A fuel cell vibration performance evaluation method based on fluid simulation

Abstract

The present invention discloses a method for evaluating the vibration performance of a fuel cell based on fluid simulation, which relates to the field of fuel cell technology and mainly includes the following steps: constructing a three-dimensional model of the fuel cell based on the structural relationship between the components in the fuel cell, and gridding the three-dimensional model; obtaining vibration data of the ship under various vibration conditions, and reconstructing and simplifying the vibration data as vibration simulation conditions; loading the vibration simulation conditions into the three-dimensional model in the form of fluid simulation, and obtaining the voltage at each grid point based on the conservation of mass and momentum; obtaining the dynamic output voltage of the fuel cell under the current vibration condition based on the average value of the voltage at each grid point; and obtaining the relationship curve between the voltage characteristic value under each vibration condition and the vibration simulation condition using the least squares method based on the voltage characteristic value of the dynamic output voltage. The present invention provides targeted suggestions for the design of the fuel cell through performance evaluation, thereby reducing the impact of some vibration conditions on the performance of the fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for evaluating fuel cell vibration performance based on fluid simulation. Background Art

[0002] Proton exchange membrane fuel cells, with their clean and efficient properties, offer a promising technological solution to the long-standing challenges of high pollution and fuel consumption in the marine energy sector. However, during voyages, ships experience continuous and intense vibrations due to the influence of ocean winds, waves, and currents, as well as vibrations transmitted between onboard equipment. This prolonged and intense vibration can significantly impact the airtightness of fuel cells, causing dramatic changes in internal heat and mass transfer, increasing consumption rates, leading to insufficient gas content, and ultimately, reverse polarity. Fuel cell components can even become damaged, compromising airtightness and causing hydrogen leaks.

[0003] Vibration testing is an important test method to measure the safety, reliability and durability of fuel cell systems. Reasonable vibration testing and analysis can effectively support product structural optimization and ensure stable performance output. Summary of the Invention

[0004] In order to better study the impact of vibration on fuel cells during ship navigation, the present invention proposes a fuel cell vibration performance evaluation method based on fluid simulation, including the following steps:

[0005] S1: Construct a three-dimensional model of the fuel cell based on the structural relationship between the components in the fuel cell and perform meshing on the three-dimensional model;

[0006] S2: Obtain the vibration data of the ship under various vibration conditions, and reconstruct and simplify the vibration data as vibration simulation conditions;

[0007] S3: Load the vibration simulation condition into the 3D model in the form of fluid simulation, and obtain the voltage at each grid point based on the conservation of mass and momentum;

[0008] S4: Obtaining the dynamic output voltage of the fuel cell under the current vibration condition according to the average value of the voltage at each grid;

[0009] S5: According to the voltage characteristic value of the dynamic output voltage, a relationship curve between the voltage characteristic value and the vibration simulation working condition under each vibration working condition is obtained by the least square method.

[0010] Furthermore, in the step S1, the grid density is set according to the measurement accuracy requirements of the target component.

[0011] Furthermore, in step S2, the vibration data is reconstructed and simplified based on Fourier transform.

[0012] Furthermore, in step S3, the mass conservation can be expressed as the following first formula:

[0013]

[0014] Where ε is the porosity of the porous medium layer inside the fuel cell, ρ g is the density of the reaction medium in the fuel cell, t is the time, is the flow velocity of the reaction medium at the grid.

[0015] Furthermore, the momentum conservation can be expressed as a second formula:

[0016]

[0017] Where p is the pressure at the grid, μ is the dynamic viscosity of the fluid in the fuel cell, is a transient term, is the convection term, is the pressure term, is the diffusion term, S m is the source item.

[0018] Furthermore, the dynamic output voltage can be obtained by substituting the following formula into the first formula and the second formula to solve:

[0019]

[0020] f(A y ,f y , t) is the vibration load; y is the direction perpendicular to the fuel cell stack, A y is the amplitude in the y direction, f y is the vibration frequency in the y direction, is the vector symbol in the y direction, S under the load vibration simulation condition m For vibration load.

[0021] Furthermore, in step S5, the voltage characteristic value can be expressed as the following formula:

[0022]

[0023] Where V out is the voltage characteristic value, T is the vibration period, n is the number of sampling times in one vibration period, i is a constant that is initially 1, and t i is the sampling time point of the i-th sampling within the vibration period, and V(t) is the dynamic output voltage at time point t.

[0024] Furthermore, the components of the fuel cell include a bipolar plate and a gas diffusion layer, a proton exchange membrane and a seal arranged in pairs, and a medium flow field and a medium inlet are provided on the bipolar plate.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The fuel cell vibration performance evaluation method based on fluid simulation described in the present invention can greatly save manpower and material resources through simulation, and provide targeted suggestions for fuel cell design through performance evaluation, thereby reducing the impact of certain vibration conditions on fuel cell performance;

[0027] (2) Provide a control theory basis for the application of fuel cells on actual ships, and reduce the impact of high-hazard vibration conditions on the performance of fuel cells;

[0028] (3) By simulating arbitrary vibration loads, the heat and mass transfer laws inside the battery are obtained, so as to better understand its external output performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A method step diagram of a fuel cell vibration performance evaluation method based on fluid simulation;

[0030] Figure 2 A schematic diagram of the components of a fuel cell;

[0031] Figure 3 This is a graph showing the relationship between dynamic output voltage and time at different vibration frequencies;

[0032] Figure 4 It is the relationship curve between vibration simulation working condition and voltage characteristic value;

[0033] Explanation of reference numerals: 1-bipolar plate, 2-sealing ring, 3-GDL, 4-proton exchange membrane DETAILED DESCRIPTION

[0034] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0035] Example 1

[0036] like Figure 2As shown, fuel cell components generally include two bipolar plates (anode and cathode), two GDLs (dielectric diffusion layers), an MEA (proton exchange membrane), and seals (the components are stacked and assembled to ensure there are no gaps between the components and that the medium is in continuous contact with the components during circulation). The bipolar plates require the addition of a medium inlet and a medium flow field (including parallel flow fields, point flow fields, interdigitated flow fields, and serpentine flow fields, which can be selected according to actual needs). In this embodiment, the inlets of the two bipolar plates are used to connect hydrogen and air, respectively.

[0037] During the voyage of a ship, the vibrations caused by wind and waves and the ship's own operation will be transmitted to the fuel cell through the hull. This will cause the gas medium to flow in a non-fixed direction in the fuel cell due to the vibration conditions after it is input into the fuel cell, resulting in differences in the flow speed and direction of the medium in different places in the fuel cell. At the same time, the gas medium in a vibrating state will also exert pressure on various components, especially the medium diffusion layer. Due to its porous structural characteristics (used to allow for more complete reactions between the media), the different flow directions and speeds of the gas medium greatly affect its diffusion and reaction speed inside the fuel cell, thus affecting the overall power supply performance of the fuel cell. At the same time, due to the sudden change in the vibration direction, the gas is also very likely to produce convection inside the fuel cell, which further increases the impact of vibration on the reaction speed of the gas inside the fuel cell.

[0038] Therefore, in order to avoid the degradation of power supply performance of fuel cells due to certain vibration conditions during the navigation of ships after the fuel cells are formally installed on ships due to lack of targeted design, it is necessary to test the power supply performance under different vibration conditions at the beginning of the design, so as to fully understand the impact of different vibration conditions on fuel cell performance and to make targeted improvements and avoidances in the future. Therefore, the present invention proposes a fuel cell vibration performance evaluation method based on fluid simulation, such as Figure 1 As shown, the steps include:

[0039] S1: Construct a three-dimensional model of the fuel cell based on the structural relationship between the components in the fuel cell and perform meshing on the three-dimensional model;

[0040] S2: Obtain the vibration data of the ship under various vibration conditions, and reconstruct and simplify the vibration data as vibration simulation conditions;

[0041] S3: Load the vibration simulation condition into the 3D model in the form of fluid simulation, and obtain the voltage at each grid point based on the conservation of mass and momentum;

[0042] S4: Obtaining the dynamic output voltage of the fuel cell under the current vibration condition according to the average value of the voltage at each grid;

[0043] S5: According to the voltage characteristic value of the dynamic output voltage, a relationship curve between the voltage characteristic value and the vibration simulation working condition under each vibration working condition is obtained by the least square method.

[0044] In this embodiment, at the beginning of the test, a three-dimensional model of each component of the fuel cell is created and combined using 3D drawing software such as SOLIDWORKS based on the mechanical structure characteristics of the fuel cell to be tested. Then, the combined three-dimensional model is imported into the ICEM (computational fluid dynamics) software to divide the interface mesh. It should be noted that since some components or component positions have high requirements for measurement accuracy, different component parts need to be divided into different grid densities according to different accuracy requirements (specific settings are made according to actual requirements and will not be explained here). By performing high-density mesh division on component parts with high-precision requirements and low-density mesh division on component parts with low-precision requirements, the analysis efficiency is improved while ensuring the calculation accuracy.

[0045] After constructing a three-dimensional grid model of the fuel cell, it is necessary to analyze the various vibration conditions encountered during actual ship navigation. However, due to the limitations of the ship's site, the uncertainty of the duration and frequency of vibration conditions, and the enormous human and financial resources required for onboard research, this paper selects the method of collecting vibration data from the actual ship and then using laboratory computers to simulate the model to measure the fuel cell's performance under different vibration conditions.

[0046] It's important to note that vibration data collected from a live ship must first be reconstructed and simplified using Fourier transforms to conform to the vibration conditions experienced by the fuel cell on board. Furthermore, the ICEM software must be used to configure the material properties of the fuel cell components, the interface configuration between components, and the boundary conditions. Because the goal is to investigate the battery's output characteristics and internal heat and mass transfer under ship vibration conditions, the boundary conditions are primarily based on the vibration parameters measured under actual shipboard operating conditions, while other settings are based on relevant experimental parameters.

[0047] Then, based on the conservation of mass (as shown in the first formula below),

[0048]

[0049] Where ε is the porosity of the porous medium layer inside the fuel cell, ρ g is the density of the reaction medium in the fuel cell, t is the time, is the flow velocity of the reaction medium at the grid, S m is the source term (i.e. the external force term).

[0050] And, based on the conservation of momentum (as shown in the second formula below),

[0051]

[0052] Where p is the pressure at the grid, μ is the dynamic viscosity of the fluid in the fuel cell, is the transient term (transient momentum), is the convection term (momentum due to convection), is the pressure term (momentum due to pressure), is the diffusion term (momentum caused by diffusion).

[0053] At the same time, after loading the simulated vibration condition, the source term is transformed into a vibration load, and the vibration load can be expressed as the following formula:

[0054]

[0055] f(A y ,f y ,t) is the vibration load; y is the direction perpendicular to the fuel cell stack, Ay is the amplitude in the y direction, f y is the vibration frequency in the y direction, is the sign of the vector in the y direction.

[0056] It is not difficult to see from the above formula that, based on the conservation of momentum and mass, by substituting the variant of the source term after loading the vibration simulation condition, and using the converted formula to perform fluid simulation using ICEM software, the voltage at each grid can be obtained according to data such as the pressure, medium flow velocity, amplitude and vibration frequency at the grid (based on the membrane phase resistance and solid phase resistance (these two resistances depend on ohmic polarization, concentration polarization and activation polarization), and solved by the law of conservation of charge).

[0057] Based on the voltage data at each grid, the dynamic output voltage of the fuel cell as a whole can be obtained by averaging the voltages at each grid between the bipolar plates. In a preferred embodiment, the relationship between the dynamic output voltage and time at different vibration frequencies is obtained through fluid dynamics simulation. Figure 3 shown.

[0058] Then, according to the dynamic output voltage, the voltage characteristic value is obtained through the following formula:

[0059]

[0060] Where V out is the voltage characteristic value, T is the vibration period, n is the number of sampling times in one vibration period, i is a constant that is initially 1, and t i is the sampling time point of the i-th sampling within the vibration period, and V(t) is the dynamic output voltage at time point t.

[0061] Repeat the above steps to obtain the voltage characteristic value under each vibration condition, and then obtain the relationship curve between the vibration simulation condition and the voltage characteristic value by the least square method. In a preferred embodiment, the relationship curve is as follows: Figure 4 As shown in the figure, it can be seen that when the amplitude remains unchanged, the voltage characteristic value decreases quadratically with increasing frequency.

[0062] Based on the obtained relationship curve and the voltage output under different vibration conditions at different grids, the component structure of the abnormal output part can be improved in a targeted manner, or the impact of specific high-impact vibration conditions on the performance of the fuel cell can be reduced during the actual navigation of the ship.

[0063] In summary, the fuel cell vibration performance evaluation method based on fluid simulation described in the present invention can greatly save manpower and material resources through simulation, and provide targeted suggestions for the design of fuel cells through performance evaluation, thereby reducing the impact of some vibration conditions on the performance of fuel cells.

[0064] It provides a control theory basis for the application of fuel cells on actual ships, reducing the impact of high-hazard vibration conditions on the performance of fuel cells; through the simulation of arbitrary vibration loads, the heat and mass transfer laws inside the battery are obtained, so as to better understand its external output performance.

[0065] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0066] In addition, in the present invention, descriptions such as "first," "second," and "one" are for descriptive purposes only and should not be understood to indicate or imply their relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0067] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0068] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A fuel cell vibration performance evaluation method based on fluid simulation, characterized in that: Including steps: S1: Construct a three-dimensional model of the fuel cell based on the structural relationship between the components in the fuel cell and perform meshing on the three-dimensional model; S2: Obtain the vibration data of the ship under various vibration conditions, and reconstruct and simplify the vibration data as vibration simulation conditions; S3: Load the vibration simulation condition into the 3D model in the form of fluid simulation, and obtain the voltage at each grid point based on the conservation of mass and momentum; S4: Obtaining the dynamic output voltage of the fuel cell under the current vibration condition according to the average value of the voltage at each grid; S5: According to the voltage characteristic value of the dynamic output voltage, a relationship curve between the voltage characteristic value and the vibration simulation working condition under each vibration working condition is obtained by the least square method; In step S3, the mass conservation is expressed as the following first formula: Where ε is the porosity of the porous medium layer inside the fuel cell, ρ g is the density of the reaction medium in the fuel cell, t is the time, is the flow velocity of the reaction medium at the grid, S m is the source term; The conservation of momentum is expressed as the second formula: Where p is the pressure at the grid, μ is the dynamic viscosity of the fluid in the fuel cell, is a transient term, is the convection term, is the pressure term, is the diffusion term; After loading the simulated vibration condition, the source term is transformed into a vibration load, and the vibration load is expressed as follows: Where, f(A y ,f y ,t) is the vibration load; y is the direction perpendicular to the fuel cell stack, Ay is the amplitude in the y direction, f y is the vibration frequency in the y direction, is the vector sign in the y direction; Based on the first and second formulas, a variation of the source term after loading the vibration simulation condition is substituted into the converted formula. ICEM software is then used to perform fluid simulation. Specifically, the voltage at each grid is obtained based on the pressure, medium flow velocity, amplitude, and vibration frequency data at that grid. Based on the voltage data at each grid, the overall dynamic output voltage of the fuel cell is obtained by calculating the mean value of the voltage at each grid between the bipolar plates. Then, according to the dynamic output voltage, its voltage characteristic value is obtained by the following formula: Where V out is the voltage characteristic value, T is the vibration period, n is the number of sampling times in one vibration period, i is a constant that is initially 1, and t i is the sampling time point of the i-th sampling within the vibration period, and V(t) is the dynamic output voltage at time point t.

2. A fuel cell vibration performance evaluation method based on fluid simulation according to claim 1, characterized in that: In step S1, the grid density is set according to the measurement accuracy requirement of the target component.

3. A fuel cell vibration performance evaluation method based on fluid simulation according to claim 1, characterized in that: In step S2, the vibration data is reconstructed and simplified according to Fourier transform.

4. A fuel cell vibration performance evaluation method based on fluid simulation according to claim 1, characterized in that: The components of the fuel cell include a bipolar plate and a gas diffusion layer arranged in pairs, a proton exchange membrane and a sealing member. A medium flow field and a medium inlet are provided on the bipolar plate.

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