A configuration and pre-tightening force synergistic optimization method for improving the sealing performance of an AEM electrolytic cell

Abstract

The application belongs to the field of electrolytic tank assembly mechanics and sealing optimization for hydrogen production by electrolysis of water, and proposes a configuration and pre-tightening force synergistic optimization method for improving the sealing performance of AEM electrolytic tank. First, a finite element model of the electrolytic tank is constructed, and the optimal number, specification and arrangement configuration of the bolts are selected through simulation comparison; the uniform pre-tightening force is calculated based on the design pressure calculation theory, and the horizontal and vertical bolt stress, deformation difference and cover arching mechanism caused by the asymmetric stiffness of the rectangular cover plate are analyzed by applying the uniform pre-tightening force. According to the bolt position, the differential pre-tightening force is distributed, and the assembly torque of each bolt is calculated as the fastening process parameter, and the optimal pre-tightening force combination is determined through multi-working condition comparison; the joint simulation check shows that the application can effectively balance the cover stress field and bolt load distribution, improve the uniformity of the sealing contact, inhibit the structural deformation and stress concentration, and significantly enhance the assembly structure stability and long-term operation reliability of the AEM electrolytic tank.

Description

Technical Field

[0001] This invention belongs to the field of assembly mechanics and sealing optimization of electrolyzers for hydrogen production by water electrolysis. Specifically, it designs a method for synergistic optimization of configuration and pre-tightening force to improve the sealing performance of AEM electrolyzers. Background Technology

[0002] With the development of the hydrogen energy industry, AEM electrolyzers are evolving towards larger scale and higher pressure, making the sealing reliability of their rectangular structures a key constraint on engineering applications. Currently, the industry generally adopts an experience-based uniform bolt preload strategy for assembly, and the selection of bolt quantity and size specifications lacks systematic mechanical justification. Due to the asymmetric stiffness of the rectangular cover plate and the complex internal loads, unreasonable bolt configurations and uniform preload patterns often lead to severe stress concentration and outward warping at the corners of the cover plate, and induce media leakage in the middle of the long side. Existing design schemes often ignore the nonlinear coupling relationship between bolt quantity, size specifications, and spatial preload distribution, failing to provide precise configuration schemes and load requirements for spatial differences, and making it difficult to fundamentally solve structural failure problems caused by improper configuration or load imbalance. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides a method for synergistic optimization of configuration and preload to improve the sealing performance of AEM electrolytic cells. This method achieves precise control over the stress distribution of the cover plate and the load state of the bolts themselves by synergistically optimizing the bolt configuration (number and specifications) and spatially differentiated preload, thereby enhancing the operational stability of AEM electrolytic cells under complex operating conditions.

[0004] The technical solution of this invention is as follows: A method for synergistic optimization of configuration and preload to improve the sealing performance of AEM electrolytic cells includes the following steps: S1. Taking the AEM electrolytic cell as the object, construct a three-dimensional finite element model including a cover plate, bipolar plate and gas diffusion layer. Set the number of bolts according to the long side span of the cover plate in the finite element model, and determine the distribution configuration of the bolts on the cover plate. S2. Using the theoretical uniform preload calculated from the electrolytic cell design pressure as a benchmark, a uniform preload is applied in the finite element model for analysis to obtain the benchmark stress state of the cover plate. According to the bolt distribution position, a differentiated preload load is distributed to each bolt, and the actual assembly torque of each bolt is calculated based on the differentiated preload. By comparing the stress distribution of the cover plate and the bolt load distribution under uniform preload and differentiated preload, the optimal preload combination is determined.

[0005] Further optimization involves making the geometry of the AEM electrolytic cell rectangular.

[0006] Further optimization is achieved by dividing the bolts in step S2 into four groups: the first group consists of bolts in the middle of the long side, the second group consists of bolts at the 1 / 4 position of the long side, the third group consists of bolts at the four corners, and the fourth group consists of bolts in the middle of the short side.

[0007] To further optimize, in step S1, the number of bolts is set to be greater than 28.

[0008] Further optimization involves setting the number of bolts to 30, and using a rectangular perimeter layout, with 8 bolts on each long side, 7 bolts on each short side, and 1 bolt at each corner, with the corner bolts counted in the number of bolts on the long sides.

[0009] Further optimization, after determining the optimal preload combination in step S2, also includes: S3. Based on the bolt configuration determined in steps S1 and S2, conduct joint simulation verification, collect data on cover plate stress distribution, full-slot bolt load and stress distribution, and complete the verification and confirmation of the synergistic optimization effect of differentiated preload strategy and bolt configuration.

[0010] Further optimization resulted in the bolt being an M18 model.

[0011] Further optimization is achieved by setting the preload of the first group to 120-130% of the standard value, the preload of the second group to 100-110% of the standard value, the preload of the third group to 85-90% of the standard value, and the preload of the fourth group to the standard value.

[0012] Further optimization: In step S2, the formula for calculating the actual torque of each bolt is as follows: In the formula, This is the actual torque. The torque coefficient, The nominal diameter of the bolt. The preload force of bolt i after differential correction is given. Beneficial effects

[0013] 1. This invention significantly reduces the leakage risk in the middle of the long side of the AEM electrolytic cell by synergistically optimizing the bolt configuration parameters (number and size) and differentiated preload. By establishing the optimal number and size of bolts and combining them with a preload strategy that strengthens the middle of the long side and releases them appropriately at the four corners, the pressure imbalance in the middle of the long side and the deflection deformation of the cover plate are effectively compensated. 2. This invention synergistically optimizes the multidimensional balance of stress distribution and deformation field between the bolt and the cover plate, improving the overall durability of the system. By comprehensively controlling the three dimensions of bolt stress distribution, bolt deformation and cover plate stress distribution, it eliminates local stress concentration and extends the fatigue life of the components. It also makes the clamping force between the cover plate and the electrode plate more consistent, thereby reducing the interfacial contact resistance and synergistically improving the structural durability of the electrolyzer and the contact electrochemical performance with the membrane electrode. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a 3D AEM electrolytic cell model; Figure 2 The diagram shows the stress distribution when the number of bolts is 18, 22, 26, 28, 30, and 32. Figure 3 A schematic diagram showing the deformation results under different numbers of bolts; Figure 4 A schematic diagram showing the stress distribution of an M18 bolt under a uniform preload. Figure 5 A schematic diagram showing the deformation of an M18 bolt under a uniform preload. Figure 6 A diagram showing the bolt numbers on the cover plate; Figure 7 A schematic diagram showing the stress distribution of bolts before and after optimizing the preload; Figure 8 This is a schematic diagram showing the stress distribution of an M18 bolt under position-differentiated preload. Figure 9 A schematic diagram showing the deformation results of an M18 bolt under position-differentiated preload; Figure 10 This is a schematic diagram showing the stress distribution of an M16 bolt under position-differentiated preload. Figure 11 This is a schematic diagram showing the deformation results of an M16 bolt under position-differentiated preload. Figure 12 This is a schematic diagram showing the stress distribution of an M20 bolt under position-differentiated preload. Figure 13 This is a schematic diagram showing the deformation results of an M20 bolt under position-differentiated preload. Figure 14 A schematic diagram showing the stress distribution of the cover plate under the preload of bolts with different positions; Figure 15 This is a schematic diagram showing the stress distribution of the cover plate under uniform bolt preload. Detailed Implementation

[0015] The technical solution of the invention will now be described in detail with reference to the accompanying drawings.

[0016] This embodiment provides a method for synergistic optimization of configuration and preload to improve the sealing performance of AEM electrolytic cells. The optimization method includes the following three steps.

[0017] S1. Taking the AEM electrolytic cell as the object, construct a three-dimensional finite element model including a cover plate, bipolar plate and gas diffusion layer. Set the number of bolts according to the long side span of the cover plate in the finite element model, and determine the distribution configuration of the bolts on the cover plate.

[0018] Specifically, taking a large rectangular AEM electrolytic cell with a cover plate size of 874 mm × 480 mm × 80 mm as an example, a three-dimensional finite element model including the cover plate, bipolar plate, and gas diffusion layer was constructed using SolidWorks 2024 software. The model structure is as follows: Figure 1 As shown. The cover plate is made of AISI 321 high-rigidity stainless steel, the bipolar plates are made of 2 mm thick titanium alloy, the effective working area is 746 mm × 280 mm, the gas diffusion layer is made of carbon fiber material with a Young's modulus of 290 GPa, and the fastening connectors are 10.9 grade double-ended studs of GB / T 901-1988 standard, with a nominal bolt length of 280 mm.

[0019] Considering the 874 mm span of the electrolytic cell's long side, the candidate range for the number of bolts was set to 22-36. An additional layout scheme was added for internal comparison. Finite element simulations were used to compare the peak bolt stress and structural deformation under 18, 22, 26, 32, and 36 bolt numbers. The simulation results are as follows: Figure 2 , Figure 3 As shown in the figure. Simulation results indicate that when the number of bolts is less than 26, the bolt spacing is too large, resulting in significant stress ripples and localized stress concentrations at the edge of the cover plate. The load-bearing capacity of a single bolt is too high, and the maximum internal stress approaches the material's yield limit. Among these, the mechanical unevenness problem is most prominent with an 18-bolt arrangement, where the transverse bolt stress is 1.25 times the lowest vertical stress value, and the transverse bolt stress is generally 10% to 15% higher than the vertical bolt stress. When the number of bolts increases to 28, with 8 bolts on one side of the long side and 6 bolts on one side of the short side, the longitudinal bolt stress fluctuation can be controlled within 20 MPa, but there is still a significant stress difference in the transverse bolts. With 30 bolts, with 8 bolts on one side of the long side and 7 bolts on one side of the short side, the stress uniformity across the bolt array is optimal, and the structural deformation is balanced. When the number of bolts increases to 32, the marginal benefit of stress optimization diminishes, the maximum stress reduction is less than 5%, and the increased opening ratio of the cover plate causes damage to the cross-sectional stiffness. Based on comprehensive comparison, this embodiment determines that 30 bolts are the optimal number of bolts to be installed, and subsequent differentiated preload distribution and specification selection are all based on this number.

[0020] S2. Based on the theoretical uniform preload calculated from the electrolytic cell design pressure, a uniform preload is applied in the finite element model for analysis to obtain the reference stress state of the cover plate. According to the bolt distribution position, a gradient preload load is distributed to each bolt, and the actual assembly torque of each bolt is calculated based on the differential preload. By comparing the stress distribution of the cover plate and the bolt load distribution under uniform preload and differential preload, the optimal preload combination is determined.

[0021] Specifically, the design pressure is 3 MPa, and the theoretical uniform preload is calculated based on the design pressure of the electrolytic cell. Based on this, the calculation formula is: In the formula, The design operating pressure of the electrolytic cell, The effective area of ​​the pressure zone of the cover plate. This represents the total number of bolts. This is the sealing safety factor.

[0022] A uniform preload is applied in the finite element model (all bolts are...). ) Analyze the data to obtain the baseline stress state of the cover plate and identify the mechanical imbalance region caused by the asymmetric stiffness of the rectangular structure. For example Figure 4 and Figure 5 As shown, taking bolt type M18 as an example, the results show that transverse bolts and vertical bolts exhibit drastically different mechanical properties: the stress and deformation of transverse bolts are significantly greater than those of vertical bolts, and the stress level of corner bolts is lower than that of bolts in the central area. This phenomenon mainly stems from the geometric characteristics of the rectangular cover plate: the transverse span of the cover plate is much larger than the vertical span, requiring the transverse bolts to resist structural deformation over a larger span, thus causing severe stress concentration in the transverse central bolts. The main operating load of the equipment has the most significant effect on the transverse structure; the structural stiffness in this direction is relatively lower, and the flexural deformation is more obvious, further exacerbating the stress level of the transverse bolts. At the same time, the preload of the transverse central bolts, superimposed with the structural compensation load generated by the warping effect of the cover plate, significantly increases its combined stress.

[0023] Because the rectangular electrolytic cell cover plate has an asymmetrical geometric span and anisotropic structural stiffness, applying a uniform preload would result in severely uneven stress and deformation distribution on the bolts and cover plate. Therefore, based on the bolt distribution location, a differentiated preload load distribution is applied to each bolt, with the specific distribution logic as follows: (1) Preload of bolts in the middle of the long side: Implement a key reinforcement strategy, and set the preload to 120-130% of the standard value. The expression is as follows: ; This step aims to overcome the maximum deflection deformation in the middle of the cover plate, which not only eliminates the area of ​​insufficient sealing pressure on the side of the cover plate, but more importantly, by suppressing the deformation of the cover plate, it significantly reduces the additional structural stress borne by the central bolts, causing the total stress to fall back to a stable range.

[0024] (2) Bolt preload at the 1 / 4 position of the long side: Implement a smooth transition strategy. In order to ensure the continuity of the interface pressure difference and avoid local stress abrupt change, the preload of the bolt at the 1 / 4 position of the long side is set to 100~110% of the standard value.

[0025] This step ensures the continuity of the interface pressure difference, while also ensuring that the stress and deformation levels of the bolts in this area are smoothly aligned with those in the central area, thus avoiding uneven stress on the fasteners caused by sudden changes in local loads.

[0026] (3) Preload of bolts at the four corners: Implement a moderate reduction strategy. To prevent the central sealing from failing due to excessive stiffness in the four corner areas, the preload of bolts at the four corners of the rectangle will be reduced to 85-90% of the standard value. The expression is as follows: This strategy prevents over-constraint in the corner areas due to excessive stiffness. Moderately reducing the preload releases redundant stiffness in the corner bolts, suppresses outward warping at the corners of the cover plate, and guides the load to the middle section of the long side, thereby improving the stress distribution of the four corner bolts and aligning it with the average value across the entire groove.

[0027] (4) Preload of bolts in the middle of the short side: Implement the standard maintenance strategy. Since the span of the rectangular cover plate in the short side direction is short and its own stiffness is sufficient to resist deformation, no special compensation is required, and the preload of bolts in the middle of the short side is maintained at the standard value. This ensures that the stress distribution between the bolts and the cover plate is within the ideal elastic range.

[0028] To meet the actual assembly process requirements, the actual torque of each bolt was calculated. : In the formula The torque coefficient, The nominal diameter of the bolt. The preload force of bolt number i is the preload force after differential correction. The optimized preload forces and corresponding torques of bolts at each position are shown in Table 1, where the 30 bolts are labeled #1, #2, #3…#30 (e.g., ...). Figure 6 ).

[0029] Table 1. Optimized bolt preload and torque values ​​at different locations By applying differentiated preload to bolts at different locations, the bolt load and stress distribution results under uniform preload conditions were compared to select the optimal preload combination. After differentiated adjustment, the stress difference between bolts decreased to approximately 6 MPa. This optimized preload distribution method not only reduced the stress level of individual bolts but also prevented excessive concentration of combined stress (preload and external load) on a few local bolts. Ultimately, the stress of all bolts tended to be consistent, and the overall peak stress of the system decreased significantly. Figure 7 and 8 As shown. Under non-uniform preload, the consistency of deformation of each bolt is significantly improved, and is stably controlled within the range of 0.1±0.02mm. Among them, bolts #4 and #5 have larger displacements under uniform preload conditions. After optimization, their deformation is reduced by 0.05mm, as shown. Figure 9 As shown. This control method enables all bolts to work together to effectively bear the load, eliminating the phenomenon of bolts being idle and unloaded, thereby reducing the load on a single fastener.

[0030] Based on the aforementioned differentiated preload distribution strategy, further optimization of bolt specifications was conducted. Maintaining the same arrangement of 30 bolts, the mechanical properties of M16, M18, and M20 nominal diameter bolts under the differentiated preload system were analyzed. Finite element simulation was used to evaluate the stress level, axial deformation, and impact on the cover plate stiffness of the bolts under the three specifications. The simulation results are as follows: Figures 10 to 14 As shown, the cross-sectional area of ​​M16 bolts is 18% smaller than that of M18, resulting in a 23% increase in axial stress under the same working conditions. This leads to insufficient axial tensile stiffness, weak constraint on the bending deformation of the cover plate, and excessive bolt elongation, which can easily cause fluctuations in the contact pressure at the sealing interface and a higher risk of preload relaxation. M20 bolts have a 22% larger cross-sectional area than M18, offering strong load-bearing capacity and low stress levels. However, they require more installation space, which can cause discontinuous stress distribution in the cover plate and increase equipment weight and production costs. Furthermore, they offer no significant performance gain under a differentiated preload control system. M18 bolts exhibit the best load adaptability within the elastic range of axial deformation. Therefore, this embodiment ultimately uses 30 M18 bolts to optimize the bolt quantity, specifications, and distribution configuration.

[0031] S3. Joint simulation verification and collaborative optimization effect check Based on the bolt configuration (number, size, distribution) and differentiated preload combinations determined in steps S1 and S2, a joint simulation verification was conducted, collecting data on cover plate stress distribution, full-slot bolt load, and stress distribution. By comparing indicators such as cover plate stress uniformity, maximum stress concentration factor, and consistency of bolt deformation before and after optimization, the synergistic optimization effect of the differentiated preload strategy and bolt configuration was verified and confirmed. If the preset sealing and structural reliability requirements are met, the scheme is confirmed as the final synergistic optimization scheme. The optimized cover plate stress distribution is shown below. Figure 14As shown, compared to the uniform preload condition before optimization ( Figure 15 The stress uniformity of the cover plate was improved by 40%, and the maximum stress concentration factor was reduced by 35%; the bolt stress distribution was as follows: Figure 8 , Figure 9 As shown, the deviation of bolt stress distribution across the entire area is significantly reduced, with no obvious stress concentration or load imbalance.

[0032] To optimize overall sealing performance, it is recommended to adjust the preload according to the location of the bolts: reduce the initial preload in high-pressure tightening areas (corner and vertical edge bolts), while significantly increasing the preload in key displacement compensation areas (lateral center bolts). This method can effectively reduce the stress gradient inside the cover plate, making the contact pressure distribution at the sealing interface more balanced, thereby improving the overall structural reliability.

[0033] Comprehensive simulation results demonstrate that this invention, through the synergistic optimization of bolt configuration and preload, effectively improves the mechanical inhomogeneity caused by the asymmetric stiffness of the rectangular AEM electrolyzer, achieving multidimensional equilibrium of the stress and displacement fields. This position-dependent differentiated preload strategy significantly enhances the mechanical properties of the anion exchange membrane (AEM) electrolyzer, ensuring its structural stability and long-term operational reliability. This method not only guarantees excellent equipment durability but also lays a crucial theoretical and engineering foundation for the optimized design of bolted connection systems in large rectangular electrolyzers. This solution does not add complex processes; relying on bolt configuration optimization and differentiated preload matching, it significantly improves the uniformity of the sealing interface contact, eliminates potential structural failure hazards, and ensures the long-term operational stability of the electrolyzer. The method of this invention has strong engineering adaptability and can provide a theoretical basis and engineering reference for the optimized design of bolted connection systems in large rectangular electrolyzers.

[0034] In summary, this invention effectively overcomes the shortcomings of the prior art and has high industrial applicability. The above embodiments are intended to illustrate the substantive content of this invention, but are not intended to limit the scope of protection of this invention. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this invention without departing from the essence and scope of protection of this invention.

Claims

1. A method for synergistic optimization of configuration and preload to improve the sealing performance of an AEM electrolytic cell, characterized in that, Includes the following steps: S1. Taking the AEM electrolytic cell as the object, construct a three-dimensional finite element model including a cover plate, bipolar plate and gas diffusion layer. Set the number of bolts according to the long side span of the cover plate in the finite element model, and determine the distribution configuration of the bolts on the cover plate. S2. Based on the theoretical uniform preload calculated from the electrolytic cell design pressure, a uniform preload is applied in the finite element model for analysis to obtain the reference stress state of the cover plate. According to the bolt distribution position, a gradient preload load is distributed to each bolt, and the actual assembly torque of each bolt is calculated based on the differential preload. By comparing the stress distribution of the cover plate and the bolt load distribution under uniform preload and differential preload, the optimal preload combination is determined.

2. The optimization method according to claim 1, characterized in that, The AEM electrolytic cell has a rectangular geometry.

3. The optimization method according to claim 1 or 2, characterized in that, In step S2, the bolts are distributed in four groups: the first group is the bolts in the middle of the long side, the second group is the bolts at the 1 / 4 position of the long side, the third group is the four corner bolts, and the fourth group is the bolts in the middle of the short side.

4. The optimization method according to claim 1, characterized in that, In step S1, the number of bolts is set to be greater than 28.

5. The optimization method according to claim 4, characterized in that, The number of bolts is set to 30, and a rectangular perimeter layout is adopted, with 8 bolts on each long side, 7 bolts on each short side, and 1 bolt on each corner. The corner bolts are included in the number of bolts on the long sides.

6. The optimization method according to claim 1, characterized in that, After determining the optimal preload combination in step S2, the following steps are also included: S3. Based on the bolt configuration determined in steps S1 and S2, conduct joint simulation verification, collect data on cover plate stress distribution, full-slot bolt load and stress distribution, and complete the verification and confirmation of the synergistic optimization effect of differentiated preload strategy and bolt configuration.

7. The optimization method according to claim 1, characterized in that, The bolt is M18.

8. The optimization method according to claim 7, characterized in that, The preload of the first group is set to 120-130% of the standard value, the preload of the second group is set to 100-110% of the standard value, the preload of the third group is set to 85-90% of the standard value, and the preload of the fourth group is set to the standard value.

9. The optimization method according to claim 1, characterized in that, In step S2, the formula for calculating the actual torque of each bolt is as follows: In the formula, This is the actual torque. The torque coefficient, The nominal diameter of the bolt. The preload force of bolt i after differential correction is given.

Images