Porous material microstructure parameter acquisition method, device, equipment and medium

Abstract

The invention provides a porous material microstructure parameter acquisition method and device, equipment and a medium. The invention provides a method for acquiring microstructure parameters of a porous material. The method comprises the following steps: acquiring a three-dimensional shape of a porous medium; based on the three-dimensional morphology of the porous medium, obtaining pore distribution and solid distribution information of the porous medium; obtaining a computational domain of the porous medium based on the pore distribution and the solid distribution information; the computational domain of the porous medium comprises centroid and radius information of inner holes of the porous medium; and based on the computational domain, performing root voronoi space segmentation, and based on the space segmentation information, obtaining local communication information of the porous medium, the local communication information including the position and size of the throat and the connection relationship between the hole and the throat. According to the method, the microstructure parameters of the porous material can be obtained, and the local communication information can be obtained, so that the internal energy and material transportation of the porous medium can be efficiently described.

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and in particular to a method, device, equipment and medium for obtaining microstructure parameters of porous materials. Background Art

[0002] As one of the key common basic researches, multiphase flow in porous media has important applications in the fields of energy and environment, such as freshwater extraction from aquifers, resource exploitation in oil and gas reservoirs, drug delivery, and microfluidics in food processing.

[0003] At present, as the problem of global climate change becomes more and more serious, carbon neutrality and sustainable development have become a global consensus. The research on multiphase flow in porous media is also gradually expanding from the traditional research direction of improving the recovery rate of oil and gas reservoir resources to the geological storage of carbon dioxide and hydrogen, electrochemical energy storage and conversion technology.

[0004] In the past few years, high-resolution X-ray imaging and image processing-based analysis and simulation techniques have developed rapidly, changing people's understanding of fluid flow in pores and promoting the research on the mechanism of multiphase flow in porous media and its engineering application. At the same time, the numerical simulation of heat and mass transfer processes in porous media has also been greatly developed. The traditional macroscopic continuity model that relies on meshing, physical field discretization and basic conservation laws can obtain some macroscopic parameters of heat and mass transfer processes in porous media, but this method focuses on macroscopic processes and cannot describe the details of local spatial structures. In recent years, micro-mesoscale models that can efficiently describe microstructural details have emerged. Pore network simulation regards porous media as composed of connected pores and solids, and the pores are connected by throats to transport materials and chemical reactions in porous media. Compared with the lattice Boltzmann method, the pore network model has a faster calculation speed and is regarded as the most efficient mesoscale model.

[0005] The pore structure of porous media has an important influence on the accuracy of pore network simulation. The most commonly used pore network construction methods in the literature are regular pore networks and pore networks constructed by random distribution methods. However, these two methods are only consistent with carbon paper and carbon felt in macroscopic parameters (porosity, gas diffusion coefficient, liquid permeability, etc.), and cannot obtain the true microstructure of porous media (pore distribution, pore size distribution, local connectivity, etc.). The pore network model that can efficiently describe the internal energy and material transport of porous media still has limitations. In addition, most of the current pore network extraction methods ignore the solid structure information, resulting in little understanding of the transport phenomena in the solid of porous media.

[0006] Therefore, it is necessary to provide a method, device, equipment and medium for obtaining microstructure parameters of porous materials to effectively solve the above problems. Summary of the invention

[0007] The invention provides a method, device, equipment and medium for acquiring microstructure parameters of porous materials.

[0008] An embodiment of the present invention provides a method for obtaining microstructure parameters of a porous material, comprising:

[0009] Obtain the three-dimensional morphology of porous media;

[0010] Based on the three-dimensional morphology of the porous medium, obtaining its pore distribution and solid distribution information;

[0011] Based on the pore distribution and the solid distribution information, a calculation domain of the porous medium is obtained;

[0012] Root Voronoi space segmentation is performed based on the computational domain, and local connectivity information of the porous medium is obtained based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the pores and the throat.

[0013] Preferably, the obtaining of the three-dimensional morphology of the porous medium comprises: performing three-dimensional scanning on the porous medium to obtain its three-dimensional morphology; or

[0014] Performing a two-dimensional scan on the cross section of the porous medium along a preset direction to obtain a plurality of two-dimensional graphs; and

[0015] A three-dimensional reconstruction is performed based on the multiple two-dimensional images to obtain the three-dimensional morphology of the porous medium.

[0016] Preferably, the three-dimensional reconstruction based on the multiple two-dimensional graphics to obtain the three-dimensional morphology of the porous medium includes:

[0017] Performing graphic preprocessing on the two-dimensional graphic, wherein the graphic preprocessing includes adjusting the two-dimensional graphic to an optimal angle and removing a background area;

[0018] Distinguishing between solid areas and pore areas in the two-dimensional graph;

[0019] The two-dimensional graphics after each division process are superimposed to form the three-dimensional morphology of the porous medium.

[0020] Preferably, obtaining the pore distribution information of the porous medium based on the three-dimensional morphology thereof includes:

[0021] Based on the three-dimensional morphology of the porous medium, the size of its three-dimensional matrix is ​​obtained, and based on the size of the three-dimensional matrix, each cross-sectional area of ​​the porous medium is obtained, and based on the cross-sectional area, the number of pixels on the cross-sectional area is obtained;

[0022] Obtaining the number of pore pixels in each cross section of the porous medium along a direction, and taking the ratio of the number of pore pixels on a cross section to the number of pixels on the cross section as the porosity of the cross section;

[0023] Based on the porosity of the corresponding cross-section of the porous medium along each direction, the porosity distribution in each direction is obtained.

[0024] Preferably, obtaining the solid distribution information of the porous medium based on the three-dimensional morphology thereof comprises:

[0025] removing noise on a cross section of the three-dimensional morphology of the porous medium based on a noise condition;

[0026] Based on the solid pixel distribution on the cross section, solid distribution information of the porous medium is obtained.

[0027] Preferably, obtaining the calculation domain of the porous medium based on the pore distribution and the solid distribution information includes:

[0028] Get the initial boundary of ball growth;

[0029] Based on the pore distribution and the solid distribution information, a distance assignment is obtained for each pixel point within the initial boundary of the sphere growth; the distance assignment is the distance value between the pixel point and the pore closest to it;

[0030] Based on the distance assignment of each pixel point within the initial boundary of the sphere growth, the center of mass and radius of the largest sphere are obtained; the information of the calculation domain includes the center of mass and radius information of the largest sphere;

[0031] Based on all pixel points occupied by the largest sphere, a new sphere growth boundary is obtained until the radius of the largest sphere reaches a set value.

[0032] Preferably, performing root Voronoi space segmentation based on the computational domain comprises:

[0033] Performing root Voronoi space segmentation on the computational domain based on a preset number of segmentations to obtain cell information; the space segmentation information includes the cell information;

[0034] Based on the cell information, obtaining a calculated overall porosity of the porous medium;

[0035] Based on the pore distribution and the solid distribution information, the overall porosity of the porous medium is obtained;

[0036] The root Voronoi space segmentation is optimized based on the comparison result of the calculated overall porosity and the detected overall porosity to update the cell information.

[0037] Preferably, obtaining the local connectivity information of the porous medium based on the spatial segmentation information comprises:

[0038] Obtaining the area of ​​the polygon corresponding to each cell in the cell information;

[0039] Based on the cell information, a weighted radius of the side length of the solid corresponding to the side of the polygon is obtained;

[0040] The length of the corresponding throat is obtained based on the weighted radius of the side length of the solid corresponding to the side of the polygon;

[0041] Based on the area of ​​the polygon corresponding to each cell in the cell information and the length of the corresponding throat, obtaining the extrusion volume of each polygon;

[0042] Based on the extrusion volume of each polygon and the length of the corresponding throat, the volume and equivalent radius of the throat, and the volume and equivalent radius of the hole are obtained; and

[0043] Based on the label information of each cell and the adjacent cells in the cell information, the connection relationship between the hole and the throat is obtained.

[0044] The present application also provides a device for obtaining microstructure parameters of porous materials, the device comprising:

[0045] An acquisition module, used for acquiring the three-dimensional morphology of the porous medium;

[0046] A first calculation module is used to obtain pore distribution and solid distribution information of the porous medium based on the three-dimensional morphology of the porous medium;

[0047] A second calculation module, used for obtaining a calculation domain of the porous medium based on the pore distribution and the solid distribution information;

[0048] The third calculation module is used to perform root Voronoi space segmentation based on the calculation domain, and obtain local connectivity information of the porous medium based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the hole and the throat.

[0049] The present application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any of the above methods when executing the computer program.

[0050] The present application also provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of any of the above-mentioned methods are implemented.

[0051] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0052] The method for obtaining the microstructure parameters of porous materials provided by the embodiment of the present invention can obtain the pore distribution and solid distribution information in the microstructure of porous materials, which shows more realistic microstructure characteristics of porous media than traditional methods, and is of great significance for understanding the heat and mass transfer inside porous media (such as the transport of substances and charges in the gas diffusion layer of proton exchange membrane fuel cells). It can also obtain the local connectivity information of porous media, that is, extract the connection relationship between the solid structure and the solid network, so as to obtain the transmission phenomenon of electrons, etc. in the solid network. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present invention, not all embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0054] Figure 1 A schematic flow chart of a method for obtaining microstructure parameters of porous materials provided by an embodiment of the present invention;

[0055] Figures 2a to 2d A schematic diagram of a two-dimensional X-ray microtomography scan provided by one embodiment of the present invention;

[0056] Figure 3 A schematic diagram of X-ray microtomography and carbon paper and carbon felt three-dimensional morphology reconstruction provided by an embodiment of the present invention;

[0057] Figure 4 A schematic diagram of the porosity distribution of carbon paper and carbon felt in different directions provided by an embodiment of the present invention;

[0058] Figure 5 A schematic diagram of carbon fiber diameter distribution provided by one embodiment of the present invention;

[0059] Figure 6 A schematic diagram of ball growth in carbon paper and carbon felt provided in one embodiment of the present invention;

[0060] Figure 7 A schematic diagram of a pore network obtained by a spherical growth model and a root-Voronoi space segmentation algorithm provided in one embodiment of the present invention;

[0061] Figure 8 A schematic diagram of a pore network obtained by random distribution method and root-Voronoi space segmentation provided in one embodiment of the present invention;

[0062] Fig. 9A schematic diagram of performing root Voronoi space segmentation on a porous medium computational domain provided by an embodiment of the present invention;

[0063] Fig.10 A distribution diagram of pore network aperture and throat diameter obtained by a ball growth model and a root-Voronoi space segmentation method provided in one embodiment of the present invention;

[0064] Fig.11 A distribution diagram of pore network pore size and throat diameter obtained by random distribution method and root Voronoi space segmentation provided in one embodiment of the present invention.

[0065] Fig.12 An embodiment of the present invention provides an effect of the liquid phase coverage of a single-side interface of a gas diffusion layer on the effective diffusion coefficient of oxygen. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0068] Based on the problems existing in the prior art, the embodiments of the present invention provide a method, device, equipment and medium for obtaining microstructure parameters of porous materials.

[0069] Figure 1 A schematic diagram of a method for obtaining microstructure parameters of porous materials provided by an embodiment of the present invention. Figure 1 , an embodiment of the present invention provides a method for obtaining microstructure parameters of a porous material, comprising:

[0070] Step S11, obtaining the three-dimensional morphology of the porous medium.

[0071] Step S12, based on the three-dimensional morphology of the porous medium, obtain its pore distribution and solid distribution information.

[0072] Step S13, obtaining the calculation domain of the porous medium based on the pore distribution and solid distribution information.

[0073] Step S14, performing root Voronoi space segmentation based on the computational domain, and obtaining local connectivity information of the porous medium based on the space segmentation information; the local connectivity information includes the position and size of the pore throat and the connection relationship between the pore and the throat.

[0074] The porous materials protected by this application may include microporous materials, mesoporous materials and macroporous materials. This application takes carbon paper and carbon felt as examples of porous media, and the carbon paper and carbon felt may include multiple carbon fibers, each of which may be arranged in roughly the same direction, that is, their axial directions may be roughly in the same direction, and irregular pores are formed between each carbon fiber. It should be noted that the porous media described in this application is not limited to carbon paper and carbon felt, and may also include porous silicon, nitrides, borides, etc.

[0075] In some embodiments, step S11 directly obtains the three-dimensional morphology of the porous medium by performing three-dimensional scanning on the porous medium. In other embodiments, step S11 may also perform two-dimensional scanning on the porous medium to obtain multiple two-dimensional images, and perform three-dimensional reconstruction based on the multiple two-dimensional images to obtain the three-dimensional morphology of the porous medium.

[0076] Specifically, the method of reconstructing a three-dimensional morphology using a two-dimensional image to obtain a two-dimensional image takes GP-H-090 carbon paper and carbon felt as an example, and cuts the carbon paper and carbon felt of the required size. Figure 3 As shown, the yz cross section of the carbon paper and carbon felt is scanned layer by layer (the carbon fiber radial cross section can be obtained) by using X-ray microtomography technology to obtain a two-dimensional image of the carbon paper and carbon felt. The step length of the scan can be set according to actual needs. The shorter the step length, the more accurate the final reconstructed three-dimensional morphology. In other embodiments, various two- or three-dimensional modern imaging technologies such as transmission electron microscope (TEM) and scanning electron microscope (SEM) can also be used.

[0077] In some embodiments, performing three-dimensional reconstruction based on multiple two-dimensional graphics to obtain the three-dimensional morphology of the porous medium includes: performing graphic preprocessing on the two-dimensional graphics, the graphic preprocessing including adjusting the two-dimensional graphics to an optimal angle and removing the background area. Differentiating the solid area and the pore area in the two-dimensional graphics. Superimposing the two-dimensional graphics after each differentiation process to form the three-dimensional morphology of the porous medium.

[0078] Specifically, Figure 2a and 2bAs shown, the two-dimensional graphic of carbon paper and carbon felt is rotated to make the angle of the image easier to process (the matrix size corresponding to the two-dimensional graphic will change accordingly). In this embodiment, the optimal angle of the two-dimensional graphic can be such that the length direction of the effective graphic in the two-dimensional graphic is the vertical direction and the width direction is the horizontal direction. In other embodiments, the length direction of the effective graphic in the two-dimensional graphic can also be set to be the horizontal direction and the length direction to be the vertical direction.

[0079] like Figure 2b and 2c As shown, the background area in the two-dimensional graph is other areas except the effective graph. The effective graph in this embodiment may include the pore graph area and the solid fiber graph area in the carbon paper and carbon felt, and the boundary between the effective graph and the background area may be the outer contour of the carbon paper and carbon felt on the cross section.

[0080] The step of distinguishing the solid area and the pore area in the two-dimensional figure can use binarization or MASK-RCNN and other methods to distinguish the solid area and the pore area in the cropped two-dimensional figure by pixels. The solid area in this embodiment can be the area occupied by the carbon fibers in the carbon paper carbon felt, and the pore area can be the pore area formed between the carbon fibers. In this embodiment, the solid in the two-dimensional figure of the carbon paper carbon felt is represented by pixel 0, and the pore is represented by pixel 1. In other embodiments, the solid in the two-dimensional figure of the carbon paper carbon felt can also be represented by pixel 1, and the pore is represented by pixel 0.

[0081] Specifically, a binarization method such as a fixed threshold method, Otsu's method, and an adaptive threshold method can be used to set pixel points in a two-dimensional graphic that are greater than a certain value as 1 pixel points, and pixel points that are less than a certain value as 0 pixel points, thereby distinguishing between solid and porous areas in the two-dimensional graphic of carbon paper and carbon felt.

[0082] Specifically, the MASK-R-CNN method is also used to manually mark the solid areas in the image (the rest are pore areas) to provide samples for machine learning. Then the convolutional neural network model is trained and verified through the obtained samples to identify the solid and pore areas of each two-dimensional image. ;

[0083] like Figure 3 As shown, after the solid and pore areas of each two-dimensional figure are identified, all the two-dimensional figures in part b) are superimposed to achieve accurate reconstruction of the three-dimensional morphology of the carbon paper and carbon felt to obtain part a). The thickness of the carbon paper and carbon felt provided in this embodiment, i.e., the superposition length, is 280 microns, but the superposition thickness of the two-dimensional figures in the embodiment of the present application is not limited to this length. This embodiment uses two-dimensional figures to construct three-dimensional morphology, which is conducive to reducing costs and has wider adaptability.

[0084] In some embodiments, obtaining pore distribution information of the porous medium based on the three-dimensional morphology in step S12 includes:

[0085] Step S121, based on the three-dimensional morphology of the porous medium, obtain the size of its three-dimensional matrix, obtain the cross-sectional area of ​​the porous medium based on the size of the three-dimensional matrix, and obtain the number of pixels on the cross-sectional area based on the cross-sectional area.

[0086] Step S122, obtaining the number of pore pixels in each cross section of the porous medium along a direction, and taking the ratio of the number of pore pixels on a cross section to the number of pixels on the cross section as the porosity of the cross section.

[0087] Step S123, based on the porosity of the corresponding cross section of the porous medium along each direction, obtain the porosity distribution in each direction.

[0088] Specifically, the size of the three-dimensional matrix of the porous medium is determined. In this embodiment, the porous medium is taken as a rectangular parallelepiped as an example.

[0089] Taking the x direction as an example, the porosity at a certain x value (for example: a0) is:

[0090] poro_x_a0=(A0) / (b*c)

[0091] Among them, A0 is the number of pore pixels (1 pixel) in the numerical matrix corresponding to the yz plane with x=a0, and (b*c) is the number of pixels in the corresponding cross section. The obtained value can be found in Figure 4 The porosity distribution in the x direction can be obtained by changing the x value from 1 to a. Similarly, the porosity distribution of the porous medium in the y direction (xz plane) and the z direction (xy plane) can be obtained.

[0092] In some embodiments, obtaining solid distribution information of the porous medium based on the three-dimensional morphology in step S12 includes:

[0093] Step S124, removing noise on the cross section of the three-dimensional morphology of the porous medium based on the noise condition.

[0094] Step S125 , obtaining solid distribution information of the porous medium based on the solid pixel distribution on the cross section.

[0095] Specifically, Figure 5As shown, the noise on the cross section of the three-dimensional morphology of carbon paper and carbon felt may include areas that do not conform to the cross-sectional area size of the real fiber, fiber stacking areas, and fiber tilting areas. The area of ​​the carbon paper and carbon felt region is used for screening to filter out areas that obviously do not conform to the cross-sectional area size of the real fiber. For example, areas with an area less than 20 and greater than 500 can be judged as noise that obviously does not conform to the cross-sectional area of ​​the real fiber and removed. The regional aspect ratio can also be used to filter out the influence of noise, fiber stacking, and fiber tilt. For example, the fiber aspect ratio range is set to [r min , r max ],r min =0.8, r max =1.2, the fibers with aspect ratios outside this range can be judged as noise and removed. In this embodiment, the regionprops function in MATLAB can be used.

[0096] Specifically, the fiber diameter is determined based on the solid pixel distribution on the cross section, including the number of pixels occupied by the fiber cross section or the number of pixels occupied by the fiber diameter. In this embodiment, the side length of each pixel can be set to 0.9 microns.

[0097] In this embodiment, the carbon fiber diameter distribution is mostly distributed between 5 microns and 10 microns, with an extreme value of 7 microns. The porosity in the yz section is relatively stable, while the porosity in the xy and xz sections fluctuates greatly between 0.65 and 0.95, with the xy section fluctuating more. The average porosity (the ratio of the number of pixels in the entire three-dimensional matrix to the total number of pixels) is 0.76.

[0098] In some embodiments, step S13 obtains the calculation domain of the porous medium based on the pore distribution and solid distribution information, including:

[0099] Step S131, obtaining the initial boundary of the ball growth.

[0100] Specifically, the initial boundary of the ball growth is the solid, physical boundary of the carbon paper and carbon felt, specifically the six outer surfaces of the rectangular carbon paper and carbon felt.

[0101] Step S132, based on the pore distribution and solid distribution information, obtain the distance assignment for each pixel point within the initial boundary of the sphere growth; the distance assignment value is the distance value between the pixel point and the pore closest to it.

[0102] Specifically, the Euclidean distance transform is calculated and a value is assigned to each pixel, which is equal to the distance from the pixel to the nearest non-zero pixel:

[0103] w(i)=min y∈Ω ||x(i)-x(`i)||

[0104] Where x(i) represents the position of any pixel i in the image, x(`i) is the position of another non-i pixel in the image, and Ω is the domain of the image.

[0105] Step S133, based on the distance assignment of each pixel point within the initial boundary of the sphere growth, the center of mass and radius of the largest sphere are obtained; the information of the calculation domain includes the center of mass and radius information of the largest sphere.

[0106] Specifically, calculate the maximum sphere mass center x i (The maximum value of the three-dimensional numerical matrix obtained by Euclidean distance transformation corresponds to the coordinates of the pixel point) and the radius w i (Weight, i.e. the value assigned to the pixel point). The pore centroid and weight in the calculation domain of carbon paper and carbon felt obtained by the ball growth model are as follows Figure 6 shown.

[0107] Step S134, obtaining a new sphere growth boundary based on all pixel points occupied by the largest sphere, until the radius of the largest sphere reaches a set value.

[0108] Specifically, all pixel points occupied by the largest sphere are added as new sphere growth boundaries. Steps S132 to S134 are repeated until the sphere radius reaches a set value, for example, the sphere radius is set to be smaller than the average fiber radius in the solid distribution information obtained based on the three-dimensional morphology of the porous medium. Specifically, the average fiber radius in the two-dimensional graph measured by X-ray microtomography technology can be used as a judgment standard.

[0109] In this embodiment, the calculation domain of the porous medium is calculated using the spherical growth model. In other embodiments, the calculation domain of the porous medium can also be calculated using algorithms such as a watershed algorithm and a medial axis transformation.

[0110] The root Voronoi space segmentation based on the computational domain in step S14 includes:

[0111] Step S141, performing root Voronoi space segmentation on the computational domain based on a preset number of segmentations to obtain cell information; the space segmentation information includes the cell information.

[0112] Step S142, obtaining the calculated overall porosity of the porous medium based on the cell information.

[0113] Step S143, based on the pore distribution and solid distribution of the porous medium, the overall porosity of the porous medium is obtained.

[0114] Step S144, based on the comparison results of the calculated overall porosity and the detected overall porosity, the root Voronoi space segmentation is optimized to update the cell information.

[0115] Specifically, the root Voronoi space segmentation of the carbon paper and carbon felt computational domain is established. Each space of the root Voronoi segmentation can be expressed as:

[0116]

[0117] Among them, the weighted space point (x i , w i ) is extracted from the reconstructed three-dimensional space matrix using the ball growth model. This formula represents the distance from a spatial point x to a spatial point x i The weighted distance of is less than to any other point x j The weighted distance of the spatial point x is determined as cell i (Actually a polyhedron).

[0118] In step S141, the number of balls N is set p That is, the number of cells, and the root Voronoi space segmentation is calculated. The information of all cells can be stored in the cell array, including the volume V of the cell i , all vertex coordinates, the length of the edge and the two vertices connected, the direction of the polygon surrounding the cell, and the labels of adjacent cells.

[0119] For example, this embodiment provides a vfn cell array example. Create a blank cell array vfn, the size of vfn is 3N p , N p is the number of cells. The i-th row and the first column of vfn contain the coordinate information of the vertices of the i-th cell. For example, the first cell polyhedron contains 26 vertices. The i-th row and the second column of vfn contain the information of the face of the i-th cell (the three columns are the vertex index, area and normal vector of the enclosed face respectively). For example, the first cell is composed of 15 faces, and the first face is surrounded by four vertices 2, 24, 23, and 4 (the vertices are arranged in the order of connection, the first edge connects the two vertices 24 and 2, the second edge connects the two vertices 24 and 23, the third edge connects the two vertices 23 and 4, and the fourth edge connects the two vertices 4 and 2), the area is 65.65, and the direction is [0.651-0.75]. The i-th row and the third column of vfn contain the information of the adjacent cells of the i-th cell. For example, the first cell is adjacent to 15 cells such as 750, 1022, and 18.

[0120] In step S142, a label (ID) is first assigned to each vertex and each vertex has only one ID. The vertex is a fiber node (i.e., a node of a solid network), and the connection relationship between all fibers is obtained based on the fiber node connected to the vertex ID and the edges (fibers) of all polygons.

[0121] Then, through the cell array, get the length L of the kth side of the jth polygon of the i-th cell ijk is the fiber length, the radius of the random cylindrical fiber r ijk , calculate the fiber volume as:

[0122]

[0123] Preferably, the randomly set fiber radius complies with the radius distribution of the fiber obtained from the three-dimensional morphology of the porous medium.

[0124] Then, calculate the total fiber volume ∑(k ijk V ijk ) (Assuming the fiber is a cylinder, considering the boundary effect) Preferably, according to the inverse number k of the number of cells to which the fiber belongs ijk Correct for solid volumes to avoid double counting.

[0125] In other embodiments, each edge of the polygon can be assigned a label (ID), and each edge has only one label, then the total volume of the fiber is ∑(V ijk ).

[0126] Then, the calculated overall porosity of the carbon paper and carbon felt is calculated based on the total volume of the fibers. The calculated overall porosity is the overall porosity calculated based on the spatial segmentation information. In step S143, the detected overall porosity of the porous medium is obtained based on the pore distribution and solid distribution information of the porous medium. That is, the detected overall porosity is the overall porosity calculated based on the data obtained by two-dimensional scanning or three-dimensional scanning detection. The two overall porosities are compared. If they are inconsistent, steps S141 to S143 are repeated until the comparison result is that the calculated overall porosity is consistent with the detected overall porosity, thereby optimizing the Root Voronoi space segmentation to update the cell information.

[0127] like Figure 7 As shown, when the number of pores increases from 100 to 800, the porosity of the network decreases from 0.94 to 0.78. In order to achieve the same porosity as the scanning results of carbon paper and carbon felt, the sphere growth model and the root-Voronoi space segmentation method take 900 pores.

[0128] In some embodiments, obtaining local connectivity information of the porous medium based on the spatial segmentation information in step S14 includes:

[0129] Step S145, obtaining the area of ​​the polygon corresponding to each cell in the cell information.

[0130] Step S146, based on the cell information, obtain the weighted radius of the side length of the solid corresponding to the side of the polygon.

[0131] Step S147, based on the weighted radius of the side length of the solid corresponding to the side of the polygon, obtain the length of the corresponding throat.

[0132] Step S148, based on the area of ​​the polygon corresponding to each cell in the cell information and the length of the corresponding throat, the extrusion volume of each polygon is obtained.

[0133] Step S149, based on the extrusion volume of each polygon and the length of the corresponding throat, the volume and equivalent radius of the throat, and the volume and equivalent radius of the hole are obtained.

[0134] Step S150, based on the label information of each cell and the adjacent cells in the cell information, the connection relationship between the pore and the throat is obtained.

[0135] Specifically, in this embodiment, the position and size information of the pore throat is obtained based on each face of the polyhedron and the fiber information on the face obtained by the Root-Voronoi space segmentation.

[0136] Step S145 extracts the area A of the jth polygon of the ith hole. ij (can be directly obtained from the cell array) and the weighted radius r of the side length of the solid corresponding to the polygon side is calculated in step S146 wm,ij :

[0137] r wm,ij =(∑(r ijk 2 L ijk ) / ∑L ijk ) 1 / 2

[0138] In step S147, the corresponding throat length L is obtained. ij =2r wm,ij .

[0139] Step S148 calculates the extrusion volume V of the jth polygon of the i-th hole f,ij (A ij L ij ), the corresponding laryngeal volume V is calculated in step S149 t,ij The equivalent radius of the throat is r t,ij They are:

[0140] V t,ij =V f,ij -∑k ijk V ijk

[0141]

[0142] Preferably, if Fig. 9 As shown, k ijk It is the reciprocal of the number of repetitions of the solid throat (i.e. the number of connected cells).

[0143] In step S149, the volume V of the ith pore is calculated. p,i and the equivalent hole radius r t,ij They are:

[0144] V p,i =V i -∑0.5V f,ij

[0145]

[0146] like Fig.10 As shown in the figure, the pore radius obtained by the ball growth model and the root-Voronoi space segmentation method is distributed in the range of 15 to 45 microns, with the vast majority distributed in the range of 15 to 35 microns, and the peak of the pore radius distribution is around 23 microns. The throat radius is distributed in the range of 0 to 40 microns, and the radius within 25 microns covers more than 90% of the number of throats.

[0147] In step S150, based on the labels of the adjacent cells of all the cells in the cell array vfn, the information of all the faces on the polyhedron and the polyhedron connected by all the faces in the global definition is determined to obtain the connection relationship between the hole and the throat.

[0148] In some embodiments, a method for obtaining microstructure parameters of porous materials includes: obtaining a two-dimensional image of a porous medium based on X-ray microtomography technology, and performing three-dimensional reconstruction of the two-dimensional image to obtain the three-dimensional morphology of the porous medium. Based on the three-dimensional morphology of the porous medium, its pore distribution and solid distribution information are obtained; based on the pore distribution and solid distribution information, the calculation domain of the porous medium is obtained using a spherical growth model. Root-Voronoi space segmentation is performed based on the calculation domain, and local connectivity information of the porous medium is obtained based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the pore and the throat. In this embodiment, it is creatively proposed to combine X-ray microtomography technology, spherical growth model and Root-Voronoi space segmentation to extract more realistic pore structure information of porous media, and at the same time, the connection relationship between the solid structure and the solid network can be extracted, so as to obtain the transmission phenomenon of electrons and the like in the solid network.

[0149] In order to compare with the pore structure constructed by the random distribution method, a pore network obtained by combining the pore random distribution method with the Root-Voronoi space segmentation is also constructed here. Figure 8 As shown in the figure, when the number of holes increases from 100 to 800, the porosity of the network decreases from 0.94 to 0.76. In order to achieve the same porosity as the scanning results of carbon paper and carbon felt, 900 holes are selected by random distribution method and root-Voronoi space segmentation. Fig.11As shown, the network pore radius constructed by the random distribution method and the root Voronoi space segmentation is distributed in the range of 5 to 40 microns, concentrated in the range of 15 to 35 microns, and the peak of the pore radius distribution is near 25 microns; the throat radius is distributed in the range of 0 to 40 microns, among which the throats with a radius within 25 microns also cover more than 90% of the number of throats.

[0150] In order to more vividly illustrate the beneficial effect of the pore network (sphere growth model and Root-Voronoi space segmentation method) constructed by the present invention on analyzing the material transport process in carbon paper and carbon felt, the oxygen transport in the cathode gas diffusion layer of a high-temperature proton exchange membrane fuel cell is taken as an example. The effectiveness of the pore network constructed by the present invention is first verified, and then the effective gas diffusion coefficient of oxygen between the pore network constructed by the present invention and the pore network constructed by the regular network and the random distribution method under different single-side boundary liquid phase coverage (such as Fig.12 As shown). Among them, the liquid phase intrusion is due to the loss of phosphoric acid in the high-temperature proton exchange membrane fuel cell and invades the gas diffusion layer due to capillary force. The results show that the results of the pore network constructed by the present invention are between the experimental results of TGP-060 and TGP-120 carbon papers, which emphasizes the validity of the model because it is consistent with the generally accepted literature that the same series of carbon papers have a uniform microstructure. In addition, when S<0.4, the pore network constructed by the present invention exhibits significant anisotropy. In addition, both the regular network and the network constructed by the random distribution method underestimate the effective gas diffusion coefficient of oxygen, indicating that the network constructed by the traditional method cannot effectively analyze the material transport process within the carbon paper and carbon felt.

[0151] The method for obtaining the microstructure parameters of porous materials provided by the embodiment of the present invention can obtain the pore distribution and solid distribution information in the microstructure of porous materials, which shows more realistic microstructure characteristics of porous media than traditional methods, and is of great significance for understanding the heat and mass transfer inside porous media (such as the transport of substances and charges in the gas diffusion layer of proton exchange membrane fuel cells). It can also obtain the local connectivity information of porous media, that is, extract the connection relationship between the solid structure and the solid network, so as to obtain the transmission phenomenon of electrons, etc. in the solid network.

[0152] Furthermore, the present application also provides a device for acquiring microstructure parameters of porous materials, including: an acquisition module for acquiring the three-dimensional morphology of the porous medium. A first calculation module for obtaining the pore distribution and solid distribution information of the porous medium based on the three-dimensional morphology of the porous medium. A second calculation module for obtaining the calculation domain of the porous medium based on the pore distribution and solid distribution information. A third calculation module for performing Root-Voronoi space segmentation based on the calculation domain, and obtaining the local connectivity information of the porous medium based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the pore and the throat. The method for acquiring microstructure parameters of porous materials implemented by each module in the device for acquiring microstructure parameters of porous materials can adopt the implementation method in any of the above-mentioned embodiments, which will not be repeated here.

[0153] Furthermore, the present application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method in any of the above embodiments when executing the computer program.

[0154] Furthermore, the present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method in any of the above embodiments are implemented.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for obtaining microstructure parameters of porous materials, characterized in that: include: Obtain the three-dimensional morphology of porous media; Based on the three-dimensional morphology of the porous medium, obtaining its pore distribution and solid distribution information; Based on the pore distribution and the solid distribution information, a calculation domain of the porous medium is obtained; Root Voronoi space segmentation is performed based on the computational domain, and local connectivity information of the porous medium is obtained based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the pores and the throat.

2. The method for obtaining microstructure parameters of porous materials according to claim 1, characterized in that: The obtaining of the three-dimensional morphology of the porous medium comprises: performing three-dimensional scanning on the porous medium to obtain its three-dimensional morphology; or Performing a two-dimensional scan on the cross section of the porous medium along a preset direction to obtain a plurality of two-dimensional graphs; and A three-dimensional reconstruction is performed based on the multiple two-dimensional images to obtain the three-dimensional morphology of the porous medium.

3. The method for obtaining microstructure parameters of porous materials according to claim 2, characterized in that: The three-dimensional reconstruction based on the multiple two-dimensional graphics to obtain the three-dimensional morphology of the porous medium includes: Performing graphic preprocessing on the two-dimensional graphic, wherein the graphic preprocessing includes adjusting the two-dimensional graphic to an optimal angle and removing a background area; Distinguishing between solid areas and pore areas in the two-dimensional graph; The two-dimensional graphics after each division process are superimposed to form the three-dimensional morphology of the porous medium.

4. The method for obtaining microstructure parameters of porous materials according to claim 1, characterized in that: The pore distribution information of the porous medium is obtained based on the three-dimensional morphology thereof, including: Based on the three-dimensional morphology of the porous medium, the size of the three-dimensional matrix is ​​obtained, and based on the size of the three-dimensional matrix, each cross-sectional area of ​​the porous medium is obtained, and based on the cross-sectional area, the number of pixels on the cross-sectional area is obtained; Obtaining the number of pore pixels in each cross section of the porous medium along a direction, and taking the ratio of the number of pore pixels on a cross section to the number of pixels on the cross section as the porosity of the cross section; Based on the porosity of the corresponding cross-section of the porous medium along each direction, the porosity distribution in each direction is obtained.

5. The method for obtaining microstructure parameters of porous materials according to claim 1, characterized in that: The solid distribution information of the porous medium is obtained based on the three-dimensional morphology thereof, including: removing noise on a cross section of the three-dimensional morphology of the porous medium based on a noise condition; Based on the solid pixel distribution on the cross section, solid distribution information of the porous medium is obtained.

6. The method for obtaining microstructure parameters of porous materials according to claim 1, characterized in that: The step of obtaining a calculation domain of the porous medium based on the pore distribution and the solid distribution information includes: Get the initial boundary of ball growth; Based on the pore distribution and the solid distribution information, a distance assignment is obtained for each pixel point within the initial boundary of the sphere growth; the distance assignment is the distance value between the pixel point and the pore closest to it; Based on the distance assignment of each pixel point within the initial boundary of the sphere growth, the center of mass and radius of the largest sphere are obtained; the information of the calculation domain includes the center of mass and radius information of the largest sphere; Based on all pixel points occupied by the largest sphere, a new sphere growth boundary is obtained until the radius of the largest sphere reaches a set value.

7. The method for obtaining microstructure parameters of porous materials according to claim 1, characterized in that: The root Voronoi space segmentation based on the computational domain comprises: Performing root Voronoi space segmentation on the computational domain based on a preset number of segmentations to obtain cell information; the space segmentation information includes the cell information; Based on the cell information, obtaining a calculated overall porosity of the porous medium; Based on the pore distribution and the solid distribution information, the overall porosity of the porous medium is obtained; The root Voronoi space segmentation is optimized based on the comparison result of the calculated overall porosity and the detected overall porosity to update the cell information.

8. The method for obtaining microstructure parameters of porous materials according to claim 7, characterized in that: The obtaining of the local connectivity information of the porous medium based on the spatial segmentation information includes: Obtaining the area of ​​the polygon corresponding to each cell in the cell information; Based on the cell information, a weighted radius of the side length of the solid corresponding to the side of the polygon is obtained; The length of the corresponding throat is obtained based on the weighted radius of the side length of the solid corresponding to the side of the polygon; Based on the area of ​​the polygon corresponding to each cell in the cell information and the length of the corresponding throat, obtaining the extrusion volume of each polygon; Based on the extrusion volume of each polygon and the length of the corresponding throat, the volume and equivalent radius of the throat, and the volume and equivalent radius of the hole are obtained; and Based on the label information of each cell and the adjacent cells in the cell information, the connection relationship between the hole and the throat is obtained.

9. A device for acquiring microstructure parameters of porous materials, characterized in that: The device comprises: An acquisition module, used for acquiring the three-dimensional morphology of the porous medium; A first calculation module is used to obtain pore distribution and solid distribution information of the porous medium based on the three-dimensional morphology of the porous medium; A second calculation module, used for obtaining a calculation domain of the porous medium based on the pore distribution and the solid distribution information; The third calculation module is used to perform root Voronoi space segmentation based on the calculation domain, and obtain local connectivity information of the porous medium based on the space segmentation information; the local connectivity information includes the position and size of the throat and the connection relationship between the hole and the throat.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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