Method for measuring the dispersion angle of a gaseous product plume after ignition of a solid propellant

Abstract

The present application belongs to the field of measuring the plume divergence angle of the gasification product of a thruster, and particularly relates to a method for measuring the plume divergence angle of the gasification product of a solid propellant after ignition, comprising the following steps: obtaining a background image before ignition of the solid propellant and a gasification product inflation movement image during the ignition process; comparing the background image and the gasification product inflation movement image to obtain a gasification product image; solving the radial distribution of radiation intensity on N cross sections of the gasification product image; determining the maximum intensity value on each cross section and calculating the position of 98% maximum intensity value on each cross section; using the least square method to perform linear regression on the positions of all 98% maximum intensity values, calculating the slope of the regression straight line, and calculating the plume divergence angle of the gasification product according to the slope of the regression straight line. The plume divergence angle measurement method provided by the present application ensures measurement efficiency and high measurement accuracy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of measuring the divergence angle of the gasification product plume of a thruster, and particularly relates to a method for measuring the divergence angle of the gasification product plume of a solid propellant after ignition. BACKGROUND

[0002] The solid-gas conversion process is an indispensable process for providing a solid propellant of a thruster, and is also a prerequisite for ensuring subsequent electromagnetic acceleration to generate thrust. The properties of the gas product, including ionization degree, temperature, initial velocity and divergence angle, will be closely related to the electromagnetic acceleration, and ultimately affect the propulsive performance of the thruster. The plume divergence angle is an important parameter for determining the efficiency of the thruster. It represents the ratio of the momentum perpendicular to the axis to the kinetic energy parallel to the axis. If the divergence angle of the gas product is larger, the plume divergence angle after electromagnetic acceleration is expected to be larger, and the utilization rate and efficiency of the propellant will be lower.

[0003] The electric thruster mainly uses a Faraday probe and a spectrum to measure the divergence angle of the jet plume. But both of these two methods are suitable for measuring the plume far from the outlet, otherwise the probe and the optical fiber will be overheated due to ion bombardment. In addition, they are invasive measurement methods, and the movement of the probe in the plume area will inevitably affect the plume in these two methods. The solid-gas conversion process of the solid propellant only occurs in a very small area around the surface of the solid propellant, and the use of the probe and the spectrum method will greatly affect its expansion movement, and the plume beam impact will cause the failure of the probe and the optical fiber probe. In addition, the probe and the spectrum method take a long time to collect, and are usually used for steady-state plume measurement, which is not suitable for transient and rapid plume measurement. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for quickly collecting and measuring the plume divergence angle of the gasification product of a solid propellant based on a high-speed camera and image processing in view of the solid-gas conversion process after the solid propellant is ignited by a laser.

[0005] The present application provides a method for measuring the divergence angle of the gasification product plume of a solid propellant after ignition, comprising the following steps:

[0006] S100, acquiring a background image before ignition of the solid propellant and a gasification product expansion movement image during the ignition process, the shooting directions of the background image and the gasification product expansion movement image being consistent and perpendicular to the axis of the solid propellant ignition site;

[0007] S200, comparing the gray values of the background image and the gasification product expansion movement image, determining the plume boundary of the gasification product expansion movement image, and segmenting the gasification product part in the gasification product expansion movement image to obtain a gasification product image;

[0008] S300: Obtain the two-dimensional irradiance distribution of the gasification product image, and solve the radial irradiance distribution map on N sections of the gasification product image based on the two-dimensional irradiance distribution of the gasification product image.

[0009] S400, based on the radial distribution diagram of irradiance on N cross sections, determine the maximum irradiance value on each cross section, and calculate the location of 98% of the maximum irradiance value on each cross section;

[0010] S500 uses the least squares method to perform linear regression on all locations with 98% maximum illuminance values, calculates the slope of the regression line, and calculates the plume divergence angle of the gasification products based on the slope of the regression line.

[0011] Furthermore, acquiring the background image before solid propellant ignition and the expansion motion diagram of the vaporization products during ignition includes:

[0012] The exposure time of the high-speed camera is determined based on the laser pulse width time of the ignition laser. The exposure time of the high-speed camera is less than one-thousandth of the laser pulse width time.

[0013] Furthermore, based on the two-dimensional irradiance distribution of the gasification product image, the radial irradiance distribution maps on N cross sections of the gasification product image are solved, including:

[0014] Establish a model for solving the irradiance at coordinate points:

[0015] ;

[0016] In the formula, It is the midpoint of the gasification products. Illuminance value; It is the illuminance value of pixel (x0-1, z0). It is the illuminance value of pixel (x0, z0);

[0017] The illuminance value corresponding to each point on the gasification product image is solved by using the coordinate point irradiance solution model, and the radial distribution map of irradiance of gas products is obtained.

[0018] Furthermore, the step of using the least squares method to perform linear regression on the locations of all 98% of the maximum illuminance values ​​includes:

[0019] The radial distribution map of irradiance is divided into an upper radial distribution map and a lower radial distribution map of irradiance, with the axis of the solid propellant ignition site as the dividing line. The least squares method is used to perform linear regression on the positions of all 98% maximum irradiance values ​​in the upper radial distribution map and the positions of all 98% maximum irradiance values ​​in the lower radial distribution map, and the coordinates of the points corresponding to the 98% maximum irradiance values ​​are calculated.

[0020] The coordinate calculation model is:

[0021] ;

[0022] ;

[0023] In the formula, is the coordinate of the point corresponding to the 98% maximum illumination value, Z s is the maximum illumination value of the current section, Z sumj is the cumulative illumination value from the 1st point to the jth point, Z sum(j+1) is the cumulative illumination value from the 1st point to the j+1th point, l is the minimum distance between adjacent points in the radial illumination distribution diagram, and is the actual length corresponding to a single pixel point.

[0024] Further, the plume divergence angle of the gasification product is calculated, including:

[0025] A plume divergence angle calculation model is established:

[0026] ;

[0027] wherein, α is the divergence angle, k’ and k’’ are the slopes of the two regression straight lines, respectively.

[0028] Further, the gray scale values of the background image and the gasification product expansion motion image are compared to determine the plume boundary of the gasification product expansion motion image, including:

[0029] The maximum gray scale value in the background image is taken as the background gray scale, and the pixel point position with a gray scale value greater than the background gray scale after the gray scale processing of the gasification product expansion motion image is considered to exist gasification product generation, and vice versa, which is considered to have no gasification product generation, thereby determining the plume boundary of the gasification product.

[0030] The plume divergence angle measurement method provided by the application does not need to invade the thruster with equipment components, does not affect the normal performance of the thruster, and is a transient and rapid plume measurement on the ignition end of the thruster, and is not limited to steady-state plume divergence angle measurement, thereby improving the measurement range, and ensuring the measurement efficiency and high measurement accuracy, in addition, the method only needs to install a high-speed camera on the side of the thruster to cooperate with image processing and calculation to obtain the plume divergence angle of the gasification product, and the measurement cost is low and the efficiency is high. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Flow chart of the measuring method in the embodiment of the present application;

[0032] Figure 2 The figure of the gasification product expansion movement after the solid propellant is ignited by laser in the embodiment of the present application;

[0033] Figure 3 The cross-sectional projection schematic diagram of the gasification product in the embodiment of the present application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0035] It should be noted that all the directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between the components in a certain specific posture (as shown in the drawings). If the specific posture changes, the directionality indications also change accordingly.

[0036] In addition, the descriptions such as “first”, “second” and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as “first”, “second” can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of “plurality” is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0037] In the present application, unless otherwise explicitly specified and limited, the terms “connection”, “fixation” and the like should be understood in a broad sense. For example, “fixation” can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection, or physical connection, or wireless communication connection; can be direct connection, or indirect connection through an intermediate medium; can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that the technical solutions can be realized by those skilled in the art. When the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope of the present application.

[0039] As shown in the accompanying drawings Figure 1 The present application provides a method for measuring the dispersion angle of the gasification product plume of a solid propellant after ignition, comprising the following steps:

[0040] S100, obtaining a background image before ignition of the solid propellant and a gasification product expansion motion image during ignition, the shooting direction of the background image and the gasification product expansion motion image being consistent and perpendicular to the axis of the solid propellant ignition site;

[0041] S100 can specifically comprise:

[0042] S101, determining the exposure time of the high-speed camera according to the laser pulse width time of the ignition laser.

[0043] The exposure time of the high-speed camera should be much smaller than the laser pulse width time of the ignition laser, and at the same time, in order to realize the transient measurement of the gasification product plume, the exposure time should be as small as possible so as to obtain as many gasification product expansion motion images as possible within one laser pulse width time. Through data analysis, it is preferred that the exposure time tb of the high-speed camera is less than one thousandth of the laser pulse width time tl.

[0044] S102, determining the placement position of the high-speed camera, installing and debugging the focal length, and ensuring that the focal point is focused on the laser spot position in the target (L) of the reaction between the laser and the surface of the solid propellant. Figure 3

[0045] As shown in the accompanying drawings Figure 3 The high-speed camera should be placed on the side of the solid propellant, the central axis of the camera lens and the central axis of the laser spot on the solid propellant are located on the same plane, and the former and the latter are perpendicular to each other. The vertical distance between the camera lens and the laser spot is L.

[0046] S103, taking a photo before laser ignition as a background image to obtain the intensity of the background light so as to remove the influence of background interference light by subsequent normalization; at the same time, keeping the camera position unchanged, taking a photo of a reference size reference object to establish the scale relationship between the picture size and the actual size.

[0047] During the measurement process, it is impossible to completely isolate the influence of light, so it is necessary to process the background light. By recording the background image by taking a photo, it is assumed that the maximum background gray value of the background image is H0. At the same time, in order to facilitate the calculation of the coordinates of the gasification product motion, the reference object with a known actual length L0 is photographed, and it is assumed that the pixel length in the picture is X0 (i.e. X0 pixel points), at this time the scale of the picture and the actual size is 1: L0 / X0.

[0048] S104, igniting the solid propellant by laser, and collecting a series of gasification product expansion motion images after laser ablation of the propellant by using the high-speed camera. ​

[0049] According to the parameters set in the previous step, the high-speed camera can collect a series of gasification product expansion movement images as shown in the following figure. Figure 2

[0050] S200, comparing the gray values of the background image and the gasification product expansion movement image, determining the plume boundary of the gasification product expansion movement image, and segmenting the gasification product part in the gasification product expansion movement image to obtain a gasification product image;

[0051] S200 can specifically include:

[0052] Determine the gasification product boundary, segment the gasification product expansion movement image, and establish a unified coordinate system.

[0053] According to the maximum background gray value H0 obtained in S103, the pixel point position with a gray value greater than H0 after the gasification product expansion movement image is processed is considered to have gasification product generation, and vice versa. The plume boundary of the gasification product is determined, and the original gasification product expansion movement image is segmented to remove the area without gasification product generation and only keep the effective gray area to obtain the gasification product image. A unified orthogonal coordinate system is established for the gasification product image with the laser spot as the coordinate origin, and the unit length of the coordinate axis is the size of a single pixel point.

[0054] S300, obtaining the two-dimensional radiation intensity distribution of the gasification product image, and solving the radiation intensity radial distribution diagram of N cross sections of the gasification product image according to the two-dimensional radiation intensity distribution of the gasification product image;

[0055] S300 can specifically include:

[0056] S301, performing RGB image processing on the gasification product image, and calculating the gray values H r / H g / H b of different pixel points in the gasification product image under the red / green / blue three channels respectively, and further calculating the illumination value Z of each pixel point to obtain the two-dimensional radiation intensity distribution of the gasification product image.

[0057] Each color can be composed of different proportions of red, blue and green in visual effect, and an RGB image is essentially a three-dimensional matrix, that is, a two-dimensional matrix of (R, G, B) triplets, where each pixel point is a three-value group corresponding to the R, G and B components of the RGB image at a specific spatial position. According to the OpenCV software library, Matlab or Python can be used to directly read the image and obtain the intensity of the image under the red, green and blue three channels respectively. Assuming that the intensity of a pixel point under the RGB three channels is I ​r , I g , I b At this time, the corresponding gray value of the red, green and blue three channels H r , H g , H b The formula (1), formula (2), formula (3) is calculated, that is:

[0058] (1)

[0059] (2)

[0060] (3)

[0061] Wherein, π Pi is the ratio of circumference to diameter, μ is the photoelectric conversion coefficient of the camera, η is the conversion coefficient between the gray value and the camera current, a is the entrance pupil diameter, f’ is the image side focal length, k is the transmittance, Y is the spectral response characteristic function of different channels, l is the actual length corresponding to a single pixel point in the corresponding image, l=X 0 / L 0.

[0062] When the gray value of a pixel point under the RGB three channels is known, the radiant intensity Z of the pixel point can be calculated according to formula (4), that is:

[0063] (4)

[0064] The radiant intensity value of each pixel point is calculated by the above method, and then the radiant intensity two-dimensional distribution map of the gasification product image can be obtained.

[0065] The present application can improve the accuracy of the obtained illumination value by pre-processing the obtained gasification product expansion motion image, and calculating the corresponding illumination value of the image according to the gray value calculated from the RGB channel conversion of the gasification product image, and then finally improving the plume dispersion angle measurement accuracy.

[0066] S302, according to the radiant intensity two-dimensional distribution of the gasification product image, the radiant intensity radial distribution map of the gasification product is solved.

[0067] If the solid propellant is heated uniformly, the gasification products will diffuse randomly in all directions, and at this time the gasification products can be considered to be cylindrical-symmetrical. When taking a picture of the gasification products from the side of the thruster, the obtained image radiance is the result of the projection of the luminous cylindrical gasification products on the x-z plane, as shown in Figure 1 Therefore, the pixel radiance on the image is the superposition of the radiance of multiple pixels on the chord of the circular cross-section of the cylindrical gasification products, and the corresponding relationship at the same axial position can be expressed as formula (5), that is:

[0068] (5)

[0069] wherein, is the radiance of the pixel (x, z) in the image, is the radiance of the corresponding point (x, y, z) in the gasification products, is the distance between the point i (x, y, z) in space and the camera. When the distance between the camera and the axis of the gasification products is much greater than the length and cross-sectional radius of the gasification products, it can be considered that the distance between any pixel in the image and the camera is equal, and is equal to the distance between the camera and the axis of the gasification products, which is L. Thus, formula (5) can be converted into formula (6).

[0070] (6)

[0071] When the laser ignites, the laser will react with the solid propellant, and the solid propellant will start to generate gasification products from the laser spot. The gasification products gradually expand and diffuse outward, and have a cylindrical-symmetrical structure. Therefore, for any circular cross-section of the gasification products, the pixel points on the same circumference have the same radiance value. As Figure 3 described, taking the cross-section at the axial direction Z1 position as an example, according to the cylindrical-symmetrical characteristics of the gasification products, the points A1 and A1', A2 and A2', A3 and A3' have the same radiance value. Therefore, the superposition of the radiance of the pixel points between the line segments A1A4 is equivalent to the superposition of the radiance of the pixel points between the line segments A1'A4. Assuming that the projection point of the chord A1B on the x-z plane is (x0, z0), at this time the radiance between the two satisfies the expression formula (7):

[0072] (7)

[0073] wherein, is the radiance value of the pixel (x0, z0), is the sum of the radiance values of all points on the chord A1B.

[0074] According to the above expression formula (7), the radiance value expression formula (8) of the pixel (x0-1, z0) in the image is:

[0075] (8)

[0076] wherein, is the luminance value of the pixel point (x0-1, z0), is the luminance value of the point in the gasification product.

[0077] When the luminance value of each pixel point in the image is known, the luminance value of any point in the gasification product can be calculated, and the calculation formula is formula (9):

[0078] (9)

[0079] Therefore, the luminance value corresponding to each point on the line segment A1'0 can be calculated by using formula (9), and the radial luminance distribution of the gasification product is obtained.

[0080] S400, according to the radial luminance distribution of the radiation on the N sections, the maximum luminance value on each section is determined, and the position of 98% of the maximum luminance value on each section is calculated.

[0081] S400 can specifically include:

[0082] S401, according to the measurement requirement, select N sections in the image, and calculate the spatial gas product radial luminance distribution corresponding to different sections respectively.

[0083] The gasification product of the solid propellant can be divided into a plurality of sections, and here N sections (N is a positive integer) are selected, that is, Z1 is selected to be different values, and the sampling of multiple sections can improve the accuracy of measurement.

[0084] Although the gasification product should theoretically satisfy the columnar distribution, it is inevitable to be disturbed by the outside world in the experiment, so the image profile of the gasification product will fluctuate slightly, and not completely form a smooth curve. Therefore, if the luminance of the upper and lower parts of the Z-axis (the axis of the ignition part of the solid propellant) is used to solve the radial distribution of the luminance of the gasification product, the results will be slightly different. The luminance of the upper part of the Z-axis is used to solve the radial distribution of the gasification product, which is called the upper radiation luminance radial distribution, and the luminance of the lower part of the Z-axis is used to solve the radial distribution of the gasification product, which is called the lower radiation luminance radial distribution. The present application uses the upper and lower radiation luminance radial distribution for calculation, which can greatly reduce the error and improve the measurement accuracy. All subsequent radial distribution solving includes the upper and lower radial distribution.

[0085] S402, according to the spatial radial luminance distribution of different sections, first determine the maximum luminance value Zs of the current section, and then calculate the position of 98% Zs of the radial distribution.

[0086] The gasification product has column symmetry characteristics, and generally the maximum illumination value Zs of the current section is equal to half of the illumination value of the intersection of the projection of the section in the image and the central axis (i.e. the Z axis). It should be noted that because the minimum unit of the image is a pixel, the minimum distance between adjacent points in the radial illumination distribution is the actual length corresponding to a single pixel, i.e. l = X0 / L0.

[0087] The position corresponding to the 98% maximum illumination value is calculated by taking the center of the circular section as the starting point and sequentially adding the illumination values of each point along the radial direction, and each time the addition obtains the cumulative illumination value Zsum of the first point to the jth point, the two cumulative illumination values closest to the 98% maximum illumination value are found, the positions of the two points corresponding to the two illumination values are obtained, and the positions are assumed to be the jth and (j+1)th points, and the coordinates of the point corresponding to the 98% maximum illumination value are calculated by linear interpolation (formula 11) .

[0088] (10)

[0089] (11)

[0090] In the formula, is the coordinates of the point corresponding to the 98% maximum illumination value, Z s is the maximum illumination value of the current section, Z sumj is the cumulative illumination value from the first point to the jth point, Z sum(j+1) is the cumulative illumination value from the first point to the (j+1)th point, l is the minimum distance between adjacent points in the radial illumination distribution, which is the actual length corresponding to a single pixel.

[0091] Based on the above method, for the upper and lower radial distributions, the coordinates of the points corresponding to the 98% maximum illumination values of the upper and lower points can be obtained, and the upper and lower points are defined as Z's 98% (x' 98% , z' 98% ) and Z''s 98% (x'' 98% , z'' 98% ). Meanwhile, the radial distribution of different sections is solved, and a series of 98% maximum illumination value points are obtained.

[0092] S500, by using the least square method, linear regression is performed on the positions of all 98% maximum illumination values, the slope of the regression line is calculated, and the divergence angle of the gasification product plume is calculated according to the slope of the regression line.

[0093] S500 can specifically include:

[0094] S501, taking Z axis as a demarcation line, linear regression is conducted on all 98% maximum luminance value points on the upper part of the Z axis, and the slope of the regression straight line is calculated and recorded as k’ ; similarly, linear regression is conducted on all 98% maximum luminance value points on the lower part of the Z axis, and the slope of the regression straight line is calculated and recorded as k’’ .

[0095] The linear regression is conducted on all 98% maximum luminance value points by using the least square method, so that the influence of experimental system error and accidental error on the measurement of the gasification product divergence angle can be reduced as much as possible.

[0096] S502, according to the slopes of the upper and lower regression straight lines, the plume divergence angle of the gasification product is calculated.

[0097] The plume divergence angle of the gasification product is calculated according to formula (12), that is:

[0098] (12)

[0099] wherein, α is the divergence angle, k’ and k’’ are the slopes of the two regression straight lines.

[0100] The present application finds two corresponding upper and lower 98% maximum luminance points in one section, then linear regression is conducted, and the size of the plume divergence angle is calculated according to the slope of the regression straight line, compared with the conventional way of directly finding one 95% maximum luminance point in one section for calculation, the present application has more accurate and reliable measurement results for the measurement of the transient plume divergence angle of the solid propellant gasification product.

[0101] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A method of measuring the divergence angle of a gaseous product plume from a solid propellant after ignition, characterized in that, The method comprises the following steps: S100, acquiring a background image before ignition of the solid propellant and a gasification product expansion movement image during ignition, the shooting directions of the background image and the gasification product expansion movement image being consistent and perpendicular to the axis of the solid propellant ignition site; S200, comparing the gray values of the background image and the gasification product expansion movement image, determining the plume boundary of the gasification product expansion movement image, segmenting the gasification product part in the gasification product expansion movement image, and obtaining a gasification product image; S300, acquiring the two-dimensional radiation intensity distribution of the gasification product image, and solving the radiation intensity radial distribution graph of N sections of the gasification product image according to the two-dimensional radiation intensity distribution of the gasification product image; S400, determining the maximum intensity value on each section according to the radiation intensity radial distribution graph of N sections, and calculating the position of 98% maximum intensity value on each section; S500, using the least square method to perform linear regression on all the positions of 98% maximum intensity value, calculating the slope of the regression straight line, and calculating the plume divergence angle of the gasification product according to the slope of the regression straight line; The least square method is used to perform linear regression on all the positions of 98% maximum intensity value, which comprises: The radiation intensity radial distribution graph is divided into an upper radiation intensity radial distribution graph and a lower radiation intensity radial distribution graph with the axis of the solid propellant ignition site as the division line, and the least square method is used to perform linear regression on all the positions of 98% maximum intensity value of the upper radiation intensity radial distribution graph and the lower radiation intensity radial distribution graph.

2. The method of claim 1, wherein the method is characterized by: The acquisition of the background image before ignition of the solid propellant and the gasification product expansion movement image during ignition comprises: According to the laser pulse width time of the ignition laser, the exposure time of the high-speed camera is determined, and the exposure time of the high-speed camera is less than one thousandth of the laser pulse width time.

3. The method of claim 1, wherein the method is characterized by: According to the two-dimensional radiation intensity distribution of the gasification product image, the radiation intensity radial distribution graph of N sections of the gasification product image is solved, which comprises: A coordinate point radiation intensity solving model is established: wherein is the luminance value of the point of the gasification product ; is the luminance value of the pixel point (x0-1, z0), is the luminance value of the pixel point (x0, z0); The radiation intensity radial distribution graph of the gasification product is obtained by using the coordinate point radiation intensity solving model to solve the corresponding intensity value of each point on the gasification product image.

4. The method for measuring the plume divergence angle of the gasification product after ignition of the solid propellant according to claim 1, wherein The calculation of the position of 98% maximum intensity value on each section comprises: The coordinate calculation model is: In the formula, is the coordinate of the point corresponding to the 98% maximum luminance value, Z s is the maximum luminance value of the current section, Z sumj is the cumulative luminance value from the 1st point to the jth point, Z sum(j+1) is the cumulative luminance value from the 1st point to the j+1th point, l is the actual length corresponding to a single pixel point.

5. The method of claim 1, wherein the method is characterized by: The calculation of the plume divergence angle of the gasification product comprises: A plume divergence angle calculation model is established: wherein α is the divergence angle, k’ and k’’ are the slopes of the two regression lines, respectively.

6. The method of claim 1, wherein the method is a method of measuring the plume divergence angle of a solid propellant ignition after-gas product, characterized by, The comparison of the gray values of the background image and the gasification product expansion movement image to determine the plume boundary of the gasification product expansion movement image comprises: The maximum gray value in the background image is taken as the background gray value, the pixel point position with a gray value greater than the background gray value after the gray value processing of the gasification product expansion movement image is considered to exist gasification product generation, otherwise it is considered that there is no gasification product generation at this position, thereby determining the plume boundary of the gasification product.

Images