi-physics field, and acts on the magnetic materials such as hydrogen and oxygen in the flow channel, so that they flow in the magnetic field environment and are affected by the Lorentz force and the Kelvin force, generating a magnetofluid effect, affecting the flow state and improving the material transport. At the same time, it changes the movement path of the charged particles in the magnetic field, improves the electric field distribution on the electrode surface and the concentration distribution of the reaction substances, thereby affecting the open circuit voltage and polarization curve of the battery; secondly, the Maxwell stress effect generated can affect the electrochemical reaction, change the interaction between the electrode and the electrolyte, and improve the catalytic performance.

[0049] Preferably, the selecting a corresponding solution domain for each added physical field includes:

[0050] The solution domains of the hydrogen fuel cell physics field in electrochemistry include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains;

[0051] The solution domains selected for the free and porous media flow physics in the cathode fluid flow include: cathode flow channel, cathode gas diffusion layer, cathode gas diffusion electrode;

[0052] The solution domains selected for the free and porous media flow physics in the anode fluid flow include: anode flow channel, anode gas diffusion layer, anode gas diffusion electrode;

[0053] The solution domains of solid and fluid heat transfer physics in heat transfer include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, and proton exchange membranes;

[0054] The solution domains selected for the magnetic field physics field in electromagnetics include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains.

[0055] Preferably, both the gas phase (hydrogen and oxygen) and the liquid phase (water) need to satisfy the mass conservation law, and the equations that need to be followed for diffusion in the porous medium and flow in the free flow region are as follows:

[0056]

[0057] In formula (8), is the vector differential operator, ρ is the fluid density, u is the velocity vector of the fluid flow, S m Represents the mass loss or gain caused by the electrochemical reaction occurring in the porous electrode;

[0058] Ohm's law models the electrochemical current and explains the ion transport in the electrolyte and the electron transport in the electrode. The activation loss produced is an important component of the electrochemical reaction:

[0059]

[0060] In formula (9), is the vector differential operator, σ i is the effective conductivity of electrolyte or gas ions, φ i is the potential of the electrode or electrolyte, Q i is the charge source term;

[0061] In porous electrodes, the local current density depends on the ion and electron potentials, but is also related to the local reactant concentration and temperature. The Butler--Volmer equation is used to simulate the electrode reaction kinetics in the cathode and anode to calculate the exchange current density of the cathode and anode:

[0062]

[0063]

[0064] in,

[0065]

[0066] In formula (10-13), i c,ct and i a，ct are the polarization current densities of the cathode and anode, respectively, i 0，c and i 0，a are the exchange current densities of the cathode and anode respectively, F is the Faraday constant, R is the molar gas constant, T is the operating temperature of the battery, C i represents the molar concentration of substance i, C i.ref represents the reference molar concentration of substance i, x02 is the molar fraction of oxygen, η is the overpotential, and n is the number of electrons transferred;

[0067] The Navier-Stokes equations are used to accurately describe the fluid flow in the free region and solve the velocity and pressure fields in the cathode and anode channels:

[0068]

[0069] In formula (14), ρ is the density, u is the velocity vector, is the vector differential operator, p is the pressure, μ is the fluid viscosity, I is the unit matrix, and F is the introduced volume force vector;

[0070] To solve the momentum transfer in the porous media region, it is necessary to correctly consider the relevant parameters such as the number of electrode pores and the size. The Darcy-Brinkman equation, a combination of continuity and momentum conservation laws, is used to perform momentum analysis in the porous media region to obtain the velocity and pressure distribution in the porous media region:

[0071]

[0072] In formula (15-16), ε is the porosity, ρ is the density, is the vector differential operator, u is the velocity vector, Q brrepresents the mass source, p is the pressure, μ is the fluid viscosity, I is the unit matrix, κ is the permeability of the porous medium, and F is the introduced volume force vector, where ε and κ are both dimensionless;

[0073] The convection and diffusion of gases in hydrogen fuel cells affect mass transport. The mass transport in the free domain and porous electrode region of the cell is simulated by the following mass transport equation:

[0074]

[0075] In formula (17-18), ρ is the density of the mixed gas, ω i is the mass fraction of component i, is a vector differential operator, j i is the diffusion mass flux of component i, u is the average velocity of the mixture, R i is the generation and consumption of component i, D e.ik is the effective diffusion coefficient in the porous medium, x k is the mole fraction of component k, w k is the mass fraction of component k, P A For pressure, is the thermal diffusion coefficient, T is the temperature, j i It plays a decisive role in the material transport between the cathode and the anode, and its size is mainly affected by the material concentration and temperature gradient;

[0076] Since the electrochemical reaction of the fuel cell generates heat, the heat generated will be transferred between the various components of the battery. The energy conservation equation is used to describe the transfer and conversion of heat:

[0077]

[0078] In formula (19), ρ is the material density, C P is the specific heat capacity, u is the velocity vector, T is the temperature, k is the thermal conductivity, and Q is the heat source term, which mainly comes from the heat generated by the electrochemical reaction.

[0079] Preferably, the step of setting boundary conditions and parameters according to the control equation of the added physical field includes:

[0080] The boundary conditions at the cathode and anode flow channel inlets were set to fully developed flow and mean inflow velocity;

[0081] The boundary conditions at the cathode and anode flow channel outlets are set to pressure, which is 1 atm;

[0082] The boundary conditions of the model walls were set to no slip;

[0083] The boundary conditions of fluid flow were set as compressible flow (Ma < 0.3);

[0084] The mixed gas introduced into the anode inlet is set to be composed of hydrogen and water vapor, and the mixed gas introduced into the cathode inlet is set to be composed of oxygen, nitrogen and water vapor, and the anode and cathode outlet boundaries are defined as convection flux;

[0085] Potential boundary conditions: set the upper surface potential of the anode gas diffusion layer to 0 V, and the upper surface boundary potential of the cathode gas diffusion layer to the battery voltage;

[0086] In the heat transfer part, the inlet fluid boundary conditions of the anode and cathode flow channels are set to the initial temperature T in ; The outer surfaces of the cathode and anode flow channels are set to convective heat flux;

[0087] In the magnetic field part, the outer surface of the air domain is set to magnetic insulation; the orientation method of the cathode and anode permanent magnets is set to specify the north and south boundaries.

[0088] Preferably, the meshing of the constructed three-dimensional simulation model is specifically as follows: selecting the flow channel inlet or flow channel outlet end face of the three-dimensional simulation model as the base face, dividing the edges of the end faces of different domains by size or distribution, using mapping to create a two-dimensional grid, and then sweeping the grid along the flow channel direction to complete the hexahedral grid division, and then using free tetrahedral grid division for the cathode and anode permanent magnets and the air domain to generate the structure and unstructured grid of the entire simulation model; the hexahedral grid division gradually becomes denser along the cathode gas diffusion layer and the anode gas diffusion layer toward the proton exchange membrane; the grids of the anode flow channel and the cathode flow channel are evenly distributed; the grid density of the cathode gas diffusion electrode and the anode gas diffusion electrode is the largest and evenly distributed, and the grid density of the proton exchange membrane is second;

[0089] The adding of the domain probe specifically includes: adding an integral probe for calculating the electrochemical current density, and the source is selected as the anode gas diffusion electrode;

[0090] The grid independence verification is specifically as follows: different numbers of grid divisions are performed on the three-dimensional simulation model, and under the condition of the same battery voltage, the change of the output average current density with different numbers of grids and the relative error are calculated and compared to determine the best grid division model.

[0091] Preferably, the determining of the research steps and performing steady-state calculations include: first solving the secondary current distribution, then respectively solving the cathode and anode free and porous media flows to obtain the velocity field and pressure field distributions, solving the solid and fluid heat transfer to obtain the temperature field distribution, and finally coupling each physical field with the magnetic field to perform steady-state calculations.

[0092] Preferably, the acquiring of the state curve or image comprises: post-processing the simulation result data in the form of a curve graph, a two-dimensional or three-dimensional distribution graph or a chart.

[0093] Compared with the prior art, the present invention discloses a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physical field coupling, which has the following beneficial effects:

[0094] 1. The numerical simulation method provided by the present invention, in addition to coupling the complex physical field of the hydrogen fuel cell itself, realizes the complex coupling of the magnetic field physical field and the hydrogen fuel cell, filling the gap in the simulation field of the coupling of the magnetic field and the hydrogen fuel cell, and can effectively promote the multiphase flow, heat and mass transfer and electrochemical physical and chemical processes in the hydrogen fuel cell, improve the temperature, pressure, speed, gas and water distribution inside the hydrogen fuel cell, reduce the activation loss and ohmic loss of the hydrogen fuel cell, and at the same time improve the output performance of the fuel cell, so that the hydrogen fuel cell has high performance.

[0095] 2. The present invention uses numerical simulation to build simulation models of hydrogen fuel cells, multiphase flow, solid and fluid heat transfer, and magnetic field multi-physics field coupling, which enables in-depth research on the interactions and influences between various physical fields from a microscopic perspective, making up for the shortcomings of experimental research, and providing a reliable numerical simulation research method for studying the performance improvement and optimization design of hydrogen fuel cells. Through multi-physics field coupling simulation, the performance changes of batteries under different working conditions can be accurately predicted, the experimental trial and error costs and cycles can be reduced, the optimal operating parameter combination can be quickly screened, and the research and development efficiency of hydrogen fuel cells can be greatly improved.

[0096] 3. The present invention has carried out parameterized global definition for the geometric dimensions, physical performance parameters, boundary conditions, etc. of the model, so that the same model framework can quickly simulate hydrogen fuel cells under different specifications, materials and working conditions by simply modifying the parameter values, greatly expanding the scope of application of the model. In terms of optimization design, it is possible to systematically adjust each parameter and observe the changes in the simulation results, accurately locate the key parameters that affect the battery performance, and thus provide a clear research direction for optimizing the battery structure and material selection. In terms of parameter sensitivity, a parameter can be changed within a certain range with the help of parameterized text. According to the degree of influence of the change in parameter value on the battery output performance, it helps to distinguish the primary from the secondary and focus on the key influencing parameters.

[0097] 4. The present invention introduces a magnetic field into a complex multi-physical field coupled hydrogen fuel cell system. The introduction of a magnetic field can increase the speed of gas in the flow field channel, intensify the convection and diffusion between molecules, and the magnetic force can effectively promote the discharge of water, leaving more pore space in the porous electrode, accelerating the redox reaction, reducing battery polarization, and improving battery performance. Using numerical simulation methods, it is possible to accurately reveal the coordinated regulation mechanism of the magnetic field on the fluid transmission and heat transfer process, provide a basis for optimizing the internal flow channel and electrode structure of the battery, effectively improve the diffusion uniformity and reaction activity of the reactants, and realize an in-depth exploration of the role and influence of the magnetic field on other physical fields and the mechanism of improving the performance of hydrogen fuel cells from a microscopic perspective.

[0098] 5. The high-performance hydrogen fuel cell model based on magnetic-fluid-thermal multi-physical field coupling constructed by the present invention can be used to optimize the design of parameters and layout of the external magnetic field. At the same time, it can optimize the design of flow field structure and parameters for irregular flow channels such as straight flow channels, serpentine flow channels, wavy flow channels and flow channels with obstacles, so as to maximize the working performance of hydrogen fuel cells and provide theoretical guidance for the physical and chemical phenomena inside hydrogen fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0100] Figure 1 A schematic diagram of the structure of a single cell of a high-performance hydrogen fuel cell direct current channel based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0101] Figure 2 A schematic diagram of the structure of a high-performance hydrogen fuel cell single-channel three-dimensional simulation model based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0102] Figure 3 A cross-sectional view of the structure of a high-performance hydrogen fuel cell single-channel three-dimensional simulation model based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0103] Figure 4 The effect diagram of meshing of the three-dimensional simulation model of a single-channel high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0104] Figure 5 Output characteristic curve diagram of a single flow channel of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0105] Figure 6 The pressure field distribution diagram in a single flow channel of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0106] Figure 7 The temperature field distribution diagram in a single flow channel of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0107] Figure 8 A distribution diagram of hydrogen in a single flow channel of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling provided by the present invention;

[0108] Fig. 9 The distribution diagram of water in a single flow channel of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physical field coupling provided by the present invention.

[0109] Reference numerals

[0110] 1. Cathode permanent magnet; 2. Cathode flow channel; 3. Cathode gas diffusion layer; 4. Cathode gas diffusion electrode; 5. Proton exchange membrane; 6. Anode gas diffusion electrode; 7. Anode gas diffusion layer; 8. Anode flow channel; 9. Anode permanent magnet; 10. Air domain. DETAILED DESCRIPTION

[0111] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0112] The embodiment of the present invention discloses a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling, comprising the following steps:

[0113] Step 1: Globally define the geometric dimensions and physical performance parameters of the high-performance hydrogen fuel cell;

[0114] Step 2: construct a three-dimensional simulation model of a high-performance hydrogen fuel cell with permanent magnets arranged at the cathode and anode according to the defined geometric size parameters, and create a specific geometric domain;

[0115] Step 3: Define and add the magnetic field and hydrogen fuel cell coupling equation expressions;

[0116] Step 4: Add the material properties and physical fields required for the 3D simulation model, select the corresponding solution domain for each physical field, and set its boundary conditions and parameters according to the control equations of the added physical fields;

[0117] Step 5: Mesh the constructed 3D simulation model, add domain probes, and perform mesh independence verification;

[0118] Step 6: Determine the research steps, perform steady-state calculations on the coupled model, post-process the result data, and obtain state curves or images.

[0119] The embodiment of the present invention takes a high-performance hydrogen fuel cell direct current channel single cell based on magnetic-fluid-thermal multi-physics field coupling as an example. Figure 1 As shown. COMSOL Multiphysics finite element software is used to globally define the geometric dimensions and physical performance parameters required in the numerical simulation process. A three-dimensional simulation model of a hydrogen fuel cell direct current channel with magnets arranged at the cathode and anode is constructed according to the defined geometric dimension parameters. A specific geometric domain is created and the magnetic field and hydrogen fuel cell coupling equation expression is defined. Then, material properties and the required physical field modules are added, and each physical field solution domain and boundary conditions are assigned. Then, meshing is performed, domain probes are added, and mesh independence verification is carried out. Finally, the solution steps of the solver are set and steady-state calculations are performed, and the calculation results are visualized. Compared with the existing numerical simulation methods, the technical solution of the present invention can promote the coupling of multiple physical fields such as electrochemistry, temperature field, flow field and material diffusion in hydrogen fuel cells by coupling the magnetic field physical field with the physical field involved in hydrogen fuel cells, which can effectively improve the distribution of temperature, pressure, gas and water inside the battery, and at the same time improve the output performance of the battery; the use of parameterized global definition settings can quickly simulate hydrogen fuel cells under different specifications, materials and working conditions, greatly expanding the scope of application of the model.

[0120] The flow field structure of the embodiments of the present invention includes, but is not limited to, straight flow channels, serpentine flow channels, wavy flow channels, lattice flow channels, and irregular flow channels such as obstacle-applied flow channels.

[0121] In one embodiment, in step 1, when the geometric dimensions and physical performance parameters of the hydrogen fuel cell are globally defined, each parameter is named and described in words, and a corresponding numerical value is assigned.

[0122] The globally defined geometric dimensions include: the length, width, and height of the battery cathode and anode flow channels, the rib width, the thickness of the gas diffusion layer, the gas diffusion electrode, and the proton exchange membrane, the length and height of the permanent magnet, and the distance between the permanent magnet and the flow channel;

[0123] The globally defined physical property parameters include: inlet mole fraction, temperature and velocity of water, hydrogen, oxygen and nitrogen, stoichiometry, transfer coefficient, reference exchange current density and active specific surface area of ​​cathode and anode, conductivity, potential and volume fraction of electrolyte, porosity, permeability, conductivity and gas pore volume fraction of gas diffusion layer, thermal conductivity, density, constant pressure heat capacity and specific heat rate of proton exchange membrane and fluid in flow channel, reference pressure and reference temperature of cathode and anode gas flow channel, residual magnetic flux density and conductivity of magnet.

[0124] By adopting parametric global definition, the construction of the following three-dimensional simulation model and the setting of various physical field parameters are facilitated, making the modeling process more efficient and convenient. At the same time, the numerical simulation research of the model framework under different specifications, sizes and working conditions can be realized.

[0125] In the embodiment of the scheme of the present invention, in step 2, a high-performance hydrogen fuel cell three-dimensional simulation model with permanent magnets arranged at the cathode and anode is constructed. Considering the reduction of the finite element calculation amount of the three-dimensional simulation model, a method of simulating and calculating one of the single flow channels and using a no-slip boundary for the model wall is adopted, such as Figure 2 and Figure 3 As shown, it is composed of a cathode permanent magnet 1, a cathode flow channel 2, a cathode gas diffusion layer 3, a cathode gas diffusion electrode 4, a proton exchange membrane 5, an anode gas diffusion electrode 6, an anode gas diffusion layer 7, an anode flow channel 8, an anode permanent magnet 9 and an air region 10.

[0126] The air domain 10 in the simulation model serves as a medium for magnetic field propagation and a boundary condition for other objects, and also provides a real simulation environment to better simulate the distribution and interaction of the magnetic field.

[0127] Since the geometric dimensions of the model are globally defined in step 1, the defined name can be directly called to complete the construction of the specific structure and size of the 3D simulation model.

[0128] Among them, a specific geometric domain is created according to the constructed three-dimensional simulation model, including the anode inlet, cathode inlet, anode outlet, cathode outlet, anode chamber, cathode chamber and membrane electrode, so as to be used for the setting of the physical field.

[0129] In one embodiment, in step 3, defining and adding the magnetic field and hydrogen fuel cell coupling equation expression specifically includes:

[0130] The expression of concentration overpotential is:

[0131]

[0132] In formula (1), ε is the concentration overpotential, R is the gas constant, T is the thermodynamic temperature, β is the number of electrons transferred in the electrode reaction, F is the Faraday constant, I is the net current density, and I d The limiting diffusion current density, where the limiting diffusion current density I d for:

[0133]

[0134] In formula (2), n is the chemical valence of the ion, F is the Faraday constant, D is the diffusion coefficient, C is the concentration of the reaction ions, and δ is the thickness of the retention layer. The magnetohydrodynamic effect generated by the combined action of the working current and the magnetic field will form a forced flow, and the forced convection phenomenon will reduce the thickness of the retention layer δ, thereby making the limiting diffusion current I d Become bigger;

[0135] Kelvin force acts on magnetic materials, thus affecting their electrocatalytic activity, accelerating mass transfer, and increasing limiting current:

[0136]

[0137] In formula (3), F k is the Kelvin force, μ0 is the vacuum permeability (4π×10 -7 H / m), is the magnetic induction gradient, χ m and c are the molar magnetic susceptibility and the concentration of electroactive species in the bulk solution, respectively;

[0138] Maxwell stress is the force generated by the interaction between the magnetic field and magnetic media such as hydrogen and oxygen, and can be described by the magnetic stress tensor:

[0139]

[0140] In formula (4), T ij is the Maxwell stress tensor, ε0 is the dielectric constant, μ0 is the vacuum permeability, E i 、E j is the component of the electric field strength E in the i and j directions, B i , B j is the component of magnetic induction intensity B in the i and j directions, δ ij is the Kronecker function; the Maxwell stress effect affects the electrochemical double layer, changes the interaction between the electrode and the electrolyte, and improves the electrocatalytic reaction;

[0141] Electromagnetic force per unit volume F f and the Maxwell stress tensor T ij The relationship is:

[0142]

[0143] In formula (5), is the vector differential operator, S is the Poynting vector, which is used to describe the vector of electromagnetic energy flux density;

[0144] The force expression of electrons in non-uniform electromagnetic fields is:

[0145]

[0146] In formula (6), F e is the force on the electron, q is the charge of the electron, E is the electric field strength, v is the electron speed, B is the magnetic induction intensity, μ⊥ is the magnetic moment, is the magnetic induction gradient;

[0147] The expressions of the components of the volume force F exerted on the magnetic fluid in the magnetic field environment in various directions are:

[0148]

[0149] In formula (7), F x 、F y 、F z is the volume force on the magnetic fluid in the x, y, and z directions, μ0 is the magnetic permeability in vacuum, H x , H y , H z are the magnetic field strengths in the x, y, and z directions, respectively, M x 、M y 、M z They are the magnetization intensities in the x, y, and z axes respectively. The magnetization intensity of the magnetic material is M = B r / μ0, where B r is the residual flux density of the permanent magnet.

[0150] In one embodiment, in step four, the required material properties and physical fields are added to the constructed three-dimensional simulation model, and the corresponding solution domain is selected for each physical field, wherein neodymium iron boron magnet material is added to the cathode permanent magnet and the anode permanent magnet, oxygen material is added to the cathode flow channel, the cathode gas diffusion layer and the cathode gas diffusion electrode, hydrogen material is added to the anode flow channel, the anode gas diffusion layer and the anode gas diffusion electrode, perfluorosulfonic acid ion exchange membrane material is added to the proton exchange membrane, and air material is added to the air domain.

[0151] Specifically, hydrogen fuel cells, free and porous media flow physics interfaces, solid and fluid heat transfer, and magnetic field physics interfaces are added to the 3D simulation model.

[0152] Among them, the hydrogen fuel cell physical field is used to obtain the electrochemical reaction, current density distribution, proton conduction and gas diffusion inside the fuel cell; the free and porous medium flow uses the Navier-Stokes equation to accurately describe the fluid flow in the free area and uses the Brinkman equation or Darcy's law to describe the fluid flow in the porous medium, so as to achieve the coupling of fluid flow in different regions and ensure the continuity of physical quantities, which is used to obtain the pressure change, gas flow distribution, velocity field distribution and material transfer inside the fuel cell; solid and fluid heat transfer is used to obtain the temperature field distribution inside the fuel cell and improve the thermal stability of the battery; the magnetic field physical field is coupled with the hydrogen fuel cell of the complex multi-physical field, and acts on the magnetic materials such as hydrogen and oxygen in the flow channel, so that the magnetic materials flow in the magnetic field environment are affected by the Lorentz force and the Kelvin force, which affects the flow state and improves the material transfer. At the same time, it will change the movement path of the charged particles in the magnetic field, improve the electric field distribution and the concentration distribution of the reactants on the electrode surface, thereby affecting the open circuit voltage and polarization curve of the battery. Secondly, the Maxwell stress effect generated can affect the electrochemical reaction, change the interaction between the electrode and the electrolyte, and improve the catalytic performance.

[0153] Specifically, select the corresponding solution domain for each added physical field, including:

[0154] The solution domains of the hydrogen fuel cell physics field in electrochemistry include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains;

[0155] The solution domains selected for the free and porous media flow physics in the cathode fluid flow include: cathode flow channel, cathode gas diffusion layer, cathode gas diffusion electrode;

[0156] The solution domains selected for the free and porous media flow physics in the anode fluid flow include: anode flow channel, anode gas diffusion layer, anode gas diffusion electrode;

[0157] The solution domains of solid and fluid heat transfer physics in heat transfer include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, and proton exchange membranes;

[0158] The solution domains selected for the magnetic field physics field in electromagnetics include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains.

[0159] In one embodiment, in step 4, coupling calculations are performed on the four added physical fields mainly through the following related control equations, and boundary conditions and parameters are set for the control equations.

[0160] For both the gas phase (hydrogen and oxygen) and the liquid phase (water), the mass conservation law must be satisfied. The equations that need to be followed for diffusion in porous media and flow in the free flow area are as follows:

[0161]

[0162] In formula (8), is the vector differential operator, ρ is the fluid density, u is the velocity vector of the fluid flow, S m Represents the mass loss or gain caused by the electrochemical reaction occurring in the porous electrode;

[0163] Ohm's law models the electrochemical current and explains the ion transport in the electrolyte and the electron transport in the electrode. The activation loss produced is an important component of the electrochemical reaction:

[0164]

[0165] In formula (9), is the vector differential operator, σ i is the effective conductivity of electrolyte or gas ions, φ i is the potential of the electrode or electrolyte, Q i is the charge source term;

[0166] In porous electrodes, the local current density depends on the ion and electron potentials, but is also related to the local reactant concentration and temperature. The Butler--Volmer equation is used to simulate the electrode reaction kinetics in the cathode and anode to calculate the exchange current density of the cathode and anode:

[0167]

[0168]

[0169] in,

[0170]

[0171] In formula (10-13), i c，ct and i a，ct are the polarization current densities of the cathode and anode, respectively, i 0，c and i 0，a are the exchange current densities of the cathode and anode respectively, F is the Faraday constant, R is the molar gas constant, T is the operating temperature of the battery, C i represents the molar concentration of substance i, C i.ref represents the reference molar concentration of substance i, xO2 is the molar fraction of oxygen, η is the overpotential, and n is the number of electrons transferred;

[0172] The Navier-Stokes equations are used to accurately describe the fluid flow in the free region and solve the velocity and pressure fields in the cathode and anode channels:

[0173]

[0174] In formula (14), ρ is the density, u is the velocity vector, is the vector differential operator, p is the pressure, μ is the fluid viscosity, I is the unit matrix, and F is the introduced volume force vector;

[0175] To solve the momentum transfer in the porous media region, it is necessary to correctly consider the relevant parameters such as the number of electrode pores and the size. The Darcy-Brinkman equation, a combination of continuity and momentum conservation laws, is used to perform momentum analysis in the porous media region to obtain the velocity and pressure distribution in the porous media region:

[0176]

[0177] In formula (15-16), ε is the porosity, ρ is the density, is the vector differential operator, u is the velocity vector, Q br represents the mass source, p is the pressure, μ is the fluid viscosity, I is the unit matrix, K is the permeability of the porous medium, F is the introduced volume force vector, where ε and κ are both dimensionless;

[0178] The convection and diffusion of gases in hydrogen fuel cells affect mass transport. The mass transport in the free domain and porous electrode region of the cell is simulated by the following mass transport equation:

[0179]

[0180]

[0181] In formula (17-18), ρ is the density of the mixed gas, ω i is the mass fraction of component i, is a vector differential operator, j i is the diffusion mass flux of component i, u is the average velocity of the mixture, R i is the generation and consumption of component i, D e.ik is the effective diffusion coefficient in the porous medium, x k is the mole fraction of component k, w k is the mass fraction of component k, P A For pressure, is the thermal diffusion coefficient, T is the temperature, j i It plays a decisive role in the material transport between the cathode and the anode, and its size is mainly affected by the material concentration and temperature gradient;

[0182] Since the electrochemical reaction of the fuel cell generates heat, the heat generated will be transferred between the various components of the battery. The energy conservation equation is used to describe the transfer and conversion of heat:

[0183]

[0184] In formula (19), ρ is the material density, C P is the specific heat capacity, u is the velocity vector, T is the temperature, k is the thermal conductivity, and Q is the heat source term, which mainly comes from the heat generated by the electrochemical reaction.

[0185] Specifically, boundary conditions and parameters are set for each added physical field, including:

[0186] The boundary conditions at the cathode and anode flow channel inlets were set to fully developed flow and mean inflow velocity;

[0187] The boundary conditions at the cathode and anode flow channel outlets are set to pressure, which is 1 atm;

[0188] The boundary conditions of the model walls were set to no slip;

[0189] The boundary conditions of fluid flow were set as compressible flow (Ma < 0.3);

[0190] The mixed gas introduced into the anode inlet is set to be composed of hydrogen and water vapor, and the mixed gas introduced into the cathode inlet is set to be composed of oxygen, nitrogen and water vapor, and the anode and cathode outlet boundaries are defined as convection flux;

[0191] Potential boundary conditions: set the upper surface potential of the anode gas diffusion layer to 0 V, and the upper surface boundary potential of the cathode gas diffusion layer to the battery voltage;

[0192] In the heat transfer part, the inlet fluid boundary conditions of the anode and cathode flow channels are set to the initial temperature T in ; The outer surfaces of the cathode and anode flow channels are set to convective heat flux;

[0193] In the magnetic field part, the outer surface of the air domain is set to magnetic insulation; the orientation method of the cathode and anode permanent magnets is set to specify the north and south boundaries.

[0194] In one embodiment, in step five, after completing the setting of each physical field of the three-dimensional simulation model, the three-dimensional model is meshed using COMSOL Multiphysics software, and then a domain probe for calculating the integral of the electrochemical current density is added. After setting the domain probe, a mesh independence verification is performed to determine the mesh setting that best suits the model to obtain more accurate simulation results.

[0195] Specifically, the constructed three-dimensional simulation model is meshed as follows: the flow channel inlet or flow channel outlet end face of the three-dimensional simulation model is selected as the base surface, the edges of the end faces of different domains are divided by size or distribution, a two-dimensional grid is created by mapping, and then the grid is swept along the flow channel direction to complete the hexahedral grid division, and then the cathode and anode permanent magnets and the air domain are meshed by free tetrahedron to generate the structure and unstructured grid of the entire simulation model; the hexahedral grid division gradually becomes denser along the cathode gas diffusion layer and the anode gas diffusion layer toward the proton exchange membrane; the grids of the anode flow channel and the cathode flow channel are evenly distributed; the grid density of the cathode gas diffusion electrode and the anode gas diffusion electrode is the largest and evenly distributed, and the grid density of the proton exchange membrane is second.

[0196] The three-dimensional simulation model with mesh division is as follows Figure 4 As shown in the figure, the division is carried out by combining hexahedral structured grid and free tetrahedral unstructured grid according to different domains, which can effectively ensure the accuracy of simulation and the quality of grid.

[0197] Specifically, a domain probe is added to calculate the integral of the electrochemical current density, and the source is selected as the anode gas diffusion electrode in order to obtain the polarization curve of the battery during the solution of the parameterized solver.

[0198] Specifically, after setting up the domain probe, grid independence verification is carried out. The three-dimensional simulation model is divided into different numbers of grids. Under the condition of the same battery voltage, the output average current density and relative error are calculated and compared with different grid numbers. If the relative error is kept within 5%, it meets the simulation accuracy requirements.

[0199] In one embodiment, in step 6, the research steps are determined, and a steady-state solution is performed on the meshed three-dimensional simulation model. After the solution is completed, some default drawings are automatically obtained, and the simulation result data can be visualized in the form of curve graphs, two-dimensional or three-dimensional distribution graphs or charts according to needs.

[0200] Specifically, the research steps are determined and the steady-state solution is performed as follows: first, the secondary current distribution is solved, then the free and porous media flow of the cathode and anode are solved respectively to obtain the distribution of the velocity field and the pressure field, the solid and fluid heat transfer is solved to obtain the temperature field distribution, and finally, each physical field is coupled with the magnetic field for a steady-state solution. The steady-state solution uses voltage as a parameter, and an operator is used to create a potential list from 0.95V to 0.4V, first using a step size of -50mV, starting from 0.8V and finally using a step size of -100mV.

[0201] The results can be visualized in the form of a curve graph as required, for example, to obtain the output characteristic curve of a hydrogen fuel cell. Add a 1D plot group and define the x-axis variable as current density (A / cm2 ), the y-axis and secondary y-axis variables are voltage (V) and power density (W / cm 2 ), then extract the corresponding expression to globally plot the curves on the y-axis and the secondary y-axis, and you can get the output characteristic curve of the battery and the data set of the output characteristic curve.

[0202] In a specific embodiment, through the scheme of the present invention, only the residual magnetic flux density of the permanent magnet (0T and 280mT) is changed to obtain all data sets of the output characteristic curve of the battery, and the data sets are imported into Origin for curve drawing, such as Figure 5 As shown in the figure, based on the operating data without magnetic field (0T), it can be seen that the presence of magnetic field can reduce the voltage loss in the battery polarization process, and the power density of the battery has also been significantly improved. The maximum power density of the battery is 0.6004W / cm 2 Increased to 0.7625W / cm with magnetic field 2 , an increase of 26.99%.

[0203] The results can be visualized in the form of a 3D distribution graph according to the requirements. For example, if you need to obtain a 3D distribution graph of the pressure field and the temperature field, add a 3D plot group, name the plotted graph in the settings window, call contour lines, surfaces, or volumes, and extract the expressions corresponding to the pressure field and temperature field to complete the plotting of the distribution graph.

[0204] In a specific embodiment, by using the solution of the present invention, only the residual magnetic flux density of the permanent magnet (0T and 280mT) is changed to study the pressure field and temperature field of the hydrogen fuel cell, and the distribution diagrams thereof are as follows: Figure 6 and Figure 7 shown. Figure 6 This is the pressure distribution diagram when the residual magnetic flux density of the permanent magnet is 0T (no magnetic field) and 280mT. After the magnetic field is applied, the pressure of the gas close to the proton exchange membrane and the catalyst layer is significantly enhanced, which facilitates the diffusion of hydrogen and oxygen and the reaction on the catalyst layer and the proton exchange membrane; at the same time, the pressure of the gas at the outlet of the flow channel is also enhanced, which reduces the loss of gas energy, improves the distribution of fluid pressure in the flow channel, and accelerates the convection and diffusion of molecules. Figure 7 This is the temperature distribution diagram for permanent magnet residual flux density of 0T (no magnetic field) and 280mT. The initial temperature of the gas is 40℃. Comparing before and after applying the magnetic field, the presence of the magnetic field promotes the electrochemical reaction of the hydrogen fuel cell, increasing its heat production, and keeping the temperature of the electrochemical reaction area inside the battery at 60-80℃, reaching the optimal operating temperature range of the hydrogen fuel cell. When no magnetic field is applied, the highest temperature inside the battery is only 63.8℃, which cannot maximize the working performance of the hydrogen fuel cell.

[0205] The results can be visualized in the form of a two-dimensional distribution map according to the needs. For example, it is necessary to study the distribution of hydrogen at the interface between the gas diffusion layer and the gas diffusion electrode on the anode side and the distribution of water in the plane located in the middle of the cathode flow channel or the anode flow channel and along the depth direction of the flow channel. Add a two-dimensional drawing group, name the drawn chart in the settings window, select the study plane, call the contour line or surface, and extract the expressions corresponding to the mole fractions of hydrogen and water to complete the drawing of the distribution map.

[0206] In a specific embodiment, by changing the residual magnetic flux density of the permanent magnet (0T and 280mT), the distribution of hydrogen at the interface between the anode gas diffusion layer and the gas diffusion electrode and the distribution of water in the plane located at the middle position of the cathode flow channel or the anode flow channel and along the depth direction of the flow channel are studied. Figure 8 and Fig. 9 shown. Figure 8 The hydrogen distribution diagram is when the permanent magnet residual flux density is 0T (no magnetic field) and 280mT. Compared with before the magnetic field is applied, the introduction of the magnetic field can promote the reaction of hydrogen in the anode flow channel and improve the utilization rate of hydrogen, thereby greatly enhancing the electrochemical reaction of the hydrogen fuel cell and improving the output performance of the battery. Fig. 9 The distribution diagram of water when the residual magnetic flux density of the permanent magnet is 0T (no magnetic field) and 280mT. After applying the magnetic field, the molar fraction of water in the flow channel is significantly reduced, and the water generated during the battery reaction is discharged in time. The timely discharge of water reduces the water content of the battery inner membrane to a certain extent, which can effectively improve the service life of the battery.

Claims

1. A high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling, characterized in that: include: Globally define the geometric dimensions and physical performance parameters of high-performance hydrogen fuel cells; Construct a 3D simulation model of a high-performance hydrogen fuel cell with permanent magnets arranged at the cathode and anode according to the defined geometric size parameters, and create a specific geometric domain; Define and add the magnetic field and hydrogen fuel cell coupling equation expressions; Add the material properties and physical fields required for the 3D simulation model, select the corresponding solution domain for each physical field, and set its boundary conditions and parameters according to the control equations of the added physical field; Mesh the constructed 3D simulation model, add domain probes, and perform mesh independence verification; Determine the research steps, perform steady-state calculations on the coupled model, post-process the result data, and obtain state curves or images.

2. According to claim 1, a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling is characterized in that: The globally defined geometric dimensions include: the length, width, and height of the battery cathode and anode flow channels, the rib width, the thickness of the gas diffusion layer, the gas diffusion electrode, and the proton exchange membrane, the length and height of the permanent magnet, and the distance between the permanent magnet and the flow channel; The globally defined physical property parameters include: inlet mole fraction, temperature and velocity of water, hydrogen, oxygen and nitrogen, stoichiometry, transfer coefficient, reference exchange current density and active specific surface area of ​​cathode and anode, conductivity, potential and volume fraction of electrolyte, porosity, permeability, conductivity and gas pore volume fraction of gas diffusion layer, thermal conductivity, density, constant pressure heat capacity and specific heat rate of proton exchange membrane and fluid in flow channel, reference pressure and reference temperature of cathode and anode gas flow channel, residual magnetic flux density and conductivity of magnet.

3. According to claim 1, a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling is characterized in that: The constructed high-performance hydrogen fuel cell three-dimensional simulation model with permanent magnets arranged at the cathode and anode includes: a cathode permanent magnet, a cathode flow channel, a cathode gas diffusion layer, a cathode gas diffusion electrode, a proton exchange membrane, an anode gas diffusion electrode, an anode gas diffusion layer, an anode flow channel, an anode permanent magnet and an air domain; The specific geometric domain created includes: an anode inlet, a cathode inlet, an anode outlet, a cathode outlet, an anode chamber, a cathode chamber and a membrane electrode, so as to be used for setting the physical field.

4. According to claim 3, a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling is characterized in that: The functions of the air domain are as follows: the air domain serves as a medium for magnetic field propagation and a boundary condition for other objects; and provides a real simulation environment to better simulate the distribution and interaction of magnetic fields.

5. According to claim 1, a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling is characterized in that: The definition and addition of the magnetic field and hydrogen fuel cell coupling equation expression specifically include: The expression of concentration overpotential is: In formula (1), ε is the concentration overpotential, R is the gas constant, T is the thermodynamic temperature, β is the number of electrons transferred in the electrode reaction, F is the Faraday constant, I is the net current density, and I d The limiting diffusion current density, where the limiting diffusion current density I d for: In formula (2), n is the chemical valence of the ion, F is the Faraday constant, D is the diffusion coefficient, C is the concentration of the reaction ions, and δ is the thickness of the retention layer. The magnetohydrodynamic effect generated by the combined action of the working current and the magnetic field will form a forced flow, and the forced convection phenomenon will reduce the thickness of the retention layer δ, thereby making the limiting diffusion current I d Become bigger; Kelvin force acts on magnetic materials, thus affecting their electrocatalytic activity, accelerating mass transfer, and increasing limiting current: In formula (3), F k is the Kelvin force, μ0 is the vacuum permeability (4π×10 -7 H / m), is the magnetic induction gradient, χ m and c are the molar magnetic susceptibility and the concentration of electroactive species in the bulk solution, respectively; Maxwell stress is the force generated by the interaction between the magnetic field and magnetic media such as hydrogen and oxygen, and can be described by the magnetic stress tensor: In formula (4), T ij is the Maxwell stress tensor, ε0 is the dielectric constant, μ0 is the vacuum permeability, E i 、E j is the component of the electric field strength E in the i and j directions, B i , B j is the component of magnetic induction intensity B in the i and j directions, δ ij is the Kronecker function; the Maxwell stress effect affects the electrochemical double layer, changes the interaction between the electrode and the electrolyte, and improves the electrocatalytic reaction; Electromagnetic force per unit volume F f and the Maxwell stress tensor T ij The relationship is: In formula (5), is the vector differential operator, S is the Poynting vector, which is used to describe the vector of electromagnetic energy flux density; The force expression of electrons in non-uniform electromagnetic fields is: In formula (6), F e is the force on the electron, q is the charge of the electron, E is the electric field strength, v is the electron speed, B is the magnetic induction intensity, μ ⊥ is the magnetic moment, is the magnetic induction gradient; The expressions of the components of the volume force F exerted on the magnetic fluid in the magnetic field environment in various directions are: In formula (7), F x 、F y 、F z is the volume force on the magnetic fluid in the x, y, and z directions, μ0 is the magnetic permeability in vacuum, H x , H y , H z are the magnetic field strengths in the x, y, and z directions, respectively, M x 、M y 、M z They are the magnetization intensities in the x, y, and z directions respectively. The magnetization intensity of the magnetic material is M = B r / μ0, where B r is the residual flux density of the permanent magnet.

6. According to claim 1, a high-performance hydrogen fuel cell numerical simulation research method based on magnetic-fluid-thermal multi-physics field coupling is characterized in that: The material properties required for adding the three-dimensional simulation model include: adding neodymium iron boron magnet material to the cathode permanent magnet and the anode permanent magnet, adding oxygen material to the cathode flow channel, the cathode gas diffusion layer and the cathode gas diffusion electrode, adding hydrogen material to the anode flow channel, the anode gas diffusion layer and the anode gas diffusion electrode, adding perfluorosulfonic acid ion exchange membrane material to the proton exchange membrane, and adding air material to the air domain; The physics fields required for adding a three-dimensional simulation model include: the hydrogen fuel cell physics interface in electrochemistry, the free and porous media flow physics interface in cathode and anode fluid flow, the solid and fluid heat transfer physics interface in heat transfer, and the magnetic field physics interface in electromagnetics.

7. The method for numerical simulation of a high-performance hydrogen fuel cell based on magnetic-fluid-thermal multi-physics field coupling according to claim 6 is characterized in that: The hydrogen fuel cell physical field in the electrochemistry is used to obtain the electrochemical reaction, current density distribution, proton conduction and gas diffusion inside the fuel cell; The free and porous medium flow physical fields in the cathode and anode fluid flows use the Navier-Stokes equation to accurately describe the fluid flow in the free area and use the Brinkman equation or Darcy's law to describe the fluid flow in the porous medium, so as to achieve the coupling of fluid flows in different areas and ensure the continuity of physical quantities, and to obtain the pressure change, gas flow distribution, velocity field distribution and material transfer inside the fuel cell; The solid and fluid heat transfer physical fields in the heat transfer are used to obtain the temperature field distribution inside the fuel cell. By simulating heat conduction, the influence of thermal conductivity between different solid materials on the overall thermal performance of the battery can be determined. Good heat transfer can reduce temperature gradients, reduce thermal stress, and improve thermal stability of the battery. The magnetic field physics field in the electromagnetics is coupled with the hydrogen fuel cell of the complex multi-physics field, and acts on the magnetic materials such as hydrogen and oxygen in the flow channel, so that they flow in the magnetic field environment and are affected by the Lorentz force and the Kelvin force, generating a magnetofluid effect, affecting the flow state and improving the material transport. At the same time, it changes the movement path of the charged particles in the magnetic field, improves the electric field distribution on the electrode surface and the concentration distribution of the reaction substances, thereby affecting the open circuit voltage and polarization curve of the battery; secondly, the Maxwell stress effect generated can affect the electrochemical reaction, change the interaction between the electrode and the electrolyte, and improve the catalytic performance.

8. The method for numerical simulation of high-performance hydrogen fuel cells based on magnetic-fluid-thermal multi-physics field coupling according to claim 1 is characterized in that: The selecting of the corresponding solution domain for each added physical field includes: The solution domains of the hydrogen fuel cell physics field in electrochemistry include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains; The solution domains selected for the free and porous media flow physics in the cathode fluid flow include: cathode flow channel, cathode gas diffusion layer, cathode gas diffusion electrode; The solution domains selected for the free and porous media flow physics in the anode fluid flow include: anode flow channel, anode gas diffusion layer, anode gas diffusion electrode; The solution domains of solid and fluid heat transfer physics in heat transfer include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, and proton exchange membranes; The solution domains selected for the magnetic field physics field in electromagnetics include: cathode and anode flow channels, cathode and anode gas diffusion layers, cathode and anode gas diffusion electrodes, proton exchange membranes, cathode and anode permanent magnets, and air domains.

9. The method for numerical simulation of high-performance hydrogen fuel cells based on magnetic-fluid-thermal multi-physics field coupling according to claim 1 is characterized in that: The step of setting boundary conditions and parameters according to the control equation of the added physical field includes: The boundary conditions at the cathode and anode flow channel inlets were set to fully developed flow and mean inflow velocity; The boundary conditions at the cathode and anode flow channel outlets are set to pressure, which is 1 atm; The boundary conditions of the model walls were set to no slip; The boundary conditions of fluid flow were set as compressible flow (Ma < 0.3); The mixed gas introduced into the anode inlet is set to be composed of hydrogen and water vapor, and the mixed gas introduced into the cathode inlet is set to be composed of oxygen, nitrogen and water vapor, and the anode and cathode outlet boundaries are defined as convection flux; Potential boundary conditions: set the upper surface potential of the anode gas diffusion layer to 0 V, and the upper surface boundary potential of the cathode gas diffusion layer to the battery voltage; In the heat transfer part, the inlet fluid boundary conditions of the anode and cathode flow channels are set to the initial temperature T in ; The outer surfaces of the cathode and anode flow channels are set to convective heat flux; In the magnetic field part, the outer surface of the air domain is set to magnetic insulation; the directions of the cathode and anode permanent magnets are set to specify the north-south boundaries.

10. The method for numerical simulation of high-performance hydrogen fuel cells based on magnetic-fluid-thermal multi-physics field coupling according to claim 1 is characterized in that: The meshing of the constructed three-dimensional simulation model is specifically as follows: selecting the flow channel inlet or flow channel outlet end face of the three-dimensional simulation model as the base face, dividing the edges of the end faces of different domains by size or distribution, using mapping to create a two-dimensional grid, and then sweeping the grid along the flow channel direction to complete the hexahedral grid division, and then using free tetrahedral grid division for the cathode and anode permanent magnets and the air domain to generate the structure and unstructured grid of the entire simulation model; the hexahedral grid division gradually becomes denser along the cathode gas diffusion layer and the anode gas diffusion layer toward the proton exchange membrane; the grids of the anode flow channel and the cathode flow channel are evenly distributed; the grid density of the cathode gas diffusion electrode and the anode gas diffusion electrode is the largest and evenly distributed, and the grid density of the proton exchange membrane is second; The adding of the domain probe specifically includes: adding an integral probe for calculating the electrochemical current density, and the source is selected as the anode gas diffusion electrode; The grid independence verification is specifically as follows: different numbers of grid divisions are performed on the three-dimensional simulation model, and under the condition of the same battery voltage, the change of the output average current density with different numbers of grids and the relative error are calculated and compared to determine the best grid division model.

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