Solid oxide fuel cell performance influence analysis method

Abstract

The invention discloses a solid oxide fuel cell performance influence analysis method which comprises the following steps: establishing a three-dimensional model of a solid oxide fuel cell according to geometric parameters of the solid oxide fuel cell; selectively adding multiple physical fields coupled with an electric field, a flow field, a temperature field and a concentration field into the constructed three-dimensional model; determining boundary conditions influencing the performance of the solid oxide fuel cell, wherein the boundary conditions comprise a gas inflow mode, operation parameters and geometric parameters; according to the selected boundary conditions, obtaining steady-state calculation results of the solid oxide fuel cell in a multi-physical field under different working conditions; and according to a steady-state calculation result, analyzing a characteristic relationship between each parameter and the solid oxide fuel cell, and carrying out reasonable analysis on factors influencing the performance of the solid fuel cell. According to the method, the performance influence factors of the solid oxide fuel cell are analyzed, and reference is provided for performance optimization.

Description

Technical Field

[0001] The present application relates to the technical field of solid oxide fuel cells, and in particular to a method for analyzing the impact of solid oxide fuel cell performance. Background Art

[0002] At present, thermal power generation occupies the main part of my country's electric energy industry. Due to the conversion of multiple energy sources such as chemical energy, thermal energy, mechanical energy, and electrical energy, the final power generation efficiency is not particularly ideal, generally only about 25%-40%. In addition, along with the combustion process, some pollutants such as NO x 、SO x And dust emissions are very serious, which is not conducive to the implementation of the green development concept.

[0003] Compared with traditional thermal power generation technology, fuel cells can directly convert chemical energy into electrical energy, avoiding the limitations of the Carnot cycle. Therefore, the conversion efficiency of fuel cells is usually significantly higher than that of traditional thermal power generation. Fuel cells can be roughly divided into: proton exchange membrane fuel cells (PEMFC), solid oxide fuel cells (SOFC), alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC) and molten carbonate fuel cells (MCFC). Among them, solid oxide fuel cells (SOFC) have gained more and more attention due to their long life, less noise and pollution, environmental friendliness, and high output current density and power density.

[0004] The commercialization of solid oxide fuel cells can improve my country's energy demand and energy system structure and alleviate the current environmental pollution problem. However, solid oxide fuel cells currently face many challenges, such as high manufacturing costs, short lifespan, and imperfect production processes. Experiments on solid oxide fuel cells are crucial to promoting their development, but the economic and time costs of experimental operations are very high, and some theoretical operating conditions cannot be implemented for safety reasons. Therefore, how to purposefully and reasonably optimize solid oxide fuel cells is a problem that must be faced. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a method for analyzing the impact of solid oxide fuel cell performance, so as to reasonably analyze the factors affecting the performance of solid oxide fuel cells and provide a reference for performance optimization. In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] Solid oxide fuel cell performance analysis methods, including:

[0007] Establishing a three-dimensional model of the solid oxide fuel cell according to geometric parameters of the solid oxide fuel cell;

[0008] Selectively add multi-physics fields coupled with electric field, flow field, temperature field and concentration field to the constructed three-dimensional model;

[0009] Determining boundary conditions that affect the performance of the solid oxide fuel cell, the boundary conditions including gas inflow patterns, operating parameters, and geometric parameters;

[0010] According to the selected boundary conditions, obtaining steady-state calculation results of the solid oxide fuel cell in multi-physical fields under different working conditions;

[0011] According to the steady-state calculation results, the relationship between each parameter and the characteristics of solid oxide fuel cells is analyzed, and the factors affecting the performance of solid fuel cells are rationally analyzed.

[0012] Compared with the prior art, the solid oxide fuel cell performance analysis method of the present invention has the following beneficial effects:

[0013] The three-dimensional model of a flat solid oxide fuel cell is used as the research object. Based on the theory of electrochemical reaction kinetic equations, a stable battery model is built by using the multi-physics field coupling method in the finite element analysis software to realize the simulation research of energy conservation, material transfer and microscopic dynamics. Through the relevant calculations of this model, the distribution trend of various parameters of the solid oxide fuel cell can be obtained; in addition, this model can accurately estimate the relationship between various parameters and the characteristics of the solid oxide fuel cell, such as setting the gas inflow mode, setting the temperature at the gas flow channel inlet, gas pressure, fuel gas flow rate, and air flow rate in the operating parameters; such as setting the macroscopic parameters and microscopic parameters in the geometric parameters; the relationship between each parameter and the characteristics of the battery is reflected in the output characteristics of the battery, the internal temperature change amplitude characteristics, the fluid dynamic characteristics, and the gas utilization efficiency characteristics. According to the set boundary conditions, the steady-state calculation results are obtained, and combined with the actual objective factors, the response characteristics of the battery performance under various conditions are reasonably summarized to provide a reference for the performance optimization research of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic cross-sectional view of a solid oxide fuel cell of this embodiment;

[0015] Figure 2a is the polarization curve of this embodiment;

[0016] Figure 2b : is the distribution of electrolyte current density under different polarization voltages of this embodiment;

[0017] Figure 2c is the gas flow velocity distribution of this embodiment;

[0018] Figure 2d: is the hydrogen mole fraction distribution and oxygen mole fraction distribution of this embodiment;

[0019] Figure 3a This is a temperature distribution cloud diagram of the battery using the downstream mode in this embodiment;

[0020] Figure 3b This is a temperature distribution cloud diagram of a battery using a countercurrent method in this embodiment;

[0021] Figure 4a The influence of different gas inflow modes on the output power density of the battery in this embodiment;

[0022] Figure 4b The influence of different gas inflow modes on the average temperature change of the battery in this embodiment;

[0023] Figure 5a The influence of different gas temperatures at the flow channel inlet on the battery output power density of this embodiment;

[0024] Figure 5b The influence of different gas temperatures at the flow channel inlet on the average temperature change of the battery in this embodiment;

[0025] Figure 6a The effect of different gas pressures at the flow channel inlet on the battery output power density of this embodiment;

[0026] Figure 6b The effect of different gas pressures at the flow channel inlet on the average temperature change of the battery in this embodiment;

[0027] Figure 7a The effect of different gas pressures at the flow channel inlet on the change of hydrogen mole fraction in this embodiment;

[0028] Figure 7b The effect of different gas pressures at the flow channel inlet on the change of oxygen mole fraction in this embodiment;

[0029] Figure 8a The influence of different air flow rates on the output power density of the battery in this embodiment;

[0030] Figure 8b The influence of different air flow rates on the average temperature change of the battery in this embodiment;

[0031] Fig. 9 : is a distribution cloud diagram of electrolyte current density at different air flow rates of this embodiment;

[0032] Fig.10a The influence of different fuel gas flow rates on the output power density of the battery in this embodiment;

[0033] Fig.10bThe influence of different fuel gas flow rates on the average temperature change of the battery in this embodiment;

[0034] Fig.11 is a distribution cloud diagram of electrolyte current density at different fuel gas flow rates of this embodiment;

[0035] Fig.12a The influence of different anode support layer heights on the output power density of the battery in this embodiment;

[0036] Figure 12b The influence of different anode support layer heights on the average temperature change of the battery in this embodiment;

[0037] Fig.13a The effect of different battery lengths on the output power density of the battery in this embodiment;

[0038] Fig.13b The effect of different battery lengths on the average temperature change of the battery in this embodiment;

[0039] Fig.14a The effect of different battery lengths on the change of hydrogen mole fraction in this embodiment;

[0040] Fig.14b The effect of different battery lengths on the change of oxygen mole fraction in this embodiment;

[0041] Fig.15a The influence of different width-to-height ratios of the flow channels of this embodiment on the output power density of the battery;

[0042] Fig.15b The influence of different width-to-height ratios of the flow channels of this embodiment on the average temperature change of the battery;

[0043] Fig.16a The influence of different cathode current collection layer heights on the output power density of the battery in this embodiment;

[0044] Fig.16b The influence of different cathode current collection layer heights on the average temperature change of the battery in this embodiment;

[0045] Fig.17a The influence of different porosities of the porous medium of this embodiment on the output power density of the battery;

[0046] Fig.17b The influence of different porosities of the porous media of this embodiment on the average temperature change of the battery;

[0047] Fig.18a The influence of different permeabilities of the porous media of this embodiment on the output power density of the battery;

[0048] Fig.18bThis is the effect of different permeabilities of the porous media of this embodiment on the average temperature change of the battery. DETAILED DESCRIPTION

[0049] In order to make the technical solutions and advantages in the embodiments of the present application more clearly understood, the exemplary embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0050] Example

[0051] This embodiment provides a method for analyzing the performance impact of a solid oxide fuel cell, comprising the following steps: establishing a three-dimensional model of the solid oxide fuel cell according to the geometric parameters of the solid oxide fuel cell; selectively adding a multi-physics field coupled with an electric field, a flow field, a temperature field, and a concentration field to the constructed three-dimensional model;

[0052] Determine the geometric and operating parameters that affect the performance of solid oxide fuel cells;

[0053] According to the selected boundary conditions, the steady-state calculation results of solid oxide fuel cells in multi-physical fields under different working conditions are obtained;

[0054] According to the steady-state calculation results, the relationship between each parameter and the characteristics of solid oxide fuel cells is analyzed, and the factors affecting the performance of solid fuel cells are rationally analyzed.

[0055] In one embodiment, Figure 1 As shown, the solid oxide fuel cell includes a cathode side current collecting plate, a cathode current collecting layer, a cathode functional layer, an electrolyte layer, an anode functional layer, an anode supporting layer and an anode side current collecting plate arranged in sequence; the cathode side current collecting plate and the anode side current collecting plate are respectively provided with flow channels arranged along the length direction, the flow channels in the cathode side current collecting plate are used for air circulation, i.e., cathode flow channels; the flow channels in the anode side current collecting plate are used for fuel gas circulation, i.e., anode flow channels; the fuel gas can be hydrogen. Among them, the cathode current collecting layer, the cathode functional layer, the anode functional layer and the anode supporting layer are used as porous media. The width of each layer in the above battery is equal to the width of the battery, and the length of each layer is equal to the length of the battery.

[0056] Among them, the reaction principle of the solid oxide fuel cell is: the fuel gas enters the anode side current collector through the anode flow channel, flows through the anode support layer, and finally reaches the anode functional layer. The air enters the cathode side current collector through the cathode flow channel. In the anode functional layer, the fuel gas undergoes an oxidation reaction and releases electrons. The electrons flow along the conductive channels of the anode support layer and the anode side current collector to form a current that can be used to drive an external load. In the cathode functional layer, oxygen obtains electrons to undergo a reduction reaction and is converted into oxygen ions. Under the action of the potential difference and concentration difference, it enters the anode functional layer to react with hydrogen to generate water or water vapor. The electrochemical reaction takes place between the anode functional layer and the cathode functional layer. The ions transmitted through the electrolyte layer realize the separation of the redox reaction, while the electrons flow out through the anode support layer and the cathode current collection layer into the circuit, completing the closed loop of electron transmission.

[0057] In one embodiment, a three-dimensional model of a solid oxide fuel cell is imported into a finite element analysis software (COMSOL), and a multi-physical field coupled with an electric field, a flow field, a temperature field, and a concentration field is established through the finite element analysis software. The finite element analysis software defines the plates corresponding to the electric field as secondary current distribution, the plates corresponding to the flow field as free and porous medium flow, the plates corresponding to the temperature field as porous medium heat transfer, and the plates corresponding to the concentration field as concentrated species transfer.

[0058] The three-dimensional model of the solid oxide fuel cell is imported into the finite element analysis software, which is used to simulate the fluid flow, heat transfer and mass transfer in the flow channel and porous media; simulate the transmission of current in the porous media; and simulate the chemical reactions of the electrolyte, electrode and gas interface in the porous media.

[0059] The added physical fields include electric field, flow field, temperature field and concentration field. After adding the physical fields, the three-dimensional model is meshed to achieve steady-state calculation.

[0060] Among them, the secondary current distribution includes the conductivity of the electrolyte layer, the conductivity of the anode functional layer, the conductivity of the cathode functional layer, the exchange current density, the conductivity of the anode support layer and the conductivity of the cathode current collection layer.

[0061] Free and porous media flows include the gas properties in the flow channel and the average gas velocity at the inlet of the flow channel. The gas properties in the flow channel include gas density and dynamic viscosity.

[0062] Porous media heat transfer includes the thermal conductivity of porous media, the density of porous media, and the specific heat capacity of porous media. Porous media heat transfer also includes the thermal conductivity of the flow channel.

[0063] Concentrated species transfer includes the molar mass of the gas and the mole fraction of the gas at the inlet of the flow channel.

[0064] The electric field and temperature field are coupled to form an electrochemical heat node, the temperature field and flow field are coupled to form a non-isothermal flow node, and the flow field and two concentration fields are coupled to form a reaction flow anode node and a reaction flow cathode node, respectively.

[0065] The geometric parameters include the length of the solid oxide fuel cell, the aspect ratio of the flow channel, the height of the anode support layer, the height of the cathode current collecting layer, the porosity of the porous medium and the permeability of the porous medium; the operating parameters include the gas temperature at the inlet of the flow channel, the gas pressure at the inlet of the flow channel and the gas flow rate.

[0066] The steady-state calculation results include polarization curve, current density distribution, gas flow rate distribution, temperature distribution inside the battery, battery output power density curve, battery average temperature curve and gas mole fraction distribution.

[0067] Exemplarily, as shown in Table 1, the boundary conditions of some operating parameters of the multi-physical fields added to the solid oxide fuel cell are set in the finite element analysis software; as shown in Table 2, the boundary conditions of some geometric parameters of the multi-physical fields added to the solid oxide fuel cell are set in the finite element analysis software. The simulation data obtained below adopts the control variable method to analyze each parameter as an influencing factor of the battery performance. When a certain parameter is controlled as a variable, the remaining parameters in Table 1 or Table 2 are defaulted to the set values, which will not be repeated below.

[0068] Table 1:

[0069] Boundary conditions Numeric Boundary conditions Numeric Gas inlet temperature (K) 1073 Anode thermal conductivity (W / (m·K)) 6 Air inlet velocity (m / s) 3 Thermal conductivity of electrolyte (W / (m·K)) 2.7 Hydrogen inlet flow rate (m / s) 0.5 Cathode thermal conductivity (W / (m·K)) 11 Initial working pressure (atm) 1 Thermal conductivity of collector plate (W / (m·K)) 20 Mole fraction of gas species on the cathode side <![CDATA[N2:O2=0.79:0.21]]> Open circuit voltage(V) 1 Mole fraction of gas species on the anode side <![CDATA[H2:H2O=0.97:0.03]]> Initial polarization value (V) 0.05

[0070] Table 2:

[0071] Boundary conditions Numeric Boundary conditions Numeric Cathode side current collector height (mm) 1.5 Battery length (mm) 40 Anode side current collector height (mm) 1.5 Battery width (mm) 2 Cathode channel width (mm) 1 Anode channel width (mm) 1 Cathode channel height (mm) 1 Anode channel height (mm) 1 Cathode current collecting layer height (mm) 0.015 Anode support layer height (mm) 0.4 Cathode functional layer height (mm) 0.01 Anode porosity 0.3 Electrolyte layer height (mm) 0.01 Cathode porosity 0.3 Anode functional layer height (mm) 0.01 <![CDATA[Anode permeability (m 2 )]]> <![CDATA[1.76×10 -11 ]]> <![CDATA[Cathode permeability (m 2 )]]> <![CDATA[1.76×10 -11 ]]>

[0072] Specifically, Figure 2a The polarization curve shown in Figure 2b The distribution of electrolyte current density under different polarization voltages is shown in FIG. Figure 2c The gas velocity distribution shown in Figure 2d The hydrogen mole fraction distribution and oxygen mole fraction distribution are shown.

[0073] like Figure 2a , Figure 2b As shown in the figure, the increase of polarization voltage will lead to the increase of active polarization, concentration polarization and resistance polarization, which will directly affect the current density. Therefore, it is necessary to consider the distribution of current density at different polarization voltages. When the polarization voltage value is small (that is, the working voltage is large), the current is mainly concentrated at the left end of the battery, that is, close to the inlet side; and as the reaction proceeds, the polarization value gradually increases, the current concentration position begins to gradually move toward the center, and the current density distribution is more uniform than in the initial state; as shown in the figure, ... Figure 2cAs shown in the figure, for the two channels, the flow velocity at the center of the channel is greater than the flow velocity near the surrounding walls, and the flow velocity gradually decreases from the center to the wall, and the flow velocity near the wall is even close to 0. When the fluid passes through the channel, the friction with the channel wall will cause the flow velocity near the channel wall to decrease. This friction effect makes the fluid velocity near the channel wall slower than the velocity at the center of the channel; near the channel wall, a boundary layer is formed due to the viscosity between the fluid and the wall, that is, the wall boundary layer effect, which is also one of the reasons why the flow velocity gradually decreases toward the surrounding walls; as shown in the figure, the flow velocity near the channel wall is reduced ... friction between the fluid and the wall, that is, the wall boundary Figure 2d As shown in the figure, as the reaction proceeds, the concentration of the gas in both channels gradually decreases along the channel direction. Combined with the reaction principle of hydrogen-oxygen fuel cells, the consumption of hydrogen is twice that of oxygen, and the concentration drop rate at the hydrogen inlet is higher than that of oxygen. However, as the reaction proceeds, the concentration of hydrogen itself will also decrease accordingly, resulting in a decrease in the hydrogen consumption rate in the second half of the channel.

[0074] The steady-state calculation results of the multi-physical field are obtained by changing the set operating parameters. The operating parameters can be changed by setting the gas temperature at the inlet of the flow channel, the gas pressure at the inlet of the flow channel, and the gas flow rate at the inlet of the flow channel.

[0075] For a planar solid oxide fuel cell, this embodiment is a single fuel cell, and the effect of the gas inflow mode on the steady-state calculation results of the solid oxide fuel cell is analyzed.

[0076] Specifically, Figure 3a As shown in FIG. 1 , when the fuel gas and air are introduced into the flow channel in a co-current manner, the temperature distribution cloud diagram of the cross section of the solid oxide fuel cell along the length direction; Figure 3b As shown, when the fuel gas and air are introduced into the flow channel in a countercurrent manner, the temperature distribution cloud diagram of the solid oxide fuel cell along the cross section in the length direction.

[0077] like Figure 3a , Figure 3b As shown in the figure, the cross-sectional temperature distribution diagram of the three-dimensional model of the solid oxide fuel cell along its length direction when the battery voltage is 0.5V shows that its distribution trend is significantly different: when using the downstream flow, the temperature increases along the flow direction, and the maximum temperature appears at the outlet side, that is, when the downstream flow flows, the overall temperature distribution shows a trend of "increasing along the flow direction"; while when the countercurrent flow is used, the temperature first increases and then decreases, and the maximum temperature is approximately in the middle of the flow channel. Although the temperatures at both ends of the flow channel are relatively low, the lowest temperature still appears at the entrance of each of the two flow channels. That is, when the countercurrent flow flows, the overall temperature distribution shows a trend of "high in the middle and low at both ends".

[0078] Comparing the temperature distribution cloud diagrams of downstream and upstream, we can find that: under the same working conditions, the temperature has different trends and value ranges. Since the initial temperature is the same, the peak value of the temperature is larger in the downstream, so the temperature change range of the downstream is greater than that of the upstream.

[0079] Specifically, Figure 4a As shown in Figure 2, the effect of different gas inflow modes on the output power density of solid oxide fuel cells; Figure 4b As shown, the effect of different gas inflow modes on the average temperature change of the solid oxide fuel cell.

[0080] like Figure 4a , Figure 4b As shown in the figure, under the same conditions, the peak output power density of the solid oxide fuel cell is significantly greater than that of the countercurrent when the downstream inflow is adopted. Moreover, when the polarization voltage value is high (that is, the operating voltage is low), the power density corresponding to the downstream is greater than that of the countercurrent at the same voltage; excessive average temperature will cause a large temperature gradient inside the battery, and excessive temperature gradient will seriously affect the service life of the battery. For a single solid oxide fuel cell, the average temperature variation range can be controlled within 100-150K. As can be seen from the figure, the overall average temperature of the battery is significantly greater than that of the downstream when the downstream is adopted, and the temperature is within an acceptable range.

[0081] Combined with actual application conditions, although the temperature of solid oxide fuel cells may be higher in the co-current mode, it is still an optional design due to its advantages in battery efficiency, thermal management and power output. The co-current design helps to improve the thermal efficiency of the battery, optimize the temperature distribution, reduce thermal stress, and increase the power density during long-term stable operation of the battery. Although the counter-current mode also has advantages under certain specific conditions, the co-current mode has more advantages in practical applications, especially in improving the overall system efficiency and reducing operating costs.

[0082] Specifically, Figure 5a As shown in Figure 2, the effect of different gas temperatures at the flow channel inlet on the output power density of the solid oxide fuel cell is shown in Figure 2. Figure 5b As shown, the effect of different gas temperatures at the flow channel inlet on the average temperature change of the solid oxide fuel cell.

[0083] like Figure 5a , Figure 5bAs shown, the gas temperature at the inlet of the solid oxide fuel cell is 800-1000℃ (corresponding to the thermodynamic temperature of 1073-1273K). The polarization voltages corresponding to the maximum values ​​of the battery power density at different temperatures are 0.5V, 0.4V and 0.2V respectively (i.e. the working voltages correspond to 0.5V, 0.6V and 0.8V). The overall changes all satisfy the trend of increasing first and then decreasing, and the change trend is the largest when the polarization voltage is 0.2-0.5V.

[0084] In addition, as the electrochemical reaction proceeds, the polarization voltage value gradually increases, and the average temperature of the battery shows an upward trend. The higher the initial temperature, the larger the average temperature change range and the faster the average temperature change rate.

[0085] from Figure 5a It is shown in Figure 1 that although the output power density is the largest at 1273K, when the polarization voltage reaches 0.5V or greater (i.e., the redox reaction proceeds to the middle and late stages), the power density change curve corresponding to 1273K almost coincides with that at 1173K, and is still above the curve corresponding to 1073K. Figure 5b It is shown that the average temperatures corresponding to the three initial temperatures are all within a reasonable range, but the peak temperature corresponding to 1273K is much larger than that of the other two groups.

[0086] Taking into account factors such as output characteristics and service life, within the common operating temperature range of the battery, the higher the gas temperature at the inlet, the greater the output power density of the battery under the same conditions, and the higher the overall average temperature of the battery. Setting the initial air temperature of 1173K at the inlet provides better power output and lower thermal stress, which is a more balanced choice that can provide better battery performance without causing excessive negative impact on battery life.

[0087] Specifically, Figure 6a As shown in Figure 2, the effect of different gas pressures at the flow channel inlet on the output power density of the solid oxide fuel cell; Figure 6b As shown, the effect of different gas pressures at the flow channel inlet on the average temperature change of the solid oxide fuel cell.

[0088] The gas pressure at the inlet of a hydrogen-oxygen solid oxide fuel cell generally ranges from 0.1 MPa to 0.3 MPa (for high-efficiency designs or extremely special applications, the gas pressure may sometimes range from 0.3 MPa to 0.5 MPa).

[0089] like Figure 6aAs shown, three groups of pressures, 0.1MPa, 0.2MPa and 0.3MPa, were selected as comparative data to analyze the effects of different initial pressures on power density and overall average temperature. The output characteristics of the battery under different gas pressures are basically the same, and the greater the pressure, the higher the power density under the same conditions; Figure 6b It is shown that when the pressure is selected as 0.2MPa and 0.3MPa, the average temperature of the battery is almost the same and is greater than the temperature corresponding to 0.1MPa.

[0090] It should be pointed out that changes in pressure will affect the adsorption and departure rate of gas on the electrode surface, and thus affect the redox reaction rate inside the battery. The greater the gas pressure at the inlet, the greater the battery output power density and the higher the average temperature of the battery.

[0091] Specifically, Figure 7a As shown in Figure 2, the effect of different gas pressures at the flow channel inlet on the change of hydrogen mole fraction; Figure 7b As shown, the effect of different gas pressures at the flow channel inlet on the change of oxygen mole fraction is used.

[0092] like Figure 6a , Figure 6b , Figure 7a , Figure 7b As shown in the figure, the change of gas mole fraction in the two flow channels under different gas pressures. It can be seen from the figure that the higher the working pressure, the smaller the rate of change of gas concentration, that is, the higher the actual mole fraction of the corresponding gas under the same voltage.

[0093] If maximizing performance is a priority, 0.3MPa can be selected as the initial pressure. However, higher pressures may also bring a series of challenges, including increased flow resistance, increased system design pressure, mechanical and thermodynamic stability issues of materials, and possible side reactions. In the choice of 0.1MPa and 0.2MPa, the change in gas concentration shows that the two are almost close; the change in the average battery temperature shows that the average battery temperature corresponding to 0.2MPa is slightly greater than 0.1MPa, and the temperature change range is within an acceptable range; considering the battery output characteristics, the power density corresponding to 0.2MPa is significantly greater than 0.1MPa. Therefore, on the whole, choosing 0.2MPa as the initial pressure can not only ensure better performance, but also optimize cost and equipment maintenance.

[0094] For the three-dimensional model of solid oxide fuel cells, this embodiment explores the influence of the flow rate at the inlet of the two flow channels on the steady-state calculation results of the solid oxide fuel cell, considering to improve the utilization efficiency of the fuel gas as much as possible and ensure the full progress of the electrochemical reaction. For a single solid oxide fuel cell, the fuel gas flow rate is generally controlled at 0-1m / s, and the air flow rate is controlled at 1-5m / s. The optional initial boundary conditions for determining the working conditions are: the fuel gas flow rate is 0.1m / s, 0.5m / s and 0.8m / s; the air flow rate is 1m / s, 3m / s and 5m / s.

[0095] When exploring the effect of gas flow rate on the performance of solid oxide fuel cells, in addition to focusing on the output characteristics of the battery, the distribution of current density is also very important. The distribution of current density directly reflects the reaction efficiency and performance uniformity of the battery. In solid oxide fuel cells, the gas flow rate affects the contact, transmission and reaction process between the gas and the electrode, and these factors are closely related to the distribution of current density.

[0096] Specifically, Figure 8a As shown in Figure 2, the effect of different air flow rates on the output power density of solid oxide fuel cells; Figure 8b As shown in Figure 2, the average temperature change of the solid oxide fuel cell is affected by different air flow rates; Fig. 9 As shown, the distribution cloud diagram of electrolyte current density under different air flow rates.

[0097] like Figure 8a , Figure 8b , Fig. 9 As shown in the figure, the greater the air flow rate, the greater the corresponding power density; when the air flow rates are 3m / s and 5m / s, the power change curves are almost overlapping, that is, after the air flow rate increases to the middle value of the selected range, the influence of the air flow rate on the battery output performance begins to decrease significantly; it is worth noting that the average battery temperature corresponding to the air flow rate of 3m / s is greater than that of the other two groups, but still within the allowable range.

[0098] like Fig. 9 As shown in the figure, the distribution characteristics of current density under different air flow rates when the working voltage is 0.5V, as the air flow rate gradually increases, the current density distribution becomes more and more uniform, and the peak value begins to gradually move to the central area; when the flow rate is 3m / s and 5m / s, the current density distribution law is almost the same.

[0099] Considering the output characteristics of the battery, the overall temperature change, and the uniformity of the internal physical field coupled steady-state calculation results, an air flow rate of 3m / s is the best choice.

[0100] Specifically, Fig.10a As shown in Figure 2, the effect of different fuel gas flow rates on the output power density of solid oxide fuel cells; Fig.10b As shown in Figure 2, the average temperature change of the solid oxide fuel cell is affected by different fuel gas flow rates; Fig.11 As shown, the distribution cloud diagram of electrolyte current density under different fuel gas flow rates.

[0101] like Fig.10a , Fig.10b , Fig.11 As shown in the figure, the overall law of the steady-state calculation results of the fuel gas flow rate is basically consistent with the law of the steady-state calculation results of the air flow rate, that is, the power density curves corresponding to the fuel gas flow rates of 0.5m / s and 0.8m / s are very close, and much larger than the power density corresponding to the fuel gas flow rate of 0.1m / s. In addition, the polarization voltage corresponding to the peak of the power density at the fuel gas flow rate of 0.1m / s is lower; similar to the battery average temperature curve corresponding to the air flow rate, when the polarization voltage is greater than 0.3V, the battery average temperature corresponding to the fuel gas flow rate of 0.5m / s is significantly greater than that of 0.1m / s, slightly greater than that of 0.8m / s, and still within the allowable range.

[0102] like Fig.11 As shown in the figure, the distribution characteristics of current density at different fuel gas flow rates when the working voltage is 0.5V, among which, when the fuel gas flow rate is low, the uneven distribution of current density is particularly obvious. At this time, the current density is basically concentrated at the inlet position, and decreases along the gas flow direction, and the degree of decrease gradually slows down.

[0103] Considering the output characteristics of the battery, the overall temperature change, and the uniformity of the internal physical field coupled steady-state calculation results, it is clear that the fuel gas flow rate is too low and does not meet the requirements for maximizing battery performance. A fuel gas flow rate of about 0.5 m / s is more appropriate.

[0104] The following obtains the steady-state calculation results of the multi-physics field by setting the changes of geometric parameters. The changes of geometric parameters can be achieved by setting macroscopic parameters and microscopic parameters. Macroscopic parameters include: anode support layer height, battery length (i.e., flow channel length), flow channel aspect ratio, cathode current collection layer height; microscopic parameters include: porous medium porosity, porous medium permeability.

[0105] Specifically, Fig.12a As shown in Figure 2, the output power density of solid oxide fuel cells is affected by different anode support layer heights. Figure 12b As shown, the effect of different anode support layer heights on the average temperature change of the solid oxide fuel cell.

[0106] like Fig.12a , Figure 12b As shown in the figure, three groups of anode support layers are selected with heights of 2×10 -4 m,4×10-4 m and 6×10 -4 mFor comparison, the battery output performance and the overall average temperature show that the thicker the anode support layer, the lower the output power density of the battery under the same conditions; the height of the anode support layer has almost no effect on the overall average temperature of the battery.

[0107] Although the anode support layer is crucial to the structural stability of the solid oxide fuel cell, the height of the anode support layer should not be too low. However, to a certain extent, an overly thick anode support layer will increase resistance loss, gas diffusion resistance and heat conduction path, thereby affecting the output power density of the battery. -4 The anode support layer height of m is more in line with performance requirements.

[0108] Specifically, Fig.13a As shown in Figure 2, different cell lengths affect the output power density of solid oxide fuel cells; Fig.13b As shown in Figure 2, the average temperature change of solid oxide fuel cells is affected by different cell lengths; Fig.14a As shown in Figure 2, the effect of different cell lengths on the change in hydrogen mole fraction; Fig.14b As shown, the effect of different cell lengths on the change in oxygen mole fraction.

[0109] like Fig.13a , Fig.13b As shown, the length of the battery in this embodiment determines the length of the two flow channels, which in turn affects the retention time of the gas in the flow channels, which will definitely affect the redox reaction and thus the output characteristics of the entire battery. -2 m,4×10 -2 m and 6×10 -2 mFor comparison, the effect of battery length on battery output performance and average temperature shows that the longer the flow channel, the lower the power density under the same conditions; the longer the flow channel, the higher the overall average temperature of the battery, the higher the final peak value, which is less conducive to the long-term operation of the battery.

[0110] In addition, since the length of the battery determines the length of the flow channel, which in turn affects the reaction, it is necessary to study the utilization of the battery fuel in addition to the output characteristics. Fig.14a , Fig.14b As shown, it shows the curve of the change of battery length to gas mole fraction. The initial mole fractions corresponding to the three groups of battery lengths are the same. As the electrochemical reaction continues, it can be seen that the longer the battery length, the faster the gas mole fraction decreases, and the corresponding gas mole fraction at the same voltage is lower.

[0111] Based on the above three sets of data, the battery length is selected as 2×10 -2The steady-state calculation results achieved by m are significantly better than those of the other two groups. Although the specific design of solid oxide fuel cells depends on the application scenario and requirements, in general, setting the cell length to a reasonable length helps improve efficiency, reduce resistance, optimize thermal management, shorten response time and reduce costs. Therefore, in many cases, it is preferred to design a shorter solid oxide fuel cell to obtain higher performance and longer service life.

[0112] Specifically, Fig.15a As shown in Figure 2, the effect of different channel width-to-height ratios on the output power density of solid oxide fuel cells; Fig.15b As shown, the effect of different channel width-to-height ratios on the average temperature change of the solid oxide fuel cell.

[0113] like Fig.15a , Fig.15b As shown in Figure 1, in addition to the flow channel length, the aspect ratio of the flow channel design will also directly affect the fluid dynamics and thermodynamic processes inside the solid oxide fuel cell, thereby affecting the distribution of the reaction gas, mass transfer, reaction rate, thermal management and energy loss. Reasonable aspect ratio design can improve the electrochemical reaction efficiency of the solid oxide fuel cell and reduce energy loss, thereby improving the overall performance and stability of the solid oxide fuel cell.

[0114] Three sets of aspect ratios are selected: 0.5, 1.0, and 1.5. According to the output characteristics of the battery and the change curve of the overall average temperature according to different aspect ratios, the larger the aspect ratio, the greater the battery output power density; when the aspect ratio is 1.5, the power density at the same voltage is much greater than the corresponding value when the aspect ratio is 0.5; and when the aspect ratio is 1.0 and 1.5, the power density changes with the polarization voltage. The larger the aspect ratio, the higher the average battery temperature.

[0115] In general, although the larger the aspect ratio, the better the battery output characteristics, but in the three sets of data selected, combined with Figure 5b As shown in the figure, when the aspect ratio is 1.5, the average temperature of the battery has exceeded the reasonable range allowed. Therefore, the aspect ratio design with an aspect ratio of 1.0 should be selected as the optimal flow channel.

[0116] Specifically, Fig.16a As shown in Figure 2, the effect of different cathode current collection layer heights on the output power density of solid oxide fuel cells is shown in Figure 2. Fig.16b As shown, the effect of different cathode current collection layer heights on the average temperature change of the solid oxide fuel cell.

[0117] like Fig.16a , Fig.16bAs shown in the figure, the cathode current collection layer is the key layer connecting the cathode material and the external circuit, which affects the electrical performance, stability and overall efficiency of the fuel cell. The heights of the three groups of cathode current collection layers are 1.0×10 -5 m, 1.5×10 -5 m and 2×10 -5 mFor comparison, the influence of different cathode current collection layers on the battery shows that the thicker the cathode current collection layer, the greater the output power density and the greater the peak value of the battery under the same conditions; the height of the current collection layer has almost no effect on the overall average temperature of the battery.

[0118] According to the power density curve comparison, the height of the cathode current collection layer is 2×10 -5 m shows the best performance. It should be pointed out that the cathode current collection layer is not as large as possible. If the cathode current collection layer is too thick, it may introduce additional resistance, which will lead to energy loss and reduced efficiency. An overly thick cathode current collection layer may increase the energy loss in the electron conduction process and reduce the overall performance of the battery. And the height is 2×10 -5 The output power density is only slightly greater than 1.5×10 -5 m corresponding to the power density. Considering the comprehensive manufacturing cost, the height of the cathode current collection layer is selected to be 1.5×10 -5 m is more suitable.

[0119] In solid oxide fuel cells, the porosity and permeability of porous media are the main characteristic parameters, and the physical properties of porous media can affect the output performance of the entire cell. Using porosity and permeability as parameters to describe the microscopic geometric properties of porous media in solid oxide fuel cells is crucial for understanding the gas transport and reaction process in the electrode layer and optimizing the performance of solid oxide fuel cells.

[0120] Specifically, Fig.17a As shown in Figure 2, the output power density of solid oxide fuel cells is affected by different porosities of porous media; Fig.17b As shown, the influence of different porosity of porous media on the average temperature change of solid oxide fuel cell.

[0121] like Fig.17a , Fig.17b As shown, porosity refers to the proportion of pores in a porous medium. The size of the porosity directly affects the diffusion and transmission of fuel gas and oxygen in the electrode.

[0122] The influence of different porosities on the output power density and equilibrium temperature of solid oxide fuel cells shows that the output power density of batteries with different porosities has a similar trend as the reaction proceeds, and the greater the porosity, the greater the peak power density of the battery, and the higher the output efficiency of the corresponding battery at the same voltage. The greater the porosity, the higher the average temperature of the battery.

[0123] However, in the actual design of solid oxide fuel cells, the larger the porosity, the better. If the porosity is too high, the porous medium may be too loose, affecting the conduction of electrons and ions, thereby reducing the performance of the battery. The power density of a porosity of 0.3 is not significantly different from that of a porosity of 0.5. After comprehensive comparison, a porosity of 0.3 is more in line with the design concept of the battery.

[0124] Specifically, Fig.18a As shown in Figure 2, the effect of different permeabilities of porous media on the output power density of solid oxide fuel cells is shown in Figure 2. Fig.18b As shown, the effect of different permeabilities of porous media on the average temperature change of solid oxide fuel cells.

[0125] like Fig.18a , Fig.18b As shown in Figure 1, permeability describes the ability of a gas or liquid to transport in a porous medium. In solid oxide fuel cells, permeability is often used to describe the transport performance of gases (such as fuel gas and oxygen) in porous media. A high permeability means that the gas can pass through the porous medium more easily, which helps to increase the diffusion rate of fuel gas and oxygen in the electrode.

[0126] The effect of permeability on the output power density and overall average temperature of solid oxide fuel cells shows that the influence of permeability is relatively small compared to porosity. Under the same voltage, the higher the permeability, the lower the power density; permeability has almost no effect on the overall average temperature of the battery.

[0127] Although the increased permeability can increase the gas transmission rate inside the battery, if the transmission rate is too fast, it will lead to a decrease in the fuel utilization rate inside the battery, thereby reducing the power density of the battery. -11 m 2 More in line with the design concept of the battery.

[0128] In this embodiment, a three-dimensional model of a flat solid oxide fuel cell is used as the research object. Based on the theory of electrochemical reaction kinetic equations, a stable battery model is built by using the multi-physics field coupling method in the finite element analysis software to realize the simulation research of energy conservation, material transfer and microscopic dynamics. Through the relevant calculations of the model, the distribution trend of various parameters of the solid oxide fuel cell can be obtained; in addition, this model can accurately estimate the relationship between various parameters and the characteristics of the solid oxide fuel cell, such as setting the gas inflow mode, setting the temperature at the gas flow channel inlet, gas pressure, fuel gas flow rate, and air flow rate in the operating parameters; such as setting the macroscopic parameters and microscopic parameters in the geometric parameters; the relationship between each parameter and the characteristics of the battery is reflected in the output characteristics of the battery, the internal temperature change amplitude characteristics, the fluid dynamic characteristics, and the gas utilization efficiency characteristics; according to the set boundary conditions, the steady-state calculation results are obtained, and combined with the actual objective factors, the response characteristics of the battery performance under various conditions are reasonably summarized to provide a reference for the performance optimization research of the battery.

[0129] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "height", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0130] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0131] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for analyzing the impact of solid oxide fuel cell performance, characterized in that: include: Establishing a three-dimensional model of the solid oxide fuel cell according to geometric parameters of the solid oxide fuel cell; Selectively add multi-physics fields coupled with electric field, flow field, temperature field and concentration field to the constructed three-dimensional model; Determining boundary conditions that affect the performance of the solid oxide fuel cell, the boundary conditions including gas inflow patterns, operating parameters, and geometric parameters; According to the selected boundary conditions, obtaining steady-state calculation results of the solid oxide fuel cell in multi-physical fields under different working conditions; According to the steady-state calculation results, the relationship between each parameter and the characteristics of the solid oxide fuel cell is analyzed, and the factors affecting the performance of the solid fuel cell are rationally analyzed.

2. The solid oxide fuel cell performance analysis method according to claim 1, characterized in that: The solid oxide fuel cell comprises a cathode side current collecting plate, a cathode current collecting layer, a cathode functional layer, an electrolyte layer, an anode functional layer, an anode supporting layer and an anode side current collecting plate which are arranged in sequence; flow channels arranged along the length direction are respectively provided in the cathode side current collecting plate and the anode side current collecting plate, the flow channels in the cathode side current collecting plate are used for air circulation, and the flow channels in the anode side current collecting plate are used for fuel gas circulation, wherein the cathode current collecting layer, the cathode functional layer, the anode functional layer and the anode supporting layer serve as porous media.

3. The solid oxide fuel cell performance analysis method according to claim 2, characterized in that: The three-dimensional model of the solid oxide fuel cell is imported into the finite element analysis software, and a multi-physical field coupled with an electric field, a flow field, a temperature field and a concentration field is established through the finite element analysis software. The finite element analysis software defines the plates corresponding to the electric field as secondary current distribution, the plates corresponding to the flow field as free and porous medium flow, the plates corresponding to the temperature field as porous medium heat transfer, and the plates corresponding to the concentration field as concentrated substance transfer.

4. The method for analyzing the impact of solid oxide fuel cell performance according to claim 3, characterized in that: The secondary current distribution includes the conductivity of the electrolyte layer, the conductivity of the anode functional layer, the conductivity of the cathode functional layer, the exchange current density, the conductivity of the anode support layer and the conductivity of the cathode current collection layer.

5. The method for analyzing the impact of solid oxide fuel cell performance according to claim 3, characterized in that: The free and porous media flows include gas properties in the flow channel and the average velocity of the gas at the entrance of the flow channel.

6. The method for analyzing the impact of solid oxide fuel cell performance according to claim 3, characterized in that: The porous medium heat transfer includes the thermal conductivity of the porous medium, the density of the porous medium and the specific heat capacity of the porous medium; the porous medium heat transfer also includes the thermal conductivity of the flow channel.

7. The method for analyzing the impact of solid oxide fuel cell performance according to claim 3, characterized in that: The concentrated species transfer includes the species molar mass of the gas and the gas mole fraction at the inlet of the flow channel.

8. The method for analyzing the impact of solid oxide fuel cell performance according to claim 3, characterized in that: The electric field and the temperature field are coupled to form an electrochemical thermal node, the temperature field and the flow field are coupled to form a non-isothermal flow node, and the flow field and the two concentration fields are coupled to form a reaction flow anode node and a reaction flow cathode node, respectively.

9. The method for analyzing the impact of solid oxide fuel cell performance according to claim 2, characterized in that: The geometric parameters include the length of the solid oxide fuel cell, the aspect ratio of the flow channel, the height of the anode support layer, the height of the cathode current collection layer, the porosity of the porous medium and the permeability of the porous medium; the operating parameters include the gas temperature at the inlet of the flow channel, the gas pressure at the inlet of the flow channel and the gas flow rate.

10. The method for analyzing the impact of solid oxide fuel cell performance according to claim 2, characterized in that: The steady-state calculation results include polarization curves, current density distribution, gas flow rate distribution, temperature distribution inside the solid oxide fuel cell, output power density curve of the solid oxide fuel cell, average temperature curve of the solid oxide fuel cell and gas mole fraction distribution.

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