Combustion metal particle three-dimensional surface panoramic microscopic imaging measurement method

Abstract

The invention discloses a burning metal particle three-dimensional surface panoramic microscopic imaging measurement method. The method comprises the following steps: collecting a dynamic panoramic microscopic image of burning metal particles; the collected panoramic microscopic image is preprocessed, the combustion metal particles are cut out independently from the panoramic microscopic image, and a binary image of the combustion metal particles and a binary image of surface oxides of the combustion metal particles are obtained; modeling combustion metal particles by using a long ellipsoid geometric model to obtain a mapping relation between the three-dimensional surface of the combustion metal particles and the two-dimensional information of the collected panoramic microscopic image; and calculating the three-dimensional surface areas of the combustion metal particles and the surface oxides thereof according to the binary image of the combustion metal particles, the binary image of the surface oxides thereof and the mapping relation. According to the measurement method, the three-dimensional surface reconstruction of the combustion metal particles can be realized, the areas of the combustion metal particles and oxides thereof can be quantitatively obtained, and the dynamic process of oxide fragments on the surfaces of the combustion metal particles can be visualized.

Description

Technical Field

[0001] The present invention relates to the field of three-dimensional visualization and measurement of multiphase flow particles, and particularly to a three-dimensional surface panoramic microscopic imaging measurement method for combusting metal particles. Background Art

[0002] The combustion of metal particles widely exists in aerospace propulsion applications such as rocket, missile propulsion, and damage equipment. The combustion of metal is different from that of traditional hydrocarbon fuels. During the combustion process of metal, there are coexisting multiphase states and a coupling relationship between multiple phases. The generated oxides will diffuse and deposit on the surface of the droplet, forming an oxidation cap or an oxidation shell. The generation and attachment of such oxides greatly affect the evaporation process during the combustion of metal particles, thereby affecting combustion and heat transfer, and ultimately bringing combustion characteristics different from those of traditional hydrocarbon droplet combustion. Therefore, online visualization and measurement of the three-dimensional droplet surface characteristics of metal particle combustion are of great significance.

[0003] Most of the commonly used metal particle visualization techniques in this field are based on high-speed microscopic imaging techniques from a single perspective. A high-precision telecentric microscopic lens is used to perform high-speed microscopic imaging on the combusting metal droplet, and the structure and surface characteristics of the metal droplet are observed by collecting the self-luminescence of the metal particle during combustion (such as Beckstead, M.W., et al. (2005). Aluminum combustion modeling in solid propellants. Journal of Propulsion and Power.). Although this method can collect very fine surface structures of metal particles, it can only obtain two-dimensional plane information and can only cover one side of the combusting metal particle, and cannot fully reflect the surface characteristics of the entire droplet. For three-dimensional imaging techniques, binocular and multi-view schemes are often used in the field of computer imaging to image an object from multiple perspectives, and then the three-dimensional point cloud and three-dimensional mesh model of the object are reconstructed through feature point matching and epipolar geometry reconstruction algorithms. This method can obtain a high-precision three-dimensional model, but the object to be imaged often needs to be stationary and have obvious features, and it cannot be applied to three-dimensional imaging of metal combustion with extremely fast reactions and micron-scale particles.

[0004] For technologies such as micro-CT (e.g., the three-dimensional surface imaging method of microscopic particles disclosed in Chinese Patent No. CN109709116A includes: preprocessing the microscopic particle sample; scanning the preprocessed microscopic particle sample with micro-CT to obtain the micro-CT data of the microscopic particle sample; performing rotational imaging on the preprocessed microscopic particle sample using a scanning electron microscope and a stepping rotary sample stage to obtain the scanning electron microscope images of the microscopic particle sample at various angles; reconstructing the micro-CT data to obtain a three-dimensional data volume including three-dimensional contour and internal structure information, and pasting the scanning electron microscope images at various angles onto the surface of the three-dimensional data volume one by one to obtain the three-dimensional full surface of the microscopic particle) and structured light imaging adopted in the field of micron-sized particles, it is difficult to handle the online visualization and measurement of the online three-dimensional surface characteristics of high-temperature metal combustion in a high-speed dynamic state.

[0005] In summary, there are still huge challenges in the three-dimensional surface reconstruction and measurement of burning metal particles. Summary of the Invention

[0006] The purpose of the present invention is to provide a three-dimensional surface panoramic microscopic imaging measurement method for burning metal particles; this measurement method can realize the reconstruction of the three-dimensional surface of burning metal particles, quantitatively obtain the areas of burning metal particles and their oxides, and visualize the dynamic process of oxide fragments on the surface of burning metal particles.

[0007] The present invention provides the following technical solutions:

[0008] A three-dimensional surface panoramic microscopic imaging measurement method for burning metal particles, the measurement method includes the following steps:

[0009] Step 1, collect panoramic microscopic images of burning metal particles in a dynamic state;

[0010] Step 2, preprocess the collected panoramic microscopic images, cut out the burning metal particles separately from the panoramic microscopic images, and obtain the binary images of the burning metal particles and the binary images of their surface oxides;

[0011] Step 3, model the burning metal particles using an oblate spheroid geometric model to obtain the mapping relationship between the three-dimensional surface of the burning metal particles and the two-dimensional information of the panoramic microscopic images collected in Step 1;

[0012] Step 4, calculate the three-dimensional surface areas of the burning metal particles and their surface oxides through the binary images of the burning metal particles and their surface oxides in Step 2, and the mapping relationship in Step 3.

[0013] In Step 2, the method of cutting out the burning metal particles separately from the panoramic microscopic images and obtaining the binary images of the burning metal particles and their surface oxides includes:

[0014] Step 2-1: Detect the burning metal particles in the panoramic microscopic image, thereby obtaining the positions of the burning metal particles in the image, and cropping to obtain the images of individual burning metal particles.

[0015] Step 2-2: Utilize the gray-scale features of the burning metal particles and their surface oxides to perform image segmentation on the cropped images of individual burning metal particles, obtaining the binary images of the burning metal particles and the binary images of their surface oxides.

[0016] In step 3, the method of using an oblate spheroid geometric model to model the burning metal particles and obtaining the mapping relationship between the three-dimensional surface of the burning metal particles and the imaging result includes:

[0017] Step 3-1: Approximate the burning metal particles using a rotationally symmetric oblate spheroid model, let the line connecting the centroid of the surface oxide of the burning metal particle and the metal particle be its axis of rotation, establish a three-dimensional coordinate system for reconstructing the burning metal particle with the camera image coordinates as the X-Y plane and the camera shooting direction as the Z-axis direction;

[0018] Step 3-2: Extract parameters from the panoramic microscopic image to calculate the attitude of the axis of rotation of the burning metal particle in the established three-dimensional coordinate system, and the attitude includes the yaw angle α and pitch angle β of the burning metal particle;

[0019] Step 3-3: Extract parameters from the panoramic microscopic image to obtain the geometric parameters required for modeling the oblate spheroid model of the burning metal particle, and the geometric parameters include the major axis a and minor axis b of the oblate spheroid model of the burning metal particle;

[0020] Step 3-4: Establish an oblate spheroid geometric model according to the attitude in step 3-2 and the geometric parameters in step 3-3, and model the burning metal particles to obtain the mapping relationship between the three-dimensional surface of the burning metal particles and the two-dimensional information of the panoramic microscopic image collected in step 1.

[0021] In step 3-1, the parametric equation of the model in the three-dimensional coordinate system for reconstructing the burning metal particle is expressed as:

[0022]

[0023] In the formula, a and b respectively represent the major axis and minor axis of the ellipsoid, and x, y, and z respectively represent the three-dimensional spatial coordinates of any point on the three-dimensional surface of the burning metal particle.

[0024] In step 3-2, extract the angle between the projection of the axis of rotation of the burning metal particle on the X-Y plane and the X-axis as the yaw angle α of the burning metal particle:

[0025] Obtain the line connecting the surface oxide of the burning metal particle and the centroid of the burning metal particle, and this line represents the major axis projection of the burning metal particle on the X-Y plane;

[0026] Determine the yaw angle α through the centroid coordinates of the surface oxide of the burning metal particle and the burning metal particle:

[0027]

[0028] In the formula, the subscripts c and d represent the centroid coordinates of the surface oxide of the burning metal particle and the burning metal particle respectively.

[0029] In step 3-2, extract the angle between the rotation axis of the burning metal particle and its projection on the X-Y plane as the pitch angle β of the burning metal particle:

[0030] The differential image between the images of the two cameras used to collect the panoramic microscopic image of the dynamic burning metal particle represents the projection of the interface between the surface oxide of the burning metal particle and the burning metal particle on the X-Y plane;

[0031] β is calculated by the following formula:

[0032]

[0033] In the formula, d b and d a respectively represent the major axis and the minor axis extracted from the projection.

[0034] In step 3-3, the method for extracting parameters from the panoramic microscopic image to obtain the geometric parameters required for modeling the long ellipsoid model of the burning metal particle includes:

[0035] Find the contour of the connected domain of the binary image of the burning metal particle, use the ellipse fitting algorithm to fit the contour, and take the major axis and minor axis of the fitted ellipse as a1 and b respectively; correct a1 according to the pitch angle attitude by the following formula:

[0036]

[0037] In the formula, a is the major axis of the long ellipsoid model of the burning metal particle, a1 and b are the major axis and minor axis of the fitted ellipse, and β is the pitch angle of the burning metal particle.

[0038] In step 3-4, the burning metal particle is modeled as:

[0039]

[0040] In the formula, R is the rotation matrix controlled by the yaw angle α and pitch angle β of the attitude angle of the burning metal particle, and x, y, z are the three-dimensional space coordinate points of the coordinate system.

[0041] In step 4, the three-dimensional surface area of the burning metal particles and their surface oxides is calculated by the following integral:

[0042]

[0043] where S c and S d represent the areas of the surface oxides of the burning metal particles and the droplets respectively, and Ω c and Ω d represent the binary images of the surface oxides of the burning metal particles and the binary image of the burning metal particles;

[0044] dS is the area element of the three-dimensional prolate spheroid in the X-Y plane, which is determined by the following expression:

[0045]

[0046] where F represents the implicit function of the prolate spheroid, is the gradient of this function.

[0047] The measurement method uses a panoramic microscopic imaging system, and the panoramic microscopic imaging system includes:

[0048] Two cameras are placed facing each other on both sides of the burning metal particles to be measured. The two cameras are arranged in a straight line. Each camera captures an image of one side view of the burning metal particles;

[0049] A synchronizer is connected to the two cameras and is used to control the shooting sequence of the two cameras;

[0050] A trigger source is connected to the two cameras and activates both cameras to start shooting at the same time;

[0051] A computer is used to receive and record the panoramic microscopic images transmitted by the two cameras and execute steps 2 - 4.

[0052] In the panoramic microscopic imaging system: the cameras are arranged facing each other on both sides of the area to be measured, and the imaging centers of the two cameras are kept on the same straight line, and objects at any position in the field of view can be kept in focus in both cameras at the same time; a synchronous signal generator is used to control the shooting sequence of the cameras, so that the frame rates of the cameras are consistent and the acquisition sequences are consistent during operation.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] The three-dimensional surface panoramic microscopic measurement method for burning metal particles provided by the present invention obtains panoramic images of burning metal particles through two cameras placed opposite to each other, and approximately models the burning metal particles by using a rotationally symmetric prolate ellipsoid, realizing the reconstruction of the three-dimensional surface of the burning metal particles and the measurement of their surface areas. It overcomes the problem that single-view imaging in existing measurement technologies cannot capture the panoramic surface dynamics of burning metal particles (i.e., the problem of incomplete acquisition of burning metal particle information by single-view imaging), realizes the panoramic real-time visualization, three-dimensional surface reconstruction and surface area measurement of burning metal particles and their surface oxides (oxidation caps or oxidation shells), and effectively reduces the area measurement error of the three-dimensional surface of burning metal particles through three-dimensional modeling;

[0055] The measurement method provided by the present invention has the advantages of non-contact, full-view coverage, and three-dimensional imaging measurement, can capture the dynamic changes on the particle surface, and is applicable to the on-line study of metal combustion kinetics in high-temperature multiphase flow environments; it provides an effective key technical means and data support for the measurement (such as distribution and movement trend) and characterization of surface oxides on metal particles during the combustion process; in addition, the present invention can also be extended to the three-dimensional characterization of asymmetric micro-scale objects such as biological cells and fuel particles, providing a general tool for combustion diagnosis, materials science and industrial process optimization, and is suitable for expansion to a wide range of industrial applications. Brief Description of the Drawings

[0056] Figure 1 It is a schematic diagram of a panoramic microscopic imaging system;

[0057] Figure 2 It is a data processing flow chart;

[0058] Figure 3 It is an effect diagram of three-dimensional reconstruction of propellant aluminum agglomerates provided in Example 1;

[0059] Figure 4 It is a panoramic microscopic image of burning aluminum agglomerates captured in Example 1;

[0060] Figure 5 It is the cropped image of burning aluminum agglomerates, the binary image of burning metal particles and the binary image of their oxides in step 4 of Example 1;

[0061] Wherein: a, the burning metal particle to be measured; 1, microscopic lens; 2, camera; 3, synchronizer; 4, trigger source; 5, computer. Detailed Embodiments

[0062] The following further illustrates the specific embodiments of the technical solutions of the present invention through examples in combination with the drawings.

[0063] As Figure 2As shown in the figure, this embodiment provides a panoramic microscopic imaging measurement method for three-dimensional surface imaging of aluminum agglomerates in propellant combustion, including the following steps:

[0064] Step 1: Establish a 360° panoramic microscopic imaging system for burning metal particles.

[0065] As Figure 1 shown, the panoramic microscopic imaging system includes:

[0066] Two cameras 2, and each camera is equipped with a microscopic lens 1, so that the equivalent pixel of the system is better than 10μm per pixel. The two cameras are placed opposite each other on both sides of the burning metal particles to be measured. The cameras are arranged in a straight line. Each camera captures the image of one side view of the burning metal particles, so that the system has the ability to capture the panoramic view of the complete surface of the burning metal particles;

[0067] A synchronizer 3, connected to the two cameras, is used to control the shooting timings of the two cameras to achieve that the two cameras shoot the images of the burning metal particles at the same frame rate and at the same moment;

[0068] A trigger source 4, connected to the two cameras, activates the two cameras simultaneously to start shooting;

[0069] A computer 5, which is used to receive and record the image data transmitted by the two cameras and process them to obtain the three-dimensional surface measurement results of the burning metal particles.

[0070] In this embodiment, two high-speed cameras are symmetrically arranged on both sides of the burning metal particles. The highest frame rate of the high-speed cameras can reach 30kHz, and the resolution is 1024×768. Object-side telecentric lenses with a working distance of 100mm are assembled on the two high-speed cameras, so that the equivalent pixel size of the system imaging is 5.96μm, and the depth of field of the system is about 600μm. The accuracy of the synchronizer reaches the ns level. The timing signal frequency is set to 30kHz, and the pulse width is 10μs. It is connected to the high-speed cameras using BNC cables. The external trigger source uses a manual switch, which is connected to the high-speed cameras through BNC cables, and the cameras are simultaneously triggered by giving a short-circuit signal. The data collected by the cameras is transmitted to the computer 5 through the network cable. The memory of the computer is 16GB, and the running storage is not less than 512GB.

[0071] Step 2: Align the imaging fields of view of the system, adjust the positions of the cameras so that the imaging fields of view of the cameras are aligned with the same area; adjust the imaging focus positions of the system so that the imaging focus positions of the cameras are aligned with the same area; use the synchronizer to control the shooting timings of the cameras; use the trigger source to control the activation time of the cameras; use a calibration board to calibrate the equivalent pixels of the imaging system.

[0072] Among them, the field of view and the focusing position of the panoramic microscopic imaging system are aligned. The specific operation is as follows: Arrange an object, preferably a needle, between the two cameras. Adjust the distances from the two cameras to the wire until the object can be clearly imaged in the cameras. Then, further adjust the two cameras so that the deviation of the imaging results of the object in the two cameras after mirroring is less than 1 pixel. Further, arrange a 200-μm wire in the fields of view of the two cameras at an angle of about 45°. Continuously fine-tune the distances between the two cameras until the focused positions in the fields of view are the same after mirroring in the images.

[0073] In this embodiment, a 200-μm wire placed obliquely in the field of view is used to align the focusing position, and the alignment error is less than 10 pixels. A needle is used to complete the field-of-view alignment, and the error is less than 1 pixel.

[0074] Among them, the panoramic microscopic imaging system is synchronized and triggered simultaneously. The specific operation is as follows: Connect the synchronizer to the two cameras, set the cameras to be controlled by an external synchronization timing signal, and give two identical timing signals through the synchronizer to control the cameras; Connect the external trigger source to the two cameras, set the cameras to be activated by an external trigger signal, and realize that the cameras start collecting at the same time.

[0075] Among them, the equivalent pixel calibration of the panoramic microscopic imaging system is as follows: Arrange a calibration plate with a known length parallel to the camera imaging plane at the camera focusing position. In this embodiment, it is a checkerboard calibration plate with a side length of 250 μm for each small block; Calculate the ratio between the known physical real length and the pixel length on the image to obtain the true physical length represented by each pixel in the real world on the image.

[0076] The burning aluminum agglomerates measured in this embodiment are generated by the combustion of the propellant. The propellant charge is a cuboid with a size of 4×4×5 mm and is placed in the middle of the panoramic microscopic imaging system to ensure that both high-speed cameras can clearly image the propellant charge.

[0077] Step 3: Acquire the panoramic microscopic images of the dynamic combustion metal particles.

[0078] Some of the panoramic microscopic images of the dynamic combustion metal particles collected in this embodiment are as Figure 4 shown.

[0079] Step 4: Preprocess the acquired images, cut out the combustion metal particles from the panoramic microscopic images separately, and obtain the binary images of the combustion metal particles and the binary images of their surface oxides.

[0080] The specific operation of step 4 is as follows: Use the trained object detection neural network algorithm to detect the burning metal particles in the collected image, so as to obtain the positions of the burning metal particles on the image, and crop the images of individual burning metal particles; Utilize the gray-scale features of the burning metal particles and their surface oxides to perform image segmentation on the cropped images of individual burning metal particles to obtain the binary images of the burning metal particles and the binary images of their surface oxides.

[0081] The image detection algorithm adopted in this embodiment is YOLOv8-n trained with a dataset made from 1538 pairs of labeled pairs, which can accurately detect aluminum agglomerates from images. The segmentation algorithm used is a two-stage clustering segmentation algorithm that couples gray-scale information and the side length of the detection box detected by the YOLOv8 network.

[0082] Some of the cropped images of individual burning metal particles and the binary images of the burning metal particles and the binary images of their surface oxides obtained by segmentation in this embodiment are as Figure 5 shown.

[0083] Step 5: Use an oblate spheroid geometric model to model the burning metal particles to obtain the mapping relationship between the three-dimensional surface of the burning metal particles and the two-dimensional information of the panoramic microscopic image collected in step 1. It specifically includes the following steps:

[0084] Step 5-1: Approximate the burning metal particles with a rotationally symmetric oblate spheroid model. Let the line connecting the centroid of the surface oxide of the burning metal particle and the metal particle be used as its rotation axis of symmetry. Establish a three-dimensional coordinate system for reconstructing the burning metal particles with the camera image coordinates as the X-Y plane and the camera shooting direction as the Z-axis direction:

[0085] Under the three-dimensional coordinate system for reconstructing the burning metal particles established with the camera image coordinates as the X-Y plane and the camera shooting direction as the Z-axis direction, the parametric equation of the model can be expressed as:

[0086]

[0087] In formula (1), a and b respectively represent the major axis and minor axis of the ellipsoid, and x, y, and z respectively represent the three-dimensional space coordinates of any point on the three-dimensional surface of the burning metal particle.

[0088] Step 5-2: Extract parameters from the panoramic microscopic image to calculate the attitude of the rotation axis of the burning metal particle in the established three-dimensional coordinate system. The attitude includes the yaw angle α and pitch angle β of the burning metal particle:

[0089] It is necessary to extract the angle between the projection of the rotation axis of the burning metal particle on the X-Y plane and the X-axis as the yaw angle α of the burning metal particle; through the obtained burning metal particle and its oxide, and through the corresponding connected domain, the centroid position of the particle and its oxide on the image can be calculated, so as to obtain the line connecting the surface oxide of the burning metal particle and the centroid of the burning metal particle, and this line represents the major axis projection of the burning metal particle on the X-Y plane. At this time, the yaw angle α can be determined by the centroid coordinates of the surface oxide of the burning metal particle and the burning metal particle.

[0090]

[0091] In formula (2), the subscripts c and d represent the centroid coordinates of the surface oxide of the burning metal particle and the burning metal particle respectively.

[0092] It is necessary to extract the angle between the rotation axis of the burning metal particle and its projection on the X-Y plane as the pitch angle β of the burning metal particle. Calculate the differential image between the two camera images, and the result represents the projection of the interface between the surface oxide of the burning metal particle and the burning metal particle on the X-Y plane. The surface oxide of the burning metal particle and the burning metal particle melt into a liquid state at high temperature, and its interface presents a ring shape due to surface tension. At this time, the length of the interface projection is equal to the height difference of the ring in the side view, and the pitch angle β can be calculated by the following formula:

[0093]

[0094] In formula (3), d b and d a represent the major axis and minor axis extracted from the projection respectively.

[0095] Step 5-3: Extract parameters from the panoramic microscopic image to obtain the geometric parameters required for modeling the long ellipsoid model of the burning metal particle. The geometric parameters include the major axis a and minor axis b of the long ellipsoid model of the burning metal particle.

[0096] Step 5-4: Establish a long ellipsoid geometric model based on the attitude and geometric parameters and model the burning metal particle to obtain the mapping relationship between the three-dimensional surface of the burning metal particle and the two-dimensional information of the panoramic microscopic image collected in Step 1:

[0097] Find the contour of the connected domain by segmenting the binary image of the burning metal particle image, use the ellipse fitting algorithm to fit the contour, and take the major axis and minor axis of the fitted ellipse as a1 and b respectively; correct a1 according to the pitch angle attitude calculated in Step 4 by the following formula:

[0098]

[0099] In formula (4), a is the major axis of the prolate ellipsoid model of the burning metal particles, a1 and b are the major and minor axes of the fitted ellipse, and β is the pitch angle of the burning metal particles. After correction, the major and minor axis parameters of the prolate ellipsoid are obtained. According to the attitude angle and the major and minor axes of the burning metal particles, the three-dimensional surface of the burning metal particles in three-dimensional space can be modeled as:

[0100]

[0101] In the formula, α and β respectively represent the yaw angle and pitch angle of the prolate ellipsoid, and a and b respectively represent the major axis and minor axis of the prolate ellipsoid.

[0102] Through the ellipsoid geometric model, the two-dimensional pixels on the obtained panoramic microscopic image can be mapped onto the three-dimensional ellipsoid surface to realize the three-dimensional reconstruction of the burning metal particles, as Figure 3 shown.

[0103] Step 6: Calculate the areas of the burning metal particles and their surface oxides to complete the measurement.

[0104] The area element dS of the three-dimensional prolate ellipsoid on the X-Y plane is determined by the following expression:

[0105]

[0106] In formula (5), F represents the implicit function of the ellipsoid of revolution, is the gradient of this function. Then the area can be calculated by the following integral:

[0107]

[0108] In formula (6), S c and S d respectively represent the areas of the surface oxides and droplets of the burning metal particles, and Ω c and Ω d represent the binary segmentation maps of the surface oxides and the burning metal particles of the burning metal particles.

[0109] Specifically calculated, the surface area of the burning aluminum agglomerate particles is 43.66×10 -2 mm 2 , and the surface area of the surface oxides of the burning aluminum agglomerate is 22.29×10 -2 mm 2 .

[0110] The panoramic microscopic imaging measurement method for the three-dimensional surface imaging of burning aluminum agglomerates in this embodiment has successfully realized the reconstruction of the three-dimensional surface of the agglomerates and the area measurement, proving the feasibility of the method and system.

[0111] In summary, the present invention provides a three-dimensional surface panoramic microscopic imaging measurement method for burning metal particles, which can realize the three-dimensional visualization of the three-dimensional surface of burning metal particles and the measurement of their surface areas, and can provide test technical support and data support for the distribution and movement trend of metal particle surface oxides during the combustion process. It is of great significance for the research in the aerospace propulsion field such as understanding the metal combustion process and combustion mechanism modeling.

[0112] The above is a detailed description of the present invention in combination with the embodiments. However, the implementation mode of the present invention is not limited by the above embodiments. Any changes, substitutions, combinations, simplifications, etc. made under the core guiding ideology of the present invention are included in the protection scope of the present invention.

Claims

1. A method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging, characterized in that: The measuring method comprises the following steps: Step 1, collecting a panoramic microscopic image of the dynamics of burning metal particles; Step 2, preprocessing the collected panoramic microscopic image, cutting out the burning metal particles from the panoramic microscopic image and obtaining a binary image of the burning metal particles and a binary image of the oxide on their surface; Step 3: Modeling the burning metal particles using a long ellipsoid geometry model to obtain a mapping relationship between the three-dimensional surface of the burning metal particles and the two-dimensional information of the panoramic microscopic image collected in step 1; Step 4: Calculate the three-dimensional surface area of ​​the burned metal particles and the oxides on their surfaces using the binary image of the burned metal particles and the binary image of the oxides on their surfaces in step 2 and the mapping relationship in step 3.

2. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 1, characterized in that: In step 2, the method of cutting out the burned metal particles from the panoramic microscopic image and obtaining a binary image of the burned metal particles and a binary image of the oxide on their surface comprises: Step 2-1, detecting the burning metal particles in the panoramic microscopic image, thereby obtaining the position of the burning metal particles on the image, and cropping to obtain an image of a single burning metal particle; Step 2-2: using the grayscale features of the burned metal particles and the oxides on their surfaces, perform image segmentation on the cropped single burned metal particle image to obtain a binary image of the burned metal particles and a binary image of the oxides on their surfaces.

3. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 1, characterized in that: In step 3, the method of modeling the burning metal particles using a prolate ellipsoid geometry model to obtain a mapping relationship between the three-dimensional surface of the burning metal particles and the imaging result includes: Step 3-1, using a rotationally symmetric long ellipsoid model to approximate the burning metal particles, taking the line connecting the center of mass of the oxide on the surface of the burning metal particles and the metal particles as its rotational symmetry axis, taking the camera image coordinates as the XY plane, and taking the camera shooting direction as the Z axis direction to establish a three-dimensional coordinate system for reconstructing the burning metal particles; Step 3-2, extracting parameters from the panoramic microscopic image to calculate the posture of the rotation axis of the burning metal particle in the established three-dimensional coordinate system, wherein the posture includes the yaw angle α and the pitch angle β of the burning metal particle; Step 3-3, extracting parameters from the panoramic microscopic image to obtain geometric parameters required for modeling a prolate ellipsoid model of a burning metal particle, wherein the geometric parameters include a major axis a and a minor axis b of the prolate ellipsoid model of a burning metal particle; Step 3-4: Establish a long ellipsoid geometric model and model the burning metal particles according to the posture in step 3-2 and the geometric parameters in step 3-3, and obtain a mapping relationship between the three-dimensional surface of the burning metal particles and the two-dimensional information of the panoramic microscopic image collected in step 1.

4. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 3, characterized in that: In step 3-1, the parameterized equation of the model in the three-dimensional coordinate system of the combustion metal particles is expressed as: Where a and b represent the major axis and minor axis of the ellipsoid, respectively, and x, y, and z represent the three-dimensional spatial coordinates of any point on the three-dimensional surface of the burning metal particle, respectively.

5. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 3, characterized in that: In step 3-2, the angle between the projection of the rotation axis of the burning metal particle on the XY plane and the X axis is extracted as the yaw angle α of the burning metal particle: Obtaining a line between the oxide on the surface of the burning metal particle and the center of mass of the burning metal particle, wherein the line represents the long-axis projection of the burning metal particle on the XY plane; The yaw angle α is determined by the coordinates of the surface oxide of the burning metal particle and the center of mass of the burning metal particle: Wherein the subscripts c and d represent the coordinates of the center of mass of the oxide on the surface of the burning metal particle and the burning metal particle, respectively.

6. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 5, characterized in that: In step 3-2, the angle between the rotation axis of the burning metal particle and its projection on the XY plane is extracted as the pitch angle β of the burning metal particle: The difference image between the two camera images used to collect the dynamic panoramic microscopic image of the burning metal particles represents the projection of the oxide on the surface of the burning metal particles and the interface of the burning metal particles on the XY plane; β is calculated by the following formula: Where d b and d a denote the major and minor axes extracted from the projection, respectively.

7. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 3, characterized in that: In step 3-3, the method of extracting parameters from the panoramic microscopic image to obtain the geometric parameters required for modeling the prolate ellipsoid model of the burning metal particles includes: The binary graph of the burning metal particles is used to find the contour of its connected domain, and the ellipse fitting algorithm is used to fit the contour. The major axis and minor axis of the fitting ellipse are a1 and b respectively; a1 is corrected according to the pitch angle attitude using the following formula: Where a is the major axis of the prolate ellipsoid model of the burning metal particle, a1 and b are the major and minor axes of the fitting ellipse, and β is the pitch angle of the burning metal particle.

8. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 3, characterized in that: In step 3-4, the burning metal particles are modeled as: Wherein R is a rotation matrix controlled by the attitude angle yaw angle α and pitch angle β of the burning metal particle, and x, y, z are the three-dimensional space coordinate points of the coordinate system.

9. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 3, characterized in that: In step 4, the three-dimensional surface area of ​​the burning metal particles and their surface oxides is calculated by the following integral: Where S c and S d Respectively represent the area of ​​oxide and droplet on the surface of burning metal particles, Ω c and Ω d It is expressed as a binary image of the oxide on the surface of the burning metal particle and a binary image of the burning metal particle, where φ represents the ratio of the area of ​​the oxide to the area of ​​the burning particle; dS is the area element of the three-dimensional prolate ellipsoid in the XY plane and is determined by the following expression: Where F is the implicit function of the rotating ellipsoid, is the gradient of this function.

10. The method for measuring the three-dimensional surface of burning metal particles by panoramic microscopic imaging according to claim 1, characterized in that: The measuring method adopts a panoramic microscopic imaging system, and the panoramic microscopic imaging system comprises: Two cameras, the two cameras are placed facing each other on both sides of the burning metal particles to be tested, and the two cameras are arranged in a straight line, and each camera captures the image of the burning metal particles from one side; A synchronizer, connected to the two cameras, for controlling the shooting timing of the two cameras; The trigger source is connected to two cameras and activates both cameras to start shooting; The computer is used to receive and record the panoramic microscopic images transmitted by the two cameras and execute steps 2 to 4.

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