A novel solid oxide fuel cell flow channel structure and optimization method thereof

Abstract

This invention designs a novel flow channel structure for a solid oxide fuel cell and its optimization method. The structure is characterized by: a cathode connector connected to the cathode electrode to form a cathode flow channel, and an anode connector connected to the anode electrode to form an anode flow channel; both the cathode and anode flow channels are rectangular direct-flow channels; a set of slotted, trapezoidal baffles connected to the cathode connector are provided within the cathode flow channel. The slotted trapezoidal structures inside the cathode flow channel are evenly spaced, with their height increasing gradually from the inlet to the outlet. This invention designs a novel flow channel structure for a solid oxide fuel cell, improving uneven gas distribution, enhancing mass transfer efficiency, and improving cell performance. This invention proposes a multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell to optimize the structural parameters of the solid oxide fuel cell.

Description

Technical Field

[0001] This invention relates to the field of solid oxide fuel cell technology, and specifically to a novel solid oxide fuel cell flow channel structure and its optimization method. Background Technology

[0002] Fuel cells are green power generation devices that directly convert the chemical energy of reactants into electrical energy. They possess advantages such as cleanliness, high efficiency, high power density, and low noise, making them one of the important research directions in the energy field of the 21st century. Hydrogen energy, as an ideal energy carrier, stands out among many new energy sources due to its high calorific value, good combustion performance, abundant reserves, and clean and environmentally friendly characteristics. Among them, solid oxide fuel cells are one of the most widely used fuel cells. Solid oxide fuel cells have advantages such as wide fuel adaptability, high energy conversion efficiency, all-solid-state operation, modular assembly, and zero pollution. Because fuel cell power generation is not limited by the Carnot cycle, it can directly convert the chemical energy in the fuel into electrical energy, exhibiting high energy conversion efficiency. Its theoretical conversion efficiency can reach 80%~90%, making it promising for applications in distributed power generation, communications, aerospace, and transportation.

[0003] Solid oxide fuel cells (SOFCs) are an important type of fuel cell with broad application prospects in energy conversion and utilization. During fuel cell operation, reactant gases enter the cell and are primarily transported through convection and diffusion, a process commonly referred to as gas mass transfer. Within the flow channels, gas transport mainly occurs via convection, while within the porous electrode structure, it primarily occurs via diffusion. The gas transport efficiency within the flow channels and porous electrodes directly affects the distribution and utilization of reactants within the cell, thus significantly influencing the fuel cell's output performance and energy conversion efficiency. However, in current technologies, insufficient gas transport capacity within the fuel cell can easily lead to uneven reactant distribution and reduced gas utilization, thereby limiting further performance improvements. Therefore, by rationally selecting fuel cell materials and optimizing the flow channel structure to enhance the convective transport capacity within the flow channels and the diffusion and transport capacity within the porous electrodes, it is crucial for improving internal gas transport conditions, increasing reactant gas utilization, and enhancing the overall performance of solid oxide fuel cells.

[0004] Currently, performance optimization of solid oxide fuel cells mainly includes two aspects: material optimization and structural design optimization. Material optimization focuses on various components of the cell, including electrode materials, electrolyte materials, and catalysts. It aims to improve the electronic and ionic conductivity of materials by enhancing their properties or developing novel materials. For example, strategies such as material nano-sizing, alloying, interface structure optimization, or the introduction of rare earth elements can further improve electrode reactivity and overall cell performance, while simultaneously reducing production costs and manufacturing complexity to some extent. Structural design optimization primarily involves rationally designing the internal structure of the fuel cell to improve the flow and mass transfer characteristics of reactant gases within the cell, thereby enhancing the cell's output performance. For example, optimizing the flow channel geometry, employing multi-stage flow channel design, or microchannel technology can increase the contact time between the reactant gases and the electrode surface, improve the mass transfer efficiency of reactants, and reduce flow resistance to some extent, thereby improving heat and mass transfer performance. Common optimization variables in existing research include electrode and electrolyte material types, porosity, reactant gas inlet velocity and flow rate, flow channel structure, and system operating temperature and pressure.

[0005] However, existing conventional direct-flow channel structures still have certain limitations, such as short contact time between gas and electrode surfaces, uneven gas distribution within the channel, and large pressure drop. These factors adversely affect the mass transfer efficiency and output power of the battery. Furthermore, uneven gas distribution within the channel can lead to insufficient fuel and oxidant supply in the later stages of the channel, resulting in uneven internal temperature distribution, increased thermal stress, and impact on battery stability and durability. To address these issues, some studies have incorporated various baffle structures within the channel to enhance gas turbulence and improve battery output power. However, these structures often generate significant flow pressure drops, leading to increased system power consumption. Therefore, designing a channel structure that reduces flow pressure drop, minimizes additional energy consumption, and improves gas distribution while ensuring improved battery output performance has become a pressing technical challenge in the optimization of solid oxide fuel cell structures. Summary of the Invention

[0006] The purpose of this invention is to provide a novel flow channel structure for solid oxide fuel cells and a multi-method coupled analysis framework to improve uneven gas distribution in the flow channel, enhance mass transfer efficiency, and improve battery performance.

[0007] To achieve the above objectives, the present invention provides a solid oxide fuel cell flow channel structure, which, from top to bottom, comprises a cathode connector, a cathode flow channel, a cathode electrode, an electrolyte, and an anode electrode. The anode flow channel and anode connector are characterized in that: the cathode connector is connected to the cathode electrode to form a cathode flow channel, and the anode connector is connected to the anode electrode to form an anode flow channel; both the cathode flow channel and the anode flow channel are rectangular straight channels; a set of slotted trapezoidal blocks are provided in the cathode flow channel and connected to the cathode connector.

[0008] Furthermore, the slotted trapezoidal structures inside the cathode flow channel are evenly distributed, and their height increases gradually from the inlet to the outlet of the cathode flow channel. A second aspect of the present invention discloses a multi-method coupling analysis framework for the above-described solid oxide fuel cell flow channel structure. This optimization analysis framework includes: S1. Establish an objective function, determine variable factors and their corresponding levels based on the optimization objective; the objective function is the power density of the fuel cell, and the variable factors are the structural parameters of the flow channel structure; establish a three-dimensional model of a solid oxide fuel cell with a novel gradient oblique slotted trapezoidal flow channel structure in COMSOL Multiphysics, and conduct mesh independence research and verification on the model; determine a suitable experimental scheme, generate multiple sets of experiments for simulation, and use the simulation results as data samples; S2. Establish the relationship between design variables and objective function using the grey relational analysis method, which includes uniformization, calculation of grey relational coefficients, calculation of grey relational degree, and sorting. S3. Verify and correct step S3 above using analysis of variance. S4. Based on the obtained uniformized matrix, a weighted normalized matrix is ​​constructed using the entropy weight method, and grey relational analysis and variance analysis are performed to obtain the contribution of factor variables to the overall performance of the model.

[0009] Specifically, the gas flow pattern of the fuel cell model is co-current. The reactant gas enters the battery through the inlet channel, diffuses into the porous electrode, and undergoes an electrochemical reaction at the three-phase boundary to generate water and release electrons. The electrons flow through the connector to the load and supply power to it. The water generated by the fuel cell is discharged from the battery in the form of water vapor along with the unreacted gas.

[0010] The cathode reaction gas is air, and the anode reaction gas is hydrogen.

[0011] The electrochemical reaction equations for the battery cathode and anode are as follows: cathode: O2 + 2e- → O2- (1) Anode: H2 + O2- → H2O + 2e- (2) The conservation equations describing the transport process in an electrochemical reaction are as follows: Conservation of mass:

[0012] Conservation of momentum:

[0013] Component conservation:

[0014] Energy conservation:

[0015] In the formula, r For density, e Porosity u For speed, g For the shear stress tensor, m For dynamic viscosity, xi For quality fraction, Dieff For the effective diffusion coefficient, ST It is an overvoltage. keff The effective thermal conductivity.

[0016] Furthermore, the parameters include operating temperature, fuel inlet flow rate, electrode porosity, electrolyte layer thickness, gradient change rate of the gradient-cut slotted trapezoidal fin structure, and spacing of the gradient-cut slotted trapezoidal fin structure; the objective function includes the output power density of the solid oxide fuel cell and the power of the auxiliary parasitic device used to transport the reactant gas; the power of the parasitic device... W prs means the following:

[0017] In the formula, m The mass flow rate of the gas. or MEC stands for the mechanical efficiency of the compressor. T in and T "out" represents the inlet and outlet temperatures, respectively.

[0018] This invention improves the output power and current density of solid oxide fuel cells while reducing concentration polarization. A gradient-cut, trapezoidal-finned baffle block within the flow channel enhances the mass transfer capacity of the reactant gas, effectively increasing the fuel cell's output power. Furthermore, a multi-method coupled analysis framework is established, providing insights for analyzing the structural and operational parameters of solid oxide fuel cells and improving optimization design efficiency.

[0019] The advantages of the gradient oblique slotted trapezoidal fin structure solid oxide fuel cell of the present invention compared with the conventional direct-flow solid oxide fuel cell are: This invention improves the power density of fuel cells and enhances the gas mass transfer process by adding gradient-cut slotted trapezoidal fin block in the cathode flow channel. It can also quantitatively evaluate the contribution of solid oxide fuel cell structural parameters and operating conditions to the system through a multi-analysis framework, which facilitates optimization. Attached Figure Description

[0020] Figure 1 is a schematic diagram of a gradient oblique groove trapezoidal fin flow channel structure of a solid oxide fuel cell according to an embodiment of the present invention.

[0021] Figure 2 for Figure 1 The image shows a plan view of the cathode side of a gradient-cut slotted trapezoidal fin flow channel in a solid oxide fuel cell, where (21) is a front view, (22) is a sectional view, and (23) is a top view. In the above figure: 1 - anode electrode; 2 - electrolyte; 3 - cathode electrode; 4 - anode flow channel; 5 - cathode flow channel; 11 - anode connector; 31 - cathode connector; h1 - minimum height of the block; h2 - maximum height of the block; E - center distance of the blocks; d - groove width; R - chamfer; S - groove.

[0022] Figure 3 This is a cross-sectional schematic diagram of a three-dimensional cathode connector.

[0023] Figure 4 This is a schematic diagram comparing the flow channel structure described in this invention with other flow channel structures, wherein (41) is a traditional direct flow channel and (42) is a gradient oblique slotted trapezoidal fin structure flow channel.

[0024] Figure 5 The performance of two solid oxide fuel cells with different flow channels is compared. (51) is a comparison of polarization curves, and (52) is a comparison of power density curves.

[0025] Figure 6 This is a flowchart of a multi-method coupling analysis framework for the flow channel structure of a solid oxide fuel cell proposed in this invention. Detailed Implementation

[0026] Currently, in the flow channel structures of solid oxide fuel cells, the cathode and anode flow channels are usually rectangular direct-flow channels. This type of flow channel has low mass transfer efficiency, poor stability, and poor durability.

[0027] The gradient-cut slotted trapezoidal finned flow channel solid oxide fuel cell of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments of the present invention are only used to illustrate the device of the present invention, but the implementation of the present invention is not limited thereto.

[0028] Example 1: The gradient oblique slotted trapezoidal fin flow channel structure provided by the present invention is shown in Figure 1. According to the requirements of enhancing mass transfer, a number of oblique slotted trapezoidal block with gradient changes are provided in the cathode flow channel.

[0029] Specifically, referring to Figures 2 and 3, the structural parameters of the novel flow channel are determined by the slot width, the center distance of the block, the chamfer, and the minimum and maximum height. The gradient-cut, slotted trapezoidal fin structure inside the flow channel is evenly distributed. Figure 4 shows a cross-sectional schematic diagram of the flow channel with the novel gradient-cut, slotted trapezoidal fin structure and a common flow channel.

[0030] Both the cathode and anode channels are rectangular direct current channels.

[0031] The optimized structural parameters of the flow channel are obtained based on a framework combining multiple analysis methods.

[0032] Example 2: Referring to Figure 1, a solid oxide fuel cell mainly includes a cathode flow channel, an anode flow channel, a cathode electrode, an electrolyte, and an anode electrode. The cathode flow channel adopts the solid oxide fuel cell flow channel structure as described in Example 1.

[0033] The gas flow pattern of the fuel cell model is co-current. The reactant gas enters the battery through the inlet channel, diffuses into the porous electrode, and undergoes an electrochemical reaction at the three-phase boundary to generate water and release electrons. The electrons flow through the connector to the load and supply power to it. The water generated by the fuel cell is discharged from the battery in the form of water vapor along with the unreacted gas.

[0034] The cathode reaction gas is air, and the anode projection gas is wet hydrogen.

[0035] The electrochemical reaction equations for the battery cathode and anode are as follows: cathode: O2 + 2e- → O2- (1) Anode: H2 + O2- → H2O + 2e- (2) The conservation equations describing the transport process in an electrochemical reaction are as follows: Conservation of mass:

[0036] Conservation of momentum:

[0037] Component conservation:

[0038] Energy conservation: ▽ (pi UiT )=▽ keff ▽T + ST (6) In the formula, r For density, e Porosity u For speed, g For the shear stress tensor, m For dynamic viscosity, xi For quality fraction, Dieff For the effective diffusion coefficient, ST It is an overvoltage. keff The effective thermal conductivity.

[0039] Referring to Figure 5, under otherwise unchanged conditions, the solid oxide fuel cell with a gradient oblique slotted trapezoidal fin structure has better output performance than other types of flow channels described in Figure 4.

[0040] This invention incorporates a gradient-cut, slotted trapezoidal fin structure as a stop block in the cathode flow channel, and optimizes the structural and operational parameters of the model using a multi-method coupled analysis framework. This invention enhances the diffusion of gas in the flow channel, thereby improving the performance of the fuel cell. This invention can obtain a high-performance solid oxide fuel cell flow channel configuration.

Claims

1. A flow channel structure for a solid oxide fuel cell, comprising, from top to bottom, a cathode connector, a cathode flow channel, a cathode electrode, an electrolyte, an anode electrode, an anode flow channel, and an anode connector, characterized in that: The cathode connector is connected to the cathode electrode to form a cathode flow channel, and the anode connector is connected to the anode electrode to form an anode flow channel; both the cathode flow channel and the anode flow channel are rectangular straight channels; a set of slotted trapezoidal blocks are provided in the cathode flow channel and connected to the cathode connector.

2. The solid oxide fuel cell flow channel structure according to claim 1, characterized in that: The gradient slotted ladder-shaped structure inside the cathode flow channel is evenly distributed, and its height increases gradually from the inlet to the outlet of the cathode flow channel.

3. A multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell, characterized in that: The parameters include operating temperature, fuel intake flow rate, electrode porosity, electrolyte layer thickness, gradient change rate of the gradient oblique grooved trapezoidal fin structure, and spacing of the gradient oblique grooved trapezoidal fin structure; the analysis results are used to establish the relationship between variables and battery performance.

4. The multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell according to claim 3, characterized in that, The specific steps are as follows: S1. Establish an objective function, determine variable factors and their corresponding levels based on the optimization objective; the objective function is the power density of the fuel cell, and the variable factors are the structural parameters of the flow channel structure; establish a three-dimensional model of a solid oxide fuel cell with a novel gradient oblique slotted trapezoidal flow channel structure in COMSOL Multiphysics, and conduct mesh independence research and verification on the model; determine a suitable experimental scheme, generate multiple sets of experiments for simulation, and use the simulation results as data samples; S2. Establish the relationship between design variables and objective function using the grey relational analysis method, which includes uniformization, calculation of grey relational coefficients, calculation of grey relational degree, and sorting. S3. Verify and correct step S3 using analysis of variance. S4. Based on the obtained uniformized matrix, construct a weighted normalized matrix using the entropy weight method, and perform grey relational analysis and variance analysis to obtain the contribution of factor variables to the overall performance of the model.

5. The multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell according to claim 4, characterized in that: In step S1, the gas flow mode of the fuel cell model is co-current. The reactant gas enters the battery through the inlet of the flow channel, enters the porous electrode through diffusion, and undergoes an electrochemical reaction at the three-phase boundary to generate water and release electrons. The electrons flow through the connector to the load and supply power to it. The water generated by the fuel cell is discharged from the battery in the form of water vapor along with the unreacted gas.

6. The multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell according to claim 5, characterized in that: The cathode reaction gas is air, and the anode reaction gas is hydrogen.

7. The multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell according to claim 6, characterized in that: The electrochemical reaction equations for the battery cathode and anode are as follows: cathode: O2+2e →O2 (1) Anode: H2 + O2 →H₂O + 2e (2).

8. The multi-method coupled analysis framework for the flow channel structure of a solid oxide fuel cell according to claim 5, characterized in that: The conservation equations describing the transport process in an electrochemical reaction are as follows: Conservation of mass: Conservation of momentum: Component conservation: Energy conservation: ▽ (pi UiT )=▽ keff ▽ T + ST (6) In the formula, ρ For density, ε Porosity u For speed, ζ For the shear stress tensor, μ For dynamic viscosity, xi For quality fraction, Dieff For the effective diffusion coefficient, ST It is an overvoltage. keff The effective thermal conductivity.

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