An industrial CT-based hydrogen storage cylinder winding layer porosity analysis method

Abstract

The present application relates to hydrogen storage cylinder detection technical field, especially to a kind of based on industrial CT's hydrogen storage cylinder winding layer porosity analysis method, specifically including the following steps: S1, industrial CT detection and image processing, S2, axial porosity statistics, S3, radial analysis region division, S4, radial porosity statistics.This method is based on the image gray value corresponding to the pore defect quality density in the industrial CT detection image of carbon fiber full winding hydrogen storage cylinder, proposes the carbon fiber winding layer porosity analysis characterization method along the direction of the axis of the cylinder and the direction of the outer contour of the liner, can effectively quantitatively analyze the distribution of the pores in the carbon fiber layer of hydrogen storage cylinder under different parts along the axis of the cylinder and different winding layer depths along the direction of the outer contour of the liner, provide intuitive data support for studying carbon fiber winding process, can greatly improve the safety of carbon fiber full winding hydrogen storage cylinder, with higher use value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of hydrogen storage cylinder testing technology, and in particular to a method for analyzing the porosity of the winding layer of hydrogen storage cylinders based on industrial CT. Background Technology

[0002] With the rapid development of the hydrogen energy industry, carbon fiber fully wound hydrogen storage cylinders have become an important hydrogen storage medium for hydrogen fuel cell vehicles, drones, and other fields due to their high strength and lightweight advantages. Compared to traditional all-metal Type I or metal-lined fiber-wound Type II cylinders, the main pressure-bearing structure of carbon fiber fully wound hydrogen storage cylinders changes from the inner liner to circumferentially and helically wound carbon fiber layers. However, this structure makes the safety of the cylinder highly dependent on the integrity of the carbon fiber winding layers. Pore defects (such as delamination and pores) are one of the key factors leading to premature failure of carbon fiber composite materials. When the volume or number of pores exceeds a certain limit, it will cause stress concentration, significantly reduce the mechanical properties of the material, and even cause safety hazards. Therefore, reliable testing methods must be used to accurately analyze the porosity of the winding layers to ensure the safety of the cylinder throughout its entire life cycle.

[0003] Currently, industrial CT (computed tomography) has demonstrated its advantages in the detection of carbon fiber windings due to its high-resolution three-dimensional imaging capabilities. However, existing porosity analysis methods only use the ratio of the total pore volume to the carbon fiber volume for simple calculations, which cannot provide a refined characterization of the complex structure of hydrogen storage cylinders.

[0004] Therefore, there is an urgent need for a method that can quantitatively analyze the pore distribution at different locations and depths of carbon fiber winding layers in order to optimize the winding process and improve the safety of gas cylinders. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of existing technologies and provide a method for analyzing the porosity of the winding layer in hydrogen storage cylinders based on industrial CT. This significantly improves the quality control level of carbon fiber wound hydrogen storage cylinders and has important application value for ensuring the safety of hydrogen energy equipment.

[0006] The technical solution adopted by this invention to achieve its technical objective is: a method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT, specifically including the following steps: S1. Industrial CT Inspection and Image Processing: For the dimensions and specifications of carbon fiber fully wound hydrogen storage cylinders, an industrial CT scanning process is designed. Based on the industrial CT inspection system for hydrogen storage cylinders, projections of the cylinders are captured, and reconstructed to obtain industrial CT images. Artifact correction and noise reduction are applied to the images, and pore defects with low grayscale values ​​are extracted. High-precision images are obtained by designing scanning processes (such as the distance from the X-ray source focus to the center of the object (SOD) and the distance from the X-ray source focus to the flat panel detector (SDD)). Artifact correction and noise reduction are then applied to improve image quality. Finally, pore defects are extracted based on grayscale differences, providing fundamental data for subsequent analysis.

[0007] S2. Axial Porosity Statistics: Using the voxel size of industrial CT images as the step size, the axial analysis region of the carbon fiber winding layer is uniformly divided along the axis of the gas cylinder. The pore volume of each layer and its ratio to the total volume of the carbon fiber winding layer are calculated. The formula for calculating the axial porosity is: ; in, axial porosity The sum of the pore volumes of each layer along the axis. The volume of each carbon fiber winding layer in the axial direction; The axial analysis region is divided with voxel size as the step size, and the pore volume is calculated in relation to the carbon fiber winding volume. This is achieved using the formula... Quantifying axial pore distribution reflects the pore density at different axial locations, helping to assess the axial structural integrity of gas cylinders.

[0008] S3. Radial Analysis Region Division: The industrial CT image of the hydrogen storage cylinder is converted into a binary image using the Euclidean distance mapping method. The shortest distance from each pixel of the carbon fiber layer to the inner liner of the cylinder is calculated, and the region of each radial layer is divided accordingly. The minimum combined distance calculation formula is as follows: ; Where k is the corresponding two-dimensional slice position, ∆ is the search range, and p is the voxel size; Industrial CT images are converted into binary images using Euclidean distance mapping. The distance calculation between pixels and the inner lining region is associated with radial layering. Radial layers are delineated using a minimum combination distance formula, ensuring that layering is based on geometric distance and providing a spatial basis for radial porosity statistics.

[0009] S4. Radial Porosity Statistics: Radial porosity is calculated by the ratio of the sum of the pore volumes in the same layer to the volume of the carbon fiber winding layer in that layer. The formula for calculating radial porosity is: ; in, Radial porosity, The sum of the pore volumes in each radial layer, Each radial layer of carbon fiber winding has a volume of 4. The pore volume and carbon fiber volume within the same radial layer are expressed by the formula Correlation. Quantifying the pore distribution at different radial depths reveals the uniformity of the winding process between layers, such as the differences between helical and circumferential winding regions.

[0010] Preferably, the axial analysis region is divided uniformly along the axial direction of the hydrogen storage cylinder using the voxel size of an industrial CT image as the step size. The voxel size directly determines the step size of the axial division, which is related to the image resolution, ensuring that the division accuracy matches the CT scan resolution and making the axial porosity statistics more scientific.

[0011] Preferably, the radial analysis region is divided based on the minimum Euclidean distance between each point of the carbon fiber winding layer and the inner liner region of the hydrogen storage cylinder in the industrial CT image. The Euclidean distance between the pixel and the inner liner region is used as the stratification standard. Radial stratification is achieved through the minimum Euclidean distance, reflecting the relationship between the pore distribution and the proximity of the inner liner, and optimizing process evaluation.

[0012] Preferably, the calculation of the minimum Euclidean distance includes: For each slice along the axis, calculate the two-dimensional Euclidean distance of each pixel to the nearest foreground within the current slice; For each pixel, search the two-dimensional Euclidean distance between adjacent slices along the axis, and finally obtain the minimum combined distance.

[0013] First, the two-dimensional Euclidean distance is calculated for each axial slice. Then, the distances between adjacent slices are searched along the axis. The combined distances are obtained to obtain the three-dimensional minimum distance. The complexity is reduced by step-by-step calculation, which can efficiently process large-scale CT data and ensure the accuracy of distance division.

[0014] Preferably, the extraction of pore defects is based on the fact that the gray value of the pore defects in the industrial CT image is lower than that of the carbon fiber winding layer region. Gray value is related to material density; low gray value regions correspond to pore defects. Utilizing density differences to automatically identify pores improves the objectivity and efficiency of defect extraction.

[0015] Preferably, the parameters of the industrial CT scanning process include: when the scanning object is the entire hydrogen storage cylinder, the SOD is 758 mm, the SDD is 1093 mm, and the voxel size is 101 μm; when the scanning object is the cylinder shoulder and body area, the SOD is 290 mm, the SDD is 1093 mm, and the voxel size is 37 μm. The scanning parameters (SOD, SDD) are matched with the detection object (whole / partial). Whole scanning ensures global analysis, while high-resolution local scanning accurately captures the pore details of key areas (such as the cylinder shoulder).

[0016] Preferably, the method is applicable to the porosity analysis of the bottleneck, shoulder, and body of carbon fiber fully wound hydrogen storage cylinders. The method is customized for different structural parts of the cylinder (bottom, shoulder, and body), covering all critical pressure-bearing areas of the cylinder, ensuring the comprehensiveness and practicality of the analysis results.

[0017] Preferably, the calculated results of axial porosity and radial porosity are used to characterize the pore distribution of the carbon fiber winding layer at different locations along the axial direction and at different winding depths along the outer contour of the inner liner. By displaying the pore distribution pattern in a two-way statistical (axial + radial) multi-dimensional manner, data support is provided for process optimization.

[0018] Preferably, the method uses industrial CT images to clearly demonstrate the aggregation of pores in the carbon fiber winding layer in the bottleneck region and the interface between the bottle shoulder and the cylinder. This visually reveals high-risk areas for pore aggregation (such as the interface), guiding targeted process improvements.

[0019] Preferably, the method distinguishes the outer spiral winding region, the outer circumferential winding region, the inner spiral winding region, and the inner circumferential winding region by radial porosity distribution, and calculates the average porosity of each region. Radial stratification is associated with the winding process type (spiral / circumferential, inner / outer), quantifying the porosity differences between different process regions (e.g., spiral > circumferential), and verifying the quality of the winding process.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This method for analyzing the porosity of the winding layer in hydrogen storage cylinders based on industrial CT enables refined porosity analysis. Through axial porosity calculation (layered statistical analysis along the cylinder axis), it can accurately identify the aggregation of pores in different locations such as the bottleneck, shoulder, and body (e.g., in Example 1, the porosity peak at the junction of the shoulder and body reaches 3.75%). Furthermore, through radial porosity calculation (based on Euclidean distance mapping layering), it can distinguish the pore distribution at different winding layer depths (e.g., inner / outer side, spiral / circular winding regions), revealing process differences (e.g., the porosity in the spiral winding region is significantly higher than that in the circumferential winding region).

[0021] This industrial CT-based method for analyzing the porosity of the winding layer in hydrogen storage cylinders offers high-precision detection and wide applicability. It supports multi-scale scanning (e.g., overall scanning at 101 μm voxels, and scanning of key local areas at 37 μm voxels), balancing global analysis with high-precision local detection (Example 2 verifies the consistency between local and overall results). It is suitable for cylinders with complex structures (e.g., irregular shoulder-to-body junctions), improving image quality through artifact correction and noise reduction to ensure accurate extraction of porosity defects.

[0022] This method for analyzing the porosity of the winding layer in hydrogen storage cylinders based on industrial CT optimizes the direct data support for the winding process. Axial and radial porosity distribution maps are attached. Figure 4 , 5 This visually displays areas of pore accumulation (such as bottlenecks and interlayer boundaries), helping to locate process defects. Comparing different winding layers (e.g., the porosity of the inner spiral winding area is 0.40%, while the outer area reaches 1.52%) provides a scientific basis for adjusting process parameters such as winding tension and layup methods. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating the steps of a method for analyzing the porosity of the winding layer in hydrogen storage cylinders based on industrial CT.

[0025] Figure 2 A schematic diagram illustrating the calculation of axial and radial porosity for a carbon fiber fully wound hydrogen storage cylinder.

[0026] Figure 3 This is a schematic diagram of a partial industrial CT image of a carbon fiber fully wound hydrogen storage cylinder.

[0027] Figure 4 The figure shows the axial porosity analysis results of the carbon fiber winding layer for a carbon fiber fully wound hydrogen storage cylinder.

[0028] Figure 5 The figure shows the radial porosity analysis results of the carbon fiber winding layer at the location of the carbon fiber fully wound hydrogen storage cylinder.

[0029] Among them: 1. Bottle neck; 2. Bottle shoulder; 3. Cylinder body; 4. Carbon fiber winding layer; 5. Gas cylinder liner; 6. Axial analysis area; 7. Radial analysis area; 8. Pore defects; 9. Air area; 10. Outer spiral winding area; 11. Outer circumferential winding area; 12. Inner spiral winding area; 13. Inner circumferential winding area. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0031] In the description of this invention, it should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to or indirectly connected to the other element.

[0032] In the description of this invention, it should be noted that the terms "center," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0033] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0034] Please see Figure 1 , Figure 1 This is a flowchart illustrating the steps of a method for analyzing the porosity of the carbon fiber winding layer in a hydrogen storage cylinder based on industrial CT. The method includes methods for calculating and analyzing the axial porosity and radial porosity of the carbon fiber winding layer in the hydrogen storage cylinder.

[0035] Please see Figure 2 , Figure 2 A schematic diagram illustrating the calculation of axial and radial porosity for a carbon fiber fully wound hydrogen storage cylinder. Among them, Figure 2 (a) is a schematic diagram of axial porosity analysis. Figure 2 (b) is a schematic diagram of radial porosity analysis. The key testing areas of the composite gas cylinder targeted by the porosity analysis characterization method include the neck 1, the shoulder 2, and the cylinder body 3. The carbon fiber winding layer 4 is covered on the outside of the inner liner 5 of the gas cylinder using a spiral and circumferential winding process.

[0036] The axial porosity analysis method divides the axial analysis region 6 along the cylinder axis, and the radial porosity analysis method divides the radial analysis region 7 along the outer contour of the inner liner.

[0037] Please see Figure 3 , Figure 3 This is a schematic diagram of a partial industrial CT image of a carbon fiber fully wound hydrogen storage cylinder. Due to differences in density, the carbon fiber winding layer 4, the cylinder liner 5, the pore defects 8, and the air region 9 exhibit significant differences in grayscale values ​​in the industrial CT image of the carbon fiber fully wound hydrogen storage cylinder.

[0038] For a fiber-wound hydrogen storage cylinder with an outer diameter of 280 mm and a nominal pressure of 35 MPa, based on the above porosity analysis and characterization method, the carbon fiber winding layer 4 is uniformly divided into axial analysis region 6 and radial analysis region 7 along the axial direction of the hydrogen storage cylinder and the outer contour direction of the inner liner, and the porosity is calculated for each layer region.

[0039] Table 1. Industrial CT scan parameters of hydrogen storage cylinders at different magnifications

[0040] The carbon fiber fully wound hydrogen storage cylinder was inspected using industrial CT based on the scanning parameters shown in Parameter 1 of Table 1. The voxel size of the industrial CT image was 101 μm. The specific steps are as follows: S1. Perform industrial CT inspection on the carbon fiber fully wound hydrogen storage cylinder according to the scanning parameters shown in Table 1. Perform artifact correction and noise reduction on the reconstructed industrial CT image of the hydrogen storage cylinder. Based on the exponential relationship between X-ray attenuation and object density, extract the low-density pore defects 8 with lower gray values ​​in the carbon fiber winding layer 4.

[0041] S2. Using the voxel size of the industrial CT image as the step size, divide the axial analysis region 6 along the gas cylinder axis. For each layer, calculate the sum of the total volume of the carbon fiber winding layer 4 and the volume occupied by the pore defects 8. The axial porosity is then: ; The above formula, axial porosity The volume of pore defects in each layer along the axis is 8. The total volume of the carbon fiber winding layer 4 in each axial region.

[0042] S3. The industrial CT image of the hydrogen storage cylinder is converted into a binary image using the Euclidean distance mapping method. This allows for the calculation of the nearest distance from each pixel in the carbon fiber layer to the foreground pixel (region 5 of the cylinder's inner liner), and the region of each radial layer is then divided accordingly. Due to the large amount of information in the industrial CT image of the hydrogen storage cylinder, the two-dimensional Euclidean distance from each pixel to the nearest foreground pixel within the current slice is calculated individually for each slice along the axial direction (i.e., the z-axis). Then, for each pixel (x, y, z), the two-dimensional Euclidean distances of adjacent slices are searched along the axial direction, ultimately obtaining the minimum combined distance. ; Where k is the corresponding two-dimensional slice position, ∆ is the search range, and p is the voxel size.

[0043] S4. Statistical analysis of radial porosity: Using the radial analysis region 7 divided by S3, the sum of the volumes of pore defects 8 within the same layer region and the total volume of the carbon fiber winding layer 4 in that layer are used to calculate the radial porosity. The formula for calculating radial porosity is as follows: ; The above formula, Radial porosity, The sum of the pore volumes in each radial layer, The volume of carbon fiber in each radial layer.

[0044] Please see Figure 4 This is a diagram showing the axial porosity analysis results of the carbon fiber winding layer in a fully wrapped carbon fiber hydrogen storage cylinder. Among them, Figure 4 (a) is an industrial CT image of a hydrogen storage cylinder with parameter 1; Figure 4 (b) is an industrial CT image of a hydrogen storage cylinder with parameter 2; Figure 4 (c) shows the axial porosity distribution of the carbon fiber layer with parameter 1. Figure 4 In the middle (d), the axial porosity distribution of the carbon fiber layer with parameter 2 is shown.

[0045] For details, please refer to [link / reference]. Figure 4 In (a) and (c), the industrial CT images of the carbon fiber fully wound hydrogen storage cylinder are relatively clear, and the axial porosity distribution is quite intuitive. The pores of the carbon fiber wound layer 4 are abundant in the bottleneck area 1 and the interface between the shoulder 2 and the cylinder 3. The average porosity of the cylinder is 0.41%, and the peak porosity at the interface between the shoulder 2 and the cylinder 3 is 3.75%.

[0046] Figure 5 This image shows the radial porosity analysis results of the carbon fiber winding layer at the location of the fully carbon fiber wound hydrogen storage cylinder. Among them, Figure 5 (a) is an industrial CT image of a carbon fiber layer with parameter 1; Figure 5 (b) is an industrial CT image of a carbon fiber layer with parameter 2. Figure 5 (c) is the radial porosity distribution of the carbon fiber layer with parameter 1; Figure 5 In the middle (d), the radial porosity distribution of the carbon fiber layer with parameter 2 is shown.

[0047] For details, please refer to [link / reference]. Figure 5 In images (a) and (c), the radial porosity distribution of the carbon fiber fully wound hydrogen storage cylinder winding layer clearly shows four regions. According to the existing reference "Multi-scale Industrial CT Detection and Cause Analysis of Defects in the Winding Layer of Hydrogen Storage Cylinders" (excerpted from Zhejiang Special Equipment Science Research Institute, 2024), these correspond to the outer spiral winding region 10, the outer circumferential winding region 11, the inner spiral winding region 12, and the inner circumferential winding region 13, respectively. In the industrial CT image of the carbon fiber winding layer of the hydrogen storage cylinder with a voxel size of 101 μm, the average porosities of the outer spiral winding region 10, the outer circumferential winding region 11, the inner spiral winding region 12, and the inner circumferential winding region 13 are 1.52%, 0.03%, 0.40%, and 0.01%, respectively. The porosity of the spiral winding region is significantly greater than that of the circumferential winding region. Furthermore, the porosity of the inner spiral winding region 12, which is closer to the inner liner, is less than that of the outer spiral winding region 10, which is farther from the inner liner. Example 2

[0048] Based on the above embodiments, this method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT performs local industrial CT inspection on the interface between the shoulder 2 and the cylinder 3 of a fiber-wound hydrogen storage cylinder with an outer diameter of 280 mm and a nominal pressure of 35 MPa, using the parameters shown in Parameter 2 of Table 1. The voxel size of the industrial CT image is 37 μm. For the irregular interface between the shoulder 2 and the cylinder 3, the porosity distribution characteristics are analyzed by repeating the above steps S1 to S4.

[0049] Please see Figure 4 In (b) and (d), the industrial CT images of the carbon fiber winding layer 4 at the interface between the shoulder 2 and the cylinder 3 of the hydrogen storage cylinder, obtained based on local scanning with parameter 2, are clear, and the axial porosity distribution is intuitive. The average porosity of the cylinder 3 region is 0.58%, and the peak value at the interface between the shoulder 2 and the cylinder 3 is 3.70%, which is consistent with the axial porosity distribution characteristics obtained based on the overall center scan with parameter 1. This proves that the method is applicable to both the overall and local analysis of the carbon fiber winding layer 4 of the hydrogen storage cylinder.

[0050] Please see Figure 5 In (b) and (d), industrial CT images of the carbon fiber winding layer 4 of a hydrogen storage cylinder with a voxel size of 37 μm show the average porosities of the outer spiral winding region 10, the outer circumferential winding region 11, the inner spiral winding region 12, and the inner circumferential winding region 13, which are 1.47%, 0.03%, 0.80%, and 0.07%, respectively. This is consistent with the axial-radial porosity distribution characteristics obtained from the overall center scan based on parameter 1, demonstrating the applicability of this method for both overall and local analysis of the carbon fiber winding layer 4 of the hydrogen storage cylinder. Analysis of the scan results based on parameter 2 also shows that the porosity of the inner spiral winding region 12 near the inner liner is less than that of the outer spiral winding region 10 far from the inner liner, proving that the spiral winding process near the inner liner is superior to that far from the inner liner.

[0051] according to Figure 4 and Figure 5 As shown, by combining the axial and radial porosity analysis methods of the carbon fiber fully wound hydrogen storage cylinder, the porosity distribution of the carbon fiber winding layer 4 along the axial direction and between layers along the outer contour of the inner liner can be quantitatively displayed, providing intuitive data support for evaluating the carbon fiber winding process of the hydrogen storage cylinder.

[0052] The solution in this embodiment can be selectively combined with solutions in other embodiments.

[0053] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or equivalent structural, procedural, or functional transformations made using the description and drawings of this invention, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of protection of this invention.

Claims

1. A method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT, characterized in that, Specifically, the following steps are included: S1. Industrial CT Inspection and Image Processing: Design an industrial CT scanning process for the size specifications of carbon fiber fully wound hydrogen storage cylinders. Based on the industrial CT inspection system for hydrogen storage cylinders, take a picture of the hydrogen storage cylinder projection, reconstruct the industrial CT image of the hydrogen storage cylinder, and perform artifact correction and noise reduction on the image to extract the pore defects with low gray value. S2. Axial Porosity Statistics: Using the voxel size of industrial CT images as the step size, the axial analysis region of the carbon fiber winding layer is uniformly divided along the axis of the gas cylinder. The pore volume of each layer and its ratio to the total volume of the carbon fiber winding layer are calculated. The formula for calculating the axial porosity is: ； in, axial porosity The sum of the pore volumes of each layer along the axis. The volume of each carbon fiber winding layer in the axial direction; S3. Radial Analysis Region Division: The industrial CT image of the hydrogen storage cylinder is converted into a binary image using the Euclidean distance mapping method. The shortest distance from each pixel of the carbon fiber layer to the inner liner of the cylinder is calculated, and the region of each radial layer is divided accordingly. The minimum combined distance calculation formula is as follows: ； Where k is the corresponding two-dimensional slice position, ∆ is the search range, and p is the voxel size; S4. Radial Porosity Statistics: Radial porosity is calculated by the ratio of the sum of the pore volumes in the same layer to the volume of the carbon fiber winding layer in that layer. The formula for calculating radial porosity is: ； in, Radial porosity, The sum of the pore volumes in each radial layer, The volume of each radial layer of carbon fiber winding is denoted as .

2. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The axial analysis region is divided with the voxel size of industrial CT images as the step size, and is uniformly divided along the axial direction of the hydrogen storage cylinder.

3. The method for analyzing the porosity of the winding layer of hydrogen storage cylinders based on industrial CT according to claim 1, characterized in that: The radial analysis region is defined based on the minimum Euclidean distance between each point of the carbon fiber winding layer and the inner liner region of the hydrogen storage cylinder in the industrial CT image.

4. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 3, characterized in that: The calculation of the minimum Euclidean distance includes: For each slice along the axis, calculate the two-dimensional Euclidean distance of each pixel to the nearest foreground within the current slice; For each pixel, search the two-dimensional Euclidean distance between adjacent slices along the axis, and finally obtain the minimum combined distance.

5. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The extraction of pore defects is based on the fact that the gray value of the pore defects in the industrial CT image is lower than the gray value of the carbon fiber winding layer area.

6. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The parameters of the industrial CT scanning process include: when the scanning object is the entire hydrogen storage cylinder, the distance from the X-ray source focal point to the center of the measured object is SOD 758mm, the distance from the X-ray source focal point to the flat panel detector is SDD 1093mm, and the voxel size is 101μm; when the scanning object is the cylinder shoulder and cylinder body area, the SOD is 290mm, the SDD is 1093mm, and the voxel size is 37μm.

7. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The method is applicable to the porosity analysis of the neck, shoulder, and body of carbon fiber fully wound hydrogen storage cylinders.

8. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The calculated results of axial porosity and radial porosity are used to characterize the pore distribution of the carbon fiber winding layer at different locations along the axial direction and at different winding layer depths along the outer contour of the inner liner.

9. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The method clearly demonstrates the aggregation of pores in the carbon fiber winding layer in the bottleneck region and the junction region between the bottle shoulder and the cylinder using industrial CT images.

10. The method for analyzing the porosity of the winding layer of a hydrogen storage cylinder based on industrial CT according to claim 1, characterized in that: The method distinguishes the outer spiral winding region, the outer circumferential winding region, the inner spiral winding region, and the inner circumferential winding region by radial porosity distribution, and calculates the average porosity of each region.

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