Flow channel optimization method for high specific power cathode closed air-cooled stack
By optimizing the flow channel structure of the cathode closed-loop air-cooled fuel cell stack, the problem of balancing low flow resistance and uniform mass transfer in flow channel design was solved, thus achieving stable operation and efficient energy conversion of the high specific power fuel cell stack.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- MENGHYDROGEN (NANTONG) POWER TECH CO LTD
- Filing Date
- 2026-04-29
- Publication Date
- 2026-07-31
AI Technical Summary
Existing serpentine and parallel flow channel designs cannot simultaneously meet the low flow resistance requirements of high specific power closed-loop air-cooled fuel cell stacks and the goal of uniform mass transfer and heat dissipation, resulting in localized flooding or film drying under high current density and excessively rapid performance degradation.
By collecting boundary parameters of the cathode stack, defining the coupling layout interval of gas transport and heat exchange, constructing a biomimetic branch flow channel and micro-ribbed turbulence structure, calibrating the width-to-height ratio parameters of the flow channel, deploying dual cooling wave channels and micron-level water guide channels, and optimizing the flow channel length and turning angle, the coordinated adaptation of gas-liquid transport and heat exchange is achieved.
It improves the uniformity of mass transfer and diffusion efficiency of the reactant gas, stabilizes the stack temperature, avoids flooding of the flow channel, reduces gas flow resistance, and improves the stack's operating efficiency and reliability.
Smart Images
Figure CN122494697A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fuel cell technology, specifically to a flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks. Background Technology
[0002] Proton exchange membrane fuel cells (PEMFCs) are widely used in portable power supplies, drones, and other fields due to their high efficiency and cleanliness, with high specific power becoming the core development direction for fuel cell stack technology. Cathode-closed air-cooled fuel cell stacks achieve gas path separation through independent cooling tanks and reaction tanks, reducing environmental interference and improving durability. They also eliminate the complex piping of liquid cooling systems, offering both compact structure and cost advantages. The flow channel, as a key structure of the bipolar plates, directly affects gas mass transfer and hydrothermal management efficiency. Its design rationality plays a decisive role in the performance stability of the fuel cell stack under high specific power conditions, making flow channel optimization a core technical path to improve the power density and lifespan of the fuel cell stack.
[0003] The invention patent application with application number 202510377601.2 discloses a high specific power cathode closed-loop air-cooled fuel cell stack. This application aims to solve the problem of "the thermal consistency problem in the prior art. The structure of the cooling channel needs further optimization design to improve the heat dissipation efficiency of the stack and improve the thermal consistency of the stack. However, the water management of the stack is a challenge in the wide temperature range of air-cooled fuel cells. The existing flow field design is difficult to balance low flow resistance, high drainage capacity and efficient heat dissipation, resulting in a decrease in battery performance or a shortened lifespan. There is currently no good solution."
[0004] However, existing serpentine and parallel flow channel designs cannot simultaneously meet the low flow resistance requirements and uniform mass transfer and heat dissipation goals of high specific power closed-loop air-cooled fuel cell stacks. Under high current density, local flooding or film drying is likely to occur, which in turn leads to excessively rapid performance degradation.
[0005] To address this, we propose a flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks. Summary of the Invention
[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a flow channel optimization method for high specific power cathode closed air-cooled fuel cell stacks, which can effectively solve the problems of the prior art.
[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions; This invention discloses a flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks, comprising: collecting boundary parameters of the cathode fuel cell stack reaction field, delineating the gas transport and heat exchange coupling layout interval, and determining the flow channel configuration reference constraint conditions; constructing a biomimetic branch flow channel in situ according to the coupling layout interval, integrally forming a micro-ribbed turbulence structure, and calibrating the flow channel aspect ratio configuration matching parameters; forming a double cooling wave groove along the outer periphery of the cathode closed flow channel configuration, limiting the axial extension path of the wave groove, and completing the coaxial layout of the cooling structure and the reaction flow channel; processing micron-level water guide grooves on the bottom surface of the flow channel, setting the flow channel inlet and outlet pressure difference calibration threshold, and deploying flow channel control nodes linked to pressure difference; cutting the flow channel length in segments according to the gas transport path, performing arc passivation treatment on the flow channel corners, and integrally processing the flow channel variable diameter acceleration transition configuration; coupling the full flow channel configuration parameters with the field boundary conditions, completing the full-domain adaptation verification of the flow channel structure, and locking the cathode flow channel forming processing parameters.
[0008] Furthermore, in the stage of calibrating the flow channel aspect ratio configuration matching parameters, a flow channel cross-section matching model is constructed based on the mass transfer characteristics of the cathode reactant gas. The optimal value of the flow channel aspect ratio is then determined through the mass transfer matching coefficient, which is calculated using the following formula: ; The expression for the flow channel cross-section matching model is as follows: ; In the formula: The mass transfer matching coefficient of the flow channel; The optimal mass transfer matching coefficient for the flow channel; The height of the flow channel cross section; The width of the flow channel cross-section; The diffusion coefficient of the cathode reaction gas; This refers to the working density of the cathode reaction gas. This represents the mainstream flow velocity of the gas within the flow channel. The optimal mass transfer matching coefficient of the flow channel Mass transfer matching coefficient of the flow channel The constant value when taking the maximum value of the entire domain.
[0009] Furthermore, the diffusion coefficient of the cathode reaction gas ; In the formula: The basic diffusion coefficient of the cathode reaction gas under standard operating conditions; The number of microribs deployed within a single flow channel branch; The total number of branch levels in the flow channel; The height of the microrib structure; The equivalent diameter of the flow channel.
[0010] Furthermore, the microribbed flow disturbance structure is integrally formed with the biomimetic branch flow channel. The microribs are arranged in a gradient along the gas diffusion path, and the extension direction of the microribs forms a preset angle with the mainstream gas direction of the flow channel. The cross-sectional configuration of the microribs is synchronously adapted and adjusted according to the branch level of the flow channel.
[0011] Furthermore, when the dual cooling wave channels are coaxially arranged with the reaction channel, the matching ratio of the wave channel depth, width, and channel cross-section is simultaneously calibrated. The wave channel configuration parameters are constrained by the cooling heat transfer efficiency coefficient, and the calculation formula for the cooling heat transfer efficiency coefficient is as follows: ; In the formula, The coefficient of performance for cooling heat transfer; This represents the total heat exchange area of the dual cooling wave channels; This represents the total surface area of the cathode reaction channel; The average temperature rise of the flow channel reaction zone; Reference temperature rise for the fuel cell stack casing; Among them, when constraining the trough configuration parameters by the cooling heat transfer efficiency coefficient, the trough depth, trough width and axial extension curvature are adjusted to keep the cooling heat transfer efficiency coefficient within the preset efficiency range.
[0012] Furthermore, the micron-level water guide channels are continuously arrayed along the length of the flow channel, the cross-section of the water guide channels has a gradually changing configuration, the density of the water guide channels is adjusted synchronously with the density of the flow channel branch nodes, and the water guide channels smoothly transition to the bottom surface of the flow channel.
[0013] Furthermore, the differential pressure linkage flow channel control node is used to collect the flow channel inlet and outlet pressure parameters in real time and compare them with the preset differential pressure calibration threshold. When the actual differential pressure is greater than the preset differential pressure calibration threshold, the gas input flow rate is gradually increased according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset upper limit value. When the actual differential pressure is less than the preset differential pressure calibration threshold, the gas input flow rate is gradually decreased according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset lower limit value.
[0014] Furthermore, the flow channel length is segmented according to the gas transmission path, the flow channel corners are rounded and blunted, and the flow channel diameter change is accelerated during the one-piece machining stage. The flow channel resistance parameters are optimized according to the gas flow characteristics, and the flow channel configuration machining accuracy is constrained by the friction coefficient. ; In the formula: This is the friction coefficient along the flow path; This is the correction factor for the radius of curvature at the flow channel corner; The effective transmission length of a single flow channel; The equivalent diameter of the flow channel; The Reynolds number for gas flow within the flow channel; Among them, when constraining the machining accuracy of the flow channel configuration by the friction coefficient, the friction coefficient is controlled within the preset resistance threshold range.
[0015] Furthermore, during the full-domain adaptation verification of the flow channel structure, the gas mass transfer uniformity, heat exchange efficiency, drainage performance and flow resistance are verified simultaneously. If all items meet the preset adaptation threshold, the verification is deemed qualified; otherwise, the flow channel configuration parameters are iteratively adjusted until the verification is passed. In the stage of locking the cathode flow channel forming processing parameters, the full flow channel configuration parameters, differential pressure control parameters, and heat exchange matching parameters after verification are integrated into an integrated processing reference parameter.
[0016] On the other hand, a high specific power cathode closed-loop air-cooled fuel cell stack is provided, wherein the cathode flow channel of the fuel cell stack is prepared and formed using the flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks. The cathode flow channel integrates a biomimetic branch flow channel, a micro-ribbed turbulence structure, a dual cooling wave groove, and a micron-level water guide groove, forming a closed flow channel system that couples gas-liquid transport and heat exchange.
[0017] Compared with the known prior art, the technical solution provided by this invention has the following beneficial effects: This invention delineates the coupling layout interval by collecting boundary parameters of the cathode fuel cell stack and constructs a biomimetic branched flow channel and micro-ribbed turbulence structure. It accurately calibrates the aspect ratio matching parameters of the flow channel to improve the uniformity of mass transfer and diffusion efficiency of the reactant gas. It arranges double cooling troughs on the outer periphery of the flow channel and optimizes the axial configuration to enhance the heat exchange efficiency of the flow channel and stabilize the temperature of the fuel cell stack reaction area. It processes an array of micron-sized water guide channels on the bottom surface of the flow channel to smoothly discharge liquid water. It dynamically adjusts the gas flow rate with pressure difference linkage control nodes to match the gas-liquid two-phase transport rate and avoids the phenomenon of water flooding in the flow channel. It also optimizes the length of the flow channel in segments and performs corner passivation and diameter change transition treatment to reduce gas flow resistance and reduce airflow energy loss. It completes the full-domain adaptation verification by coupling the parameters of the entire flow channel and boundary conditions, and uniformly locks the molding and processing parameters. Finally, it achieves the coordinated adaptation of the mass transfer, heat exchange, drainage and flow performance of the flow channel, thereby ensuring the stable operation of the cathode closed air-cooled fuel cell stack and optimizing the stability and overall energy efficiency of the fuel cell stack operation. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.
[0019] Figure 1 This is a flowchart illustrating the flow channel optimization method for high specific power cathode closed-circuit air-cooled fuel cell stacks. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0021] The present invention will be further described below with reference to embodiments. Example
[0022] The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks in this embodiment is as follows: Figure 1 As shown, it includes: Collect boundary parameters of the cathode stack reaction field, delineate the gas transport and heat exchange coupling layout interval, and determine the reference constraint conditions of the flow channel configuration. Based on the in-situ construction of the coupled layout section, a biomimetic branch flow channel is constructed, and an integral micro-ribbed turbulence structure is formed. The width-to-height ratio configuration matching parameters of the flow channel are calibrated. In the stage of calibrating the flow channel aspect ratio configuration matching parameters, a flow channel cross-section matching model is constructed based on the mass transfer characteristics of the cathode reactant gas. The optimal value of the flow channel aspect ratio is determined by the mass transfer matching coefficient. The formula for calculating the mass transfer matching coefficient is as follows: ; The expression for the flow channel cross-section matching model is as follows: ; In the formula: The mass transfer matching coefficient of the flow channel; The optimal mass transfer matching coefficient for the flow channel; The height of the flow channel cross section; The width of the flow channel cross-section; The diffusion coefficient of the cathode reaction gas; This refers to the working density of the cathode reaction gas. This represents the mainstream flow velocity of the gas within the flow channel. The above formula combines the channel cross-sectional height, width, cathode reaction gas diffusion coefficient, working density and mainstream flow velocity to construct the mass transfer matching relationship. The optimal mass transfer matching coefficient with the largest value in the whole domain is used to lock the channel width-to-height ratio, so that the channel cross-sectional parameters are accurately adapted to the gas mass transfer characteristics. Starting from the essence of mass transfer, the optimal matching between channel configuration and mass transfer efficiency is achieved. Optimal mass transfer matching coefficient of flow channel Mass transfer matching coefficient of the flow channel A constant value when the maximum value of the entire domain is obtained; Cathode reaction gas diffusion coefficient ; In the formula: The basic diffusion coefficient of the cathode reaction gas under standard operating conditions; The number of microribs deployed within a single flow channel branch; The total number of branch levels in the flow channel; The height of the microrib structure; The equivalent diameter of the flow channel; The above formula takes the basic diffusion coefficient of the cathode reaction gas under standard working conditions as the benchmark, and combines the number of microribs in a single flow channel branch with the total number of branch levels of the flow channel to complete the correction calculation. It can accurately reflect the actual effect of microribs and biomimetic branch flow channels on gas diffusion, and allow the diffusion coefficient to be dynamically adapted with the flow channel structure parameters, providing more accurate data that fits the actual working conditions for flow channel mass transfer matching calculation. The micro-ribbed turbulence structure is integrally formed with the biomimetic branch flow channel. The micro-ribs are arranged in a gradient along the gas diffusion path. The extension direction of the micro-ribs is at a preset angle with the mainstream gas direction of the flow channel. The cross-sectional configuration of the micro-ribs is synchronously adapted and adjusted according to the branch level of the flow channel. The preset included angle is calibrated according to the mainstream gas flow velocity and diffusion path direction in the flow channel. The included angle is set to decrease in a gradient as the flow channel branch level increases. When the micro-rib cross-section configuration is adapted and adjusted, the higher the branch level, the greater the width-to-thickness ratio of the micro-rib cross-section, and the height of the micro-rib is adapted proportionally to the height of the branch flow channel cross-section. A double cooling wave groove is configured along the outer periphery of the cathode closed flow channel, which limits the axial extension path of the wave groove and completes the coaxial layout of the cooling structure and the reaction flow channel. When the dual cooling wave channels are coaxially arranged with the reaction channel, the matching ratio of the wave channel depth, width, and channel cross-section is simultaneously calibrated. The wave channel configuration parameters are constrained by the cooling heat transfer efficiency coefficient. The formula for calculating the cooling heat transfer efficiency coefficient is as follows: ; In the formula, The coefficient of performance for cooling heat transfer; This represents the total heat exchange area of the dual cooling wave channels; This represents the total surface area of the cathode reaction channel; The average temperature rise of the flow channel reaction zone; Reference temperature rise for the fuel cell stack casing; The above formula quantifies the cooling heat exchange efficiency by using the ratio of the total heat exchange area of the dual cooling troughs, the total surface area of the cathode reaction channel, the average temperature rise of the channel reaction domain and the reference temperature rise of the stack shell. This constrains the configuration parameters such as the trough depth and width, so that the heat exchange efficiency is stabilized within the preset range, and the coaxial high-efficiency heat exchange of the cooling structure and the reaction channel is achieved, thereby solving the problem of poor heat exchange adaptability of closed air-cooled stacks. Among them, when constraining the trough configuration parameters by the cooling heat transfer efficiency coefficient, the trough depth, trough width and axial extension curvature of the trough are adjusted to keep the cooling heat transfer efficiency coefficient within the preset efficiency range. Micron-level water guide grooves are processed on the bottom surface of the flow channel, the pressure difference calibration threshold of the flow channel inlet and outlet is set, and flow channel control nodes linked by pressure difference are set up. Micron-level water guide channels are continuously arrayed along the length of the flow channel. The cross-section of the water guide channels has a gradually changing configuration. The density of the water guide channels is adjusted synchronously with the density of the flow channel branch nodes. The water guide channels and the bottom surface of the flow channel are smoothly transitioned. Specifically, the smooth transition between the water guide channel and the bottom surface of the flow channel is achieved by the edge of the water guide channel opening and the bottom surface of the flow channel being connected by a rounded chamfer, with the chamfer radius being proportionally matched to the depth of the water guide channel. The differential pressure linkage flow channel control node is used to collect the flow channel inlet and outlet pressure parameters in real time and compare them with the preset differential pressure calibration threshold. When the actual differential pressure is greater than the preset differential pressure calibration threshold, the gas input flow rate is gradually increased according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset upper limit value. When the actual differential pressure is less than the preset differential pressure calibration threshold, the gas input flow rate is gradually decreased according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset lower limit value, so as to regulate the gas phase flow rate and liquid phase discharge rate in the flow channel to match, stabilize the gas-liquid two-phase transmission state and suppress cathode flow channel flooding. The preset adjustment step size is determined by coupling the flow channel volume, the gas flow cross-sectional area of a single branch flow channel, and the rated supply flow rate of the cathode reaction gas. The step size value is positively correlated with the fluctuation amplitude of the gas-liquid two-phase transmission in the flow channel, ensuring that the flow adjustment is shock-free and without sudden changes. The flow channel length is cut into segments according to the gas transmission path, the flow channel corners are rounded and blunted, and the flow channel variable diameter accelerated transition configuration is machined in one piece. The flow channel length is segmented according to the gas transport path, the flow channel corners are rounded and blunted, and the flow channel diameter change is accelerated during the one-piece machining transition stage. The flow channel resistance parameters are optimized according to the gas flow characteristics, and the flow channel configuration machining accuracy is constrained by the friction coefficient. ; In the formula: This is the friction coefficient along the flow path; This is the correction factor for the radius of curvature at the flow channel corner; The effective transmission length of a single flow channel; The equivalent diameter of the flow channel; The Reynolds number for gas flow within the flow channel; This formula integrates the flow channel corner radius correction coefficient, the effective transmission length of a single flow channel segment, the equivalent diameter, and the gas Reynolds number to accurately calculate the flow channel friction resistance. It then uses a preset resistance threshold to determine the flow channel segment length, corner radius, and transition size, thereby optimizing the flow channel resistance parameters, effectively reducing gas transmission loss, and improving the flow channel transmission stability. Among them, when constraining the machining accuracy of the flow channel configuration by the friction coefficient, the friction coefficient is controlled within the preset resistance threshold range, thereby constraining and determining the machining accuracy of the flow channel segment length, corner radius and diameter transition dimension. Flow channel corner radius correction factor The value range is [0.6, 1]. The larger the ratio of the corner radius to the equivalent diameter of the flow channel, the closer the value of the flow channel corner radius correction coefficient is to the lower limit of the range. Couple the full flow channel configuration parameters with the field boundary conditions to complete the full-domain adaptation verification of the flow channel structure and lock the cathode flow channel forming and processing parameters. During the full-domain adaptation verification of the flow channel structure, the gas mass transfer uniformity, heat exchange efficiency, drainage performance and flow resistance are verified simultaneously. If all items meet the preset adaptation threshold, the verification is deemed qualified; otherwise, the flow channel configuration parameters are iteratively adjusted until the verification is passed. During the stage of locking the cathode flow channel forming processing parameters, the verified full flow channel configuration parameters, differential pressure control parameters, and heat exchange matching parameters are integrated into a unified processing reference parameter.
[0023] A high specific power cathode closed-loop air-cooled fuel cell stack, wherein the cathode flow channel of the stack is prepared and formed using a flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks; The cathode flow channel integrates a biomimetic branch flow channel, a micro-ribbed turbulence structure, dual cooling wave channels, and a micron-level water guide channel, forming a closed flow channel system that couples gas-liquid transport and heat exchange.
[0024] In this embodiment, the method described above accurately determines the flow channel configuration parameters based on the actual operating conditions of the fuel cell stack, optimizes the diffusion and flow state of the gas in the flow channel, improves the uniformity of the supply of reactive gas, and the external cooling structure can efficiently remove the heat generated by the reaction, stabilize the operating temperature of the fuel cell stack, and the water guiding structure at the bottom of the flow channel can smoothly discharge liquid water. Combined with dynamic pressure difference adjustment, water accumulation in the flow channel is avoided. Optimizing the flow channel corners and transition structures can reduce airflow resistance and reduce energy loss. The processing standards are determined through full-domain parameter verification to ensure stable operation of the fuel cell stack and effectively improve the working efficiency and operational reliability of the air-cooled fuel cell stack.
[0025] It should be noted that: In the above embodiments, the biomimetic branch channel can be constructed in situ. Those skilled in the art need to understand the basis for the hierarchical division of the branch channel, the angle of the branch path layout, the number of branches at a single level, and the rules for the calibration of the intersection nodes. The above parameters are determined in combination with the boundary parameters of the cathode stack reaction field and the gas transport coupling range. The number of branch levels is divided into 2-4 levels based on the rated power of the stack and the cathode reaction gas flux. The angle between the branch path and the central axis of the channel is controlled between 15° and 45°. The number of branches at a single level is positively correlated with the total width of the channel, which can ensure that the gas distribution uniformity deviation of the branch channel does not exceed 5%.
[0026] The preset angle between the microribbed turbulence structure and the mainstream direction needs to be precisely calibrated according to the mainstream gas velocity and diffusion path in the flow channel. The angle of the first-level branch flow channel is set to 30°-45°, the second-level branch decreases to 20°-30°, and the third-level and above branches decrease to 10°-20°. The width-to-thickness ratio of the microrib cross section increases by 1.2-1.5 times with the increase of the branch level. The height of the microrib is taken as 1 / 5-1 / 3 of the height of the corresponding branch flow channel cross section. The spacing of the microribs along the gas diffusion path is 1 / 4-1 / 2 of the equivalent diameter of the flow channel, which can maintain stable gas mass transfer efficiency while enhancing the turbulence effect.
[0027] The axial extension path of the dual cooling troughs is defined by a sinusoidal curve, with the peaks and troughs corresponding to the high-heat reaction areas of the flow channel. The trough depth is 1 / 4 to 1 / 3 of the flow channel cross-sectional height, and the trough width is 1 / 5 to 1 / 4 of the flow channel cross-sectional width. The preset efficiency range of the cooling heat transfer efficiency coefficient is 0.7 to 0.9. By adjusting the axial curvature radius of the troughs, the heat transfer area can be precisely matched with the surface area of the reaction flow channel, thus meeting the requirements for uniform heat transfer in the stack cooling.
[0028] The micron-level water guiding channel adopts a trapezoidal gradient configuration with a wider top and narrower bottom. The channel opening width is 50-100μm, the channel bottom width is 20-50μm, and the channel depth is 30-60μm. The water guiding channels are arranged in an array with a spacing of 1-2mm along the length of the flow channel. The arrangement density increases synchronously with the flow channel branch node density at a ratio of 1:1.2. The radius of the rounded chamfer at the edge of the water guiding channel opening is 1 / 3-1 / 2 of the channel depth to achieve a smooth transition between the channel body and the bottom surface of the flow channel, thus structurally avoiding liquid phase retention and accumulation.
[0029] In the flow channel control node with differential pressure linkage, the differential pressure calibration threshold of the flow channel inlet and outlet is determined based on the rated operating current density of the fuel cell stack, with a value range of 5-15 kPa. The preset adjustment step size is calculated by coupling the flow channel volume, the cross-sectional area of a single branch flow, and the rated supply flow rate. The step size value is 2%-5% of the rated flow rate. The preset upper limit of the gas phase flow velocity is 1.5-2.0 m / s, and the lower limit is 0.5-1.0 m / s. The fluctuation amplitude of the gas-liquid two-phase transmission is controlled within ±10% to ensure that there is no impact or sudden change in the flow rate adjustment process.
[0030] The flow channel friction coefficient is preset to a resistance threshold range of 0.02-0.05, the ratio of the flow channel corner radius to the equivalent diameter is controlled at 0.3-0.6, and the corresponding corner radius correction coefficient is 0.6-0.8. The flow channel diameter change acceleration transition configuration adopts a conical transition form, the transition section length is 3-5 times the equivalent diameter of the flow channel, and the diameter change shrinkage ratio is 1.1-1.3, which effectively reduces the flow channel friction resistance and local resistance loss.
[0031] The full-domain adaptation verification of the flow channel structure should be judged by quantitative thresholds. The qualified thresholds are: gas mass transfer uniformity not less than 95%, heat exchange efficiency not less than 85%, drainage rate not less than 0.8 mL / min, and flow resistance not more than 20 kPa. When iterating, the mass transfer uniformity and heat exchange efficiency are the core indicators. Each adjustment of the flow channel aspect ratio, micro-rib parameters or corrugated groove size should not exceed 5% until all indicators meet the preset thresholds. Then, the full parameters are integrated to lock the cathode flow channel forming and processing benchmark.
[0032] Application example: Taking a closed-loop air-cooled cathode stack of a high-specific-power hydrogen fuel cell for vehicles with a rated power of 80kW as the implementation object, the cathode flow channel structure optimization design and fabrication were carried out: In the early stages of implementation, staff collected complete boundary parameters of the cathode reaction field of the fuel cell stack, including inlet pressure, operating temperature, rated gas flow rate, and shell heat dissipation limit. They precisely delineated the coupling layout range between cathode-side gas transmission and fuel cell heat exchange. Combining the overall assembly dimensions of the fuel cell stack and the reaction condition tolerance standards, they determined three types of benchmark constraints for the flow channel configuration: dimensional tolerance, pressure resistance, and heat exchange efficiency. This provided clear design boundaries for the subsequent flow channel structure design.
[0033] Based on the defined coupling layout interval, a three-level biomimetic branched flow channel was constructed in situ. The main body of the flow channel and the microribbed turbulence structure were manufactured using an integrated molding process. After the structural layout was completed, the aspect ratio configuration matching parameters of the flow channel were calibrated. Parameter calculations were performed in conjunction with the mass transfer characteristics of the cathode reaction gas, and the optimal mass transfer matching coefficient of the flow channel was finally determined to be a fixed value. The optimal ratio of the flow channel cross-section height to width perfectly matches the mass transfer requirements of the fuel cell reactor reaction. Simultaneously, the value of the cathode reaction gas diffusion coefficient was calibrated, and the number of microribs and the total branch level within the flow channel were matched to ensure the diffusion and transport efficiency of the gas within the flow channel. The microrib structure is arranged in a gradient along the gas diffusion path. The angle between its extension direction and the mainstream gas direction in the flow channel decreases with increasing branch level. The higher the branch level, the greater the aspect ratio of the microrib cross-section, and the height of the microrib is proportionally matched to the height of the branch flow channel cross-section.
[0034] Two sets of symmetrical dual cooling troughs are arranged on the outer periphery of the cathode closed flow channel, limiting the troughs to extend in a straight line along the stack axis, achieving precise coaxial arrangement of the cooling structure and the reaction flow channel. The matching ratio of trough depth, trough width and flow channel cross-section is simultaneously calibrated. After parameter calculation and adjustment, the cooling heat transfer efficiency coefficient is stably maintained within the preset efficiency range, fully meeting the heat dissipation requirements under high specific power operation of the stack.
[0035] A continuous array of micron-sized water guide channels is fabricated on the bottom surface of the entire flow channel. These channels employ a gradient cross-section design, and their density is adjusted synchronously with the density of the flow channel branch nodes. The edges of the water guide channel openings smoothly transition to the bottom surface of the flow channel via rounded chamfers, with the chamfer dimensions proportional to the channel depth. A pre-set pressure difference calibration threshold is established at the inlet and outlet of the flow channel. Pressure difference linkage control nodes are deployed at the inlet and outlet ends of the flow channel. These nodes collect inlet and outlet pressure data in real time and compare them with the calibration threshold. Based on the pressure difference deviation, the gas input flow rate is adjusted in fixed steps to precisely match the gas phase velocity and liquid phase discharge rate within the flow channel, stabilizing the gas-liquid two-phase transmission state. This effectively suppresses the cathode flow channel flooding problem from both structural and control perspectives. The adjustment step size is adapted to the flow channel volume and the rated gas supply flow rate, ensuring no flow shocks or sudden changes throughout the entire process.
[0036] Following the complete transport path of the cathode reaction gas, the flow channel is divided into four precisely cut segments. All flow channel corners are rounded and passivated, and the variable diameter transition configuration is machined simultaneously and integrally. The flow channel resistance parameters are optimized based on gas flow characteristics. Calculations show that the flow channel friction coefficient is stably controlled within a preset resistance threshold range. This, in turn, ensures the machining accuracy of the flow channel segment lengths, corner radius, and variable diameter transition dimensions. The flow channel corner radius correction coefficient is tailored to the corner size specifications, effectively reducing resistance losses during gas flow.
[0037] After completing the full flow channel structure design, all flow channel configuration parameters were coupled with the fuel cell stack field boundary conditions to conduct a full-domain adaptation verification of the flow channel structure. Simultaneously, four core indicators—gas mass transfer uniformity, heat transfer efficiency, drainage performance, and flow resistance—were verified. All indicators met the preset adaptation thresholds, and the verification was deemed successful. The verified flow channel configuration parameters, differential pressure control parameters, and heat transfer matching parameters were then integrated into unified processing reference parameters, completing the final parameter locking for the cathode flow channel optimization design.
[0038] The cathode flow channel of this 80kW high-specific-power cathode closed-loop air-cooled fuel cell stack for vehicles was prepared using the aforementioned optimized method. The finished flow channel integrates a biomimetic branched flow channel, a micro-ribbed turbulence structure, dual cooling wave channels, and micron-level water guiding channels, forming a complete gas-liquid transport and heat exchange coupled closed-loop flow channel system. On-vehicle testing demonstrated that the cathode flow channel of this fuel cell stack exhibits excellent mass transfer uniformity, and its heat dissipation efficiency meets the requirements of continuous high-power output. There are no issues such as channel flooding or gas flow obstruction throughout the process. Flow resistance losses are low, and the stability of the stack's output power, operational reliability, and overall service life are significantly improved, making it suitable for the high-load, long-range operation requirements of automotive fuel cells.
[0039] In summary, the method described in the above embodiments delineates the coupling layout interval by collecting boundary parameters of the cathode stack and constructing a biomimetic branched flow channel and micro-ribbed turbulence structure. It accurately calibrates the aspect ratio matching parameters of the flow channel to improve the uniformity of mass transfer and diffusion efficiency of the reactant gas. It arranges double cooling troughs on the outer periphery of the flow channel and optimizes the axial configuration to enhance the heat exchange efficiency of the flow channel and stabilize the temperature of the stack reaction area. It processes an array of micron-sized water guide channels on the bottom surface of the flow channel to smoothly discharge liquid water. It dynamically adjusts the gas flow rate with pressure difference linkage control nodes to match the gas-liquid two-phase transport rate and avoids the phenomenon of water flooding in the flow channel. It also optimizes the length of the flow channel in segments and performs corner passivation and diameter transition treatment to reduce gas flow resistance and reduce airflow energy loss. It couples the parameters of the entire flow channel with the boundary conditions to complete the full-domain adaptation verification and uniformly locks the molding and processing parameters. Finally, it completes the coordinated adaptation of mass transfer, heat exchange, drainage and flow performance of the flow channel, thereby ensuring the stable operation of the cathode closed air-cooled stack and optimizing the stability and overall energy efficiency of the stack operation.
[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for flow channel optimization for high specific power cathode closed air-cooled stack, characterized in that, include: Collect boundary parameters of the cathode stack reaction field, delineate the gas transport and heat exchange coupling layout interval, and determine the reference constraint conditions of the flow channel configuration. Based on the in-situ construction of the coupled layout section, a biomimetic branch flow channel is constructed, and an integral micro-ribbed turbulence structure is formed. The width-to-height ratio configuration matching parameters of the flow channel are calibrated. A double cooling wave groove is configured along the outer periphery of the cathode closed flow channel, which limits the axial extension path of the wave groove and completes the coaxial layout of the cooling structure and the reaction flow channel. Micron-level water guide grooves are processed on the bottom surface of the flow channel, the pressure difference calibration threshold of the flow channel inlet and outlet is set, and flow channel control nodes linked by pressure difference are set up. The flow channel length is cut into segments according to the gas transmission path, the flow channel corners are rounded and blunted, and the flow channel variable diameter accelerated transition configuration is machined in one piece. By coupling the full-channel configuration parameters with the field boundary conditions, the full-domain adaptation verification of the channel structure is completed, and the cathode channel forming and processing parameters are locked.
2. The flow channel optimization method for high specific power cathode- oriented closed air-cooled stack according to claim 1, characterized in that, In the stage of calibrating the flow channel aspect ratio configuration matching parameters, a flow channel cross-section matching model is constructed based on the mass transfer characteristics of the cathode reactant gas. The optimal value of the flow channel aspect ratio is determined by the mass transfer matching coefficient. The formula for calculating the mass transfer matching coefficient is as follows: ； In the formula, the expression of the flow passage cross section matching model is: ; wherein: is the flow channel mass transfer matching coefficient; is the flow channel optimal mass transfer matching coefficient; is the flow channel cross-sectional height; is the flow channel cross-sectional width; is the cathode reaction gas diffusion coefficient; is the cathode reaction gas working density; is the gas main flow velocity in the flow channel; The optimal mass transfer matching coefficient of the flow channel Mass transfer matching coefficient of the flow channel The constant value when taking the maximum value of the entire domain.
3. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 2, characterized in that, The cathode reaction gas diffusion coefficient ; In the formula: The basic diffusion coefficient of the cathode reaction gas under standard operating conditions; The number of microribs deployed within a single flow channel branch; The total number of branch levels in the flow channel; The height of the microrib structure; The equivalent diameter of the flow channel.
4. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, The microribbed turbulence structure is integrally formed with the biomimetic branch flow channel. The microribs are arranged in a gradient along the gas diffusion path. The extension direction of the microribs forms a preset angle with the mainstream gas direction of the flow channel. The cross-sectional configuration of the microribs is synchronously adapted and adjusted according to the branch level of the flow channel.
5. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, When the dual cooling wave channels are coaxially arranged with the reaction channel, the matching ratio of the wave channel depth, width, and channel cross-section is simultaneously calibrated. The wave channel configuration parameters are constrained by the cooling heat transfer efficiency coefficient, which is calculated using the following formula: ； In the formula, The coefficient of performance for cooling heat transfer; This represents the total heat exchange area of the dual cooling wave channels; This represents the total surface area of the cathode reaction channel; The average temperature rise of the flow channel reaction zone; Reference temperature rise for the fuel cell stack casing; Among them, when constraining the trough configuration parameters by the cooling heat transfer efficiency coefficient, the trough depth, trough width and axial extension curvature are adjusted to keep the cooling heat transfer efficiency coefficient within the preset efficiency range.
6. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, The micron-level water guide channels are continuously arrayed along the length of the flow channel. The cross-section of the water guide channels has a gradually changing configuration. The density of the water guide channels is adjusted synchronously with the density of the flow channel branch nodes, and the water guide channels smoothly transition to the bottom surface of the flow channel.
7. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, The differential pressure linkage flow channel control node is used to collect the flow channel inlet and outlet pressure parameters in real time and compare them with the preset differential pressure calibration threshold. When the actual differential pressure is greater than the preset differential pressure calibration threshold, the gas input flow rate is increased step by step according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset upper limit value. When the actual differential pressure is less than the preset differential pressure calibration threshold, the gas input flow rate is decreased step by step according to the preset adjustment step size until the flow channel gas phase flow rate matches the preset lower limit value.
8. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, The flow channel length is segmented according to the gas transport path, the flow channel corners are rounded and blunted, and the flow channel diameter change is accelerated during the one-piece machining transition stage. The flow channel resistance parameters are optimized according to the gas flow characteristics, and the flow channel configuration machining accuracy is constrained by the friction coefficient. ； In the formula: This is the friction coefficient along the flow path; This is the correction factor for the radius of curvature at the flow channel corner; The effective transmission length of a single flow channel; The equivalent diameter of the flow channel; The Reynolds number for gas flow within the flow channel; Among them, when constraining the machining accuracy of the flow channel configuration by the friction coefficient, the friction coefficient is controlled within the preset resistance threshold range.
9. The flow channel optimization method for high specific power cathode closed-loop air-cooled fuel cell stacks according to claim 1, characterized in that, During the full-domain adaptation verification of the flow channel structure, the gas mass transfer uniformity, heat exchange efficiency, drainage performance and flow resistance are verified simultaneously. If all items meet the preset adaptation threshold, the verification is deemed qualified; otherwise, the flow channel configuration parameters are iteratively adjusted until the verification is passed. In the stage of locking the cathode flow channel forming processing parameters, the full flow channel configuration parameters, differential pressure control parameters, and heat exchange matching parameters after verification are integrated into an integrated processing reference parameter.
10. A high specific power cathode closed-loop air-cooled fuel cell stack, characterized in that, The cathode flow channel of the fuel cell stack is prepared and shaped using the flow channel optimization method for high specific power cathode closed air-cooled fuel cell stacks as described in any one of claims 1 to 9. The cathode flow channel integrates a biomimetic branch flow channel, a micro-ribbed turbulence structure, a dual cooling wave groove, and a micron-level water guide groove, forming a closed flow channel system that couples gas-liquid transport and heat exchange.